Ignition device for internal combustion engine

Abstract

To provide a technique capable of dissipating heat generated in a primary coil and an ignitor.SOLUTION: An ignition device 1B for an internal combustion engine has an ignition coil, an ignitor, a case, a resin part, and a cover. The ignition coil has a primary coil, a secondary coil, and an iron core 60 for electromagnetically coupling the primary coil and the secondary coil, and supplies a high voltage to an ignition plug. The ignitor controls current flowing in the primary coil. The case exposes a part of the iron core 60, while storing the ignition coil and the ignitor. The resin part embeds a gap inside the case. The cover covers an exposure part which is a part exposed from the resin part of the iron core 60. The cover is made of metal or ceramic, and is interposed between the exposure part and an exterior space while being brought into contact with the exposure part. Thereby, heat generated in the primary coil and the ignitor can be more dissipated to the exterior space through the iron core and the cover.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] Conventionally, an ignition device for an internal combustion engine uses an ignition coil that boosts a low voltage supplied from a power supply device to several thousand volts. The ignition coil includes a primary coil, a secondary coil, and an iron core for electromagnetically coupling the primary coil and the secondary coil. The primary coil, the secondary coil, and the iron core are housed in a case and fixed at a predetermined position in the case. A conventional ignition coil is described in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6585123 Summary of the Invention [Problem to be solved by the invention]

[0004] The ignition coil (100) of Patent Document 1 is composed of a primary coil (10), a secondary coil (20), and an iron core that combines an I-shaped central iron core (30) and a U-shaped peripheral iron core (40) to form a closed magnetic circuit structure (paragraph 0017). The ignition coil (100) is housed in a case (70). A molded resin (90) that provides electrical insulation and physically fixes each component is filled in the case (70) up to the vicinity of the case opening surface (70a). A part of the peripheral iron core (40) is exposed from the resin surface (92) of the molded resin (90) (paragraph 0024).

[0005] In Patent Document 1, the exposed portion of the outer circumferential iron core (40) is covered with at least one of a first resin cover (60) and a second resin cover (50) (paragraphs 0025-0027, 0029, 0031). In addition to the structure in Patent Document 1, there are other structures in which a part of the outer circumferential iron core of the ignition coil is left exposed from the case and uncovered, and in which the entire core including the outer circumferential iron core is covered with molded resin inside the case.

[0006] On the other hand, in ignition coils with large discharge energy, such as those used in high-power reciprocating engines that have become widespread in recent years, a large current flows through the primary side when the primary coil is charged. This causes the primary coil and igniter to generate a large amount of heat, which may lead to melting or malfunction of various parts. Therefore, there is room for devising a structure near the ignition coil to better dissipate the heat generated in the primary coil and igniter.

[0007] An object of the present invention is to provide a technology that enables the generated heat to be more effectively dissipated by improving the structure in the vicinity of the ignition coil, even when the primary coil or igniter generates a large amount of heat. [Means for solving the problem]

[0008] In order to solve the above problems, the first invention of the present application is an ignition device for an internal combustion engine, comprising an ignition coil, an igniter, a case, a resin part, and a cover. The ignition coil comprises a primary coil, a secondary coil, and an iron core that electromagnetically couples the primary coil and the secondary coil, and supplies a high voltage to an ignition plug. The igniter controls the current flowing through the primary coil. The case houses the ignition coil and the igniter while exposing a portion of the iron core. The resin part fills the gap inside the case. The cover covers an exposed portion of the iron core that is exposed from the resin part. The cover is made of metal or ceramic, and is in contact with the exposed portion while being interposed between the exposed portion and an external space.

[0009] A second aspect of the present invention is the ignition device of the first aspect, wherein the cover is made of aluminum.

[0010] A third invention of the present application is an ignition device of the first or second invention, wherein the cover has a plate-shaped portion that contacts the exposed portion, and heat dissipation fins that protrude toward the external space from multiple points on the plate-shaped portion.

[0011] A fourth invention of the present application is an ignition device according to any one of the first to third inventions, wherein the core has a central core and an outer periphery core. The central core is located radially inward from the primary coil and the secondary coil and extends in the axial direction. The outer periphery core is located radially outward from the secondary coil and connects both axial ends of the central core. The exposed portion is a part of the outer periphery core.

[0012] A fifth aspect of the present invention is the ignition device according to any one of the first to fourth aspects, wherein the exposed portion has an uneven shape on a surface located outside the case, and the cover has an uneven surface that fits into and comes into contact with the uneven shape of the exposed portion.

[0013] A sixth aspect of the present invention is the ignition device of the third aspect, wherein the cover further includes a first extension portion extending from the plate-shaped portion into the internal space of the case, and the igniter contacts the first extension portion directly or indirectly via a first metal heat dissipation auxiliary member fixed to the igniter.

[0014] A seventh aspect of the present invention is the ignition device of the fourth aspect, wherein a first cavity, which is a tunnel-shaped cavity, is formed inside the resin part, and a second cavity, which is a tunnel-shaped cavity, is formed inside the central core. The ignition device further has a cooling pipe capable of cooling the core by flowing a cooling medium inside. The cooling pipe is inserted from the external space of the case into the internal space, reciprocates while being disposed in the first cavity and the second cavity, and is drawn out to the external space.

[0015] An eighth aspect of the present invention is the ignition device of the seventh aspect, wherein the igniter contacts the cooling pipe directly or indirectly via a first heat dissipation auxiliary member made of metal that is fixed to the igniter.

[0016] A ninth aspect of the present invention is the ignition device of the fourth aspect, wherein a first cavity, which is a tunnel-shaped cavity, is formed inside the resin part, and a second cavity, which is a tunnel-shaped cavity, is formed inside the central core. The ignition device further includes a first heat pipe. A portion of the first heat pipe is disposed in the first cavity and the second cavity, and another portion is sandwiched between the exposed portion and the cover.

[0017] A tenth aspect of the present invention is the ignition device of the ninth aspect, further comprising a second heat pipe, a portion of which is disposed in the first cavity and another portion of which is sandwiched between the exposed portion and the cover. The igniter is in direct contact with the second heat pipe or indirectly contact with the second heat pipe via a first metal heat dissipation auxiliary member fixed to the igniter.

[0018] An eleventh invention of the present application is the ignition device of the fourth invention, further comprising a second heat dissipation auxiliary member made of aluminum in contact with the central core. The cover has a plate-shaped portion, a heat dissipation fin, and a second extension portion. The plate-shaped portion contacts the exposed portion. The heat dissipation fins protrude from a plurality of points on the plate-shaped portion toward the external space. The second extension portion extends from the plate-shaped portion into the internal space of the case. The second heat dissipation auxiliary member contacts the second extension portion.

[0019] A twelfth aspect of the present invention is an ignition device according to any one of the first to eleventh aspects, wherein the primary coil includes a first primary coil and a second primary coil. The first primary coil is formed by winding a first primary conductor around the iron core. The second primary coil is formed by winding a second primary conductor around the iron core at a position different from the first primary coil. The ignition device further includes a power supply device and the spark plug. The power supply device applies a DC voltage to one end of the first primary coil and one end of the second primary coil. The spark plug ignites fuel by discharging in a gap based on a high voltage induced in the secondary coil. The igniter includes a first switching element, a second switching element, and a control unit. The first switching element is inserted in a first primary side ground wire connecting the other end of the first primary coil and a ground point, and is capable of switching between passing and cutting off a primary current flowing from the power supply device to the first primary coil. The second switching element is inserted in a second primary side ground wire connecting the other end of the second primary coil and a ground point, and is capable of switching between passing and cutting off a primary current flowing from the power supply device to the second primary coil. The control unit controls the opening and closing of the first switching element and the opening and closing of the second switching element. The control unit selects and executes one of a-1) a first charging control in which a primary current is caused to flow through the first primary coil by closing the first switching element to charge the first primary coil, and a-2) a second charging control in which a primary current is caused to flow through the second primary coil by closing the second switching element to charge the second primary coil, and then b) executes a discharge control in which the first switching element or the second switching element that was closed in the first charging control or the second charging control is switched to an open state to induce a high voltage at one end of the secondary coil to discharge the spark plug. The control unit alternately selects between the process a-1) and the process a-2). Effect of the Invention

[0020] According to the first to twelfth aspects of the present invention, the heat generated in the primary coil and the igniter can be dissipated to the outside space through the iron core and the cover in a large amount, which makes it possible to suppress the temperature rise of each part and the occurrence of malfunctions.

[0021] In particular, according to the second aspect of the present invention, the heat dissipation performance of the cover can be improved and the manufacturing costs can be reduced.

[0022] In particular, according to the third aspect of the present invention, by providing the heat dissipation fins, the surface area of ​​the cover is increased, allowing for more efficient heat dissipation.

[0023] In particular, according to the fifth aspect of the present invention, the contact area between the iron core and the cover is increased, so that more heat can be transferred from the iron core to the cover and dissipated more efficiently via the cover.

[0024] In particular, according to the sixth aspect of the present invention, the heat generated in the igniter can be directly transferred to the cover and dissipated more efficiently through the cover.

[0025] In particular, according to the seventh aspect of the present invention, the heat generated in the central core and the primary coil can be further cooled by using the cooling pipe.

[0026] In particular, according to the eighth aspect of the present invention, the heat generated in the igniter can be further cooled by using a cooling pipe.

[0027] In particular, according to the ninth aspect of the present invention, the heat generated in the central core and the primary coil can be further cooled by using the first heat pipe.

[0028] In particular, according to the tenth aspect of the present invention, the heat generated in the igniter can be further cooled by using the second heat pipe.

[0029] In particular, according to the eleventh aspect of the present invention, heat generated in the central core can be efficiently conducted to the cover via the second heat dissipation auxiliary member, and can further be efficiently dissipated via the cover.

[0030] In particular, according to the twelfth aspect of the present invention, by alternately passing a primary current through the first primary coil and the second primary coil to charge them, the amount of heat generated per unit time in each primary coil can be reduced. [Brief description of the drawings]

[0031] [Figure 1] 1 is a block diagram showing a schematic diagram of an operating environment of an ignition device for an internal combustion engine according to a first embodiment; [Diagram 2] 1 is a perspective view of an ignition device according to a first embodiment. [Diagram 3] 1 is a vertical sectional view of an ignition device according to a first embodiment. [Figure 4] FIG. 6 is a perspective view of an ignition device according to a second embodiment. [Diagram 5] FIG. 6 is a vertical sectional view of an ignition device according to a second embodiment. [Figure 6] FIG. 6 is a vertical sectional view of an ignition device according to a second embodiment. [Figure 7] FIG. 4 is a vertical sectional view of an ignition device according to a first modified example. [Figure 8] FIG. 11 is a vertical sectional view of an ignition device according to a second modified example. [Figure 9] FIG. 11 is a vertical sectional view of an ignition device according to a third embodiment. [Figure 10] FIG. 11 is a vertical sectional view of an ignition device according to a third embodiment. [Figure 11] FIG. 11 is a cross-sectional view of an ignition device according to a third embodiment. [Figure 12] FIG. 11 is a vertical sectional view of an ignition device according to a third modified example. [Figure 13] FIG. 11 is a cross-sectional view of an ignition device according to a third modified example. [Figure 14] FIG. 11 is a vertical sectional view of an ignition device according to a fourth embodiment. [Figure 15] FIG. 11 is a vertical sectional view of an ignition device according to a fourth embodiment. [Figure 16] FIG. 13 is a vertical sectional view of an ignition device according to a fifth embodiment. [Figure 17] FIG. 13 is a block diagram that illustrates an operating environment of an ignition device for an internal combustion engine according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings.

[0033] <1. First embodiment> <1-1. Ignition device configuration> First, the configuration of an ignition device 1 for an internal combustion engine according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram that shows a schematic operating environment of the ignition device 1 according to the first embodiment. As described later, the primary coil L1 and secondary coil L2 of the ignition coil 103 included in the ignition device 1 of this embodiment are arranged in a direction in which they are stacked on top of each other, but in Fig. 1, they are shown adjacent to each other for ease of understanding.

[0034] The ignition device 1 of this embodiment is mounted on a vehicle body 100 such as an automobile, and applies a high voltage to an ignition plug 113 for an internal combustion engine to generate a spark discharge. As shown in Fig. 1, the vehicle body 100 is equipped with the ignition plug 113, a power supply device 102 (battery), and an ECU 101 (Engine Control Unit) in addition to the ignition device 1. In a broad sense, the ignition plug 113, the power supply device 102, and the ECU 101 can be considered to be included in the ignition device 1.

[0035] The spark plug 113 is a device for realizing an ignition operation in a combustion chamber of an internal combustion engine. The spark plug 113 is electrically connected to one end 822 of a secondary coil L2 (described later) of the ignition coil 103 via a conductor 121. The spark plug 113 is interposed between one end 822 of the secondary coil L2 and a ground point (ground 151). The spark plug 113 has a center electrode 141 and a ground electrode 142. When a high voltage is induced in the secondary coil L2 of the ignition coil 103 and this high voltage exceeds a breakdown voltage in a gap d between the center electrode 141 and the ground electrode 142, a discharge occurs in the gap d, and a spark is generated. This ignites the fuel filled in the internal combustion engine. That is, the spark plug 113 ignites the fuel by discharging in the gap d based on the high voltage induced in one end 822 of the secondary coil L2.

[0036] The power supply device 102 is a storage battery capable of charging and discharging DC power. In this embodiment, the power supply device 102 is electrically connected to one end 811 of a primary coil L1 (described later) of the ignition coil 103 via a power line 150, which is a conductor. The power supply device 102 applies a DC voltage to one end 811 of the primary coil L1 of the ignition coil 103 via the power line 150.

[0037] The ECU 101 is a computer that comprehensively controls the transmission of the vehicle body 100, the operation of airbags, and the like.

[0038] FIG. 2 is a perspective view of the ignition device 1 according to the present embodiment. As shown in FIG. 2, the ignition device 1 has a three-dimensional shape in which the length in the longitudinal direction is longer than the length in the lateral direction. FIG. 3 is a vertical cross-sectional view of the ignition device 1 cut along a vertical cross section extending in the longitudinal direction of FIG. 2. However, the shape of the ignition device 1 is not limited to this. In addition, in FIG. 2 and subsequent figures, the "vertical direction" is defined for ease of explanation, but the direction in which the ignition device 1 is disposed during manufacture and use of the ignition device 1 is not limited to this. As shown in FIG. 1 to FIG. 3, the ignition device 1 has an ignition coil 103, an igniter 104, a case 105, a resin part 106, a cover 107, and a diode 114. Note that in FIG. 1 to FIG. 3, some members and some hatching in the cross-sectional views are omitted.

[0039] As shown in FIG. 3, the ignition coil 103 has a bobbin 40, a primary coil L1, a secondary coil L2, and an iron core 60. In the following description of the ignition coil 103, a direction parallel to the central axis Bc of the bobbin 40 is referred to as the "axial direction", a direction perpendicular to the central axis Bc of the bobbin 40 is referred to as the "radial direction", and a direction along the circumference of the central axis Bc of the bobbin 40 is referred to as the "circumferential direction". The "parallel direction" also includes a substantially parallel direction, and the "perpendicular direction" also includes a substantially perpendicular direction. The longitudinal direction is substantially parallel to the axial direction.

[0040] The bobbin 40 includes a primary bobbin 41 and a secondary bobbin 42 that can be connected to each other. The primary bobbin 41 and the secondary bobbin 42 each extend in a cylindrical shape along a central axis Bc. The primary bobbin 41 and the secondary bobbin 42 are made of a material such as a resin.

[0041] The primary coil L1 is formed by winding a conductor wire about one hundred and several tens of times around the central axis Bc on the outer peripheral surface of the primary bobbin 41 and laminating the conductor wire in a plurality of layers in the radial direction. Hereinafter, the conductor wire wound around the primary bobbin 41 is referred to as the "primary conductor wire 81". After the formation of the primary coil L1 is completed, the secondary bobbin 42 is disposed so as to cover the outer peripheral surface of the primary coil L1 and is connected to the primary bobbin 41. Then, a conductor wire different from the primary conductor wire 81 is wound around the outer peripheral surface of the secondary bobbin 42 about ten thousand times around the central axis Bc and laminating the conductor wire in a plurality of layers in the radial direction, thereby forming the secondary coil L2. Hereinafter, the different conductor wire wound around the secondary bobbin 42 is referred to as the "secondary conductor wire 82".

[0042] In this way, by arranging the primary coil L1 and the secondary coil L2 so as to be stacked on top of each other, it is possible to reduce the size of the entire ignition coil 103 including these coils. However, the primary coil L1 and the secondary coil L2 do not have to be wound while being stacked on top of each other in this way, and may be arranged adjacent to each other as shown in FIG.

[0043] The core 60 has a structure in which a central core 601 and an outer circumferential core 602 are combined. The central core 601 and the outer circumferential core 602 are each formed of a laminated steel plate in which silicon steel plates are laminated. More specifically, the central core 601 has an I-shape formed by laminating silicon steel plates along the central axis Bc. The central core 601 is inserted into a space 410 on the radial inside of the primary bobbin 41. That is, the central core 601 is located radially inside the primary coil L1 and the secondary coil L2, and extends in the axial direction.

[0044] The outer core 602 has a U-shape formed by laminating silicon steel plates. The outer core 602 is located radially outward of the secondary bobbin 42 and the secondary coil L2, and connects both axial ends of the central core 601. This allows the core 60 to form a closed magnetic circuit structure that electromagnetically couples the primary coil L1 and the secondary coil L2. Furthermore, a magnet 603 is provided on one of the two connection surfaces between the central core 601 and the outer core 602 to generate a magnetic flux in the magnetic path in the opposite direction to the magnetic flux generated in the primary coil L1.

[0045] As described above, one end 811 of the primary coil L1 is connected to the power line 150 extending from the power supply device 102. The other end 812 of the primary coil L1 is connected to the igniter 104, which will be described later. Under the control of the igniter 104, a low DC voltage is applied from the power supply device 102 to one end 811 of the primary coil L1, and a gradually increasing primary current begins to flow through the primary coil L1.

[0046] One end 822 of the secondary coil L2 is connected to the spark plug 113. The wire diameter of the secondary conductor 82 is smaller than that of the primary conductor 81. The number of turns of the secondary conductor 82 in the secondary coil L2 is greater than that of the primary conductor 81 in the primary coil L1. For example, the number of turns of the secondary conductor 82 in the secondary coil L2 is about 100 times the number of turns of the primary conductor 81 in the primary coil L1. As a result, the ignition coil 103 boosts the low-voltage DC power supplied from the power supply device 102 to several thousand to several tens of thousands of volts when the primary current is cut off. That is, a high voltage is induced in the secondary coil L2. The secondary coil L2 then supplies the induced high-voltage power to the spark plug 113. As a result, an electric spark is generated in the spark plug 113, and the fuel is ignited.

[0047] As shown in FIG. 1, the other end 821 of the secondary coil L2 opposite to the one end 822 to which the ignition plug 113 is connected is electrically connected to the power supply device 102 via a conductor 122. In this embodiment, the other end 821 of the secondary coil L2 is electrically connected to the power supply line 150. A diode 114 is inserted in the conductor 122. The diode 114 is connected in series with the secondary coil L2. The diode 114 is arranged such that the direction from the one end 822 to the other end 821 of the secondary coil L2 is the forward direction.

[0048] As a result, in the charging control described below, when charging (ON) by passing a primary current through the primary coil L1, an induced current due to a voltage induced in the secondary coil L2 by the gradually increasing primary current is prevented from flowing in the reverse direction in the diode 114. As a result, since the induced current can be prevented from flowing to the spark plug 113, it is possible to suppress discharge from occurring in the spark plug 113 when it is ON, i.e., at an abnormal timing.

[0049] In addition, a noise suppression resistor (not shown) for reducing ignition noise in the ignition coil 103 may be further inserted in the conductor 121 connecting the one end 822 of the secondary coil L2 and the ignition plug 113.

[0050] The igniter 104 is a semiconductor device electrically connected to the primary coil L1 and controls the current flowing through the primary coil L1. The igniter 104 is also electrically connected to the ECU 101 and receives a signal (hereinafter referred to as an "EST signal") from the ECU 101. The igniter 104 includes a switching element 70 and a driving IC 91. The igniter 104 may be integrated with the electronic circuit of the ECU 101.

[0051] The switching element 70 is, for example, an insulated gate bipolar transistor (IGBT). The switching element 70 is inserted in a conductor 123 that connects the other end 812 of the primary coil L1 and a ground point (ground 152). C (collector) of the switching element 70 is connected to the other end 812 of the primary coil L1. E (emitter) of the switching element 70 is connected to the ground point (ground 152). G (gate) of the switching element 70 is connected to the drive IC 91.

[0052] This allows the switching element 70 to switch between passing and blocking the primary current flowing from the power supply device 102 to the primary coil L1. When the switching element 70 is in a closed state, the primary current flows from the power supply device 102 to the primary coil L1. When the switching element 70 is in an open state, the primary current flowing to the primary coil L1 is blocked. However, instead of an IGBT, another type of transistor such as a MOSFET may be used for the switching element 70.

[0053] The drive IC 91 is a control unit that controls switching of the switching element 70 based on an EST signal received from the ECU 101. The drive IC 91 has a logic device connected to the switching element 70. The logic device includes, for example, a logic circuit, a processor, a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), or an application-specific integrated circuit (ASIC). The logic device performs arithmetic processing for operating the ignition device 1 to ignite the ignition plug 113.

[0054] Case 105 is a container made of insulating resin that forms the outer shape of ignition device 1 and houses various parts including ignition coil 103 and igniter 104. Case 105 has main housing portion 71, connector portion 73, and fixing portion 74.

[0055] The main housing portion 71 has a concave shape that opens vertically upward. Hereinafter, the opening located at the top of the main housing portion 71 will be referred to as "opening 700". The space inside the main housing portion 71 will be referred to as "internal space 710". The ignition coil 103 and the igniter 104 are housed in the internal space 710. As shown in FIG. 3, the ignition coil 103 is housed in the internal space 710 with the axial direction of the ignition coil 103 facing the horizontal direction of the case 105. Furthermore, the igniter 104 is disposed next to the ignition coil 103. Also, conductors and the like connected to the ignition coil 103 and the igniter 104 are appropriately disposed.

[0056] In the manufacturing process of the ignition device 1, a thermosetting molded resin (epoxy resin) for insulating and fixing each part is poured into the internal space 710 with each part including the ignition coil 103 and the igniter 104 arranged therein. The molded resin fills the internal space 710 up to the vicinity of the opening 700. As a result, after the molded resin hardens, a resin part 106 that fills the gap inside the case 105 is formed. As a result, each part including the ignition coil 103 and the igniter 104 is held in an appropriate position in the internal space 710. In the following, the upper surface of the resin part 106 will be referred to as the "resin upper surface 108."

[0057] When the resin portion 106 is formed, a part (upper part) of the outer circumferential core 602 is exposed outside (above) the internal space 710. That is, the case 105 exposes a part of the core 60. Hereinafter, the part of the outer circumferential core 602 that is exposed outside from the resin upper surface 108 will be referred to as the "exposed part 604". That is, the exposed part 604 is a part of the outer circumferential core 602, and is a part that is exposed from the resin portion 106. Hereinafter, the part of the surface of the exposed part 604 of the outer circumferential core 602 that extends approximately horizontally at the top will be referred to as the "exposed surface 605".

[0058] Before the molding resin is poured, as shown in Fig. 3, the surface of the outer core 602 is covered with a cap 72, except for the exposed surface 605, the contact surface with the central core 601, and the contact surface with the magnet 603. The cap 72 is made of, for example, an elastomer that is easily peeled off from the resin part 106. This makes it possible to suppress the occurrence of cracks even if the primary coil L1 generates heat or cools after the resin part 106 is formed, causing each part to thermally expand or contract.

[0059] Furthermore, before the molding resin is poured, a part of the outer core 602 is covered with the cap 72, and the exposed surface 605 is further covered with the cover 107. By covering the exposed part 604 with the cover 107, the exposed part 604 is protected from the outside air and the like, and the intrusion of moisture and the like is suppressed. Furthermore, the cover 107 is a heat dissipation member for efficiently dissipating heat from the outer core 602. The cover 107 in this embodiment is made of aluminum. This can further improve the heat dissipation performance and heat conduction performance of the cover 107, and can suppress the manufacturing cost of the cover 107. However, the cover 107 may be made of metal or ceramic, as long as it is made of a material with excellent heat dissipation performance.

[0060] Moreover, exposed surface 605 is directly covered by cover 107 without being covered by cap 72. Cover 107 is embedded in molding resin at its periphery while fitting to the sides of outer peripheral core 602 and cap 72, and is fixed integrally with outer peripheral core 602 and cap 72. As a result, after the molding resin hardens, cover 107 is in contact with exposed portion 604 and is interposed between exposed portion 604 and the external space.

[0061] However, after pouring the molding resin, the exposed surface 605 of the outer core 602 may be covered with the cover 107. For example, after the molding resin has hardened, the cover 107 and the outer core 602 may be press-fitted together or fixed with an adhesive. In this way, when the outer core 602 and the cover 107 are fitted together or fixed together after the molding resin has hardened, the cover 107 is not embedded in the molding resin. As a result, cracks in the molding resin caused by the cover 107 can be suppressed.

[0062] A connector portion 73 is formed on a side of the main accommodating portion 71. Wiring including the conductor 123 extending from the igniter 104 and the power line 150 extending from the primary conductor 81 are drawn to the outside of the case 105 through the inside of the connector portion 73 and connected to the ECU 101 and the power supply device 102. A fixing portion 74 is formed on a side of the main accommodating portion 71 opposite the connector portion 73. The fixing portion 74 is a portion that protrudes from the main accommodating portion 71 in a substantially triangular prism shape for mounting and fixing the ignition device 1 to an engine block.

[0063] <1-2. Operation of the ignition device> Next, a description will be given of the operation of the ignition device 1. As described above, a DC voltage is applied to one end 811 of the primary coil L1 from the power supply device 102 via the power line 150. The other end 812 of the primary coil L1 is connected to the switching element 70. The driving IC 91 controls the switching of the switching element 70 based on an EST signal received from the ECU 101.

[0064] When the ignition device 1 is operated, first, the signal level of the EST signal transmitted from the ECU 101 to the drive IC 91 is changed from L to H. Then, the drive IC 91 switches the switching element 70 from an open state to a closed state based on the EST signal. This causes a primary current to flow through the primary conductor 81 forming the primary coil L1, and the primary coil L1 is charged. This process of charging the primary coil L1 by passing a primary current through it is referred to as "charging control." In addition, an electromagnetic flux is generated in the primary coil L1, and a magnetic field corresponding to the electromagnetic flux acts on the iron core 60.

[0065] In addition, a potential difference (hereinafter referred to as "ON-state voltage") occurs between both ends 821, 822 of the secondary coil L2 electromagnetically coupled to the primary coil L1 via the iron core 60 due to mutual induction. In this embodiment, at this time, the maximum value of the voltage applied to one end 822 of the secondary coil L2 is a positive value (e.g., several hundred volts), and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is a negative value (e.g., several hundred volts below zero). The maximum value of the ON-state voltage is calculated by multiplying the voltage value (e.g., 12 V) of the DC voltage applied to one end 811 of the primary coil L1 via the power line 150 from the power supply device 102 by the ratio of the number of turns of the secondary coil L2 to the number of turns of the primary coil L1.

[0066] Here, while the charging control is being performed, the primary coil L1 and the igniter 104 may generate heat. In particular, in an ignition coil 103 with a large discharge energy, such as that used in a high-output reciprocating engine, a large current flows through the primary side, and the primary coil L1 and the igniter 104 generate a large amount of heat. However, in the ignition device 1 of this embodiment, an aluminum cover 107 with excellent heat dissipation and heat conduction performance is interposed between the exposed portion 604 of the iron core 60 and the external space. Therefore, the heat generated in the primary coil L1 and the igniter 104 can be efficiently transferred from the exposed portion 604 to the cover 107 via the conductor 123 and the iron core 60, and can be efficiently dissipated from the cover 107 to the external space. This makes it possible to suppress the temperature rise of each part and suppress the occurrence of malfunctions.

[0067] As described above, the diode 114 is connected in series with the secondary coil L2 in the conductor 122 connecting the other end 821 of the secondary coil L2 and the power supply device 102. The diode 114 is arranged so that the direction from one end 822 to the other end 821 of the secondary coil L2 is the forward direction. Therefore, even if the voltage applied to one end 822 of the secondary coil L2 becomes larger than the voltage applied to the other end 821 of the secondary coil L2 when a primary current flows through the primary coil L1, it is possible to prevent an induced current (secondary current) from flowing from the power supply device 102 side to the one end 822 side via the other end 821 of the secondary coil L2. This makes it possible to prevent discharge from occurring at an abnormal timing in the ignition plug 113 when an ON-time voltage is generated.

[0068] After the charging control is performed, the signal level of the EST signal transmitted from the ECU 101 to the driving IC 91 is changed from H to L. Then, the driving IC 91 switches the switching element 70 from a closed state to an open state to cut off the primary current flowing from the power supply device 102 to the primary coil L1. As a result, an induced electromotive force is induced by mutual induction in the secondary coil L2 electromagnetically coupled to the primary coil L1 via the iron core 60. In this embodiment, a negative high voltage is induced at one end 822 of the secondary coil L2. At this time, the voltage value applied to the one end 822 of the secondary coil L2 ranges from minus several thousand V to tens of thousands V with respect to the ground point (ground 151).

[0069] Furthermore, the absolute value of the negative high voltage induced at one end 822 of the secondary coil L2 exceeds the breakdown voltage in the gap d of the spark plug 113. This causes breakdown in the gap d of the spark plug 113. Then, a current is generated that flows from the ground point (ground 151) through the ground electrode 142 of the spark plug 113 to the center electrode 141 of the spark plug 113 (see FIG. 1), further through the secondary coil L2, and also flows in the forward direction through the diode 114.

[0070] As a result, a discharge occurs in the gap d of the spark plug 113, generating a spark and igniting the fuel filled in the internal combustion engine. That is, the spark plug 113 ignites the fuel by discharging in the gap d based on the negative high voltage induced in one end 822 of the secondary coil L2. Note that the process of switching the switching element 70 to the open state in this manner, cutting off the primary current flowing to the primary coil L1, and inducing a high voltage in one end 822 of the secondary coil L2 to discharge in the gap d of the spark plug 113 is referred to as "discharge control." Thereafter, when the absolute value of the negative high voltage induced in one end 822 of the secondary coil L2 falls below the dielectric breakdown voltage in the gap d of the spark plug 113, the discharge in the gap d of the spark plug 113 ends.

[0071] <2. Second embodiment> Next, a second embodiment of the present invention will be described. In the following, differences from the first embodiment will be mainly described, and duplicated descriptions of parts equivalent to those of the first embodiment will be omitted. In addition, members having structures equivalent to those of the first embodiment will be described with the same reference numerals as those of the first embodiment.

[0072] FIG. 4 is a perspective view of an ignition device 1B according to a second embodiment. FIG. 5 is a longitudinal cross-sectional view of the ignition device 1B taken along a vertical cross section extending in the longitudinal direction of FIG. 4. FIG. 6 is a longitudinal cross-sectional view of the ignition device 1B taken along a vertical cross section extending in the lateral direction of FIG. 4. As shown in FIGS. 4 to 6, the cover 107B of the second embodiment has a plate-shaped portion 75B and a heat dissipation fin 76B. The cover 107B of the second embodiment is formed of a metal or ceramic having excellent heat dissipation and heat conduction properties, such as aluminum, like the cover 107 of the first embodiment.

[0073] The plate-shaped portion 75B is a portion that contacts the exposed portion 604 of the outer peripheral core 602 when the exposed portion 604 is covered by the cover 107B. The heat dissipation fins 76B protrude from a plurality of portions of the plate-shaped portion 75B toward the external space. The cover 107B has such a structure, so that the surface area of ​​the cover 107B is increased, and the heat dissipation performance can be further improved. This allows the heat generated in the primary coil L1 and the igniter 104 to be more efficiently transmitted from the exposed portion 604 to the cover 107B via the conductor 123 and the core 60, and furthermore, to be more efficiently dissipated from the heat dissipation fins 76B of the cover 107B to the external space. As a result, the temperature rise of each portion can be more effectively suppressed, and the occurrence of malfunctions can be more effectively suppressed.

[0074] As shown in Fig. 4, each of the heat dissipating fins 76B is in the form of a plate extending in both the longitudinal and vertical directions. However, the shape of the heat dissipating fins 76B is not limited thereto. The shape of the heat dissipating fins 76B may be determined in consideration of the direction of the air current around the location where the ignition device 1B is disposed. The heat dissipating fins 76B may also be in the form of a rod protruding from the plate-shaped portion 75B toward the external space.

[0075] FIG. 7 is a vertical cross-sectional view of the ignition device 1C of the first modification taken along a vertical cross-section extending in the longitudinal direction. As shown in FIG. 7, the cover 107C of this modification further includes a first extension 77C in addition to the plate-shaped portion 75C and the heat dissipation fins 76C having the same structures as the plate-shaped portion 75B and the heat dissipation fins 76B of the second embodiment. The first extension 77C extends from the plate-shaped portion 75C to the internal space 710C of the case 105. In addition, the first extension 77C extends in a plate shape in parallel to the circuit board and the like included in the igniter 104 in the internal space 710C. The igniter 104 directly contacts the first extension 77C.

[0076] This allows the heat generated in the igniter 104 to be directly transferred to the cover 107C, and then dissipated more efficiently from the heat dissipation fins 76C of the cover 107C to the outside space. As a result, the temperature rise of each part can be further suppressed, and the occurrence of malfunctions can be further suppressed. A gap 109C is formed between the igniter 104 and the outer circumferential iron core 602 and the cap 72, with the resin part 106C interposed therebetween. However, the igniter 104 may be adjacent to the outer circumferential iron core 602 and the cap 72.

[0077] Also, igniter 104 may be fixed to a first auxiliary heat dissipation member (not shown) made of a metal plate or the like having excellent thermal conductivity, which is provided separately, and the first auxiliary heat dissipation member may be fixed to first extension portion 77C. That is, igniter 104 may be in contact with first extension portion 77C directly or indirectly via the first auxiliary heat dissipation member made of metal that is fixed to igniter 104.

[0078] Fig. 8 is a longitudinal cross-sectional view of an ignition device 1D of a second modified example taken along a vertical cross-section extending in the short-side direction. As shown in the second modified example of Fig. 8, an exposed portion 604D of a peripheral core 602D has an uneven shape on an exposed surface 605D, which is a surface located outside the case 105. Also, an uneven surface 751D that fits into the uneven shape of the exposed surface 605D is formed on a plate-shaped portion 75D of a cover 107D. That is, the cover 107D has an uneven surface 751D that fits into and comes into contact with the uneven shape of the exposed portion 604D.

[0079] With this structure, the contact area between iron core 60D and cover 107D is increased, allowing more heat to be transferred from iron core 60D to cover 107D and more efficiently dissipated from heat dissipation fins 76D of cover 107D to the external space.

[0080] <3. Third embodiment> Next, a third embodiment of the present invention will be described. In the following, differences from the first and second embodiments will be mainly described, and duplicated descriptions of parts equivalent to the first and second embodiments will be omitted. In addition, members having structures equivalent to the first or second embodiment will be described with the same reference numerals as the first or second embodiment.

[0081] Fig. 9 is a longitudinal cross-sectional view of the ignition device 1E of the third embodiment taken along a vertical cross-section extending in the longitudinal direction. Fig. 10 is a longitudinal cross-sectional view of the ignition device 1E of the third embodiment taken along a vertical cross-section extending in the lateral direction. Fig. 11 is a transverse cross-sectional view of the ignition device 1E of the third embodiment taken along a horizontal cross-section extending in the longitudinal direction.

[0082] As shown in Figs. 9 to 11, a first cavity 111E, which is a tunnel-shaped cavity, is formed inside the resin part 106E. A second cavity 112E, which is a tunnel-shaped cavity, is formed inside the central core 601E. The ignition device 1E of this embodiment is further provided with a cooling pipe 120E. A known water-cooled device is used for the cooling pipe 120E, in which a cooling medium such as cooling water or cooling gas flows to cool the core 60E.

[0083] In this embodiment, the cooling pipe 120E is configured by two pipes arranged in a loop shape to circulate the cooling medium. Specifically, the cooling pipe 120E is inserted from the external space of the case 105 into the internal space 710E, and travels back and forth while being arranged in the first cavity 111E and the second cavity 112E, and is then drawn out to the external space. With this structure, the heat generated in the central core 601E and the surrounding primary coil L1 in contact with the cooling pipe 120E can be further cooled by the cooling pipe 120E. As a result, the temperature rise in the respective parts in the vicinity of these can be further suppressed, and the occurrence of malfunctions can be further suppressed.

[0084] In this embodiment, the igniter 104 is fixed to a first heat dissipation auxiliary member 160E made of a metal plate with excellent thermal conductivity, and the first heat dissipation auxiliary member 160E is in contact with the cooling pipe 120E. This allows the heat generated in the igniter 104 to be further cooled by using the cooling pipe 120E. However, the igniter 104 may be in direct contact with the cooling pipe 120E. That is, the igniter 104 may be in indirect contact with the cooling pipe 120E directly or via the first heat dissipation auxiliary member 160E made of metal and fixed to the igniter 104.

[0085] FIG. 12 is a longitudinal cross-sectional view of the ignition device 1F of the third modified example taken along a vertical cross-section extending in the longitudinal direction. FIG. 13 is a transverse cross-sectional view of the ignition device 1F of the third modified example taken along a horizontal cross-section extending in the longitudinal direction. As shown in the third modified example of FIG. 12 and FIG. 13, a first cavity 111F, which is a tunnel-shaped cavity, is formed inside the resin part 106F. In addition, a second cavity 112F, which is a tunnel-shaped cavity, is formed inside the central iron core 601F. In addition, the ignition device 1F of this embodiment is further provided with two first heat pipes 130F and one second heat pipe 140F made of metal (for example, copper). However, the respective numbers of the first heat pipes 130F and the second heat pipes 140F provided in the ignition device 1F are not limited to this.

[0086] The first heat pipe 130F and the second heat pipe 140F are each filled with a cooling medium, and are made of known materials that can transfer heat and cool the iron core 60F and the igniter 104 by evaporating or condensing the cooling medium as it moves.

[0087] In this modification, two first heat pipes 130F and one second heat pipe 140F are arranged adjacent to each other in the short side direction. A part of each of the two first heat pipes 130F is arranged in the first cavity 111F and the second cavity 112F, and the other part is sandwiched between the exposed part 604F of the outer circumferential core 602F and the cover 107F. With this structure, the heat generated in the central core 601F and the primary coil L1 in contact with the first heat pipe 130F can be further cooled by the first heat pipe 130F.

[0088] Also, a part of the second heat pipe 140F is disposed in the first hollow portion 111E, and another part is sandwiched between the exposed portion 604 of the outer peripheral iron core 602 and the cover 107. Also, in this modification, the igniter 104 is fixed to the first heat dissipation auxiliary member 160F made of a metal plate having excellent thermal conductivity, and the first heat dissipation auxiliary member 160F is in contact with the second heat pipe 140F. This allows the heat generated in the igniter 104 to be further cooled using the second heat pipe 140F. However, the igniter 104 may be in direct contact with the second heat pipe 140F. That is, the igniter 104 may be in indirect contact with the second heat pipe 140F directly or via the first heat dissipation auxiliary member 160F made of metal and fixed to the igniter 104.

[0089] <4. Fourth embodiment> Next, a fourth embodiment of the present invention will be described. In the following, differences from the first to third embodiments will be mainly described, and duplicated descriptions of parts equivalent to the first to third embodiments will be omitted. Furthermore, members having structures equivalent to the first to third embodiments will be described with the same reference numerals as the first to third embodiments.

[0090] FIG. 14 is a vertical cross-sectional view of the ignition device 1G of the fourth embodiment, taken along a vertical cross-section extending in the longitudinal direction. FIG. 15 is a vertical cross-sectional view of the ignition device 1G of the fourth embodiment, taken along a vertical cross-section extending in the lateral direction. As shown in FIG. 14, the cover 107G of this embodiment has a second extension portion 78G in addition to the plate-shaped portion 75G that contacts the exposed portion 604 of the outer core 602 and the heat dissipation fins 76G that protrude from a plurality of points on the plate-shaped portion 75G toward the external space. The second extension portion 78G extends from the plate-shaped portion 75G to the internal space 710G of the case 105.

[0091] As shown in FIG. 15, the ignition device 1G of this embodiment further includes a second heat dissipation auxiliary member 170G made of aluminum and in contact with the central core 601G. Specifically, the second heat dissipation auxiliary member 170G is made of two plates and extends in the axial direction while sandwiching the periphery of the central core 601G from both sides on the radial inside of the primary bobbin 41. The second heat dissipation auxiliary member 170G contacts the second extension portion 78G at its end in the axial direction. With this structure, the heat generated in the central core 601G can be efficiently transferred to the cover 107G via the second heat dissipation auxiliary member 170G, and can be efficiently dissipated via the cover 107G.

[0092] <5. Fifth embodiment> Next, a fifth embodiment of the present invention will be described. In the following, differences from the first to fourth embodiments will be mainly described, and duplicated descriptions of parts equivalent to the first to fourth embodiments will be omitted. In addition, members having structures equivalent to the first to fourth embodiments will be described with the same reference numerals as the first to fourth embodiments.

[0093] FIG. 16 is a vertical cross-sectional view of the ignition device 1H of the fifth embodiment, cut along a vertical cross-section extending in the longitudinal direction. FIG. 17 is a block diagram that typically illustrates an operating environment of the ignition device 1H of the fifth embodiment. As illustrated in FIG. 16 and FIG. 17, in the ignition coil 103H of this embodiment, a first primary coil L11 and a second primary coil L12 are provided as the primary coil L1. The first primary coil L11 is formed by winding a first primary conductor 801H around the iron core 60H. The second primary coil L12 is formed by winding a second primary conductor 802H around the iron core 60H at a position different from the first primary coil L11. The power supply device 102H applies a DC voltage to one end of the first primary coil L11 and one end of the second primary coil L12.

[0094] The igniter 104H also includes a first switching element 701H, a second switching element 702H, and a driving IC 91H. The first switching element 701H is inserted into a first primary grounding wire 124H that connects the other end of the first primary coil L11 to a ground point (ground 152), and can switch between energizing and blocking the primary current that flows from the power supply device 102H to the first primary coil L11. The second switching element 702H is inserted into a second primary grounding wire 125H that connects the other end of the second primary coil L12 to a ground point (ground 152), and can switch between energizing and blocking the primary current that flows from the power supply device 102H to the second primary coil L12. The driving IC 91H is a control unit that controls the opening and closing of the first switching element 701H and the opening and closing of the second switching element 702H.

[0095] The driving IC 91H of this embodiment selects and executes either a-1) a first charging control in which a primary current is caused to flow through the first primary coil L11 to charge the first primary coil L11 by closing the first switching element 701H, or a-2) a second charging control in which a primary current is caused to flow through the second primary coil L12 to charge the second primary coil L12 by closing the second switching element 702H, and then b) executes a discharge control in which the first switching element 701H or the second switching element 702H, which was closed in the first charging control or the second charging control, is switched to an open state to induce a high voltage at one end of the secondary coil L2, thereby discharging the ignition plug 113, and alternately selects between process a-1) and process a-2).

[0096] That is, in this embodiment, the first primary coil L11 and the second primary coil L12 are charged by alternately passing a primary current through them, and then the charge stored in either the first primary coil L11 or the second primary coil L12 is used to discharge the spark plug 113. By controlling in this manner, the number of times each primary coil L11, L12 is charged per unit time is reduced. As a result, the amount of heat generated per unit time in each primary coil L11, L12 can be suppressed, and the temperature rise in each portion near these can be suppressed, thereby further suppressing the occurrence of malfunctions.

[0097] <6. Other Modifications> Although the exemplary embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0098] The ignition device of the present invention may be installed not only in vehicles such as automobiles, but also in various devices such as generators and industrial machinery, and may be used to generate an electric spark in the spark plug of an internal combustion engine to ignite fuel.

[0099] The detailed shape and structure of the above ignition device may be appropriately modified without departing from the spirit of the present invention. Furthermore, the elements appearing in the above embodiment and modified examples may be appropriately combined without causing any contradiction. [Explanation of symbols]

[0100] 1,1B,1C,1D,1E,1F,1G,1H Ignition device 60,60D,60E,60F,60H Iron core 70 Switching element 75B, 75C, 75D, 75G (Cover) Plate-shaped Part 76B, 76C, 76D, 76G (Cover) Heat sink fins 77C (Cover) First Extension 78G (Cover) Second Extension 81 Primary conductor 82 Secondary conductor 91,91H Driver IC (control unit) 101 ECU 102,102H Power supply 103,103H Ignition coil 104,104H Igniter 105 cases 106,106C,106E,106F Resin part 107, 107B, 107C, 107D, 107F, 107G Cover 111E,111F 1st cavity 112E,112F 2nd cavity 113 Spark plug 120E cooling pipe 130F 1st heat pipe 140F 2nd heat pipe 160E, 160F First heat dissipation auxiliary member 170G Second heat dissipation auxiliary material 601, 601E, 601F, 601G central core 602, 602D, 602F Outer core 604,604D,604F Exposed part 701H First switching element 702H Second switching element 710, 710C, 710E, 710G (case) internal space 751D (Cover) Uneven Surface 801H 1st Primary Conductor 802H Second Primary Conductor L1 Primary coil L11 1st primary coil L12 Second primary coil L2 Secondary coil

Claims

1. An ignition device for an internal combustion engine, comprising: an ignition coil including a primary coil, a secondary coil, and an iron core that electromagnetically couples the primary coil and the secondary coil, and supplies a high voltage to an ignition plug; an igniter that controls a current flowing through the primary coil; a case that houses the ignition coil and the igniter and exposes a portion of the iron core; a resin portion that fills a gap inside the case; a cover that covers an exposed portion of the iron core that is exposed from the resin portion; having The cover is made of metal or ceramic, and is in contact with the exposed portion and is interposed between the exposed portion and an external space.

2. 2. The ignition device according to claim 1, An ignition device, wherein the cover is made of aluminum.

3. 3. The ignition device according to claim 1 or 2, The cover is A plate-shaped portion in contact with the exposed portion; heat dissipation fins protruding from a plurality of points on the plate-shaped portion toward an external space; An ignition device having

4. 2. The ignition device according to claim 1, The iron core is a central core located radially inward of the primary coil and the secondary coil and extending in an axial direction; an outer core located radially outward of the secondary coil and connecting both axial ends of the central core; having An ignition device, wherein the exposed portion is a part of the outer circumferential core.

5. 3. The ignition device according to claim 1 or 2, the exposed portion has an uneven surface located on the outside of the case, The cover has an uneven surface that fits into and comes into contact with the uneven shape of the exposed portion.

6. 4. The ignition device according to claim 3, The cover is a first extension portion extending from the plate portion into an internal space of the case; and An ignition device, wherein the igniter is in direct contact with the first extension portion or indirectly through a first heat dissipation auxiliary member made of metal that is fixed to the igniter.

7. 5. The ignition device according to claim 4, A first cavity portion which is a tunnel-shaped cavity is formed inside the resin portion, A second cavity portion which is a tunnel-shaped cavity is formed inside the central core, The ignition device is A cooling tube capable of cooling the iron core by flowing a cooling medium therethrough. and an ignition device, wherein the cooling pipe is inserted from the exterior space of the case to the interior space, reciprocates while being disposed in the first cavity and the second cavity, and is drawn out to the exterior space.

8. 8. The ignition device according to claim 7, The igniter is in direct contact with the cooling pipe or indirectly through a first heat dissipation auxiliary member made of metal that is fixed to the igniter.

9. 5. The ignition device according to claim 4, A first cavity portion which is a tunnel-shaped cavity is formed inside the resin portion, A second cavity portion which is a tunnel-shaped cavity is formed inside the central core, The ignition device is a first heat pipe, a portion of which is disposed in the first cavity and the second cavity, and another portion of which is sandwiched between the exposed portion and the cover; The ignition device further comprises:

10. 10. The ignition device of claim 9, a second heat pipe, a portion of which is disposed in the first cavity and another portion of which is sandwiched between the exposed portion and the cover; and The igniter is in direct contact with the second heat pipe or indirectly contact with the second heat pipe via a first heat dissipation auxiliary member made of metal and fixed to the igniter.

11. 5. The ignition device according to claim 4, A second heat dissipation auxiliary member made of aluminum that contacts the central core. and The cover is A plate-shaped portion in contact with the exposed portion; heat dissipation fins protruding from a plurality of points on the plate-shaped portion toward an external space; A second extension portion extending from the plate portion into the internal space of the case. having The second heat dissipation auxiliary member contacts the second extension portion.

12. 3. The ignition device according to claim 1 or 2, The primary coil is a first primary coil formed by winding a first primary conductor around the iron core; a second primary coil formed by winding a second primary conductor around the iron core at a position different from that of the first primary coil; Including, The ignition device is a power supply device that applies a DC voltage to one end of the first primary coil and one end of the second primary coil; the spark plug ignites fuel by discharging in a gap based on a high voltage induced in the secondary coil; and The igniter is a first switching element that is inserted in a first primary side ground line that connects the other end of the first primary coil and a ground point and is capable of switching between passing and blocking a primary current that flows from the power supply device to the first primary coil; a second switching element that is inserted in a second primary side ground line that connects the other end of the second primary coil and a ground point and is capable of switching between energization and interruption of a primary current that flows from the power supply device to the second primary coil; a control unit that controls the opening and closing of the first switching element and the opening and closing of the second switching element; having The control unit is a-1) a first charging control for charging the first primary coil by causing a primary current to flow through the first switching element in a closed state; a-2) a second charging control for charging the second primary coil by causing a primary current to flow through the second switching element in a closed state; After selecting and executing one of the b) Discharge control in which the first switching element or the second switching element, which has been closed in the first charging control or the second charging control, is switched to an open state to induce a high voltage at one end of the secondary coil, thereby discharging the ignition plug. Run An ignition device that alternately selects the step a-1) and the step a-2).

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