JPH0942680A - microwave - Google Patents

Abstract

(57) Abstract: A cooked food placed on a rotating dish can be heated uniformly and the electric field strength is prevented from locally concentrating in the heating chamber. SOLUTION: The microwave oven of the present invention includes a first rotary shaft 9 rotatably provided on the inner bottom portion of a heating chamber 3 so as to project upward and to rotate. A cylindrical second rotary shaft 10 is provided concentrically and rotatably on the outer circumference, and the rotary net 6 is rotatably driven by the second rotary shaft 10. The rotary plate 7 disposed on the upper side of the first rotary shaft 9 is rotationally driven by the first rotary shaft 9, and the first rotary shaft 9 and the second rotary shaft 9 are
The rotary shaft 10 is rotated at a different rotation speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven configured to heat a food on a rotary plate while rotating the rotary plate while the rotary plate is placed on the rotary net.

[0002]

In the microwave oven, a rotary net is rotatably provided on the inner bottom of the heating chamber, and a rotary dish is detachably mounted on the rotary net. . In this case, the rotary plate and the rotary net are configured to be integrally driven to rotate. Here, the rotary dish is made of, for example, heat-resistant glass, and the rotary net is made of, for example, a lattice-shaped steel plate subjected to enamel treatment. Further, of the microwaves supplied from the magnetron into the heating chamber, the microwaves reflected on the inner bottom surface of the heating chamber are passed through the rotary net and the rotary plate to be applied to the food on the rotary plate. There is.

In this structure, the microwave is hardly radiated to the portion (shadow portion) corresponding to the grid portion of the rotary net in the bottom portion of the cooked food. On the other hand, the microwave is sufficiently irradiated to the bottom surface portion other than the above portion of the cooked food. For this reason, there is a problem that uneven heating occurs in the food and the electric field strength is locally concentrated in the heating chamber.

Therefore, an object of the present invention is to provide a microwave oven capable of uniformly heating cooked food and preventing local concentration of the electric field intensity in the heating chamber.

[0005]

The microwave oven according to the present invention comprises:
A heating chamber that heats a food by microwaves supplied from a magnetron, a first rotation shaft that is provided on the inner bottom of the heating chamber so as to project upward, and is rotatably provided, and the first rotation shaft. It is rotatably driven by a cylindrical second rotary shaft that is concentrically provided on the outer periphery of the rotary shaft and is rotatably provided, and one of the first rotary shaft and the second rotary shaft. The rotary net and the rotary plate that is arranged above the rotary net and is driven to rotate by the other of the first rotary shaft and the second rotary shaft. It is characterized in that the rotation shaft and the second rotation shaft are configured to rotate at different rotation speeds.

According to the above construction, the rotary disc and the rotary net are rotated at different rotation speeds by rotating the first rotation shaft and the second rotation shaft at different rotation speeds.
As a result, the correspondence between the bottom surface of the cooked food on the rotating dish and the grid-like portion of the rotary net shifts according to the rotation, so that the microwaves are evenly applied to the bottom surface of the cooked food. Become. As a result, the food is uniformly heated, and the electric field strength is not locally concentrated in the heating chamber.

Further, in the above structure, the first rotary shaft disposed inside is provided so as to penetrate the rotary net, and the rotary disc is rotationally driven by the first rotary shaft to be disposed outside. It is preferable that the rotary net is rotationally driven by the second rotary shaft. Further, a sliding part or three or more roller means is provided on the outer peripheral part of the rotary net or rotary plate,
The rotary plate is configured to be rotatable relative to the rotary net by the sliding unit or three or more roller means, and the load acting on the rotary plate is applied to the sliding unit or 3
It is an even more preferable configuration to act on the rotary net through one or more roller means.

Furthermore, a first gear provided so as to rotate integrally with the first rotary shaft is provided, which is provided concentrically above the first gear and integrally with the second rotary shaft. A second gear provided so as to rotate, a third gear provided so as to be rotationally driven by a motor and meshing with the first gear, and further rotationally driven by the motor. A fourth gear that is provided and meshes with the second gear may be provided. With this configuration, it is possible to easily realize a configuration in which the first rotation shaft and the second rotation shaft are rotated at different rotation speeds with a simple configuration.

On the other hand, the first rotary shaft is rotatably supported via bearings press-fitted into the upper and lower ends of the cylindrical second rotary shaft, and the second rotary shaft is also supported by the heating chamber. It is preferable to rotatably support the mounting frame provided on the outer bottom portion of the bearing via a bearing. In this case, a weight sensor for detecting the weight of the food item placed on the rotary plate via the rotary plate, the roller means, the rotary net, the second rotary shaft, the second gear and the first gear is used. It is a good configuration to have. Further, it is even more preferable that the third gear and the fourth gear are composed of integrally formed two-stage gears, and that the two-stage gears are rotationally driven by one motor.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to a microwave oven with a heater will be described below with reference to the drawings. First, in FIG. 4 showing a schematic overall configuration of a microwave oven, an outer box 1 constituting a main body of the microwave oven is provided with an inner box 2 having a rectangular box shape with an open front surface.
The inside of the inner box 2 is a heating chamber 3. Outer box 1
A door 4 that opens and closes the front opening of the heating chamber 3 is provided on the front surface of, and an operation panel 5 is provided on the right side of the door 4.

Further, a machine room is provided on the right side of the heating chamber 3 in the outer box 1, and the magnetron, its drive circuit, and a fan device (not shown) for cooling the magnetron are provided in the machine room. Is provided. The magnetron is a waveguide (not shown) into the heating chamber 3.
The microwave oven is configured to heat and cook the food contained in the heating chamber 3 by supplying microwaves therethrough.

Further, the ceiling and bottom of the heating chamber 3 are
A flat heater (not shown) is provided. In addition, a hot air supply device (not shown) for circulating hot air into the heating chamber is provided on the back surface of the heating chamber 3. The above-mentioned heater or hot air supply device is configured to heat and cook (cook in the oven or grill) the food contained in the heating chamber 3.

As shown in FIG. 1, a rotary shaft 8 for rotationally driving the rotary net 6 and the rotary plate 7 is provided at a substantially central portion of the inner bottom of the heating chamber 3 so as to project upward. ing. The rotary shaft 8 is composed of, for example, a first rotary shaft 9 made of ceramic, and a cylindrical second rotary shaft 10 concentrically provided on the outer periphery of the first rotary shaft 9. In this case, as shown in FIG. 2, annular bearings 11 and 12 made of oil-impregnated metal or the like are press-fitted and fixed to the upper end portion and the lower end portion of the second rotary shaft 10. These bearings 1
By inserting the first rotary shaft 9 into the inside of 1 and 12,
The first rotating shaft 9 is rotatably supported by the second rotating shaft 10.

The upper end of the first rotary shaft 9 projects upward from the upper end of the second rotary shaft 10, and the lower end of the first rotary shaft 9 is the lower end of the second rotary shaft 10. Protruding downward from the section. At the lower end of the first rotating shaft 9 protruding downward, the first gear 13 is provided so as to rotate integrally.
Is integrally formed, for example, and is configured so that the lower end portion of the first gear covers the lower end portion of the first rotating shaft 9. Further, the second gear 14 is integrally provided at the lower end portion of the second rotating shaft 19, so that the second gear 14 can integrally rotate. The second gear 14 is rotatably mounted on the first gear 13. As a result, the second gear 14 is concentrically provided above the first gear 13.

The support mechanism for rotatably supporting the rotary shaft 8 (that is, the first rotary shaft 9 and the second rotary shaft 10) and the drive mechanism for rotationally driving the rotary shaft 8 will be described in detail.
First, a through hole 15a (see also FIG. 2) for inserting the rotary shaft 8 is formed in a substantially central portion of the bottom wall portion 15 of the heating chamber 13. A mounting plate 16 is fixed to the lower surface of the bottom wall portion 15 by welding or the like.
A first frame 17 is attached to the lower surface of 6 by being screwed. The second frame 18 is attached to the lower portion of the first frame 17.

The bottom wall portion 1 of the first frame 17
No. 5 has a through hole 17a in a portion corresponding to the through hole 15a.
(See FIG. 2) is formed, and the rotary shaft 8 is inserted into the through hole 17a. In this case, the through hole 17
In the burring portion 17b formed when forming a,
An annular bearing 19 made of oil-impregnated metal or the like is press-fitted and fixed. Then, by inserting the second rotary shaft 10 of the rotary shaft 8 into the bearing 19, the second rotary shaft 1
0 is rotatably supported with respect to the first frame 17.

A weight sensor 20 having a well-known structure is attached to the lower surface of the second frame 18 by, for example, screwing. The weight sensor 20 is composed of a fixed substrate 21 and a movable plate 22 provided on the lower surface of the fixed substrate 21 and composed of a leaf spring or the like. In this case, the through hole 17a of the first frame 17 of the second frames 18
A through hole 18a is formed in a portion corresponding to.
By inserting the lower end of the first rotating shaft 9 of the rotating shaft 8 (that is, the lower end of the first gear 13) into the through hole 18a, the lower end of the first rotating shaft 9 is weighed. Sensor 20
The movable plate 22 is rotatably abutted on the movable plate 22.

Here, the burring portion 18b formed when the through hole 18a is formed is rotatably (slidingly) fitted into the groove 13a formed in the lower end portion of the first gear 13. There is. As a result, the lower end portion of the first rotating shaft 9 becomes the second
It is rotatably supported by the frame 18. In this case, all the loads acting on the first rotating shaft 9 and the first gear 13 are configured to act on the weight sensor 20.

A motor (RT motor) 23 is attached to the lower surface of the step portion 18c formed at the right end of the second frame 18 in FIG. The rotation shaft 24 of the motor 23 penetrates the step portion 18c and projects upward. A two-stage gear 25 is provided on the protruding end of the rotary shaft 24 so as to rotate integrally therewith. The two-stage gear 25 is composed of a lower gear 26 and an upper gear 27. The lower gear 26 meshes with the first gear 13 of the first rotating shaft 9 to form a third gear. The upper gear 27 meshes with the second gear 14 of the second rotating shaft 10 to form a fourth gear. The central upper part of the two-stage gear 25 (upper fourth gear 27) is fitted into a through hole 17c formed in the first frame 17 and rotatably supported.

In the case of this structure, when the motor 23 is rotationally driven, the third gear 26 and the fourth gear 27 are rotated, so that the first gear 13 and the second gear 14 are rotationally driven. Therefore, the first rotary shaft 9 and the second rotary shaft 10 are configured to be rotationally driven. here,
The outer diameter dimension (that is, the number of teeth) of the first gear 13 is smaller than the outer diameter dimension (that is, the number of teeth) of the second gear 14. The outer diameter dimension (that is, the number of teeth) of the third gear 26 is the outer diameter dimension of the fourth gear 27 (that is, the number of teeth).
The number of teeth is smaller than the number of teeth. Accordingly, when the motor 23 is rotated, the rotation speed of the first rotation shaft 9 becomes, for example, twice the rotation speed of the second rotation shaft 10, in other words, the rotation of the first rotation shaft 9. The number (rotation angle) is 2 of the rotation number (rotation angle) of the second rotation shaft 10.
It is configured to double. Then, in the case of the present embodiment, the rotation speed of the first rotation shaft 9 is set to, for example, about 10 rpm, and the rotation speed of the second rotation shaft 10 is set to, for example, about 5 rp.
It is set to m. The number of teeth of the first gear 13 and the number of teeth of the third gear 26 are made equal.

On the other hand, as shown in FIG. 1, the second rotary shaft 1
A rotary net 6 is detachably attached to the upper end portion of 0. Here, as shown in FIG. 3, the rotary net 6 is formed by subjecting the surface of a circular steel plate in a lattice shape to enamel treatment. The rotary net 6 is in the shape of a circular dish as a whole, and as shown in FIG. 1, has a flat portion 28 and a flange portion 29 provided on the outer peripheral portion of the flat portion 28 so as to rise upward. are doing. Many openings 28 a are formed in the flat portion 28. In addition, the flat portion 28
A through hole 28b through which the upper end of the first rotating shaft 9 is inserted is formed in the central part of the. The inner diameter of the through hole 28b is smaller than the outer diameter of the second rotating shaft 10 and larger than the outer diameter of the first rotating shaft 9.

Further, the through hole 2 in the lower surface of the flat portion 28.
A cylindrical portion 30 is welded to the peripheral portion of 8b so as to project downward. The inner diameter of the cylindrical portion 30 is
The outer diameter of the second rotating shaft 10 is slightly larger than that of the second rotating shaft 10.
The upper end portion of is configured to be detachably fitted.
Then, when the upper end portion of the second rotating shaft 10 is fitted into the cylindrical portion 30, the cylindrical portion 3 has a rotation preventing structure (not shown).
0 (that is, the rotary net 6) and the second rotary shaft 10 are configured to rotate integrally.

On the outer peripheral surface of the flange portion 29 of the rotary net 6, there are three roller means, for example, a roller 31.
Is rotatably provided via a pin 32. These three rollers 31 are arranged at substantially equal intervals. The rotary plate 7 is detachably arranged on the upper side of the rotary net 6. The rotary plate 7 is made of heat-resistant glass, for example. On the lower surface of the rotary plate 7,
A fitting recess 3 that fits in the center of the upper end of the first rotating shaft 9
3 is formed, and an annular convex portion 34 to be mounted on the roller 32 of the rotary net 6 is formed on the peripheral edge portion. In this case, when the upper end portion of the first rotating shaft 9 is fitted into the fitting recess 33 of the rotating plate 7, the rotating plate 7 and the first rotating shaft 9 are integrally rotated by a rotation stopper structure (not shown). Has become. Further, since the annular convex portion 34 on the lower surface of the rotary dish 7 is placed on the roller 32 that freely rotates, the rotary dish 7 is configured to be rotatable with respect to the rotary net 6.

Next, the operation of the above configuration will be described. When the motor 23 is rotated, the third gear 26 and the fourth gear 2
The gears 26 and 2 are driven by rotating 7
The first gear 13 and the second gear 14 meshing with 7 are rotationally driven. As a result, the first rotary shaft 9 and the second rotary shaft 9
Since the rotary shaft 10 of the rotary shaft is rotated,
Is driven to rotate. At this time, the rotation speed (10 rpm) of the first rotation shaft 9 is equal to the rotation speed (5 r of the second rotation shaft 10).
pm), that is, the rotational speed of the rotary plate 7 is twice the rotational speed of the rotary net 6. Therefore, when the rotary plate 7 and the rotary net 6 start rotating clockwise from the position shown in FIG.
As shown in FIG. 5, when the rotary plate 7 rotates half a turn, the rotary net 6 rotates one quarter turn.

In the above embodiment, when microwaves are supplied from the magnetron into the heating chamber 3 to heat the food placed on the rotating dish 7 by microwave oven, the first rotating shaft 9 is moved to the first position. The rotating plate 7 is rotated at a rotation speed twice as high as the rotation speed of the rotary shaft 6 by rotating the rotary plate 7 at a rotation speed twice as high as the rotation speed of the rotary shaft 6. This allows
Since the correspondence between the bottom surface of the cooked food on the rotating dish 7 and the grid-like portions of the rotary net 6 is shifted depending on the rotation, the entire bottom surface of the cooked food is microwaved (especially in the heating chamber 3). The microwave reflected on the bottom surface) is uniformly irradiated. As a result, the food can be cooked evenly,
It is possible to prevent the electric field strength from being locally concentrated in the heating chamber 3.

In the case of the above embodiment, the first rotary shaft 9 provided inside the rotary shaft 8 is provided so as to penetrate the rotary net 6, and the rotary plate 7 is driven by the first rotary shaft 9. A second rotating shaft 10 which is rotationally driven and is arranged outside
Thus, the rotary net 6 is configured to be rotationally driven. Accordingly, it is possible to easily realize a configuration in which the two rotating shafts 9 and 10 arranged concentrically independently drive the rotary tray 7 and the rotary net 6 which are stacked in two stages.

Further, in the above embodiment, three rollers 31 are provided.
Is provided on the outer peripheral portion of the rotary net 6 and the rotary tray 7 is placed on these three rollers 31 so that the rotary tray 7 can be rotated with respect to the rotary net 6. It is possible to realize a structure in which the rotary plate 7 is freely rotated with a simple structure. In this case, since the load (weight of the food to be cooked) acting on the rotary dish 7 is applied to the rotary net 6 via the three rollers 31, the rotary dish 7 is stabilized on the rotary net 6. Can be rotated.

Furthermore, in the above embodiment, the first gear 1
3 is provided so as to rotate integrally with the first rotating shaft 9, and a second gear 14 is provided above the first gear 13 so as to rotate concentrically and integrally with the second rotating shaft 10. Then, a third gear 26 meshing with the first gear 13 is provided to be rotationally driven by the motor 23, and a fourth gear 27 meshing with the second gear 14 is rotationally driven by the motor 23. Set up in. As a result, the first rotating shaft 9 and the second rotating shaft 10 are rotated at different rotation speeds,
Specifically, the configuration in which the rotation speed of the first rotation shaft 9 is twice the rotation speed of the second rotation shaft 10 can be easily realized with a simple configuration.

On the other hand, in the above embodiment, the first rotary shaft 9
Is rotatably supported via bearings 11 and 12 which are press-fitted into the upper and lower ends of the second rotating shaft 10 having a cylindrical shape, and the second rotating shaft 10 is attached to the outer bottom of the heating chamber 3. The first mounting frame 17 provided is rotatably supported via a bearing 19. As a result, the first rotary shaft 9
It is possible to surely and easily realize a configuration in which the second rotating shaft 10 and the second rotating shaft 10 are rotatable with respect to each other, and to securely and easily realize a structure in which the second rotating shaft 10 is rotatably supported by the first mounting frame 17. it can.

In the above embodiment, the weight of the cooked food placed on the rotary dish 7 is calculated by changing the weight of the rotary dish 7, the roller 31, the rotary net 6, the second rotary shaft 10, the second gear 14 and the second gear 14. A weight sensor 20 for detecting the gear 13 is provided. With this configuration, the weight of the food on the rotating dish 7 can be accurately detected while the rotating dish 7 and the rotating net 6 are rotated at different speeds. Further, in the above embodiment, the third gear 26 and the fourth gear 27 are constituted by the integrally formed two-step gear 25, and the two-step gear 25 is rotationally driven by the one motor 23. did. As a result, the number of parts can be reduced, and the configuration in which the rotary plate 7 and the rotary net 6 are rotated at different speeds can be realized with an even simpler configuration.

In the above embodiment, the rotation speed of the first rotary shaft 9 is set to twice the rotation speed of the second rotary shaft 10. However, the present invention is not limited to this, and it is less than twice or two. It may be set to exceed double. Further, in the above-described embodiment, the rotation speed of the first rotating shaft 9 is set to be higher than the rotating speed of the second rotating shaft 10. However, on the contrary, the rotating speed of the first rotating shaft 9 is set to the second rotating speed. The rotational speed of the rotary shaft 10 may be slower than that of the rotary shaft 10, and in short, the rotational speeds of the two rotary shafts 9 and 10 may be different from each other.

Further, in the above embodiment, three rollers 31 are used.
Is provided on the rotary net 6, but four or more rollers may be provided on the rotary net 6. In addition, three or more rollers 31 are mounted on the rotary plate 7
It may be configured to be provided in. On the other hand, instead of the roller 31, a ball is rotatably housed in a ball receiving portion provided on the flange portion 29 of the rotary net 6, and the rotary plate 7 is placed on the ball.
May be mounted. In this case, it is preferable that three or more balls are rotatably provided on the rotary net 6.

Further, the provision of the roller 31 is stopped,
The lower surface of the rotary dish 7 may be directly slidably mounted on the flange 29 of the rotary net 6. in this case,
The upper surface portion of the flange portion 29 of the rotary net 6 and the lower surface portion of the rotary dish 7 that comes into contact with the flange portion 29 may be made of a material and shape that facilitates sliding.

Further, in the above embodiment, one motor 23
Although the two rotating shafts 9 and 10 are rotated by the above, the two rotating shafts 9 and 10 may be rotated by two motors instead. Furthermore, although the first gear 13 is integrally molded with the first rotating shaft 9, the first gear 13 as a separate member may be fitted and fixed to the first rotating shaft 9. Further, although the second gear 14 and the second rotary shaft 10 are integrally formed, that is, configured by one member, instead of this, the second gear 14 is replaced by the second rotary shaft 10.
May be integrally formed with the second rotary shaft 10, and the first gear 14 which is a separate member may be fitted and fixed to the second rotary shaft 10.
On the other hand, although the third gear 26 and the fourth gear 27 are composed of one member (two-stage gear 25), they may be composed of two members (two gears).

[0035]

As is apparent from the above description, the present invention rotatably drives the first rotary shaft for rotating one of the rotary plate and the rotary net and the other of the rotary plate and the rotary net. Since the second rotating shaft is rotated at a different rotation speed, the bottom surface of the cooking product placed on the rotating dish is uniformly irradiated with microwaves, and the cooking product is uniformly distributed. It has an excellent effect that the electric field strength can be prevented from being locally concentrated in the heating chamber as well as being heated.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of the vicinity of a bottom surface of a heating chamber showing an embodiment of the present invention.

FIG. 2 is an enlarged vertical front view of the periphery of a first rotary shaft and a second rotary shaft.

FIG. 3 (a) is a top view of a rotary net and a rotary dish, and FIG. 3 (b) is a top view showing a state in which the rotary net is rotated by a quarter turn (half turn of the rotary dish)

FIG. 4 is a perspective view of the entire microwave oven.

[Explanation of symbols]

3 is a heating chamber, 6 is a rotary net, 7 is a rotary plate, 9 is a first rotary shaft, 10 is a second rotary shaft, 11, 12 are bearings, 13 is a first gear, and 14 is a second gear. , 15 is a bottom wall portion, 15a is a through hole, 17 is a first frame, 17a is a through hole, 17
b is a burring portion, 18 is a second frame, 18a is a through hole, 18b is a burring portion, 19 is a bearing, 20 is a weight sensor, 23 is a motor, 24 is a rotating shaft, 25 is a two-stage gear, and 26 is a first gear. 3 is a gear, 27 is a fourth gear, 28b is a through hole, 29 is a flange portion, 30 is a cylindrical portion, 31 is a roller (roller means), 32 is a pin, 33 is a fitting concave portion, and 34 is an annular convex portion. Show.

Claims (7)

[Claims] 1. A heating chamber for heating a food item by microwaves supplied from a magnetron, and a first rotating shaft projecting upward and rotatably provided on an inner bottom of the heating chamber. A cylindrical second rotation shaft that is concentrically provided on the outer periphery of the first rotation shaft and is rotatably provided, and either the first rotation shaft or the second rotation shaft. A rotary net which is rotatably driven by one side; and a rotary plate which is arranged above the rotary net and is rotationally driven by the other of the first rotary shaft or the second rotary shaft. A microwave oven, wherein the first rotary shaft and the second rotary shaft are configured to rotate at different rotational speeds. 2. A first rotary shaft arranged inside is provided so as to penetrate the rotary net, and a rotary plate is rotationally driven by this first rotary shaft, and a second rotary shaft arranged outside is provided. The microwave oven according to claim 1, wherein the rotary net is rotationally driven by the shaft. 3. A sliding part or three or more roller means is provided on an outer peripheral portion of a rotary net or a rotary dish, and the rotary plate is opposed to the rotary net by the sliding part or three or more roller means. And the load acting on the rotary plate is applied to the sliding portion or 3
The microwave oven according to claim 1 or 2, wherein the microwave oven is configured to act on the rotary net through one or more roller means. 4. A first gear provided so as to rotate integrally with a first rotating shaft, and a first gear concentrically provided above the first gear and a second gear.
A second gear that is provided so as to rotate integrally with the rotating shaft of the third gear, a third gear that is provided so as to be rotationally driven by a motor, and that meshes with the first gear, and is rotationally driven by the motor. The microwave oven according to any one of claims 1 to 3, further comprising a fourth gear that is provided in such a manner as to mesh with the second gear. 5. The first rotating shaft is rotatably supported via bearings press-fitted into the upper and lower ends of a cylindrical second rotating shaft, and the second rotating shaft is The microwave oven according to any one of claims 1 to 4, wherein the microwave oven is rotatably supported by a mounting frame provided on an outer bottom portion of the heating chamber via a bearing. 6. The weight of the food placed on the rotating dish is
The rotary plate, roller means, rotary net, second rotary shaft, second
6. The microwave oven according to claim 4, further comprising a weight sensor that detects the weight through the gear and the first gear. 7. The third gear and the fourth gear are composed of integrally formed two-stage gears, and the two-stage gears are rotationally driven by one motor. Item 7. A microwave oven according to any one of Items 4 to 6.