Ignition device

Abstract

To provide a technique capable of suppressing discharge at unexpected timing in an ignition plug.SOLUTION: The ignition plug 101 is connected to the other end L22 of the second secondary coil Ep22 of the ignition coil 104, and one end L22 of the second secondary coil Eg22 is connected to one end L12 of the first secondary coil Eg12. The other end Ep12 is connected to the ground point 152. A DC voltage is applied to one ends L11 and L21 of the respective primary coils Ep11 and Ep21, and the other ends Eg11 and Eg21 are connected to the ground point 152. The ignition plug 101 ignites fuel by discharging at the plug gap d by a high voltage induced at one end L12 of the first secondary coil Eg12 or the other end L22 of the second secondary coil Ep22. A closed magnetic circuit is formed by the first through iron core passing through the inside of the first primary coil L11, the one end-side outer peripheral iron core, the second through iron core passing through the inside of the second primary coil L21, and the other-end-side outer peripheral iron core.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, an ignition device is mounted on an internal combustion engine including an SI (spark ignition) reciprocating engine used in an automobile or the like. An ignition coil of the ignition device boosts a low DC voltage supplied from a battery to several thousand to several tens of thousands of volts under the control of an ECU (Engine Control Unit), supplies the voltage to a spark plug, and generates an electric spark to ignite the fuel. An example of a conventional ignition device is described in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-96381 Summary of the Invention [Problem to be solved by the invention]

[0004] The ignition coil (20) of Patent Document 1 includes a core (21) that forms a magnetic circuit, a primary coil (L1A) for positive discharge, a primary coil (L1B) for negative discharge, and a secondary coil (L2). The primary coil (L1A), the primary coil (L1B), and the secondary coil (L2) are wound around the same core (21) (see paragraph 0037 and FIG. 1). Then, at time t1, the ignition signal (IGt2) switches from off to on, turning on the semiconductor switch (SWB). This causes a primary current (I1B) to start flowing from the battery (30) to the primary coil (L1B), and charging for negative discharge begins (see paragraph 0041). Next, at time t2, the ignition signal (IGt1) switches from off to on, the semiconductor switch (SWA) turns on, and a primary current (I1A) begins to flow from the battery (30) to the primary coil (L1A), and charging for positive discharge begins (paragraph 0042).

[0005] Subsequently, at time t3, the ignition signal (IGt1) switches from on to off, causing the semiconductor switch (SWA) to turn off and cut off the current to the primary coil (L1A). This initiates the discharge of the charge energy stored in the primary coil (L1A), causing the secondary voltage (V2) to rise so that the potential of the center electrode (41) of the spark plug (40) becomes suddenly higher than the potential of the ground electrode (42). As a result, a positive discharge begins in the direction in which current flows from the center electrode (41) to the ground electrode (42) (see paragraph 0043). Subsequently, at time t5, the ignition signal (IGt2) switches from on to off, causing the semiconductor switch (SWB) to turn off and cut off the current to the primary coil (L1B). This causes the discharge of the charge energy stored in the primary coil (L1B) to begin, and the secondary voltage (V2) drops so that the potential of the center electrode (41) becomes suddenly lower than the potential of the ground electrode (42) (FIG. 3(e)). As a result, the state switches from a positive discharge state to a negative discharge state (paragraph 0045).

[0006] In recent years, fuels containing hydrogen have been widely used in spark ignition (SI) reciprocating engines. The use of fuels containing hydrogen is thought to contribute to the realization of a so-called low-carbon society. However, hydrogen has the characteristics of being easily flammable even at relatively low temperatures and having a fast combustion rate. Therefore, for example, if a slight discharge occurs at an unexpected timing in an ignition plug, the fuel may ignite and burn. This can lead to abnormal combustion, such as backfires, in which flames blow back from the engine's combustion chamber to the intake system; afterfires, in which fuel remaining in the engine's exhaust gas burns in the exhaust passage; or pre-ignition, in which the timing of ignition cannot be controlled.

[0007] An object of the present invention is to provide a technique capable of suppressing discharge from occurring at unexpected times in a spark plug. [Means for solving the problem]

[0008] To solve the above problems, the first invention of the present application provides an ignition device having an ignition coil for an internal combustion engine and an ignition plug connected to the ignition coil, wherein the ignition coil has a first primary coil, a first secondary coil, a first through core, a second primary coil, a second secondary coil, a second through core, a one-end outer core, and an other-end outer core. The first primary coil comprises a first primary winding, one end of which is applied with a DC voltage and the other end of which is connected to ground. The first secondary coil comprises a first secondary winding. The first through core passes through the inside of the first primary coil and the inside of the first secondary coil, electromagnetically coupling the first primary coil and the first secondary coil. The second primary coil comprises a second primary winding, one end of which is applied with the DC voltage and the other end of which is connected to ground. The second secondary coil is composed of a second secondary winding. The second through core passes through the inside of the second primary coil and the inside of the second secondary coil, electromagnetically coupling the second primary coil and the second secondary coil. The one-end outer core connects one end of the first through core to one end of the second through core. The other-end outer core connects the other end of the first through core to the other end of the second through core. The first through core, the one-end outer core, the second through core, and the other-end outer core form a closed magnetic circuit. When the DC voltage is applied to the first primary coil, a positive electromotive force is induced in the first secondary coil from the other end to the one end. When the DC voltage is applied to the second primary coil, a negative electromotive force is induced in the second secondary coil from the one end to the other end. The spark plug is connected to the other end of the second secondary coil via a first wiring, which is a conductor. The spark plug ignites fuel by discharging in a plug gap based on a high voltage induced at one end of the first secondary coil or a high voltage induced at the other end of the second secondary coil. One end of the second secondary coil is connected to one end of the first secondary coil via a second wiring, which is a conductor. The other end of the first secondary coil is connected to a ground point directly or indirectly via a third wiring, which is a conductor.

[0009] The second invention of the present application is an ignition device of the first invention, wherein when the DC voltage is applied to the first primary coil and when the DC voltage is applied to the second primary coil, magnetic fluxes are generated in the closed magnetic circuit in opposite directions.

[0010] A third invention of the present application is the ignition device of the first or second invention, further comprising a center core disposed between the first through core and the second through core and forming a magnetic path connecting the one-end outer peripheral core and the other-end outer peripheral core, such that when the DC voltage is applied to the first primary coil, at least a portion of the magnetic flux generated in the first through core passes through the center core, and when the DC voltage is applied to the second primary coil, at least a portion of the magnetic flux generated in the second through core passes through the center core.

[0011] A fourth invention of the present application is the ignition device of the third invention, wherein the central core has a central gap that separates the central core into two or more portions. A first coupling coefficient indicating the proportion of magnetic flux that passes through the second penetrating core out of the magnetic flux generated in the first penetrating core when the DC voltage is applied to the first primary coil is greater than 0 and less than 1. Furthermore, a second coupling coefficient indicating the proportion of magnetic flux that passes through the first penetrating core out of the magnetic flux generated in the second penetrating core when the DC voltage is applied to the second primary coil is greater than 0 and less than 1.

[0012] A fifth aspect of the present invention is the ignition device of any one of the first to fourth aspects, further comprising a power supply device, a first switching element, a second switching element, a first control unit, and a second control unit. The power supply device applies the DC voltage to one end of the first primary coil and one end of the second primary coil. The first switching element is interposed between the other end of the first primary coil and a ground and is capable of switching between conducting and cutting off a first primary current flowing from the power supply device to the first primary coil. The second switching element is interposed between the other end of the second primary coil and a ground and is capable of switching between conducting and cutting off a second primary current flowing from the power supply device to the second primary coil. The first control unit controls the switching of the first switching element. The second control unit controls the switching of the second switching element.

[0013] A sixth aspect of the present invention is the ignition device of the fifth aspect, wherein the first control unit performs first energization control and first discharge control. The first energization control is control in which the first primary current flows through the first primary coil by closing the first switching element, thereby generating a magnetomotive force. The first discharge control is control in which, after performing the first energization control, the first switching element is switched to an open state, thereby inducing a high voltage at one end of the first secondary coil, thereby causing a discharge in the plug gap of the spark plug. The second control unit performs second energization control and second discharge control. The second energization control is control in which the second primary current flows through the second primary coil by closing the second switching element at the timing when the first control unit performs the first energization control, thereby generating a magnetomotive force. The second discharge control is a control in which, after the first control unit performs the first discharge control, the second switching element is switched to an open state to induce a high voltage at the other end of the second secondary coil, thereby causing continuous discharge in the plug gap of the spark plug. [Effects of the Invention]

[0014] According to the first to sixth inventions of the present application, when a DC voltage is applied to the first primary coil and the second primary coil (ON), by connecting one end of the first secondary coil where a positive electromotive force is induced in the direction from the other end, and one end of the second secondary coil where a positive electromotive force is induced in the direction from the other end, the directions of the electromotive forces are opposite to each other, and the electromotive forces can be canceled out.

[0015] In particular, according to the fourth aspect of the present invention, magnetic energy can be stored in the center gap when the first primary coil and the second primary coil are energized. As a result, when a spark discharge occurs in the spark plug, the magnetic energy stored in the center gap can be released through the spark plug. As a result, the discharge energy in the spark plug can be further increased. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a block diagram illustrating a schematic operating environment of an ignition device for an internal combustion engine. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view of an ignition coil as viewed from below. [Figure 3] 10 is a graph showing, in time series, the waveform of a first EST signal, the waveform of a second EST signal, the waveform of the sum of a first primary current flowing through a first primary coil and a second primary current flowing through a second primary coil, the waveform of an output current, and the waveform of an output voltage. [Figure 4] FIG. 10 is a schematic vertical cross-sectional view of an ignition coil according to a first modified example, viewed from below. [Figure 5] FIG. 10 is a schematic vertical cross-sectional view of an ignition coil according to a second modified example, viewed from below. [Figure 6] FIG. 10 is a schematic vertical cross-sectional view of an ignition coil according to a third modified example, viewed from below. [Figure 7] FIG. 10 is a schematic vertical cross-sectional view of an ignition coil according to a fourth modified example, viewed from below. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. Note that the components described in these embodiments are merely examples and are not intended to limit the scope of the present invention. Furthermore, in the drawings, the dimensions and numbers of each part may be exaggerated or simplified as necessary for ease of understanding.

[0018] <1. Ignition device configuration> First, the configuration of an ignition device 1 for an internal combustion engine according to one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically illustrating the operating environment of the ignition device 1. Note that the first primary coil L11 and the first secondary coil L12 of the ignition coil 104 included in the ignition device 1 are arranged in a stacked direction relative to each other, but in FIG. 1, they are illustrated as being adjacent to each other for ease of understanding. Similarly, the second primary coil L21 and the second secondary coil L22 of the ignition coil 104 are arranged in a stacked direction relative to each other, but in FIG. 1, they are illustrated as being adjacent to each other for ease of understanding.

[0019] The ignition device 1 of this embodiment is mounted on an internal combustion engine such as an SI (spark ignition) reciprocating engine mounted on a vehicle body 100 such as an automobile, and applies a high voltage to generate a spark discharge to an ignition plug 101. The ignition device 1 is provided for each of one or more cylinders of the internal combustion engine.

[0020] 1, the internal combustion engine is equipped with a spark plug 101 in addition to the ignition device 1, and the vehicle body 100 is equipped with a power supply device 102 (battery) and an ECU 103 (Engine Control Unit). In a broad sense, the spark plug 101, the power supply device 102, and the ECU 103 can also be considered to be included in the ignition device 1.

[0021] The spark plug 101 is a device for realizing an ignition operation in a combustion chamber of an internal combustion engine. The spark plug 101 is electrically connected to the other end Ep22 of a second secondary coil L22 (described later) of the ignition coil 104 via a conductor (hereinafter referred to as "first wiring Cg22"). The spark plug 101 is interposed between the other end Ep22 of the second secondary coil L22 and a ground point 151.

[0022] Furthermore, one end Eg22 of the second secondary coil L22 opposite to the other end Ep22 to which the spark plug 101 is connected is electrically connected to one end Eg12 of a first secondary coil L12 (described later) of the ignition coil 104 via a conductor (hereinafter referred to as "second wiring Cg12"). That is, in the ignition device 1 of this embodiment, one common spark plug 101 is provided for the first coil set 40 having the first secondary coil L12 and the second coil set 50 having the second secondary coil L22.

[0023] A high voltage is induced in the first secondary coil L12 and / or the second secondary coil L22. When the high voltage induced at one end Eg12 of the first secondary coil L12 or the high voltage induced at the other end Ep22 of the second secondary coil L22 exceeds the breakdown voltage in the gap between the center electrode 161 and the ground electrode 162 of the spark plug 101 (see FIG. 1; hereinafter referred to as "plug gap d"), a discharge occurs in the plug gap d, generating a spark. This ignites the fuel filled in the internal combustion engine. That is, the spark plug 101 ignites the fuel by discharging a spark in the plug gap d based on the high voltage induced at one end Eg12 of the first secondary coil L12 or the high voltage induced at the other end Ep22 of the second secondary coil L22.

[0024] 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 each of a first primary coil L11 and a second primary coil L21 of an ignition coil 104 (described later) via a conductor (hereinafter referred to as a "power line 150"). The power supply device 102 applies a DC voltage via the power line 150 to each of one end Ep11 of the first primary coil L11 and one end Ep21 of the second primary coil L21 of the ignition coil 104.

[0025] Note that a conductor (hereinafter referred to as "third wiring Cp12") is connected to the other end Ep12 of the first secondary coil L12, which is opposite to the end Eg12 to which the second wiring Cg12 is connected. The third wiring Cp12 is electrically connected to the power supply line 150 and is connected to a ground point (ground) 152 (see FIG. 1) via the power supply device 102. However, the third wiring Cp12 may be directly connected to the ground point 152 without being connected to the power supply line 150. In other words, it is sufficient that the other end Ep12 of the first secondary coil L12 is connected to the ground point 152 directly or indirectly via the third wiring Cp12, which is a conductor.

[0026] The ECU 103 is an existing computer that comprehensively controls the operation of the transmission and engine of the vehicle body 100 .

[0027] As shown in FIG. 1, the ignition device 1 includes an ignition coil 104, a first igniter 105, and a second igniter .

[0028] FIG. 2 is a schematic vertical cross-sectional view of the ignition coil 104 as viewed from below. In FIG. 2, components such as the power supply 102 connected to the ignition coil 104 are indicated by two-dot chain lines. As shown in FIG. 2, the ignition coil 104 includes a first coil set 40, a second coil set 50, and an iron core 60. The first coil set 40 and the second coil set 50 are arranged side by side in the horizontal direction. The first coil set 40 and the second coil set 50 are connected in series to one spark plug 101. The first coil set 40 includes a first bobbin 41, a first primary coil L11, and a first secondary coil L12. The second coil set 50 includes a second bobbin 51, a second primary coil L21, and a second secondary coil L22. The ignition coil 104 is integrally housed together with the first igniter 105 and the second igniter 106 in a resin case (not shown).

[0029] In the following description of the ignition coil 104, a direction parallel to the first center axis Bc1 of the first bobbin 41 is referred to as the "first axial direction," a direction perpendicular to the first center axis Bc1 is referred to as the "first radial direction," and a direction along an arc centered on the first center axis Bc1 is referred to as the "first circumferential direction." Furthermore, a direction parallel to the second center axis Bc2 of the second bobbin 51 is referred to as the "second axial direction," a direction perpendicular to the second center axis Bc2 is referred to as the "second radial direction," and a direction along an arc centered on the second center axis Bc2 is referred to as the "second circumferential direction." Furthermore, the term "parallel direction" includes a direction that is approximately parallel, and the term "orthogonal direction" includes a direction that is approximately perpendicular. Furthermore, the first center axis Bc1 and the second center axis Bc2 are approximately parallel and approximately horizontal.

[0030] The first bobbin 41 includes a first primary bobbin 411 and a first secondary bobbin 412 that are connectable to each other. The first primary bobbin 411 and the first secondary bobbin 412 each extend cylindrically along a first central axis Bc1. The first secondary bobbin 412 is disposed on the outside of the first primary bobbin 411 in a first radial direction. The first primary bobbin 411 and the first secondary bobbin 412 are made of, for example, resin. The first primary coil L11 is formed by winding a conducting wire (hereinafter referred to as the "first primary winding 811") around the outer circumferential surface of the first primary bobbin 411 in a first circumferential direction around the first central axis Bc1. That is, the first primary coil L11 is made of the first primary winding 811.

[0031] After the formation of the first primary coil L11 is completed, the first secondary bobbin 412 is disposed so as to cover the outer peripheral surface of the first primary coil L11 and is connected to the first primary bobbin 411. Then, a conductor wire separate from the first primary winding 811 (hereinafter referred to as the "first secondary winding 812") is wound around the outer peripheral surface of the first secondary bobbin 412 in a first circumferential direction centered on the first central axis Bc1, thereby forming the first secondary coil L12. That is, the first secondary coil L12 is made of the first secondary winding 812. By arranging the first primary coil L11 and the first secondary coil L12 so as to be stacked on top of each other in this manner, the entire ignition coil 104 including these coils can be made more compact. However, the first primary coil L11 and the first secondary coil L12 do not necessarily have to be wound while being stacked on top of each other in this manner, but may also be arranged adjacent to each other in the first axial direction, for example.

[0032] The second bobbin 51 includes a second primary bobbin 511 and a second secondary bobbin 512 that are connectable to each other. The second primary bobbin 511 and the second secondary bobbin 512 each extend cylindrically along a second central axis Bc2. The second secondary bobbin 512 is disposed on the outer side of the second primary bobbin 511 in the second radial direction. The second primary bobbin 511 and the second secondary bobbin 512 are made of, for example, resin. The second primary coil L21 is formed by winding a conducting wire (hereinafter referred to as the "second primary winding 821") around the outer circumferential surface of the second primary bobbin 511 in a second circumferential direction centered on the second central axis Bc2. That is, the second primary coil L21 is made of the second primary winding 821.

[0033] After the formation of the second primary coil L21 is completed, the second secondary bobbin 512 is disposed so as to cover the outer circumferential surface of the second primary coil L21 and is connected to the second primary bobbin 511. Then, a conductor wire separate from the second primary winding 821 (hereinafter referred to as the "second secondary winding 822") is wound around the outer circumferential surface of the second secondary bobbin 512 in a second circumferential direction centered on the second central axis Bc2, thereby forming the second secondary coil L22. That is, the second secondary coil L22 is made of the second secondary winding 822. By arranging the second primary coil L21 and the second secondary coil L22 so as to be stacked on top of each other in this manner, the entire ignition coil 104 including these coils can be made more compact. However, the second primary coil L21 and the second secondary coil L22 do not necessarily have to be wound while being stacked on top of each other in this manner, but may also be arranged adjacent to each other in the second axial direction, for example.

[0034] The iron core 60 of this embodiment has a structure in which a first through core 61, a second through core 62, a one-end outer periphery core 63, a second-end outer periphery core 64, and a center core 65 are combined together. The first through core 61, the second through core 62, the one-end outer periphery core 63, the second-end outer periphery core 64, and the center core 65 are each formed, for example, from a laminated steel plate in which silicon steel plates are stacked. Note that a silicon steel plate is generally an electromagnetic steel plate formed by rolling heat-treated steel in which a few percent of silicon is mixed into iron. However, the first through core 61, the second through core 62, the one-end outer periphery core 63, the second-end outer periphery core 64, and the center core 65 may each be made of a steel plate other than a silicon steel plate. In addition, each of the first through core 61, the second through core 62, the one end side outer peripheral core 63, the other end side outer peripheral core 64, and the center core 65 may be a powder iron core formed from a sintered material.

[0035] The first through core 61 extends substantially horizontally and in a columnar shape along the first center axis Bc1. The first through core 61 is inserted into a space 410 on the inside in the first radial direction of the first primary bobbin 411. That is, the first through core 61 passes through the inside of the first primary coil L11 and the inside of the first secondary coil L12. The second through core 62 extends substantially horizontally and in a columnar shape along the second center axis Bc2. The second through core 62 is inserted into a space 510 on the inside in the second radial direction of the second primary bobbin 511. That is, the second through core 62 passes through the inside of the second primary coil L21 and the inside of the second secondary coil L22.

[0036] In this embodiment, the one-end outer periphery iron core 63 and the other-end outer periphery iron core 64 each extend substantially horizontally and columnarly in a direction substantially perpendicular to the first center axis Bc1 and the second center axis Bc2. The one-end outer periphery iron core 63 is connected to one end 611 of the first through core 61 in the first axial direction and one end 621 of the second through core 62 in the second axial direction. That is, the one-end outer periphery iron core 63 connects the one end 611 of the first through core 61 to the one end 621 of the second through core 62. The other-end outer periphery iron core 64 is connected to the other end 612 of the first through core 61 in the first axial direction and the other end 622 of the second through core 62 in the second axial direction. That is, the other-end outer periphery iron core 64 connects the other end 612 of the first through core 61 to the other end 622 of the second through core 62.

[0037] This forms a ring-shaped closed magnetic circuit that connects the first through core 61, the one-end outer peripheral core 63, the second through core 62, and the other-end outer peripheral core 64 in this order. The first through core 61 electromagnetically couples the first primary coil L11 and the first secondary coil L12. The second through core 62 electromagnetically couples the second primary coil L21 and the second secondary coil L22.

[0038] The center core 65 extends substantially horizontally and in a columnar shape substantially parallel to the first center axis Bc1 and the second center axis Bc2. When the ignition coil 104 is viewed from above, the center core 65 is located between the first through core 61 and the second through core 62. One end 651 of the center core 65 is connected to the one-end outer periphery core 63. The other end 652 of the center core 65 is connected to the other-end outer periphery core 64. In other words, the center core 65 is located between the first through core 61 and the second through core 62, and forms a magnetic path connecting the one-end outer periphery core 63 and the other-end outer periphery core 64.

[0039] This forms a single annular closed magnetic circuit that is connected in this order to the first through core 61, a portion of the other end side outer periphery core 64, the center core 65, and a portion of the one end side outer periphery core 63. Also, a single annular closed magnetic circuit is formed that is connected in this order to the second through core 62, a portion of the other end side outer periphery core 64, the center core 65, and a portion of the one end side outer periphery core 63.

[0040] In addition, one gap (hereinafter referred to as "center gap 650") is provided at the middle position in the first axial direction or the second axial direction of the center core 65 of this embodiment. As a result, the center core 65 is separated from the portion close to the one-end-side outer peripheral core 63 and the portion close to the other-end-side outer peripheral core 64 by the center gap 650. The size of the center gap 650 is adjustable. However, the number and positions of the center gaps 650 formed in the center core 65 are not limited to this. In other words, it is sufficient that the center core 65 has at least one center gap 650, which is a gap that separates the center core 65 into two or more portions. The effect of forming the center gap 650 will be described in detail later.

[0041] As described above, one end Ep11 of the first primary coil L11 is connected to the power supply line 150, which is a conductor extending from the power supply device 102. The other end Eg11 of the first primary coil L11 is connected to the ground point 152 via the first igniter 105, which will be described later. Under the control of the first igniter 105, a low DC voltage is applied from the power supply device 102 to one end Ep11 of the first primary coil L11, and a first primary current that gradually increases begins to flow through the first primary coil L11 (see the first primary current I1a from time t0 to time t1 in FIG. 3, which will be described later).

[0042] Furthermore, in this embodiment, when the first primary coil L11 is viewed from the other end 612 toward the one end 611 of the first penetrating core 61 that penetrates the inside of the first primary coil L11 in the first radial direction (i.e., from bottom to top on the page of FIG. 2), the first primary winding 811 is wound counterclockwise from one end Ep11 to the other end Eg11. As a result, when a low DC voltage from the power supply device 102 is applied to the one end Ep11 of the first primary coil L11, an electromagnetic flux φa is generated in the D1 direction from the one end 611 toward the other end 612 of the first penetrating core 61 according to the right-hand screw rule. Then, a magnetic field corresponding to the electromagnetic flux φa acts on the iron core 60.

[0043] A portion of the electromagnetic flux φa travels through a closed annular magnetic path connecting the first through core 61, the other-end outer periphery core 64, the second through core 62, and the one-end outer periphery core 63 in this order. That is, a portion of the electromagnetic flux φa becomes "magnetic flux that does not pass through the center core 65." Meanwhile, the remaining portion of the electromagnetic flux φa travels through a closed annular magnetic path connecting the first through core 61, a portion of the other-end outer periphery core 64, the center core 65, and a portion of the one-end outer periphery core 63 in this order. That is, the remaining portion of the electromagnetic flux φa becomes "magnetic flux that passes through the center core 65." In other words, when a DC voltage from the power supply 102 is applied to the first primary coil L11, at least a portion of the magnetic flux generated in the first through core 61 passes through the center core 65.

[0044] Furthermore, the proportion of the electromagnetic flux φa that is "magnetic flux that does not pass through the center core 65" and "magnetic flux that passes through the center core 65" is determined by factors such as the size of the center gap 650 in the center core 65. The larger the center gap 650, the greater the proportion of "magnetic flux that does not pass through the center core 65." If the center gap 650 becomes too large and the center core 65 itself is almost nonexistent, almost all of the electromagnetic flux φa will be "magnetic flux that does not pass through the center core 65." On the other hand, the smaller the center gap 650, the greater the proportion of "magnetic flux that passes through the center core 65." If the center gap 650 is almost nonexistent, almost all of the electromagnetic flux φa will be "magnetic flux that passes through the center core 65."

[0045] Hereinafter, the ratio of the magnetic flux that does not pass through the center core 65 to the electromagnetic flux φa, which is the magnetic flux generated in the first through core 61 when a DC voltage from the power supply 102 is applied to the first primary coil L11, will be referred to as the "first coupling coefficient." That is, the "first coupling coefficient" indicates the ratio of the magnetic flux that passes through the second through core 62 to the electromagnetic flux φa. If the center gap 650 is too large and almost all of the electromagnetic flux φa passes through the second through core 62, the "first coupling coefficient" will be approximately 1. On the other hand, if the center gap 650 is too small and almost all of the electromagnetic flux φa passes through the center core 65, the "first coupling coefficient" will be approximately 0 (zero). In this embodiment, the first coupling coefficient is greater than 0 and less than 1.

[0046] Furthermore, when a DC voltage from the power supply 102 is applied to the first primary coil L11 (when ON), an induced electromotive force is induced in the first secondary coil L12, which is electromagnetically coupled to the first primary coil L11 via the iron core 60, and a potential difference occurs between both ends Ep12, Eg12 of the first secondary coil L12. The positive or negative of the potential difference induced between both ends Ep12, Eg12 of the first secondary coil L12 depends on the winding direction of the first secondary coil L12. In this embodiment, when viewed from the other end 612 side of the first penetrating iron core 61 toward the one end 611 side, the first secondary winding 812 is wound clockwise from the other end Ep12 toward the one end Eg12.

[0047] Furthermore, when a DC voltage from the power supply device 102 is applied to the first primary coil L11 (when the power supply device 102 is ON), a positive electromotive force is induced from the other end Ep12 of the first secondary coil L12 toward one end Eg12. That is, when the power supply device 102 is ON, one end Eg12 of the first secondary coil L12 has a higher voltage than the other end Ep12. Hereinafter, the potential difference between one end Eg12 and the other end Ep12 of the first secondary coil L12 will be referred to as the "ON voltage." The maximum value of the ON voltage is calculated by multiplying the voltage value of the DC voltage applied to one end Ep11 of the first primary coil L11 from the power supply device 102 via the power line 150 by the ratio of the number of turns of the first secondary coil L12 to the number of turns of the first primary coil L11.

[0048] For example, let us say that the DC voltage applied to one end Ep11 of the first primary coil L11 is 12 V. If the number of turns in the first primary coil L11 is 100 and the number of turns in the first secondary coil L12 is 8,000, then the ratio of the number of turns in the first secondary coil L12 to the number of turns in the first primary coil L11 is 80. Therefore, the maximum ON voltage is calculated as 12 × 80 = 960 V. As a result, the maximum voltage applied to one end Eg12 of the first secondary coil L12 is, for example, approximately +480 V, and the minimum voltage applied to the other end Ep12 of the first secondary coil L12 is, for example, approximately -480 V. In some cases, it may be assumed that the maximum value of the voltage applied to one end Eg12 of the first secondary coil L12 is about 960 V, and the minimum value of the voltage applied to the other end Ep12 of the first secondary coil L12 is about 0 V. Meanwhile, at this time, the voltage applied to the power line 150 is 12 V.

[0049] The wire diameter of the first secondary winding 812 is smaller than that of the first primary winding 811. The number of turns of the first secondary winding 812 in the first secondary coil L12 is greater (for example, approximately 80 times or more) than the number of turns of the first primary winding 811 in the first primary coil L11. As a result, when the first primary current is interrupted, the first coil set 40 boosts the low-voltage DC power supplied from the power supply device 102 to, for example, several thousand to several tens of thousands of volts. That is, a high voltage is induced in the first secondary coil L12. The first secondary coil L12 then supplies the induced high-voltage power to the spark plug 101 via the second wiring Cg12 and the first wiring Cg22. This generates an electric spark in the spark plug 101, igniting the fuel.

[0050] As described above, one end Ep21 of the second primary coil L21 is connected to the power supply line 150, which is a conductor extending from the power supply device 102. The other end Eg21 of the second primary coil L21 is connected to the ground point 152 via the second igniter 106, which will be described later. Under the control of the second igniter 106, a low DC voltage is applied from the power supply device 102 to one end Ep21 of the second primary coil L21, and a gradually increasing second primary current begins to flow through the second primary coil L21 (see the second primary current I1b from time t0 to time t1 in FIG. 3, which will be described later).

[0051] Furthermore, in this embodiment, when the second primary coil L21 is viewed from the other end 622 side toward the one end 621 side of the second penetrating core 62 that penetrates the inside of the second radial direction of the second primary coil L21 (i.e., from bottom to top on the page of FIG. 2), the second primary winding 821 is wound counterclockwise from one end Ep21 to the other end Eg21. As a result, when a low DC voltage is applied to one end Ep21 of the second primary coil L21 from the power supply device 102, an electromagnetic flux φb is generated in the direction D2 from the one end 621 side toward the other end 622 side of the second penetrating core 62 according to the right-hand screw rule. Then, a magnetic field corresponding to the electromagnetic flux φb acts on the iron core 60.

[0052] The D2 direction and the D1 direction are opposite directions in one annular closed magnetic circuit connected in order of the first through core 61, the one end side outer periphery iron core 63, the second through core 62, and the other end side outer periphery iron core 64. That is, in this embodiment, when a DC voltage is applied to the first primary coil L11 and when a DC voltage is applied to the second primary coil L21, magnetic fluxes directed in opposite directions are generated in one annular closed magnetic circuit connected in order of the first through core 61, the one end side outer periphery iron core 63, the second through core 62, and the other end side outer periphery iron core 64.

[0053] Furthermore, a portion of the electromagnetic flux φb travels through a closed annular magnetic path connecting the second through core 62, the other-end outer periphery core 64, the first through core 61, and the one-end outer periphery core 63, in that order. That is, a portion of the electromagnetic flux φb becomes "magnetic flux that does not pass through the center core 65." Meanwhile, the remaining portion of the electromagnetic flux φb travels through a closed annular magnetic path connecting the second through core 62, a portion of the other-end outer periphery core 64, the center core 65, and a portion of the one-end outer periphery core 63, in that order. That is, the remaining portion of the electromagnetic flux φb becomes "magnetic flux that passes through the center core 65." In other words, when a DC voltage from the power supply 102 is applied to the second primary coil L21, at least a portion of the magnetic flux generated in the second through core 62 passes through the center core 65.

[0054] Furthermore, the proportion of the electromagnetic flux φb that is "magnetic flux that does not pass through the center core 65" and "magnetic flux that passes through the center core 65" is determined by factors such as the size of the center gap 650 in the center core 65. The larger the center gap 650, the greater the proportion of "magnetic flux that does not pass through the center core 65." If the center gap 650 becomes too large and the center core 65 itself is almost nonexistent, almost all of the electromagnetic flux φb will be "magnetic flux that does not pass through the center core 65." On the other hand, the smaller the center gap 650, the greater the proportion of "magnetic flux that passes through the center core 65." If the center gap 650 is almost nonexistent, almost all of the electromagnetic flux φb will be "magnetic flux that passes through the center core 65."

[0055] Hereinafter, the proportion of the electromagnetic flux φb, which is the magnetic flux generated in the second through core 62 when a DC voltage from the power supply 102 is applied to the second primary coil L21, that does not pass through the center core 65 will be referred to as the "second coupling coefficient." That is, the "second coupling coefficient" indicates the proportion of the electromagnetic flux φb that passes through the first through core 61. If the center gap 650 is too large and almost all of the electromagnetic flux φb passes through the first through core 61, the "second coupling coefficient" will be approximately 1. On the other hand, if the center gap 650 is too small and almost all of the electromagnetic flux φb passes through the center core 65, the "second coupling coefficient" will be approximately 0 (zero). In this embodiment, the second coupling coefficient is greater than 0 and less than 1.

[0056] Furthermore, when a DC voltage from the power supply device 102 is applied to the second primary coil L21 (when ON), an induced electromotive force is induced in the second secondary coil L22, which is electromagnetically coupled to the second primary coil L21 via the iron core 60, and a potential difference occurs between both ends Ep22, Eg22 of the second secondary coil L22. The positive or negative of the potential difference induced between both ends Ep22, Eg22 of the second secondary coil L22 depends on the winding direction of the second secondary coil L22. In this embodiment, when viewed from the other end 622 side of the second penetrating iron core 62 toward the one end 621 side, the second secondary winding 822 is wound clockwise from the other end Ep22 toward the one end Eg22.

[0057] Furthermore, when a DC voltage from the power supply device 102 is applied to the second primary coil L21 (when the power supply device 102 is ON), a positive electromotive force is induced from the other end Ep22 of the second secondary coil L22 toward one end Eg22. That is, when the power supply device 102 is ON, one end Eg22 of the second secondary coil L22 has a higher voltage than the other end Ep22. Hereinafter, the potential difference between one end Eg22 and the other end Ep22 of the second secondary coil L22 will be referred to as the "ON voltage." The maximum value of the ON voltage is calculated by multiplying the voltage value of the DC voltage applied to one end Ep21 of the second primary coil L21 via the power line 150 from the power supply device 102 by the ratio of the number of turns of the second secondary coil L22 to the number of turns of the second primary coil L21.

[0058] For example, let us say that the DC voltage applied to one end Ep21 of the second primary coil L21 is 12 V. If the number of turns in the second primary coil L21 is 100 and the number of turns in the second secondary coil L22 is 8000, then the ratio of the number of turns in the second secondary coil L22 to the number of turns in the second primary coil L21 is 80. Therefore, the maximum ON voltage is calculated as 12 × 80 = 960 V. Therefore, the maximum voltage applied to one end Eg22 of the second secondary coil L22 is, for example, approximately +480 V, and the minimum voltage applied to the other end Ep22 of the second secondary coil L22 is, for example, approximately -480 V. In some cases, it may be assumed that the maximum value of the voltage applied to one end Eg22 of the second secondary coil L22 is about 960 V, and the minimum value of the voltage applied to the other end Ep22 of the second secondary coil L22 is about 0 V. Meanwhile, at this time, the voltage applied to the power line 150 is 12 V.

[0059] As described above, one end Eg22 of the second secondary coil L22 is electrically connected to one end Eg12 of the first secondary coil L12 via the second wiring Cg12. When a DC voltage from the power supply device 102 is applied to the first primary coil L11 (when ON), a positive electromotive force is induced from the other end Ep12 of the first secondary coil L12 toward the one end Eg12. When a DC voltage from the power supply device 102 is applied to the second primary coil L21 (when ON), a negative electromotive force is induced from the one end Eg22 of the second secondary coil L22 toward the other end Ep22.

[0060] Therefore, when a DC voltage from the power supply device 102 is applied to the first primary coil L11 and the second primary coil L21 (when the power supply device 102 is ON), the positive electromotive force induced from the other end Ep12 of the first secondary coil L12 toward one end Eg12 and the negative electromotive force induced from one end Eg22 of the second secondary coil L22 toward the other end Ep22 cancel each other out. This makes it possible to sufficiently suppress the absolute value of the potential difference applied between the other end Ep12 of the first secondary coil L12 and the other end Ep22 of the second secondary coil L22. As a result, when the spark plug 101 is ON, i.e., at an abnormal timing, discharge can be suppressed, and induced current can be suppressed from flowing through the spark plug 101.

[0061] The wire diameter of the second secondary winding 822 is smaller than the wire diameter of the second primary winding 821. The number of turns of the second secondary winding 822 in the second secondary coil L22 is greater than the number of turns of the second primary winding 821 in the second primary coil L21 (for example, approximately 80 times or more). As a result, when the second primary current is interrupted, the second coil set 50 boosts the low-voltage DC power supplied from the power supply device 102 to, for example, several thousand to several tens of thousands of volts. That is, a high voltage is induced in the second secondary coil L22. The second secondary coil L22 then supplies the induced high-voltage power to the spark plug 101 via the first wiring Cg22. This allows the electric spark generated in the spark plug 101 to be maintained for a longer period of time.

[0062] The first igniter 105 is a semiconductor device connected to the first primary coil L11 and controls the current flowing through the first primary coil L11. The first igniter 105 is electrically connected to the ECU 103 and receives a signal (hereinafter referred to as a "first EST signal S1") from the ECU 103. The first igniter 105 includes a first switching element 71 and a first drive IC 72. The first igniter 105 may be integrated with the electronic circuit of the ECU 103.

[0063] The first switching element 71 may be, for example, an insulated gate bipolar transistor (IGBT). The first switching element 71 is interposed between the other end Eg11 of the first primary coil L11 and a ground point 152. A collector (C) of the first switching element 71 is connected to the other end Eg11 of the first primary coil L11. An emitter (E) of the first switching element 71 is connected to the ground point 152. A gate (G) of the first switching element 71 is connected to the first driving IC 72.

[0064] This allows the first switching element 71 to switch between passing and blocking the first primary current flowing from the power supply device 102 to the first primary coil L11. When the first switching element 71 is in a closed state, the first primary current flows from the power supply device 102 to the first primary coil L11. When the first switching element 71 is in an open state, the first primary current flowing to the first primary coil L11 is blocked. However, other types of transistors may be used for the first switching element 71.

[0065] The first drive IC 72 controls the switching of the first switching element 71 based on a first EST signal S1 received from the ECU 103. The first drive IC 72 corresponds to a "first control unit" of the present invention. The first drive IC 72 has a logic device connected to the first switching element 71. 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 to operate the ignition device 1 and ignite the spark plug 101.

[0066] The second igniter 106 is a semiconductor device connected to the second primary coil L21 and controls the current flowing through the second primary coil L21. The second igniter 106 is electrically connected to the ECU 103 and receives a signal (hereinafter referred to as a "second EST signal S2") from the ECU 103. The second igniter 106 includes a second switching element 73 and a second drive IC 74. The second igniter 106 may be integrated with the electronic circuit of the ECU 103.

[0067] The second switching element 73 is, for example, an insulated gate bipolar transistor (IGBT). The second switching element 73 is interposed between the other end Eg21 of the second primary coil L21 and the ground point 152. C (collector) of the second switching element 73 is connected to the other end Eg21 of the second primary coil L21. E (emitter) of the second switching element 73 is connected to the ground point 152. G (gate) of the second switching element 73 is connected to the second drive IC 74.

[0068] This allows the second switching element 73 to switch between passing and blocking the second primary current flowing from the power supply device 102 to the second primary coil L21. When the second switching element 73 is in a closed state, the second primary current flows from the power supply device 102 to the second primary coil L21. When the second switching element 73 is in an open state, the second primary current flowing to the second primary coil L21 is blocked. However, other types of transistors may be used for the second switching element 73.

[0069] The second drive IC 74 controls the switching of the second switching element 73 based on the second EST signal S2 received from the ECU 103. The second drive IC 74 corresponds to the "second control unit" of the present invention. The second drive IC 74 has a logic device connected to the second switching element 73. 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 operates the ignition device 1 to perform arithmetic processing for maintaining the electric spark generated in the spark plug 101 for a longer period of time.

[0070] <2. Operation of the ignition device> Next, we will explain the operation of the ignition device 1. Figure 3 is a graph showing, in time series, the waveform of the first EST signal S1, the waveform of the second EST signal S2, the waveform of the sum of the first primary current I1a flowing through the first primary coil L11 and the second primary current I1b flowing through the second primary coil L21, the waveform of the output current, and the waveform of the output voltage when the ignition device 1 is operated.

[0071] In FIG. 3, the first primary current I1a is positive in the direction from one end Ep11 of the first primary coil L11 to the other end Eg11. The second primary current I1b is positive in the direction from one end Ep21 of the second primary coil L21 to the other end Eg21. The output current indicates the value of the induced current flowing through the spark plug 101. The output current is shown negative in the direction from the other end Ep22 of the second secondary coil L22 to one end Eg22. The output voltage indicates the value of the voltage applied to the other end Ep22 of the second secondary coil L22 with respect to the ground point 151.

[0072] 3, when the ignition device 1 is operated, first, at time t0, the signal level of the first EST signal S1 transmitted from the ECU 103 to the first drive IC 72 is changed from L to H, and simultaneously the signal level of the second EST signal S2 transmitted from the ECU 103 to the second drive IC 74 is changed from L to H. Then, the first drive IC 72 switches the first switching element 71 from an open state to a closed state based on the first EST signal S1. As a result, a low DC voltage from the power supply device 102 is applied to one end Ep11 of the first primary coil L11. Then, a first primary current I1a flows through the first primary winding 811 that forms the first primary coil L11, and a magnetomotive force is generated in the first primary coil L11. Hereinafter, such a process in which the first driving IC 72 passes the first primary current I1a through the first primary coil L11 to generate a magnetomotive force will be referred to as "first energization control."

[0073] Furthermore, the second driving IC 74 switches the second switching element 73 from an open state to a closed state based on the second EST signal S2. As a result, a low DC voltage is applied from the power supply device 102 to one end Ep21 of the second primary coil L21. Then, a second primary current I1b flows through the second primary winding 821 that forms the second primary coil L21, generating a magnetomotive force in the second primary coil L21. Hereinafter, this process in which the second driving IC 74 passes the second primary current I1b through the second primary coil L21 to generate a magnetomotive force at the timing when the first driving IC 72 performs the above-mentioned "first energization control" is referred to as "second energization control."

[0074] When viewed from the other end 612 of the first through core 61 toward the one end 611 (i.e., from bottom to top on the paper in FIG. 2), the first primary winding 811 is wound counterclockwise from one end Ep11 to the other end Eg11. When a low DC voltage is applied from the power supply 102 to the one end Ep11 of the first primary coil L11, an electromagnetic flux φa is generated in the direction D1 from the one end 611 of the first through core 61 toward the other end 612, according to the right-hand rule. A magnetic field corresponding to the electromagnetic flux φa acts on the core 60. As described above, a portion of the electromagnetic flux φa travels through a closed magnetic path passing through the center core 65. At this time, magnetic energy can be stored in the center gap 650 (leakage magnetic path) of the center core 65.

[0075] Furthermore, in this embodiment, when a DC voltage is applied to the first primary coil L11 from the power supply device 102 (when ON), a positive electromotive force is induced in the direction from the other end Ep12 to one end Eg12 of the first secondary coil L12, which is electromagnetically coupled to the first primary coil L11 via the iron core 60. That is, when ON, one end Eg12 of the first secondary coil L12 has a higher voltage than the other end Ep12. The maximum value of the voltage applied to one end Eg12 of the first secondary coil L12 is, for example, about several hundred volts.

[0076] When viewed from the other end 622 of the second through core 62 toward the one end 621 (i.e., from bottom to top on the paper in FIG. 2), the second primary winding 821 is wound counterclockwise from one end Ep21 to the other end Eg21. When a low DC voltage is applied from the power supply 102 to the one end Ep21 of the second primary coil L21, an electromagnetic flux φb is generated in the direction D2, from the one end 621 to the other end 622 of the second through core 62, according to the right-hand rule. A magnetic field corresponding to the electromagnetic flux φb acts on the core 60. As described above, a portion of the electromagnetic flux φb travels through a closed magnetic path passing through the center core 65. At this time, magnetic energy can be stored in the center gap 650 (leakage magnetic path) of the center core 65.

[0077] Furthermore, in this embodiment, when a DC voltage from the power supply device 102 is applied to the second primary coil L21 (when ON), a positive electromotive force is induced in the direction from the other end Ep22 to one end Eg22 of the second secondary coil L22, which is electromagnetically coupled to the second primary coil L21 via the iron core 60. That is, when ON, one end Eg22 of the second secondary coil L22 has a higher voltage than the other end Ep22. The maximum value of the voltage applied to one end Eg22 of the second secondary coil L22 is, for example, about plus several hundred volts. On the other hand, the minimum value of the voltage applied to the other end Ep22 of the second secondary coil L22 is, for example, about minus several hundred volts.

[0078] As described above, one end Eg22 of the second secondary coil L22 is electrically connected to one end Eg12 of the first secondary coil L12 via the second wiring Cg12. When a DC voltage from the power supply device 102 is applied to the first primary coil L11 (when ON), a positive electromotive force of, for example, several hundred volts is induced from the other end Ep12 of the first secondary coil L12 toward the one end Eg12. When a DC voltage from the power supply device 102 is applied to the second primary coil L21 (when ON), a negative electromotive force of, for example, several hundred volts is induced from the one end Eg22 of the second secondary coil L22 toward the other end Ep22.

[0079] Therefore, between time t0 and time t1 (described later), the positive electromotive force induced from the other end Ep12 of the first secondary coil L12 toward the one end Eg12 and the negative electromotive force induced from the one end Eg22 of the second secondary coil L22 toward the other end Ep22 cancel each other out. This sufficiently reduces the absolute value of the potential difference between the other end Ep12 of the first secondary coil L12 and the other end Ep22 of the second secondary coil L22. As a result, when the spark plug 101 is turned on, i.e., at an abnormal timing, discharge is prevented from occurring, and induced current is prevented from flowing through the spark plug 101.

[0080] Next, at time t1, which is later than time t0, the signal level of the first EST signal S1 transmitted from the ECU 103 to the first drive IC 72 is changed from H to L. The first drive IC 72 then switches the first switching element 71 from closed to open, interrupting the first primary current I1a flowing from the power supply device 102 to the first primary coil L11. The second primary current I1b continues to flow from the power supply device 102 to the second primary coil L21. Mutual induction occurs in the first secondary coil L12, which is electromagnetically coupled to the first primary coil L11 via the iron core 60. A blocking magnetic flux is generated in the opposite direction to the above-described conducting magnetic flux φa, and a large induced electromotive force is induced. At this time, the voltage applied to one end Eg12 of the first secondary coil L12 ranges from minus several thousand volts to several tens of thousands of volts relative to the ground point 152. As a result, the voltage (output voltage) applied to the other end Ep22 of the second secondary coil L22 also becomes a negative high voltage (see the output voltage at time t1' in FIG. 3).

[0081] As a result, an electric spark is generated in the spark plug 101 connected to the other end Ep22 of the second secondary coil L22, igniting the fuel, and an induced current (output current) flows through the spark plug 101. The induced current flows from the ground point (ground) 151 to the center electrode 161 of the spark plug 110 via the ground electrode 162 of the spark plug 110 (see FIG. 1). The induced current then flows through the second secondary coil L22 from the other end Ep22 to one end Eg22, then through the second wiring Cg12 to the first secondary coil L12 from one end Eg12 to the other end Ep12, and then through the power line 150 and the power supply device 102 to the ground point 152. Hereinafter, the process in which the first driving IC 72 performs the above-mentioned "first current flow control," then cuts off the first primary current I1a flowing through the first primary coil L11, and induces a high voltage at one end Eg12 of the first secondary coil L12, thereby discharging at the plug gap d of the spark plug 101, will be referred to as "first discharge control."

[0082] At this time, the second switching element 73 is in a closed state, generating a magnetomotive force in the second primary coil L21. An electromagnetic flux φb is generated in the second through core 62, flowing from one end 621 to the other end 622. A magnetic field corresponding to the electromagnetic flux φb acts on the core 60. The direction of the electromagnetic flux φb (direction D2) is the same as the blocking magnetic flux, which is opposite to the electromagnetic flux φa, in the annular closed magnetic circuit connecting the second through core 62, the other-end outer circumferential core 64, the first through core 61, and the one-end outer circumferential core 63 in this order. This amplifies the magnetic flux generated in the closed magnetic circuit. This increases the current and ignition energy (discharge energy) supplied to the spark plug 101. This further stabilizes ignition at the plug gap d.

[0083] At this time, a portion of the interrupting magnetic flux, which is directed in the opposite direction to the above-described conducting electromagnetic flux φa, travels through a closed annular magnetic path that connects the first through core 61, a portion of the one-end outer core 63, the center core 65, and a portion of the other-end outer core 64 in this order. At this time, magnetic energy accumulated in the center gap 650 (leakage magnetic path) of the center core 65 is released and supplied to the spark plug 101. As a result, the current and ignition energy (discharge energy) supplied to the spark plug 101 can be further increased. That is, in this embodiment, magnetic energy can be accumulated in the center gap 650 when the first primary coil L11 and the second primary coil L21 are energized. As a result, when a discharge occurs in the spark plug 101 thereafter, the magnetic energy accumulated in the center gap 650 can be released via the spark plug 101. As a result, the discharge energy in the spark plug 101 can be further increased.

[0084] Subsequently, at time t2, which is later than times t1 and t1', the signal level of the second EST signal S2 transmitted from the ECU 103 to the second drive IC 74 is changed from H to L. The second drive IC 74 then switches the second switching element 73 from a closed state to an open state, interrupting the second primary current I1b flowing from the power supply device 102 to the second primary coil L21. As a result, in the second secondary coil L22, which is electromagnetically coupled to the second primary coil L21 via the iron core 60, a blocking magnetic flux is generated in the opposite direction to the above-mentioned conducting magnetic flux φb due to mutual induction, and an induced electromotive force is induced. More specifically, the output voltage rises so that the potential of the center electrode 161 becomes higher than the potential of the ground electrode 162.

[0085] As a result, while maintaining a flame generated near the plug gap d, an induced current (output current) flows through the spark plug 101 in the opposite direction to the induced current in the above-mentioned "first discharge control." This induced current flows from the power supply device 102 side, via the power line 150, through the first secondary coil L12 from the other end Ep12 to one end Eg12, and then through the second wiring Cg12, through the second secondary coil L22 from one end Eg22 to the other end Ep22. The induced current then flows further through the center electrode 161 of the spark plug 110 toward the ground electrode 162 and to the ground point 151. Hereinafter, the process in which the first driving IC 72 performs the "first discharge control" and then the second driving IC 74 cuts off the second primary current I1b flowing to the second primary coil L21 and induces a high voltage at the other end Ep22 of the second secondary coil L22, thereby causing continuous discharge at the plug gap d of the spark plug 101, will be referred to as the "second discharge control."

[0086] However, as described above, in the "first discharge control," the electromagnetic flux φb generated by the second primary current I1b flowing through the second primary coil L21 and the magnetic energy accumulated in the center gap 650 are released together through the spark plug 101. This reduces the magnetic energy accumulated in the iron core 60, including the center gap 650 (leakage magnetic path). As a result, in the "second discharge control," the ignition energy (discharge energy) released through the spark plug 101 is suppressed. That is, in this embodiment, the ignition energy (discharge energy) released through the spark plug 101 is concentrated in the "first discharge control" process, that is, concentrated in the "first discharge control" process. Then, at time t3, the value of the induced current (output current) flowing through the plug gap d becomes approximately zero, and the discharge ends.

[0087] <3. Modifications> Although exemplary embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. In the following description, components having the same structure as those in the above-described embodiments will be denoted by the same reference numerals as those in the above-described embodiments.

[0088] In the above embodiment, the center gap 650 is provided near the center position of the center core 65 in the first axial direction or the second axial direction in the core 60 of the ignition coil 104. However, as shown in the first modified example in FIG. 4, the center core 65B may be formed only from the portion connected to the one-end outer peripheral core 63. A center gap 650B may be formed between the center core 65B and the other-end outer peripheral core 64. It is sufficient that a ring-shaped closed magnetic path similar to that in the above embodiment is formed.

[0089] As shown in a second modified example in FIG. 5, the central core 65 does not have to be provided. As shown in the second modified example of FIG. 5, in the core 60C of the ignition coil 104C, in addition to an annular closed magnetic circuit connecting the first through core 61, the other end side outer circumferential iron core 64, the second through core 62, and the one end side outer circumferential iron core 63 in this order, and an annular closed magnetic circuit connecting the second through core 62, the other end side outer circumferential iron core 64, the first through core 61, and the one end side outer circumferential iron core 63 in this order, there may be formed an annular closed magnetic circuit "not passing through the second through core 62" connecting the first through core 61, a portion of the other end side outer circumferential iron core 64, and a portion of the one end side outer circumferential iron core 63 in this order, and an annular closed magnetic circuit "not passing through the first through core 61" connecting the second through core 62, a portion of the other end side outer circumferential iron core 64, and a portion of the one end side outer circumferential iron core 63 in this order.

[0090] Furthermore, as shown in a third modified example in Fig. 6, the center core 65 and the other-end-side outer periphery core 64 do not have to be provided. As shown in the third modified example in Fig. 6, in the core 60D of the ignition coil 104D, in addition to an annular closed magnetic circuit connecting the first through core 61, the second through core 62, and the one-end-side outer periphery core 63 in this order, and an annular closed magnetic circuit connecting the second through core 62, the first through core 61, and the one-end-side outer periphery core 63 in this order, it is sufficient if an annular closed magnetic circuit "not passing through the second through core 62" connecting the first through core 61 and a part of the one-end-side outer periphery core 63 in this order and an annular closed magnetic circuit "not passing through the first through core 61" connecting the second through core 62 and a part of the one-end-side outer periphery core 63 in this order are formed.

[0091] As shown in a fourth modified example in FIG. 7 , the first coil set 40E and the second coil set 50E of the ignition coil 104E may be disposed adjacent to each other in the first axial direction and the second axial direction. The common core 66E may extend through the first primary coil L11 and the first secondary coil L12 of the first coil set 40E. The common core 66E may extend through the second primary coil L21 and the second secondary coil L22 of the second coil set 50E. As shown in the fourth modified example in FIG. 7 , the ignition coil 104E may include an annular closed magnetic path connecting the common core 66E to the space outside the first coil set 40E in the first radial direction, and another annular closed magnetic path connecting the common core 66E to the space outside the second coil set 50E in the second radial direction.

[0092] In the above embodiment, in the "first discharge control" in which the ignition energy (discharge energy) released through the spark plug 101 is concentrated, the voltage (output voltage) applied to the other end Ep22 of the second secondary coil L22 is a negative high voltage. Then, in the "first discharge control," an induced current (output current) flows from the ground point 151 through the spark plug 101, resulting in a so-called "negative discharge." However, by switching the order of energization and de-energization of the primary coils L11 and L21 each time the "first discharge control" and the "second discharge control" are performed, the voltage (output voltage) applied to the other end Ep22 of the second secondary coil L22 may alternate from a negative high voltage to a positive high voltage to a negative high voltage to a positive high voltage, and so on. When a positive high voltage is generated, a so-called "positive discharge" is generated, in which an induced current (output current) flows from the power supply device 102 to the ground point 151 via the first secondary coil L12, the second secondary coil L22, and the spark plug 110. This makes it possible to suppress wear of the electrodes due to discharge.

[0093] 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.

[0094] 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 embodiments and modifications may be appropriately combined without causing any contradiction. [Explanation of symbols]

[0095] 1 Ignition device 40,40E 1st coil set 50,50E Second coil set 60,60C,60D iron core 61 First through core 62 Second through core 63 One end outer core 64 Other end outer peripheral iron core 65,65B center iron core 66E common core 71 first switching element 72 First driving IC (first control unit) 73 Second switching element 74 Second driving IC (second control unit) 101 Spark plug 102 Power supply 104, 104C, 104D, 104E ignition coil 105 First Igniter 106 Second Igniter 110 Spark plug 150 Power line 151 Grounding point 152 Grounding point 161 (spark plug) center electrode 162 (spark plug) ground electrode 611 (One end of the first through core) 612 (the other end of the first through-core) 621 (One end of the second through core) 622 (the other end of the second through-core) 650,650B Center Gap 651 (One end of the central iron core) 652 (the other end of the central core) 811 First primary winding 812 1st secondary winding 821 Second Primary Winding 822 Secondary Winding Cg22 1st wiring Cg12 2nd wiring Cp12 3rd wiring Eg11 (the other end of the first primary coil) Eg12 (One end of the first secondary coil) Eg21 (other end of second primary coil) Eg22 (one end of the second secondary coil) Ep11 (one end of the first primary coil) Ep12 (other end of first secondary coil) Ep21 (one end of the second primary coil) Ep22 (other end of second secondary coil) I1a First primary current I1b Second primary current L11 1st primary coil L12 First secondary coil L21 Second primary coil L22 Secondary coil

Claims

1. An ignition device having an ignition coil for an internal combustion engine and an ignition plug connected to the ignition coil, The ignition coil is a first primary coil having a first primary winding, one end of which is applied with a DC voltage and the other end of which is connected to a ground; a first secondary coil comprising a first secondary winding; a first through core that passes through an inside of the first primary coil and an inside of the first secondary coil and electromagnetically couples the first primary coil and the first secondary coil; a second primary coil having a second primary winding, one end of which is applied with the DC voltage and the other end of which is connected to a ground; a second secondary coil comprising a second secondary winding; a second through core that passes through an inside of the second primary coil and an inside of the second secondary coil and electromagnetically couples the second primary coil and the second secondary coil; a one-end-side outer peripheral core that connects one end of the first through core and one end of the second through core; an outer peripheral core on the other end side that connects the other end of the first through core and the other end of the second through core; and a closed magnetic circuit is formed by the first through core, the one end side outer peripheral core, the second through core, and the other end side outer peripheral core, When the DC voltage is applied to the first primary coil, a positive electromotive force is induced in the first secondary coil in a direction from the other end to the one end, When the DC voltage is applied to the second primary coil, a negative electromotive force is induced in the second secondary coil in a direction from one end to the other end, the ignition plug is connected to the other end of the second secondary coil via a first wiring that is a conductor, and ignites fuel by discharging in a plug gap based on a high voltage induced at one end of the first secondary coil or a high voltage induced at the other end of the second secondary coil; one end of the second secondary coil is connected to one end of the first secondary coil via a second wiring that is a conductor; The other end of the first secondary coil is connected to a ground point directly or indirectly via a third wiring that is a conductor.

2. 10. The ignition device according to claim 1, An ignition device in which, when the DC voltage is applied to the first primary coil and when the DC voltage is applied to the second primary coil, magnetic fluxes are generated in the closed magnetic circuit in opposite directions to each other.

3. 10. The ignition device according to claim 1, a central core that is disposed between the first through core and the second through core and forms a magnetic path that connects the one end side outer peripheral core and the other end side outer peripheral core; whereby When the DC voltage is applied to the first primary coil, at least a part of the magnetic flux generated in the first through core passes through the center core, An ignition device, wherein when the DC voltage is applied to the second primary coil, at least a portion of the magnetic flux generated in the second through core passes through the center core.

4. 4. The ignition device according to claim 3, The central iron core has a central gap formed therein, which is a gap that separates the central iron core into two or more portions, a first coupling coefficient indicating a ratio of magnetic flux passing through the second penetrating core to magnetic flux generated in the first penetrating core when the DC voltage is applied to the first primary coil is greater than 0 and less than 1; an ignition device, wherein a second coupling coefficient indicating a proportion of magnetic flux that passes through the first penetrating iron core out of magnetic flux generated in the second penetrating iron core when the DC voltage is applied to the second primary coil is greater than 0 and less than 1.

5. An ignition device according to any one of claims 1 to 4, a power supply device that applies the DC voltage to one end of the first primary coil and one end of the second primary coil; a first switching element that is interposed between the other end of the first primary coil and a ground point and that is capable of switching between energization and interruption of a first primary current that flows from the power supply device to the first primary coil; a second switching element that is interposed between the other end of the second primary coil and a ground point and that is capable of switching between energization and interruption of a second primary current that flows from the power supply device to the second primary coil; a first control unit that controls switching of the first switching element; a second control unit that controls switching of the second switching element; The ignition device further comprises:

6. 6. The ignition device according to claim 5, The first control unit a first current supply control for causing the first primary current to flow through the first primary coil by closing the first switching element to generate a magnetomotive force; a first discharge control in which, after the first energization control is performed, the first switching element is switched to an open state to induce a high voltage at one end of the first secondary coil, thereby causing a discharge in the plug gap of the spark plug; and The second control unit a second energization control in which the second switching element is closed at a timing when the first control unit performs the first energization control, thereby causing the second primary current to flow through the second primary coil and generating a magnetomotive force; a second discharge control in which, after the first control unit has performed the first discharge control, the second switching element is switched to an open state to induce a high voltage at the other end of the second secondary coil, thereby causing continuous discharge in the plug gap of the spark plug; An ignition device.

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