Internal-combustion engines – High tension ignition system – Having a specific mounting of system component
Reexamination Certificate
2000-12-04
2003-06-10
Kwon, John (Department: 3747)
Internal-combustion engines
High tension ignition system
Having a specific mounting of system component
C336S096000
Reexamination Certificate
active
06575151
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ignition coil for an internal combustion engine to make a sparkling discharge on a ignition plug of the internal combustion engine such as a vehicle engine.
2. Description of Related Art
FIG. 6
shows a cross sectional view of a conventional ignition coil of an internal combustion engine disclosed in Japanese Utility Model Registration No. 3039423.
In the drawing there are shown an iron core
1
forming closed magnetic circuit, a gap
1
a
formed in the closed magnetic circuit, an actuated magnetic portion
1
b
of the iron core around which an primary coil
2
and secondary coil
3
are wound and the axis line
1
c
of the actuated magnetic portion of the iron core. The primary coil
2
is wound around a primary bobbin
2
a
and aligned. The secondary coil
3
also wound around a secondary bobbin (not shown) and aligned.
An switching unit
4
is disposed in parallel with the actuated magnetic portion
1
b
and provided with switching element
4
a
such as bipolar transistor and IGBT or the like. The primary coil
2
and a terminal
5
a
of a connector
5
are connected electrically one another with a conductor
6
. A high voltage tower
7
outputs an electrical high voltage generated at the secondary coil
3
. After the above described elements are disposed in a case
8
, they are hardened stiffly in an oven together being immersed in vacuum by injection of a resin
9
through an opening
8
a
of case
8
.
FIG. 7
shows a preferred embodiment of the ignition coil, described in
FIG. 6
, mounted to the internal combustion engine.
The drawing shows ignition coil
10
described in
FIG. 6
, the internal combustion engine
11
, the ignition plug
11
a,
an axis line
11
b
of the ignition plug corresponding to the direction of screwing the ignition plug into the internal combustion engine and an adapter
10
a
connected to the ignition coil
10
wherein it is provided with conductor
10
b
inside and connects a ignition plug
11
a
with ignition coil
10
disposed inside a plug hole
11
c
. The ignition coil
10
is disposed at the top of the ignition plug of each cylinder lid wherein the axis line
1
c
of the actuated magnetic portion of the iron core and an axis line
11
b
of the ignition plug are perpendicular to each other.
For example, in the case where, as DOHC engine shown in
FIG. 8
, the ignition coil
10
is mounted in a narrow gap between the projections of the cam shield
50
used for the suction and exhaust, the switching unit
4
is disposed at the top of the actuated magnetic portion
1
b
being parallel to the axis line
1
c
of the actuated magnetic portion as shown in FIG.
9
. The total width of the ignition coil may be minimized into minimum dimension L
W
excluding the dimension of the switching unit
4
.
In case of mounting the ignition coil
10
to the internal combustion engine of the vehicle of which the hood
51
is low, as shown in
FIG. 10
, the total height of the IG coil needs to be decreased. As shown in
FIG. 11
the switching unit
4
is disposed at the opposite side against the corresponding surface
1
d
of the iron core, sandwiching the activated magnetic portion
1
b,
being parallel to the axis line
1
c
of the activated magnetic portion. By this way the total hight of the ignition coil may be minimized into minimum dimension L
H
excluding the dimension of the switching unit
4
.
The motion of the ignition coil will be described according to the FIG.
12
.
Synchronizing to the ON OFF motion of the ignition signal generated from an engine control unit
20
, the switching element
4
a
repeats the ON and OFF of the primary current to the primary coil
2
. When the primary current starts to flow, the current is not dashed but increased in the form of chopping waves proportional to the time of the current flow by an inductance of a magnetic circuit and the primary current is intercepted instantly by the OFF motion of the ignition signal. In the primary coil
2
an electromotive force is generated at the interception of the primary current. In the secondary coil
3
, a high voltage is generated proportional to the multiple number of the turns of both the primary coil
2
and the secondary coil
3
, this high voltage is supplied to the ignition plug
11
a
through the high voltage tower
7
and the adapter conductor
10
b.
A center electrode supplied the high voltage from the ignition coil and a side electrode connected to the earth are disposed at the top end of the ignition plug
11
a
and begins the discharge electricity when the air mixture of the fuel between the electrodes caused an isolation breakage by the supplied high voltage. This discharge is called the inductive discharge. The energy supplied from the primary coil of the ignition coil is injected in a mixed air in each cylinder of the internal combustion engine and forms the firing source in the discharge channel and grows it and finally sets fire to the fuel. The output voltage and energy of the ignition coil are almost proportional to the interception current value of the primary current, therefor in result it is proportional to the flowing time of the electricity.
In the process of being converted to the magnetic energy of the iron core, the energy supplied from the primary coil
2
is limited by the magnetic flux saturation of the iron core
1
. The maximum magnetic flux density of the iron core
1
is “magnetic flux density of the magnetic material used for the iron core for instance silicon steel plate etc.”דan area of the iron core section.” At the present time the required energy for the engine not requiring the large output energy of the ignition coil especially is about 23 mJ and as for the lean burn engine which appears in recent years and the engine which emits a jet inside the cylinder, the required energy is about 45 mJ. As the result of examining it based upon the iron core used for the ignition coil, it is recognized that required section area of the iron core of the actuated magnetic portion is more than 50 mm
2
. This area may realize the energy of more than 23 mJ.
Disposing the magnet in the gap with the polarity having an opposite magnetic direction against the actuated magnetic direction of the primary coil and using it from the condition in which the iron core is saturated in the magnetic field having opposite direction against the actuated magnetic direction, the energy accumulated in the magnetic circuit becomes twice as much. This method may realize the energy of about 45 mJ.
BRIEF SUMMARY OF THE INVENTION
Object of the Invention
One of the main elements defining the length of the ignition coil axis direction is the turning length of the primary coil. It corresponds to the dimension L
0
in FIG.
6
. For example in the prior art, the primary coil
2
wound by 150T having the maximum finished outside dimension is about 0.5 mm. In a primary bobbin
2
a
the coil should be a multiple layer like double layers or four layers because the starting position and the ending one of the coil should be coincides with each other. In the prior art the ignition coil has double layer and the length L
0
of the winding wire is 0.55 mm×(150T/2 layer)=37.5 mm. As the length L
1
of the case is about 45 mm, it is recognized that about 90% of it are the dimension of the primary coil.
The cylinder span L
k
(
FIG. 7
) of the internal combustion engine of around 1500 cc vehicle is about 90 mm, therefor in the case of mounting the conventional ignition coil shown in
FIG. 6
at the condition shown in
FIG. 7
, considering:
Case length L
1
+dimension to mount the iron core L
2
: 16 mm+connector dimension length L
3
: 22 mm+allowance of the dimension for insertion and removal: 10 mm, it is recognized that there is no more space.
If we design the ignition coil acceptable for the cylinder span L
K
of about 105 mm based upon the consideration of a big cylinder span engine, it is necessary to keep the case length L
1
within 60 mm.
The small diameter of the prim
Koiwa Mitsuru
Murata Shigemi
Kwon John
Mitsubishi Denki & Kabushiki Kaisha
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