JPH05317172A - Electric rice boiler - Google Patents

Abstract

PURPOSE:To enable the obtaining of rice to match preference of a user by eliminating unevenness in cooking up by reducing the unevenness of temperature within a pot in an electrical rice boiling apparatus which performs an induction heating using a heating coil. CONSTITUTION:First and second heating coils 6 and 7 are arranged to perform an induction heating of a pot 3 with the supply of a high frequency current from an inverter circuit 10 and the first heating coil 6 for heating the bottom surface of the pot 3 is made up of a plurality of heating coil elements 6a-6d. A controller 9 which controls heating outputs of the heating coils 6 and 7 vary heating outputs of the heating coil elements 6a-6d sequentially to cause a convection forcibly within the pot 3 thereby eliminating unevenness in cooking.

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 that uses a heating coil for induction heating.

[0002]

2. Description of the Related Art Conventionally, an electric rice cooker of this type has been disclosed in Japanese Patent Laid-Open No.
What was described in the 24988 gazette was general. The configuration will be described below with reference to FIG. 7.

As shown in the figure, a rice cooker main body (hereinafter referred to as the main body) 81 is provided with an accommodating portion 83 for accommodating a pan 82 therein, and the 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 1st heating coil 85 is arrange | positioned in the position which opposes the central part of the bottom face of the pan 82, and induction-heats the central part of the bottom face of the pan 82. The 2nd heating coil 86 is arrange | positioned in the position which opposes the bottom face outer peripheral part and side surface lower part of the pan 82, and induction-heats the bottom face outer peripheral part and side surface lower part of the pan 82. The first heating coil 85 and the second heating coil 86 are provided along the outer peripheral portion of the pan 82, and the respective heating coils 85 and 86 are placed on the support base 87 with a gap therebetween, and below the support base 87. Ferrite cores 88 that absorb leakage flux are radially provided on the side. The pan detecting device 89 detects the presence or absence of the pan 82, and is provided so as to contact the center of the bottom surface of the pan 82. The signal of the pan detecting device 89 is input to the control unit 90, which controls the inverter circuit 91 provided at the bottom of the main body 81 that supplies the high-frequency current to the first heating coil 85 and the second heating coil 86. In addition to controlling the oscillation, the operation display unit 92 provided on the upper portion of the main body 81 is controlled.

In the above structure, when the pan 82 is inserted into the storage portion 83, the pan detection device 89 operates, and the control portion 90 sends a heating start signal to the inverter circuit 91 to enter the 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 causes the first heating coil 85 and the second heating coil 86 to operate. A high-frequency current is supplied, and the first heating coil 85 and the second heating coil 86 uniformly induction-heat the entire bottom surface and lower side portion of the pot 82, and a sequence according to the amount of rice and water in the pot 82. To cook rice.

[0005]

In such a conventional electric rice cooker, the first heating coil 85 and the second heating coil 86 uniformly induction-heat the entire bottom surface and lower side surface of the pan 82. However, when the amount of cooked rice is large and the pan 82 is large, the area of the bottom surface of the pan 82 is also large, and in the latter half of the cooking, when the rice and water that have started gelatinization are mixed, It is extremely difficult to cause stable convection of rice and water in the whole, and boiling starts locally from an unspecified place, and once boiling begins, convection occurs in the commonly known crab hole formed in this part. The rice was concentrated and heated, and this portion became soft rice, and the hard rice that was insufficiently heated at the part away from the crab hole had a problem that uniform and even rice could not be obtained.

The present invention has been made to solve the above problems, and an object of the present invention is to reduce the temperature unevenness in the pan to eliminate the unevenness of the cooked rice and to obtain the rice suitable for the user.

[0007]

In order to achieve the above object, the present invention controls a heating coil for induction heating a pot, an inverter circuit for supplying a high frequency current to the heating coil, and a heating output of the heating coil. The heating coil, at least a portion of the heating coil for heating the bottom surface of the pot is constituted by a plurality of heating coil elements, and the control device sequentially changes the heating output of the heating coil element. What you have done is the means to solve the problem.

[0008]

According to the present invention, by the above-mentioned means for solving the problems, the temperature distribution in the pan can be changed by sequentially changing the heating output of the heating coil element, and convection can be forcibly caused at a place where the heating output is large. , You can cook evenly cooked rice.

[0009]

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

As shown in FIG. 1, a lid 2 which can be opened and closed is provided on an upper portion of a main body 1, and a pot storage portion 4 for storing a pot 3 is provided in the main body 1 and between the pot 3 and the pot storage portion 4. An air layer 5 is formed on the. The first heating coil 6 is for induction-heating the bottom surface of the pan 3, is provided on the bottom surface of the pan housing portion 4, and is composed of a plurality of donut-shaped heating circuit elements 6a, 6b, 6c, 6d. A second heating coil 7 is provided on the outer bottom portion of the pan storage portion 4, and a third heating coil 8 is provided on the outer side portion thereof. The control device 9 includes a first heating coil 6 and a second heating coil 7.
Also, the oscillation output of the inverter circuit 10 that supplies the 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 portion 4 and contact the outer bottom portion of the pan 3 to detect the temperature of the object to be heated in the pan 3. The ferrite core 12 is the first
Is disposed below the heating coil 6 and the second heating coil 7 of
Prevents magnetic flux from leaking downward. Similarly, leakage of the magnetic flux from the third heating coil 8 is caused by the ferrite core 1
It is prevented by 3.

As shown in FIG. 2, the control device 9 includes a control means 14, a switching element driving means 15, a first relay driving means 16, a second relay driving means 17, a third relay driving means 18, and a third relay driving means 18. 4 relay drive means 19 and 5
The switching element drive means 15 drives a switching element (not shown) of the inverter circuit 10, and the first to fourth relay drive means 16 to 19 of the control means 14 are included. The relay contacts 21, 22, 23, and 24 are sequentially operated by the outputs, and the heating outputs of the heating coil elements 6a to 6d are switched. 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 the relay contacts 21 to 24 are connected to the normally open contact a, the heating output of the heating coil element is I am trying to grow. The fifth relay drive means 20 operates the relay contact 25 during heat retention to switch between the first heating coil 6 and the second heating coil 7 and the third heating coil 8. The inverter circuit 10 is operated by the output of the rectifier 28 connected from the commercial power source 26 via the switch 27, and the controller 9 is applied with a DC voltage from the DC power source 30 connected via the transformer 29.

In the above configuration, the operation 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 drive means 16 to 19
Thus, the relay contacts 21 to 24 are connected to the normally closed contact b to make the heating coil elements 6a to 6d of the first heating coil 6 have the same heating output, and the inverter circuit 10 causes the first heating coil 6 and the second heating coil 6 A high-frequency current is supplied to the heating coil 7 to induction-heat the pot 3, and the precooking step is performed. After the pre-cooking process is completed, the heating output is increased to shift to the cooking process.
The cooking process shifts to the latter half and the temperature inside the pan 3 is approximately 80 ° C.
When it becomes (point a in FIG. 3), the control means 14 controls the first to fourth points.
The relay driving means 16 to 19 are sequentially driven, and the relay contacts 21 to 24 are sequentially connected to the a contact at predetermined time intervals.
As a result, among the heating coil elements 6a to 6d, the heating coil element connected to the a contact has a large heating output, and the pot at this location is also heated intensively, forcibly including rice in the process of gelatinization. A so-called crab hole is generated which causes convection and causes water to boil. This convection is caused by the heating coil element 6a-
By increasing the heating output of 6d sequentially, it can be generated at multiple points in the pot 3, and the crab holes are generated at these points, forcing the convection in a wide range to evenly cook. You can 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, reduces the heating output of the first and second heating coils 6 and 7, and the fifth relay driving means. 20 is driven to switch the relay contact 25 at a predetermined cycle, and the first heating coil 6 and the second heating coil 7 and the third heating coil 8 are kept warm.

In the first embodiment, the heating outputs of the heating coil elements 6a to 6d of the first heating coil 6 are sequentially switched, but the second heating coil 7 is similarly heated. May be sequentially switched to generate convection. Further, the number of heating coil elements and the switching method are not limited to those in the above embodiment.

Further, 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 changed,
In addition, duty control may be performed to change the ratio of the time of supplying the high frequency current to the heating coil elements 6a to 6d and the time of not supplying the high frequency current. The point is that the heating output of each heating coil element can be varied. ..

Next, a second embodiment of the present invention will be described with reference to FIGS.
Will be described with reference to. In the present embodiment, as shown in FIG. 4, a plurality of heating coil elements 6 provided on the bottom surface of the pan storage portion.
a, 6b, 6c, 6d and relay contacts 26, 27, 28,
The connection with 29 and 30 has been changed. That is, the first to fourth relay contacts 26 to 29 are connected in parallel with the heating coil elements 6a to 6d, and the first to fourth relay driving means 16 to.
The relay contacts 26 to 29 are turned on by operating 19. In addition, 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 including the heating coil elements 6a to 6d.
The second heating coil 7 and the first heating coil 6
To the connection with the third heating coil 8. Since the other components are the same as those in the first embodiment, the same reference numerals are given to the components and the description thereof will be omitted.

Regarding the operation of the electric rice cooker having the above-mentioned configuration, FIG.
And it demonstrates 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 input in step 51. It is determined whether or not the input temperature T has reached the precooking temperature Ta (about 50 ° C.) (step 52), and if it has not reached the precooking temperature Ta, the fifth contact is set to the a side, and the first 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 precooking time has elapsed. If the precooking time has not elapsed, the program of the subroutine 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 so that only the first relay contact 26 is turned off. 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 only the second relay contact 27 is turned off in step 72 to supply a high frequency current to the heating coil element 6b and the second heating coil 7. This state is maintained for a predetermined time t (step 73), 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. In this way, 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 the series of operations for turning off the first relay contact 26 to the fourth relay contact 29 described above is completed, the temperature T input in step 51 of FIG. 5 is performed again, and the temperature T becomes the precooking temperature Ta. If not reached, the subroutine of FIG. 6 is executed again, each heating coil element 6a to 6d is sequentially driven, and if the temperature T reaches the precooking temperature Ta, the oscillation operation of the inverter circuit 10 is stopped (step 5).
6). If it is determined in step 57 that the precooking time has not elapsed, the temperature T is input again in step 51, and the first heating coil 6 is adjusted so that the temperature T becomes the precooking temperature Ta.
And heating control of the second heating coil is performed. If it is determined that the pre-cooking time has elapsed (steps 55 and 57),
The temperature T is input in step 58.

In step 59, it is judged whether or not the input temperature T has reached the cooking temperature Tb (140 ° C.), and if not, it is determined in step 60 whether the fifth relay contact 30 is the a side or the b side. To judge. If the fifth relay contact 30 is on the a side in step 60, the fifth relay contact 30 is set to the b side (step 62). Conversely, if the fifth relay contact 30 is on the b side.
If it is determined to be the side, the fifth relay contact 30 is set to the side a (step 62). When the switching of the fifth relay contact 30 is completed, in 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, the heating coil elements 6a to 6d of the first heating coil 6 are sequentially driven, and then the process returns to the temperature T input of step 58 shown in FIG. And step 59
Until the temperature T input in step 4 reaches the cooking temperature Tb, the second heating coil 7 and the third heating coil 8 are alternately heated by switching the fifth relay contact 30, and each of the first heating coil 6 is heated. The heating coil elements 6a to 6d are sequentially heated. Then, when the temperature T input 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 completed.

As described above, in the second embodiment, since the high frequency current is supplied to one of the heating coil elements 6a to 6d in the first heating coil 6, the heating output of one heating coil element is increased. It is possible to forcibly cause convection in this part and also increase the strength of convection, and it is possible to generate crab holes for sufficient convection even in a state where rice and water, which have started gelatinization, are mixed. By sequentially increasing the heating outputs of the heating coil elements 6a to 6d, a plurality of crab holes are generated in the pan 3 and convection for evenly cooking can be forcibly generated in a wide range.

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

[0022]

As is apparent from the above embodiments, according to the present invention, a heating coil for induction heating a pot, an inverter circuit for supplying a high frequency current to the heating coil, and a heating output of the heating coil are controlled. The heating coil, at least a portion that heats the bottom surface of the pot is configured by a plurality of heating coil elements, and the control device sequentially changes the heating output of the heating coil element. From this, it is possible to reduce the temperature unevenness in the pan and eliminate the unevenness of the cooked rice, and it is possible to obtain the rice that suits the taste of the user.

[Brief description of drawings]

FIG. 1A is a vertical cross-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] Block circuit diagram of the electric rice cooker

[Fig. 3] 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 the 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 vertical sectional view of a conventional electric rice cooker.

[Explanation of symbols]

 3 pan 6 first heating coil (heating coil) 6a, 6b, 6c, 6d heating coil element 7 second heating coil (heating coil) 9 controller 10 inverter circuit

Claims (2)

[Claims] 1. A heating coil for induction-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,
An electric rice cooker in which at least a portion of the heating coil that heats the bottom surface of the pot is composed of a plurality of heating coil elements, and the control device sequentially changes the heating output of the heating coil elements. 2. The electric rice cooker according to claim 1, wherein the control device is configured to sequentially change the heating output of the heating coil element in the latter half of the cooking.