Inductor devices – Coil with crossed turns
Reexamination Certificate
1999-12-14
2001-06-26
Mai, Anh (Department: 2832)
Inductor devices
Coil with crossed turns
C336S190000, C336S222000
Reexamination Certificate
active
06252483
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to an electromagnetic coil suitable for use under application of high voltage, and more particularly to an ignition coil which develops high voltage to produce a spark as for ignition purposes in an internal combustion engine.
2. Background of Related Art
Japanese Patent Second Publication No. 2-18572 and Japanese Patent First Publication Nos. 2-106910 and 60-107813 teach conventional electromagnetic coils. These electromagnetic coils are made up of a plurality of slant winding layers oriented at a given angle to the length of a spool so that each of the slant winding layers presents a circular cone. In the following discussion, this type of electromagnetic coil will be referred to as a slant winding electromagnetic coil. The slant winding electromagnetic coils may be distinguished in the shape of winding layers from typical electromagnetic coils made up of cylindrical winding layers each extending in a lengthwise direction of a bobbin.
In such a slant winding electromagnetic coil, since each winding layer, as discussed above, extends radially so as to form a circular cone, the number of turns thereof is smaller than that of each of the cylindrical winding layers. This means that it is possible to decrease the number of turns of adjacent two of the winding layers to decrease a potential difference between the adjacent winding layers, thereby avoiding the dielectric breakdown for realizing an electromagnetic coil suitable for use under application of high voltage.
Such an electromagnetic coil is, as discussed in the above publications, suitable for use in an ignition coil for internal combustion engines. Particularly, this type of electromagnetic coil may be employed as a secondary winding for developing high voltage in combination with a primary winding.
The results of tests performed by the inventors of this application, however, showed that it was very difficult to arrange slant winding layers on a spool perfectly in an industrial manufacturing process, especially because an automatic winding machine which makes coils at high speeds is usually used in the industrial manufacturing process, and it is necessary to use thin wire for achieving the compact and lightweight structure of a coil.
The slant winding requires the formation of a cone-shaped winding using a leading portion of wire to define a reference surface for arranging slant winding layers in a lengthwise direction of a spool. In order to form the cone-shaped winding easily, it is useful to make an irregular winding of a triangle shape in cross section using a leading portion of wire, but a drawback is encountered in that it is difficult to develop a potential difference across each turn of the irregular winding at a constant level.
In the slant winding process, winding layers made of a trailing portion of wire may be shifted or crumbled.
The turns of wire may be disordered at the end of winding due to a variation in length of a spool, a variation in tensile force acting on the wire during winding, or undesirable insertion of a portion of the wire into a groove formed in a flange provided at an end of the spool for withdrawing an end of the wire.
When the above discussed irregular winding or irregularity of the winding caused by the disorder of the turns is included in the slant winding layers, it may cause some of the turns creating high voltages to be arranged adjacent to each other. It thus becomes difficult to estimate and manage the potential difference between the turns so that it is difficult to achieve high insulation expected in the slant winding electromagnetic coils.
SUMMARY OF THE INVENTION
It is therefore a principal object of the present invention to avoid the disadvantages of the prior art.
According to one aspect of the present invention, there is provided an electromagnetic coil which comprises a winding member having a given length; a lower voltage winding portion wound around a first length of the winding member, the lower voltage winding portion including a plurality of winding layers overlapped with each other and inclined at a given angle to the first length of the winding member, each of the winding layers being made up of a collection of turns of wire; a higher voltage winding portion wound around a second length of the winding member continuing from the first length, the high voltage winding portion including a plurality of winding layers overlapped with each other and inclined at a given angle to the second length of the winding member, each of the winding layers being made up of a collection of turns of the wire so that an arrangement of the collection of the turns of the wire of the higher voltage winding portion is more regular than that of the lower voltage winding portion.
In the preferred mode of the invention, the turns of the wire of each of the winding layers of the lower voltage winding portion and the higher voltage winding portion are arranged coaxially with each other. The coaxial arrangement of the collection of the turns of the higher voltage winding portion is more regular than that of the lower voltage winding portion.
The lower voltage winding portion includes an irregular winding made up of turns of the wire arranged irregularly.
According to another aspect of the invention, there is provided an electromagnetic coil which comprises a winding member having a given length; a lower voltage winding portion wound around a first length of the winding member, the lower voltage winding portion including a plurality of winding layers overlapped with each other and inclined at a given angle to the first length of the winding member, each of the winding layers of the lower voltage winding portion including a collection of turns made up of a leading portion of wire; and a higher voltage winding portion wound around a second length of the winding member, the high voltage winding portion including a plurality of winding layers overlapped with each other and inclined at a given angle to the second length of the winding member continuing from the first length, each of the winding layers including a collection of turns made up of a trailing portion of the wire.
In the preferred mode of the invention, the winding layers of the lower voltage winding portion and the higher voltage winding portion is arranged long the length of the winding member so as to define a conical surface tapered decreased in diameter as reaching from the lower voltage winding portion to the higher voltage winding portion.
An irregular winding portion is further provided in the lower voltage winding portion, which is formed with turns of the wire wound irregularly.
The electromagnetic coil is a secondary winding of an ignition coil for an internal combustion engine.
The electromagnetic coil is a high voltage developing coil which develops a high voltage through electromagnetic induction. The higher voltage winding portion includes adjacent two of the winding layers which have the number of turns t
H
given by the following equation:
t
H
≦n
T
/V
OUT
×180
where n
T
is a total number of turns of the lower and higher winding portions, and V
OUT
is an output voltage outputted by the electromagnetic coil.
The higher voltage winding portion is smaller in diameter than the lower voltage winding portion.
The higher voltage winding portion may be decreased in diameter than the lower voltage winding portion at a given rate.
The winding member is formed with a spool having formed at an end thereof a flange which has a tapered surface engaging the higher voltage winding portion.
The tapered surface of the flange is oriented at an obtuse angle to a longitudinal center line of the spool.
The flange of the spool has formed therein an opening through which the trailing portion of the wire passes. The opening is located in a radial direction of the spool above an outer peripheral portion of an end of the higher voltage winding portion engaging the flange.
The opening is formed with a groove extending inward from an outer peripheral portion
Kawano Keisuke
Kojima Masami
Nakazawa Katsumi
Oosuka Kazutoyo
Satou Yoshitaka
Mai Anh
Nippondenso Co. Ltd.
Pillsbury & Winthrop LLP
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