JP2000100640A - Ignition coil for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dielectric durability by preventing the electric field concentration of a secondary coil lead line part in an ignition coil in an independent ignition type in an inner secondary coil structure. SOLUTION: A center core 1, secondary coil 3 wound around a secondary bobbin 2, and primary coil 5 wound around a primary bobbin 4 are concentrically arranged in a coil case 6 in this order from the inside. This ignition coil is directly connected with each ignition plug of an internal combustion engine so as to be used. A lead line 3a of the secondary coil 3 from a winding end edge 3' of the secondary coil 3 to a high voltage terminal 13 is provided in a layer-shaped coil leading structure as regular winding and two layer winding or more. Also, the bobbin thickness at a part 2a equivalent to the layer-shaped coil part of the secondary coil lead line 3a of the secondary bobbin 2 is made thicker than the bobbin thickness at the original coil part of the secondary coil 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine and, more particularly, to an ignition coil for an internal combustion engine of an independent ignition type which is mounted in each plug hole of the engine and is used directly connected to each ignition plug. About.

[0002]

2. Description of the Related Art In recent years, an independent ignition type ignition coil device for an internal combustion engine, which is introduced into a plug hole of an engine and directly connected to each ignition plug, has been put to practical use. This type of ignition coil device is called an in-plug type because at least a part of the coil portion is introduced and mounted in the plug hole, and the coil portion is elongated in a pencil shape because it is inserted into the plug hole. It is commonly referred to as a pencil coil, and contains a center core (a stack of many silicon steel plates with a magnetic core), a primary coil, and a secondary coil inside a slender cylindrical coil case.

[0003] Primary and secondary coils are usually wound around respective bobbins, and are arranged concentrically around a center core. The insulation of the coil is assured by injecting and hardening an insulating resin or enclosing an insulating oil in the coil case housing the primary and secondary coils.

A known example is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-255.
719, JP-A-9-7860 and JP-A-9-960
17662, JP-A-8-93616, JP-A-8-97057, JP-A-8-144916, JP-A-8-203775, JP-A-9-16770
No. 9 and the like. Further, in the pencil coil, consideration is given to providing a side core on the outer periphery of the coil case in order to suppress leakage magnetic flux passing through the outer periphery of the coil.

[0005] The pencil coil has a primary coil inside,
There are two types, one with the secondary coil placed outside and the other with the secondary coil placed inside and the primary coil placed outside. The latter method (inner secondary coil structure) is the former method (outer secondary coil structure). There is an advantage in output characteristics as compared with the case of (1).

That is, assuming a pencil coil in which an insulating resin (eg, epoxy resin) is injected and hardened into the constituent members of the coil, the outer secondary coil structure has a secondary coil and a low-voltage primary coil inside the secondary coil. (It can be regarded as almost the ground voltage.) In addition to the occurrence of the electrostatic stray capacitance, the electrostatic stray capacitance also occurs between the secondary coil and the side core (ground voltage). Compared to the extra stray capacitance on the side core side, the electrostatic stray capacitance of the outer secondary coil structure tends to increase (in the case of the inner secondary coil structure, the electrostatic stray capacitance between the secondary coil and the primary coil tends to increase). A stray capacitance is generated, and between the primary coil and the side core, since both the primary coil and the side core are at the ground voltage, substantially no electrostatic stray capacitance is generated).

The secondary voltage output and its rise characteristics are affected by the electrostatic stray capacitance. As the electrostatic stray capacitance increases, the output decreases and the rise is delayed. Therefore, it is considered that an inner secondary coil structure having a small electrostatic stray capacitance is more suitable for miniaturization and high output.

[0008]

An independent ignition type internal combustion engine ignition coil of this type is disclosed, for example, in Japanese Patent Laid-Open No. 9-1677.
As disclosed in Japanese Patent Application Publication No. 09-09, a secondary coil lead wire from the end of winding of a secondary coil wound on a secondary bobbin to a high voltage terminal is drawn out as a single thin wire.

According to such a secondary coil lead-out structure, between the high-voltage single line (secondary coil lead-out line) and the edge of the center core, or between the secondary coil lead-out line and one end of the magnet disposed at one end of the center core. Between the secondary coil lead wire and the low-voltage primary coil, or between the secondary coil lead wire and the low-voltage side core, the electric field concentration is likely to occur, which may cause dielectric breakdown. The details of the conventional secondary coil lead wire structure and its electric field concentration will be described in the embodiments of the present invention in comparison with the present invention.

The present invention has been made in view of the above points, and an object of the present invention is to improve the insulation durability by preventing the electric field concentration at the secondary coil lead wire portion in an independent ignition type ignition coil having an inner secondary coil structure. To make it happen.

[0011]

The present invention is basically configured as follows to achieve the above object.

That is, in an independent ignition type internal combustion engine ignition coil having a so-called inner secondary coil structure, a lead wire of the secondary coil extending from the winding end of the secondary coil wound around the secondary bobbin to the high voltage terminal. Is characterized in that it has a layered winding draw-out structure of two or more layers by aligned winding.

[0013] According to the above configuration, since the lead-out portion of the secondary coil has a layered winding lead-out structure of two or more layers, the windings of the lead-out portion are densely packed without gaps. Electric field concentration between the center core, the primary coil, and the side core can be prevented. Here, the draw-out portion of the secondary coil is formed of two or more layers in order to eliminate the gap between the windings and to function the above-described electric field concentration.

For example, while the primary winding of the secondary coil wound on the secondary bobbin has a winding structure of 15 layers or more, the secondary coil extending from the end of winding of the secondary coil to the high voltage terminal is formed. The number of lead wires is reduced from 2 layers to 10 layers or less. In addition, by making the number of winding layers of the secondary coil lead portion smaller than the number of winding layers of the secondary coil in this way, the thickness of the secondary bobbin high-pressure portion can be increased. Withstand voltage can be improved. As a result, the insulation durability of the ignition device for an internal combustion engine can be improved.

[0015]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partially omitted longitudinal sectional view showing an ignition coil for an internal combustion engine according to one embodiment of the present invention, and FIG. 2 is a partially enlarged sectional view thereof.

An elongated cylindrical coil case (exterior case)
6, a center coil 1, a secondary coil 3 wound on the secondary bobbin 2, and a primary coil 5 wound on the primary bobbin 4 are arranged in order from the center (inside) to the outside. A thermosetting insulating resin (epoxy resin in this example) 8 is filled so as to eliminate voids. In the secondary bobbin 2, a soft epoxy resin (so-called elastomer) 9 having elasticity at least at room temperature or a silicone rubber instead of the center core 1 and a magnet 10 arranged at both ends thereof are filled so as to fill the periphery thereof. It is filled so that thermal stress can be relaxed by the difference in linear expansion coefficient between the center core 1 and the secondary bobbin 2.

A side core 7 is provided on the outer surface of the coil case 6.
Is attached. The side core 7 forms a magnetic path in cooperation with the center core 1, and is formed by rolling a thin silicon steel sheet or a directional silicon steel sheet of about 0.2 to 0.5 mm into a tube and stacking one to four sheets. I have. However, in order to prevent short-circuiting of the magnetic flux for one turn, at least one cut on the circumference of the side core 7 is provided.

The center core 1 is formed by pressing and laminating a large number of silicon steel sheets or oriented silicon steel sheets of about 0.2 to 0.5 mm. Magnets 10 are arranged at both axial ends of the center core 1 so as to be adjacent to the center core 1. The magnet 10 generates a magnetic flux in a direction opposite to a coil magnetic flux passing through the center core 1, thereby operating the ignition coil below the saturation point of the magnetization curve of the core. The magnet 10 may be arranged only at one end of the center core 1.

In order to absorb the difference in the coefficient of linear expansion of the center core 1 and the magnet 10 in the axial direction with respect to the secondary bobbin 2 and the epoxy resin 8, foaming is carried out in the axial direction along with the center core 1 and the magnet 10 as a thermal stress buffering member. A rubber plate 11 is arranged.

The coil case 6 is formed of, for example, polybutylene terephthalate (hereinafter, referred to as "PBT"), polyphenylene sulfide (hereinafter, referred to as "PPS"), or the like.

The primary bobbin 4 is formed of a thermoplastic synthetic resin, for example, PPS or modified polyphenylene oxide (hereinafter referred to as “modified PPO”), and the primary coil 5 wound around the primary bobbin 4 has a thickness of 0.3 to 1. Approximately 0 to 10 mm enameled wire per layer, several layers per layer, a total of 100 ~
It is a winding wound about 300 times.

The secondary bobbin 2 is also made of, for example, PPS or metamorphic P
Molded with a thermoplastic resin such as PO. Secondary bobbin 2
Has a bottomed cylindrical shape, and is housed in the secondary bobbin 2 such that the foamed rubber 11, the magnet 10, and the center core 1 can be received at the bottom of the secondary bobbin with the resin circulation hole 12.

The secondary bobbin 2 also has a role of interposing between the center core 1 and the secondary coil 3 to insulate the high voltage generated in the secondary coil 3. In order to insulate the high voltage generated in the secondary coil 3, the thickness of the secondary bobbin 2 is set to 0.5 to 1.5.
mm, and in order to prevent electric field concentration and stress concentration between the secondary coil 3 and the center core 1, the center core 1 is positioned so as not to contact the inner peripheral side of the secondary bobbin 2,
The soft epoxy 9 is injected under a vacuum (for example, 4 Torr or less), cured and fixed.

The secondary coil 3 has a wire diameter of 0.03 to 0.06.
mm using enameled wire of about mm
Approximately 00 times, it is divided and wound between a large number of flanges 2 ′ arranged on the secondary bobbin 2. The winding of the secondary coil 3 has 15 layers or more.

Prior to the description of the lead-out structure up to the high voltage terminal 13 of the secondary coil 3, the configuration of the drive circuit for the ignition coil will be described with reference to FIG. 6 in addition to FIG. FIG. 6 shows a configuration example of the ignition coil drive circuit used in the present embodiment.

A unit (hereinafter, referred to as an igniter) 19 of the ignition coil drive circuit is disposed above a coil portion including the above-described center core 1, primary coil 5, secondary coil 3, and the like. More specifically, the igniter 19 is provided in an igniter case (circuit case) 34 connected to the upper end of the coil case 6, and the periphery thereof is covered with the epoxy 8 to be insulated.

The igniter 19 comprises an insulated gate bipolar transistor (hereinafter referred to as "IGBT") 25, a current limiting circuit 26, an input resistor 27 and the like as shown in FIG.

The IGBT 25 includes a main IGBT 20 and a sub IGBT 21.

The current detecting load 22 includes a sub-IGBT 21
And the ground (GND). IG
A bidirectional Zener diode 23 made of polysilicon having excellent temperature characteristics is provided between the gate and the collector of the BT 25.
And the primary voltage is clamped at 350-500V. A bleeder resistor 24 is inserted between the input and GND so that the contact current at the input signal connection is 1 mA or more. The terminals 33 of the igniter shown in FIG. 1 are plated so that sufficient connection reliability can be obtained even with Sn plating. Reference numeral 30 denotes a copper or aluminum metal plate for heat dissipation.

The primary coil 5 has one end connected to the + terminal of the battery 31 and the other end connected to the igniter 19, and is controlled to be energized by the igniter 19. On the other hand, the secondary coil 3 has one end connected to the + side of the battery 31 via a common terminal with the primary coil (one end of the secondary coil 3 is on the low voltage side), and is on the high voltage side of the secondary voltage. The other end is connected to the high voltage terminal 13 via a leaf spring 40. With the above configuration, when the primary coil 5 is turned off, a high voltage is induced in the secondary coil 3 and the ignition plug 1
8 is supplied with ignition energy.

As shown in FIG. 2, the leaf spring 40 and the high voltage terminal 13 are arranged below the secondary bobbin 2. The high voltage generated in the secondary coil 3 is supplied to the ignition plug 18 via the high voltage terminal 13, the spring 14, and the like, and the portion where the ignition plug 18 is inserted is insulated by a rubber boot 15 such as silicon rubber.

Here, the drawing structure of the secondary coil 3 is as follows.
This will be described with reference to FIGS. 3A is a perspective view showing a lower portion of the secondary bobbin 2, FIG. 3B is a perspective view showing a lower portion of the secondary bobbin 2 of the conventional example, and FIG. 4 (b) and 4 (c) are views from the bottom surface of the secondary bobbin, FIG. 5 (a) is a plan view of the leaf spring 40, FIG. 5 (b) is a right side view thereof, and FIG. (C) is FIG.
It is an AA sectional view of (a).

The secondary bobbin 2 has a cylindrical portion 2b for receiving the leaf spring 40 and the high voltage terminal 13 downward from the bottom thereof.
Is extended.

As shown in FIG. 5, the leaf spring 40 is formed by cutting out a part of the center of a metal plate 40a having a substantially circular shape, leaving a part of the metal plate 40a, and raising it in an inclined manner. 40b, and projecting portion 40b is tied (wrapped portion) at the end of secondary coil lead wire 3a.
And

FIG. 4A shows the cylindrical portion 2b of the secondary bobbin 2.
As shown in FIG. 5, a slit 2c is provided in the vertical direction, and when a metal plate 40a with a leaf spring 40 is inserted into the cylindrical portion 2b, the binding portion 40b projects outward through the slit 2c. 4 (b)]. This binding part 40b
After the end 3a 'of the secondary coil lead wire 3a is entangled, it is bent down as shown by the arrow in FIG.

As shown in FIG. 2, the secondary bobbin 2 has a winding position of the secondary coil lead wire 3a (lead wire winding) between the winding end 3 'of the secondary coil 3 and the binding portion 40b. 2a) is provided. The secondary coil lead wire winding portion 2a is located below the lower end of the center core 1 as shown in FIG. 2 (that is, one end of the secondary bobbin 2 extends to the high voltage terminal 13 side than one end of the center core). Established
The extension line 2a of the secondary bobbin has the secondary coil lead wire 3a wound in two layers or more in an aligned winding), and the secondary coil lead wire winding portion 2a is a secondary coil in which a high voltage is induced. 3 in a position that can be distinguished from the original winding portion. The secondary coil lead wire 3a from the winding end 3 'of the secondary coil 3 to the high voltage terminal 13 is wound in the secondary coil lead wire winding portion 2a in two or more layers by aligned winding. It has a line drawing structure.

Here, the reason why the layered winding lead-out structure of two or more layers is adopted is that in the case of a single-layered winding, the winding cannot be properly aligned and a gap is formed between the windings.

In the present embodiment, the secondary coil 3 has a winding structure in which the primary winding portion (high-voltage generating portion) has 15 or more layers, whereas the lead wire 3a of the secondary coil has two to three layers. It has a ten-layer winding structure. Further, by reducing the number of windings of the secondary coil lead-out portion (arrangement) 3a from two to ten or less, the thickness of the bobbin of the lead-out portion 3a which is the highest pressure portion of the secondary bobbin 2 (the bobbin thickness at the reference numeral 2a). ) Is made thicker than the original secondary coil winding portion.

According to this embodiment, since the lead portion 3a of the secondary coil has a layered winding lead structure having two or more layers, the windings of the lead portion 3a are densely packed without gaps.
The secondary coil extraction portion 3a and the edge of the center core 1,
Electric field concentration between the edges of the primary coil 5 and the side core 7 can be prevented.

On the other hand, in the conventional case, FIG.
As shown in (b), the secondary coil lead wire 3a from the winding end 3 'of the secondary coil to the binding portion 40b is 1
Since the book is pulled out as it is, a structure in which electric field concentration easily occurs is obtained.

FIGS. 7A and 7B show the high voltage terminal 13 from the winding end 3 'of the secondary coil 3 in the conventional secondary coil drawing structure of the inner secondary coil system and the secondary coil drawing structure of the present invention. 4 shows the results of an electric field analysis of the high voltage portion up to.

As shown in FIG. 7 (a), when the secondary coil lead 3a is directly drawn out as a single line, the lead 3
7A, the electric field concentration does not occur around the secondary coil lead wire 3a as shown in FIG. 7B. By forming the lead wire 3 into a three-layered layered winding structure, the electric field strength of the winding portion can be reduced to one third as compared with the conventional case. Further, according to the present embodiment, the thickness of the bobbin at the portion 2a corresponding to the winding portion of the secondary coil lead wire 3a to be the high voltage portion of the secondary bobbin 2 is made thicker than the primary winding portion of the secondary coil. By increasing the thickness, the withstand voltage can be improved.

[0044]

As described above, according to the present invention, in an independent ignition type ignition coil having an inner secondary coil structure, it is possible to prevent electric field concentration in a secondary coil lead wire portion and improve insulation durability. it can.

[Brief description of the drawings]

FIG. 1 is a partially omitted longitudinal sectional view showing an ignition coil for an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of FIG.

FIG. 3A is a perspective view showing a lower portion of a secondary bobbin used in the embodiment, and FIG. 3B is a perspective view showing a lower portion of a secondary bobbin of a conventional example.

FIG. 4A is a front view showing a lower portion of a secondary bobbin used in the embodiment, and FIGS. 4B and 4C are views of the secondary bobbin viewed from the bottom.

FIG. 5A is a plan view of a leaf spring used in the embodiment,
FIG. 5B is a right side view of the same, and FIG.

FIG. 6 is an ignition circuit diagram in the embodiment.

FIG. 7 is a diagram showing the results of an electric field analysis of a high-voltage portion from the end of winding of the secondary coil to the high-voltage terminal in the conventional secondary coil extraction structure of the inner secondary coil system and the secondary coil extraction structure of the present invention.

[Explanation of symbols]

1 ... Center core, 2 ... Secondary bobbin, 3 ... Secondary coil,
3 ': end of secondary coil winding; 3a: secondary coil lead-out portion (lead wire); 4: primary bobbin; 5: primary coil; 6: coil case; 13: high voltage terminal;

Continued on the front page (72) Inventor Noboru Sugiura 2520 Ojitakaba, Hitachinaka City, Ibaraki Prefecture Inside the Automotive Equipment Division of Hitachi, Ltd. Automotive Equipment Division

Claims (4)

[Claims] 1. A center core, a secondary coil wound on a secondary bobbin, and a primary coil wound on a primary bobbin are arranged concentrically inside a coil case in that order from the inside, and are directly connected to each spark plug of the internal combustion engine. In the independent ignition type ignition coil for an internal combustion engine to be used, the lead wire of the secondary coil from the winding end end of the secondary coil to the high voltage terminal has a layered winding lead structure in which two or more layers of winding are aligned and wound. An ignition coil for an internal combustion engine. 2. An end of the secondary bobbin located on a high voltage side of the secondary coil and one end of the center core, the one end of the secondary bobbin extending toward the high voltage terminal side from the one end of the center core. 2. The ignition coil for an internal combustion engine according to claim 1, wherein the lead wire of the secondary coil is wound in an extended winding of the secondary bobbin in two or more layers. 3. The secondary coil is divided into a total of about 10,000 to 30,000 times using an enamel wire, and
The ignition coil for an internal combustion engine according to claim 1 or 2, wherein the lead wire of the secondary coil has a layered winding lead structure having two to ten layers, while the winding wire has five or more layers. 4. A bobbin thickness of a portion of the secondary bobbin corresponding to a layered winding portion of a lead wire of the secondary coil is made thicker than a bobbin thickness of an original winding portion of the secondary coil. An ignition coil for an internal combustion engine according to any one of claims 1 to 3.