EP2009958A2

EP2009958A2 - Method of preheating microwave oven

Info

Publication number: EP2009958A2
Application number: EP08158882A
Authority: EP
Inventors: Yong Soo Shin
Original assignee: Daewoo Electronics Co Ltd
Current assignee: WiniaDaewoo Co Ltd
Priority date: 2007-06-25
Filing date: 2008-06-24
Publication date: 2008-12-31
Also published as: KR20080113493A; EP2009958A3

Abstract

Disclosed herein is a method of preheating a microwave oven. The method includes driving a cooling fan motor for a predetermined preheating duration if a preheating operation is performed by setting a preheating temperature and inputting a preheating signal; determining whether an internal temperature of a cooking chamber reaches the preheating temperature while continuously driving all available heaters of the microwave oven; and maintaining the preheating temperature for a preheating temperature maintaining duration by driving the cooling fan motor while selectively driving the available heaters, if the internal temperature reaches the preheating temperature.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of preheating a microwave oven, and more particularly to a method of preheating a multi-function microwave oven that can eliminate odor due to previous cooking during a preheating operation, reduce cooking duration through a rapid preheating operation, and can display time for maintaining a preheating temperature before a cooking operation such that a user can control the preheating temperature while checking the displayed time.

2. Description of the Related Art

Various types of devices have been proposed for heating foods. As an example of the most primitive form of heating device, there is a container that directly contacts a heating source. In this case, items to be cooked are placed in the container and then heated for cooking.
Further, many cooking devices directly or indirectly using electricity have been developed. For instance, there is a microwave oven employing microwaves as a heating source. The microwave oven uses electricity to generate and radiate microwaves to an item to be cooked, oscillating molecules therein. Oscillation of the molecules in the item causes heating thereof.
In general, a microwave oven is a kitchen device that irradiates an item to be cooked with high-frequency waves emitted from a magnetron, and heats both an interior and exterior of the item. The microwave oven is widely used since it has advantages of sharply reducing a cooking duration due to high thermal efficiency thereof; reducing nutritive loss while cooking, thawing, and warming food; and cooking the food directly within a storage container.
Additionally, a single-function microwave oven has been recently proposed that cooks food with 2450 MHz microwaves emitted by the magnetron. Further, examples of a multi-function microwave oven employing other functions in addition to the microwave-based heating function include a grill-type microwave oven having a grill function with grill heaters provided at upper and lower sides of a cooking chamber, a convection-type microwave oven having an oven function with a convection fan for convection of hot air, etc.
Fig. 1 is a block diagram schematically illustrating a typical multi-function microwave oven.
In Fig. 1, the multi-function microwave oven includes a key input unit 10 through which a cooking signal is input, a power supply 20 to supply power, a timer 30 to measure cooking duration, a temperature sensor 40 to detect an internal temperature of a cooking chamber, a grill heater 60 to supply thermal energy to a grill, a convection heater 70 to supply thermal energy to the interior of the cooking chamber, a convection motor 80 to provide power for driving a fan to distribute heat uniformly throughout the cooking chamber, a cooling fan motor 90 to cool an electric component chamber and the cooking chamber, a controller 50 to control the microwave oven in response to a cooking signal input through the key input unit 10, and a display unit 100 to display a control state of a controller 50 and an operation state of the microwave oven.
Operation of the microwave oven will be described as follows.
With the microwave oven powered on, a cooking duration and a cooking temperature are input through the key input unit 10. Then, a cooking signal is transferred to the controller 50, which in turn controls the convection heater 70, grill heater 60, convection motor 80, and cooling fan motor 90 in response to the cooking signal to cook food in the cooking chamber while monitoring the internal temperature of the cooking chamber through the temperature sensor 40. At this time, the operation state of the microwave oven is displayed on the display unit 100.
If the multi-function microwave oven is operated with an oven function and a cooking target is directly cooked inside the cooking chamber without a preheating operation, it takes a great deal of time to reach a proper temperature, which increases a total cooking duration and causes unsatisfactory cooking of the cooking target due to excessive water loss of the cooking target. Accordingly, it is necessary to perform the preheating operation for adjusting the internal temperature of the cooking chamber to a preset preheating temperature.
When performing the foregoing preheating operation, however, the total cooking duration is extended due to time for the preheating operation in addition to time for cooking.
Further, after reaching the preheating temperature through the preheating operation, the preheating temperature must be maintained for a predetermined duration, and the preheating operation is stopped if the cooking operation is not performed. However, it is difficult for a user to know the remaining preheating temperature maintaining duration, and, if the user consumes time for preparation of cooking, it is necessary for the user to restart the preheating operation since the preheating temperature is not maintained.
Also, if a door is opened and closed after the preheating operation has been completed, the microwave oven assumes a cooking target has been placed therein to start a substantial cooking operation, and stops the preheating operation. However, even when a user merely opens and closes the door without any intention, the microwave oven stops the preheating operation and does not perform any operation for maintaining the preheating temperature, thereby lowering the preheating temperature. Accordingly, when the user starts to perform the substantial cooking, the preheating operation must be performed again or the cooking may not be normally performed.
Furthermore, a previous cooking odor may remain in the multi-function microwave oven. Thus, even when a new cooking operation is performed with the microwave oven, the previous cooking odor can affect newly cooked food.

SUMMARY OF THE INVENTION

The present invention is conceived to solve the problems of the conventional techniques as described above, and an aspect of the present invention is to provide a method of preheating a microwave oven, e.g. a multi-function microwave oven, that can eliminate odor due to previous cooking during a preheating operation, reduce cooking duration through a rapid preheating operation, and can display time for maintaining a preheating temperature before a cooking operation such that a user can control the preheating temperature while checking the displayed time.
In accordance with one aspect of the present invention, a method of preheating a microwave oven includes: driving a cooling fan motor for a predetermined preheating duration if a preheating operation is performed by setting a preheating temperature and inputting a preheating signal; determining whether an internal temperature of a cooking chamber reaches the preheating temperature, while continuously driving all available heaters of the microwave oven; and maintaining the preheating temperature for a preheating temperature maintaining duration by driving the cooling fan motor while selectively driving the available heaters, if the internal temperature reaches the preheating temperature.
The available heaters may include a grill heater and a convection heater.
The determination as to whether the internal temperature reaches the preheating temperature may include stopping the preheating operation if the internal temperature does not reach the preheating temperature even when the predetermined preheating time has elapsed.
The cooling fan motor may be driven with a lapse of a predetermined time after the internal temperature has reached the preheating temperature.
The convection motor may be driven when the cooling fan motor is driven.
The method may further include displaying a remaining preheating temperature maintaining duration, while maintaining the preheating temperature.
The method may further include performing an operation corresponding to a cooking key, if the cooking key is input in the maintaining of the preheating temperature.
With this configuration, when the multi-function microwave oven performs the preheating operation, the cooling fan is initially operated to ventilate the cooking chamber and then all available heaters are continuously driven so that the internal temperature of the cooking chamber can rapidly reach the preheating temperature, thereby reducing the total cooking duration. Further, while the preheating temperature is maintained, the preheating operation is stopped only by input of the cooking key, thereby preventing the preheating operation from stopping due to opening and closing of the door.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

Fig. 1 is a block diagram of a typical multi-function microwave oven;
Fig. 2 is a flowchart illustrating a method of preheating a microwave oven according to one embodiment of the present invention; and
Fig. 3 is a graph of an internal temperature of a cooking chamber during a preheating operation according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of the present invention will be described with reference to the accompanying drawings in which like numerals and symbols refer to like elements throughout. Further, these embodiments do not limit the scope of the present invention and are given by way of illustration only. Accordingly, it should be appreciated that various modifications and changes can be made by a person having ordinary knowledge in the art without departing from the spirit and scope of the present invention.
Fig. 2 is a flowchart of a method of preheating a microwave oven according to one embodiment of the present invention.
According to this embodiment of the present invention, when a multi-function microwave oven performs cooking with an oven function, a preheating temperature is set for a preheating operation, and then, the preheating operation is performed in response to a preheating signal input through a key input unit 10. In the preheating operation, a cooling fan motor 90 is first driven for a predetermined preheating duration to ventilate a cooking chamber such that a previous cooking odor can be eliminated. Further, the cooking chamber is controlled to have an internal temperature equal to an external temperature in order to allow various elements such as a temperature sensor to efficiently operate for achieving a stable control operation, in S10.
After driving the cooling fan motor 90 for the predetermined preheating duration, all available heaters such as a grill heater 60 and a convection heater 70 are continuously driven until the internal temperature of the cooking chamber reaches the preset preheating temperature so as to rapidly reach the preheating temperature in S12.
At this time, the cooling fan motor 90 is in a suspended state after operation for the predetermined duration.
Meanwhile, when driving the grill heater 60 and the convection heater 70 provided in the microwave oven, if only one of the grill heater 60 and the convection heater 70 is available due to local or power problems, the available heater is continuously driven until the internal temperature reaches the preheating temperature.
When the internal temperature of the cooking chamber reaches the preset preheating temperature by driving the total available heaters, the cooling fan motor 90 is driven and the available heaters are selectively driven to maintain the preheating temperature.
When driving the cooling fan motor 90, a convection motor 80 may be driven together with the cooling fan motor 90 in S 18.
However, if the available heaters are fully driven but the internal temperature does not reach the preheating temperature for the preheating duration, the preheating operation is stopped and a warning is displayed in S16.
When the cooling fan motor 90 is driven after reaching the preheating temperature, a driving time for the cooling fan motor 90 is delayed for a certain time to prevent the internal temperature from being sharply lowered from the preheating temperature if the cooling fan motor 90 is suddenly driven. Accordingly, when the internal temperature is raised above the preheating temperature by a certain temperature, the cooling fan motor 90 is driven to maintain the preheating temperature for a preheating temperature maintaining duration.
In this manner, while the preheating temperature is maintained, a remaining preheating temperature maintaining duration is displayed such that a user can check the remaining preheating temperature maintaining duration, in S22.
While maintaining the preheating temperature until the preheating temperature maintaining duration expires, it is determined whether a cooking key is input in S24. If the cooking key is input, the cooking operation corresponding to the cooking key is performed in S26.
On the other hand, if the preheating temperature maintaining duration has expired under a state that there is no input of the cooking key, the preheating operation is stopped in S28.
Thus, stopping the preheating operation during the preheating temperature maintaining duration depends only on the determination as to whether the cooking key has been input. Accordingly, if the door is opened and closed without any input of the cooking key, the preheating operation is performed to continuously maintain the preheating temperature for the preheating temperature maintaining duration.
Fig. 3 is a graph of an internal temperature of a cooking chamber during a preheating operation according to one embodiment of the present invention.
As shown therein, the cooling fan motor 90 is initially driven for a predetermined preheating duration so that the internal temperature of the cooking chamber becomes equal to the external temperature. Then, the available heaters are continuously operated to rapidly raise the internal temperature. When the internal temperature reaches the preheating temperature, the available heaters are selectively controlled while continuously driving the cooling fan motor 90, thereby stably maintaining the preheating temperature at an average of 230°C.
According to an embodiment of the present invention, an inner state of the cooking chamber and an operating state of a temperature sensor are more stably maintained by continuously driving the cooling fan motor 90 than by intermittently driving the cooling fan motor 90, so that a stable control can be performed while maintaining the preheating temperature.
As described above, according to the present invention, when performing a preheating operation, the multi-function microwave oven initially operates a cooling fan not only to ventilate a cooking chamber to eliminate a previous cooking odor, but also to control the cooking chamber to have an internal temperature equal to an external temperature, thereby smoothly operating various components such as the temperature sensor to achieve a stable control operation.
Further, all available heaters are continuously driven during a preheating operation without operating a cooling fan motor, so that the internal temperature of the cooking chamber can rapidly reach the preheating temperature, reducing the total cooking duration.
Further, while the preheating temperature is maintained, not only is a remaining preheating temperature maintaining duration displayed, but also the preheating operation can be stopped only by input of a cooking key. Thus, the preheating operation is prevented from stopping due to opening and closing of the door, thereby enhancing user convenience.
Although the present invention has been described with reference to the embodiments and the accompanying drawings, the present invention is not limited to these embodiments. It should be understood that various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present invention as defined by the accompanying claims.

Claims

A method of preheating a microwave oven, comprising:
driving a cooling fan motor for a predetermined preheating duration if a preheating operation is performed by setting a preheating temperature and inputting a preheating signal;

determining whether an internal temperature of a cooking chamber reaches the preheating temperature, while continuously driving all available heaters of the microwave oven; and

maintaining the preheating temperature for a preheating temperature maintaining duration by driving the cooling fan motor while selectively driving the available heaters, if the internal temperature reaches the preheating temperature.
The method according to claim 1, wherein the available heaters comprise a grill heater and a convection heater.
The method according to claim 1, wherein the determination as to whether the internal temperature reaches the preheating temperature comprises stopping the preheating operation if the internal temperature does not reach the preheating temperature even when the predetermined preheating duration has elapsed.
The method according to claim 1, wherein the cooling fan motor is driven with a lapse of a predetermined time after the internal temperature has reached the preheating temperature.
The method according to claim 1 or 4, wherein a convection motor is driven when the cooling fan motor is driven.
The method according to claim 1, further comprising:
displaying a remaining preheating temperature maintaining duration while maintaining the preheating temperature.
The method according to claim 1, further comprising:
performing an operation corresponding to a cooking key, if the cooking key is input in the maintaining of the preheating temperature.