JP5630332B2 - Method for manufacturing ignition coil for internal combustion engine - Google Patents

Description

  The present invention relates to a method of manufacturing an ignition coil for an internal combustion engine that generates a voltage to be applied to an ignition plug in the internal combustion engine.

  An internal combustion engine ignition coil (hereinafter simply referred to as an “ignition coil”) is for applying a high voltage to an ignition plug attached to an internal combustion engine to ignite an air-fuel mixture. A secondary coil or the like is sealed with a resin molded body made of a thermosetting resin or the like.

  Conventionally, by preparing a precursor of a liquid resin molded body, impregnating this liquid precursor between the lines of the primary winding and between the lines of the secondary winding, by heating and curing the precursor, The primary coil and the secondary coil are sealed with a resin molded body (see, for example, Patent Documents 1 and 2).

  Moreover, the resin molding contains fillers, such as a silica, in thermosetting resin, and in recent years, content of a filler has increased in order to ensure a high withstand voltage lifetime. In patent document 2, content of the filler with respect to a resin molding is 65 weight% or more.

JP 2005-2310 A JP 2009-278074 A

  However, in practice, when the content of the filler in the resin molded body is increased to 65% by weight or more, the liquid precursor is impregnated between the primary windings and between the secondary windings as follows. A problem arises in that the filler settles in the liquid precursor in the previous stage of the process.

  That is, in order to seal the primary coil and the secondary coil with a resin molded body, a liquid precursor in which a filler is dispersed in a thermosetting resin in a predetermined container is manufactured, and then the manufactured liquid precursor is manufactured. The body is transferred to a sealing device via a pipe, and a liquid precursor is injected into the primary coil and the secondary coil from the nozzle of the sealing device.

  At this time, since the filler settles in the container in which the liquid precursor is manufactured, facilities and management such as a stirring blade for dispersing the filler in the container are required. Further, since the filler settles in the pipe even when the pipe is transferred, it is necessary to manage conditions such as the flow velocity in the pipe so as not to settle the filler.

  In view of the above, the present invention provides an ignition coil for an internal combustion engine that can seal a primary coil and a secondary coil while suppressing sedimentation of the filler even if the content of the filler in the resin molded body is increased. It aims to provide a method.

In order to achieve the above object, according to the first aspect of the present invention, as a precursor of a resin molding, a solid material in which a filler is dispersed in an epoxy resin and a resin component of a curing agent is pulverized, and the pulverized material is shaped into a predetermined shape. Preparing a hardened bulk precursor,
Prepare the primary coil (13) and the secondary coil (15) in a state before being sealed with the resin molded body, and add a functional group to the surface of the secondary winding (151) to improve the wettability. A pretreatment step to improve,
After the pretreatment step, an impregnation step of impregnating the precursor between the wires of the primary winding and between the wires of the secondary winding while imparting fluidity to the precursor by heating,
Curing the precursor have a forming a resin molded body,
When the primary coil (13) and the secondary coil (15) are prepared, when the secondary winding (151) is wound around the bobbin-shaped secondary spool (14) having the collar (141), the collar The ratio (a1 / b1) between the height (a1) of the part (141) and the interval (b1) between the collar part (141) and the secondary winding (151) is 0 or more and 1.6 or less. And
The pretreatment process is characterized in that plasma treatment is performed on the surface of the secondary winding (151) .

  According to this, in the step before the step of impregnating the precursor between the lines of the primary and secondary windings, in the step of impregnating the precursor between the lines of the primary and secondary windings with the precursor as a solid substance Because the precursor is made fluid by heating, the liquid precursor is produced, and the settling of the filler in the precursor is suppressed compared to the case where the primary coil and the secondary coil are sealed using this precursor. it can.

  Therefore, according to the present invention, even if the content of the filler in the resin molded body is increased, the primary coil and the secondary coil can be sealed while suppressing sedimentation of the filler.

Further, according to the present invention, when the secondary winding (151) is wound around the bobbin-shaped secondary spool (14) having the collar (141), the height (a1) of the collar (141). And the ratio (a1 / b1) of the interval (b1) between the collar portion (141) and the secondary winding (151) is 0 or more and 1.6 or less, and in the pretreatment step, the secondary winding (151) By performing the plasma treatment on the surface, it is possible to prevent the occurrence of an unimpregnated portion of the resin inside the secondary winding, as will be described later.

In the first aspect of the present invention, as in the second aspect, the ratio (a1 / b1) is preferably 1.5 or more. In the invention described in claim 1 or 2 , for example, as described in claim 3 , an ortho cresol novolac epoxy resin can be used as the epoxy resin and a novolac curing agent can be used as the curing agent.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

It is a figure showing the section composition of ignition coil 1 concerning a 1st embodiment. In the manufacturing method which concerns on 1st Embodiment, it is sectional drawing of the metal mold | die which has arrange | positioned the ignition coil before sealing inside. FIG. 3 is an enlarged view of a secondary spool 14 and a secondary coil 15 in FIG. 2. It is a figure which shows the plasma processing which concerns on an Example. It is a figure which shows the plasma processing which concerns on an Example.

  First, a basic configuration of the ignition coil 1 according to the present embodiment will be described. FIG. 1 is a schematic diagram of a longitudinal section of the ignition coil 1.

  The ignition coil 1 is inserted into a plug hole (not shown) formed in the engine head and connected to a spark plug (not shown). As shown in FIG. 1, the ignition coil 1 includes a central core 11, a primary spool 12, a primary coil 13, a secondary spool 14, a secondary coil 15, and an outer peripheral core 16.

  The central core 11 is formed by laminating magnetic materials and has a cylindrical shape as a whole. The central core 11 is provided such that its axial direction is substantially perpendicular to the axial direction of the plug hole.

  The primary spool 12 is made of a hard resin such as PP or PE, and is provided substantially concentrically with the central core 11 on the outer peripheral side of the central core 11.

  The primary coil 13 is formed by winding a primary winding 131 having a circular cross section around a bobbin-shaped primary spool 12. Note that the primary coil 13 is formed by winding a copper wire having a diameter of 0.3 to 0.8 mm for 100 to 230 turns.

  The secondary spool 14 is made of a hard resin such as PP or PE, and is provided substantially concentrically with the central core 11 on the outer peripheral side of the primary coil 13. The secondary spool 14 has flange portions 141 and 142 at both ends in the axial direction.

  The secondary coil 15 is located outside the primary coil, and is formed by winding a secondary winding 151 having a circular cross section around a bobbin-shaped secondary spool 14. The secondary coil 15 is formed by winding a copper wire having a diameter of 30 μm or more and 100 μm or less, preferably 40 to 50 μm, using a winding method such as 10,000 to 20000 turns and oblique winding.

  The outer peripheral core 16 is provided on the outer periphery of the central core 11, the primary spool 12, the primary coil 13, the secondary spool 14 and the secondary coil 15. The outer peripheral core 16 is formed by laminating magnetic materials and has a box shape opening toward the plug hole as a whole. A pair of opposing side surfaces of the outer core 16 are opposed to both end surfaces of the central core 11, thereby forming a closed magnetic path that suppresses magnetic energy loss between the central core 11 and the outer core 16. ing.

  The ignition coil 1 includes an igniter 17 that is electrically connected to the primary coil 13 and a connector portion 18 that electrically connects the igniter 17 and an external power source.

  The ignition coil 1 having such a configuration is sealed with a resin molded body 20. The resin molded body 20 is interposed between the primary coil 13 and the secondary coil 15 and electrically insulates both. The resin molded body 20 also exists between the lines of the primary winding 131 and between the lines of the secondary winding 151, and electrically insulates the windings. The resin molded body 20 is formed by dispersing a filler in a resin component made of a thermosetting resin, and is formed by heat curing a precursor of a resin molded body. In the present specification, the resin composition before heat curing is referred to as a precursor, and the resin composition obtained by heat curing the precursor is referred to as a resin molded body.

  The resin molded body 20 has a protrusion 201 that protrudes toward the plug hole. This protrusion 201 is inserted into the plug hole. A metal terminal 21 for electrically connecting the secondary winding 151 constituting the secondary coil 15 and the spark plug is provided inside the protruding portion 201.

  In the above configuration, when the igniter 17 having a built-in switching element cuts off the current flowing through the primary coil 13 by a signal from an engine control unit (not shown), the number of 40 is increased by the mutual induction between the primary and secondary coils 13 and 15. A high voltage of kV is generated in the secondary coil 15. The high voltage generated in the secondary coil 15 is guided to the spark plug, and spark discharge is generated at the tip of the spark plug.

  Next, a method for manufacturing the ignition coil 1 will be described. In this embodiment, the ignition coil 1 is manufactured mainly through a step of preparing a pellet-shaped precursor, a pretreatment step aiming at improving the wettability of the secondary winding, and a sealing step using a resin molded body.

  In the step of preparing a pellet-shaped precursor, a thermosetting resin (main agent), a curing agent, and a filler are mixed. At this time, the powdery main agent and curing agent and a filler having a desired shape are dry mixed. In addition to these materials, additives such as coupling materials may be added.

  An ortho-cresol novolak-type or bisphenol-type epoxy resin is used as the main agent, and a phenol-type is used as the curing agent. In this embodiment, a phenolic curing agent having a large molecular weight is used in order to make the precursor solid.

  As the filler, silica, talc, calcium carbonate, calcium silicate, aerosil and the like can be used. The addition amount of the filler is preferably 65% by weight or more and 80% by weight or less, with the entire precursor being 100% by weight. This is because, as disclosed in Patent Document 2, a good high withstand voltage life can be obtained by setting it to 65% by weight or more, and when it exceeds 80% by weight, the amount of epoxy resin is reduced, so that resin molding is performed. This is because the adhesion of the body is impaired.

  Subsequently, the mixed main agent, curing agent and filler are kneaded while heating. At this time, the heating temperature is set to about 80 ° C., for example, and the main agent, the curing agent and the filler are made into a uniform melt.

  Subsequently, the melt is cooled to a solid and the solid is pulverized. For example, it is cooled on a cold iron plate at about 20 ° C. to form a plate-like solid, and then pulverized to obtain a pulverized product. Iron removal is performed on the obtained pulverized product.

  Subsequently, the pulverized product is further dry mixed and then tableted into an arbitrary shape. At this time, for example, a pressure of several tens of t is applied. In this way, a solid substance in which a filler is dispersed in the epoxy resin and the resin component of the curing agent is pulverized, and a massive (pellet-shaped) precursor obtained by solidifying the pulverized substance into a predetermined shape is prepared. At this time, for example, the amount of precursor used for one sealing is made into one pellet.

  In the pretreatment process aiming at improving the wettability of the secondary winding, an ignition coil in a state before being sealed with the resin molding is prepared, and plasma treatment is performed on the surface of the secondary winding. Thereby, the precursor easily penetrates between the secondary windings by imparting a functional group having good compatibility with the resin component to the surface of the secondary winding. For example, activated oxygen atoms are imparted as functional groups to the surface of the secondary winding by plasma treatment under atmospheric pressure. In addition to the plasma treatment, the surface treatment of the winding may be performed by UV treatment for irradiating ultraviolet rays or corona treatment by corona discharge.

  In the sealing step using the resin molded body, a step of impregnating the precursor between the wires of the primary winding and between the wires of the secondary winding is performed. Specifically, the impregnation is performed by a transfer molding method using a mold using a pellet-shaped precursor. FIG. 2 shows a cross-sectional view of a mold in which an ignition coil before sealing is arranged. In FIG. 2, the ignition coil 1 is shown with the primary spool 12 and the primary coil 13 omitted.

  First, as shown in FIG. 2, the ignition coil 1 before sealing is set inside the upper mold 301 and the lower mold 302. Subsequently, the molds 301 and 302 are heated, and the preheated pellet-shaped precursor is put into the injection port 303 of the mold. By heating the mold, the precursor is also heated and fluidity is generated in the precursor. By pressing the fluidized precursor with a plunger (piston) and transferring it to the primary and secondary coils, Impregnation between the primary winding and between the secondary winding. The molding pressure at this time is 6 to 10 MPa, for example.

  Thereafter, by performing a step of thermosetting the precursor to form a resin molded body under a predetermined temperature condition, the ignition coil 1 sealed with the resin molded body 20 is manufactured as shown in FIG. The

  As described above, the manufacturing method of the present embodiment performs the impregnation by the transfer molding method using the pellet-shaped precursor in the step of impregnating the precursor between the wires of the primary and secondary windings. is there.

  Therefore, according to the present embodiment, in the previous stage of the step of impregnating the precursor between the lines of the primary and secondary windings, the precursor is made into a pellet-like solid, and the precursor is made of the primary and secondary windings. Immediately before impregnation between the wires, the precursor is made fluid by heating, so that a liquid precursor is produced and used to seal the primary and secondary coils in the precursor. Sedimentation of the filler can be suppressed.

  Here, when the inventor actually manufactured the ignition coil 1, when impregnation was performed by a transfer molding method using a pellet-shaped precursor, the fluidity of the precursor during impregnation was low, and the secondary winding Since 151 is thin with a wire diameter of 30 to 100 μm, it was found that an unimpregnated portion of the precursor (resin molded body) is likely to occur in a region R1 surrounded by a broken line in FIG. 3 in the secondary winding. A region R1 surrounded by a broken line in FIG. 3 is a region inside the secondary winding 151 close to the flange portion 141 on one end side in the axial direction of the secondary spool 14. In addition, the axial direction one end side of the secondary spool 14 is a low pressure side of the secondary spool 14, and is a side where the number of stages of the secondary winding 151 is large.

  Therefore, as in this embodiment, before the step of impregnating the precursor between the wires of the primary winding and between the wires of the secondary winding, a pretreatment step aimed at improving the wettability of the secondary winding is performed. Thus, the precursor can easily penetrate between the secondary windings.

  Further, as shown in an embodiment described later, the ratio (a1 / b1) between the height a1 of the collar portion 141 of the secondary spool 14 and the interval b1 between the collar portion 141 and the secondary winding 151 is 0 or more and 1. By setting it to 6 or less, an unimpregnated part can be eliminated.

  Therefore, according to the present embodiment, even if the content of the filler in the resin molded body is increased, the primary coil 13 and the secondary coil 15 can be sealed while suppressing the sedimentation of the filler, and further, the secondary coil The resin molded body 20 can be satisfactorily impregnated between the wires of the winding 151.

  Examples of the present invention and comparative examples are shown below.

In Examples 1 to 3 and Comparative Examples 1 and 2, the height a1 of the flange portion 141 of the secondary spool 14 and the distance b1 between the flange portion 141 and the secondary winding 151 are as shown in Table 1 below. The ignition coil 1 was manufactured by the manufacturing method of the above-mentioned embodiment. Then, the presence or absence of the non-impregnated part of the resin molding 20 was investigated by carrying out SEM observation (200-500 times) of the partial cross section of the ignition coil 1 sealed with the resin molding 20. Various conditions are as follows.
[Precursor composition]
Main agent: orthocresol novolak
Curing agent: phenol filler: crushed silica (particle size 20-200 μm)
Addition amount of filler: 70% by weight
[Secondary winding]
Secondary winding diameter: 50 μm
[Pretreatment process]
Using “Aiplasma” manufactured by Matsushita Electric Works, under the following conditions, as shown in FIG. 4, oxygen activated by plasma generated under atmospheric pressure is irradiated from the irradiation unit 401 to the secondary winding 151. did. At this time, as shown in FIG. 5, a total of four times were performed on one bobbin by performing plasma processing on each region obtained by dividing the entire surface of the secondary winding 151 into four parts. FIG. 5 is a view of the secondary coil 15 as viewed from the axial direction.
Excitation voltage: 140W
Irradiation distance L1: 5 mm from the irradiation unit 401 to the secondary winding 151
Irradiation speed S1: 30 mm / s
Oxygen flow rate: 0.027 L / min
Argon flow rate: 2.14 L / min
[Transfer mold process]
Molding pressure: 6-7MPa
Mold closing time: 5 minutes Mold temperature: 150 ° C
On the other hand, in Comparative Examples 3 to 12, the height a1 of the flange portion 141 of the secondary spool 14 and the interval b1 between the flange portion 141 and the secondary winding 151 are the dimensions shown in Table 2 below, and the above-described embodiment. The ignition coil 1 was manufactured without performing the pretreatment process for the manufacturing method. About other conditions, it is the same as Examples 1-3. Then, the presence or absence of the non-impregnated part of the resin molding 20 was investigated by carrying out SEM observation (200-500 times) of the partial cross section of the ignition coil 1 sealed with the resin molding 20.

  As shown in Table 1, the ratio (a1 / b1) between the height a1 of the collar 141 and the distance b1 between the collar 141 and the secondary winding 151 is 1.6 when pre-processing is performed. In Examples 1 to 3 below, the resin was satisfactorily impregnated between the wires of the secondary winding 151. On the other hand, in Comparative Examples 1 and 2 in which the ratio (a1 / b1) between the height a1 of the collar 141 and the interval b1 between the collar 141 and the secondary winding 151 exceeds 1.6, There was an unimpregnated portion of resin between the wires of the next winding 151.

  On the other hand, as shown in Table 2, in Comparative Examples 3 to 12 where the pretreatment was not performed, the ratio (a1 / b1) between the height a1 of the collar 141 and the interval b1 between the collar 141 and the secondary winding 151 Despite this, there was an unimpregnated portion of resin between the wires of the secondary winding 151.

1 Ignition Coil 13 Primary Coil 131 Primary Winding 15 Secondary Coil 151 Secondary Winding 20 Resin Molded Body

Claims (3)

A primary coil (13) formed by winding the primary winding (131) a plurality of times;
A secondary coil (15) formed by winding a secondary winding (151) having a wire diameter of 30 to 100 μm a plurality of times;
A resin molded body (20) impregnated between the lines of the primary winding (131) and between the lines of the secondary winding (151) and sealing the primary coil (13) and the secondary coil (15). )
In the method of manufacturing an ignition coil for an internal combustion engine, the resin molded body (20) includes the resin molded body as 100% by weight and contains a filler in an amount of 65% by weight to 80% by weight.
As a precursor of the resin molded body, pulverizing a solid material in which a filler is dispersed in an epoxy resin and a resin component of a curing agent, and preparing the bulky precursor obtained by solidifying the pulverized material into a predetermined shape;
The primary coil (13) and the secondary coil (15) in a state before being sealed with the resin molded body are prepared, and a functional group is imparted to the surface of the secondary winding (151). A pretreatment process to improve wettability,
After the pretreatment step, an impregnation step of impregnating the precursor between the wires of the primary winding and between the wires of the secondary winding while imparting fluidity to the precursor by heating,
Wherein curing the precursor possess and forming the resin molded body,
When the primary coil (13) and the secondary coil (15) are prepared, when the secondary winding (151) is wound around a bobbin-shaped secondary spool (14) having a collar portion (141). Further, the ratio (a1 / b1) between the height (a1) of the collar portion (141) and the interval (b1) between the collar portion (141) and the secondary winding (151) is 0 or more and 1.6. Prepare the following,
In the pretreatment step, a plasma treatment is performed on the surface of the secondary winding (151) . The method for manufacturing an ignition coil for an internal combustion engine according to claim 1, wherein the ratio (a1 / b1) is 1.5 or more. The method for producing an ignition coil for an internal combustion engine according to claim 1 or 2 , wherein an ortho-cresol novolac epoxy resin is used as the epoxy resin, and a novolac curing agent is used as the curing agent.

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