Ignition coil
The ignition coil integrates a resin resistor to address parasitic capacitance issues, enabling efficient discharge of residual charge within the coil assembly, reducing complexity and cost by eliminating the need for external components.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- DIAMOND&ZEBRA ELECTRIC MFG CO LTD
- Filing Date
- 2024-11-20
- Publication Date
- 2026-06-01
AI Technical Summary
Existing ignition coils for internal combustion engines face issues with parasitic capacitance leading to residual charge retention, particularly in hydrogen fuel engines, which can cause improper combustion due to improper discharge timing, and adding external resistors increases cost and complexity.
An ignition coil design that integrates a resin resistor within the coil assembly, allowing residual charge to be discharged to ground without external components, using a thermosetting resin with a filler to maintain a small volume and high resistance value.
The integrated resin resistor effectively discharges residual charge to ground, suppressing parasitic capacitance effects while reducing assembly complexity and cost, ensuring efficient ignition without external components.
Smart Images
Figure 2026089194000001_ABST
Abstract
Description
Technical Field
[0001] This specification discloses an ignition coil for an internal combustion engine.
Background Art
[0002] An ignition coil for an internal combustion engine generally outputs the high voltage generated in a coil assembly having a primary coil and a secondary coil to a spark plug mounted in a combustion chamber of the internal combustion engine. The spark plug receives the high voltage and generates a discharge between a positive electrode and a negative electrode to ignite the fuel.
[0003] The occurrence of an abnormal state in a line connecting the output of the coil assembly and the spark plug can cause malfunction of the spark plug, failure of the ignition coil, generation of noise, etc. To prevent the occurrence of an abnormal state, various high-voltage elements may be attached to this line in series or in parallel. An example of an ignition coil having a high-voltage element is reported in Japanese Unexamined Patent Application Publication No. 2002-61560.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] A parasitic capacitance exists between the positive and negative electrodes of a spark plug. When a discharge occurs in the spark plug, the charge may not be fully released, and charge may remain in this parasitic capacitance. This charge retention is particularly likely to occur in internal combustion engines using hydrogen fuel, which has a high combustion rate. The residual charge can be discharged at an improper timing, which can cause improper combustion in the internal combustion engine. To create a path for releasing the residual charge, one could consider connecting the line from the ignition coil to the spark plug to ground via a resistor. However, a high resistance value is required for this ground bus to not affect normal operation. Resistors that achieve this resistance value are generally large and difficult to house inside the ignition coil. Adding a resistor as an external component increases costs and assembly complexity.
[0006] The inventor's intention is to provide an ignition coil that enables the discharge of residual charge in the spark plug without the need for external components. [Means for solving the problem]
[0007] An ignition coil according to one embodiment comprises a coil assembly having a primary coil and a secondary coil, an output terminal for outputting the output of the coil assembly to the outside, a ground terminal electrically connected to an external ground, a resin resistor with one end electrically connected to the output terminal and the other end electrically connected to the ground terminal, and a case for housing the coil assembly and the resin resistor. [Effects of the Invention]
[0008] This ignition coil includes a resin resistor, one end of which is electrically connected to the output terminal and the other end of which is electrically connected to the ground terminal. When the ignition coil is installed in an internal combustion engine, the output terminal is connected to the spark plug. If residual charge is generated on the spark plug, this charge is discharged to ground through the output terminal of the ignition coil, the resin resistor, and the ground terminal. Because this resin resistor can be implemented in a small volume, it can be integrated into the ignition coil. With this ignition coil, residual charge is suppressed without the need for external components. [Brief explanation of the drawing]
[0009] [Figure 1] Figure 1 is a perspective view showing an ignition coil according to one embodiment. [Figure 2] Figure 2 is a cross-sectional view along the line II-II in Figure 1. [Figure 3] Figure 3 is a perspective view showing the ignition coil case from Figure 1. [Figure 4] Figure 4 is an enlarged cross-sectional view of a portion of Figure 2. [Figure 5] Figure 5 is a perspective view that is an enlarged portion of Figure 3. [Figure 6] Figure 6 is a circuit diagram of the ignition coil shown in Figure 1. [Modes for carrying out the invention]
[0010] Preferred embodiments will be described in detail below, with reference to drawings as appropriate.
[0011] Figure 1 is a perspective view showing an ignition coil 2 according to one embodiment. Figure 2 is a cross-sectional view along line II-II in Figure 1. In Figure 1-2, arrow X represents the front of the ignition coil 2. The opposite direction is the rear. Arrow Y represents the right side of the ignition coil 2. The opposite direction is the left side. Arrow Z represents the top of the ignition coil 2. The opposite direction is the bottom. In this embodiment, the ignition coil 2 is for a hydrogen-fueled engine. As shown in Figure 1, the ignition coil 2 comprises a case 4, a connector section 6, an output tower 8, a coil assembly 10, and a filler 12. As shown in Figure 2, the ignition coil 2 further comprises an igniter 14 and a reed 16.
[0012] Figure 3 is a perspective view showing case 4. A portion of the output tower 8 is also shown in Figure 3. As shown in Figure 3, case 4 is a hollow box shape. In this embodiment, case 4 has an opening 18 extending from the top surface to the front surface (the surface on the connector portion 6 side). Case 4 is provided with a flange portion 20 extending rearward from the rear surface. The flange portion 20 is provided with a hole 22 that penetrates vertically and a bushing 24 that covers the inner circumferential surface of the hole 22. Although not shown, the ignition coil 2 is fixed to the engine by passing a bolt through the hole 22 and a hole provided in the engine. The part of case 4 other than the bushing 24 (case body 26) is made of resin. Preferred materials for the case body 26 include PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), and PET (polyethylene terephthalate). The bushing 24 is made of metal. Preferred materials for the bushing 24 include steel and aluminum alloy.
[0013] As shown in Figure 2, the connector section 6 is located at the front of the case 4. Signals are input to the connector section 6 from the outside. As shown in Figures 1 and 2, the connector section 6 comprises a cylindrical section 28, a base section 30, and connector terminals 32. The cylindrical section 28 is cylindrical with an open front. The connector terminals 32 are located inside the cylindrical section 28. There are multiple connector terminals 32. For example, the connector terminals 32 include signal connector terminals, power connector terminals, and ground connector terminals. The base section 30 is plate-shaped. In this embodiment, the base section 30 covers the portion of the opening 18 of the case 4 that is located at the front.
[0014] As shown in Figure 2, the coil assembly 10 is housed in case 4. The coil assembly 10 comprises a primary coil 34, a secondary coil 36, an iron core 38, a cover 40, and a cap 42. The primary coil 34 is formed by winding wire around the iron core 38, and the secondary coil 36 is formed by winding wire around the outside of the primary coil 34. The iron core 38 comprises a central iron core 38a and an outer iron core 38b. The central iron core 38a passes through the center of the primary coil 34 and the secondary coil 36. The outer iron core 38b extends from one end of the central iron core 38a, around the top of the primary coil 34 and the secondary coil 36, to the other end of the central iron core 38a. The number of turns of wire in the secondary coil 36 is significantly greater than the number of turns of wire in the primary coil 34. As a result, a high voltage is generated in the secondary coil 36 by changing the current in the primary coil 34. The output of the secondary coil 36 becomes the output of the coil assembly 10. The wires of the primary coil 34 and the secondary coil 36 are typically copper wires.
[0015] Cover 40 covers the outer peripheral iron core 38b. In this embodiment, cover 40 is made of an elastomer that is easily peelable from the filler 12. Cover 40 prevents cracks in the filler 12 caused by the expansion, contraction, and expansion of the outer peripheral iron core 38b due to heat. Cap 42 covers the upper portion of the outer peripheral iron core 38b. As shown in FIG. 1, cap 42 is exposed from the filler 12. Cap 42 protects the outer peripheral iron core 38b from the outside. Cap 42 is made of a resin with excellent durability. Preferred materials for cap 42 include PBT, PPS, and PET.
[0016] As shown in FIG. 2, igniter 14 is housed inside case 4. Igniter 14 is located between coil assembly 10 and connector portion 6. A control signal from the outside is input to igniter 14 via signal connector terminal 32. Igniter 14 switches the conduction and interruption of the current in primary coil 34 according to the control signal.
[0017] As shown in FIG. 2, output tower 8 is located below case 4. Output tower 8 has a cylindrical shape extending downward from case 4. In this embodiment, as shown in FIG. 2, output tower 8 includes a cap terminal 44 and a rod-shaped resistor 46 inside. In this embodiment, resistor 46 has a resistor body and metal caps covering the upper and lower ends of the resistor body. Cap terminal 44 is placed on one end of resistor 46. In this embodiment, the other end of resistor 46 serves as the outlet for the output signal from ignition coil 2. That is, in this embodiment, the other end of resistor 46 functions as output terminal 48 of ignition coil 2. When this ignition coil 2 is mounted on an internal combustion engine, output terminal 48 is electrically connected to the spark plug. For example, output terminal 48 is connected to the input of the spark plug via a spring. Lead 16 connects the output of coil assembly 10 and cap terminal 44. Lead 16 is made of a metal with excellent conductivity.
[0018] Figure 4 is an enlarged cross-sectional view of a part of Figure 2. This figure shows the lower rear part of the ignition coil 2. As shown in Figure 4, this ignition coil 2 further includes a resin resistor 50, a first connection wire 52, and a second connection wire 54. Figure 5 is an enlarged perspective view of a part of Figure 3. This figure shows the lower rear part of the case 4. Figure 5 also shows the first connection wire 52 and the conductive adhesive 56. This ignition coil 2 further includes a conductive adhesive 56.
[0019] The resin resistor 50 is located inside the case 4. As shown in Figure 5, a depression 58 is provided inside the case 4. The resin resistor 50 is filled in this depression 58. The resin resistor 50 is formed by curing a fluid resin resistor. In this embodiment, the resin resistor 50 is made of a thermosetting resin containing a filler. In this embodiment, the volume resistivity of the resin resistor 50 is 10 2 Ω·m or more and 10 4 Ω·m or less, and the amount of the filler is adjusted. As a preferable thermosetting resin, an epoxy resin is exemplified. The thermosetting resin may be a phenolic resin or an unsaturated polyester resin. As preferable fillers, glass fiber, alumina (Al2O2), and metal powders such as copper or aluminum alloy are exemplified.
[0020] The first connection wire 52 is located inside the case 4. In this embodiment, one end of the first connection wire 52 is connected to the lead 16. The first connection wire 52 is electrically connected to the output terminal 48 via the lead 16, the cap terminal 44, and the resistor 46. The first connection wire 52 extends to the depression 58 of the case 4. The other end of the first connection wire 52 is exposed inside the depression 58. The first connection wire 52 is made of a metal having excellent conductivity. Typically, the first connection wire 52 is made of copper or an aluminum alloy.
[0021] The second connecting wire 54 is located inside the case 4. As shown in Figure 4, one end of the second connecting wire 54 is connected to the bushing 24. The second connecting wire 54 passes inside the case body 26 and extends to the recess 58 in the case 4. The other end of the second connecting wire 54 is exposed inside the recess 58. The second connecting wire 54 is made of a metal with good conductivity. The second connecting wire 54 is typically made of copper or an aluminum alloy.
[0022] Although the conductive adhesive 56 is thin and therefore not visible in Figure 4, the conductive adhesive 56 consists of a first conductive adhesive 56 located between the first connecting wire 52 and the resin resistor 50, and a second conductive adhesive 56 located between the second connecting wire 54 and the resin resistor 50. Figure 5 shows the second conductive adhesive 56. The first conductive adhesive 56 bonds the first connecting wire 52 to the resin resistor 50, and the second conductive adhesive 56 bonds the second connecting wire 54 to the resin resistor 50. In this embodiment, the volume resistivity of the conductive adhesive 56 is 1.0 × 10⁻⁶. -6 Ω m or more 1.0×10 -2 The conductivity is Ω·m or less. In this embodiment, epoxy adhesives, urethane adhesives, or silicone adhesives are used as the conductive adhesive 56. Examples of preferred conductive adhesives 56 include silver paste, nickel paste, gold paste, palladium paste, and carbon paste.
[0023] The resin resistor 50 is electrically connected to the output terminal 48 via a first conductive adhesive 56 and a first connecting wire 52. The resin resistor 50 is electrically connected to the bushing 24 via a second conductive adhesive 56 and a second connecting wire 54. As described above, when the bolt is passed through the hole 22 in the flange portion 20, the bushing 24 comes into contact with the bolt. The bolt is normally at ground potential. The second connecting wire 54 is connected to the engine ground via the bushing 24. The bushing 24 functions as the ground terminal 60 of this ignition coil 2.
[0024] The filler 12 fills the gaps that occur inside the case 4. The filler 12 is formed from a cured fluid filler. In this embodiment, the filler 12 is made of a thermosetting resin. The filler 12 insulates the secondary coil 36, which generates high voltage, from other components. For this reason, a thermosetting resin with excellent insulating properties is selected as the material for the filler 12. In addition, in order to fill every corner of the gaps inside the case 4 with resin, a thermosetting resin with low viscosity before curing is selected as the material for the filler 12. Epoxy resin is an example of a preferred filler 12.
[0025] Figure 6 shows the circuit diagram of the ignition coil 2 shown in Figure 1. This figure shows the ignition coil 2 installed in the engine. This figure also includes the circuit diagram of the spark plug 62. This circuit diagram shows the elements that make up the ignition coil 2 as an igniter 14, primary coil 34, secondary coil 36, resistor 46, and resin resistor 50. Furthermore, the external terminals of the ignition coil 2 are shown as a signal connector terminal 32a, a power connector terminal 32b, a ground connector terminal 32c, an output terminal 48, and a ground terminal 60 (bushing 24). The circuit diagram of the spark plug 62 also shows the parasitic capacitance C between the positive and negative electrodes.
[0026] In this ignition coil 2, the igniter 14 is switched on and off by a control signal input to the signal connector terminal 32a, which in turn switches the conduction and interruption of the current in the primary coil 34. When the current in the primary coil 34, which was in a conducting state, is interrupted, a high voltage is generated in the secondary coil 36 by induced electromotive force. This high voltage is applied to the spark plug 62 from the output terminal 48 via the resistor 46. This causes a discharge at the spark plug 62, which ignites the fuel in the internal combustion engine.
[0027] In the discharge of the spark plug 62, the charge may not be sufficiently released, and charge may remain in the parasitic capacitance. In this ignition coil 2, the residual charge is discharged to ground through the ground terminal 60 via the resistor 46 and the resin resistor 50. In Figure 6, the flow of residual charge is shown by arrow A.
[0028] In this embodiment, the ignition coil 2 is manufactured in the following steps. (S1) Step of forming a case 4 to which the first connecting wire 52 and the second connecting wire 54 are attached. (S2) Step of attaching the output tower 8 to case 4. (S3) Step of attaching the connector part 6 to the case 4. (S4) Step of filling the recess 58 of case 4 with resin resistive material. (S5) Step of housing the coil assembly 10 in case 4. (S6) Step of filling the case 4 with filler. (S7) Step of curing the resin resist and filler.
[0029] In step S1, the first connecting wire 52 and the second connecting wire 54 are prepared. These are set in predetermined positions in the mold for forming the case 4. The case 4 with the first connecting wire 52 and the second connecting wire 54 attached is formed by injection molding.
[0030] In step S2, the output tower 8, including the cap terminals 44 and resistor 46, is mounted on the underside of the case 4. The perspective view in Figure 3, mentioned earlier, shows the state after this step is completed.
[0031] The resin portion of the output tower 8 may be formed integrally with the case 4 by injection molding during the manufacturing of the case 4. In this case, the cap terminals 44 and resistors 46 are attached in step S2.
[0032] In step S3, the connector section 6, to which the igniter 14 is attached, is mounted to the case 4. The base 30 of the connector section 6 closes the front portion of the opening 18 of the case 4. The igniter 14 may also be attached at the same time as the coil assembly 10 is housed in the case 4 in step S5, which will be described later.
[0033] In step S4, conductive adhesive 56 is applied to the respective ends of the first connecting wire 52 and the second connecting wire 54, which are exposed in the recess 58 of case 4. Then, the recess 58 is filled with a fluid resin resistive agent.
[0034] In step S5, the coil assembly 10 is housed in the case 4. Leads 16 are pre-attached to the coil assembly 10. The coil assembly 10 with the leads 16 is positioned so that the leads 16 are electrically connected to the cap terminals 44 and the first connecting wire 52.
[0035] In step S6, a fluid filler is poured into case 4 through the upper opening 18. The fluid filler fills the gaps inside case 4.
[0036] In step S7, the resin resist and filler are cured. In this embodiment, the resin resist and filler are cured by heating. As a result, the resin resist becomes a resin resistor 50 and the filler becomes a filler 12. This completes the assembly of the ignition coil 2.
[0037] The effects and advantages of this embodiment will be explained below.
[0038] In this embodiment, the ignition coil 2 includes a resin resistor 50, one end of which is electrically connected to the output terminal 48 and the other end of which is electrically connected to the ground terminal 60. When the ignition coil 2 is installed in an internal combustion engine, the output terminal 48 is connected to the spark plug 62. When residual charge is generated in the spark plug 62, this residual charge is discharged to the ground via the output terminal 48, the resin resistor 50, and the ground terminal 60 of the ignition coil 2. The resin resistor 50 can be built into the ignition coil 2 because it can achieve a large resistance value in a small volume. In this ignition coil 2, the discharge of residual charge from the spark plug 62 is achieved without any external components.
[0039] The resistance value of the resin resistor 50 is preferably 1 MΩ or more. By setting the resistance value of the resin resistor 50 to 1 MΩ or more, the influence of the line connecting the output terminal 48 to ground via the resin resistor 50 on the normal operation of the ignition coil 2 is suppressed. For example, the reduction in output current to the spark plug due to the output current from the ignition coil 2 flowing to the resin resistor 50 side is suppressed. From this viewpoint, the resistance value of the resin resistor 50 is more preferably 3 MΩ or more. The resistance value of the resin resistor 50 is preferably 10 MΩ or less. By setting the resistance value of the resin resistor 50 to 10 MΩ or less, the volume of the resin resistor 50 can be reduced. The influence of this resin resistor 50 on the volume of the ignition coil 2 is suppressed. Furthermore, by setting the resistance value of the resin resistor 50 to 10 MΩ or less, residual charge can be released in a short time. Residual charge can be released efficiently. From these viewpoints, the resistance value of the resin resistor 50 is more preferably 8 MΩ or less.
[0040] The resistance value of the resin resistor 50 can be changed by altering its volume resistivity and the size of the recess 58 in case 4. The resistance value of the resin resistor 50 can also be set to match the output of the engine in which this ignition coil is installed.
[0041] In this embodiment, the resin resistor 50 is made of a thermosetting resin containing a filler. In many cases, thermosetting resin is used as a filler 12 to fill gaps in the case 4 during the manufacture of the ignition coil 2. By making the resin resistor 50 a thermosetting resin containing a filler, the filler 12 and the resin resistor 50 can be formed in a single heat treatment. This makes it possible to easily and efficiently manufacture the ignition coil 2 including the resin resistor 50.
[0042] In this embodiment, a first conductive adhesive 56 is located between the resin resistor 50 and the first connecting wire 52, and a second conductive adhesive 56 is located between the resin resistor 50 and the second connecting wire 54. The conductive adhesive 56 prevents delamination between the first connecting wire 52 and the second connecting wire 54, which are metal, and the resin resistor 50, which is mainly composed of resin. The conductive adhesive 56 can improve the reliability of the connection between the first connecting wire 52 and the second connecting wire 54 and the resin resistor 50.
[0043] In this embodiment, case 4 has a recess 58, and the first connecting wire 52 and the second connecting wire 54 extend to this recess 58. As a result, a resin resistor 50 can be formed by filling the recess 58 with a resin resistor and curing it, thereby electrically connecting to the first connecting wire 52 and the second connecting wire 54. This facilitates the manufacture of the ignition coil 2 equipped with the resin resistor 50.
[0044] In the embodiments described above, the bushing 24 was used as the ground terminal 60 to which the resin resistor 50 is connected. The ground connector terminal 32 may also be used as the ground terminal to which the resin resistor 50 is connected. In this case, the recess in the case 4 to which the resin resistor 50 is filled is provided near the connector portion 6. A connecting wire is provided that is electrically connected to the ground connector terminal 32 and extends to this recess.
[0045] In the embodiments described above, no element is present between the output of the coil assembly 10 and the resistor 46. An element such as a diode may be present between the output of the coil assembly 10 and the resistor 46. The type and placement of this element are determined so as not to hinder the discharge of residual charge to ground via the resin resistor 50.
[0046] As described above, this embodiment makes it possible to realize an ignition coil that can release residual charge without external components. From this, the advantages of this embodiment are clear.
[0047] [Disclosure items] The following items constitute a disclosure of preferred embodiments.
[0048] [Item 1] A coil assembly comprising a primary coil and a secondary coil, An output terminal for outputting the output of the coil assembly to the outside, A ground terminal that is electrically connected to an external ground, A resin resistor, one end of which is electrically connected to the output terminal and the other end of which is electrically connected to the ground terminal, A case housing the coil assembly and the resin resistor An ignition coil equipped with a ignition coil.
[0049] [Item 2] The ignition coil described in item 1, wherein the resistance value of the resin resistor is 1 MΩ or more and 10 MΩ or less.
[0050] [Item 3] The ignition coil according to item 1 or 2, wherein the resin resistor is a thermosetting resin containing a filler.
[0051] [Item 4] The case comprises a flange portion that incorporates a conductive bushing, An ignition coil according to any one of items 1 to 3, wherein the bushing is the ground terminal.
[0052] [Item 5] The system further comprises a first connection line electrically connected to the output terminal and a second connection line electrically connected to the ground terminal, The aforementioned case has a recess inside, The first connecting wire and the second connecting wire each extend to the recess, An ignition coil according to any one of items 1 to 4, wherein the resin resistor is filled into the recess, thereby electrically connecting the first connecting wire and the second connecting wire, respectively, to the resin resistor.
[0053] [Item 6] The ignition coil according to item 5, wherein a conductive adhesive is present between each of the first and second connecting wires and the resin resistor.
[0054] [Item 7] A step of forming a case having a recess inside, to which a first connecting wire extending to the recess and a second connecting wire extending to the recess are attached. The step of filling the recess with a fluid resin resistive agent, A step of housing the coil assembly inside the case, The step of filling the case with a fluid filler, and The step of curing the resin resistive agent and filler. Includes, A method for manufacturing an ignition coil, wherein the first connecting wire is electrically connected to the output terminal and the second connecting wire is electrically connected to the ground terminal. [Industrial applicability]
[0055] The ignition coil described above is used in various internal combustion engines, such as hydrogen fuel internal combustion engines and fossil fuel internal combustion engines. [Explanation of Symbols]
[0056] 2. Ignition coil 4 cases 6. Connector section 8. Output Tower 10. Coil Assembly 12...filler 14. Igniter 16. Lead 18. Opening of the case 20.. Flange section 22. Holes in the flange section 24. Bushing 26... Case body 28...Cylinder part 30...Base 32... Connector terminals 34... Primary coil 36...Secondary coil 38... Iron core 40...cover 42... Cap 44... Cap terminals 46...Resistor 48...Output terminals 50... Resin resistors 52...First connection line 54...Second connecting line 56. Conductive adhesive 58... indentation 60...Ground terminal 62... Spark plugs
Claims
1. A coil assembly comprising a primary coil and a secondary coil, An output terminal for outputting the output of the coil assembly to the outside, A ground terminal that is electrically connected to an external ground, A resin resistor, one end of which is electrically connected to the output terminal and the other end of which is electrically connected to the ground terminal, A case housing the coil assembly and the resin resistor An ignition coil equipped with a ignition coil.
2. The ignition coil according to claim 1, wherein the resistance value of the resin resistor is 1 MΩ or more and 10 MΩ or less.
3. The ignition coil according to claim 1 or 2, wherein the resin resistor is a thermosetting resin containing a filler.
4. The case comprises a flange portion that incorporates a conductive bushing, The ignition coil according to claim 1 or 2, wherein the bushing is the ground terminal.
5. The system further comprises a first connection line electrically connected to the output terminal and a second connection line electrically connected to the ground terminal, The aforementioned case has a recess inside, The first connecting wire and the second connecting wire each extend to the recess, The ignition coil according to claim 1 or 2, wherein the resin resistor is filled into the recess, thereby electrically connecting the first connecting wire and the second connecting wire to the resin resistor, respectively.
6. The ignition coil according to claim 5, wherein a conductive adhesive is present between each of the first and second connecting wires and the resin resistor.
7. A step of forming a case having a recess inside, to which a first connecting wire extending to the recess and a second connecting wire extending to the recess are attached. The step of filling the recess with a fluid resin resistive agent, A step of housing the coil assembly inside the case, The step of filling the case with a fluid filler, and The step of curing the resin resistive agent and filler. Includes, A method for manufacturing an ignition coil, wherein the first connecting wire is electrically connected to the output terminal and the second connecting wire is electrically connected to the ground terminal.