JP5201180B2 - rice cooker - Google Patents

Description

  The present invention relates to an induction heating type rice cooker, and more particularly to a technique using a ceramic product as an inner pot for cooking rice.

  Generally, a rice cooker has a plurality of heating means such as an induction coil, a heat retaining heater, and a lid heater, and it is very convenient to automatically cook rice and heat by using these heating means to provide the optimum rice to the user. It is widely known as an instrument.

  That is, the process of the rice cooker includes, as shown in FIG. 5, a water absorption process for absorbing sufficient water into the rice, a temperature raising process for raising rice by heating and a steaming process after the temperature raising process. It consists of a rice cooking process and a heat insulation process after the rice cooking process. In each process, a plurality of heating means such as an induction coil, a heat insulation heater and a lid heater are based on a detection signal of a temperature sensor that detects the temperature of the inner pot. The output is controlled and optimal process control is performed.

  Also, the inner pot for conventional rice cooking is made of metal, for example, the outer wall of the inner pot is made of stainless steel, the inner wall is made of aluminum, and the inner wall of the aluminum is multi-layered with a fluorine coat inside When cooking rice, the induction coil is in a state where a predetermined gap is secured between the inner pot and the protective frame which is the inner case by hooking the flange formed on the upper part of the inner pot to the upper opening end of the protective frame. Is energized to heat the inner pot by induction (see, for example, Patent Document 1).

  By the way, since the inner pan made of metal has the property that it is easy to heat and cool, the temperature of rice is rapidly raised at the time of cooking, and the taste when cooked is still insufficient. Moreover, since it is easy to cool after cooking rice, the energy used to heat the rice becomes large, which is not sufficient for energy saving measures.

  Therefore, in order to compensate for the drawbacks of such a metal inner pot, it is conceivable to use a ceramic pot. That is, since the ceramic product has a larger heat capacity than the metal product, the rate of temperature increase during cooking is relatively gentle, and the heat storage property is good, so that cooked rice can be cooked deliciously. Moreover, when there is unprocessed rice in the inner pot, the whole inner pot can be reheated in a microwave oven, and since heat storage is good, there is an advantage that a warm state can be maintained for a long time after reheating.

  However, simply replacing the conventional metal inner pot with a clay pot causes the following various problems. In other words, the finished dimensions of the entire earthenware pan are likely to vary depending on the moisture content during firing, firing conditions, and the like, and the dimensional accuracy is poor compared to that made of metal. For this reason, when the flange part formed in the upper part of the inner pot is hooked on the upper opening end of the protective frame, the distance between the inner pot and the induction coil varies from product to product. As described above, when the distance between the inner pot and the induction coil varies for each product, the resonance condition between the two also fluctuates and the rice cooking performance deteriorates.

  Also, when the bottom of the inner pot is placed directly on the protective frame to avoid the above inconvenience, the earthenware pot is non-conductive, so it cannot be heated by induction as it is, silver paste etc. on the bottom wall of the earthenware pot facing the induction coil However, even in this case, since the thermal conductivity of the ceramic itself is poor, only the portion where the heating element is formed is likely to become high temperature. Therefore, when the bottom part of the inner pot is placed directly on the protective frame, when the protective article is made of synthetic resin, there is a problem that it cannot withstand the temperature and melts.

  In order to solve the above problems, the applicant has already filed an earthenware pot having a structure in which a ring-shaped leg portion is provided on the bottom wall surface and a gap is provided between the heating element and the protective frame.

  By the way, it is conceivable to share the heating control by making the gap provided between the heating element and the protective frame the same between the earthen pot and the metal pan, including those already filed by the applicant. The detection temperature, resonance characteristics, and heating and so forth differ from the pan, and there is a problem that it is difficult to share the heating control by simply making the gap the same.

  Also, even if legs are provided at the bottom of the earthenware pot, if the height of the legs varies from product to product (single earthenware alone), the distance between the earthenware pot and the induction coil varies, and the resonance conditions vary from product to product. Becomes worse.

JP 2000-70145 A

  In order to solve the above problems, the present invention prepares heating control suitable for clay pots and metal pans in advance, and uses delicious cooking rice that takes advantage of the advantages of both pans by using the heating control suitable for each. It is an object of the present invention to provide a rice cooker that can improve the rice cooking performance by reducing the variation in leg height for each product (single pot alone).

  In order to achieve the above object, the present invention adopts the following configuration.

The present invention is a clay pot rice cooker comprising a clay pot, an inner case for storing the clay pot, heating means for heating the clay pot, and a control device for controlling the heating state of the heating means, wherein the heating means A bottom induction coil and a side induction coil, the earthenware pot has a heating element facing the bottom induction coil and the side induction coil, and the heating control by the control device is a water absorption process, a temperature increase process. A steaming step and a heat-retaining step, and the bottom portion of the earthen pot is provided with a leg portion having a small height change for each product between the bottom portion induction coil and the side portion induction coil, and for each product of the leg portion. It is characterized in that the fluctuation of the resonance condition due to the variation of the height is reduced.

  The invention of the present application improves the rice cooking performance by providing a leg portion with a small height change for each product at the bottom of the clay pot and reducing the fluctuation of the resonance condition due to the height variation for each product of the leg portion. be able to.

Vertical section of the rice cooker showing the state that the clay pot is set in the inner case Longitudinal cross section of rice cooker showing metal pan set on inner case Front view of the operation panel System block diagram of control circuit part of rice cooker Time chart from the cooking process to the heat insulation process Flow chart of switching control Flow chart of water absorption process Flow chart of temperature rising process Flow chart of steaming process Flow chart of heat insulation process Partial longitudinal sectional view of a rice cooker with a clay pot showing the first automatic detection mechanism Partial vertical section of a rice cooker with a metal pan showing the first automatic detection mechanism Partial vertical section of a rice cooker with a clay pot showing the second automatic detection mechanism Partial longitudinal sectional view of a rice cooker set with a metal pan showing the second automatic detection mechanism Schematic cross section of temperature switch Resonance waveform diagram of the third automatic detection mechanism Resonance waveform diagram of the fourth automatic detection mechanism Resonance waveform diagram of the fifth automatic detection mechanism

  FIG. 1 is a vertical cross-sectional view of a rice cooker showing a state in which a clay pot is set in the inner case, and FIG. 2 is a vertical cross-sectional view of the rice cooker showing a state in which a metal pan such as a multilayer structure is set in the inner case.

  The rice cooker includes a rice cooker body 1 and a lid body 2 that opens and closes an upper opening of the rice cooker body 1, and the lid body 2 is supported by the rice cooker body 1 through a hinge unit 3 so as to be freely opened and closed.

  The rice cooker main body 1 has an outer case 5 made of a synthetic resin-made integrally molded product. Inside the outer case 5, an earthen pot 6 that is an inner pot made of ceramics is detachably set. An inner case 7 that is a protective frame along the shape of the earthenware pot 6 is provided outside the earthenware pot 6. The inner case 7 is made of a heat-resistant synthetic resin such as polyethylene terephthalate, for example, and a sensor insertion hole 7a is formed at the center of the bottom portion for allowing the temperature sensor 9 made of a thermistor to face.

  The upper end of the inner case 7 is integrally coupled to the upper end of the outer case 5 via the shoulder member 8, and a space portion 10 is formed inside the outer case 5, the inner case 7, and the shoulder member 8. When the earthenware pan 6 is a metal pan, the shoulder member 8 is a hooking member to which a flange 28a formed at the upper end portion of the pan is hooked as shown in FIG.

  Outside the inner case 7, a bottom induction coil 11 and a side induction coil 12 for induction heating the earthenware pan 6 are provided. The bottom induction coil 11 and the side induction coil 12 are provided concentrically around the center of the bottom of the inner case 7 at each position of the bottom of the inner case 7 and the curved portion extending from the bottom to the peripheral side. Yes.

  A synthetic resin coil support 13 is provided outside the bottom induction coil 11 and the side induction coil 12, and the coil support 13 is attached to the inner case 7 with screws or the like. 11 and the side induction coil 12 are positioned and fixed at predetermined positions shown in the figure, and a ferrite core 15 for confining a magnetic field is provided outside the coil support base 13. A heat retaining heater 14 is provided on the outer peripheral side portion of the upper portion of the inner case 7.

  The earthenware pan 6 is made of ceramics such as fired ceramics or glass, and a ring-shaped leg portion 6 a that contacts the bottom of the inner case 7 is formed on the bottom of the earthenware pot 6. The legs 6a are not limited to the ring shape, and may be formed locally or radially.

  The leg 6 a is provided between the bottom induction coil 11 on the bottom side of the inner case 7 and the side induction coil 12 on the bending side, and a certain gap S 1 is formed between the inner case 7 and the leg 6 a. It is formed at a predetermined height. Further, the earthenware pan 6 is provided with a bottom heating element 11a and a side heating element 12a made of a metal film at locations facing the bottom induction coil 11 and the side induction coil 12, respectively.

  The bottom heating element 11a and the side heating element 12a are formed, for example, by applying and baking a silver paste or the like. Since the leg 6a of the earthenware pan 6 has an uneven surface, it is difficult to form a heating element. However, the leg 6a is formed on either side of the bottom induction coil 11 or the side induction coil 12. Because it is out of position, there is no effect on rice cooking performance. The heating element may have a structure in which a metal such as a copper foil or a stainless steel net is embedded in advance in the earthenware pot 6 in advance.

  When the rice cooking switch is turned on, the bottom heating element 11a and the side heating element 12a are heated by Joule heat caused by eddy currents induced by the bottom induction coil 11 and the side induction coil 12, and the clay pot is heated by the heating of both heating elements. 6 is heated.

  Furthermore, the dome-shaped central portion 6b with which the temperature sensor 9 at the bottom of the earthenware pan 6 abuts is formed to be slightly thinner to the extent that the strength is not impaired as compared with the other portions. Thus, by making the central part 6b of the earthenware pan 6 thin, heat from the bottom heating element 11a and the side heating element 12a is easily conducted to the thin central part 6b. The power supplied to the bottom induction coil 11 and the side induction coil 12 can be appropriately controlled.

  Reference numeral 18 denotes an operation panel constituting an operation unit. As shown in FIG. 3, the operation panel 18 includes various switches 16, that is, various types of rice cooker switch 16 a, heat retention switch 16 b, white rice, quick cooker, non-washed rice, and the like. A menu switch 16c for setting a menu, a timer switch 16d for setting time, a cancel switch 16e for canceling the setting, an earthenware pot / metal pan changeover switch 16f used in this embodiment, and a liquid crystal display unit 17 are provided.

  Reference numeral 19 is a microcomputer board on which a microcomputer is mounted, 20 is a power board on which a power supply circuit having an inverter and the like for controlling energization to the bottom induction coil 11 and the side induction coil 12 is mounted, and 21 is each of the above-mentioned A substrate cooling fan for cooling the substrates 19 and 20. Reference numeral 24 denotes an aluminum inner lid constituting the lid body 2, 25 denotes a lid heater provided on the upper portion of the inner lid 24, 26 denotes a steam discharge port, and 27 denotes a handle.

  As shown in the figure, the shape of the earthenware pan 6 is substantially the same as that of the conventional metal pan 28 shown in FIG. 2, and when the earthenware pan 6 is used, the metal pan 28 is removed and used. When the earthenware pan 6 is used, the earthenware pan 6 is supported by the inner case 7 by the ring-shaped legs 6a. However, in the case of the metal pan 28, as shown in FIG. The flange 28a formed on the inner case 7 is supported by being hooked to the shoulder member 8 provided at the upper opening end of the inner case 7.

  In the case of the earthenware pot 6, even if the overall finished size varies from product to product, the change in the height of the leg 6a formed at the bottom is extremely small, so the earthenware pot 6, the bottom induction coil 11 and the side induction coil 12 The variation in the distance between them is reduced, the resonance conditions by the bottom heating element 11a and the side heating element 12a, the bottom induction coil 11 and the side induction coil 12 provided on the surface are stabilized, and the rice cooking performance is improved. In addition, by providing the leg 6a at the bottom of the earthenware pot 6, a gap S1 is generated between the portion of the heating element formed in the earthenware pot 6 and the inner case 7, so that the both 6 and 7 are not in direct contact with each other. There is no inconvenience that the inner case 7 made of synthetic resin melts even when the location where the heating element is formed becomes locally high.

  Further, when the earthenware pan 6 is used, unlike the conventional metal pan 28, it is not necessary to form the flange 28a for hooking on the upper part of the inner case 7 at the upper end portion thereof, so that the flange portion has insufficient strength. There is no risk of damage.

  Next, FIG. 4 shows an outline of control circuits such as an induction coil, a heat retaining heater, a lid heater, and the like centering on the microcomputer control device 100 for rice cooking and heat retaining control. In the figure, reference numeral 40 is a microcomputer control unit (CPU) for rice cooking / warming control, and the microcomputer control unit 40 is centered on a microcomputer, for example, a temperature detection circuit unit, an induction coil drive control circuit unit, an oscillation circuit unit, A reset circuit unit, a drive control circuit unit such as a heat retaining heater and a lid heater, a power supply circuit unit, a liquid crystal display unit, and an operation switch are provided.

  A pot temperature detection signal from the temperature sensor 9 is input to a temperature detection circuit 48 provided corresponding to the temperature sensor 9 that is in contact with the bottom wall of the earthenware pot 6 or the metal pot 28. The induction coil drive control circuit unit is formed by, for example, a pulse width modulation circuit 46, a synchronous trigger circuit 53, an IGBT drive circuit 45, an IGBT 50, and a resonance capacitor 51. The resonant capacitor 51 includes a large-capacity metal pan capacitor 51a and a small-capacity clay pan capacitor 51b. The microcomputer 51 controls the switching by the relay 51c and performs heating control in a resonance state suitable for each pan. .

  The relay 51c is switched to a small-capacity earthenware capacitor 51b when the earthenware pot 6 is selected by the earthing pot / metal pot switching switch 16f of the operation switch 16, and when the metal pot 28 is selected, the relay 51c is used for a large-capacity metal pot. The capacitor 51a is switched to and the pan used in the display unit 17 is displayed as shown in FIG.

  And by the microcomputer control unit 40, the output values of the bottom induction coil 11 and the side induction coil 12 and the ON duty ratio at the same output value suitable for the earthenware pan 6 or the metal pan 28 corresponding to each step of rice cooking and heat insulation. (For example, n seconds / 16 seconds) is selected, and by controlling the pulse width modulation circuit 46 and the like, rice cooking and heat retention control suitable for the earthenware pan 6 or the metal pan 28 are performed, and uniform water absorption action and uneven heating are achieved. Appropriate heating output control is realized in order to realize a good heat-retaining action as well as cooking of no rice.

  Reference numeral D denotes a flywheel diode of the IGBT 45, reference numeral 55 denotes a rectifier circuit including a diode bridge for driving the induction coil inserted between the home AC power source 57, and reference numeral 52 denotes a smoothing circuit thereof.

  On the other hand, reference numeral 14 is the above-described heat retaining heater, 25 is a lid heater, the heat retaining heater 14 is turned on and off at a desired output and duty ratio by a heat retaining heater driving circuit 56, and the lid heater 25 is turned on and off at a desired output and duty ratio, respectively. It is designed to be driven. Further, reference numeral 17 denotes a display unit such as a liquid crystal or LED, 43 denotes a notification unit such as a buzzer, 16 denotes various operation switches such as a rice cooking switch 16a, a heat retention switch 16b, a timer switch 16d, or a clay pot / metal pot switch 16f, 47 Is an oscillation circuit for generating a clock reference control signal, and 44 is a reset circuit. The pot detection switch 30 and the pot detection circuit 30a are used in other examples shown in FIGS.

  Next, rice cooking and heat insulation control performed using the above-described microcomputer control unit 40 will be described with reference to the time chart of FIG.

  In the rice cooking process, there is a water-absorbing process for causing the rice to absorb water by raising the output of the induction coils 11 and 12 to a predetermined value. When sufficient water is absorbed in the rice, the output is rapidly increased. , There is a temperature rising process to cook rice at a stretch, the total number of rice in the inner pot is determined based on the temperature rising time in this temperature rising process, and based on the total number of the rice Boiling maintenance time is determined. Thereafter, the rice cooked in the steaming process is sufficiently steamed to bring the rice into an optimal state and the rice cooking process is completed. In addition, the temperature change from the temperature raising process to the steaming process is higher in the clay pot as shown in the figure. If the temperature is high, yellowing occurs, and therefore cooling is performed by the cooling fan 21 as necessary.

  When the rice cooking process is completed, the process proceeds to a heat retaining process. As described above, the temperature change from the temperature raising process to the steaming process is higher in the clay pot, so in the heat retention process immediately after cooking rice, the timing when the heat insulation heater 14 is turned on is delayed compared to the metal pot 28. You can also. In addition, in the heat insulation process, as shown in FIG. 10, the control of the clay pot 6 and the metal pot 28 is performed in substantially the same manner.

  Next, flowcharts such as switching control of the earthenware pan 6 or the metal pan 28 and rice cooking control will be described with reference to FIGS. In addition, the characteristics of the earthenware pot heating of this invention are as follows, and it is as usual about a metal pot.

(1) Since the earthenware pot has poor heat conduction, the heat from the induction coil is difficult to be transmitted to the whole. Therefore, the heating amount from the side surface is increased by extending the energization time of the heat retaining heater and the lid heater. (2) The earthenware pot has a narrow range of power values for obtaining good resonance conditions. Therefore, a weak amount of electric power is not used, and a predetermined amount of electric power is obtained by shortening the energization time to the coil while keeping the strong electric power. Therefore, the heating output of the heating source in the vicinity of the end of the rice cooking process can be made larger in the clay pot than in the metal pot.

  First, the flowchart of the switching control of the clay pot 6 or the metal pot 28 will be described with reference to FIG. When the rice cooking switch 16a of the various switches 16 is pressed, the rice cooking process starts, but before that, the kind of the pan set in the inner case 7 is detected.

  In this embodiment, it is determined by which pot is selected by the earthenware pot / metal pot changeover switch 16f shown in FIG. In step S1, it is determined whether a clay pot has been selected. When the earthenware pot 6 is selected by the earthenware pot / metal pot changeover switch 16f, the display unit 17 displays the earthenware pot, and an affirmative determination is made in step S1, and the process proceeds to step S2 where the resonance capacitor 51 is replaced with a small-capacitance capacitor 51b. Switch to. This switching is performed by the relay 51c being switched by the microcomputer control unit 40. The reason for using the small-capacitance capacitor 51b in the case of the earthenware pan 6 is to obtain a predetermined amount of power by shortening the energization time to the coil while keeping the strong power as in (2) above.

  Subsequently, it progresses to step S3, the power setting value for earthenware pots which consists of an electric power value and a duty ratio is selected in step S3, and it progresses to the water absorption process of step S6.

  When the metal pot 28 is selected by the earthenware pot / metal pot changeover switch 16f, the display unit 17 displays the metal pot, and a negative determination is made in step S1 and the process proceeds to step S4. Switch to capacitor 51a. This switching is performed by the relay 51c being switched by the microcomputer control unit 40.

  Subsequently, it progresses to step S5, the power setting value for metal pans which consists of a power value and a duty ratio is selected in step S5, and it progresses to the water absorption process of step S6. And if it progresses to a water absorption process, control, such as a rice cooking process shown in FIGS. 7-10, will be performed.

  FIG. 7 shows the water absorption process. When the water absorption process starts, it is determined whether the pan set in the inner case 7 is the earthen pan 6 in step S1. In the present embodiment, it is determined by which pot is selected by the earthenware pot / metal pot switch 16f as in the case of FIG. When an affirmative determination is made in step S1, the process proceeds to step S2 and a timer is started to measure the water absorption process time. Next, in step S3, it is determined whether the temperature of the pan is 40 ° C. or higher. This temperature is detected by the temperature sensor 9.

  If an affirmative determination is made in step S3, the process proceeds to step S4, step S5, and step S6 in turn, the induction coils 11 and 12 are turned off, the heat retaining heater 14 is controlled by ON control with a duty ratio of 4/16, and the lid heater 25 is similarly used. Control is performed by ON control with a duty ratio of 4/16. Then, it progresses to step S10, it is determined whether the water absorption time exceeded predetermined value by step S10, and if predetermined time has not passed, it will return to step S3 and will repeat the same step. If it is determined in step S10 that the predetermined time has elapsed, the process proceeds to a temperature raising process in step S11.

  If a negative determination is made in step S3, the process proceeds to step S7, step S8, and step S9 in sequence, and the induction coils 11 and 12 are controlled by ON control with 90% output and a duty ratio of 4/16, and the warming heater 14 is controlled with a duty ratio. The lid heater 25 is similarly controlled by ON control with a duty ratio of 8/16. Then, it progresses to step S10, it is determined whether the water absorption time exceeded predetermined value by step S10, and if predetermined time has not passed, it will return to step S3 and will repeat the same step. If it is determined in step S10 that the predetermined time has elapsed, the process proceeds to a temperature raising process in step S11.

  If it is determined in step S1 that the pan set in the inner case 7 is the metal pan 28, the process proceeds to step S12, and a timer is started to measure the water absorption process time. Next, in step S13, it is determined whether the pan temperature is 40 ° C. or higher. This temperature is detected by the temperature sensor 9.

  If an affirmative determination is made in step S13, the process proceeds to step S14, step S15, and step S16 sequentially to turn off the induction coils 11 and 12, and the heat retaining heater 14 is controlled by ON control with a duty ratio 2/16 that is smaller than that in the case of a clay pot. The lid heater 25 is controlled by ON control with a duty ratio 3/16 which is smaller than that of the earthenware pot. Thereafter, the process proceeds to step S20.

  If a negative determination is made in step S13, the process proceeds to step S17, step S18, and step S19 in sequence, and the induction coils 11 and 12 are controlled by ON control with a 60% output smaller than that in the case of the earthenware pot and a duty ratio of 6/16. The heat retaining heater 14 is controlled by ON control with a duty ratio 4/16 smaller than that of the earthenware pot, and the lid heater 25 is controlled by ON control with a duty ratio 6/16 smaller than that of the earthenware pot. Then, it progresses to step S20, it is determined whether the water absorption time exceeded predetermined value by step S20, and if predetermined time has not passed, it will return to step S13 and will repeat the same step. If it is determined in step S20 that the predetermined time has elapsed, the process proceeds to a temperature raising process in step S11.

  FIG. 8 shows the temperature raising step. First, it is determined whether or not the pot set in the inner case 7 is a clay pot 6 in step S1. Step S1 is determined by which pot is selected by the earthenware pot / metal pot switch 16f as in the case of FIG. If an affirmative determination is made in step S1, a temperature raising process is started in step S2.

  When the temperature raising process starts, the process proceeds to step S3, step S4, and step S5 in sequence, and the induction coils 11 and 12 are controlled by ON control with 100% output and a duty ratio of 16/16, and the heat retaining heater 14 is controlled with a duty ratio of 6/16. The lid heater 25 is turned off. Then, it progresses to step S6 and it is determined whether the temperature of a pan is 100 degreeC or more. This temperature is detected by the temperature sensor 9.

  If a negative determination is made in step S6, the process returns to step S3 and the same steps are repeated. If it is determined in step S6 that the temperature is 100 ° C. or higher, the process proceeds to step S7, step S8, and step S9 sequentially, and the induction coils 11 and 12 are controlled by ON control with an output of 80% and a duty ratio of 10/16. 14 is controlled by ON control with a duty ratio of 8/16, and the lid heater 25 is controlled by ON control with a duty ratio of 6/16. Then, it progresses to step S10 and it is determined whether the temperature of a pan is 130 degreeC or more. This temperature is detected by the temperature sensor 9.

  If a negative determination is made in step S10, the process returns to step S7 and the same steps are repeated. If it is determined in step S10 that the temperature is 130 ° C. or higher, the process proceeds to the steaming process.

  If it is determined in step S1 that the pan set in the inner case 7 is the metal pan 28, the process proceeds to step S11 to start the temperature raising process. When the temperature raising process starts, the process proceeds to step S12, step S13, and step S14 in sequence, and the induction coils 11 and 12 are controlled by ON control with 100% output and a duty ratio of 16/16 as in the case of the earthenware pot. 25 is turned off. Then, it progresses to step S15 and it is determined whether the temperature of a pan is 100 degreeC or more. This temperature is detected by the temperature sensor 9.

  If a negative determination is made in step S15, the process returns to step S12 and the same steps are repeated. If it is determined in step S15 that the temperature is 100 ° C. or higher, the process proceeds to step S16, step S17, and step S18 in sequence, and the induction coils 11 and 12 are controlled by ON control with an output of 60% smaller than the earthenware pot and a duty ratio of 14/16. The heat retaining heater 14 is controlled by ON control with a duty ratio 4/16 smaller than that of the clay pot, and the lid heater 25 is controlled by ON control with the same duty ratio 6/16 as that of the clay pot. Then, it progresses to step S19 and it is determined whether the temperature of a pan is 120 degreeC or more. This temperature is detected by the temperature sensor 9.

  If a negative determination is made in step S19, the process returns to step S16 and the same steps are repeated. If it determines with it being 120 degreeC or more by step S19, it will progress to a steaming process.

  FIG. 9 shows the steaming process. When the steaming process starts, a timer is started in step S1, and it is determined whether the pot set in the inner case 7 is a clay pot 6 in step S2. It is determined by which pot is selected by the earthenware pot / metal pot switch 16f. If an affirmation judging is made at Step S2, it will progress to Step S3 and will judge whether the temperature of a pan is 115 ° C or more. This temperature is detected by the temperature sensor 9.

  If an affirmative determination is made in step S3, the process proceeds to step S4, step S5, and step S6 in turn, the induction coils 11 and 12 are turned off, the heat retaining heater 14 is controlled by the ON control with a duty ratio of 6/16, and the lid heater 25 is duty cycle. Control by ON control with a ratio of 4/16. Then, it progresses to step S10.

  If a negative determination is made in step S3, the process proceeds to step S7, step S8, and step S9 in sequence, and the induction coils 11 and 12 are controlled by ON control with an output of 80% and a duty ratio of 6/16, and the warming heater 14 is controlled with a duty ratio. The lid heater 25 is controlled by ON control with a duty ratio of 4/16. Then, it progresses to step S10, it is determined whether the steaming time exceeded predetermined value by step S10, and if predetermined time has not passed, it will return to step S3 and will repeat the same step. When it is determined in step S10 that the predetermined time has elapsed, rice cooking ends.

  If it is determined in step S2 that the pan set in the inner case 7 is the metal pan 28, the process proceeds to step S11 to determine whether the pan temperature is 110 ° C. or higher. This temperature is detected by the temperature sensor 9. If an affirmative determination is made in step S11, the process proceeds to step S12, step S13, and step S14 in sequence, the induction coils 11 and 12 are turned off, and the heat retaining heater 14 is controlled by ON control with a duty ratio 2/16 that is smaller than that in the case of a clay pot. The lid heater 25 is controlled by ON control with the same duty ratio 4/16 as that of the clay pot. Thereafter, the process proceeds to step S18.

  If a negative determination is made in step S11, the process proceeds to step S15, step S16, and step S17 in sequence, and the induction coils 11 and 12 are controlled by ON control with a 60% output smaller than that of the earthenware pan and with a duty ratio of 8/16. The heat retaining heater 14 is controlled by ON control with a duty ratio 2/16 smaller than that of the earthenware pot, and the lid heater 25 is controlled by ON control with the same duty ratio 4/16 as the earthenware pot. Thereafter, the process proceeds to step S18, where it is determined whether the steaming time exceeds a predetermined value in step S18. If the predetermined time has not elapsed, the process returns to step S11 and the same steps are repeated. If it is determined in step S18 that the predetermined time has elapsed, rice cooking ends.

  FIG. 10 shows the heat retention process. When the heat insulation process starts, it is determined whether the pot set in the inner case 7 is the earthen pot 6 in step S1. It is determined by which pot is selected by the earthenware pot / metal pot switch 16f. If an affirmation judging is made at Step S1, it will progress to Step S2 and will judge whether the temperature of a pan is 72 ° C or more. This temperature is detected by the temperature sensor 9.

  When an affirmative determination is made in step S2, the process proceeds to step S3, step S4, and step S5 in turn, the induction coils 11 and 12 are turned off, the heat retaining heater 14 is controlled by ON control with a duty ratio of 1/16, and the lid heater 25 is duty cycle. Control is performed by ON control with a ratio of 4/16, and then the process returns to step S2 and the same steps are repeated unless the heat insulation process is completed.

  If a negative determination is made in step S2, the process proceeds to step S6, step S7, and step S8 in sequence, and the induction coils 11 and 12 are controlled by ON control with an output of 80% and a duty ratio of 0.75 / 16, and the heat retaining heater 14 is controlled. Control is performed by ON control with a duty ratio of 3/16, and the lid heater 25 is controlled by ON control with a duty ratio of 4/16. Thereafter, the process returns to Step S2 and the same steps are repeated unless the heat insulation process is completed.

  If it is determined in step S1 that the pan set in the inner case 7 is the metal pan 28, the process proceeds to step S9 to determine whether the pan temperature is 72 ° C or higher. This temperature is detected by the temperature sensor 9. When an affirmative determination is made in step S9, the process proceeds to step S10, step S11, and step S12 in turn, and the induction coils 11 and 12 are turned off as in the case of the clay pot, and the heat retaining heater 14 is controlled by ON control with a duty ratio of 1/16. The lid heater 25 is controlled by ON control with a duty ratio of 4/16, and then the process returns to step S9 and the same steps are repeated unless the heat insulation process is terminated.

  If a negative determination is made in step S9, the process proceeds to step S13, step S14, and step S15 in sequence, and the induction coils 11 and 12 are controlled by ON control with an output of 60% smaller than that of the earthenware pot and a duty ratio of 1/16. The heat insulation heater 14 is controlled by ON control with a duty ratio 2/16 smaller than that of the earthenware pot, and the lid heater 25 is controlled by ON control with the same duty ratio 4/16 as the earthenware pot, and then the process returns to step S9 and the heat insulation process. The same steps are repeated unless is finished.

  Next, an automatic detection mechanism that automatically detects the type of pan when the earthenware pan 6 or the metal pan 28 is set in the inner case 7 will be described. By providing such an automatic detection mechanism, no matter which pan is used, it is not necessary for the user to switch the setting with a switch, so that convenience is further improved.

  11 and 12 show a first example. As described above, the metal pan 28 is set in such a manner that its flange 28a is placed on the shoulder member 8, and the distance h between its bottom and the inner surface of the inner case 7 is made as short as possible. As described above, the earthenware pan 6 is placed on the inner surface of the inner case 7 with the ring-shaped legs 6a, and the distance H between the heating elements 11a, 12a and the inner surface of the inner case 7 varies depending on the height of the legs 6a. However, according to the experiment, it was found that the resonant condition is more stable when the earthenware pan 6 is provided with a relatively large distance between the heating elements 11a, 12a and the inner surface of the inner case 7.

  Therefore, the distance H between the heating elements 11a and 12a and the inner surface of the inner case 7 is set longer than the distance h of the metal pot 28 in advance, and the temperature sensor is set when the pot is set in the inner case 7. The type of pan is automatically detected based on the moving distance of 9.

  FIG. 15 shows an outline of the pan detection switch 30. The pan detection switch 30 is provided in the temperature sensor 9, and the distance between the heating elements 11 a and 12 a and the inner surface of the inner case 7 is set to a distance H of the earthenware pan 6 in comparison with the distance h of the metal pan 28. Keep it longer. Then, when the pan is set in the inner case 7, the amount of shrinkage of the temperature sensor 9 becomes larger when the set pan is the metal pan 28. Therefore, when the earthenware pan 6 is set, the pan detection switch 30 is turned off as shown in FIG. 15A, and when the metal pan 28 is set as shown in FIG. 15B. The pan detection switch 30 is turned on. When the earthenware pan 6 is set, the relay 51c is switched to the small capacity capacitor 51b side, and when the metal pot 28 is set, the relay 51c is switched to the large capacity capacitor 51a side. In the case of this first example, the pan detection switch 30 and pan detection circuit 30a of FIG. 4 are used.

  13 and 14 show a second example. The second example is characterized in that the pan detection switch 30 is provided in the upper end portion of the shoulder member 8 instead of the one disposed in the temperature sensor 9 of the first example, and the metal pan 28 has its flange 28a. The earthenware pan 6 is set so as to be placed on the shoulder member 8, whereas the earthenware pan 6 is used not to be placed on the shoulder member 8.

  That is, as shown in the figure, a pan detection switch 30 is provided at the upper end of the shoulder member 8. Then, when the earthenware pot 6 is set in the inner case 7, the flange of the earthenware pot 6 does not come into contact with the upper end portion of the shoulder member 8, so that the pot detection switch 30 remains off. However, when the metal pan 28 is set, the flange 28a presses the pan detection switch 30 and is turned on. When the earthenware pan 6 is set, the relay 51c is switched to the small capacity capacitor 51b side, and when the metal pot 28 is set, the relay 51c is switched to the large capacity capacitor 51a side. Also in the case of the second example, the pan detection switch 30 and the pan detection circuit 30a of FIG. 4 are used.

  FIG. 16 shows a third example, FIG. 16 (A) shows a resonance waveform when using a clay pot, and FIG. 16 (B) shows a resonance waveform when using a metal pot. In the third example, the type of the pan is automatically detected by the microcomputer control unit 40 based on the difference between the resonance voltages of the pans.

  That is, it has been confirmed that the earthenware pot 6 and the metal pot 28 have different power output methods. For example, the distance H between the inner surface of the inner case 7 and the earthenware pan 6 is set to 3.5 mm, the distance h between the inner surface of the inner case 7 and the metal pan 28 is set to 2 mm, and the input voltage is set to 1000 W. When the earthenware pan 6 is used, the resonance voltage is 528 V as shown in FIG. 16A, and when the metal pan 28 is used, the resonance voltage is 576 V, which is a higher value than the earthenware pan 6 as shown in FIG. Become. In the third example, the resonance voltage is detected by the microcomputer control unit 40, and when the resonance voltage is detected to be low, it is automatically determined that the earthenware pan 6 is set, and the relay 51c is connected to the small-capacitance capacitor. The control suitable for the earthenware pot 6 is automatically switched to the 51b side, and when the resonance voltage is detected to be high, it is automatically determined that the metal pot 28 is set, and the relay 51c is set to a large capacity capacitor. The control suitable for the metal pan 28 is automatically performed by switching to the 51a side.

  FIG. 17 shows the fourth example, FIG. 17 (A) shows a resonance waveform when using a clay pot, and FIG. 17 (B) shows a resonance waveform when using a metal pot. In the fourth example, the type of the pan is automatically detected by the microcomputer control unit 40 based on the difference in the ON time of the IGBT with the predetermined power of each pan.

  That is, it has been confirmed that the earthenware pot 6 and the metal pot 28 have different power output methods. For example, as in the third example, the distance H between the inner surface of the inner case 7 and the earthenware pan 6 is 3.5 mm, the distance h between the inner surface of the inner case 7 and the metal pan 28 is 2 mm, and the input voltage is 1000 W. Take a resonance waveform in each pan. Since the IGBT ON time substantially coincides with the time when the current becomes the maximum, the time when the current becomes the maximum is shorter when the clay pot 6 is used than when the metal pot 28 is used. In the fourth example, the microcomputer control unit 40 detects the time when the current, which is the ON time of the IGBT, becomes maximum. When the time is detected to be short, it is automatically determined that the earthenware pan 6 is set. Then, the relay 51c is switched to the small-capacitance capacitor 51b, and the control suitable for the clay pot 6 is automatically performed. If the time is detected for a long time, it is automatically determined that the metal pot 28 is set. The control suitable for the metal pan 28 is automatically performed by switching to the large-capacitance capacitor 51a side.

  FIG. 18 shows a fifth example, FIG. 18 (A) shows a resonance waveform when using a clay pot, and FIG. 18 (B) shows a resonance waveform when using a metal pot. In the fifth example, the type of the pan is automatically detected by the microcomputer control unit 40 based on the difference in frequency at the predetermined power of each pan.

  That is, it has been confirmed that the earthenware pot 6 and the metal pot 28 have different power output methods. For example, as in the third and fourth examples, the distance H between the inner surface of the inner case 7 and the earthenware pan 6 is 3.5 mm, the distance h between the inner surface of the inner case 7 and the metal pan 28 is 2 mm, and the input voltage is When the resonance waveform is taken with each pan at 1000 W and the frequency in both pans is examined, it becomes 35.84 KHz when the clay pot 6 is used, and 30.58 KHz when the metal pot 28 is used, and the frequency of the clay pot 6 is higher. . In the fifth example, when the frequency is detected by the microcomputer control unit 40 and the frequency is detected high, it is automatically determined that the earthenware pan 6 has been set, and the relay 51c is moved to the small-capacitance capacitor 51b side. Control suitable for the switching earthenware pan 6 is automatically performed, and when the frequency is detected to be low, it is automatically determined that the metal pan 28 is set, and the switching metal pan 28 is switched to the large capacity capacitor 51a side. The control suitable for is automatically performed. Thus, the kind of pan is automatically detected by various automatic detection mechanisms, and heating control corresponding to the pan can be automatically performed.

DESCRIPTION OF SYMBOLS 1 ... Rice cooker main body 2 ... Cover body 3 ... Hinge unit 5 ... Outer case 6 ... Earthenware pan 6a ... Leg part 6b ... Center part 7 ... Inner case 7a ... Sensor insertion hole 8 ... Shoulder member 9 ... Temperature sensor 10 ... Space part 11 ... Bottom induction coil 11a ... Bottom heating element 12 ... Side induction coil 12a ... Side heating element 13 ... Coil support 14 ... Heat insulation 15 ... Ferrite core 16 ... Operation switch 16a ... Rice cooker switch 16b ... Heat insulation switch 16c ... Menu switch 16d ... Timer switch 16e ... Cancel switch 16f ... Metal pan changeover switch 17 ... Display unit 18 ... Operation panel 19 ... Microcomputer board 20 ... Power supply board 21 ... Cooling fan 24 ... Inner lid 25 ... Lid heater 28 ... Metal pan 28a ... Flange 30 ... Pan detection switch 30a ... Pan detection circuit 40 ... Microcomputer control unit 43 ... Notification unit 44 Reset circuit 45... IGBT drive circuit 46... Pulse width modulation circuit 47... Oscillation circuit 48... Temperature detection circuit 50. Synchronous trigger circuit 54 ... Lid heater drive circuit 55 ... Rectifier circuit 56 ... Insulation heater drive circuit 57 ... Home AC power supply 100 ... Microcomputer controller

Claims (1)

An earthenware pot, an inner case for storing the earthenware pot, a heating means for heating the earthenware pot, and a clay pot rice cooker provided with a control device for controlling the heating state of the heating means,
The heating means has a bottom induction coil and a side induction coil,
The earthenware pot has a heating element facing the bottom induction coil and the side induction coil,
The heating control by the control device has a water absorption process, a temperature raising process, a steaming process and a heat retaining process,
At the bottom of the earthenware pot, a leg portion having a small height change for each product is provided between the bottom induction coil and the side induction coil, and fluctuations in resonance conditions due to variations in the height of the leg portion for each product. Rice cooker characterized in that it is made smaller.

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