JPH07111930B2 - Ignition coil for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ignition coil for an internal combustion engine, and more particularly to prevention of resin cracking due to a difference in thermal expansion between a core and a casting resin in the ignition coil.

[Prior Art] Conventionally, an ignition coil has a rod-shaped core, which is a ferromagnetic material, arranged at the center of an electrically insulating resin casing having a hole at one end and an opening at the other end. The rod-shaped core is externally fitted with a resin-made primary bobbin tightly fitted or integrally formed with the rod-shaped core and a primary coil formed of a primary winding formed by winding a copper wire around the primary bobbin. ing. Also this 1
A secondary coil made of a resin-made secondary bobbin fitted on the primary winding and a secondary negative wire formed by winding a copper wire around the secondary bobbin is fitted on the secondary coil. Then, after the connection terminals of the primary coil and the high voltage terminals of the secondary coil are attached, an electrically insulating casting resin such as an epoxy resin is injected and molded, and is integrally insulated and fixed in the casing. There is.

[Problems to be Solved by the Invention] However, in the conventional ignition coil having the above-described configuration, the coefficient of thermal expansion of the rod-shaped core and the casting resin, and the rod-shaped core and the primary bobbin molding resin over time when used for a long time. Therefore, there is a problem in that the casting resin and the primary bobbin molding resin are cracked in a cooling / heating cycle by repeatedly operating and stopping the internal combustion engine.

Therefore, in order to solve the above-mentioned problems,
In the publication, a gap is formed between the open end of the resin-made primary bobbin and the end face of the core, and the rod-shaped core moves in the gap in the primary bobbin, and an ignition coil that absorbs the difference in thermal expansion coefficient is disclosed. Exists. However, in the conventional ignition coil having the above-described configuration, the open end of the primary bobbin needs to be projected from the case opening (cast resin surface), which lacks compactness.
It has a structure with large restrictions.

It is an object of the present invention to provide a compact ignition coil for an internal combustion engine that surely prevents cracking of the resin and prevents leakage of the resin from the vicinity of the high voltage terminal of the secondary coil.

[Means for Solving the Problems] In order to achieve the above object, the ignition coil for an internal combustion engine of the present invention has an electrically insulating tubular resin casing having a hole at one end and an opening at the other end, A core is arranged, a primary coil is provided on the outer circumference of the core, and a secondary coil is further arranged on the outer circumference of the primary coil.
In an ignition coil for an internal combustion engine in which a high voltage terminal of a next coil is attached and an electrically insulating resin is cast in the casing, the ignition coil for an internal combustion engine is brought into contact with an end face of the core, and is inserted into a hole of the casing and the inside of the casing. A structure was adopted in which an elastic wire body was embedded in which a high voltage terminal that was fitted to the terminal of the ignition plug was embedded while connecting the next coil.

[Operation and Effect of the Invention] With the above configuration, the ignition coil for an internal combustion engine of the present invention has the following operation and effect.

The core is movably held by abutting the end face of the core and fitting the entire elastic in which the secondary coil is connected inside and the high voltage terminal fitted to the terminal of the ignition plug is embedded in the hole of the casing. Therefore, it is possible to absorb the thermal stress of the thermal cycle due to the difference in thermal expansion coefficient between the core and the resin, and improve the cold heat resistance.

Further, since the bottom hole of the casing is reliably sealed by the elasticity as a whole, it is possible to prevent the resin from leaking from the casing.

Furthermore, without the core protruding from the casing opening,
The ignition coil is compact because it is housed in the casing.

[Embodiment] An ignition coil of an internal combustion engine of the present invention will be described based on an embodiment shown in the drawings.

FIG. 1 shows a main part of a two-cycle gasoline engine equipped with an ignition coil for an internal combustion engine according to the present invention.
FIG. 2 shows an ignition coil.

Reference numeral 1 denotes an ignition coil for directly supplying a high voltage to an ignition plug 9 of a two-wheeled vehicle cycle gasoline engine (hereinafter abbreviated as engine) 8.

The ignition coil 1 includes an electrically insulating resin cylindrical casing (a plug cap in this embodiment) 10 and the casing 10.
A rod-shaped core 2 disposed inside, an elastic plug body 3 for movably holding the rod-shaped core 2, primary coils and 4 externally fitted to the rod-shaped core 2, and externally fitted to the primary coil 4. Secondary coil 6
It has and.

One end of the casing 10 has a large diameter round hole 12 and a small diameter round hole.
It has a bottom 11 on which 13 is formed. This casing 10
The ignition coil mounting member (14) has a leg portion (17) formed with a flange portion (16) that fits in the inner peripheral groove (15) of the mounting member (14). Casing 10
Has a cylindrical portion 18 extending upward in the drawing from the large diameter round hole 12 and the small diameter round hole 13 of the bottom portion 11. The other end of the cylindrical portion 18 has an injection opening for injecting a casting resin described later.
It is 19.

The rod-shaped core 2 has a ferromagnetic system such as ferrite and is arranged at the center of the casing 10. The axial end surface 21 of the rod-shaped core 2 is in contact with the elastic plug body 3.

The elastic end body 3 is made of a synthetic resin having excellent heat resistance and sealing properties such as acrylic rubber and silicone rubber. Elastic plug 3
Has a short sectional shape, and is recessed in the end surface 32 of the upper end 31 in the figure.
Forming 33. The axial end surface 21 of the rod-shaped core 2 is press-fitted into the recess 33. Further, the elastic plug body 3 is provided with a cylindrical portion 35 which is press-fitted and fixed in the small-diameter round hole 13 of the casing 10 at the lower end portion 34 in the drawing. Further, between the end portions 31 and 34, a disc-shaped portion 36 fitted in the large-diameter round hole 12 of the casing 10 is provided.

The primary coil 4 has a primary winding 40 that is wound around the rod-shaped core 2 with a predetermined gap. Rod-shaped core 2 and primary winding
The gap between 40 and 40 is filled with casting resin.

The primary winding 40 is formed by winding a self-bonding electric wire having a wire diameter of 0.3 mm to 1.0 mm in a substantially cylindrical shape, for example, about 50 to 200 times. The primary winding 40 has one end connected to a connection terminal 41 supplied with a primary DC current from a battery (not shown) and the other end connected to a grounding terminal 42. Lower end of the primary winding 40 in the figure
43 contacts the end surface 32 of the elastic plug body 3. The winding specification of the primary winding 40 is selected according to the voltage of the battery, the presence / absence of a resistor for limiting the primary DC current, and the performance specification of the engine 8.

The secondary coil 6 has a resin-made secondary bobbin 5 fitted onto the primary winding 40, and a secondary winding 60 wound around the secondary bobbin 5.

The secondary bobbin 5 has a comb-shaped cylindrical spool 51 around which the secondary winding 60 is directly wound, and frame portions 52 at both ends. The frame-shaped portion 52 is held by the disc-shaped portion 36 of the elastic plug body 3,
The inner peripheral surface 53 is fixed to the outer periphery 37 of the end 31 of the elastic body 3.

The secondary winding 60 is formed by winding a self-fusion power source having a wire diameter of 0.02 mm to 0.06 mm around the spool 51, for example, about 10000 to 20000 times. Also, one end of the secondary winding 60 is connected to the high voltage terminal 61,
The other end is connected to the ground terminal 42.

The high-voltage terminal 61 has a tubular portion 62 and a plug connecting fitting 63, and a part 64 of the tubular portion 62 is embedded in the elastic plug body 3. Further, one end 65 of the tubular portion 62 elastically holds the high voltage terminal 93 of the spark plug 9. Therefore, the spark plug 9
Thus, the vibration of the engine 8 transmitted to the ignition coil 1 can be absorbed by the elastic plug body 3. In addition to this, in the tubular portion 62, there is also a method in which the terminal 93 of the ignition plug 9 is elastically contacted and held in the tubular portion 62 by a conductive elastic body such as a coil spring.
Further, the other end 62 of the tubular portion 62 has a brim shape, and the winding end of the secondary winding 60 is connected thereto.

The secondary winding 60 generates a secondary high voltage (for example, 15 to 25 KVT) generated based on the change in the coil magnetic flux when the primary DC current supplied to the primary winding 40 is interrupted by the interrupter. Supply to the spark plug 9.

After these are housed in the casing 10, an electrically insulating casting resin 7 such as an epoxy resin is injected into the casing 10 through the injection opening 19 and is integrally fixed in the casing 10. In this case, the injection opening 19 becomes the casting resin surface.

The engine 8 includes a cylinder head 81, a cylinder block 82, a piston 83, a combustion chamber 84, and an engine cover 85 for mounting the ignition coil 1.

The spark plug 9 includes an insulator 91, a terminal 93 protruding from a rear end 92 of the insulator 91, a mounting bracket 94, a center electrode 95 and an outer electrode.
Composed of 96. The spark plug 9 has an engine cover 85.
It is fastened to a spark plug attachment screw hole 86 formed in the cylinder head 81 through a spark plug insertion hole 87 provided in the.

The operation of the ignition coil device 1 of this embodiment will be described with reference to the drawings.

First, the rod-shaped core 2 is press-fitted and fixed to the elastic plug body 3 so that the axial end surface 21 of the rod-shaped core 2 fits into the recess 33 of the elastic body 3 in which the high-voltage terminal 61 is embedded. Then, the primary winding 40 wound beforehand with a predetermined diameter is externally fitted to the outer periphery of the rod-shaped core 2 with a predetermined gap. At this time, the winding 43 of the primary winding 40 is in contact with the end surface 32 of the elastic plug body. After the secondary winding 60 is wound around the secondary bobbin 5 in layers, the secondary bobbin 5 is fixed to the outer circumference 37 of the end 31 of the elastic plug 3 by press fitting.

The elastic plug 3 is inserted into the small-diameter round hole 13 in the bottom 11 of the casing 10.
The elastic plug body 3 is fixed in the casing 10 by press-fitting the cylindrical portion 35 of. After that, the casting resin 7 is injected from the injection opening of the casing 10, so that the rod-shaped core 2, the primary coil 4, and the secondary coil 6 are integrally insulated and fixed in the casing 10.

In addition, the cylindrical portion 62 of the high-voltage terminal 61 embedded in the elastic plug body 3
Then, the ignition coil 1 is attached to the spark plug 9 so as to strongly hold the terminal 93 of the spark plug 9. Then, the flange portion 16 of the casing 10 is fitted into the inner circumferential groove 15 of the ignition coil mounting member 14, and the ignition coil 1 is attached to the engine cover 85.

Ignition coil 1 mounted on engine 8 in this manner
In general, since the difference in the coefficient of thermal expansion between the rod-shaped core 2 and the casting resin 3 is greatly different, cracking occurs in the casting resin 3 due to concentration of thermal stress when used for a long period of time. In order to prevent the occurrence of cracks in the casting resin 7, it is possible to absorb the thermal stress between the rod-shaped core 2 and the casting resin 3.

Therefore, in this embodiment, the elastic force of the elastic plug body 3 is used so as not to prevent the rod-shaped core 2 from moving during the cooling / heating cycle. It absorbs the thermal stress of the thermal cycle. Therefore, it is possible to reliably prevent the cracking of the casting resin 7 due to the cooling / heating cycle.

In addition, the elastic plug 3 allows a small-diameter round hole at the bottom 11 of the casing 10.
Since 13 is reliably sealed, the casting resin 7 can be prevented from leaking from the casing 10.

Furthermore, since the rod-shaped core 2 is housed in the casing 10 without protruding from the injection opening 19 of the casing 10,
The ignition coil 1 is compact.

In this embodiment, the ignition coil for the internal combustion engine of the present invention is used as the ignition coil of the two-cycle gasoline engine for two-wheeled vehicles, but it may be used as the ignition coil of other internal combustion engines.

In this embodiment, the elastic plug is made of synthetic resin such as rubber, but other elastic bodies may be used.

Although the rod-shaped core made of ferrite is used as the core in the present embodiment, a laminated core made of silicon steel plate may be used. In this case, the casing is a short tube.

In the present embodiment, the primary winding is used, which is wound around the primary coil, but a primary winding wound around a hollow primary bobbin with both ends open may be used. .

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a two-cycle gasoline engine for a two-wheeled vehicle equipped with an ignition coil of an internal combustion engine of the present invention, and FIG. 2 is an enlarged cross-sectional view of the main part of FIG. In the figure, 1 ... Ignition coil, 2 ... Rod-shaped core, 3 ... Elastic plug,
4 ... Primary coil, 5 ... Secondary bobbin, 6 ... Secondary coil, 7 ... Cast resin, 9 ... Spark plug, 10 ... Casing, 11 ... Bottom, 12 ... Large diameter circle Hole, 13 ... small diameter round hole,
21 …… Axial end face, 41 …… Connecting terminal, 60 …… Secondary winding,
61 …… High voltage terminal, 93 …… terminal

Claims (1)

[Claims] 1. A core is provided in an electrically insulating tubular resin casing having a hole at one end and an opening at the other end, and a primary coil is provided on the outer periphery of the core, and the primary coil is further provided. Ignition for an internal combustion engine, in which a secondary coil is arranged on the outer periphery of the casing, a connection terminal to the primary coil and a high-voltage terminal of the secondary coil are attached, and an electrically insulating resin is cast in the casing. In the coil, an elastic plug body, which is in contact with the end surface of the core and which has the high-voltage terminal fitted to the terminal of the spark plug and which is internally connected to the secondary coil, is fitted into the hole of the casing. An ignition coil for an internal combustion engine, which is characterized by: