Transformer assembling method, transformer,...

Details Transformer assembling method, transformer,... Transformer assembling method, transformer,...

2000-08-25

2002-08-20

Mai, Anh (Department: 2832)

Inductor devices

With outer casing or housing

C336S119000, C336S092000, C336S208000

Reexamination Certificate

active

06437673

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a transformer assembling method, a transformer, and a transformer-mounted substrate, or to an art most preferably applicable to, for example, a transformer for switching power supply units using a ferrite core. More particularly, this invention is concerned with a power supply unit having a components-mounted substrate or a power supply unit included in a recording apparatus, for example, an AC adaptor used as a power supply for electronic equipment or a power supply unit connected to the AC adaptor.
In general, a switching power supply unit can be designed to be more compact and lightweight than a dropper power supply unit, and has the advantage of exhibiting high conversion efficiency. The switching power supply unit is therefore widely adopted for various usages ranging from the usage as a built-in power supply to be incorporated in a compact equipment to the usage as an AC adaptor. Since the switching power supply unit has thus prevailed, various kinds of electronic equipment that are compact and lightweight can be readily carried about with females or children. The contribution of the switching power supply unit to industries has been highly appreciated.
Referring to the drawings, a transformer to be mounted on a substrate for this kind of switching power supply unit will be described briefly. In the front view of
FIG. 46
, a coil
103
is formed on a bobbin
102
, and a core
101
is inserted into the bore of the bobbin
102
a
. Thereafter, as shown in
FIG. 47
, an adhesive is applied to illustrated regions or the transformer is impregnated with a varnish as shown in FIG.
48
. Thus, a finished good is completed.
Using the above components, the transformer
100
is designed to be relatively flat, and mounted on a substrate. Thus, the transformer contributes to a compact and lightweight design of a power supply.
However, when the transformer
100
designed to be compact and lightweight and mounted on a substrate is incorporated in a power supply unit, there arises a problem that it may incur an excessive impact load because of improper handling during transportation.
Moreover, when the transformer
100
designed to be compact and lightweight and mounted on a substrate is incorporated in a power supply to be used as an AC adaptor placed on a desktop, since a power cord may be hooked to cause such an event that the power supply falls off the desktop, unprecedented measures must be taken in order to enable the power supply to resist an excessive impact load.
As already known, when an impact load works in this way, the excessive impact load is concentrated on the transformer whose weight is larger than the other various electronic components of the power supply.
The broken state of a transformer is serious when an external force works, as shown in
FIG. 43
, on a components-mounted substrate
20
in a direction of an arrow F. In other words, when an external force works, a moment oriented in a direction of an arrow M works on a transformer
100
. A tensile force acts abruptly on one of thin parts
102
a
of the bobbin
102
firmly soldered to the pattern-printed area of the substrate
20
via lead pins
12
connected to the secondary winding of the transformer
100
. As a result, as already known, a breakdown phenomenon or a phenomenon that a transformer is ruptured at the thin part
102
a
thereof takes place.
A countermeasure against the rupture is such that the thin parts
102
a
united with both ends of the coil
103
formed on the bobbin are, as shown in
FIG. 44A
that is the front view of the bobbin
102
and
FIG. 44B
that is the right-hand side view of the bobbin, chamfered for the purpose of reinforcement. The anti-breakdown strength of the bobbin
102
is thus improved.
Another fixing method proposed is, as disclosed in Japanese Unexamined Patent Publication Nos. 6-96965 and 6-163278, such that a transformer itself is stowed in a housing for holding the whose transformer and gaps are filled with a resin.
Moreover, according to Japanese Unexamined Patent Publication No. 9-214156, ribs are interposed between radiating plates that are components to be mounted on a substrate. Even when the substrate is dropped, the ribs prevent the substrate from deforming to an extent exceeding a limit. The anti-impact resistivity of the substrate is thus improved.
Furthermore, in many cases, a containing means included in a power supply unit is composed of an upper case and lower case which are separated from each other up and down with a substrate between them. Supporting members are extended from the upper case and lower case in order to immobilize the substrate horizontally and vertically.
The sectional view of
FIG. 45
shows an example of a known holding structure for a substrate. There are shown upper and lower cases
213
and
214
for an AC adaptor, a substrate
220
to be held by the cases, screws
221
for tightening the upper case
213
and lower case
214
, a transformer
100
, radiating plates
222
and
223
, and an aluminum electrolytic capacitor
225
. On each radiating plate, heat-dissipation components, for example, a power transistor, FET, and diode are fixed using screws.
Ribs
213
b
that are supporting members successively extending from the upper case
213
are abutting on the substrate
220
and thus locking it. Ribs
214
b
are successively formed on the lower case
214
, and abutting on and holding the bottom of the substrate
220
. This helps the substrate
220
resist an impact load including a drop, and prevents deformation-based breakdown of the substrate
20
.
However, according to the known structure shown in
FIG. 45
, many members such as the ribs must be formed inside the cases in order to prevent deformation of the substrate
20
as greatly as possible.
Furthermore, in many cases, a containing means of a power supply unit is composed of an upper case and lower case that are separated from each other up and down with a substrate between them. Supporting members are extended from the upper case and lower case in order to immobilize the substrate horizontally and vertically.
Referring to the drawings, a transformer to be mounted on a substrate for a switching power supply will be reiterated.
FIG. 46
is a sectional view showing a major portion of a transformer
100
that has been generally adopted in the past. The transformer and a core are impregnated with a varnish and thus secured. In this drawing, a coil
103
is formed on a bobbin
102
, and a core
101
is inserted into the bore of the bobbin
102
. Thereafter, adhesives
105
and
106
are applied to illustrated regions. This results in a finished good. In
FIG. 48
, the whole outer circumference of the transformer is coated with a varnish
108
, whereby a finished good is completed.
In the above structures, the transformer
100
is placed to be relatively flat and then mounted on a substrate. The transformer contributes to a compact and lightweight design of a power supply.
Next, a transformer to be mounted on a substrate for a switching power supply unit will be described briefly.
FIGS. 47 and 48
are oblique views of the appearance of a transformer
100
that has generally been adopted in the past.
FIG. 47
shows a transformer of a type having a core secured using adhesives, and
FIG. 48
shows a transformer of a type having a core secured using a varnish with which the transformer is impregnated.
In
FIG. 47
, a coil
103
is formed on a bobbin
102
, and a core
101
is inserted into the bore of the bobbin
102
. Thereafter, adhesives
105
and
106
are applied to illustrated regions in order to secure the core, whereby a finished good is completed. In
FIG. 48
, the whole outer circumference of the transformer is coated with a varnish
108
, whereby a finished good is completed.
Whichever of the structures is adopted, the transformer
100
is designed to be relatively flat and then mounted on a substrate. The structure constitutes to a compact and lightweight design of a power supply.
However, there is a problem that aft

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