Ignition coil assembly structure for an internal combustion engine

A housing structure of an ignition coil assembly for an internal combustion engine is disclosed, in which the coil assembly and the igniter are accommodated in a single casing. The coil assembly is wound around a leg of a rectangular core having a yoke portion running parallel to it. The casing accommodates the coil assembly and the leg of the core carrying it, leaving exposed to the outside the yoke of the core; a space is formed between a side of the coil assembly and a side wall of the casing. A plate-shaped heat sink abutting on the yoke of the core at its lower end extneds witin the casing between the coil assembly and the casing through said space, forming within the space a hollow receptacle between opposing surfaces of the coil assembly and the casing. The igniter is mounted to the heat sink within the hollow receptacle. The housing structure is attached to the body of an automobile, etc., at a surface of the heat sink abutting on the yoke of the core.

BACKGROUND OF THE INVENTION 
This invention relates to housing structures of ignition coil assemblies 
for internal combustion engines, which comprise, in addition to an 
ignition coil, an igniter circuit for controlling the primary current 
supplied to the ignition coil. 
Conventional ignition systems for internal combustion engines of automotive 
vehicles generally comprise breaker points for interrupting the primary 
current in the ignition coil, in synchrony with the rotation of the 
engine. Recently, however, ignition systems have been developed which 
utilize semiconductor circuits (i.e., igniters) instead of the breaker 
points. FIG. 1 shows, in a circuit diagram, the portion of such an 
ignition system including the ignition coil 1 and the igniter 2, wherein 
the igniter 2 constitutes the control circuit for controlling the current 
supplied to the primary coil winding 1a of the ignition coil 1. In the 
case of conventional housing structures of these igniter or semiconductor 
type ignition systems for an engine of an automotive vehicle, the ignition 
coil 1 and the igniter 2 are accomodated in respective separate casings, 
wherein the casing accomodating the igniter 2 is mounted to the casing 
accomodating the ignition coil 1, or alternatively, the casing of the 
igniter 2 is accommodated within the distributor of the ignition system. 
The above conventional housing structure of the ignition coil assembly of 
the igniter type ignition systems has the following disadvantage: The 
provision of separate casings for the ignition coil and the igniter 
increases the dimensions and production costs of the ignition coil 
assemblies. 
SUMMARY OF THE INVENTION 
It is therefore a primary object of this invention to provide an ignition 
coil assembly structure for an internal combustion engine which is small 
in size, easy to assemble, and low in cost. 
The above object is accomplished in accordance with the principle of this 
invention in an ignition coil assembly structure in which the coil 
assembly of the ignition coil and the control circuit for controlling the 
primary current in the ignition coil are accomodated in a single casing: 
The coil assembly including the primary and the secondary coil windings of 
the ignition coil is wound around a leg of a rectangular core, which 
comprises a yoke portion that runs parallel to the leg portion thereof but 
carries no coil windings of the ignition coil. The casing accomodates the 
coil assembly and the leg portion of the yoke carrying it, leaving exposed 
to the outside at least a portion of the yoke portion of the rectangular 
core; a space is formed between an outer side surface of the coil assembly 
and a side wall of the casing. Further, the ignition coil assembly 
structure according to this invention comprises a plate-shaped heat sink 
of a good heat conducting material abutting on the yoke portion of the 
core at an end portion thereof; the heat sink extends within the casing 
between the coil assembly and the casing, through the space formed between 
a side surface of the coil assembly and a side wall of the casing, thereby 
forming within said space a hollow receptacle between the opposing 
surfaces of the casing and the heat sink. The control circuit for 
controlling the primary current in the coil assembly is mounted on the 
heat sink within the hollow receptacle. The ignition coil assembly 
structure is attached to an appropriate attachment portion of the 
automotive vehicle carrying the internal combustion engine or of the 
internal combustion engine itself. 
In a preferred form, the ignition coil assembly structure further comprises 
the following: a fixing means, such as a fixing screw, for fixing the 
control circuit to the heat sink, extending through a hole formed in the 
side wall of the casing partitioning the hollow receptacle; an amount of 
resin material filling the hollow receptacle; and a label attached to a 
side surface of the casing so as to close the hole formed in the side wall 
of the casing. Further, it is preferred that the casing has windows formed 
in side walls thereof such that portions of the heat sink are exposed to 
the outside of the casing, so as to facilitate the radiation of heat from 
the heat sink. It is also preferred that the casing is divided into two 
portions: a cup-shaped main portion enclosing the coil assembly and the 
leg portion of the core and opening in an axial direction of the coil 
assembly; and a lid portion closing the opening of the main portion and 
carrying electrical terminals for the coil assembly and the control 
circuit. 
The novel features which are believed to be characteristic of this 
invention are set forth with particularity in the appended claims. This 
invention itself, however, both as to its structure and method of 
assembling it, together with further objects and advantages thereof, may 
best be understood from the following detailed description of the 
preferred embodiment in connection with the accompanying drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIGS. 1 through 3 of the drawings, an embodiment of this 
invention is described. 
The electrical circuit organization of the ignition coil assembly structure 
according to the embodiment of this invention is similar to that of the 
above-mentioned conventional igniter type ignition coil assembly; thus, as 
shown in FIG. 1, the electrical circuit of the ignition coil assembly 
structure of the embodiment comprises: an ignition coil 1 having a primary 
coil winding 1a and a secondary coil winding 1b; and an igniter circuit 2, 
including a power transistor 2a and a control unit 2b, for controlling the 
on-off operations of the power transistor 2a. The power transistor 2a is 
turned on and off in response to the control signal from the control unit 
2b. Each time the power transistor is turned off, the primary current, 
supplied from the battery B via the ignition siwtch S and flowing through 
the primary coil 1a and the power transistor 2a, is interrupted, and a 
high ignition voltage is thus induced across the secondary coil 1b of the 
ignition coil 1, which ignition voltage is supplied therefrom to a spark 
plug of an internal combustion engine (not shown) via a distributor (not 
shown). 
FIGS. 2 and 3 show the housing structure of the ignition coil assembly 
whose circuit diagram is shown in FIG. 1; FIG. 2 is a side view of the 
ignition coil assembly structure as viewed from left in FIG. 3, and FIG. 3 
is a front view thereof as viewed from right in FIG. 2. Let us first 
describe the construction of the ignition coil assembly structure in the 
assembled state, which structure is generally designated by reference 
numeral 3 in FIGS. 2 and 3: 
The bulk of the ignition coil assembly structure 3 is occupied by a 
rectangular core 4 of a laminated soft magnetic material and a coil 
assembly 5 wound around a leg of the core 4, which together constitute the 
ignition coil 1 of the circuit shown in FIG. 1. The rectangular core 4 
comprises a yoke portion 4a (which serves to complete the magnetic circuit 
of the ignition coil but carries no coil windings therearound) running 
parallel to the leg carrying the coil assembly 5; the coil assembly 5 
comprises a primary and a secondary coil 1a and 1b shown in FIG. 1. The 
coil assembly 5 and the leg of the core 4 carrying the coil assembly 5 are 
accomodated within a casing 6, which leaves exposed to the outside thereof 
at least a portion of the yoke portion 4a of the core 4. (In the case of 
this embodiment the entire yoke portion 4a is outside of the casing 6 and 
hence is exposed to the outside.) The casing 6, made for example of a 
synthetic resin, is devided into two portions: a substantially cup-shaped 
main portion 6A opening in an axial direction of the coil assembly 5 
(toward right in FIG. 2) and having rectangular heat-radiation windows (or 
openings) 65 and 66 through which a portion of the heat sink 7 is exposed; 
and a lid plate 6B carrying a high voltage secondary terminal 64 (coupled 
to the secondary coil winding 1b of FIG. 1) and an electrical connector 63 
including a plurality of terminals for the control circuit 8 (which 
comprises the igniter 2 of the circuit shown in FIG. 1). Between a side 
wall (at the left in FIG. 3) of the casing 6 and the opposing side surface 
of the coil assembly 5 is formed a rectangular space, constituting a 
hollow receptacle or pocket portion 61 for accomodating the control 
circuit 8, as described below. A plate-shaped heat sink 7, which abut on 
the yoke portion 4a of the core 4 at an L-shaped lower end portion (see 
FIG. 3) and side extensions thereof having holes 12 formed in registry 
with the holes 12 extending through the core 4 (see FIG. 2), extends 
through the above-mentioned rectangular space along the side surface of 
the coil assembly 5, so as to form within the space the hollow receptacle 
or pocket portion 61 between the opposing surfaces of the heat sink 7 and 
the side walls of the casing 6; the portion of the heat sink 7 within the 
pocket portion 61 constitutes an attachment portion 72 for the control 
circuit 8 corresponding to the igniter 2 of the circuit of FIG. 1. 
Further, portions of the heat sink 7 at the windows 65 and 66 formed in 
the casing 6 are directly exposed to the outside air for facilitating 
radiation of heat therefrom. The heat sink 7 is formed by a press from a 
plate of a good heat conducting material such as aluminum, copper, or an 
alloy thereof. The control circuit 8, including a power transistor 2a for 
controlling the primary current in the coil assembly 5 is mounted to the 
attachment portion 72 of the heat sink 7 by means, for example, of a 
fixing screw 81 extending through a hole 62 formed in the side wall of the 
main portion 6A of the casing 6. The space 9 formed within the casing 6 
above the coil assembly 5 is filled with an epoxy resin, while the pocket 
portion 61 is filled with a silicone gel. The hole 62 is closed by a label 
10 identifying the type, the name of the producer, and the lot number of 
the ignition coil assembly structure. 
As shown in FIG. 3, the ignition coil assembly structure 3 is mounted to an 
attachment portion 11 formed at an appropriate portion of the automotive 
vehicle carrying the internal combustion engine or at a portion of the 
internal combustion engine itself. Namely, the bolts 13 extending through 
the attachment-holes 12 formed through the core 4 and the heat sink 7 are 
screwed into threaded holes 11a formed in the attachment portion 11, so as 
to mount the ignition coil assembly structure 3 to the attachment portion 
11 at the attachment surface 73 of the heat sink 7 opposite to a surface 
71 thereof abutting on the yoke portion 4a of the core 4. 
Next, let us describe the method of assembling the ignition coil assembly 
structure 3 of FIGS. 2 and 3. 
Before assembled, the rectangular core 4 is capable of being disassembled 
into a pair of U-shaped halves (with the legs of the two U's extending in 
the opposite horizontal directions in FIG. 2). Thus, the substantially 
cup-shaped main portion 6A of the casing 6 is molded integrally with one 
of the U-shaped half of the core 4 having the legs of U extending toward 
right in FIG. 2, together with the heat sink 7, whose L-shaped end is kept 
pressed against the yoke portion 4a of the core 4 during the molding 
process. The lid 6B may be molded integrally with the coil assembly 5, or 
as a separate piece apart therefrom. The molded cup-shaped main portion 6A 
opens toward the right in FIG. 2; thus, the coil assembly 5 and the 
control circuit 8 are fitted into respective positions within the main 
portion 6A of the casing 6, and the control circuit 8 is fixed by a fixing 
screw 81 extending through the hole 62 in the casing 6, the hole 62 being 
closed by a label 10. After the electrical connections are made among the 
coil assembly 5 and the control circuit 8 within the main portion 6A of 
the casing 6, and the connector 63 and the high voltage secondary terminal 
64 on the lid 6B of the casing 6, the space 9 and the pocket portion 61 
are filled with an epoxy resin and a silicone gel, respectively. 
Thereafter, the lid 6B is fitted onto the opening of the main portion 6A 
of the casing 6, and the remaining U-shaped half of the core 4 is fixed to 
the half of the core 4 molded with the main portion 6A of the casing 6. 
This completes the assembling operation of the ignition coil assembly 
structure 3; the assembled structure 3 is attached to the attachment 
portion 11 as described above. 
The method of operation of the ignition coil assembly structure of FIGS. 1 
through 3 is as follows. As is well known to those skilled in the art, the 
control unit 2b of the igniter 2 shown in FIG. 1 (which igniter 2 is 
comprised by the control circuit 8 of FIG. 3) receives from a signal 
generator (not shown) disposed within the distributor (not shown) a 
pulse-shaped signal corresponding to the rotational angle of the 
crankshaft of the internal combustion engine; the control unit 2b of the 
circuit of FIG. 1 controls the on-off of the power transistor 2a in 
accordance with this signal indicating the rotational position of the 
crankshaft. Each time the power transistor 2a is turned off to interrupt 
the current flowing through the primary coil winding 1a of the ignition 
coil 1, a pulse-shaped high voltage is induced across the secondary coil 
winding 1b. The coil assembly 5 shown in FIG. 3 comprises the primary and 
the secondary coils 1a and 1b of FIG. 1. Thus, the high voltage induced in 
the coil assembly 5 is supplied via the secondary terminal 64 to the 
distributor (not shown) through a high tension cord (not shown) 
electrically coupled to the secondary terminal 64. The heat generated in 
the power transistor in the control circuit 8 during these operations, and 
that generated in the coil assembly 5, etc., are transmitted to the heat 
sink 7, from which a portion of the received heat is radiated to the 
outside air via the windows 65 and 66 of the casing 6, and a portion 
thereof is transmitted to the attachment portion 11 via the attachment 
surface 73 of the heat sink 7. Further, a portion of the heat generated in 
the control circuit 8 is transmitted effectively to the casing 6 via the 
resin material (i.e., silicone gel) filling the pocket portion 61, to be 
radiated from the outside surface of the casing 6. 
The advantage resulting from the housing structure of the ignition coil 
assembly according to the embodiment of this invention is as follows. 
Since the control circuit 8 and the coil assembly 5 are accomodated within 
a single casing 6, the ignition coil assembly structure can be reduced in 
size. Further, the main portion 6A of the casing 6 is molded integrally 
with a half portion of the core 4 together with the heat sink 7, and in 
addition, the control circuit 8 is accomodated within a pocket portion 61 
formed within the casing 6, wherein the hole 62 for letting through the 
fixing screw 81 for fixing the control circuit 8 to the heat sink 7 is 
closed by the simple means of a label 10; thus, the assembling procedure 
of the ignition coil assembly structure is simple and can be effected 
easily and speedily without loss of time and labor. 
While description has been made above of the particular embodiment of this 
invention, it will be understood that many modifications may be made 
without departing from the spirit thereof. For example, although the 
casing 6 is devided into the cup-shaped main portion 6A and the lid 
portion 6B in the case of the above embodiment, this invention is not 
limited to that particular type of the casing. Similarly, this invention 
is not limited to the particular type of core 4 which can be disassembled 
into two U-shaped halves, nor to the particular type of circuit structure 
(shown in FIG. 1) of the control circuit 8. Further, the heat-radiation 
windows 65 and 66 may be dispensed with. The appended claims are 
contemplated to cover any such modifications as fall within the true 
spirit and scope of this invention.