Boosting transformer for high-frequency heating device

Details Boosting transformer for high-frequency heating device Boosting transformer for high-frequency heating device

2000-06-02

2001-10-02

Philogene, Haissa (Department: 2821)

Electric lamp and discharge devices: systems

Combined load device or load device temperature modifying...

Distributed parameter resonator-type magnetron

C219S760000, C219S756000, C336S182000, C363S021040

Reexamination Certificate

active

06297593

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to boosting transformers used in high-frequency heating devices.
2. Description of the Background Art
Conventional Art
Conventionally, high-frequency heating devices such as microwave ovens have used a boosting transformer configured as shown in FIG.
19
. Such conventional transformer first of all has a winding including a primary winding
20
and a secondary winding
21
and a filament winding
23
. These windings are coupled together via a magnetic circuit formed of a magnetic body in the form of two ferrite cores
24
. As shown in the
FIG. 19
cross section, windings
20
,
21
,
23
are each arranged in the direction of the height of the boosting transformer, i.e., the lateral direction in the figure. Primary winding
20
has a width in the direction of the height of the boosting transformer W
1
and a thickness as measured when the winding is stacked T
1
, wherein width W
1
≧thickness T
1
, and secondary winding
21
also has a similar width-thickness relationship.
As such, the boosting transformer is sized to have a height large relative to its width and depth. This has been a limitation in determining where such boosting transformer should be attached in a high-frequency heating device which is complicated and has a high voltage line arranged therein and also has a complicated internal structure.
If the secondary winding has an insufficiently divided width, a problem will occur as described below: normally, the secondary winding receives a high voltage, which is, between the top and end of the winding, an instant, maximal voltage of 6 kv to 10 kv. As shown in
FIG. 21
, secondary winding
21
is successively wound around an insulation member
25
in the direction of the arrow and thus successively stacked, and it completes when it reaches a winding count as defined. If secondary winding
21
is provided as described above, however, secondary winding
21
provided through such process will inevitably have a portion failing to align and thus displaced.
In providing a secondary winding, as described above, the winding is labeled V
0
at its top, V
1
, V
2
, . . . at its return points and V
9
at its end, as shown in FIG.
21
. As such, if the secondary winding is provided in alignment, the winding normally has the V
9
position adjacent to the V
7
position. However, if at the ending, V
9
position the winding is displaced down from its appropriate layer level, the displaced winding will be processed adjacent to the winding positioned at V
5
or V
3
. If a winding have such displacement, in proportion to the number of such displacements the winding will receive a voltage twice to triple a voltage which a winding provided in alignment would receive.
Conventionally, a secondary winding has been divided normally into two to three blocks to reduce its width W to prevent any significant displacement thereof and thus reduce a voltage that would otherwise be applied.
In a boosting transformer, each winding and a magnetic body must be insulated from each other. To achieve such insulation, insulation members
25
,
26
are provided as shown in FIG.
19
. Insulation member
25
is structured to provide a plurality of protruding, dividing walls surrounding primary winding
20
, secondary winding
21
and filament winding
23
to insulate such windings from each other and also divide the high-voltage generating, secondary winding normally into two to three blocks, as described above (in
FIG. 19
, three blocks). Insulation member
25
thus structured results in the transformer having an increased height. Insulation member
26
insulates windings
20
,
21
,
23
and core
24
from each other.
Furthermore, in providing the aforementioned magnetic circuit to provide a permeability adjusted to match the circuit's operating state, insulation members
25
,
26
are structured to allow ferrite core
24
to have a gap
22
. As a result, when the boosting transformer operates a magnetic flux varies and ferrite core
24
thus oscillates and produces a noise. Accordingly, to prevent such noise a core fixing band
27
or an adhesive or the like must be used to fix ferrite core
24
to reduce the noise. This degrades the workability and reliability of the transformer and increases the cost for the same.
Furthermore, conventionally a boosting transformer is assembled through a procedure as shown in
FIG. 20
, having the following steps:
in a first step, primary winding
20
, secondary winding
21
and filament winding
23
are successively wound around insulation member
25
;
in a second step, insulation member
26
is attached to insulation member
25
;
in a third step, two cores
24
are inserted into the combination of insulation members
25
and
26
;
in a fourth step, core fixing band
27
is attached to fix ferrite core
24
; and
in a fifth step, the above is soldered to a temporarily fixed terminal to complete a boosting transformer.
Since such assembling procedure is taken, to produce a boosting transformer each winding must be wound around an insulation member or it could not have a magnetic material attached thereto. As such, in its production the boosting transformer must be processed through a carefully considered procedure and it is thus produced inefficiently
SUMMARY OF THE INVENTION
To overcome the conventional disadvantage described as above, one object of the present invention is to provide a boosting transformer sized and shaped to have its height reduced relative to its width and depth to be readily accommodated internal to a high-frequency heating device having a high-voltage line arranged therein and a complicated structure.
Another object of the present invention is to provide an approach for eliminating a noise produced when a ferrite core oscillates in operating a boosting transformer, and also to prevent such approach from degrading the workability and reliability of the boosting transformer and increasing the cost for the same.
Still another object of the present invention is to produce a boosting transformer through a process having steps simplified to produce the same more efficiently.
In order to achieve the above objects, the present invention provides a boosting transformer for a high-frequency heating device to overcome such disadvantages as resulting from conventional systems, having a configuration, function and effect as described below.
In the present invention, a boosting transformer for a high-frequency heating device is used in a high-frequency heating device configured to rectify a commercial, alternating power supply to obtain a direct-current voltage which is in turn converted by an inverter circuit to a high-frequency voltage which is in turn boosted by a boosting transformer and thus supplied to a magnetron. The boosting transformer includes an insulation member, and a primary winding and a secondary winding provided on the insulation member and mutually insulated by the insulation member. The present invention is characterized in structure in that the primary winding and the secondary winding each have a width (W
1
, W
2
) and a thickness as measured when each winding is stacked (T
1
, T
2
), the width (W
1
, W
2
) being smaller than the thickness (T
1
, T
2
).
Thus, the primary winding and the secondary winding, having an significant effect in shaping the boosting transformer, can be shaped flat to allow the transformer to be readily attached internal to a high-frequency heating device having a high-voltage line arranged therein and a complicated structure.
Furthermore, reducing a winding in width allows the winding to receive a reduced voltage for each layer thereof if the secondary winding is not divided when it is provided. As such, if a secondary winding receiving a high voltage fails to align and is thus displaced down as it is provided, it would only have a reduced inter-winding potential difference. As such, it can hardly suffer an inter-winding dielectric breakdown and the boosting transformer can thus be enhanced in reliability.
Furthermore, providin

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