JPH0590884U - microwave - Google Patents

Abstract

(57) [Summary] [Purpose] Foods of various shapes and sizes are heated uniformly and efficiently regardless of their shapes and sizes. [Configuration] A waveguide 3 is provided outside the heating chamber 2. A turntable 10 for placing food is provided inside the heating chamber 2. A horizontal microwave radiation part 12b electromagnetically coupled to the waveguide 3 is provided above the turntable 10 in the heating chamber 2.
A radiation antenna 12 having Radiation antenna 12,
The radiating part 12b is movable so that the vertical position thereof is variable.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 This invention relates to a microwave oven.

[0002]

[Problems to be solved by conventional techniques and devices]

 In the microwave oven, in order to uniformly and efficiently heat food (object to be heated), microwaves must be uniformly applied to each part of the food to be heated. Therefore, conventionally, a metal stirrer was provided near the waveguide port in the heating chamber to stir microwaves with the stirrer, or the food placing turntable provided in the heating chamber was set to be rotatable. , I was stirring the microwaves by rotating the table. In addition, a crankshaft-shaped rod antenna that is electromagnetically coupled to the microwave generation means and is rotatable and a plurality of auxiliary antennas that are parallel to this are provided in the heating chamber, and the rod antenna is used during cooking. A microwave oven has also been proposed, in which secondary rotation is performed to feed a plurality of auxiliary antennas, and microwaves are diffusely reflected to uniformly irradiate food with microwaves (see Japanese Utility Model Publication No. 62-150894). ..

However, in these conventional microwave ovens, the oscillation output of the magnetron fluctuates depending on the shape and type of food, and there is a trade-off between heating uniformity and heating efficiency. Difficult to heat food.

That is, in the microwave oven which stirs the microwave radiated from the waveguide port of the top wall of the heating chamber at the time of cooking and the microwave oven described in Japanese Utility Model Laid-Open No. 62-150894, For foods that are extremely small compared to the size of the heating chamber, or for thin and wide foods that are placed away from the waveguide mouth, it is possible to heat uniformly and efficiently. Can not. On the other hand, a microwave oven that rotates a table on which food is placed during cooking can uniformly and efficiently heat wide and thin foods, but it can be used for extremely small foods and tall foods. , You can't do this kind of heating. It is considered that this is because a part of the radio wave is reflected by the food and excites the natural resonance mode in the refrigerator due to the distance between the radiation source and the food. That is, when the resonance mode is excited, the reflected wave from the food is reduced only at each frequency of the resonance mode. Moreover, this also causes a problem that the matching condition of the magnetron, which is the microwave oscillation source, is difficult to be satisfied, and the magnetron cannot be operated at the maximum output. And this problem also makes it impossible to heat food efficiently.

Therefore, as a microwave oven that solves such a problem, the resonance mode of the heating chamber is changed by elevating and lowering a circular table for placing food, the food is rotated, and at the portion where the food is present. There has been proposed a microwave oven in which the distribution of microwaves is suitable (see Japanese Patent Laid-Open No. 59-71291).

However, since this microwave oven has a structure for raising and lowering the food placing table, it is necessary to increase the torque of the drive motor to rotate the table in a stable state even when the weight of the food is large. is there. Moreover, since the heating chamber is in the shape of a rectangular parallelepiped and the table is circular, a gap is created between the corner of the heating chamber and the table, and as a result, microwaves are coupled to unnecessary cavities below the table. And bring loss.

An object of the present invention is to solve the above-mentioned problems and to provide a microwave oven that can uniformly and efficiently heat food of any shape.

[0008]

[Means for Solving the Problems]

 In the microwave oven according to the present invention, the waveguide is provided outside the heating chamber, the food placing turntable is provided inside the heating chamber, and the waveguide is provided above the turntable in the heating chamber. A radiation antenna having an electromagnetically coupled horizontal microwave radiation unit is movably provided so that the vertical position of the radiation unit can be changed.

In the above microwave oven, a sensor for detecting the electric field strength in the waveguide or the heating chamber is provided, and at least one movable impedance element is provided in the waveguide, and the electric field detected by the sensor is provided. It is preferable to change the output of the microwave radiated from the radiating part of the radiating antenna by moving the impedance element based on the strength.

[0010]

[Action]

 A waveguide is provided outside the heating chamber, and a radiation antenna having a horizontal microwave radiation section electromagnetically coupled to the waveguide is provided above the food placing table in the heating chamber. Since the radiating part is movably installed so that the vertical position can be changed, the distance between the radiating part of the radiating antenna and the food is adjusted according to the shape and size of the food, and as a result, The radiant part can be brought close to the optimum position that can heat food with high efficiency. Therefore, the food can be efficiently heated. The reason is as follows. That is, the thermal energy generated in the food by dielectric heating and used for cooking is given by the following equations (1) to (3). However, due to the microwave current flowing through the radiating antenna, an induction electromagnetic field that does not contribute to dielectric heating due to microwave radiation is induced on the antenna surface, and the food surface has conductivity due to the presence of ions. , Induced eddy currents flow on the surface of food. The thermal energy generated on the surface of the food by this eddy current is given by the following equations (4) to (6). The total heat energy given to the food is given by the following equation (7), which is constant when the output is constant.

[0011]

[Formula 1] In the formula, L ... Antenna length, r ... Distance between antenna and food, c ... Light speed, ε ... Dielectric constant of food, δ ... Electrical conductivity of food.

As is clear from the above formulas (1) to (7), when the distance between the food and the radiation antenna becomes large, the total heat energy given to the food is generated inside the food and used for cooking. The heat energy that is generated decreases rapidly. However, with this configuration, it is possible to bring the radiation part of the radiation antenna closer to the food according to the shape and size of the food, and as a result, the thermal energy that contributes to dielectric heating is increased. can do. Therefore, the food can be efficiently heated.

Moreover, by bringing the radiation antenna close to the food, the reflected waves from the food are uniformly reduced without depending on the frequency. Therefore, the matching condition of the magnetron, which is the microwave oscillation source, can be easily adjusted. It is established and the magnetron can always operate at maximum output. Therefore, this also efficiently heats the food.

Further, since the food placing turntable is provided inside the heating chamber, the whole food can be uniformly heated by rotating the food placing turntable during cooking.

Further, a sensor for detecting the electric field strength in the waveguide or the heating chamber is provided, and at least one movable impedance element is provided in the waveguide, and the electric field detected by the sensor is provided. If the output of the microwave radiated from the radiating part of the radiating antenna is changed by moving the impedance element based on the strength, the change in the electric field strength due to the absorption of heat energy into the food will occur. Then, it becomes possible to change the output of the microwave radiated from the radiating part of the radiating antenna so as to optimize the situation in accordance with the progress of cooking.

[0016]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. In addition, in the following description, the left and right in FIGS. 1 and 2 are referred to as the left and right. The lower side of FIG. 1 and the right side of FIG. 3 are referred to as the front, and the opposite side is referred to as the rear.

1 to 3 show the overall configuration of the main part of the microwave oven, and FIGS. 4 and 5 show the configuration of each part thereof.

1 to 3, a rectangular parallelepiped heating chamber (2) is provided in a box body (1) constituting the outer shell of a microwave oven, and a heating chamber (2) in the box body (1) is provided. A waveguide (3) is formed on the right side of the. The output antenna (5) of the magnetron (4) projects into the waveguide (3). The front opening of the heating chamber (2) is opened and closed by the door (6). Further, on the right side of the heating chamber (2) on the front wall of the box (1), there is provided an operation panel (8) having a key input section having various operation keys for heating and cooking (7). ..

At the lower end of the heating chamber (2), there is provided a food loading turntable (10) which is rotated by a rotation drive mechanism (9). On the left side wall of the heating chamber (2) is provided an optical sensor (11) used to detect the height of the food placed on the turntable (10).

A crankshaft-shaped microwave radiation antenna (12) electromagnetically coupled to the waveguide (3) is provided above the turntable (10) in the heating chamber (2). .. As shown in FIG. 4, the radiating antenna (12) includes a horizontal rotating shaft (12a), a horizontal radiating part (12b) arranged at a position deviated from the rotating shaft (12a), It consists of an arm part (12c) that connects both parts (12a) and (12b) together, and a rotating shaft part (12a) is rotatably supported by a bearing (13) on the right side wall of the heating chamber (2). ing. The radiation antenna (12) has a coaxial structure and includes a center conductor (14) electromagnetically coupled to the waveguide (3). A coupling member (15) for electromagnetically coupling the central conductor (14) and the waveguide (3) is tightly fitted around the right half of the rotating shaft portion (14a) of the central conductor (14). It is fixed. From the rotating shaft part (14a) of the central conductor (14) to the lower part of the arm part (14c), a radiation prevention sleeve (16) that prevents unnecessary radiation of microwaves is coaxially fitted around the surrounding part. Has been. In addition, from the radiating part (14b) of the center conductor (14) to the upper part of the arm part (14c), a protective sleeve that does not block the radiation of microwaves and protects the center conductor (14) is provided around it. 17) is fitted coaxially. The rotating shaft part (14a) of the central conductor (14) and the right end part of the coupling member (15) project into the waveguide (3), and the end part is guided through the coupling member (18). The shaft (19a) of the electric motor (19) provided outside the pipe (3) is connected so as not to rotate with respect to each other. When the electric motor (19) is activated, the radiation antenna (12) rotates around the rotating shaft (12a), and the resulting radiation portion (12b) moves in an arc when viewed from both the left and right sides. The vertical position of the lever is variable. The movement route is shown by the one-dot chain line arrow in FIG. For example, in the case of wide and thin food, the radiation part (12b) is located at the position shown by the chain line in Fig. 3, and in the case of large food, it is located at the position shown by the solid line in Fig. 3. To be.

An electric field intensity sensor (20) for detecting the electric field intensity is provided in the waveguide (3). A movable short-circuiter (movable impedance element) (21) is provided in the waveguide (3) below the magnetron (4) so as to be vertically movable. As shown in FIG. 5, the movable short circuiter (21) is connected to the electric motor (23) arranged below the movable short circuiter (21) via a known transmission mechanism (22) and can be moved up and down by the electric motor (23). Is designed to set the output from the radiating antenna (12) to the optimum value. That is, by changing the distance between the radiating antenna (12) and the movable short circuiter (21), the power source impedance viewed from the radiating antenna (12) can be changed.

FIG. 6 schematically shows the structure of the microwave oven of the present invention. In FIG. 6, the microprocessor (24) is provided with a rotary drive mechanism (9) of the turntable (10), a key input section provided on the operation panel (8) for giving operating conditions, and a power source for operating the magnetron (4) ( 25), the optical sensor (11) and the electric field strength sensor (20) are connected. In addition, the radiation antenna driving electric motor (19) and the movable short circuit driving electric motor (23) are connected to the microprocessor (24). The operation of the microprocessor (24) is as follows. That is, the microprocessor (24) operates the radiation antenna driving electric motor (19) in response to the height of the food detected by the optical sensor (11), which causes the radiation antenna (12) to rotate. The part (12a) is rotated around the center, and the horizontal radiation part (12b) and the food are brought close to an optimum position for efficient heating and stopped at this position. Then, the turntable (10) is rotated and a microwave is oscillated from the output antenna (5) of the magnetron (4). This microwave is transmitted to the radiation antenna (12) through the waveguide (3) and is radiated from the horizontal radiation part (12b) to cook the food. As the adjustment progresses, the electric energy is absorbed by the food as heat energy, and the electric field strength changes. The microprocessor (24) measures the heat energy absorbed by the food product based on the electric field strength in the waveguide (3) detected by the electric field strength sensor (20) and is programmed in advance. By comparing the threshold value and moving the movable short-circuiter (21) by activating the motor for driving the movable short-circuiter (23), the output from the radiation antenna (12) can be optimized according to the cooking condition of the food. Perform feedback control so that the output is obtained.

With such a configuration, when cooking food, its shape and size are detected by the optical sensor (11), and the distance between the horizontal radiation section (12b) and the food is optimal for efficient heating. The radiation antenna (12) is rotated about the rotating shaft (12a) so as to approach the position, and is stopped at this position. In this state, the turntable (10) is rotated and the microwave oscillated from the output antenna (5) of the magnetron (4) is transmitted to the radiation antenna (12) via the waveguide (3). The food is heated by being radiated from the horizontal radiation part (12b). As the food is cooked, the heat energy absorbed by the food is measured based on the electric field strength detected by the electric field strength sensor (20). Then, the movable short circuiter (21) is moved so that the output of the radiation antenna (12) is controlled to be the optimum output in the cooking state. In this way, the distribution state of microwaves is adapted to the shape and size of the food, and as a result, the food is heated uniformly and efficiently.

FIG. 7 shows another embodiment of the present invention. In FIG. 7, a movable stub (movable impedance element) (30) is provided in the waveguide (3) instead of the movable short circuiter (21). The movable stub (30) is passed through the left side wall of the waveguide (3) so as to be movable in the left and right directions. The movable stub (30) is connected to the electric motor (32) arranged on the right side of the movable stub (31) via a known transmission mechanism (31), and is moved in the left and right direction by the electric motor (32). It is designed to set the output from the radiation antenna (12) to an optimum value. That is, by inserting the movable stub (32) into the waveguide (3), an inductive and capacitive reactance element can be constructed, and the length of insertion into the waveguide (3) can be increased. The reactance can be changed by changing. By loading this reactance on the antenna impedance, it becomes possible to match it with the power source impedance.

In the above, rotation of the radiation antenna (12) is automatically rotated by an electric motor according to the shape and size of the food to be heated detected by the optical sensor (11). However, the user may rotate the radiation antenna (12) so that the radiation part (12b) comes to a predetermined position according to the shape and size of the food. Further, in the above, by moving the movable short circuiter (21) or the movable stub (30) when the electric field strength changes, the output from the radiation antenna (12) is optimized according to the food cooking state. Although the output antenna is controlled so as to output, the radiation antenna (12) may be rotated at the same time to change the distance between the radiation portion (12b) and the food. Furthermore, although the electric field strength sensor (20) is provided in the wave guide tube (3) in the above, it may be provided in the heating chamber (2).

[0026]

[Effect of the device]

 According to the microwave oven of the present invention, as described above, foods having various shapes and sizes can be uniformly and efficiently heated regardless of the shapes and sizes. Therefore, it is possible to cook with high efficiency without uneven heating.

Further, the sensor for detecting the electric field strength in the waveguide or the heating chamber is provided, and when the waveguide is provided with at least one movable impedance element, heat energy to food is increased. It is also possible to change the output of the microwave wave radiated from the radiating part of the radiating antenna based on the change in the electric field strength due to the absorption of the radiant energy, depending on the progress of cooking, so as to optimize the situation.

[Brief description of drawings]

FIG. 1 is a schematic horizontal sectional view of a microwave oven according to an embodiment of the present invention.

FIG. 2 is a schematic front view in which a part of the microwave oven of the embodiment of the present invention is cut away.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is an enlarged vertical sectional view showing a portion of a radiation antenna.

FIG. 5 is an enlarged vertical sectional view showing a lower portion of the waveguide.

FIG. 6 is a diagram showing an electrical configuration of the microwave oven of the present invention.

FIG. 7 is a view corresponding to FIG. 5 showing another embodiment of the present invention.

[Explanation of symbols]

 2 heating chamber 3 waveguide 10 food placing turntable 12 radiation antenna 12a radiation section

Claims (2)

[Scope of utility model registration request] 1. A waveguide is provided outside the heating chamber, a food placing turntable is provided inside the heating chamber, and the waveguide is electromagnetically provided at a portion above the turntable in the heating chamber. A microwave oven in which a radiating antenna having a horizontal microwave radiating section coupled to the radiating section is movably provided so that the vertical position of the radiating section is variable. 2. A waveguide is provided with a sensor for detecting the electric field strength in the heating chamber, and the waveguide is provided with at least one or more movable impedance elements, and based on the electric field strength detected by the sensor. The microwave oven according to claim 1, wherein the output of the microwave radiated from the radiating portion of the radiating antenna is changed by moving the impedance element.