JPH1074650A - Engine spark coil device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To thin the thickness of an insulating resin to be filled in the space around the secondary coil for gaining the required dielectric strength to miniaturize the whole spark coil device by setting up the low dielectric strength between the secondary coil layers, and securing the layer thickness of the insulating resin proper for the voltage distribution state of the wound around secondary coil. SOLUTION: This spark coil device is integrally formed by implanting a coil case containing an assembled body of the spark coil body with an insulating resin. In this case, a secondary coil 7 is bank wound in the axtial direction, while obliquely overlapping the coil strand and slope-winding so as to reduce the coil diameter in the winding direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition coil device for an engine.

[0002]

2. Description of the Related Art A secondary coil in a conventional engine ignition coil device uses a coil bobbin divided into a plurality of sections by flanges at both ends and a plurality of ribs provided therebetween to form a coil wire in each section. The coils wound in the axial direction are stacked in several stages.However, in order to secure the dielectric strength of the coil wound in each section, increase the number of sections or increase the thickness of the ribs. And the coil bobbin becomes large, and the ignition coil device becomes large.

For this reason, conventionally, a bank winding is used which can secure the dielectric strength between layers of the coil by winding the element wire of the secondary coil on the coil bobbin without ribs obliquely and winding it one by one in the axial direction. By doing
The size of the ignition coil device is reduced (see Japanese Patent Application Laid-Open No. 60-107813).

[0004]

The problem to be solved is that the bank winding, in which the coil wires are uniformly wound in the axial direction while being superposed diagonally, has a disadvantage in the voltage distribution of the wound secondary coil. In order to ensure a corresponding dielectric strength against the outside, it is necessary to take a sufficient thickness of the insulating resin filled around the secondary coil.

[0005] This is particularly achieved by injecting an insulating resin into a cylindrical coil case in which an assembly of an open-magnetic-path-type ignition coil is placed, and integrally forming the cylinder coil portion of the engine. In the ignition coil device which is provided in the formed cylinder hole and directly attached to the ignition plug, the thickness of the insulating resin filled around the secondary coil due to the restriction of the diameter of the cylinder hole. However, there is a problem in that the diameter of the coil case becomes large in order to secure the withstand voltage by sufficiently taking the above into consideration.

[0006]

According to the present invention, a primary coil bobbin having a primary coil wound therein is coaxially provided inside a secondary coil bobbin having a secondary coil wound thereon. In an ignition coil device for an engine in which an assembly of an ignition coil having a core inserted in a hollow shaft is put in a coil case, and an insulating resin is injected into the coil case to be integrally formed, a secondary coil When adopting bank winding in which wires are wound in the axial direction while overlapping diagonally, so that the layer thickness of the insulating resin can be reduced according to the voltage distribution state of the wound secondary coil. By adopting a slope winding in which the coil diameter becomes smaller in the winding direction, the size of the ignition coil device can be effectively reduced.

[0007]

FIG. 1 shows an ignition coil device of an open magnetic circuit type engine which is directly attached to an ignition plug to which the present invention is applied.

[0008] It comprises a cylindrical coil case 1 in which an ignition coil assembly is placed, a plug cover 2 fitted and mounted in an opening below the coil case 1, and a coil cover. Low-voltage terminal socket 3 fitted and mounted on the outside of the upper opening of case 1
It consists of a part.

A primary coil 5 is provided inside the coil case 1.
A coil bobbin 8 around which a secondary coil 7 is wound is coaxially incorporated outside a coil bobbin 6 around which is wound, and a rod-shaped core 9 is inserted into a hollow shaft of the coil bobbin 6 on the primary side. Is stored. Core 9
The permanent magnets 10 are attached to both ends of each of them so that a large change in the amount of magnetic flux can be obtained when the primary current is interrupted.

As shown in FIG. 2, the core 9 is made of a plurality of iron plates having different widths so that the space factor in the hollow shaft of the cylindrical coil bobbin 6 can be increased to improve the efficiency of magnetic flux generation. By lamination, the cross section has a substantially circular shape.

At the lower end of the secondary coil pobin 8, a mounting portion 11 for a high voltage terminal is formed integrally with the central portion thereof and protrudes therefrom. Further, a contact spring 13 for making an electrical connection with the ignition plug 15 is mounted on the high-voltage terminal 12 which is bonded and attached to the mounting portion 11.

When the assembly of the ignition coil is accommodated in the coil case 1, the contact spring 13 projects out of the tubular hole 4 formed in the center portion of the plug case 2, and Of the mounting portion 11 is press-fitted into the hole 4 and the assembly is
It is designed to be positioned at a predetermined position.

With the ignition coil assembly positioned in the coil case 1 in a predetermined position, the coil case 1
An insulating resin such as a molten epoxy is injected from an opening above the resin, and the resin is solidified to be integrally formed.

At this time, in order to prevent the injected insulating resin from entering the portion of the core 9, the permanent magnets 10 provided at both ends of the core 9 are respectively covered, and a relatively large portion generated in the longitudinal direction of the core 9 is formed. A damper member is provided for absorbing thermal stress and preventing a crack in the solidified insulating resin around.

The coil case 1 is made of a magnetic material such as a silicon steel plate having conductivity and high magnetic permeability, and the ground terminal 27 in the low voltage terminal socket 3 and the coil case 1 are brought into contact with each other to establish an electrical connection therebetween. As a result, the coil case 1 is maintained at the ground potential.

Thus, the coil case 1 exerts an electromagnetic shielding effect, and the role of the side core is such that most of the magnetic flux generated by the open magnetic circuit type ignition coil assembly is concentrated on the coil case 1 portion. As a result, it is possible to effectively prevent the generated magnetic flux from spreading and passing through the surrounding cylinder block of the engine to be demagnetized to lower the secondary output voltage.

Further, since the coil case 1 is maintained at the ground potential, it is possible to prevent electric shock due to leakage discharge from the internal high voltage portion. Then, corona discharge locally generated between the secondary coil 7 and the coil case 1 is suppressed, and the insulation durability of the mold resin interposed therebetween is improved.

In addition, the discharge generated through the gap between the coil case 1 and the cylinder head is eliminated, so that it is possible to effectively prevent the control system of the engine and surrounding equipment from causing radio interference.

In order to suppress eddy current loss, a gap is formed in the coil case 1 in the longitudinal direction so that the cross section is C-shaped, as shown in FIG.
A slit 18 of about 1.5 mm is provided.

Then, inside the coil case 1,
An elastic member 17 such as rubber or elastomer is provided.

Thus, the elastic member 1 is placed between the coil case 1 and the mold resin injected and solidified therein.
With the interposition of 7, thermal stress due to temperature change is reduced by the elastic member 17, thereby effectively preventing the occurrence of cracks in the mold resin.

At the end of the plug cover 2, an ignition plug 15
Is mounted. When the ignition plug 15 is inserted into the plug rubber 16, the tip of the ignition plug 15 comes into contact with the contact spring 13 to establish an electrical connection.

An igniter 19 is housed inside the low voltage terminal socket 3.

When the low-voltage terminal socket 3 is fitted into the coil case 1, the elastic member 17 provided inside the coil case 1 is folded outward and the folded portion 2 is formed.
The low-voltage terminal socket 3 is fitted in 9 so as to enhance the sealing performance.

FIG. 3 shows the internal structure of the low voltage terminal socket 3 when the cap 20 is removed.

With the cap 20 attached to the low-voltage terminal socket 3, when a casting nozzle is inserted through a hole 22 formed in the cap 20 to inject an insulating resin into the interior, the cap 20 in the low-voltage terminal socket 3 is inserted. The cap 20 is integrally fixed by injecting an insulative resin to a level at which the tips of the plurality of ribs 21 provided on the inner side can be used.

The plurality of ribs 21 provided on the cap 20 disperse the thermal stress applied to the solidified insulating resin with a change in temperature, and cracks occur in the upper part of the igniter 19. Is effectively prevented.

When the coil case 1 is buried in a portion of the cylinder hole 23 formed in the girder head portion of the engine, the opening of the cylinder hole 23 is formed in the lower portion of the low voltage terminal socket 3 in the coil case 1. Is sealed.

In a state where the coil case 1 is buried in the cylinder hole 23, the ignition coil device is moved by a bolt 26 through a bolt seat 25 formed integrally with the low-voltage terminal socket 3 by a bolt 26. Attached to the side.

When the ignition coil device is attached to the cylinder head side by bolts 26, the difference in longitudinal contraction, which is the largest due to heat expansion, is outside the elastic member 17 provided inside the coil case 1. To be folded back.

According to the present invention, in the present invention, in particular, as shown in FIG. 5, the secondary coil 7 is overlapped obliquely with the coil bobbin 8 at an angle θ (eg, 25 °). The bank is wound one by one in the axial direction. Then, by gradually reducing the number of windings of each layer, a slope winding is made such that the coil diameter D decreases in the winding direction indicated by the arrow in the figure.

In this case, the secondary coil 7 is not wound uniformly in the longitudinal direction of the secondary coil 7, but is wound in the middle of the secondary coil 7.

However, adopting the bank winding eliminates the need for a comb-shaped rib having a cross-sectional shape for securing the required dielectric strength in the case of the split winding. The secondary coil 7 can be wound while ensuring the withstand voltage between the layers.

By adopting the slope winding, the layer of the insulating resin filled between the coil case 1 and the secondary coil 7 is moved in the winding direction of the secondary coil 7 (indicated by an arrow in the figure). It is possible to reduce the thickness of the insulating resin filled around the secondary coil 7 in order to obtain a required withstand voltage so that the insulating resin can be formed in a shape suitable for the voltage distribution state. Become. Therefore, in particular, the diameter of the coil case 1 can be reduced, and the size of the ignition coil device can be effectively reduced.

Further, by adopting the slope winding, the diameter of the flange 81 of the coil bobbin 8 at the high pressure portion at the end of the winding of the secondary coil 7 can be reduced. Alternatively, the flange 81 can be completely eliminated.

Thus, as shown in FIG. 1, the flange 81 of the coil bobbin 8 at the high pressure portion at the end of the winding of the secondary coil 7
Is sufficiently spaced without contacting the coil case 1 side, and it is possible to prevent a leak from occurring on the surface of the coil case 1 through the flange 81. In addition, it is possible to prevent the flange 81 from breaking due to thermal contraction.

The secondary coil bobbin 8 has a flange 8
A plurality of protrusions 28 are provided around the periphery at a position distant from the coil case 1, and when the ignition coil assembly is inserted into the coil case 1, the protrusions 28 contact the coil case 1 side to perform center positioning. Have to be able to.

Since the projection 28 is provided at a position distant from the high voltage portion of the secondary coil 7, no leak is generated on the surface of the coil case 1 through the projection 28.

FIG. 6 shows a case where an inner slope winding is employed by using a coil bobbin 8 'in which the diameter of the shaft portion changes so as to increase in the winding direction of the coil. In this case, compared to the case of the outer slope winding shown in FIG. 5,
It becomes possible to effectively prevent the coil from winding.

[0040]

As described above, in the ignition coil device for an engine according to the present invention, the secondary coil employs a bank winding wound in the axial direction of the coil bobbin while coil wires are superposed obliquely, and the winding direction In this case, the slope winding is adopted so that the coil diameter becomes smaller, so that the withstand voltage between the layers of the secondary coil can be set low, and the voltage distribution state of the wound secondary coil is reduced. The thickness of the insulating resin filled around the secondary coil is reduced in order to obtain the required insulation withstand voltage, making it possible to reduce the size of the entire ignition coil device. It has the advantage that it can be achieved.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an embodiment of an ignition coil device for an engine according to the present invention.

FIG. 2 is a cross-sectional view of the core in the embodiment.

FIG. 3 is a plan view when the cap of the low-voltage terminal socket in the embodiment is removed.

FIG. 4 is a transverse sectional view of a coil case portion in the embodiment.

FIG. 5 is a front sectional view showing a secondary coil employing a bank winding and an outer slope winding and a coil bobbin thereof.

FIG. 6 is a front sectional view showing a secondary coil employing a bank winding and an inner slope winding and a coil bobbin thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coil case 2 Plug cover 3 Low voltage terminal socket 5 Primary coil 6 Primary coil bobbin 7 Secondary coil 8 Secondary coil bobbin 9 Core 81 Collar of secondary coil pobin

Claims (3)

[Claims] A primary coil bobbin on which a primary coil is wound is provided coaxially inside a secondary coil bobbin on which a secondary coil is wound, and a core is inserted into a hollow shaft of the primary coil bobbin. The ignition coil assembly is placed in a coil case, and an insulating resin is injected into the coil case to integrally form the ignition coil device of the engine. The coil is made into a bank winding in which the coil wires are wound one by one in the axial direction while being superposed diagonally, and the coil diameter is reduced in the winding direction by reducing the number of turns of each layer. An ignition coil device for an engine, which is wound. 2. The ignition coil device for an engine according to claim 1, wherein the diameter of the flange at the coil winding end of the secondary coil bobbin is smaller than the diameter of the flange at the coil winding end. 3. The ignition coil device for an engine according to claim 1, wherein a flange at an end of coil winding of the coil bobbin on the secondary side is eliminated.