JPH0521242A - Ignition coil for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve reliability to an ignition coil by molding a core using a thermoplastic material which can always maintain good junction state with a core and thermosetting resin. CONSTITUTION:Cores 2, 3 are molded to form a mold layer 4 of a thermoplastic material which is formed by mixing thermoplastic elastomer with a modifier having adhesive property to at least metal and affinity to resin. A primary coil assembly 10 and a secondary coil assembly 20 are mounted on the cores 2, 3 and they are contained inside a case 30. Then, thermosetting resin is filled. Thereby, the mold layer 4 is closely joined with the cores 2, 3 and thermosetting resin and bubbles are not generated at a junction part even at the time of heat shock.

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, after molding a core with a thermoplastic material,
The present invention relates to an ignition coil in which a primary coil and a secondary coil are wound, and these are housed in a case and filled with a thermosetting resin.

[0002]

2. Description of the Related Art An ignition coil for an internal combustion engine comprises a metal core wound with a primary coil and a secondary coil, which are housed in a case and filled with a thermosetting resin. Type ignition coil is popular.

In such a resin mold type ignition coil, for example, as described in Japanese Utility Model Publication No. 57-35021, there is a difference in thermal expansion coefficient between the metal core and the resin to be filled. There is a risk that the resin will crack due to the heat shock due to the temperature change, and a high voltage will leak from the secondary side output section to the core via the crack. In this publication, a pair of E-shaped cores are molded with a thermoplastic resin in order to prevent the leakage and to eliminate the variation in the air gap for preventing magnetic saturation, and these molded cores are made of resin stays. It has been proposed to be fixed relatively by.

[0004]

In the ignition coil described in the above publication, the core is molded with the thermoplastic resin, which can prevent cracks of the thermosetting resin filled in the case. Has been done. However, since the bonding force between the core and the thermoplastic resin is weak, an air layer is formed at the time of heat shock, and corona discharge may occur in the core via the air layer and the thermosetting resin may deteriorate.

As a thermoplastic material for molding the core, if a thermoplastic elastomer is used instead of the resin described in the above publication, it is effective because it is rich in elasticity and absorbs thermal expansion. However, also in this case, it is unavoidable that bubbles are formed between the core and the thermoplastic elastomer at the time of heat shock. Therefore, corona discharge may still occur to the core via the bubbles.

Therefore, the present invention is an ignition coil for an internal combustion engine in which a primary coil and a secondary coil are wound around a core and accommodated in a case, and a thermosetting resin is filled in the core and the thermosetting resin. It is an object of the present invention to mold a core with a thermoplastic material capable of always maintaining a good bonding state to improve reliability of an ignition coil.

[0007]

In order to achieve the above object, the present invention provides a core forming a magnetic path, a primary coil and a secondary coil wound around the core, the primary coil and the secondary coil, and An ignition coil for an internal combustion engine, comprising: a case for accommodating the core, wherein the case is filled with a thermosetting resin. A thermoplastic elastomer is modified to have adhesiveness to metal and affinity to resin. The material is mixed to form a thermoplastic material, the core is molded with the thermoplastic material, and then the primary coil and the secondary coil are wound.

In the ignition coil for an internal combustion engine, it is desirable to use ethylene / acrylic acid ester / maleic anhydride terpolymer as the modifier.

[0009]

In the ignition coil for an internal combustion engine of the present invention, the core is molded with the thermoplastic material, and then the primary coil and the secondary coil are wound. Then, after these are housed in the case, they are filled with a thermosetting resin. Since the thermoplastic material is a mixture of the above-mentioned modifier in the thermoplastic elastomer, it is adhered and joined to the core and the thermosetting resin,
No air bubbles are generated at the joint even during heat shock.

In the ignition coil for an internal combustion engine configured as described above, when the primary current supplied to the primary coil is interrupted, the magnetic flux changes in the core and a high voltage is induced in the secondary coil. On the other hand, no corona discharge occurs. .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an ignition coil for an internal combustion engine of the present invention will be described below with reference to the drawings. 1 to 3 show an embodiment of an ignition coil according to the present invention, in which an ignition coil 1 has a pair of U-shaped cores 2 and 3, and a primary coil assembly 10 and a secondary coil assembly are respectively provided on both legs of the ignition coil 1. The secondary coil assembly 20 is attached.

The cores 2 and 3 are, as shown in FIG.
With legs 2a, 3a and second legs 2b, 3b of the
It is a V-shaped iron core and is formed by laminating a plurality of grain-oriented silicon steel plates whose rolling direction is the vertical direction of FIG. As is well known, the grain-oriented silicon steel sheet exhibits extremely good magnetic properties in the rolling direction, but the magnetic properties deteriorate at angles different from the rolling direction. Therefore, in the cores 2 and 3, the connecting portion 2 orthogonal to the rolling direction
The widths of c and 3c are set to be 1.5 to 1.8 times the width of the second leg portions 2b and 3b in the rolling direction. For example, when a magnetic flux density of 1.7 T (tesla) is allowed in the rolling direction, the magnetic flux density of 1.1 T is the limit in the direction of 45 ° with respect to the rolling direction, so the longitudinal direction of the second leg portions 2b, 3b The width Wc of the connecting portions 2c and 3c extending in the direction orthogonal to the direction is Wc≈Wb × with respect to the width Wb of the second arm portions 2b and 3b in the longitudinal direction.
The relationship is set to 1.7 / 1.1. Also,
The widths of the first legs 2a and 3a are 1.5 to 2 ... of the widths of the second legs 2b and 3b in consideration of the relationship with the permanent magnet 5 described later.
It is set to 6 times, and is set to about 2 times in this embodiment.

The cores 2 and 3 are molded by a thermoplastic material, and a mold layer 4 is closely formed on each core. As the thermoplastic material forming the mold layer 4, for example, a polyolefin-based thermoplastic elastomer (TPE) mixed with a modifying agent in a predetermined ratio is used. As is well known, this thermoplastic elastomer is a polymeric material that has rubber elasticity at the same level as vulcanized rubber at normal temperature, is easily plasticized at high temperature, and can be molded by the same processing method as a thermoplastic resin. .. As the modifier to be mixed with the thermoplastic elastomer, an ethylene / acrylic acid ester / maleic anhydride terpolymer having excellent adhesiveness to metal, affinity for resin, and rubber elasticity is used. The ratio is 5 to 40%.

The mold layer 4 is not formed on the end surfaces of the first leg portions 2a, 3a and the second leg portions 2b, 3b of the cores 2, 3 which face each other. Further, in this embodiment, as shown in FIG. 4, the mold layers 4 are formed only on the front and back surfaces on the first leg portions 2a, 3a side and on both side surfaces on the second leg portions 2b, 3b side. The mold layer 4 may be formed on the entire surface excluding the end face.

As the permanent magnet 5, a rare earth magnet of a sintered body of samarium-cobalt (Sm-Co) type metal, which has a large residual magnetic flux density and is hard to be demagnetized, is used. For example,
Normal magnetic flux density is 0.8T (Tesla), temperature 150
A material that does not demagnetize until the magnetic flux density in the opposite direction reaches 0.7 T when the primary coil 12 is energized is used.

The permanent magnet 5 is substantially square, and the width of one side thereof is within a range of 1.5 to 2.6 times the width of one side of the second leg portions 2b, 3b of the cores 2, 3 in cross section. The width is set to about twice in this embodiment, and is equal to the width of one side of the cross section of the first leg portions 2a and 3a. The width of the other side of the permanent magnet 5 is set to be the same as the width (thickness) of the other side of the second leg portions 2b and 3b of the cores 2 and 3, so that the cross-sectional area of the permanent magnet 5 is the core. The area of the cross section of the second leg portions 2b, 3b is the same as the area of the cross section of the first leg portions 2a, 3a of the second and third portions 1.
It is about twice within the range of 5 to 2.6 times. The permanent magnet 5 is arranged so as to be in a direction opposite to the direction of the magnetic flux formed in the cores 2 and 3 when the primary coil 12 is energized.

A primary coil assembly 10 is mounted around the first legs 2a and 3a of the cores 2 and 3. The primary coil assembly 10 is formed by winding a primary coil 12 around a primary bobbin 11. The primary bobbin 11 is a resin cylindrical body having a substantially rectangular cross section formed by insert resin molding and having the primary terminals 13a and 13b shown in FIG. 3, and has flange portions 11a formed at both ends thereof. The windings of the primary coil 12 are wound in two layers or four layers. Figure 3
As shown in FIG. 3, both ends of the winding of the primary coil 12 are wound around the primary terminals 13a and 13b, respectively, and soldered.

A secondary coil assembly 20 is mounted around the second legs 2b and 3b of the cores 2 and 3. The secondary coil assembly 20 is formed by winding a secondary coil 22 around a secondary bobbin 21. The secondary bobbin 21 is a resin tubular body formed by insert resin molding, having a secondary terminal 23b shown in FIG. 2, and having a plurality of flange portions 21a formed at predetermined intervals in the axial direction and having a substantially rectangular cross section. .. Therefore, a plurality of grooves 21b are formed between the flange portions 21a, and the winding of the secondary coil 22 is sequentially wound in the grooves 21b from the upper side to the lower side in FIGS.

As shown in FIG. 3, a support 21c is formed on the upper flange 21a so as to extend in the axial direction, and the secondary terminal 2 is formed in a groove (not shown) formed in the support 21c.
3a is fitted. The winding start of the winding of the secondary coil 22 is wound around the secondary terminal 23a and soldered. The winding end of the secondary coil 22 is wound around the secondary terminal 23b and soldered.
The secondary terminal 23b is provided with a hole provided with a claw, and the connection portion 7 of the high-voltage terminal 7, which will be described later, is formed in this hole.
a is press-fitted.

The case 30 is a housing made of synthetic resin and has a secondary connector portion 30a formed on the bottom. A high-voltage terminal 7 having a bottomed cylindrical body is housed in the secondary connector portion 30a by insert resin molding, and a connecting portion 7a extending from the bottom portion penetrates the bottom surface of the secondary connector portion 30a to form a case. It extends into 30.

An opening is formed on the side surface of the case 30, and the connector 6 is fitted in this opening. The connector 6 is formed by insert resin molding with the built-in connector terminals 6a and 6b. The connector terminal 6a is connected to a battery (not shown), and the connector terminal 6b is connected to a control circuit (not shown), commonly known as an igniter.

The primary coil assembly 10 and the secondary coil assembly 20 are arranged side by side, and the first and second leg portions 3a and 3b of the one core 3 are inserted into the hollow portions of the primary coil assembly 10 and the secondary bobbin assembly 20, respectively. After accommodating the magnet 5, the other core 2
The first and second leg portions 2a and 2b are inserted. As a result, the permanent magnet 5 causes the first leg 2 of each of the cores 2 and 3 to move.
It is sandwiched between a and 3a. When these assemblies are housed in the case 30, the connection portion 7a of the high-voltage terminal 7 is press-fitted into the hole of the secondary terminal 23b and electrically connected.

The connector terminals 6a and 6b of the connector 6 mounted on the case 30 and the primary terminals 13a and 13b of the primary coil assembly 10 are joined by resistance welding. In addition, the lead 8b of the diode 8 is sandwiched by the claws 6c provided upright on the connector terminal 6b and then joined by resistance welding, and the lead 8a of the diode 8 is joined to the secondary terminal 23a of the secondary coil assembly 20 by resistance welding. To be joined.
The diode 8 prevents a spark plug (not shown) from flying due to a voltage of 1 to 3 kV generated when the primary coil 12 is energized.

After the respective parts are arranged in the case 30 as described above, a thermosetting synthetic resin,
For example, epoxy resin is filled and cured, and the resin portion 9
Is formed. As a result, the primary coil 12 and the secondary coil 22 are impregnated and fixed, and the insulation that can withstand the high output voltage of the secondary coil 22 is secured. Also, the core 2,
Since the mold layer 4 formed in No. 3 has an affinity for the synthetic resin, the resin portion 9 is in close contact with and bonded to the mold layer 4.

In the ignition coil 1 having the above structure, for example, the upper side of the permanent magnet 5 in FIG. 1 is the N pole, and the flow of magnetic flux circulates in the cores 2 and 3 to form a closed loop. ing. There is almost no leakage of magnetic flux in this state. When the primary coil 12 is energized by a control circuit (not shown) and a primary current is supplied, the magnetic flux flows in the direction opposite to the magnetization direction of the permanent magnet 5. When the primary current is cut off, a counter electromotive force is induced in the secondary coil 22 and a high voltage of 30 to 40 kV is generated. This high voltage is applied to the secondary terminal 23b,
It is applied to a spark plug (not shown) via the high voltage terminal 7.

In the ignition coil 1, a mold layer 4 is formed on each of the cores 2 and 3, and the thermoplastic material forming the mold layer 4 has adhesiveness to metal and affinity to resin. Since it is a thermoplastic elastomer mixed with the modifying material, the core 2, 3 and the mold layer 4 and the mold layer 4 and the resin portion 9 are affected by the heat shock applied to the ignition coil 1. Without any trouble, the closely bonded state is maintained. That is, the thermal shock resistance is excellent, the occurrence of corona discharge to the cores 2 and 3 is prevented, and the deterioration of the resin portion 9 is suppressed. Therefore, good reliability as an ignition coil can be secured.

[0027]

Since the present invention is configured as described above, it has the following effects. That is, in the ignition coil for an internal combustion engine of the present invention, the thermoplastic elastomer is mixed with a modifier having at least an adhesive property to a metal and an affinity to a resin to form a thermoplastic material. Since it is configured to be molded, bubbles are not formed between the core and the thermosetting resin during heat shock, and it has excellent thermal shock resistance and ensures good reliability as an ignition coil. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an ignition coil according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of an ignition coil according to an embodiment of the present invention.

FIG. 3 is a plan view of an ignition coil according to an embodiment of the present invention.

FIG. 4 is a perspective view of a core forming an ignition coil according to an embodiment of the present invention.

[Explanation of symbols]

1 Ignition coil 2 core, 2a 1st leg part, 2b 2nd leg part,
2c connecting portion 3 core, 3a second leg portion, 3b second leg portion,
3c Connection part 4 Mold layer 5 Permanent magnet 6 Connector 7 High voltage terminal, 7a Connection part 9 Resin part 10 Primary coil assembly 11 Primary bobbin 12 Primary coil 13a, 13b Primary terminal 20 Secondary coil assembly 21 Secondary bobbin 22 Secondary coil 23a , 23b Secondary terminal 30 Case 30a Secondary connector part

Claims (1)

Claims: 1. A core comprising a magnetic path, a primary coil and a secondary coil wound around the core, and a case accommodating the primary coil, the secondary coil and the core. In an ignition coil for an internal combustion engine in which the case is filled with a thermosetting resin, a thermoplastic elastomer is mixed with a modifier having at least an adhesive property to a metal and an affinity to a resin to form a thermoplastic material. An ignition coil for an internal combustion engine, characterized in that the core is molded with the thermoplastic material, and then the primary coil and the secondary coil are wound.