Ignition coil for internal combustion engine

Abstract

To provide an ignition coil for an internal combustion engine that can improve the heat dissipation of an igniter while maintaining the insulation properties of a primary coil and a secondary coil.SOLUTION: An igniter 43 is arranged to face the low-voltage end face core portion 423 of an outer core 42. A coil case 5 is partitioned into a coil housing portion 511 housing at least a part of a primary coil, a secondary coil, and an inner core 41 and an igniter housing portion 512 housing at least a part of the igniter 43 by the low-voltage end surface core portion 423. A first filling material 71 fills a gap in the coil housing portion 511. A second filling material 72 is made of a material having a higher thermal conductivity than the first filling material 71 and fills a gap inside the igniter housing portion 512.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an ignition coil for an internal combustion engine. [Background technology]

[0002] An ignition coil for an internal combustion engine is used to ignite a mixture of fuel and combustion air in a combustion chamber of the engine as an internal combustion engine. The ignition coil includes a primary coil, a secondary coil arranged coaxially around the outer periphery of the primary coil and magnetically coupled to the primary coil, an inner core and an outer core for passing magnetic flux generated by the primary coil and secondary coil, and an igniter for energizing the primary coil. Each of the components, such as the primary coil, the secondary coil, the inner core, the outer core, and the igniter, is arranged in a coil case, and the gaps in the coil case are filled with a resin material that insulates and fixes each of the components.

[0003] For example, in the ignition coil for an internal combustion engine described in Patent Document 1, an opening is formed in a sheet portion provided in a coil case, and a control board constituting an igniter is disposed outside the sheet portion. The control board is molded from a polymer material with high thermal conductivity, and a part of the control board is open through the opening to a chamber of the coil case in which the coil and the like are disposed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2020 / 031020 publication Summary of the Invention [Problem to be solved by the invention]

[0005] In an ignition coil, a resin material with excellent insulating properties is filled in the coil case to protect the ignition coil from dielectric breakdown. On the other hand, in order to effectively dissipate heat from the igniter, it is desired to select a resin material with excellent heat dissipation properties. However, in conventional ignition coils including the one in Patent Document 1, no special ingenuity is given to the type of resin material filled in the coil case.

[0006] 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 improve the heat dissipation performance of the igniter while maintaining the insulation of the primary coil and secondary coil. [Means for solving the problem]

[0007] One aspect of the present invention is A primary coil (2) having a central axis parallel to the axial direction (L); A secondary coil (3) arranged concentrically outside the primary coil; an inner core (41) disposed inside the primary coil; an outer core (42) having a rectangular ring shape including a pair of side core portions (421) arranged parallel to the axial direction outside a side surface (411) of the inner core, and a pair of end surface core portions (422, 423) arranged parallel to a width direction (W) perpendicular to the axial direction outside an end surface (412) of the inner core; an igniter (43) disposed opposite a low-voltage side end surface core portion (423) of the pair of end surface core portions; a coil case (5) partitioned by the low-voltage side end surface core portion into a coil accommodating portion (511) in which at least a portion of the primary coil, the secondary coil, and the inner core are accommodated, and an igniter accommodating portion (512) in which at least a portion of the igniter is accommodated; A first filling material (71) filled in the gap in the coil accommodating portion; a second filling material (72) that is filled in the gap in the igniter accommodating portion and has a higher thermal conductivity than the first filling material; picture, The first filling material and the second filling material contain a base resin made of a thermosetting resin and a filler made of a metal oxide, The content of the filler in the first filling material and the second filling material is 30% by volume or more and 60% by volume or less, At least one of the type of the filler and the content of the filler in the first filling material and the second filling material is different, so that the thermal conductivity of the second filling material is higher than that of the first filling material and the dielectric constant of the first filling material is lower than that of the second filling material; the filler constituting the second filling material is made of a metal oxide having a higher thermal conductivity than the filler constituting the first filling material; The filler constituting the first filling material is made of a metal oxide having a lower dielectric constant than the filler constituting the second filling material. It is found in an ignition coil (1) for an internal combustion engine. Another aspect of the present invention is A primary coil (2) having a central axis parallel to the axial direction (L); A secondary coil (3) arranged concentrically outside the primary coil; an inner core (41) disposed inside the primary coil; an outer core (42) having a rectangular ring shape including a pair of side core portions (421) arranged parallel to the axial direction outside a side surface (411) of the inner core, and a pair of end surface core portions (422, 423) arranged parallel to a width direction (W) perpendicular to the axial direction outside an end surface (412) of the inner core; an igniter (43) disposed opposite a low-voltage side end surface core portion (423) of the pair of end surface core portions; a coil case (5) partitioned by the low-voltage side end surface core portion into a coil accommodating portion (511) in which at least a portion of the primary coil, the secondary coil, and the inner core are accommodated, and an igniter accommodating portion (512) in which at least a portion of the igniter is accommodated; A first filling material (71) filled in the gap in the coil accommodating portion; a second filling material (72) that is filled in the gap in the igniter housing and has a higher thermal conductivity than the first filling material, The igniter is in an ignition coil for an internal combustion engine, which is pressed by projections (55A, 55B) projecting from the inside of the coil case and contacts the low-voltage side end surface core portion. Yet another aspect of the present invention is A primary coil (2) having a central axis parallel to the axial direction (L); A secondary coil (3) arranged concentrically outside the primary coil; an inner core (41) disposed inside the primary coil; an outer core (42) having a rectangular ring shape including a pair of side core portions (421) arranged parallel to the axial direction outside a side surface (411) of the inner core, and a pair of end surface core portions (422, 423) arranged parallel to a width direction (W) perpendicular to the axial direction outside an end surface (412) of the inner core; an igniter (43) disposed opposite a low-voltage side end surface core portion (423) of the pair of end surface core portions; a coil case (5) partitioned by the low-voltage side end surface core portion into a coil accommodating portion (511) in which at least a portion of the primary coil, the secondary coil, and the inner core are accommodated, and an igniter accommodating portion (512) in which at least a portion of the igniter is accommodated; A first filling material (71) filled in the gap in the coil accommodating portion; a second filling material (72) that is filled in the gap in the igniter housing and has a higher thermal conductivity than the first filling material, The present invention relates to an ignition coil for an internal combustion engine, in which a rib (59A) or groove (59B) is provided on at least one of the bottom (52) and side wall (54) of the coil case, which contacts the low-voltage side end face core portion and closes the gap between the coil case and the low-voltage side end face core portion. Effect of the Invention

[0008] In the ignition coil for an internal combustion engine according to the embodiment, a coil housing portion and an igniter housing portion are provided in the coil case, and different types of filling materials are filled in the coil housing portion and the igniter housing portion. Specifically, the coil housing portion and the igniter housing portion are partitioned by the low-voltage side end face core portion of the outer core, and the gap in the igniter housing portion is filled with a second filling material having a higher thermal conductivity than the first filling material filled in the gap in the coil housing portion. With this configuration, the second filling material different from the first filling material can be used to improve the heat dissipation from the igniter to the outer core. In addition, the first filling material can be, for example, a material having better insulating properties than the second filling material.

[0009] Therefore, according to the ignition coil for an internal combustion engine of the above aspect, it is possible to improve the heat dissipation performance of the igniter while maintaining the insulation performance of the primary coil and the secondary coil.

[0010] In addition, the symbols in parentheses for each component shown in one aspect of the present invention indicate a correspondence with the symbols in the figures in the embodiment, but do not limit each component to only the contents of the embodiment. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram showing a cross section of an entire ignition coil according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram showing an enlarged cross-sectional view of a part of FIG. 1 according to the first embodiment. [Diagram 3] FIG. 3 is an explanatory diagram showing a part of the ignition coil according to the first embodiment, taken along line III-III in FIG. 2, with the first filling material and the second filling material omitted. [Figure 4] FIG. 4 is an explanatory diagram showing an enlarged cross section of a part of FIG. 1 with the first filling material omitted according to the first embodiment. [Diagram 5] FIG. 5 is an explanatory diagram showing a part of the ignition coil according to the first embodiment by a cross section taken along line III-III in FIG. 2, with the primary coil, the secondary coil, and the first filler material omitted. [Figure 6] FIG. 6 is a graph showing the relationship between the filler content and the thermal conductivity for the first filling material and the second filling material according to the first embodiment. [Figure 7] FIG. 7 is a graph showing the relationship between the filler content and the viscosity of the first filling material and the second filling material according to the first embodiment. [Figure 8] FIG. 8 is a graph showing the relationship between the thermal conductivity and the relative dielectric constant for the first filling material and the second filling material according to the first embodiment. [Figure 9] FIG. 9 is an explanatory diagram showing an enlarged cross-sectional view of a part of another ignition coil according to the first embodiment. [Figure 10] FIG. 10 is an explanatory diagram showing an enlarged cross section of a part of an ignition coil according to the second embodiment. [Figure 11] FIG. 11 is an explanatory diagram showing an enlarged cross section of a part of the ignition coil according to the second embodiment, which cross section corresponds to the cross section taken along line III-III in FIG. [Figure 12] FIG. 12 is an explanatory diagram showing an enlarged cross-sectional view of a part of another ignition coil according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A preferred embodiment of the above-mentioned ignition coil for an internal combustion engine will be described with reference to the drawings. <Embodiment 1> As shown in Figs. 1 to 3, the ignition coil 1 for an internal combustion engine includes a primary coil 2, a secondary coil 3, an inner core 41, an outer core 42, an igniter 43, a coil case 5, a first filling material 71, and a second filling material 72. The primary coil 2 is formed in a coil shape around a central axis parallel to the axial direction L. The secondary coil 3 is formed in a coil shape around a central axis parallel to the axial direction L, and is arranged concentrically outside the primary coil 2. The inner core 41 is arranged inside the primary coil 2. The outer core 42 has a rectangular ring shape formed by a pair of side core parts 421 arranged in parallel to the axial direction L outside the side surface 411 of the inner core 41, and a pair of end surface core parts 422, 423 arranged in parallel to the width direction W perpendicular to the axial direction L outside the end surface 412 of the inner core 41.

[0013] The igniter 43 is disposed facing the low-voltage side end surface core part 423, which is one of the pair of end surface core parts 422, 423. The coil case 5 is partitioned by the low-voltage side end surface core part 423 into a coil accommodating part 511 in which at least a part of the primary coil 2, the secondary coil 3, and the inner core 41 is accommodated, and an igniter accommodating part 512 in which at least a part of the igniter 43 is accommodated. The first filling material 71 is filled in the gap in the coil accommodating part 511. The second filling material 72 is made of a material having a higher thermal conductivity than the first filling material 71, and is filled in the gap in the igniter accommodating part 512.

[0014] The ignition coil 1 for an internal combustion engine according to this embodiment will be described in detail below. (Ignition coil 1) As shown in FIG. 1, an ignition coil 1 is disposed in a cylinder head cover 8 in an engine as an internal combustion engine of a vehicle, and is used to generate a spark discharge in a combustion chamber of the cylinder head from a spark plug disposed in the cylinder head. The ignition coil 1 of this embodiment is for mounting on a vehicle. The ignition coil 1 has a coil body 11 constituted by a primary coil 2, a secondary coil 3, a coil case 5, etc., and a joint portion 12 protruding from the coil body 11 for electrically connecting the secondary coil 3 and the spark plug via a high-voltage terminal 45 and a spring 46. The coil body 11 is disposed in the cylinder head cover 8, and the joint portion 12 is disposed in a plug hole 81 of the cylinder head cover 8.

[0015] (Axial direction L, mounting direction D, width direction W) As shown in Figs. 1 to 5, the axial direction L refers to the direction in which the central axes of the primary coil 2 and the secondary coil 3 extend. In the axial direction L, the side where a high voltage is generated in the secondary coil 3 is referred to as the high-voltage side L1, and the opposite side of the high-voltage side L1 is referred to as the low-voltage side L2. The mounting direction D refers to the direction perpendicular to the axial direction L, in which the bottom 52 and the opening 53 of the coil case 5 are aligned. In the mounting direction D of the coil case 5, the side where the bottom 52 is located and where the spark plug is arranged is referred to as the bottom side D1, and the side opposite the bottom side D1 and where the opening 53 is located is referred to as the opening side D2. The direction perpendicular to both the axial direction L and the mounting direction D is referred to as the width direction W.

[0016] (Primary coil 2) 1, the primary coil 2 is formed by winding a magnet wire as a winding around the outer circumferential surface of the square tube portion 22 of the primary spool 21. The primary coil 2 is formed of a conductive conductor and an insulating coating layer provided around the conductor. The primary coil 2 is repeatedly energized and cut off by a switching element of an igniter 43 that receives a command from the engine control device.

[0017] (primary spool 21) As shown in FIG. 1, the primary spool 21 is formed by a molding of a thermoplastic resin. The primary spool 21 has a cylindrical shape with the primary coil 2 wound around it. In this embodiment, the primary spool 21 and a connector section 24 for electrically connecting the igniter 43 to an external engine control device are integrally molded as a spool molding 210. The spool molding 210 has a square cylindrical angular tube section 22 through which the inner core 41 is inserted on the inner periphery and the primary coil 2 is wound on the outer periphery, a connector section 24, and a relay section 23 that relays the angular tube section 22 and the connector section 24. The connector section 24 may be formed as a connector separately from the angular tube section 22 of the primary spool 21.

[0018] The connector portion 24 is provided with a connector conductor 25 by insert molding, the connector conductor 25 being connected to the igniter conductor 431 of the igniter 43. The connector portion 24 is formed in a state of protruding to the outside of the coil case 5.

[0019] (Secondary coil 3) 1, the secondary coil 3 is disposed coaxially with the primary coil 2 on the outside of the primary coil 2. The secondary coil 3 is formed by winding a magnet wire as a winding around the outer circumferential surface of the rectangular tube portion 32 of the secondary spool 31. The secondary coil 3 is formed of a conductive conductor and an insulating coating layer provided around the conductor.

[0020] The secondary coil 3 has a smaller winding than the primary coil 2, and the number of windings is greater than that of the primary coil 2. The secondary coil 3 generates an induced electromotive force by mutual induction when the current to the primary coil 2 is cut off. The central axes of the primary coil 2 and the secondary coil 3 are oriented in a direction perpendicular to the opening 53 of the coil case 5. The low-voltage side L2 end of the secondary coil 3 winding is connected to the ground or power supply terminal of the igniter 43. The high-voltage side L1 end of the secondary coil 3 winding is connected to a high-voltage terminal 45 that is connected to the center electrode of the spark plug.

[0021] (Secondary spool 31) 1, the secondary spool 31 is formed by molding a thermoplastic resin. The secondary spool 31 has a rectangular cylindrical portion 32 and a plurality of flange portions 33 that protrude outwardly around the entire circumference of the rectangular cylindrical portion 32 at a plurality of locations in the axial direction L. The flange portions 33 divide the outer circumference of the rectangular cylindrical portion 32 into a plurality of recesses (slots) aligned in the axial direction L.

[0022] (Inner core 41) As shown in Figs. 1 to 3, an inner core 41 is disposed inside (on the inner circumferential side of) the primary coil 2, for passing magnetic flux generated by the primary coil 2 and the secondary coil 3. The inner core 41 in this embodiment is formed by laminating a plurality of plate-shaped electromagnetic steel sheets made of a soft magnetic material. The inner core 41 is formed in a rectangular parallelepiped shape, and has four side faces 411 parallel to the axial direction L and two end faces 412 perpendicular to the axial direction L. The inner core 41 may be formed by compression molding powder made of a soft magnetic material.

[0023] (Outer core 42) As shown in Figs. 1 to 3, an outer core 42 is disposed on the outside (outer periphery) of the secondary coil 3 for passing magnetic flux generated by the primary coil 2 and the secondary coil 3. The outer core 42 in this embodiment is formed by laminating a plurality of plate-shaped electromagnetic steel sheets made of a soft magnetic material. The outer core 42 is formed in a quadrangular ring shape with the inner core 41 disposed on the inside in a cross section seen from the mounting direction D. The outer core 42 may be formed by compression molding powder made of a soft magnetic material.

[0024] The pair of side core parts 421 of the outer core 42 are located outside the secondary coil 3 and the secondary spool 31 on both sides in the width direction W. The pair of end core parts 422, 423 of the outer core 42 are located on both sides L1, L2 in the axial direction L of the secondary coil 3 and the secondary spool 31 and are connected to the pair of side core parts 421. The igniter 43 is disposed facing the low-voltage side end core part 423 located on the low-voltage side L2 in the axial direction L of the secondary coil 3 in the outer core 42. There is almost no gap between the igniter 43 and the low-voltage side end core part 423, and almost no second filling material 72 is disposed. There may be a gap of 0.1 to 0.5 mm between the igniter 43 and the low-voltage side end core part 423, which is filled with the second filling material 72.

[0025] A closed magnetic path through which magnetic flux passes is formed by the inner core 41 and the outer core 42. A permanent magnet 44 is disposed between the inner core 41 and the outer core 42 to prevent magnetic saturation.

[0026] (Core cover 6) 1, a core cover 6 is provided on at least the inside of the high-voltage side end face core portion 422 of the outer core 42 and on each surface of the bottom side D1 and the opening side D2 in the mounting direction D. The core cover 6 is used to reduce the gap between the secondary coil 3 and the outer core 42 to reduce the filling amount of the first filling material 71 and to more appropriately ensure insulation between the secondary coil 3 and the outer core 42.

[0027] (Igniter 43) As shown in Figs. 1 to 3, the ignition coil 1 includes an igniter 43 for repeatedly energizing and cutting off the primary coil 2 upon receiving a command from an engine control device. The igniter 43 is disposed facing the low-voltage side L2 of the low-voltage side end surface core portion 423 of the outer core 42 in the axial direction L of the primary coil 2 and the secondary coil 3. The igniter 43 is disposed between the connector portion 24 attached to the coil case 5 and the low-voltage side end surface core portion 423. The igniter 43 includes a circuit forming portion provided with electronic components such as switching elements forming a switching circuit, a heat sink integrated with the circuit forming portion, a molded resin covering the circuit forming portion and the heat sink, and an igniter conductor 431 drawn from the circuit forming portion to the outside of the molded resin.

[0028] The multiple igniter conductors 431 and the multiple connector conductors 25 are joined to each other by soldering, welding, etc. In addition, the multiple igniter conductors 431 are joined to the conductors connected to both ends of the winding of the primary coil 2 and to the conductor connected to the end of the low-voltage side L2 of the winding of the secondary coil 3 by soldering, welding, etc.

[0029] As shown in FIG. 2, the end face 432 of the opening side D2 of the igniter 43 in the mounting direction D is located closer to the bottom side D1 in the mounting direction D than the end face 424 of the opening side D2 of the low-voltage side end face core part 423 of the outer core 42. In other words, the distance h1 from the opening 53 of the coil case 5 to the end face 432 of the opening side D2 of the igniter 43 in the mounting direction D is greater than the distance h2 from the opening 53 of the coil case 5 to the end face 424 of the opening side D2 of the low-voltage side end face core part 423 in the mounting direction D. With this configuration, the end face 432 of the opening side D2 of the igniter 43 in the mounting direction D can be covered with the second filling material 72. Therefore, heat dissipation from the igniter 43 to the outer core 42 can be made more effective.

[0030] (Coil case 5) As shown in Fig. 1, the coil case 5 is formed as a molded product of thermoplastic resin. The coil case 5 has a housing portion 51 that houses the primary coil 2, the secondary coil 3, the inner core 41, the outer core 42, the igniter 43, etc. The coil case 5 has an opening 53 for disposing a coil assembly in which the primary coil 2, the primary spool 21, the secondary coil 3, the secondary spool 31, the inner core 41, the outer core 42, the igniter 43, etc. are assembled, in the housing portion 51. The coil case 5 has a bottom portion 52 located on the side of the joint portion 12, a side wall portion 54 standing from the periphery of the bottom portion 52, and an opening portion 53 located on the opening side D2 in the mounting direction D of the side wall portion 54.

[0031] Here, Fig. 2 shows the ignition coil 1 in a state where the first filler material 71 and the second filler material 72 are filled in the coil case 5, and Fig. 3 shows the ignition coil 1 in a state where the first filler material 71 and the second filler material 72 are not filled in the coil case 5. Figs. 4 and 5 show the ignition coil 1 in a state where the coil case 5 is not filled with the first filler material 71.

[0032] The primary coil 2, the secondary coil 3, and a part of the core cover 6 are located on the opening side D2 further than the end face of the opening side D2 in the mounting direction D of the outer core 42. Strictly speaking, the coil accommodating portion 511 separated from the igniter accommodating portion 512 by the low-voltage side end face core portion 423 is a portion located on the bottom side D1 further than the end face of the opening side D2 in the mounting direction D of the outer core 42. However, in this embodiment, the coil accommodating portion 511 also includes a portion on the opening side D2 further than the end face of the opening side D2 in the mounting direction D of the outer core 42.

[0033] In this embodiment, as shown in Fig. 2 and Fig. 3, the low-voltage side end surface core portion 423 of the outer core 42 forms an igniter accommodating portion 512 in a part of the accommodating portion 51 of the coil case 5 on the low-voltage side L2 in the axial direction L of the low-voltage side end surface core portion 423. The coil accommodating portion 511 is formed as a portion of the accommodating portion 51 excluding the igniter accommodating portion 512. Fig. 3 and Fig. 5 show the ignition coil 1 in a state where the first filling material 71 and the second filling material 72 are not filled, as viewed from the opening side D2 in the mounting direction D. Also, in Fig. 5, the primary coil 2 and the secondary coil 3 are omitted.

[0034] The igniter accommodating section 512 is formed by the low-voltage side end face core portion 423 contacting the inner surface of the bottom portion 52 of the coil case 5 and the inner surfaces of the side wall portions 54 of the coil case 5 to partition the accommodating section 51. More specifically, the igniter accommodating section 512 is formed by the low-voltage side end face core portion 423 of the outer core 42 and the ends of the low-voltage side L2 in the axial direction L of the pair of side core portions 421 contacting the inner surface of the bottom portion 52 of the coil case 5 and the inner surfaces of the side wall portions 54 of the coil case 5.

[0035] 2, the igniter accommodating portion 512 is formed on the low-voltage side L2 in the axial direction L from the low-voltage side end face core portion 423, as a portion on the bottom side D1 from the end face 424 of the opening side D2 of the low-voltage side end face core portion 423. The coil accommodating portion 511 is formed on the high-voltage side L1 in the axial direction L with respect to the igniter accommodating portion 512 and on the opening side D2 in the mounting direction D with respect to the igniter accommodating portion 512.

[0036] 2 and 3, a portion of the side wall 54 on the low-voltage side L2 in the axial direction L of the coil case 5 is formed by a connector wall 241 of the connector portion 24. The coil case 5 is formed with an attachment notch 56 into which the connector portion 24 of the spool molded body 210 is attached. Clamping portions 242 that clamp the edges of the attachment notch 56 from both sides are formed on the end of the connector wall 241 on the bottom side D1 in the attachment direction D and on both ends in the width direction W.

[0037] 1, a tower portion 57 constituting the joint portion 12 is formed on the bottom portion 52 located on the bottom side D1 in the mounting direction D of the coil case 5. A seal rubber 58 for sealing between the ignition coil 1 and the plug hole 81 is attached to the tower portion 57.

[0038] (First filling material 71 and second filling material 72) As shown in Figs. 1 to 5, the first filling material 71 filled in the coil accommodating portion 511 and the second filling material 72 filled in the igniter accommodating portion 512 are made of different materials according to their respective applications. The first filling material 71 and the second filling material 72 contain a base resin made of a thermosetting resin and a filler made of a metal oxide. The base resin is made of a thermosetting resin such as an epoxy resin. The filler is contained to improve the properties of the base resin.

[0039] Metal oxides constituting the filler include alumina (aluminum oxide) and silica (silicon dioxide). The filler content in the first filling material 71 and the second filling material 72 is 30% by volume or more and 60% by volume or less. If the filler content is less than 30% by volume, the first filling material 71 and the second filling material 72 may not sufficiently obtain required characteristics such as a low dielectric constant or high thermal conductivity. If the filler content is more than 60% by volume, the viscosity of the first filling material 71 and the second filling material 72 may become high, making it difficult to fill the first filling material 71 into the coil accommodating portion 511 and the second filling material 72 into the igniter accommodating portion 512.

[0040] Generally, the thermal conductivity of metal oxides is higher than that of resins. Therefore, when the filling rate of the filler in the first filling material 71 and the second filling material 72 is increased, the thermal conductivity of the first filling material 71 and the second filling material 72 is increased. In addition, generally, the melting point of metal oxides is higher than the melting point of resins. Therefore, when the filling rate of the filler in the first filling material 71 and the second filling material 72 is increased, the viscosity of the base resin in the first filling material 71 and the second filling material 72 when melted is increased.

[0041] Fig. 6 shows the relationship between the filler content [volume %] and the thermal conductivity [W / (m·K)] at 25°C for the first filling material 71 and the second filling material 72. Fig. 7 shows the relationship between the filler content [volume %] and the viscosity [Pa·s] at 60°C for the first filling material 71 and the second filling material 72. There is a relationship in which the higher the filler content, the higher the thermal conductivity and the higher the viscosity. Figs. 6 and 7 show the case where silica is used as the filler.

[0042] In particular, since it is preferable for the second filling material 72 to have a high thermal conductivity, it is effective to increase the filler content compared to the first filling material 71. On the other hand, as the filler content increases, the viscosity increases, and the filling ability into the gaps in the housing portion 51 of the coil case 5 tends to decrease. Therefore, it is also necessary to keep the filler content at an appropriate value or less.

[0043] In this embodiment, the base resin constituting the first filling material 71 and the base resin constituting the second filling material 72 are the same. Furthermore, the filler content in the second filling material 72 is higher than the filler content in the first filling material 71. With this configuration, it is easy to make the thermal conductivity of the second filling material 72 higher than the thermal conductivity of the first filling material 71. The filler content in the second filling material 72 may be higher by 1 volume % or more than the filler content in the first filling material 71.

[0044] In this embodiment, at least one of the type of filler and the filler content in the first filling material 71 and the second filling material 72 is different, so that the thermal conductivity of the second filling material 72 is higher than that of the first filling material 71, and the dielectric constant of the first filling material 71 is lower than that of the second filling material 72. With this configuration, it is possible to appropriately ensure the characteristics required for the first filling material 71 and the characteristics required for the second filling material 72. In this embodiment, both the type of filler and the filler content in the first filling material 71 and the second filling material 72 are different from each other.

[0045] In this embodiment, the filler constituting the second filling material 72 is made of a metal oxide having a higher thermal conductivity than the filler constituting the first filling material 71. The filler constituting the first filling material 71 is made of a metal oxide having a lower dielectric constant than the filler constituting the second filling material 72. With these configurations, the characteristics required for the first filling material 71 and the characteristics required for the second filling material 72 can be more appropriately ensured.

[0046] Thermal conductivity indicates how easily heat is transferred from one substance to another, and the higher the value, the easier the heat is transferred. In particular, it is preferable that the second filler material 72 easily transfers heat from the igniter 43 to the outer core 42, and therefore it is preferable that the second filler material 72 has high thermal conductivity.

[0047] The dielectric constant indicates the ease of dielectric polarization of a material, in other words, the ease of storing electric charge; the higher (larger) this value, the harder it is to store electric charge. In other words, the higher the dielectric constant, the lower the insulating properties and the lower the dielectric breakdown voltage. In particular, it is preferable that the second charged material has a high dielectric breakdown voltage of the primary coil 2 and the secondary coil 3, and a low dielectric constant. The dielectric constant may be indicated by the relative dielectric constant, which is the ratio to the dielectric constant in a vacuum state.

[0048] Strictly speaking, the values ​​of thermal conductivity and dielectric constant vary depending on temperature. When comparing the first filling material 71 and the second filling material 72, or when comparing the filler in the first filling material 71 and the filler in the second filling material 72, the values ​​of thermal conductivity and dielectric constant are all values ​​at the same temperature.

[0049] 8 shows the relationship between the thermal conductivity [W / (m·K)] and the relative dielectric constant [-] at 25°C for the fillers used in the first filling material 71 and the second filling material 72. The example shows a case where a silica-based filler is used as the filler in the first filling material 71 and an alumina-based filler is used as the filler in the second filling material 72. The silica-based filler is composed of a metal oxide containing silica as the main component, in other words, 50% by mass or more. The alumina-based filler is composed of a metal oxide containing alumina as the main component, in other words, 50% by mass or more.

[0050] The thermal conductivity and dielectric constant of the silica-based filler are relatively low compared to those of the alumina-based filler. On the other hand, the thermal conductivity and dielectric constant of the alumina-based filler are relatively high compared to those of the silica-based filler. With these configurations, it is easy to form a state in which the thermal conductivity and dielectric constant of the second filling material 72 are higher than those of the first filling material 71.

[0051] The first filling material 71 is filled in the coil accommodating portion 511 and used as an insulating and fixing resin for insulating and fixing the components of the ignition coil 1, such as the primary coil 2, the primary spool 21, the secondary coil 3, the secondary spool 31, the inner core 41, and the outer core 42, in the coil case 5. The second filling material 72 is filled in the igniter accommodating portion 512 and used as an insulating and fixing resin for insulating and fixing the igniter 43 in the coil case 5.

[0052] (Manufacturing method of ignition coil 1) In manufacturing the ignition coil 1, the primary coil 2 is formed on the outer periphery of the square tube portion 22 of the primary spool 21, and the secondary coil 3 is formed on the outer periphery of the square tube portion 32 of the secondary spool 31. The inner core 41 is disposed on the inner periphery side of the primary coil 2, and the outer core 42 is disposed on the outer periphery side of the secondary coil 3. The igniter 43 is disposed facing the low-voltage side L2 in the axial direction L of the low-voltage side end face core portion 423 of the outer core 42. The igniter conductor 431 of the igniter 43 is joined to the connector conductor 25 of the connector portion 24.

[0053] 3, the coil assembly to which the components are assembled is inserted into the coil case 5 from the opening 53 of the coil case 5 toward the bottom side D1 in the mounting direction D. At this time, the pair of side core portions 421 of the outer core 42 slide on the inner wall surfaces of the side wall portions 54 of the coil case 5, and the coil assembly is inserted into the coil case 5 until the low-voltage side end surface core portion 423 of the outer core 42 abuts against the bottom portion 52 of the coil case 5. Then, the low-voltage side end surface core portion 423 divides the inside of the coil case 5 into a coil accommodating portion 511 and an igniter accommodating portion 512. The igniter 43 is disposed in the igniter accommodating portion 512 on the low-voltage side L2 in the axial direction L of the outer core 42.

[0054] 4 and 5, the second filling material 72 is injected into the igniter accommodating portion 512 of the coil case 5. At this time, the second filling material 72 is filled up to the vicinity of the end face 424 of the opening side D2 in the mounting direction D of the low-voltage side end face core portion 423. Then, the igniter 43 is buried in the second filling material 72.

[0055] 2, the first filling material 71 is injected into the coil housing 511 of the coil case 5. At this time, the first filling material 71 is filled up to the end face of the opening side D2 of the outer core 42 in the mounting direction D at a position adjacent to the igniter housing 512, and further filled up to the vicinity of the opening 53 of the coil case 5, including the portion of the opening side D2 of the igniter housing 512 in the mounting direction D. In this way, when the first filling material 71 and the second filling material 72 are hardened, each component part such as the primary coil 2, the primary spool 21, the secondary coil 3, the secondary spool 31, the inner core 41, the outer core 42, the core cover 6, and the igniter 43 is fixed to each other in an insulated state, and the ignition coil 1 is formed.

[0056] (Action and effect) In the ignition coil 1 for an internal combustion engine of this embodiment, the coil case 5 is provided with a coil housing portion 511 and an igniter housing portion 512, and the first filling material 71 and the second filling material 72 filled in the coil housing portion 511 and the igniter housing portion 512 are different in type. Specifically, the coil housing portion 511 and the igniter housing portion 512 are partitioned by the low-voltage side end surface core portion 423 of the outer core 42, and the gap in the igniter housing portion 512 is filled with the second filling material 72 having a higher thermal conductivity than the first filling material 71 filled in the gap in the coil housing portion 511. With this configuration, the second filling material 72 different from the first filling material 71 can be used to improve the heat dissipation from the igniter 43 to the outer core 42.

[0057] Moreover, the first filling material 71 is made of a material having a lower dielectric constant and superior insulating properties compared to the second filling material 72. With this configuration, it is possible to ensure the voltage resistance of the ignition coil 1 when a current flows through the primary coil 2 and the secondary coil 3.

[0058] Therefore, according to the ignition coil 1 for an internal combustion engine of this embodiment, the heat dissipation property of the igniter 43 can be improved while maintaining the insulation property of the primary coil 2 and the secondary coil 3.

[0059] (Other configurations) 9, the igniter 43 may be pressed by protrusions 55A, 55B protruding from the inside of the coil case 5 and come into contact with the low-voltage side end face core portion 423. With this configuration, the igniter 43 can be easily brought into contact with the low-voltage side end face core portion 423, and heat dissipation from the igniter 43 to the outer core 42 can be further improved. FIG 9 shows the ignition coil 1 in a state in which the coil case 5 is not filled with the first filling material 71 and the second filling material 72.

[0060] The coil case 5 also includes a connector wall portion 241 of the connector portion 24 that forms a part of the coil case 5. Both a protrusion 55A protruding from the inner wall surface of the coil case 5 and a protrusion 55B protruding from the inner wall surface of the connector wall portion 241 of the connector portion 24 may be formed, or either one of them may be formed.

[0061] <Embodiment 2> In the ignition coil 1 of this embodiment, a device is devised to improve the sealing between the coil accommodating portion 511 and the igniter accommodating portion 512. Specifically, as shown in Fig. 10 and Fig. 11, the bottom portion 52 and the side wall portion 54 of the coil case 5 are provided with ribs 59A that contact the low-voltage side end face core portion 423 and close the gap between the coil case 5 and the low-voltage side end face core portion 423. The ribs 59A of this embodiment are provided at a position on the bottom portion 52 of the coil case 5 that faces an end face on the high-voltage side L1 in the axial direction L of the low-voltage side end face core portion 423 from the high-voltage side L1, and at a position on the side wall portion 54 of the coil case 5 that faces an end face on the low-voltage side L2 in the axial direction L of the pair of side face core portions 421 from the low-voltage side L2. The rib 59A may be formed only on the end face of the high-voltage side L1 in the axial direction L of the low-voltage side end face core portion 423 in the bottom portion 52 of the coil case 5 at a position facing the high-voltage side L1.

[0062] 12, a groove 59B may be provided in the bottom 52 of the coil case 5, which comes into contact with the low-voltage side end surface core part 423 and closes the gap between the coil case 5 and the low-voltage side end surface core part 423. The groove 59B is formed in a shape into which the low-voltage side end surface core part 423 fits. In this case, the low-voltage side end surface core part 423 may be formed in a shape that protrudes toward the bottom side D1 in the mounting direction D beyond the pair of side surface core parts 421. Then, the end part of the low-voltage side end surface core part 423 on the bottom side D1 in the mounting direction D may be fitted into the groove 59B.

[0063] Furthermore, when the position of the end face of the bottom side D1 in the mounting direction D of the entire outer core 42 is the same in the mounting direction D, the inner surface of the bottom 52 of the coil case 5 may be appropriately designed so that the low-voltage side end face core part 423 fits into the groove 59B. Furthermore, both the rib 59A and the groove 59B may be formed in the coil case 5 at a position facing the low-voltage side end face core part 423. For example, the groove 59B may be formed in the bottom 52 of the coil case 5, and the rib 59A may be formed in the side wall part 54 of the coil case 5.

[0064] Other configurations, functions, and effects of the ignition coil 1 of this embodiment are similar to those of embodiment 1. Also, in this embodiment, components denoted by the same reference numerals as those in embodiment 1 are similar to those in embodiment 1.

[0065] The present invention is not limited to the respective embodiments, and further different embodiments can be configured without departing from the scope of the present invention. The present invention also includes various modified examples, modifications within the scope of equivalents, etc. Furthermore, the combinations and forms of various components envisioned from the present invention are also included in the technical spirit of the present invention. [Explanation of symbols]

[0066] 1 Ignition coil 41 Inner Core 42 Outer Core 423 Low voltage side end face core part 43 Igniter 5 Coil case 511 Coil storage section 512 Ignitor housing 71 1st filling material 72 Second filling material

Claims

1. A primary coil (2) having a central axis parallel to the axial direction (L); A secondary coil (3) arranged concentrically outside the primary coil; an inner core (41) disposed inside the primary coil; an outer core (42) having a rectangular ring shape including a pair of side core portions (421) arranged parallel to the axial direction outside a side surface (411) of the inner core, and a pair of end surface core portions (422, 423) arranged parallel to a width direction (W) perpendicular to the axial direction outside an end surface (412) of the inner core; an igniter (43) disposed opposite a low-voltage side end surface core portion (423) which is one of the pair of end surface core portions; a coil case (5) partitioned by the low-voltage side end surface core portion into a coil accommodating portion (511) in which at least a portion of the primary coil, the secondary coil, and the inner core are accommodated, and an igniter accommodating portion (512) in which at least a portion of the igniter is accommodated; A first filling material (71) filled in the gap in the coil accommodating portion; a second filling material (72) that is filled in the gap in the igniter housing and has a higher thermal conductivity than the first filling material; The first filling material and the second filling material contain a base resin made of a thermosetting resin and a filler made of a metal oxide, The content of the filler in the first filling material and the second filling material is 30% by volume or more and 60% by volume or less, At least one of the type of the filler and the content of the filler in the first filling material and the second filling material is different, so that the thermal conductivity of the second filling material is higher than that of the first filling material and the dielectric constant of the first filling material is lower than that of the second filling material; the filler constituting the second filling material is made of a metal oxide having a higher thermal conductivity than the filler constituting the first filling material; An ignition coil (1) for an internal combustion engine, wherein the filler constituting the first filling material is made of a metal oxide having a lower dielectric constant than the filler constituting the second filling material.

2. 2. The ignition coil for an internal combustion engine according to claim 1, wherein said igniter is pushed by a protrusion (55A, 55B) protruding from an inside of said coil case, and contacts said low-voltage side end surface core portion.

3. 3. An ignition coil for an internal combustion engine as described in claim 1 or 2, wherein at least one of the bottom (52) and side wall (54) of the coil case is provided with a rib (59A) or groove (59B) that contacts the low-voltage side end face core portion and closes the gap between the coil case and the low-voltage side end face core portion.

4. A primary coil (2) having a central axis parallel to the axial direction (L); A secondary coil (3) arranged concentrically outside the primary coil; an inner core (41) disposed inside the primary coil; an outer core (42) having a rectangular ring shape including a pair of side core portions (421) arranged parallel to the axial direction outside a side surface (411) of the inner core, and a pair of end surface core portions (422, 423) arranged parallel to a width direction (W) perpendicular to the axial direction outside an end surface (412) of the inner core; an igniter (43) disposed opposite a low-voltage side end surface core portion (423) which is one of the pair of end surface core portions; a coil case (5) partitioned by the low-voltage side end surface core portion into a coil accommodating portion (511) in which at least a portion of the primary coil, the secondary coil, and the inner core are accommodated, and an igniter accommodating portion (512) in which at least a portion of the igniter is accommodated; A first filling material (71) filled in the gap in the coil accommodating portion; a second filling material (72) that is filled in the gap in the igniter housing and has a higher thermal conductivity than the first filling material; The igniter is pressed by a protrusion (55A, 55B) protruding from the inside of the coil case and contacts the low-voltage side end surface core portion.

5. 5. An ignition coil for an internal combustion engine as described in claim 4, wherein at least one of the bottom (52) and side wall (54) of the coil case is provided with a rib (59A) or groove (59B) that contacts the low-voltage side end face core portion and closes the gap between the coil case and the low-voltage side end face core portion.

6. A primary coil (2) having a central axis parallel to the axial direction (L); A secondary coil (3) arranged concentrically outside the primary coil; an inner core (41) disposed inside the primary coil; an outer core (42) having a rectangular ring shape including a pair of side core portions (421) arranged parallel to the axial direction outside a side surface (411) of the inner core, and a pair of end surface core portions (422, 423) arranged parallel to a width direction (W) perpendicular to the axial direction outside an end surface (412) of the inner core; an igniter (43) disposed opposite a low-voltage side end surface core portion (423) which is one of the pair of end surface core portions; a coil case (5) partitioned by the low-voltage side end surface core portion into a coil accommodating portion (511) in which at least a portion of the primary coil, the secondary coil, and the inner core are accommodated, and an igniter accommodating portion (512) in which at least a portion of the igniter is accommodated; A first filling material (71) filled in the gap in the coil accommodating portion; a second filling material (72) that is filled in the gap in the igniter housing and has a higher thermal conductivity than the first filling material; An ignition coil for an internal combustion engine, wherein at least one of the bottom (52) and side wall (54) of the coil case is provided with a rib (59A) or groove (59B) that contacts the low-voltage side end face core portion and closes the gap between the coil case and the low-voltage side end face core portion.

7. The first filling material and the second filling material contain a base resin made of a thermosetting resin and a filler made of a metal oxide, The content of the filler in the first filling material and the second filling material is 30% by volume or more and 60% by volume or less, An ignition coil for an internal combustion engine as described in any one of claims 4 to 6, wherein at least one of the type of filler and the filler content in the first filling material and the second filling material is different, so that the thermal conductivity of the second filling material is higher than that of the first filling material and the dielectric constant of the first filling material is lower than that of the second filling material.

8. 8. The ignition coil for an internal combustion engine according to claim 1, wherein a content of said filler in said second filling material is higher than a content of said filler in said first filling material.

Images