Ignition device
The ignition device addresses abnormal combustion in hydrogen-containing fuels by using diodes and resistors to manage coil currents and residual charges, ensuring controlled ignition and reducing engine risks.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- DIAMOND&ZEBRA ELECTRIC MFG CO LTD
- Filing Date
- 2022-06-07
- Publication Date
- 2026-06-30
Smart Images
Figure 0007882694000001 
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Figure 0007882694000003
Abstract
Description
Technical Field
[0001] The present invention relates to an ignition device for an internal combustion engine.
Background Art
[0002] Conventionally, an ignition device is mounted on an internal combustion engine including a SI (spark ignition) reciprocating engine used in an automobile or the like. The ignition coil of the ignition device boosts the DC low voltage supplied from a battery to several thousand volts to several tens of thousands of volts under the control of an ECU (Engine Control Unit), supplies it to a spark plug, generates an electric spark, and ignites fuel. Examples of conventional ignition devices are described in, for example, Patent Document 1.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] Patent Document 1 discloses an ignition system (1) for an internal combustion engine having the following configuration. First, the primary coil (21) of the ignition coil (2) is connected to a DC power source (VB+) such as an onboard battery, and the supply and interruption of the primary current (I1) flowing through the primary coil (21) is switched by the on / off control of the main switching element (4) (paragraph 0015, Figure 1). In addition, one end of the secondary coil (22), which is magnetically coupled to the primary coil (21) via an iron core, is connected to a spark plug (3), and the other end is connected to a DC power supply line via an ON voltage prevention diode (23). As a result, when the primary current (I1) of the ignition coil (2) is interrupted, a high voltage is generated on the secondary side, causing dielectric breakdown in the discharge gap of the spark plug (3), and a secondary current (I2) flows in the forward direction of the ON voltage prevention diode (23) (paragraphs 0016, 0029). On the other hand, the reverse polarity ON voltage generated in the secondary coil (22) when current is first supplied to the primary coil (21) is suppressed by the ON voltage prevention diode (23) (paragraph 0017).
[0005] In recent years, hydrogen-containing fuels have been widely used in SI (spark ignition) reciprocating engines. Using hydrogen-containing fuels is thought to contribute to the realization of a so-called low-carbon society. However, hydrogen has the characteristics of being easily combustible even at relatively low temperatures and having a fast combustion rate. For this reason, for example, if a small discharge occurs at an unexpected timing in the spark plug, the fuel may ignite and burn. In this case, there is a risk of causing abnormal combustion such as backfire, where flames blow back from the engine's combustion chamber to the intake system, afterfire, where residual fuel in the engine's exhaust gas burns in the exhaust passage, or pre-ignition, where the timing of ignition cannot be controlled.
[0006] The objective of the present invention is to provide a technology that can suppress the occurrence of discharge at unexpected timings (abnormal timings) in a spark plug. [Means for solving the problem]
[0007] To solve the above problems, the first invention of the present application provides an ignition device for an internal combustion engine using a fuel containing at least hydrogen, comprising an ignition coil, a power supply, a switching element, a spark plug, a first reverse current prevention diode, and a first resistor. The ignition coil is formed by the electromagnetic coupling of a primary coil and a secondary coil. The power supply applies a DC voltage to one end of the primary coil via a power line. The switching element is interposed between the other end of the primary coil and a ground point and can switch the supply or interruption of the primary current flowing from the power supply to the primary coil. The spark plug ignites the fuel by discharging in a gap based on a high voltage induced at one end of the secondary coil. The first reverse current prevention diode is interposed in one of two first connecting lines wired in parallel between the other end of the secondary coil and the power supply or ground point, and is a diode that is forward in the direction from one end to the other end of the secondary coil. The first resistor is interposed in the other of the two first connecting wires. The resistance value of the first resistor is 1 MΩ or more. Furthermore, the other of the two first connecting lines further includes a first limiting diode, which is a Zener diode or avalanche diode, interposed in series with the first resistor and oriented forward in the direction from one end to the other of the secondary coil, wherein the breakdown voltage of the first limiting diode is smaller than the dielectric breakdown voltage at the gap of the spark plug.
[0009] This application 2 The invention is an ignition device according to the first invention, wherein the resistance value of the first resistor is 10 MΩ or less.
[0010] This application 3The invention relates to an ignition system for an internal combustion engine using a fuel containing at least hydrogen, comprising an ignition coil, a power supply, a switching element, a spark plug, a second reverse current blocking diode, and a second resistor. The ignition coil is formed by the electromagnetic coupling of a primary coil and a secondary coil. The power supply applies a DC voltage to one end of the primary coil via a power line. The switching element is interposed between the other end of the primary coil and a ground point and is capable of switching the supply or interruption of the primary current flowing from the power supply to the primary coil. The spark plug ignites the fuel by discharging in a gap based on a high voltage induced at one end of the secondary coil. The second reverse current blocking diode is interposed in one of two second connecting wires wired in parallel between one end of the secondary coil and the spark plug, and is a diode that is forward in the direction from one end of the secondary coil to the other. The second resistor is interposed in the other of the two second connecting wires. The resistance value of the second resistor is 1 MΩ or more. Furthermore, the other of the two second connecting lines further includes a second limiting diode, which is a Zener diode or avalanche diode, interposed in series with the second resistor and oriented forward in the direction from one end to the other of the secondary coil, wherein the breakdown voltage of the second limiting diode is smaller than the dielectric breakdown voltage at the gap of the spark plug.
[0012] This application 4 The invention is, 3 The ignition device of the invention, wherein the resistance value of the second resistor is 10 MΩ or less.
[0013] This application 5 The inventions are as follows: 4 An ignition device according to any one of the inventions up to the present invention, further comprising a control unit that controls the switching of the switching element, wherein the control unit performs charging control, which charges the primary coil by flowing a primary current through the switching element by closing it, and discharge control, which, after performing the charging control, switches the switching element to an open state to induce a high voltage at one end of the secondary coil, thereby causing a discharge in the gap of the spark plug.
[0014] This application 6 The inventions are as follows: 5An ignition device according to any one of the inventions up to the present invention, having a stray capacitance formed between one end of the secondary coil and the spark plug.
[0015] This application 7 The invention is, 1 Invention or the 3 The ignition device of the invention has a breakdown voltage of 2kV or less. [Effects of the Invention]
[0016] The first invention of this application to the first invention 7 According to the invention, when a primary current is applied to the primary coil (ON state), current flows through the resistor and a voltage is applied, thereby reducing the ON state voltage generated in the secondary coil L2. This suppresses the occurrence of discharge in the spark plug when it is ON. Furthermore, it reduces the residual energy remaining near one end of the secondary coil and near the spark plug after the discharge has finished. As a result, it further suppresses the occurrence of discharge at an abnormal timing in the spark plug afterward.
[0017] In particular, the first of this application 1 According to the invention, after the discharge ends, no further discharge occurs in the spark plug, and the current flows in the reverse direction in the first limiting diode towards the secondary coil. This cancels out residual charge near one end of the secondary coil and near the spark plug, reducing residual energy in these areas. As a result, it is possible to further suppress the occurrence of abnormal timing discharges in the spark plug.
[0018] In particular, the first of this application 2 According to the invention, by reducing the resistance value of the first resistor to a certain extent, it is possible to maintain a current above a certain level flowing towards the secondary coil through the first resistor after the discharge is complete. This cancels out residual charge near one end of the secondary coil and near the spark plug, thereby further reducing residual energy remaining at these locations.
[0019] In particular, the first of this application 3According to the invention, after the discharge ends, without causing discharge again in the ignition plug, the current flows in the reverse direction in the second limiting diode and toward the vicinity of the ignition plug. Thereby, the charges remaining in the vicinity of one end of the secondary coil, the vicinity of the ignition plug, etc. are canceled, and the residual energy remaining in these locations can be reduced. As a result, in the ignition plug, it is possible to further suppress the occurrence of discharge at an abnormal timing thereafter.
[0020] In particular, according to the 4 invention, by making the resistance value of the second resistor small to a certain extent, after the discharge ends, the current flowing toward the vicinity of the ignition plug through the second resistor can be maintained at a certain level or more. Thereby, the charges remaining in the vicinity of one end of the secondary coil, the vicinity of the ignition plug, etc. are canceled, and the residual energy remaining in these locations can be further reduced.
Brief Description of the Drawings
[0021] [Figure 1] It is a block diagram schematically showing the operating environment of an ignition device for an internal combustion engine according to the first embodiment. [Figure 2] It is a longitudinal sectional view of an ignition coil according to the first embodiment. [Figure 3] It is a graph showing, in time series, the waveform of the EST signal, the waveform of the current (secondary current) flowing through the secondary coil, and the voltage (secondary voltage) generated at one end of the secondary coil when operating the ignition device according to the first embodiment. [Figure 4] It is a block diagram schematically showing the operating environment of an ignition device for an internal combustion engine according to the first modification. [Figure 5] It is a block diagram schematically showing the operating environment of an ignition device for an internal combustion engine according to the second embodiment. [Figure 6] It is a block diagram schematically showing the operating environment of an ignition device for an internal combustion engine according to the second modification. [Figure 7] It is a block diagram schematically showing the operating environment of an ignition device for an internal combustion engine according to the third modification. [Figure 8]This is a block diagram schematically showing the operating environment of an ignition system for an internal combustion engine according to the fourth modified example. [Modes for carrying out the invention]
[0022] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings.
[0023] <1. First Embodiment> <1-1. Ignition System Configuration> First, the configuration of the ignition device 1 for an internal combustion engine, which is the first embodiment of the present invention, will be described with reference to the drawings. Figure 1 is a schematic block diagram showing the operating environment of the ignition device 1 according to the first embodiment. As will be described later, the primary coil L1 and secondary coil L2 of the ignition coil 103 included in the ignition device 1 are arranged in a stacking direction with respect to each other, but in Figure 1, they are shown adjacent to each other for ease of understanding.
[0024] The ignition device 1 of this embodiment is installed in an internal combustion engine, such as an SI (spark ignition) reciprocating engine, used in a vehicle body 100, such as an automobile, and is a device that applies a high voltage to the spark plug 113 to generate a spark discharge. As shown in Figure 1, in addition to the ignition device 1, the vehicle body 100 is also equipped with the spark plug 113, a power supply unit 102 (battery), and an ECU 105 (Engine Control Unit). In a broader sense, the spark plug 113, the power supply unit 102, and the ECU 105 can also be considered as being included in the ignition device 1.
[0025] The spark plug 113 is a device for ignition in the combustion chamber of an internal combustion engine. The spark plug 113 is electrically connected to one end 822 of the secondary coil L2 of the ignition coil 103, which will be described later, via a conductor (hereinafter referred to as the "second connecting wire 121"). The spark plug 113 is interposed between one end 822 of the secondary coil L2 and the ground point. When a high voltage is induced in the secondary coil L2 of the ignition coil 103, and this high voltage exceeds the dielectric breakdown voltage in the gap d (see Figure 1) between the center electrode 141 and the ground electrode 142 of the spark plug 113, a discharge occurs in the gap d and a spark is generated. This ignites the fuel filled in the internal combustion engine. In other words, the spark plug 113 ignites the fuel by discharging in the gap d based on the high voltage induced in one end 822 of the secondary coil L2.
[0026] In this embodiment, hydrogen or a mixture of hydrogen and other substances is used as fuel. That is, the ignition device 1 for the internal combustion engine uses a fuel containing at least hydrogen.
[0027] Furthermore, the second connecting wire 121 and the spark plug 113 have a capacitance component of approximately 15-20 pF. That is, a capacitance component is formed between one end 822 of the secondary coil L2 and the spark plug 113. Hereafter, this capacitance component will be referred to as the "stray capacitance Cs," which is a hypothetical definition. As shown in Figure 1, the stray capacitance Cs can be schematically represented in parallel with the spark plug 113 in the block diagram.
[0028] The power supply unit 102 is a power supply unit (storage battery) capable of charging and discharging DC power. In this embodiment, the power supply unit 102 is electrically connected to the primary coil L1 of the ignition coil 103, which will be described later, via a conductor (hereinafter referred to as the "power line 150"). The power supply unit 102 applies a DC voltage to one end 811 of the primary coil L1 of the ignition coil 103 via the power line 150.
[0029] The ECU105 is an existing computer that comprehensively controls the vehicle's transmission, airbags, and other functions.
[0030] The ignition device 1 includes an ignition coil 103, an igniter 104, a first reverse current prevention diode 111, a first resistor 112, and a first limiting diode 114.
[0031] Figure 2 is a longitudinal cross-sectional view of the ignition coil 103. As shown in Figure 2, the ignition coil 103 comprises a bobbin 40, a primary coil L1, a secondary coil L2, and an iron core 60. Note that in Figure 2, the primary coil L1 and secondary coil L2 are shown in a partially simplified manner. Furthermore, in the following description of the ignition coil 103, the direction parallel to the central axis Bc of the bobbin 40 will be referred to as the "axial direction," the direction perpendicular to the central axis Bc of the bobbin 40 will be referred to as the "radial direction," and the direction along the arc centered on the central axis Bc of the bobbin 40 will be referred to as the "circumferential direction." In addition, the "parallel direction" includes a direction that is approximately parallel, and the "perpendicular direction" also includes a direction that is approximately perpendicular.
[0032] The bobbin 40 includes a primary bobbin 41 and a secondary bobbin 42 that can be connected to each other. The primary bobbin 41 and the secondary bobbin 42 each extend cylindrically along the central axis Bc. The secondary bobbin 42 is positioned radially outside the primary bobbin 41. For example, resin is used as the material for the primary bobbin 41 and the secondary bobbin 42.
[0033] The primary coil L1 is formed by winding a conductor (hereinafter referred to as "primary conductor 81") around the outer surface of the primary bobbin 41 in a circumferential direction around the central axis Bc. After the formation of the primary coil L1 is complete, the secondary bobbin 42 is positioned to cover the outer surface of the primary coil L1 and connected to the primary bobbin 41. Then, the secondary coil L2 is formed by winding a conductor (hereinafter referred to as "secondary conductor 82"), different from the primary conductor 81, around the outer surface of the secondary bobbin 42 in a circumferential direction around the central axis Bc. By arranging the primary coil L1 and the secondary coil L2 in this way, stacking them on top of each other, the entire ignition coil 103 including them can be miniaturized. However, the primary coil L1 and the secondary coil L2 may be arranged adjacent to each other, as shown in Figure 1, rather than being stacked and wound on top of each other in this way.
[0034] The core 60 has a structure in which a central core 601 and an outer core 602 are combined. The central core 601 and the outer core 602 of the core 60 are each formed from laminated steel sheets, for example, silicon steel sheets. The central core 601 extends along the central axis Bc of the bobbin 40. The central core 601 is also inserted into the radially inner space 410 of the primary bobbin 41. The outer core 602 passes radially outside the secondary bobbin 42 and the secondary conductor 82, connecting the axial ends of the central core 601. As a result, the core 60 forms a closed magnetic circuit structure that electromagnetically couples the primary coil L1 and the secondary coil L2. That is, the ignition coil 103 is formed by the electromagnetic coupling of the primary coil L1 and the secondary coil L2 to each other.
[0035] As shown in Figure 1, a power line 150, which is a conductor extending from the power supply device 102, is connected to one end 811 of the primary coil L1. The other end 812 of the primary coil L1 is connected to an igniter 104, which will be described later. Controlled by the igniter 104, a low DC voltage from the power supply device 102 is applied to one end 811 of the primary coil L1, and a gradually increasing primary current begins to flow through the primary coil L1.
[0036] One end 822 of the secondary coil L2 is connected to the spark plug 113. The diameter of the secondary conductor 82 is smaller than the diameter of the primary conductor 81. Also, the number of turns of the secondary conductor 82 in the secondary coil L2 (e.g., 8000 turns) is about 80 times or more than the number of turns of the primary conductor 81 in the primary coil L1 (e.g., 100 turns). As a result, as will be described in detail later, when the primary current is interrupted, the ignition coil 103 boosts the low-voltage DC power supplied from the power supply 102 to several thousand volts to tens of thousands of volts. That is, a high voltage is induced in the secondary coil L2. The secondary coil L2 then supplies the induced high-voltage power to the spark plug 113. This generates an electric spark at the spark plug 113, igniting the fuel.
[0037] As shown in Figure 1, the other end 821 of the secondary coil L2, opposite to the end 822 to which the spark plug 113 is connected, is electrically connected directly or indirectly to the power supply unit 102 via two conductors (hereinafter referred to as "first connection line 122a" and "first connection line 122b"). The first connection lines 122a and 122b are wired in parallel between the other end 821 of the secondary coil L2 and the power supply unit 102. In this embodiment, the other end 821 of the secondary coil L2 is electrically connected to the power line 150 via either the first connection line 122a or the first connection line 122b.
[0038] In this embodiment, a first reverse current blocking diode 111 is interposed in the first connection line 122a, which is one of the two first connection lines 122a and 122b. The first reverse current blocking diode 111 is connected in series with the secondary coil L2. In this embodiment, a normal diode that has the function of allowing current to flow in only one direction is used for the first reverse current blocking diode 111. In addition, the first reverse current blocking diode 111 is forward in the direction from one end 822 to the other end 821 of the secondary coil L2.
[0039] In this embodiment, the first resistor 112 is interposed in the first connecting wire 122b, which is the other of the two first connecting wires 122a and 122b. The first resistor 112 is connected in series with the secondary coil L2. The resistance value of the first resistor 112 in this embodiment is 1 MΩ or more and 10 MΩ or less.
[0040] In this embodiment, a first limiting diode 114 is further interposed in the first connecting line 122b, which is the other of the two first connecting lines 122a and 122b. The first limiting diode 114 is connected in series with the secondary coil L2 and the first resistor 112, respectively. In this embodiment, a Zener diode is used for the first limiting diode 114. However, an avalanche diode may also be used for the first limiting diode 114. Furthermore, the first limiting diode 114 is forward in the direction from one end 822 to the other end 821 of the secondary coil L2.
[0041] Furthermore, in this invention, the first limiting diode 114 is one whose breakdown voltage is smaller than the dielectric breakdown voltage at the gap d of the spark plug 113. The breakdown voltage of the first limiting diode 114 used in this embodiment is 2kV or less. The effects of setting the breakdown voltage of the first limiting diode 114 to 2kV or less will be described in detail later.
[0042] As will be described in detail later, when the switching element 70 of the igniter 104 is closed and the primary coil L1 is charged by flowing a primary current (ON state), a potential difference is generated across the ends 821 and 822 of the secondary coil L2. In this embodiment, when ON, one end 822 of the secondary coil L2 has a higher voltage than the other end 821. Hereinafter, the potential difference between one end 822 and the other end 821 of the secondary coil L2 will be referred to as the "ON state voltage". The maximum value of the ON state voltage is calculated by multiplying the voltage value of the DC voltage applied from the power supply device 102 to one end 811 of the primary coil L1 via the power line 150 by the ratio of the number of turns of the secondary coil L2 to the number of turns of the primary coil L1.
[0043] For example, if the DC voltage applied to one end 811 of the primary coil L1 is 12V, the number of turns of the primary coil L1 is 100, and the number of turns of the secondary coil L2 is 8000, then the ratio of the number of turns of the secondary coil L2 to the number of turns of the primary coil L1 is 80, and the maximum value of the ON voltage is calculated to be 12 × 80 = 960V. Therefore, the maximum voltage applied to one end 822 of the secondary coil L2 will be, for example, around +480V, and the minimum voltage applied to the other end 821 of the secondary coil L2 will be, for example, around -480V. In some cases, the maximum voltage applied to one end 822 of the secondary coil L2 may be around 0V, and the minimum voltage applied to the other end 821 of the secondary coil L2 may be around -960V. Meanwhile, in this case, the voltage applied to the power line 150 is 12V.
[0044] As described above, the breakdown voltage of the first limiting diode 114 is 2kV or less (for example, 490V). Therefore, when primary current is flowing through the primary coil L1 (ON), if the voltage applied to the power line 150 (cathode side of the first limiting diode 114) (for example, +12V) is greater than the difference between the minimum voltage applied to the other end 821 of the secondary coil L2 (anode side of the first limiting diode 114) (for example, -480V) and the breakdown voltage of the first limiting diode 114 (for example, 490V), then current will flow in the reverse direction through the first limiting diode 114. That is, current flows from the power supply unit 102 side to the secondary coil L2 side via the first connecting line 122b. Note that no current flows through the first connecting line 122a, which has the first reverse current prevention diode 111 interposed therein.
[0045] However, a first resistor 112 is interposed in series with the first limiting diode 114 in the first connection line 122b. The resistance value of the first resistor 112 is 1 MΩ or more. As a result, when current flows through the first connection line 122b, a voltage is applied across the first resistor 112, which reduces the ON voltage generated in the secondary coil L2. Consequently, it is possible to suppress discharge in the spark plug 113 during the ON phase, i.e., at an abnormal timing.
[0046] On the other hand, when a primary current is flowing through the primary coil L1 (when ON), if the voltage applied to the power line 150 (the cathode side of the first limiting diode 114) (e.g., +12V) does not exceed the breakdown voltage of the first limiting diode 114 (e.g., 5500V) when the voltage applied to the other end 821 of the secondary coil L2 (the anode side of the first limiting diode 114) (e.g., -480V) is not greater than the difference, then it is possible to suppress current flowing in the reverse direction of the first limiting diode 114, i.e., through the first connecting line 122b to the secondary coil L2 side. In other words, even in this case, it is possible to suppress discharge from occurring in the spark plug 113 when ON, i.e., at an abnormal timing.
[0047] The igniter 104 is a semiconductor device connected to the primary coil L1 and controls the current flowing through the primary coil L1. The igniter 104 is also electrically connected to the ECU 105 and receives signals (hereinafter referred to as "EST signals") from the ECU 105. The igniter 104 includes a switching element 70 and a drive IC 71. The igniter 104 may be integrated with the electronic circuitry of the ECU 105.
[0048] For example, an insulated-gate bipolar transistor (IGBT) is used as the switching element 70. The switching element 70 is interposed between the other end 812 of the primary coil L1 and the ground. The collector (C) of the switching element 70 is connected to the other end 812 of the primary coil L1. The emitter (E) of the switching element 70 is connected to ground. The gate (G) of the switching element 70 is connected to the driver IC 71.
[0049] This allows the switching element 70 to switch between supplying or interrupting the primary current flowing from the power supply 102 to the primary coil L1. When the switching element 70 is closed, primary current flows from the power supply 102 to the primary coil L1. When the switching element 70 is open, the primary current flowing to the primary coil L1 is interrupted. However, other types of transistors may be used for the switching element 70.
[0050] The drive IC 71 is a control unit that controls the switching of the switching element 70 based on the EST signal received from the ECU 105. The drive IC 71 has a logic device connected to the switching element 70. The logic device includes, for example, a logic circuit, a processor, a CPLD (complex programmable logic device), an FPGA (field-programmable gate array), or an ASIC (application-specific integrated circuit). The logic device performs calculations to operate the ignition device 1 and ignite the spark plug 113.
[0051] <1-2. Operation of the ignition system> Next, the operation of the ignition device 1 will be explained. Figure 3 is a graph showing the waveform of the EST signal, the waveform of the current flowing through the secondary coil L2 (secondary current), and the voltage generated at one end 822 of the secondary coil L2 (secondary voltage) in time series when the ignition device 1 is operated. Note that in Figure 3, the secondary current is shown as negative when flowing from one end 822 to the other end 821 of the secondary coil L2, and as positive when flowing from the other end 821 to one end 822. Also, the secondary voltage in Figure 3 shows the value of the voltage applied at one end 822 of the secondary coil L2 relative to the ground point.
[0052] As described above, a DC voltage (for example, 12V) is applied to one end 811 of the primary coil L1 from the power supply unit 102 via the power line 150. The other end 812 of the primary coil L1 is connected to the switching element 70. The drive IC 71 controls the switching of the switching element 70 based on the EST signal received from the ECU 105. As shown in Figure 3, when operating the ignition device 1, first at time t0, the signal level of the EST signal transmitted from the ECU 105 to the drive IC 71 is changed from L to H. Then, based on the EST signal, the drive IC 71 switches the switching element 70 from the open state to the closed state. As a result, a primary current flows through the primary conductor 81 that forms the primary coil L1, and the primary coil L1 is charged (hereinafter, this process of charging the primary coil L1 by flowing a primary current is referred to as "charging control"). Also, an electromagnetic flux is generated in the primary coil L1, and a magnetic field corresponding to the electromagnetic flux acts on the iron core 60.
[0053] Furthermore, at both ends 821 and 822 of the secondary coil L2, which is electromagnetically coupled to the primary coil L1 via the iron core 60, a potential difference, i.e., an ON voltage (for example, 960V), is generated due to mutual induction. As a result, the maximum voltage across one end 822 of the secondary coil L2 is a positive value (for example, around +480V), and the minimum voltage across the other end 821 of the secondary coil L2 is a negative value (for example, around -480V). At this time, the voltage across the power line 150 is, for example, 12V.
[0054] Here, a first connecting wire 122b, which connects the other end 821 of the secondary coil L2 to the power line 150, has a first resistor 112 and a first limiting diode 114 interposed between them. The first limiting diode 114 is forward in the direction from one end 822 to the other end 821 of the secondary coil L2, and the breakdown voltage of the first limiting diode 114 is 2kV or less (for example, 490V). Therefore, when primary current is supplied to the primary coil L1 (ON), if the voltage applied to the power line 150 (cathode side of the first limiting diode 114) (e.g., +12V) is greater than the difference between the minimum voltage applied to the other end 821 of the secondary coil L2 (anode side of the first limiting diode 114) (e.g., -480V) and the breakdown voltage of the first limiting diode 114 (e.g., 490V), then current flows in the reverse direction in the first limiting diode 114. That is, current (secondary current) flows from the power supply unit 102 side to the secondary coil L2 side via the first connecting line 122b. Note that no current flows through the first connecting line 122a because the first reverse current prevention diode 111, which is forward in the direction from one end 822 to the other end 821 of the secondary coil L2, is interposed there.
[0055] However, a first resistor 112 is interposed in series with the first limiting diode 114 in the first connection line 122b. The resistance value of the first resistor 112 is 1 MΩ or more. As a result, when current flows through the first connection line 122b, a sufficiently large voltage is applied across the first resistor 112, and consequently, the ON voltage and secondary voltage generated in the secondary coil L2 can be reduced. As a result, discharge at the spark plug 113 during the ON phase, i.e., at an abnormal timing, can be suppressed.
[0056] On the other hand, when a primary current is flowing through the primary coil L1 (when ON), if the voltage applied to the power line 150 (cathode side of the first limiting diode 114) (e.g., +12V) does not exceed the breakdown voltage of the first limiting diode 114 (e.g., 5500V) when the voltage applied to the other end 821 of the secondary coil L2 (anode side of the first limiting diode 114) (e.g., -480V) is not greater than the difference, then it is possible to suppress the flow of current (secondary current) in the reverse direction of the first limiting diode 114, i.e., through the first connecting line 122b to the secondary coil L2 side. In other words, even in this case, it is possible to suppress the occurrence of discharge in the spark plug 113 when ON, i.e., at an abnormal timing.
[0057] After charging control is performed, at time t1, the signal level of the EST signal transmitted from ECU 105 to drive IC 71 is changed from H to L. The drive IC 71 then switches the switching element 70 from a closed state to an open state, interrupting the primary current flowing from the power supply 102 to the primary coil L1. This induces an induced electromotive force in the secondary coil L2, which is electromagnetically coupled to the primary coil L1 via the iron core 60, due to mutual inductance. In this embodiment, a negative high voltage is induced at one end 822 of the secondary coil L2. At this time, the voltage value applied to one end 822 of the secondary coil L2 (the value of the secondary voltage) ranges from several thousand volts to tens of thousands of volts relative to the ground point.
[0058] Furthermore, the absolute value of the negative high voltage induced at one end 822 of the secondary coil L2 exceeds the dielectric breakdown voltage at the gap d of the spark plug 113. This causes dielectric breakdown at the gap d of the spark plug 113. Then, a current is generated that flows from the ground point, through the ground electrode 142 of the spark plug 113 to the center electrode 141 of the spark plug 113 (see Figure 1), further through the secondary coil L2, and also flows forward through the first reverse current prevention diode 111 and the first limiting diode 114. In this embodiment, most of the current flows forward through the first reverse current prevention diode 111, a portion flows forward through the first limiting diode 114, and flows to the ground point via the power supply unit 102.
[0059] As a result, a discharge occurs in the gap d of the spark plug 113, generating a spark that ignites the fuel filled in the internal combustion engine. In this invention, the process of switching the switching element 70 to the open state to interrupt the primary current flowing to the primary coil L1 and inducing a high voltage at one end 822 of the secondary coil L2, thereby causing a discharge in the gap d of the spark plug 113, is called "discharge control." When the absolute value of the negative high voltage induced at one end 822 of the secondary coil L2 falls below the dielectric breakdown voltage at the gap d of the spark plug 113 (time t2), the discharge at the gap d of the spark plug 113 temporarily ends.
[0060] As described above, a stray capacitance Cs consisting of a capacitance component of about 15-20 pH is formed between one end 822 of the secondary coil L2 and the spark plug 113. Therefore, even after the discharge at the gap d of the spark plug 113 has ended (time t2), residual charge may still remain near the one end 822 of the secondary coil L2, the second connecting wire 121, or near the center electrode 141 of the spark plug 113. In this embodiment, negative charge remains at these locations. As a result, at time t2, the voltage value at one end 822 of the secondary coil L2 (hereinafter referred to as "residual voltage value Rv") is negative (for example, minus 3kV) relative to the ground point. Note that the absolute value of the residual voltage value Rv is smaller than the dielectric breakdown voltage at the gap d of the spark plug 113. However, if this situation is left untreated, there is a risk that a discharge may occur again at the gap d of the spark plug 113 at an unexpected time, such as when a pressure change occurs within the internal combustion engine.
[0061] Therefore, in the present invention, the first limiting diode 114 used has a breakdown voltage smaller than the absolute value of the dielectric breakdown voltage and residual voltage Rv at the gap d of the spark plug 113. The breakdown voltage of the first limiting diode 114 used in this embodiment is 2kV or less. In the above example, the residual voltage Rv at one end 822 of the secondary coil L2 (anode side of the first limiting diode 114) is a negative value (for example, minus 3kV). On the other hand, the voltage applied to the power line 150 (cathode side of the first limiting diode 114) is a positive value (for example, plus 12V), and is greater than the difference exceeding the breakdown voltage of the first limiting diode 114 relative to the residual voltage Rv.
[0062] As a result, after the discharge ends, no further discharge occurs at the spark plug 113, and a current flows in the reverse direction from the power supply 102 to the first limiting diode 114 in a short time. That is, current (secondary current) flows from the power supply 102 to the secondary coil L2 via the first connecting wire 122b. Note that no current flows through the first connecting wire 122a because the first reverse current prevention diode 111, which is forward in the direction from one end 822 to the other end 821 of the secondary coil L2, is interposed there.
[0063] This cancels out residual charge near one end 822 of the secondary coil L2, the second connecting wire 121, or near the center electrode 141 of the spark plug 113, thereby reducing the absolute value of the voltage applied to one end 822 of the secondary coil L2 (secondary voltage) and reducing residual energy remaining at these points. As a result, even if pressure changes occur within the internal combustion engine afterward, it is possible to further suppress the occurrence of discharge at the gap d of the spark plug 113 at an abnormal timing.
[0064] Furthermore, as described above, the resistance value of the first resistor 112 is 10 MΩ or less. By making the resistance value of the first resistor 112 relatively small, it is possible to maintain a current above a certain level flowing from the power supply 102 to the secondary coil L2 via the first connecting wire 122b after the discharge is complete. This makes it possible to further reduce residual energy remaining near one end 822 of the secondary coil L2, the second connecting wire 121, or near the center electrode 141 of the spark plug 113.
[0065] Furthermore, this phenomenon after the discharge ends continues until the potential difference between the voltage applied to one end 822 of the secondary coil L2 on the anode side of the first limiting diode 114 (secondary voltage) and the voltage applied to the power supply line 150 on the cathode side of the first limiting diode 114 becomes equal to the breakdown voltage of the first limiting diode 114. Here, since the absolute value of the voltage applied to one end 822 of the secondary coil L2 (secondary voltage) is significantly larger than the absolute value of the voltage applied to the power supply line 150, this phenomenon can be considered to continue until the absolute value of the secondary voltage (indicated as "Vz" in Figure 3) becomes approximately equal to the breakdown voltage of the first limiting diode 114. Furthermore, the absolute value of the voltage at one end 822 of the secondary coil L2 (secondary voltage) is further reduced by the flow of ion current through the gap d between the center electrode 141 and the ground electrode 142 of the spark plug 113, and by the flow of leakage current through the first limiting diode 114.
[0066] As described above, in this embodiment, first, as charge control, when a primary current is applied to the primary coil L1 (ON state), current flows from the power supply unit 102 to the secondary coil L2 side via the first connecting line 122b. At this time, current flows through the first resistor 112 and a voltage is applied, thereby reducing the ON state voltage generated in the secondary coil L2.
[0067] Furthermore, after the discharge ends, current (secondary current) flows from the power supply unit 102 through the first connecting line 122b and in the reverse direction through the first limiting diode 114 toward the secondary coil L2. This cancels out residual charge near one end 822 of the secondary coil L2, the second connecting line 121, or near the center electrode 141 of the spark plug 113, thereby reducing the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 and reducing residual energy remaining at these points. In other words, without causing another discharge at the spark plug 113, the absolute value of the secondary voltage can be reduced in a short time until it is approximately equal to the breakdown voltage of the first limiting diode 114. As a result, even if a pressure change occurs in the internal combustion engine afterward, it is possible to suppress the occurrence of a discharge at the gap d of the spark plug 113 at an abnormal timing. As a result, even in internal combustion engines that use hydrogen-containing fuels, which have the characteristics of being easily combustible even at relatively low temperatures and having a fast combustion rate, it is possible to suppress ignition of the fuel at an abnormal timing, leading to a reduction in damage to the engine and other components.
[0068] Note that the first limiting diode 114 is not necessarily required. Figure 4 is a schematic block diagram showing the operating environment of the ignition device 1 according to the first modified example. In the first modified example of Figure 4, the first reverse current prevention diode 111 is interposed in the first connection line 122a, which is one of the two first connection lines 122a and 122b that are wired in parallel between the other end 821 of the secondary coil L2 and the power supply unit 102. The first reverse current prevention diode 111 is a diode that is forward in the direction from one end 822 to the other end 821 of the secondary coil L2. In addition, only the first resistor 112 is interposed in the first connection line 122b, which is the other of the two first connection lines 122a and 122b.
[0069] In the first modified example, as part of the charge control, when a primary current is applied to the primary coil L1 (ON state), current flows from the power supply 102 to the secondary coil L2 via the first connecting line 122b, and current flows through the first resistor 112, applying a voltage, thereby reducing the ON state voltage generated in the secondary coil L2. As a result, discharge at the spark plug 113 during the ON state, i.e., at an abnormal timing, can be suppressed.
[0070] Furthermore, as a discharge control measure, switching the switching element 70 from a closed state to an open state interrupts the primary current flowing from the power supply 102 to the primary coil L1, inducing a negative high voltage ranging from several thousand volts to tens of thousands of volts at one end 822 of the secondary coil L2. This causes dielectric breakdown at the gap d of the spark plug 113. Then, a current is generated that flows from the ground point, through the ground electrode 142 of the spark plug 113 to the center electrode 141 of the spark plug 113 (see Figure 4), further through the secondary coil L2, and in the forward direction through the first connecting wire 122a with the first reverse current prevention diode 111 interposed, or through the first connecting wire 122b with the first resistor 112 interposed. As a result, a discharge occurs at the gap d of the spark plug 113, generating a spark that ignites the fuel filled in the internal combustion engine.
[0071] Furthermore, after the discharge ends, without another discharge occurring at the spark plug 113, a current flows quickly from the power supply unit 102 to the secondary coil L2 via the first connecting wire 122b through which the first resistor 112 is inserted. This cancels out any residual charge near one end 822 of the secondary coil L2, the second connecting wire 121, or the center electrode 141 of the spark plug 113, thereby reducing the absolute value of the voltage applied to one end 822 of the secondary coil L2 (secondary voltage) and reducing the residual energy remaining at these points. As a result, even if pressure changes occur in the internal combustion engine afterward, it is possible to further suppress the occurrence of abnormal timing discharges at the gap d of the spark plug 113.
[0072] <2. Second Embodiment> Next, a second embodiment of the present invention will be described. In the following description, the differences from the first embodiment will be the main focus, and parts that are equivalent to the first embodiment will not be explained again.
[0073] Figure 5 is a schematic block diagram showing the operating environment of the ignition device 1 according to the second embodiment. As shown in Figure 5, in the second embodiment, one end 822 of the secondary coil L2 is electrically connected to the spark plug 113 directly or indirectly via two conductors (hereinafter referred to as "second connection line 121a" and "second connection line 121b"). The second connection lines 121a and 121b are wired in parallel between one end 822 of the secondary coil L2 and the spark plug 113. The other end 821 of the secondary coil L2 is connected to the power line 150 via the first connection line 122.
[0074] Furthermore, in this embodiment, a second reverse current blocking diode 131 is interposed in the second connection line 121a, which is one of the two second connection lines 121a and 121b. The second reverse current blocking diode 131 is connected in series with the secondary coil L2. In this embodiment, a normal diode that has the function of allowing current to flow in only one direction is used for the second reverse current blocking diode 131. Also, the second reverse current blocking diode 131 is forward in the direction from one end 822 to the other end 821 of the secondary coil L2.
[0075] In this embodiment, a second resistor 132 is interposed in the second connecting wire 121b, which is the other of the two second connecting wires 121a and 121b. The second resistor 132 is connected in series with the secondary coil L2. The resistance value of the second resistor 132 in this embodiment is 1 MΩ or more and 10 MΩ or less.
[0076] In this embodiment, a second limiting diode 134 is further interposed in the second connecting line 121b, which is the other of the two second connecting lines 121a and 121b. The second limiting diode 134 is connected in series with the secondary coil L2 and the second resistor 132, respectively. A Zener diode is used for the second limiting diode 134 in this embodiment. However, an avalanche diode may also be used for the second limiting diode 134. The second limiting diode 134 is forward in the direction from one end 822 to the other end 821 of the secondary coil L2. The second limiting diode 134 has the same configuration as the first limiting diode 114 in the first embodiment.
[0077] Furthermore, in this invention, the second limiting diode 134 is one whose breakdown voltage is smaller than the dielectric breakdown voltage at the gap d of the spark plug 113. The breakdown voltage of the second limiting diode 134 used in this embodiment is 2kV or less. In addition, a stray capacitance Cs consisting of a capacitance component of about 15 to 20 pH is formed between one end 822 of the secondary coil L2 and the spark plug 113.
[0078] In the second embodiment, first, as part of the charge control, when a primary current is applied to the primary coil L1 (ON state), an ON state voltage (e.g., 960V) is generated at both ends 821 and 822 of the secondary coil L2. The maximum voltage applied to one end 822 of the secondary coil L2 is a positive value (e.g., approximately +480V), and the minimum voltage applied to the other end 821 of the secondary coil L2 is a negative value (e.g., approximately -480V). Meanwhile, the voltage applied to the power line 150 is, for example, 12V.
[0079] Therefore, current flows from the power supply unit 102 to the secondary coil L2 via the power line 150 and the first connecting line 122. Here, a second resistor 132 is interposed in the second connecting line 121b that connects one end 822 of the secondary coil L2 to the spark plug 113. The resistance value of the second resistor 132 is 1 MΩ or more. As a result, when current flows through the second connecting line 121b, a voltage is applied across the second resistor 132, which reduces the ON voltage and secondary voltage generated in the secondary coil L2. As a result, it is possible to suppress discharge at the spark plug 113 during the ON phase, i.e., at an abnormal timing.
[0080] Furthermore, as a discharge control measure, switching the switching element 70 from a closed state to an open state interrupts the primary current flowing from the power supply 102 to the primary coil L1, inducing a negative high voltage ranging from several thousand volts to tens of thousands of volts at one end 822 of the secondary coil L2. This causes dielectric breakdown at the gap d of the spark plug 113. Then, a current is generated that flows from the ground point, through the ground electrode 142 of the spark plug 113, toward the center electrode 141 of the spark plug 113 (see Figure 5), and forward through the second connecting wire 121a with the second reverse current prevention diode 131 interposed, or through the second connecting wire 121b with the second resistor 132 interposed, and further toward the secondary coil L2. As a result, a discharge occurs at the gap d of the spark plug 113, generating a spark that ignites the fuel filled in the internal combustion engine.
[0081] Furthermore, after the discharge ends, current (secondary current) flows from the power supply unit 102 through the power line 150 and the first connecting line 122 towards the vicinity of one end 822 of the secondary coil L2, the second connecting line 121b, and the vicinity of the center electrode 141 of the spark plug 113. This cancels out any residual charge near the one end 822 of the secondary coil L2, the second connecting line 121b, or the vicinity of the center electrode 141 of the spark plug 113, thereby reducing the absolute value of the voltage (secondary voltage) applied to the one end 822 of the secondary coil L2 and reducing the residual energy remaining at these locations. In other words, the absolute value of the secondary voltage can be reduced in a short time without another discharge occurring at the spark plug 113. As a result, even if a pressure change occurs in the internal combustion engine afterward, it is possible to suppress the occurrence of a discharge at the gap d of the spark plug 113 at an abnormal timing. This helps to suppress ignition of the fuel at an abnormal timing, even in internal combustion engines that use hydrogen-containing fuels, which have the characteristics of burning easily even at relatively low temperatures and burning quickly, thereby reducing damage to the engine and other components.
[0082] Furthermore, as described above, the resistance value of the second resistor 132 is 10 MΩ or less. By making the resistance value of the second resistor 132 relatively small, it is possible to maintain a current above a certain level from the power supply unit 102 to the vicinity of the center electrode 141 of the spark plug 113 via the second connecting line 121b after the discharge is complete. This makes it possible to further reduce the residual energy remaining near the center electrode 141 of the spark plug 113.
[0083] Note that the second limiting diode 134 is not necessarily required. Figure 6 is a schematic block diagram showing the operating environment of the ignition device 1 according to the second modified example. In the second modified example of Figure 6, the second reverse current prevention diode 131 is interposed in the second connection wire 121a, which is one of the two second connection wires 121a and 121b that are wired in parallel between one end 822 of the secondary coil L2 and the spark plug 113. The second reverse current prevention diode 131 is a diode that is forward in the direction from one end 822 to the other end 821 of the secondary coil L2. In addition, only the second resistor 132 is interposed in the second connection wire 121b, which is the other of the two second connection wires 121a and 121b.
[0084] In the second modified example, as part of the charge control, when a primary current is supplied to the primary coil L1 (ON state), a current (secondary current) flows from the power supply unit 102 to the secondary coil L2 via the power line 150 and the first connecting line 122. At this time, current flows through the second resistor 132, and a voltage is applied, which reduces the ON state voltage generated in the secondary coil L2. As a result, discharge at the spark plug 113 during the ON state, i.e., at an abnormal timing, can be suppressed.
[0085] Furthermore, as a discharge control measure, switching the switching element 70 from a closed state to an open state interrupts the primary current flowing from the power supply 102 to the primary coil L1, inducing a negative high voltage ranging from several thousand volts to tens of thousands of volts at one end 822 of the secondary coil L2. This causes dielectric breakdown at the gap d of the spark plug 113. Then, a current is generated that flows from the ground point, through the ground electrode 142 of the spark plug 113, toward the center electrode 141 of the spark plug 113 (see Figure 6), and forward through the second connecting wire 121a with the second reverse current prevention diode 131 interposed, or through the second connecting wire 121b with the second resistor 132 interposed, and further toward the secondary coil L2. As a result, a discharge occurs at the gap d of the spark plug 113, generating a spark that ignites the fuel filled in the internal combustion engine.
[0086] Furthermore, after the discharge ends, without another discharge occurring at the spark plug 113, a current (secondary current) flows in a short time from the power supply unit 102 through the power line 150 and the first connecting line 122 towards the vicinity of one end 822 of the secondary coil L2, the second connecting line 121b, and the vicinity of the center electrode 141 of the spark plug 113. This cancels out any residual charge near the one end 822 of the secondary coil L2, the second connecting line 121b, or the vicinity of the center electrode 141 of the spark plug 113, reducing the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 and reducing the residual energy remaining at these locations. As a result, even if a pressure change occurs in the internal combustion engine afterward, it is possible to further suppress the occurrence of abnormal timing discharges at the gap d of the spark plug 113.
[0087] <3. Variant> Although exemplary embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above.
[0088] In the above embodiments and modifications, the charging control was configured such that the voltage applied to one end 822 of the secondary coil L2 was positive, and the voltage applied to the other end 821 of the secondary coil L2 was negative. Furthermore, in the discharge control, the configuration was such that a negative high voltage ranging from several thousand volts to tens of thousands of volts was induced at one end 822 of the secondary coil L2. However, the positive and negative signs of the voltage values appearing at both ends 821 and 822 of the secondary coil L2 may be reversed by changing the winding direction of the primary conductor 81 in the primary coil L1 or the winding direction of the secondary conductor 82 in the secondary coil L2. In this case, the forward and reverse directions of the first reverse current blocking diode 111 inserted in the first connection line 122a, the first limiting diode 114 inserted in the first connection line 122b in the first embodiment, the second reverse current blocking diode 131 inserted in the second connection line 121a in the second embodiment, and the second limiting diode 134 inserted in the second connection line 121b in the second embodiment can be reversed.
[0089] In the first embodiment described above, the cathode side of the first reverse current prevention diode 111 and the cathode side of the first limiting diode 114, and the other end 821 of the secondary coil L2 were each connected to the positive side of the power supply 102. However, as shown in the third modified example in Figure 7, these may also be connected to the ground. That is, the first reverse current prevention diode 111 may be inserted in one of the two first connecting lines 122a and 122b that are wired in parallel between the other end 821 of the secondary coil L2 and the ground, and the first limiting diode 114 may be inserted in the other of the first connecting lines 122a and 122b, and each may be a diode that is forward in the direction from one end 822 to the other end 821 of the secondary coil L2. However, as shown in the fourth modified example in Figure 8, these may be connected to a grounding point.
[0090] In the third and fourth modified examples, first, as part of the charge control, when a primary current is applied to the primary coil L1 (ON state), an ON state voltage (e.g., 960V) is generated at both ends 821 and 822 of the secondary coil L2. The maximum voltage applied to one end 822 of the secondary coil L2 is a positive value (e.g., approximately +480V), and the minimum voltage applied to the other end 821 of the secondary coil L2 is a negative value (e.g., approximately -480V).
[0091] In the third modified example, a first reverse current prevention diode 111 and a first limiting diode 114 are interposed in the first connecting lines 122a and 122b. In the fourth modified example, a second reverse current prevention diode 131 and a second limiting diode 134 are interposed in the second connecting lines 121a and 121b. These diodes are in the forward direction from one end 822 to the other end 821 of the secondary coil L2. As a result, the current flows from one end 822 to the other end 821 of the secondary coil L2 and then to the ground, thereby reducing the ON voltage and secondary voltage generated in the secondary coil L2. Consequently, discharge at the ON position, i.e., at an abnormal timing, can be suppressed in the spark plug 113.
[0092] Furthermore, as a discharge control measure, switching the switching element 70 from a closed state to an open state interrupts the primary current flowing from the power supply 102 to the primary coil L1, inducing a negative high voltage ranging from several thousand volts to tens of thousands of volts at one end 822 of the secondary coil L2. This causes dielectric breakdown at the gap d of the spark plug 113. In the third modified example, a current (secondary current) is generated that flows from the ground point, through the ground electrode 142 of the spark plug 113 to the center electrode 141 of the spark plug 113 (see Figure 7), from one end 822 to the other end 821 of the secondary coil L2, and flows forward through the first connecting line 122a with the first reverse current prevention diode 111 interposed, or through the first connecting line 122b with the first limiting diode 114 interposed, and further flows toward the ground point.
[0093] In the fourth modified example, a current (secondary current) is generated that flows from the ground point, through the ground electrode 142 of the spark plug 113, to the center electrode 141 of the spark plug 113 (see Figure 8), and in the forward direction through the second connecting wire 121a, which has a second reverse current prevention diode 131 interposed therein, or through the second connecting wire 121b, which has a second limiting diode 134 interposed therein, and flows from one end 822 to the other end 821 of the secondary coil L2, and further toward the ground point. As a result, a discharge occurs in the gap d of the spark plug 113, generating a spark that ignites the fuel filled in the internal combustion engine.
[0094] Furthermore, after the discharge is complete, in the third modified example, current (secondary current) flows from the ground point through the first connecting wires 122a and 122b towards the vicinity of one end 822 of the secondary coil L2, the second connecting wire 121, and the vicinity of the center electrode 141 of the spark plug 113. In the fourth modified example, current (secondary current) flows from the ground point through the first connecting wire 122 towards the vicinity of one end 822 of the secondary coil L2, the second connecting wires 121a and 121b, and the vicinity of the center electrode 141 of the spark plug 113.
[0095] This reduces the residual energy remaining in these areas. In other words, it is possible to reduce the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 in a short time without another discharge occurring at the spark plug 113. As a result, even if a pressure change occurs in the internal combustion engine afterward, it is possible to suppress the occurrence of a discharge at the gap d of the spark plug 113 at an abnormal timing. As a result, even in internal combustion engines that use hydrogen-containing fuels that are easily combusted even at relatively low temperatures and have a fast combustion speed, it is possible to suppress ignition of the fuel at an abnormal timing, leading to a reduction in damage to the engine and other components.
[0096] 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 is used to generate an electric spark at the spark plug of an internal combustion engine to ignite fuel.
[0097] The shape and structure of the ignition device described above may be modified as appropriate without departing from the spirit of the present invention. Furthermore, the elements that appear in the above embodiments and modifications may be combined as appropriate without creating any inconsistencies. [Explanation of Symbols]
[0098] 1 Ignition device 60 Iron Heart 70 switching elements 81 Primary conductor 82 Secondary conductor 102 Power supply 103 Ignition coil 104 Igniter 105 ECU 111 First reverse current blocking diode 112 1st resistor 113 Spark plug 114 First limiting diode 121, 121a, 121b Second connection line 122, 122a, 122b First connection line 131 Second reverse current blocking diode 132 2nd resistor 134 Second limiting diode 150 Power line 811 One end of the primary coil 812 The other end of the primary coil 821 Other end of secondary coil 822 One end of the secondary coil Cs swimming capacity 71. Drive IC (control unit) L1 Primary coil L2 Secondary Coil Rv residual voltage value d (spark plug) gap
Claims
1. An ignition system for an internal combustion engine using a fuel containing at least hydrogen, An ignition coil is formed by the electromagnetic coupling of a primary coil and a secondary coil, A power supply device that applies a DC voltage to one end of the primary coil via a power supply line, A switching element is interposed between the other end of the primary coil and the ground point, and is capable of switching the supply or interruption of the primary current flowing from the power supply to the primary coil. A spark plug that ignites the fuel by discharging in a gap based on a high voltage induced at one end of the secondary coil, A first reverse current prevention diode is inserted in one of the two first connecting wires that are wired in parallel between the other end of the secondary coil and the power supply or ground point, and is a diode that is forward in the direction from one end to the other end of the secondary coil. A first resistor is inserted in the other of the two first connecting wires, It has, The resistance value of the first resistor is 1 MΩ or more. In the other of the two first connecting lines, a first limiting diode, which is a Zener diode or avalanche diode, is interposed in series with the first resistor and is forward in the direction from one end to the other of the secondary coil. It further possesses, An ignition system wherein the breakdown voltage of the first limiting diode is less than the dielectric breakdown voltage at the gap of the spark plug.
2. An ignition device according to claim 1, An ignition device in which the resistance value of the first resistor is 10 MΩ or less.
3. An ignition system for an internal combustion engine using a fuel containing at least hydrogen, An ignition coil is formed by the electromagnetic coupling of a primary coil and a secondary coil, A power supply device that applies a DC voltage to one end of the primary coil via a power supply line, A switching element is interposed between the other end of the primary coil and the ground point, and is capable of switching the supply or interruption of the primary current flowing from the power supply to the primary coil. A spark plug that ignites the fuel by discharging in a gap based on a high voltage induced at one end of the secondary coil, A second reverse current blocking diode is inserted in one of the two second connecting wires that are wired in parallel between one end of the secondary coil and the spark plug, and is a diode that is forward in the direction from one end of the secondary coil to the other end, A second resistor is inserted in the other of the two second connecting wires, It has, The resistance value of the second resistor is 1 MΩ or more. In the other of the two second connecting lines, a second limiting diode, which is a Zener diode or avalanche diode, is interposed in series with the second resistor and is forward in the direction from one end to the other of the secondary coil. It further possesses, An ignition system in which the breakdown voltage of the second limiting diode is less than the dielectric breakdown voltage at the gap of the spark plug.
4. An ignition device according to claim 3, An ignition device in which the resistance value of the second resistor is 10 MΩ or less.
5. An ignition device according to any one of claims 1 to 4, Control unit that controls the switching of the switching element It further possesses, The control unit, By closing the switching element, a charging control is performed to charge the primary coil by flowing a primary current through it. After performing the aforementioned charging control, the switching element is switched to an open state to induce a high voltage at one end of the secondary coil, thereby discharging the gap of the spark plug. An ignition device that performs this function.
6. An ignition device according to any one of claims 1 to 4, Stray capacity formed between one end of the secondary coil and the spark plug An ignition device having the following features.
7. An ignition device according to claim 1 or claim 3, An ignition device in which the breakdown voltage is 2 kV or less.