RU2531870C2 - Apparatus for transmitting microwave energy from generator to microwave oven chamber - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: apparatus for transmitting microwave energy from a generator to a microwave oven chamber is an assembly unit consisting of a magnetron generator and a double-element stripline antenna mounted inside the microwave oven chamber and which excites a circularly polarised electromagnetic field. The energy output of the magnetron is directly electrically connected to the antenna radiator, which considerably reduces (to 4%) loss of microwave energy in the magnetron-antenna-microwave oven chamber line. The design of the double-element stripline antenna with in-phase supply, matched with the microwave oven chamber to a voltage standing-wave ratio (VSWR) of about 1.5 using three short-circuit bars with diameter of 10 mm and length of 26 mm, enables to excite, inside the microwave oven chamber, a circularly polarised electromagnetic field whose energy distribution uniformity coefficient in an equivalent load is equal to 94%.

EFFECT: high efficiency of operation and uniform distribution of microwave sources.

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Description

Technical field

The invention relates to microwave technology, in particular to electric heaters that use the energy of the microwave field, and is intended to transfer microwave energy from the generator to the chamber of the microwave oven.

State of the art

A device for transmitting microwave energy from a generator to a chamber of a microwave oven is a pyramidal shortened horn antenna connected through a communication hole to a rectangular waveguide resonator, into the cavity of which the output of microwave energy from a source - a magnetron generator is immersed [1]. (Such devices are used in almost all models of the profit centers of Samsung Electronics, LG and several other companies).

The main disadvantages of this device are the substantially non-uniform distribution of the microwave field energy in the chamber cavity, the dependence of the indicated distribution and the furnace efficiency on the volume, mass and location of the processed product in the chamber, which leads to uneven heating and poor-quality cooking, as well as to an increase in energy consumption from power network.

The distribution uniformity coefficient of heating sources is α = (38 ÷ 40)% in the absence of rotation and α = 64% when the processed product is rotated on a dielectric platform. (The measurements were performed according to [7]. The efficiency of energy transfer from the magnetron to the chamber decreases by (18 ÷ 20)% due to active and reactive losses in the multi-link transmission line.

The closest technical solutions to the invention are a microwave oven with a diagonal EMF exciter with circular polarization in the working chamber [2] and a device for transmitting microwave energy to a closed cavity resonator [3].

In these devices, the main element is a strip antenna, which excites circularly polarized EMF in the working chamber and forms a uniform distribution of microwave heating sources (α> 90%) in the equivalent load [2, 3].

In the device [2], a two-element strip antenna consists of a radiator, which has the shape of a compressed figure eight and is made as a whole from a sheet metal with high electrical conductivity, and a quasi-ellipsoidal screen, also made of sheet metal with high electrical conductivity and rigidly fixed through a hole in the center mechanically with good galvanic contact on the outer conductor of the coaxial segment of the coaxial waveguide transition (CVC), with each of the branches of the emitter - "eight" for providing in-phase supply is connected mechanically and electrically to the characteristic points by means of bushings with high electrical conductivity with a metal screen and the center of symmetry of the "eight" is connected to the center conductor of the coaxial segment KVP to input waveguide which receives energy from the microwave generator.

The main disadvantages of this device are:

a) noticeable active and reactive losses (10 ÷ 12%) of microwave energy in a multi-link transmission line between the generator and the MVP chamber;

b) the difficulty of individually matching the impedance of the strip antenna with the impedance of the heating chamber (resonator with load), which leads to an increase in the amount of work in the process of creating a MVP with different sizes of heating chambers;

c) low level of manufacturability of the strip antenna design, which is essential in mass production.

The device [3] is an assembly unit including a magnetron, the energy output of which is immersed in a tunable rectangular resonator, and microwave energy is supplied to the input of the strip antenna from its cavity using the built-in waveguide-coaxial transition. The latter is used as an exciter of EMF with circular polarization in resonator heating chambers for various purposes.

The main disadvantages of this device are the same as in [2], however, the level of energy loss is less (~ 8%), and therefore this device is used in technological equipment with microwave heating with a power of more than 3 kW.

Significant energy losses during its sewerage from the microwave generator to the heating chamber, the insufficient level of manufacturability of the structures of EMF pathogens in the cavity of the working chambers impede the widespread use of strip antennas in household and industrial appliances using microwave heating.

Disclosure of the invention.

The main objective of the invention is to increase the efficiency of the device for transmitting microwave energy from the generator to the chamber of the microwave oven, to implement a highly uniform distribution of microwave heating sources in the load of the chamber, and to achieve the level of manufacturability of the design that meets the requirements for organizing mass production.

This is achieved due to the fact that the device for transmitting microwave energy from the generator to the MVP chamber, which is an assembly unit including a magnetron, the energy output of which is immersed in a tunable rectangular resonator, and microwave energy is supplied from its cavity using the built-in waveguide-coaxial transition at the input of a strip antenna mounted and fixed on one of the walls inside the MVP heating chamber and exciting in the EMF chamber with circular polarization, according to of the invention, a device for transmitting microwave energy from the generator to the MVP chamber is formalized in the form of a nodal assembly unit, including Fig. 1: magnetron generator 1, magnetron mounting flange 2 on the wall 3 of the MVP working chamber, microwave energy output from the magnetron resonator, from above covered with a ceramic shell 8, and from below - with a metal cap 9 of thin (0.24 mm thick) high-temperature metal; two-element strip antenna with common-mode power supply, the details of which are emitter 6, Fig. 1, made as a solid elongated in the direction of the OX axis, Fig. 2, quasi-ellipsoidal disk with a length of ~ λ and a width of λ / 2 (λ is the wavelength in free space) and made of sheet with high electrical conductivity metal 1 mm thick; screen 3 as part of the wall surface of the heating chamber of the MEP; three short-circuit (KZ) racks 4 of well-conducting metal on top, Fig. 1, mechanically detachably connected with a good galvanic contact to the screen surface (walls 3), and bottom KZ racks are mechanically connected with a good galvanic contact by screws 7 through holes 10, 11, 12, Fig. 2, with a radiator 6, in the central hole of which 13 with D = 15.2 mm, a metal cap 9 for energy output from magnetron 1 is installed and soldered around the entire perimeter.

Due to the fact that the design of the node assembly of the device for transmitting microwave energy from the generator to the MVP heating chamber, Fig. 1, provides a direct connection of the magnetron energy output with the strip antenna and the MVP working chamber, as well as due to the good matching of the antenna with the loaded chamber, energy loss in the path the magnetron-antenna-heating chamber is significantly reduced and amounts to ~ 4%.

Due to the qualitative matching of the two-element strip antenna with the load (1 liter of water in a glass vessel) of the MVP heating chamber, achieved at a distance = 26 mm, Fig. 1, between the emitter 6 and screen 3 and the optimal position of the antenna phase center when it is connected to the heating chamber through hole 5 in the upper wall, a highly uniform distribution of microwave heating sources is realized, which corresponds to α≈94%.

Since the design of the nodal assembly, Fig. 1, does not contain a rectangular resonator and KVP, its level of manufacturability is significantly increased, and manufacturing costs are significantly reduced. This makes the microwave energy converter a very promising device for use in domestic MVPs and in industrial equipment.

A brief description of the drawings.

Figure 1 shows a sketch of the assembly unit of the device for transmitting microwave energy from the generator to the MVP chamber, made on a 1: 1 scale. This device has been manufactured and investigated, and the results have become the basis for the preparation of this application.

Below is a description of the parts and elements of the device according to Fig. 1, as well as information about the magnetron and the MEP that were used in the manufacture and study of the layout of this device.

Magnetron 1, model M24FA-410A, manufacturer Galanz, 2011; magnetron flange 2; wall of the working chamber 3 MVP, manufacturer "Saturn", the volume of the working chamber is 17 l, 2011 edition; KZ stand 4, material LS-59 brass, diameter 10 mm, height 26 mm; emitter 6, material stainless steel sheet, thickness 1 mm, Fig. 2 shows a sketch of the emitter 6 in a scale of 1: 1, respectively, holes 10, 11, 12 are designed to connect screws 7 of the emitter 6 to the short racks 4, and the hole 13, Fig. 2, for soldering the emitter 6 with a metal cap 9 of the energy output from the magnetron 1; the ceramic shell 8 provides protection for the energy output of magnetron 1. It should be noted that the choice of the type of magnetron and the model of the MEP are not fundamental.

The best embodiment of the invention.

The device for transmitting microwave energy from the generator to the MVP chamber, Fig. 1, is a nodal assembly unit, which includes a strip antenna with two-phase supply in-phase, the output of magnetron energy, which is an integral part of the antenna structure, and part of the surface of the MVP heating chamber wall, acting as a strip antenna screen.

The assembly and installation of the device in the cavity of the MVP chamber is carried out in the following order. Three short-circuit posts of rack 4 are mechanically installed with a good galvanic contract on the inner surface of wall 3 and fixed with screws (not shown in Fig. 1).

Then the magnetron 1 is installed, the energy output of which is immersed in the cavity of the MVP chamber through the hole 5 in the wall 3.

After that, the emitter 6 is mounted: through the corresponding holes 10, 11, 12 it is attached to the short stands by 4 screws 7, and the metal cap 9 with a collet connector (not shown in Fig. 1) is connected to the ceramic shell 8 of the energy output from magnetron 1.

As follows from the description of the device for transmitting microwave energy from the generator to the MVP chamber, its components and elements are simple in design, their manufacture does not present difficulties and does not need unique equipment. An exception is the metal cap 9, however, the technology for the production of such parts has long been mastered in precision instrumentation.

Industrial applicability.

In the process of creating a device for transmitting microwave energy from the generator to the MVP chamber, a complex of research and testing of a prototype was performed. As a result of these works, the optimal dimensions of the short racks 4 (diameter 10 mm, length 26 mm), as well as the coordinates of points 10, 11, 12 of their connection with the emitter 6, respectively, point 10 (-30, 12), point 11 (40 , 15), point 12 (36, -22), Fig. 2. A two-element strip antenna with a quasi-ellipsoidal emitter in the form of a thin disk with dimensions of length λ, width λ / 2, thickness 1 mm was matched to the free space before the VSWR of input 1, 2 in the frequency band (2.4 ÷ 2.5 ) GHz and up to an VSWR of input 1.52 when installed in the cavity of the MVP chamber with an equivalent cassette load according to the international standard [7].

The coordinates of the antenna phase center coincide with the coordinates of the center of symmetry of the surface of the upper wall of the Saturn MVP chamber. The optimal mode of operation of the device corresponds to the position of the emitter 6, in which the angle between its main axis of symmetry and the horizontal axis of symmetry of the surface of the upper wall 3 of the MVP camera is ± 6 °.

According to [7], the value of the coefficient of uniformity of the distribution of microwave heating sources was determined α = 94%, and the energy losses during its transfer from the generator to the MVP chamber, which amounted to 4%, were measured.

It was experimentally confirmed that without a strip antenna, the device is capable of transmitting 100% of the magnetron output energy from the generator to the MVP chamber, however, the coefficient α≈72%. Nevertheless, the set property of the converter expands the possibilities of its application.

There is every reason to argue that, according to operational and technological criteria, a device for transmitting microwave energy from a generator to a MVP chamber has prospects for industrial applications.

Information sources

1. Microwave Owen M245. (Owner's Instruction Code No. 6861707A (2007), Samsung Electronics. RK.

2. Microwave. Patent No. 2393650 of the Russian Federation, 06/27/2010, Author Patent holder Zhilkov V.S.

3. Device for transfer of microwave energy into a defined volume. US Patent Application Publication. Zhylkov et al. Pub-No its 2010/0126987 A1, May 27, 2010.

4. E.I. Nefedov et al. Microstrip emitting and resonant devices. From the Technique, 1990

5. Yu.V. Shubarin. Microwave Antennas. KSU Publishing House, 1960

6. Antennas and microwave device. Ed. prof. D.I. Voskresensky. Publishing House Sovradio, 1972

7. Norme International CEI IEC. International Standard 60705. Edition 3.2.2006-03.

Claims (4)

1. A device for transmitting microwave energy from the generator to the chamber of the microwave oven (MEP), which is an assembly unit that includes a magnetron, the energy output of which is immersed in a tunable rectangular resonator, and microwave energy is supplied to the input from its cavity using a waveguide-coaxial transition a strip antenna mounted and fixed on one of the walls inside the MVP camera and exciting an electromagnetic field (EMF) with circular polarization, characterized in that the device for transmitting energy and from the generator to the MVP chamber, it is made in the form of a nodal assembly unit including a magnetron generator, a magnetron mounting flange on the wall of the MVP working chamber, microwave energy output from the magnetron resonator, covered with a ceramic shell on top, and a thin high-temperature metal metal cap, from below two-element strip antenna with common-mode power supply, the details of which are a radiator made in the form of a solid quasi-ellipsoidal disk elongated in the direction of the OX axis, ~ λ long, wide another λ / 2 (λ is the wavelength in free space) and made of 1 mm thick sheet with high electrical conductivity, a screen as part of the wall surface of the heating chamber of the MVP, three short-circuit (KZ) racks of well-conducting metal on top, mechanically detachable with good galvanic contact connected to the surface of the screen (wall), and below the short circuit racks are connected mechanically with good galvanic contact by screws through holes with a radiator, in the central hole of which a unit is installed and connected with D = 15.2 mm around the entire perimeter is a metal cap for removing microwave energy from a magnetron. 2. The device according to claim 1, characterized in that to provide in-phase power to the left and right branches of the two-element strip antenna, the metal cap for outputting energy from the magnetron is electrically (with good galvanic contact) connected to the antenna radiator through the hole, while the coordinates of the centers of symmetry of the metal cap and the quasiellipsoidal disk of the emitter are the same. 3. The device according to claim 1, characterized in that its optimal mode of operation, in which the uniformity coefficient of the distribution of microwave heating sources α = 94%, and the energy loss from transmission from the magnet to the antenna ~ 4%, takes place if: linear dimensions Short racks are 10 mm in diameter, 26 mm in length; the outer diameter of the metal cap of the energy output from the magnetron is 15.2 mm; the angle between the longitudinal axis of symmetry of the emitter and the longitudinal axis of symmetry of the upper wall of the MVP chamber is ± 6 °. 4. The device according to claim 1, characterized in that the metal wall of the MEP heating chamber is used as the screen of a two-element strip antenna with common-mode power.

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