Ignition device

Abstract

This invention provides an ignition device capable of suppressing discharge in the spark plug at abnormal times. An ignition device for an internal combustion engine using hydrogen-containing fuel includes an ignition coil comprising a primary coil and a secondary coil, a power supply device, a switching element, a spark plug, and a limiting diode. The switching element switches the primary current flowing to or from the primary coil. The spark plug discharges in the gap based on a high voltage induced at one end of the secondary coil. The limiting diode is forward-biased in the direction from one end of the secondary coil to the other end; the limiting diode is a Zener diode or an avalanche diode. The breakdown voltage of the limiting diode is greater than the maximum on-state voltage, which is obtained by multiplying the DC voltage applied to one end of the primary coil by the ratio of the number of turns in the secondary coil to the number of turns in the primary coil.

Description

Technical Field

[0001] This invention relates to an ignition device for an internal combustion engine. Background Technology

[0002] Conventional internal combustion engines, including SI (spark ignition) reciprocating engines, used in automobiles and other vehicles, are equipped with ignition devices. The ignition coil of the ignition device is controlled by the ECU (Engine Control Unit) to boost the low DC voltage supplied from the battery to several thousand to tens of thousands of volts and supply it to the spark plug, thereby generating an electric spark to ignite the fuel. For example, a conventional ignition device is described in Patent Document 1.

[0003] Existing technical documents

[0004] Patent documents

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

[0006] The problem the invention aims to solve

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

[0008] In recent years, hydrogen-containing fuels have been widely used in SI (spark ignition) reciprocating engines. It is believed that using hydrogen-containing fuels contributes to the realization of a so-called low-carbon society. However, hydrogen also has the characteristic of being easily combustible at relatively low temperatures and burning quickly. Therefore, for example, if a slight discharge occurs unexpectedly in the spark plug, the fuel may ignite and burn. In this case, abnormal combustion may occur, such as backfire (blowing the flame back from the engine's combustion chamber to the intake side), afterfire (afterburning of residual fuel in the exhaust gas in the exhaust path), or premature ignition (where the timing of ignition cannot be controlled).

[0009] The purpose of this invention is to provide a technique that can suppress discharge in spark plugs at unexpected times.

[0010] Solution for solving the problem

[0011] To address the aforementioned problems, the first invention of this application is an ignition device for an internal combustion engine using fuel containing at least hydrogen. The ignition device includes an ignition coil, a power supply, a switching element, a spark plug, and a limiting diode. The ignition coil is formed by electromagnetic coupling between 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 inserted between the other end of the primary coil and a ground point, enabling switching on or off of the primary current flowing from the power supply to the primary coil. The spark plug discharges in a gap based on the high voltage induced at one end of the secondary coil, thereby igniting the fuel. The limiting diode is inserted into a first or second connecting line and is positively oriented from one end of the secondary coil towards the other end; the limiting diode is a Zener diode or an avalanche diode. Furthermore, the first connecting line is a wire that directly or indirectly connects the other end of the secondary coil to the power supply or ground point. Additionally, the second connecting line is a wire that connects one end of the secondary coil to the spark plug. Furthermore, the breakdown voltage of the limiting diode is greater than the maximum value of the voltage when switched on. Additionally, the maximum value of the voltage when switched on is calculated by multiplying the DC voltage applied by the power supply to one end of the primary coil by the ratio of the number of turns in the secondary coil to the number of turns in the primary coil.

[0012] The effects of the invention

[0013] According to the first invention of this application, when a primary current flows through the primary coil (when switched on), the switching-on voltage generated in the secondary coil can be reduced. This suppresses discharge in the spark plug during switching-on. Furthermore, after the discharge ends, the current flows in reverse through the limiting diode, thereby reducing residual energy remaining near the spark plug. As a result, subsequent discharge in the spark plug at abnormal times can be further suppressed. Attached Figure Description

[0014] Figure 1 This is a block diagram schematically illustrating the operating environment of the ignition device for an internal combustion engine according to the first embodiment.

[0015] Figure 2 This is a longitudinal cross-sectional view of the ignition coil according to the first embodiment.

[0016] Figure 3 It is a graph showing the waveform of the EST signal when the ignition device according to the first embodiment is operated, the waveform of the secondary current flowing in the secondary coil, and the voltage generated at one end of the secondary coil (secondary voltage) in a time sequence.

[0017] Figure 4 This is a block diagram schematically illustrating the operating environment of the ignition device for an internal combustion engine involved in the first modification.

[0018] Figure 5 This is a block diagram schematically illustrating the operating environment of the ignition device for an internal combustion engine involved in the second modification.

[0019] Figure 6 This is a block diagram schematically illustrating the operating environment of the ignition device for an internal combustion engine involved in the third variation. Detailed Implementation

[0020] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

[0021] <1. First Implementation Method>

[0022] <1-1. Structure of the Ignition Device>

[0023] First, the structure 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 accompanying drawings. Figure 1 This is a block diagram schematically illustrating the operating environment of the ignition device 1 according to the first embodiment. Furthermore, as 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 direction that overlaps with each other. However, in Figure 1 In order to make it easier to understand, the primary coil L1 and the secondary coil L2 are shown in the diagram.

[0024] The ignition device 1 in this embodiment, for example, is mounted on an internal combustion engine such as an SI (spark ignition) reciprocating engine used in a vehicle body 100 of an automobile, and is a device that applies a high voltage to cause the spark plug 113 to generate a spark discharge. Additionally, as... 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). Furthermore, broadly speaking, the spark plug 113, the power supply device 102, and the ECU 105 can also be considered as being included in the ignition device 1.

[0025] Spark plug 113 is a device used to initiate ignition in the combustion chamber of an internal combustion engine. Spark plug 113 is electrically connected via a wire to one end 822 of the secondary coil L2 of ignition coil 103 (described later). Hereinafter, this wire connecting spark plug 113 to one end 822 of the secondary coil L2 is referred to as "secondary connection wire 121". Spark plug 113 is inserted between one end 822 of the secondary coil L2 and the ground point (ground). A high voltage is induced in the secondary coil L2 of ignition coil 103. When this high voltage exceeds the gap d between the center electrode 141 and the ground electrode 142 of spark plug 113 (see reference...),... Figure 1 When the insulation breakdown voltage at point ) is reached, a discharge occurs in gap d, generating a spark. This ignites the fuel in the internal combustion engine. Specifically, spark plug 113 discharges in gap d based on the high voltage induced at one end 822 of the secondary coil L2, thereby igniting the fuel.

[0026] Furthermore, in this embodiment, hydrogen, or a mixture of hydrogen and other substances, is used as fuel. That is, a fuel containing at least hydrogen is used in the ignition device 1 for the internal combustion engine.

[0027] Additionally, a capacitance of approximately 15pF to 20pF exists in the second connection wire 121 and spark plug 113. That is, a capacitance is formed between one end 822 of the secondary coil L2 and the spark plug 113. This capacitance is referred to below as the virtually defined "parasitic capacitance Cs". Figure 1 As shown, the parasitic capacitance Cs can be schematically represented in parallel with spark plug 113 in the block diagram.

[0028] The power supply device 102 is a device capable of charging and discharging DC power. That is, the power supply device 102 is a battery. In this embodiment, the power supply device 102 is electrically connected to the primary coil L1 of the ignition coil 103 (described later) via a wire. Hereinafter, the wire extending from the power supply device 102 will be referred to as the "power 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 line 150.

[0029] ECU 105 is an existing computer that comprehensively controls the operation of the vehicle body 100's transmission, airbags, and other systems.

[0030] The ignition device 1 includes an ignition coil 103, an igniter 104, and a limiting diode 114.

[0031] Figure 2 This is a longitudinal cross-sectional view of ignition coil 103. (See diagram below.) Figure 2 As shown, the ignition coil 103 includes a winding drum 40, a primary coil L1, a secondary coil L2, and an iron core 60. Furthermore, in Figure 2 In the diagram, the primary coil L1 and the secondary coil L2 are shown in a simplified manner. Furthermore, 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," the direction orthogonal to the central axis Bc of the winding drum 40 is referred to as the "radial direction," and the direction along an arc centered on the central axis Bc of the winding drum 40 is referred to as the "circumferential direction." Additionally, the term "parallel direction" is assumed to include generally parallel directions, and the term "orthogonal direction" is assumed to include generally orthogonal directions.

[0032] The winding cylinder 40 includes a primary winding cylinder 41 and a secondary winding cylinder 42 that can be interconnected. The primary winding cylinder 41 and the secondary winding cylinder 42 each extend in a cylindrical shape along the central axis Bc. Furthermore, the secondary winding cylinder 42 is disposed radially outside the primary winding cylinder 41. The primary winding cylinder 41 and the secondary winding cylinder 42 are made of, for example, resin.

[0033] The primary coil L1 is formed by winding a wire circumferentially around the central axis Bc on the outer peripheral surface of the primary winding cylinder 41. This wire is referred to below as the "primary wire 81". After the primary coil L1 is formed, the secondary winding cylinder 42 is arranged to cover the outer peripheral surface of the primary coil L1, and the secondary winding cylinder 42 is connected to the primary winding cylinder 41. Then, the secondary coil L2 is formed by winding a wire different from the primary wire 81 circumferentially around the central axis Bc on the outer peripheral surface of the secondary winding cylinder 42. This different wire is referred to below as the "secondary wire 82". By arranging the primary coil L1 and the secondary coil L2 in a stacked manner, the ignition coil 103, including these primary coils L1 and secondary coils L2, can be miniaturized. However, the primary coil L1 and the secondary coil L2 are not limited to being stacked and wound in this manner; they can also be wound as follows: Figure 1 That's how they're configured to be adjacent to each other.

[0034] The core 60 has a structure consisting of a central core 601 and an outer peripheral core 602. The central core 601 and the outer peripheral core 602 are formed, for example, from laminated steel plates obtained by laminating silicon steel sheets. The central core 601 extends along the central axis Bc of the winding cylinder 40. Furthermore, the central core 601 penetrates the space 410 radially inside the primary winding cylinder 41. The outer peripheral core 602 connects the two axial ends of the central core 601 at a position radially outward from the secondary winding cylinder 42 and the secondary conductor 82. 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 the mutual electromagnetic coupling of the primary coil L1 and the secondary coil L2.

[0035] like Figure 1 As shown, a power line 150, 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 the igniter 104, which will be described later. By being 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, thereby initiating the flow of a gradually increasing primary current in the primary coil L1.

[0036] One end 822 of the secondary coil L2 is connected to the spark plug 113. The wire diameter of the secondary wire 82 is smaller than that of the primary wire 81. Furthermore, the number of turns of the secondary wire 82 in the secondary coil L2 (e.g., 8000 turns) is approximately 80 times or more than the number of turns of the primary wire 81 in the primary coil L1 (e.g., 100 turns). Thus, as detailed later, when the primary current is cut off, the ignition coil 103 boosts the low-voltage DC power supplied from the power supply unit 102 to several thousand to tens of thousands of volts. 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. This causes an electric spark to be generated in the spark plug 113 to ignite the fuel.

[0037] In addition, such as Figure 1 As shown, the other end 821 of the secondary coil L2, opposite to the end 822 connected to the spark plug 113, is electrically connected directly or indirectly to the power supply device 102 via a wire. Hereinafter, this wire used to connect the other end 821 of the secondary coil L2 to the power supply device 102 is referred to as the "first connecting line 122". In this embodiment, the other end 821 of the secondary coil L2 is electrically connected to the power supply line 150. Furthermore, in this embodiment, a limiting diode 114 is inserted into the first connecting line 122. The limiting diode 114 is connected in series with the secondary coil L2. Additionally, the limiting diode 114 is positively oriented in the direction from one end 822 of the secondary coil L2 toward the other end 821 of the secondary coil L2. In this embodiment, a Zener diode is used as the limiting diode 114. However, an avalanche diode could also be used as the limiting diode 114.

[0038] As detailed later, when the switching element 70 of the igniter 104 is closed to allow primary current to flow through the primary coil L1 to charge it (on-state), a potential difference is generated between the two ends 821 and 822 of the secondary coil L2. In this embodiment, when on-state, the voltage at one end 822 of the secondary coil L2 becomes higher than the voltage at the other end 821 of the secondary coil L2. 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 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.

[0039] For example, when 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, and the number of turns of the secondary coil L2 is set to 8000, the ratio of the number of turns of the secondary coil L2 to the number of turns of the primary coil L1 is 80. Therefore, the maximum voltage when switched on is calculated to be 12 × 80 = 960V. Thus, the maximum voltage applied to one end 822 of the secondary coil L2 is, for example, approximately +480V, and the minimum voltage applied to the other end 821 of the secondary coil L2 is, for example, approximately -480V. Alternatively, depending on the situation, it can be assumed that the maximum voltage applied to one end 822 of the secondary coil L2 is approximately 0V, and the minimum voltage applied to the other end 821 of the secondary coil L2 is approximately -960V. On the other hand, the voltage applied to the power supply line 150 is 12V at this time.

[0040] Here, in this invention, the limiting diode 114 described above is a limiting diode whose breakdown voltage is greater than the maximum voltage when switched on. In this embodiment, the breakdown voltage of the limiting diode 114 is 1kV or higher. On the other hand, in the example described above, the minimum voltage applied to the other end 821 of the secondary coil L2 (the anode side of the limiting diode 114) is approximately -480V. Furthermore, the voltage applied to the power supply line 150 (the cathode side of the limiting diode 114) is +12V. Therefore, it is possible to suppress reverse current flowing through the limiting diode 114 when primary current flows in the primary coil L1 (when switched on). That is, it is possible to suppress current flowing to the secondary coil L2 side via the first connection line 122. Therefore, it is possible to suppress discharge in the spark plug 113 at an abnormal time when switched on.

[0041] Furthermore, in this invention, a limiting diode 114 with a breakdown voltage lower than the insulation breakdown voltage at the gap d of the spark plug 113 is used. The limiting diode 114 used in this embodiment has a breakdown voltage of 2kV or less. Details of the effects obtained by setting the breakdown voltage of the limiting diode 114 to 2kV or less will be described later.

[0042] Ignition 104 is a semiconductor device connected to the primary coil L1 to control the current flowing in the primary coil L1. Additionally, ignition 104 is electrically connected to the ECU 105 and receives signals from the ECU 105. Hereinafter, the signals received from the ECU 105 will be referred to as the "EST signal". Ignition 104 includes a switching element 70 and a driver IC 71. Furthermore, ignition 104 can also be integrated with the electronic circuitry of the ECU 105.

[0043] Switching element 70 is, for example, an insulated gate bipolar transistor (IGBT). Switching element 70 is inserted between the other end 812 of the primary coil L1 and the ground point (ground). The collector (C) of switching element 70 is connected to the other end 812 of the primary coil L1. The emitter (E) of switching element 70 is connected to ground. The gate (G) of switching element 70 is connected to the driver IC 71.

[0044] Thus, the switching element 70 can switch the primary current flowing from the power supply device 102 to the primary coil L1 on or off. When the switching element 70 is in the closed state, the primary current flows from the power supply device 102 to the primary coil L1. When the switching element 70 is in the open state, the primary current flowing to the primary coil L1 is cut off. However, other types of transistors can also be used for the switching element 70.

[0045] The driver 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 driver IC 71 has a logic device connected to the switching element 70. This logic device may include, for example, logic circuits, processors, CPLDs (complex programmable logic devices), FPGAs (field-programmable gate arrays), or ASICs (application-specific integrated circuits). The logic device performs calculations to activate the ignition device 1 to ignite the spark plug 113.

[0046] <1-2. Operation of the ignition device>

[0047] Next, the operation of ignition device 1 will be explained. Figure 3 It is a time-series graph showing the waveforms of the EST signal when the ignition device 1 is activated, the waveform of the secondary current flowing in the secondary coil L2, and the voltage (secondary voltage) generated at one end 822 of the secondary coil L2. Furthermore, regarding... Figure 3 The secondary current, when flowing forward in the limiting diode 114, is illustrated as negative, and when flowing backward in the limiting diode 114, it is illustrated as positive. Regarding Figure 3 The diagram shows the voltage value of one end 822 of the secondary coil L2 relative to the ground point (ground).

[0048] As described above, a DC voltage (e.g., 12V) is applied from the power supply unit 102 to one end 811 of the primary coil L1 via the power line 150. The other end 812 of the primary coil L1 is connected to the switching element 70. Furthermore, the driver IC 71 controls the switching of the switching element 70 based on the EST signal received from the ECU 105. Figure 3 As shown, when the ignition device 1 is activated, firstly, at time t0, the signal level of the EST signal sent from the ECU 105 to the drive IC 71 is changed from L to H. Then, the drive IC 71 switches the switching element 70 from an open state to a closed state based on the EST signal. As a result, a primary current flows through the primary wire 81 forming the primary coil L1, charging the primary coil L1. This process of charging the primary coil L1 by flowing a primary current through it will be referred to as "charging control." Furthermore, an electromagnetic flux is generated in the primary coil L1, and the corresponding magnetic field acts on the iron core 60.

[0049] Furthermore, a potential difference is generated between the two ends 821 and 822 of the secondary coil L2, which is electromagnetically coupled to the primary coil L1 via the iron core 60, through mutual inductance. That is, a turn-on voltage (e.g., 960V) is generated at the two ends 821 and 822 of the secondary coil L2. As a result, the maximum value of the voltage applied to one end 822 of the secondary coil L2 becomes a positive value (e.g., approximately positive 480V), and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 becomes a negative value (e.g., approximately negative 480V). Here, in this embodiment, a limiting diode 114 is inserted into the first connection line 122. The limiting diode 114 is forward-biased in the direction from one end 822 of the secondary coil L2 toward the other end 821 of the secondary coil L2. In addition, the breakdown voltage of the limiting diode 114 is 1kV or more, which is greater than the maximum value of the turn-on voltage. Therefore, reverse current flowing through the limiting diode 114 can be suppressed. That is, it can suppress the flow of current to the secondary coil L2 side via the first connection line 122. As a result, it can suppress the discharge in the spark plug 113 at an abnormal time when it is turned on.

[0050] After charging control is performed, at time t1, the signal level of the EST signal sent from ECU 105 to drive IC 71 is changed from H to L. Then, drive IC 71 switches switching element 70 from a closed state to an open state, thereby cutting off the primary current flowing from power supply device 102 to primary coil L1. As a result, an induced electromotive force is induced in the secondary coil L2, which is electromagnetically coupled to the primary coil L1 via iron core 60, through 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 at one end 822 of the secondary coil L2 reaches a negative value of several thousand V to tens of thousands of V relative to the ground point (ground).

[0051] Furthermore, 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. Therefore, insulation breakdown occurs at the gap d of the spark plug 113. Then, a voltage is generated from the ground point (ground) through the ground electrode 142 of the spark plug 113 to the center electrode 141 of the spark plug 113 (see reference). Figure 1 The current flows further into the secondary coil L2 and is positively oriented in the limiting diode 114. As a result, a spark is generated by discharging at the gap d of the spark plug 113, thereby igniting the fuel filled in the internal combustion engine. Furthermore, in this invention, the process of cutting off the primary current flowing to the primary coil L1 by switching the switching element 70 to the off state, thereby inducing a high voltage at one end 822 of the secondary coil L2 and causing discharge at the gap d of the spark plug 113, is called "discharge control". 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 insulation 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.

[0052] Here, as described above, a parasitic capacitance Cs consisting of approximately 15 pF to 20 pF of electrostatic capacitance is formed between one end 822 of the secondary coil L2 and the spark plug 113. Therefore, even at the point where the discharge temporarily ends at the gap d of the spark plug 113 (time t2), residual charge remains near the center electrode 141 of the spark plug 113, the second connecting wire 121, or one end 822 of the secondary coil L2. In this embodiment, negative charge remains at these locations. Consequently, at time t2, the voltage value at one end 822 of the secondary coil L2 becomes negative relative to the ground point (ground) (e.g., -3 kV). Hereinafter, this voltage value at one end 822 of the secondary coil L2 at time t2 will be referred to as the residual voltage value Rv. Furthermore, the absolute value of the residual voltage value Rv is smaller than the insulation breakdown voltage at the gap d of the spark plug 113. However, if this situation is ignored, there is a possibility that discharge may occur again in the gap d of spark plug 113 at unexpected times, such as when the pressure inside the internal combustion engine changes later.

[0053] Therefore, in this invention, a limiting diode 114 is used, whose breakdown voltage is smaller than the absolute value of the insulation breakdown voltage at the gap d of the spark plug 113 and the residual voltage value Rv. The limiting diode 114 used in this embodiment has a breakdown voltage of 2kV or less. In the example above, the residual voltage value Rv (anode side of the limiting diode 114) at one end 822 of the secondary coil L2 is negative (e.g., negative 3kV). On the other hand, the voltage applied to the power supply line 150 (cathode side of the limiting diode 114) is positive 12V, and the potential is significantly higher than the residual voltage value Rv. As a result, current flows in the reverse direction from the power supply device 102 side to the limiting diode 114 for a short period of time (time t2 to time t3). That is, current flows through the first connection line 122 to the vicinity of one end 822 of the secondary coil L2.

[0054] This eliminates residual charge near the center electrode 141 of the spark plug 113, the second connecting wire 121, or one end 822 of the secondary coil L2. Furthermore, it reduces the absolute value of the voltage (secondary voltage) generated at one end 822 of the secondary coil L2, thus reducing residual energy in these areas. As a result, even if the pressure inside the internal combustion engine changes subsequently, it can suppress unexpected discharge at the gap d of the spark plug 113. This phenomenon continues until the potential difference between the voltage (secondary voltage) generated at one end 822 of the secondary coil L2 on the anode side of the limiting diode 114 and the voltage applied to the power line 150 on the cathode side of the limiting diode 114 equals the breakdown voltage of the limiting diode 114. Here, the absolute value of the voltage (secondary voltage) generated at one end 822 of the secondary coil L2 is significantly greater than the absolute value of the voltage applied to the power line 150. Therefore, this phenomenon can be considered to continue until the secondary voltage (at one end 822 of the secondary coil L2) equals the breakdown voltage of the limiting diode 114. Figure 3 The absolute value of the voltage (Vz) is approximately equal to the breakdown voltage of the limiting diode 114. Furthermore, the absolute value of the voltage at one end 822 of the secondary coil L2 (secondary voltage) will decrease further (from time t3 to time t4) due to 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 the flow of leakage current in the limiting diode 114.

[0055] Furthermore, as described above, the breakdown voltage of the limiting diode 114 is lower than the insulation breakdown voltage at the gap d of the spark plug 113. Therefore, it is possible to allow current flowing from the power supply unit 102 side into the limiting diode 114 in reverse direction and via the first connection line 122 to the vicinity of one end 822 of the secondary coil L2. As a result, residual energy is reduced, thus suppressing the re-discharge at the gap d of the spark plug 113 after time t2, i.e., at an abnormal time.

[0056] As described above, in this invention, when the primary current flows through the primary coil L1 (when it is turned on), the current is prevented from flowing in reverse through the limiting diode 114 and towards the secondary coil L2. This suppresses the abnormal discharge that occurs in the spark plug 113 at the moment of turn-on. On the other hand, after the discharge ends, the current is reversed through the limiting diode 114 and flows towards the vicinity of one end 822 of the secondary coil L2, thereby reducing residual energy near the center electrode 141 of the spark plug 113, the second connecting wire 121, or one end 822 of the secondary coil L2. This suppresses the re-discharge at the gap d of the spark plug 113 at the moment of abnormal discharge. As a result, even in internal combustion engines using fuel containing hydrogen, which has the characteristics of being easily combusted at relatively low temperatures and having a fast combustion rate, the abnormal ignition of the fuel can be suppressed, thereby preventing damage to the engine, etc.

[0057] Furthermore, in this embodiment, by inserting a limiting diode 114 into the first connecting line 122 of the ignition coil 103, a structure that solves the problem of the present invention can be provided. On the other hand, in conventional ignition coils, there is a situation where other components, different from Zener diodes and avalanche diodes, are arranged at a position corresponding to the first connecting line. That is, in this embodiment, it is only necessary to replace other components in conventional ignition coils with the limiting diode 114. Therefore, the operability of manufacturing the ignition device 1 of this embodiment can be improved and manufacturing costs can be reduced.

[0058] <2. Variations>

[0059] The exemplary embodiments of the present invention have been described above, but the present invention is not limited to the embodiments described above.

[0060] Figure 4 This is a block diagram schematically illustrating the operating environment of the ignition device 1 according to the first modified example. In the above embodiment, the limiting diode 114 is inserted into the first connection line 122 that connects the other end 821 of the secondary coil L2 to the power supply line 150. However, as Figure 4 As shown in the first modification, the limiting diode 114 can also be inserted into the second connecting wire 121 that connects one end 822 of the secondary coil L2 to the spark plug 113. Furthermore, in this modification, the limiting diode 114 is also positively oriented in the direction from one end 822 of the secondary coil L2 toward the other end 821 of the secondary coil L2. Additionally, the limiting diode 114 in this modification uses a limiting diode 114 with the same specifications as in the embodiment described above. Furthermore, the structure of all parts of the ignition device 1 in this modification, except for the limiting diode 114, is the same as the structure of all parts of the ignition device 1 in the embodiment described above, except for the limiting diode 114.

[0061] In this modified example, firstly, when a primary current flows through the primary coil L1 to charge it as a charging control (when switched on), a potential difference is generated between the two ends 821 and 822 of the secondary coil L2 through mutual inductance. That is, when switched on, a switching voltage (e.g., 960V) is generated at the two ends 821 and 822 of the secondary coil L2. Furthermore, the maximum voltage applied to one end 822 of the secondary coil L2 is positive (e.g., approximately positive 480V), and the minimum voltage applied to the other end 821 of the secondary coil L2 is negative (e.g., approximately negative 480V). Here, in this modified example, a limiting diode 114 is inserted into the second connection line 121. The limiting diode 114 is positive in the direction from one end 822 of the secondary coil L2 toward the other end 821 of the secondary coil L2. Therefore, reverse current flow from the power supply device 102 side into the limiting diode 114 can be suppressed. That is, it can suppress the flow of current through the first connecting wire 122 to the secondary coil L2 and the spark plug 113. As a result, it can suppress the abnormal discharge that occurs in the spark plug 113 at the moment of energization.

[0062] Furthermore, after the discharge is complete, current flows from the power supply unit 102 side through the first connecting line 122 to the secondary coil L2 and spark plug 113, thereby reducing residual energy near the center electrode 141 of spark plug 113, the second connecting line 121, or one end 822 of the secondary coil L2. That is, by reversing the current flow in the limiting diode 114, residual energy near the center electrode 141 of spark plug 113, the second connecting line 121, or one end 822 of the secondary coil L2 can be reduced. This prevents re-discharge at the gap d of spark plug 113 at an abnormal time after the discharge is complete.

[0063] In the above-described embodiments and the first variation, the voltage applied to one end 822 of the secondary coil L2 during charging control is positive, and the voltage applied to the other end 821 of the secondary coil L2 is negative. Furthermore, during discharging control, a negative high voltage of several thousand to tens of thousands of V is induced at one end 822 of the secondary coil L2. However, the positive and negative values ​​of the voltages presented at the two ends 821 and 822 of the secondary coil L2 can 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 orientations of the limiting diode 114 inserted into the first connecting line 122 or the second connecting line 121 can be reversed.

[0064] In the above-described embodiments and the first variation, the cathode side of the limiting diode 114 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 5 The second variation and Figure 6 As shown in the third variation, the cathode side of the limiting diode 114 and the other end 821 of the secondary coil L2 are connected to a ground point (ground). That is, the limiting diode 114 can also be inserted into the first connecting line 122 that directly or indirectly connects the other end 821 of the secondary coil L2 to the ground point (ground), and the direction from one end 822 of the secondary coil L2 toward the other end 821 of the secondary coil L2 is positive. This limiting diode 114 is a Zener diode or an avalanche diode.

[0065] like Figure 5 and Figure 6 As shown, in the second and third modifications, firstly, when a primary current flows through the primary coil L1 to charge the primary coil L1 as a charging control (when switched on), a potential difference is generated between the two ends 821 and 822 of the secondary coil L2 through mutual inductance. That is, when switched on, a switching voltage (e.g., 960V) is generated at the two ends 821 and 822 of the secondary coil L2. Furthermore, the maximum value of the voltage applied to one end 822 of the secondary coil L2 is positive (e.g., approximately positive 480V), and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is negative (e.g., approximately negative 480V). Here, in the second modification, a limiting diode 114 is inserted into the first connection line 122. In the third modification, a limiting diode 114 is inserted into the second connection line 121. The limiting diode 114 is positive in the direction from one end 822 of the secondary coil L2 toward the other end 821 of the secondary coil L2. Therefore, by allowing current to flow from one end 822 of the secondary coil L2 to the other end 821 and further to the ground point (ground), the voltage is reduced during swivel. As a result, it is possible to suppress discharge in the spark plug 113 at an abnormal moment during swivel.

[0066] Furthermore, after the discharge is complete, by reversing the current flow from the ground point (ground) side through the limiting diode 114 to one end 822 of the secondary coil L2 and near the center electrode 141 of the spark plug 113, residual energy remaining near the center electrode 141 of the spark plug 113, the second connecting wire 121, or one end 822 of the secondary coil L2 can be reduced. This prevents re-discharge from occurring in the gap d of the spark plug 113 at an abnormal time after the discharge is complete.

[0067] The ignition device of the present invention can be used not only in automobiles and other vehicles, but also in various devices such as generators and industrial machinery, and is used to generate an electric spark in the spark plug of an internal combustion engine to ignite fuel.

[0068] The shape and structure of the ignition device described above can be appropriately modified without departing from the spirit of the invention. Furthermore, the elements appearing in the above embodiments and variations can be appropriately combined without creating contradictions.

[0069] Explanation of reference numerals in the attached figures

[0070] 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; 114: Limiting diode; 121: Secondary connection wire; 122: Primary connection wire; 150: Power supply wire; 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: Driver IC (control unit); L1: Primary coil; L2: Secondary coil; Rv: Residual voltage value; d: (Spark plug) gap.

Claims

1. An ignition device for an internal combustion engine using fuel containing at least hydrogen. The ignition device has: An ignition coil is formed by the electromagnetic coupling between 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 line; A switching element, inserted between the other end of the primary coil and a ground point, is capable of switching the primary current flowing from the power supply device to the primary coil on or off. A spark plug, which discharges in the gap based on a high voltage induced at one end of the secondary coil, thereby igniting the fuel; A limiting diode, inserted into a first or second connecting line, and positively oriented in the direction from one end of the secondary coil to the other end of the secondary coil, wherein the limiting diode is a Zener diode or an avalanche diode, wherein the first connecting line is a connecting line that directly or indirectly connects the other end of the secondary coil to the power supply or ground point, and the second connecting line is a connecting line that connects one end of the secondary coil to the spark plug; and The control unit controls the switching of the switching elements. The breakdown voltage of the limiting diode is greater than the maximum value of the voltage when switched on, and is below 2kV. The maximum value of the voltage when switched on is obtained by multiplying the DC voltage applied by 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. The control unit performs the following controls: The charging control involves closing the switching element to allow primary current to flow through the primary coil, thereby charging the primary coil. Discharge control involves switching the switching element to the off state after the charging control is performed, thereby inducing a high voltage at one end of the secondary coil, which in turn causes discharge to occur in the spark plug gap. From the point when the discharge at the gap of the spark plug temporarily ends, the current flows in reverse in the limiting diode.

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

3. The ignition device according to claim 1 or claim 2, wherein, It also has a parasitic capacitance formed between one end of the secondary coil and the spark plug.

4. The ignition device according to claim 1 or claim 2, wherein, The breakdown voltage is lower than the insulation breakdown voltage at the gap of the spark plug.

5. The ignition device according to claim 1 or claim 2, wherein, The limiting diode is inserted into the first connecting line.

6. The ignition device according to claim 1 or claim 2, wherein, The limiting diode is inserted into the second connection line.

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