JP3193310B2 - Induction heating 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 induction heating cooker applied to a rice cooker, a cooking pot and the like.

[0002]

2. Description of the Related Art As shown in FIG. 6, a conventional induction heating cooker has an induction heating circuit 21 for inductively heating an object to be cooked, and heats the object to be kept warm. And a resistance heater 22 for the purpose. Induction heating circuit 21
Is connected to a DC power supply circuit 23 that converts an AC voltage of a commercial AC power supply 24 into a DC voltage and supplies the DC voltage to the induction heating circuit 21. The DC power supply circuit 23 and the resistance heater 22 are connected in parallel to a commercial AC power supply 24, and a triac 25 is connected to the resistance heater 22 in series. The induction heating circuit 21 and the resistance heater 22 are independently controlled.

[0003]

However, in the conventional induction heating cooker, since the output of the resistance heater 22 is constant, only the ON / OFF control by the triac 25 can be performed. Further, since the induction heating circuit 21 consumes a large amount of power and has a limited power variable width, it cannot be used for heat retention or the like that requires a small amount of power. The present invention has been made in view of the above problems, and has as its object to make the output of a resistance heater variable and to obtain high power and low power in an induction heating circuit.

[0004]

In order to solve the above-mentioned problems, the present invention provides an induction heating circuit having an induction heating coil for induction heating an object to be heated, and a control for changing the output of the induction heating circuit. A DC power supply circuit connected to the commercial AC power supply, for converting the AC voltage of the commercial AC power supply to a DC voltage and supplying the DC voltage to the induction heating circuit, and a heating target connected to the commercial AC power supply. An induction heating cooker having a resistance heater for heating, wherein the DC power supply circuit and the resistance heater are connected in series to the commercial AC power supply, and switch means for short-circuiting the resistance heater is provided.

In the invention having the above-described structure, the DC power supply circuit of the induction heating circuit and the resistance heater are connected in series, so that a commercial AC voltage is distributed to these DC power supply circuit and the resistance heater by respective resistors. The applied partial pressure acts. As a result, the output of the DC power supply circuit is reduced, so that the induction heating circuit can be used for heat retention or the like that requires a small amount of power. Also, when the output of the induction heating circuit is changed,
The resistance of the DC power supply circuit changes, and as a result, the output of the resistance heater can be changed.

Further, when the resistance heater is short-circuited by the switch means, the commercial AC power is not applied to the resistance heater, and only the DC power supply circuit is applied. Therefore, the DC power supply circuit can supply a large amount of electric power to the induction heating circuit, and can be used for rice cooking or cooking requiring a large amount of electric power. In the above invention, a series circuit including a second resistance heater and a triac for controlling ON / OFF of the second resistance heater is provided.
It is preferable that the DC power supply circuit and the resistance heater are connected in parallel with each other or in series with the DC power supply circuit. Thereby, in addition to the heat retention in the low output state by the first resistance heater and the induction heating circuit, the heat retention by the second resistance heater can be variably performed.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an electric circuit of an induction heating cooker (rice cooker) according to a first embodiment of the present invention. The commercial AC power supply 1 has a resistance heater 2 and a DC power supply circuit 3 connected in series. As shown in FIG. 2, the resistance heater 2 is disposed on the lid 5 of the rice cooker 4 and keeps the rice in the rice cooker 4 warm. A relay 6 is connected in parallel to the resistance heater 2 as switch means for short-circuiting the resistance heater 2. The DC power supply circuit 3 includes a diode bridge circuit 7 for rectifying the AC voltage of the commercial AC power supply 1 and a smoothing capacitor 8 for smoothing the DC rectified by the diode bridge circuit 7.

The DC power supply circuit 3 includes an induction heating circuit 9.
(Hereinafter, this induction heating circuit 9 is referred to as an induction heater to compare it with the resistance heater 2.) As shown in FIG. 2, the induction heating heater 9 includes an induction heating coil 10 provided at the bottom of a container body 4a for accommodating the rice cooker 4, and a transistor 11 (IGBT) connected in series to the induction heating coil 10. ). A capacitor 12 constituting an LC resonance circuit together with the induction heating coil 10 is connected in parallel to the induction heating coil 10, and a diode 13 is connected between the emitter and the collector of the transistor 11.

The control unit 14 is composed of a microcomputer, and is provided so as to be brought into pressure contact with a cover sensor 15 disposed on the cover 5 of the rice cooker 4 and near the bottom of the side surface of the rice cooker 4 in cooperation with a built-in timer. The resistance heater 2 and the induction heater 9 are controlled based on the temperature detected by the bottom sensor 16. That is, the control unit 14 controls the transistor 1
By driving the transistor 11 by switching the transistor 11 by applying a driving pulse to the base of the first heater 1 and supplying a high-frequency current to the induction heating coil 10, the output of the induction heater 9
Change from W to 500 W (resistance heater 2 short-circuit power). The control unit 14 outputs an ON signal to the relay 6 connected in parallel with the resistance heater 2 to short-circuit the resistance heater 2 and turn off the resistance heater 2.

Next, the rice cooking and warming operation by the control unit 14 will be described with reference to FIGS. 1 to 3 and Table 1.

[Table 1]

First, in the preheating step, the relay heater 6 is turned off by outputting an ON signal to short-circuit the resistance heater 2 and the output of the induction heater 9 is set to 300 W to start preheating. When the bottom sensor 16 detects 50 ° C. or higher, the output of the induction heater 9 is turned off, and the bottom sensor 1 is turned off.
6 becomes less than 50 ° C., the output of the induction heater 9 becomes 30
0W. In this way, the rice cooker 4 is maintained at 50 ° C., and after 10 minutes, the process proceeds to the rice cooking process.

In the rice cooking step, the output of the induction heater 9 is set to 500 W while the resistance heater 2 is turned off, and rice cooking is started. Eventually, when the cooked rice in the rice cooker 4 boils and the lid sensor 15 detects 85 ° C., the output of the induction heater 9 is reduced to 200 W, and after 5 minutes, the output of the induction heater 9 is reduced to 300 W. To increase. And the bottom sensor 16
When the rice cooking is completed by detecting the temperature of 115 ° C., the process shifts to the spotting process.

In the mura processing step, an OFF signal is output to the relay 6 to energize the resistance heater 2 and the induction heater 9 is turned on.
Operate in the same state as at the time of 00W output. Resistance Ri of the apparent direct-current power supply circuit 3 during 500W output of the induction heater 9 becomes the commercial AC voltage V and 100 [V], Ri = V 2 / W = 100 2/500 = 20 [Ω] Therefore, the resistance heater 2 (resistance Rr = 100 [Ω])
And the divided voltages Vr and Vi of the DC power supply circuit 3 are as follows: Vr = 100 × 100 / (100 + 20) ≒ 83 [V] Vi = 100 × 20 / (100 + 20) ≒ 17 [V] As a result, the resistance heater 2 and the output Wr of the induction heater 9, Wi, ^{respectively, Wr = Vr 2 / Rr =} 83 2/100 ≒ 69 [W] Wi = Vi 2 / Ri = 17 2/20 ≒ 14 [ W].

When the resistance heater 2 is energized in the uneven process, a partial pressure acts on the resistance heater 2 and the DC power supply circuit 3, and the actual output of the induction heater 9 is greatly reduced to 14W. Therefore, at the start of the mura process, the output of the induction heater 9 can be reduced only by energizing the resistance heater 2 without turning off the induction heater 9, and the output of the resistance heater 2 having a relatively high output can be reduced. ,
The soup of the inner surface of the lid 5 is removed.

After maintaining the low output state of the induction heater 9 and the resistance heater 2 for 5 minutes as described above, the resistance heater 2 is turned off, and the induction heater 9 is set to an output of 300 W and the output of the 10/30 ( It operates with a duty ratio of (10 seconds on for 30 seconds), heats for 2 minutes, and performs extra skipping between rice. Next, by energizing the resistance heater 2 again, a low output state is established by the induction heater 9 and the resistance heater 2 in the same manner as described above. After maintaining this state for 5 minutes, the process proceeds to the heat retaining step.

In the heat retaining step, when the bottom sensor 16 detects 70 ° C. or higher, the relay 6 is turned on to short-circuit the resistance heater 2, thereby turning off the output of the resistance heater 2 and turning off the output of the induction heater 9. I do. When the temperature of the bottom sensor 16 becomes lower than 70 ° C., the relay 6 is turned off to energize the resistance heater 2 and the induction heater 9 is operated in the same state as when 100 W is output.

[0018] Here, the resistance Ri of the apparent direct-current power supply circuit 3 during 100W output of the induction heater 9, since the ^{Ri = V 2 / W = 100} 2/100 = 100 [Ω], the resistance heater 2 ( Resistance Rr = 100 [Ω])
And the divided voltages Vr and Vi of the DC power supply circuit 3 are as follows: Vr = 100 × 100 / (100 + 100) = 50 [V] Vi = 100 × 100 / (100 + 100) = 50 [V] As a result, the output Wr of the resistance heater 2 and the induction heater 9, Wi, ^{respectively, Wr = Vr 2 / Rr =} 50 2/100 = 25 [W] Wi = Vi 2 / Ri = 50 2/100 = 25 [ W].

When the output of the induction heater 9 is changed in this way, the apparent resistance of the DC power supply circuit 3 changes, and the partial pressure acting on the resistance heater 2 changes accordingly. Not only the output of the resistance heater 2
Output also changes. Therefore, by appropriately changing the outputs of the resistance heater 2 and the induction heater 9, it is possible to perform appropriate heat retention control. For example, it is possible to increase the output of the resistance heater 2 at the start of the heat retention to perform the soup skipping, and to reduce the output of the resistance heater 2 at the time of the heat retention parallel.

Next, another embodiment will be described.

FIG. 4 shows a second embodiment. In this embodiment, a second resistance heater 17 and the on / off control of the second resistance heater 17 are added to the circuit of the embodiment shown in FIG. A series circuit including a triac 18 is connected in parallel to the DC power supply circuit 3. FIG.
Shows a third example. In this embodiment, a second resistor is added to the circuit of the embodiment shown in FIG. 1 (the arrangement of the resistance heater 2 and the DC power supply circuit 3 is reversed). A series circuit composed of a heater 17 and a triac 18 for controlling ON / OFF of the second resistance heater 17 is connected in parallel to a series circuit composed of the resistance heater 2 and the DC power supply circuit 3. The induction heating circuit 9 in these embodiments is the same as that in the first embodiment, and thus the description and illustration are omitted.

As shown in FIG. 2, the second resistance heater 17 of the second and third embodiments is arranged in a container body 4a for accommodating the rice cooker 4, and heats the body of the rice cooker 4. It has become. The second resistance heater 17 is controlled independently of the first resistance heater 2 and the induction heater 9.
In these embodiments, in addition to keeping the heat from the lid and the bottom in the low output state by the first resistance heater 2 and the induction heater 9, the second resistance heater 17 can keep the body warm.

[0023]

As is apparent from the above description, according to the present invention, since the DC power supply circuit and the resistance heater are connected in series to the commercial AC power supply, a partial pressure acts on the DC power supply circuit and the resistance heater. The induction heating circuit can be used for heat retention or the like that requires small electric power. In addition, since the resistance of the DC power supply circuit changes due to the change in the output of the induction heating circuit, the output of the resistance heater can be changed as a result, and the heat retention and the like can be precisely controlled.

Further, according to the present invention, since the switch means for short-circuiting the resistance heater is provided, the switch means is turned on to short-circuit the resistance heater, and the commercial AC power is applied only to the DC power supply circuit. High power can be supplied to the induction heating circuit, and rice cooking and cooking requiring high power can be performed. Further, a series circuit including a second resistance heater and a triac for controlling ON / OFF of the second resistance heater is connected in parallel to a series circuit including a DC power supply circuit and a resistance heater or to a DC power supply circuit. Since the connection is established, the second resistance heater can variably hold the heat in the low output state by the first resistance heater and the induction heating circuit.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a rice cooker according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of a rice cooker.

FIG. 3 is a diagram showing changes in outputs of a resistance heater and an induction heater in a rice cooking process, and changes in detection temperatures of a lid sensor and a bottom sensor.

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

FIG. 5 is an electric circuit diagram of a rice cooker according to a third embodiment of the present invention.

FIG. 6 is an electric circuit diagram of a conventional rice cooker.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Commercial AC power supply, 2 ... Resistance heater, 3 ... DC power supply circuit, 4 ... Rice cooker, 6 ... Relay (switch means), 9 ... Induction heating circuit, 10 ... Induction heating coil.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-10159 (JP, A) JP-A-5-163025 (JP, A) JP-A-5-290965 (JP, A) JP-A-3-3 45224 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) A47J 27/00 H05B 6/12

Claims (2)

(57) [Claims] 1. An induction heating circuit having an induction heating coil for induction heating an object to be heated, a control unit for changing an output of the induction heating circuit, and an AC voltage of the commercial AC power supply connected to a commercial AC power supply. A DC power supply circuit for converting the DC voltage into a DC voltage and supplying the DC voltage to the induction heating circuit; and a resistance heater connected to the commercial AC power supply and heating the object to be heated. An induction heating cooker comprising: a circuit and the resistance heater connected in series to the commercial AC power supply; and switch means for short-circuiting the resistance heater. 2. A series circuit comprising a second resistance heater and a triac for controlling ON / OFF of the second resistance heater is connected to a series circuit comprising the DC power supply circuit and the resistance heater or the DC power supply. The induction heating cooker according to claim 1, wherein the induction heating cooker is connected in parallel to the circuit.