Ignition coil for internal combustion engine and internal combustion engine equipped with same

Abstract

To provide an ignition coil for an internal combustion engine and an internal combustion engine equipped with the same that can reliably ensure sealing between an ignition coil case and a plug hole opening, and improve ease of assembly.SOLUTION: An ignition coil 1 includes a case 2 that accommodates a component, one flange portion 3, and an elastic member having a seal portion. The seal portion seals between the case 2 and the opening of a plug hole while being compressed in the vertical direction Z between the case 2 and an internal combustion engine. The outer surface of the case 2 facing the seal portion in the vertical direction Z is defined as a case sealing surface 21. Further, the surface of the flange portion 3 that is brought into contact with a fixed portion in the vertical direction Z is defined as a flange contact surface 32. At this time, the angle α between the first imaginary surface 21S parallel to the case sealing surface 21 and the second imaginary surface 32S parallel to the flange contact surface 32 is 170°≤α<180°.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an ignition coil for an internal combustion engine and an internal combustion engine equipped with the same. [Background technology]

[0002] For example, as disclosed in Patent Document 1, an ignition coil is known that includes a case with a mounting flange for mounting to an internal combustion engine and an elastic member with a sealing portion that is sandwiched between the case and the cylinder head cover of the internal combustion engine. In the ignition coil described in Patent Document 1, an annular ridge is formed around the entire periphery of the sealing portion of the elastic member. Furthermore, this annular ridge is formed so that at least one of the height and width is different near the fastening portion between the ignition coil and the cylinder head cover and in other areas. This aims to secure a good seal between the ignition coil and the cylinder head cover while fixing the ignition coil to the cylinder head cover with a single fastening member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 05-001863 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the ignition coil described in Patent Document 1, the case and the elastic member are separate components. Furthermore, the protrusions formed on the seal portion of the elastic member differ in at least one of height and width between the area near the fastening point between the ignition coil and the cylinder head cover and other areas. Therefore, when assembling the ignition coil to the cylinder head cover, it is necessary to circumferentially position the seal portion relative to the ignition coil case, which can reduce assembly efficiency. Furthermore, if the circumferential positioning of the seal portion relative to the ignition coil case is insufficient, there is a risk that sufficient sealing between the ignition coil and the cylinder head cover cannot be ensured. Therefore, there is room for further improvement in terms of sealing performance between the ignition coil and the cylinder head cover and ease of assembly.

[0005] The present invention has been made in consideration of such problems, and aims to provide an ignition coil for an internal combustion engine that can reliably ensure sealing between the ignition coil case and the opening of the plug hole and can improve assembly ease, as well as an internal combustion engine equipped with the same. [Means for solving the problem]

[0006] One aspect of the present invention is a device comprising: a case (2) for accommodating components; a flange portion (3) that protrudes outward from the case and is fixed to a fixed portion (51) of the internal combustion engine (10) by a fixing member (31); An ignition coil (1) for an internal combustion engine, comprising: an elastic member (4) attached to the outside of the case, When a direction parallel to a fixing direction of the flange portion relative to the fixed portion by the fixing member is defined as a vertical direction (Z), in a state where the ignition coil is attached to the internal combustion engine, the flange portion abuts against the fixed portion in the vertical direction, the elastic member has a seal portion (41) that seals the gap between the case and an opening (501) of a spark plug hole (50) of the internal combustion engine in a state in which the elastic member is compressed in the vertical direction between the case and the internal combustion engine when the ignition coil is attached to the internal combustion engine, The flange portion is formed with an insertion portion (33) through which the fixing member is inserted along the fixing direction, When the ignition coil is attached to the internal combustion engine, a distance between the center axis of the spark plug hole and the insertion portion in a direction perpendicular to the center axis (50C) of the spark plug hole is defined as L, and a thickness of the flange portion is defined as T. The distance L is 25 to 40 mm, and the thickness T is 10 to 30 mm. the flange portion and the case are made of synthetic resin, When the outer surface of the case facing the seal portion in the up-down direction is defined as a case sealing surface (21), and the surface of the flange portion that abuts against the fixed portion in the up-down direction is defined as a flange abutting surface (32), The angle α between a first imaginary plane (21S) parallel to the case sealing surface and a second imaginary plane (32S) parallel to the flange abutment surface is 170°≦α ≦178° This is found in ignition coils for internal combustion engines.

[0007] Another aspect of the present invention is an ignition coil (1) including a case (2) for accommodating components, one flange portion (3) protruding outward from the case, and an elastic member (4) attached to the outside of the case; a fixed portion (51) to which the flange portion is fixed by a fixing member (31); an internal combustion engine (10) having a plug hole (50) inside which a part of the ignition coil is disposed, When a direction parallel to a fixing direction of the flange portion relative to the fixed portion by the fixing member is defined as a vertical direction (Z), the flange portion and the fixed portion abut against each other in the vertical direction, the elastic member has a seal portion (41) that seals the gap between the case and an opening wall portion (502) that forms the opening portion (501) of the plug hole in a state where the elastic member is compressed in the up-down direction, When the outer surface of the case facing the seal portion in the up-down direction is defined as a case sealing surface (21) and the upper end surface of the opening wall portion facing the seal portion in the up-down direction is defined as a wall portion sealing surface (503), the case sealing surface and the wall portion sealing surface are each in pressure contact with the seal portion in the up-down direction, The flange portion is formed with an insertion portion (33) through which the fixing member is inserted along the fixing direction, When the ignition coil is attached to the internal combustion engine, a distance between the center axis of the spark plug hole and the insertion portion in a direction perpendicular to the center axis (50C) of the spark plug hole is defined as L, and a thickness of the flange portion is defined as T. The distance L is 25 to 40 mm, and the thickness T is 10 to 30 mm. the flange portion and the case are made of synthetic resin, When a surface of the flange portion that abuts against the fixed portion in the up-down direction is defined as a flange abutment surface (32), and a surface of the fixed portion that abuts against the flange abutment surface is defined as a fixed portion abutment surface (511), an angle α formed between a first imaginary plane (21S) parallel to the case sealing surface and a second imaginary plane (32S) parallel to the flange abutment surface when the flange is not fixed to the fixed portion; The angle β formed by a third imaginary plane (503S) parallel to the wall sealing surface and a fourth imaginary plane (511S) parallel to the fixed portion abutting surface is: The following formula (4) In an internal combustion engine, the following relationship is satisfied: 2°≦ β-α≦10° (4) [Effects of the Invention]

[0008] In the above ignition coil, the angle α is in the range of 170°≦α<180°. Therefore, when the flange portion is fixed to the fixed portion of the internal combustion engine using the fixing member, a seal between the ignition coil case and the opening of the spark plug hole can be reliably ensured. Furthermore, the ignition coil can be assembled to the internal combustion engine without having to position the seal portion circumferentially relative to the case. As a result, a seal between the ignition coil case and the opening of the spark plug hole can be reliably ensured, and assembly can be facilitated.

[0009] The internal combustion engine satisfies the above formula (2). Therefore, when the flange portion is fixed to the fixed portion by the fixing member, a seal between the ignition coil case and the opening of the plug hole can be reliably ensured. Furthermore, the ignition coil can be assembled to the internal combustion engine without having to position the seal portion circumferentially relative to the case. As a result, a seal between the ignition coil case and the opening of the plug hole can be reliably ensured and assembly can be improved.

[0010] As described above, according to the above aspect, it is possible to provide an ignition coil for an internal combustion engine and an internal combustion engine equipped with the same, which can reliably ensure sealing between the ignition coil case and the opening of the spark plug hole and can improve assembly. In addition, the symbols in parentheses in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention. [Brief explanation of the drawings]

[0011] [Figure 1] 2 is a cross-sectional view of the ignition coil taken along the vertical direction in the first embodiment. FIG. [Figure 2] 3 is a cross-sectional view of the ignition coil taken along the vertical direction with the elastic member removed in the first embodiment. FIG. [Figure 3] 3 is a cross-sectional view showing a state in which the ignition coil is attached to the internal combustion engine in the first embodiment. FIG. [Figure 4] 2 is a cross-sectional view of the spark plug hole and the vicinity thereof taken along the vertical direction of the internal combustion engine in the first embodiment. FIG. [Figure 5] 3 is a cross-sectional view along the vertical direction of the ignition coil attached to the internal combustion engine in the first embodiment, showing the distance L and the thickness T of the flange portion. FIG. [Figure 6] 10 is a graph showing the relationship between the angle α and the compressive stress of the seal portion in Experimental Example 1. [Figure 7] 10 is a graph showing the relationship between the thickness T of the flange portion and the angle α when the compressive stress of the seal portion is 0.095 MPa or more in Experimental Example 2. [Figure 8] 10 is a graph showing the relationship between the value of "angle β - angle α" and the compressive stress of the seal portion in Experimental Example 3. [Figure 9] 10 is a graph showing the relationship between the thickness T of the flange portion and the value of "angle β - angle α" when the compressive stress of the seal portion is 0.095 MPa or more in Experimental Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Embodiment 1) An embodiment of an ignition coil for an internal combustion engine and an internal combustion engine including the same will be described with reference to FIGS. 1 to 3, the ignition coil 1 for an internal combustion engine of this embodiment includes a case 2 that houses components, one flange portion 3, and an elastic member 4. The flange portion 3 protrudes outward from the case 2, and is fixed to a fixed portion 51 of the internal combustion engine 10 by a fixing member 31, as shown in FIGS.

[0013] The direction parallel to the fixing direction of the flange portion 3 to the fixed portion 51 by the fixing member 31 is defined as the vertical direction Z. At this time, when the ignition coil 1 is attached to the internal combustion engine 10, the flange portion 3 abuts against the fixed portion 51 in the vertical direction Z.

[0014] The elastic member 4 also has a seal portion 41. When the ignition coil 1 is attached to the internal combustion engine 10, the seal portion 41 is compressed in the vertical direction Z between the case 2 and the internal combustion engine 10, and seals the gap between the case 2 and the opening 501 of the spark plug hole 50 of the internal combustion engine 10.

[0015] As shown in FIGS. 1 and 2, the outer surface of the case 2 facing the seal portion 41 in the vertical direction Z is the case sealing surface 21. The surface of the flange portion 3 that abuts against the fixed portion 51 in the vertical direction Z is the flange abutment surface 32. As shown in FIG. 2, the angle α between a first imaginary plane 21S parallel to the case sealing surface 21 and a second imaginary plane 32S parallel to the flange abutment surface 32 is 170°≦α<180°. Preferably, the angle α is 174°≦α≦178°. More preferably, the angle α is 175°≦α≦177°. These ranges for the angle α can be derived from Experimental Examples 1 and 2, which will be described later.

[0016] Furthermore, the flange portion 3 is formed with an insertion portion 33 through which the fixing member 31 is inserted along the fixing direction. As shown in FIG. 5, when the ignition coil 1 is attached to the internal combustion engine 10, the distance between the central axis 50C of the spark plug hole 50 and the insertion portion 33 in a direction perpendicular to the central axis 50C of the spark plug hole 50 is defined as L, and the thickness of the flange portion 3 is defined as T. In this case, the angle α satisfies the following formula (1). Note that the following formula (1) can be derived from Experimental Example 2, which will be described later. 176.6-(0.141L 2 -6.1L+101.3) / T 1.1 <α< 180.6-(0.141L 2 -6.1L+101.3) / T 1.1 ···(1)

[0017] The ignition coil 1 of this embodiment is connected to a spark plug installed in an internal combustion engine of an automobile or the like, and can be used as a means for applying high voltage to the spark plug. In this embodiment, the ignition coil 1 is attached to the internal combustion engine 10 by inserting a portion of it into a spark plug hole 50 formed in a cylinder head cover 5 of the internal combustion engine 10, as shown in Fig. 4. In this specification, in the vertical direction Z, the side of the ignition coil 1 attached to the internal combustion engine 10 that faces the spark plug 100 is referred to as the lower side Z1, and the opposite side is referred to as the upper side Z2.

[0018] 1 and 2, the case 2 of the ignition coil 1 has a case body 22, a connector portion 23 for connecting the ignition coil 1 to the outside, and a cylindrical tower portion 24. The connector portion 23 is fitted into the case body 22. The case body 22 and the tower portion 24 are integrally formed.

[0019] The case body 22 accommodates components such as a coil body 6 that generates a high voltage and an igniter 11. The coil body 6 has a primary coil 61 and a secondary coil 62 that are magnetically coupled to each other.

[0020] The case body 22 is filled with a sealing resin 15. As a result, components such as the coil body 6 arranged inside the case body 22 are sealed with the sealing resin 15. The sealing resin 15 can be, for example, an epoxy resin.

[0021] The tower portion 24 protrudes downward Z1 from the case main body 22. The tower portion 24 is formed so that its central axis 24C is aligned with the vertical direction Z1. In this specification, the circumferential direction means the direction along the circumference of a circle centered on the central axis 24C of the tower portion 24 when the ignition coil 1 is viewed from the vertical direction Z (not shown). The radial direction means the radial direction of a circle centered on the central axis 24C of the tower portion 24 when the ignition coil 1 is viewed from the vertical direction Z. As shown in FIG. 4, when the ignition coil 1 is attached to the internal combustion engine 10, the central axis 50C of the spark plug hole 50 is also the central axis 24C of the tower portion 24.

[0022] In this embodiment, a portion of the outer surface at the lower end of the case main body 22 serves as the case sealing surface 21. The case sealing surface 21 is formed radially outward from the tower portion 24. In this embodiment, the case sealing surface 21 is substantially perpendicular to the central axis 24C of the tower portion 24 and is formed in an annular shape. The case sealing surface 21 is in pressure contact with the seal portion 41 in the up-down direction Z over the entire circumferential direction.

[0023] 1, the connector portion 23 is provided on the opposite side of the flange portion 3, sandwiching the coil body 6, in the direction in which the coil body 6 and the flange portion 3 are aligned. The connector portion 23 protrudes from the case body 22 toward the opposite side of the flange portion 3 in the direction in which the coil body 6 and the flange portion 3 are aligned.

[0024] The connector portion 23 has a connector terminal 231 on the inside. For example, when the ignition coil 1 is mounted on a vehicle, the connector terminal 231 is connected to a control device (not shown). The connector terminal 231 is also connected to a terminal of the igniter 11. The igniter 11 applies and cuts off current to the primary coil 61 in response to an ignition signal determined by the control device.

[0025] Further, a conductive terminal 241 is disposed on the tower portion 24. The conductive terminal 241 is connected to the secondary coil 62 via a high-voltage terminal 621. As described above, when the igniter 11 cuts off the current to the primary coil 61, a high voltage is generated in the secondary coil 62 by electromagnetic induction. The generated high voltage generates a discharge spark in a discharge gap (not shown) of the spark plug 100 (see FIG. 4 ), which is electrically connected to the secondary coil 62 via the conductive terminal 241. The generated discharge spark then ignites the air-fuel mixture in a combustion chamber (not shown) of the internal combustion engine 10.

[0026] In this embodiment, the flange portion 3 is integrally formed with the case 2. The flange portion 3 is located radially outward of the elastic member 4. The flange portion 3 and the case 2 may be made of synthetic resin such as PBT (polybutylene terephthalate) and PBS (polybutylene succinate). In this embodiment, the flange portion 3 and the case 2 are made of PBT.

[0027] 1 , when the flange portion 3 is not fixed to the fixed portion 51, the flange abutment surface 32 of the flange portion 3 is formed so as to be inclined with respect to the case sealing surface 21 and the central axis 24C of the tower portion 24. The flange abutment surface 32 and the case sealing surface 21 are formed continuously. The upper end surface 34 of the flange portion 3 is formed so as to be substantially parallel to the flange abutment surface 32. In other words, the upper end surface 34 is also formed so as to be inclined with respect to the case sealing surface 21 and the central axis 24C of the tower portion 24.

[0028] In this embodiment, the insertion portion 33 of the flange portion 3 is an insertion hole through which the fixing member 31 is inserted. The insertion portion 33 is formed so that its opening direction is substantially perpendicular to the flange abutment surface 32 and the upper end surface 34. In other words, the central axis 33C of the insertion portion 33 is substantially perpendicular to the flange abutment surface 32 and the upper end surface 34, and is inclined with respect to the central axis 24C of the tower portion 24.

[0029] 5, the thickness T of the flange portion 3 is the length of the flange portion 3 in the opening direction of the insertion portion 33. The thickness T can be, for example, 10 to 30 mm. In this embodiment, the thickness T of the flange portion is 15 mm.

[0030] Strictly speaking, the distance L can be determined based on the center 33P of the upper end of the insertion portion 33. In other words, the distance L can be the distance between the central axis 50C and the center 33P in a direction perpendicular to the central axis 50C of the spark plug hole 50 when the ignition coil 1 is attached to the internal combustion engine 10. The distance L can be set to, for example, 25 to 40 mm. In this embodiment, the distance L is 30 mm.

[0031] An elastic member 4 is fitted into the tower portion 24. The elastic member 4 is fitted into the tower portion 24 so as to cover the tower portion 24 from the outside in the radial direction. The elastic member 4 has rubber elasticity and insulating properties. The elastic member 4 can be made of an elastomer such as silicone rubber, isoprene rubber, or natural rubber. In this embodiment, the elastic member 4 is made of silicone rubber. The elastic member 4 has a generally rotating body shape with the central axis 24C of the tower portion 24 as its axis of rotation.

[0032] As shown in FIG. 1 , the elastic member 4 has a fitting portion 42, a radially extending portion 43, and a downwardly extending portion 44. The fitting portion 42 has a through-hole formed therethrough in the up-down direction Z. The tower portion 24 fits into the through-hole of the fitting portion 42. The radially extending portion 43 extends radially outward from the upper end of the fitting portion 42. The radially extending portion 43 is formed along the outer surface of the case main body 22. The downwardly extending portion 44 extends from the radially outer end of the radially extending portion 43 toward the lower side Z1. The radially extending portion 43 and the downwardly extending portion 44 are each formed in an annular shape.

[0033] 5, a portion of the radially extending portion 43 and the downwardly extending portion 44 form the seal portion 41. The portion of the radially extending portion 43 and the downwardly extending portion 44 that form the seal portion 41 are compressed in the up-down direction Z over the entire circumferential direction by the case body 22 and an opening wall portion 502 described below, thereby sealing the gap between the case body 22 and the opening 501 of the spark plug hole 50. In other words, the seal portion 41 is formed in an annular shape.

[0034] 4, the pole joint 12 is further fitted from the lower side Z1 into the fitting portion 42 of the elastic member 4. In other words, the tower section 24 and the pole joint 12 are connected to each other via the fitting portion 42.

[0035] The pole joint 12 has a cylindrical shape that is long in the vertical direction Z. The pole joint 12 can be made of, for example, a resin that is harder than the elastic member 4 and has insulating properties. A spring 14 that is elastically deformable in the vertical direction Z and has conductivity is disposed inside the pole joint 12 and the tower portion 24. The spring 14 electrically connects the secondary coil 62 and the spark plug 100.

[0036] A plug cap 13 is fitted onto the lower end of the pole joint 12. With the ignition coil 1 attached to the internal combustion engine 10, a spark plug 100 is fitted inside the plug cap 13. The plug cap 13 may be made of, for example, an insulating elastomer.

[0037] Next, the internal combustion engine 10 of this embodiment will be described. As shown in Figures 4 and 5, the internal combustion engine 10 of this embodiment has an ignition coil 1, a fixed portion 51, and a spark plug hole 50. A portion of the ignition coil 1 is disposed inside the spark plug hole 50. The flange portion 3 and the fixed portion 51 abut against each other in the vertical direction Z. The seal portion 41 is compressed in the vertical direction Z between the case 2 and an opening wall portion 502 that forms the opening 501 of the spark plug hole 50, and seals the gap between the case 2 and the opening 501.

[0038] The upper end surface of the opening wall portion 502 facing the seal portion 41 in the vertical direction Z is the wall portion sealing surface 503. At this time, the case sealing surface 21 and the wall portion sealing surface 503 are in pressure contact with the seal portion 41 in the vertical direction Z.

[0039] The surface of the fixed portion 51 that abuts against the flange abutment surface 32 is defined as the fixed portion abutment surface 511. As shown in FIG. 3 , when the flange portion 3 is not fixed to the fixed portion 51, the angle formed by a third imaginary plane 503S parallel to the wall sealing surface 503 and a fourth imaginary plane 511S parallel to the fixed portion abutment surface 511 is defined as angle β. In this case, when the flange portion 3 is not fixed to the fixed portion 51, the angles α and β satisfy the relationship of the following formula (2). Note that the following formula (2) can be derived from Experimental Example 4, which will be described later. 0°<β-α≦10° (2)

[0040] Furthermore, it is preferable that the value of "angle β - angle α" is 2°≦β-α≦6°. It is more preferable that the value of "angle β - angle α" is 3°≦β-α≦5°. In this embodiment, angle β is 180°. That is, in this embodiment, third imaginary surface 503S and fourth imaginary surface 511S are parallel to each other.

[0041] Furthermore, the internal combustion engine 10 satisfies the following formula (3): The following formula (3) can be derived from Experimental Example 4, which will be described later. (0.141L 2 -6.1L+101.3) / T 1.1 -0.6<β-α< (0.141L 2 -6.1L+101.3) / T 1.1 +3.4 (3)

[0042] In this embodiment, the ignition coil 1 is attached to the cylinder head cover 5 of the internal combustion engine 10. When attaching the ignition coil 1 to the internal combustion engine 10, a portion of the ignition coil 1 is inserted from the upper side Z2 into a plug hole 50 that opens to the upper side Z2. Specifically, as shown in FIG. 4 , the pole joint 12 fitted with the plug cap 13 is inserted into the plug hole 50 from the upper side Z2, and the plug cap 13 is fitted from the upper side Z2 onto the spark plug 100 that is arranged on the lower side Z1 of the plug hole 50. Thereafter, the flange portion 3 is fixed to a fixed portion 51 formed on the cylinder head cover 5, thereby attaching the ignition coil 1 to the internal combustion engine 10.

[0043] 5, in a state in which the flange portion 3 is fixed to the fixed portion 51, the central axis 33C of the insertion portion 33 is substantially parallel to the central axis 50C of the spark plug hole 50 and the central axis 24C of the tower portion 24. In addition, in this embodiment, the wall sealing surface 503 and the fixed portion abutment surface 511 are each substantially perpendicular to the central axis 50C.

[0044] In this embodiment, the fixing member 31 is a bolt having a head 311 and a shaft 312, as shown in FIG. 4 . The shaft 312 extends from the head 311 toward a lower side Z1. A male thread is formed on the outer peripheral surface of the shaft 312. The outer diameter of the head 311 is larger than the inner diameter of the insertion portion 33. When the ignition coil 1 is attached to the internal combustion engine 10, the lower side Z1 surface of the head 311 is in pressure contact with the upper end surface 34 of the flange portion 3 in the up-down direction Z. The lower side Z1 surface of the head 311 is formed so as to be substantially perpendicular to the central axis 33C of the insertion portion 33. The lower side Z1 surface of the head 311 and the upper end surface 34 of the flange portion 3 are substantially parallel to each other.

[0045] In this embodiment, the fixed portion 51 is formed so as to protrude from the upper surface 52 of the cylinder head cover 5 toward the upper side Z2. A recess 512 for fixing the fixing member 31 is formed in the fixed portion 51. The recess 512 is formed so as to be recessed from the fixed portion abutment surface 511 toward the lower side Z1. A female thread portion is formed on the inner circumferential surface of the recess 512.

[0046] In this embodiment, the fixing member 31 is inserted into the insertion portion 33, and then screwed into the fixed portion 51, thereby fixing the flange portion 3 to the fixed portion 51. Specifically, as shown by arrow M in Fig. 3 , the fixing member 31 is inserted into the insertion portion 33, and the shaft portion 312 of the fixing member 31 is screwed into the recess 512 toward the lower side Z1, thereby fixing the flange portion 3 to the fixed portion 51. In this embodiment, the flange portion 3 is fixed to the fixed portion 51 by one fixing member 31.

[0047] The opening wall 502 that defines the opening 501 of the spark plug hole 50 has an annular protrusion 53. The annular protrusion 53 is formed so as to protrude from the upper surface 52 of the cylinder head cover 5 toward the upper side Z2. In this embodiment, the upper end surface of the annular protrusion 53 forms the wall sealing surface 503.

[0048] When the flange portion 3 is fixed to the fixed portion 51 by the fixing member 31, the flange abutment surface 32 is pressed against the fixed portion abutment surface 511, and the case 2 and the opening wall portion 502 compress the seal portion 41 in the vertical direction Z. As a result, the seal portion 41 seals the gap between the case 2 and the opening 501. That is, the seal portion 41 is in close contact with both the case sealing surface 21 and the wall sealing surface 503, sealing the gap between them. Furthermore, when the flange portion 3 is fixed to the fixed portion 51, the angle α formed by the first imaginary plane 21S parallel to the case sealing surface 21 and the second imaginary plane 32S parallel to the flange abutment surface 32 is larger than the angle α when the flange portion 3 is not fixed to the fixed portion 51. In other words, by fixing the flange portion 3 to the fixed portion 51, the flange portion 3 and the case 2 are slightly deformed, and the angle between the first imaginary plane 21S and the second imaginary plane 32S becomes larger than before the flange portion 3 was fixed to the fixed portion 51.

[0049] Next, the effects of this embodiment will be described. In the above-described ignition coil 1, the range of angle α is 170°≦α<180°. Therefore, when the flange portion 3 is fixed to the fixed portion 51 by the fixing member 31, it is possible to reliably ensure sealing between the case 2 of the ignition coil 1 and the opening 501 of the spark plug hole 50. Furthermore, it is possible to assemble the ignition coil 1 to the internal combustion engine 10 without having to position the seal portion 41 circumferentially relative to the case 2. As a result, it is possible to reliably ensure sealing between the case 2 and the opening 501 and improve ease of assembly.

[0050] If the angles α and β were each 180°, when the flange portion was fixed to a fixed portion of an internal combustion engine, the compressive stress of the seal portion would be less uniform in the circumferential direction, potentially reducing the sealing performance of the seal portion. That is, when the flange portion was fixed to a fixed portion, a relatively large vertical force would act on the seal portion near the flange portion, while a relatively small vertical force would act on the seal portion away from the flange portion. Therefore, in the ignition coil 1 of this embodiment, the angle α is set to 170°≦α<180°. Therefore, as shown in FIG. 5 , when the portion of the seal portion 41 near the flange portion 3 is designated as the flange-side seal portion 413, the compressive stress of the opposite-side seal portion 414, which is the portion of the seal portion 41 opposite the flange-side seal portion 413 across the center axis 24C, can be increased. That is, the compressive stress of the opposite-side seal portion 414, which is the portion of the seal portion 41 away from the flange portion 3, can be increased. This makes it easier for the compressive stress of the seal portion 41 to be relatively uniform over the entire circumferential direction. As a result, it is possible to reliably ensure sealing between the case 2 and the opening 501. This makes it possible to reliably prevent water from entering the inside of the spark plug hole 50 through the opening 501. The opposite-side seal portion 414 is a portion of the seal portion 41 that is positioned 180° circumferentially away from the flange-side seal portion 413.

[0051] Moreover, it is preferable that the angle α is set to 174°≦α≦178°. In this case, the sealing performance between the case 2 and the opening 501 can be ensured more reliably.

[0052] It is more preferable that the angle α is set to 175°≦α≦177°, in which case the sealing performance between the case 2 and the opening 501 can be ensured even more reliably.

[0053] The angle α satisfies the above formula (1). Therefore, when the flange portion 3 is fixed to the fixed portion 51 by the fixing member 31, the sealing performance between the case 2 and the opening 501 can be ensured more reliably.

[0054] The longer the distance L, the more easily the flange portion 3 and the case 2 deform when the flange portion 3 is fixed to the fixed portion 51. Furthermore, the thinner the thickness T, the more easily the flange portion 3 deforms when the flange portion 3 is fixed to the fixed portion 51. Therefore, by adjusting the angle α to an appropriate angle depending on the distance L and the thickness T, it is possible to more reliably ensure sealing between the case 2 and the opening 501 of the spark plug hole 50. In other words, by making the relationship between the angle α, the distance L, and the thickness T satisfy the relationship shown in the above formula (1), it is possible to more reliably ensure sealing between the case 2 and the opening 501.

[0055] The internal combustion engine 10 satisfies the above formula (2). Therefore, when the flange portion 3 is fixed to the fixed portion 51 by the fixing member 31, the sealing performance between the case 2 and the opening 501 can be reliably ensured. Furthermore, the ignition coil 1 can be assembled to the internal combustion engine 10 without having to position the seal portion 41 circumferentially relative to the case 2. As a result, the sealing performance between the case 2 and the opening 501 can be reliably ensured, and assembly can be performed with ease.

[0056] Furthermore, it is preferable that the value of "angle β-angle α" is 2°≦β-α≦6°. In this case, the sealing performance between case 2 and opening 501 can be ensured more reliably.

[0057] Furthermore, it is more preferable that the value of "angle β - angle α" is 3°≦β-α≦5°. In this case, the sealing performance between case 2 and opening 501 can be ensured even more reliably.

[0058] The internal combustion engine 10 satisfies the above formula (3). Therefore, when the flange portion 3 is fixed to the fixed portion 51 by the fixing member 31, the sealing performance between the case 2 and the opening 501 can be more reliably ensured.

[0059] In this embodiment, the elastic member 4 has a generally rotating body shape with the central axis 24C of the tower portion 24 as its axis of rotation. Therefore, the ignition coil 1 can be assembled to the internal combustion engine 10 without having to determine the circumferential position of the seal portion 41 relative to the case 2. As a result, the ease of assembly can be improved.

[0060] As described above, according to this embodiment, it is possible to provide an ignition coil 1 for an internal combustion engine and an internal combustion engine 10 equipped with the same, which can reliably ensure sealing between the case 2 of the ignition coil 1 and the opening 501 of the spark plug hole 50 and can improve assembly ease.

[0061] In the first embodiment, the angle β is 180°. However, the angle β can be, for example, smaller than 180° as long as the above formula (2) is satisfied. The angle β can also be, for example, larger than 180° as long as the above formula (2) is satisfied. In this case, the angle α can also be, for example, 180° or larger in correspondence with the angle β as long as the above formula (2) is satisfied.

[0062] In the first embodiment, the coil body 6 is disposed outside the spark plug hole 50. However, the ignition coil and the internal combustion engine may also be configured so that the coil body is disposed inside the spark plug hole.

[0063] In the first embodiment, the elastic member 4, the pole joint 12, and the plug cap 13 are separate members. However, the ignition coil may be configured such that the portion from the seal portion to the plug cap is made of a single elastic member.

[0064] In the first embodiment, the case sealing surface 21 and the flange abutment surface 32 are formed continuously. However, the ignition coil may be configured such that the case sealing surface and the flange abutment surface are formed at positions spaced apart from each other. Specifically, for example, by shifting the position of the flange portion upward compared to the first embodiment, the case sealing surface and the flange abutment surface may be formed at positions spaced apart from each other in the up-down direction.

[0065] (Experimental Example 1) In this example, as shown in the graph of Fig. 6, the relationship between the angle α and the compressive stress of the seal portion was analyzed using a plurality of ignition coils having different values ​​of the angle α while having the same basic structure as in embodiment 1. Specifically, the compressive stress of the flange-side seal portion 413 (see Fig. 5) and the opposite-side seal portion 414 (see Fig. 5) when the ignition coil was installed in an internal combustion engine was analyzed.

[0066] In this example, a compressive stress of 0.095 MPa or greater in both the flange-side seal portion 413 and the opposite-side seal portion 414 is used as the criterion for ensuring sufficient sealing between the ignition coil case and the plug hole opening. When this criterion is met, it is believed that sufficient sealing between the ignition coil case and the plug hole opening can be ensured throughout the entire circumferential direction of the seal portion. Therefore, the angle α that satisfies this criterion was determined from the above analysis results. The experimental conditions were silicone rubber for the seal portion, and PBT for the flange and case. The distance L was 30 mm, the flange thickness T was 15 mm, the seal portion outer diameter was 30 mm, and the angle β was 180°. The seal portion used had an interference of 1.2 mm when the angle α was 180°. In other words, the seal portion used had a maximum vertical length when the ignition coil was installed in the internal combustion engine that was 1.2 mm shorter than the maximum vertical length in the free state when the angle α was 180°.

[0067] The graph in Figure 6 shows that the smaller the angle α, the greater the compressive stress in the opposite-side seal portion 414. On the other hand, when the angle α is relatively large, the compressive stress in the opposite-side seal portion 414 is relatively small. Figure 6 also shows that a relatively large angle α can relatively increase the compressive stress in the flange-side seal portion 413, but the surface pressure on the connector side of the seal portion is relatively low, which tends to result in relatively small compressive stress in the opposite-side seal portion 414. In particular, when the angle α is 180°, the compressive stress in the opposite-side seal portion 414 is small compared to other angles analyzed for compressive stress in the seal portion, and does not meet the above criteria. When the angle α is relatively large, the amount of compression in the flange-side seal portion 413 is relatively large, resulting in relatively large compressive stress in the flange-side seal portion 413. When the flange-side seal portion 413 is subjected to a load, the case body is subjected to an upward force as a reaction. This is thought to result in the case sealing surface of the case body being more likely to be positioned higher in the portion away from the flange than in the portion near the flange. Therefore, when the angle α is relatively large, the compressive stress is considered to be relatively small in the opposite seal portion 414, which is farther from the flange portion. Furthermore, when the angle α is too small, the compressive stress of the flange-side seal portion 413 is less than 0.095 MPa, which does not satisfy the above criteria. When the angle α is too small, the compression amount of the opposite seal portion 414 is relatively large, and the opposite seal portion 414 is close to being unable to elastically deform in the compression direction, which is considered to be why the flange-side seal portion 413 is not sufficiently compressed by the case. On the other hand, when the angle α is 174°≦α≦178°, the above criteria are satisfied. From these results, it is considered that by setting the angle α to 174°≦α≦178°, sufficient surface pressure can be more reliably obtained around the entire circumferential direction of the seal portion, thereby ensuring sufficient sealing between the ignition coil case and the spark plug hole opening. Furthermore, by setting the angle α to 175°≦α≦177°, it is believed that the sealing performance between the ignition coil case and the opening of the spark plug hole can be more sufficiently ensured.

[0068] (Experimental Example 2) In this example, as shown in the graph in FIG. 7 , multiple ignition coils with the same basic structure as in the first embodiment but with different values ​​for angle α, distance L, and flange thickness T were used to analyze the compressive stress of the seal when the angle α, distance L, and flange thickness T were changed. Specifically, the distance L was changed within a range of 25 to 40 mm, and the thickness T was changed within a range of 10 to 30 mm, and the value of angle α that satisfies the above criteria was analyzed. In FIG. 7 , the dashed line graph for each distance L indicates the largest angle α value that satisfies the above criteria, i.e., the upper limit of the angle α that satisfies the above criteria. Also, in FIG. 7 , the solid line graph for each distance L indicates the smallest angle α value that satisfies the above criteria, i.e., the lower limit of the angle α that satisfies the above criteria. For example, when the distance L is 40 mm and the flange thickness T is 10 mm, the upper limit of the angle α that satisfies the above criteria is 174°, and the lower limit of the angle α that satisfies the above criteria is 170°. In other words, when the distance L is 40 mm and the flange thickness T is 10 mm, the ignition coil satisfies the above criteria when the angle α is 170°≦α≦174°. Other experimental conditions are the same as those in Experimental Example 1.

[0069] The graph in FIG. 7 reveals that, even if the distance L is the same, the greater the thickness T of the flange portion, the greater the value of the angle α that satisfies the above criteria. It also reveals that, even if the thickness T is the same, the greater the distance L, the smaller the value of the angle α that satisfies the above criteria. Furthermore, the analysis results of this example revealed that when the distance L and thickness T are varied, the above criteria are met when the angle α is in the range of 170°≦α<180°. In other words, when the distance L is varied between 25 and 40 mm and the thickness T is varied between 10 and 30 mm, it is believed that sufficient sealing between the ignition coil case and the spark plug hole opening can be ensured by adjusting the angle α within the range of 170°≦α<180°. Furthermore, the relationship between the value of the angle α that satisfies the above criteria and the distance L and thickness T is expressed by the above formula (1). Here, the left side of formula (1) corresponds to the graph shown by the solid line in FIG. 7, and the right side of formula (1) corresponds to the graph shown by the dashed line in FIG. 7.

[0070] Furthermore, the thinner the flange thickness T, the more easily the flange deforms. Therefore, it is believed that the thinner the flange thickness, the smaller the angle α, making it possible to adjust the flange so as to satisfy the above criteria. Furthermore, it is believed that the longer the distance L, the smaller the angle α, making it possible to adjust the flange so as to satisfy the above criteria.

[0071] (Experimental Example 3) In this example, as shown in the graph of FIG. 8, multiple internal combustion engines with different values ​​of "angle β - angle α" were used to analyze the relationship between the "angle β - angle α" and the compressive stress of the seal portion, while maintaining the same basic structure as in Example 1. Furthermore, from the analysis results, the value of "angle β - angle α" that satisfies the above criteria was determined. Furthermore, in this example, the angle β was set to 178° for each internal combustion engine. Furthermore, the internal combustion engines used had an angle α ranging from 169° to 178°. In other words, the relationship between the "angle β - angle α" and the compressive stress of the seal portion was analyzed using internal combustion engines with an "angle β - angle α" value ranging from 0° to 9°. Furthermore, the seal portion used had an interference of 1.2 mm when the angle α was 178°. In other words, the seal portion used had an interference of 1.2 mm when the "angle β - angle α" value was 0°. Other experimental conditions were the same as those in Experimental Example 1.

[0072] The graph in FIG. 8 indicates that the larger the value of "angle β - angle α," the greater the compressive stress in the opposite-side seal portion 414 (see FIG. 5). On the other hand, when the value of "angle β - angle α" is relatively small, the compressive stress in the opposite-side seal portion 414 is relatively small. According to FIG. 8, when the value of "angle β - angle α" is relatively small, the compressive stress in the flange-side seal portion 413 (see FIG. 5) can be relatively large, but the surface pressure on the connector side of the seal portion is relatively low, which tends to result in relatively small compressive stress in the opposite-side seal portion 414. In particular, when the value of "angle β - angle α" is 0°, the compressive stress in the opposite-side seal portion 414 is small compared to other values ​​analyzed for the compressive stress of the seal portion, and does not satisfy the above criteria. When the value of "angle β - angle α" is relatively small, the amount of compression in the flange-side seal portion 413 is relatively large, resulting in relatively large compressive stress in the flange-side seal portion 413. When the flange-side seal portion 413 is subjected to a load, the case body receives an upward force as a reaction. This likely leads to the case sealing surface of the case body being more likely to be located at a higher position away from the flange than at a position near the flange. Therefore, when the "angle β - angle α" value is relatively small, the compressive stress in the opposite seal portion 414, which is located away from the flange, is likely to be relatively small. Furthermore, when the "angle β - angle α" value is too large, the compressive stress in the flange-side seal portion 413 is less than 0.095 MPa, which does not satisfy the above criteria. When the "angle β - angle α" value is too large, the compression amount of the opposite seal portion 414 becomes too large, and the opposite seal portion 414 approaches a state where it cannot elastically deform in the compression direction. This is likely because the flange-side seal portion 413 is not sufficiently compressed by the case. On the other hand, when the "angle β - angle α" value is 2°≦β-α≦6°, the above criteria are satisfied. From these results, it is believed that by setting the value of "angle β - angle α" to 2°≦β-α≦6°, sufficient surface pressure can be obtained more reliably around the entire circumferential direction of the seal portion, and sufficient sealing can be ensured between the ignition coil case and the opening of the spark plug hole.Furthermore, it is believed that by setting the value of "angle β - angle α" to 3°≦β-α≦5°, the sealing performance between the ignition coil case and the opening of the spark plug hole can be more sufficiently ensured.

[0073] (Experimental Example 4) In this example, the compressive stress of the seal portion was analyzed when the "angle β - angle α" value, the distance L, and the flange thickness T were varied using multiple internal combustion engines with the same basic structure as in Example 1, but with different values ​​for "angle β - angle α," distance L, and flange thickness T. Specifically, as shown in the graph in FIG. 9 , the distance L was varied within a range of 25 to 40 mm, and the thickness T was varied within a range of 10 to 30 mm, and the "angle β - angle α" value that satisfied the above criteria was analyzed. In FIG. 9 , the solid line graph for each distance L indicates the upper limit value of "angle β - angle α" that satisfied the above criteria. Also, in FIG. 9 , the dashed line graph for each distance L indicates the lower limit value of "angle β - angle α" that satisfied the above criteria. The other experimental conditions were the same as in Experimental Example 3.

[0074] The graph in Figure 9 reveals that, even if the distance L is the same, the larger the flange thickness T, the smaller the "angle β - angle α" value that satisfies the above criteria. It also reveals that, even if the thickness T is the same, the larger the distance L, the larger the "angle β - angle α" value that satisfies the above criteria. Furthermore, the analysis results of this example revealed that when the distance L and thickness T are varied, the "angle β - angle α" value satisfies the above criteria when it is in the range of 0° < β - α ≦ 10°. In other words, when the distance L is varied between 25 and 40 mm and the thickness T is varied between 10 and 30 mm, it is believed that sufficient sealing between the ignition coil case and the spark plug hole opening can be achieved by adjusting the "angle β - angle α" value within the range of 0° < β - α ≦ 10°. Furthermore, the above formula (3) expresses the relationship between the "angle β - angle α" value that satisfies the above criteria, the distance L, and the thickness T. Here, the left side of the above formula (3) corresponds to the graph shown by the dashed line in FIG. 9, and the right side of the above formula (3) corresponds to the graph shown by the solid line in FIG.

[0075] It is also believed that the thinner the flange portion is, the more the "angle β - angle α" value can be increased to satisfy the above criteria. It is also believed that the longer the distance L is, the more the "angle β - angle α" value can be increased to satisfy the above criteria.

[0076] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments within the scope of the present invention. [Explanation of symbols]

[0077] 1...ignition coil, 2...case, 3...flange portion, 4...elastic member, 10...internal combustion engine, 21...case sealing surface, 21S...first imaginary surface, 31...fixing member, 32...flange abutting surface, 32S...second imaginary surface, 41...sealing portion, 50...spark plug hole, 51...fixed portion, 501...opening, Z...vertical direction

Claims

1. a case (2) for accommodating the components; a flange portion (3) that protrudes outward from the case and is fixed to a fixed portion (51) of the internal combustion engine (10) by a fixing member (31); An ignition coil (1) for an internal combustion engine, comprising: an elastic member (4) attached to the outside of the case, When a direction parallel to a fixing direction of the flange portion relative to the fixed portion by the fixing member is defined as a vertical direction (Z), in a state where the ignition coil is attached to the internal combustion engine, the flange portion abuts against the fixed portion in the vertical direction, the elastic member has a seal portion (41) that seals between the case and an opening (501) of a spark plug hole (50) of the internal combustion engine in a state in which the elastic member is compressed in the vertical direction between the case and the internal combustion engine when the ignition coil is attached to the internal combustion engine, The flange portion has an insertion portion (33) through which the fixing member is inserted along the fixing direction, When the ignition coil is attached to the internal combustion engine, the distance between the central axis of the spark plug hole and the insertion portion in a direction perpendicular to the central axis (50C) of the spark plug hole is defined as L, and the thickness of the flange portion is defined as T. The distance L is 25 to 40 mm, and the thickness T is 10 to 30 mm. the flange portion and the case are made of synthetic resin, When the outer surface of the case facing the seal portion in the up-down direction is defined as a case sealing surface (21), and the surface of the flange portion that abuts against the fixed portion in the up-down direction is defined as a flange abutment surface (32), An ignition coil for an internal combustion engine, wherein an angle α formed by a first imaginary plane (21S) parallel to the case sealing surface and a second imaginary plane (32S) parallel to the flange abutment surface satisfies 170°≦α≦178°.

2. An ignition coil for an internal combustion engine as described in claim 1, wherein the angle α is 174° or more.

3. An ignition coil for an internal combustion engine as described in claim 2, wherein the angle α is 175°≦α≦177°.

4. An ignition coil for an internal combustion engine as described in any one of claims 1 to 3, wherein the flange portion and the case are made of polybutylene terephthalate or polybutylene succinate.

5. The flange portion has an insertion portion (33) through which the fixing member is inserted along the fixing direction, 2. An ignition coil for an internal combustion engine as described in claim 1, wherein, when the ignition coil is attached to the internal combustion engine, the distance between the center axis of the spark plug hole and the insertion portion in a direction perpendicular to the center axis (50C) of the spark plug hole is L, and the thickness of the flange portion is T, the following formula (1) is satisfied: 176.6-(0.141L ２ -6.1L+101.3) / T １．１ <a< 180.6-(0.141L ２ -6.1L+101.3) / T １．１ ・・・(1)

6. An ignition coil (1) including a case (2) for accommodating components, one flange portion (3) protruding outward from the case, and an elastic member (4) attached to the outside of the case; a fixed portion (51) to which the flange portion is fixed by a fixing member (31); and a plug hole (50) in which a part of the ignition coil is disposed, When a direction parallel to a fixing direction of the flange portion relative to the fixed portion by the fixing member is defined as a vertical direction (Z), the flange portion and the fixed portion abut against each other in the vertical direction, The elastic member has a seal portion (41) that seals the gap between the case and an opening wall portion (502) that forms the opening portion (501) of the spark plug hole in a state where the elastic member is compressed in the up-down direction, When the outer surface of the case facing the seal portion in the vertical direction is defined as a case sealing surface (21) and the upper end surface of the opening wall portion facing the seal portion in the vertical direction is defined as a wall portion sealing surface (503), the case sealing surface and the wall portion sealing surface are each in pressure contact with the seal portion in the vertical direction, The flange portion has an insertion portion (33) through which the fixing member is inserted along the fixing direction, When the ignition coil is attached to the internal combustion engine, the distance between the central axis of the spark plug hole and the insertion portion in a direction perpendicular to the central axis (50C) of the spark plug hole is defined as L, and the thickness of the flange portion is defined as T. The distance L is 25 to 40 mm, and the thickness T is 10 to 30 mm. the flange portion and the case are made of synthetic resin, When a surface of the flange portion that abuts against the fixed portion in the up-down direction is defined as a flange abutment surface (32), and a surface of the fixed portion that abuts against the flange abutment surface is defined as a fixed portion abutment surface (511), an angle α formed between a first imaginary plane (21S) parallel to the case sealing surface and a second imaginary plane (32S) parallel to the flange abutment surface when the flange portion is not fixed to the fixed portion; an angle β formed by a third imaginary plane (503S) parallel to the wall portion sealing surface and a fourth imaginary plane (511S) parallel to the fixed portion abutment surface satisfies the relationship of the following formula (4). ２°≦β－α≦１０° ・・・（４）

7. An internal combustion engine as described in claim 6, wherein the value of β-α is 6° or less.

8. An internal combustion engine as described in claim 7, wherein the value of β-α is 3°≦β-α≦5°.

9. An internal combustion engine as described in any one of claims 6 to 8, wherein the flange portion and the case are made of polybutylene terephthalate or polybutylene succinate.

10. The flange portion has an insertion portion (33) through which the fixing member is inserted along the fixing direction, 7. The internal combustion engine according to claim 6, wherein the following formula (3) is satisfied, where L is a distance between a center axis of the spark plug hole and the insertion portion in a direction perpendicular to the center axis (50C) of the spark plug hole, and T is a thickness of the flange portion. (0.141�) ２ -6.1L+101.3) / T １．１ -0.6<β-α< (0.141L ２ -6.1L+101.3) / T １．１ +3.4 ・・・(3)

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