JPH0666425A - Microwave oven - Google Patents

Abstract

PURPOSE:To provide a microwave oven capable of obtaining the constant finish of cooking at all times without being affected by a power frequency. CONSTITUTION:The title microwave oven comprises: a cavity 2 wherein a material to be cocked is set; an upper heater 3 for heating the material; a humidity sensor 7 for detecting humidity in the cavity 2; a fan 9 for stirring air in the cavity 2; a frequency detecting unit adapted to detect a power frequency; and a fan operating unit adapted to operate and control the fan on the basis of a result detected by the frequency detecting unit. Whether a power frequency is 50Hz or 60Hz, the microwave oven controls cooking so as to have the same cooking finish.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven.

[0002]

2. Description of the Related Art Conventionally, this type of microwave oven has been disclosed in Japanese Patent Publication No.
9-8723. In this product, an exhaust duct is provided at the exhaust opening of the cavity, and when exhausting the internal air from the duct with a fan, a sensor such as a thermistor is placed in the exhaust duct to physically detect the air flow in the exhaust duct. Such changes are detected, and heating control is performed based on the detection result. Further, the rotation speed of the motor for driving the fan can be controlled from the outside, and by changing the rotation speed of the fan, the flow rate of the air flow can be changed to change the finished state.

[0003]

Generally, for example, when the power supply frequency is high, the motor rotation speed is high, and when the power supply frequency is low, the motor rotation speed is low. It is known that the number of rotations of also changes.

Therefore, in the above-mentioned conventional example, the motor for driving the fan does not control the rotation speed according to the power supply frequency, so that the rotation speed of the fan changes if the power supply frequency is different.
If the rotation speed of the fan changes, the amount of air flow to the sensor, especially the amount of humidity air to the humidity sensor, changes.
Even if the same humidity is detected, the detection level of the humidity sensor will change, and the time it takes for the humidity sensor to reach the finish detection level at which cooking is finished will increase or decrease, and the finish state of cooking will change, At the end of cooking, there was a risk that cooking was over-prepared or that it was not completed.

The present invention solves this problem.

[0006]

[Means for Solving the Problems] Means of the present invention for solving the above problems include a cavity for accommodating food to be cooked,
A heater that heats the food, a humidity sensor that detects the humidity in the cavity, a fan that blows air in the cavity, a frequency detector that detects the power supply frequency, and a detector of the frequency detector. The fan drive unit controls the drive of the fan based on the result.

Further, the fan drive unit is configured to control the rotation speed of the fan by phase control and to turn on all phase angles for a certain period of time from the start of operation.

[0008]

Function: That is, the power supply frequency is 50 Hz in the frequency detection unit.
Whether the frequency is 60 Hz or not, and based on the result, the fan drive unit increases or decreases the rotation speed of the fan so that the rotation speed will be the same even if the power supply frequency is different. The amount of air is made the same, and the humidity detection state is made to be the same.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is a frame of a microwave oven,
2 is a cavity provided in the frame 1, 3 is an upper heater provided in the upper portion of the cavity 2, 4 is a lower heater also provided in the lower portion, and 5 is a cooking placed directly above the lower heater 4. A turntable on which an object is placed, 6 is a rotary motor that rotationally drives the turntable 5, 7 is a humidity sensor that detects the humidity in the cavity 2, 8 is a magnetron that generates microwaves, and 9 is the magnetron 8. Cooling fan for cooling, 10 is a fan motor for rotating the fan 9, 1
Reference numeral 1 is a high voltage transformer for obtaining a high voltage supplied to the magnetron 8, and 12 is a waveguide for guiding the microwave generated in the magnetron 8 into the cavity 2.

The humidity sensor 7 is provided in a sensor box 13 which communicates with a ventilation hole 2c provided in an upper portion of one side wall 2a of the cavity 2.

The cooling air from the cooling fan 9 is
The air is also blown into the cavity 2 from the ventilation hole 2d of the other side wall 2b of the cavity 2.

In FIG. 2, 14a and 14b are door switches which are turned on when a door (not shown) is closed, and 15 is a monitor switch which is turned off when the door is closed,
The door switch 14a is connected to the power line, and the door switch 14a
b is connected to the ground line, and the monitor switch 15 is connected between the power supply line and the ground line.

Reference numeral 16 is a lamp for illuminating the inside of the cavity 2, which is connected in parallel with the rotary motor 6. Reference numeral 17 is a turntable relay, which is connected in series with a parallel circuit of the lamp 16 and the rotary motor 6.

Reference numeral 18 is a triac connected in series to the fan motor 10, and controls the rotation speed of the fan motor 10 by controlling the conduction angle of the triac 18.

Reference numeral 19 is an upper heater relay connected in series to the upper heater 3, and 20 is a lower heater relay connected in series to the lower heater 4.

Reference numeral 21 is a magnetron relay, which turns the magnetron 8 on and off by turning it on and off.

Reference numeral 22 is a high voltage circuit for supplying high voltage power to the magnetron 8 and is composed of a high voltage transformer 11, a high voltage capacitor 23 and a high voltage diode 24.

Reference numeral 25 is a door sensing switch for detecting opening / closing of the door, 26 is a keyboard having a start switch, a temperature setting key, etc., 28 is a control circuit for controlling heating of the microwave oven, and 29 is a buzzer for notifying the end. is there. The control circuit 28 includes a fan drive unit 30 that controls the rotation speed of the fan motor 10, and a frequency detection unit 31 that detects whether the power supply frequency is 50 Hz or 60 Hz.

The operation of this structure will be described with reference to FIGS. 3 and 4. In step S1, the process waits until there is a key input, and if there is a key input, it is determined in step S2 whether the automatic grill course has been selected. If a course other than the automatic grill course is selected, the process proceeds to the next step in step S3. Subsequent operations are omitted in the embodiment of the present invention.

When the automatic grill course is selected in step S2, the operation waits until the start key is operated in step S4. When the start key is operated, the finish setting level V is set in step S5, the turntable relay 17 is turned on in step S6, and the turntable 5 starts rotating.

The finish setting level V set in step S5 is set so that cooking is terminated when the detection level detected by the humidity sensor 7 reaches the setting level V.

In step S7, the frequency detector 31 of the control circuit 28 determines whether the power supply frequency is 50 Hz or 60 Hz. When it is determined that the frequency is 50 Hz in step S7, after turning on the triac 18 for 0.5 seconds in step S8,
In step S9, phase control is set in the fan driving unit 30 so that the triac 18 is turned on 5.2 msec after the power source has crossed zero.

That is, since the half cycle of 50 Hz is 10 ms, the fan motor 10 is energized for 4.8 ms of the half cycle. Therefore, the fan 9 is about 800 rp
It will rotate during heating at a rotation speed of m.

If it is determined that the frequency is 60 Hz in step S7, the triac 18 is turned on for 0.5 seconds in step S10, and then the triac 18 is turned on to the fan drive unit 30 in step S11 3.1 msec after the power source has crossed zero. Set the phase control so that

That is, since the half cycle of 60 Hz is 8.3 ms, the fan motor 10 is energized for 5.2 ms of the half cycle. This energization time has a frequency of 50
The time is set so that the rotation speed of the fan 9 is 800 rpm, which is the same as that at the time of Hz.

Thereafter, in step S12, the upper heater relay 19 is turned on and the upper heater 3 is turned on. After that, in step S13, the detection level VS of the humidity sensor 7 is detected, in step S14 it is detected whether or not the detection level VS reaches the set level V set in step S5, and this operation is continued until it reaches.

When it is determined in step S14 that the detection level VS has reached the set level V, the upper heater relay 19 is turned off to turn off the upper heater 3 in step S15, and the ON signal to the triac 18 is turned on in step S16. The transmission is stopped to stop the fan motor 10, the turntable relay 17 is turned off in step S17 to stop the rotation of the turntable, and then the buzzer is sounded in step S18 to notify the end.

In the present embodiment, the fan drive section 30 controls the conduction angle of the triac 18 to control the phase of the fan motor 10 to control the rotation speed. However, an inverter circuit is used to control the fan motor. The rotation speed of 10 may be controlled.

[0029]

According to the present invention, even if the power supply frequency changes, the finish of cooking is not affected, and it is possible to realize the cooking in which a constant finish is always obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a microwave oven of the present invention.

FIG. 2 is a control circuit diagram of the microwave oven of the present invention.

FIG. 3 is an operation flowchart diagram of automatic grill cooking of the microwave oven of the present invention.

FIG. 4 is a flowchart of the operation continued from FIG. 3;

[Explanation of symbols]

 2 Cavity 3 Upper heater 7 Humidity sensor 9 Fan 30 Fan drive unit 31 Frequency detection unit

Claims (2)

[Claims] 1. A cavity for storing food, a heater for heating the food, a humidity sensor for detecting humidity in the cavity, a fan for blowing air in the cavity, and a power supply frequency. A microwave oven, comprising: a frequency detection unit for detecting the temperature of the fan; and a fan drive unit for driving and controlling the fan based on the detection result of the frequency detection unit. 2. The fan drive unit controls the rotation speed of the fan by phase control and turns on all phase angles for a certain period from the start of operation.
Microwave oven described in.