Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-12-06
2002-02-12
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S092000, C174S1170FF, C336S092000
Reexamination Certificate
active
06346673
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates a noise preventing split ferrite core for a flat cable which is used to suppress not only noise conducting through the flat cable but also noise radiating therefrom and a noise preventing component, a wiring harness and an electronic apparatus which adopt therein the same noise preventing split ferrite core.
2. Description of the Related Art
Conventionally, in order to prevent noise from various types of electronic apparatus, for example, personal computers, a ferrite core is mounted on a cable connecting electronic apparatus. There are cables of various configurations and a flat cable is one of them. A ferrite core is, of course, mounted on such a flat cable for prevention of noise therefrom.
As a ferrite core for noise prevention from a flat cable, a ferrite core
1
shown in
FIG. 12
has been used for that purpose and the ferrite core
1
has an inside diameter (or an inner sectional configuration) having a flat O-shaped (or a flat ring-like) configuration which corresponds to the outside diameter (or the outer sectional configuration) of a flat cable FC.
Moreover, a split ferrite core shown in
FIG. 13
has also been used to facilitate attachment to and detachment from a flat cable. In this case, the ferrite core
1
is constructed such that the flat cable FC is held between split ferrite core bodies
1
a
,
1
b
which are abutted against each other.
A ferrite core attached to a flat cable needs to be fixed at an attached position such that the ferrite core does not move along the flat cable. This is because, if a ferrite core moves over a flat cable in an electronic apparatus after it is attached to the flat cable, the ferrite core comes into collision with a housing or component of the apparatus that is located adjacent thereto, this possibly leading to a failure of the ferrite core or a failure inside the electronic apparatus. In addition, the noise eliminating effect of the ferrite core differs depending on its position on the flat cable and therefore a change in the position of the ferrite core on the flat cable may affect the noise eliminating effect of the ferrite core. Thus, an optimum noise eliminating effect may not be obtained when the ferrite core moves over the flat cable.
As methods for fixing the ferrite core on the flat cable that have been used heretofore, in some cases the ferrite core and the flat cable are fixed to each other with an adhesive, an adhesive tape or the like, while in other cases the ferrite core is fixed to the housing of the electronic apparatus or on a substrate of the electronic apparatus which are located in proximity thereto.
However, these methods require labor hours. In particular, when an adhesive is used, a certain length of time is required before it sets up, and the ferrite core needs to be held at a position where it should be fixed until the adhesive is solidified. Thus, this method is disadvantageous in that a long production lead time is required. Moreover, with this method using an adhesive, if the ferrite core happens to be required to be removed for some reason, for instance, due to occurrence of a failure or defect in the ferrite core after it is fixed or occurrence of a disconnection of or defect in the flat cable, the ferrite core cannot be detached after the set adhesive is first removed and such work requires an extremely great deal of labor hours. In particular, where the flat cable and the ferrite core are secured to each other with an adhesive, there may be caused a failure in the coating of the flat cable or a disconnection of the flat cable while the adhesive is being removed, and if this happens, there may be caused a risk of the ferrite core and the flat cable being discarded.
With a view to overcoming a drawback as described above, components as shown in
FIG. 14
are proposed for fixing the ferrite core (produced by TOKIN under a trade name of FPD-CL-1 Camp) of an integral-type. This component
5
is characterized in that it is attached to end surfaces of end portions of a ferrite core
1
, respectively, and that it can be fixed onto an electronic apparatus housing or a substrate
10
with a screw
7
and a nut
8
using a hole
6
formed in the component
5
.
However, workability in attaching the ferrite core
5
to the electronic apparatus housing or the substrate
10
with the screw
7
and the nut
8
is not necessarily good. For instance, when trying to attach the ferrite core
1
to the electronic apparatus housing or the substrate
10
with the components
5
, first of all, the components
5
are mounted on the ferrite core
1
, and thereafter the ferrite core is fixed to the housing or the substrate
10
while the components
5
have to be held in the mounted positions by hand so that they should not come off the ferrite core. In addition, where the ferrite core
1
is removed after it has once been fixed in place, the ferrite core
1
cannot be removed before the whole set of the core and components are detached from the substrate. Moreover, since the ferrite core
1
used together with the components
5
is of an integral type, the ferrite core
1
has to be attached to a flat cable FC before a connection of the flat cable FC is completed, in other words, for instance, before a terminal is connected to the flat cable FC or the flat cable FC is connected to the electronic apparatus, and even if the ferrite core or the flat cable so attached has to be replaced for some reason, for instance, due to a failure or a defect in the ferrite core or a disconnection or a defect of the flat cable, the ferrite core or the flat cable cannot be replaced with ease, thus the working efficiency being deteriorated.
On the contrary, in the case of a split ferrite core, the ferrite core can be attached to the flat cable in any stage. In addition, the core can be detached from the cable with ease due to the construction of the split ferrite core. However, as with the integral-type ferrite core, if the fixing method is used in which an adhesive or an adhesive tape is used as a fixing means, there are caused the same problems as those inherent in the integral-type ferrite core.
With a view to overcoming the above drawback, a component as shown in
FIGS. 15 and 16
is proposed (produced by Kitagawa Kogyo under a trade name of EFC-40-N/S, disclosed on page
14
of the “EMI Preventing Ferrite Technical Information”) for split ferrite core. This component
15
is characterized in that a case
16
is provided with a function to cover a ferrite core
1
by split ferrite core bodies
1
a
,
1
b
which are abutted against each other.
However, provision of such a function to the case
16
ends in a complicated construction and higher costs. In addition, since the inside diameter of the split ferrite core bodies
1
a
,
1
b
cannot be varied, it is not possible to hold the flat cable between the split ferrite core bodies
1
a
,
1
b
so securely that the ferrite core is not allowed to move thereover; therefore, a bottom of the component
15
needs to be fixed to an electronic apparatus housing or a substrate with a tape with adhesives on both sides or an adhesive.
Furthermore, in the case of conventional integral-type or split ferrite cores, they are selected such that the inside diameter (or the inner sectional configuration) thereof matches the dimensions of a flat cable inserted thereinto. The ferrite core can provide a better noise eliminating effect as the impedance value becomes higher which is obtained when the flat cable is inserted through the ferrite core, and the magnitude of impedance is determined by the magnetic permeability and configuration of a material for the ferrite core. With the magnetic permeability of the material for the ferrite core remaining constant, an impedance value obtained is in proportion to the effective sectional area of the ferrite core and is in inverse proportion to the length of an effective magnetic path. Therefore, it is desirable to select a ferrite core having a configuration which can provide as wide a
Nguyen Chau N.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDK Corporation
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