Ignition coil

Abstract

An ignition coil 2 according to one embodiment comprises a primary coil 16, a secondary coil 18, a rod-shaped resistor 28, and a high-voltage terminal 22 that electrically connects an output of the secondary coil 18 to the resistor 28. The high-voltage terminal 22 includes a cap 22 having an inner peripheral surface 50 and an inner bottom surface 52 and covering an end of the resistor 28. The ignition coil 2 further comprises at least one airway 55 connecting the inner bottom surface 52 and the outside.

Description

[Technical Field]

[0001] The present specification discloses an ignition coil for an internal combustion engine. [Background technology]

[0002] A typical ignition coil includes a primary coil and a secondary coil for generating high voltage, a resistor for reducing electrical noise, and a high-voltage terminal that electrically connects the secondary coil and the resistor. The high voltage from the secondary coil is applied to the resistor via the high-voltage terminal, and is then applied via the resistor to a spark plug installed in the combustion chamber of the high-voltage internal combustion engine. This voltage application causes a spark to be discharged from the spark plug, igniting the fuel in the internal combustion engine.

[0003] Resistors are usually rod-shaped. To ensure a secure connection between the high-voltage terminal and the resistor, a high-voltage terminal with a cap-shaped connection portion with the resistor may be used. An example of an ignition coil having such a high-voltage terminal is disclosed in JP 2019-96788 A. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2019-96788 Summary of the Invention [Problem to be solved by the invention]

[0005] When assembling an ignition coil, the resistor is covered with the cap of the high-voltage terminal. At this time, a large force may be required to insert the cap due to air remaining between the tip of the resistor and the cap. This makes it difficult to attach the resistor to the cap and may cause damage to the top of the resistor. An ignition coil that allows easy connection between the high-voltage terminal and the resistor is desired.

[0006] The present inventors have an intention to provide an ignition coil in which a high voltage terminal and a resistor can be easily connected. [Means for solving the problem]

[0007] An ignition coil according to one embodiment includes a primary coil, a secondary coil, a rod-shaped resistor, and a high-voltage terminal electrically connecting the output of the secondary coil to the resistor. The high-voltage terminal includes a cap having an inner circumferential surface and an inner bottom surface and covering an end of the resistor. The ignition coil further includes at least one air passage connecting the inner bottom surface to the outside. [Effects of the Invention]

[0008] This ignition coil has an air passage connecting the inside bottom surface of the cap to the outside. When the cap is placed on the resistor, any air remaining between the tip of the resistor and the cap is released to the outside through this air passage. With this ignition coil, the cap can be inserted into the resistor without applying a large amount of force. With this ignition coil, the high-voltage terminal and the resistor can be easily connected. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing an ignition coil according to an embodiment. [Figure 2] FIG. 2(a) is a perspective view showing the cap of the high voltage terminal of the ignition coil of FIG. 1 and a resistor, and FIG. 2(b) is an exploded view of FIG. 2(a). [Figure 3] FIG. 3 is a perspective view showing the cap of FIG. 2(a). [Figure 4] 4(a) is a cross-sectional view taken along line IVa-IVa in FIG. 3, and FIG. 4(b) is a cross-sectional view showing a state in which a resistor is inserted into the cap of FIG. 4(a). [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. 4(b). [Figure 6] 6(a) and 6(b) are cross-sectional views showing a cap and a resistor of an ignition coil according to another embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing a cap and a resistor of an ignition coil according to still another embodiment. [Figure 8] FIG. 8(a) is a perspective view showing a cap of an ignition coil according to still another embodiment, and FIG. 8(b) is a bottom view of the cap of FIG. 8(a). [Figure 9] FIG. 9 is a bottom view showing a cap of an ignition coil according to still another embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a cap and a resistor of an ignition coil according to still another embodiment. [Figure 11] FIG. 11 is a bottom view of the cap of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

[0011] FIG. 1 is a cross-sectional view showing an ignition coil 2 according to one embodiment. In FIG. 1, arrow X indicates the front of the ignition coil 2. The opposite is the rear. Arrow Z indicates the upward direction of the ignition coil 2. The opposite is the downward direction. This ignition coil 2 is used for an internal combustion engine. As shown in FIG. 1, this ignition coil 2 includes a coil assembly 4, a connector portion 6, and an output portion 8. In this ignition coil 2, a filler 9 made of a thermosetting resin further fills any internal gaps. FIG. 1 also shows a plug boot 10 and a spring 12 attached to the ignition coil 2.

[0012] The coil assembly 4 includes a case 14, a primary coil 16, a secondary coil 18, an iron core 20, and a high-voltage terminal 22. The primary coil 16, the secondary coil 18, the iron core 20, and the high-voltage terminal 22 are housed in the case 14. The primary coil 16 is formed by winding wire around the iron core 20, and the secondary coil 18 is formed by winding wire around the outside of the primary coil 16. The number of turns of wire in the secondary coil 18 is significantly greater than the number of turns of wire in the primary coil 16. As a result, by changing the current in the primary coil 16, a high voltage is generated in the secondary coil 18.

[0013] The high-voltage terminal 22 is electrically connected to the output terminal of the secondary coil 18, and is also electrically connected to a resistor 28 of the output section 8, which will be described later. The output of the secondary coil 18 is applied to the resistor 28 via the high-voltage terminal 22. The high-voltage terminal 22 includes an arm 24 and a cap 26. One end of the arm 24 is connected to the output terminal of the secondary coil 18, and the other end is connected to the cap 26. The high-voltage terminal 22 is made of a metal with excellent conductivity. Preferred materials for the high-voltage terminal 22 include an aluminum alloy and copper.

[0014] 1, the connector section 6 is located in front of the coil assembly 4. The connector section 6 includes a cylindrical section 30, an external terminal 32, an igniter 34, and a case 36. The case 36 of the connector section 6 is formed integrally with the case 14 of the coil assembly 4.

[0015] The cylindrical portion 30 has a cylindrical shape that is open at the front. A plurality of external terminals 32 are located inside the cylindrical portion 30. Some of the external terminals 32 are connected to an igniter 34. The igniter 34 is located at the rear of the cylindrical portion 30. The igniter 34 is a switch that controls the conduction and interruption of current in the primary coil 16 in response to an external signal. A case 36 covers the periphery of the igniter 34.

[0016] As shown in FIG. 1, the output section 8 is located below the coil assembly 4. The output section 8 has a cylindrical shape extending downward from the coil assembly 4. The output section 8 has a rod-shaped resistor 28 therein. In the embodiment shown in FIG. 1, a plug boot 10 and a spring 12 are attached to the output section 8. The high voltage generated in the secondary coil 18 is input to the resistor 28 via a high-voltage terminal 22 and sent from the resistor 28 to the spring 12. When the ignition coil 2 is attached to the engine, the spring 12 connects to the spark plug.

[0017] FIG. 2(a) is an enlarged perspective view of the resistor 28 and the cap 26 of the high-voltage terminal 22, and FIG. 2(b) is an exploded view of FIG. 2(a). The resistor 28 is rod-shaped. In this embodiment, the resistor 28 is cylindrical. The resistor 28 has an upper portion 28a, a central portion 28b, and a lower portion 28c. The outer diameters of the upper portion 28a and the lower portion 28c are slightly larger than the outer diameter of the central portion 28b. As shown in FIG. 1, when the ignition coil 2 is installed in an internal combustion engine, the lower portion 28c of the resistor 28 contacts the spring 12. Although not shown, the tip of this spring 12 is connected to the spark plug. The upper portion 28a of the resistor 28 is covered with the cap 26. The resistor 28 has appropriate electrical resistance and inductance values to suppress electrical noise (conductive noise and radiative noise) caused by discharge at the spark plug.

[0018] The size of the outer diameter of the resistor 28 may be constant from the top end to the bottom end. The shape of the resistor 28 does not have to be cylindrical. For example, the resistor 28 may be a rectangular pillar.

[0019] 2(a) and 2(b), the cap 26 is cylindrical. A recess 42 is provided on the upper surface of the cap 26. As shown in FIG. 1, the tip of the arm 24 has a downwardly convex bent portion, which fits into the recess 42 of the cap 26. This connects the cap 26 and the arm 24.

[0020] FIG. 3 is a perspective view of the cap 26, viewed from diagonally below. As shown in FIGS. 2(b) and 3, the cap 26 has a cavity 44 therein. An opening 48 of the cavity 44 is provided in the bottom surface 46 of the cap 26. The cavity 44 forms an inner circumferential surface 50 and an inner bottom surface 52 in the cap 26. The inner circumferential surface 50 extends in the vertical direction (the direction in which the resistor 28 extends). The corners between the bottom surface 46 and the inner circumferential surface 50 of the cap 26 are rounded. As shown in FIG. 2(a), the upper portion 28a of the resistor 28 is fitted into the cavity 44. The upper surface 29 of the resistor 28 is in contact with the inner bottom surface 52 of the cap 26. The cap 26 covers one end of the resistor 28. In this embodiment, the cap 26 covers the upper portion 28a of the resistor 28. This electrically connects the high voltage terminal 22 and the resistor 28 .

[0021] FIG. 4(a) is a cross-sectional view taken along line IVa-IVa in FIG. 3. This is a cross-section perpendicular to the extension direction of the resistor 28 when the resistor 28 is not inserted into the cavity 44. In FIG. 4(a), the two-dot chain line represents the inscribed circle Ic of the inner circumferential surface 50. In this cross-section, the inner circumferential surface 50 has a substantially polygonal shape. In this embodiment, the inner circumferential surface 50 has a roughly hexagonal shape. In this cross-section, the inner circumferential surface 50 has six sides. In this embodiment, the inner circumferential surface 50 of the cap 26 and the inscribed circle Ic are in contact at three points.

[0022] FIG. 4(b) is a cross section perpendicular to the direction of extension of the resistor 28 when the resistor 28 is inserted into the cavity 44 and covered by the cap 26. This figure shows the resistor 28 inserted in FIG. 4(a). In this embodiment, the outer peripheral surface 53 of the resistor 28 is formed slightly larger than the inscribed circle Ic shown in FIG. 4(a). Therefore, the inner peripheral surface 50 of the cap 26 in FIG. 4(b) is slightly deformed compared to the inner peripheral surface 50 in FIG. 4(a). As shown in FIG. 4(b), the inner peripheral surface 50 of the cap 26 and the outer peripheral surface 53 of the resistor 28 are in contact at multiple points 54. In this embodiment, the inner peripheral surface 50 of the cap 26 and the outer peripheral surface 53 of the resistor 28 are in contact at three points 54. This contact secures the cap 26 to the resistor 28. In other words, the point 54 where the cap 26 and the resistor 28 contact each other is located at a position where the cap 26 can be fixed to the resistor 28 .

[0023] As shown in FIG. 4( b), in this cross section, the inner circumferential surface 50 has an edge that contacts the outer circumferential surface 53 of the resistor 28 and an edge that does not contact the outer circumferential surface 53 of the resistor 28. Of the edges of the inner circumferential surface 50, the edge that contacts the outer circumferential surface 53 of the resistor 28 is referred to as a contact edge 56. Of the edges of the inner circumferential surface 50, the edge that does not contact the outer circumferential surface 53 of the resistor 28 is referred to as a non-contact edge 58. In this embodiment, the number of contact edges 56 and the number of non-contact edges 58 are three. The contact edge 56 is sandwiched between two non-contact edges 58. The contact edges 56 and the non-contact edges 58 are arranged alternately.

[0024] In this specification, the phrase "the inner surface 50 of the cap 26 and the outer surface 53 of the resistor 28 are in "point contact" means that at the position where the inner surface 50 of the cap 26 and the outer surface 53 of the resistor 28 are in contact, the length of this contact portion measured in the circumferential direction of the resistor 28 is 5% or less of the outer circumferential length of the resistor 28.

[0025] In this embodiment, the three contacting sides 56 are substantially the same length. The three contacting sides 56 may have different lengths. In this embodiment, the three non-contacting sides 58 are substantially the same length. The three non-contacting sides 58 may have different lengths.

[0026] The contacting edge 56 does not have to be sandwiched between two non-contacting edges 58. Multiple contacting edges 56 may be continuous. There may be no non-contacting edge 58. Multiple non-contacting edges 58 may exist between two contacting edges 56.

[0027] As will be described later, the number of points 54 where the inner circumferential surface 50 of the cap 26 and the outer circumferential surface 53 of the resistor 28 contact each other does not have to be 3. The number of points 54 where the inner circumferential surface 50 of the cap 26 and the outer circumferential surface 53 of the resistor 28 contact each other may be 3 or more and 6 or less.

[0028] FIG. 5 is a cross-sectional view taken along line VV in FIG. 4(b). As shown in FIG. 5, gaps 55 exist between the inner circumferential surface 50 and the outer circumferential surface 53 at positions other than the positions where the inner circumferential surface 50 and the outer circumferential surface 53 are in contact at points. These gaps 55 extend from the inner bottom surface 52 to the outside. When the cap 26 is placed on the resistor 28, air between the inner bottom surface 52 and the top surface 29 of the resistor 28 is discharged to the outside through these gaps 55. These gaps 55 are air passages 55 connecting the inner bottom surface 52 and the outside. In this embodiment, the inner circumferential surface 50 and the outer circumferential surface 53 are in contact at three points 54, and thus three air passages 55 are formed between these points 54.

[0029] The effects of this embodiment will be described below.

[0030] In this ignition coil 2, a gap 55 is provided between the inner peripheral surface 50 of the cap 26 and the outer peripheral surface 53 of the resistor 28. When the cap 26 is placed over the resistor 28, air remaining between the top surface 29 of the resistor 28 and the inner bottom surface 52 of the cap 26 is released to the outside through this gap 55. This gap 55 is an air passage 55 connecting the inner bottom surface 52 of the cap 26 with the outside. In this ignition coil 2, the cap 26 can be inserted into the resistor 28 without applying a large force. In this ignition coil 2, the high-voltage terminal 22 and the resistor 28 can be easily connected. Damage to the upper portion 28a of the resistor 28 is prevented when the cap 26 is placed over the resistor 28.

[0031] Generally, the size and shape of the outer diameter of resistors can vary from product to product. For example, in the case of cylindrical resistors, the outer diameter shape can deviate from a perfect circle. This variation can make it difficult to attach the cap to the resistor. In some cases, the cap cannot be placed in the correct position on the resistor, or the top of the resistor can be damaged. There is a demand for an ignition coil that allows easy and reliable connection between the high-voltage terminal and the resistor.

[0032] In this ignition coil 2, in a cross section perpendicular to the direction in which the resistor 28 extends, the outer peripheral surface 53 of the resistor 28 and the inner peripheral surface 50 of the cap 26 of the high-voltage terminal 22 are in contact at three points 54. Because the outer peripheral surface 53 of the resistor 28 and the inner peripheral surface 50 of the cap 26 of the high-voltage terminal 22 are in point contact, the contact area between the resistor 28 and the cap 26 is small. Furthermore, because the outer peripheral surface 53 of the resistor 28 and the inner peripheral surface 50 of the cap 26 of the high-voltage terminal 22 are in point contact, even if the outer diameter or shape of the resistor 28 varies, the area of the portion of the inner peripheral surface 50 that must deform is small. The inner peripheral surface 50 of the cap 26 can be flexibly deformed. Even if the outer diameter or shape of the resistor 28 varies, the ignition coil 2 allows the high-voltage terminal 22 and the resistor 28 to be easily connected. Furthermore, since the inner peripheral surface 50 of the cap 26 contacts the resistor 28 at three points 54, the cap 26 can be stably fixed to the resistor 28. In this ignition coil 2, the high-voltage terminal 22 and the resistor 28 can be reliably connected.

[0033] In this embodiment, the inner circumferential surface 50 has a contact edge 56 and a non-contact edge 58. Compared to when the inner circumferential surface 50 has only the contact edge 56, it is possible to make the inner circumferential surface 50 closer to a circular shape. This makes it possible to reduce the variation in thickness between the inner circumferential surface 50 and the outer circumferential surface of the cap 26 depending on the position. This contributes to realizing excellent strength of the cap 26.

[0034] In this embodiment, the contact side 56 is sandwiched between the non-contact sides 58. The non-contact sides 58 are located on both sides of the contact side 56. This allows the inner circumferential surface 50 of the cap 26 to flexibly deform when the resistor 28 comes into contact with the contact sides 56. In this ignition coil 2, the high-voltage terminal 22 and the resistor 28 can be easily connected.

[0035] As shown in Figures 4(a) and (b), in this embodiment, the corners of the contacting edge 56 and the non-contacting edge 58 are rounded. The symbol C in Figure 4(a) represents the intersection position between the contacting edge 56 and the non-contacting edge 58 when the contacting edge 56 and the non-contacting edge 58 are extended assuming that the corners are not rounded. When the corners of the contacting edge 56 and the non-contacting edge 58 are not rounded, the intersection position is the angle between the contacting edge 56 and the non-contacting edge 58. In this specification, the length of the contacting edge 56 and the non-contacting edge 58 is defined as the distance between the two intersection positions C located at both ends of the edge. The double-headed arrow L1 represents the length of the contacting edge 56. The double-headed arrow L2 represents the length of the non-contacting edge 58 adjacent to the contacting edge 56.

[0036] It is preferable that the length L1 of the contact edge 56 be longer than the length L2 of the non-contact edge 58 adjacent to the contact edge 56. By making the length L1 longer than the length L2, the inner circumferential surface 50 of the cap 26 can flexibly deform when the resistor 28 contacts the contact edge 56. In this ignition coil 2, the high-voltage terminal 22 and the resistor 28 can be easily connected. From this perspective, it is more preferable that the length of each contact edge 56 be longer than the lengths of all the other non-contact edges 58.

[0037] The length L1 is preferably 1.5 times or more the length L2. By making the length L1 1.5 times or more the length L2, the inner circumferential surface 50 of the cap 26 can flexibly deform when the resistor 28 contacts the contact edge 56. In this ignition coil 2, the high-voltage terminal 22 and the resistor 28 can be easily connected. The length L1 is preferably 2.5 times or less the length L2. By making the length L1 2.5 times or less the length L2, the inner circumferential surface 50 can be made to have a shape close to a circle. This reduces the variation in thickness between the inner circumferential surface 50 and the outer circumferential surface 53 of the cap 26 depending on the position. This contributes to achieving excellent strength of the cap 26.

[0038] 6(a) is a cross-sectional view of an ignition coil according to another embodiment, showing a cap 60 of a high-voltage terminal and a resistor 62. This is a cross section perpendicular to the direction in which the resistor 62 extends, at a position where the resistor 62 is covered by the cap 60. This ignition coil is the same as the ignition coil 2 in FIG. 1, except for the cap 60.

[0039] As shown in FIG. 6( a), in this embodiment, the inner peripheral surface 64 of the cap 60 has a substantially octagonal shape. In this embodiment, the inner peripheral surface 64 is configured with eight sides. As shown in FIG. 6( a), the inner peripheral surface 64 of the cap 60 and the outer peripheral surface 66 of the resistor 62 contact each other at multiple points 68. In this embodiment, the inner peripheral surface 64 of the cap 60 and the outer peripheral surface 66 of the resistor 62 contact each other at four points 68. This contact secures the cap 60 to the resistor 62. In this embodiment, the number of contact edges 70 and the number of non-contact edges 72 are four. The contact edge 70 is sandwiched between two non-contact edges 72. The contact edges 70 and the non-contact edges 72 are arranged alternately. A gap 67 exists between the inner peripheral surface 64 and the outer peripheral surface 66. This gap 67 is an air passage 67 connecting the inner bottom surface of the cap 60 to the outside.

[0040] In this ignition coil, a gap 67 is provided between the inner peripheral surface 64 of the cap 60 and the outer peripheral surface 66 of the resistor 62. When the cap 60 is placed on the resistor 62, air remaining between the top surface of the resistor 62 and the inner bottom surface 52 of the cap 60 is released to the outside through this gap 67. In this ignition coil, the cap 60 can be inserted into the resistor 62 without applying a large amount of force. In this ignition coil, the high-voltage terminal and the resistor 62 can be easily connected. Damage to the top of the resistor 62 when the cap 60 is placed on the resistor 62 is prevented.

[0041] In this ignition coil, in a cross section perpendicular to the direction in which the resistor 62 extends, the outer peripheral surface 66 of the resistor 62 and the inner peripheral surface 64 of the cap 60 of the high-voltage terminal are in contact at four points 68. Because the outer peripheral surface 66 of the resistor 62 and the inner peripheral surface 64 of the cap 60 of the high-voltage terminal are in point contact, the contact area between the resistor 62 and the cap 60 is small. Furthermore, because the outer peripheral surface 66 of the resistor 62 and the inner peripheral surface 64 of the cap 60 of the high-voltage terminal are in point contact, the inner peripheral surface 64 of the cap 60 can flexibly deform. Even if the outer diameter or shape of the resistor 62 varies, this ignition coil allows the high-voltage terminal and the resistor 62 to be easily connected. Furthermore, because the inner peripheral surface 64 of the cap 60 is in contact with the resistor 62 at four points 68, the cap 60 can be stably fixed to the resistor 62. This ignition coil allows the high-voltage terminal and the resistor 62 to be reliably connected.

[0042] 6(b) is a cross-sectional view of an ignition coil according to yet another embodiment, showing a cap 80 of a high-voltage terminal and a resistor 82. This is a cross-section perpendicular to the direction in which the resistor 82 extends, at a position where the resistor 82 is covered by the cap 80. This ignition coil is the same as the ignition coil 2 in FIG. 1, except for the cap 80.

[0043] As shown in FIG. 6(b), in this embodiment, the inner peripheral surface 84 of the cap 80 has a substantially dodecagonal shape. In this embodiment, the inner peripheral surface 84 is formed with twelve sides. As shown in FIG. 6(b), in this embodiment, the inner peripheral surface 84 of the cap 80 and the outer peripheral surface 86 of the resistor 82 contact each other at six points 88. This contact secures the cap 80 to the resistor 82. In this embodiment, the number of contact edges 90 and the number of non-contact edges 92 are six. The contact edge 90 is sandwiched between two non-contact edges 92. The contact edges 90 and the non-contact edges 92 are arranged alternately. A gap 87 exists between the inner peripheral surface 84 and the outer peripheral surface 86. This gap 87 is an air passage 87 connecting the inner bottom surface of the cap 80 to the outside.

[0044] Although not shown, in an ignition coil according to yet another embodiment, the inner peripheral surface has a substantially decagonal shape. In this embodiment, the inner peripheral surface is formed of ten sides. In this embodiment, the inner peripheral surface of the cap and the outer peripheral surface of the resistor are in contact at five points. This contact secures the cap to the resistor. In this embodiment, the number of contacting edges and the number of non-contacting edges are five. The contacting edge is sandwiched between two non-contacting edges. The contacting edges and the non-contacting edges are arranged alternately. A gap exists between the inner peripheral surface and the outer peripheral surface. This gap is an air passage connecting the inner bottom surface of the cap to the outside.

[0045] 7 is a cross-sectional view of an ignition coil according to yet another embodiment, showing a cap 100 of a high-voltage terminal and a resistor 102. This is a cross-section perpendicular to the direction in which the resistor 102 extends, at a position where the resistor 102 is covered by the cap 100. This ignition coil is the same as the ignition coil 2 in FIG. 1, except for the cap 100.

[0046] As shown in FIG. 7 , in this embodiment, the inner peripheral surface 104 of the cap 100 and the outer peripheral surface 106 of the resistor 102 are in contact at three points 108. In this embodiment, the number of contact edges 110 and the number of non-contact edges 112 are three. The contact edge 110 is sandwiched between two non-contact edges 112. The contact edges 110 and the non-contact edges 112 are arranged alternately. A gap 107 exists between the inner peripheral surface 104 and the outer peripheral surface 106. As shown in FIG. 7 , in this embodiment, the non-contact edges 112 are curved. The non-contact edges 112 are arc-shaped.

[0047] In this ignition coil, in a cross section perpendicular to the direction in which the resistor 102 extends, the outer peripheral surface 106 of the resistor 102 and the inner peripheral surface 104 of the cap 100 of the high-voltage terminal contact each other at three points 108. Furthermore, in this embodiment, the non-contact edge 112 is arc-shaped, which reduces the thickness between the outer peripheral surface 106 and the inner peripheral surface 104 of the cap 100 at this portion. This allows the inner peripheral surface 104 of the cap 100 to flexibly deform. Even if the outer diameter or shape of the resistor 102 varies, this ignition coil allows the high-voltage terminal and the resistor 102 to be easily connected. Furthermore, because the inner peripheral surface 104 of the cap 100 contacts the resistor 102 at three points 108, the cap 100 can be stably fixed to the resistor 102. This ignition coil allows the high-voltage terminal and the resistor 102 to be reliably connected.

[0048] The shape of the ignition coil cap is not limited to the shape in the above embodiment. For example, the contact edge may be curved. It is sufficient that the outer circumferential surface of the resistor and the inner circumferential surface of the high-voltage terminal cap are in contact at three to six points.

[0049] From the viewpoint of making it easier to connect the high-voltage terminal and the resistor, the number of points at which the outer surface of the resistor and the inner surface of the cap of the high-voltage terminal come into contact is more preferably 5 or less, even more preferably 4 or less, and most preferably 3.

[0050] Figure 8(a) is a perspective view of a cap 120 of a high-voltage terminal of an ignition coil according to yet another embodiment, viewed obliquely from below. Figure 8(b) is a bottom view of the cap 120 of Figure 8(a). This ignition coil is the same as the ignition coil 2 shown in Figure 1, except for the cap 120.

[0051] As shown in FIG. 8(a), the cap 120 has a cavity 122 inside. This cavity 122 forms an inner circumferential surface 124 and an inner bottom surface 126 in the cap 120. The inner circumferential surface 124 extends in the vertical direction (the direction in which the resistor extends). As shown in FIG. 8(a), a groove 128 is formed in the inner circumferential surface 124 of the cap 120. When viewed from the bottom, the inner circumferential surface 124 is substantially circular except for the groove 128. The upper part of the resistor is fitted into this cavity 122. At this time, the inner circumferential surface 124 comes into contact with the outer circumferential surface of the resistor. The cap 120 covers one end of the resistor. This electrically connects the high-voltage terminal and the resistor.

[0052] As shown in FIG. 8(a), in this embodiment, three grooves 128 are provided in the inner circumferential surface 124. As shown in FIG. 8(b), these three grooves 128 are provided at substantially equal intervals. Each groove 128 extends from the end on the inner bottom surface 126 side to the end on the bottom surface 130 side. When the cap 120 is placed on the resistor, air between the inner bottom surface 126 and the upper surface of the resistor is exhausted to the outside through this groove 128. The groove 128 is an air passage 128 connecting the inner bottom surface 126 to the outside.

[0053] This ignition coil has a groove 128 that connects the inner bottom surface 126 of the cap 120 to the outside. When the cap 120 is placed on the resistor, any air remaining between the top surface of the resistor and the inner bottom surface 126 of the cap 120 is released to the outside through this groove 128. With this ignition coil, the cap 120 can be inserted into the resistor without applying a large amount of force. With this ignition coil, the high-voltage terminal and the resistor can be easily connected. Damage to the top of the resistor when the cap 120 is placed on the resistor is prevented.

[0054] In Figure 8(b), the double-headed arrow W indicates the width of the groove 128. From the viewpoint of effectively discharging air between the inner bottom surface 126 and the upper surface of the resistor when the cap 120 is placed on the resistor, the width W is preferably 0.5 mm or more, more preferably 1.0 mm or more, and even more preferably 2.0 mm or more. From the viewpoint of ease of processing, the width W is preferably 5 mm or less.

[0055] In Figure 8(b), the double-headed arrow D indicates the depth of the groove 128. From the viewpoint of effectively discharging air between the inner bottom surface 126 and the upper surface of the resistor when the cap 120 is placed on the resistor, the depth D is preferably 0.5 mm or more, more preferably 1.0 mm or more, and even more preferably 1.2 mm or more. From the viewpoint of ease of processing, the depth D is preferably 3 mm or less.

[0056] The three grooves 128 are preferably provided at equal intervals. In this way, when the cap 120 is placed on the resistor, air between the inner bottom surface 126 and the upper surface of the resistor can be uniformly discharged through each groove 128. In this ignition coil, the high-voltage terminal and the resistor can be easily connected.

[0057] Figure 9 is a bottom view showing a cap 140 of a high-voltage terminal of an ignition coil according to yet another embodiment. In this ignition coil, grooves 144 are formed in an inner peripheral surface 142 of the cap 140. In this embodiment, two grooves 144 are formed. This ignition coil is the same as the ignition coil shown in Figure 8 except for the number of grooves 144.

[0058] In this embodiment, the two grooves 144 are provided at opposing positions. In this way, when the cap 140 is placed on the resistor, air between the inner bottom surface 146 and the upper surface of the resistor can be uniformly discharged from each groove 144. In this ignition coil, the high-voltage terminal and the resistor can be easily connected.

[0059] The number of grooves 144 may be four or more, or may be one. From the viewpoint of effectively discharging air remaining between the top surface of the resistor and the inner bottom surface 146 of the cap 140, the number of grooves 144 is preferably two or more. From the viewpoint of ease of processing, the number of grooves 144 is preferably six or less, more preferably five or less, and even more preferably four or less.

[0060] Fig. 10 is a cross-sectional view of a cap 150 of a high-voltage terminal and a resistor 152 of an ignition coil according to yet another embodiment. Fig. 10 shows a cross section cut along a plane parallel to the direction in which the high-voltage terminal extends. Fig. 11 is a bottom view showing the cap 150 of Fig. 10. This ignition coil is the same as the ignition coil 2 shown in Fig. 1, except for the cap 150.

[0061] As shown in FIG. 10 , the cap 150 has a hole 158 extending from the inner bottom surface 154 to the top surface 156. As shown in FIG. 10 , in this embodiment, one opening of the hole 158 is located at the bottom of a recess 160 in the top surface 156. As shown in FIG. 11 , the other opening of the hole 158 is located in the center of the inner bottom surface 154. When viewed from the bottom, the inner circumferential surface 155 of the cap 150 is substantially circular. The inner circumferential surface 155 contacts the outer circumferential surface of the resistor. When the cap 150 is placed over the resistor 152, air between the inner bottom surface 154 and the top surface 162 of the resistor 152 is exhausted to the outside through the hole 158. The hole 158 is an air passage 158 connecting the inner bottom surface 154 to the outside.

[0062] In this ignition coil, a hole 158 is provided that connects the inner bottom surface 154 of the cap 150 to the outside. When the cap 150 is placed over the resistor 152, any air remaining between the upper surface 162 of the resistor 152 and the inner bottom surface 154 of the cap 150 is released to the outside through this hole 158. In this ignition coil, the cap 150 can be inserted into the resistor 152 without applying a large amount of force. In this ignition coil, the high-voltage terminal and the resistor 152 can be easily connected. Damage to the upper part of the resistor 152 when the cap 150 is placed over the resistor 152 is prevented.

[0063] The opening of hole 158 is preferably provided in the center of inner bottom surface 154. In this way, when cap 150 is placed over resistor 152, air between inner bottom surface 154 and upper surface 162 of resistor 152 can be uniformly discharged through hole 158. In this ignition coil, the high-voltage terminal and resistor 152 can be easily connected.

[0064] In Figure 11, the double-headed arrow E indicates the inner diameter of hole 158. The inner diameter E is preferably 0.5 mm or more. By making the inner diameter E 0.5 mm or more, air remaining between top surface 162 of resistor 152 and inner bottom surface 154 of cap 150 is effectively released to the outside through hole 158. From this perspective, the inner diameter E is more preferably 1.0 mm or more.

[0065] 1, the bent portion of the arm fits into a recess 160 in the top surface 156 of the cap 150. The bent portion comes into contact with the surface of the recess 160, ensuring a good contact area between the arm and the cap 150. If the inner diameter E of the hole 158 exceeds 2.0 mm, the corner of the bent portion will easily fit into the opening of the hole 158, potentially reducing the contact area. From the perspective of ensuring a good contact area between the arm and the cap 150, the inner diameter E is preferably 2.0 mm or less.

[0066] The above describes, as embodiments of an ignition coil having an air passage, an ignition coil in which the outer peripheral surface of the resistor and the inner peripheral surface of the cap are in point contact, an ignition coil in which the inner peripheral surface of the cap has a groove, and an ignition coil in which the cap has a hole extending from the inner bottom surface to the top surface. An ignition coil may have more than one of these features. For example, in an ignition coil according to yet another embodiment, the outer peripheral surface of the resistor and the inner peripheral surface of the cap may be in point contact, and the cap may have a hole extending from the inner bottom surface to the top surface. In yet another embodiment, the ignition coil may be in which the inner peripheral surface of the cap has a groove, and the cap may have a hole extending from the inner bottom surface to the top surface.

[0067] As described above, in this embodiment, an ignition coil is obtained in which the high voltage terminal and the resistor can be easily connected. This clearly shows the superiority of this embodiment.

[0068] [Disclosure items] The following items are disclosures of preferred embodiments.

[0069] [Item 1] a primary coil, a secondary coil, a rod-shaped resistor, and a high-voltage terminal that electrically connects the output of the secondary coil to the resistor; the high-voltage terminal includes a cap having an inner circumferential surface and an inner bottom surface and covering an end of the resistor; An ignition coil for an internal combustion engine, further comprising at least one air passage connecting the inner bottom surface with the outside.

[0070] [Item 2] In a cross section perpendicular to the direction in which the resistor extends at the position covered by the cap, the outer circumferential surface and the inner circumferential surface of the resistor are in contact with each other at three to six points, 2. The ignition coil according to claim 1, wherein one of the air passages is a gap between the outer circumferential surface and the inner circumferential surface.

[0071] [Item 3] 3. The ignition coil according to item 2, wherein the outer peripheral surface of the resistor and the inner peripheral surface of the cap are in contact with each other at three points in the cross section.

[0072] [Item 4] 4. The ignition coil according to item 2 or 3, wherein in the cross section, the inner circumferential surface has a plurality of contact sides that contact the resistor at points and a plurality of non-contact sides that do not contact the resistor, and each contact side is sandwiched between two non-contact sides.

[0073] [Item 5] 5. The ignition coil according to item 4, wherein the length of each of the contacting sides is longer than the length of the adjacent non-contacting sides.

[0074] [Item 6] 6. The ignition coil according to item 5, wherein the length of each contact side is 1.5 to 2.5 times the length of the adjacent non-contact line side.

[0075] [Item 7] 7. The ignition coil according to any one of items 2 to 6, wherein in the cross section, the inner circumferential surface of the resistor is polygonal.

[0076] [Item 8] 8. The ignition coil according to any one of items 1 to 7, wherein a groove is provided on the inner circumferential surface, extending from an end on the inner bottom surface side, and one of the air passages is the groove.

[0077] [Item 9] Item 9. An ignition coil according to item 8, wherein the number of grooves is two, and one groove and the other groove are provided at a position opposite each other.

[0078] [Item 10] 9. The ignition coil according to item 8, wherein the number of grooves is three, and the grooves are equally spaced.

[0079] [Item 11] 11. The ignition coil of any one of items 1 to 10, wherein the cap has a hole extending from the inner bottom surface to the top surface of the cap, and one of the air passages is the hole.

[0080] [Item 12] Item 12. An ignition coil according to item 11, wherein the opening of the hole is located at the center of the bottom surface.

[0081] [Item 13] Item 13. The ignition coil according to item 11 or 12, wherein the inner diameter of the hole is 0.5 mm or more and 2.0 mm or less. [Industrial Applicability]

[0082] The ignition coil described above is used in various internal combustion engines. [Explanation of symbols]

[0083] 2. Ignition coil 4. Coil assembly 6 Connector part 8. Output section 10. Plug boots 12. Spring 14, 36... Case 16 Primary coil 18 Secondary coil 20···Iron core 22 High voltage terminal 24...Arm 26, 60, 80, 100, 120, 140, 150... High voltage terminal caps 28, 62, 82, 102, 152...Resistor 29, 162... Top of resistor 30...Cylinder part 32 External terminal 34. Igniter 42, 160... recess 44, 122...Cavity 46, 130... bottom 48...Aperture 50, 64, 84, 104, 124, 142, 155...Inner surface of cap 52, 126, 146, 154...Inner bottom of cap 53, 66, 86, 106... Resistor outer surface 54, 68, 88, 108...Touch points 55, 67, 87, 107... Gap (airway) 56, 70, 90, 110... Contact side 58, 72, 92, 112... Non-contacting edges 128, 144··· groove (airway) 156···Top of cap 158...hole

Claims

1. a primary coil, a secondary coil, a rod-shaped resistor, and a high-voltage terminal that electrically connects the output of the secondary coil to the resistor; the high-voltage terminal includes a cap having an inner circumferential surface and an inner bottom surface and covering an end of the resistor; An ignition coil for an internal combustion engine, further comprising at least one air passage connecting the inner bottom surface with the outside.

2. In a cross section perpendicular to the direction in which the resistor extends at the position covered by the cap, the outer circumferential surface and the inner circumferential surface of the resistor are in contact with each other at three to six points, The ignition coil according to claim 1 , wherein one of the air passages is a gap between the outer circumferential surface and the inner circumferential surface.

3. 3. The ignition coil according to claim 2, wherein the outer peripheral surface of the resistor and the inner peripheral surface of the cap are in contact with each other at three points in the cross section.

4. 4. The ignition coil according to claim 2, wherein in the cross section, the inner circumferential surface has a plurality of contact edges that make point contact with the resistor and a plurality of non-contact edges that do not make contact with the resistor, and each contact edge is sandwiched between two non-contact edges.

5. The ignition coil according to claim 4 , wherein the length of each of the contacting sides is longer than the length of the adjacent non-contacting sides.

6. 6. The ignition coil according to claim 5, wherein the length of each of the contacting wire sides is 1.5 to 2.5 times the length of the adjacent non-contacting wire side.

7. 7. The ignition coil according to claim 2, wherein the inner circumferential surface of the cap is polygonal in cross section.

8. 8. The ignition coil according to claim 1, wherein a groove is provided on the inner circumferential surface, extending from an end on the inner bottom surface side, and one of the air passages is the groove.

9. 9. The ignition coil according to claim 8, wherein the number of said grooves is two, and one groove and the other groove are provided at positions opposite each other.

10. 9. The ignition coil of claim 8, wherein the number of grooves is three and the grooves are equally spaced.

11. 11. An ignition coil as claimed in any one of claims 1 to 10, wherein the cap has a hole extending from the inner bottom surface to the top surface of the cap, and one of the air passages is the hole.

12. 12. The ignition coil of claim 11, wherein the hole opening is located at the center of the bottom surface.

13. 13. The ignition coil according to claim 11 or 12, wherein the inner diameter of the hole is 0.5 mm or more and 2.0 mm or less.

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