JPH06223962A - Microwave oven - Google Patents

Abstract

PURPOSE:To uniformly and effectively heat an object to be heated without vertically moving the object. CONSTITUTION:Microwaves generated by a magnetron 15 are fed into a cooking chamber 13 constituted of an inner box 12 from a radiation port 17a. A reflector unit 20 is provided at the outside portion of an opening section 12a formed on the left side wall face of the inner box 12. The reflector unit 20 is constituted so that a reflector 35 provided in a fitting box 34 is reciprocated between a projection position (a) and an immersion position (b) by a stepping motor 32. The phase of the reflected waves of microwaves is continuously changed by the reciprocating motion of the reflector 35, and the distribution of the electric field intensity in the cooking chamber 13 is changed with the passage of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven for heating an object to be heated by supplying a microwave into a cooking chamber.

[0002]

2. Description of the Related Art In a microwave oven for microwave heating, the unevenness of the electric field is generated depending on the position in the cooking chamber due to the standing wave of the microwave, and heating unevenness of the object to be heated is likely to occur. There is. Therefore, it is necessary to devise a method for uniformly heating the entire object to be heated. Where first
The outline of the principle of uneven heating will be briefly described with reference to FIG.

Generally, a microwave oven converts the microwave of 2450 MHz output from the magnetron 1 into the waveguide 2
Through the inside of the cooking chamber 3 having a width of, for example, about 34 cm to create an electric field in the cooking chamber 3
Induction heating. In this case, the wave period λ of the microwave is about 12 cm, and the propagation state (wave period and spread) of the microwave radiated from the predetermined point P at the exit of the waveguide 2 is indicated by the periodic line L.

Since one microwave wave travels between cycles, there is a portion with large energy and a portion with small energy between them, and unevenness of the electric field is generated in the cooking chamber 3. For example, if the portion of the periodic line L has a peak of energy, the energy becomes small in the middle portion between the periodic lines L, so that the heating target A has uneven heating.
In addition, the heating state actually greatly depends on the molecular structure of the object A to be heated.

Conventionally, in order to improve the uneven heating caused by the unevenness of the electric field depending on the position in the cooking chamber and to uniformly heat the object A to be heated, a structure as shown in FIGS. Has been adopted.

That is, in the structure shown in FIG. 10, a stirrer fan 4 (which rotates a blade-shaped radio wave reflector) is provided on the ceiling of the cooking chamber 3, and the incident angle of microwaves is changed to eliminate the peak energy. I am trying. Also, FIG.
In FIG. 1, the turntable 5 on which the article A to be heated is placed is provided on the bottom surface of the cooking chamber 3, and by rotating this, the position of the article A to be heated is changed to achieve uniform heating. I am trying. Furthermore, the thing shown in FIG. 12 is equipped with both the above-mentioned stirrer fan 4 and the turntable 5.

The one shown in FIG. 13 corresponds to the one shown in FIG.
This is a further improvement of the one described above. By mounting a roller 7 on the lower surface of the turntable 6 and rolling it on a roller receiver 8 having wavy undulations, the turntable 6 can be moved up and down simultaneously with rotation. It is the one.
According to this, the object A to be heated not only rotates but also moves up and down, so that even the objects A to be heated having various shapes, especially those having a large height dimension, can be effectively heated uniformly. You can do it.

[0008]

The structure as shown in FIG. 10 to FIG. 13 can obtain a certain effect in improving the heating unevenness of the object A to be heated. However, FIG.
In the structures shown in FIGS. 0 to 12, the effect of uniform heating cannot be said to be sufficient, and the effect of uniform heating is superior to those shown in FIG.
Even in the above structure, since the object to be heated A is moved up and down, there are the following problems.

That is, milk or liquor contained in a cup may be placed on the turntable 6 as the object A to be heated. Even in such a case, the drink in the cup may be spilled. In order to prevent this, the turntable 6 must be smoothly moved up and down while keeping it horizontal. For this reason, extremely high accuracy is required for the mechanism for moving up and down, and there is a situation in which smoothness of up and down movement is lost due to deterioration over time such as abrasion, and it is difficult to prevent this.
In addition, there is a case where the heavy object A to be heated must be moved up and down, a large driving force is required for the drive system, and high accuracy as described above is required, and a large cost increase is also required. I was invited.

In addition, since there is a case where the object A to be heated having a large height is placed and the smooth vertical movement is required as described above, the stroke of the vertical movement of the turntable 6 is small. However, the effect of uniform heating was not obtained as expected.
Furthermore, there is a problem that the user feels anxiety that the cup may fall if the cup containing the drink moves up and down.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a microwave oven capable of effectively achieving uniform heating of an object to be heated without vertically moving the object to be heated. is there.

[0012]

The microwave oven of the present invention comprises:
It is characterized in that the wall surface of the cooking chamber is provided with a radio wave reflector that reciprocates in the retracting direction with respect to the inside of the cooking chamber.

Further, in this case, it is more effective if the radio wave reflector is configured to diffusely reflect microwaves.

[0014]

According to the above means, the microwave supplied into the cooking chamber hits the radio wave reflector provided on the wall surface of the cooking chamber and is reflected. The object to be heated contained in the cooking chamber is subjected to dielectric heating by being placed in an electric field formed by the radiated microwaves and the reflected microwaves.

At this time, since the radio wave reflector reciprocates in and out of the cooking chamber, the microwave reflection position, that is, the reflection angle, changes with time, and the phase of the reflected wave is continuous. Will change. Therefore, even if there is a part with large energy and a part with small energy during one wave of the microwave, the distribution of the electric field strength in the cooking chamber is always changed with the change of the phase. become.

If the radio wave reflector is configured to diffusely reflect microwaves, the microwaves will be reflected in random phases, and the electric field strength in the cooking chamber can be made more uniform. .

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment (corresponding to claim 1) of the present invention will be described below with reference to FIGS. First, the overall configuration of the microwave oven according to the present embodiment will be briefly described with reference to FIG. This microwave oven includes a rectangular box-shaped outer box 11 and a rectangular box-shaped inner box 12 having an open front surface.
Is arranged. The inside of this inner box 12 is the cooking chamber 1.
It is said to be 3. Although not shown, on the front surface of the outer box 11, an opening (doorway) communicating with the inner box 12 (the cooking chamber 13) is provided, and a door for closing the opening is attached so as to be openable and closable. There is.

A machine room 14 is provided on the right side in the drawing of the cooking room 13 in the outer box 11. This machine room 1
In 4, the magnetron 15 and the circuit for driving it,
A control device 16 including a microcomputer and the like are provided. Microwaves generated by the magnetron 15 pass through the waveguide 17 and are supplied into the cooking chamber 13 from a radiation port 17a opening on the right side wall of the inner box 12.

A turntable 18 on which an object to be heated (not shown) is placed is provided at the bottom of the cooking chamber 13, and the turntable 18 is provided at the outer bottom of the inner box 12. It is adapted to be rotationally driven by a motor 19. Furthermore, the inner box 1 facing the radiation port 17a
2, a circular opening 12a is formed on the left side wall surface over most of the surface, and a reflector unit 20 to be described later in detail is provided on the outer side portion of the opening 12a. .

An operation panel 21 is provided on the right side of the front surface of the outer box 11 (to the right of the door). The operation panel 21 is provided with keys 22 such as a "warm" key 22a, a "thaw" key 22b, a start key 22c, a cancel key 22d, and a knob 23 for setting a heating time, and the time and cooking mode. A display unit 24 is provided for displaying (whether it is warm or thawed) and the like.

The control device 16 controls the magnetron 15 and the like in accordance with a control program based on the operation of the operation panel 21 by the user, and executes heating and cooking. At this time, the power supply 25 is connected to an inverter circuit 27 for driving the magnetron 15 and a relay 28 for driving the motor 19 via a door switch 26 that is closed when the door is closed. The control device 16 controls driving and stopping of the turntable 18 by turning on and off the relay 28.

The magnetron 15 is driven via the inverter circuit 27, the high frequency transformer 29, and the high voltage circuit 30, and the inverter circuit 27 is controlled by the controller 16 by the inverter control circuit 31. It is designed to be controlled via. Further, the control device 16 controls a stepping motor 32 of a reflector unit 20 described later via a drive circuit 33.

Now, regarding the reflector unit 20,
It will be described with reference to FIGS. 1 and 2. This reflector unit 2
0 is equipped with a reflector 35 as a radio wave reflector in a mounting box 34, and a stepping motor 32 causes the reflector 35 to reciprocate in and out of the cooking chamber 13, that is, in the left and right direction in the drawing. Is configured.

As shown in FIG. 2, the mounting box 34 is in the form of a thin box whose right side surface is open, and a bearing 36 is mounted at the center of the left side wall thereof. A shaft member 37 having a female screw portion 37a that opens at the left end surface is supported by the bearing 36 so as to be slidable in the thrust direction (left and right direction in the drawing). At this time, the bearing 36 and the shaft member 37 are fitted by a so-called D cut, and the shaft member 37 is in a rotation stop state.

The reflecting plate 35 is made of a metal that reflects microwaves with a high reflectance and is formed in a thin disk shape having a size corresponding to the opening 12a on the left side wall surface of the inner box 12, and has a central portion at the center thereof. Is attached to the tip (right end) of the shaft member 37 so as to be substantially parallel to the left side wall surface. In this case, the surface (right wall surface) of the reflection plate 35 is a flat reflection surface.

The stepping motor 32 is attached to the motor mounting plate 38 on the left outer surface of the mounting box 34.
Is installed through. This stepping motor 3
A male screw portion 39a is formed on the output shaft 39 of No. 2, and the male screw portion 39a is formed on the female screw portion 3 of the shaft member 37.
It is screwed to 7a.

Thus, for example, the stepping motor 32
By the positive rotation of the
5 is displaced to the right, that is, in the direction in which it is pushed (extruded) into the cooking chamber 13, and by the reverse rotation of the stepping motor 32, the shaft member 37 is moved to the left and the reflecting plate 35 is moved from the left, that is, from the cooking chamber 13. It is displaced in the retracting direction. As will be described later in the description of the operation, the stepping motor 32 is rotated in the normal and reverse directions by the control device 16 via the drive circuit 33 (see FIG. 3). It reciprocates between the pushing position indicated by the solid line in 2 and the retracted position indicated by the alternate long and two short dashes line in FIGS. 1B and 2.

The reflector unit 2 constructed as described above
No. 0 is attached so that the flange-shaped portion 34a at the right end of the mounting box 34 is placed on the periphery of the opening 12a of the inner box 12 from the outer surface side. At this time, the opening 12a of the inner box 12 is provided with a partition plate 40 made of, for example, transparent heat-resistant glass that transmits microwaves so as to close the opening 12a. It prevents people from touching 35.

Next, the operation of the above configuration will be described with reference to FIGS. 4 to 6 show the control device 16
Is a flow chart showing the procedure of control executed by
Of these, FIG. 4 shows an interrupt routine, and FIGS. 5 and 6 show a main routine. Incidentally, FIG. 5 and FIG.
Although it is a single flowchart, it is shown divided into two drawings because of space limitations.

First, the interrupt routine of FIG. 4 will be briefly described. This interrupt routine is always executed at regular time intervals when the main routine described later is executed, and here, the cancel key 22d and the opening / closing of the door are detected. That is, when the user presses the cancel key 22d of the operation panel 21 (step S
If Yes in 31), the all clear process is executed (step S32).

The open / close state of the door is detected by detecting the on / off state of the door switch 26 (step S
33), if the door switch 26 is on, that is, the door is closed (Yes), 1 is set in the variable TC (step S3).
4) If the door switch 26 is off, that is, the door is open (No in step S33), the variable TC is cleared to 0 (step S35). As is apparent from FIG. 3, when the door switch 26 is off, that is, when the door is open, power supply to the magnetron 15 and the turntable driving motor 19 is prohibited.

Next, the main routine of FIGS. 5 and 6 will be described. When cooking, the user
First, the object to be heated is placed on the turntable 18, housed in the cooking chamber 13, and the door is closed. Thereafter, the operation panel 21 is operated to select a desired cooking mode and set a cooking time.

A cooking mode is selected in steps S1 to S4, and a cooking time is set in steps S5 and S6. That is, depending on the user, the "warm up" key 22
When a is operated (step S1), the cooking mode is set and cooking is set, and that effect is displayed on the display unit 24 (step S2). On the other hand, when the "thawing" key 22b is operated (step S3), the cooking mode is set to thaw cooking, and that effect is displayed on the display unit 24 (step S3).
4). After the selection of this cooking mode, when the knob 23 is rotated by the user (step S5), the cooking time is set according to the rotation amount and the time is displayed on the display unit 24 (step S5). S6).

Now, the cooking can be started, and the user waits for the start key 22c to be pressed (step S9). In this case, the start key 22c is
The set cooking time is not 0 minutes (step S7), and the variable TC is 1, that is, the door is closed (step S7).
8) will be accepted on condition.

When the start key 22c is turned on (Yes in step S9, see FIG. 6 below), in steps S10 to S18, the energization control of the stepping motor 32 of the reflector unit 20 is performed as described later. Be seen. At the same time, heating and cooking are started, and the countdown of the set time and the display of the display unit 24 are performed (step S19). The heating and cooking are performed by giving a start permission signal to the inverter control circuit 31 (step S20) to drive the magnetron 15 and energize the motor 19 to rotate the turntable 18. By driving the magnetron 15, the generated microwaves are supplied from the radiation port 17a into the cooking chamber 13 through the waveguide 17, and the object to be heated on the turntable 18 is placed in the electric field formed by the microwaves. , Dielectric heating, warming or thawing.

Such heating and cooking is continuously executed until the time reaches 0 minutes by the countdown of the set time (step S21), and when the set time has elapsed (Yes in step S21), the heating and cooking is completed. Then, the all clear process is performed (step S22). The output control method of the magnetron 15 is different due to the difference in the cooking mode.

A variable CW having a value of 0 or 1 is used for controlling the energization of the stepping motor 32 in steps S10 to S18. If the value of the variable CW is 0 (Yes in step S10), a positive rotation pulse is given to the stepping motor 32, and the reflection plate 35 is moved to the right (extrusion direction) ( Step S11). On the other hand, if the value of the variable CW is 1 (Yes in step S12), a reverse rotation pulse is given to the stepping motor 32, and the reflection plate 35 is moved to the left (immersion direction). (Step S13).

At this time, the rotation angle (the given number of pulses) of the stepping motor 32 is constantly checked, and when the stepping motor 32 rotates a predetermined angle in the forward rotation direction, that is, when the reflection plate 35 reaches the pushing position (step S1).
(Yes in 4), the value of the variable CW is set to 1 (step S15). On the other hand, stepping motor 3
When 2 rotates in the reverse rotation direction by a predetermined angle, that is, when the reflection plate 35 reaches the retracted position (Yes in step S16), the variable CW
Is set to 0 (step S17).

As a result, the reflecting plate 35 has the pushing position indicated by the solid line in FIGS. 1A and 2 during the heating and cooking.
It is configured to constantly reciprocate between the retracted position shown by the two-dot chain line in FIGS. 1 (b) and 2. The rotation angle (pulse number) of the stepping motor 32 is 1
It is stored in the non-volatile memory when the heating and cooking of one time is completed, and the control of the stepping motor 32 is continued from that time when the next cooking and heating is executed.

Thus, in this embodiment, the cooking chamber 13
Since the reflecting plate 35 is disposed on the left wall surface of the microwave oven, the microwave radiated from the radiation port 17a into the cooking chamber 13 travels leftward in the cooking chamber 13 and hits the reflecting plate 35 to be reflected to the right. It will progress toward you. In FIG. 1, the propagation state (wave period and spread) of the microwave radiated from the center point P of the radiation port 17a at this time is shown by periodic lines L1 to L1.
It is indicated by L11. The object to be heated contained in the cooking chamber 13 is dielectrically heated by being placed in an electric field formed by the microwaves.

At this time, the reflection plate 35 is constantly reciprocating between the pushing position shown in FIG. 1A and the immersion position shown in FIG. The angle changes with time, and the phase of the reflected wave changes continuously. For example, the positions of the periodic lines L3 and L9 are shown in FIG.
Comparing (a) and (b), it can be understood that the phase of the reflected wave is largely deviated.

Here, there is a portion with large energy and a portion with small energy in one wave of the microwave, and the cooking chamber 13
There are circumstances in which the distribution of the strength of the electric field occurs in the inside,
With the above-mentioned change in the phase of the reflected microwaves, the magnitude distribution of the electric field strength in the cooking chamber 13 is constantly changed with time. Therefore, the object to be heated is always placed in an electric field whose strength changes, and the entire object is heated uniformly.

By the way, the reflection plate 35 having the above-mentioned function is limited to a partial change in the phase of the microwave even when a small reflector is reciprocated, so that the larger the reflection surface area, the smaller the reflection surface area. It is clear that it is more effective than Here, the problem is how much the area of the reflection surface of the radio wave reflector is required. According to the experiments and studies of the present inventors, if the area of 25% or more of one surface of the cooking chamber 13 is, It has become clear that the effect of uniform heating can be sufficiently obtained.

As described above, according to this embodiment, the cooking chamber 13
Since a reflection plate 35 that reciprocates in and out of the inside of the cooking chamber 13 is provided on the wall surface of the cooking chamber 13 to change the magnitude distribution of the electric field strength in the cooking chamber 13, FIG. Unlike the conventional structure that moves the heated object up and down like the conventional structure shown in Fig. 1, evenly moving the heated object does not cause spillage of drinks, high cost, user's anxiety, etc. The heating can be extremely effectively performed.

Further, particularly in the present embodiment, the area of the reflection plate 35 is large so as to occupy most of the left wall surface of the cooking chamber 13, so that the impedance matching can be improved. That is, since the reciprocating reflector 35 is large, the same effect as changing the width dimension and shape of the cooking chamber 13 can be obtained. For example, by adjusting the reciprocating stroke of the reflector 35, the best impedance matching can be achieved. Can be easily obtained. As a result, it is possible to obtain the effect of improving the heating efficiency and extending the life of the magnetron 15.

7 and 8 show a second embodiment of the present invention (corresponding to claim 2). This embodiment is different from the first embodiment in the structure of the reflector unit 51. In the first embodiment, the structure is merely that the reflection plate 35 having a flat reflection surface is reciprocated. But
In addition to this, in the present embodiment, the reflection plate 5 serving as a radio wave reflector is added.
2 is configured to diffusely reflect microwaves.

That is, as shown in FIG.
The disk is made of a metal that reflects microwaves with a high reflectance, and is formed by having, for example, four blade pieces 53 made of the same metal on its surface. Further, although not shown in detail, spur gear-shaped teeth are formed over the entire circumference on the outer peripheral portion of the reflection plate 52. As shown in FIG. 7, the reflection plate 52 is rotatably attached to the tip of the shaft member 54 and provided in the attachment box 55. As described above, rotation of the stepping motor 32 causes the reflection plate 52 to move to the push-out position and the retracted position. It is designed to reciprocate between.

A rotation motor 56 is attached to the lower portion of the rear surface of the mounting box 55, and its output shaft protruding into the mounting box 55 has a thrust direction (left and right) which meshes with teeth on the outer periphery of the reflection plate 52. A long gear 57 is attached in the (direction). The teeth on the outer periphery of the reflection plate 52 are configured to slide in the thrust direction with respect to the gear 57, and are rotated about the shaft member 54 by the rotation of the gear 57.

The control device (not shown) rotates the stepping motor 32 in the normal and reverse directions at the time of heating and cooking.
The rotation motor 56 is driven, whereby the reflection plate 52 is rotated while reciprocating in the left-right direction between the pushing position and the retracted position.

According to this structure, the phase of the reflected wave can be continuously changed by reciprocating the reflecting plate 52 in the left-right direction, similarly to the above-described embodiment, and the electric field in the cooking chamber 13 can be changed. You can change the magnitude distribution of the strength of the. Then, in addition to that, the microwave is reflected in a random phase by the rotation of the reflection plate 52 having the blade pieces 53, and the electric field strength in the cooking chamber 13 becomes more uniform. As a result, uniform heating of the object to be heated can be achieved more effectively.

In the second embodiment, the reflection plate 5
2 is reciprocated in the left-right direction by the stepping motor 32 and is rotated by the rotation motor 56. However, the reflection plate 5 is rotated by one drive source (motor).
It may be configured to perform both reciprocating movement and rotation of the two. Further, the blade piece 53 is provided on the surface of the reflection plate 52, but as a configuration for irregularly reflecting the microwave,
The reflecting surface of the reflecting plate 52 may be formed in an uneven shape.

In addition, the present invention is not limited to the above-mentioned respective embodiments. For example, the position where the radio wave reflector is provided is not limited to the left wall surface, but the vertical and horizontal directions in the cooking chamber,
Any of the inner wall surface portions can obtain substantially the same actions and effects, and can be appropriately modified and implemented within a range not departing from the gist.

[0053]

As is apparent from the above description, according to the microwave oven of the present invention, the wall surface of the cooking chamber is provided with the radio wave reflector that reciprocates in the retracting direction with respect to the inside of the cooking chamber. Since it is provided, it is possible to change the magnitude distribution of the electric field strength in the cooking chamber over time, and as a result, it is possible to effectively heat the object to be heated uniformly without moving the object to be heated up and down. It has an excellent effect that it can be done.

Further, if the radio wave reflector is configured to diffusely reflect microwaves, the microwaves will be reflected in random phases, and the electric field strength in the cooking chamber can be made more uniform. The uniform heating of the object to be heated can be achieved more effectively.

[Brief description of drawings]

FIG. 1 shows a first embodiment of the present invention, and is a diagram showing a propagation state of microwaves in a cooking chamber when a reflection plate is at an extrusion position (a) and when the reflection plate is at an immersion position (b).

FIG. 2 is an enlarged vertical sectional front view of a reflector unit portion.

FIG. 3 is a diagram showing an overall configuration of a microwave oven.

FIG. 4 is a flowchart showing an interrupt routine.

FIG. 5 is a flowchart showing a main routine (No. 1).

FIG. 6 is a flowchart showing a main routine (No. 2).

FIG. 7 is a diagram corresponding to FIG. 2 showing a second embodiment of the present invention.

FIG. 8 is a perspective view of a reflector.

FIG. 9 is a diagram for explaining the principle of occurrence of unevenness in the strength of an electric field.

FIG. 10 is a schematic vertical sectional front view of a conventional microwave oven.

FIG. 11 is a view corresponding to FIG. 10 showing another conventional example.

FIG. 12 is a view corresponding to FIG. 10 showing a different conventional example.

FIG. 13 is a view corresponding to FIG. 10 showing still another conventional example.

[Explanation of symbols]

In the drawings, 11 is an outer box, 12 is an inner box, 12a is an opening, 1
3 is a cooking chamber, 15 is a magnetron, 16 is a controller, 1
7 is a waveguide, 17a is a radiation port, 18 is a turntable,
20 and 51 are reflector units, 32 is a stepping motor, 34 and 55 are mounting boxes, 35 and 52 are reflectors (radio wave reflectors), 37 and 54 are shaft members, 40 is a partition plate, 53 is a blade piece, 56 Is a rotation motor, and 57 is a gear.

Claims (2)

[Claims] 1. A method of heating an object to be heated housed in a cooking chamber by supplying microwaves to the cooking chamber, wherein a wall surface portion of the cooking chamber appears in and out of the cooking chamber. A microwave oven provided with a radio wave reflector that reciprocates in a predetermined direction. 2. The microwave oven according to claim 1, wherein the radio wave reflector is configured to diffusely reflect microwaves.