JPH09330831A - Ignition coil for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition coil for an internal combustion engine which can suitably hold a circuit element, primary and secondary coils as accommodated within a casing all with use of insulating material. SOLUTION: In the ignition coil, primary and secondary coils 12 and 22 accommodated within a casing 60, a circuit element (ignitor 8) to be connected to the primary coil 12 is also accommodated within the casing 60, and a circuit substrate 80 having circuit elements mounted thereon is also accommodated within the casing 60 as it is. And one type of insulating material is filled within the casing 60 in such a condition that the circuit element is connected to the primary coil 12. The insulating material is desirably silicone gel.

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, and more particularly to a case where a primary coil and a secondary coil are housed in a case, and a circuit element connected to the primary coil is housed in the case and The present invention relates to an ignition coil for an internal combustion engine, which is filled with an insulating material.

[0002]

2. Description of the Related Art Recently, there has been a demand for the development of an ignition coil for an internal combustion engine which is small in size and easy to wire and assemble, and an ignition coil in which a circuit element for controlling energization of a primary coil is housed in a case is known. Has been. For example, Japanese Utility Model Publication No. 6-27939 proposes an ignition coil of an internal combustion engine in which a primary coil and a secondary coil are fixed in a coil housing part by an insulating resin layer and a switching module is fixed in an auxiliary housing part. Has been done. It is described that this switching module is composed of a switching element chip and a hybrid IC attached to the bottom of a metal case, a synthetic resin lid, and a silicon gel filled in the case. Then, for example, it is described that an epoxy resin to which a powder of a material having good thermal conductivity such as silicon or alumina is added as a filler is vacuum-cast and cured in a case to form an insulating resin layer.

Further, Japanese Patent Laid-Open No. 6-66239 discloses that
Assemble the power switch and ignition coil,
Next, a method of manufacturing an internal combustion engine ignition device has been proposed in which a power switch and an ignition coil are connected by wiring to form an assembly, and the entire assembly is molded using an insulating resin. According to the publication, the power switch is composed of a power transistor and a current limiting circuit, and conventionally, a single piece which is solid-sealed with a resin as an IC package body is press-fitted into the case, so that the connection work takes time and the assembly work is performed. The problem of poor sex is described. Therefore, after assembling the IC package body and the ignition coil,
The package body and the ignition coil are wire-connected to form an assembly, and then the entire assembly is transfer molded using an insulating resin.

Further, in Japanese Unexamined Patent Publication No. Hei 6-325953, in order to improve the heat dissipation of the circuit element and to reduce the man-hours for injecting the resin, the circuit element electrically connected to the ignition coil is provided with fins in advance. An ignition coil for an internal combustion engine is proposed in which a circuit module is formed by enclosing it with a body, and the circuit module and the ignition coil are housed in a case and simultaneously injected and cured with one type of resin. Then, in that embodiment, a thermoplastic elastomer or the like is used as the elastic body, and an epoxy resin is used as the resin injected into the case.

[0005]

In the ignition coils described in the above publications, the circuit elements for controlling the energization of the primary coil have different names such as a switching module, a power switch, an IC package, and a circuit module. However, it is formed separately from the case of the ignition coil and is sealed with an insulating material. Therefore, at least two kinds of insulating materials are used as the filling insulating material for the ignition coil. For example, JP-A-6-3
Although it is described as one type of resin in Japanese Patent No. 25953, it is described that the circuit module is sealed with an elastic body such as a thermoplastic elastomer, although it is certainly one type of resin for the case. Therefore, two kinds of insulating materials are used for the ignition coil.

As described in Japanese Utility Model Publication No. 6-27939, the circuit element is recently encapsulated in silicone gel to form one unit, which is housed in the case of the ignition coil and then epoxy resin. Are being injected. This is the result of considering the characteristics of silicone gel such as adhesiveness, moisture resistance, vibration resistance, insulation, and heat resistance. However, when epoxy resin or the like is injected into the case, the silicone in the circuit element unit is When the epoxy resin or the like enters the gap of the gel, or when air bubbles are generated in the epoxy resin or the like, the function of the circuit element may be impaired. Further, since the epoxy resin is constrained by the inner core when the epoxy resin shrinks, the strain is large and the stress at this time may cause cracking.

Therefore, according to the present invention, the primary coil and the secondary coil are housed in a case, the circuit element connected to the primary coil is housed in the case, and the case is filled with an insulating material. An object of the present invention is to provide an ignition coil for an internal combustion engine capable of appropriately holding all of the circuit element, the primary coil, and the secondary coil housed in the case with an insulating material.

[0008]

In order to solve the above problems, the present invention provides an internal combustion engine in which a primary coil and a secondary coil are housed in a case, and a circuit element connected to the primary coil is housed in the case. In the engine ignition coil,
The substrate on which the circuit element is arranged is housed in the case as it is, and one kind of insulating material is filled in the case in a state where the circuit element is connected to the primary coil.

Silicon gel is preferably used as the insulating material. Here, the silicone gel is a kind of low-temperature curing type silicone rubber, which is obtained by reducing the crosslinking density of silicone rubber to make it extremely soft, and is used as a potting material.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of an ignition coil for an internal combustion engine of the present invention will be described below with reference to the drawings. FIG. 6 shows an entire ignition coil for an internal combustion engine according to an embodiment of the present invention. A case 60 has an igniter portion 60d of a casing having an opening at the top and a cylindrical shape extending downward from the bottom surface thereof. This is a container-like housing made of synthetic resin, which has a coil portion 60a and a high-voltage terminal portion 60b.

As shown in FIGS. 1 and 2, an inner core 10, which is a columnar member of the present invention, a primary coil 12, a secondary coil assembly 20,
The outer core 30 and a pair of auxiliary cores and permanent magnets (represented by 40 and 50, respectively) are housed therein. The igniter 8 is housed in the igniter section 60d, and the connector section 60c is integrally formed.
Further, as shown in FIGS. 1 and 2, the high-voltage terminal portion 60b has a built-in high-voltage terminal 7, and on the outer surface thereof, as shown in FIG. 1, a plug cap 70 formed of an insulating material such as rubber into a cylindrical shape. Is installed.

The igniter 8 has a built-in circuit element for controlling the primary current of the primary coil 12 and is also called an ignition module. Usually, the circuit element is sealed with silicone gel, but in the present embodiment, It refers to a state in which circuit elements are mounted on the circuit board 80. That is, as shown in FIG. 4, a circuit board 80 is bonded to a heat sink 88 made of aluminum, and circuit elements such as a drive circuit 85 and a switching transistor 86 are mounted on the circuit board 80. Through holes 8 a are formed in the heat sink 88 and the circuit board 80, and the positioning posts 60 are formed in the through holes 8 a.
e is configured to be inserted. Note that FIG. 2 shows a state in which the circuit board 80, the heat dissipation plate 88 and the like are removed.

The inner core 10 of this embodiment is made of a laminated body in which a plurality of magnetic flat plates (for example, silicon steel plates) are joined by stacking, and as shown in FIGS. 1 and 2, an intermediate portion having a substantially circular cross section. 10a and enlarged portion 10 of rectangular cross section
It is formed in a columnar body having b at both ends. Here, stacking refers to forming a concave portion (represented by Sa and Sb in FIG. 1) on one surface and a convex portion on the other surface at the time of press forming for each of the plurality of flat plates. To
It is a means for forming a laminate by press-fitting the convex portions of the surfaces facing each other into the concave portions and sequentially superposing them. In the drawings,
Hatching of the cross section of the inner core 10 is omitted because it is difficult to determine the hatching.

The outer surface of the inner core 10 is powder-coated to form an insulating coating film 11. This insulating coating 11
Is formed over the entire length of the intermediate portion 10a of the inner core 10 and is also formed in the enlarged portion 10b adjacent thereto. As described above, in this embodiment, the insulating coating film 11 is formed on a part of the enlarged portion 10b, but it may be formed on all side surfaces. Thus, each silicon steel plate of the inner core 10 is hard to peel off, and sufficient bonding strength is secured. And
The primary coil 12 is provided on the outer peripheral surface of the insulating coating film 11 of the intermediate portion 10a.
Is wound in two or four layers. At this time, since the insulating coating film 11 portion of the enlarged portion 10b functions similarly to the collar portion of the conventional primary bobbin, it can be appropriately wound.

A holder 14 is mounted in the recess 10c of the inner core 10 as shown in FIGS. Primary terminals 15 and 16 are integrally supported on the holder 14, respectively, and both ends of the winding of the primary coil 12 are connected to the respective base ends thereof. Further, the secondary coil assembly 20 is arranged so as to surround the inner core 10 and the primary coil 12. The secondary coil assembly 20 is shown in FIG.
As shown in FIG. 2, the secondary coil 22 is attached to the secondary bobbin 21.
Is wound. The secondary bobbin 21 is a resin cylindrical body in which a plurality of collar portions 21a are formed at predetermined intervals in the axial direction, and the secondary coil 22 is provided in a plurality of annular grooves formed between the collar portions 21a. The windings are sequentially wound. An annular groove 21d is formed along the outer periphery of the upper end flange 21a. Then, the extension portion 21 of the secondary bobbin 21
A secondary terminal 17 is attached to c, and one end of the winding of the secondary coil 22 on the winding start side is connected to the secondary terminal 17. Further, a secondary terminal 18 is provided on the winding end side, the base end portion of which is fitted into the groove 21d of the flange portion 21a, and the tip end portion thereof is bent in a crank shape and extends in the axial direction. Is formed in. Thus, the other end of the winding of the secondary coil 22 is led out from the groove (not shown) of the flange 21a and wound around the base end of the secondary terminal 18.

On the other hand, the outer core 30 forming a magnetic circuit together with the inner core 10 is formed in a cylindrical shape by a silicon steel plate as shown in FIGS. 1 and 2, and is fitted to the outside of the coil portion 60a of the case 60. There is. Further, as shown in FIGS. 1 and 2, rectangular permanent magnets 50 are disposed at both ends in the axial direction of the inner core 10, and an auxiliary core 40 formed by laminating a substantially rectangular silicon steel plate outside the permanent magnets 50. Is arranged. The permanent magnets 50 arranged at both ends are arranged such that the directions of the generated magnetic fluxes are the same and are opposite to the direction of the magnetic flux formed in the inner core 10 when the primary coil 12 is energized. . Thus, the inner core 10, the permanent magnet 50, the auxiliary core 40, and the outer core 30 described above form a magnetic circuit.

Then, as shown in FIG. 3, first to fourth connector terminals 61 to 64 are arranged in parallel in a connector portion 60c formed integrally with the case 60. An igniter terminal 81 is provided on the base end side of the first to fourth connector terminals 61 to 64.
To 84 are connected. Further, the primary terminals 15 and 16 are connected to the connector terminals 61 and 63 together with the igniter terminals 81 and 83, and the primary coil 12
It is configured such that the energization to is controlled intermittently. That is, the first connector terminal 61 is a power source (not shown).
The primary terminal 15 is connected to the base end together with the igniter terminal 81, and the primary terminal 15 is connected to the secondary terminal 1 as shown in FIG.
8 are connected. Also, the igniter terminal 83
A primary terminal 16 is connected to the.

In manufacturing and assembling the ignition coil having the above structure, the inner core 10 is formed by stacking a plurality of silicon steel plates as described above.
Then, the intermediate portion 10a and the enlarged portion 10 of the inner core 10
An insulating coating film 11 is formed on the outer surface of b, and the intermediate portion 10a
The winding of the primary coil 12 is wound around the insulating coating film 11.

On the other hand, the outer core 30 is formed of a silicon steel plate in a cylindrical shape and is press-fitted to the outside of the coil portion 60a of the case 60, or the silicon steel plate is wound to the outside of the coil portion 60a. Also, the secondary coil 22 is attached to the secondary bobbin 21.
Is wound to form the secondary coil assembly 20.
Then, in the hollow portion of the secondary bobbin 21, the primary coil 12
While the inner core 10 wound with is housed, the permanent magnets 50 and the auxiliary cores 40 are attached to both axial ends of the inner core 10, respectively, and the inner core 10, the secondary coil assembly 20, etc. are housed in the case 60. It

Further, the igniter 8 is housed in the igniter portion 60d of the case 60, is connected to the connector terminals 61 to 64, and both ends of the winding of the primary coil 12 are respectively connected via the primary terminals 15 and 16. 61 and 63 are connected. Further, the high voltage terminal 7 is press-fitted into the high voltage terminal portion 60b and electrically connected to the secondary terminal 17. Then, the secondary coil 2
One end of the second winding is connected to the connector terminal 61 via the secondary terminal 18, and the other end is connected to the secondary terminal 17
Is connected to the high-voltage terminal 7 via.

After that, the coil portion 60a and the igniter portion 60d are filled with silicone gel and cured to form the insulating portion 13 in the coil portion 60a as shown by the dotted lines in FIGS. Specifically, in a state where the inside of the case 60 is depressurized by vacuuming, a low-viscosity silicone gel is injected and then heat-cured, the primary coil 12 and the secondary coil 22 are impregnated and fixed, and the igniter 8 is also attached. The circuit element of is fixed. Thus, these electrical connection parts are properly insulated, and further, the insulation property capable of withstanding the high output voltage of the secondary coil 22 is secured. The coil portion 60a and the high-voltage terminal portion 60b, the igniter portion 60d, and the connector portion 60c shown in FIG.
The a and the igniter portion 60d may be joined together.

Thus, the ignition coil for an internal combustion engine of this embodiment has the outer shape shown in FIG. 6, and the plug cap 70 is attached to the outside of the coil portion 60a and the high voltage terminal portion 60b. Via this plug cap 70, it is attached to an internal combustion engine (not shown) and connected to an ignition plug (not shown). When the primary current of the primary coil 12 is interrupted in this state, a counter electromotive force is induced in the secondary coil 22 and 30 to 4
A high voltage of 0 kv is generated and this high voltage is output to the spark plug. As a result, spark discharge occurs in the electrode portion of each ignition plug, and the compressed air-fuel mixture in each combustion chamber (not shown) is ignited.

As described above, in the ignition coil for the internal combustion engine of the present embodiment, the primary coil 12 and the secondary coil 22 are impregnated and fixed by the silicone gel of one kind of insulating material, and the circuit element of the igniter 8 is provided. Is fixed. Since the silicone gel has excellent moisture resistance, the solder joint portion of the circuit element is appropriately protected, and since the silicone gel has excellent vibration resistance and heat resistance, the thin winding of the secondary coil and the circuit element are excellent. Is properly protected against vibration, heat shock, etc., not only ensuring the insulation of the primary coil 12 and the secondary coil 22, but also the circuit elements of the igniter 8 are appropriately protected and a predetermined ignition performance is maintained. can do.
Further, since the specific gravity of the silicone gel is smaller than that of the epoxy resin used in the conventional ignition coil, the weight is reduced.

[0024]

Since the present invention is configured as described above, the following effects can be obtained. That is, in the ignition coil for an internal combustion engine of the present invention, the substrate on which the circuit element is arranged is housed in the case as it is, and the case is filled with one kind of insulating material in a state where the circuit element is connected to the primary coil. Since the circuit element, the primary coil and the secondary coil are all configured, the circuit element, the primary coil and the secondary coil can be reliably retained while maintaining the insulation, and the predetermined ignition performance can be maintained with a simple configuration.

Further, as described in claim 2, in the case where the insulating material is a silicone gel, the characteristics of the silicone gel such as adhesiveness, moisture proofness, vibration proofness, insulation and heat resistance are effectively utilized. However, not only the protection of the circuit element but also the protection of the primary coil and the secondary coil can be appropriately performed, and the weight can be reduced. The stress generated when the silicone gel shrinks is about 1/1000 that of the epoxy resin.
Since it is small, cracking due to shrinkage can be significantly reduced.

[Brief description of drawings]

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

FIG. 2 is a vertical cross-sectional view showing a state in which an igniter is removed in the internal combustion engine ignition coil according to the embodiment of the present invention.

FIG. 3 is a plan view showing a state in which an igniter is removed in the internal combustion engine ignition coil according to the embodiment of the present invention.

FIG. 4 is a plan view of an igniter used in an embodiment of the present invention.

5 is a cross-sectional view of the coil portion of the ignition coil for the internal combustion engine according to the embodiment of the present invention, which is a cross-sectional view taken along the line AA of FIG.

FIG. 6 is a perspective view of an internal combustion engine ignition coil according to an embodiment of the present invention.

[Explanation of symbols]

 8 Igniter (Circuit Element) 10 Inner Core 10a Middle Part 10b Enlarged Part 11 Insulating Coating Film 12 Primary Coil 13 Insulating Part 14 Holder 15,16 Primary Terminal 17,18 Secondary Terminal 20 Secondary Coil Assembly 21 Secondary Bobbin 22 Secondary Coil 30 Outer core 40 Auxiliary core 50 Permanent magnet 60 Case

Claims (2)

[Claims] 1. An ignition coil for an internal combustion engine, wherein a primary coil and a secondary coil are housed in a case, and a circuit element connected to the primary coil is housed in the case.
The substrate on which the circuit element is arranged is housed in the case as it is, and the case is filled with one kind of insulating material in a state where the circuit element is connected to the primary coil. Ignition coil for internal combustion engine. 2. The ignition coil for an internal combustion engine according to claim 1, wherein the insulating material is silicone gel.