JP2003124042A - Ignition coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition coil wherein a covering tube is eliminated for the center core. SOLUTION: This ignition coil 1 is provided with a bar-like core body 13 made of magnetic material, a secondary coil 21 wound around the outer circumference of the core body 13, a secondary spool 20 that is arranged between the core body 13 and secondary coil 21 and is wound by the secondary coil 21, a primary coil 24 wound around the outer circumference of the secondary coil 21, a primary spool 23 that is arranged between the secondary coil 21 and the primary coil 24 and is wound by the primary coil 23, and a cylindrical case 11 arranged on the outer circumference side of the primary coil 24. The case 11 is filled with a resin insulation material 26 to mold and fix the secondary and primary coils 21 and 24. A cylindrical member 17 comprised of hard tube is arranged on the outer circumference of the core body 13, and the cylindrical member 17 is projected from the shaft end 13a of the core body 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition coil, and more particularly to a so-called stick coil installed in a plug hole of each cylinder of an internal combustion engine.

[0002]

2. Description of the Related Art As an ignition coil, for example, an ignition coil for an internal combustion engine is known as a so-called stick type ignition coil which is mounted in a plug hole of each cylinder.

This type of ignition coil includes a central core arranged on the cylinder axis of a plug hole, a secondary coil located on the outer periphery of the central core and wound around the outer periphery of the central core, and the secondary coil. A primary coil that is coaxially wound around the outer peripheral side and a case that accommodates the components that configure these ignition coils are provided.
In order to ensure the insulation between the parts assembled in this case, a resin filler is filled.

Generally, each member constituting the ignition coil arranged in the ignition coil, that is, in the case, is made of a different material such as metal or resin so that the expansion coefficient between the members is different. Depending on the change in the operating environment temperature, thermal stress resulting from the difference in expansion coefficient, that is, the difference in thermal expansion and contraction may occur in the resin insulating material, and cracks such as cracks and breaks may occur in the resin insulating material. The crack is likely to propagate starting from the edge of each member in contact with the resin insulating material. On the other hand, the central core is formed into a round bar shape by laminating, for example, silicon steel plates in the radial direction, and the edge portions are formed to form not only the corner portions of the round bar but also the outer peripheral surface of the round bar. Many are present at each corner of the silicon steel sheet.

For this reason, cracks may occur in the filler due to the above-mentioned thermal stress due to the difference in expansion coefficient between the central core and the filler. To alleviate this thermal stress, the central core is made of soft material. The buffer tube is covered.

[0006]

In the conventional structure, it is necessary to cover the central core with the coating tube, particularly, it is necessary to thermally contract the core to integrate the core with the central core.

The present invention has been made in view of the above circumstances, and therefore an object thereof is to provide an ignition coil which can reduce the labor of coating the central core with the coating tube.

[0008]

According to claim 1 of the present invention, a rod-shaped central core made of a magnetic material, an inner peripheral coil wound around the outer peripheral side of the central core, a central core and an inner peripheral side. An inner-circumferential-side spool that is arranged between the coil and the inner-circumferential-side coil, and an outer-circumferential-side coil wound around the outer-circumferential-side of the inner-circumferential-side coil; And an outer peripheral spool around which the winding of the outer peripheral coil is wound, and a cylindrical case disposed on the outer peripheral side of the outer peripheral coil. The case is filled with a resin insulating material. Is an ignition coil in which the inner peripheral coil and the outer peripheral coil are molded and fixed, and a buffer member made of a hard tube is arranged between the central core and the inner spool, and It projects from the shaft end of the core.

Since a buffer member made of a hard tube is arranged between the central core and the inner peripheral side spool, for example, cracks start from the edge portions of a plurality of laminated steel plates formed on the central core. Even if it occurs, the crack can be prevented from propagating in the radial direction. Furthermore, since this cushioning member is arranged so as to project from the shaft end of the central core, even when the resin insulating material filled in the case of the ignition coil contacts the surface of the shaft end of the central core, for example, It is possible to prevent the development of cracks inside the buffer member protruding from the axial end portion of the central core.

Moreover, in the central core provided with the cushioning member, since the cushioning member is formed of a hard tube, there is no need for heat shrinking like a soft tube such as a heat shrinking tube, and the number of processing steps in manufacturing the ignition coil is reduced. It can be reduced.

According to a second aspect of the present invention, the buffer member is formed in a bottomed cylindrical body, and the central core is housed at an axially intermediate position of the bottomed cylindrical body.

Thus, the cushioning member is arranged so as to cover the outer peripheral side of the central core and project from the corners of the shaft end of the central core or the edges of a plurality of steel plates formed on the surface of the shaft end. it can.

Further, for example, as a structure in which the inner circumference of the cushioning member is in close contact with the outer circumference of the central core, the central core is inserted and assembled into the opening of the bottomed tubular body of the cushioning member, so that the cushioning can be easily performed with the central core. The members can be integrally formed.

According to the third aspect of the present invention, the inner peripheral side spool or the outer peripheral side spool is provided with a bottom portion for holding the end portion of the cushioning member, and the bottom portion can be inserted into the cushioning member axially inside. A step portion is formed.

Thus, the inner peripheral side spool or the outer peripheral side spool is provided with the bottom portion for holding the end portion of the cushioning member, and the step portion which can be inserted into the cushioning member in the axial direction is formed on the bottom portion. , Regardless of whether or not the inner periphery of the cushioning member is in close contact with the outer periphery of the central core, the central core is arranged inside the axial direction of the cushioning member, that is, the cushioning member is projected from the axial end portion of the central core. be able to.

According to the fourth aspect of the present invention, a buffer body having a thickness larger than that of the buffer member is disposed on at least one of both axial ends of the central core.

The cracks in the resin insulating material in contact with the surface of the central core are affected by thermal expansion and contraction due to the difference in expansion coefficient. Therefore, the central core formed in a rod shape is generally longer than the outer peripheral side. The effect of thermal expansion and contraction between both ends of the shaku is large.

On the other hand, in the ignition coil of the present invention,
It is not necessary to provide a buffer body thicker than the cushioning member on the both shaft end portions side, and it is possible to absorb the influence of thermal expansion and contraction, that is, the thermal stress by providing it on at least one of the both shaft end portions.

According to claim 5 of the present invention, the cushioning member comprises:
Greater than the tensile strength of resin insulation.

That is, even if a crack occurs in the resin insulating material due to the effect of thermal expansion and contraction due to the difference in expansion coefficient, the buffer member has a higher tensile strength as a mechanical strength than the resin insulating material, so that cracking or cracking occurs. Without causing cracks such as, by elastically deforming due to the hard tube of the cushioning member, the stress caused by the cracks is absorbed by the elastic deformation,
Or dispersible.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment in which the ignition coil of the present invention is applied to an ignition coil for an internal combustion engine and is embodied will be described.
It will be described with reference to the drawings.

FIG. 1 is a vertical sectional view showing a schematic structure of an ignition coil according to an embodiment of the present invention. FIG. 2 shows II in FIG.
It is the cross-sectional view seen from -II. FIG. 3 is an enlarged partial cross-sectional view of a portion within a line III around the central core and the cushioning member, which is a main part of the present invention in FIG.

As shown in FIG. 1, the ignition coil 1 is housed in a plug hole formed for each cylinder in an upper portion of an engine block (not shown), and an ignition plug (not shown) and a lower portion in FIG. It is electrically connected.

The ignition coil 1 has a cylindrical housing 11 made of a resin material as a cylindrical case of the ignition coil 1.
The accommodation chamber 11a formed in the housing 11 accommodates the central core portion 12, the secondary spool 20, the secondary coil 21, the primary spool 23, the primary coil 24, the outer peripheral core 25, and the like. There is.

The housing 11 covers the outer periphery of the head portion 11b and the outer peripheral core 25 in which the connector portion 30 and the bracket portion 32 for fixing the ignition coil 1 to the engine block are integrated, and the ignition coil main body portion ( Specifically, the secondary coil 21 as an inner peripheral side coil, the cylindrical portion 11c that protects the primary coil 24 as an outer peripheral side coil, and the like are fitted and attached to the ignition plug (specifically, the secondary coil). A first high-voltage terminal 40 to which the high-voltage side winding of 24 is connected, and a second high-voltage terminal 41 electrically connecting the first high-voltage terminal 40 and a spring 42 made of a conductive material that contacts the terminal of the spark plug. Etc. are housed) and a high-voltage tower section 11d is included.
The connecting portions of the head portion 11b, the tubular portion 11c, and the high-voltage tower portion 11d have a press-fitting structure, and are bonded and sealed with an adhesive or the like.

The epoxy resin 26 filled in the housing chamber 11a of the housing 11 penetrates between the respective members in the ignition coil 1 and serves as a resin insulating material to ensure the electrical insulation between the members. Specifically, the housing chamber 11a is filled with a casting resin (epoxy resin in the present embodiment) 26 having electrical insulation as a resin insulating material, and both coils 21,
24 and other parts are fixed to the mold. In addition, at the connecting portion between the tubular portion 11c and the high-voltage tower portion 11d,
In order to prevent the epoxy resin 26 from cracking due to the difference in thermal expansion and contraction between the outer peripheral core 25 and the housing 11, for example, an elastic cushioning member 11e is attached to the lower end of the outer peripheral core 25.

The central core portion 12 is composed of a core body 13 and permanent magnets (not shown) arranged at both axial ends of the core body 13. In addition, in the present embodiment, the case of the core body 13 having no permanent magnet will be described below. In solving the problems of the present invention, regardless of whether or not the central core portion 12 has a permanent magnet, the problem is solved by the ignition coil 1 of the present invention. Therefore, a central core having a permanent magnet is provided. Detailed description of the unit 12 is omitted.

As shown in FIGS. 1 and 2, the core body 13 is formed in a rod shape made of a magnetic material (a silicon steel plate in this embodiment), and a thin silicon steel plate has a substantially circular cross section. Are assembled by stacking in the radial direction.

Between the outer circumference of the core body 13 and the inner circumference of the secondary spool 20, a hard tube made of a resin material (polyethylene terephthalate resin (PET) in this embodiment) is used as a buffer member. The tubular member 17 of is arranged. Further, the cap 19 is fitted to the central core portion 12 having the tubular member 17 on the outer peripheral side. In addition,
The cap 19 and the secondary spool 20 as the inner peripheral side spool form a case member that surrounds the outer periphery of the central core portion 12.

The details of the tubular member 17 will be described later.

The secondary coil (inner peripheral coil) 21 is arranged on the outer peripheral side of the central core portion 12 (specifically, the outer peripheral side of the cylindrical member 17 disposed on the outer peripheral side of the core body 13), and the secondary coil The winding on the high voltage side of 21 is electrically connected to the spark plug, and the control signal from the igniter 60 for controlling the high voltage generated in the secondary coil 21 is input to the outside of the secondary coil 21. Primary coil (outer peripheral side coil) 24
Are arranged.

In the ignition coil, the voltage input to the primary coil 24 is boosted and output from the secondary coil 21, so that the number of turns of the secondary coil 21 is larger than that of the primary coil 24. The wire diameter of the winding of the secondary coil 21 is smaller than that of the winding of the primary coil 24.

The secondary spool (inner side spool) 20 is
As shown in FIG. 1 and FIG. 2, a resin having a bottomed tubular shape is provided on the outer peripheral side of the tubular member 17 and is provided with a central core portion 12 and a bottom portion 20a for holding the end portion of the tubular member 17. In the embodiment, it is formed of an electrically insulating material such as PPE resin). The secondary coil 21 is wound around the outer periphery of the secondary spool 20, and a dummy coil 22 is further wound around the high voltage side of the secondary coil 21 in a single turn. The dummy coil 22 electrically connects the secondary coil 21 and the first high voltage terminal 40. The coil on the high voltage side of the secondary coil 21 is not a single wire, but a dummy coil 22
And the first high-voltage terminal 40 are electrically connected, the surface area of the electrically connecting portion between the secondary coil 21 and the first high-voltage terminal 40 is increased, and electric field concentration on the electrically connecting portion is avoided. There is.

The secondary coil 21 has a structure similar to that shown in FIGS.
As shown in, the coil is wound such that the thickness of the coil (the number of coil winding steps) decreases toward the higher voltage side.

Details of the bottom portion 20a of the secondary spool 20 around which the secondary coil 21 is wound, particularly, the central core portion 12
The structure for holding the end of the tubular member 17 will be described later.

The primary spool (outer peripheral side spool) 23 is
As shown in FIGS. 1 and 2, the secondary coil 21 is arranged on the outer peripheral side and is formed in an approximately cylindrical shape with an electrically insulating material such as resin (PPE resin in the present embodiment). The primary coil 24 is wound around the outer circumference of the primary spool 23.

A thin film 23a made of resin (PET in this embodiment) may be wound on the outer peripheral surface of the primary spool 23 (between the primary coil 24 and the primary spool 23). With this thin film 23a,
The primary spool 23 and the resin insulating material 26 as the molding resin are prevented from completely adhering.

The outer peripheral core 25 is mounted on the outer side of the primary coil 24 and is formed of a magnetic material such as a thin silicon steel plate into a substantially cylindrical shape.

Further, the central portion of the first high voltage terminal 40 constitutes a claw portion bent in the direction of inserting the second high voltage terminal 41. The second high voltage terminal 41 is electrically connected to the first high voltage terminal 40 by inserting the tip of the second high voltage terminal 41 into the claw portion. The high voltage end winding of the dummy coil 22 is electrically connected to the first terminal 40 by fusing, soldering, or the like. The spring 42 is electrically connected to the second high voltage terminal 41 and also electrically connected to the ignition plug when the ignition coil 1 is inserted into the plug hole. A plug cap 43 made of rubber is attached to the open end of the housing 11 on the high voltage side, and an ignition plug is inserted into the plug cap 43.

The connector 30 has a terminal 31
Is insert molded, and this terminal 31
An igniter 60 as a switching circuit is electrically connected to a winding end of the primary coil 24 so as to supply a control signal to the primary coil 24.

The igniter 60 may be housed in the ignition coil 1 (specifically, the head portion 11b) as shown in FIG. 1 and supplied to the igniter 60 from the outside via the terminal 31. Alternatively, an igniter 60 for supplying a control signal to the primary coil 24 may be provided outside the ignition coil 1 and a control signal may be supplied to the primary coil 24 via the terminal 31.

The ignition coil 1 having the above-mentioned structure is provided with the igniter 60 via the terminal 31 of the connector section 30.
When the control signal output from the primary coil 24 is supplied to the primary coil 24, a high voltage is generated in the secondary coil 21 according to the voltage input to the primary coil 24. This high voltage causes the dummy coil 22, the first terminal 40, the second high voltage terminal 41,
It is applied to the spark plug through the spring 42.

On the other hand, since the members constituting the ignition coil arranged in the ignition coil 1, that is, the housing 11, are made of different materials such as metal and resin, the expansion coefficient between the members is different. For example, in accordance with a change in the operating environment temperature, a thermal stress due to a difference in expansion coefficient, that is, expansion and contraction due to a temperature change, that is, a difference in thermal expansion and contraction occurs between the members. When thermal stress is generated, the primary and secondary spools 21 and 24 formed of a resin material having a lower mechanical strength such as tensile strength than the metal material and the resin insulating material 26 for resin molding, particularly resin insulation A crack such as a crack or a break may occur in the material 26.

Specifically, for example, the expansion coefficient of the resin insulating material 26 made of epoxy resin and the secondary spool 21 made of PPE resin surrounding the outer circumference of the core body 13 is determined by the core body 13 made of a silicon steel plate.
Is larger than the expansion coefficient of. Therefore, the resin insulating material 26
When the core body 13 of the central core portion 12 is in direct contact with the core body 13 and the core body 13 and the resin insulating material 26 repeatedly undergo thermal expansion and contraction, cracks may occur in the resin insulating material 26 that is in contact with the core body 13. .

The crack is likely to propagate from the edge of each member in contact with the resin insulating material 26 as a starting point. On the other hand, the core main body 13 is formed in a round bar shape by laminating silicon steel plates in the radial direction, and the edge portion which is a crack, that is, the starting point for the crack to propagate is not only a round bar-shaped corner portion but also a round bar shape. A large number are present at each corner of the laminated silicon steel plates forming the outer peripheral surface.

Therefore, in the conventional structure, for example, the core body 13 is integrally formed by heat-shrinking the tubular member made of a soft resin such as a polyolefin resin. However, in the case of the conventional tubular member made of the soft tube, there is a problem that the time and effort required for heat shrinkage when the core body 13 is covered and assembled increases man-hours in the manufacturing process and increases the product cost.

Therefore, the edge portion of the surface of the core main body 13 due to the structure around the central core portion 12, which is a main part of the ignition coil of the present invention, and in particular due to the difference in the thermal expansion coefficient of each component forming the ignition coil 1. A structure for preventing the development of cracks in the resin insulating material 26 caused by the above will be described below with reference to FIGS. 1 and 3.

First, the tubular member is made of a hard tube made of PET, and is arranged so as to cover the core body 13 at a predetermined interval on the outer peripheral side of the core body 13, as shown in FIG. ing. Furthermore, this tubular member 13
Is at least the corner of the round bar-shaped core body 13 is the tubular member 1.
3 so as not to be exposed to the outside of the core body 13.
It is arranged so as to project from 3a.

As a result, first, the cylindrical member 17 as a cushioning member made of a hard tube is arranged on the outer peripheral side of the core body 13 and the inner peripheral side of the secondary spool 20, so that, for example, the housing of the ignition coil 1 is provided. Even when the resin insulating material 26 filled in 11 contacts the outer peripheral surface 13b (see FIG. 2) of the core body 13 via the tubular member 17, the edges of the plurality of steel plates formed by being laminated on the outer periphery of the core body 13 Even if a crack is generated in the resin insulating material 26 starting from the portion 13 bp, the progress of the crack stops at the tubular member 17, and it is possible to prevent the crack from further extending in the radial direction. Further, since the tubular member 17 is arranged so as to project from the shaft end portion 13a of the core body 13,
For example, even when the resin insulating material 26 filled in the housing 11 of the ignition coil 1 is in contact with the surface of the shaft end portion 13a, the crack progresses within the range of the tubular member 17 protruding from the shaft end portion 13a, It is possible to prevent the development of cracks on the outside.

Moreover, the central core portion 1 provided with the tubular member 17
2, that is, in the core body 13, since the tubular member 17 is formed of a hard tube, there is no need for heat shrinking like a soft tube that can be heat shrunk, such as a polyolefin type,
In manufacturing the ignition coil 1, the number of processing steps can be reduced.

As shown in FIG. 3, the secondary coil 2 has a structure in which the core body 13 is arranged inside the tubular member 17.
By setting the shape of the bottom portion 20a of the secondary spool 20 around which the coil 1 is wound as follows, the assembly of the ignition coil 1 is performed, and in particular, the end portions of the core body 13 and the tubular member 17 are attached to the bottom portion 20a of the secondary spool 20. It can be easily held and assembled.

That is, as shown in FIG. 3, the bottom portion 20a has a step portion 2 which can be inserted into the axial direction of the tubular member 17.
0ah is formed. Accordingly, the core body 13 can be arranged inside the tubular member 17 in the axial direction regardless of whether or not the inner periphery of the tubular member 17 is in close contact with the outer periphery of the core body 13.

The shape of the step portion 20ah is shown in FIG.
As shown in FIG. 2, the insertion hole 20b formed in the central portion of the bottom portion 20a has a structure in which the second high-voltage terminal 41 is inserted and electrically connected to the claw portion formed in the central portion of the first high-voltage terminal. It is desirable to form it so as to have an inner circumference substantially coaxial with. As a result, in the ignition coil 1 housed in the plug hole, when the housing 11 that protects each member that constitutes the ignition coil 1 is made longer and thinner, the housing 11 can be easily moved in the axial direction. It is possible to facilitate the resin moldability such that the resin can be formed.

The cylindrical member 17 described in the present embodiment.
Uses a resin material whose tensile strength is higher than that of the resin insulating material 26 and tensile strength. As a result, even if a crack occurs in the resin insulating material 26 due to the effect of thermal expansion and contraction due to the difference in expansion coefficient, the tubular member 17 has a higher tensile strength as mechanical strength than the resin insulating material 26, so that a crack, Without causing cracks such as cracks, by continuing elastic deformation due to the mechanical strength of the hard tube of the tubular member, depending on the amount of deformation of the elastic deformation, absorption of stress causing cracks, or dispersion It is possible.

(Modification) As a first modification, instead of the shape of the cylindrical body of the cylindrical member 17 described in the above embodiment, a cylindrical member having the shape of a bottomed cylindrical body shown in FIG. 4 is used. The ignition coil 1 may be provided with 17. FIG. 4 is a vertical cross-sectional view showing a tubular member as a cushioning member of the first modified example.

As shown in FIG. 4, the tubular member 17 includes a cylindrical portion 17a, an annular portion 17b formed at one end of the cylindrical portion 17a, and an opening 1 formed at the other end.
It consists of 7c. The opening portion 17c is formed so as to be inserted into the step portion 20ah formed on the bottom portion 20a of the secondary spool 20 described in the above embodiment, and the tubular member 17 is shown in FIG. Cylindrical member 17 in the vertical direction shown
Is arranged so that it is housed in the ignition coil 1 as shown in FIG.

As a result, the tubular member 17 is fixed to the core body 13
It can be arranged so as to cover the outer peripheral surface 13b side and project from the corners of the shaft end 13a of the core body 13 or the edge portions of the plurality of steel plates formed on the surface of the shaft end.

Further, for example, as a structure in which the inner circumference of the tubular member 17 is in close contact with the outer circumference of the core body 13, the core body 13 is inserted and assembled from the opening 17c of the tubular member 17, so that the core body 13 and the tubular body can be easily assembled. The member 17 can be integrally formed.

As a second modification, the core body 1
A buffer 17d (e.g., a rubber material or a single-pore sponge in the present embodiment) having a wall thickness thicker than that of the tubular member 17 may be arranged on at least one of both ends 13a of 3 (see FIG. 5). The buffer 17d may be formed by increasing the wall thickness of the annular portion 17b (see FIG. 4) of the bottomed tubular body described in the first modification.

As in the conventional structure, the cushioning member 17d having a wall thickness thicker than that of the tubular member 17 (specifically, the cylindrical portion 17a) is provided at both shaft end portions 13.
It is not necessary to provide each on the a side, and it is possible to absorb the influence of thermal expansion and contraction, that is, the thermal stress by merely providing it on at least one of both shaft end portions 13a.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a schematic configuration of an ignition coil according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II in FIG.

FIG. 3 is an enlarged partial cross-sectional view of a portion within a line III around a central core and a cushioning member, which are main parts of the present invention in FIG.

FIG. 4 is a vertical cross-sectional view showing a cushioning member of a first modified example.

FIG. 5 is a vertical sectional view showing a configuration of an ignition coil according to a second modification.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ignition coil 11 Housing (case) 12 Central core part 13 Core body 13a Shaft end parts 13b, 13bp Outer peripheral surface, edge part (corner part of silicon steel plates formed in rod shape by laminating in radial direction) 17 Cylindrical member (cushioning) Member 17a Cylindrical portion 17b Annular portion 17c Opening 17d Buffer 19 Cap 20 Secondary spool (inner circumferential spool) 20a Bottom 20ah Step portion 21 Secondary coil (inner circumferential coil) 23 Primary spool (outer circumferential spool) 24 Secondary coil (inner side coil) 25 Outer core 26 Epoxy resin (resin insulation material)

Claims (5)

[Claims] 1. A rod-shaped central core made of a magnetic material, an inner peripheral side coil wound around the outer peripheral side of the central core, and an inner peripheral side provided between the central core and the inner peripheral side coil. An inner peripheral spool around which the winding of the side coil is wound, an outer peripheral coil wound on the outer peripheral side of the inner peripheral coil, and arranged between the inner peripheral coil and the outer peripheral coil,
An outer peripheral spool around which the winding of the outer peripheral coil is wound, and a cylindrical case arranged on the outer peripheral side of the outer peripheral coil are provided, and the case is filled with a resin insulating material to form the inner periphery. An ignition coil in which the side coil and the outer peripheral side coil are fixed in a mold, and a cushioning member made of a hard tube is arranged between the central core and the inner peripheral side spool, and the cushioning member is An ignition coil projecting from an axial end portion of the central core. 2. The cushioning member is formed in a bottomed tubular body, and the central core is housed at an axially intermediate position of the bottomed tubular body. Ignition coil. 3. The inner circumference side spool or the outer circumference side spool includes a bottom portion that holds an end portion of the cushioning member, and the bottom portion has a step portion that can be inserted into the cushioning member in the axial direction. It is formed, The ignition coil of Claim 1 or Claim 2 characterized by the above-mentioned. 4. A cushioning body having a thickness larger than that of the cushioning member is disposed on at least one of both axial end portions of the central core. Ignition coil according to item. 5. The ignition coil according to claim 1, wherein the cushioning member is larger than the tensile strength of the resin insulating material.