JPH0719660B2 - Microwave oven - Google Patents

Description

The present invention relates to microwave ovens, and more particularly to ovens equipped with a tungsten halogen lamp as a means for browning foods conditioned by microwave energy.

This type of microwave oven is described in British Patent Publication No.
2152790A, one example of which is:
Two heater units, each containing two tungsten halogen lamps, are placed in a predetermined position adjacent to the opening of the oven cavity, and the infrared radiation generated by those lamps causes the food in the oven cavity to be detected. It is released towards and thereby gives the food its optimum browning. Each lamp comprises a tungsten filament supported by a spiral support within a sealed halogenated quartz tube.

In order to prevent lamp breakage, it is necessary to protect those lamps from the microwave energy in the cavities, and for this purpose, in one embodiment of the above mentioned British Patent Publication 2152790A, the cavities are A protective screen is provided having a number of apertures located over the apertures and sized to be transparent to infrared radiation and impermeable to microwave energy. As an alternative or additional protection to the lamp, a microwave comprising a waveguide sized and arranged relative to the lamp to prevent transmission of microwave energy from within the oven cavity to the lamp. A choke device can be used.

However, the use of choke equipment alone does not provide sufficient protection for the lamp and there is still the tendency to be exposed to microwave energy sufficient to cause ionization of the gas filling the lamp. This can result in arcing and / or localized hot spots within the lamp that can interfere with the regeneration halogen cycle or burn up the lamp filament, significantly reducing lamp life. sell.

Accordingly, the present invention is exposed to microwave energy by preventing arcing or the formation of local hot spots or overheating of the lamp that can occur when conventional lamps are exposed to microwave energy. It also aims to provide an improved tungsten-halogen lamp that is less susceptible to damage.

According to the invention, it comprises a microwave energy source and at least one infrared source, said at least 1
One infrared source comprises an infrared lamp consisting of a tungsten filament supported by a number of spaced support coils in a tubular halogenated tube, each support coil having one end attached to the filament. A microwave oven comprising a first wire portion and a second wire portion formed by curving the first wire portion at the other end and curling around the inner wall of the tubular body, There is provided the microwave oven, wherein the wire portion is composed of less than one turn portion of the coil to prevent arcing between adjacent regions due to exposure to the microwave energy. It

The gaseous fill of this tungsten halogen lamp is
The main component is nitrogen with a halogen additive to prevent arcing between the ends of the lamp and / or the filament that can occur when other gases such as argon are used instead of nitrogen. It is preferable.

Each end of the lamp filament in the tube is provided with an electrical connector for connecting the filament to a power source located outside the lamp, and each electrical connector of the lamp filament is a metal case containing the lamp. Is preferably arranged to be shielded from microwave energy by the walls of the wall, thereby preventing the formation of local hot spots in the electrical connector.

If more than one lamp is housed in one unit, the location of the electrical connection between the lamps is outside that unit to prevent circulating high frequency currents in the lamp. It is preferable.

Also, the length of the lead wires of each lamp arranged in the unit is preferably minimized to prevent high frequency currents from being generated in those lead wires.

Embodiments of the present invention will be described below with reference to the drawings.

The microwave oven shown in FIG. 1 comprises an oven cavity 1 having a turntable 2 on which a conventional waveguide is emitted from a source (not shown). The food is supported to be cooked by the microwave energy delivered into the oven cavity 1 by means of tubes 3, stirrers and / or other suitable means.

Two lamp units 4, 5 are arranged outside the cavity 1 at predetermined positions adjacent to the openings in the side wall 6 and the top wall 7 of the cavity. Each lamp unit 4, 5 has a tungsten
It consists of a metal case 8 containing a halogen lamp, around which the heat dissipation from the units 4, 5 is prevented and which partly reflects the infrared radiation emitted by the lamp and also provides support for the lamp. for,
A heat insulating or ceramic material 10 is provided.

The lamp 9 emits radiation in the near infrared range in the wavelength band 0.8-5 μm with a peak at about 1.2 μm.

On each opening to the cavity 1 the interior of the lamp or unit is damaged and / or polluted by food particles or other cooking products released from the food being cooked in the cavity 1. Protective screen made of any suitable infrared transparent material, such as glass ceramic, to prevent
11 are arranged.

In this way, the infrared radiation emitted by the lamp 9 is fed into the oven cavity 1 through the screen 11 in order to char the food being cooked by the microwave energy, in this case the lamp unit. 4,5
Are arranged in a predetermined position so as to obtain an optimum browning effect.

The protective screen 11 does not prevent the lamp from being exposed to microwave energy, so that microwave energy is transferred from the lamp filament to the lamp leads and out of the cavity 1 where microwave energy is allowed. It is leaked to the extent that it cannot be done. To prevent such leakage, the end of each lamp is provided with a microwave energy attenuator attached to the case 8 as shown at 13, which will be described in more detail later. Explained.

One of the lamp units 4 is shown in more detail in plan view in FIG. In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals as in FIG.

Each lamp 9 of the unit 4 comprises a linear or coiled tungsten filament 14 supported in a tubular quartz tube 15 by a number of spaced support coils as shown at 16. , Those coils 16
Each have a first portion wrapped around a filament 14 at one end and a second portion that extends radially within the quartz tube 15 and is curled around the inner wall of the tube 15. Forming part.

Each end of the filament 14 has a flying lead 12 or other suitable connector through a molybden foil 17 and tail wire 18 sealed within a pinch seal 19 of a quartz tube 15 for connecting to a power source for the lamp. Electrically connected to. The end 20 of the tail wire 18 emerging from the pinch seal 19 is in the form of a short coil which is connected to the winding at the end of the filament 14 to provide the electrical connection.

The quartz tube 15 is filled with a gaseous fill, which contains a halogen additive, to provide a regenerative halogen cycle for extended lamp filament life.

The pinch seal at the end of each lamp is preferably housed in a ceramic housing, as indicated at 21, with the housing for pinch seal 19 removed to show the pinch seal construction. ceramic·
The housing 21 is provided to protect the pinch seal from mechanical damage and / or overheating due to exposure to infrared radiation from the filament.

As shown in FIG. 1, the end of the lamp is housed in a microwave attenuator 13, and the microwave attenuator at one end of the unit shown in FIG. 2 simplifies the illustration. Have been removed because.

An example of a suitable microwave attenuator is shown in FIG. 3 and device 13 comprises a conventional quarter wave choke.
This choke has a rectangular cross section and is a shorted metal stub
This stub 22 fits over the ceramic end cap 23 of the lamp and surrounds the lamp lead 24. The stub 22 has a length corresponding to one-quarter of the wavelength of the microwave energy, creating an electrical open circuit for the propagating microwave, which causes the propagating microwave to travel along the lamp lead 24. To be transmitted. The stubs 22 preferably house the end caps of both lamps in each unit, but each lamp may be provided with individual stubs.

The temperature of the pinch seal of the lamp should not exceed about 350 ° C. to prevent damage to the lamp due to overheating, which is why many or all of the sidewalls of the microwave attenuator 13 and the substrate are Provide a hole (not shown),
It is therefore preferred to improve the air circulation and reduce heat transfer from the oven cavity.

The microwave attenuator 13 blocks microwave leakage,
It does not act to protect the lamp from microwave energy and is insufficient to prevent damage to the lamp and shorten the life of the lamp by itself. The main cause of lamp failure due to exposure to microwave energy is the arc in the lamp that occurs when the gaseous fill is ionized by microwave energy and the formation of local hot spots within the lamp. .

In order to substantially reduce the damage to the lamp by microwave energy, the present invention provides one or more lamps to mitigate the arcing and / or local hot spot problems described above. Correction is made.

The first modification is to the support coils 16; in conventional tungsten halogen lamps, those support coils are one or more complete turns of the curled wire section around the inner wall of the tube, typically four. / 3 turns.
However, when the length of the coil is reduced to less than one turn, preferably 3/4 or 7/8 turns, as shown in FIG. 2, and the lamp is exposed to microwave energy, It has been found to be advantageous to prevent arcs that tend to occur between adjacent turns of conventional support coils. In the preferred construction, the coil diameter is 7.7 ~
7.8 mm and the gap left in the coil turns around the inner wall of the tube is 2-3 mm.

The second modification is to the gaseous fill of the lamp, which has traditionally been the predominant constituent of an inert gas, usually argon, containing a sufficient amount of halogen additive to produce a regeneration cycle. I am trying. However,
Since a filling containing nitrogen as a main component containing a halogen additive is less likely to be ionized by microwave energy than a conventionally used filling, and therefore an arc is less likely to occur between the end portion of the lamp and / or the filament, It has been found to be particularly beneficial to use this filling.

The third modification of the lamp is tail wire 18 and filament 14
For the positioning of electrical connections between the ends of the. When this connection is exposed to microwave energy of relatively high intensity, it creates localized hot spots that can be visually impaired to the user of the microwave oven and can shorten lamp life. In order to prevent the formation of such hot spots, one wall of the casing 8 is adjoined, as indicated by the connection between the tail wire 18 and the filament 14 which is adjacent to the wall 25 of the metal casing 8. The lamp is configured such that the electrical connection is shielded from microwave energy by disposing the electrical connection.
In this way, the metal casing 8 acts as a shield to keep the electrical connections from microwave energy.

Therefore, it can be envisaged to use one or more, and preferably all three, of the above mentioned modifications, substantially reducing the risk of the lamp being damaged by microwave energy and increasing the operating life of the lamp. .

In another embodiment, the lamp unit shown in FIGS. 4-6 comprises an upper casing 30 and a lower casing 31, both of which casings being formed of a metal such as stainless steel. Preferably. This unit contains two infrared lamps 32, 33, each lamp being a straight or coiled tungsten supported in a halogenated quartz tube 36 by a supporting coil 35 modified as described above. -Has a filament 34. Each end of each lamp has a ceramic end
It is sealed by a pinch seal (not shown) inserted in the cap 37, and a lead wire 38 for connecting the filament to an external power source (not shown) is led out from the ceramic end cap 37. ing.

Adjacent to the lamps 32, 33 is a layer 10 of thermally insulating material, which is preferably a ceramic fiber and is capable of reflecting the infrared radiation emitted by the lamps. The lamps 32, 33 are held to the unit near the ends by a thermally insulating rectangular section 40, which can be a ceramic fiber. These lamps are also held by two dividing walls 41, 42 separating the filament portion from their ends.

The lower casing 31 is open, at least in the vicinity of the lamp filament, so that the infrared radiation generated by the lamp can be emitted from the unit.

This unit is positioned to open into the oven cavity when used in a microwave oven,
The microwave energy in the oven allows foods cooked to be browned by infrared radiation.

In addition to one or more of the above modifications to the lamp, an electrical connection between the lamps of the unit to prevent overheating and thus flaring of the lamp caused by the lamp being exposed to microwave energy. It has been found to be beneficial to have the lamp formed outside the unit and / or to minimize the length of the lamp leads within the unit.

For this purpose, the leads 38 for the lamp are led out separately from the unit and each lead is provided with a quarter-wave choke 43 which blocks the transmission of microwave energy along it. When brought out of the unit, the external leads 44 can be connected together to a common power source (not shown).

Since the lamps are separated from each other in the unit, overheating of the lamps and thus the generation of circulating high frequency currents in the lamps which causes flare is prevented.

Additionally or alternatively, the leads 38 in the unit
Is minimized, which prevents the generation of high frequency currents in the leads.

Furthermore, the unit consisting of the upper and lower casings 30, 31 is designed for high rigidity and strength,
The individual chokes 43 are fixed to the unit casing by screws (not shown), and these two features help reduce the leakage of microwave energy from the unit.

FIG. 7 shows another configuration of the microwave attenuator shown in FIGS. 1 to 5. FIG. 7 is an end perspective view of the lamp unit, showing the two end caps 45, 46 on the lamp of the unit. In this configuration, lamp leads 47, 48 extend laterally from end caps 45, 46, respectively, and pass through two microwave attenuators 49, 50, respectively. Two devices 49, 50
A metal mesh 51 is provided between and surrounds the end caps 45 and 46, and the metal mesh 51 is attached to the metal casing 52 of the unit. The metal mesh 51 allows sufficient cooling of the lamp ends and prevents leakage of microwave energy propagating along the lamp leads.

The microwave attenuator shown in the drawings is shown in FIGS.
It may consist of any suitable device, such as the quarter-wave choke shown.

Other suitable devices may include a microwave absorbing material such as ferrite that absorbs microwaves as they propagate through the lamp leads. A conventional embodiment of such a device comprises one or more ferrite beads screwed onto the lamp leads and encased within a metal sleeve.

[Brief description of drawings]

1 is a schematic cross-sectional view of a microwave oven equipped with a tungsten halogen lamp unit, FIG. 2 is a more detailed schematic plan view of the lamp unit shown in FIG. 1 according to the present invention, and FIG. 2 is a sectional view taken along the line I--I of FIG. 2, FIG. 4 is a schematic bottom view of the lamp unit according to the second embodiment of the present invention, and FIG. 5 is taken along the line II--II of FIG. 6 is a schematic sectional view taken along line III-III of FIG. 5, and FIG. 7 is a schematic perspective view showing a part of a lamp unit according to a third embodiment of the present invention. is there. In the drawing, 9 is an infrared lamp, 8 is a metal casing, 13 is a microwave attenuator, 14 is a tungsten filament, 15 is a tube, 16 is a support coil, 18 and 20 are electrical connections, and 30 and 31 are units. , 32 and 33 respectively indicate lamps.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Alex Leopold Halberstatt London, Golders Greene, Parkway 20 UK (72) Inventor Stefan John Newton Sally, Haslemere, Shotter Hill, Ryan Lane 92 (72) ) Inventor Susan Marie Crocker 26 Edward St. Roads, St. Edwards, Southsea, Hampshire, England (56) References JP-A-59-177886 (JP, A) JP-A-56-73888 (JP, A) Actual development Sho-54- 46057 (JP, U) Actually opened 62-43489 (JP, U) Actually opened 36-17481 (JP, Y1)

Claims (7)

[Claims] 1. A microwave energy generating source and at least one infrared ray generating source (9), wherein the at least one infrared ray generating source (9) is provided in a tubular halogenated tube (15). It comprises an infrared lamp (9) consisting of a tungsten filament (14) supported by spaced support coils (16), said support coils (16) each having one end attached to said filament (14). A microwave oven comprising a first wire portion and a second wire portion which is formed by curling the first wire portion at the other end and curling around the inner wall of the tube (15), The second wire portion is composed of one or less turns of the coil to prevent arcing between adjacent regions due to exposure to the microwave energy. The microwave oven characterized in that it is 2. A microwave oven according to claim 1, wherein the gaseous filling of the tube (15) is an arc between the ends of the lamp (9) and / or the filament (14). The microwave oven, wherein nitrogen as a main component is added with halogen to prevent generation. 3. The microwave oven according to claim 1 or 2, wherein the infrared source (9) is used.
Comprises a metal casing (8), each end of the filament (14) being provided with an electrical connection (18, 20) to a power source located outside the lamp (9), The electrical connection (18, 20) is positioned so as to be shielded from microwave energy by the wall (25) of the metal casing (8), whereby at the electrical connection (18, 20). Said microwave oven adapted to prevent the formation of local hot spots. 4. The microwave oven according to any one of claims 1 to 3, wherein the microwave source (9) is 1
Unit (30, with more lamps (32, 33)
31), wherein the electrical connection between the lamps is exposed to microwave energy so that the lamp (3
2, 33) The microwave oven arranged outside the unit (30, 31) so as to prevent generation of high-frequency current circulating inside. 5. A microwave oven as claimed in any one of claims 1 to 4, wherein the infrared source (9) comprises at least one lamp (32, 33).
31) and the length of the lead wire (38) of each lamp (32, 33) located in the unit (30, 31) is within the lead wire due to exposure to microwave energy. The microwave oven being minimized to prevent high frequency currents from being generated. 6. A microwave oven according to claims 1-5, wherein each end of the lamp (9) prevents microwave energy from leaking out of the oven. The microwave oven contained within. 7. The microwave oven according to claim 6, wherein the microwave attenuator (13) is a quarter
Said microwave oven consisting of a wavelength choke.