JP2010153170A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooker capable of uniformly heating a pan. <P>SOLUTION: Among a plurality of heating coils, the shortest distance between two heating coils arranged on the closest position is set to be not more than a distance two times the distance from the two heating coils to a surface, on which a pan is put, through a top plate. When one pan is heated while at least two heating coils are simultaneously operated, the frequencies of currents flowing in the two heating coils are set to be the same, the currents are synchronized, and a phase difference between the currents is set to be from π/2 to 0, so that an induction heating cooker capable of uniformly heating the pan is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

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 put the same electric power, and the heating efficiency is deteriorated. Further, the latter means has a problem that high 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 problem, an induction heating cooker according to the present invention includes a top plate for placing a pan, and a plurality of plates arranged in substantially the same plane below the top plate and having different circular centers. A heating coil; an inverter that supplies power to the plurality of heating coils; a control unit that controls the output of the inverter; and an operation unit that instructs the control unit to start / stop heating or set a heating power. Of the plurality of heating coils, the shortest distance between the two heating coils arranged closest to each other is twice the distance through the top plate from the two heating coils to the mounting surface of the pan. When heating one pan by operating at least the two heating coils at the same time, the currents flowing through the two heating coils have the same frequency and are synchronized. Phase difference is obtained by the fact characterized that it is between [pi / 2 to 0.

  As a result, the currents flowing in the two adjacent heating coils have the same frequency, are synchronized, and the phase difference between the currents is between π / 2 and 0, so that the magnetic fields between the two heating coils cancel each other. Since the magnetic field is not strongly generated between the two heating coils so as not to be overheated, the pan can be heated uniformly while shortening the distance between the two heating coils to reduce the installation area. The interference between magnetic fields is likely to occur as the distance between the two heating coils is shorter and the distance between the heating coil and the pan is longer. Therefore, clarify the relationship between the distance between the two heating coils and the distance between the heating coil and the pan. By this, the pan can be heated more uniformly.

  According to the induction heating cooker of the present invention, the currents flowing in the two adjacent heating coils have the same frequency and are synchronized, and the phase difference between the currents is between π / 2 and 0, so that The magnetic field between the heating coils cancels each other, and a strong magnetic field is generated between the two heating coils so that the heating coil is not overheated. Therefore, the pan is heated evenly while shortening the distance between the two heating coils to reduce the installation area. can do. The interference between magnetic fields is likely to occur as the distance between the two heating coils is shorter and the distance between the heating coil and the pan is longer. Therefore, clarify the relationship between the distance between the two heating coils and the distance between the heating coil and the pan. By this, the pan can be heated more uniformly.

1st invention arrange | positions the electric power to the top plate for mounting a pan, the several heating coil which is arrange | positioned on the substantially the same plane under the said top plate, and has a different circular center, and the said several heating coil An inverter for controlling the output of the inverter, and an operation unit for instructing the control unit to start / stop heating, set a heating power, etc., and are closest to each other among the plurality of heating coils. The shortest distance between the two heating coils is set to be not more than twice the distance from the two heating coils to the mounting surface of the pan via the top plate, and at least the two heating coils are simultaneously When operating one pan, the currents flowing through the two heating coils have the same frequency and are synchronized, and the phase difference between the currents is between π / 2 and 0.

  As a result, the magnetic field between the two heating coils cancels each other out, and the magnetic field between the two heating coils is strongly generated so that the heating is not overheated. Therefore, the distance between the two heating coils is shortened to reduce the installation area. Can also heat the pan evenly. The interference between magnetic fields is likely to occur as the distance between the two heating coils is shorter and the distance between the heating coil and the pan is longer. Therefore, clarify the relationship between the distance between the two heating coils and the distance between the heating coil and the pan. By this, the pan can be heated more uniformly.

  In particular, the second invention includes a state in which the induction heating cooker according to the first invention includes a phase difference switching unit, and a phase difference between currents flowing through the two heating coils is between π and π / 2, and π Switch between / 2 and 0.

  By this, it is not necessary to heat the pan uniformly, and when high power and high heating is required, the current phase difference is set between π and π / 2, so that the two heating coils Since the magnetic field is strengthened cooperatively, the generated magnetic field can be efficiently contributed to heating, and heating can be performed with high heating efficiency.

  Furthermore, in the coordinated operation of the magnetic field that operates the current phase difference between π and π / 2, the outside of the plurality of heating coils operating at the same time, especially the line connecting the centers of the two heating coils and the outer diameter of the heating coil In the vicinity of the tangential direction of the heating coil with the point where it intersects with the magnetic field, the magnetic fields cancel each other out, making it difficult for the magnetic field to leak away from the heating coil, reducing the radiation level to the cooker user or causing the control circuit to malfunction. It is possible to provide an induction heating cooker with high safety such as making it difficult to wake up. In particular, when the size of the heating pan is smaller than the total size of the heating coils that operate simultaneously to heat one pan, the effect is significant, so it is effective to perform heating in a small pan by cooperative operation. is there.

  In addition, a complicated means for arbitrarily controlling the phase difference can be obtained by changing the electrical connection using, for example, a relay or the like to change the phase difference to only two patterns of π and 0. Without being provided, an induction heating cooker having different heating characteristics can be realized easily and inexpensively.

  In the third invention, in particular, the inverter according to the first or second invention is composed of a plurality of inverters, the plurality of heating coils are divided into heating coil groups corresponding to the number of the plurality of inverters, and the same heating coil group is provided. The heating coils are connected in series or in parallel, and are connected to the inverters corresponding one-to-one for each of the heating coil groups.

  By making the number of inverters plural, it is not necessary to operate the inverter connected to the heating coil that does not need to be energized when there are no pans or there are parts that do not require heating It is possible to provide an induction heating cooker that does not generate a magnetic field and reduce the heating efficiency or increase the leakage magnetic field.

  In addition, since the current flowing through the heating coil can be adjusted by individually changing the operation of the inverter, for example, it is possible to provide a place that wants to be heated strongly and weakly in the same pan, and induction with various heating patterns. A cooker can be provided.

Furthermore, by devising the arrangement and connection of the heating coils, even if the number of inverters and the number of heating coils are not in a one-to-one relationship, the two closest heating coils in all the heating coils cancel the magnetic field. It is possible to perform a matching operation or a cooperative operation.

  In the fourth aspect of the invention, in particular, when the phase difference of the induction heating cooker of the third aspect of the invention is switched, the timing at which the switching elements constituting the inverter transition to a conductive state or a non-conductive state between the plurality of inverters. This is done by shifting.

  Thus, by controlling the phase difference of the current flowing through the heating coil by shifting the timing at which the switching element is turned on and off between the two inverters, the phase difference of the current flowing through the heating coil is arbitrarily set to π to 0 Can be easily created.

  Moreover, with the above control method, a phase difference can be created between two different inverters even if the number of switching elements constituting one inverter is the minimum number. Even if it exists, it becomes possible to implement | achieve the induction heating cooking appliance which can be heated uniformly.

  5th invention makes the number of the heating coils which operate | move especially in order to heat one pot of the induction heating cooking appliance of any one of 2nd-4th invention to an even number.

  As a result, a plurality of heating coils are arranged according to a predetermined rule, and the number of heating coils to be operated at the same time is an even number. The leakage magnetic field is weakest on a straight line that is perpendicular to the line connecting the centers of the coils and passes through the center point of the line connecting the heating coils. The lowest point of the leakage magnetic field can be located at the desired location.

  In addition, when one pan is heated with three or more heating coils, it is assumed that a magnetic field is coordinated or canceled by adjacent heating coils. In the operation that cancels the magnetic field, even if the heating coil is odd, the operation can be performed by all the adjacent heating coils. However, in the operation that cooperates the magnetic field, at least one point that cannot be coordinated occurs if the heating coil is odd. Therefore, a cooperative operation cannot be realized between all adjacent heating coils. Therefore, an even number of heating coils for heating one pan can perform an operation of coordinating magnetic fields among all the adjacent heating coils, so that heating can be performed with high output / high efficiency.

  6th invention is the said operation | movement operated nearest from the place which operates an induction heating cooking appliance among the said several heating coils which operate | move simultaneously especially of the induction heating cooking appliance of any one invention of 2-5. The two heating coils are arranged so as to be substantially parallel to one side of the casing closest to the place to be operated.

  The closer the distance from the heating coil, the stronger the magnetic field. When heating a single pan using multiple heating coils, the arrangement of the two heating coils operating closest to the location where the user operating the cooker or the cooker is located is described above. As described above, the exposure to the leakage magnetic field is minimized by arranging it so as to be perpendicular to the line connecting the centers of the two heating coils and near the straight line passing through the center point of the line connecting the heating coils. Therefore, it is possible to provide a highly safe cooker especially for a pacemaker user.

  According to a seventh aspect of the invention, in particular, the induction heating cooker according to any one of the first to sixth aspects includes a magnetic shielding ring for reducing a leakage magnetic field, and the magnetic shielding ring operates simultaneously to heat one pot. Arrange to surround all possible heating coils.

  The leakage magnetic field when the magnetic field is coordinated is less likely to leak away from the heating coil because the magnetic fields generated from the heating coils cancel each other. However, when the operation of canceling the magnetic field is performed, the shape tends to leak. Therefore, a magnetic shield ring is required to reduce the leakage of the magnetic field to the outside of the heating coil. Therefore, by arranging heating coils that can operate at the same time to heat one pan and arrange the magnetic shielding ring on the outer periphery of the plurality of heating coils, the electromotive force generated in the magnetic shielding ring is plural heating coils. It is possible to prevent the magnetic field from leaking to the outer periphery of the magnetic shielding ring by the current flowing through the magnetic shielding ring.

  Moreover, when the same number of magnetic shield rings as the heating coils are arranged so as to have the same circle center as the conventional induction heating cooker, different heating coils such as magnetic field cancellation and coordination are generated. Since the interference of the magnetic field does not occur, it is more effective in the present invention to arrange one magnetic shield ring on the outer periphery of the plurality of heating coils.

  In the eighth aspect of the invention, in particular, when the phase difference between the currents flowing through the two heating coils of the induction heating cooker of the second aspect is between π / 2 and 0, the phase difference of the current is between π and It is characterized by being higher than the operating frequency when it is between π / 2.

  Since the inductance changes between the cancellation operation and the cooperative operation, the resonance frequency also changes when the resonance capacitors are the same. Since the magnetic field cancellation operation has a smaller inductance than the cooperative operation, the resonance frequency becomes higher. Further, the resistance is smaller in the canceling operation. Therefore, the operating frequency when the phase difference of the current that is the canceling operation is between π / 2 and 0 and the operating frequency when the phase difference of the current that is the cooperative operation is between π and π / 2 are the same. Even if the same pan is heated, depending on the setting of the operating frequency and the impedance of the heating coil including the pan, the rated power cannot be output during cooperative operation, or the operating frequency during canceling operation. It is conceivable that the frequency becomes lower than the resonance frequency and zero voltage switching cannot be performed, thereby causing an increase in loss or destruction of the switching element. Therefore, it is effective that the operating frequency of the switching element is higher in the canceling operation than in the cooperative operation.

  In the ninth aspect of the invention, in particular, the adjustment of the electric power of the induction heating cooker according to any one of the first to eighth aspects of the invention is performed by adjusting at least one of a conduction time, a duty, or an operating frequency of the switching element constituting the inverter. Change and do.

  With the configuration using a plurality of inverters, various power control methods such as duty and operating frequency can be applied to power adjustment as long as the phase difference between the inverters is constant. In particular, a power adjustment method such as Duty control that does not change the frequency is effective in the present invention because it has a great merit that even if two burners are operated at the same time and the operating frequency is matched, no roaring interference sound is generated. .

  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. 1 are arranged below the top plate 11. In FIG. 1, the two heating coils 13 arranged closest to each other are representatively represented from the plurality of heating coils 12. Is illustrated. 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 easy to use for the user.

  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.

  FIG. 2 is a top view of the heating coil showing the positional relationship of the heating coil 12 according to the first embodiment of the present invention. The plurality of heating coils 12 are arranged in a matrix, and FIG. 2 shows nine heating coils as a representative. The content of the present invention can be obtained if there are two or more heating coils having different circular centers. For example, by arranging four heating coils in two rows and two columns, it corresponds to a circular pan. Approaching the realization of a circular heatable region, or placing the six heating coils in a position rotated by π / 3 from the center position of the pan placement region, or bringing the heatable region closer to a circular shape, or The arrangement of the heating coils can be changed according to the size and shape of the required heatable area, such as simply realizing a circular heatable area by arranging two elliptical heating coils side by side, and in a matrix form It is not limited to arrangement.

  FIG. 3 is a side view of the heating coil showing the arrangement relationship of the heating coils. As shown in FIG. 3, when the distance between the two heating coils 13 arranged closest to each other is a, and the distance between the heating coil and the pan is b, the heating coil has a relationship of 0 ≦ a ≦ 2b. Place. The basis for this will be described later.

  FIG. 4 is a diagram for defining the direction of current in the two heating coils 13. The current flowing in the left heating coil 27 in FIG. 4 is I1, the current flowing in the right heating coil 28 is I2, and the case where the current flows counterclockwise in both heating coils is a positive value.

  FIG. 5 is a diagram illustrating 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 in 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 twice or less the distance b from the heating coil to the mounting surface of the pan, the magnetic field on the heating coil wire is strongly generated and the portion where the pan becomes high temperature is approaching. Improvements in heat retention and an increase in the amount of heat transferred between the heating coils contribute, and as a result, the pan can be heated uniformly. In addition, since the strength of the magnetic field is inversely proportional to the square of the distance from the current flowing through the heating coil, the magnetic field generated from the nearby heating coil becomes dominant at points other than on the bisector of the two heating coils. Is not completely attenuated, and by heating appropriately, the heating balance can be improved and the pan can be heated uniformly.

  FIG. 6 is a diagram showing a current waveform when the phase difference θ between the current I1 and the current 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 magnetic field interference between the adjacent heating coils a can be ignored in terms of the amount of heat generation, and the heat generation amount of the pan is an addition when operating with only one heating coil.

FIG. 7 shows the center point of each of the two heating coils when electric power is input to two heating coils having an outer diameter of 8 cm and an inner diameter of 3 cm that are electrically connected in series, and the enamel pan is heated. It is a figure which shows the ratio with respect to a certain reference value by measuring the relationship between the distance of the pan in the direction of the line segment and the temperature rise, with the midpoint of the line segment to be connected as 0 cm. Here, in this experiment, the distance b between the upper surface of the top plate 11 and the two heating coils 13 is 5 mm and 12 mm. The distance a between the two heating coils is 0 mm, that is, the two heating coils are arranged in contact with each other.

  A certain reference value sets the maximum temperature rise point on a line connecting the center points of the two heating coils to 100%. In FIG. 7, since the end face of one heating coil is located at 0 cm and 8 cm, the maximum temperature rise value between the positions of 0 cm to 4 cm inside the position of the center point 4 cm of one heating coil is used as a reference. Yes. Thereby, it is easy to compare the relationship between the distance a and the distance b at 0 cm to 4 cm, where the interference of the magnetic field generated from the other heating coil is greatly affected. In the two heating coils, since interference hardly occurs at the position of 4 cm to 8 cm, it will not be described in detail in this embodiment. For example, if the heating coils are arranged in a matrix as shown in FIG. A chain of interference occurs, and the phenomenon described with respect to 0 cm to 4 cm occurs symmetrically at a position of 4 cm to 8 cm, and uniform heating can be achieved.

  When the distance a between the two heating coils is 0 mm, the maximum temperature rise occurred at 2 cm between 0 cm and 4 cm. Therefore, the temperature rise ratio is shown in FIG. ing. In this embodiment, if the definition of the presence / absence of temperature unevenness is 10%, it can be seen that there is no temperature unevenness of 95% or more at any position between 0 cm and 4 cm, and heating is extremely uniform.

  When the distance b between the upper surface of the top plate 11 and the two heating coils 13 is 5 mm and 12 mm, it can be seen that the pot 17 can be heated more uniformly when the distance b is 12 mm. This is because the distance between the pan 17 and the two heating coils 13 is long, so that the propagation distance until the magnetic field is absorbed by the pan 17 is extended, and magnetic field interference often occurs.

  Since the magnetic field is more likely to pass through the pan 17 that is a magnetic material than the air or the top plate 11 that is a non-magnetic material, the magnetic path is changed by bringing the magnetic material closer to the heating coil, and magnetic field interference is less likely to occur. Become. In other words, the farther the distance b between the heating coil that is the source of the magnetic field and the pan 17 that is the object to be heated, the easier the interference of the magnetic field occurs, and the pan 17 can be heated uniformly. It becomes less and heating efficiency worsens.

  FIG. 8 is a diagram showing experimental results when the distance between two heating coils is changed to 15 mm from the experimental state of FIG.

  In FIG. 8, since the end face of one heating coil is located at 1.5 cm and 9.5 cm, it is between 0 cm to 5.5 cm, which is inside the center point of 5.5 cm of one heating coil. It is based on the maximum temperature rise value at.

  When the distance a between the two heating coils is 15 mm, the maximum temperature rise occurred at 3 cm between 0 cm and 5.5 cm. Therefore, the temperature rise ratio is shown in FIG. It is shown. The reason why the position of the maximum temperature rise has moved outward as compared with FIG. 7 is that the heating coil itself has moved outward.

  FIG. 9 is a diagram showing changes in the magnetic flux loop depending on whether or not the pan 17 is placed on the top plate 11. In the case of FIG. 9A in which the pan 17 is not placed on the top plate 11, since there is no magnetic body that generates distortion in the magnetic flux loop above the heating coil, the magnetic flux flows through the heating coil as shown by the solid line. The shape draws a beautiful circle centered at the source. Since the heating coil is formed by winding a plurality of coil wires on substantially the same plane, the synthesized magnetic flux is as shown by the broken line in FIG. 9A, but is closest to the other heating coil where interference occurs most. A solid line represents the magnetic flux generated from the outer diameter of the current source, that is, the heating coil.

  In the case of FIG. 9B in which the pan 17 is placed on the top plate 11, the magnetic flux loop has a shape that is crushed from above due to the influence of the pan 17 that is a magnetic body. In addition, since the pan 17 is a magnetic substance, it absorbs the magnetic field, so that a strong magnetic field does not propagate farther than when the pan 17 is not placed.

  If the magnetic flux loop is not distorted up to the distance of a / 2 where the magnetic field interference occurs at least, the minimum magnetic field interference for heating the pan 17 uniformly occurs. In order not to greatly distort the loop of magnetic flux to a distance of a / 2, it is necessary that a ≦ 2b, which is a condition that the distance a / 2 is shorter than the distance b to the pan. .

  This can also be seen from FIG. 7 and FIG. In the experiment shown in FIG. 7, since the distance a is 0 mm, uniform heating with a temperature increase ratio within 10% can be achieved regardless of whether the distance b is 5 mm or 12 mm. In the experiment shown in FIG. 8, since the distance a is 15 mm, the distance b must be 7.5 mm or more in order to satisfy a ≦ 2b. Since the condition is satisfied when the distance b is 12 mm, uniform heating with a temperature increase ratio within 10% can be achieved. However, since the condition is not satisfied when the distance b is 5 mm, the region where the interference of the magnetic field has an effect on the uniform heating of the pan 17 becomes small. As a result, the temperature rise ratio becomes 10% or more, and in this embodiment, it is positioned that uniform heating is not possible. In order to make the temperature rise ratio within 10%, it is necessary experimentally to satisfy a ≦ 2b, so the distance a between the heating coils is defined.

  The phase difference θ that can uniformly heat the pan 17 can be substantially determined by the relationship between the distance between the heating coil and the mounting surface of the pan 17 via the top plate 11 and the distance between the heating coils, but more accurately. When it is desired to heat the pan 17 uniformly, a temperature sensor for measuring the temperature of the pan 17 may be provided to control the phase difference according to the temperature state of the pan 17. In that case, if it is judged that the temperature of the pan 17 above the center between the heating coils is higher than the temperature of the pan 17 above the heating coil wire, the temperature of the pan 17 above the center between the heating coils is reduced by reducing the phase difference θ. Try to lower. Conversely, when it is determined that the temperature of the pan 17 above the center between the heating coils is lower than the temperature of the pan 17 above the heating coil wire, the phase difference θ is increased to increase the pan above the center between the heating coils. The temperature of 17 is raised.

(Embodiment 2)
FIG. 10 is a block diagram showing the configuration of the induction heating cooker according to the second embodiment of the present invention. 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, FIG. 11 is a diagram showing a current waveform when the phase difference θ is π. As shown in FIG. 11, the magnetic fields generated from the two heating coils cooperate most strongly. When the magnetic field is coordinated by the relationship between the coil distance a <coil radius b, the temperature of the pan above the center point between the heating coils rises more than when the phase difference θ is operated at π / 2, and the temperature distribution becomes worse. However, since cancellation of magnetic fields is reduced, 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 is a diagram illustrating an example of a relationship between the number of inverters and the number of heating coils and a 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 causing a high-frequency current to flow 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.

  FIG. 14 is a diagram illustrating a gate signal and a current waveform of the switching element. 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, FIG. 15 shows a diagram showing the relationship of the gate signal when the phase difference is changed. 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 I2 flowing through the right heating coil 28 when the current I1 flowing through the left heating coil 27 is positive is Since the current I2 becomes 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 number of heating coils and the direction of current for heating one pan 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 is a diagram illustrating a relationship between magnetic fields generated from respective coils when current directions are made the same between two adjacent heating coils in the sixth embodiment.

  When the magnetic fields are coordinated, a large magnetic field loop is formed as indicated by the solid arrow in FIG. 6, and as a result, the magnetic field is sufficiently applied to the pan 17 immediately above the heating coil (region A). 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 the diagram showing the magnetic field region affecting the distance between the two heating coils in FIG. 18, when the current Ia flowing through the heating coil and the current Ib are in the same direction, the region A is near the arrangement surface of the heating coil. Since there is almost no leakage of the magnetic field at, a highly safe cooker 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 has a heating unit 12 that heats one pan with four heating coils, an intake / exhaust port 29 that serves as an air passage 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 the diagram showing the relationship between the arrangement of the heating coils in the induction cooking device of FIG. 19 and the operation position of the user, among the four heating coils that operate simultaneously to heat one pan, use of the cooking device The two heating coils that operate closest to the place where the user is located are arranged so as to be substantially parallel to one side of the casing closest to the place where the user is located. 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 wears a wristwatch that is weak to magnetism is operated by using an induction heating cooker, the effect of preventing malfunction is increased and cooking is performed safely. An induction heating cooker can be provided.

(Embodiment 7)
FIG. 20 is a diagram showing an arrangement relationship between the heating coil and the magnetic shielding ring of the induction heating cooker that heats one pan with the four heating coils in the seventh embodiment.

  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 is a diagram showing 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 in the eighth embodiment. 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 a state in which the time ratio Duty, which is the ratio between the conduction state and the non-conduction state of the first switching element 23 and the second switching element 24 in the ninth embodiment, is changed to other than 0.5. It is a figure which shows the electric current waveform which flows into two adjacent heating coils. 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.

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 heating coil side view which shows the arrangement | positioning 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 the center of two heating coils, and the temperature rise ratio of an enamel pan at the distance between heating coils of 0 mm The figure which shows the relationship between the distance from the center of two heating coils, and the temperature rise ratio of an enamel pan at the distance between heating coils of 15 mm Diagram showing the loop shape of the magnetic flux depending on the presence or absence of a pan 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.

Explanation of symbols

11 Top plate 12 Multiple heating coils 13 Two heating coils arranged closest to each other 14 Inverter 15 Control unit 16 Operation unit 17 Pan (to-be-heated object)
DESCRIPTION OF SYMBOLS 18 Phase difference switching part 19 Commercial power supply 20 Rectification part 21 Filter part 22 Inverter and load 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 Intake / exhaust port 30 IH cooking heater (housing)
31 Device user position 32 Magnetic shield ring

Claims (9)

A top plate for placing a pan; a plurality of heating coils disposed in substantially the same plane below the top plate and having different circular centers; an inverter for supplying power to the plurality of heating coils; and the inverter A control unit for controlling the output of the control unit, and an operation unit for instructing the control unit to start / stop heating or set a heating power, and two of the plurality of heating coils arranged closest to each other. The shortest distance between the heating coils is not more than twice the distance from the two heating coils to the mounting surface of the pan via the top plate, and at least the two heating coils are operated simultaneously to form one pan. Induction heating cooker characterized in that the current flowing through the two heating coils has the same frequency and is synchronized, and the phase difference between the currents is between π / 2 and 0. It has a phase difference switching unit, and switches between a state where the phase difference of the current flowing through the two heating coils is between π and π / 2 and a state where it is between π / 2 and 0 The induction heating cooker according to claim 1. The inverter comprises a plurality of inverters, the plurality of heating coils are divided into heating coil groups corresponding to the number of the plurality of inverters, the heating coils in the same heating coil group are connected in series or in parallel, and each heating coil group The induction heating cooker according to claim 1, wherein the induction heating cooker is connected to the inverter corresponding to the one to one. The induction heating cooking according to claim 3, wherein the switching of the phase difference is performed by shifting the timing at which the switching elements constituting the inverter transition to a conductive state or a non-conductive state between the plurality of inverters. vessel. The induction heating cooker according to any one of claims 2 to 4, wherein the number of heating coils operating to heat one pan is an even number. Among the plurality of heating coils that operate simultaneously, the two heating coils that operate closest to the place where the induction heating cooker is operated are arranged so as to be substantially parallel to one side of the casing closest to the position where the induction heating cooker is operated. The induction heating cooker according to any one of claims 2 to 5, wherein: A magnetic shielding ring for reducing a leakage magnetic field is provided, and the magnetic shielding ring is arranged so as to surround all the heating coils that operate simultaneously to heat one pan. The induction heating cooker as described in any one of -6. The operating frequency when the phase difference between the currents flowing through the two heating coils is between π / 2 and 0 is higher than the operating frequency when the phase difference between the currents is between π and π / 2. The induction heating cooker according to claim 2. The induction heating according to any one of claims 1 to 8, wherein the adjustment of electric power is performed by changing at least one of a conduction time, a duty, and an operating frequency of the switching elements constituting the inverter. Cooking device.