CA2139598A1

CA2139598A1 - Microwave oven

Info

Publication number: CA2139598A1
Application number: CA002139598A
Authority: CA
Inventors: Ji Won Kim
Original assignee: Gold Star Co Ltd
Current assignee: LG Electronics Inc
Priority date: 1994-02-28
Filing date: 1995-01-05
Publication date: 1995-08-29
Also published as: JPH07269882A; KR960011459B1; KR950025352A; KR960009636B1; JP2721814B2

Abstract

A microwave oven including a turntable lifting/lowering device capable of vertically moving a turntable by an operation of a spiral gear, thereby achieving a stability even when a liquid food is cooked, and capable of eliminating use of any supporting member and rotation die adapted to achieve the vertical movement of the turntable, thereby very simplifying the inner construction of a heating chamber. The microwave oven also includes an automatic thawing device capable of eliminating use of any weight sensor and thawing a food on the basis of the total thawing time and the thawing mode determined by use of the temperature of the food and the moisture amount generated from the food varying depending on the processing of the cooking and capable of carrying out the thawing while vertically moving a turntable by a turntable lifting/lowering device, thereby achieving a uniform and sufficient thawing of the food. The microwave oven achieves a grille cooking under a condition that a food to be cooked approximates to a heater by the turntable lifting/lowering device and achieving a combination cooking by heating the food alternatingly by microwaves and the heater while moving a turntable upwards and downwards, thereby uniformly cooking all portions of the food.

Description

2139~98 MICROWAVE OVEN

BACKGROUND OF THE INVFNTION

Field of the Invention The present invention relates to a microwave oven, and more particularly to a microwave oven capable of automatically performing a grille cooking and a combination cooking under a control of a microcomputer while vertically moving its turntable and capable of automatically thawing a food.

Description of the Prior Art FIGS. lA and lB are an exploded perspective view and a sectional view respectively illustrating a construction and an operation of a conventional turntable lifting/lowering device equipped in a microwave oven. FIG. 2 is a block diagram illustrating a conventional automatic thawing method using a weight sensor. On the other hand, FIGS. 3A and 3B are schematicsectional viewsrespectively illustrating operations of a conventional grille/combination cooking device.
As shown in FIGS. lA and lB, the conventional turntable lifting/lowering device adapted to verLically move a turntable includes a rotation shaft 2 vertically extending from a central portion of a recessed bottom surface la of a heating chamber 1 of the microwave oven toward the interior of heating 2l39~98 chamber 1.
A support member 3 having a downwardly-convex tray shape is ~itted around the upper portion of the rotation shaft 2.
The support member 3 is provided at its upper end with a cam surface. The support member 3 is fixedly mounted on the bottom surface of heating chamber 1. Over the support member 3, a cross-shape rotation die 4 and a turntable 6 are coupled to the rotation shaft 2 so that they rotate by the rotation of the rotation shaft 2. Beneath the bottom surface of heating chamber ;, a motor 7 for rotating the turntable 6 is disposed.
In order to rotate the cross-shape rotation die 4 and the turntable 6 together by the rotation of the rotation shaft 2, the upper surface of the cross-shape rotation die 4 is coupled to the lower surface of the turntable 6. The cross-shape rotation die 4 is provided at its bottom surface with four wheels 5 adapted to be in contact with the cam surface of support member 3 so that it can roll along the cam surface.
Operation of the turntable lifting/lowering device 101 having the above-mentioned construction will now be descried.
As the motor 7 is driven, the drive force from the motor 7 is transmitted to the cross-shape rotation die 4 via the rotation shaft 2, thereby causing the cross-shape rotation die 4 and the turntable ~ to rotate.
As the cross-shape rotation die 4 rotates, its wheels 5 rolls along the cam surface provided at the upper end of ~139598 support member 3 to enhance the cooking effect. Accordingly, the cross-shape rotation die 4 and the turntable 6 reciprocate vertically while rolling along the cam surface of the support member 3. -Since the turntable 6 moves upwards and downwards along the cam surface of support member 3 during coo~ing of a food, the conventional turntable lifting/lowering device 101 enables the food to be subjected to microwaves uniformly ~ore or less.
In this conventional turntable lifting/lowering device 101, however, an overflow of the food may be generated where the food is at a liquid state because the turntable 6 moves upwards and downwards during its rolling along the cam surface. Although such a food overflow may not be generated in this case, the user feels uneasy about the food overflow.
Furthermore, the inner construction of the microwave oven equipped with the conventional turntable lifting/lowering device is complex because of the provision of the support member and the cross-shape rotation die. The construction of the turntable lifting/lowering device is difficult to allow microwaves to reach up to the bottom surface of the food even though the food is uniformly heated by virtue of the vertical movements of the turntable. As a result, there is a problem that the uniform heating at all portions of the food is not ensured.
Where the conventional automatic thawing method shown in FIG. 2 is applied to the microwave oven having the above-mentioned construction, a weight sensor (not shown) is used to sense the weight of a food laid on the turntable 6. In accordance with the thawing method, the food weight sensed by the weight sensor is sent to a microcomputer which is denoted by the reference numeral ~ in FIG. 2. On the basis of the received food weight, .he microcomputer 8 determines the automatic thawing time and the output level of microwaves generated from a magnetron. This will be described in detail.
When a thawing operation is initiated by a manipula-tion of the user, the weight sensor senses the weight of the food u~der a control of the microcomputer 8. The microcomputer 8 compares the sensed food weight with various data stored therein about the relation between the weight and the thawing time and the relation between the weight and the microwave output mode and thereby determines an appropriate thawing time and an appropriate thawing mode. Based on the determined thawing time and microwave output level, driving of the magnetron is controlled. By the controlled magnetron, microwaves are emitted, thereby thawing the ~ood.
The thawing operation will now be described in detail in conjunction with the case of thawing a whole chicken. Where the weight of the chicken sensed by the microcomputer 8 is 800g, the thawing time may be determined as 20 minutes at the microwave output level of 70%, 10 minutes at the microwave output level of 20%, 10 minutes at the microwave output level of 30%, or 20 minutes at the microwave output level of 10% by the microcomputer 8.
In accordance with this conventional thawing method, however, an improper thawing may be carried out because an improper thawing mode is inputted due to a limited number of thawing modes previously set. Moreover, the conventional thawing method is troublesome because the total thawing time associated with the food weight should be predetermined depending on the kind of food and stored. In addition, the conventional thawing method requires the provision of the ~eight sensor for sensing the weight of food.
On the other hand, the conventional microwave oven include a construction for achieving a grille cooking. An example of such a construction is illustrated in FIG. 3A. As shown in FIG. 3A, a heater 9 is disposed at the upper portion of the heating chamber. A separate shelf 10 is separably disposed in the interior of the heating chamber 1 such that it extends across the upper portion of the heating chamber 1.
The shelf 10 serves to position a food near the heater 9.
Where a grille cooking is to be carried out, the user lays a food to be cooked on the shelf 10 and then initiates an operation for the grille cooking, thereby causing ~he heater 9 to be energized. As the heater 9 heats the food, .he grille cooking is carried out.

2139~98 In order to carry out the grille cooking by use of the conventional construction, however, the shelf should be mounted in the heating chamber every time when the grille cooking is begun. After completion of-the grille cooking, the shelf has to be separated from the heating chamber and to be stored in a convenient place. Such works are troublesome.
Moreover, the user may suffer a burn upon handling the shelf heated in the heating chamber. Although a browning effect, that is, the phenomenon that the food is changed at its surface to have a tasty yellowish surface is obtained at the surface of the food facing the heater, the conventional construction is difficult to obtain the browning effect at the surface of the food being in contact with the shelf. In some cases, there is a problem that the user should turn the food directly.
In addition to the heater g mentioned above, the conventional microwave oven also include a construction for achieving a combination cooking. An example of such a construction is illustrated in FIG. 3B. As shown in FIG. 3B, a magnetron 11 is disposed at an appropriate portlon of one outer side wall of the heating chamber 1.
In order to carry out the combination cooking by use of the conventional construction, first, the shelf is removed from the heating chamber. As an operation for the combination cooking under this condition, the magnetron 11 is driven for a predetermined time, thereby achieving a heating by microwaves. After completion of the heating by the magnetron 11, the heater 9 is driven to achieve the grille cooking.
Where the combinatlon cooking is carried out using the above-mentioned construction, there is a problem that the food is not cooked uniformly, but cooked excessively at its specific portion because the food on the turntable moves upwards and downwards only in a slight movement range along the cam surface during the cooking involving the heating by the heater and the heating the radio frequency heating by the magnetron.

SUMMARY OF THE INVENTION

Therefore, an object of the invention is to provide a microwave oven including a turntable lifting/lowering device capable of achieving a smooth vertical movement of a turntable and minimizing the shaking phenomenon of the turntable, thereby preventing the overflow phenomenon of a food laid on the turntable, capable of eliminating use of any supporting member and rotation die adapted to achieve the vertical movement of the turntable, thereby very simplifying the inner construction of a heating chamber, and capable of establishing a circumstance enabling the food to be uniformly cooked even at the bottom surface thereof.

Another object of the invention is to provide a microwave oven including an automatic thawing device capable of eliminating use of any weight sensor and thawing a food on the basis ~of--the- -total thawing time and the thawing mode determined by use of the temperature of the food and the moisture amount generated from the food varying depending on the processing of the cooking and capable of carrying out the thawing while vertically moving a turntable by a turntable lifting/lowering device, thereby achieving a uniform and sufficient thawing of the food, and a method for automatically thawing a food in the microwave oven equipped with the automatlc thawing device.
Another object of the invention is to provide a grille/combination type microwave oven capable of eliminating any shelf adapted to be used for a grille cooking, achieving the grille cooking under a condition that a food to be cooked approximates to a heater by a turntable lifting/lowering device and achieving a combination cooking by heating the food alternatingly by microwaves and the heater while moving a turntable upwards and downwards, thereby uniformly cooking all portions of the food and eliminating the inconvenience and the safety problem involved upon handling the shelf.
In accordance with the present invention, these object can be accomplished by providing a turntable driving device of a microwave oven comprising: a turntable disposed in the ~139598 , microwave oven and adapted to move upwards and downwards and rotate while laying a food to be cooked thereon; a rotation shaft coupled at an upper end thereof to a central portion of ~ -the turntable at a bottom surface of the turntable, the rotation shaft extending downwards from the turntable; a turntable lifting/lowering gear integral with an upper portion of the rotation shaft around the rotation shaft, the turntable lifting/lowering gearing being provided at an outer surface thereof with spiral teeth; a middle gear portion provided at the outer surface of the turntable liftingJlowering gear; a turntable rotating gear fitted around a lower portion of the rotation shaft; powering means adapted to supply a power for the vertical movement and rotation of the turntable; control means adapted to control the powering means; power transmission means adapted to transmit the power f~om the powering means to the turntable lifting/lowering gear and the turntable rotating gear; and position sensing means adapted tb sense a maximum height of the turntable upon lifting and a minimum height of the turntable upon lowering.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and aspects of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which:

21395~8 FIG. lA is an exploded perspective view illustrating a construction of a conventional turntable lifting/lowering device equipped in a microwave oven;
--- FIG. lB is a schematic sectional view illustrating an operation of the turntable lifting/lowering device shown in FIG. 1;
FIG. 2 is a block diagram illustrating a conventional automatic thawing method using a weight sensor;
FIG. 3A is a schematic sectional view illustrating an grille cooking operation of a conventional microwave oven;
FIG. 3B is a schematic sectional view illustrating a combination cooking operation of the conventional microwave oven;
FIG. 4 is a schematic view illustrating a turntable lifting/lowering device for the microwave oven in accordance with a first embodiment of the present invention;
FIG. 5 is a sectional view illustrating a coupling between a turntable lifting/lowering gear and a turntable rotating gear in the turntable lifting/lowering device of FIG.
4;
FIG. 6 is a schema.ic view illustrating a turntable lifting/lowering device for the microwave oven in accordance with a second embodiment of the present invention;
FIG. 7 is a schematic view illustrating a turntable lifting/lowering device for the microwave oven in accordance with a third embodiment of the present invention;
FIG. 8 is a schematic view illustrating the automatic thawing device of the microwave oven in accordance with the present invention;
FIG. 9 is a circuit diagram of the automatic thawing device shown in FIG. 8;
FIG. 10 is a diagram illustrating an automatic thawing method in a microwave oven in accordance with the present invention;
FIG. 11 is a timing diagram illustrating a relation ~etween the timing of the automatic thawing method of the p.resent invention and the microwave output level;
FIG. 12A is a graph illustrating a variation in temperature sensed for an automatic thawing in the microwave oven in accordance with the present invention;
FIG. 12B is a graph illustrating a variation in moisture amount sensed for the automatic thawing in the microwave oven in accordance with the present invention;
FIG. 13A is a schematic sectional view illustrating a grille cooking operation carried out in the microwave oven in accordance with the present invention;
FIG. 13B is a schematic sectional view illustrating a combination cooking operation carried out in the microwave oven in accordance with the present invention; and FIG. 14 is a flow chart illustrating a grille/combination cooking control method in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, constructions of a microwave oven, a turntable lifting/lowering device, an automatic thawing device and a grille/combination cooking control device will be described.
Referring to FIG. 4, there is illustrated a first embodiment of the turntable lifting/lowering device for the microwave oven in accordance with the present invention. As shown in FIG. 4, the turntable lifting~lowering device which is denoted by the reference numeral 105 in FIG. 4 includes a rotation shaft 22D coupled at its upper end to the central portion of a turntable 21, on which a food to be cooked is laid, at the bottom surface of the turntable 21. The turntable 21 is constructed to move upwards and downwards and rotate while laying the food thereon. The rotation shaft 22D
extends downwards from the turntable 21.
Around the rotation shaft 22D, a turntable lifting/lowering gear 22 is fitted such that it rotates integrally with the rotation shaft 22D. In the illustrated case, the turntable lifting/lowering gear 22 is formed integrally with the rotation shaft 22D. The turntable lifting/lowering gear 22 is provided at its outer surface with 2139~98 spiral teeth. The turntable lifting/lowering gear 22 includes three gear portions 22A, 22B and 22C. Beneath the turntable lifting/lowering gear 22, a turntable rotating gear 23 is fitted around the lower portion of the rotation--shaft 22D.
In one side of the rotation shaft 22D, a gear shaft 29 is disposed in parallel to the rotation shaft 22D such that it is spaced a predetermined distance from the rotation shaft 22D.
The turntable lifting/lowering device 105 also includes a motor 24 adapted to supply a power for the upward and downward movements and rotation of the turntable 21. The motor 24 is coupled to a microcomputer 30 for controlling normal and reverse rotations of the motor 24. Coupled to the motor 24 is a motor shaft gear 25 adapted to transmit the power generated from the motor 24 to other parts of the turntable lifting/lowering device 105. The motor shaft gear 25 is engaged with a middle gear 26 mounted on the lower portion of the gear shaft 29.
Above the middle gear 26, a turntable rotation driving gea- 27 is mounted on the gear shaft ~9. The turntable rotation driving gear 27 is engaged with the turntable rotating gear 23. Disposed above the turntable rotation driving gear 27 is a turntable lifting/lowering driving gear 28 mounted on the gear shaft 29 and provided at its outer surface with spiral teeth. The turntable lifting/lowering driving gear 28 is engaged with the middle gear portion 22A.

In the case of the turntable lifting/lowering device 105, the motor 24 constitutes powering means 121. On the other hand, the motor shaft gear 25, the middle gear 26, the turntable rotation driving gear 27, the turntable lifting/lowering driving gear 28 and the gear shaft 29 constitute power transmission means 122. Also the microcomputer 30 serves as control means 123.
The turntable lifting/lowering device 105 further includes a pair of position sensing means 124 disposed above and beneath the turntable lifting/lowering gear 22 and adapted to sense an upper limit position and a lower limit position of the turntable 21 during the vertical movement of the turntable 21, respectively.
As shown in FIGS. 4 and 5, the position sensing means 124 are constituted by the upper-limit and lower-limit gear portions of the turntable lifting/lowering gear 22, namely, a lower idler gear 22B and an upper idler gear 22C, respectively.
That is, the turntable lifting/lowering gear 22 is constituted by the central gear portion 22A engaged with the turntable lifting/lowering driving gear 28, the lower-limit idler gear 22B provided at its upper gear portion and adapted tG cut off the power transmission between the turntable lif~ing/lowering gear 22 and the turntable lifting/lowering driving gear 28, and the upper-limit idler gear 22C provided 2139~98 at its lower gear portion and adapted to cut off the power transmission between the turntable lifting~lowering gear 22 and the turntable lifting/lowering driving gear 28.
As shown in FIG. 5, the rotation shaft 22D extending S downwards from the turntable lifting/lowering gear 22 has a circular shape and is fitted in a central hole of the cylindrical turntable rotating gear 23 such that it is rotatably supported in the central hole of the turntable rotating gear 23. By the-rotation shaft 22D, the turntable lifting/lowering gear 22 and the turntable rotating gear 23 are coupled to each other.
. Supporting grooves 22E uniformly spaced are provided at the outer surface of the portion of rotation shaft 22D
disposed in the turntable rotating gear 23, as shown in FIG.
5. The turntable rotating gear 23 is provided at its inner surface with grooves 23A respectively facing the supporting grooves 22E.
In each of the grooves 23A, a supporting protrusion piece 23C biased by a spring 23B is disposed. The tip of each supporting protrusion piece 23C is received in each corresponding supporting groove 22E. By this construction, the turntable lifting/lowering gear 22 can rotate by the rotation of the turntable rotating gear 23 and move upwards and downwards while rotating.
Now, operation of the turntable lifting/lowering device 105 to move the turntable 21 upwards and downwards will be described.
As the motor 24 is driven normally or reversely under a control of the microcomputer 30 shown in FIG.~- 4, the motor shaft gear 25 coupled to the motor 24 rotates, thereby causing the middle gear 26 engaged with the motor shaft gear 25 to rotate.
As the middle gear 26 rotates, the gear shaft 29 rotates, thereby causing the turntable rotation driving gear 27 and the turntable lifting/lowering driving gear 28 to rotate.
By the rotation of the turntable rotation driving gear 27, the turntable rotating gear 23 rotates, so that the rotation shaft 22D coupled to the turntable rotating gear 23 rotates, thereby causing the turntable lifting/lowering gear 22 to rotate.
As the turntable lifting/lowering gear 22 rotates, the turntable 21 coupled to the upper end of the turntable lifting/lowering gear 22 rotates.
At the same time, the turntable lifting/lowering gear 22 also moves upwards or downwards by the rotation of the turntable lifting/lowering driving gear 28 engaged with the central gear portion 22A. By the upward and downward movement of the turntable lifting/lowering gear 22, the turntable 21 moves upwards and downwards.
That is, the turntable 21 moves upwards and downwards while rotating. Such simultaneous vertical movement and rotation of the turntable 21 is achieved because the rotation shaft 22D is coupled to the turntable rotating gear 23 by the spring-loaded supporting protrusion pieces 23C.
The principle of limiting the maximum height of the turntable 23 upon lifting and the minimum height of the turntable 23 upon lowering will now be described.
When the turntable lifting/lowering gear 22 moves upwards to the maximum height, its upper-llmit idler gear 22C is engaged with the turntable lifting/lowering driving gear 28.
In this case, the turntable lifting/lowering gear 22 moves upwards no longer even though the turntable lifting/lowering driving gear 28 transmits its rotation force to the turntable lifting/lowering gear 22.
In similar, when the turntable lifting/lowering gear 22 moves downwards to the maximum height as the motor 24 rotates in a direction reverse to that in the above case, its lower-limit idler gear 22B is engaged with the turntable lifting/lowering driving gear 28. In this case, the turntable lifting/lowering gear 22 moves downwards no longer even though the turntable lifting/lowering driving gear 28 transmits its rotation force to the turntable lifting/lowering gear 22.
As apparent from the above description, the turntable lifting/lowering device 105 in accordance with the first embodiment of the present invention can achieve a safe cooking 2139~98 of a liquid food because the turntable 21 can move vertically without any shaking. The turntable lifting~lowering device 105 also simplifies the inner construction of the heating chamber of microwave oven. Since the turntable lifting/lowering device 105 has the construction capable of lifting the food to a high level in the heating chamber, it is possible to obtain a direct heating effect by microwave even at the bottom surface of the food and thereby to uniformly cook the food.
Referring to FIG. 6, there is illustrated a second embodiment of the turntable lifting/lowering device for the microwave oven in accordance with the present invention. In FIG. 6, elements respectively corresponding to those in FIGS.
4 and 5 are denoted by the same reference numerals and their description will be omitted.
As shown in FIG. 6, the turntable lifting/lowering device which is denoted by the reference numeral 106 in FIG. 6 includes a circular switch plate 31 adapted to sense the upper limit position and the lower limit position of the turntable 21. The circular switch plate 31 is attached to the lower surface of the turntable lifting/lowering gear 22 so that it moves vertically together with the turntable lifting/lowering gear Z2.
Disposed above and beneath the circular switch pla.e 31 are an upper-limit sensing switch 32 adapted to sense the - 213g598 circular switch plate 31 at the maximum height upon lifting and a lower-limit sensing switch 33 adapted to sense the circular switch plate 31 at the minimum height upon lowering.
Sensing si-gnals-from the upper-limit and lower-limit sensing switches 32 and 33 are sent to the microcomputer 30.
In the turntable lifting/lowering device 106 in accordance with the second embodiment, when the turntable lifting/lowering gear 22 moves upwards to the maximum height, the circular switch plate 31 comes into contact with the upper-limit sensing switch 32, thereby causing the upper-limit sensing switch 32 to be switched on. When the turntable lifting/lowering gear 22 moves downwards to the minimum height, it comes into contact with the lower-limit sensing switch 33, thereby causing the lower-limit sensing switch 33 to be switched on.
When the microcomputer 30 senses .he switched-on state OI
the switch 32 or 33, it determines that the turntable 21 has moved to the upper-limit maximum height or the lower-limit minimum height. When such a determination is made, the microcomputer 30 controls the motor 24 o be reversely driven.
Referring to FIG. 7, there is illustrated a third embodiment of the turntable lifting/lowering device for the microwave oven in accordance with the present invention. In FIG. 7, elements respectively corresponding to those in FIGS.
4 to 6 are denoted by the same reference numerals and their description will be omitted. In FIG. 7, the turntable lifting/lowering device is denoted by the reference numeral 107.
In the third embodiment, the powering means and the power transmission means are provided dually, respectively, in order to control the rotation of the turntable 21 and the vertical movement of the turntable 21 independently.
That is, the powering means comprises a turntable rotating motor 24A adapted to supply a power for rotating the turntable 21 and a turntable lifting/lowering motor 24B
adapted to supply a power for lifting and lowering the turntable 21.
The power transmission means comprises rotation a power transmission unit 125 and a lifting/lowering power transmission unit 126. The power transmission unit 125 includes a motor shaft gear 25A coupled to the turntable rotating motor 24A, a middle gear 26A engaged with the motor shaft gear 25A and adapted to transmit the power generated from the turntable rotating motor 24A to other parts of the turntable lifting/lowering device 107, a turntable rotation driving gear 27 operatively connected to the middle gear 26A
on the same axis and engaged with the turntable rotating gear 23, and a gear shaft 29A adapted to couple the middle gear 26A
and the turntable rotation driving gear 27 to each other on the same axis. On the other hand, the lifting/lowering power transmission unit 126 includes a motor shaft gear 25B coupled to the turntable lifting/lowering motor 24B, a middle gear 26B
engaged with the motor shaft gear 25B and adapted to transmit the power generated from the turntable lifting/lowering motor 24B to other parts of the turntable lifting/lowering device 107, a turntable lifting/lowering driving gear 28 operatively connected to the middle gear 26B on the same axis and engaged with the turntable lifting/lowering gear 22, and a gear shaft 29B adapted to couple the middle gear 26B and the turntable lifting/lowering driving gear 28 to each other on the same axis.
The turntable lifting/lowering motor 24B is constituted by a stepping motor in order to achieve an easy control for the vertical position and the vertical movement speed.
In the turntable lifting/lowering device 107 in accordance with the third embodiment, when the turntable rotating motor 24A is driven under a control of the microcomputer 30, the motor shaft gear 25A coupled to the turntable rotating motor 24A rotates, thereby causing the middle gear 26A engaged with the motor shaft gear 25A to rotate. The rotation force of the middle gear 26A is transmitted to the turntable rotation driving gear 27 via the gear shaft 29A. By the rotation of the turntable rotation driving gear 27, the turntable rotating gear 23 rotates, so that the turntable lifting/lowering gear 22 and the turntable ~139598 21 rotate in accordance with the principle explained ln conjunction with the first embodiment.
On the other hand, when the turntable lifting/lowering motor 24B is driven under a control of the microcomputer 30, the motor shaft gear 25B coupled to the turntable lifting/lowering motor 24B rotates, thereby causing the middle gear 26B engaged with the motor shaft gear 25B to rotate. The rotation force of the middle gear 26B is transmitted to the turntable lifting/lowering driving gear 28 via the gear shaft 29B. As the turntable lifting/lowering driving gear 28 rotates, the turntable lifting/lowering gear 22 rotates, so that the turntable lifting/lowering gear 22 and the turntable 21 moves vertically.
When the turntable 21 moves upwards and downwards while rotating, its upper-limit height and lower-limit height are sensed by the circular switch plate 31, the upper-limit- i sensing switch 32 and the lower-limit sensing switch 33 so that the vertical movement and rotation of the turntable 21 can be controlled by the microcomputer 30.
As the microcomputer 30 controls the turntable rotating motor 24A and the turntable lifting/lowering motor 24B which is the stepping motor, the vertical movement speed of the turntable 21 and the position of the turntable 21 can be controlled. Accordingly, it is possible to obtain an appropriate turntable height and an appropriate turntable movement speed depending on the kind of cooking.
On the other hand, FIG. 8 is a schematic view illustrating the automatic thawing device of the microwave oven in accordance with the present invention. In FIG. 8, the automatic thawing device is denoted by the reference numeral 108. FIG. ~ is a circuit diagram of the automatic thawing device shown in FIG. 8.
As shown in FIG. 8, a turntable 21 is disposed at the bottom surface of a heating chamber 34 of the microwave oven.
Beneath the heating chamber 34, a turntable lifting/lowering device 109 is installed so as to vertically move and rotate the turntable 21.
In the interior of the heating chamber 34, a heater 35 is disposed at the upper portion of the heating chamber 34 so as to carry out a grille cooking of a food laid on the turntable 21. A magnetron 11 is disposed at one outer side wall of .he heating chamber 1 so as to carry out a cooking by microwaves.
At an appropriate portion of the side wall of heating chamber 1 attached with the magnetron 36, a throughout hole (not shown~ is provided. The throughout hole allows microwaves emitted from the magnetron 36 to be introduced in the interior of the heating chamber 34 therethrough.
Above the heater 25, an intake port 34A is provided at one side wall of the heating chamber 34. The intake port 34A
serves to introduce an external air in the interior of the 21395g8 heating chamber 34. At the other side wall of the heating chamber 34 not provided with the intake port 34A, an exhaust port 34B is provided.
Near the exhaust port 34B, temperature sensing-means 37 is disposed. Moisture sensing means 38 is disposed at the upper wall of the heating chamber 34.
In the automatic thawing device 108 having the above-mentioned construction, when the user lays a food on the turntable 21 and then selects a thawing mode, the turntable lifting/lowering device 109 is driven under a control of a control unit 39 which is a microcomputer. As the turntable lifting/lowering device 109 is driven, the turntable 21 moves upwards and downwards while rotating. For a predetermined initiation time, a variation in the temperature around the exhaust port 34B is sensed by the temperature sensing means 37. Simultaneously, a variation in the moisture generated from the food is sensed by the moisture sensing means 38.
On the basis of the results of the sensing operations, the microcomputer 39 determines the total thawing time Tt and the output level of microwaves at every time interval. Based on the determined total thawing time and the output level of microwaves, the heater 35 and the magnetron 36 are controlled at every time interval. In such a manner, the thawing operation is carried out.
As shown in FIG. 9, the a-~tomatic thawing circuit ~13g598 includes the control unit 39. As mentioned above, this control unit 39 controls the turntable lifting/lowering device 109 and the magnetron 36 on the basls of the temperature variation sensed by the temperature sensing means 37 and the moisture variation sensed by the moisture sensing means 38 and thereby executes a thawing control. The automatic thawing circuit further includes a chaos simulator 40 for receiving the temperature and moisture variations sensed for the initial sensing time, outputting chaos da~a for an appropriate thawing on the basis of the received temperature and moisture variations, and sensing the chaos data to the control unit 39.
The temperature sensing means 37 and the moisture sensing means 38 constitute a sensor input unit 200 shown in FIG. 9.
The turntable lifting/lowering device 109 and the magnetron 36 constitute a driving load 300. As mentioned above, the control unit 39 is constituted by the microcomputer.
Now, the automatic thawing method in accordance with the present invention will be described in conjunction with FIG.
10. As shown in FIG. 10, the automatic thawing method includes four steps, that is, the first step of determining the number N of changeable thawing modes and a sensing time Ts by the microcomputer 39 when a thawing mode operation is set by a user under a condition that a food to be thawed has been laid on the turntable 21, and driving the temperature sensing means 37 and the moisture sensing means 38 for the sensing 21 395g8 time Ts under a control of the microcomputer 39, thereby sensing a variation in temperature and a variation in moisture amount, the second step of determining a thawing time Td and an initial chaos data value P0 on the basis of the temperature and moisture variations sensed at the first step, the third step of outputting chaos data associated with each thawing mode on the basis of the initial chaos data value P0 determined at the second step, and the fourth step of determining an output level of microwaves and a thawing time associated with each thawing mode on the basis of the chaos data outputted at the third step, and driving the magnetron 36 on the basis of the determined microwave output level and the determined thawing time.
Operation of the automatic thawing device 108 will now be descrlbed in more detail.
At the beginning stage of the cooking, the temperature sensing means 37 senses a variation in temperature of the food. Simultaneously, the moisture sensing means 38 senses a variation in the moisture (vapor) generated from the food.
The sensed temperature and moisture variations are applied to the microcomputer 39.
Upon receiving the temperature and moisture variations, the microcomputer 39 determines an initial chaos data value on the basis of the temperature and moisture variations and then sends the initial chaos data value to the chaos simulator 40.

Based on the received initial chaos data value, the chaos simulator 40 generates chaos data for an appropriate thawing and then sends the chaos data to the microcomputer 39.
Upon receiving the chaos data from the chaos simulator 40, the microcomputer 39 determines a thawing time and an output level of microwaves on the basis of the chaos data and controls the driving load 300 on the basis of the determined thawing time and the determined output level of microwaves.
Thus, an automatic thawing is executed.
During the automatic thawing operation, the turntable 21 continues its upward and downward movements. As a result, the microwaves emitted from the magnetron 36 are uniformly applied to all portions of the food. Accordingly, an optimum thawing is achieved.
The thawing procedure executed by the control unit (microcomputer~ 39 will now be described in conjunction with FIGS. 10 and 11.
First, the microcomputer 39 receives variations in sensing signals respectively outputted from the temperature sensing means 37 and the moisture sensing means 38 for the predetermined sensing time Ts. For simplicity of the description, the following description will be made in conjunction with an example wherein under a condition that the number of changeable modes initially taken is set by 12, as shown in FIG. 11, a temperature variation of 30 as shown in ~139598 FIG. 12A and a moisture variation of 20% decrease as shown in FIG. 12B are detected by the microcomputer 39.
Based on the temperature and moisture variations sensed --for the initial sensing time Ts, the initial chaos data value P0 (for example, P0 = 1.2) to be sent to the chaos simulator ~0 is determined by the microcomputer 39. Simultaneously, the total thawing time Td (for example, 48 minutes) is determined by the microcomputer 39.
Based on the initial chaos value P0 (P0 = 1.2) received, the chaos simulator 40 generates chaos data which is, in turn, sent to the microcomputer 39.
Assumes that the chaos simulator 40 generates chaos data of 1.2 _ 3.6 _ 6.5 - 2.4 _ 3.3 _ 7.8 _ 9.5 _ 8.8 _ 6.6 _ 4.5 _ 3.1 _ 2.6 _ ..... in a sequential manner. Among these chaos data, only ones corresponding to the number N (N = 12) of changeable modes are taken. The remaining chaos data are disregarded.
The microcomputer 39 receives the chaos data obtained from the chaos simulator 40 in the above-mentioned manner and then divides the previously determined total thawing time Td by the number N of changeable modes (N = 12) to determine a mode time Tm for each mode. In this example, the mode time Tm is 4 minutes (48 minutes/12 = 4 minutes).
Based on the determined mode time Tm and the chaos data, the microcomputer controls the output level of the magnetron 36 so as to ac,hieve an appropriate thawing.
In other words, the magnetron 36 outputs microwaves at intervals of 4 minutes at output levels of 12% 36% _ 65% _ -24% _ 33% _ 78% - 95% _ 88% _ 25% _ 85% _ 6~% _ 45% in a sequential manner. In such a manner, the food is thawed totally for 48 minutes.
As apparent from the above description, it is pogsible to achieve the thawing most approximating to that achieved under the natural condition because the thawing of food is carried out under the control of the microcomputer. Since no weight sensor is used, the manufacture cos. of the microwave oven can be reduced.
FIGS. 13A and 13B are schematic views respectively illustrating the grille/combination cooking control device in accordance with the present invention.
The grille/combination cooking control device which is denoted by the reference numeral 110 in FIGS. 13A and 13B is constructed by incorporating the turntable rotating motor 24A
and the turntable lifting/lowering motor 24B of the turntable lifting/lowering device 107 of FIG. 7 in accordance with the third embodiment of the present invention in the automatic thawing device 108 of FIGS. 8 and 9. In FIGS. 13A and 13B, elements respectively corresponding to those in FIGS. 7 to 9 are denoted by the same reference numerals.
FIG. 14 is a flow chart illustrating a grille/combination ~139598 cooking control method in accordance with the present invention. This method includes five steps, that is, the first step of determining whether a current cooking mode corresponds to the combination cooking mode or the grille cooking mode, the second step of when the current cooking mode has been determined to correspond to the grille cooking mode at the first step, lifting the turntable 21 to the maximum height, and then turning on the grille heater 35 while rotating the turntable 21 at a fixed position of the maximum height, thereby executing the grille cookiny, the third step of when ~he current cooking mode has been determined to correspond to the combination cooking at the first step, determining whether the current cooking mode corresponds to the microwave heating mode or the heater heating mode, the fourth step of when the current cooking mode has been determined to correspond to the combination cooking mode, turning on the magnetron 36 while moving the turntable 21 upwards and downwards and rotating the turntable 21, and the fifth step of when the current cooking mode has been determined to correspond to the heater heating mode, turning on the grille heater 35 while moving the turntable 21 upwards and downwards and rotating the turntable 21.
Now, the cooking control operation carried out in the grille/combination type microwave oven will be described in conjunction with FIG. 7, FIGS. 13A and 13B and FIG. 14.

As shown in FIG. 14, first, the microcomputer receives a cooking selection information from the user and determines whether the current cooking mode corresponds to the grille cooking mode or the combination cooking mode on the basis of-~~~~--~~
the received cooking selection information.
Where the grille cooking mode has been selected, the stepping motor, that is, th-e turntable lifting/lowering motor 24B shown in FIG. 7 is driven under a control of the microcomputer so that the turntable 21 is lifted to the maximum height. When the maximum height is sensed by the sensing switch 32, the turntable 21 is lifted no longer.
Thereafter, the grille heater 35 is energized, so that a heat is generated from the grille heater 35 to execute the cooking. During the cooking operation of the grille heater 35, the turntable rotating motor 24B is driven.
Since the turntable 21 rotates at a position near the grille heater 35, the heat generated from the grille heater 35 is uniformly applied to the food. As a result, a highest browning effect is obtained.
After a predetermined grille cooking time has elapsed, the turntable lifting/lowering motor 24B is driven again so as to lower the turntable 21 to the minimum height. When the minimum height is sensed by the sensing switch 33, the turntable 21 is fixed at the minimum height. Under this condition, the cooking operation is completed.

~139598 On the other hand, where the current cooking mode selected corresponds to the combination cooking mode, the cooking is executed while alternatingly repeating the heating by the microwaves and the heating by the heater. ~ ~
5Now, a control for the combination cooking will be described in detail.
When the microcomputer detects the combination cooking mode, it determines whether the current combination cooking mode corresponds to the microwave heating mode or the heater 0heating mode.
Where the current combination cooking mode has been determined to correspond to the microwave heating mode, the magnetron 36 is driven to execute the cooking by the microwaves. Simultaneously, the turntable rotating motor 24A
15and the turntable lifting/lowering motor 24B are driven, thereby causing the turntable to move upwards and downwards while rotating.
In this case, the turntable lifting/lowering motor 24B is driven at an i~creased speed so as to decrease the 20lifting/lowering interval of the turntable 21. Under this condition, the food can be uniformly heated.
When the current point of time reaches a mode change point in process of the microwave heating cooking operation, the current cooking mode is changed into the heater heating 25mode. At the heater heating mode, the heater 35 is driven to execute the g~ille cooking, In this case, the turntable rotating motor 24A and the turntable lifting~lowering motor 24B are driven, thereby causing the turntable to move upwards and downwards while rotating, in simil-ar--to~-the microwave heating mode.
In the heater heating mode, however, the turntable lifting/lowering motor 24B is driven at a lower speed than in the microwave heating mode so as to obtain a sufficient grille cooking effect of the food.
As the vertical movement speed of the turntable 21 is low in process of the grille cooking in the heater heating mode, the heat from the heater 35 is gently transferred up to the side surface and lower portion of the food. Accordingly, a sufficient browning effect of the food is obtained after completion of the cooking.
When the current point of time reaches a mode change point in process of the grille cooking in the heater heating mode, the current cooking mode is changed into the microwave heating mode again. The operation in the microwave heating mode is then repeated.
The above procedure is repeated up to the cooking end time. That is, the microwave Aeating and grille heater heating are alternatingly repeated to execute the combination cooking. When a predetermined combination cooking time has elapsed, the turntable lifting/lowering motor 24B is driven so - ~139~98 as to lower the turntable 21 to the minimum height. When the minimum height is sensed by the sensing switch 33, the turntable 21 is fixed at the minimum height. Under this condition, the combination~cooking operation is completed.
As the turntable 21 is positioned at its lowermost position after completion of the cooking, the user can take out the food easily.
Alternatively, the cooking of food may be controlled by determining the vertical movement speed of the turntable 21 depending on heating times of the microwave heating mode and the heater heating mode by use of the chaos simulator 40 shown in FIG. 9.
In this case, a natural cooking effect can be expected by controlling the vertical movement speed of the turntable 21 based on chaos data selected depending on the mode change between the microwave heating mode and the heater heating mode for the total cooking time. For example, the cooking time and the vertical movement speed of the turntable are controlled in a sequential manner respectively to be microwave heating-10 seconds and 2 mmjsec _ heater heating-50 seconds and 1.82 mm~sec _ microwave heating-10 seconds and 2.5 mm/sec _ heater heating-50 seconds and 3.4 mm~sec .... .
As apparent from the above description, the present invention provides a microwave oven including a turntable lifting/lowering device capable of vertically moving a turntable by an operation of a spiral gear, thereby achieving a stability even when a liquid food is cooked, and capable of eliminating use of any supporting member and rotation die adapted to achieve-the vertical movement of the turntable, thereby very simplifying the inner construction of a heating chamber. Since the microwave oven eliminates use of any weight sensor, the manufacture cost is reduced. The microwave oven in accordance with the present invention achieves a thawing approximating to that achieved under the natural condition because the thawing of food i3 carried out based on data obtained by simulating variations in t~mperature and ~oisture upon thawing in a simulator. The microwave oven also eliminates use of any shelf upon performing a grille cooking and a combination cooking. Consequently, it is possible to uniformly cook the food and to ensure a maximum grille cooking effect.
Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, addi.ions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A turntable driving device of a microwave oven comprising:
a turntable disposed in the microwave oven and adapted to move upwards and downwards and rotate while laying a food to be cooked thereon;
a rotation shaft coupled at an upper end thereof to a central portion of the turntable at a bottom surface of the turntable, the rotation shaft extending downwards from the turntable;
a turntable lifting/lowering gear integral with an upper portion of the rotation shaft around the rotation shaft, the turntable lifting/lowering gearing being provided at an outer surface thereof with spiral teeth;
a middle gear portion provided at the outer surface of the turntable lifting/lowering gear;
a turntable rotating gear fitted around a lower portion of the rotation shaft;
powering means adapted to supply a power for the vertical movement and rotation of the turntable;
control means adapted to control the powering means;
power transmission means adapted to transmit the power from the powering means to the turntable lifting/lowering gear and the turntable rotating gear; and position sensing means adapted to sense a maximum height of the turntable upon lifting and a minimum height of the turntable upon lowering.

2. A turntable driving device in accordance with claim 1, wherein the rotation shaft is provided with at an outer surface thereof with supporting grooves uniformly spaced from one another.

3. A turntable driving device in accordance with claim 2, wherein the turntable rotating gear is provided at an inner surface thereof with grooves respectively facing the supporting grooves.

4. A turntable driving device in accordance with claim 3, wherein the turntable rotating gear is provided with spring-loaded supporting protrusion pieces respectively received in the grooves of the turntable rotating gear, each of the supporting protrusion pieces having a tip received in each corresponding one of the supporting grooves of the rotation shaft.

5. A turntable driving device in accordance with claim 1, wherein the powering means comprises:
a motor adapted to supply a drive power for the turntable lifting/lowering gear and the turntable rotating gear, a gear shaft disposed in one side of the rotation shaft in parallel to the rotation shaft such that it is spaced a predetermined distance from the rotation shaft, a motor shaft gear coupled to the motor above the motor and adapted to receive the power generated from the motor, a middle gear mounted on the gear shaft and engaged with the motor shaft gear, a turntable rotation driving gear mounted on the gear shaft above the middle gear and engaged with the turntable rotating gear, and a turntable lifting/lowering driving gear mounted on the gear shaft above the turntable rotation driving gear and provided at an outer surface thereof with spiral teeth, the turntable lifting/lowering driving gear being engaged with the middle gear portion provided at the turntable lifting/lowering gear; and the control means comprises:
a microcomputer for executing a control for normal and reverse rotation drivings of the motor.

6. A turntable driving device in accordance with claim 1, wherein the powering means comprises:

a turntable lifting/lowering motor adapted to supply a power for the vertical movement of the turntable, and a turntable rotating motor adapted to supply a power for the rotation of the turntable;
the power transmission means comprises:
lifting/lowering power transmission means, and rotation power transmission means; and the control means comprises:
the turntable lifting/lowering motor, and the turntable rotating motor.

7. A turntable driving device in accordance with claim 6, wherein the lifting/lowering power transmission means comprises:
a gear shaft disposed in one side of the rotation shaft in parallel to the rotation shaft such that it is spaced a predetermined distance from the rotation shaft;
a motor shaft gear coupled to the turntable lifting/lowering motor above the turntable lifting/lowering motor and adapted to receive the power generated from the turntable lifting/lowering motor;
a middle gear mounted on the gear shaft and engaged with the motor shaft gear; and a turntable lifting/lowering driving gear mounted on the gear shaft above the middle gear and provided at an outer surface thereof with spiral teeth, the turntable lifting/lowering driving gear being engaged with the middle gear portion provided at the turntable lifting/lowering gear.

8. A turntable driving device in accordance with claim 6, wherein the rotation power transmission means comprises:
a gear shaft disposed in one side of the rotation shaft in parallel to the rotation shaft such that it is spaced a predetermined distance from the rotation shaft;
a motor shaft gear coupled to the turntable rotating motor above the turntable rotating motor and adapted to receive the power generated from the turntable rotating motor;
a middle gear mounted on the gear shaft and engaged with the motor shaft gear; and a turntable rotation driving gear mounted on the gear shaft above the middle gear and provided at an outer surface thereof with spiral teeth, the turntable rotation driving gear being engaged with the middle gear portion provided at the turntable rotating gear.

9. A turntable driving device in accordance with claim 1, wherein the position sensing means comprises:
a lower-limit idler gear provided at an upper portion of the turntable lifting/lowering gear and adapted to cut off the power transmission between the turntable lifting/lowering gear and the turntable lifting/lowering driving gear; and an upper-limit idler gear provided at a lower portion of the turntable lifting/lowering gear and adapted to cut off the power transmission between the turntable lifting/lowering gear and the turntable lifting/lowering driving gear.

10. A turntable driving device in accordance with claim 1, wherein the position sensing means comprises:
a circular switch plate attached to a lower surface of the turntable lifting/lowering gear so that it moves vertically together with the turntable lifting/lowering gear;
an upper-limit sensing switch disposed above the circular switch plate and adapted to sense the circular switch plate at a predetermined maximum height upon lifting; and a lower-limit sensing switch disposed beneath the circular switch plate and adapted to sense the circular switch plate at a predetermined minimum height upon lowering.

11. An automatic thawing control device of a microwave oven comprising:
a turntable disposed on a bottom surface of a heating chamber of the microwave oven;
a turntable lifting/lowering unit disposed beneath the heating chamber and adapted to move upwards and downwards and rotate the turntable;

a heater disposed at an upper portion of the heating chamber in the interior of the heating chamber and adapted to perform a grille cooking of a food laid on the turntable;
a magnetron disposed at one side wall of the heating chamber in outside of the heating chamber and adapted to perform a cooking by microwaves;
an intake port provided at one side wall of the heating.
chamber above the heater and adapted to introduce an external air in the interior of the heating chamber;
an exhaust port provided at the other side wall of the heating chamber not provided with the intake port and adapted to vent an exhaust gas generated in the heating chamber;
temperature sensing means disposed near the exhaust port and adapted to sense a variation in temperature around the exhaust port for a predetermined initial time;
moisture sensing means disposed at an upper wall of the heating chamber and adapted to a variation in moisture amount generated from the food for the predetermined initial time, and a microcomputer adapted to control the turntable lifting/lowerlng device and receive the temperature variation sensed by the temperature sensing means and the moisture variation sensed by the moisture sensing means.

12. An automatic thawing control device in accordance with claim 11, wherein the microcomputer determines an initial chaos data value on the basis of the received temperature variation and moisture variation and sends the determined initial chaos data value to a chaos simulator.

13. An automatic thawing control device in accordance with claim 12, wherein the chaos simulator generates chaos data about an appropriate thawing operation on the basis of the received initial chaos data value and sends the chaos data to the microcomputer so that the microcomputer determines a thawing time and an output level of microwaves on the basis of the chaos data.

14. An automatic thawing control method in a microwave oven, comprising the steps of:
(a) determining the number of changeable thawing modes and a sensing time when a thawing mode operation is set under a condition that a food to be thawed has been laid on a turntable of the microwave oven;
(b) driving temperature sensing means and moisture sensing means for the sensing time, thereby sensing a variation in temperature and a variation in moisture amount;
(c) determining a thawing time and an initial chaos data value on the basis of the temperature and moisture variations sensed at the step (b);

(d) outputting chaos data associated with each thawing mode on the basis of the initial chaos data value determined at the step (c);
(e) determining an output level of microwaves and a thawing time associated with each thawing mode on the basis of the chaos data outputted at the step (d); and (f) driving a magnetron on the basis of the determined microwave ou-put level and the determined thawing time.

15. A grille/combination cooking control device of a microwave oven comprising:
a turntable disposed on a bottom surface of a heating chamber of the microwave oven;
a turntable lifting/lowering unit disposed beneath the heating chamber and adapted to move upwards and downwards and rotate the turntable;
a heater disposed at an upper portion of the heating chamber in the interior of the heating chamber and adapted to perform a grille cooking of a food laid on the turntable;
a magnetron disposed at one side wall of the heating chamber in outside of the heating chamber and adapted to perform a cooking of the food by microwaves;
an intake port provided at one side wall of the heating chamber above the heater and adapted to introduce an external air in the interior of the heating chamber;

an exhaust port provided at the other side wall of the heating chamber not provided with the intake port and adapted to vent an exhaust gas generated in the heating chamber;
temperature sensing means disposed near the exhaust port;
moisture sensing means disposed at an upper wall of the heating chamber;
a microcomputer adapted to receive a cooking selection information from a user and determine whether the cooking selection information corresponds to a grille cooking or a combination cooking; and position sensing means adapted to sense an upper limit position and a lower limit position of the turntable.

16. A grille/combination cooking control device in accordance with claim 15, wherein the position sensing means comprises:
a circular switch plate operatively connected to the turntable so that it moves vertically together with the turntable;
an upper-limit sensing switch disposed above the circular switch plate and adapted to sense the circular switch plate at a predetermined maximum height upon lifting; and a lower-limit sensing switch disposed beneath the circular switch plate and adapted to sense the circular switch plate at a predetermined minimum height upon lowering.

17. A grille/combination cooking control method in a microwave oven, comprising the steps of:
(a) determining whether a current cooking mode corresponds to a combination cooking mode or a grille cooking mode;
(b) when the current cooking mode has been determined to correspond to the grille cooking mode at the step (a); lifting a turntable of the microwave oven to a predetermined maximum height, and then turning on a grille heater while rotating the turntable at a fixed position of the maximum height, thereby executing a grille cooking;
(c) when the current cooking mode has been determined to correspond to the combination cooking at the step (a), determining whether the current cooking mode corresponds to a microwave heating mode or a heater heating mode;
(d) when the current cooking mode has been determined to correspond to the combination cooking mode, turning on a magnetron while moving the turntable upwards and downwards and rotating the turntable; and (e) when the current cooking mode has been determined to correspond to the heater heating mode, turning on the grille heater while moving the turntable upwards and downwards and rotating the turntable.

18. A grille/combination cooking control method in accordance with claim 17, further comprising the step of downwards moving the turntable to the minimum height after completion of the cooking so that the user can take out the food easily.

19. A grille/combination cooking control method in accordance with claim 17, wherein the vertical movement speed of the turntable is controlled by a chaos simulator such that it is lower in the microwave heating mode than in the heater heating mode.