JPH0312436B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a control device for a microwave oven equipped with means for detecting boiling of food during stewing, rice cooking, etc.

<Prior art> Microwave ovens equipped with a heating function using microwaves and a heating function using a heater use microwave heating to cook stews, rice, etc., and detect boiling of food using a humidity sensor. There is. For this reason, a humidity sensor is required, which increases the cost, and if there is no humidity sensor,
There is a problem in that boiling of food cannot be detected and appropriate heating control becomes difficult.

<Object of the invention> The present invention focuses on the above-mentioned problems, and detects boiling without using a humidity sensor by using a temperature sensor provided for adjusting the temperature inside the refrigerator during heating by a heater. This was done with the aim of reducing the cost of microwave ovens.

<Structure of the Invention> In order to achieve the above object, the present invention provides a convexion fan that has both functions of heating by microwaves and heating by a heater, and is activated when heating is performed by the heater; In a microwave oven equipped with a temperature sensor disposed in a circulating flow to detect the internal temperature during heating by a heater, the convection fan is operated for a certain period of time every time a certain period of time elapses during microwave heating. , boiling detection means that calculates the difference between the detected values of the temperature sensor before and after the operation of the convection fan, and determines that the food is boiling when the difference between the detected values exceeds a preset reference value. It is characterized by the fact that it has been established.

<Example> The present invention will be specifically described below with reference to an illustrated example.

1 and 2 are schematic structural diagrams of a microwave oven according to the present invention. 1 is magnetron, 2
is a waveguide, 3 is a cooling fan for the magnetron, 4
is an exhaust duct, and the cooling air from the cooling fan 3 is sucked in from the intake port 5 as shown by the solid arrow.
After the magnetron 1 has been cooled, it is exhausted from the chamber interior 6 through the exhaust duct 4 and from the exhaust port 7. Also,
11 is a convection fan, 12 is a temperature sensor using, for example, a thermistor, and 13 is a heater. This convection fan 11 has a heater 1
The temperature sensor 1 is operated during heating by the temperature sensor 1, and generates a circulating flow in the refrigerator interior 6 and the storage section 15 through the holes in the punching plate 16 as indicated by the broken line arrows.
2 is arranged on the side of the storage section 15 of the punching plate 16 to detect the temperature of the circulating flow, and the temperature adjustment control is performed based on the detection result.

FIG. 3 is a diagram showing the configuration of the control circuit. 2
1 is a microcomputer, 22 is an operation panel, and both are connected via an interface 23. A microwave heating relay 24 and a heater relay 26 are connected to the interface 23, and an A/D Temperature sensor 12 is connected via converter 27 . The microcomputer 21 includes a CPU 28, ROM 29, and RAM 3.
0, etc., and operates each relay 24, 25, 26 according to the operation of various operation keys 31 provided on the operation panel 22, the detected temperature of the temperature sensor 12, etc., or performs other predetermined controls. It is configured to do the following. Microwave heating relay 24
, a contact 24a that opens and closes the circuit of the magnetron drive circuit 1a and the cooling fan motor 3a, a heater relay 25, a contact 25a that opens and closes the circuit of the heater 13, and a convection fan relay 26.
are respectively provided with contacts 26a for opening and closing circuits of the convection fan motor 11a, and each of these circuits is connected to a power plug 33 via a latch switch 32.

Next, the operation will be explained. In the case of stewed dishes, rice cooking, etc., the relay 24 is activated to perform microwave heating, but the microcomputer 21
Based on the control program stored in the ROM 29 in advance, the relays 24 and 26 are operated to continue microwave heating for a time tμ as shown in FIG.
The operation of operating the convection fan 11 for a time tc is repeated (repetition means), and the temperature Ts detected by the temperature sensor 12 when the convection fan 11 starts operating, and the temperature Te detected when the operation stops are determined by the microcomputer 21, respectively. (temperature difference detection means).

As shown in FIG. 4, the detected temperatures Ts and Te gradually rise over time, but the temperature sensor 12
Convexion fan 11
The detected temperature is Ts＜Te. Experiments have confirmed that this difference in detected temperature increases as the temperature inside the refrigerator 6 increases, and becomes especially large when the food boils and high-temperature water vapor exists in the refrigerator interior 6. So, the difference in detected temperature
When Te-Ts reaches a certain reference value A, it can be determined that the food is boiled (determination means). Since this reference value A varies depending on the type of microwave oven, time tμ, tc, etc., an appropriate value is selected through experiments and stored in the ROM 29 in advance.

In this example, boiling is not determined when the above-mentioned detected temperature difference Te-Ts reaches the reference value A (that is, the state of Te-Ts≧A) is detected, but this state is If the boiling occurs n times in a row, it is determined that boiling has occurred and the microwave heating is stopped, thereby moving to the next stage of control. This is to prevent cooking failures due to misidentification and to sufficiently boil the food, and the value of n may be set as appropriate depending on the type of cooking and the like.

Incidentally, it goes without saying that the above-mentioned detected temperatures Ts and Te are cleared each time, and the latest detection results are always used.

FIG. 5 shows a flowchart for the control described above.

<Effects of the Invention> As is clear from the description of the embodiments above, the present invention utilizes a temperature sensor that is generally provided for temperature control during heater heating, and measures the temperature before and after operation of the convection fan. By comparing the difference in sensor detection value with the reference value,
Since boiling of the food is detected, boiling can be detected without providing a humidity sensor, which has the advantage of reducing the cost of the microwave oven.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a schematic structure of a microwave oven according to the present invention, FIG. 2 is a plan view of the same as above, and FIG. FIG. 4 is an explanatory diagram of the operation of the control circuit, and FIG. 5 is a flowchart of the control. 1... Magnetron, 1a... Magnetron drive circuit, 11... Convexion fan, 11a
... Convection fan motor, 12 ... Temperature sensor, 13 ... Heater, 21 ... Microcomputer, 28 ... CPU, 29 ... ROM.

Claims (1)

[Claims] 1 A convection fan that has both microwave heating and heater heating functions, and is activated when the heater heats, and detects the temperature inside the refrigerator due to heating by the heater installed in the circulating airflow by the convection fan. In a microwave oven equipped with a temperature sensor, the temperature sensor is provided in a storage part of a cabinet back plate, and the microwave heating is continued for a predetermined period of time, and the microwave heating is stopped and a convection fan is turned on for a predetermined period of time. means for alternately repeating the operation of rotating the convection fan; means for determining a temperature difference by detecting the internal temperature of the convection fan when the convection fan starts operating and when the operation stops, using the temperature sensor; 1. A control device for a microwave oven, comprising boiling determination means for determining that food has boiled when the temperature reaches a preset specific reference value.