JP2013029057A - Ignition coil for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition coil for an internal combustion engine, which has superior mountability to the internal combustion engine, is secured in stable connection with a spark plug, and can reliably prevent intrusion of moisture through a plug hole into a combustion chamber.SOLUTION: The ignition coil 1 for the internal combustion engine includes a coil body 2, a high voltage tower part 3 and a boot 4. The boot 4 has a base end side fitting part 421 fitted to the high voltage tower part 3, a front end side fitting part 422 fitted to the spark plug 5, an opposing part (flange 43) opposed to an inner circumferential surface of an opening of a communication hole, a base end side tube 44 provided adjacently to the base end side with respect to the opposing part, a front end side tube 45 provided adjacently to the front end side with respect to the opposing part, and a seal 46 for sealing between an inner wall of the plug hole and the boot 4, on the front end side than the front end side tube 45. An outer diameter D2 of the front end side tube 45 is smaller than an outer diameter D1 of the base end side tube 44.

Description

  The present invention relates to an ignition coil for an internal combustion engine for igniting by applying a high voltage to a spark plug disposed in the internal combustion engine.

  An internal combustion engine such as a vehicle engine is provided with a spark plug for igniting an air-fuel mixture and an ignition coil for applying a high voltage to the spark plug for ignition. That is, the ignition coil is disposed in the internal combustion engine in a state of being connected to the base end portion of the spark plug (Patent Documents 1 and 2).

  Here, since the spark plug is disposed with its tip portion exposed to the combustion chamber, the plug hole for disposing the spark plug is open to the combustion chamber. The internal combustion engine is provided with an injector for supplying fuel to the combustion chamber. Therefore, in the internal combustion engine, an injector hole for arranging the injector is formed so as to communicate with the combustion chamber. In particular, in a direct-injection internal combustion engine that directly injects fuel into the combustion chamber, the injector hole and the plug hole are formed close to each other in the vicinity of the tip (near the combustion chamber). Moreover, in order to bring the opening end of the injector hole to the combustion chamber close to the opening end of the plug hole, it may be necessary to form the plug hole obliquely.

JP-A-8-261127 JP 2008-280946 A

  However, by forming the plug hole obliquely, it may be necessary to bend the boot portion of the ignition coil connected to the spark plug obliquely with respect to the coil body portion. In this case, unless the ignition coil is manufactured by accurately defining the inclination direction of the plug hole with respect to the coil main body, it may be difficult to attach the internal combustion engine. Therefore, the manufacturing cost of the ignition coil can be improved, and the productivity can be a factor in assembly work for the internal combustion engine.

  Therefore, it is conceivable that the boot portion is formed straight at the time of manufacturing the ignition coil, and the boot portion is bent along the plug hole and inclined at the time of attachment to the internal combustion engine. However, in this case, if the bent portion of the boot portion is not fixed, the boot portion interferes with the inner wall surface of the plug hole, and the boot portion cannot be smoothly inserted into the internal combustion engine. Connection work may be difficult. Further, it may be difficult to obtain a stable connection state between the spark plug and the ignition coil.

  Further, if the plug hole and the injector hole are arranged close to each other, it may be difficult to form both of them independently of each other. In other words, the plug hole and the injector hole may have to communicate with each other before the combustion chamber. In particular, when the axial length of the injector is relatively short (in the case of a so-called short injector), it is necessary to increase the inner diameter of the injector hole by the amount of the injector connector provided at the base end. As a result, it is more likely that the injector hole and the plug hole need to communicate with each other.

  In such a case, as disclosed in Patent Documents 1 and 2, even if a seal portion that prevents moisture from entering the plug hole is provided at the base end portion of the boot portion, if moisture enters from the injector hole, Eventually, moisture may enter the plug hole, and moisture may enter the combustion chamber through the plug hole.

  The present invention has been made in view of such a background, and is excellent in mountability to an internal combustion engine, ensures a stable connection with a spark plug, and ensures the ingress of moisture into the combustion chamber through the plug hole. It is an object of the present invention to provide an ignition coil for an internal combustion engine that can be prevented.

One aspect of the present invention is a high-voltage tower in which a coil main body portion in which a primary coil and a secondary coil are housed in a coil case, and a high-voltage output terminal that outputs a high voltage generated in the coil main body portion are held inside. And a cylindrical connection that connects the high-pressure tower portion and the base end portion of the spark plug together with an electrical connection portion for electrically connecting the high-pressure output terminal and the spark plug mounted in the plug hole of the internal combustion engine. An ignition coil for an internal combustion engine comprising a boot portion of
The boot portion is configured to be inserted into a communication hole communicating with the plug hole,
The boot portion includes a proximal end fitting portion that is fitted to the high pressure tower portion, a distal end fitting portion that is fitted to the proximal end portion of the spark plug, the proximal end fitting portion, and the above A facing portion facing the inner peripheral surface of the opening of the communication hole between the front end side fitting portion, a proximal end side cylinder portion provided adjacent to the proximal end side with respect to the facing portion, and the above There is a distal end side cylindrical portion provided adjacent to the distal end side with respect to the opposing portion, and a seal portion that seals between the inner wall of the plug hole and the boot portion on the distal end side with respect to the distal end side cylindrical portion. And
The ignition coil for an internal combustion engine is characterized in that the outer diameter of the distal end side cylindrical portion is smaller than the outer diameter of the proximal end side cylindrical portion (claim 1).

  In the ignition coil, the boot portion is formed by forming the proximal end side tubular portion and the distal end side tubular portion on both sides in the axial direction with the facing portion as a boundary. The outer diameter of the tip side cylinder portion is smaller than the outer diameter. Accordingly, when the boot portion is inserted into the communication hole communicating with the plug hole, the boot portion is easily bent at the proximal end portion of the distal end side cylindrical portion, that is, at the portion adjacent to the distal end side with respect to the facing portion. be able to. In other portions, the boot portion can be prevented from bending as much as possible.

  Thereby, even when the spark plug is disposed obliquely with respect to the opening direction of the opening portion of the communication hole, the portion of the boot portion on the tip side of the facing portion facing the opening portion of the communication hole is spark plug. And can be smoothly inserted and arranged in the communication hole in parallel. That is, the axis of the spark plug in which the axial direction of the distal end side cylinder portion is inclined with respect to the opening direction of the opening portion in a state where the axial direction of the proximal end side cylinder portion is aligned with the opening direction of the opening portion It can be easily matched with the direction. As a result, the mounting property of the ignition coil to the internal combustion engine can be improved, and the connection stability of the ignition coil to the spark plug can be ensured.

  Further, as described above, the boot portion can be easily bent at a desired location. Therefore, when manufacturing the ignition coil, it is not necessary to bend the boot portion in advance, and the boot portion can be straightened. it can. In other words, for example, when an ignition coil having a straight boot portion is prepared and assembled to an internal combustion engine, the boot portion can be easily bent along the shape of the communication hole. Therefore, at the time of mounting on the internal combustion engine, there are no restrictions on the assembly due to the direction of the ignition coil, and the assembly work is facilitated. Furthermore, since there is no restriction on the directivity between the coil body portion and the boot portion in the ignition coil, the boot portion can be easily assembled to the coil body portion.

The boot portion includes a seal portion that seals between the inner wall of the plug hole and the boot portion on the distal end side with respect to the distal end side cylindrical portion. Thereby, even if moisture enters the communication hole, it is possible to reliably prevent moisture from entering the combustion chamber from the plug hole.
In particular, when the injector hole and the plug hole provided in the internal combustion engine communicate with each other in front of the combustion chamber, even if moisture enters from the injector hole, the presence of the seal portion causes moisture to enter the combustion chamber through the plug hole. Can be surely prevented from entering.

  Further, since the sealing by the sealing portion can be performed on the tip side from the tip tube portion, it is not necessary to perform sealing in the opening portion of the communication hole, that is, in the vicinity of the facing portion. Therefore, the degree of freedom in designing the shape of the opening of the communication hole can be increased. As a result, for example, it is possible to connect the communication hole to the injector hole so that the opening of the communication hole can be used as an opening for an injector or an opening for a spark plug. Become.

  As described above, according to the above-described aspect, it is excellent in mountability to the internal combustion engine, can ensure a stable connection with the spark plug, and can surely prevent moisture from entering the combustion chamber through the plug hole. An ignition coil for an internal combustion engine can be provided.

1 is a partial cross-sectional front view of an ignition coil for an internal combustion engine in Embodiment 1. FIG. 1 is a front view of an ignition coil mounted on a cylinder head in Embodiment 1. FIG. FIG. 3 is a top explanatory view of a cylinder head in the first embodiment. Sectional drawing by the plane orthogonal to the axial direction of the base end side cylinder part of a boot part in Example 1. FIG. Sectional drawing of the collar part (opposing part) of the boot part contact | abutted to the internal peripheral surface of the opening part of a communicating hole in Example 1. FIG. The partial cross section front view of the ignition coil for internal combustion engines in Example 2. FIG. FIG. 6 is a partial cross-sectional front view of an ignition coil for an internal combustion engine in a third embodiment. The front view of the ignition coil for internal combustion engines in Example 4. FIG. The diagram of the stress analysis result in example 1 of an experiment. Explanatory drawing of the analytical calculation model in Experimental example 1. FIG. The diagram of the stress analysis result in example 2 of an experiment. Front explanatory drawing of the ignition coil with which the cylinder head in the comparative example was mounted | worn. The upper surface explanatory drawing of the cylinder head in a comparative example.

  The outer diameter of the base end side cylinder part and the outer diameter of the tip end side cylinder part each mean the maximum diameter. That is, when the proximal end side cylinder part or the distal end side cylinder part is circular in the cross-sectional shape orthogonal to the axial direction, the diameter of the circle shall mean the “outer diameter”, otherwise In the case of this shape, it means the diameter of the circumscribed circle having the above-mentioned cross-sectional shape. Therefore, for example, by forming a rib extending in the axial direction on the outer peripheral surface of the base end side cylinder portion so as to protrude radially outward, the outer diameter of the base end side cylinder portion is set to the tip end side cylinder. You may make it larger than the said outer diameter of a part.

  In addition, the cross-sectional shape of the base end side cylindrical portion and the distal end side cylindrical portion is preferably circular, but in the case of other shapes, the cross sectional shape is preferably rotationally symmetric more than 3 times, More preferably, it has a rotational symmetry of 4 times or more.

Moreover, the said boot part can be comprised with rubber | gum, such as silicone rubber, for example. Moreover, the said boot part can also be comprised with an integral molded object, and can also be comprised combining a some molded object.
Further, the facing portion may be constituted by a collar portion protruding to the outside of the boot portion. That is, the opposed portion may have an outer diameter larger than that of the proximal end side cylindrical portion. And the said opposing part may be comprised so that it may contact | abut to the internal peripheral surface of the opening part of the said communicating hole.
Moreover, the said collar part may be formed in the perimeter in the circumferential direction of the outer periphery of the said boot part, and may be formed partially.
The internal combustion engine is preferably a direct injection internal combustion engine that directly injects fuel into the combustion chamber.

  Moreover, in the ignition coil for an internal combustion engine, it is preferable that the distal end side cylindrical portion has a thin portion that is thinner than other portions at the base end portion. In this case, the boot portion can be easily and reliably bent at the proximal end portion of the distal end side cylindrical portion, that is, at the portion adjacent to the distal end side of the opposed portion.

  Moreover, it is preferable that the said thin part has thickness of 0.5 mm or more. In this case, the strength of the thin portion of the boot portion can be sufficiently ensured.

Moreover, it is preferable that the said boot part is provided with the guide part which protruded outside between the said opposing part and the said seal part (Claim 4). In this case, the guide portion can be slid with respect to the inner wall surface of the communication hole when the boot portion is inserted into the communication hole. Thereby, the said boot part can be smoothly inserted in a communicating hole, and a boot part can be easily and reliably fitted to a spark plug in a front end side fitting part.
In addition, the said guide part may be formed in the perimeter in the circumferential direction of the outer periphery of the said boot part, and may be formed partially.

  The boot portion includes a proximal rubber member provided with the proximal fitting portion, a distal rubber member provided with the distal fitting portion, the proximal rubber member, and the distal rubber. An intermediate resin member disposed between the two members is connected in the axial direction, and the opposed portion, the proximal side tubular portion, and the distal end side tubular portion are formed on the proximal end rubber member. (Claim 5).

In this case, the material cost of the boot part can be reduced. That is, the portions other than the base end side fitting portion and the distal end side fitting portion are portions that do not need to have particularly large elasticity and flexibility, and there is freedom of material selection. Therefore, by selecting a relatively inexpensive material using this portion as the intermediate resin member, the cost of the boot portion can be reduced, and the cost of the ignition coil can be reduced. In addition, the base end side rubber member and the front end side rubber member are respectively disposed in portions that form the base end side fitting portion and the front end side fitting portion, thereby ensuring a stable fitting state. Can do. Further, by forming the opposed portion, the proximal end side tubular portion, and the distal end side tubular portion on the proximal end side rubber member, it is possible to easily and reliably realize the bending of the boot portion at a predetermined location. Can do.
In addition, the said base end side rubber member and the said front end side rubber member can be comprised by silicone rubber, EPDM (ethylene-propylene-diene rubber), etc., for example. The intermediate resin member can be made of, for example, PPS (polyphenylene sulfide resin), PBT (polybutylene terephthalate resin), or the like.

  Moreover, it is preferable that the full length L1 of the said base end side rubber member and the full length L2 of the said intermediate | middle resin member satisfy | fill L2 / L1 <= 2. In this case, the full length of the base end side rubber member can be sufficiently ensured without increasing the length of the boot portion. Thereby, it becomes easy to form the base end part of the said front end side cylinder part which is a site | part to be bent in a desired position.

Example 1
An ignition coil for an internal combustion engine according to an embodiment will be described with reference to FIGS.
The ignition coil 1 of this example is provided with the coil main-body part 2, the high voltage | pressure tower part 3, and the cylindrical boot part 4, as shown in FIG. 1, FIG.
The coil body 2 is configured by housing a primary coil and a secondary coil in a coil case.
The high-voltage tower unit 3 holds a high-voltage output terminal 31 that outputs a high voltage generated in the coil body unit 2 inside.
The boot portion 4 includes an electrical connection portion 41 for electrically connecting the high-voltage output terminal 31 and the spark plug 5 mounted in the plug hole 61 of the internal combustion engine, and the base portion of the high-pressure tower portion 3 and the spark plug 5. Are connected to each other.

The boot portion is configured to be inserted into a communication hole 62 that communicates with the plug hole 61.
Further, the boot portion 4 includes a proximal end fitting portion 421 that fits into the high-pressure tower portion 3 and a distal end fitting portion 422 that fits into the proximal end portion of the spark plug 5. Between the base end side fitting part 421 and the front end side fitting part 422, the opposing part which opposes the internal peripheral surface of the opening part 621 of the communicating hole 62 is provided. The facing portion is constituted by a flange portion 43 protruding outward.

  The boot portion 4 includes a proximal-side cylindrical portion 44 provided adjacent to the proximal end side with respect to the flange portion 43, and a distal-end-side cylindrical portion provided adjacent to the distal end side with respect to the flange portion 43. 45. Further, a seal portion 46 (an axial contact portion 461 and a radial contact portion) that seals the space between the inner wall of the plug hole 61 and the boot portion 4 at the front end side of the front end side cylinder portion 45 in the boot portion 4. 462) is formed.

The flange 43 is configured such that at least a part thereof is in contact with the inner peripheral surface of the opening 621 of the communication hole 62 communicating with the plug hole 61 in the internal combustion engine.
The outer diameter D2 of the distal end side tubular portion 45 is smaller than the outer diameter D1 of the proximal end side tubular portion 44.

  Here, the outer diameter D1 of the proximal end side cylinder part 44 and the outer diameter D2 of the distal end side cylinder part 45 mean the maximum diameter, respectively. That is, when the proximal end side cylinder part 44 and the distal end side cylinder part 45 are circular in the cross-sectional shape orthogonal to the axial direction, the diameter of the circle shall mean the above “outer diameter”, otherwise In the case of this shape, it means the diameter of the circumscribed circle having the above-mentioned cross-sectional shape.

In this example, as shown in FIG. 4, the base end side cylinder portion 44 has a shape in which a rib 441 extending in the axial direction is formed to protrude outward in the radial direction on a cylindrical outer peripheral surface. The ribs 441 are equally arranged at four locations in the circumferential direction, and this cross-sectional shape is a so-called four-fold rotationally symmetric shape. Therefore, as shown in FIG. 4, the outer diameter D1 of the base end side cylindrical portion 44 is between the outer end portions of the pair of ribs 441 that are formed to protrude on opposite sides in the cross-sectional shape orthogonal to the axial direction. It becomes the distance.
On the other hand, the distal end side cylinder portion 45 has a cylindrical shape and, as shown in FIG. 2, is not particularly provided with a rib or the like, and therefore, a circular diameter which is an outer contour appearing in a cross section orthogonal to the axial direction is an outer diameter. D2.
And the outer diameters D1 and D2 defined in this way have a relationship of D1> D2.

The difference between the outer diameter D1 and the outer diameter D2 is preferably 0.5 mm or more, and more preferably 1.0 mm or more. Further, the outer diameter D2 is preferably 12 mm or more for manufacturing reasons, and preferably 31 mm or less for mounting reasons on the internal combustion engine.
Specifically, in this example, the outer diameter D1 is 22 mm and the outer diameter D2 is 18 mm.

  The collar portion 43 is formed in an annular shape over the entire circumference of the outer peripheral surface of the boot portion 4. And the collar part 43 protrudes to the radial direction outer side rather than the rib 441 of the base end side cylinder part 44. FIG. Further, as shown in FIG. 5, the flange portion 43 abuts a part of the outer peripheral edge thereof against the inner peripheral surface of the opening 621 of the communication hole 62.

As shown in FIG. 1, the distal end side cylindrical portion 45 has a thin portion 451 having a thinner thickness than other portions at the base end portion. The thin portion 451 is formed by partially increasing the inner diameter of the inner surface of the boot portion 4. That is, the outer diameter of the distal end side cylinder part 45 is the same in the thin part 451 and other parts, but by making the inner peripheral surface of the boot part 4 partially penetrated, the thin part 451 is It is formed.
Moreover, the thin part 451 has a thickness of 0.5 mm or more. Specifically, in this example, the thickness of the thin portion 451 is 3 mm, which is 2 mm thinner than the thickness of 5 mm at other portions of the distal end side cylinder portion 45.

The boot portion 4 includes a guide portion 47 that protrudes outward between the flange portion 43 and the seal portion 46. The guide portion 47 is formed in an annular shape over the entire circumference of the outer peripheral surface of the boot portion 4.
A seal portion 46 is formed on the front end side of the boot portion 4 with respect to the guide portion 47. The seal portion 46 includes an axial contact portion 461 that contacts the inner wall of the plug hole 61 toward the distal end side in the axial direction, and a radial contact portion 462 that contacts the inner wall of the plug hole 61 toward the radially outer side. Prepare. Both the axial contact portion 461 and the radial contact portion 462 are formed in an annular shape over the entire circumference. In addition, two radial contact portions 462 are formed side by side in the axial direction on the tip side of the axial contact portion 461.

  As shown in FIG. 2, the internal combustion engine to which the spark plug 5 and the ignition coil 1 are mounted is provided with a plug hole 61 in the cylinder head 6 formed in the upper part of the combustion chamber 60 and a communication hole communicating with the plug hole 6. 62. One end of the plug hole 61 opens into the combustion chamber 60. In addition, an injector 71 for injecting fuel into the combustion chamber 60 is attached to the cylinder head 6. The injector hole 64 in which the injector 71 is disposed communicates with the communication hole 62. That is, the plug hole 61 and the injector hole 64 are connected by the communication hole 62 between the combustion chamber 60 and the opening 621.

  In this example, the injector 71 is a so-called short injector, and its axial length is short. An injector connector 72 for connecting a signal line for transmitting an open / close signal of the injector 71 is attached to the proximal end portion of the injector 71. In addition, a fuel rail 73 for supplying fuel to the injector 71 is connected to the injector 71. The fuel rail 73 is inserted into the communication hole 62 in the cylinder head 6 and connected to the injector 71.

  The plug hole 61 is inclined in the cylinder head 6. Specifically, the plug hole 61 is formed in an inclined state with respect to a forward / backward direction of a piston (not shown) in the internal combustion engine. The spark plug 5 attached to the plug hole 61 is inclined with respect to the axial direction of the injector 71 attached to the injector hole 64 while the axial direction thereof is inclined with respect to the advancing / retreating direction of the piston. The injector 71 is disposed in parallel with the piston reciprocation direction. In addition, the injector hole 64 opens into the combustion chamber 60 on the tip end side of the injector 71. The opening on the distal end side of the injector 71 and the opening of the plug hole 61 with respect to the combustion chamber 60 are independent of each other, but are arranged close to each other.

Further, the cylinder head 6 includes a plurality of combustion chambers 60, and includes communication holes 62 corresponding to the respective combustion chambers 60. The plurality of communication holes 62 are arranged side by side in the direction in which the injector 71 and the spark plug 5 are arranged.
The injector 71, the fuel rail 73, the spark plug 5, and the ignition coil 1 that are disposed corresponding to the same combustion chamber 60 are configured to be detachable from the openings 621 that are separated from each other on the base end side. Yes. That is, the cam cover 69 that covers the upper portion of the cylinder head 6 has a plurality of openings 621, and the injector 71 and the ignition coil 1 that are arranged corresponding to the same combustion chamber 60 can be connected from different openings 621. It is configured to be detachable.

  Further, as shown in FIGS. 2 and 3, the adjacent communication holes 62 are connected to each other at their base ends. Thus, the ignition coil 1 and the injector 71 arranged in the adjacent communication hole 62 are configured to be detachable from the same opening 621. That is, the opening 621 provided in the upper part between the adjacent combustion chambers 60 is provided for both the spark plug 5 and the ignition coil 1 for one combustion chamber 60 and the injector 71 for the other combustion chamber 60. Open.

  When the ignition coil 1 is mounted on the cylinder head 6 configured as described above, the ignition coil 1 in the state shown in FIG. 1 is inserted into the communication hole 62 from the opening 621 from the tip of the boot portion 4. That is, in a state before being mounted on the cylinder head 6, the boot portion 4 is formed straight and is not bent.

When the boot portion 4 is inserted into the communication hole 62, the boot portion 4 is made to follow the inclined wall surface 622 inclined in the communication hole 62. Specifically, the boot part 4 is moved to the tip side while the guide part 47 provided in the boot part 4 is brought into contact with the inclined wall surface 622 and is slid.
Then, the front end side fitting portion 422 of the boot portion 4 is fitted to the proximal end portion of the spark plug 5 that is already mounted in the plug hole 61. At this time, the coil spring-like electrical connection portion 41 (FIG. 1) held inside the boot portion 4 contacts the terminal at the base end portion of the spark plug 5.
Further, the seal portion 46 is in close contact with the inner wall of the plug hole 61, thereby sealing the plug hole 61 at the upper end portion of the plug hole 61.

  Further, in a state where the ignition coil 1 is mounted on the cylinder head 6 (a state where the ignition coil 1 is fixed to the internal combustion engine with a bolt or the like), the base end side cylinder portion 44 is disposed in parallel to the vertical direction, that is, the piston forward / backward direction. Is done. On the other hand, the distal end side cylinder portion 45 is disposed obliquely with respect to the vertical direction, that is, the forward and backward direction of the piston. Therefore, the distal end side tubular portion 45 and the proximal end side tubular portion 44 are bent with respect to each other. This bending is performed at the stage of inserting the ignition coil 1 into the cylinder head 6. That is, as described above, the boot portion 4 is gradually bent when the guide portion 47 of the distal end side tubular portion 45 is slid on the inclined wall surface 622 of the communication hole 62. At this time, the deformation concentrates on the proximal end portion of the distal end side cylinder portion 45, which is a portion where the outer diameter of the boot portion 4 becomes small, with the flange portion 43 as a boundary, and the boot portion 4 is bent locally at this portion. To do. And since the thin part 451 is formed in this part, it is easy to deform | transform especially compared with another site | part.

Therefore, in the thin portion 451 which is the base end portion of the distal end side cylinder portion 45, the boot portion 4 is bent at an appropriate angle, and the ignition coil 1 is attached to the cylinder head 6 in this state.
Further, the flange portion 43 formed in the boot portion 4 is brought into contact with the inner peripheral surface of the opening 621 provided in the cam cover 69, whereby the ignition coil 1 is positioned in the radial direction (FIG. 5).

  In this state, the coil main body 2 is fixed to the boss 691 provided on the cam cover 69 by bolts (not shown) at the flange portion 21. As a result, the coil body 2 is fixed to the cylinder head 6 at the correct position in the correct posture. And the position and attitude | position of the connector part 22 provided in the coil main-body part 2 will be arrange | positioned as designed.

Next, the function and effect of this example will be described.
In the ignition coil 1, the boot portion 4 is formed by forming the proximal end side tubular portion 44 and the distal end side tubular portion 45 on both sides in the axial direction with the flange portion 43 as a boundary, and the proximal end side tubular portion 44. The outer diameter D2 of the distal end side cylinder portion 45 is smaller than the outer diameter D1 of the front end. Thus, when the boot portion 4 is inserted into the communication hole 62 that communicates with the plug hole 61, the proximal end portion of the distal end side cylindrical portion 45, that is, the portion adjacent to the distal end side with respect to the flange portion 43 can be easily Can be bent. In other portions, the boot portion 4 can be prevented from bending as much as possible.

  Thereby, even when the spark plug 5 is disposed obliquely with respect to the opening direction of the opening portion 621 of the communication hole 62, the boot portion 4 is more than the flange portion 43 contacting the opening portion 621 of the communication hole 62. The tip side portion can be smoothly inserted and arranged in the communication hole 62 in parallel with the spark plug 5. That is, the spark plug in which the axial direction of the distal end side cylindrical portion 45 is inclined with respect to the opening direction of the opening 621 in a state where the axial direction of the proximal end side cylindrical portion 44 is aligned with the opening direction of the opening 621. It can be easily matched with the axial direction of 5. As a result, it is possible to improve the mounting property of the ignition coil 1 to the internal combustion engine (cylinder head 6) and to secure the connection stability of the ignition coil 1 to the spark plug 5.

  Further, as described above, since the boot portion 4 can be bent easily at a desired location, it is not necessary to bend the boot portion 4 in advance when the ignition coil 1 is manufactured. I can leave. That is, for example, when the ignition coil 1 including the boot part 4 in a straight state is prepared, and when the ignition coil 1 is assembled to the cylinder head 6, the boot part 4 is easily bent along the shape of the communication hole 62. be able to. Therefore, at the time of mounting on the cylinder head 6, there is no restriction on assembly due to the directionality of the ignition coil 1, and the assembly work is facilitated. Furthermore, since there is no restriction on the directionality of the coil body 2 and the boot part 4 in the ignition coil 1, the boot part 4 can be easily assembled to the coil body 2.

Further, the boot portion 4 includes a seal portion 46 that seals between the inner wall of the plug hole 62 and the boot portion 4 on the distal end side with respect to the distal end side cylindrical portion 45. Thereby, even if moisture enters the communication hole 62, it is possible to reliably prevent moisture from entering the combustion chamber 60 from the plug hole 61.
In particular, in the state where the injector hole 64 provided in the cylinder head 6 and the plug hole 61 communicate with the communication hole 62 in front of the combustion chamber 60, even if moisture enters from the injector hole 64, Due to the presence, moisture can be reliably prevented from entering the combustion chamber 60 through the plug hole 61. Although not shown, a seal portion that prevents moisture from entering the combustion chamber 60 is also formed at the tip of the injector hole 64.

  Further, since the seal portion 46 can perform sealing at the distal end side with respect to the distal end cylindrical portion 45, it is not necessary to perform sealing at the opening portion 621 of the communication hole 62, that is, in the vicinity of the flange portion 43. Therefore, the design freedom of the shape of the opening 621 of the communication hole 62 can be increased. As a result, the communication hole 62 can be communicated with the injector hole 64, and the opening 621 of the communication hole 62 can be used as the opening for the injector 71 or the opening for the spark plug 5.

Moreover, the front end side cylinder part 45 has the thin part 451 in the base end part. Therefore, the boot portion 4 can be easily and reliably bent at the proximal end portion of the distal end side tubular portion 45, that is, at the portion adjacent to the distal end side of the flange portion 43.
Moreover, since the thin part 451 has a thickness of 0.5 mm or more, the strength in the thin part 451 of the boot part 4 can be sufficiently ensured.

  Further, since the boot portion 4 includes the guide portion 47, when the boot portion 4 is inserted into the communication hole 62, the guide portion 47 is slid with respect to the inner wall surface (inclined wall surface 622) of the communication hole 62. Can do. Thereby, the boot part 4 can be smoothly inserted into the communication hole 62, and the boot part 4 can be easily and reliably fitted to the spark plug 5 at the distal end side fitting part 422.

  As described above, according to this example, it is excellent in mountability to the internal combustion engine, can ensure a stable connection with the spark plug, and can reliably prevent moisture from entering the combustion chamber through the plug hole. An ignition coil for an internal combustion engine can be provided.

(Example 2)
In this example, as shown in FIG. 6, the shape of the thin portion 451 provided in the boot portion 4 is changed from the shape shown in the first embodiment.
That is, the thin-walled portion 451 in the ignition coil 1 of this example is formed by making the proximal end portion of the distal end side tubular portion 45 of the boot portion 4 larger in inner diameter and smaller in outer diameter than other portions. It is. That is, the thin portion 451 is formed by partially punching both the inner peripheral surface and the outer peripheral surface of the distal end side cylinder portion 45.
Others are the same as in the first embodiment.
Also in the case of this example, the same effect as Example 1 can be obtained.

(Example 3)
In this example, as shown in FIG. 7, the shape of the thin portion 451 provided in the boot portion 4 is changed from the shape shown in the first and second embodiments.
That is, the thin part 451 in the ignition coil 1 of this example is formed by making the base end part of the front end side cylinder part 45 of the boot part 4 smaller in outer diameter than other parts. However, the inner diameter of the proximal end portion of the distal end side cylinder portion 45 is the same as that of other portions.

In this example, as a method for partially reducing the outer diameter of the distal end side cylinder portion 45, a rib 452 is provided on the distal end side portion of the portion to be the thin portion 451. The ribs 452 extend along the axial direction and project outward in the radial direction. Further, the ribs 452 are arranged at equal intervals at four locations in the circumferential direction of the distal end side cylindrical portion 45. Accordingly, the portion provided with the rib 452 has an outer diameter larger than that of the thin portion 451, and the thin portion 451 is locally formed at a desired position.
Others are the same as in the first embodiment.
Also in the case of this example, the same effect as Example 1 can be obtained.

Example 4
In this example, as shown in FIG. 8, the boot portion 4 is configured by connecting the following three members.
That is, the boot portion 4 includes a proximal rubber member 401 having a proximal fitting portion 421, a distal rubber member 402 having a distal fitting portion 422, a proximal rubber member 401, and a distal side. An intermediate resin member 403 disposed between the rubber member 402 and the rubber member 402 is connected in the axial direction.

The flange portion 43, the proximal end side tubular portion 44, and the distal end side tubular portion 45 are formed on the proximal end side rubber member 401.
The proximal end rubber member 401 and the distal end rubber member 402 are made of silicone rubber, and the intermediate resin member 403 is made of PPS (polyphenylene sulfide resin) or PBT (polybutylene terephthalate).

The intermediate resin member 403 includes a guide portion 47.
In addition, both end portions of the intermediate resin member 403 are fitted to the proximal rubber member 401 and the distal rubber member 402 from the inside.
Moreover, the full length L1 of the base end side rubber member 401 and the full length L2 of the intermediate resin member 403 satisfy L2 / L1 ≦ 2. Specifically, in this example, L1 = 55 mm and L2 = 80 mm.
Others are the same as in the first embodiment.

  In the case of this example, the material cost of the boot part 4 can be reduced. That is, the portions other than the base end side fitting portion 421 and the distal end side fitting portion 422 are portions that do not need to have particularly large elasticity and flexibility, and there is freedom of material selection. Therefore, the cost of the boot portion 4 can be reduced and the cost of the ignition coil 1 can be reduced by selecting a relatively inexpensive material as the intermediate resin member 403. In addition, the base end side rubber member 401 and the front end side rubber member 402 are arranged in the portions forming the base end side fitting portion 421 and the tip end side fitting portion 422, respectively, thereby ensuring a stable fitting state. can do. Further, by forming the flange portion 43, the proximal end side tubular portion 44, and the distal end side tubular portion 45 in the proximal end side rubber member 401, the bending of the boot portion 4 at a predetermined location can be easily and reliably realized. Can do.

Further, when the total length L1 of the base end side rubber member 401 and the total length L2 of the intermediate resin member 403 satisfy L2 / L1 ≦ 2, the base end side rubber member is maintained while maintaining a predetermined length of the boot portion 4. The full length of 401 can be sufficiently secured. Thereby, it becomes easy to form the base end part of the front end side cylinder part 45 which is a site | part which wants to be bent in a desired position.
In addition, the same effects as those of the first embodiment are obtained.

(Experimental example 1)
In this example, as shown in FIG. 9, an example of analyzing a part to which a bending stress is applied and a change in its size due to a difference between the outer diameter D1 of the proximal end side cylinder portion 44 and the outer diameter D2 of the distal end side cylinder portion 45 is analyzed. It is.
In this example, an analytical calculation model 10 as shown in FIG. 10 is prepared. The model 10 imitates the outer shape of the boot portion 4 in the ignition coil 1 of the first embodiment, and particularly imitates the portion of the flange portion 43, the proximal end side tubular portion 44, and the distal end side tubular portion 45. is there. However, the model 10 is not provided with a portion corresponding to the thin portion 451.

That is, the model 10 includes a flange portion 13 corresponding to the flange portion 43 in the boot portion 4, a proximal end side cylindrical portion 14 corresponding to the proximal end side cylindrical portion 44, and a distal end side cylindrical portion corresponding to the distal end side cylindrical portion 45. Fifteen. The material was silicone rubber.
The axial length of the base end side cylindrical portion 14 is 22 mm, the axial length of the distal end side cylindrical portion 15 is 103 mm, the axial length (thickness) of the flange portion 13 is 5 mm, and the outer diameter of the flange portion 13 is 28 mm. did. Moreover, the thickness of the base end side cylinder part 14 is 2.5 mm, and the thickness of the front end side cylinder part 15 is 5 mm. Moreover, the outer diameter d1 of the base end side cylinder part 14 is changed between 16-22 mm, the outer diameter d2 of the front end side cylinder part 15 is also changed, and both difference (d1-d2) is variously changed, Bending stress analysis calculation was performed. This (d1-d2) corresponds to (D1-D2) in the first embodiment.

  As shown in FIG. 10, the bending stress analysis calculation is performed by fixing the base end 140 of the base end side cylinder portion 14 and applying a load f to the tip end 150 of the tip end side cylinder portion 15 in a direction perpendicular to the axial direction. Do by calling. Then, a load is applied until the distal end side cylinder portion 14 is inclined at a predetermined angle. This predetermined angle corresponds to the inclination angle (inclination angle with respect to the vertical direction) of the plug hole 61 shown in the first embodiment, and is specifically 18 °.

As a result of bending stress analysis calculation, when d1−d2 is negative, that is, when the outer diameter d2 of the distal end side cylinder portion 15 is larger than the outer diameter d1 of the proximal end side cylinder portion 14, the maximum stress is calculated. It was found that the end side cylinder portion 14 was applied. As shown in FIG. 9, the stress was relatively high at about 0.9 MPa when d1-d2≈-2 mm.
On the other hand, when d1-d2 is positive, that is, when the outer diameter d2 of the distal end side cylindrical portion 15 is smaller than the outer diameter d1 of the proximal end side cylindrical portion 14, the maximum stress is the proximal end portion of the distal end side cylindrical portion 15. That is, it has been found that it is applied to a portion adjacent to the front end side with respect to the collar portion 13. The stress was as low as about 0.3 MPa as shown in FIG.
It was also found that in the case of d1-d2 ≧ 1, the magnitude of the stress did not change even when the value of d1-d2 was increased.

  From the above results, it is considered that the following can be said in the boot portion 4 of the actual ignition coil 1. That is, by making the outer diameter D2 of the distal end side cylindrical portion 45 smaller than the outer diameter D1 of the proximal end side cylindrical portion 44, the maximum stress can act on the proximal end portion of the distal end side cylindrical portion 45. It can be bent at this part. By setting D1> D2, the maximum stress can be reduced. In particular, if D1−D2 ≧ 1 mm, the boot portion 4 can be moved to a desired position (without causing excessive stress in the bent portion). It can be easily bent at the base end portion of the front end side cylinder portion 45.

(Example 2)
In this example, as shown in FIG. 11, the relationship between the thickness of the thin portion 451 and the stress acting on the thin portion 451 when bent in the thin portion 451 is examined.
That is, the same analytical calculation model as in Experimental Example 1 was provided with a thin portion similar to the thin portion 451 of Example 1, and the bending stress analysis calculation similar to Experimental Example 1 was performed. And as a model, what prepared the thickness of the thin part to 0.5 mm-5 mm was prepared. Bending stress analysis calculation was performed on each model, and the stress applied to the thin wall portion was analyzed. The result is shown in FIG.

As shown in the figure, the stress acting on the thin portion gradually increases as the thickness of the thin portion decreases, but the value is less than 0.4 MPa, and the material strength (allowable stress considering safety 3) .2 MPa).
Therefore, it can be seen that if the thickness of the thin portion is 0.5 mm or more, sufficient strength can be secured and the strength of the boot portion 4 is not affected.

(Comparative example)
This example is an example of an internal combustion engine in which an ignition coil 9 is assembled to a cylinder head 6 in which a plug hole 61 and an injector hole 64 are formed independently of each other, as shown in FIGS.

  The internal combustion engine of this example is also a direct injection type internal combustion engine, and the plug hole 61 is formed obliquely in order to bring the opening end of the injector hole 64 and the opening end of the plug hole 61 close to the combustion chamber 60. . However, unlike the first embodiment, the injector 710 is a so-called long injector, and its axial length is long. Therefore, the injector connector 72 provided at the base end portion of the injector 710 can be disposed above the cylinder head 6 and outside the injector hole 64. Therefore, the injector hole 64 can be formed relatively thin, and can be formed independently of each other without connecting the injector hole 64 and the plug hole 61. Accordingly, the opening 641 on the proximal end side of the injector hole 64 and the opening 611 on the proximal end side of the plug hole 61 are independent from each other.

  Therefore, the ignition coil 9 may be sealed not at the fitting portion with the spark plug 5 but at the opening 611 on the proximal end side of the plug hole 61. That is, since the plug hole 61 and the injector hole 64 do not communicate with each other, moisture cannot enter the combustion chamber 60 from the injector hole 64 through the plug hole 61. Therefore, in order to prevent moisture from entering the combustion chamber 60 from the plug hole 61, it is only necessary to seal at the opening 611 on the proximal end side of the plug hole 61, that is, the opening at the top of the cylinder head 6. Therefore, in this example, a seal rubber portion 99 is provided at the base end portion of the boot portion 94 of the ignition coil 9 to seal between the opening portion 611 on the base end side of the plug hole 61 and the ignition coil 9. .

  On the other hand, as shown in the first embodiment (FIG. 2), when the plug hole 61 and the injector hole 64 communicate with each other through the communication hole 62, the base end side of the boot portion 94 as in this example. If the seal rubber part 99 is provided, the moisture cannot be prevented from entering the combustion chamber 60 from the injector hole 64 through the plug hole 61. Therefore, in the first embodiment, as shown in FIGS. 1 and 2, a seal portion 46 is provided on the outer periphery of the end portion of the boot portion 4 and the fitting portion with the spark plug 5.

  Further, in the ignition coil 9 of the present example, the boot portion 94 is bent and the tip portion thereof is inclined. However, unlike the ignition coil 1 of the first to fourth embodiments, it does not have the flange portion 43 and is bent. The diameter is not changed between the proximal end side and the distal end side of the portion 941. Therefore, in practice, it is difficult to bend the boot portion 94 at an appropriate position as shown in FIG.

  On the other hand, in the ignition coils 1 according to the first to fourth embodiments, the boot portion 4 is provided with the flange portion 43 so that the proximal end side cylindrical portion 44 and the distal end side cylindrical portion 45 on the proximal end side and the distal end side are outside. By setting the diameters D1 and D2 to D1> D2, as described above, the boot portion 4 can be easily bent at a desired position.

DESCRIPTION OF SYMBOLS 1 Ignition coil 2 Coil main-body part 3 High voltage | pressure tower part 31 High voltage | pressure output terminal 4 Boot part 41 Electrical connection part 421 Base end side fitting part 422 Front end side fitting part 43 Gutter part 44 Base end side cylinder part 45 Front end side cylinder part 46 Seal part 5 Spark plug 60 Combustion chamber 61 Plug hole 62 Communication hole 621 Opening part D1 Outer diameter of the base end side cylinder part D2 Outer diameter of the front end side cylinder part

Claims (6)

A coil main body portion in which a primary coil and a secondary coil are accommodated in a coil case, a high voltage tower portion that holds a high voltage output terminal that outputs a high voltage generated in the coil main body portion, and the high voltage output terminal And a spark plug mounted in the plug hole of the internal combustion engine, and a cylindrical boot portion for connecting the high-pressure tower portion and the base end portion of the spark plug. An ignition coil for an internal combustion engine,
The boot portion is configured to be inserted into a communication hole communicating with the plug hole,
The boot portion includes a proximal end fitting portion that is fitted to the high pressure tower portion, a distal end fitting portion that is fitted to the proximal end portion of the spark plug, the proximal end fitting portion, and the above A facing portion facing the inner peripheral surface of the opening of the communication hole between the front end side fitting portion, a proximal end side cylinder portion provided adjacent to the proximal end side with respect to the facing portion, and the above There is a distal end side cylindrical portion provided adjacent to the distal end side with respect to the opposing portion, and a seal portion that seals between the inner wall of the plug hole and the boot portion on the distal end side with respect to the distal end side cylindrical portion. And
An ignition coil for an internal combustion engine, characterized in that an outer diameter of the distal end side cylinder portion is smaller than an outer diameter of the proximal end side cylinder portion.   2. The ignition coil for an internal combustion engine according to claim 1, wherein the distal end side cylinder portion has a thin wall portion that is thinner than other portions at a base end portion thereof. 3. coil.   The ignition coil for an internal combustion engine according to claim 2, wherein the thin portion has a thickness of 0.5 mm or more.   The ignition coil for an internal combustion engine according to any one of claims 1 to 3, wherein the boot portion includes a guide portion that protrudes outward between the facing portion and the seal portion. An ignition coil for an internal combustion engine.   The ignition coil for an internal combustion engine according to any one of claims 1 to 3, wherein the boot portion includes a proximal rubber member provided with the proximal end fitting portion, and the distal end fitting portion. A distal end side rubber member provided, and an intermediate resin member disposed between the proximal end side rubber member and the distal end side rubber member are connected in the axial direction, and the opposing portion and the proximal end side cylinder are connected to each other. An ignition coil for an internal combustion engine, wherein the portion and the distal end side cylindrical portion are formed on the proximal end side rubber member.   6. The ignition coil for an internal combustion engine according to claim 5, wherein a total length L1 of the base end side rubber member and a total length L2 of the intermediate resin member satisfy L2 / L1 ≦ 2. Ignition coil.

Images