Ignition coil and ignition device

Abstract

To provide an ignition coil for an internal combustion engine capable of performing a DCO ignition method capable of reducing in size and increasing in energy.SOLUTION: In an ignition coil 104, a power supply device 102 is applied to one end of each of a first primary coil L11 and a second primary coil L21, and the other end is connected to a ground point 152. A first iron core 61 penetrates an inside of the first primary coil L11 and an inside of a first secondary coil L12. A second iron core 62 penetrates the inside of the second primary coil L21 and the inside of a second secondary coil L22, and one ends 611 and 621 of the iron cores 61 and 62 are connected to each other and the other ends 612 and 622 are connected to each other, whereby one closed magnetic path is formed. When a DC voltage is applied to the first primary coil L11, a magnetic flux directed from the other end 612 to the one end 611 is formed in the first iron core 61, and when the DC voltage is applied to the second primary coil L21, the magnetic flux directed from the other end 622 to the one end 621 is formed in the second iron core 62.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, in internal combustion engines of automobiles and the like, lean combustion, in which a lean fuel with a lower air-fuel ratio than the stoichiometric air-fuel ratio is burned, has been used to improve fuel efficiency in response to resource depletion. Furthermore, the use of carbon-free ammonia as a fuel has been considered in order to realize a decarbonized society in response to global warming. However, these fuels are generally less flammable than gasoline and require high energy for ignition. Therefore, various ignition methods have been considered to effectively burn these fuels, such as multiple ignition methods in which a spark plug discharges multiple times in succession and dual coil offset (DCO) ignition methods in which a spark plug continuously discharges for a certain period of time around the ignition timing. For example, Patent Document 1 discloses an ignition system for an internal combustion engine that employs DCO ignition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6005943 Summary of the Invention [Problem to be solved by the invention]

[0004] The ignition device for an internal combustion engine in Patent Document 1 is composed of ignition coils Ca and Cb, igniters IGTa and IGTb, and a case body (10) that houses them (see paragraph 0021 and Figures 1-2). The ignition coil Ca includes a primary coil La1, a secondary coil La2, and an iron core Ma, and the ignition coil Cb has a similar configuration (see paragraph 0022). The secondary coils La2 and Lb2 of each ignition coil Ca and Cb are connected to a common spark plug PG. When an ignition signal is input, the ignition device boosts the bias voltage Vout of the DC-DC converter and applies the boosted voltage to the spark plug PG. As a result, high voltages from both ignition coils Ca and Cb are applied to the spark plug PG (see paragraphs 0025 and 0027).

[0005] However, when forming a closed magnetic circuit of an iron core in each of the two ignition coils Ca and Cb, as in Patent Document 1, there is a problem that the entire device becomes large. Therefore, there is room to improve the structure of each ignition coil and iron core in order to make the entire device smaller and easier to install in an internal combustion engine.

[0006] An object of the present invention is to provide a technology that improves the structure of an ignition coil for an internal combustion engine capable of implementing the DCO ignition system and enables the overall device to be made more compact. [Means for solving the problem]

[0007] In order to solve the above problems, a first invention of the present application is an ignition coil for an internal combustion engine, comprising a first primary coil, a first secondary coil, a first iron core, a second primary coil, a second secondary coil, and a second iron 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 a ground. The first secondary coil comprises a first secondary winding. The first iron 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 a ground. The second secondary coil comprises a second secondary winding. The second iron 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. One end of the first iron core is connected to one end of the second iron core, and the other end of the first iron core is connected to the other end of the second iron core, thereby forming a closed magnetic circuit. When the DC voltage is applied to the first primary coil, a magnetic flux is generated in the first iron core from the other end to one end. When the DC voltage is applied to the second primary coil, a magnetic flux is generated in the second iron core from the other end to one end.

[0008] A second aspect of the present invention is an ignition device including the ignition coil of the first aspect, a power supply device, a first switching element, a second switching element, a first control unit, a second control unit, and an ignition plug. 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. The spark plug ignites fuel by discharging in a gap based on a high voltage induced at the other end of the first secondary coil and / or a high voltage induced at the other end of the second secondary coil.

[0009] A third aspect of the present invention is the ignition device of the second aspect, wherein the first control unit performs primary energization control, discharge control, and boost control. The primary energization control is control in which the first primary current flows through the first primary coil by closing the first switching element to generate a magnetomotive force. The discharge control is control in which, after performing the primary energization control, the first switching element is switched to an open state to induce a high voltage at the other end of the first secondary coil, thereby causing a discharge in the gap of the spark plug. The second control unit also performs boost control and discharge control. The boost control performed by the second control unit 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 discharge control, thereby amplifying the magnetic flux generated in the closed magnetic circuit. By performing the boost control, the second control unit simultaneously performs primary current control, which causes the second primary current to flow through the second primary coil to generate a magnetomotive force. The discharge control performed by the second control unit is a control in which, after the second control unit performs the boost control, the second control unit switches the second switching element to an open state to induce a high voltage at the other end of the second secondary coil, thereby causing continuous discharge in the gap of the spark plug. At the timing when the second control unit performs the discharge control, the first control unit further performs the boost control, which causes the first primary current to flow through the first primary coil to amplify the magnetic flux generated in the closed magnetic circuit, by switching the first switching element to a closed state again.

[0010] A fourth aspect of the present invention is the ignition device of the third aspect, wherein the first control unit performs the primary current control and then alternately repeats the discharge control and the boost control multiple times, and the second control unit performs the boost control every time the first control unit performs the discharge control, and performs the discharge control every time the first control unit performs the boost control. [Effects of the Invention]

[0011] According to the first to fourth aspects of the present application, the iron cores used in the two coil sets are connected to each other to form one closed magnetic circuit, thereby making it possible to reduce the size of the entire ignition coil including the iron cores.

[0012] In particular, according to the third aspect of the present invention, the flame generated around the plug can be maintained for a longer period by amplifying the magnetic flux generated in the closed magnetic circuit by passing a second primary current through the second primary coil at the timing when discharge control of the first primary coil is performed. Also, the flame generated around the plug can be maintained for a longer period by passing a first primary current through the first primary coil at the timing when discharge control of the second primary coil is performed to amplify the magnetic flux generated in the closed magnetic circuit.

[0013] In particular, according to the fourth aspect of the present invention, the flame generated around the plug can be maintained for an even longer period of time. [Brief explanation of the drawings]

[0014] [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 longitudinal sectional view of an ignition coil. [Figure 3] FIG. 2 is a schematic longitudinal sectional view of an ignition coil. [Figure 4] 10 is a graph showing, in time series, the waveform of a first EST signal, the waveform of a first primary current, the waveform of a first secondary current, the waveform of a second EST signal, the waveform of a second primary current, the waveform of a second secondary current, and a waveform obtained by adding together the waveforms of the first secondary current and the second secondary current when the ignition device is operated. [Figure 5] FIG. 4 is an explanatory diagram schematically showing the direction of magnetic flux during primary current supply control. [Figure 6] FIG. 4 is an explanatory diagram schematically showing the direction of magnetic flux during discharge control. [Figure 7] FIG. 4 is an explanatory diagram schematically showing the direction of magnetic flux during discharge control. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] 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 schematically illustrating the operating environment of the ignition device 1 according to the first embodiment. As will be described later, 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.

[0017] The ignition device 1 of this embodiment is mounted on an internal combustion engine such as an SI (spark ignition) reciprocating engine used in 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.

[0018] 1, the vehicle body 100 is equipped with the ignition device 1, as well as the ignition plug 101, a power supply device 102 (battery), and an ECU 103 (Engine Control Unit). In a broad sense, the ignition plug 101, the power supply device 102, and the ECU 103 can also be considered to be included in the ignition device 1.

[0019] 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 Eg12 of a first secondary coil L12 of an ignition coil 104 (described later) via a conductor (hereinafter referred to as a "first secondary-side ground wire Cg12"). The spark plug 101 is interposed between the other end Eg12 of the first secondary coil L12 and a ground point (ground) 151. The spark plug 101 is also electrically connected to the other end Eg22 of a second secondary coil L22 of the ignition coil 104 (described later) via a conductor (hereinafter referred to as a "second secondary-side ground wire Cg22"). The spark plug 101 is interposed between the other end Eg22 of the second secondary coil L22 and the ground point (ground) 151. That is, in the ignition device 1, one spark plug 101 is provided in common for a first coil set 40 and a second coil set 50, which will be described later.

[0020] A high voltage is induced in the first secondary coil L12 and / or the second secondary coil L22 of the ignition coil 104. When the sum of the high voltage induced in the other end Eg12 of the first secondary coil L12 and the high voltage induced in the other end Eg22 of the second secondary coil L22 exceeds the breakdown voltage in the gap d (see FIG. 1) between the center electrode 161 and the ground electrode 162 of the spark plug 101, a discharge occurs in the 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 in the gap d based on the high voltage induced in the other end Eg12 of the first secondary coil L12 and / or the high voltage induced in the other end Eg22 of the second secondary coil L22.

[0021] In this embodiment, the fuel used is a lean fuel in which the fuel ratio is lower than the stoichiometric air-fuel ratio, or ammonia, which does not contain carbon, but the fuel used in the ignition device 1 of the present invention is not limited to these.

[0022] The power supply device 102 is a power supply device (storage battery) capable of charging and discharging DC power. In this embodiment, the power supply device 102 is electrically connected to a first primary coil L11, a first secondary coil L12, a second primary coil L21, and a second secondary coil L22 of an ignition coil 104 (described later) via conductors (hereinafter referred to as "power lines 150"). The power supply device 102 applies a DC voltage to one end Ep11 of the first primary coil L11, one end Ep12 of the first secondary coil L12, one end Ep21 of the second primary coil L21, and one end Ep22 of the second secondary coil L22 of the ignition coil 104 via the power line 150. However, as described later, a first diode 131 and a second diode 132 are provided to prevent a current from flowing through the first secondary coil L12 and the second secondary coil L22 due to the voltage of the power supply device 102.

[0023] The ECU 103 is an existing computer that comprehensively controls the operation of the transmission and engine of the vehicle body 100 .

[0024] The ignition device 1 includes an ignition coil 104 , a first igniter 105 , a second igniter 106 , a first diode 131 , and a second diode 132 .

[0025] 2 and 3 are schematic longitudinal cross-sectional views of the ignition coil 104. In FIGS. 2 and 3, components of the power supply device 102, other than the ignition coil 104, are indicated by dashed double-dashed lines. As shown in FIGS. 2 and 3, 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 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, together with the first igniter 105 and the second igniter 106, are integrally housed in a separately provided coil case (not shown).

[0026] 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." Also, 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." Also, the term "parallel direction" includes a direction that is approximately parallel, and the term "orthogonal direction" includes a direction that is approximately orthogonal. In this embodiment, the first center axis Bc1 and the second center axis Bc2 are approximately parallel.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The iron core 60 has a structure in which a first iron core 61, a second iron core 62, a one-end connection iron core 63, and an other-end connection iron core 64 are combined together. The first iron core 61, the second iron core 62, the one-end connection iron core 63, and the other-end connection iron core 64 of the iron core 60 are formed, for example, from laminated steel plates in which silicon steel plates are stacked. The first iron core 61 extends in a columnar shape along the first center axis Bc1. The first iron core 61 is inserted into the space 410 on the inside of the first primary bobbin 411 in the first radial direction. That is, the first iron core 61 penetrates the inside of the first primary coil L11 and the inside of the first secondary coil L12. The second iron core 62 extends in a columnar shape along the second center axis Bc2. The second iron core 62 is inserted into the space 510 on the inside in the second radial direction of the second primary bobbin 511. That is, the second iron core 62 passes through the inside of the second primary coil L21 and the inside of the second secondary coil L22.

[0032] In this embodiment, the one-end connection core 63 and the other-end connection core 64 extend columnarly in a direction substantially perpendicular to the first center axis Bc1 and the second center axis Bc2, respectively. The one-end connection core 63 connects one end 611 of the first core 61 in the first axial direction to one end 621 of the second core 62 in the second axial direction. That is, the one end 611 of the first core 61 and the one end 621 of the second core 62 are connected via the one-end connection core 63. The other-end connection core 64 connects the other end 612 of the first core 61 in the first axial direction to the other end 622 of the second core 62 in the second axial direction. That is, the other end 612 of the first core 61 and the other end 622 of the second core 62 are connected via the other-end connection core 64.

[0033] This forms a single annular closed magnetic circuit in which the first core 61, the one-end connecting core 63, the second core 62, and the other-end connecting core 64 are connected in this order. The first core 61 electromagnetically couples the first primary coil L11 and the first secondary coil L12. The second core 62 electromagnetically couples the second primary coil L21 and the second secondary coil L22.

[0034] 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 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 gradually increasing first primary current I1a (see t0-t1 in FIG. 4) begins to flow through the first primary coil L11.

[0035] Furthermore, in this embodiment, when the first primary coil L11 is viewed from the other end 612 side toward the one end 611 side of the first iron core 61 penetrating the inside in the first radial direction (i.e., from bottom to top on the page of FIG. 2), the first primary winding 811 is wound clockwise from one end Ep11 toward 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 is generated in the one direction D1 according to the right-hand screw rule. In other words, when a DC voltage from the power supply device 102 is applied to the first primary coil L11, an electromagnetic flux is generated in the first iron core 61 from the other end 612 toward the one end 611.

[0036] In this embodiment, when the first secondary coil L12 is viewed from the other end 612 side toward the one end 611 side of the first iron core 61 that penetrates the inside of the first radial direction (i.e., from bottom to top on the paper surface of FIG. 2), the first secondary winding 812 is wound clockwise from one end Ep12 toward the other end Eg12. The other end Eg12 of the first secondary coil L12 is connected to the ignition plug 101 via a first secondary-side ground wire Cg12. The wire diameter of the first secondary winding 812 is smaller than the wire diameter of the first primary winding 811. The number of turns of the first secondary winding 812 in the first secondary coil L12 is approximately 100 times or more the number of turns of the first primary winding 811 in the first primary coil L11. As a result, as will be described in detail later, when the first primary current I1a is interrupted, the ignition coil 104 boosts the low-voltage DC power supplied from the power supply device 102 to 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. This generates an electric spark in the spark plug 101, igniting the fuel.

[0037] As shown in FIG. 1, a first diode 131 is connected in series with the first secondary coil L12 to the first secondary-side ground wire Cg12. The first diode 131 has a forward direction from the other end Eg12 to one end Ep12 of the first secondary coil L12. This prevents an induced current caused by a voltage induced in the first secondary coil L12 by the first primary current I1a, which gradually increases when the first primary coil L11 is energized, from flowing in the reverse direction to the ignition plug 101. As described above, the power supply line 150, which is a conductor extending from the power supply device 102, is connected to one end Ep12 of the first secondary coil L12.

[0038] 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 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 I1b (see t1-t2 in FIG. 4) begins to flow through the second primary coil L21.

[0039] 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 iron core 62 penetrating the inside in 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 clockwise from the one end Ep21 toward the other end Eg21. As a result, when a low DC voltage from the power supply device 102 is applied to the one end Ep21 of the second primary coil L21, an electromagnetic flux is generated in the other direction D2 opposite to the one direction D1 described above, according to the right-hand screw rule. In other words, when a DC voltage from the power supply device 102 is applied to the second primary coil L21, an electromagnetic flux is generated in the second iron core 62 from the other end 622 toward the one end 621.

[0040] In this embodiment, when the second secondary coil L22 is viewed from the other end 622 side toward the one end 621 side of the second iron core 62 penetrating the inside of the second radial direction (i.e., from bottom to top on the paper surface of FIG. 2), the second secondary winding 822 is wound clockwise from one end Ep22 toward the other end Eg22. The other end Eg22 of the second secondary coil L22 is connected to the ignition plug 101 via a second secondary-side ground wire Cg22. 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 approximately 100 times or more the number of turns of the second primary winding 821 in the second secondary coil L22. As a result, as will be described in detail later, when the second primary current I1b is interrupted, the ignition coil 104 boosts the low-voltage DC power supplied from the power supply device 102 to 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. This allows the electric spark generated in the spark plug 101 to be maintained for a longer period of time.

[0041] As shown in FIG. 1, a second diode 132 is connected in series with the second secondary coil L22 to the second secondary-side ground wire Cg22. The second diode 132 has a forward direction from the other end Eg22 to one end Ep22 of the second secondary coil L22. This prevents an induced current caused by a voltage induced in the second secondary coil L22 by the second primary current I1b, which gradually increases when the second primary coil L21 is energized, from flowing in the reverse direction to the ignition plug 101. As described above, the power supply line 150, which is a conductor extending from the power supply device 102, is connected to one end Ep22 of the second secondary coil L22.

[0042] As described above, in this embodiment, in one ignition coil 104, the first iron core 61 inserted inside the first coil set 40 and the second iron core 62 inserted inside the second coil set 50 are connected to each other to form one closed magnetic circuit. This allows the entire ignition coil 104, including the iron core 60, to be more compact than when a closed magnetic circuit is formed for each coil set 40, 50. Furthermore, by configuring the iron core 60 in this manner, as described below, the magnetic flux generated in the closed magnetic circuit can be amplified, thereby increasing the ignition energy supplied to the spark plug 101 and achieving high energy. As a result, the ignition device 1 including the ignition coil 104 can be more easily installed in an internal combustion engine. Furthermore, the reduction in the number of parts leads to a reduction in the manufacturing cost of the entire device.

[0043] 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.

[0044] 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 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 152. A gate (G) of the first switching element 71 is connected to the first driving IC 72.

[0045] This allows the first switching element 71 to switch between conducting and blocking the first primary current I1a 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 I1a 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 I1a flowing to the first primary coil L11 is blocked. However, other types of transistors may be used for the first switching element 71.

[0046] 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.

[0047] 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.

[0048] 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 a ground 152. A collector (C) of the second switching element 73 is connected to the other end Eg21 of the second primary coil L21. An emitter (E) of the second switching element 73 is connected to the ground 152. A gate (G) of the second switching element 73 is connected to the second driving IC 74.

[0049] This allows the second switching element 73 to switch between conducting and blocking the second primary current I1b 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 I1b 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 I1b flowing to the second primary coil L21 is blocked. However, other types of transistors may be used for the second switching element 73.

[0050] The second drive IC 74 controls the switching of the second switching element 73 based on a second EST signal S2 received from the ECU 103. The second drive IC 74 corresponds to a "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 performs arithmetic processing to operate the ignition device 1 and ignite the spark plug 101.

[0051] <1-2. Operation of the ignition device> Next, a description will be given of the operation of the ignition device 1. Fig. 4 is a graph showing, in time series, the waveform of the first EST signal S1, the waveform of the first primary current I1a flowing through the first primary coil L11, the waveform of the first secondary current I2a flowing through the first secondary coil L12, the waveform of the second EST signal S2, the waveform of the second primary current I1b flowing through the second primary coil L21, the waveform of the second secondary current I2b flowing through the second secondary coil L22, and the waveform obtained by adding together the waveforms of the first secondary current I2a and the second secondary current I2b when the ignition device 1 is operated.

[0052] In FIG. 4, the first primary current I1a is shown as being positive in the direction from one end Ep11 of the first primary coil L11 to the other end Eg11. The first secondary current I2a is shown as being negative in the direction from the other end Eg12 of the first secondary coil L12 to one end Ep12. The second primary current I1b is shown as being positive in the direction from one end Ep21 of the second primary coil L21 to the other end Eg21. The second secondary current I2b is shown as being negative in the direction from the other end Eg22 of the second secondary coil L22 to one end Ep22.

[0053] As shown in FIG. 4, 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. 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 is applied from the power supply device 102 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, generating a magnetomotive force in the first primary coil L11. Hereinafter, this process of passing the first primary current I1a through the first primary coil L11 to generate a magnetomotive force is referred to as "primary current control."

[0054] As described above, when viewed from the other end 612 side of the first core 61 toward the one end 611 side, the first primary winding 811 is wound clockwise from one end Ep11 to the other end Eg11. Therefore, when a low DC voltage from the power supply 102 is applied to one end Ep11 of the first primary coil L11, an electromagnetic flux φa1 is generated in the one direction D1 according to the right-hand rule. That is, an electromagnetic flux φa1 is generated in the first core 61 in the one direction D1 from the other end 612 to the one end 611, and a magnetic field corresponding to the electromagnetic flux φa1 acts on the iron core 60 (FIG. 5).

[0055] At this time, a small 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 in the second secondary coil L22, which is also electromagnetically coupled to the first primary coil L11 via the iron core 60. As described above, when viewed from the other end 612 of the first iron core 61 toward the one end 611, the first secondary winding 812 is wound clockwise from one end Ep12 to the other end Eg12. Therefore, when an induced current (first secondary current I2a) attempts to flow in response to the induced electromotive force, the induced current (first secondary current I2a) flows in the reverse direction through the first diode 131 connected in series with the first secondary coil L12 and is therefore blocked by the first diode 131. As a result, no induced current (first secondary current I2a) flows through the first secondary coil L12 (see time t0-t1 of the first secondary current I2a in FIG. 4).

[0056] On the other hand, when viewed from the other end 622 side of the second iron core 62 toward the one end 621 side, the second secondary winding 822 is wound clockwise from one end Ep22 to the other end Eg22. Therefore, when an induced current (second secondary current I2b) attempts to flow in response to the induced electromotive force, the induced current (second secondary current I2b) flows forward through the second diode 132 connected in series with the second secondary coil L22 and is not blocked by the second diode 132. As a result, the induced current (second secondary current I2b) flows through the second secondary coil L22 (see time t0-t1 of the second secondary current I2b in FIG. 4). However, the induced current (second secondary current I2b) is weak and, in principle, does not generate an electric spark in the spark plug 101.

[0057] After the primary energization control is performed, at time t1, 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, 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. The first drive IC 72 then switches the first switching element 71 from closed to open, interrupting the primary current (first primary current I1a) flowing from the power supply device 102 to the first primary coil L11. As a result, in the first secondary coil L12 that is electromagnetically coupled to the first primary coil L11 via the iron core 60, a mutual induction action generates an interruption magnetic flux φs1 in the other direction D2 shown in FIG. 6 , which is opposite to the one direction D1 of the above-described energization magnetic flux φa1, and a large induced electromotive force is induced. At this time, the voltage value applied to the other end Eg12 of the first secondary coil L12 ranges from minus several thousand volts to several tens of thousands volts with respect to the ground point (ground) 152.

[0058] As described above, when viewed from the other end 612 of the first core 61 toward the one end 611, the first secondary winding 812 is wound clockwise from one end Ep12 to the other end Eg12. Therefore, when an induced current (first secondary current I2a) attempts to flow in response to the induced electromotive force, the induced current (first secondary current I2a) flows forward through the first diode 131 connected in series with the first secondary coil L12 and is therefore not blocked by the first diode 131. As a result, a large induced current (second secondary current I2b) flows through the first secondary coil L12 (see time t1-t2 of the first secondary current I2a in FIG. 4). This generates an electric spark in the spark plug 101 connected to the other end Eg12 of the first secondary coil L12, thereby igniting the fuel. Hereinafter, this process of interrupting the first primary current I1a flowing through the first primary coil L11 and inducing a high voltage at the other end Eg12 of the first secondary coil L12 to discharge in the gap d of the spark plug 101 will be referred to as "discharge control."

[0059] At the same time that the first driving IC 72 starts the discharge control, the second driving IC 74 switches the second switching element 73 from an open state to a closed state. This applies a low DC voltage from the power supply 102 to one end Ep21 of the second primary coil L21. 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. That is, the second driving IC 74 performs primary current control to pass the second primary current I1b through the second primary coil L21 to generate a magnetomotive force. As described above, when viewed from the other end 622 of the second core 62 toward the one end 621, the second primary winding 821 is wound clockwise from one end Ep21 to the other end Eg21. Therefore, when a low DC voltage is applied from the power supply device 102 to one end Ep21 of the second primary coil L21, an electromagnetic flux φb1 is generated in the other direction D2 due to the right-hand rule. That is, an electromagnetic flux φb1 is generated in the second iron core 62, traveling in the other direction D2 from the other end 622 to the one end 621, and a magnetic field corresponding to the electromagnetic flux φb1 acts on the iron core 60 (FIG. 6).

[0060] As described above, the core 60 of the present invention forms only one annular closed magnetic path by connecting the first core 61, the one-end connecting core 63, the second core 62, and the other-end connecting core 64 in this order. The interrupting magnetic flux φs1 generated during discharge control by the first driving IC 72 and the conducting magnetic flux φb1 generated by energizing the second primary coil L21 are directed in the same direction D2 in the closed magnetic path. Therefore, during discharge control by the first driving IC 72, energizing the second primary coil L21 under control of the second driving IC 74 amplifies the magnetic flux generated in the closed magnetic path of the core 60. Hereinafter, this process of the second driving IC 74 closing the second switching element 73 at the timing when the first driving IC 72 performs discharge control, thereby causing the second primary current I1b to flow through the second primary coil L21 and amplifying the magnetic flux generated in the closed magnetic path of the iron core 60, will be referred to as "boost control." In other words, by performing this "boost control," the second driving IC 74 simultaneously performs primary current control, which causes the second primary current I1b to flow through the second primary coil L21 and generates a magnetomotive force.

[0061] In this way, by passing the second primary current I1b through the second primary coil L21 at the timing of performing discharge control of the first primary coil L11 and amplifying the magnetic flux generated in the closed magnetic circuit of the iron core 60, it is possible to increase the current and ignition energy supplied to the spark plug 101 (see time t1-t2 of the first secondary current I2a in FIG. 4). As a result, even when burning lean fuel or a flame-resistant fuel such as ammonia, the flame generated around the spark plug 101 can be maintained for a longer period of time.

[0062] Furthermore, after the second drive IC 74 has performed boost control, at time t2, 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, and 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. The second drive IC 74 then switches the second switching element 73 from closed to open, interrupting the primary current (second primary current I1b) flowing from the power supply 102 to the second primary coil L21. As a result, in the second secondary coil L22 electromagnetically coupled with the second primary coil L21 via the iron core 60, a mutual induction action occurs, generating a blocking magnetic flux φs2 in one direction D1 shown in FIG. 7, which is opposite to the other direction D2 of the conducting magnetic flux φb1 in FIG. 6, and a large induced electromotive force is induced. At this time, the voltage value applied to the other end Eg22 of the second secondary coil L22 ranges from minus several thousand volts to several tens of thousands volts with respect to the ground point (ground) 152.

[0063] As described above, when viewed from the other end 622 of the second core 62 toward the one end 621, the second secondary winding 822 is wound clockwise from one end Ep22 to the other end Eg22. Therefore, when an induced current (second secondary current I2b) attempts to flow in response to the induced electromotive force, the induced current (second secondary current I2b) flows forward through the second diode 132 connected in series with the second secondary coil L22 and is not blocked by the second diode 132. As a result, a large induced current (second secondary current I2b) flows through the second secondary coil L22 (see time t2-t3 of the second secondary current I2b in FIG. 4). As a result, the flame generated around the spark plug 101 connected to the other end Eg22 of the second secondary coil L22 can be maintained for a longer period of time. That is, after performing boost control, the second driving IC 74 switches the second switching element 73 to the open state at time t2, thereby inducing a high voltage at the other end Eg22 of the second secondary coil L22, thereby performing discharge control to continuously discharge in the gap d of the spark plug 101.

[0064] At time t2, simultaneously with the second driving IC 74 starting the discharge control, the first driving IC 72 switches the first switching element 71 from the open state to the closed state. This causes a low DC voltage from the power supply 102 to be applied to one end Ep11 of the first primary coil L11. A first primary current I1a flows through the first primary winding 811 that forms the first primary coil L11, generating a magnetomotive force in the first primary coil L11. As described above, when viewed from the other end 612 of the first core 61 toward the one end 611, the first primary winding 811 is wound clockwise from one end Ep11 to the other end Eg11. Therefore, when a low DC voltage from the power supply 102 is applied to one end Ep11 of the first primary coil L11, an electromagnetic flux φa2 is generated in the one direction D1, according to the right-hand rule. That is, an electromagnetic flux φa2 is generated in the first core 61 from the other end 612 to the one end 611 in one direction D1, and a magnetic field corresponding to the electromagnetic flux φa2 acts on the iron core 60 (FIG. 7).

[0065] Here, the blocking magnetic flux φs2 and the conducting magnetic flux φa2 are directed in the same direction D1 in the closed magnetic path formed in the iron core 60. Therefore, during discharge control by the second driving IC 74, the first driving IC 72 controls the first primary coil L11 to be energized, thereby amplifying the magnetic flux generated in the closed magnetic path of the iron core 60. In this manner, in this embodiment, when the second driving IC 74 performs discharge control, the first driving IC 72 closes the first switching element 71 again, thereby further performing boost control to pass the first primary current I1a through the first primary coil L11 and amplify the magnetic flux generated in the closed magnetic path of the iron core 60. As a result, the current supplied to the spark plug 101 and the ignition energy can be increased (see the second secondary current I2b from time t2 to time t3 in FIG. 4). As a result, even when burning lean fuel or a flame-retardant fuel such as ammonia, the flame generated around the spark plug 101 can be maintained for a longer period of time.

[0066] Furthermore, in this embodiment, at time t3, 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, 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. Furthermore, at time t4, 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, and simultaneously 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. Furthermore, at time t5, 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, 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. Furthermore, at time t6, 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.

[0067] As described above, in this embodiment, the first driving IC 72 performs the primary energization control, then performs the discharge control, and then alternates between the boost control and the discharge control multiple times. That is, the first driving IC 72 performs the primary energization control, then alternates between the discharge control and the boost control multiple times. The second driving IC 74 performs the boost control and the primary energization control simultaneously when the first driving IC 72 first performs the discharge control, and then alternates between the discharge control and the boost control multiple times in accordance with the control switching by the first driving IC 72. That is, the second driving IC 74 performs the boost control each time the first driving IC 72 performs the discharge control, and performs the discharge control each time the first driving IC 72 performs the boost control. By performing such control, the flame generated around the ignition plug 101 can be maintained for a longer period of time, even when burning lean fuel or a flame-retardant fuel such as ammonia. However, the number of times that the first driving IC 72 and the second driving IC 74 switch between the respective controls can be determined appropriately.

[0068] <2. Modifications> Although exemplary embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0069] In the above embodiment, a low DC voltage from the power supply device 102 is applied to one end of each coil, and the other end of each coil is connected to ground. Furthermore, when viewed from the other end of the iron core that penetrates the inside of each coil toward one end, the winding that forms each coil is wound clockwise from one end to the other end. However, a low DC voltage from the power supply device 102 may be applied to the other end of each coil, and one end of each coil may be connected to ground. In this case, it is sufficient that the winding that forms each coil is wound counterclockwise from one end to the other end when viewed from the other end of the iron core that penetrates the inside of each coil toward one end.

[0070] The ignition coil and 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.

[0071] The detailed shapes and structures of the above-described ignition coil and ignition device may be appropriately modified without departing from the spirit of the present invention. Furthermore, the elements appearing in the above-described embodiments and modifications may be appropriately combined without causing any contradiction. [Explanation of symbols]

[0072] 1 Ignition device 60 Iron Core 61 First iron core 62 Second 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 Ignition coil 105 First Igniter 106 Second Igniter 150 Power line 611 (First iron core) one end 612 (the other end of the first iron core) 621 (One end of the second iron core) 622 (the other end of the second iron core) 811 First primary winding 812 1st secondary winding 821 Second Primary Winding 822 Secondary Winding d (spark plug) gap Eg11 (the other end of the first primary coil) Eg12 (other end of first secondary coil) Eg21 (other end of second primary coil) Eg22 (other end of second secondary coil) Ep11 (one end of the first primary coil) Ep12 (one end of the first secondary coil) Ep21 (one end of the second primary coil) Ep22 (one end of the second secondary coil) L11 1st primary coil L12 First secondary coil L21 Second primary coil L22 Secondary coil

Claims

1. An ignition coil for an internal combustion engine, 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 iron 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 iron 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; and one end of the first iron core is connected to one end of the second iron core, and the other end of the first iron core is connected to the other end of the second iron core, thereby forming one closed magnetic circuit; When the DC voltage is applied to the first primary coil, a magnetic flux is generated in the first iron core from the other end to the one end, When the DC voltage is applied to the second primary coil, a magnetic flux is generated in the second iron core from the other end to the one end.

2. An ignition coil according to claim 1; 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; an ignition plug that ignites fuel by discharging in a gap based on a high voltage induced at the other end of the first secondary coil and / or a high voltage induced at the other end of the second secondary coil; An ignition device having

3. 3. The ignition device according to claim 2, The first control unit a primary current 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 discharge control in which, after the primary current control is performed, the first switching element is switched to an open state to induce a high voltage at the other end of the first secondary coil, thereby causing a discharge in the gap of the spark plug; and The second control unit boost control, which causes the second primary current to flow through the second primary coil and amplifies the magnetic flux generated in the closed magnetic circuit by closing the second switching element at the timing when the first control unit performs the discharge control; a discharge control in which, after the boost control is performed, 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 a continuous discharge in the gap of the spark plug; and The first control unit boost control in which the first switching element is closed at the timing when the second control unit performs the discharge control, thereby causing the first primary current to flow through the first primary coil and amplifying the magnetic flux generated in the closed magnetic circuit; Further, the ignition device.

4. 4. The ignition device according to claim 3, the first control unit performs the primary current control, and then alternately repeats the discharge control and the boost control multiple times; The second control unit performs the boost control every time the first control unit performs the discharge control, and performs the discharge control every time the first control unit performs the boost control.

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