JP2022143012A - Ignition coil for internal combustion engine - Google Patents

Abstract

To provide an ignition coil for an internal combustion engine in which the thermal tress of a charging resin is hardly concentrated.SOLUTION: An ignition coil 1 for an internal combustion engine comprises a primary coil 2, a secondary coil 3, an inside core 41, an outside core 42, a core cover 6 and the like. The core cover 6 is arranged at an inside face 423 of a pair of side face core parts 421 of the outside core 42. An average thickness of the secondary coil 3 in a radial direction of a region located at a high-voltage side L1 in an axial direction L is thin compared with an average thickness of a region located at a low-voltage side L2 in the axial direction L. An average cross section area in a cross section orthogonal to the axial direction L of the region arranged at the inside face 423 located at the high-voltage side L1 of a pair of the side face core parts 421 in the axial direction L of the core cover 6 is larger compared with an average cross section in a cross section orthogonal to the axial direction L of the region arranged at the inside face 423 located at the low-voltage side L2 of a pair of the side face core parts 421 in the axial direction L of the core cover 6.SELECTED DRAWING: Figure 3

Description

The present invention relates to ignition coils for internal combustion engines.

Ignition coils for internal combustion engines are used to ignite a mixture of fuel and combustion air in the combustion chamber of an internal combustion engine. The ignition coil includes a primary coil, a secondary coil that is coaxially arranged on the outer peripheral side of the primary coil and is magnetically coupled to the primary coil, an inner core and an outer core that allow the magnetic flux generated by the primary coil and the secondary coil to pass through, and the like. It has In addition, each component such as the primary coil, secondary coil, inner core, and outer core is placed inside the coil case, and the gaps in the coil case are filled with filling resin that insulates and fixes each component. It is

In the secondary coil, a higher voltage is generated in one direction closer to the spark plug when the primary coil is de-energized. In order to prevent the ignition coil from increasing in size and ensure the withstand voltage performance of the ignition coil, the following devices have been devised. That is, a plurality of flanges are provided on the outer periphery of the secondary spool around which the secondary coil is wound, the distance between the flanges narrowing in the axial direction toward the high voltage side in the axial direction. Further, in the recesses between the flanges, the diameter of the secondary coil winding is made smaller toward the recesses located on the higher voltage side in the axial direction of the secondary spool. As a result, the potential difference between the windings of the secondary coil is prevented from becoming large at the portion of the secondary coil located on the high voltage side, and the distance from the core cover provided for the outer coil is increased. there is An ignition coil having such a structure is disclosed in Patent Document 1, for example.

JP 2017-45760 A

In the ignition coil disclosed in Patent Document 1 and the like, the thickness of the filling resin filled in the gap between the secondary coil and the core cover is greater at a portion located on the high voltage side in the axial direction of the secondary spool. Become. Therefore, in the cooling-heat cycle when the ignition coil is used, the amount of thermal deformation (the amount of thermal expansion and the amount of thermal contraction) of the portion of the filling resin located on the low voltage side in the axial direction is greater than that of the filling resin in the axial direction. The portion positioned on the high voltage side undergoes a large amount of thermal deformation. As a result, due to the difference in the amount of thermal deformation between the low voltage side and the high voltage side of the filling resin in the axial direction, thermal stress may concentrate on the filling resin.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ignition coil for an internal combustion engine, which can make it difficult for thermal stress to concentrate in a filling resin.

One aspect of the present invention is
a primary coil (2);
a secondary spool (31) concentrically arranged outside said primary coil;
a secondary coil (3) wound in the radial direction (R) and the axial direction (L) of the outer periphery of the secondary spool, and the generated voltage increases toward the high voltage side (L1) in the axial direction;
an inner core (41) located inside the primary coil;
A pair of side core portions (421) arranged parallel to the axial direction outside the side surfaces (411) of the inner core, and a width direction (421) perpendicular to the axial direction outside the end surface (412) of the inner core. W), an outer core (42) having a quadrangular annular shape with a pair of end face core portions (422) arranged in parallel with each other;
a core cover (6) provided on a surface of the outer core including inner side surfaces (423) located inside at least a pair of the side core portions;
A coil having an opening (53) located on the opening side (D2) of the outer core and accommodating the primary coil, the secondary spool, the secondary coil, the inner core, the outer core and the core cover. case (5);
A filling resin (7) filled in a gap in the coil case,
The average radial thickness (u1) of the portion of the secondary coil located on the high voltage side in the axial direction is the same as that of the portion of the secondary coil located on the low voltage side (L2) in the axial direction. smaller than the average thickness (u2) in the radial direction,
The average cross-sectional area (a1) in the cross section perpendicular to the axial direction of the portion of the core cover provided on the inner surface of the pair of side core portions on the high voltage side in the axial direction is 3, larger than the average cross-sectional area (a2) in the cross section perpendicular to the axial direction of the portion provided on the inner surface of the pair of side core portions on the low voltage side in the axial direction, for an internal combustion engine in the ignition coil (1) of the

In the ignition coil for an internal combustion engine of one aspect, the shape of the core cover provided on the surface of the outer core is devised. Specifically, in the core cover, the average cross-sectional area in the cross section perpendicular to the axial direction of the portion provided on the inner surface of the pair of side core portions on the high voltage side in the axial direction is It is larger than the average cross-sectional area in the cross section orthogonal to the axial direction of the portion provided on the inner surface of the side core portion on the low voltage side in the axial direction. On the other hand, the average radial thickness of the portion of the secondary coil located on the high-voltage side in the axial direction is smaller than the average radial thickness of the portion of the secondary coil located on the low-voltage side in the axial direction. .

With these configurations, the size of the gap between the secondary coil and the core cover at the portion located on the high voltage side in the axial direction is brought close to the size of the gap at the portion located on the low voltage side in the axial direction. be able to. As a result, the average thickness of the portion of the filling resin that is filled between the secondary coil and the core cover is set to: can be close. As a result, the amount of thermal expansion and thermal contraction occurring in the filled resin during the cooling/heating cycle during the use of the ignition coil is reduced in the portion located on the high voltage side in the axial direction and the portion located on the low voltage side in the axial direction. , can be near.

Therefore, according to the ignition coil for an internal combustion engine of the aspect, concentration of thermal stress can be made difficult to occur in the filled resin.

"The average radial thickness of the portion of the secondary coil located on the high-voltage side in the axial direction" is the average thickness of the portion on the high-voltage side relative to the central position of the entire axial length of the secondary coil. value. Further, "the average radial thickness of the portion of the secondary coil located on the low-voltage side in the axial direction" is the thickness of the portion on the low-voltage side relative to the central position of the entire axial length of the secondary coil. should be the average value of

"Average cross-sectional area in a cross section orthogonal to the axial direction of the portion of the core cover provided on the surface of the pair of side core portions on the high voltage side in the axial direction" It may be the average value of the cross-sectional area of the portion on the high voltage side of the central position in the entire length of the portion provided on the surface of the side core portion. In addition, "the average cross-sectional area in the cross section perpendicular to the axial direction of the portion of the core cover provided on the surface of the pair of side core portions on the low voltage side in the axial direction" is, The average value of the cross-sectional areas of the portions on the lower voltage side than the central position in the entire length of the portions provided on the surfaces of the pair of side core portions may be used.

In addition, although the reference numerals in parentheses of each component shown in the present invention indicate the correspondence with the reference numerals in the drawings in the embodiment, each component is not limited only to the contents of the embodiment.

FIG. 1 is an explanatory diagram showing a cross section of an ignition coil according to Embodiment 1. FIG. FIG. 2 is an explanatory diagram showing a cross section of the coil assembly of the ignition coil according to the first embodiment. FIG. 3 is an explanatory view showing an enlarged cross-section of the periphery of the secondary coil, the outer core, the core cover, the filling resin, etc. according to the first embodiment. FIG. 4 is an explanatory view showing a cross section of a position on the high voltage side in the axial direction of the ignition coil, corresponding to line IV-IV in FIG. 3, according to the first embodiment. FIG. 5 is an explanatory diagram showing a cross section of a position on the low voltage side in the axial direction of the ignition coil, corresponding to line VV in FIG. 3, according to the first embodiment. 6 is a perspective view showing a coil intermediate in which a primary coil, a primary spool, a secondary coil, a secondary spool, an inner core, etc. are integrated according to the first embodiment; FIG. 7 is a perspective view of a core cover according to the first embodiment; FIG. FIG. 8 is a graph showing the relationship between the position of each split coil portion of the secondary coil and the strength of the electric field generated in the portion of the filled resin that faces the position of each split coil portion in the radial direction according to the first embodiment; be. 9 is a perspective view showing an outer core and a core cover according to Embodiment 2. FIG. FIG. 10 is an explanatory diagram showing a cross section of a position on the high voltage side in the axial direction of the ignition coil, corresponding to line IV-IV in FIG. 3, according to the second embodiment. FIG. 11 is an explanatory diagram showing a cross section of a position on the high voltage side in the axial direction of the ignition coil, corresponding to line VV in FIG. 3, according to the second embodiment. FIG. 12 is an explanatory diagram showing a state in which the coil assembly is arranged in the coil case according to the third embodiment. FIG. 13 is an explanatory view showing the periphery of the end portion on the low voltage side in the axial direction of the core cover according to the third embodiment; FIG. 14 shows a state in which a coil intermediate body in which a primary coil, a primary spool, a secondary coil, a secondary spool, an inner core, etc. are integrated according to a fourth embodiment is assembled to a core cover attached to an outer core; It is an explanatory diagram. FIG. 15 is an explanatory diagram showing another coil intermediate in which the primary coil, primary spool, secondary coil, secondary spool, inner core, etc. are integrated according to the fourth embodiment.

A preferred embodiment of the above ignition coil for an internal combustion engine will be described with reference to the drawings.
<Embodiment 1>
As shown in FIG. 1, the ignition coil 1 for an internal combustion engine of this embodiment includes a primary coil 2, a secondary spool 31, a secondary coil 3, an inner core 41, an outer core 42, a core cover 6, a coil case 5 and a filling. A resin 7 is provided. The primary coil 2 is energized and de-energized. The secondary spool 31 is arranged concentrically outside the primary coil 2 . The secondary coil 3 is wound around the outer periphery of the secondary spool 31 in the radial direction R and the axial direction L, and the generated voltage increases toward the high voltage side L1 in the axial direction L.

As shown in FIGS. 2-5, the inner core 41 is arranged inside the primary coil 2 . The outer core 42 includes a pair of side core portions 421 arranged parallel to the axial direction L on the outside of the side surfaces 411 of the inner core 41, and a pair of side core portions 421 arranged in the width direction W perpendicular to the axial direction L on the outside of the end surface 412 of the inner core 41. It has a quadrangular ring shape with a pair of end surface core portions 422 arranged in parallel. The core cover 6 is provided on the surface of the outer core 42 including the inner side surfaces 423 located inside at least the pair of side core portions 421 . The coil case 5 has an opening 53 located on the opening side D2 of the outer core 42 and accommodates the primary coil 2, the secondary spool 31, the secondary coil 3, the inner core 41, the outer core 42 and the core cover 6. It is. The filling resin 7 fills the gap in the coil case 5 .

As shown in FIGS. 3 to 5, in the secondary coil 3, the average thickness u1 in the radial direction R of the portion located on the high voltage side L1 in the axial direction L is is smaller than the average thickness u2 in the radial direction R of . In the core cover 6, the average cross-sectional area a1 in the cross section perpendicular to the axial direction L of the portion provided on the inner side surface 423 located on the high voltage side L1 in the axial direction L of the pair of side core portions 421 is the core cover 6 larger than the average cross-sectional area a2 in the cross section orthogonal to the axial direction L of the portion provided on the inner side surface 423 located on the low voltage side L2 in the axial direction L of the pair of side core portions 421 in 6.

The ignition coil 1 of this embodiment will be described in detail below.
(Ignition coil 1)
As shown in FIG. 1, an ignition coil 1 is arranged on a cylinder head cover 8 in an engine as an internal combustion engine of a vehicle to generate spark discharge in a combustion chamber of the cylinder head from a spark plug arranged in the cylinder head. used for The ignition coil 1 of this embodiment is for vehicle use. The ignition coil 1 includes a coil body 11 including a primary coil 2, a secondary coil 3, a coil case 5, etc., and a coil body 11 projecting from the coil body 11 to connect the secondary coil 3 and the spark plug to a high-voltage terminal 45 and a spring. and a joint portion 12 for electrical connection via 46 . The coil body portion 11 is arranged on the cylinder head cover 8 and the joint portion 12 is arranged on the plug hole 81 of the cylinder head cover 8 .

(Axial direction L, mounting direction D, width direction W)
As shown in FIGS. 1 to 7, the axial direction L is 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 on which a high voltage is generated in the secondary coil 3 is called a high voltage side L1, and the side opposite to the high voltage side L1 is called a low voltage side L2. The mounting direction D is a direction orthogonal to the axial direction L and is a direction in which the bottom portion 52 and the opening portion 53 of the coil case 5 are aligned. In the mounting direction D of the coil case 5, the side where the bottom portion 52 is located and the spark plug is arranged is called a bottom side D1, and the side opposite to the bottom side D1 where the opening 53 is located is called an opening side D2. . A direction orthogonal to both the axial direction L and the mounting direction D is called a width direction W. As shown in FIG.

(Radial direction R, circumferential direction C)
A direction extending radially from the center axis of the primary coil 2 and the secondary coil 3 is called a radial direction R. As shown in FIG. A direction around the central axis of the primary coil 2 and the secondary coil 3 is called a circumferential direction C. As shown in FIG. The primary coil 2, the secondary coil 3, and the like of this embodiment are formed in a square tubular shape, and the circumferential direction C of this embodiment is the circumferential direction C of the square ring. Moreover, the mounting direction D and the width direction W are included in the radial direction R.

(Primary coil 2)
As shown in FIGS. 1 to 5, the primary coil 2 is formed by winding a magnet wire as a winding around the outer peripheral surface of the tubular 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 energized by the switching element of the igniter 43 that receives a command from the engine control device.

(Secondary coil 3)
As shown in FIGS. 1-5, the secondary coil 3 is arranged coaxially with the primary coil 2 outside the primary coil 2 . The secondary coil 3 is formed by winding a magnet wire as a winding around the outer peripheral surface of the tubular 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.

The windings of the secondary coil 3 are thinner than the windings of the primary coil 2 and the number of windings of the secondary coil 3 is greater than that of the primary coil 2 . The secondary coil 3 generates an induced electromotive force due to mutual induction when the primary coil 2 is de-energized. 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 end L2 of the winding of the secondary coil 3 is connected to the ground or power supply terminal at the igniter 43 . The end of the winding of the secondary coil 3 on the high voltage side L1 is connected to a high voltage terminal 45 connected to the center electrode of the spark plug.

(inner core 41)
As shown in FIGS. 2 and 3 , an inner core 41 is arranged inside (inner peripheral side) of the primary coil 2 to pass the magnetic flux generated by the primary coil 2 and the secondary coil 3 . The inner core 41 of 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 cuboid shape and has four side surfaces 411 parallel to the axial direction L and two end surfaces 412 perpendicular to the axial direction L. As shown in FIG. The inner core 41 may be formed by compression-molding powder made of a soft magnetic material.

(outer core 42)
As shown in FIGS. 2 to 5, an outer core 42 is arranged outside (peripheral side) of the secondary coil 3 to allow magnetic flux generated by the primary coil 2 and the secondary coil 3 to pass therethrough. The outer core 42 of this embodiment is formed by laminating a plurality of plate-like electromagnetic steel sheets made of a soft magnetic material. The outer core 42 is formed in a quadrangular ring shape in which the inner core 41 is arranged inside in a cross section viewed from the mounting direction D. As shown in FIG. The outer core 42 may be formed by compression-molding powder made of a soft magnetic material.

The pair of side core portions 421 of the outer core 42 are positioned on both sides in the width direction W outside the secondary coil 3 and the secondary spool 31 . A pair of end surface core portions 422 of the outer core 42 are positioned on both sides L1 and L2 of the secondary coil 3 and the secondary spool 31 in the axial direction L and connected to a pair of side surface core portions 421 . The igniter 43 is arranged facing the end surface core portion 422 of the outer core 42 located on the low voltage side L<b>2 in the axial direction L of the secondary coil 3 . Almost no gap is formed between the igniter 43 and the end face core portion 422, and the filling resin 7 is hardly arranged.

The inner core 41 and the outer core 42 form a closed magnetic circuit through which magnetic flux passes. A permanent magnet 44 is arranged between the inner core 41 and the outer core 42 to prevent magnetic saturation.

(igniter 43)
As shown in FIGS. 1 and 2, the ignition coil 1 includes an igniter 43 that repeatedly energizes and interrupts the primary coil 2 in response to a command from the engine control device. The igniter 43 is arranged to face the low voltage side L2 of the end surface core portion 422 of the outer core 42 in the axial direction L of the primary coil 2 and the secondary coil 3 . The igniter 43 is arranged between the connector portion 24 attached to the coil case 5 and the end surface core portion 422 of the outer core 42 . The igniter 43 includes a circuit forming portion provided with electronic parts such as switching elements that form a switching circuit, a heat sink integrated with the circuit forming portion, a mold resin covering the circuit forming portion and the heat sink, and a circuit forming portion. and an igniter conductor 431 drawn out of the mold resin from the part.

(Primary spool 21)
As shown in FIGS. 1 to 5, the primary coil 2 is wound around the outer circumference of the primary spool 21 . The primary spool 21 is formed of a thermoplastic resin molding. The primary spool 21 has a tubular portion 22 around which the primary coil 2 is wound. In this embodiment, the primary spool 21 and the connector portion 24 are integrally formed as the spool molded body 210 . The spool molded body 210 includes a rectangular tubular portion 22, flange portions 221 formed at both ends of the tubular portion 22 in the axial direction L, a connector portion 24, and a relay portion that relays the tubular portion 22 and the connector portion 24. 23. The connector portion 24 may be formed separately from the tubular portion 22 of the primary spool 21 as a connector.

The winding of the primary coil 2 is wound around the outer peripheral surface between the flanges 221 of the tubular portion 22 of the primary spool 21 . A connector conductor 25 connected to the igniter conductor 431 of the igniter 43 is provided in the connector portion 24 by insert molding. The connector portion 24 is formed so as to protrude outside the coil case 5 . The plurality of igniter conductors 431 and the plurality of connector conductors 25 are joined together by soldering, welding, or the like. In addition, the plurality of igniter conductors 431 are connected to the conductor connected to both ends of the winding of the primary coil 2 and the conductor connected to the end of the winding of the secondary coil 3 on the low voltage side L2, soldering, They are joined together by welding or the like.

(Secondary spool 31)
As shown in FIGS. 1 to 5, the secondary coil 3 is wound around the outer circumference of the secondary spool 31 . The secondary spool 31 is formed of a thermoplastic resin molding. The secondary spool 31 has a tubular portion 32 having a square tubular shape and a plurality of flange portions 33 projecting outward along the entire circumference of the tubular portion 32 at a plurality of locations in the axial direction L. The collar portion 33 partitions the outer periphery of the tubular portion 32 into a plurality of recessed portions (slots) 321 arranged in the axial direction L. As shown in FIG. Part of the thickness in the radial direction R of the portion forming the recess 321 located on the high voltage side L1 in the axial direction L of the cylindrical portion 32 of the secondary spool 31 is the recess located on the low voltage side L2 in the axial direction L. It is larger than the thickness in the radial direction R of the portion forming 321 .

As shown in FIG. 3, the width in the axial direction L of the plurality of recesses 321 positioned on the high voltage side L1 in the axial direction L is equal to the width in the axial direction L of the plurality of recesses 321 positioned on the low voltage side L2 in the axial direction L. less than width. In the present embodiment, the width of the plurality of recesses 321 in the axial direction L is smaller for those located on the high voltage side L1 in the axial direction L. As shown in FIG. The brim portion 33 is appropriately formed with transition grooves for crossing between the recesses 321 where the windings of the secondary coil 3 are adjacent to each other.

The windings of the secondary coil 3 are sequentially wound as the divided coil portions 30 on a plurality of concave portions 321 formed between the flange portions 33 . As shown in FIG. 4, the average thickness u1 in the radial direction R of the split coil portions 30 arranged in the plurality of recesses 321 located on the high voltage side L1 in the axial direction L is equal to the average thickness u1 in the axial direction L is smaller than the average thickness u2 in the radial direction R of the split coil portions 30 arranged in the plurality of recessed portions 321 located on the low voltage side L2 of. In other words, the winding of the secondary coil 3 wound on the multiple recesses 321 located on the high voltage side L1 in the axial direction L is wound on the multiple recesses 321 located on the low voltage side L2 in the axial direction L. The secondary coil 3 is wound thinner in the radial direction R than the winding of the secondary coil 3 .

Here, the average thickness u1 in the radial direction R of the split coil portions 30 arranged in the plurality of recessed portions 321 located on the high voltage side L1 in the axial direction L is greater than the center position of the secondary coil 3 over the entire length in the axial direction L. is the average thickness u1 of the split coil portions 30 arranged in the plurality of recesses 321 located on the high voltage side L1. The average thickness u2 in the radial direction R of the split coil portions 30 arranged in the plurality of recesses 321 located on the low voltage side L2 in the axial direction L is lower than the central position of the secondary coil 3 in the axial direction L. The average thickness u2 of the split coil portions 30 arranged in the plurality of concave portions 321 located on the side L2 may be used.

If the divided coil portion 30 arranged in the recessed portion 321 including the center position of the entire length of the secondary coil 3 in the axial direction L is excluded from the average thickness u1 of the high voltage side L1 and the average thickness u2 of the low voltage side L2, good. The average thicknesses u1 and u2 may be the average values of the thicknesses of the plurality of split coil portions 30 .

In this embodiment, the thickness of the split coil portion 30 in the radial direction R is smaller as the split coil portion 30 is positioned closer to the high voltage side L1 in the axial direction L. As shown in FIG. Further, the number of turns of the winding of the secondary coil 3 wound around the plurality of recesses 321 is smaller for the recesses 321 located on the high voltage side L1 in the axial direction L. As shown in FIG. The distance between the outer circumference of the secondary coil 3 and the side core portion 421 of the outer core 42 increases toward the high voltage side L1 in the axial direction L.

(core cover 6)
As shown in FIGS. 4, 5 and 7, the core cover 6 reduces the gap S between the secondary coil 3 and the outer core 42 to reduce the filling amount of the filling resin 7, so that the secondary coil 3 and the outer core 42 more appropriately. The core cover 6 is provided inside the outer core 42 and on each surface of the bottom side D1 and the opening side D2 in the mounting direction D. As shown in FIG. More specifically, the core cover 6 includes a pair of inner cover portions 61 arranged on inner side surfaces 423 of the pair of side core portions 421 and a pair of inner cover portions 61 connected to the pair of side surface core portions 421 . It has a pair of opening side cover portions 63 arranged on the opening surface 425 positioned on the opening side D2 in the mounting direction D in the core portion 421 . In addition, the core cover 6 of this embodiment is connected to the pair of inner cover portions 61 and arranged on the bottom surface 424 of the pair of side core portions 421 located on the bottom side D1 in the mounting direction D. 62 as well.

The inner cover portion 61 is also arranged on the inner side surface 423 of the end surface core portion 422 on the high voltage side L1 in the axial direction L, being connected to the portions arranged on the inner side surface 423 of the pair of side core portions 421. . The opening side cover portion 63 is connected to the portions of the pair of side core portions 421 that are arranged on the opening surface 425, and is also arranged on the opening surface 425 of the end surface core portion 422 on the high voltage side L1 in the axial direction L. The bottom cover portion 62 is connected to the portions of the pair of side core portions 421 that are arranged on the bottom surface 424, and is also arranged on the bottom surface 424 of the end surface core portion 422 on the high voltage side L1 in the axial direction L. In other words, the core cover 6 faces the inner side surface 423, the opening surface 425 and the bottom surface 424 of the pair of side surface core portions 421 and the end surface core portion 422 on the high voltage side L1.

As shown in FIG. 4, the average thickness t1 in the width direction W of the portion of the pair of inner cover portions 61 located on the high voltage side L1 in the axial direction L is, as shown in FIG. is greater than the average thickness t2 in the width direction W of the portion located on the low-voltage side L2 in the axial direction L. With this configuration, the thickness of the inner cover portion 61 in the width direction W is increased at the portion on the high voltage side L1 where the thickness of the secondary coil 3 in the radial direction R is small, so that the secondary coil 3 and the inner cover portion 61 are separated from each other. It is possible to suppress variation in the size of the gap S filled with the filling resin 7 at each portion in the axial direction L between .

Here, the average thickness t1 in the width direction W of the portion of the pair of inner cover portions 61 located on the high voltage side L1 in the axial direction L is higher than the central position of the entire length of the inner cover portion 61 in the axial direction L. The average value of the thickness of the portion located on the side L1 may be used. The average thickness t2 in the width direction W of the portion of the pair of inner cover portions 61 located on the low voltage side L2 in the axial direction L is closer to the low voltage side L2 than the central position of the entire length of the inner cover portion 61 in the axial direction L. The average value of the thickness of the position may be used.

As shown in FIG. 3, in the core cover 6 of the present embodiment, the thickness of the pair of inner cover portions 61 in the width direction W is greater at portions located on the high voltage side L1 in the axial direction L. As shown in FIG. In other words, the thickness in the width direction W of the pair of inner cover portions 61 is reduced by the amount that the thickness in the radial direction R of the secondary coil 3 decreases toward the high voltage side L1 in the axial direction L. The portion located on the high voltage side L1 of L is larger. In addition, the inner surface of the inner cover portion 61 is formed in a tapered shape that approaches the inner side in the width direction W as it goes toward the high voltage side L1 in the axial direction L. As shown in FIG. With this configuration, it is possible to more effectively suppress variation in the size of the gap S filled with the filling resin 7 at each location in the axial direction L between the secondary coil 3 and the inner cover portion 61 .

As shown in FIGS. 4 and 5, the overall size of the opening side cover portion 63 in the mounting direction D is larger than the size of the bottom side cover portion 62 in the mounting direction D and the size of the inner cover portion 61 in the width direction W. . The opening side cover portion 63 of this embodiment is formed of a plurality of ribs 631 arranged in the mounting direction D. As shown in FIG. More specifically, two ribs 631 are formed side by side on the bottom side D1 and the opening side D2 in the mounting direction D, and are connected to the inner cover portion 61. Between the two ribs 631, the filling resin A groove 632 filled with 7 is formed.

A projection 633 for facilitating attachment of the core cover 6 to the outer core 42 is formed on the surface of the opening-side cover portion 63 facing the opening surface 425 of the outer core 42 . A projection 621 for facilitating attachment of the core cover 6 to the outer core 42 is also formed on the surface of the bottom cover portion 62 facing the bottom surface 424 of the outer core 42 . The protrusions 621 and 633 are formed at a plurality of locations in the axial direction L of the core cover 6 . Further, an opening hole 611 through which the inner core 41 is inserted is formed in the portion of the inner cover portion 61 arranged inside the end surface core portion 422 on the high voltage side L1 (low voltage side L2).

As shown in FIG. 7 , the outer core 42 is formed by combining two parts separated at a pair of end surface core portions 422 . The core cover 6 is formed by combining two parts separated at a portion facing the end surface core portion 422 on the high voltage side L1.

(Coil case 5)
As shown in FIGS. 1 and 4 to 6, the coil case 5 is formed as a thermoplastic resin molding. 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, and the like. The coil case 5 is formed with an opening 53 for arranging the coil assembly 10 in the accommodating portion 51. The opening 53 is formed at the end of the opening side D2 in the mounting direction D of the accommodating portion 51. It is The coil assembly 10 is formed by assembling a primary coil 2, a primary spool 21, a secondary coil 3, a secondary spool 31, an inner core 41, an outer core 42, a core cover 6, an igniter 43, and the like. Further, the liquid filling resin 7 is injected into the gap inside the coil case 5 from the opening 53 .

As shown in FIGS. 1 and 6, a connector portion 24 of a spool molding 210 is arranged in a portion of the coil case 5 for electrically connecting the igniter 43 to an external engine control device. The spool molded body 210 is formed by resin insert molding in which the inner core 41 is arranged in the cylindrical portion 22 of the primary spool 21 and the connector conductor 25 is arranged in the connector portion 24 .

The coil case 5 is formed with a mounting notch 56 to which the connector portion 24 of the spool molded body 210 is mounted. A wall portion of the coil case 5 is partially formed by the connector wall portion 241 of the connector portion 24 . Holding portions 242 for holding the edges of the mounting notch 56 from both sides are formed at the end portion of the bottom side D1 in the mounting direction D and the end portions on both sides in the width direction W of the connector wall portion 241 .

Further, as shown in FIG. 1 , a tower portion 57 that constitutes the joint portion 12 is formed on the bottom portion 52 positioned 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 .

(Filled resin 7)
As shown in FIGS. 1 and 3 to 5, the filling resin 7 includes the primary coil 2, the primary spool 21, the secondary coil 3, the secondary spool 31, the inner core 41, the outer core 42, and the ignition coils such as the igniter 43. It is used as an insulating fixing resin for insulating and fixing the component part 1 in the coil case 5 . The filling resin 7 is made of a thermosetting resin. A coil assembly 10 assembled with a primary coil 2, a primary spool 21, a secondary coil 3, a secondary spool 31, an inner core 41, an outer core 42, a core cover 6, an igniter 43, etc. is arranged in a coil case 5. After that, a liquid thermosetting resin is injected into the gap in the coil case 5, and the liquid thermosetting resin is cured. The primary coil 2, primary spool 21, secondary coil 3, secondary spool 31, inner core 41, outer core 42, core cover 6, igniter 43, etc. in the coil case 5 are made by the filling resin 7 made of thermosetting resin. They are fixed together in an insulated state.

(Effect)
In the ignition coil 1 for an internal combustion engine of this embodiment, the shape of the core cover 6 provided on the surface of the outer core 42 is devised. Specifically, the cross-sectional area of the cross section perpendicular to the axial direction L of the core cover 6 is increased toward the higher voltage side L1 in the axial direction L. As shown in FIG. In particular, in the present embodiment, the cross-sectional area of the inner cover portion 61 is increased toward the portion located on the high voltage side L1 in the axial direction L. As shown in FIG. On the other hand, the thickness of the secondary coil 3 in the radial direction R is smaller at a portion located on the high voltage side L1 in the axial direction L. In addition, the cross-sectional area of the gap S in the width direction W between the secondary coil 3 and the inner cover portion 61 and the cross-sectional area of the filling resin 7 filled in this gap S are substantially uniform throughout the axial direction L. be.

With these configurations, the size of the gap S between the secondary coil 3 and the inner cover portion 61 can be made as uniform as possible from the low voltage side L2 to the high voltage side L1 in the axial direction L. can. As a result, the thickness of the portion of the filling resin 7 filled between the secondary coil 3 and the inner cover portion 61 is made as uniform as possible from the portion on the low voltage side L2 to the portion on the high voltage side L1 in the axial direction L. can do. As a result, the amount of thermal expansion and thermal contraction occurring in the filling resin 7 in the cooling/heat cycle during use of the ignition coil 1 is made uniform as much as possible from the low voltage side L2 to the high voltage side L1 in the axial direction L. can do.

Therefore, according to the ignition coil 1 for an internal combustion engine of this embodiment, it is possible to make it difficult for thermal stress to concentrate at the portion of the filling resin 7 filled between the secondary coil 3 and the inner cover portion 61 . . In addition, cracks are less likely to occur in the portion of the filling resin 7, and the insulation of the ignition coil 1 can be ensured for a long time.

FIG. 8 shows the positions of the split coil portions 30 of the secondary coil 3 arranged in the plurality of recesses 321 of the secondary spool 31, and the positions of the filling resin 7 facing the positions of the split coil portions 30 in the radial direction R. The relationship between the strength of the electric field [kV/mm] generated at the site and the conventional ignition coil (comparative product) and the ignition coil 1 of the present embodiment (implemented product) are shown. The positions of the split coil portions 30 are shown as N1 to N6 in order from the one located on the low voltage side L2 in the axial direction L. As shown in FIG.

The conventional ignition coil shows the case where the thickness in the radial direction R of the split coil portion 30 arranged in each recess 321 is substantially constant in the entire axial direction L from the low voltage side L2 to the high voltage side L1. In the ignition coil 1 of this embodiment, the thickness in the radial direction R of the split coil portion 30 arranged in each recess 321 is smaller as the split coil portion 30 is positioned closer to the high voltage side L1 in the axial direction L. As shown in FIG.

The position of each split coil portion 30 is shown as the center position in the axial direction L of each split coil portion 30 . The intensity of the electric field generated at the portion of the filling resin 7 is formed by arranging the inner cover portion 61 of the core cover 6 and the filling resin 7 between the split coil portions 30 of the secondary coil 3 and the outer core 42. is the strength of the electric field produced in the pseudo-capacitor.

In FIG. 8, in the conventional ignition coil (comparative product), since the voltage increases toward the high voltage side L1 of the secondary coil 3, the portion located on the high voltage side L1 in the axial direction L is filled more. The strength of the electric field generated in the resin 7 is remarkably increased. In addition, the difference in strength of the electric field generated in the filling resin 7 between the portion on the low voltage side L2 and the portion on the high voltage side L1 in the axial direction L is remarkable. On the other hand, in the ignition coil 1 (implemented product) of the present embodiment, the difference in strength of the electric field generated in the filling resin 7 between the low voltage side L2 portion and the high voltage side L1 portion in the axial direction L is reduced. there is

Furthermore, in the ignition coil 1 of the present embodiment, by using a material that has a lower dielectric constant than the material that forms the filling resin 7 as the material that forms the core cover 6, the low voltage side L2 in the axial direction L is It is possible to further reduce the difference in strength of the electric field generated in the filling resin 7 between the portion and the portion on the high voltage side L1.

Specifically, the core cover 6 of this embodiment is made of polypropylene resin, and the filling resin 7 of this embodiment is made of epoxy resin. The dielectric constant of the polypropylene resin is about 2.2 to 2.6, and the dielectric constant of the epoxy resin used in this embodiment is larger than that of the polypropylene resin, and is about 2.5 to 6.0. is.

In the ignition coil 1 of this embodiment, the volume occupied by the inner cover portion 61 increases in the gap S between the split coil portion 30 and the inner core 41 located on the high voltage side L1 in the axial direction L. The volume occupied by the filling resin 7 is reduced. As a result, in the ignition coil 1 of this embodiment, the strength of the electric field generated in the filling resin 7 positioned on the high voltage side L1 in the axial direction L is reduced, and the portion on the low voltage side L2 in the axial direction L and the high voltage side It is considered that the difference in the strength of the electric field generated in the filling resin 7 between the portion of L1 and the portion of L1 is further reduced.

This also suppresses deterioration of the portion of the filling resin 7 filled between the secondary coil 3 and the inner cover portion 61, so that the insulation of the ignition coil 1 can be maintained for a long time.

<Embodiment 2>
In this embodiment, as shown in FIGS. 9 to 11, the configuration for reducing variation in the axial direction L of the size of the gap S between the secondary coil 3 and the inner cover portion 61 is replaced with the core of the first embodiment. An example realized by a core cover 6 different from the cover 6 is shown.

In the core cover 6 of this embodiment, a corner portion 64 formed by the inner cover portion 61 and the opening-side cover portion 63 is formed in a curved surface that bulges outward. The curved corner portion 64 may have any shape as long as it has a curved portion. may be formed. Further, the radius of curvature of the corner portion 64 may vary within a cross section orthogonal to the axial direction L, and may be expressed as an average value of the radius of curvature.

The opening-side cover portion 63 of this embodiment is not formed as a plurality of ribs 631, but is formed as one block shape. Then, as shown in FIG. 10, the average curvature radius r1 of the corner portion 64 of the portion of the core cover 6 located on the high voltage side L1 in the axial direction L is, as shown in FIG. It is smaller than the average radius of curvature r2 of the corner portion 64 located on the low voltage side L2 in the direction L. With this configuration, the thickness in the width direction W of the opening side cover portion 63 is increased at the portion on the high voltage side L1 where the thickness in the radial direction R of the secondary coil 3 is reduced. As a result, in this embodiment, the amount of thermal expansion and thermal contraction occurring in the filling resin 7 in the thermal cycle when the ignition coil 1 is used is reduced from the portion on the low voltage side L2 in the axial direction L to the portion on the high voltage side L1 in the axial direction L. can be approached more uniformly.

Here, the average curvature radius r1 of the corner portion 64 of the portion of the core cover 6 located on the high voltage side L1 in the axial direction L is the axial direction L may be the average value of the curvature radius of the portion located on the high voltage side L1 from the center position in the entire length of the . The average curvature radius r2 of the corner portion 64 of the core cover 6 located on the low voltage side L2 in the axial direction L is The average value of the radius of curvature of the portion positioned on the low voltage side L2 from the central position may be used.

In the core cover 6 of this embodiment, the radius of curvature of the corner portion 64 formed by the inner cover portion 61 and the opening side cover portion 63 is smaller in the portion located on the high voltage side L1 in the axial direction L. With this configuration, the amount of thermal expansion and thermal contraction occurring in the filling resin 7 during the cooling/heating cycle when the ignition coil 1 is used is more uniform from the low voltage side L2 to the high voltage side L1 in the axial direction L. can be brought closer to

The configuration of the core cover 6 of the present embodiment is used in combination with the configuration in which the thickness in the width direction W of the pair of inner cover portions 61 shown in the first embodiment differs at each portion in the axial direction L. As shown in FIG. Further, the opening side cover portion 63 of this embodiment may be formed as the plurality of ribs 631 shown in the first embodiment, as indicated by the two-dot chain line in FIG.

Other configurations, effects, etc. of the ignition coil 1 of this embodiment are the same as those of the first embodiment. Also in the present embodiment, constituent elements indicated by the same reference numerals as those in the first embodiment are the same as those in the first embodiment.

<Embodiment 3>
As shown in FIGS. 12 and 13, in this embodiment, even when a crack occurs in the filling resin 7 filled in the gap S between the secondary coil 3 and the core cover 6, the crack 2 shows an example in which a contrivance is made to prevent the extension of the winding ends 201 and other conductors of the primary coil 2 .

The primary spool 21 of this embodiment has a shape that prevents cracks generated in the filling resin 7 from extending. As shown in FIGS. 6, 12 and 13, the primary spool 21 protrudes from the cylindrical portion 22 toward the opening side D2 in the mounting direction D, and extends outward in the axial direction L of the opening side cover portion 63 of the core cover 6. has a protrusion 26 facing the low voltage side L2 of the . The protruding portions 26 are formed so as to face the ends of the pair of opening side cover portions 63 on the low voltage side L2 in the axial direction L. As shown in FIG. A holding portion 261 that holds the winding end portion 201 of the primary coil 2 is provided at a portion of the primary spool 21 located on the low voltage side L2 in the axial direction L relative to the projecting portion 26 .

As shown in FIG. 12, the opening side cover portion 63 protrudes from the opening surface 425 of the side core portion 421 toward the opening portion 53 side of the coil case 5, in other words, from the opening surface 425 toward the opening side D2 in the mounting direction D. The amount x1 is smaller than the amount x2 of the projecting portion 26 of the primary spool 21 projecting from the opening surface 425 toward the opening side D2 in the mounting direction D.

In the cooling/heating cycle when the ignition coil 1 of this embodiment is used, when a crack occurs in the portion of the filling resin 7 filled in the gap S between the secondary coil 3 and the inner cover portion 61, the protruding portion 26 , the crack is prevented from extending to the low voltage side L2 in the axial direction L. This prevents cracks from extending to conductors such as the winding ends 201 of the primary coil 2 .

Other configurations, effects, etc. of the ignition coil 1 of this embodiment are the same as those of the first and second embodiments. Further, in the present embodiment as well, the components indicated by the same reference numerals as those in the first and second embodiments are the same as those in the first and second embodiments.

<Embodiment 4>
In this embodiment, as shown in FIGS. 12 and 14, a core cover 6 attached to an outer core 42 is integrated with a primary coil 2, a primary spool 21, a secondary coil 3, a secondary spool 31, an inner core 41, and the like. An example of devising to appropriately maintain the assembled state of the coil intermediate body 100 is shown. In this embodiment, the shape of the primary spool 21 forming the coil intermediate 100 is devised.

A space maintaining portion 27 protrudes from the tubular portion 22 in the width direction W of the primary spool 21 and is fitted between the pair of inner cover portions 61 of the core cover 6 to maintain the space between the pair of inner cover portions 61. is formed. The gap maintaining portion 27 of this embodiment is formed by a pair of tapered ribs 271 projecting from the cylindrical portion 22 to both sides in the width direction W at the boundary portion between the cylindrical portion 22 and the relay portion 23 of the primary spool 21 .

The width in the width direction W of the pair of tapered ribs 271 as the gap maintaining portion 27 changes slightly from the opening side D2 in the mounting direction D toward the bottom side D1. In other words, the end face in the width direction W of the tapered rib 271 is formed as a tapered surface located inward in the width direction W as it goes to the bottom side D1. On the other hand, inner side surfaces 612 in the width direction W of the pair of inner cover portions 61 of the core cover 6 are formed as linear surfaces parallel to the mounting direction D. As shown in FIG.

The width of the pair of tapered ribs 271 on the bottom side D1 in the mounting direction D in the width direction W is w1; When the width in the width direction W of the inner side surface 612 of the inner cover portion 61 is w3, there is a relationship of w1<w3<w2. Then, as shown in FIGS. 12 and 13, the coil intermediate 100 assembled with the primary coil 2, the primary spool 21, the secondary coil 3, the secondary spool 31, the inner core 41, etc. is attached to the outer core 42. When arranged inside the core cover 6 , the pair of tapered ribs 271 are fitted between the pair of inner cover portions 61 of the core cover 6 .

Since the portion of the core cover 6 on the low voltage side L2 in the axial direction L is positioned at the end of the U-shaped core cover 6, it is assumed that the core cover 6 is deformed inward after the core cover 6 is molded by the molding die. Therefore, when the coil intermediate body 100 is assembled to the core cover 6 attached to the outer core 42 , the gap between the pair of inner cover parts 61 can be properly maintained by the gap maintaining part 27 . Thereby, the thickness in the width direction W of the filling resin 7 filled in the gap S between the secondary coil 3 and the pair of inner cover portions 61 can be appropriately maintained.

Further, as shown in FIG. 15 , the gap maintaining portion 27 may be configured by a pair of deformation projections 272 provided on the side surface of the primary spool 21 in the width direction W instead of the pair of tapered ribs 271 . In this case, the width w4 in the width direction W between the tips of the pair of protrusions 272 is made smaller than the width w3 in the width direction W of the inner side surfaces 612 of the pair of inner cover portions 61 . When the coil intermediate 100 is inserted inside the core cover 6 of the outer core 42, the pair of protrusions 272 undergo plastic deformation or elastic deformation, thereby appropriately maintaining the distance between the pair of inner cover portions 61. be able to.

Other configurations, effects, etc. of the ignition coil 1 of this embodiment are the same as those of the first to third embodiments. Further, in the present embodiment as well, constituent elements indicated by the same reference numerals as those in the first to third embodiments are the same as those in the first to third embodiments.

The present invention is not limited to only each embodiment, and further different embodiments can be configured without departing from the scope of the invention. In addition, the present invention includes various modifications, modifications within the equivalent range, and the like. Further, the technical idea of the present invention also includes combinations, forms, and the like of various constituent elements assumed from the present invention.

REFERENCE SIGNS LIST 1 ignition coil 2 primary coil 3 secondary coil 31 secondary spool 41 inner core 42 outer core 5 coil case 6 core cover 7 filling resin

Claims (6)

a primary coil (2);
a secondary spool (31) concentrically arranged outside said primary coil;
a secondary coil (3) wound in the radial direction (R) and the axial direction (L) of the outer periphery of the secondary spool, and the generated voltage increases toward the high voltage side (L1) in the axial direction;
an inner core (41) located inside the primary coil;
A pair of side core portions (421) arranged parallel to the axial direction outside the side surfaces (411) of the inner core, and a width direction (421) perpendicular to the axial direction outside the end surface (412) of the inner core. W), an outer core (42) having a quadrangular annular shape with a pair of end face core portions (422) arranged in parallel with each other;
a core cover (6) provided on a surface of the outer core including inner side surfaces (423) located inside at least a pair of the side core portions;
A coil having an opening (53) located on the opening side (D2) of the outer core and accommodating the primary coil, the secondary spool, the secondary coil, the inner core, the outer core and the core cover. case (5);
A filling resin (7) filled in a gap in the coil case,
The average radial thickness (u1) of the portion of the secondary coil located on the high voltage side in the axial direction is the same as that of the portion of the secondary coil located on the low voltage side (L2) in the axial direction. smaller than the average thickness (u2) in the radial direction,
The average cross-sectional area (a1) in the cross section perpendicular to the axial direction of the portion of the core cover provided on the inner surface of the pair of side core portions on the high voltage side in the axial direction is 3, larger than the average cross-sectional area (a2) in the cross section perpendicular to the axial direction of the portion provided on the inner surface of the pair of side core portions on the low voltage side in the axial direction, for an internal combustion engine ignition coil (1). The core cover includes a pair of inner cover portions (61) arranged on the inner side surfaces of the pair of side core portions, and a pair of inner cover portions (61) connected to the pair of inner cover portions to extend the opening side of the pair of side core portions. and a pair of opening side cover portions (63) arranged on the opening surface (425) located in the
The average thickness (t1) in the width direction of the portion of the pair of inner cover portions located on the high voltage side in the axial direction is equal to the average thickness (t1) of the portion of the pair of inner cover portions located on the low voltage side in the axial direction. 2. An ignition coil for an internal combustion engine according to claim 1, wherein the average thickness (t2) in the width direction of the . A corner portion (64) formed by the inner cover portion and the opening side cover portion is formed into a curved surface,
The average radius of curvature (r1) of the corners of the portion located on the high voltage side in the axial direction is smaller than the average radius of curvature (r2) of the corners of the portion located on the low voltage side in the axial direction. 3. An ignition coil for an internal combustion engine as claimed in claim 2. The secondary spool has a tubular portion (32) having a tubular shape and a plurality of flange portions (33) projecting outward along the entire circumference of the tubular portion at a plurality of locations in the axial direction,
The secondary coil is sequentially wound around a plurality of concave portions (321) formed between the collar portions as a divided coil portion (30),
The average radial thickness (u1) of the split coil portions arranged in the plurality of recesses located on the high-voltage side in the axial direction is arranged in the plurality of recesses located on the low-voltage side in the axial direction. 4. The ignition coil for an internal combustion engine according to claim 2, wherein the average thickness (u2) in the radial direction of the divided coil portion is smaller than that of the divided coil portion. A cylindrical portion (22) around which the primary coil is wound, and a protruding portion (26) that protrudes from the cylindrical portion and faces the outer side of the opening side cover portion of the core cover in the axial direction. further comprising a primary spool (21) having
The projection amount (x1) of the opening side cover portion from the opening surface to the opening side of the coil case is the distance of the opening portion of the coil case from the opening surface of the projection portion of the primary spool. The ignition coil for an internal combustion engine according to any one of claims 2 to 4, which is smaller than the amount of protrusion (x2) to the side. The primary spool has a gap maintaining part ( 27) is formed on the ignition coil for an internal combustion engine according to claim 5.

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