JP2000036423A - Ignition coil for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the secondary coil compact by providing the approximately same number of windings in each dividing groove of the secondary bobbin winding of the secondary coil. SOLUTION: Respective bobbins 1 and 2 are molded of the electric insulating material such as synthetic resin. In the secondary coil bobbin 2, a plurality of dividing grooves 5... having the specified width are formed in the longitudinal direction. In these respective dividing grooves 5 of the secondary coil 2, the same number of the secondary coils 2a which become about 1:80-120 at the winding ratio with the primary coil 1a are wound. In this case, all the dividing grooves 5... the secondary coil bobbin 2 are made to have the uniform width, the same number of windings is provided and the longitudinal direction of the secondary coil bobbin 2 is shortened. Furthermore, the coils are wound uniformly around each dividing groove 5.... The height of the winding is suppressed to the low height along the entire body. The length in the longitudinal direction of the secondary coil 2 is shortened. In addition, the interlayer voltage at the respective dividing grooves 5... are suppressed to the low values. The layer shortage between the electric wires is positively prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition coil for an internal combustion engine which supplies a high voltage to an ignition plug of the internal combustion engine to generate spark discharge.

[0002]

2. Description of the Related Art FIG. 6 is a sectional view of a conventional ignition coil for an internal combustion engine (hereinafter referred to as "ignition coil"). In the figure, a conventional ignition coil is provided with a primary coil 101a wound around an outer periphery and a primary coil bobbin 101 having an iron core 103 passing therethrough, and a secondary coil 102a wound around a concentric outer side of the primary coil bobbin 101. And the secondary coil bobbin 102 is housed in an insulating case 104 having an opening at the bottom and having a case opening 120 on the side opposite to the bottom,
The bottom opening is closed by one end 101m of the primary coil bobbin 101, and the primary / secondary coils 101a, 102 are formed by a thermosetting resin 108 which is poured into the insulating case 104 and cured.
a and the iron core 103 are fixed in an insulating case 104. The iron core 103 is composed of two substantially U-shaped laminated iron cores made of silicon steel, and each end face of the two laminated iron cores is arranged in one set inside the primary coil bobbin 101 and the other set on the outer wall side of the insulating case 104. And are joined by an adhesive, welding, or the like, and constitute a magnetic circuit that forms a closed magnetic circuit as a whole.

Each of the bobbins 101 and 102 is formed of an electrical insulating material such as a synthetic resin, and
Have narrow dividing grooves 151, 15 at both ends in the longitudinal direction.
2 and eight division grooves 150 having a predetermined width are formed therebetween. These division grooves 15 of the secondary coil bobbin 102 are formed.
A secondary coil 102a having a winding ratio of, for example, 1:80 to 120 with respect to the primary coil 101a is wound around each of 0, 151, and 152.

The insulating case 104 is formed of an insulating material such as a synthetic resin, and a primary terminal (not shown) is provided at one end of a case opening 120 of the insulating case 104 in a longitudinal direction (a direction perpendicular to the plane of FIG. 6). However, a high-voltage terminal (not shown) is provided at the other end.

Further, the primary coil 101a and the primary terminal are electrically connected at a connection portion P1, and the secondary coil 102a and the high voltage terminal are electrically connected at a connection portion Q1, respectively. After a predetermined current is applied to the primary coil 101a, When shut off,
The high voltage current generated in the secondary coil 102a is supplied from a high voltage terminal to a spark plug via a high tension cord.

The high voltage until the spark plug generates a spark discharge is almost uniformly distributed to the entire secondary coil 102a. At the moment when the spark discharge occurs, the sharp change in the potential of the secondary coil The voltage sharing between both ends (winding start and winding end) of 102a increases. Therefore, in order to alleviate the voltage distribution that increases at both ends of the secondary coil 102a, the narrow grooves 151 and 152 located at both ends of the secondary coil bobbin 102 (particularly the division grooves 152 located at the high voltage side) are used. The number of turns is smaller than the number of turns in the other division grooves 150.

[0007]

However, even when the number of turns of the divided grooves 151 and 152 at both ends of the secondary coil bobbin 102 is reduced as in the above-mentioned conventional ignition coil, the divided grooves 151 and 152 for that purpose are not It is also necessary to secure a so-called discarded winding groove. Therefore, a space is required for the number of windings, and the space is wasted, so that the secondary coil 102a can be reduced in size (reduced in length). In the way.

Further, the dividing grooves 15 at both ends of the secondary bobbin 102
When the number of windings of 1, 152 is reduced, the number of windings of the other divided grooves 150 is increased by the reduced amount, and the winding height is increased. Therefore, the outer diameter of the secondary coil 102a is increased. This also hinders downsizing of the secondary coil 102a.

[0009] The present invention has been proposed in view of the above,
It is an object of the present invention to provide an ignition coil for an internal combustion engine that can reduce the size of a secondary coil by eliminating the need for a waste winding groove.

[0010]

In order to achieve the above object, according to the present invention, a secondary coil is provided in an ignition coil for an internal combustion engine which supplies a high voltage to an ignition plug of the internal combustion engine to generate spark discharge. A characteristic feature is that substantially the same number of turns is applied to each divided groove of the secondary bobbin.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view showing an ignition coil according to the present invention, and FIG. 2 is a sectional view taken along line AA of FIG.
In these figures, an ignition coil according to the present invention supplies a high voltage to an ignition plug of an internal combustion engine to generate a spark discharge. A primary coil 1a is wound around an outer periphery and a primary core 3 passes through an inner periphery. Coil bobbin 1 and secondary coil 2a
And a secondary coil bobbin 2 disposed concentrically outside the primary coil bobbin 1 and housed in an insulating case 4 having an opening at the bottom and having a case opening 12 on the side opposite to the bottom. The bottom opening is closed at one end 1m of the primary coil bobbin 1, and the primary / secondary coils 1a, 2a and the iron core 3 are placed in the insulating case 4 with a thermosetting resin 8 cast into the insulating case 4 and cured. It is fixed and configured.

The iron core 3 is composed of two substantially U-shaped laminated iron cores made of silicon steel, and the end faces of the two laminated iron cores are arranged in one set inside the primary coil bobbin 1 and in the other set in the insulating case 4. Are joined together by an adhesive, welding, or the like on the outer wall side, and constitute a magnetic circuit that forms a closed magnetic circuit as a whole.

Each of the bobbins 1 and 2 is formed of an electrically insulating material such as a synthetic resin, and the secondary coil bobbin 2 is formed with eight divided grooves 5 having a predetermined width in the longitudinal direction. In each of the divided grooves 5 of the secondary coil bobbin 2, a secondary coil 2a having a winding ratio of, for example, 1:80 to 120 with respect to the primary coil 1a is wound to the same number.

The insulating case 4 is formed of an insulating material such as a synthetic resin. A primary terminal 6 is provided at one end of the case opening 12 of the insulating case 4 in the longitudinal direction (X direction in FIG. 1), and a high voltage terminal is provided at the other end. Terminals 7 are provided respectively.

Further, the primary coil 1a and the primary terminal 6 are electrically connected at a connection portion P, and the secondary coil 2a and the high voltage terminal 7 are electrically connected at a connection portion Q.
When a predetermined current is supplied to the secondary coil, the secondary coil 2
The high-voltage current generated at a is supplied from the high-voltage terminal 7 to the ignition plug via the high tension cord.

The high voltage until the spark plug generates a spark discharge is almost uniformly distributed to the entire secondary coil 2a, that is, to each of the divided grooves 5, but at the moment when the spark discharge occurs, the sharp voltage is increased. Secondary coil 2a
, The shared voltage at both ends (start of winding and end of winding) increases. Next, the shared voltage will be described.

FIG. 3 is a diagram showing an equivalent circuit of the secondary coil. In the drawing, S1, S2,..., And S8 are sections 1 (S1) in which the divided grooves 5 of the secondary coil 2a shown in FIG.
1), section 2 (S2),..., Section 8 (S
8). Each section S1 to S8 of the equivalent circuit includes a resistor R, a coil L, and a capacitor C
And is represented by

FIG. 4 is a diagram showing a shared voltage in each section calculated using the equivalent circuit of FIG. 3, and FIG. 5 is a diagram showing an interlayer voltage obtained from the shared voltage. In these figures, a solid line shows the case of the secondary coil 2a of the present invention wound by the same number in each divided groove, and a broken line shows a conventional ignition coil having a so-called discarded winding groove in which the number of turns of the secondary coil end grooves is reduced. Is shown.

When the discharge starting voltage at the moment when the spark discharge occurs is 25 kV, the sharing voltage E in each section at the start of the discharge is calculated using the above-described equivalent circuit, as shown in FIG. In FIG. 4, the sharing voltage E is represented by a sharing ratio (%) with respect to the entire voltage.

In the case of the conventional ignition coil in which the number of turns in the both ends of the secondary coil is reduced, it is true that the ends of the two ends (sections 1 and 2).
The sharing voltage E of the section 8) becomes lower, but the sharing voltage E of the adjacent sections 2 and 7 becomes higher. As shown in FIG. 5, the potential difference per turn (one turn) obtained by dividing the shared voltage E by the number of turns of the section, that is, the interlayer voltage Δe between adjacent wires, is particularly, as shown in FIG. It is very high in the section 8 on the high pressure side where the number of times is small.

On the other hand, in the case of the secondary coil 2a of the present invention in which the winding is uniformly applied to all the divided grooves, the shared voltage ΔE of the grooves at both ends (section 1, section 8) is slightly higher as shown in FIG. However, since the number of windings in the section is the same as the number of windings in other sections and is considerably larger than in the past, the voltage per turn, that is, the interlayer voltage Δe between adjacent wires is As shown in FIG. 5, a low value can be stably maintained over the entire section including the high-pressure side section 8, so that a layer short between the electric wires can be reliably prevented.

As described above, in this embodiment, since all the divided grooves 5 of the secondary coil bobbin 2 have the same width and the same number of turns, the so-called discarded winding grooves conventionally provided are omitted. Therefore, the length direction of the secondary coil bobbin 2 can be shortened.

Further, since the winding can be evenly wound in each of the divided grooves 5, the winding height can be suppressed so as not to be high throughout, and the radial direction of the secondary coil 2a can be shortened. As described above, both the length direction and the radial direction of the secondary coil 2 can be shortened, which can greatly contribute to downsizing of the secondary coil 2a.

The interlayer voltage .DELTA.e in each of the divided grooves 5...
Can be suppressed low as a whole, and layer short-circuiting between the electric wires can be reliably prevented, and therefore, the ignition coil can be made highly reliable.

[0025]

As described above, according to the ignition coil for an internal combustion engine of the present invention, the number of turns of all the divided grooves of the secondary bobbin is made substantially the same, so that the so-called discarded winding grooves conventionally provided. Can be omitted, and therefore, the length direction of the secondary bobbin can be shortened. In addition, since the winding can be performed substantially evenly in each of the divided grooves, the winding height can be suppressed so as not to increase over the whole, and the radial direction of the secondary coil can be shortened. As described above, both the length direction and the radial direction of the secondary coil can be shortened, which can greatly contribute to downsizing of the secondary coil.

Further, since the interlayer voltage in each of the divided grooves can be kept low throughout, it is possible to reliably prevent a layer short circuit between the electric wires, and therefore, it is possible to make the ignition coil highly reliable. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an ignition coil according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram showing an equivalent circuit of a secondary coil.

FIG. 4 is a diagram showing a shared voltage in each section calculated using the equivalent circuit of FIG. 3;

FIG. 5 is a diagram showing an interlayer voltage obtained from a shared voltage in each section.

FIG. 6 is a sectional view of a conventional ignition coil.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary coil bobbin 1a Primary coil 2 Secondary coil bobbin 2a Secondary coil 3 Iron core 4 Insulation case 5 Dividing groove 6 Primary terminal 7 High voltage terminal 8 Thermosetting resin 12 Case opening E Sharing voltage L coil P connection part Q connection part Δe interlayer Voltage

Claims (2)

[Claims] In an internal combustion engine ignition coil for supplying a high voltage to an ignition plug of an internal combustion engine to generate spark discharge, substantially the same number of turns is applied to each divided groove of a secondary bobbin for winding a secondary coil. An ignition coil for an internal combustion engine, wherein the ignition coil is applied. 2. The ignition coil for an internal combustion engine according to claim 1, wherein each of the divided grooves has a substantially equal width.