JP2019120228A - Ignitor for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost ignition device capable of easily ensuring an insulating sealing property in a pressure contact portion between a joint portion and a spark plug. An ignition device (1) for an internal combustion engine, which has a spark plug (2) and an ignition coil (3). The spark plug 2 has a center electrode 21, an insulating insulator 23, a housing 24, and a head terminal 25. The ignition coil 3 has a coil main body portion 31 and a joint portion 32 provided with a conduction member 33 inside. The joint portion 32 is a tubular body made of an elastic member, and has a pressure welding inner wall surface 321 that is pressed against the outer peripheral surface of the insulating insulator 23 of the spark plug 2 on the tip side, and a tip side on the base end side of the pressure welding inner wall surface 321. It has an annular step portion 322 facing the above. The spark plug 2 has an annular plug shoulder portion 26 facing the proximal end side on at least one of the insulating insulator 23 and the head terminal 25. The step portion 322 abuts on the plug shoulder portion 26, and a gap C is formed between the tip of the joint portion 32 and the base end of the housing 24. [Selection diagram] Fig. 1

Description

  The present invention relates to an ignition device for an internal combustion engine having an ignition plug and an ignition coil.

The internal combustion engine is provided with an igniter having an igniter plug which generates a discharge in the combustion chamber to ignite the fuel, and an igniter coil which applies a high voltage to the igniter plug. The ignition coil is electrically connected to a proximal end of an ignition plug mounted in a plug hole of the internal combustion engine.
As an ignition coil, there is one having a cylindrical joint portion in which a conductive member for electrically connecting to the ignition plug is disposed inside. The proximal end portion of the spark plug is fitted to the distal end portion of the joint portion and in contact with the distal end portion of the conductive member, the spark plug and the ignition coil are electrically and structurally connected. It becomes.

  As described above, it is desirable that at least the tip end portion of the joint portion of the ignition coil be formed of an elastically deformable member in order to be fitted to the ignition plug. Therefore, in general, as the joint portion, one in which an elastic member such as rubber is attached to the end of a joint body made of resin, or one in which the entire joint portion is constituted by an elastic member such as rubber is used. ing.

  The ignition coil having the joint of the latter structure is advantageous in cost because the number of parts can be reduced. An ignition coil of this type is disclosed, for example, in Patent Document 1. In this ignition coil, a plug boot of an elastic body is attached to a coil case accommodating the primary coil and the secondary coil. The plug boot constitutes the entire joint portion. And the conduction | electrical_connection member is arrange | positioned inside a plug boot.

JP, 2010-98191, A

However, in the ignition coil in which the entire joint portion is formed of an elastic body, there are the following problems.
When mounting the joint portion of the ignition coil to the spark plug mounted in the plug hole, the joint portion is pushed toward the front end side in the axial direction toward the spark plug. At this time, a pressure contact force corresponding to the fitting space between the insulator of the spark plug and the joint portion acts between the insulator and the joint portion. The frictional force corresponding to the pressure contact force acts on the joint portion as an axial insertion load.

  When the entire joint portion is made of an elastic body, the insertion load is applied to the entire joint portion, and the entire joint portion is axially compressively deformed according to the insertion load. Then, the amount of compressive deformation of the joint is likely to be large. That is, since the amount of compressive deformation increases as the total length in the axial direction of the elastic body increases, the amount of compressive deformation of the joint portion tends to increase when the entire joint portion is made of an elastic body. Along with this, the variation in the amount of compressive deformation of the joint portion also tends to be large.

  The fact that the amount of compressive deformation of the joint portion is large is not particularly a problem because it can be coped with by designing in consideration of the amount of deformation. However, an increase in the variation in the amount of compressive deformation is disadvantageous in the following viewpoints, for example.

  That is, when the variation in the amount of compressive deformation of the joint portion is large, the variation in the axial length (hereinafter referred to as “pressure contact length” as appropriate) of the pressure contact portion between the insulator and the joint portion of the spark plug There is a risk of becoming large. The pressure contact length needs to be kept in a preset range in consideration of the influence on the insulation sealing property and the like. That is, when the press-contact length is too short, the insulation sealability can not be sufficiently secured. On the contrary, if the press-contact length is too long, the joint portion may come in contact with the housing of the spark plug to cause thermal deterioration of the joint portion.

  In addition, although it is also considered to perform design which can enlarge the tolerance | permissible_range of press-contacting length, the enlargement of a spark plug will be caused in that case. Also, in order to reduce the amount of compressive deformation of the joint portion, it is conceivable to increase the cross-sectional area of the cross section orthogonal to the axial direction, but also in this case, there is a risk of increasing the size of the joint portion and the material cost Is difficult to reduce.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a low-cost igniter which is easy to secure the insulation sealing property at the pressure contact portion between the joint portion and the ignition plug.

One aspect of the present invention is an ignition device (1) for an internal combustion engine, comprising: an ignition plug (2) mounted on the internal combustion engine; and an ignition coil (3) for supplying a high voltage to the ignition plug. ,
The spark plug is held inside a center electrode (21), an insulator (23) holding the center electrode inside, a housing (24) holding the insulator inside, and the insulator And a head terminal (25) projecting to the base end side of the insulator.
The ignition coil includes a coil main body (31) including a primary coil and a secondary coil, and a conductive member for electrically connecting the high voltage output terminal (311) of the coil main body and the head terminal of the spark plug And 33) a joint portion (32) provided on the inside,
The joint portion is a cylindrical body made of an elastic member and has a pressure-contacting inner wall surface (321) which is in pressure contact with the outer peripheral surface of the insulator of the ignition plug at the tip end side, and An annular step (322) facing the tip side;
The spark plug has an annular plug shoulder (26) facing the proximal end on at least one of the insulator and the head terminal;
The step portion is in contact with the plug shoulder portion, and a gap (C) is formed between the tip end of the joint portion and the base end of the housing.

  In the igniter, the joint portion of the ignition coil has an annular step portion facing the tip end side on the base end side of the pressure-contacting inner wall surface. The stepped portion is in contact with the plug shoulder. Thereby, it is possible to suppress the variation in axial length (hereinafter referred to as “pressure contact length”) of the pressure contact portion between the pressure contact inner wall surface of the joint portion and the outer peripheral surface of the insulator.

  That is, when the joint portion is pushed toward the spark plug until the stepped portion abuts on the plug shoulder, an insertion load corresponding to the pressure contact force between the pressure-contacting inner wall surface and the outer circumferential surface of the insulator is axially applied to the joint portion. Act in the direction. Along with this, the joint portion made of the elastic member is compressed and deformed in the axial direction. However, the stepped portion and the plug shoulder abut, and in this abutting portion, the joint and the insulator are positioned in the axial direction. Therefore, the variation in the amount of compressive deformation of the portion on the tip end side from the stepped portion corresponds to the variation in the pressure contact length. Conversely, the variation in the amount of compressive deformation of the portion on the proximal side of the step portion in the joint portion does not affect the variation in the pressure contact length.

  The length from the stepped portion to the tip end can be made significantly shorter than the total length of the joint portion. Therefore, the variation in press-contact length can be significantly reduced.

  Moreover, the number of parts which comprise a joint part can be reduced by setting it as the above. Therefore, the cost of the ignition coil can be reduced, and thus, a low cost ignition device can be obtained.

As described above, according to the above aspect, it is possible to provide a low-cost igniter that is easy to secure the insulation sealing property at the pressure contact portion between the joint portion and the spark plug.
The reference numerals in parentheses described in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described later, and the technical scope of the present invention is limited. It is not a thing.

FIG. 2 is a front view, partly in cross section, of the ignition device in the first embodiment. FIG. 2 is a partial cross-sectional front view of the ignition device in the vicinity of the spark plug in Embodiment 1; FIG. 2 is a front view of the spark plug in the first embodiment. IV view of FIG. FIG. 2 is a front view, partly in cross section, of an ignition coil according to a first embodiment. FIG. 2 is a cross-sectional front view of a joint portion in Embodiment 1; VII-VII arrow sectional drawing of FIG. FIG. 5 is a front view, partly in section, of the state in which the spark plug is mounted in the plug hole in the first embodiment. FIG. 8 is a front view, partly in cross section, of an ignition device around a spark plug in a second embodiment. FIG. 14 is a partial cross-sectional front view of an ignition device around a spark plug in a third embodiment. FIG. 14 is a partial cross-sectional front view of an ignition device around a spark plug in a fourth embodiment. The partial cross section front view of an ignition device in a comparison form. The partial cross section front view of an ignition coil in a comparison form.

(Embodiment 1)
Embodiments of an ignition device for an internal combustion engine will be described with reference to FIGS. 1 to 8.
The igniter 1 for an internal combustion engine, as shown in FIGS. 1 and 2, has an ignition plug 2 mounted in a plug hole 41 of the internal combustion engine, and an ignition coil 3 for supplying a high voltage to the ignition plug 2.

  As shown in FIGS. 2 to 4, the spark plug 2 has a center electrode 21, an insulator 23, a housing 24, and a head terminal 25. The insulator 23 holds the center electrode 21 inside. The housing 24 holds the insulator 23 inside. The head terminal 25 is held inside the insulator 23 and protrudes to the proximal end side of the insulator 23.

  As shown in FIGS. 1 and 5, the ignition coil 3 has a coil body 31 and a joint 32. The coil body 31 is formed by housing a primary coil and a secondary coil in a case. The joint portion 32 is provided with the conduction member 33 inside. The conduction member 33 electrically connects the high voltage output terminal 311 of the coil body 31 and the head terminal 25 of the spark plug 2.

  As shown in FIGS. 5 to 7, the joint portion 32 is a cylindrical body made of an elastic member. The joint portion 32 has a press-contacting inner wall surface 321 pressed against the outer peripheral surface of the insulator 23 of the spark plug 2 at the tip end side, and an annular step portion 322 facing the tip end side at the base end side of the press-contacting inner wall surface 321. .

As shown in FIG. 3 and FIG. 4, the spark plug 2 has an annular plug shoulder 26 facing the proximal end on at least one of the insulator 23 and the head terminal 25. In the present embodiment, the plug shoulder 26 is provided on the proximal end face of the insulator 23.
As shown in FIG. 2, the stepped portion 322 is in contact with the plug shoulder 26. A gap C is formed between the distal end of the joint portion 32 and the proximal end of the housing 24.

In the present specification, in the axial direction, the side on which the spark plug 2 is disposed with respect to the ignition coil 3 is referred to as a distal end side, and the opposite side is referred to as a proximal end.
The joint portion 32 has a head contact surface 323 in contact with the side surface of the head terminal 25 on the base end side of the step portion 322.

  The spark plug 2 has a ground electrode 22 which protrudes from the tip of the housing 24 and is bent inward as shown in FIG. The ground electrode 22 is disposed opposite to the center electrode 21 with a spark discharge gap provided. A mounting screw portion 241 for fixing the spark plug 2 to the plug hole 41 is formed on the outer peripheral surface of the housing 24. Further, on the base end side of the mounting screw portion 241, a hexagonal portion 242 for engaging a tool is formed.

  The insulator 23 held inside the housing 24 protrudes from the housing 24 to the proximal side. A portion of the insulator 23 which protrudes from the housing 24 to the proximal side is referred to as a forceps head 231. A corrugation 232 is formed on a part of the outer peripheral surface of the forceps head 231 on the proximal side. And the head terminal 25 protrudes from the forceps head 231 to the base end side. As shown in FIG. 4, the base end surface of the forceps head 231 is annularly exposed on the outer peripheral side of the head terminal 25 when viewed from the base end side in the axial direction. This annular portion is the plug shoulder 26.

  As shown in FIGS. 5 and 6, the ignition coil 3 has a high pressure tower portion 310 protruding from the coil body portion 31. The high voltage tower portion 310 holds the high voltage output terminal 311 inside. In the high voltage tower portion 310, a resistor 312 is also disposed. The resistor 312 is interposed between the high voltage output terminal 311 and the conductive member 33 in the joint portion 32. The conduction member 33 is formed of a spring which elastically deforms in the axial direction.

  The proximal end of the joint 32 fits into the high pressure tower 310. The joint portion 32 is a cylindrical member made of rubber, and is configured to be elastically deformable. The joint portion 32 has a substantially cylindrical shape. An annular collar 324 is formed at the proximal end of the joint 32. The collar portion 324 is configured to be in close contact with the proximal end portion of the plug hole 41 so as to close the plug hole 41, as shown in FIG.

  As shown in FIG. 6, a tip fitting portion 326 for inserting the forceps head 231 of the spark plug 2 is provided at the tip of the joint portion 32. A pressure-contacting inner wall surface 321 is formed inside the tip fitting portion 326. That is, the outside portion of the pressure-contacting inner wall surface 321 in the joint portion 32 is the tip fitting portion 326. A stepped portion 322 is formed on the proximal end side of the pressure-contacting inner wall surface 321, and a head contact surface 323 is formed on the proximal end side of the stepped portion 322. The inner diameter of the head contact surface 323 is smaller than the inner diameter of the pressure-contacting inner wall surface 321. In the joint portion 32, the thickness of the tip fitting portion 326 in the radial direction is thinner than that of other portions.

  As shown in FIG. 1, the spark plug 1 is mounted in the plug hole 41 so that its tip end is exposed to the combustion chamber 42. That is, the center electrode 21 and the ground electrode 22 are exposed to the combustion chamber 42.

  The joint portion 32 of the ignition coil 3 is inserted and arranged in the plug hole 41. The distal end fitting portion 326 of the joint portion 32 is fitted to the forceps head 231 of the spark plug 2, and the conducting member 33 is in contact with the head terminal 25. The pressure-contacting inner wall surface 321 of the joint portion 32 is in pressure contact with the outer peripheral surface of the forceps head 231.

  Here, the corrugation 232 is formed on the forceps head 231, and the pressure-contacting inner wall surface 321 is disposed to face the forceps head 231 over a range including the entire formation area of the corrugation 232. The pressure-contacting inner wall surface 321 may not necessarily be in pressure contact with the concave surface of the corrugation 232. Even when this portion is not pressure-welded, if the portion not pressure-welded exists in the area of the pressure-welded portion between the pressure-welding inner wall surface 321 and the joint portion 32, as shown in FIG. The “pressure contact length Lp1” shown in FIG. 2 is defined.

  The distal end of the joint portion 32 is disposed slightly proximal to the distal end of the forceps head 231. That is, a slight gap C is formed between the distal end of the joint portion 32 and the proximal end of the housing 24. The gap C can have, for example, an axial distance of about 1 to 3 mm. In the present embodiment, the tip end position of the joint portion 32 coincides with the tip end position of the pressure-contacting inner wall surface 321.

  As shown in FIG. 2, the step portion 322 at the base end of the pressure-contacting inner wall surface 321 is in contact with the plug shoulder portion 26 in the axial direction. As described above, the plug shoulder 26 is formed on the proximal end surface of the insulator 23, that is, the proximal end surface of the insulator head 231. As shown in FIGS. 3 and 4, a terminal flange portion 251 which is a part of the head terminal 25 is disposed on the proximal end surface of the forceps head 231. The proximal end surface of the forceps head 231 on the outer peripheral side of the terminal collar 251 is the plug shoulder 26 in this embodiment.

  As shown in FIG. 2, the step portion 322 is in contact with at least a part of the inner peripheral side of the plug shoulder 26 from the axial proximal end side. A head contact surface 323 formed on the base end side of the stepped portion 322 is in contact with the outer peripheral surface of the head terminal 25. Here, the head contact surface 323 may not be particularly in pressure contact with the head terminal 25. In addition, a part of the tip end side of the head contact surface 323 is a relief part 323 a for releasing the terminal collar part 251. The head contact surface 323 is in contact with the outer peripheral surface of the head terminal 25.

Next, a method of assembling the ignition device 1 in the present embodiment will be described.
First, as shown in FIG. 8, the spark plug 2 is attached to the plug hole 41. The spark plug 2 is fixed to the engine head 40 by screwing the mounting screw portion 241 to the female screw portion 412 of the plug hole 41.

  Next, the ignition coil 3 shown in FIG. 5 is mounted on the engine head 40 as shown in FIG. At this time, the joint portion 32 is inserted into the plug hole 41, and the tip fitting portion 326 is axially pushed toward the spark plug 2. That is, while press-fitting the forceps head 231 of the spark plug 2 inside the tip fitting portion 326 of the joint portion 32, the joint portion 32 is pushed to the tip side. At this time, the joint portion 32 is elastically compressed in the axial direction by the insertion load according to the pressure-contacting force between the pressure-contacting inner wall surface 321 and the outer peripheral surface of the forceps head 231.

  That is, as shown in FIG. 5, the total length La0 of the joint portion 32 before attachment to the plug hole 41 is longer than the total length La1 (see FIG. 1) after attachment to the plug hole 41. The joint portion 32 of the full length La0 is compressed and deformed in the axial direction to be the full length La1. In the joint portion 32 before mounting in the plug hole 41, as shown in FIG. 5, the length La0 of the pressure-contacting inner wall surface 321 is also the length after mounting in the plug hole 41, ie, the pressure-contact length Lp1 (see FIG. 1) Longer than. The pressure-contacting inner wall surface 321 having the length Lp0 is axially deformed in a compressive manner to have a length Lp1.

  The pressing of the joint portion 32 is performed until the step portion 322 of the joint portion 32 abuts on the plug shoulder portion 26. During this time, the tip fitting portion 326 is elastically compressed in the axial direction according to the insertion load. That is, the formation region of the pressure-contacting inner wall surface 321 in the axial direction of the joint portion 32 is elastically compressed according to the insertion load.

  Further, from the state where the step portion 322 abuts on the plug shoulder portion 26, the ignition coil 3 is further pushed to the tip side. The joint portion 32 is pushed to the distal end side until the coil body portion 31 of the ignition coil 3 abuts on the seat surface at the proximal end portion of the plug hole 41. At this time, in the joint portion 32, a portion on the proximal side from the step portion 322 is elastically compressed.

  And coil main part 31 is fixed to engine head 40 by a fastening member etc. which omit illustration. Thus, the ignition device 1 having the ignition plug 2 and the ignition coil 3 mounted on the engine head 40 is obtained.

Next, the operation and effect of the present embodiment will be described.
In the igniter 1, the joint portion 32 of the ignition coil 3 has an annular step portion 322 facing the tip end side on the proximal end side of the pressure-contacting inner wall surface 321. The stepped portion 322 is in contact with the plug shoulder 26. Thereby, it is possible to suppress variation in axial length (that is, press-contact length Lp1) of a press-contact portion between the press-contact inner wall surface 321 of the joint portion 32 and the outer peripheral surface of the insulator 23.

  That is, when the joint portion 32 is pushed toward the spark plug 2 until the step portion 322 abuts on the plug shoulder portion 26, an insertion load corresponding to the pressure contact force between the pressure-contacting inner wall surface 321 and the outer peripheral surface of the insulator 23 Acts on the joint 32 in the axial direction. Along with this, the joint portion 32 made of an elastic member is compressively deformed in the axial direction.

  However, the step portion 322 and the plug shoulder portion 26 are in contact with each other, and in this contact portion, the joint portion 32 and the insulator 23 are positioned in the axial direction. Therefore, the variation in the amount of compressive deformation of the distal end fitting portion 326 which is the portion on the distal end side from the step portion 322 corresponds to the variation in the pressure contact length Lp1. Conversely, the variation in the amount of compressive deformation of the portion of the joint 32 closer to the proximal end than the step portion 322 does not affect the variation in the press-contact length Lp1.

  The lengths Lp0 and Lp1 of the distal end fitting portion 326 can be made significantly shorter than the total lengths La0 and La1 of the joint portion 32. Therefore, the amount of compressive deformation (i.e., Lp0-Lp1) of the portion on the tip side from the step portion 322 in the joint portion 32 can also be significantly reduced, and thus, the variation in the pressure contact length Lp1 is significantly suppressed. Can.

  Moreover, the number of parts which comprise the joint part 32 can be reduced by setting it as the above. Therefore, cost reduction of the ignition coil 3 can be achieved, and as a result, the low cost ignition device 1 can be obtained.

  The joint portion 32 also has a head contact surface 323. This facilitates increasing the radial width of the plug shoulder 26. Therefore, the contact width between the step 322 and the plug shoulder 26 can be increased. As a result, the stepped portion 322 can be more easily brought into contact with the plug shoulder portion 26.

  In the present embodiment, the plug shoulder 26 is formed at the proximal end of the insulator 23. As a result, the portion where the step portion 322 is in pressure contact becomes a part of the insulator 23, so the insulation between the head terminal 25 and the housing 24 can be further improved.

  As described above, according to the present embodiment, it is possible to provide a low-cost igniter that is easy to secure the insulation sealing property at the pressure contact portion between the joint portion and the ignition plug.

Second Embodiment
The present embodiment is a form of the ignition device 1 in which the plug shoulder 26 is a portion formed on the head terminal 25 as shown in FIG.
In particular, in the present embodiment, the proximal end surface of the terminal collar portion 251 of the head terminal 25 is a plug shoulder 26. That is, as described above, the head terminal 25 of the spark plug 2 is formed with the terminal collar portion 251 protruding to the outer peripheral side. The terminal flange portion 251 has its front end surface in contact with the base end surface of the insulator 23. And the level | step-difference part 322 of the joint part 32 is contact | abutted to the base end surface of the terminal collar part 251. As shown in FIG. That is, the base end face of the terminal collar 251 is the plug shoulder 26 that contacts the step 322.

  The other configuration is the same as that of the first embodiment. In addition, the code | symbol same as the code | symbol used in already-appeared embodiment among the code | symbol used in Embodiment 2 or subsequent ones represents the component similar to the thing in already-appeared embodiment, etc., unless shown.

In the present embodiment, the plug shoulder 26 which receives the load from the abutting step 322 is a part of the metal head terminal 25. Therefore, when assembling the joint portion 32, the risk of damaging the spark plug 2 can be reduced. That is, no load is applied to the insulator 23 directly from the step portion 322. This makes it easy to suppress concerns such as chipping at the corners and the like of the ceramic insulator 23. .
In addition, it has the same operation effect as Embodiment 1.

(Embodiment 3)
This embodiment is a form of the ignition device 1 using the ignition plug 2 in which the insulator 23 is not provided with a corrugation as shown in FIG.
In the ignition device 1 of the first embodiment, as shown in FIGS. 2 and 3, the spark plug 1 in which the corrugation 232 is provided on the insulator 23 is used, but in the present embodiment, the corrugation is provided on the insulator 23 Absent. And as shown in FIG. 10, the outer peripheral surface of the forceps head 231 is an outer peripheral surface of a cylinder over substantially the entire length in the axial direction. However, the outer peripheral surface of the base end portion of the insulator 23 is a tapered portion 233 whose diameter decreases toward the base end side.

A plug shoulder 26 is formed on the base end face of the insulator 23. The stepped portion 322 of the joint portion 32 is in contact with the plug shoulder portion 26. Further, a recess 252 is formed on the base end face of the head terminal 25. The tip of the conducting member 33 is disposed in the recess 252.
The other configuration is the same as that of the first embodiment.
Also in this embodiment, the same effects as those of the first embodiment are obtained.

(Embodiment 4)
In the ignition device 1 of the present embodiment, as shown in FIG. 11, in the internal combustion engine, the joint portion 32 has the proximal end portion 32B and the distal end portion 32T in which the axial directions are mutually inclined. It is attached.
That is, in the present embodiment, the axial direction of the plug hole 41 is bent halfway. Then, along the bent plug hole 41, the joint portion 32 has a shape in which it is bent halfway. The joint portion 32 disposed in the plug hole 41 has a proximal end portion 32B and a distal end portion 32T whose axial directions are mutually inclined.

  The plug hole 41 has a bent portion 411, a proximal end side hole portion 41B on the proximal end side of the bent portion, and a distal end side hole portion 41T on the distal end side of the bent portion. The spark plug 2 is disposed in the front end side hole 41T. The joint portion 32 is disposed across the tip end side hole portion 41T and the base end side hole portion 41B in the plug hole 41. Therefore, the joint portion 32 is bent along the bent plug hole 41.

The joint portion 32 is not bent in the state before being attached to the plug hole 41, and can be bent along the plug hole 41 at the time of attachment. However, the joint portion 32 can also be bent in the state before being attached to the plug hole 41.
The other configuration is the same as that of the first embodiment.

As described above, the joint portion 32 is entirely constituted by the elastic member. Therefore, even when the plug hole 41 is bent, the joint portion 32 can be bent and fitted in a shape along the plug hole 41. And the problem can be solved effectively by taking the composition which made the level difference part 322 contact the plug shoulder 26 to the above-mentioned subject which arises when joint part 32 is constituted by an elastic member. . That is, even in the case where the joint portion 32 is bent so that the axial direction of the base end side portion 32B and the axial direction of the distal end side portion 32T are mutually inclined, the joint portion 32 and the spark plug 2 are effectively effective. It is easy to ensure the insulation sealability at the pressure contact portion with the
In addition, it has the same operation effect as Embodiment 1.

(Comparison form)
In the present comparative embodiment, as shown in FIG. 12, the step portion 322 of the joint portion 32 of the ignition coil 93 is not in contact with the plug shoulder portion 26 and is in the form of the ignition device 9.

  In this case, when the joint 32 is pushed toward the spark plug 2, the step 322 does not abut the plug shoulder 26. Therefore, the variation of the total amount of compressive deformation δ9 of the joint portion 32 becomes the variation of the press contact length La1 as it is.

  And the insertion load of the joint part 32 will act on the whole joint part 32 substantially equally. That is, the entire joint portion 32 is compressively deformed by the insertion load caused by the frictional force between the pressure-contacting inner wall surface 321 of the joint portion 32 and the outer peripheral surface of the insulator 23. Then, the variation in the amount of compressive deformation of the joint portion 32 tends to be large according to the variation in the insertion load. That is, the variation in the axial length (that is, the press-contact length Lp1) of the press-contact portion between the press-contacting inner wall surface 321 and the outer peripheral surface of the insulator 23 tends to be large.

Generally, the amount of compressive deformation δ in the axial direction of a homogeneous and accurate cylindrical elastic body is calculated by the following equation (1).
δ = FL / (ES) (1)
Here, F is an axial compression force, L is an axial length of the cylinder, E is an elastic modulus of the elastic body, and S is a cross-sectional area of a cross section orthogonal to the axial direction of the elastic body.

  As described above, the compression deformation amount δ9 of the joint portion 32 is approximately calculated by applying each parameter to the joint portion 32 when assembled to the spark plug 2 as the above-described elastic body. In this case, in the above equation (1), the insertion load is substituted for F, and the total axial length La0 (see FIG. 13) of the joint portion 32 before compression is substituted for L.

  Then, in the comparative embodiment, the amount of compressive deformation δ9 of the joint portion 32 due to the insertion load is δ9 ≒ FLa0 / (ES), and is approximately proportional to the overall axial length La0 of the joint portion 32. Then, the variation of the amount of compressive deformation δ9 also becomes the variation of the press contact length La1 as it is.

  On the other hand, in the first embodiment, the variation in the amount of compressive deformation δ1 of the distal end fitting portion 326 due to the insertion load is the variation in the press contact length La1. Therefore, in the above equation (1), the axial length Lp0 of the distal end fitting portion 326 is substituted into L. This is because, as described above, the portion on the proximal side of the step portion 322 in the joint portion 32 has a fixed size after compressive deformation. Then, the amount of compressive deformation δ1 of the distal end fitting portion 326 in the first embodiment is δ1 ≒ FL p0 / (ES).

  As described above, Lp0 can be made much smaller than the total length La0 of the joint portion 32. Therefore, the amount of compressive deformation δ1 in the first embodiment can be made extremely smaller than the amount of compressive deformation δ9 in the comparative embodiment. Then, the variation in the amount of compressive deformation δ1 can also be largely reduced, and the variation in the press-contact length Lp1 can be suppressed.

  The present invention is not limited to the above embodiments, and can be applied to various embodiments without departing from the scope of the invention. For example, the shape of the ignition coil is not limited to that shown in the embodiment, and the connection position between the coil body and the joint may be changed variously.

Reference Signs List 1 ignition device 2 ignition plug 21 center electrode 23 insulator 24 housing 3 ignition coil 31 coil body portion 32 joint portion 321 pressure welding inner wall surface 322 stepped portion

Claims (5)

An ignition device (1) for an internal combustion engine, comprising: an ignition plug (2) mounted on the internal combustion engine; and an ignition coil (3) for supplying a high voltage to the ignition plug,
The spark plug is held inside a center electrode (21), an insulator (23) holding the center electrode inside, a housing (24) holding the insulator inside, and the insulator And a head terminal (25) projecting to the base end side of the insulator.
The ignition coil includes a coil main body (31) including a primary coil and a secondary coil, and a conductive member for electrically connecting the high voltage output terminal (311) of the coil main body and the head terminal of the spark plug And 33) a joint portion (32) provided on the inside,
The joint portion is a cylindrical body made of an elastic member and has a pressure-contacting inner wall surface (321) which is in pressure contact with the outer peripheral surface of the insulator of the ignition plug at the tip end side, and An annular step (322) facing the tip side;
The spark plug has an annular plug shoulder (26) facing the proximal end on at least one of the insulator and the head terminal;
The igniter for an internal combustion engine, wherein the stepped portion abuts on the plug shoulder portion, and a gap (C) is formed between a tip end of the joint portion and a base end of the housing.   The ignition device for an internal combustion engine according to claim 1, wherein the joint portion has a head contact surface (323) in contact with the side surface of the head terminal on the base end side of the stepped portion.   The joint according to claim 1 or 2, wherein the joint is attached to the internal combustion engine in a state having a proximal end portion (32B) and a distal end portion (32T) in which the axial directions are mutually inclined. Ignition device for internal combustion engines.   The ignition device for an internal combustion engine according to any one of claims 1 to 3, wherein the plug shoulder is formed at a proximal end of the insulator.   The igniter for an internal combustion engine according to any one of claims 1 to 4, wherein the plug shoulder is formed on the head terminal.

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