Electric heating – Microwave heating – With control system
Reexamination Certificate
1999-10-29
2001-03-06
Leung, Philip H. (Department: 3742)
Electric heating
Microwave heating
With control system
C219S711000, C099S325000, C426S241000, C426S524000
Reexamination Certificate
active
06198084
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application entitled DEFROSTING METHOD USING INFRARED SENSOR FOR MICRO WAVE OVEN earlier filed in the Korean Industrial Property Office on Jul. 12, 1999 and there duly assigned Ser. No. 27971/1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microwave oven for cooking food by using high frequency microwaves which are generated from a magnetron, and more particularly to a defrosting method for a microwave oven for sensing a temperature of the food by using an infrared sensor and for determining a defrost completion time in accordance with the detected temperature of the food.
2. Description of the Prior Art
Generally, a microwave oven is an appliance for cooking food by using high frequency microwaves which are generated from a magnetron. Such a microwave oven is widely used due to its advantages such as high heat efficiency, quick cooking process, and less loss of nutrients.
The conventional microwave oven is shown in
FIG. 1
, in which the microwave oven includes a body
10
, and cooking and device chambers
12
and
14
formed within the body
10
. The food to be cooked is placed in the cooking chamber
12
, while the cooking chamber
12
is opened/closed by a door
20
mounted on the front side thereof.
The cooking chamber
12
further includes a rotatable plate
16
for placing food, which is arranged on the bottom side of the cooking chamber
12
. The device chamber
14
includes various devices for generating and emitting the high frequency microwaves into the cooking chamber
12
, such as a magnetron
17
, a high voltage transformer
18
, a wave guide (not shown), and a cooking fan
19
, etc.
On the front side of the device chamber
14
, an operation panel
30
is formed, through which a user inputs cooking operational commands. The food is cooked in accordance with the commands inputted through the operation panel
30
by a control part (not shown) which is formed on a rear side of the operation panel
30
for controlling the respective operations of the devices.
When the devices of the device chamber
14
are operated, the high frequency microwaves generated from the magnetron
17
are guided through the wave guide into the cooking chamber
12
. The high frequency microwaves guided into the interior of the cooking chamber
12
are emitted to the food directly, or indirectly by being reflected against the walls of the cooking chamber
12
.
The high frequency microwave which is emitted to the food, vibrates the water molecules contained within the food and generates the heat for cooking the food. In addition to the cooking operation, the microwave oven is further used for defrosting frozen food, or for warming liquid such as water, or beverages.
Particularly when defrosting frozen food, the high frequency microwave is emitted to the frozen food for a predetermined time, which is set in accordance with the weight of the frozen food. A method for defrosting food by a conventional microwave oven is described below with reference to the flow chart shown in FIG.
2
.
First, the weight of the frozen food is measured (Step S
1
). In the past, the weight of the food has been directly inputted by the user's estimation through a keypad of the operation panel
30
. Recently, however, the weight of the food can be measured by a weight sensor.
After measuring the weight of the food, the defrosting time is set in accordance with the measured weight of the food (Step S
2
). Next, the magnetron
17
is operated for a predetermined time (Step S
3
). When the predetermined time elapses (Step S
4
), the magnetron
17
is stopped and the defrosting process is completed (Step S
5
).
The conventional defrosting method for the microwave oven, however, has the following drawbacks:
Usually, the user places frozen food in the receptacle before the defrosting process, in order to prevent the water, which is generated out of the food during the defrosting process, from dropping onto the rotatable plate
16
. In this case, the weight sensor, which is employed in the microwave oven, recognizes the total weight of the food and the receptacle as the weight of the food.
Accordingly, the defrosting time is inaccurately set. As a result, the problem arises in the accuracy of food cooking time in that the food is partially overheated, or the like.
Further, according to the conventional defrosting method, the magnetron
17
is driven for the predetermined time which is set in accordance with the weight of the food.
This means that foods having a temperature of −20 Celsius degree or −5 Celsius degree may undergo the same defrosting process for the same period of time, only if the weights thereof are the same as each other. Accordingly, the food can not be defrosted accurately.
SUMMARY OF THE INVENTION
The present invention has been developed to overcome the above-mentioned problems of the prior art, and accordingly, it is an object of the present invention to provide a method for a microwave oven for consistently defrosting food accurately, regardless of the frozen degree of the food, or the presence/absence of the receptacle.
The above object is accomplished by a defrosting method for a microwave oven according to the present invention, including the steps of: determining an initial value by detecting a surface temperature of food to defrost; determining a defrost completion value in accordance with the initial value which is determined in the step of determining the initial value; detecting a current value of an infrared sensor on a regular time basis while driving a magnetron; and completing the defrosting process if the current value reaches the completion value.
In the step of determining the initial value, an output value of the infrared sensor is detected at a predetermined regular time basis while a rotatable tray for placing the food is rotated, and the initial value is obtained from the lowest output value among a plurality of output values which are detected.
In the step of driving the magnetron, a gap between the initial value and the completion value is divided into at least two divisions, and a power rate of the magnetron is varied in accordance with the respective divisions.
In the step for detecting the current value, the output value of the infrared sensor is detected at a predetermined regular time basis while the rotatable tray for placing the food is rotated, and the current value is obtained from the lowest output value among the output values which are detected.
The power rate of the magnetron of the respective divisions, is decreased from the value which is closer to the initial value to the value which is closer to the completion value.
According to the present invention, the microwave oven is controlled by using output value of the sensor corresponding to the surface temperature of food to be defrosted. Accordingly, the defrosting can be accurately performed, regardless of the frozen degree of the food, and presence/absence of the receptacle for food.
REFERENCES:
patent: 5545880 (1996-08-01), Bu et al.
patent: 6013907 (2000-01-01), Lee
patent: 58-110929 (1983-07-01), None
patent: 62-169937 (1987-07-01), None
patent: 5-39929 (1993-02-01), None
Bushnell , Esq. Robert E.
Leung Philip H.
Samsung Electronics Co,. Ltd.
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