JP4022886B2 - Electromagnetic induction heating cooker - Google Patents

Description

  The present invention relates to an electromagnetic induction heating cooker, and more particularly to an induction heating cooker that cooks food by heating a cooking container with electromagnetic induction loss of a cooking container by generating a magnetic field using an electromagnetic induction coil.

  Conventionally, a high-frequency magnetic field is generated by an electromagnetic induction coil of an electromagnetic induction heating cooker without using an ultrasonic vibrator, and the cooking vessel provided in the cooker is ultrasonically vibrated so as not to generate noise. Thus, proposals have been made for an electromagnetic induction heating cooker that can cook delicious rice by promoting water absorption of rice in the container.

JP 2003-61816 A

  Such a conventional electromagnetic induction heating cooker is heated by electromagnetic induction by supplying a high-frequency current from an inverter to an electromagnetic induction coil facing a cooking container in which an object to be heated is accommodated. At this time, a magnetic flux modulation plate made of a diamagnetic material is provided between the center of the bottom surface of the cooking container and the electromagnetic induction coil, so that the magnetic flux modulation plate disturbs the magnetic flux generated around the electromagnetic induction coil, thereby generating vibration. By making the resonance frequency of the cooking container coincide with the frequency of the high-frequency current supplied to the electromagnetic induction coil, the vibration of the cooking container is amplified and the cooking container vibrates ultrasonically.

FIG. 9 is a schematic explanatory view showing the shape of an inner pot which is a conventional cooking container. 9A is a cross-sectional view of the inner hook, and FIG. 9B is a plan view seen from the lower surface. The inner hook 101 is formed in a shape in which a bottom portion 102, a trunk portion 103, and an edge portion 104 extending outward are continuous through bent portions 105 and 106, respectively. In a rice cooker that is a conventional electromagnetic induction heating cooker, when the inner pot 101 is set inside the rice cooker body, an appropriate position of the edge 104 of the inner pot 101 is supported by the suspension member 107, and the bottom 102 and the body In general, the portion 103 is held in a suspended state. However, in such a configuration, when the inner hook 101 vibrates ultrasonically, there is a technique that considers the relationship between the contact position of the suspension member 107 that directly contacts the inner hook 101 and the vibration level of the inner hook 101. There wasn't. This invention is made | formed in view of the said subject, and it aims at providing the electromagnetic induction heating cooking appliance which can vibrate an inner pot more efficiently.

In order to achieve the above object, an electromagnetic induction heating cooker according to the present invention has an edge extending outwardly, and heats the cooking container with a cooking container for storing an object to be heated and a generated magnetic field. An induction heating coil provided opposite to the outer surface of the cooking container ; a suspension material that supports an edge of the cooking container; and a temperature sensor that supports substantially the center of the bottom surface of the cooking container; The suspension position that supports the edge of the cooking container is substantially matched with the antinode position of the vibration displacement of the wavelength (λ) in the resonance mode of the longitudinal vibration characteristic of the cooking container obtained using the following equation , and The resonance frequency of the cooking vessel calculated from the wavelength and sound velocity in the resonance mode is matched with the high-frequency current flowing through the induction heating coil .
λ = 4L / (2n−1)
Here, L: length from the support position of the bottom of the inner hook to the end of the inner hook, n: order (1, 2,...)

According to the electromagnetic induction heating cooker of the present invention, it is possible to provide an electromagnetic induction heating cooker that can more efficiently vibrate the cooking container and transmit ultrasonic vibration.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a rice cooker as an electromagnetic induction heating cooker according to the present invention. As shown in the figure, a rice cooker 1 as electromagnetic induction heating in the present embodiment has a housing portion 4 for housing an inner pot 3 as a cooking container inside a main body 2, and on the outer periphery of the housing portion 4. The induction heating coil 5 provided opposite to the outer surface of the inner pot 3 is disposed. The induction heating coil 5 generates a magnetic field when a high frequency current is supplied from the inverter 6 and heats the inner hook 3 by the generated magnetic field. The induction heating coil 5 is provided substantially opposite to the bottom surface 3a of the inner pot 3. The inner peripheral coil 5a and the outer peripheral coil 5b provided to face the bent portion 3c that gently connects the bottom surface 3a and the side surface 3b of the inner hook 3. Further, an inner hook temperature sensor 7 for detecting the temperature of the inner hook 3 is disposed at the center bottom of the bottom face 3 a of the inner hook 3.

  A lid 8 is provided on the upper portion of the rice cooker body 2 so as to be rotatable with respect to the body 2. A detachable lower lid 9 is provided below the lid body 8, and a lid temperature sensor 10 for detecting the lid temperature is provided on the lower lid 9. In front of the main body 2, an operation panel 11 provided with a rice cooking key (not shown) pressed by the user at the start of rice cooking is provided, and the main body 2 on the back surface of the operation panel 11 includes a microcomputer or the like. Means 12 are provided. This control means 12 recognizes the rice cooking state based on the temperature detected from the temperature sensor 7 for the inner pot and the temperature sensor 10 for the lid, and controls the above-described inverter 6 based on this, thereby the induction heating coil 5. Is used to control the magnetic field generated and adjust the heating of the inner pot 3.

  FIG. 2 is a plan view of the rice cooker 1 according to an embodiment of the present invention, as viewed from above with the lid 8 and the inner pot 3 removed from the main body 2. As shown in the figure, a magnetic flux modulation plate 13 is provided between the inner hook 3 and the electromagnetic induction coil 5a around the inner hook temperature sensor 7 located at the center of the bottom surface of the inner hook 3. The magnetic flux modulation plate 13 is a ring-shaped plate made of any one of diamagnetic materials such as copper, silver, gold, graphite, and bismuth, and the magnetic flux generated around the electromagnetic induction coil 5 is modulated by the magnetic flux of the diamagnetic material. When the plate 13 is disturbed, the disk portion corresponding to the bottom portion 3 a of the inner hook 3 is vibrated, and the frequency of the high-frequency current supplied to the electromagnetic induction coil 5 by the inverter 6 is reduced in the disk portion corresponding to the bottom portion 3 a of the inner hook 3. The vibration is amplified by matching with the resonance frequency.

  Here, how to obtain the resonance frequency f and the wavelength λ of the resonance mode of the cooking container will be described. The inner hook 3 has an axisymmetric shape with respect to an axis 15 perpendicularly intersecting with the center of the bottom surface 3a, and the inner shaft is pressed by a spring so as to be in contact with the bottom surface 3a of the inner hook 3. A temperature sensor 7 is disposed. For this reason, the inner hook 3 can be regarded as a simple support beam supported at the shaft center. The resonance frequency f [Hz] and wavelength λ [m] of the inner hook 3 due to the longitudinal vibration at this time can be obtained by the following equations.

f = (2n−1) × C / 4L (Formula 1)
λ = C / f = 4L / (2n−1) (Formula 2)
Here, C: sound velocity [m / s], L: length of inner hook [m], λ: wavelength [m], n: order (1, 2,...).

  FIG. 3 is a schematic diagram in which the inner hook 3 is replaced with a simple support beam 14 in order to obtain the resonance frequency f and wavelength λ of the inner hook 3. In FIG. 3, the order n is changed from 1 to 5. The state of vibration displacement in each resonance mode is shown as a resonance mode waveform 16. In the waveform 16 in the resonance mode of each order in FIG. 3, the antinode portion having a large amplitude indicates a portion where the vibration displacement is large and the node portion indicates a portion where the vibration displacement is zero. Thus, the resonance of the longitudinal vibration of the inner hook 3 has a characteristic that the vibration displacement at the center position of the shaft 15 becomes zero and the number of nodes increases one by one as the order n increases.

  In accordance with the model as described above, the resonance frequency of a generally shaped inner hook is calculated, and the stress of the inner hook when a high frequency current is passed through the electromagnetic induction coil 5 at the same frequency as the resonance frequency is simulated. I expressed it as a stress distribution diagram. FIG. 4 is a stress distribution diagram in which the stress applied to the inner hook 3 is simulated. In the figure, the vertical axis represents the magnitude of the stress, and the horizontal axis represents a rod-like shape with the central axis 15 of the inner hook bottom surface 3a being zero, and the distance from the center of the inner hook bottom face 3a is expressed numerically. Further, in the same figure, the resonance mode waveform 16a is also overlapped to schematically represent the longitudinal vibration characteristics of the inner hook.

  As shown in FIG. 4, there are two places where the stress 17 is greatly generated. First, the first portion 17a is in the vicinity of the electromagnetic induction coil 5b on the outer peripheral side, and the second portion 17b is in the vicinity of the suspension material that supports the inner hook 3 (near the edge 3d extending outward of the inner hook 3). It was. The first occurrence point 17a of the stress 17 is due to the electromagnetic force generated from the electromagnetic induction coil 5 and is located at the antinode of the waveform 16a in the resonance mode as shown in FIG. You can see that it is generated.

  On the other hand, the inventors of the present invention, at the second generation location 17b of the stress 17, consumes useless energy, adversely affects the vibration generated in the vicinity of the electromagnetic induction coil 5, and near the electromagnetic induction coil 5. It has been found that the stable vibration of the inner hook 3 is hindered and the vibration level of the inner hook 3 is reduced. And after earnestly researching the cause of this stress, it was found that the suspension position of the suspension material supporting the inner hook 3 is deeply involved.

  In the simulation, when the change in stress was examined while changing the suspension position of the suspension material supporting the inner hook 3, the stress generated when the suspension position was in the vicinity of the position of the node of the waveform 16a in the resonance mode increased. That is, the closer the suspension position is to the position of the node of the resonance mode waveform 16a where vibration is difficult (the closer the vibration displacement is to the zero position), the more the stress generated at the suspension position is amplified and the higher the value is. is there. Furthermore, it was also found that the suspension structure of the inner pot 3 in the conventional rice cooker generally has a configuration in which the suspension member 107 is disposed near the position of the node of the waveform 16a in the resonance mode.

  Therefore, based on the above-described results, the suspension position of the suspension member that supports the inner hook 3 is arranged at the peak or valley position (antinode position) of the waveform 16 of the resonance mode of the inner hook 3. FIG. 5 is a view showing a state where the suspension member 18 is arranged at a location where the vibration displacement of the resonance mode waveform 16 of the inner hook 3 is large.

  In such a state where the inner hook 3 is supported, when a high frequency current is applied to the electromagnetic induction coil 5 at the same frequency as the resonance frequency of the inner hook 3 obtained by the above-described equation 1, the inner hook 3 resonates and is severe. Vibrated. And the stress which generate | occur | produces in the position of the suspension material 18 was able to be reduced in the suspension position shown in FIG. Thus, it was confirmed that the stress generated at the position of the suspension member 18 is reduced by arranging the suspension member 18 at the position of the antinode of the waveform 16 of the resonance mode in which the inner hook 3 easily vibrates.

  In the simulation described above, the sound pressure when the suspension material is arranged at the position of the node in the resonance mode waveform of the inner hook 3 and the sound pressure when it is arranged at the position of the belly in the resonance mode waveform of the inner hook 3 are as follows. When measured, the results shown in Table 1 were obtained.

  As shown in Table 1, the sound pressure when the suspension material is arranged at the node position in the resonance mode waveform of the inner hook 3 is 7.5 [mV], and the suspension material is in the resonance mode waveform of the inner hook 3. A sound pressure of 9.4 [mV] was obtained when the sound pressure was placed at the position of the stomach. As described above, it was confirmed that a higher sound pressure (= vibration) can be obtained by placing the suspension material at the position of the antinode in the resonance mode waveform of the inner hook 3 as an actual measurement value.

  As described above, according to the electromagnetic induction heating cooker according to the present invention, the suspension material for suspending the inner pot for storing the object to be heated is disposed at the position of the corrugated antinode in the resonance mode of the inner pot. An electromagnetic induction overheating cooker that can reduce the stress generated near the suspension material that adversely affects the vibration of the kettle, can obtain greater vibration than before, efficiently vibrates the inner kettle, and cooks delicious rice Can be provided.

  The rice cooker 1 which is the electromagnetic induction heating cooker in this Embodiment was actually cooked. As shown in FIG. 1, in the inner pot 3, rice 19 and an appropriate amount of water 20 to be absorbed by the rice 19 are put. In the inner hook 3, a suspension member 18 is disposed at the position of the antinode of the waveform 16 of the resonance mode in which the inner hook 3 easily vibrates, and the edge 3 d extending outward of the inner hook 3 is suspended by the suspension member 18. It is held by being.

  FIG. 6 is a temperature change graph schematically showing the temperature of the rice 19 in each rice cooking process, and FIG. 7 is a timing chart of the operation of the electromagnetic induction coil 5. The inner pot 3 in which rice 19 and an appropriate amount of water 20 are placed is set in the rice cooker body 2, the lid 8 is closed, and a rice cooking switch (not shown) is inserted to start cooking. Then, a current flows through the electromagnetic induction coil 5 and heat and mechanical force are generated in the inner hook 3 by electromagnetic induction.

  In the preheating process at the beginning of rice cooking in FIG. 6, heating is performed while controlling the energization to the electromagnetic induction coil 5 as shown in FIG. 7 so that the temperature of the rice does not exceed 60 ° C. by the magnetic field from the electromagnetic induction coil 5. After about 15 minutes preheating (water absorption promotion) process, the rice cooking process was started. Also in the rice cooking process, the inner pot 3 continues to generate heat by energizing the electromagnetic induction coil 5 as in the preheating process, and the fact that the temperature in the inner pot 3 has reached approximately 100 ° C. is the temperature sensor 7 for the inner pot and the temperature sensor 10 for the lid. Then, as shown in FIG. 7, the power supply to the electromagnetic induction coil 5 was controlled, and rice cooking was continued while appropriately adjusting the heating amount. At this time, even if there is too much heating amount, the temperature in the inner pot 3 maintains 100 degreeC. After the boiling was continued, when it was detected through the temperature sensor 7 for the inner pot 3 that the water in the inner pot 3 was exhausted, the control of the inverter 6 was stopped and the steaming process was started. In the steaming process, in order to keep the temperature of the inner pot 1 at 100 ° C., energization to the electromagnetic induction coil 6 was intermittently continued for about 15 minutes.

  In this way, when the rice cooked by the rice cooker in which the suspension material 18 is arranged at the belly position of the waveform 16 of the resonance mode in which the inner pot 3 easily vibrates, the inner pot is efficiently vibrated. I was able to cook delicious rice.

Embodiment 2. FIG.
The inventors of the present invention have made further studies, and as a result, a resonance mode in which the inner hook 3 easily vibrates in the vicinity of the bent portion 3e existing between the edge portion 3d and the trunk portion 3b of the inner hook 3. It was confirmed that the belly of the waveform 16 tends to appear. For this reason, as shown in FIG. 8, by adopting a configuration in which the suspension member 18 is disposed close to the inner peripheral side of the inner hook 3 and in the vicinity of the bent portion 3e, the inner wall 3 is gradually relieved by the waveform 16 in the resonance mode. Even if the position of the suspension member 18 is not confirmed, the suspension member 18 can be easily disposed at the position of the corrugated antinode in the resonance mode of the inner hook 3.

  In this way, by moving the suspension position of the suspension material 18 to the inner peripheral side of the inner hook 3, the suspension material 18 can be disposed at the position of the corrugated antinode in the resonance mode of the inner hook 3. The stress generated in the vicinity of the material 18 can be reduced, and the vibration of the inner hook 3 can be improved as compared with the prior art. In the present embodiment, the suspension member 18 is disposed so that the position of the suspension member 18 is the position of the corrugated antinode in the resonance mode existing in the edge portion 3d of the inner hook 3. The same effect can be obtained even if it is arranged so as to be in the antinode position of the waveform in the resonance mode.

It is sectional drawing which shows the rice cooker as an electromagnetic induction heating cooking appliance of this invention. It is the top view which removed the cover body and the inner pot of the rice cooker which is one Embodiment of this invention from the main body, and was seen from the upper direction. It is the schematic diagram which replaced the inner pot with the simple support beam in order to obtain | require the resonant frequency f and wavelength (lambda) of the inner pot which is a cooking container. It is the stress distribution figure which simulated the stress concerning an inner hook. It is a figure which shows the place which has arrange | positioned the suspension material in the location where the vibration displacement of the waveform in a resonance mode of an inner hook is large. It is the graph of the temperature change which showed typically the temperature of the rice of each rice cooking process. It is a timing chart of operation of an electromagnetic induction coil. It is sectional drawing which shows the place which made the suspension material approach the bending part. It is a schematic explanatory drawing which shows the shape of the inner pot which is the conventional cooking container.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Rice cooker (electromagnetic induction heating cooker), 2 Rice cooker main body, 3 Cooking container, 4 Storage part, 5 Induction heating coil, 6 Inverter, 7 Inner pot temperature sensor, 8 Lid, 9 Lower lid, 10 Lid Temperature sensor, 11 Operation panel, 12 Control means, 13 Magnetic flux modulation plate, 14 Simple support beam, 15 Central axis, 16 Resonance mode waveform, 17 Stress, 18 Suspension material, 19 Rice, 20 Water.

Claims (1)

A cooking container having an edge extending outward and storing an object to be heated , an induction heating coil provided facing the outer surface of the cooking container that heats the cooking container with a generated magnetic field, and the cooking A suspension for supporting the edge of the container , and a temperature sensor for supporting substantially the center of the bottom surface of the cooking container ,
The suspension position at which the edge of the cooking container is supported by the suspension material substantially coincides with the antinode position of the vibration displacement of the wavelength (λ) in the resonance mode of the longitudinal vibration characteristic of the cooking container obtained using the following equation: An electromagnetic induction heating cooker characterized in that the resonance frequency of the cooking container calculated from the wavelength and sound velocity in the resonance mode is matched with the high-frequency current flowing through the induction heating coil .
λ = 4L / (2n−1)
Here, L: length from the support position of the bottom of the inner hook to the end of the inner hook, n: order (1, 2,...)

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