JPS6026274B2 - microwave oven - Google Patents

Description

[Detailed description of the invention] The present invention relates to a microwave oven.

Japanese Patent Application No. 53-142148 filed by the same applicant as the present application discloses a combination microwave heating and electric heating type microwave oven in which microwave energy is supplied from the bottom of the microwave oven enclosure. has been done.

However, in such microwave ovens, the radiant supply means are placed below the food being heated, which can lead to food spillage and other undesirable effects that reduce the efficiency of the cooling system. Additionally, when high temperature self-cleaning is used, the radiator must be constructed of a material such as steel that can withstand such temperatures. The present invention uses a single multi-element radiator that is powered from a common connection point and generates a plurality of substantially directional radiation patterns directed towards the object to be heated, providing a smaller spacing between the radiator elements than the subordinate radiators by producing, with at least one of the plurality of elements, a pattern with polarizations in planes having substantially different angles;
It is disclosed that the desired heating pattern can be achieved by causing the radiator pattern to be produced by different elements of the radiator.

More particularly, the polarization of one of said radiation patterns lies in a plane substantially parallel to the axis of rotation of the radiator. Preferably, the plurality of radiator elements are mouths in a waveguide-shaped filled region fed by a common connection, such as a coaxial line, and the microwave energy reaches different radiator elements at different phases. be made to do. The improved uniformity of the heating pattern within the food produced by such independent radiation patterns occurs even when the food is placed directly within the direct radiation pattern of the radiating element, reducing the large amount of microwave energy. A portion is absorbed by the food as direct radiation from the radiator rather than as radiation reflected from the microwave enclosure walls. The present invention provides a fixed cover that is transparent to microwave energy and can be placed over the radiator in the microwave oven to protect the radiator from food particles and conduction or cooking vapors on the radiator. I will disclose that.

More particularly, the permeable cover is supported by a protrusion on the bottom wall of the microwave cavity to provide a space for air to pass through the microwave oven. To maintain the radiator at a temperature below that of the microwave oven when electrical resistance heating is used, air is directed outside through the mouth of the radiator over the inner surface portion of the cover adjacent to the radiator. I am guided. More specifically, the cover may be made of, for example, Pyroceram or Rayceram.
5 powders such as neriko-baked boards sold under (eram). Constructed from commercially available high temperature materials that can withstand temperatures in excess of 10,000F. This glued board cover is inverted in a fixed position over the rotary radiator and acts as a heat shield during periods of high temperature microwave operation, such as cleaning cycles, so that the radiator can be attached to the microwave wall. The temperature should remain significantly lower than the surface temperature. According to the invention, the walls of the microwave oven are preferably made of common steel coated with a high temperature ceramic, such as enamel, so that radiation into the microwave oven when there is no food present, which is a large load. The microwave energy generated is partially absorbed by the microwave oven arm, thus preventing undesirably strong electric field patterns from forming within the microwave oven. The radiator can be made of a highly conductive metal such as aluminum that is protected from the high temperatures of microwave ovens. The present invention further provides a door leak sealing structure that incorporates a common hot gas vapor leak sealing means for combination microwave ovens, and a low loss microwave choke leak sealing structure between the air leak sealing means and the inside of the microwave oven. The microwave choke leak-tight structure allows air to be continuously blown through the microwave without substantially reducing the rate at which food is heated by microwave energy or resistive heating. Disclose the microwave oven that has become.

More specifically, this choke structure can be formed either on the door or on the microwave wall, e.g.
It provides a high impedance in series with the input transmission line structure in the main operating frequency range of the microwave oven, such as between kilomegahers and 2.5 kilomegas. According to the invention, a wire mesh of tubular shape is supported on a tubular body made of woven fiberglass and this is supported on a tubular structure made of steel silk of a larger diameter to provide a spring action. This provides additional magnetic properties to the elastic hot vapor barrier.

According to the present invention, the blocking effect of microwave energy in the main frequency range is applied to the input transmission line section of the choke-type microwave door blocking means by microwave energy in the periphery around the input transmission line structure. This can be increased by providing means for inhibiting the transmission of energy.

More particularly, such means may consist of an impedance discontinuity, such as a slot in one of the walls of said input transmission line structure. Further in accordance with the invention, such slots preferably extend through the wall and into the choke structure to further aid in inhibiting peripheral mode propagation in the choke structure. Such a choke type leakage prevention means is disposed within the microwave oven between the high temperature air leakage prevention means and the inside of the microwave oven. According to the invention, the food is placed on a shelf in a radiation pattern from a rotating radiator, preferably formed from a highly conductive, low loss material such as aluminum, and is thus exposed to microwave radiation. Most of the energy is absorbed as it passes through the food before reflecting off the walls of the microwave.

Highly efficient heating with microwave energy is thus achieved even if the walls of the microwave oven are made of an inexpensive high temperature material such as enameled steel that absorbs microwave energy to a small extent. According to the present invention, a magnetron is closely coupled to a microwave oven enclosure through coupling mechanisms such as waveguides, coaxial transitions, and multi-element radiators, thereby improving the efficiency of the magnetron and thus reducing the input electrical energy. The conversion into microwave energy that is coupled into the food to be heated is enhanced. More specifically, if a small piece of food on a metal tray is placed in a microwave oven, most of the microwave energy radiated into the microwave will come from the metal tray or the wall on the opposite side of the microwave. It is reflected back towards the rotating radiator and reaches a common connection, such as the center conductor of a coaxial line transition, with substantially different phases, resulting in a relatively small amount of energy being reflected. Returned to the magnetron. In addition, for heating the microwave oven, an electric resistance heater is provided, either separately or directly on the top of the microwave oven enclosure and extending through a microwave choke in the microwave enclosure wall to be connected to the power source. Used in combination with microwave energy, this is used to treat microwave enclosure walls during a self-cleaning cycle.

When only microwave energy is used, the deposition of cooking vapors on surfaces through which the microwave energy passes is inhibited by reheating such surfaces with the microwave energy. However, this somewhat reduces the efficiency of the transfer of microwaves to the food to be heated, and therefore air directed beyond the surface of the cover will cause such air to pass by a microwave energy generator such as a magnetron. The magnetron is first heated by passing it through the air, which cools the magnetron and heats the air to a temperature about 2 ○ (4 piF) higher than room temperature.
Therefore, cooking steam does not adhere to the microwave-transparent cover. According to the invention, the air heated by the magnetron flows through the microwave oven without being substantially cooled, so that the steam or other cooking vapor swarms are carried away during the cooking process and are removed from the door. There are no emissions from the microwave through the door when it is opened. The present invention will be explained below with reference to the drawings.

1, 2 and 3, a door 12 defines a microwave cavity which is closed and receives microwave energy from a rotating radiator 14 located at the bottom of the microwave oven. An enclosure 10 is shown.

The radiator 14 is supplied with microwave energy from the magnetron 16 through a waveguide 18 and a coaxial line 20, which is rigidly connected to the rotary radiator 14 and connected to the waveguide 18. It has a center conductor 20 extending therethrough to a gear reduction motor 24. Electric motor 24
is attached to the bottom of the waveguide 18 and the center conductor 22
, and the radiator 14 is rotated. A coaxial line 20 is rigidly connected to the top wall of the waveguide 18 and passes through the bottom wall of the enclosure 10 to a pienum 2 within the radiator 14.
8 and has an outer conductor 26 extending into the outer conductor 8 . As shown in more detail in FIG. 2, the fill region 28 has a top plate 30 having a plurality of ports 32 connected to the center conductor 22 and spaced at different distances from the axis of the center conductor 22. .

Microwave energy is radiated from fill region 28 through spout 32 and fixed cover 34 into microwave enclosure 10 . The fixed cover 34 is transparent to microwave energy and prevents cooking particles and steam from impinging on the radiator 14. Lower fill area cover 38 of radiator 14
prevents radial outward radiation of microwave energy and directs it through the mouth 32, the lower surface of which covers the enclosure 1 so that the radiator 14 can rotate freely.
is located well above the bottom wall of the

The entrance of the cover 38 surrounds the upper end of the outer coaxial conductor 26 , and the conductor 26 extends slightly into the fill region 28 so that the microwave energy is transferred to the radiator 14 .
radiation into the enclosure 10 from below. The length of outer conductor 26 extending into fill region 28 can be adjusted to improve impedance matching conditions. As shown in FIG. 1, the substantially conical waveguide leading to the coaxial line transition member 40 extends upwardly from the plate metal bottom of the waveguide 18 into a conical shape surrounding the center conductor 22. It is formed by performing a die forging die.

A tubular member 42 is welded to the upper end of the conical transition member 40 and extends downwardly through the center conductor 22 a distance effectively equal to an electrical quarter wavelength at the frequency of the magnetron 16. This creates a choking effect on the energy that tends to escape from the waveguide 18 towards the motor 24. A sleeve bearing 44 of dielectric material is placed between the tubular member 42 and the center conductor 22 to prevent arcing in the bearing 44. The center conductor 22 is reduced in diameter just below the lower end of the tubular member 42 to create an area where it rests on an oil-filled blue body bearing 46 supported by a plate 48 that attaches the motor 24 to the bottom of the waveguide 18. There is.

Both ends of the waveguide 18 are closed by a shorting member 501,
These shorting members 50 are arranged to create a substantially flat standing wave ratio between the output probe of the magnetron 16 and the medium zero conductor 22.

As shown in FIGS. 1 and 2, the mouth 3 of the radiator
2 are each supplied with microwave energy through individual waveguide sections having axes that are at 120° to each other and whose inner ends form a common connection area that includes the center conductor 22. A shaped impedance matching cone 52 is welded to the center conductor 22 and increases in radius as it approaches the top plate 30 of the fill area 28. The waveguide sections formed by the sides of the fill region 28 are of different lengths, so that from the center conductor 22 to the fill region 28
The energy radiated therein reaches the mouth portion 32 with different phase differences. For further details on such a radiator, reference may be made to the above-mentioned Tokubuta No. 53-142148. According to the invention, one of the ports 32 has a vertical entrance 54 to create a radiation polarization pattern parallel to the axis of rotation of the radiator 14.

Therefore, the combination of heating patterns produced by the multiple radiation patterns from the mouth 32 is different at different distances above the radiator 14, and the waves from the mouth 54 are vertically polarized, so that these The waves reach the food with a different phase and polarization, preferably such that the reflection of the waves back towards the radiator 14
At the junction of the filled region waveguides at position 2 there is a substantial cancellation of the electric field vectors and energy is passed through the mouth 32 to the enclosure 1.
chosen to reflect back into the interior of 0. Preferably, this effect is chosen to be greatest when the microwave empty arm has no food disposed within it or when the food is disposed within the metal mesh. Therefore, under such conditions, maintaining a low microwave energy electric field efficiency,
Therefore, the magnetron 16 is coupled to the microwave oven enclosure in a manner that operates near maximum efficiency in converting the magnetron's electrical energy input to microwave energy output while maintaining low wall losses within the waveguide 18. I can do it. According to the invention, the microwave enclosure 10 defining the cavity can be made of a relatively lossy or energy absorbing material that absorbs, for example, a few percent of the incident and reflected microwave energy. can.

Such materials are, for example, the common steel plate coated with the common enamel used in common microwave ovens, all of which are well known. In addition, conventional internal firing units 60 and heating units 62 may be provided adjacent the upper and lower walls of the enclosure 10, supported by conventional fastening means in a known manner. However, in the case of the heating unit 62, it is preferably made in an arcuate shape so that its closest portion is spaced apart around the periphery of the cover 34 so as not to overheat the cover 34. According to the invention, the meat grilling unit 60 and the heating unit 62
is a shielded electrical resistance heating unit connected to a power supply via the rear wall of the enclosure 10. The outer shields of these units are grounded to the walls of the enclosure 10 by taps 64, which are attached to these shields, for example by welding or compression, and screwed to the rear wall of the enclosure 10. There is. A tubular microwave choke element 66, preferably of a length effectively one-quarter wavelength of the microwave frequencies within the enclosure 10, is attached to the enclosure 1 by welding.
0 and surrounds the shield, but is separated from the shield by the enamel coating on the choke element 66. Electrical connections to power and control terminals can be made to the heater and broiler units in a known manner. Any desired shape for the radiator 14 can be used.

An example that gives good results at 2.45 kilometres, has a width of 1 to 16 centimeters (4 inches) and a length of 2.54 cm.
Using a centimeter (1 inch) waveguide, the diameter is 1.
Power is supplied by a 27 cm (1/2 inch) center conductor 22 and a 5.08 cm (2 inch) diameter outer conductor 26.

Waveguide 1 with a width of 10.16 cm (4 inches)
8 is shown as having a height of 5.08 centimeters (2 inches), and the distances from one shorting member 50 to the center of the magnetron output, the axis of the center conductor 22, and the other shorting plate 50 are each 1.905 cm. centimeter (3/4
inches), 10.7 centimeters (5 inches) and 26.035 centimeters (101/4 inches). The food 70' can be placed in a cage 74, for example in a mesh rack 72 above the radiator 14, which cage 74 is preferably microwave energy transparent and is comprised of a microwave energy transparent material such as Pyroceram. It is placed on the board 76.

The mesh rack 72 is made of, for example, a welded wire rod with a cutout considerably larger than the inlet/2, and is inserted into the enclosure 1 by means of a groove 78 in the side wall of the enclosure 10 or in any other desired manner.
Adjustable support to various levels within 0. Air blower 8
Air from 0 is blown into the interior of the enclosure 10 through the cooling fins of the magnetron 16, for example, through a conduit 82, through the entrance of the waveguide 18, through the transmission line 20, The enclosure 1 belongs to the portion where the edge of the cover 34 passes through the opening 32 and rests on the raised positioning protrusion 68 formed on the bottom wall of the enclosure.
through the space between the bottom wall of the 0 and the lower edge of the cover 34 and over the heating unit 62 to allow the air to flow over the food 70 during cooking.

This air is then exhausted through the top of the enclosure 10 or through the equipment box 84 into the center of the surface burner unit 86. During the self-cleaning cycle of the microwave oven, the temperature of the microwave oven energizes the upper heating unit 62 to vaporize deposits on the walls of the enclosure 10 and remove the vapor from the brackets by convection into the filtration box 84. 40 B○ (750 T) and 5 T
Temperatures can reach temperatures between 90°C (11000F).

Air is also drawn by convection into the interior of the enclosure 10 over the inner surface of the radiator 14 and the cover 34, which may be made of, for example, Pyroceram, thereby softening the radiator 14 and the aluminum and causing the upper surface 37 of the cover 34 to soften. Pi○
The temperature is maintained below a temperature that allows heating to a self-cleaning temperature for the Pyroceram surface, such as 7000F (7000F) to 900F (480C). A thermal insulator 88 made of, for example, fiberglass is surrounded by a metal skin 90 and the enclosure 10 is moved in a known manner.
located around.

A light 92 illuminates the interior of the enclosure 10 through an apertured metal plate 94 coated with transparent pyroceram 96. According to the invention, the door 12 is prevented from absorbing significant amounts of microwave energy from the interior of the enclosure 10 by microwave sealing means disposed between the interior of the enclosure 10 and the steam sealing means. It has high temperature steam leakage prevention means. This leak-stopping means is explained in the specification of Tokkyo Sho 53-142148 mentioned above. Closing entrance 32 and vertical checkpoint 5
The dimensions of 4 can be any desired size, and here, for the sake of example, it has been improved using a radiator of reduced size than that shown in Tokugan Shoka No. 142148 cited above. However, the distance and size of the slot 32 covered by the edge 56 is less radial than the farthest slot shown in the previously cited application. It is located closer to the rotation axis of the container 14.

The edge 56 covering the slot 32 orients the average radiation pattern emanating from the vertical entrance 54 at an angle toward the axis of rotation of the radiator 14. Vertical Sekiguchi 54
The shape of the radiation pattern from the other aperture 32 is governed by the size and shape of the gates 32 and 54. Because the radiation pattern from aperture 54 is directed inwardly toward axis of rotation 104, additional heating occurs at the center of the food. Such heating varies depending on the position of the silk sheath 72 in the support groove 78; when the silk sheath 72 is in its uppermost position, most of the microwave energy from the sekiguchi 54 is transmitted across the microwave. It is guided under the food and reflected from the wall. However, when the silk is in its lowest position, most of the microwave energy from the vertical entrance 54 hits the food directly, especially when the food is large, and therefore most of the microwave energy is It is important to bind the food to the center of the food. The other mouth 32 emits waves that are horizontally polarized in a radiation pattern, the average direction of which is upward and substantially parallel to the axis of rotation. Such a radiating structure provides an improved heating pattern in which the majority of the microwave energy hits the food before reflection from the microwave enclosure walls, and the spout provides a The radiation is relatively largely decoupled from direct radiation so as not to affect the radiation pattern from other ports prior to impact of the pattern energy on the microwave enclosure wall.

This is the special pig Sho 53-1421 mentioned earlier with the gap between the mouth parts.
This is achieved even if it is smaller than that of the structure of No. 48, so that the cover 34 placed over the entire radiation is relatively
A piece of the same size is fine. Most of the air blown into the microwave enclosure 10 through the radiator 14 flows from the radiator to the mouth 32.
The air is emitted from the cover 34 and hits the inner surface of the cover 34, and this air therefore flows along this surface and between the protrusions 68 that support the cover edge at a high point above the floor of the enclosure 10.
It passes under the green part of No. 4 and is discharged.

This completes the description of the embodiment of the invention presented herein.
However, those skilled in the art will appreciate that various modifications may be made within the scope of the invention. For example, other auxiliary heat sources such as a gas flame or hot air may be used in place of an electric resistance heater, and any desired timer and control system may be used. The following may be mentioned as one embodiment of the present invention.

an enclosure having an inlet gateway and a closure member; and means for radiating microwave energy from a common microwave energy source into the enclosure in a plurality of independent and overlapping radiation intensity patterns having different polarizations. Equipped with
at least one of the radiation intensity patterns has an axis that is not substantially parallel to the axis of the other radiation intensity patterns; A microwave oven comprising means for supporting said object within a radiation intensity pattern.

[Brief explanation of drawings]

Figure 1 is a vertical sectional view of a combination microwave oven embodying the present invention with the door closed, and Figure 2 is a line 2 in Figure 1.
A vertical cross-sectional view of the microwave oven of FIG. 1 taken along -2;
3 is a horizontal sectional view of the microwave oven of FIG. 1 taken along line 3-3 in FIG. 1 with the door open; FIG. 4 is an enlarged fragmentary view of the portion shown in FIG. 3; Figure 5 is line 5-5 in Figure 4.
FIG. 5 is a vertical cross-sectional view of the microwave oven portion of FIG. 4 taken along . 10: Enclosure, 12: Door, 14: Rotary radiator, 16
: Magnetron, 18: Waveguide, 20: Coaxial line, 22
: Center conductor, 24: Electric motor, 26: Outer conductor, 28:
filling area, 32: mouth, 34: cover, 42: tubular member, 50: shorting member, 54: vertical entrance, 60: grilling unit, 62: heating unit, 66: microwave choke element, 70: food, 72 :It's a net, 74:Look. Kyoun G ノ〃G2 ~ Reed

Claims (1)

[Scope of Claims] 1. A microwave energy conductive enclosure having an elongated resistive heating element disposed adjacent to and substantially parallel to the bottom surface of the enclosure; a multi-element rotating radiator disposed in a central bottom region of the enclosure; a fixed concave cover with an opening facing the radiator and transparent to the microwave energy; , a side surface of the cover extends between the radiator and the resistive heating element to provide thermal insulation for the radiator, and edges of the cover are spaced apart from each other on a bottom surface of the enclosure. removably retained by at least three protrusions, said protrusions lifting said edge above a bottom of said enclosure to define a gap between said edge and said bottom. a concave cover, and a waveguide connected to a coaxial conductor for coupling microwave energy from the magnetron to the radiator, the waveguide and the coaxial conductor being connected to the radiator during self-cleaning of the microwave oven. providing a convection path for air into the enclosure, wherein a portion of the convective air hits the radiator and reduces its temperature significantly below its self-cleaning temperature; a waveguide flowing into the enclosure through a gap of
Microwave oven consisting of. 2. The microwave oven of claim 1, wherein the radiator is made of aluminum. 3. The microwave oven of claim 2, wherein the radiator comprises a flat plate having substantially parallel sections.