JP4244750B2 - Ignition coil for internal combustion engine - Google Patents

Description

  The present invention relates to prevention of stress applied to an ignition coil for an internal combustion engine, particularly an igniter.

  An internal combustion engine ignition coil is used in an internal combustion engine to operate a spark plug for igniting (igniting) an air-fuel mixture. Case, primary coil and secondary coil housed in case, igniter housed in case and blocking primary coil current to generate high voltage in secondary coil, injected into clearance in case and hardened Insulating resin.

  In an atmosphere in which an internal combustion engine ignition coil is used, the temperature rises and falls repeatedly. Here, the resin mold that molds (packages) the electronic components of the igniter and the insulating resin that is filled around the winding portion and the igniter have different linear expansion coefficient rates. Due to repeated temperature changes, stress is applied from the insulating resin to the resin mold, igniting the igniter and causing the electronic component to malfunction.

In consideration of this, in the conventional ignition coil shown in FIG. 4 (see Patent Document 1), a cushioning material is provided in an insulating resin (potting resin) 104 enclosing the coil winding portions 101a and 101b and the igniter 102 in the case 100. (Thermoplastic elastomer) 106 is provided. That is, a portion of the igniter 102 embedded in the insulating resin 104 is overcoated with the buffer material 106. In this way, the buffer material 106 is brought into contact with the igniter 102, thereby preventing the occurrence of stress in the igniter 102.

  The above-described conventional example is characterized in that the buffer material 106 is brought into contact with the igniter 102, thereby obtaining advantages such as downsizing the ignition coil and preventing damage to the igniter 102. On the other hand, there is room for improvement in the following points.

First, the stress of the resin mold of the igniter 102 may increase locally. Specifically, it is difficult to completely eliminate the gap between the igniter 102 and the buffer material 106, and the insulating resin 104 may enter a gap that partially exists between the two. Then, the igniter 102 and the buffer material 106 are locally bonded at the portion where the insulating resin 104 has entered, and thermal stress concentrates on this portion. As a result, the possibility of breakage from the boundary between the bonded portion and the non-bonded portion increases.

  Second, when the ignition coil is assembled, it may not be easy to accommodate the igniter 102 in the buffer material 106. At the time of assembly, the igniter 102 is set in the case 100 while being accommodated in the buffer material 106, and a resin material is injected. Here, there may be a manufacturing error or the like in the outer dimension of the igniter 102 and / or the inner dimension of the buffer material 106. If the tolerance between the outer dimension and the inner dimension is brought close to zero in order to ensure contact between the igniter 102 and the buffer material 106, it becomes difficult to accommodate the igniter 102 in the buffer material 106.

  Third, the cost of the cushioning material 106 may increase. Since the shape of the buffer material 106 corresponds to the shape of the igniter 102, the design of the buffer material 106 also needs to be changed when the design of the igniter 102 is changed. If the cushioning material 106 having various shapes is manufactured in correspondence with the igniters 102 having various shapes, the cost increases.

  The present invention has been made in view of the above circumstances, and prevents internal stress from being generated in a resin mold or the like of an igniter, can easily accommodate the igniter in a buffer material, and can be applied to igniters having various shapes. An object is to provide an ignition coil for an engine.

  The basic technical idea of the present invention is that when the igniter is wrapped with a cushioning material, a gap is intentionally formed between the two and the gap is filled with an insulating resin. In addition, filling the gap with insulating resin is to eliminate the problems of the conventional example, and the stress applied to the resin mold due to the difference in thermal deformation between the resin mold and the insulating resin is absorbed by the buffer material as in the conventional example. To do.

An ignition coil for an internal combustion engine according to the present invention, wherein as described in claim 1, the primary coil and the secondary coil and which is housed in the first housing portion of the case; stored in the second housing portion of the case, 1 An igniter that cuts off the primary current of the secondary coil and generates a high voltage in the secondary coil; at least a predetermined clearance that is larger than the outer dimensions of the igniter and between the outer surface of the igniter and the inner surface of the cushioning material And a cushioning material capable of accommodating the igniter in the second accommodating portion; and an insulating resin filled in the first accommodating portion, the second accommodating portion, and the gap. It is characterized by.

  In this ignition coil for an internal combustion engine, the cushioning material wrapped around the igniter absorbs the force applied to the igniter from the insulating resin around the igniter. The insulating resin between the igniter and the buffer material is evenly filled in the gap between the two to ensure a wide contact area.

  An ignition coil for an internal combustion engine according to a second aspect of the present invention is the ignition coil according to the first aspect, wherein the cushioning material has a bottom wall portion facing the bottom surface of the igniter, a side wall portion facing the side surface, and an end wall portion facing the end surface; Is filled in the gap between the bottom surface of the igniter and the bottom wall of the cushioning material, the side resin filled in the gap between the side and side walls, and the gap between the end face and the end wall. Including the end face resin part.

An ignition coil for an internal combustion engine according to a third aspect of the present invention is the ignition coil for an internal combustion engine according to the second aspect, which holds the upper end of the primary spool around which the primary coil is wound and the secondary spool around which the secondary coil is wound, A positioning means for the cushioning material is formed between the cushioning material and the holder. The ignition coil for an internal combustion engine according to claim 4 is the ignition coil according to claim 3, wherein a part of the positioning means secures a clearance between the bottom surface of the igniter and the bottom wall portion of the cushioning material. Ignition coil of claim 5, in claim 2, the second housing portion to integrated connector terminal of the case has a buffer material in the Day Gunaita and positioning. An ignition coil for an internal combustion engine according to a sixth aspect is the invention according to any one of the first to fifth aspects, wherein the igniter and the insulating resin can be expanded and contracted independently under a cooling cycle. The internal combustion engine ignition coil according to claim 7 is the coil according to any one of claims 1 to 6, wherein the elastic coefficient of the cushioning material is smaller than the elastic coefficient of the insulating resin.

  According to the ignition coil for an internal combustion engine according to the present invention, since the igniter and the buffer material are in contact with each other over a wide area through the insulating resin, an increase in local stress in the igniter (particularly, the resin mold) is prevented. . In addition, since the tolerance between the igniter and the buffer material can be increased, the igniter can be easily accommodated in the buffer material, and one type of buffer material can be shared by a plurality of types of igniters, thereby enabling standardization.

According to the ignition coil for an internal combustion engine of the second aspect, it is possible to prevent the local stress from increasing on the bottom surface, the side surface, and the end surface side of the igniter. According to the ignition coil for an internal combustion engine of the third aspect, the cushioning material and thus the igniter can be positioned reliably and easily in the second housing portion of the case by using the holder for positioning the center core, the secondary spool and the primary spool. . According to the ignition coil for an internal combustion engine according to the fourth aspect, when setting the shock absorbing material accommodating the igniter in the second accommodating portion, it is possible to reliably and easily secure the clearance on the bottom surface side of the igniter. According to the ignition coil for an internal combustion engine of the fifth aspect, it is possible to reliably and easily position the cushioning material and thus the igniter in the second housing portion of the case using the terminal of the connector that supplies a predetermined signal to the ignition coil. According to the ignition coil for an internal combustion engine of the sixth aspect, the linear expansion coefficient of the insulating resin material under the cooling / heating cycle can be configured according to the type of the igniter. According to the ignition coil for an internal combustion engine of the seventh aspect, by making the elastic coefficient of the buffer material smaller than the elastic coefficient of the insulating resin, it is possible to cope with a finer stress change.

The ignition coil for an internal combustion engine includes a case, a central core, a primary spool and a primary coil, a secondary spool and a secondary coil, an igniter, a cushioning material, and an insulating resin.
<Case>
The case includes a cylindrical first housing portion that houses a primary coil, a secondary coil, and the like, and a box-shaped second housing portion that houses an igniter, a cushioning material, and the like. A holder can be attached to the upper ends of the central core, primary spool, and secondary spool in the first accommodating portion, and these can be positioned and held in a predetermined relationship in the radial direction and the axial direction.
<Ignita>
The igniter is supplied from a DC power source and cuts off a current flowing through the primary coil, and generates a high voltage in the secondary coil. The electronic component is molded by a resin mold and has, for example, a rectangular parallelepiped shape defined by an upper surface, a lower surface (bottom surface), a pair of side surfaces, and a pair of end surfaces.
<Buffer material>
The cushioning material made of resin, rubber or the like absorbs and relaxes stress applied from the insulating resin to the resin mold or in the opposite direction. What is necessary is just to have the shape which wraps an igniter, for example, it can be set as the box shape (container shape) which opened upwards. The box-shaped cushioning material has a bottom wall portion, a pair of side wall portions, and a pair of end wall portions.

In order for the buffer material to relieve stress, it is necessary that its elastic coefficient is smaller than that of the insulating resin. For example, when the elastic coefficient E of the insulating resin is 8200 MPa, the elastic coefficient E of the buffer material made of resin can be about 5400 MPa, and the elastic coefficient E of the buffer material made of rubber can be about 100 MPa. The smaller the elastic modulus, the greater the stress absorption / relaxation effect. In this respect, rubber is preferable to the insulating resin.
<Insulating resin>
There is a gap between the outer surface of the igniter and the inner surface of the cushioning material. Specifically, the bottom surface of the igniter and the bottom wall portion of the cushioning material are opposed to the side surface of the igniter and the side wall portion of the cushioning material, and the end surface of the igniter and the end wall portion of the cushioning material are opposed to a predetermined clearance. Yes (not in contact). Insulating resin is poured into these gaps and cured to form a bottom resin part, a side resin part, and an end resin part, respectively. In addition, the insulating resin is filled in the gap between the buffer material and the second housing part or in the first housing part.
<Positioning of igniter and cushioning material>
When the cushioning material is placed on the holder and the protrusion formed on the holder is passed through the hole formed in the bottom wall portion of the cushioning material, the cushioning material is positioned with respect to the holder. If the projection of the holder is brought into contact with the bottom surface of the igniter, a clearance is reliably ensured between the bottom surface of the igniter and the bottom wall portion of the cushioning material. Further, the buffer material, that is, the igniter can be positioned in the second housing portion by using a terminal of a connector that supplies a predetermined signal to the ignition coil.

<Example>
Embodiments of the present invention will be described below with reference to the accompanying drawings.
(Constitution)
The ignition coil for an internal combustion engine shown in FIGS. 1 and 2 includes a case 10, a central core 20, a primary coil 28 and a secondary coil 23, an igniter 35 that cuts off a primary current flowing through the primary coil 28, and a buffer. It consists of a material 40 and an insulating resin 45. Among these, the insulating case 10 includes a cylindrical portion 12 that houses the primary coil 28 and the secondary coil 23, and a box-shaped portion 15 that houses an igniter 35 and the like. The cylindrical portion 12 accommodates the central core 20, the primary spool 27, the secondary spool 22, and the like.

  A cylindrical and insulating secondary spool 22 is disposed on the outer peripheral side of a cylindrical central core 20 formed by stacking a plurality of thin silicon steel plates, and a secondary coil 23 is wound around the outer peripheral surface thereof. A cylindrical and insulating primary spool 27 is concentrically disposed on the outer peripheral side of the secondary spool 22, and a primary coil 28 is wound around the outer peripheral surface thereof. The spaces between the central core 20 and the secondary spool 22, between the secondary coil 23 and the primary spool 27, and between the primary coil 28 and the cylindrical portion 12 are filled with insulating resin (not shown), respectively. Has been.

  A holder 30, an igniter 35, a buffer material (separator) 40, and the like are disposed in the box-shaped portion 15. The holder 30 is fitted to the upper ends of the center core 20, the secondary spool 22 and the primary spool 27, and positions and holds them.

  An igniter 35 is disposed above the holder 30 via a buffer material (separator) 40, and an insulating resin 45 is filled between the igniter 35 and the box-shaped portion 15. The box-shaped cushioning material 40 wraps the rectangular parallelepiped igniter 35 while maintaining the gaps 43a to 43c. That is, the buffer material 40 includes a bottom wall portion 41a, a pair of side wall portions 41b, and a pair of end wall portions 41c. The bottom wall portion 41a faces the lower surface 36a of the igniter 35 with a clearance 43a, the side wall portion 41b faces the side surface 36b with a clearance 43b, and the end wall portion 41c faces the end surface 36c with a clearance 43c. Yes.

  The gaps 43a, 43b and 43c are filled with insulating portions 46a, 46b and 46c of the insulating resin 45, respectively. The insulating resin 45 further includes a resin portion 47 a filled in the space above the igniter 35 in the buffer material 40 and a resin portion 47 b filled in the space between the buffer material 40 and the box-shaped portion 15.

  A protrusion 31 formed on the upper surface of the holder 30 extends upward through a through hole 41 d formed in the bottom wall portion 41 a of the cushioning material 40, and its upper end is in contact with the bottom surface 36 a of the igniter 35. A connector pin 49 of the connector 48 integrated with the box-shaped portion 15 is connected to the terminals (terminals) 51 of the igniter 35, the ends of the primary coil 23 and the secondary coil 28.

When assembling the cushioning material 40 and the igniter 35, the igniter 35 is accommodated in the cushioning material 40 from its upper opening and placed on the holder 30. Thereafter, a resin material is poured into the box-shaped portion 15 and cured to become an insulating resin 45.
(Function)
Since the operation of the ignition coil for an internal combustion engine is known per se, a detailed description is omitted. During operation of the ignition coil, stress acts on the resin mold (not shown) of the igniter 35 from the insulating resin 45 due to the temperature rise and fall. This stress is absorbed and alleviated by the buffer material 40 interposed between the igniter 35 and the insulating resin 45. Details will be described below in the column of effects.
(effect)
According to this embodiment, the following effects can be obtained. First, the occurrence of stress in the igniter 35 due to the difference in linear expansion coefficient between the resin mold of the igniter 35 and the insulating resin 45 is prevented. For example, the elastic deformation of the buffer material 40 absorbs the expansion larger than the insulating resin 45 of the igniter 35 when the temperature rises. The buffer material 40 covers all surfaces other than the upper opening of the igniter 35, and can absorb and relieve transmission of force (deformation) from all these directions. That is, thanks to the presence of the buffer material 40, the igniter 35 and the insulating resin 45 can expand and contract independently.

  Second, the igniter 35 can be easily accommodated in the buffer material 40. The distance between the side wall portions 41b of the separator 40 and the distance between the both end walls 41c are larger than the length and width of the igniter 35, respectively. Therefore, the igniter 35 can be accommodated in the buffer material 40 without fine adjustment of the relative position between the igniter 35 and the buffer material 40.

  Third, it is possible to share (standardize) one type of cushioning material 40 for accommodating a plurality of types of igniters 35. This is because the internal dimensions of the buffer material 40 are larger than the external dimensions of the igniter 35, and the gaps 43a to 43c cancel out the external dimension differences between the plural types of igniters 35.

Fourth, the positioning of the buffer material 40 and the igniter 35 is reliable. This is because the protrusion 31 of the holder 30 penetrates the through hole 41 d of the buffer material 45. In addition, the protrusion 31 abuts against the bottom surface 36a of the igniter 35 to ensure a clearance 43a.
<Modification>
As a modification of the above embodiment, the terminal 51 of the igniter 35 can be connected to the connector pin 49 and the igniter 35 can be floated in the cushioning material 40 as a cantilever support by the terminal 51.

  Moreover, it can also be set as the structure where the front-end | tip of the side wall part 41b and the end wall part 41c of the box-shaped buffer material 40 does not protrude from the upper surface of insulating resin (the front-end | tip is left inside the insulating resin 45). In this way, even if the buffer material 40 and the insulating resin 45 are peeled off, it is possible to prevent moisture from entering from the peeled portion. Even in this structure, since the cushioning material 40 is located around the igniter 35, the effect of absorbing and relaxing stress can be expected.

  Japanese Utility Model Publication No. 53-50338 (related technology) discloses an ignition in which an amplifier 72 and an ignition coil 74 are accommodated in the same case 70 and a resin 76 is filled in the case 70, as shown in FIG. An apparatus is disclosed. An insulating plate 78 that partitions the ignition coil 74 and the amplifier unit 72 is fitted and fixed in a groove provided on the side surface of the case 70.

  However, the above embodiment differs from this related technique in the following points. First, in the embodiment, the buffer material 40 has a container shape and surrounds the bottom surface 36a, the side surface 36b, and the end surface 36c of the igniter 35. On the other hand, in the related art, the insulating plate 78 surrounds only the bottom surface and one side surface of the amplifier section 72.

  Further, the cushioning material 40 of the embodiment does not have an upper wall and the upper space of the igniter 35 is open, whereas the ceiling portion of the case 70 is located just above the amplifier 72 of the related art and is opened. Not. Further, the igniter 35 of the embodiment is positioned in the cushioning material 40 by the protrusion 31 of the holder 30 that contacts the bottom surface 36a, a terminal extending from the igniter 35, and the like. On the other hand, the positioning method is not described in the amplifier 72 of the related art.

It is principal part sectional drawing of the ignition coil for internal combustion engines by the Example of this invention. It is a principal part top view of FIG. It is a front section of related technology. It is a principal part longitudinal cross-sectional view of the conventional ignition coil.

Explanation of symbols

10: Case 12: Cylindrical portion 15: Box-shaped portion 23: Primary coil 28: Secondary coil 30: Holder 35: Igniter 36a: Bottom surface 36b: Side surface 36c: End surface 40: Buffer material 41a: Bottom wall portion 41b: Side wall portion 41c: End wall portions 43a, 43b, 43c: Clearance 45: Insulating resin 46a, 46b, 46c: Resin portion

Claims (7)

A primary coil and a secondary coil housed in the first housing portion of the case;
An igniter for generating a second received in the receiving section, a high voltage to the secondary coil to block the primary current before Symbol primary coil of the case,
At least an inner dimension that is larger than the outer dimension of the igniter and that allows a predetermined clearance to be formed between the outer surface of the igniter and the inner surface of the cushioning material, and the igniter is disposed in the second housing portion. Cushioning material that can be accommodated in,
An insulating resin filled in the first housing portion, the second housing portion, and the gap;
An ignition coil for an internal combustion engine comprising: The cushioning material includes a bottom wall portion facing the bottom surface of the igniter, a side wall portion facing the side surface, and an end wall portion facing the end surface,
The insulating resin includes a bottom resin portion filled in a clearance between the bottom surface of the igniter and the bottom wall portion of the buffer material, a side resin portion filled in a clearance between the side surface and the side wall portion, and the end surface and the end. The ignition coil for an internal combustion engine according to claim 1, comprising an end surface resin portion filled in a clearance with the wall portion.   And a holder that holds the upper end of the primary spool on which the primary coil is wound and the secondary spool on which the secondary coil is wound and is positioned below the cushioning material. The ignition coil for an internal combustion engine according to claim 2, wherein positioning means for the cushioning material is formed between the internal combustion engine and the ignition coil.   The ignition coil for an internal combustion engine according to claim 3, wherein a part of the positioning means secures a clearance between a bottom surface of the igniter and a bottom wall portion of the cushioning material.   The ignition coil for an internal combustion engine according to claim 2, wherein a terminal of a connector integrated with the second housing portion of the case positions the igniter within the cushioning material. The ignition coil for an internal combustion engine according to any one of claims 1 to 5, wherein the igniter and the insulating resin can expand and contract independently under a cooling and heating cycle. The ignition coil for an internal combustion engine according to any one of claims 1 to 6, wherein an elastic coefficient of the cushioning material is smaller than an elastic coefficient of the insulating resin.

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