Ignition coil

Abstract

To provide an ignition coil having an improved assemblability and abrasion resistance while maintaining insertability of a joint part and suppressing shaft deviation, when installed to a bent-shaped plug hole.SOLUTION: An ignition coil includes a joint part made of a cylindrical elastic body which is bendable and deformable, with a tip end side attached to an ignition plug arranged at a plug hole having a bent part and with a base end side attached to a coil body part arranged at a base end inlet part having a large inner diameter than the bent part. The joint part has a plurality of first ribs extending along an axial line L provided on an outer peripheral surface of a body cylindrical part facing the bent part, and has a plurality of second ribs extending along the axial line provided on an outer peripheral surface of a base end cylindrical part positioned on the base end side. When viewed in a direction along the axial line, a maximum diameter of the first rib diameter represented by a diameter of a virtual circumscription circle that circumscribes with tip ends of the plurality of first ribs of the body cylindrical part is smaller than a maximum diameter of the second rib diameter represented by a diameter of a virtual circumscription circle connecting tip ends of the plurality of second ribs of the base end cylindrical part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ignition coil used in an ignition device of an internal combustion engine. [Background technology]

[0002] An ignition device installed in an internal combustion engine includes an ignition coil for applying a high voltage to an ignition plug facing a combustion chamber. In recent years, high-efficiency internal combustion engines have been required to be compact in order to improve fuel efficiency, and the cylinder head and other components in which the ignition device is installed are also becoming more complex in internal structure and more restricted in terms of installation locations. For this reason, studies are being conducted to make the plug hole in which the ignition plug is located a curved shape in order to make the installation structure of the ignition coil more compact.

[0003] In this case, it is required that the joint part of the ignition coil fitted to the spark plug is made of, for example, a one-piece molded product made of freely bendable rubber or the like, and bent into the plug hole. As an example, Patent Document 1 discloses an ignition coil device for an internal combustion engine, which includes a cylindrical plug boot serving as the joint part, and in which a thin-walled part facing the bent part of the plug hole is formed on the plug boot, which has insulating properties and flexibility. This allows the thin-walled part to be easily bent when the plug boot is inserted into the spark plug in a plug hole of a constant diameter that is bent in the middle. Furthermore, by providing a guard part protruding in the radial direction at the tip of the plug boot, the axial centers are easily aligned, improving the ease of insertion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4267042 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when installing an ignition device in a bent plug hole, it is necessary to insert a tool into the plug hole. Therefore, in reality, it is difficult to make the plug hole diameter constant as in Patent Document 1, and the inner diameter of the plug hole on the inlet side of the bent part is larger than the ignition plug side. In that case, if the entire joint part is an elastic body, local compression or deflection is likely to occur due to the compressive force when the plug is inserted. Therefore, it is not easy to install the joint part while simultaneously suppressing axial misalignment at the bent part of the plug hole and its tip side and base end side. In addition, in a shape having a thin part as in Patent Document 1, for example, if the thin part and the bent part come into contact due to axial misalignment, wear may occur due to vibration when the engine is installed, and the withstand voltage may decrease.

[0006] The present invention has been made in consideration of such problems, and aims to provide an ignition coil that can suppress axial misalignment while maintaining the insertability of the joint part when the ignition coil is installed into a plug hole with a curved shape, thereby improving assembly ease and wear resistance. [Means for solving the problem]

[0007] One aspect of the present invention is An ignition coil (1) that supplies high voltage to an ignition plug (P) disposed in a plug hole (H) having a bent portion (H1), a coil body (11) disposed at a base end inlet portion (H2) of the plug hole having an inner diameter larger than that of the bent portion; a joint portion (2) made of a bendable, cylindrical elastic body, the base end of which is attached to the coil body portion and the tip end of which is attached to the ignition plug, In the joint portion, a plurality of first ribs (31) extending along the axis (L) are provided on an outer peripheral surface of the main body tubular portion (21) including a portion facing the bent portion, and a plurality of second ribs (32) extending along the axis are provided on an outer peripheral surface of a base end tubular portion (22) located on the base end side relative to the main body tubular portion, When viewed from a direction along the axis, the maximum diameter d1 of a first rib diameter represented by the diameter of an imaginary circumscribing circle (C1) that has its center (c1) at the axis of the main body cylindrical portion and circumscribing the tips of the first ribs, and the maximum diameter d2 of a second rib diameter represented by the diameter of an imaginary circumscribing circle (C2) that has its center (c2) at the axis of the base end cylindrical portion and circumscribing the tips of the second ribs have a relationship of d2>d1 in this ignition coil. Effect of the Invention

[0008] According to the ignition coil having the above-mentioned configuration, the first rib provided on the main body tube portion of the joint portion and the second rib provided on the base end tube portion increase the rigidity of the joint portion. In addition, the rib shape extending along the axis acts as a guide to improve ease of insertion into the plug hole. Therefore, the main body tube portion can bend and deform while suppressing axial misalignment along the shape of the curved plug hole, and the first rib is coaxially arranged at a location facing the bent portion. In addition, the base end tube portion provided with the second rib with a larger maximum diameter is arranged on the base end inlet side, which has a larger inner diameter than the bent portion, to suppress axial misalignment and regulate displacement due to vibration, etc., thereby suppressing deterioration of characteristics due to wear.

[0009] As described above, according to the above aspect, when the ignition coil is installed into a bent plug hole, it is possible to provide an ignition coil that can suppress axial misalignment while maintaining the insertability of the joint portion, thereby improving assembly ease and wear resistance. In addition, the symbols in parentheses described in the claims and the means for solving the problems indicate a correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a partially sectional front view of the ignition device with an ignition coil assembled thereto according to the first embodiment. [Diagram 2] 3 is a partially sectional front view of the ignition device showing an assembly process of the ignition coil in the first embodiment. FIG. [Diagram 3]FIG. 2 is a front view of the ignition coil according to the first embodiment. [Figure 4] 4 is a cross-sectional view of the ignition coil according to the first embodiment, taken along line II and line II-II in FIG. 3. [Diagram 5] 3A and 3B are cross-sectional views of the ignition coil according to the first embodiment, taken along lines III-III and IV-IV in FIG. [Figure 6] 2 is a vertical cross-sectional view of a main part of the ignition coil according to the first embodiment. FIG. [Figure 7] FIG. 11 is a diagram for explaining an assembly process of the ignition coil in the comparative embodiment 1. [Figure 8] FIG. 11 is a diagram for explaining an assembly process of the ignition coil in the comparative embodiment 1. [Figure 9] FIG. 11 is a cross-sectional view of a main part showing an assembled state of an ignition coil in a comparative embodiment 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Embodiment 1) An embodiment of an ignition coil will be described with reference to Figs. 1, an ignition coil 1 is electrically connected to an ignition plug P provided in an internal combustion engine such as a vehicle engine, and is used to supply high voltage. The ignition plug P is disposed in a plug hole H having a bent portion H1, and the ignition coil 1 includes a coil main body portion 11 disposed in a base end inlet portion H2 of the plug hole H, and a joint portion 2.

[0012] A spark plug hole H provided in a cylinder head or the like has a bent shape with a bent portion H1 in the middle. A base end inlet portion H2 of the spark plug hole H has an inner diameter larger than that of the bent portion H1. The joint portion 2 is made of a cylindrical elastic body that can be bent and deformed, and is attached at its base end to the coil main body portion 11 inside the spark plug hole H and at its tip end to the ignition plug P.

[0013] 2, the base end side refers to the entrance side when the joint part 2 is inserted and attached to the ignition plug P in the extending direction of the bent plug hole H, and is the side on which the coil main body part 11 is arranged. The opposite side is called the tip side, and is the side on which the ignition plug P is arranged. Note that in the bent plug hole H, the axis L2 at the base end side of the bent part H1 does not coincide with the axis L1 at the tip side, and therefore the extending direction of the plug hole H, which is the direction along the axes L1, L2, also changes.

[0014] In the assembled state shown in Fig. 1, the joint part 2 has a main body tubular part 21 including a portion facing the bent part H1, and a base end tubular part 22 located on the base end side of the main body tubular part 21. As shown in Fig. 3, a plurality of first ribs 31 extending along the axis L are provided on the outer circumferential surface of the main body tubular part 21. Furthermore, a plurality of second ribs 32 extending along the axis L are provided on the outer circumferential surface of the base end tubular part 22. The first ribs 31 and the second ribs 32 protrude in a direction perpendicular to the axis L, i.e., outward in the radial direction X.

[0015] 4, when viewed from the direction along the axis L, the first rib diameter in the main body tubular portion 21 is represented by the diameter of a virtual circumscribing circle C1 that has the axis of the main body tubular portion 21 as its center c1 and circumscribing the tips of the first ribs 31, and the second rib diameter in the base end tubular portion 22 is represented by the diameter of a virtual circumscribing circle C2 that has the axis of the base end tubular portion 22 as its center c2 and circumscribing the tips of the second ribs 32. In this case, the maximum diameter d1 of the first rib diameter and the maximum diameter d2 of the second rib diameter have a relationship of d2>d1. In other words, the joint portion 2 is configured so that the maximum outer diameter in the base end tubular portion 22 is larger than the maximum outer diameter in the main body tubular portion 21.

[0016] With this configuration, when the joint portion 2 of the ignition coil 1 is inserted into the bent plug hole H, the first rib 31 and the second rib 32 act as guides, improving ease of insertion. In addition, the first rib 31 and the second rib 32 increase rigidity, allowing assembly while suppressing axial misalignment. The first rib 31 is disposed to face the bent portion H1, and the second rib 32, which has a larger maximum outer diameter than the first rib 31, is disposed on the inlet side, which has a larger inner diameter than the bent portion H1.

[0017] Specifically, the multiple first ribs 31 can be continuously arranged on the tip side and base side of the portion facing the bent portion H1 of the plug hole H. In this case, when the main body tubular portion 21 including the first ribs 31 is bent and deformed in accordance with the bending shape of the plug hole H, the first ribs 31 are arranged to straddle the bent portion H1, thereby enhancing the effect of suppressing displacement due to axial misalignment and vibration during insertion.

[0018] Furthermore, the second ribs 32 can be disposed continuously from the base end side to the tip end side, facing the end portion on the base end side including the base end inlet portion H2. This increases the axial rigidity on the base end side of the joint portion 2, and enhances the effect of suppressing displacement due to axial misalignment and vibration during insertion. Also, when assembling the coil main body 11 after the joint portion 2 is inserted, axial misalignment is suppressed, improving the ease of assembly. A more specific shape of the joint portion 2 will be described later.

[0019] Next, the structure for assembling the ignition coil 1 into the plug hole H will be described in detail. Fig. 2 shows a state before the joint portion 2 is bent during the assembling of the ignition coil 1, and Fig. 1 shows a state after the ignition coil 1 is assembled. In Figs. 1 and 2, the plug hole H in which the joint portion 2 of the ignition coil 1 is accommodated has a tip half portion H21 located on the tip side of the bent portion H1 and a base half portion H22 located on the base side of the bent portion H1. The tip half portion H21 is a circular hole of a substantially constant diameter that reaches the mounting portion of the ignition plug P, and the base half portion H22 has a tapered hole shape that gradually expands in diameter from the bent portion H1 toward the base side. The bent portion H1 is provided at an intermediate position in the extension direction of the plug hole H, and may be located on the tip side or the base side of the position shown in the figure.

[0020] The spark plug hole H is provided at a predetermined position of the cylinder head E1 for each cylinder of the engine, and the axis L1 of the tip half H21 is inclined with respect to the axis L2 of the base half H22. The axis L2 extends in a direction perpendicular to the first surface E11 of the cylinder head E1 where the base half H22 opens. The bending angle of the bent portion H1 is represented by the inclination angle θ of the axis L1 with respect to the axis L2 (see FIG. 1), which is the same as the taper angle of the base half H22 here. That is, in the left half of the cross section shown in the figure, the inner peripheral surface of the tip half H21 continues to the inner peripheral surface of the base half H22 without bending, and the bent portion H1 is formed in the opposite right half.

[0021] At this time, a first inner diameter D1 at the tip half H21 of the spark plug hole H and a second inner diameter D2 at the base end inlet H2 opening on the base end side of the base end half H22 have a relationship of D2>D1 (see FIG. 2). Therefore, the joint portion 2 is provided with a main body tubular portion 21 arranged across the bent portion H1 and a base end tubular portion 22 on the base end side thereof, and a first rib 31 and a second rib 32 are provided on each of them. The main body tubular portion 21 is arranged opposite a part of the tip half H21 and a part of the base end half H22 that are continuous with each other across the bent portion H1, and the base end tubular portion 22 is arranged opposite a part of the base end half H22 that includes the base end inlet H2.

[0022] In Fig. 1, the spark plug P is disposed so as to close a tip hole H3 continuing from the tip half H21. The tip hole H3 is a circular hole of a substantially constant diameter smaller than the tip half H21, and the tip of the spark plug P is disposed so as to face a combustion chamber (not shown). The spark plug P has a head terminal P2 (see Fig. 2) protruding from the base end side of the insulator P1, a housing P3 that holds the insulator P1 inside, a center electrode P4 protruding from the insulator P2 to the tip side, and a ground electrode P5 that faces the center electrode P4. The spark plug P has a mounting screw portion formed on the outer circumferential surface of the housing P3, and a hexagonal portion for engaging a tool formed on the base end side thereof so as to be fastened and fixed in the plug hole H.

[0023] 3 to 5, the joint part 2 is a cylindrical integral molding made of an elastic material having insulating properties such as rubber, and is configured to be freely elastically deformed according to the shape of the plug hole H and be held in a bent state. The joint part 2 has a straight-shaped tip tubular part 23 at the tip side of the main body tubular part 21, which is fitted to the head side of the insulator P1 of the ignition plug P, and has a straight-shaped intermediate tubular part 24 between the main body tubular part 21 and the base end tubular part 22. The tip tubular part 23 and the intermediate tubular part 24 have a flat cylindrical surface without ribs on the outer circumferential surface, and have a shape with a substantially constant outer diameter. The thickness is thinner and the rigidity is lower than that of the part having ribs, so that they are more likely to be elastically deformed. The outer diameter d3 of the tip tubular part 23 and the outer diameter d4 of the intermediate tubular part 24 have a relationship of d4>d3 (see FIG. 5).

[0024] As shown in FIG. 2, a conductive member 4 that electrically connects the coil body 11 and the spark plug P is housed in a cylindrical hole 20 that passes through the joint portion 2 in the axial direction. The conductive member 4 is formed of a spring that elastically deforms in the axial direction. The tip of the conductive member 4 is located inside the cylindrical tip portion 23, and the tip portion 23 is inserted from the base end side of the insulator P1 so that the conductive member 4 abuts against the head terminal P2. The axial length of the tip portion 23 can be appropriately set so as to obtain a desired fitting dimension, taking into consideration the amount of compressive deformation when inserted into the head of the ignition plug P, etc.

[0025] As shown in Fig. 4, the main body tubular portion 21 of the joint portion 2 has a plurality of first ribs 31 in the shape of a convex stripe that protrude outward in the radial direction X from a plurality of points on the outer circumferential surface. Here, the plurality of first ribs 31 are provided at eight or so points on the outer circumferential surface, each of which has a roughly trapezoidal cross-sectional shape, protrudes radially, and has an overall gear-like outer shape. These plurality of first ribs 31 extend parallel to each other along the axis L of the joint portion 2, and are formed over the entire length from the base end side to the tip end side of the main body tubular portion 21, that is, from the tip position of the intermediate tubular portion 24 to the base end position of the tip tubular portion 23 (see Fig. 3).

[0026] As shown in FIG. 3, the first ribs 31 have a tapered portion 311 at the tip end that slopes downward toward the tip. At this time, the first rib diameter, which is the diameter of the imaginary circumscribing circle C1 shown in FIG. 4, at the tip end of the main body tube portion 21 gradually decreases toward the tip side. In the main body tube portion 21 except for the tip end, the first rib diameter is approximately constant and is a maximum diameter d1. The tip of the tapered portion 311 is connected to the tip tube portion 23. In this case, the minimum diameter d11 of the first rib diameter is equal to or larger than the outer diameter d3 of the tip tube portion 23 shown in FIG. 5, and the relationship is d1>d11≧d3. At the tip end where the tapered portion 311 is formed, the first rib diameter increases toward the base end and approaches the maximum diameter d1.

[0027] In this manner, the first ribs 31 of the main body tube portion 21 have the tapered portions 311 at the ends on the tip side, so that the entire body has a tapered shape that narrows toward the tip, which can further improve the ease of insertion.

[0028] The main body tube portion 21 is connected to the intermediate tube portion 24 having a substantially constant diameter at the base end side while the first rib diameter is kept at a substantially constant maximum diameter d1. In this case, the outer diameter d4 of the intermediate tube portion 24 shown in FIG. 5 is equal to or larger than the maximum diameter d1 of the first rib diameter, and is larger than the outer diameter d3 of the tip tube portion 23 (i.e., d4≧d1>d11≧d3). In order to achieve such a relationship, the main body tube portion 21 is formed such that the portions between the first ribs 31 adjacent to each other in the circumferential direction, i.e., the portions where the first ribs 31 are not formed, gradually become thicker toward the base end side and protrude radially outward. As a result, at the end portion on the intermediate tube portion 24 side, the rigidity becomes higher toward the base end side, and the protruding height of the first rib 31 becomes relatively lower.

[0029] The first ribs 31 are preferably arranged evenly on the outer circumferential surface of the main body tubular portion 21 so as to be spaced at approximately equal intervals in the circumferential direction. The protruding ends of the first ribs 31 face the inner circumferential surface of the plug hole H arranged outward in the radial direction X with a gap therebetween. The larger the gap, the better the insertability, but there is a risk of axial misalignment. Therefore, it is preferable that the inner circumferential surface and the first ribs 31 are arranged close to each other at the periphery of the bent portion H1 and its tip side with a small gap within a range that does not impair insertability. In this case, the first inner diameter D1 at the tip half portion H21 (see FIG. 2) and the maximum diameter d1 of the first rib diameter (see FIG. 4) have a relationship of D1>d1.

[0030] The axial length of the main body tubular portion 21 on which the first rib 31 is arranged is not necessarily limited, and can be appropriately set according to the position of the bent portion H1 in the plug hole H. Specifically, taking into consideration the length of the tip tubular portion 23 attached to the ignition plug P, the length of the base end tubular portion 22, etc., the base end position of the first rib 31 can be set to a position in the range of 30% to 80% from the tip end position of the joint portion 2 (i.e., the tip end of the tip tubular portion 23). It is preferable to set the axial length of the first rib 31 to be longer in the above range so that the base end position of the first rib 31 is closer to the base end side than the bent portion H1, in order to improve the rigidity of the joint portion 2. In addition, in general, a seal portion 25 is integrally provided on the base end side of the joint portion 2, and in that case, the length of the joint portion 2 (hereinafter referred to as the joint length as appropriate) refers to the length including the seal portion 25 (i.e., the axial length from the tip position of the tip tubular portion 23 to the base end position of the seal portion 25). The seal portion 25 will be described later.

[0031] The number of first ribs 31 is not necessarily limited, but may be formed at, for example, three or more locations on the outer peripheral surface from the viewpoint of improving insertability as a guide when inserting into the plug hole H. Preferably, the number of first ribs can be appropriately set within the range of four to ten locations on the outer peripheral surface so as to obtain the desired insertability and rigidity depending on the outer diameter of the base end side or tip end side of the main body tubular portion 21, the inner diameter of the opposing plug hole H, etc. The width and protruding height of the first ribs 31 can also be appropriately set in the same way.

[0032] 6, at the base end side of the plug hole H, the joint part 2 is fitted into the high voltage tower part 12 protruding from the coil main body part 11. The high voltage tower part 12 holds the high voltage terminal 13 and the resistor 131 inside, and the base end tubular part 22 of the joint part 2 is extrapolated from the tip side of the high voltage tower part 12, so that the high voltage tower part 12 is inserted into the tubular hole 20 and the base end of the conductive member 4 abuts against the resistor 131. This electrically connects the high voltage terminal 13 and the conductive member 4 via the resistor 131.

[0033] The coil body 11 includes an insulating coil case 14 disposed on the base end side of the high voltage tower 12, and contains a primary coil 151 and a secondary coil 152 arranged concentrically, a central core 161 disposed inside thereof, and an outer circumferential core 162 disposed on the outer circumferential side thereof. This allows the high voltage generated in the secondary coil 152 to be output from the high voltage terminal 13, relayed by the conductive member 4, and applied to the spark plug P.

[0034] 4, the base end tubular portion 22 of the joint part 2 has a plurality of second ribs 32 arranged thereon, protruding outward in the radial direction X from a plurality of positions on the outer circumferential surface. Here, the plurality of second ribs 32 are provided at eight or so positions on the outer circumferential surface, each of which has a roughly trapezoidal cross-sectional shape, protruding radially, and has an overall gear-like outer shape. These plurality of second ribs 32 extend parallel to one another along the axis L of the joint part 2, and are formed over the entire length from the base end side of the base end tubular portion 22 to the tip side, i.e., the base end position of the intermediate tubular portion 24.

[0035] As shown in FIG. 3, the second ribs 32 have a tapered portion 321 at the tip end that slopes downward toward the tip end. At this time, the tip end of the base end tubular portion 22 has a second rib diameter, which is the diameter of the imaginary circumscribing circle C2 described above, that gradually decreases toward the tip end. The second ribs 32 also have a gentle slope in the base end tubular portion 22 except for the tip end, and the second rib diameter becomes a maximum diameter d2 at the base end end of the base end tubular portion 22. Specifically, it is desirable that the base end tubular portion 22 has a slope equivalent to the taper angle of the base end half portion H22 so that the base end tubular portion 22 contacts the inner peripheral surface of the base end side of the plug hole H with a surface. The slope of the tapered portion 321 is larger than that of the base end tubular portion 22 on the base end side, and the tip of the tapered portion 321 connects to the intermediate tubular portion 24. In this case, the minimum diameter d21 of the second rib diameter is equal to or larger than the outer diameter d4 of the intermediate tubular portion 24 shown in Fig. 5, and the relationship is d2>d21≧d4. At the tip end where the tapered portion 321 is formed, the second rib diameter becomes larger toward the base end and approaches the maximum diameter d2.

[0036] In this manner, the second ribs 32 have the tapered portion 321 on the tip side, so that the entire portion becomes tapered, thereby making it possible to further improve the ease of insertion.

[0037] The second ribs 32 are preferably arranged evenly on the outer peripheral surface of the base end tubular portion 22 so as to be spaced at approximately equal intervals in the circumferential direction. The protruding ends of the second ribs 32 face the inner peripheral surface of the plug hole H arranged outward in the radial direction X with a gap therebetween. The larger the gap, the better the insertability, but there is a risk of axial misalignment. Therefore, it is preferable that the inner peripheral surface on the inlet side of the base end half portion H22 and the second rib 32 are arranged close to each other with a small gap within a range that does not impair insertability. In this case, the second inner diameter D2 at the base end inlet portion H2 and the maximum diameter d2 of the second rib diameter have a relationship of D2>d2 (>D1>d4≧d1>d11≧d3).

[0038] The axial length of the base end tubular portion 22 on which the second rib 32 is disposed is not necessarily limited, but is desirably set according to the joint length including the seal portion 25 so that the axial length of the first rib 31 straddling the bent portion H1 is longer than the axial length of the base end tubular portion 22. Specifically, the tip position of the second rib 32 inserted into the base end inlet portion H2 of the spark plug hole H can be set, for example, to a position in the range of 1% to 20% from the base end position of the joint portion 2 (i.e., the base end of the seal portion 25) and can be set according to the arrangement of the first rib 31 on the tip side so that the effect of axial alignment on the inlet side of the base end half portion H22 in the spark plug hole H can be obtained. Preferably, the tip position of the second rib 32 is set to a position 5% or more from the base end of the joint portion 2 and is desirably set appropriately within a range in which the length of the first rib 31 is secured. This ensures the length of surface contact with the inner circumferential surface of the spark plug hole H near the base end inlet portion H2, thereby enhancing the function as a rib.

[0039] The number of second ribs 32 is not necessarily limited, but may be formed at, for example, three or more locations on the outer peripheral surface from the viewpoint of improving ease of insertion as a guide when inserting into the plug hole H. Preferably, the number of second ribs can be appropriately set within a range of four to ten locations on the outer peripheral surface so as to obtain the desired ease of insertion and rigidity depending on the shape of the base end half portion H2 in which the base end tubular portion 22 is arranged, the inner diameter of the opposing base end inlet portion H2, etc. The width and protruding height of the second ribs 32 can also be appropriately set in the same manner.

[0040] In FIG. 1 and FIG. 2, a seal portion 25 is disposed between the base end inlet portion H2 and the coil main body portion 11 on the base end side of the spark plug hole H. The seal portion 25 is made of rubber and is integrally provided on the base end side of the base end tubular portion 22 of the joint portion 2, forming a part of the joint portion 2. In this case, the seal portion 25 can be formed so as to protrude outward in the radial direction X from the base end of the base end tubular portion 22 in a flange shape and cover the base end inlet portion H2 of the spark plug hole H. The base end inlet portion H2 has a shape that protrudes in an annular shape on the first surface E11 of the cylinder head E1 where the base end of the spark plug hole H opens, and functions as a locking portion that locks the seal portion 25. The seal portion 25 can seal the base end opening of the spark plug hole H by locking the protruding end, which is bent in an L-shaped cross section, with the base end inlet portion H2.

[0041] The coil main body 11 is provided with a mounting flange 141 that protrudes from the side of the coil case 14. The mounting flange 141 is provided with a through hole 142 for inserting a bolt, and a support base E12 having a screw hole E13 formed therein protrudes from a first surface E11 of the opposing cylinder head E1. With this configuration, the mounting flange 141 is disposed on the support base E12, and by fastening a bolt (not shown), the coil main body 11 can be fixed to the base end side of the spark plug hole H via the seal portion 25, and the spark plug hole H can be air-tightly sealed by the seal portion 25.

[0042] The ignition coil 1 is assembled into the plug hole H, for example, as follows. First, as shown in FIG. 2, the joint part 2, the base end of which is fitted into the coil main body part 11, is inserted from the base end inlet part H2 of the plug hole H toward the tip side of the plug hole H in which the ignition plug P is attached. The joint part 2 is inserted coaxially with the axis L1 of the tip half part H21 of the plug hole H, using the first rib 31 provided on the main body tube part 21 as a guide. In addition, the tapered part 311 is provided at the tip part of the first rib 31, so that the first rib 31 is prevented from being caught. In this case, even if the gap between the maximum diameter d1 of the first rib diameter and the inner diameter D1 of the tip half part H21 is reduced, the insertion force is not increased, and the rigidity is improved, so that the axis alignment is facilitated. As a result, the tip tube part 23 of the joint part 2 can be coaxially inserted around the ignition plug P.

[0043] Next, the main body tubular portion 21 of the joint portion 2 is bent at the bent portion H1 of the plug hole H so as to follow the bent shape, and is further inserted into the tip side of the plug hole H. As a result, the tip side of the joint portion 2 can be bent and deformed so that the axis L of the first rib 31 is coaxial with the axis L2 of the base end half portion H22 on the base end side of the portion facing the bent portion H1 while keeping the tip end tubular portion 23 coaxial with the ignition plug P. Then, on the base end side of the plug hole H, the base end tubular portion 22 of the joint portion 2 is attached to the inside of the base end inlet portion H2 using the second rib 32 as a guide. In this case as well, the tapered portion 321 provided at the tip portion of the second rib 32 improves the insertability, and the gap between the maximum diameter d2 of the second rib diameter and the inner diameter D2 of the base end half portion H22 can be reduced to restrict them to a coaxial position.

[0044] In this case, as shown in FIG. 7 as Comparative Example 1, if the joint part 2 does not have the second rib 32 and has a constant diameter from the part corresponding to the bent part H1 to the base end, it is not easy to align the axis when assembling the joint part 2 to the base end opening edge part while bending the joint part 2 along the bent shape of the plug hole H (for example, in the direction shown by the arrow in FIG. 7). In addition, as shown in FIG. 8, the gap between the inner diameter D2 of the base end inlet part H2 and the outer diameter of the joint part 2 becomes large. In that case, when the mounting bolt B is tightened and fixed to the mounting flange part 141 of the coil main body part 11, a force in the rotation direction acts (for example, in the direction shown by the arrow in FIG. 8), and the joint part 2 is likely to be misaligned. Accordingly, it is necessary to provide a rotation stopper or the like to suppress the misalignment of the coil main body part 11.

[0045] Furthermore, as shown in Comparative Example 2 in Fig. 9, in a configuration in which a part of the joint portion 2 is thin-walled, it becomes easier to deform along the bent shape, but when it comes into contact with the bent portion H1, the contact portion (e.g., portion A shown in Fig. 9) may wear. For example, when the ignition coil 1 is mounted on an engine and is subjected to vibration or the like and displaced while in contact with the bent portion H1, the thickness gradually becomes thinner due to wear, which may lead to a decrease in the withstand voltage.

[0046] In contrast, the joint part 2 having the configuration of this embodiment includes a first rib 31 facing the bent part H1 and a second rib 32 facing the base end inlet part H2, and can suppress axial misalignment over the entire length of the joint part 2. Also, by arranging the second rib 32 at the base end inlet part H2, the joint part 2 can be constrained to be coaxial, making it possible to eliminate the need for a rotation stopper during assembly.

[0047] Furthermore, since the first rib 31 and the second rib 32 improve rigidity, even if the first rib 31 comes into contact with the bent portion H1, displacement due to vibration or the like is suppressed. Even if displacement occurs, it will only come into contact with the first rib 31 extending in the axial direction. Therefore, the main body portion of the main body tubular portion 21 will not experience a reduction in thickness due to wear, and a decrease in voltage resistance is prevented.

[0048] (Other embodiments) In the above-mentioned embodiment 1, the conductive member 4 arranged inside the joint portion 2 is configured as a spring and is electrically connected to the high-voltage terminal 13 via the resistor 131 of the high-voltage tower portion 12, but it is sufficient if it is configured of a conductive member that is bendable and deformable together with the joint portion 2. Also, in the above-mentioned embodiment 1, the ignition coil has been described as an application example to a vehicle engine, but it may also be used in an internal combustion engine of a cogeneration system or the like. In addition, among the symbols used in the first and subsequent embodiments, the same symbols as those used in the previous embodiments represent the same components, etc. as those in the previous embodiments, unless otherwise specified.

[0049] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the scope of the present invention. For example, the configuration of the coil body of the ignition coil and the connection structure with the joint portion can be modified in various ways. The features of the present invention are as follows. [1] An ignition coil (1) that supplies high voltage to an ignition plug (P) disposed in a plug hole (H) having a bent portion (H1), a coil body (11) disposed at a base end inlet portion (H2) of the plug hole having an inner diameter larger than that of the bent portion; a joint portion (2) made of a bendable, cylindrical elastic body, the base end of which is attached to the coil body portion and the tip end of which is attached to the ignition plug, In the joint portion, a plurality of first ribs (31) extending along the axis (L) are provided on an outer peripheral surface of the main body tubular portion (21) including a portion facing the bent portion, and a plurality of second ribs (32) extending along the axis are provided on an outer peripheral surface of a base end tubular portion (22) located on the base end side relative to the main body tubular portion, An ignition coil, when viewed from a direction along the axis, wherein a maximum diameter d1 of a first rib diameter represented by the diameter of an imaginary circumscribing circle (C1) that has its center (c1) at the axis of the main body cylindrical portion and circumscribing the tips of the multiple first ribs, and a maximum diameter d2 of a second rib diameter represented by the diameter of an imaginary circumscribing circle (C2) that has its center (c2) at the axis of the base end cylindrical portion and circumscribing the tips of the multiple second ribs, have a relationship of d2>d1. [2] The ignition coil according to [1], wherein the first rib is continuously arranged on the tip side and base end side of the portion facing the bent portion. [3] The ignition coil according to [1] or [2], wherein the first rib has a tapered portion (311) at a tip end portion, in which the diameter of the first rib becomes smaller toward the tip side. [4] The ignition coil according to any one of [1] to [3], wherein the second rib is disposed continuously from the base end side to the tip end side, facing the base end side end portion including the base end inlet portion. [5] The ignition coil according to any one of [1] to [4], wherein the second rib has a tapered portion (321) at an end portion on the tip side, in which the diameter of the second rib becomes smaller toward the tip side. [6] An ignition coil described in any one of [1] to [5], wherein a maximum diameter d1 of the first rib diameter and a first inner diameter D1 which is the inner diameter of the plug hole at the bent portion have a relationship of D1>d1, and a maximum diameter d2 of the second rib diameter and a second inner diameter D2 which is the inner diameter of the plug hole at the base end inlet portion have a relationship of D2>d2. [7] An ignition coil according to any one of [1] to [6], wherein the joint portion is provided with a straight-shaped tip tubular portion (23) that is fitted into the head of the ignition plug, and is located further forward than the main body tubular portion, and an outer diameter d3 of the tip tubular portion and a maximum diameter d1 and a minimum diameter d11 of the first rib diameter have a relationship of d1>d11≧d3. [8] The ignition coil described in [7], wherein the joint portion has a straight-shaped intermediate cylindrical portion (24) between the main body cylindrical portion and the base end cylindrical portion, and an outer diameter d4 of the intermediate cylindrical portion and a maximum diameter d2 and a minimum diameter d21 of the second rib diameter have a relationship of d2>d21≧d4. [9] The ignition coil according to [8], wherein an outer diameter d3 of the tip cylindrical portion and an outer diameter d4 of the intermediate cylindrical portion have a relationship of d4>d3. [Explanation of symbols]

[0050] 1 Ignition coil 11 Coil body 2 Joint 21 Main body cylinder 22 Proximal cylinder part 23 Tip tube part 24 Intermediate cylinder part 31 First Rib 32 Second Rib 311, 321 Tapered section H plug hole H1 bent part

Claims

1. An ignition coil (1) for supplying high voltage to an ignition plug (P) disposed in a plug hole (H) having a bent portion (H1), a coil body (11) disposed at a base end inlet portion (H2) of the spark plug hole having an inner diameter larger than that of the bent portion; a joint portion (2) made of a bendable, cylindrical elastic body, the base end of which is attached to the coil main body and the tip end of which is attached to the ignition plug, In the joint portion, a plurality of first ribs (31) extending along the axis (L) are provided on an outer peripheral surface of a main body tubular portion (21) including a portion facing the bent portion, and a plurality of second ribs (32) extending along the axis are provided on an outer peripheral surface of a base end tubular portion (22) located on the base end side relative to the main body tubular portion, The first ribs are continuously arranged toward the distal end and the proximal end of the main body tube portion, with a portion facing the bent portion interposed therebetween, An ignition coil in which, when viewed from a direction along the axis, a maximum diameter d1 of a first rib diameter represented by the diameter of an imaginary circumscribing circle (C1) that has its center (c1) at the axis of the main body cylindrical portion and circumscribing the tips of the multiple first ribs, and a maximum diameter d2 of a second rib diameter represented by the diameter of an imaginary circumscribing circle (C2) that has its center (c2) at the axis of the base end cylindrical portion and circumscribing the tips of the multiple second ribs have a relationship of d2 > d1.

2. 2. The ignition coil according to claim 1, wherein the first rib is formed over an entire length of the tubular main body portion, and is deformed into a shape that conforms to the bent portion at a portion facing the bent portion.

3. 3. The ignition coil according to claim 2, wherein the first rib has a tapered portion (311) at a tip end portion, the first rib having a diameter that decreases toward the tip end.

4. 2. The ignition coil according to claim 1, wherein the second rib is disposed continuously from the base end side to the tip end side, facing the end portion on the base end side including the base end inlet portion.

5. 5. The ignition coil according to claim 4, wherein the second rib has a tapered portion (321) at a tip end portion, the second rib having a diameter that decreases toward the tip end.

6. 2. The ignition coil according to claim 1, wherein a maximum diameter d1 of the first rib diameter and a first inner diameter D1 which is the inner diameter of the spark plug hole at the bent portion have a relationship of D1 > d1, and a maximum diameter d2 of the second rib diameter and a second inner diameter D2 which is the inner diameter of the spark plug hole at the base end inlet portion have a relationship of D2 > d2.

7. 7. The ignition coil of claim 6, wherein the joint portion has a straight-shaped tip tubular portion (23) that is fitted into the head of the ignition plug and is located further forward than the main body tubular portion, and an outer diameter d3 of the tip tubular portion and a maximum diameter d1 and a minimum diameter d11 of the first rib diameter have a relationship of d1 > d11 ≥ d3.

8. 8. The ignition coil according to claim 7, wherein the joint portion has a straight-shaped intermediate cylindrical portion (24) between the main body cylindrical portion and the base end cylindrical portion, and an outer diameter d4 of the intermediate cylindrical portion and a maximum diameter d2 and a minimum diameter d21 of the second rib diameter have a relationship of d2 > d21 ≥ d4.

9. 9. The ignition coil according to claim 8, wherein an outer diameter d3 of the tip cylindrical portion and an outer diameter d4 of the intermediate cylindrical portion have a relationship of d4>d3.

Images