JP2008028142A - Transformer for magnetron drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transformer for magnetron drive which exhibits a high heat resistance and is small-sized as a whole by improving the heat resistance of heater windings and enabling to reduce their size. <P>SOLUTION: Since the heater windings 5 are formed of aluminum conductor which exhibits a higher heat resistance than copper, the heat resistance of the heater windings 5 can be improved. Also, since it exhibits a higher workability than copper, the lamination factor of the windings can be easily improved, and the size of the heater windings 5 can be reduced. In this way, the transformer 1 for magnetron drive can be obtained which exhibits a high heat resistance and is small-sized as a whole. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high voltage transformer for driving a magnetron for driving a magnetron used in a microwave oven, a commercial dryer, or the like.

  Generally, a transformer has a primary winding and a secondary winding wound around a core, and copper (Cu) having a high conductivity is used as a conductor of the primary winding and the secondary winding. By the way, in a magnetron driving transformer used for a microwave oven or a commercial dryer, a heater winding for driving a magnetron heater is provided in addition to a primary winding and a secondary winding for supplying high voltage to the magnetron. It has been. The magnetron driving transformer generates a heater current between the heater winding and the cathode of the magnetron to drive the heater of the magnetron, and a high voltage is supplied to the magnetron, thereby generating a microwave from the magnetron.

On the other hand, it has been conventionally known that aluminum (Al) having the second highest conductivity after Cu is used as a conductor of a primary winding and a secondary winding of a transformer (for example, Patent Document 1). In general, Al is less expensive than Cu, and Al is mainly used for the purpose of cost reduction.
JP 7-226323 A

  However, in the conventional transformer for driving a magnetron, for example, when a heat resistance performance of a maximum allowable temperature of 240 ° C. (S type) is required as an insulating material, the heater current is also a large current, and the heater winding is made thicker. Since it is necessary to increase the heat resistance of the heater, there is a problem in that it is difficult to reduce the size of the transformer because the heater winding is enlarged.

  The present invention has been made in view of the above-described conventional problems. By improving the heat resistance of the heater winding and enabling the miniaturization, the transformer for driving a magnetron that is highly heat resistant and reduced in size as a whole transformer. The purpose is to provide.

  In order to achieve the above object, a transformer for driving a magnetron according to the present invention has a primary winding, a secondary winding, and a heater winding wound around a core, and drives a magnetron. The heater winding is made of an aluminum conductor.

  According to the above configuration, since the heater winding is made of an aluminum conductor having higher heat resistance than copper, the heat resistance of the heater winding can be improved, and it is easy because it is superior in workability compared to copper. In addition, the space factor of the winding can be improved, and the heater winding can be downsized, and a transformer for driving a magnetron that is highly heat resistant and downsized as a whole can be obtained.

  Preferably, the heater winding is enamel-coated aluminum wire, silicon rubber-coated aluminum wire, silicon rubber-coated enamel-coated aluminum wire, polyethylene terephthalate (PET) braided silicon rubber-coated aluminum wire, polyethylene terephthalate (PET) It consists of a coated electric wire comprising braided silicon rubber coated enamel coated aluminum wire, polytetrafluoroethylene (PTFE) coated aluminum wire, or polytetrafluoroethylene (PTFE) coated enamel coated aluminum wire. Therefore, by using the above-described covered electric wire as the heater winding, it is possible to obtain insulation similar to that of a copper conductor covered electric wire.

  Preferably, the core includes a first core piece and a second core piece, and the heater winding is pressed between the first and second core pieces to change the cross-sectional shape. Therefore, since aluminum is easily deformed by pressing, the cross-sectional shape of the heater winding becomes flat, and the gap between the winding and the core and between the windings is reduced, so that the space factor of the winding is increased. The winding can be made smaller.

  Preferably, the heater winding has an irregular shape including a rectangular shape and an elliptical cross-sectional shape. Therefore, when the winding cross-sectional shape is irregular, the space between the winding and the core and between the windings is reduced compared to the circular shape, so that the space factor of the winding can be increased. The wire can be made smaller.

  Preferably, the heater winding is provided between the primary winding and the secondary winding, and a pass core is formed between the primary winding and the heater winding. Therefore, the output voltage can be kept substantially constant with respect to the fluctuation of the input voltage by utilizing the leakage magnetic flux of the pass core.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a front view showing a magnetron driving transformer 1 according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view thereof. 1A is a high-voltage transformer for driving a magnetron for driving, for example, a magnetron used in a microwave oven, and is an outer iron type step-up transformer. The transformer 1 includes a core 2, a primary winding 3 wound around the core 2, a secondary winding 4, and a heater winding 5 provided between the primary winding 3 and the secondary winding 4. Further, a pass core 7 is provided between the primary winding 3 and the heater winding 5.

  The core 2 includes a first core piece, such as an E-shaped core 2E, and an I-shaped core 2I, each of which is formed by stacking plate materials (laminated cores) such as E-type and I-type silicon steel plates, respectively. Such a second core piece is joined at the butting portion 9. By joining the E-shaped core 2E and the I-shaped core 2I, two winding housing portions (window portions) 6 are formed between the both legs and middle legs of the E-shaped core 2E and the I-shaped core 2I. . A primary winding 3, a secondary winding 4, a heater winding 5, and a pass core 7 are attached to the window portion 6.

  As will be described later, the transformer 1 supplies a high voltage to the magnetron by the primary winding 3 and the secondary winding 4, and drives the heater of the magnetron by the heater winding 5 (FIG. 3). Further, the output voltage is held substantially constant by the pass core 7 with respect to fluctuations in the input voltage using the leakage magnetic flux.

  As shown in FIG. 2, the transformer 1 includes a primary winding 3, a pass core 7, a heater winding 5, and a secondary winding in order from the top in a winding housing portion (window) 6 in the E-shaped core 2 </ b> E. The winding 4 is fitted and assembled through an insulating material 8, and the I-shaped core 2I and the E-shaped core 2E are welded at the butting portion 9 (FIG. 1A), and then the entire varnish is impregnated. Formed. The primary and secondary windings 3 and 4 are made of, for example, a copper (Cu) conductor.

  The heater winding 5 is made of an aluminum (Al) conductor, and has a normal circular shape (round line) as shown in FIG. 1B. For example, the heater winding 5 is wound three times in a spiral shape. The heater winding 5 includes enamel-coated aluminum wire, silicon rubber-coated aluminum wire, silicon rubber-coated enamel-coated aluminum wire, polyethylene terephthalate (PET) braided silicon rubber-coated aluminum wire, or polyethylene terephthalate (PET) braid. A coated electric wire such as a silicon rubber-coated enamel-coated aluminum wire, a polytetrafluoroethylene (PTFE) -coated aluminum wire, or a polytetrafluoroethylene (PTFE) -coated enamel-coated aluminum wire is used. Thereby, the insulation similar to the covered electric wire of Cu conductor can be obtained.

  At the time of assembling the transformer 1 described above, as shown in FIG. 1B, the primary winding 3 and the like from the window 6 in the E-shaped core 2E to the extent that the sectional shape of the heater winding 5 is circular. In a state where the contents are slightly overflowed, the E-shaped core 2E is pressed in the X direction by the I-shaped core 2I and assembled. Due to the pressing by the I-shaped core 2I, Al is more malleable (formability) than Cu. Therefore, as shown in FIG. 1A, the heater winding 5 made of an Al conductor has a circular cross-sectional shape. Is deformed into an oval shape, and the stored item is compressed in the longitudinal direction X by that amount and stored in the window portion 6. As a result, the heater winding 5 having a circular cross section before the assembly of the transformer 1 is plastically deformed into an elliptical cross section after the assembly, thereby reducing the gap between the winding and the core and between the windings. Winding space factor is improved.

  When Al is used for the heater winding, the heat resistance is higher than Cu, but the electrical conductivity is lower than Cu, so it is necessary to increase the wire diameter. Thus, the transformer can be reduced in size. In addition, the Al winding has a smaller elastic force (spring back) than the Cu winding, and the winding distortion is small, so that the shaping is good.

  Further, for example, when the maximum allowable temperature is 240 ° C. (S type), mica (quartz) having high heat resistance, quartz, or the like is used as a material for device insulation such as the insulating material 8.

  The transformer 1 configured as described above is used for driving the magnetron 26 in the high-frequency heating apparatus shown in the example of FIG. In this commercial power supply type high-frequency heating device (microwave oven), electric power is supplied from the commercial power supply 21 to the primary winding 3 of the transformer 1. The output voltage of the secondary winding 4 of the transformer 1 is rectified and smoothed by the half-wave rectifier circuit 25 and supplied to the magnetron 26 as a DC high voltage. The magnetron 26 whose heater is driven by the heater winding 5 of the transformer 1 receives microwaves and generates microwaves.

  As described above, in the transformer 1, since the heater winding 5 is made of an Al conductor having higher heat resistance than Cu, the heat resistance of the heater winding 5 can be improved, and the workability is higher than that of Cu. Therefore, the space factor of the winding can be easily improved and the heater winding 5 can be downsized. Thereby, the magnetron driving transformer 1 that is highly heat-resistant and miniaturized as a whole transformer can be obtained.

  A second embodiment of the present invention is shown in FIG. 4, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. In the second embodiment, the heater winding 5A is processed in advance into an irregular shape such as a rectangular shape (rectangular wire) having a square cross section. This processing is obtained by pressing the coated electric wire described above after coating or before coating. In this case, since Al is superior to Cu in molding processability and machinability, the corner portion of the rectangular wire can be easily processed to be small, so that the heater winding 5A is small when wound around the core 2. Can be Other configurations are the same as those of the first embodiment. Note that the cross-sectional shape of the heater winding 5A may be an elliptical shape instead of a rectangular shape.

  In the second embodiment, since the cross-sectional shape of the heater winding 5A has an irregular shape including a rectangular shape and an elliptical shape, the cross-sectional shape is between the winding and the core, between the windings, compared to a circular shape. Therefore, the space factor of the winding can be increased, and the heater winding 5A can be downsized. Since Al has a lower electrical conductivity than Cu, the wire diameter of the winding is thick, but since Al is excellent in workability, the cross-sectional shape of the heater winding 5 can be easily processed into an irregular shape. This makes it possible to reduce the size of the winding. Thereby, the magnetron driving transformer 1 that is highly heat-resistant and miniaturized as a whole transformer can be obtained.

    In each embodiment, although the E-shaped core and the I-shaped core are used for the first core piece and the second core piece, the present invention is not limited to this. For example, an E-shaped core and an E-shaped core are used. It may be used.

It is a front view of the transformer for magnetron drive concerning a 1st embodiment of the present invention. It is a disassembled perspective view of the same embodiment. It is an electric circuit diagram which shows the high frequency heating apparatus which can apply the transformer for magnetron drive of this invention. It is a front view of the transformer for magnetron drive concerning a 2nd embodiment.

Explanation of symbols

1: Magnetron drive transformer 2: Core 3: Primary winding 4: Secondary winding 5: Heater winding 6: Winding storage 7: Pass core

Claims (5)

A magnetron driving transformer for driving a magnetron, in which a primary winding, a secondary winding and a heater winding are wound around a core,
A magnetron driving transformer in which the heater winding is made of an aluminum conductor. 2. The heater winding according to claim 1, wherein the heater winding includes enamel-coated aluminum wire, silicon rubber-coated aluminum wire, silicon rubber-coated enamel-coated aluminum wire, polyethylene terephthalate braided silicon rubber-coated aluminum wire, polyethylene terephthalate braided silicon. A magnetron driving transformer comprising a coated electric wire including a rubber-coated enamel-coated aluminum wire, a polytetrafluoroethylene-coated aluminum wire, or a polytetrafluoroethylene-coated enamel-coated aluminum wire. 2. The magnetron drive according to claim 1, wherein the core includes a first core piece and a second core piece, and the heater winding is pressed between the first and second core pieces to deform a cross-sectional shape. Transformer. 2. The magnetron driving transformer according to claim 1, wherein the heater winding has an irregular shape including a rectangular shape and an elliptic shape in cross section. 2. The magnetron according to claim 1, wherein the heater winding is provided between the primary winding and the secondary winding, and further, a pass core is formed between the primary winding and the heater winding. Drive transformer.

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