Ignition device

Abstract

The invention relates to an ignition device. Provided is a technique for converging residual energy remaining in the vicinity of a spark plug or the like at the end of discharge in advance. An ignition device for an internal combustion engine using fuel containing hydrogen includes an ignition coil, a power supply device, a switching element for switching on / off a primary current, an ignition plug for discharging on the basis of a high voltage induced at one end of a secondary coil, a first limiter diode, and a first resistor. Two first connecting lines are wired in parallel between one end of the secondary coil and the spark plug. The first limiter diode is inserted into the first connection line, is forward from one end of the secondary coil toward the other end, and has a breakdown voltage that is equal to or greater than the maximum value of the voltage at the time of ON, and that is smaller than the discharge maintaining voltage of the spark plug. The first resistor is inserted into the first connecting line and has a resistance value of 10-50 Momega (inclusive).

Description

Technical Field

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

[0002] In the past, internal combustion engines including SI (spark ignition) reciprocating engines used in automobiles and the like were equipped with ignition devices. The ignition coil of the ignition device boosts the low voltage of direct current supplied from a battery to several thousand V to several tens of thousands V under the control of an ECU (Engine Control Unit) and supplies it to a spark plug, so that an electric spark is generated to ignite the fuel. For example, an example of a conventional ignition device is described in Patent Document 1.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 6517088 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] Patent document 1 discloses an ignition device (1) for an internal combustion engine having the following structure. First, a primary coil (21) of an ignition coil (2) is connected to a DC power source (VB+) such as a vehicle battery. Then, the primary current (I1) flowing in the primary coil (21) is switched on and off by controlling the on (ON) and off (OFF) of a main switch element (4) (paragraphs 0015, Figure 1 ). In addition, one end of the secondary coil (22) magnetically coupled to the primary coil (21) by means of an iron core is connected to the spark plug (3). The other end of the secondary coil (22) is connected to a DC power supply line via a diode (23) for preventing a voltage from being turned on. Thus, when the primary current (I1) of the ignition coil (2) is cut off, a high voltage is generated on the secondary side, and insulation breakdown occurs in the discharge gap of the spark plug (3). In addition, when the primary current (I1) of the ignition coil (2) is cut off, the secondary current (I2) flows in the forward direction of the diode (23) for preventing a voltage from being turned on (paragraphs 0016 and 0029). On the other hand, when power is first supplied to the primary coil (21), a voltage of opposite polarity generated in the secondary coil (22) is suppressed by the diode (23) for preventing a voltage from being turned on (paragraph 0017).

[0008] In recent years, fuels containing hydrogen have been mostly used in SI (spark ignition) reciprocating engines. It is believed that the use of fuels containing hydrogen will contribute to the realization of a so-called low-carbon society. However, on the other hand, hydrogen has the characteristics of being easy to burn even at relatively low temperatures and having a fast combustion speed. Therefore, for example, when a slight discharge occurs in the spark plug at an unexpected time, the fuel may be ignited and burn. In this case, abnormal combustion may occur, such as backfire in which the fire is blown back from the combustion chamber of the engine to the intake device side, spontaneous ignition combustion (after fire) in which the fuel remaining in the exhaust gas of the engine burns in the exhaust flow path, or pre-ignition in which the timing of ignition cannot be controlled.

[0009] In addition, when the discharge of the spark plug in one cycle formed in the combustion chamber of one or more cylinders of the internal combustion engine ends, and when there is residual energy near the spark plug, the risk of igniting the fuel and burning at an unexpected time in the next cycle increases. More specifically, in the intake process of the next cycle, the pressure in the cylinder becomes low. Moreover, when the new mixed gas flows in, the discharge occurs due to the residual energy, and the risk of igniting the fuel and burning further increases. In particular, when the rotation speed in each cylinder is high, since the next cycle starts immediately, it is necessary to make the residual energy converge closer to zero earlier.

[0010] The present invention aims to provide a technique that can suppress discharge at unexpected timing (abnormal timing) in a spark plug, and in particular, to provide a technique that can make residual energy remaining near the spark plug and the like when the spark plug discharge ends approach zero and converge early.

[0011] Solutions for solving problems

[0012] In order to solve the above problems, the first invention of the present application is an ignition device for an internal combustion engine using a fuel containing at least hydrogen, the ignition device having an ignition coil, a power supply device, a switching element, a spark plug, a first limiter diode and a first resistor. The ignition coil is formed by mutual electromagnetic coupling of a primary coil and a secondary coil. The power supply device applies a DC voltage to one end of the primary coil via a power line. The switching element is inserted between the other end of the primary coil and a ground point, and can switch on or off the primary current flowing from the power supply device to the primary coil. The spark plug discharges in the gap based on the high voltage induced at one end of the secondary coil, thereby igniting the fuel. The first limiter diode is inserted in one of the two first connecting wires wired in parallel between one end of the secondary coil and the spark plug, and is forward in the direction from one end of the secondary coil to the other end, and the first limiter diode is a Zener diode or an avalanche diode. The first resistor is inserted in the other of the two first connecting wires. The breakdown voltage of the first limiter diode is greater than or equal to a value calculated by multiplying a voltage value of the DC voltage applied from the power supply device to one end of the primary coil by a ratio of the number of turns of the secondary coil to the number of turns of the primary coil, and is smaller than a discharge maintenance voltage at the gap of the spark plug. The resistance value of the first resistor is greater than or equal to 10 MΩ and less than or equal to 50 MΩ.

[0013] A second invention of the present application is the ignition device according to the first invention, wherein the breakdown voltage is 1 kV or more.

[0014] Regarding the third invention of the present application, in the ignition device according to the first invention or the second invention, the breakdown voltage is 2 kV or less.

[0015] The fourth invention of the present application is an ignition device for an internal combustion engine using a fuel containing at least hydrogen, the ignition device having an ignition coil, a power supply device, a switching element, a spark plug, a second limiter diode and a second resistor. The ignition coil is formed by mutual electromagnetic coupling between a primary coil and a secondary coil. The power supply device applies a DC voltage to one end of the primary coil via a power line. The switching element is inserted between the other end of the primary coil and a ground point, and can switch the connection or disconnection of the primary current flowing from the power supply device to the primary coil. The spark plug discharges in the gap based on the high voltage induced at one end of the secondary coil, thereby igniting the fuel. The second limiter diode is inserted in one of the two second connecting wires wired in parallel between the other end of the secondary coil and the power supply device or the ground point, and is forward in the direction from one end of the secondary coil to the other end, and the second limiter diode is a Zener diode or an avalanche diode. The second resistor is inserted in the other of the two second connecting wires. The breakdown voltage of the second limiter diode is greater than or equal to a value calculated by multiplying a voltage value of the DC voltage applied from the power supply device to one end of the primary coil by a ratio of the number of turns of the secondary coil to the number of turns of the primary coil, and is smaller than a discharge maintenance voltage at the gap of the spark plug. The resistance value of the second resistor is greater than or equal to 10 MΩ and less than or equal to 50 MΩ.

[0016] A fifth invention of the present application is the ignition device according to the fourth invention, wherein the breakdown voltage is 1 kV or more.

[0017] Regarding the sixth invention of the present application, in the ignition device according to the fourth invention or the fifth invention, the breakdown voltage is 2 kV or less.

[0018] Regarding the seventh invention of the present application, the ignition device according to any one of the first to sixth inventions further comprises a control unit for controlling the switching of the switch element. The control unit performs the following controls: charging control, by closing the switch element, causing a primary current to flow through the primary coil to charge the primary coil; and discharging control, after performing the charging control, switching the switch element to an open state to induce a high voltage at one end of the secondary coil, thereby causing discharge in the gap of the spark plug. The absolute value of the voltage induced at one end of the secondary coil at the end time of the discharge control is greater than the absolute value of the voltage induced at one end of the secondary coil at the start time of the discharge control.

[0019] An eighth invention of the present application is the ignition device according to any one of the first to seventh inventions, further comprising a parasitic capacitance formed between one end of the secondary coil and the spark plug.

[0020] Effects of the Invention

[0021] According to the first to eighth inventions of the present application, when a primary current flows through the primary coil (when turned on), the current flowing through the secondary coil can be suppressed by a limiting diode and a resistor connected in parallel to each other. Thus, discharge in the spark plug when turned on can be suppressed. In addition, after the discharge is completed, the absolute value of the voltage value caused by the residual energy remaining near one end of the secondary coil, near the spark plug, etc. can be first reduced to the breakdown voltage of the limiting diode at once. In addition, the current then flows through the resistor, thereby enabling the absolute value of the voltage value to be reduced toward zero earlier. As a result, discharge in the spark plug at abnormal timing can be further suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a block diagram schematically showing an operating environment of the ignition device for the internal combustion engine according to the first embodiment.

[0023] Figure 2 It is a longitudinal sectional view of the ignition coil according to the first embodiment.

[0024] Figure 3 This is a result of measuring the relationship between the resistance value of the first resistor and the on-time voltage when the primary current flows through the primary coil (when the primary coil is turned on) according to the first embodiment.

[0025] Figure 4 The graph shows the waveform of the EST signal when the ignition device according to the first embodiment is operated, the waveform of the current flowing through the secondary coil (secondary current), and the waveform of the voltage applied to one end of the secondary coil (secondary voltage) in time series.

[0026] Figure 5 The results are obtained by measuring the time until the absolute value of the voltage applied to one end of the secondary coil (secondary voltage) converges to 200 V by simulation while changing the residual initial voltage using the ignition device according to the first embodiment.

[0027] Figure 6 This is a block diagram schematically showing an operating environment of an ignition device for an internal combustion engine according to the second embodiment.

[0028] Figure 7 This is a block diagram schematically showing an operating environment of an ignition device for an internal combustion engine according to a first modified example.

[0029] Figure 8 This is a block diagram schematically showing an operating environment of an ignition device for an internal combustion engine according to a second modification. DETAILED DESCRIPTION

[0030] Hereinafter, an exemplary embodiment of the present invention will be described with reference to the accompanying drawings. In addition, the structural elements described in the present embodiment are merely illustrative and are not intended to limit the scope of the present invention to these. In addition, in the accompanying drawings, the size and number of each part are sometimes exaggerated or simplified as needed for easy understanding.

[0031] <1. First Embodiment>

[0032] <1-1. Structure of ignition device>

[0033] First, the structure of an ignition device 1 for an internal combustion engine as a first embodiment of the present invention will be described with reference to the drawings. Figure 1 1 is a block diagram schematically showing the operating environment of the ignition device 1 according to the first embodiment. As described later, the primary coil L1 and the secondary coil L2 of the ignition coil 103 included in the ignition device 1 are arranged to be stacked on each other. Figure 1 In the figure, for easy understanding, the primary coil L1 and the secondary coil L2 are shown adjacent to each other.

[0034] 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 is a device for applying a high voltage for generating spark discharge at a spark plug 113. The ignition device 1 is provided in each of one or more cylinders of the internal combustion engine.

[0035] In addition, if Figure 1 As shown, in addition to the ignition device 1, the vehicle body 100 also includes the spark plug 113, the power supply device 102 (battery), and the ECU 105 (Engine Control Unit). In a broad sense, the spark plug 113, the power supply device 102, and the ECU 105 can also be considered to be included in the ignition device 1.

[0036] The spark plug 113 is a device for realizing ignition in the combustion chamber of the internal combustion engine. The spark plug 113 is electrically connected to one end 822 of the secondary coil L2 of the ignition coil 103 described later via a wire. Hereinafter, the wire is referred to as the "first connecting wire 121". The spark plug 113 is inserted between one end 822 of the secondary coil L2 and the grounding point (ground) 151. A high voltage is induced in the secondary coil L2 of the ignition coil 103. When the high voltage exceeds the gap d (refer to Figure 1), discharge occurs in the gap d to generate sparks. Thus, the fuel filled in the internal combustion engine is ignited. That is, the spark plug 113 discharges in the gap d based on the high voltage induced at one end 822 of the secondary coil L2, thereby igniting the fuel.

[0037] In addition, in the present embodiment, hydrogen or a mixture of hydrogen and other substances is used as the fuel. That is, the ignition device 1 for the internal combustion engine uses a fuel containing at least hydrogen.

[0038] In addition, there is an electrostatic capacitance component of about 15pF to 20pF between the first connecting wire 121 and the spark plug 113. That is, an electrostatic capacitance component is formed between the end 822 of the secondary coil L2 and the spark plug 113. Hereinafter, this electrostatic capacitance component is referred to as a virtually defined "parasitic capacitance Cs". Figure 1 As shown, parasitic capacitance Cs can be schematically represented in parallel with spark plug 113 in the block diagram.

[0039] The power supply device 102 is a power supply device (battery) capable of charging and discharging DC power. In the present embodiment, the power supply device 102 is electrically connected to the primary coil L1 of the ignition coil 103 described later via a conductor. Hereinafter, the conductor is referred to as a "power supply line 150". The power supply device 102 applies a DC voltage to one end 811 of the primary coil L1 of the ignition coil 103 via the power supply line 150.

[0040] The ECU 105 is a conventional computer that comprehensively controls the transmission of the vehicle body 100 , the operation of the airbag, and the like.

[0041] The ignition device 1 includes an ignition coil 103 , an igniter 104 , a first limiter diode 131 , and a first resistor 132 .

[0042] Figure 2 1 is a longitudinal cross-sectional view of the ignition coil 103. Figure 2 As shown, the ignition coil 103 has a winding drum 40, a primary coil L1, a secondary coil L2 and an iron core 60. Figure 2 , the primary coil L1 and the secondary coil L2 are illustrated in a simplified manner. In addition, in the following description of the ignition coil 103, the direction parallel to the central axis Bc of the winding drum 40 is referred to as the "axial direction". In addition, the direction orthogonal to the central axis Bc of the winding drum 40 is referred to as the "radial direction". In addition, the direction along the arc centered on the central axis Bc of the winding drum 40 is referred to as the "circumferential direction". In addition, the "parallel direction" is set to also include a substantially parallel direction, and the "orthogonal direction" is set to also include a substantially orthogonal direction.

[0043] The winding drum 40 includes a primary winding drum 41 and a secondary winding drum 42 that can be connected to each other. The primary winding drum 41 and the secondary winding drum 42 extend in a cylindrical shape along the central axis Bc. In addition, the secondary winding drum 42 is arranged on the radially outer side of the primary winding drum 41. The material of the primary winding drum 41 and the secondary winding drum 42 is, for example, resin.

[0044] The primary coil L1 is formed by winding a conductive wire on the outer circumference of the primary winding drum 41 along the circumferential direction centered on the central axis Bc. Hereinafter, this conductive wire is referred to as the "primary conductive wire 81". After the formation of the primary coil L1 is completed, the secondary winding drum 42 is arranged in a manner covering the outer circumferential surface of the primary coil L1, and the secondary winding drum 42 is connected to the primary winding drum 41. Then, the secondary coil L2 is formed by winding a conductive wire different from the primary conductive wire 81 on the outer circumferential surface of the secondary winding drum 42 along the circumferential direction centered on the central axis Bc. Hereinafter, this different conductive wire is referred to as the "secondary conductive wire 82". By arranging the primary coil L1 and the secondary coil L2 in a stacked manner like this, the ignition coil 103 including these primary coil L1 and secondary coil L2 can be miniaturized as a whole. However, the primary coil L1 and the secondary coil L2 are not limited to being wound in a stacked manner like this, but can also be wound in a stacked manner like this. Figure 1 So arranged adjacent to each other.

[0045] The core 60 has a structure in which a center core 601 and an outer core 602 are combined. The center core 601 and the outer core 602 of the core 60 are respectively formed of laminated steel plates obtained by laminating silicon steel plates, for example. The center core 601 extends along the center axis Bc of the winding drum 40. In addition, the center core 601 passes through the radially inner space 410 of the primary winding drum 41. The outer core 602 passes through a position radially outside the secondary winding drum 42 and the secondary conductor 82 and connects the two axial ends of the center core 601. Thus, 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 electromagnetically coupling the primary coil L1 and the secondary coil L2.

[0046] like Figure 1 As shown, a conductor extending from the power supply device 102, i.e., a power line 150, 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 described later. A low voltage of a direct current from the power supply device 102 is applied to one end 811 of the primary coil L1 by being controlled by the igniter 104. Then, a gradually increasing primary current begins to flow through the primary coil L1.

[0047] One end 822 of the secondary coil L2 is connected to the spark plug 113 via the first connecting wire 121. The wire diameter of the secondary wire 82 is smaller than the wire diameter of the primary wire 81. In addition, the number of turns of the secondary wire 82 in the secondary coil L2 (for example, 8000 turns) is about 80 times or more the number of turns of the primary wire 81 in the primary coil L1 (for example, 100 turns). Therefore, as described in detail later, when the primary current is cut off, the ignition coil 103 boosts the low-voltage DC power supplied from the power supply device 102 to several thousand V to tens of thousands of V. That is, a high voltage is induced in the secondary coil L2. Then, the secondary coil L2 supplies the induced high-voltage power to the spark plug 113. As a result, an electric spark is generated in the spark plug 113 to ignite the fuel.

[0048] In addition, the first connecting wire 121 has two conductors wired in parallel with each other. Hereinafter, the two conductors are referred to as "first connecting wire 121a" and "first connecting wire 121b". That is, the two first connecting wires 121a and 121b are wired in parallel between one end 822 of the secondary coil L2 and the spark plug 113.

[0049] In addition, in the present embodiment, a first limiter diode 131 is inserted into the first connection line 121a, which is one of the two first connection lines 121a and 121b. The first limiter diode 131 is connected in series with the secondary coil L2. In the present embodiment, a Zener diode is used as the first limiter diode 131. However, an avalanche diode may also be used as the first limiter diode 131. In addition, the first limiter diode 131 is forward in the direction from one end 822 toward the other end 821 of the secondary coil L2.

[0050] In the present invention, as the first limiter diode 131, a diode having a breakdown voltage that is greater than or equal to the maximum value of the "on-time voltage" described later and less than the "discharge maintenance voltage" at the gap d of the spark plug 113 is used. The "discharge maintenance voltage" refers to a voltage that should be applied to the gap d between the center electrode 161 and the ground electrode 162 of the spark plug 113 in order to maintain discharge. The breakdown voltage of the first limiter diode 131 of the present embodiment is greater than or equal to 1 kV and less than or equal to 2 kV. The effect of setting the breakdown voltage of the first limiter diode 131 to such a value will be described in detail later.

[0051] In addition, in the present embodiment, the first resistor 132 is inserted into the other of the two first connecting wires 121a and 121b, that is, the first connecting wire 121b. The first resistor 132 is connected in series with the secondary coil L2. In addition, the resistance value of the first resistor 132 in the present embodiment is greater than or equal to 10MΩ and less than or equal to 50MΩ. The effect of setting the resistance value of the first resistor 132 to such a value will be described in detail later.

[0052] In addition, if Figure 1 As shown, the other end 821 of the secondary coil L2 on the opposite side to the end 822 connected to the spark plug 113 is electrically connected to the power supply device 102 directly or indirectly via a wire. Hereinafter, this wire is referred to as a "second connecting wire 122". In the present embodiment, the other end 821 of the secondary coil L2 is electrically connected to the power supply line 150 via the second connecting wire 122.

[0053] As described in detail later, when the switch element 70 of the igniter 104 is closed and the primary current is passed through the primary coil L1 for charging, a potential difference is generated between the one end 822 and the other end 821 of the secondary coil L2. Hereinafter, the period during which the primary current is passed through the primary coil L1 for charging is referred to as "on time". The positive or negative voltage induced between the one end 822 and the other end 821 of the secondary coil L2 depends on the winding direction of the secondary coil L2. In the present embodiment, when it is turned on, the one end 822 of the secondary coil L2 is higher than the other end 821. In addition, the potential difference between the one end 822 and the other end 821 of the secondary coil L2 is referred to as "on time voltage" below. The maximum value of the on time voltage is calculated by multiplying the voltage value of the DC voltage applied from the power supply device 102 to the 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.

[0054] For example, the voltage value of the DC voltage applied to one end 811 of the primary coil L1 is set to 12V, the number of turns of the primary coil L1 is set to 100 turns, and the number of turns of the secondary coil L2 is set to 8000 turns. Therefore, the ratio of the number of turns of the secondary coil L2 to the number of turns of the primary coil L1 is 80, so the maximum value of the voltage when turned on is calculated to be 12×80=960V. Therefore, the maximum value of the voltage applied to one end 822 of the secondary coil L2 is, for example, about positive 480V, and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is, for example, about negative 480V. In addition, depending on the situation, it is also possible to assume that the maximum value of the voltage applied to one end 822 of the secondary coil L2 is about 0V, and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is about negative 960V. On the other hand, the voltage applied to the power line 150 at this time is 12V.

[0055] Therefore, the current flows from the power supply device 102 side to the secondary coil L2 side via the power supply line 150 and the second connection line 122. Here, the first limiter diode 131 is inserted into the first connection line 121a of the first connection line 121 that connects the one end 822 of the secondary coil L2 to the spark plug 113. As described above, the breakdown voltage of the first limiter diode 131 is 1 kV or more. That is, in the present embodiment, the breakdown voltage of the first limiter diode 131 is set to be not less than the maximum value (voltage difference) of the voltage applied to the one end 822 of the secondary coil L2 relative to the ground point (ground) 151 when the primary current flows through the primary coil L1. In other words, the breakdown voltage of the first limiter diode 131 is set to be not less than the maximum value (voltage difference) of the voltage applied to the cathode side of the first limiter diode 131 relative to the voltage applied to the anode side of the first limiter diode 131 when turned on. Therefore, no current flows in the first connection line 121a into which the first limiter diode 131 is inserted.

[0056] In addition, a first resistor 132 is inserted into the first connecting wire 121b in the first connecting wire 121. As described above, the resistance value of the first resistor 132 is greater than 10MΩ. In this way, by setting the resistance value of the first resistor 132 to a sufficiently large value, the current flowing through the first connecting wire 121b can be sufficiently reduced when connected. As a result, the connection-time voltage generated in the secondary coil L2 and the voltage (secondary voltage) generated at one end 822 of the secondary coil L2 can be suppressed when connected. As a result, in the spark plug 113, discharge can be suppressed when connected, that is, at an abnormal time. In addition, as a reference, in Figure 3 2 shows the result of measuring the relationship between the resistance value of the first resistor 132 and the voltage at the time of the ON state when the primary current flows through the primary coil L1 (at the time of the ON state) using the ignition device 1 according to the present embodiment. Figure 3 The following is a result of measuring the relationship between the resistance value of the first resistor 132 and the on-time voltage while changing the resistance value of the first resistor 132 to a plurality of patterns.

[0057] The igniter 104 is a semiconductor device connected to the primary coil L1 to control the current flowing in the primary coil L1. In addition, the igniter 104 is electrically connected to the ECU 105 and receives a signal from the ECU 105. Hereinafter, this signal is referred to as an "EST signal". The igniter 104 has a switching element 70 and a driver IC 71. In addition, the igniter 104 can also be integrated with the electronic circuit of the ECU 105.

[0058] The switch element 70 uses, for example, an insulated gate bipolar transistor (IGBT). The switch element 70 is inserted between the other end 812 of the primary coil L1 and the grounding point (ground) 152. The C (collector) of the switch element 70 is connected to the other end 812 of the primary coil L1. The E (emitter) of the switch element 70 is connected to the grounding point (ground) 152. The G (gate) of the switch element 70 is connected to the driver IC 71.

[0059] Thus, the switch element 70 can switch on or off the primary current flowing from the power supply device 102 to the primary coil L1. When the switch element 70 is in a closed state, the primary current flows from the power supply device 102 to the primary coil L1. When the switch element 70 is turned off, the primary current flowing to the primary coil L1 is cut off. However, other types of transistors can also be used as the switch element 70.

[0060] The driver IC 71 is a control unit that controls the switching of the switch element 70 based on the EST signal received from the ECU 105. The driver IC 71 has a logic device connected to the switch 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 a calculation process for operating the ignition device 1 to ignite the spark plug 113.

[0061] <1-2. Operation of the ignition device>

[0062] Next, the operation of the ignition device 1 will be described. Figure 4 The waveform of the EST signal when the ignition device 1 is operated, the waveform of the current (secondary current) flowing through the secondary coil L2, and the voltage (secondary voltage) generated at one end 822 of the secondary coil L2 are respectively shown in time series. Figure 4 The secondary current is shown in the figure with the direction from one end 822 to the other end 821 of the secondary coil L2 as "negative" and the direction from the other end 821 to one end 822 of the secondary coil L2 as "positive". Figure 4 The secondary voltage of FIG. 1 illustrates the value of the voltage applied to one end 822 of the secondary coil L2 relative to the ground point (ground).

[0063] As described above, a DC voltage is applied to one end 811 of the primary coil L1 from the power supply device 102 via the power supply line 150. For example, a DC voltage of 12V is applied to one end 811 of the primary coil L1. In addition, the other end 812 of the primary coil L1 is connected to the switching element 70. In addition, the driver IC 71 controls the switching of the switching element 70 based on the EST signal received from the ECU 105. In addition, in the present embodiment, after the mixed gas containing fuel is supplied and filled into each combustion chamber of one or more cylinders of the internal combustion engine, each ignition device 1 is actuated just before reaching TDC (top dead center). Figure 4 As shown, when the ignition device 1 is actuated, 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.

[0064] Then, the driver IC 71 switches the switch element 70 from the open state to the closed state based on the EST signal. As a result, the primary current flows through the primary conductor 81 forming the primary coil L1 to charge the primary coil L1. Hereinafter, such a process of flowing the primary current through the primary coil L1 to charge the primary coil L1 is referred to as "charging control". In addition, an electromagnetic flux is generated in the primary coil L1, and a magnetic field corresponding to the electromagnetic flux acts on the iron core 60.

[0065] In addition, a potential difference, i.e., a voltage when turned on, is generated by mutual inductance between the two ends 821 and 822 of the secondary coil L2 that are electromagnetically coupled to the primary coil L1 by means of the iron core 60. For example, a potential difference of 960V is generated between one end 822 and the other end 821. As a result, the maximum value of the voltage applied to one end 822 of the secondary coil L2 is a positive value, and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is a negative value. For example, the maximum value of the voltage applied to one end 822 of the secondary coil L2 is about positive 480V, and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is about negative 480V. At this time, the voltage applied to the power line 150 is, for example, 12V.

[0066] Therefore, the current flows from the power supply device 102 side to the secondary coil L2 side via the power supply line 150 and the second connection line 122. Here, the first limiter diode 131 is inserted into the first connection line 121a of the first connection line 121 that connects the one end 822 of the secondary coil L2 to the spark plug 113. As described above, the breakdown voltage of the first limiter diode 131 is 1 kV or more. That is, in the present embodiment, the breakdown voltage of the first limiter diode 131 is a value not lower than the maximum value (voltage difference) of the voltage applied to the one end 822 of the secondary coil L2 relative to the ground point (ground) 151 when the primary current flows through the primary coil L1. In other words, the breakdown voltage of the first limiter diode 131 is a value not lower than the maximum value (voltage difference) of the voltage applied to the cathode side of the first limiter diode 131 relative to the voltage applied to the anode side of the first limiter diode 131 when turned on. Therefore, no current flows in the first connection line 121a into which the first limiter diode 131 is inserted.

[0067] In addition, the first resistor 132 is inserted into the first connecting wire 121b in the first connecting wire 121. As described above, the resistance value of the first resistor 132 is greater than 10MΩ. In this way, by setting the resistance value of the first resistor 132 to a sufficiently large value, the current flowing through the first connecting wire 121b can be sufficiently reduced when connected. As a result, the connection voltage generated in the secondary coil L2 and the voltage (secondary voltage) generated at one end 822 of the secondary coil L2 can be suppressed when connected. As a result, in the spark plug 113, discharge can be suppressed when connected, that is, at an abnormal time.

[0068] After the charging control is performed, at time t1, the signal level of the EST signal sent from the ECU 105 to the driver IC 71 is changed from H to L. Then, the driver IC 71 switches the switch element 70 from the closed state to the open state to cut off the primary current flowing from the power supply device 102 to the primary coil L1. As a result, an induced electromotive force is induced by mutual inductance in the secondary coil L2 that is electromagnetically coupled to the primary coil L1 by means of the iron core 60. In this embodiment, a negative high voltage is induced at one end 822 of the secondary coil L2. At this time, the voltage value (the value of the secondary voltage) applied to one end 822 of the secondary coil L2 reaches a negative several thousand V to tens of thousands V relative to the grounding point (ground).

[0069] In addition, the absolute value of the negative high voltage induced at one end 822 of the secondary coil L2 exceeds the insulation breakdown voltage at the gap d of the spark plug 113. As a result, insulation breakdown occurs at the gap d of the spark plug 113. Then, a current is generated from the ground point (ground) 151 to the center electrode 161 of the spark plug 113 via the ground electrode 162 of the spark plug 113 (see Figure 1). The current flows forward in the first limiting diode 131 or flows through the first resistor 132, and then flows through the secondary coil L2. In this embodiment, most of the current flows forward in the first limiting diode 131, and a part of the current flows through the first resistor 132, and then flows to the grounding point (ground) 153 via the power supply device 102.

[0070] As a result, sparks are generated by discharge in the gap d of the spark plug 113, igniting the fuel filled in the combustion chamber of the internal combustion engine. When the fuel in the combustion chamber burns, the pressure in the combustion chamber rises, and the piston moves from TDC (top dead center) to BDC (bottom dead center).

[0071] In the present invention, the process of switching the switch element 70 to the off state to cut off the primary current flowing to the primary coil L1 so as to induce a high voltage at the one end 822 of the secondary coil L2 and cause discharge in the gap d of the spark plug 113 is referred to as "discharge control". When the absolute value of the negative high voltage induced at the one end 822 of the secondary coil L2 becomes lower than the discharge maintenance voltage at the gap d of the spark plug 113 (time t2), the discharge at the gap d of the spark plug 113 is temporarily terminated.

[0072] Here, the insulation breakdown voltage and discharge maintenance voltage at the gap d of the spark plug 113 are greatly affected by the pressure in the combustion chamber. The voltage for insulation breakdown in the gap d of the spark plug 113 and the voltage for maintaining discharge in the gap d are roughly proportional to the pressure in the combustion chamber. In addition, these voltages represent the absolute value of the high voltage induced at one end 822 of the secondary coil L2. In addition, as described above, by performing "discharge control", the fuel in the combustion chamber burns and the pressure rises. Therefore, when the pressure in the combustion chamber is high or the fuel burns and the flow becomes violent, the absolute value of the high voltage induced at one end 822 of the secondary coil L2 sometimes becomes higher.

[0073] like Figure 4 As shown, in this embodiment, "discharge control" is also performed, whereby the absolute value of the negative high voltage induced at one end 822 of the secondary coil L2 temporarily approaches zero from the value (Ds) at the start time of "discharge control", but then increases again due to the pressure increase or flow in the filling combustion chamber. Moreover, the value De at the end time of "discharge control" is a value with a larger absolute value than the value Ds at the start time of "discharge control". That is, in this embodiment, the absolute value of the voltage induced at one end 822 of the secondary coil L2 at the end time of discharge control is larger than the absolute value of the voltage induced at one end 822 of the secondary coil L2 at the start time of discharge control.

[0074] In addition, as described above, a parasitic capacitance Cs composed of an electrostatic capacitance component of about 15pF to 20pF is formed between one end 822 of the secondary coil L2 and the spark plug 113. Therefore, there is a situation where, even at the time point (time t2) when the discharge at the gap d of the spark plug 113 temporarily ends, there is still a charge remaining near the one end 822 of the secondary coil L2, the first connecting wire 121, or near the center electrode 161 of the spark plug 113. In the present embodiment, negative charges remain in these locations. As a result, at time t2, the residual voltage value of one end 822 of the secondary coil L2 becomes a negative value relative to the grounding point (ground). In addition, the residual voltage value represents the value (De) at the end time point of "discharge control". At time t2, the residual voltage value of one end 822 of the secondary coil L2 is, for example, negative tens of thousands of V relative to the grounding point (ground).

[0075] In addition, at time t2, the pressure in the combustion chamber is high, and the absolute value of the residual voltage value is smaller than the discharge maintenance voltage at the gap d of the spark plug 113. However, if this situation is ignored, it is possible that discharge will occur again at the gap d of the spark plug 113 at an unexpected timing, such as when the pressure in the internal combustion engine changes. In addition, the so-called unexpected timing includes, for example, the timing when the pressure in the cylinder becomes low and a new mixed gas flows in during the intake process of the next cycle.

[0076] Therefore, in the present invention, as the first limiter diode 131, a diode having a breakdown voltage smaller than the discharge maintenance voltage at the gap d of the spark plug 113 and the absolute value of the above-mentioned residual voltage value (De) is used. The breakdown voltage of the first limiter diode 131 used in the present embodiment is 2 kV or less. On the other hand, in the above-mentioned example, the residual voltage value (De) at one end 822 of the secondary coil L2 is a negative value, and the absolute value of the value exceeds the breakdown voltage of the first limiter diode 131. In addition, the residual voltage value (De) at one end 822 of the secondary coil L2 is the residual voltage value (De) on the cathode side of the first limiter diode 131, for example, negative tens of thousands of volts.

[0077] Therefore, after the discharge is completed, the spark plug 113 does not discharge again, and the current flows immediately from the power supply device 102 side to the reverse direction of the first limiter diode 131. That is, the current (secondary current) flows from the power supply device 102 side through the second connection line 122 toward the secondary coil L2 side.

[0078] As a result, it is possible to eliminate the residual charge near one end 822 of the secondary coil L2, the first connecting wire 121, or near the center electrode 161 of the spark plug 113, and suddenly reduce the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2, thereby reducing the residual energy remaining in these locations. As a result, the absolute value of the voltage applied to the center electrode 161 of the spark plug 113 is suddenly reduced to the breakdown voltage of the first limiting diode 131. Hereinafter, the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 after the reduction is referred to as the "residual initial voltage Vo". Figure 4 As shown, at the time point (time t2) when the discharge ends, the absolute value of the voltage (secondary voltage) applied to the one end 822 of the secondary coil L2 decreases suddenly, and can be regarded as a "residual initial voltage Vo".

[0079] In addition, as described above, the first connection line 121b is wired in parallel with the first connection line 121a in which the first limiter diode 131 is inserted, and the first resistor 132 is inserted in the first connection line 121b. After the voltage value applied to the center electrode 161 of the spark plug 113 is reduced to the breakdown voltage (residual initial voltage Vo) of the first limiter diode 131, the current mainly flows through the first connection line 121b. More specifically, the current (secondary current) flows from the power supply device 102 side through the second connection line 122 and the secondary coil L2 in the first connection line 121b in which the first resistor 132 is inserted.

[0080] In addition, in the present embodiment, the resistance value of the first resistor 132 is 50 MΩ or less. Thus, by reducing the resistance value of the first resistor 132, the current flowing from the power supply device 102 side through the first connecting wire 121b after the discharge is completed can be maintained at a constant level or above. As a result, the residual energy remaining near the one end 822 of the secondary coil L2, the first connecting wire 121, or the center electrode 161 of the spark plug 113 can be further reduced, and can be converged to zero earlier.

[0081] In the ignition device 1 according to the present embodiment, the absolute value "Vt" of the voltage after time t from the time point when the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 becomes the breakdown voltage (residual initial voltage Vo) of the first limiter diode 131 can be calculated by the formula "Vt = Vo × exp (-t / (C × R))". In this formula, "C" represents the value of the above-mentioned "parasitic capacitance Cs", and "R" represents the resistance value of the first resistor 132. In addition, "voltage after time t" represents "voltage after the voltage is reduced".

[0082] In addition, for reference, Figure 5, the results of measuring the time until the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 converges to 200V by simulation when the resistance value of the first resistor 132 is "10MΩ", "22MΩ", and "33MΩ" using the ignition device 1 involved in this embodiment. In addition, Figure 5 The results are shown in which the time required for the absolute value of the voltage applied to one end 822 of the secondary coil L2 to converge to 200 V is measured while changing the residual initial voltage Vo [kV].

[0083] As described above, in this embodiment, at the time point when the discharge ends (time t2), the "residual initial voltage Vo" is suddenly reduced to the breakdown voltage of the first limiter diode 131. That is, the "residual initial voltage Vo" is suddenly reduced to less than 2 kV. Figure 5 As shown, it was confirmed that even when the resistance value of the first resistor 132 was "10 MΩ", "22 MΩ" or "33 MΩ", the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 converged to 200 V within about 3.5 milliseconds.

[0084] Here, as described above, the ignition device 1 of the present embodiment is used for a high-speed internal combustion engine. For example, in an internal combustion engine with a rotation speed of 16000 rpm, when discharge control is performed near TDC (top dead center), the intake process in the next cycle starts after about 3.75 ms. As described above, in the present embodiment, even when the resistance value of the first resistor 132 is "10MΩ", "22MΩ", or "33MΩ", the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 converges to 200 V within about 3.5 milliseconds. Thus, it is confirmed that the occurrence of discharge can be suppressed and the fuel can be ignited even in the intake process in the next cycle.

[0085] As described above, in the present embodiment, first, as a charge control, when the primary current flows through the primary coil L1 (when it is turned on), the current flowing through the secondary coil L2 can be suppressed by the first limiter diode 131 and the first resistor 132 connected in parallel to each other. As a result, the voltage generated in the secondary coil L2 when it is turned on can be reduced. As a result, the discharge in the spark plug 113 when it is turned on can be suppressed.

[0086] In addition, after the discharge is completed, the current (secondary current) flows from the power supply device 102 side through the second connection line 122 and the secondary coil L2 in the first limiter diode 131 in the reverse direction at once. As a result, the residual charge near the one end 822 of the secondary coil L2, the first connection line 121, or the center electrode 161 of the spark plug 113 can be eliminated at once. As a result, the absolute value of the voltage value caused by the residual energy remaining in these parts can be first reduced to the breakdown voltage of the first limiter diode 131 at once. Furthermore, the current then flows through the first resistor 132, thereby making it possible to reduce the absolute value of the voltage value caused by the residual energy remaining in these parts toward zero earlier.

[0087] As a result, even if the pressure in the internal combustion engine changes later, it is possible to suppress discharge at an abnormal timing in the gap d of the spark plug 113. As a result, even in an internal combustion engine using a fuel containing hydrogen having the characteristics of being easy to burn at a relatively low temperature and having a high combustion speed, it is possible to suppress ignition of the fuel at an abnormal timing, thereby suppressing damage to the engine and the like.

[0088] <2. Second Embodiment>

[0089] Next, a second embodiment of the present invention will be described. In addition, the following description will focus on the differences from the first embodiment, and duplicate descriptions of the same parts as the first embodiment will be omitted.

[0090] Figure 6 2 is a block diagram schematically showing the operating environment of the ignition device 1 according to the second embodiment. Figure 6 As shown, in the second embodiment, one end 822 of the secondary coil L2 is electrically connected to the spark plug 113 directly or indirectly via a conductive wire. Hereinafter, this conductive wire is referred to as a "first connection wire 221".

[0091] In addition, the other end 821 of the secondary coil L2 on the opposite side to the one end 822 connected to the spark plug 113 is electrically connected to the power supply device 102 directly or indirectly via two wires. Hereinafter, the two wires are referred to as "second connection wire 222a" and "second connection wire 222b". The second connection wires 222a and 222b are wired in parallel between the other end 821 of the secondary coil L2 and the power supply device 102. In the present embodiment, the other end 821 of the secondary coil L2 is electrically connected to the power supply line 150 via the second connection wire 222a or the second connection wire 222b.

[0092] In addition, in the present embodiment, a second limiting diode 231 is inserted into the second connecting wire 222a, one of the two second connecting wires 222a and 222b. The second limiting diode 231 is connected in series with the secondary coil L2. The second limiting diode 231 of the present embodiment uses a Zener diode. However, an avalanche diode may also be used for the second limiting diode 231. In addition, the second limiting diode 231 is forward in the direction from one end 822 of the secondary coil L2 toward the other end 821.

[0093] In addition, in the present embodiment, a diode having a breakdown voltage that is not less than the maximum value of the voltage when turned on and is less than the discharge maintenance voltage at the gap d of the spark plug 113 is used as the second limiter diode 231. That is, the breakdown voltage of the second limiter diode 231 is not less than a value calculated by multiplying the voltage value of the DC voltage applied from the power supply device 102 to the one end 811 of the primary coil L1 via the power supply 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. In addition, the breakdown voltage of the second limiter diode 231 in the present embodiment is not less than 1 kV and not more than 2 kV.

[0094] In addition, in the present embodiment, the second resistor 232 is inserted into the second connecting wire 222b, which is the other of the two second connecting wires 222a and 222b. The second resistor 232 is connected in series with the secondary coil L2. In addition, the resistance value of the second resistor 232 in the present embodiment is greater than or equal to 10MΩ and less than or equal to 50MΩ. In addition, a parasitic capacitance Cs composed of an electrostatic capacitance component of about 15pF to 20pF is formed between one end 822 of the secondary coil L2 and the spark plug 113.

[0095] In the present embodiment, first, as a charging control, when the primary current flows through the primary coil L1 (when turned on), a voltage when turned on is generated at both ends 821 and 822 of the secondary coil L2. For example, a potential difference of 960V is generated between one end 822 and the other end 821 of the secondary coil L2. The maximum value of the voltage applied to one end 822 of the secondary coil L2 is a positive value, and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is a negative value. For example, the maximum value of the voltage applied to one end 822 of the secondary coil L2 is about positive 480V, and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is about negative 480V. On the other hand, at this time, the voltage applied to the power line 150 is, for example, 12V.

[0096] Therefore, a current flows from the power supply device 102 side to the secondary coil L2 side via the power supply line 150. Here, a second limiter diode 231 is inserted into the second connection line 222a that connects the other end 821 of the secondary coil L2 to the power supply line 150. As described above, the second limiter diode 231 is forward in the direction from the one end 822 toward the other end 821 of the secondary coil L2. In addition, the breakdown voltage of the second limiter diode 231 is 1 kV or more. That is, in this embodiment, the breakdown voltage of the second limiter diode 231 is set to a voltage difference not lower than the minimum value of the voltage value applied to the power supply line 150 when the primary current flows through the primary coil L1 relative to the voltage applied to the other end 821 of the secondary coil L2. In other words, the breakdown voltage of the second limiter diode 231 is set to a voltage difference not lower than the minimum value of the voltage value applied to the cathode side of the second limiter diode 231 relative to the voltage applied to the anode side of the second limiter diode 231 when turned on. The minimum value of the voltage applied to the other end 821 of the secondary coil L2 is, for example, negative 480 V. The voltage value applied to the power line 150 is, for example, positive 12 V. Therefore, no current flows through the second connection line 222 a in which the second limiter diode 231 is inserted.

[0097] In addition, a second resistor 232 is inserted into the second connecting wire 222b. As described above, the resistance value of the second resistor 232 is greater than 10MΩ. In this way, by setting the resistance value of the second resistor 232 to a sufficiently large value, the current flowing through the second connecting wire 222b can be sufficiently reduced when connected. As a result, the connection voltage generated in the secondary coil L2 and the voltage (secondary voltage) generated at one end 822 of the secondary coil L2 can be suppressed when connected. As a result, in the spark plug 113, discharge can be suppressed when connected, that is, at an abnormal time.

[0098] In addition, as a discharge control, the switch element 70 is switched from the closed state to the open state to cut off the primary current flowing from the power supply device 102 to the primary coil L1. As a result, a negative high voltage of several thousand to tens of thousands of volts is induced at one end 822 of the secondary coil L2. As a result, insulation breakdown occurs in the gap d of the spark plug 113. In addition, a current is generated from the ground point (ground) 151 to the center electrode 161 of the spark plug 113 via the ground electrode 162 of the spark plug 113 (see Figure 6 ). The current flows through the first connection line 221 and the secondary coil L2, flows forward in the second limiter diode 231 or flows through the second resistor 232. In the present embodiment, most of the current flows forward in the second limiter diode 231, and a part of the current flows through the second resistor 232, and then flows to the ground point (ground) 153 via the power supply device 102.

[0099] As a result, a spark is generated by discharge in the gap d of the spark plug 113, igniting the fuel filled in the combustion chamber of the internal combustion engine. In addition, when the absolute value of the negative high voltage induced at one end 822 of the secondary coil L2 is lower than the discharge maintenance voltage at the gap d of the spark plug 113, the discharge at the gap d of the spark plug 113 is temporarily terminated.

[0100] In addition, similarly to the first embodiment, as the second limiter diode 231, a diode having a breakdown voltage smaller than the insulation breakdown voltage at the gap d of the spark plug 113 and the absolute value of the residual voltage value (De) at one end 822 of the secondary coil L2 at the end of the discharge is used. The breakdown voltage of the second limiter diode 231 used in this embodiment is 2 kV or less. At this time, the residual voltage value (De) at one end 822 of the secondary coil L2 is a negative value. In addition, the residual voltage value (De) at one end 822 of the secondary coil L2 is the residual voltage value (De) on the anode side of the second limiter diode 231, for example, tens of thousands of negative volts. On the other hand, the voltage applied to the power line 150 is, for example, 12 V. That is, the voltage applied to the cathode side of the second limiter diode 231 is, for example, 12 V.

[0101] Therefore, after the discharge is completed, the spark plug 113 does not discharge again, and the current flows immediately from the power supply device 102 side to the reverse direction of the second limiter diode 231. That is, the current (secondary current) flows from the power supply device 102 side to the secondary coil L2 side via the second connection line 222a.

[0102] As a result, the residual charge near the one end 822 of the secondary coil L2, the first connecting wire 221, or the center electrode 161 of the spark plug 113 can be eliminated, and the absolute value of the voltage (secondary voltage) applied to the one end 822 of the secondary coil L2 can be reduced immediately, thereby reducing the residual energy remaining in these locations. As a result, the absolute value of the voltage (secondary voltage) applied to the one end 822 of the secondary coil L2 can be reduced immediately to a value equivalent to the breakdown voltage of the second limiter diode 231.

[0103] In addition, as described above, the second connection line 222b is wired in parallel with the second connection line 222a in which the second limiter diode 231 is inserted, and the second connection line 222b is inserted with the second resistor 232. After the voltage value at the one end 822 of the secondary coil L2 is reduced to a value of the same degree as the breakdown voltage of the second limiter diode 231, the current flows through the second connection line 222b. More specifically, the current (secondary current) flows from the power supply device 102 side to the secondary coil L2 via the second connection line 222b in which the second resistor 232 is inserted.

[0104] In addition, in the present embodiment, the resistance value of the second resistor 232 is 50 MΩ or less. Thus, by reducing the resistance value of the second resistor 232, the current flowing from the power supply device 102 side through the second connecting wire 222b after the discharge is completed can be maintained at a constant level or above. As a result, the residual energy remaining near the one end 822 of the secondary coil L2, the first connecting wire 221, or the center electrode 161 of the spark plug 113 can be further reduced, and can be converged to zero earlier.

[0105] As described above, in the present embodiment, first, as a charge control, when the primary current flows through the primary coil L1 (when it is turned on), the current flowing through the secondary coil L2 can be suppressed by the second limiter diode 231 and the second resistor 232 connected in parallel to each other. As a result, the voltage generated in the secondary coil L2 when it is turned on can be reduced. As a result, the discharge in the spark plug 113 when it is turned on can be suppressed.

[0106] In addition, after the discharge is completed, the current (secondary current) flows from the power supply device 102 side through the second connection line 222a to the second limiter diode 231 in the reverse direction at once. As a result, the charge remaining near the one end 822 of the secondary coil L2, the first connection line 221, or the center electrode 161 of the spark plug 113 can be eliminated at once. As a result, the absolute value of the voltage value caused by the residual energy remaining in these parts can be first reduced to a value of the same level as the breakdown voltage of the second limiter diode 231. Then, the current flows through the second resistor 232, thereby making it possible to reduce the absolute value of the voltage value caused by the residual energy remaining in these parts toward zero earlier.

[0107] As a result, even if the pressure in the internal combustion engine changes later, it is possible to suppress discharge at an abnormal timing in the gap d of the spark plug 113. As a result, even in an internal combustion engine using a fuel containing hydrogen having the characteristics of being easy to burn at a relatively low temperature and having a high combustion speed, it is possible to suppress ignition of the fuel at an abnormal timing, thereby suppressing damage to the engine and the like.

[0108] In addition, as described above, in the first embodiment, the first limiter diode 131 and the first resistor 132 are provided on the side of the one end 822 of the secondary coil L2, whereas in the present embodiment, the second limiter diode 231 and the second resistor 232 are provided on the side of the other end 821 of the secondary coil L2. However, in many cases, the secondary coil L2 itself also has a parasitic capacitance composed of a small electrostatic capacitance component. Therefore, when the second limiter diode 231 and the second resistor 232 are provided on the side of the other end 821 of the secondary coil L2, the electrostatic capacitance component of the secondary coil L2 itself is further superimposed on the electrostatic capacitance component of about 15pF to 20pF formed between the one end 822 of the secondary coil L2 and the spark plug 113.

[0109] As a result, the influence of the superimposed electrostatic capacitance component becomes larger, the above-mentioned voltage at the time of on-state becomes larger, and the residual energy at the time when the above-mentioned discharge is temporarily terminated may increase. Therefore, these limiter diodes and resistors are preferably arranged on the side of one end 822 of the secondary coil L2. However, from the perspective of ensuring the ease of installation space for the second limiter diode 231 and the second resistor 232, it is sometimes preferable to arrange them on the side of the other end 821 of the secondary coil L2 as in the second embodiment.

[0110] <3. Modifications>

[0111] As mentioned above, although the exemplary embodiment of the present invention was described, the present invention is not limited to the above-mentioned embodiment.

[0112] In the above-mentioned embodiment and modification, the voltage applied to one end 822 of the secondary coil L2 is positive in charge control, and the voltage applied to the other end 821 of the secondary coil L2 is negative. In addition, a high negative voltage of negative thousands to tens of thousands of volts is induced at one end 822 of the secondary coil L2 in discharge control. However, the positive and negative voltage values ​​at the two ends 821 and 822 of the secondary coil L2 may be reversed by changing the winding direction of the primary wire 81 in the primary coil L1 and the winding direction of the secondary wire 82 in the secondary coil L2. In this case, the forward and reverse directions of the first limiter diode 131 inserted in the first connection line 121a in the first embodiment and the second limiter diode 231 inserted in the second connection line 222a in the second embodiment may be reversed.

[0113] In the first embodiment described above, the cathode side of the first limiting diode 131 and the other end 821 of the secondary coil L2 are respectively connected to the positive side of the power supply device 102. However, it is also possible to Figure 7As shown in the first modified example, the cathode side of the first limiter diode 131 and the other end 821 of the secondary coil L2 are connected to the ground point (ground) 154. In addition, in the above-mentioned second embodiment, the cathode side of the second limiter diode 231 and the other end 821 of the secondary coil L2 are connected to the positive side of the power supply device 102. However, it is also possible to Figure 8 As shown in the second modification example, the cathode side of the second limiter diode 231 and the other end 821 of the secondary coil L2 are connected to the ground point (ground) 154.

[0114] That is, the second limiter diode 231 may be inserted into one of the two second connection lines 222a and 222b wired in parallel between the other end 821 of the secondary coil L2 and the grounding point (ground) 154, and the second limiter diode 231 may be a Zener diode or an avalanche diode in the direction from the one end 822 of the secondary coil L2 toward the other end 821. In addition, the second resistor 232 may be inserted into the other of the two second connection lines 222a and 222b.

[0115] In the first and second variants, first, as a charging control, when the primary current flows through the primary coil L1 (when turned on), a voltage at the time of turning on is generated at both ends 821 and 822 of the secondary coil L2. For example, a potential difference of 960V is generated between one end 822 and the other end 821 of the secondary coil L2. The maximum value of the voltage applied to the one end 822 of the secondary coil L2 is a positive value, and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is a negative value. For example, the maximum value of the voltage applied to the one end 822 of the secondary coil L2 is about positive 480V, and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is about negative 480V.

[0116] Here, in the first modification, the first limiter diode 131 and the first resistor 132 are inserted into the first connecting wires 121a and 121b. In addition, in the second modification, the second limiter diode 231 and the second resistor 232 are inserted into the second connecting wires 222a and 222b. The first limiter diode 131 and the second limiter diode 231 are each in the forward direction from the one end 822 of the secondary coil L2 toward the other end 821. Therefore, the current flows from the one end 822 of the secondary coil L2 toward the other end 821 and further toward the grounding point (ground) 154, thereby reducing the on-time voltage and the secondary voltage generated in the secondary coil L2. As a result, in the spark plug 113, it is possible to suppress discharge at the time of on-time, that is, at an abnormal time.

[0117] In addition, as a discharge control, when the switch element 70 is switched from the closed state to the open state to cut off the primary current flowing from the power supply device 102 to the primary coil L1, a negative high voltage of several thousand to tens of thousands of volts is induced at one end 822 of the secondary coil L2. As a result, insulation breakdown occurs in the gap d of the spark plug 113. In addition, in the first modified example, a current (secondary current) is generated from the ground point (ground) 151 to the center electrode 161 of the spark plug 113 via the ground electrode 162 of the spark plug 113 (see Figure 7 The current further flows forward in the first connection line 121a into which the first limiting diode 131 is inserted, or flows in the first connection line 121b into which the first resistor 132 is inserted, flows from one end 822 to the other end 821 of the secondary coil L2, and then flows toward the grounding point (ground) 154.

[0118] In the second modification, a current (secondary current) is generated from the ground point (ground) 151 to the center electrode 161 of the spark plug 113 via the ground electrode 162 of the spark plug 113 (see Figure 8 ). The current further flows from one end 822 of the secondary coil L2 to the other end 821, and flows forward in the second connection line 222a in which the second limiter diode 231 is inserted, or flows in the second connection line 222b in which the second resistor 232 is inserted, and then flows toward the ground point (ground) 154. As a result, a spark is generated by discharge in the gap d of the spark plug 113, and the fuel filled in the internal combustion engine is ignited.

[0119] In addition, after the discharge is completed, in the first modification, the current (secondary current) flows from the ground point (ground) 154 through the secondary coil L2 in the first limiter diode 131 in the reverse direction at once. As a result, the charge remaining near the one end 822 of the secondary coil L2, the first connecting wire 121, or the center electrode 161 of the spark plug 113 can be eliminated at once. As a result, the absolute value of the voltage value caused by the residual energy remaining in these parts can be first reduced to the breakdown voltage of the first limiter diode 131 at once. And, thereafter, the current flows from the ground point (ground) 154 through the first resistor 132, thereby, the absolute value of the voltage value caused by the residual energy remaining in these parts can be reduced to zero earlier.

[0120] In the second modification, after the discharge is completed, the current (secondary current) enters the second clipping diode 231 in the reverse direction from the grounding point (ground) 154 and flows toward the secondary coil L2 all at once. As a result, the charge remaining near the one end 822 of the secondary coil L2, the first connecting wire 221, or the center electrode 161 of the spark plug 113 can be eliminated all at once. As a result, the absolute value of the voltage value caused by the residual energy remaining in these parts can be first reduced to the breakdown voltage of the second clipping diode 231 all at once. And, the current then flows from the grounding point (ground) 154 via the second resistor 232, thereby making it possible to reduce the absolute value of the voltage value caused by the residual energy remaining in these parts toward zero earlier.

[0121] The ignition device of the present invention may be a device mounted on a vehicle such as an automobile, various devices such as a generator, or industrial machinery, and may be used to generate an electric spark in a spark plug of an internal combustion engine to ignite fuel.

[0122] The shape and structure of the details of the above-mentioned ignition device may be appropriately changed within the scope not departing from the gist of the present invention. In addition, the various elements appearing in the above-mentioned embodiments and modified examples may be appropriately combined within the scope not causing contradictions.

[0123] Description of Reference Numerals

[0124] 1: ignition device; 60: iron core; 70: switching element; 81: primary wire; 82: secondary wire; 102: power supply device; 103: ignition coil; 104: igniter; 105: ECU; 113: spark plug; 121, 121a, 121b: first connecting wire; 122: second connecting wire; 131: first limiting diode; 132: first resistor; 150: power supply line; 221: first connecting wire; 222a, 222b: second connecting wire; 231: second limiting diode; 232: second resistor; 811: one end of the primary coil; 812: the other end of the primary coil; 821: the other end of the secondary coil; 822: one end of the secondary coil; Cs: parasitic capacitance; 71: drive IC (control unit); L1: primary coil; L2: secondary coil; d: gap (of the spark plug).

Claims

1. An ignition device for an internal combustion engine using a fuel containing at least hydrogen, the ignition device comprising: An ignition coil, which is formed by mutual electromagnetic coupling of a primary coil and a secondary coil; a power supply device for applying a DC voltage to one end of the primary coil via a power line; a switching element inserted between the other end of the primary coil and a ground point, capable of switching on or off a primary current flowing from the power supply device to the primary coil; a spark plug that discharges across a gap based on a high voltage induced at one end of the secondary coil, thereby igniting the fuel; a first limiter diode inserted in one of two first connection wires wired in parallel between one end of the secondary coil and the spark plug and having a forward direction from one end of the secondary coil toward the other end, the first limiter diode being a Zener diode or an avalanche diode; and a first resistor inserted in the other of the two first connecting lines, wherein the breakdown voltage of the first limiting diode is greater than or equal to a value calculated by multiplying the voltage value of the DC voltage applied from the power supply device to one end of the primary coil by the ratio of the number of turns of the secondary coil to the number of turns of the primary coil, and is smaller than the discharge maintenance voltage at the gap of the spark plug, The resistance value of the first resistor is greater than or equal to 10 MΩ and less than or equal to 50 MΩ.

2. The ignition device according to claim 1, wherein: The breakdown voltage is above 1 kV.

3. The ignition device according to claim 1 or 2, wherein: The breakdown voltage is below 2 kV.

4. An ignition device for an internal combustion engine using a fuel containing at least hydrogen, the ignition device comprising: An ignition coil, which is formed by mutual electromagnetic coupling of a primary coil and a secondary coil; a power supply device for applying a DC voltage to one end of the primary coil via a power line; a switching element inserted between the other end of the primary coil and a ground point, capable of switching on or off a primary current flowing from the power supply device to the primary coil; a spark plug that discharges across a gap based on a high voltage induced at one end of the secondary coil, thereby igniting the fuel; a second limiting diode inserted in one of two second connection lines wired in parallel between the other end of the secondary coil and the power supply device or the ground point, and having a forward direction in a direction from one end of the secondary coil toward the other end, the second limiting diode being a Zener diode or an avalanche diode; as well as a second resistor inserted in the other of the two second connecting lines, wherein the breakdown voltage of the second limiting diode is greater than or equal to a value calculated by multiplying the voltage value of the DC voltage applied from the power supply device to one end of the primary coil by the ratio of the number of turns of the secondary coil to the number of turns of the primary coil, and is smaller than the discharge maintenance voltage at the gap of the spark plug, The resistance value of the second resistor is greater than or equal to 10 MΩ and less than or equal to 50 MΩ.

5. The ignition device according to claim 4, wherein: The breakdown voltage is above 1 kV.

6. The ignition device according to claim 4 or 5, wherein: The breakdown voltage is below 2 kV.

7. The ignition device according to claim 1 or 4, wherein: A control unit is further provided, the control unit controlling the switching of the switch element, The control unit performs the following control: charging control, by closing the switch element, causing a primary current to flow through the primary coil to charge the primary coil; and Discharge control, after the charging control is performed, the switch element is switched to an off state so that a high voltage is induced at one end of the secondary coil, thereby causing discharge to occur in the gap of the spark plug, The absolute value of the voltage induced at the one end of the secondary coil at the end time point of the discharge control is larger than the absolute value of the voltage induced at the one end of the secondary coil at the start time point of the discharge control.

8. The ignition device according to claim 1 or 4, wherein: There is also a parasitic capacitance formed between one end of the secondary coil and the spark plug.

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