JP3149538B2 - Electric rice cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric rice cooker for induction heating using a heating coil.

[0002]

2. Description of the Related Art Conventionally, this type of electric rice cooker is disclosed in
What was described in 24988 gazette was common. Hereinafter, the configuration will be described with reference to FIG.

As shown in the figure, a rice cooker main body (hereinafter referred to as a main body) 81 is provided with a storage portion 83 for storing a pot 82 therein, and an upper portion of the main body 81 is covered with an upper lid 84.
Can be taken out by opening and closing the upper lid 84. The first heating coil 85 is arranged at a position facing the center of the bottom of the pot 82, and induction heats the center of the bottom of the pot 82. The second heating coil 86 is arranged at a position facing the outer peripheral portion of the bottom surface and the lower portion of the side surface of the pan 82, and performs induction heating on the outer peripheral portion of the bottom surface of the pan 82 and the lower portion of the side surface. The first heating coil 85 and the second heating coil 86 are provided along the outer peripheral portion of the pot 82, and the heating coils 85 and 86 are placed on a support 87 with a gap therebetween. On the side, a ferrite core 88 for absorbing leakage magnetic flux is radially provided. The pan detection device 89 detects the presence or absence of the pan 82 and is provided so as to be in contact with the center of the bottom surface of the pan 82. The signal of the pan detection device 89 is input to the control unit 90, and the control unit 90 controls the inverter circuit 91 provided at the bottom of the main body 81 that supplies a high-frequency current to the first heating coil 85 and the second heating coil 86. Oscillation is controlled and the operation display unit 92 provided on the upper part of the main body 81 is controlled.

In the above configuration, when the pan 82 is inserted into the storage section 83, the pan detection device 89 is activated, the control section 90 sends a heating start signal to the inverter circuit 91, and enters a heating standby state. When the cooking mode is set by the cooking menu key of the operation display unit 92, the control unit 90 controls the operation of the inverter circuit 91, and the inverter circuit 91 controls the first heating coil 85 and the second heating coil 86. A high-frequency current is supplied, and the first heating coil 85 and the second heating coil 86 uniformly inductively heat the entire bottom surface and the lower side portion of the pot 82, and a sequence according to the amounts of rice and water in the pot 82. Cook with rice.

[0005]

In such a conventional electric rice cooker, the first heating coil 85 and the second heating coil 86 uniformly and inductively heat the entire bottom surface and the lower portion of the side surface of the pot 82. In particular, when the amount of cooked rice is large and the pot 82 is large, the area of the bottom surface of the pot 82 is also large. It is extremely difficult to cause stable convection of the rice and water in the whole as a whole, and boiling starts locally from an unspecified location, and once boiling begins, it convects into the commonly known crab hole in this area Is concentrated and heated, and this portion becomes soft rice, and at a portion away from the crab hole, it becomes hard rice with insufficient heating, so that there is a problem that rice without uniform cooking cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to reduce unevenness in temperature in a pot to eliminate unevenness in cooking and to obtain rice suitable for a user's preference.

[0007]

In order to achieve the above object, the present invention provides a heating coil for inductively heating a pot, an inverter circuit for supplying a high-frequency current to the heating coil, and a heating output of the heating coil. A heating device for heating the bottom surface of the pot, at least a portion of the heating coil that heats the bottom surface of the pot is configured of a plurality of heating coil elements. Is a means for solving the problem that the heating output is sequentially varied.

[0008]

According to the present invention, the temperature distribution in the pot can be changed by sequentially changing the heating output of the heating coil element, and convection can be forcibly generated at a location where the heating output is large. , You can cook even rice.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, a lid 2 which can be opened and closed is provided at an upper portion of a main body 1, and a pan storage section 4 for storing a pan 3 is provided in the main body 1. The air layer 5 is formed at the bottom. The first heating coil 6 is for inductively heating the bottom surface of the pot 3, is provided on the bottom surface of the pot storage unit 4, and includes a plurality of donut-shaped heating circuit elements 6 a, 6 b, 6 c, 6 d. A second heating coil 7 is provided on the outer bottom of the pot storage unit 4, and a third heating coil 8 is provided on the outer side. The control device 9 includes a first heating coil 6 and a second heating coil 7.
Further, the oscillation output of the inverter circuit 10 that supplies a high-frequency current to the third heating coil 8 is controlled. Temperature detection means 1
1 is configured to penetrate a hole provided at the bottom of the pan storage unit 4 and abut on the outer bottom of the pan 3 so as to detect the temperature of an object to be heated in the pan 3. The ferrite core 12 is
Disposed below the heating coil 6 and the second heating coil 7,
The magnetic flux is prevented from leaking downward. Similarly, the leakage of the magnetic flux from the third heating coil 8 is caused by the ferrite core 1
3 prevents it.

As shown in FIG. 2, the control unit 9 includes a control unit 14, a switching element driving unit 15, a first relay driving unit 16, a second relay driving unit 17, a third relay driving unit 18, 4th relay drive means 19 and 5th
The switching element driving means 15 drives a switching element (not shown) of the inverter circuit 10, and the first to fourth relay driving means 16 to 19 The relay outputs 21, 22, 23, and 24 are sequentially operated according to the outputs to switch the heating outputs of the heating coil elements 6a to 6d. When the relay contacts 21 to 24 are connected to the normally closed contact b, the heating outputs of the heating coil elements 6a to 6d are the same, and when connected to the normally open contact a, the heating output of the heating coil elements becomes I'm trying to get bigger. The fifth relay drive means 20 operates the relay contact 25 at the time of keeping the temperature, and switches between the first heating coil 6, the second heating coil 7, and the third heating coil 8. The inverter circuit 10 is operated by the output of a rectifier 28 connected via a switch 27 from a commercial power supply 26, and the control device 9 is applied with a DC voltage from a DC power supply 30 connected via a transformer 29.

The operation of the above configuration will be described with reference to FIG. 3. The inverter circuit 10 controls the oscillation output by controlling the ON time of the switching element driven by the switching element driving means 15. First,
The control means 14 includes first to fourth relay driving means 16 to 19
Thereby, the relay contacts 21 to 24 are connected to the normally closed contact b, and the respective heating coil elements 6 a to 6 d of the first heating coil 6 are set to the same heating output, and the first heating coil 6 and the second heating coil 6 A high-frequency current is supplied to the heating coil 7 to inductively heat the pot 3 to execute a pre-cooking step. After the pre-cooking step is completed, the heating output is increased and the process proceeds to the cooking step.
The cooking process shifts to the latter half and the temperature in the pot 3 is about 80 ° C
When (point a in FIG. 3) is reached, the control means 14 performs the first to fourth steps.
Are sequentially driven to connect the relay contacts 21 to 24 to the a contact sequentially at predetermined time intervals.
As a result, among the heating coil elements 6a to 6d, the heating coil element connected to the contact a has a large heating output, and the pot at this point is also heated intensively, forcibly including the rice being gelatinized. Convection occurs, and a hole where water is boiled by the convection, a so-called crab hole, is generated. This convection is caused by the heating coil elements 6a-
By sequentially increasing the heating output of 6d, it can be generated at a plurality of locations in the pot 3, and the crab holes are generated at these locations, and convection for evenly cooking is forced to occur in a wide range. Can be. When the rice cooking is completed, the control means 14 shortens the ON time of the switching element by the switching element driving means 15 to reduce the heating output of the first and second heating coils 6 and 7, and controls the fifth relay driving means. By driving the relay 20, the relay contact 25 is switched at a predetermined cycle, and the first heating coil 6, the second heating coil 7, and the third heating coil 8 keep the temperature.

In the first embodiment, the heating outputs of the heating coil elements 6a to 6d of the first heating coil 6 are sequentially switched. However, the heating output of the second heating coil 7 is similarly changed. May be sequentially switched to cause convection. Further, the number of heating coil elements and the switching method are not limited to the above-described embodiment.

In order to switch the heating output of the heating coil elements 6a to 6d, the number of coil turns of the heating coil elements 6a to 6d is changed.
The frequency of the high-frequency current supplied to 6d may be varied,
Further, duty control may be performed to change the ratio between the time during which the high-frequency current is supplied to each of the heating coil elements 6a to 6d and the time during which the high-frequency current is not supplied. .

Next, a second embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. In this embodiment, as shown in FIG. 4, a plurality of heating coil elements 6 provided on the bottom of
a, 6b, 6c, 6d and relay contacts 26, 27, 28,
The connection with 29 and 30 is changed. That is, the first to fourth relay contacts 26 to 29 are connected in parallel with the respective heating coil elements 6a to 6d, and the first to fourth relay driving means 16 to
By operating 19, each of the relay contacts 26 to 29 is turned on. Further, by operating the fifth relay driving means 20, the relay contact 30 is switched from the a side to the b side, and the first heating coil 6 comprising the heating coil elements 6a to 6d is switched.
Connection between the first heating coil 6 and the second heating coil 7.
To the third heating coil 8. Since the other components are the same as those of the first embodiment, the same reference numerals are given to the same components and the description is omitted.

FIG. 5 shows the operation of the electric rice cooker having the above configuration.
This will be described with reference to FIG. In FIG. 5, when the operation of the electric rice cooker is started, the temperature T of the temperature detecting means 11 is inputted in step 51. It is determined whether or not the input temperature T has reached the pre-cooking temperature Ta (approximately 50 ° C.) (Step 52). The heating coil 6 and the second heating coil 7 are connected (step 53). Next, the switching element driving means 15 is operated to operate the inverter circuit 10 (step 54), and a high-frequency current is supplied to the first heating coil 6 and the second heating coil 7. In step 55, it is determined whether or not the pre-cooking time has elapsed. If the pre-cooking time has not elapsed, a subroutine program shown in FIG. 6 is executed.

The subroutine of FIG. 6 will be described. In step 70, the first to fourth relay driving means 16 to 19 are controlled to turn off only the first relay contact 26. That is, the high-frequency current from the inverter circuit 10 is supplied to the heating coil element 6a and the second heating coil 7. This state is maintained for a predetermined time t (step 71), and then, in step 72, only the second relay contact 27 is turned off, and a high-frequency current is supplied to the heating coil element 6b and the second heating coil 7. This state is maintained for a predetermined time t (step 73), and then only the third relay contact 28 is turned off (step 74), and this state is maintained for a predetermined time t (step 75). In step 76, only the fourth relay contact 29 is turned off, and this state is maintained for a predetermined time t. As described above, the high-frequency current is sequentially supplied to the heating coil elements 6a to 6d of the first heating coil 6, and the induction heating by the heating coil elements 6a to 6d is sequentially performed.

When a series of operations for turning off the first relay contact 26 to the fourth relay contact 29 described above is completed, the input of the temperature T in step 51 of FIG. 5 is performed again, and the temperature T becomes the pre-cooking temperature Ta. If not, the subroutine of FIG. 6 is executed again, and the heating coil elements 6a to 6d are sequentially driven. If the temperature T has reached the pre-cooking temperature Ta, the oscillation operation of the inverter circuit 10 is stopped (step 5).
6). If it is determined in step 57 that the pre-cooking time has not elapsed, the temperature T is input again in step 51, and the first heating coil 6 is set so that the temperature T becomes the pre-cooking temperature Ta.
And the heating control of the second heating coil. If it is determined that the pre-cooking time has elapsed (steps 55 and 57),
The temperature T of step 58 is input.

In step 59, it is determined whether or not the input temperature T has reached the cooking temperature Tb (140 ° C.). If not, it is determined in step 60 whether the fifth relay contact 30 is on the a side or the b side. Judge. If the fifth relay contact 30 is on the a side in step 60, the fifth relay contact 30 is set on the b side (step 62).
If it is determined to be the side, the fifth relay contact 30 is set to the a side (step 62). When the switching of the fifth relay contact 30 is completed, at step 63, the inverter circuit 1
0 is operated, and the subroutine shown in FIG. 6 is executed again. In the subroutine of FIG. 6, after sequentially driving the respective heating coil elements 6a to 6d of the first heating coil 6, the process returns to the temperature T input of step 58 shown in FIG. And step 59
Until the temperature T input in step (c) reaches the cooking temperature Tb, alternate heating of the second heating coil 7 and the third heating coil 8 by switching the fifth relay contact 30 and each of the first heating coil 6 The heating coil elements 6a to 6d are sequentially heated. Then, when the temperature T inputted in step 59 reaches the cooking temperature Ta, the oscillation of the inverter circuit 10 is stopped in step 64, and the rice cooking is terminated.

As described above, in the second embodiment, since the high-frequency current is supplied to one of the first heating coil elements 6a to 6d, the heating output of one heating coil element is increased. The convection in this portion is forcibly generated, the convection strength can be increased, and a crab hole for sufficient convection can be generated even in a mixed state of rice and water that has been gelatinized. By sequentially increasing the heating outputs of the heating coil elements 6a to 6d, a plurality of crab holes can be generated in the pot 3 and convection for cooking can be forcibly generated in a wide range.

In the second embodiment, a high-frequency current is sequentially supplied to each of the heating coil elements 6a to 6d of the first heating coil 6 in both the pre-cooking step and the rice cooking step. The high-frequency current supply to each of the heating coil elements 6a to 6d may be sequentially performed. Further, the number of heating coil elements and the method of sequentially supplying high-frequency current to each heating coil element are not limited to the above-described embodiment.

[0022]

As is apparent from the above embodiments, according to the present invention, a heating coil for inductively heating a pan, an inverter circuit for supplying a high-frequency current to the heating coil, and a heating output of the heating coil are controlled. and a control device which, in the heating coil, form part of heating the bottom of at least the pot at a plurality of heating coil elements, wherein the control device, before
Since the heating output of the multiple heating coil elements that heat the bottom part of the pot is changed sequentially, it is possible to reduce the unevenness in temperature in the pot and eliminate uneven cooking, and to suit the user's preference. You can get rice.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view of an electric rice cooker according to a first embodiment of the present invention. FIG. 1B is a perspective view of first and second heating coils of the electric rice cooker.

FIG. 2 is a block circuit diagram of the electric rice cooker.

FIG. 3 is a temperature characteristic diagram of the electric rice cooker during rice cooking.

FIG. 4 is a block circuit diagram of an electric rice cooker according to a second embodiment of the present invention.

FIG. 5 is a flowchart showing control contents of the electric rice cooker.

FIG. 6 is a flowchart showing a main part of control contents of the electric rice cooker.

FIG. 7 is a longitudinal sectional view of a conventional electric rice cooker.

[Explanation of symbols]

 3 Pot 6 First heating coil (heating coil) 6a, 6b, 6c, 6d Heating coil element 7 Second heating coil (heating coil) 9 Controller 10 Inverter circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-114789 (JP, A) JP-A-2-291815 (JP, A) JP-A-5-245037 (JP, A) 10824 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) A47J 27/00

Claims (2)

(57) [Claims] 1. A heating coil for inductively heating a pot, an inverter circuit for supplying a high-frequency current to the heating coil, and a control device for controlling a heating output of the heating coil,
At least a portion of the heating coil that heats the bottom surface of the pan is configured with a plurality of heating coil elements, and the control device sequentially varies heating outputs of the plurality of heating coil elements that heat the bottom portion of the pan. Electric rice cooker with configuration. 2. The electric rice cooker according to claim 1, wherein the control device is configured to sequentially vary the heating output of the heating coil element in the latter half of the cooking.