JP2023179016A - Ignition device - Google Patents

Abstract

To provide a technique which can prevent an electric discharge in an ignition plug at an abnormal timing.SOLUTION: An ignition device 1 for an internal combustion engine using a fuel containing hydrogen has an ignition coil 103 including a primary coil L1 and a secondary coil L2, a power supply device 102, a switching element 70, an ignition plug 113, a first backflow prevention diode 111, and a first resistance 112. The switching element 70 make a switch to carrying or interrupting a primary current flowing to the primary coil L1. The ignition plug 113 discharges electric on the basis of a high voltage inducted at one end 822 of the secondary coil L2. Between the other end 821 of the secondary coil L2 and the power supply device 102, two first connection lines 122a, 122b are arranged in parallel. The first backflow prevention diode 111 is inserted in the first connection line 122a, and has a forward direction from the one end 822 of the secondary coil L2 to the other end 821. The first resistance 112 is inserted in the first connection line 122b, and has a resistance value of 1 MΩ or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ignition device for an internal combustion engine.

Conventionally, internal combustion engines including SI (spark ignition) reciprocating engines used in automobiles and the like are equipped with an ignition device. The ignition coil of the ignition device boosts the low DC voltage supplied from the battery to several thousand to tens of thousands of V under the control of the ECU (Engine Control Unit), supplies it to the spark plug, and generates an electric spark. ignite the fuel. An example of a conventional ignition device is described in, for example, Patent Document 1.

Patent No. 6517088

Patent Document 1 discloses an ignition device (1) for an internal combustion engine having the following configuration. First, the primary coil (21) of the ignition coil (2) is connected to a DC power source (VB+) such as an on-board battery, and the primary coil (21) flowing through the primary coil (21) is controlled by the on/off control of the main switching element (4). The current (I1) is turned on and off (paragraph 0015, FIG. 1). Also, 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 is connected to the ON voltage prevention diode (23). It is connected to the DC power supply line through. As a result, when the primary current (I1) of the ignition coil (2) is interrupted, a high voltage is generated on the secondary side, causing dielectric breakdown in the discharge gap of the ignition plug (3), and the ON voltage prevention diode (23). A secondary current (I2) flows in the forward direction. (paragraph 0016,0029). On the other hand, the reverse polarity ON voltage generated in the secondary coil (22) at the start of energization to the primary coil (21) is suppressed by the ON voltage prevention diode (23) (paragraph 0017).

In recent years, fuels containing hydrogen have been increasingly used in SI (spark ignition) reciprocating engines. It is believed that the use of fuel 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 burning rate. Therefore, for example, if a slight discharge occurs at an unexpected timing in the spark plug, the fuel may ignite and burn. In this case, abnormalities such as backfire, where flame blows back from the engine's combustion chamber toward the intake system, afterfire, where fuel remaining in the engine exhaust gas burns in the exhaust flow path, or pre-ignition, where the ignition timing cannot be controlled, may occur. There is a risk of combustion.

An object of the present invention is to provide a technique that can suppress discharge from occurring at an unexpected timing (abnormal timing) in a spark plug.

In order to solve the above problems, a first invention of the present application is an ignition device for an internal combustion engine using fuel containing at least hydrogen, which includes an ignition coil, a power supply device, a switching element, a spark plug, and a first invention. It has a backflow prevention diode and a first resistor. The ignition coil is formed by electromagnetically coupling a primary coil and a secondary coil to each other. 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 between energization and interruption of the primary current flowing from the power supply device to the primary coil. The spark plug ignites the fuel by discharging in the gap based on a high voltage induced at one end of the secondary coil. The first backflow prevention diode is inserted in one of two first connection wires wired in parallel between the other end of the secondary coil and the power supply device or the ground point, and This is a diode that has a forward direction in the direction from one end of the coil to the other end. The first resistor is inserted in the other of the two first connection lines. The resistance value of the first resistor is 1 MΩ or more.

A second invention of the present application is the ignition device of the first invention, wherein the other of the two first connection wires is inserted in series with the first resistor, and the other of the two first connection wires is connected to the other end of the secondary coil. It further comprises a first limiting diode, which is a Zener diode or an avalanche diode, which is forward in the direction towards the end, and the breakdown voltage of the first limiting diode is less than the breakdown voltage at the gap of the spark plug.

A third invention of the present application is the ignition device of the first invention, in which the resistance value of the first resistor is 10 MΩ or less.

A fourth invention of the present application is an ignition device for an internal combustion engine using fuel containing at least hydrogen, which includes an ignition coil, a power supply device, a switching element, a spark plug, a second backflow prevention diode, and a second backflow prevention diode. has a resistance. The ignition coil is formed by electromagnetically coupling a primary coil and a secondary coil to each other. 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 between energization and interruption of the primary current flowing from the power supply device to the primary coil. The spark plug ignites the fuel by discharging in the gap based on a high voltage induced at one end of the secondary coil. The second backflow prevention diode is inserted in one of two second connection wires wired in parallel between one end of the secondary coil and the spark plug, and This is a diode that has a forward direction in the direction toward the other end. The second resistor is inserted in the other of the two second connection lines. The resistance value of the second resistor is 1 MΩ or more.

A fifth invention of the present application is the ignition device according to the fourth invention, wherein the other of the two second connection wires is inserted in series with the second resistor, and the other one of the two second connection wires is connected to the other end of the secondary coil. It further comprises a second limiting diode, which is a Zener diode or an avalanche diode, which is forward in the direction towards the end, and the breakdown voltage of the second limiting diode is less than the breakdown voltage at the gap of the spark plug.

A sixth invention of the present application is the ignition device according to the fourth invention, in which the resistance value of the second resistor is 10 MΩ or less.

A seventh invention of the present application is the ignition device according to any one of the first to sixth inventions, further comprising a control unit that controls switching of the switching element, and the control unit is configured to control switching of the switching element. After the charging control is performed, the switching element is switched to the open state and one end of the secondary coil is charged. Discharge control is performed in which discharge is caused in the gap of the spark plug by inducing a high voltage.

An eighth invention of the present application is the ignition device according to any one of the first to sixth inventions, which has a stray capacitance formed between one end of the secondary coil and the spark plug.

A ninth invention of the present application is the ignition device according to the second invention or the fifth invention, wherein the breakdown voltage is 2 kV or less.

According to the first to ninth inventions of the present application, when a primary current is passed through the primary coil (ON time), current flows through the resistor and voltage is applied, so that the ON time occurs in the secondary coil L2. Voltage can be reduced. Thereby, it is possible to suppress discharge from occurring in the spark plug when it is turned on. Further, after the discharge ends, residual energy remaining near one end of the secondary coil, near the spark plug, etc. can be reduced. As a result, subsequent occurrence of discharge at abnormal timing in the spark plug can be further suppressed.

In particular, according to the second invention of the present application, after the discharge ends, the current flows in the opposite direction in the first limiting diode toward the secondary coil without causing discharge to occur again in the ignition plug. Thereby, it is possible to cancel the electric charge remaining in the vicinity of one end of the secondary coil, the vicinity of the spark plug, etc., and reduce the residual energy remaining in these places. As a result, subsequent occurrence of discharge at abnormal timing in the spark plug can be further suppressed.

In particular, according to the third invention of the present application, by reducing the resistance value of the first resistor to a certain extent, it is possible to maintain the current flowing toward the secondary coil through the first resistor at a certain level or more after the discharge ends. . This cancels out the charge remaining near one end of the secondary coil, near the spark plug, etc., and further reduces the residual energy remaining at these locations.

In particular, according to the fifth invention of the present application, after the discharge ends, the current flows in the opposite direction in the second limiting diode toward the vicinity of the spark plug without causing discharge to occur again in the spark plug. Thereby, it is possible to cancel the electric charge remaining in the vicinity of one end of the secondary coil, the vicinity of the spark plug, etc., and reduce the residual energy remaining in these places. As a result, subsequent occurrence of discharge at abnormal timing in the spark plug can be further suppressed.

In particular, according to the sixth aspect of the present application, by reducing the resistance value of the second resistor to a certain extent, it is possible to maintain the current flowing toward the vicinity of the spark plug via the second resistor to a certain level or more after the discharge ends. This cancels out the charge remaining near one end of the secondary coil, near the spark plug, etc., and further reduces the residual energy remaining at these locations.

FIG. 1 is a block diagram schematically showing an operating environment of an ignition device for an internal combustion engine according to a first embodiment. FIG. 2 is a longitudinal cross-sectional view of the ignition coil according to the first embodiment. The waveform of the EST signal, the waveform of the current flowing through the secondary coil (secondary current), and the voltage generated at one end of the secondary coil (secondary voltage) when operating the ignition device according to the first embodiment. , are graphs shown in chronological order. FIG. 2 is a block diagram schematically showing an operating environment of an ignition device for an internal combustion engine according to a first modification. FIG. 2 is a block diagram schematically showing an operating environment of an ignition device for an internal combustion engine according to a second embodiment. FIG. 3 is a block diagram schematically showing an operating environment of an ignition device for an internal combustion engine according to a second modification. FIG. 3 is a block diagram schematically showing an operating environment of an ignition device for an internal combustion engine according to a third modification. FIG. 12 is a block diagram schematically showing an operating environment of an ignition device for an internal combustion engine according to a fourth modification.

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

<1. First embodiment>
<1-1. Ignition system configuration>
First, the configuration of an ignition device 1 for an internal combustion engine, which is a first embodiment of the present invention, will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing the operating environment of the ignition device 1 according to the first embodiment. As will be described later, the primary coil L1 and the secondary coil L2 of the ignition coil 103 included in the ignition device 1 are arranged in a direction in which they are stacked on each other, but in FIG. 1, these are shown for ease of understanding. They are shown adjacent to each other.

The ignition device 1 of this embodiment is installed in an internal combustion engine such as an SI (spark ignition) reciprocating engine used in a vehicle body 100 of an automobile, for example, and applies a high voltage to a spark plug 113 to generate spark discharge. It is a device. Further, as shown in FIG. 1, the vehicle body 100 includes, in addition to the ignition device 1, the spark plug 113, a power supply device 102 (battery), and an ECU 105 (Engine Control Unit). Note that, 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.

The spark plug 113 is a device for realizing an ignition operation in a combustion chamber of an internal combustion engine. The spark plug 113 is electrically connected to one end 822 of a secondary coil L2 of the ignition coil 103, which will be described later, via a conducting wire (hereinafter referred to as "second connection wire 121"). The spark plug 113 is inserted between one end 822 of the secondary coil L2 and a ground point. A high voltage is induced in the secondary coil L2 of the ignition coil 103, and when this high voltage exceeds the dielectric breakdown voltage at the gap d (see FIG. 1) between the center electrode 141 and the ground electrode 142 of the ignition plug 113, the gap A discharge occurs at point d, producing a spark. As a result, the fuel filled in the internal combustion engine is ignited. That is, the spark plug 113 ignites the fuel by discharging in the gap d based on the high voltage induced at one end 822 of the secondary coil L2.

Note that in this embodiment, hydrogen or a mixture of hydrogen and another substance is used as the fuel. That is, the ignition device 1 for an internal combustion engine uses fuel containing at least hydrogen.

Further, the second connection line 121 and the spark plug 113 have a capacitance component of about 15 to 20 pF. That is, a capacitance component is formed between one end 822 of the secondary coil L2 and the spark plug 113. Hereinafter, this capacitance component will be referred to as a hypothetically defined "stray capacitance Cs." As shown in FIG. 1, the stray capacitance Cs can be schematically represented in parallel with the spark plug 113 in a block diagram.

The power supply device 102 is a power supply device (storage battery) that can charge and discharge DC power. In this embodiment, the power supply device 102 is electrically connected to a primary coil L1 of an ignition coil 103, which will be described later, via a conductive wire (hereinafter referred to as "power wire 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.

The ECU 105 is an existing computer that comprehensively controls the transmission, airbag operation, etc. of the vehicle body 100.

The ignition device 1 includes an ignition coil 103, an igniter 104, a first backflow prevention diode 111, a first resistor 112, and a first limiting diode 114.

FIG. 2 is a longitudinal cross-sectional view of the ignition coil 103. As shown in FIG. 2, the ignition coil 103 includes a bobbin 40, a primary coil L1, a secondary coil L2, and an iron core 60. In addition, in FIG. 2, the primary coil L1 and the secondary coil L2 are partially simplified and illustrated. In the following description of the ignition coil 103, a direction parallel to the central axis Bc of the bobbin 40 is referred to as an "axial direction", a direction orthogonal to the central axis Bc of the bobbin 40 is referred to as a "radial direction", and a direction parallel to the central axis Bc of the bobbin 40 is referred to as a "radial direction". The direction along the arc centered at is referred to as the "circumferential direction." Further, the "parallel directions" include substantially parallel directions, and the "perpendicular directions" include substantially orthogonal directions.

The bobbin 40 includes a primary bobbin 41 and a secondary bobbin 42 that can be connected to each other. The primary bobbin 41 and the secondary bobbin 42 each extend in a cylindrical shape along the central axis Bc. Further, a secondary bobbin 42 is arranged outside the primary bobbin 41 in the radial direction. For example, resin is used as the material for the primary bobbin 41 and the secondary bobbin 42.

The primary coil L1 is formed by winding a conducting wire (hereinafter referred to as "primary conducting wire 81") around the outer peripheral surface of the primary bobbin 41 in the circumferential direction around the central axis Bc. After the formation of the primary coil L1 is completed, the secondary bobbin 42 is arranged and connected to the primary bobbin 41 so as to cover the outer peripheral surface of the primary coil L1. A conductor wire (hereinafter referred to as "secondary conductor wire 82") that is different from the primary conductor wire 81 is wound around the outer peripheral surface of the secondary bobbin 42 in the circumferential direction around the central axis Bc. A secondary coil L2 is formed. In this way, by arranging the primary coil L1 and the secondary coil L2 so as to be stacked on each other, the entire ignition coil 103 including these can be downsized. However, the primary coil L1 and the secondary coil L2 are not limited to being wound while being stacked on each other in this way, but may also be arranged adjacent to each other as shown in FIG.

The iron core 60 has a structure in which a central iron core 601 and an outer peripheral iron core 602 are combined. The center core 601 and the outer core 602 of the core 60 are each formed of, for example, a laminated steel plate in which silicon steel plates are laminated. The central iron core 601 extends along the central axis Bc of the bobbin 40. Further, the center core 601 is inserted into a space 410 inside the primary bobbin 41 in the radial direction. The outer core 602 passes radially outside the secondary bobbin 42 and the secondary conducting wire 82 and connects both ends of the center core 601 in the axial direction. Thereby, the iron 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 to each other.

As shown in FIG. 1, a power line 150, which is a conducting wire extending from the power supply device 102 described above, 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. Under the control of the igniter 104, a low DC voltage from the power supply device 102 is applied to one end 811 of the primary coil L1, and a gradually increasing primary current begins to flow through the primary coil L1.

One end 822 of the secondary coil L2 is connected to the spark plug 113. The wire diameter of the secondary conducting wire 82 is smaller than the wire diameter of the primary conducting wire 81. Further, the number of turns of the secondary conducting wire 82 in the secondary coil L2 (for example, 8000 turns) is about 80 times or more the number of turns (for example, 100 turns) of the primary conducting wire 81 in the primary coil L1. As a result, as will be described in detail later, the ignition coil 103 boosts the low voltage DC power supplied from the power supply device 102 to several thousand volts to tens of thousands of volts when the primary current is cut off. That is, a high voltage is induced in the secondary coil L2. The secondary coil L2 then supplies the induced high voltage power to the spark plug 113. This causes an electric spark to be generated in the ignition plug 113 to ignite the fuel.

As shown in FIG. 1, the other end 821 of the secondary coil L2 opposite to the one end 822 to which the spark plug 113 is connected has two conductive wires (hereinafter referred to as "first connection wire 122a" and It is directly or indirectly electrically connected to the power supply device 102 via a "first connection line 122b"). The first connection lines 122a and 122b are wired in parallel between the other end 821 of the secondary coil L2 and the power supply device 102. In this embodiment, the other end 821 of the secondary coil L2 is electrically connected to the power supply line 150 via the first connection line 122a or the first connection line 122b.

Further, in this embodiment, the first backflow prevention diode 111 is inserted in the first connection line 122a, which is one of the two first connection lines 122a and 122b. The first backflow prevention diode 111 is connected in series with the secondary coil L2. The first backflow prevention diode 111 of this embodiment is a normal diode that has the function of allowing current to flow in only one direction. Further, the first backflow prevention diode 111 is in the forward direction in the direction from one end 822 of the secondary coil L2 to the other end 821.

Further, in this embodiment, the first resistor 112 is inserted in the first connection line 122b, which is the other of the two first connection lines 122a and 122b. The first resistor 112 is connected in series with the secondary coil L2. Further, the resistance value of the first resistor 112 of this embodiment is 1 MΩ or more and 10 MΩ or less.

Further, in this embodiment, the first limiting diode 114 is further inserted in the first connecting line 122b, which is the other of the two first connecting lines 122a and 122b. The first limiting diode 114 is connected in series with the secondary coil L2 and the first resistor 112, respectively. A Zener diode is used as the first limiting diode 114 in this embodiment. However, an avalanche diode may be used as the first limiting diode 114. Further, the first limiting diode 114 is in the forward direction in the direction from one end 822 of the secondary coil L2 to the other end 821.

Further, in the present invention, a diode whose breakdown voltage is smaller than the dielectric breakdown voltage at the gap d of the spark plug 113 is used as the first limiting diode 114. The breakdown voltage of the first limiting diode 114 used in this embodiment is 2 kV or less. The effect of setting the breakdown voltage of the first limiting diode 114 to 2 kV or less will be described in detail later.

As will be described in detail later, when the switching element 70 of the igniter 104 is closed and the primary current is passed through the primary coil L1 to charge it (when ON), a potential difference is generated between both ends 821 and 822 of the secondary coil L2. In this embodiment, when the secondary coil L2 is turned on, one end 822 of the secondary coil L2 has a higher voltage than the other end 821. Hereinafter, the potential difference between one end 822 and the other end 821 of the secondary coil L2 will be referred to as "ON voltage". The maximum value of the ON voltage is determined by the voltage value of the DC voltage applied from the power supply device 102 to one end 811 of the primary coil L1 via the power line 150, and the number of turns of the secondary coil L2 relative to the number of turns of the primary coil L1. It is calculated by multiplying the ratio of numbers.

For example, if the voltage value of the DC voltage applied to one end 811 of the primary coil L1 is 12V, the number of turns of the primary coil L1 is 100, and the number of turns of the secondary coil L2 is 8000, then the primary coil Since the ratio of the number of turns of the secondary coil L2 to the number of turns of L1 is 80, the maximum value of the ON voltage is calculated as 12×80=960V. Therefore, the maximum value of the voltage applied to one end 822 of the secondary coil L2 is, for example, about +480V, and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is, for example, about -480V. Further, in some cases, it may be assumed 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 -960V. On the other hand, at this time, the voltage applied to the power supply line 150 is 12V.

Here, as described above, the breakdown voltage of the first limiting diode 114 is 2 kV or less (for example, 490 V). Therefore, when the primary current flows through the primary coil L1 (when ON), the minimum voltage (for example, -480V) applied to the other end 821 (anode side of the first limiting diode 114) of the secondary coil L2 ), the voltage value (for example, plus 12 V) applied to the power supply line 150 (the cathode side of the first limiting diode 114) becomes larger than the difference exceeding the breakdown voltage (for example, 490 V) of the first limiting diode 114. In this case, current flows in the opposite direction in the first limiting diode 114. That is, the current flows from the power supply device 102 side to the secondary coil L2 side via the first connection line 122b. Note that no current flows through the first connection line 122a into which the first backflow prevention diode 111 is inserted.

However, the first resistor 112 is inserted in the first connection line 122b in series with the first limiting diode 114. The resistance value of the first resistor 112 is 1 MΩ or more. Thereby, when a current flows through the first connection line 122b, a voltage is applied to the first resistor 112, and as a result, the ON voltage generated in the secondary coil L2 can be reduced. As a result, it is possible to suppress discharge from occurring in the spark plug 113 when it is turned on, that is, at abnormal timing.

On the other hand, when the primary current flows through the primary coil L1 (when ON), the minimum value of the voltage applied to the other end 821 (anode side of the first limiting diode 114) of the secondary coil L2 (for example, -480V) On the other hand, if the voltage value (for example, plus 12 V) applied to the power supply line 150 (the cathode side of the first limiting diode 114) does not become larger than the difference exceeding the breakdown voltage (for example, 5500 V) of the first limiting diode 114. In this case, it is possible to prevent the current from flowing in the opposite direction in the first limiting diode 114, that is, through the first connection line 122b to the secondary coil L2 side. That is, even in this case, it is possible to suppress discharge from occurring in the spark plug 113 when it is turned on, that is, at an abnormal timing.

The igniter 104 is a semiconductor device that is connected to the primary coil L1 and controls the current flowing through the primary coil L1. Further, the igniter 104 is electrically connected to the ECU 105 and receives a signal (hereinafter referred to as "EST signal") from the ECU 105. The igniter 104 includes a switching element 70 and a drive IC 71. Note that the igniter 104 may be integrated with the electronic circuit of the ECU 105.

For example, an insulated gate bipolar transistor (IGBT) is used as the switching element 70. The switching element 70 is inserted between the other end 812 of the primary coil L1 and a ground point (ground). C (collector) of the switching element 70 is connected to the other end 812 of the primary coil L1. E (emitter) of the switching element 70 is connected to ground. G (gate) of the switching element 70 is connected to the drive IC 71.

Thereby, the switching element 70 can switch between energization and interruption of the primary current flowing from the power supply device 102 to the primary coil L1. When the switching element 70 is in the closed state, a primary current flows from the power supply device 102 to the primary coil L1. When the switching element 70 becomes open, the primary current flowing through the primary coil L1 is cut off. However, other types of transistors may be used as the switching element 70.

The drive IC 71 is a control unit that controls switching of the switching element 70 based on the EST signal received from the ECU 105. Drive IC 71 has a logic device connected to switching element 70. Logic devices include, for example, logic circuits, processors, CPLDs (complex programmable logic devices), FPGAs (field-programmable gate arrays), or ASICs (application-specific integrated devices). circuit), etc. The logic device performs arithmetic processing to operate the ignition device 1 and ignite the spark plug 113.

<1-2. Ignition system operation>
Next, the operation of the ignition device 1 will be explained. FIG. 3 shows the waveform of the EST signal, the waveform of the current flowing through the secondary coil L2 (secondary current), and the voltage (secondary voltage) generated at one end 822 of the secondary coil L2 when the ignition device 1 is operated. This is a graph showing each of these in chronological order. Regarding the secondary current in FIG. 3, the direction from one end 822 of the secondary coil L2 to the other end 821 is negative, and the direction from the other end 821 of the secondary coil L2 to one end 822 is shown as positive. . Regarding the secondary voltage in FIG. 3, the value of the voltage applied to one end 822 of the secondary coil L2 with respect to the ground point (ground) is illustrated.

As described above, a DC voltage (for example, 12V) is applied from the power supply device 102 to one end 811 of the primary coil L1 via the power supply line 150. Further, the other end 812 of the primary coil L1 is connected to the switching element 70. Further, the drive IC 71 controls switching of the switching element 70 based on the EST signal received from the ECU 105. As shown in FIG. 3, when operating the ignition device 1, first at time t0, the signal level of the EST signal transmitted from the ECU 105 to the drive IC 71 is changed from L to H. Then, the drive IC 71 switches the switching element 70 from the open state to the closed state based on the EST signal. As a result, a primary current flows through the primary conducting wire 81 forming the primary coil L1, and the primary coil L1 is charged with an electric charge (hereinafter, such a primary current flows through the primary coil L1 to charge the primary coil L1). This process is called "charging control"). In addition, electromagnetic flux is generated in the primary coil L1, and a magnetic field corresponding to the electromagnetic flux acts on the iron core 60.

Furthermore, a potential difference, that is, an ON voltage (for example, 960 V) is generated at both ends 821 and 822 of the secondary coil L2, which is electromagnetically coupled to the primary coil L1 via the iron core 60, due to mutual induction. As a result, the maximum value of the voltage applied to one end 822 of the secondary coil L2 becomes a positive value (for example, approximately +480V), and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 becomes a negative value (for example, (approximately -480V). At this time, the voltage applied to the power supply line 150 is, for example, 12V.

Here, the first resistor 112 and the first limiting diode 114 are inserted into the first connection line 122b that connects the other end 821 of the secondary coil L2 and the power supply line 150. The first limiting diode 114 has a forward direction in the direction from one end 822 to the other end 821 of the secondary coil L2, and the breakdown voltage of the first limiting diode 114 is 2 kV or less (for example, 490 V). Therefore, when the primary current flows through the primary coil L1 (when ON), the minimum voltage (for example, -480V) applied to the other end 821 (anode side of the first limiting diode 114) of the secondary coil L2 ), the voltage value (for example, plus 12 V) applied to the power supply line 150 (the cathode side of the first limiting diode 114) becomes larger than the difference exceeding the breakdown voltage (for example, 490 V) of the first limiting diode 114. In this case, current flows in the opposite direction in the first limiting diode 114. That is, the current (secondary current) flows from the power supply device 102 side to the secondary coil L2 side via the first connection line 122b. Note that since the first backflow prevention diode 111 is inserted in the first connection line 122a so that the forward current direction is from one end 822 to the other end 821 of the secondary coil L2, no current flows.

However, the first resistor 112 is inserted in the first connection line 122b in series with the first limiting diode 114. The resistance value of the first resistor 112 is 1 MΩ or more. As a result, when a current flows through the first connection line 122b, a sufficiently large voltage is applied to the first resistor 112, and as a result, the ON voltage and secondary voltage generated in the secondary coil L2 are reduced. can be reduced. As a result, it is possible to suppress discharge from occurring in the spark plug 113 when it is turned on, that is, at abnormal timing.

On the other hand, when the primary current flows through the primary coil L1 (when ON), the minimum value of the voltage applied to the other end 821 (anode side of the first limiting diode 114) of the secondary coil L2 (for example, -480V) On the other hand, if the voltage value (for example, plus 12 V) applied to the power supply line 150 (the cathode side of the first limiting diode 114) does not become larger than the difference exceeding the breakdown voltage (for example, 5500 V) of the first limiting diode 114. In this case, it is possible to prevent the current (secondary current) from flowing in the opposite direction in the first limiting diode 114, that is, through the first connection line 122b to the secondary coil L2 side. That is, even in this case, it is possible to suppress discharge from occurring in the spark plug 113 when it is turned on, that is, at an abnormal timing.

After performing charging control, at time t1, the signal level of the EST signal transmitted from the ECU 105 to the drive IC 71 is changed from H to L. Then, the drive IC 71 switches the switching 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 in the secondary coil L2 which is electromagnetically coupled to the primary coil L1 via the iron core 60 due to mutual induction. In this embodiment, a negative high voltage is induced at one end 822 of the secondary coil L2. At this time, the voltage value (secondary voltage value) applied to one end 822 of the secondary coil L2 ranges from minus several thousand volts to tens of thousands of volts with respect to the ground point (ground).

Further, the absolute value of the negative high voltage induced at one end 822 of the secondary coil L2 exceeds the dielectric breakdown voltage at the gap d of the spark plug 113. This causes dielectric breakdown in the gap d of the spark plug 113. Then, the current flows from the ground point (ground) to the center electrode 141 of the spark plug 113 via the ground electrode 142 of the spark plug 113 (see FIG. 1), and further flows through the secondary coil L2 and the first backflow prevention diode 111. A current flows through the first limiting diode 114 in the forward direction. In this embodiment, most of the current flows through the first reverse current prevention diode 111 in the forward direction, a part of the current flows through the first limiting diode 114 in the forward direction, and flows to the ground point (ground) via the power supply device 102.

As a result, a discharge occurs in the gap d of the spark plug 113, thereby generating a spark and igniting the fuel filled in the internal combustion engine. In addition, in the present invention, by switching the switching element 70 to the open state in this way, cutting off the primary current flowing to the primary coil L1, and inducing a high voltage at one end 822 of the secondary coil L2, the spark plug The process of causing discharge in the gap d of 113 is called "discharge control". Note that when the absolute value of the negative high voltage induced at one end 822 of the secondary coil L2 becomes lower than the dielectric breakdown voltage at the gap d of the spark plug 113 (time t2), the discharge at the gap d of the spark plug 113 temporarily stops. finish.

Here, as described above, a stray capacitance Cs consisting of a capacitance component of about 15 to 20 pH is formed between one end 822 of the secondary coil L2 and the spark plug 113. Therefore, even when the discharge in the gap d of the spark plug 113 once ends (time t2), the area still remains near one end 822 of the secondary coil L2, the second connection line 121, or the center electrode 141 of the spark plug 113. etc., charges may remain. In this embodiment, negative charges remain at these locations. As a result, at time t2, the voltage value at one end 822 of the secondary coil L2 (hereinafter referred to as "residual voltage value Rv") becomes a negative value (for example, -3 kV) with respect to the ground point (ground). Become. Note that the absolute value of the residual voltage value Rv is smaller than the dielectric breakdown voltage at the gap d of the spark plug 113. However, if this situation is left unaddressed, there is a risk that discharge will occur again in the gap d of the spark plug 113 at an unexpected timing, such as when a change in pressure occurs in the internal combustion engine.

Therefore, in the present invention, a diode whose breakdown voltage is smaller than the dielectric breakdown voltage at the gap d of the spark plug 113 and the absolute value of the residual voltage value Rv is used as the first limiting diode 114. The breakdown voltage of the first limiting diode 114 used in this embodiment is 2 kV or less. In the above example, the residual voltage value Rv at one end 822 (anode side of the first limiting diode 114) of the secondary coil L2 is a negative value (for example, -3 kV). On the other hand, the voltage applied to the power supply line 150 (the cathode side of the first limiting diode 114) has a positive value (for example, plus 12 V) and exceeds the breakdown voltage of the first limiting diode 114 with respect to the residual voltage value Rv. It becomes larger than the difference.

As a result, after the discharge ends, a current flows from the power supply device 102 side to the first limiting diode 114 in the opposite direction for a short time without causing discharge to occur again in the ignition plug 113. That is, the current (secondary current) flows from the power supply device 102 side to the secondary coil L2 side via the first connection line 122b. Note that since the first backflow prevention diode 111 is inserted in the first connection line 122a so that the forward current direction is from one end 822 to the other end 821 of the secondary coil L2, no current flows.

As a result, the electric charge remaining near one end 822 of the secondary coil L2, the second connection wire 121, or the vicinity of the center electrode 141 of the spark plug 113 is canceled out, and the voltage applied to the one end 822 of the secondary coil L2 (secondary voltage ), and the residual energy remaining at these locations can be reduced. As a result, even if a pressure change occurs in the internal combustion engine thereafter, it is possible to further suppress discharge from occurring in the gap d of the spark plug 113 at an abnormal timing.

Further, as described above, the resistance value of the first resistor 112 is 10 MΩ or less. In this way, by reducing the resistance value of the first resistor 112 to a certain extent, the current flowing from the power supply device 102 side to the secondary coil L2 side via the first connection line 122b after discharge is maintained at a certain level or more. can do. Thereby, the residual energy remaining near one end 822 of the secondary coil L2, the second connection line 121, the center electrode 141 of the spark plug 113, etc. can be further reduced.

Note that this phenomenon after the discharge ends is caused by the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 located on the anode side of the first limiting diode 114 and the power supply located on the cathode side of the first limiting diode 114. The potential difference with the voltage across line 150 continues until it equals the breakdown voltage of first limiting diode 114. Here, since the absolute value of the voltage applied to one end 822 of the secondary coil L2 (secondary voltage) is significantly larger than the absolute value of the voltage applied to the power supply line 150, this phenomenon is caused by the secondary voltage ( 3) is approximately equal to the breakdown voltage of the first limiting diode 114. Note that the absolute value of the voltage (secondary voltage) at one end 822 of the secondary coil L2 is determined by whether an ionic current flows through the gap d between the center electrode 141 of the spark plug 113 and the ground electrode 142, or This is further reduced by allowing a leakage current to flow through the 1-limiting diode 114.

As described above, in the present embodiment, first, when the primary current is passed through the primary coil L1 (when ON) as charge control, the current flows from the power supply device 102 side through the first connection line 122b. At this time, a current flows through the first resistor 112 and a voltage is applied thereto, thereby reducing the ON voltage generated in the secondary coil L2.

Furthermore, after the discharge ends, the current (secondary current) flows from the power supply device 102 side to the secondary coil L2 side via the first connection line 122b and the first limiting diode 114 in the opposite direction. It flows. As a result, the electric charge remaining near one end 822 of the secondary coil L2, the second connection wire 121, or the vicinity of the center electrode 141 of the spark plug 113 is canceled out, and the voltage applied to the one end 822 of the secondary coil L2 (secondary voltage ), and the residual energy remaining at these locations can be reduced. That is, the absolute value of the secondary voltage can be reduced to approximately equal to the breakdown voltage of the first limiting diode 114 in a short time without causing discharge in the spark plug 113 again. As a result, even if a pressure change occurs in the internal combustion engine thereafter, it is possible to suppress discharge from occurring in the gap d of the spark plug 113 at an abnormal timing. As a result, even in internal combustion engines that use fuel containing hydrogen, which has the characteristics of being easy to burn even at relatively low temperatures and having a high burning rate, this will prevent the fuel from igniting at abnormal timing, leading to less damage to the engine, etc. .

Note that the first limiting diode 114 does not necessarily have to be provided. FIG. 4 is a block diagram schematically showing the operating environment of the ignition device 1 according to the first modification. In the first modification of FIG. 4, the first connection line is one of the two first connection lines 122a and 122b wired in parallel between the other end 821 of the secondary coil L2 and the power supply device 102. At 122a, a first anti-backflow diode 111 is inserted. The first backflow prevention diode 111 is a diode that has a forward direction in the direction from one end 822 of the secondary coil L2 to the other end 821. Furthermore, only the first resistor 112 is inserted in the first connection line 122b, which is the other of the two first connection lines 122a and 122b.

In the first modification, first, as charge control, when a primary current is passed through the primary coil L1 (when ON), the current flows from the power supply device 102 side to the secondary coil L1 through the first connection line 122b. When the current flows to the coil L2 side and the voltage is applied to the first resistor 112, the ON voltage generated in the secondary coil L2 can be reduced. As a result, it is possible to suppress discharge from occurring in the spark plug 113 when it is turned on, that is, at abnormal timing.

Furthermore, as discharge control, when the switching element 70 is switched from the closed state to the open state and the primary current flowing from the power supply device 102 to the primary coil L1 is cut off, one end 822 of the secondary coil L2 is applied with a voltage of minus several thousand V to A high negative voltage of tens of thousands of volts is induced. This causes dielectric breakdown in the gap d of the spark plug 113. Then, the current flows from the ground point (ground) to the center electrode 141 of the spark plug 113 via the ground electrode 142 of the spark plug 113 (see FIG. 4), and further flows through the secondary coil L2 and the first backflow prevention diode 111. A current flows in the forward direction through the first connection line 122a in which the resistor 112 is inserted, or a current flows in the first connection line 122b in which the first resistor 112 is inserted. As a result, a discharge occurs in the gap d of the spark plug 113, thereby generating a spark and igniting the fuel filled in the internal combustion engine.

Further, after the discharge ends, the current is transferred from the power supply device 102 side to the secondary circuit through the first connection wire 122b in which the first resistor 112 is inserted, without causing discharge again in the spark plug 113. It flows toward the coil L2 side. As a result, the electric charge remaining near one end 822 of the secondary coil L2, the second connection wire 121, or the vicinity of the center electrode 141 of the spark plug 113 is canceled out, and the voltage applied to the one end 822 of the secondary coil L2 (secondary voltage ), and the residual energy remaining at these locations can be reduced. As a result, even if a pressure change within the internal combustion engine occurs thereafter, it is possible to further suppress discharge from occurring at abnormal timing in the gap d of the spark plug 113.

<2. Second embodiment>
Next, a second embodiment of the present invention will be described. Note that the following description will focus on the differences from the first embodiment, and redundant description of portions that are equivalent to the first embodiment will be omitted.

FIG. 5 is a block diagram schematically showing the operating environment of the ignition device 1 according to the second embodiment. As shown in FIG. 5, in the second embodiment, one end 822 of the secondary coil L2 is connected to It is directly or indirectly electrically connected to the spark plug 113. The second connection lines 121a and 121b are wired in parallel between one end 822 of the secondary coil L2 and the spark plug 113. Note that the other end 821 of the secondary coil L2 is connected to the power supply line 150 via the first connection line 122.

Moreover, in this embodiment, the second backflow prevention diode 131 is inserted in the second connection line 121a, which is one of the two second connection lines 121a and 121b. The second backflow prevention diode 131 is connected in series with the secondary coil L2. The second backflow prevention diode 131 of this embodiment is a normal diode that has the function of allowing current to flow in only one direction. Further, the second backflow prevention diode 131 is in the forward direction in the direction from one end 822 of the secondary coil L2 to the other end 821.

Further, in this embodiment, the second resistor 132 is inserted in the second connection line 121b, which is the other of the two second connection lines 121a and 121b. The second resistor 132 is connected in series with the secondary coil L2. Further, the resistance value of the second resistor 132 of this embodiment is 1 MΩ or more and 10 MΩ or less.

Furthermore, in this embodiment, a second limiting diode 134 is further inserted in the second connecting line 121b, which is the other of the two second connecting lines 121a and 121b. The second limiting diode 134 is connected in series with the secondary coil L2 and the second resistor 132, respectively. A Zener diode is used as the second limiting diode 134 in this embodiment. However, an avalanche diode may be used as the second limiting diode 134. Further, the second limiting diode 134 is in the forward direction in the direction from one end 822 of the secondary coil L2 to the other end 821. The second limiting diode 134 has the same configuration as the first limiting diode 114 of the first embodiment.

Further, in the present invention, as the second limiting diode 134, a diode whose breakdown voltage is smaller than the dielectric breakdown voltage at the gap d of the spark plug 113 is used. The breakdown voltage of the second limiting diode 134 used in this embodiment is 2 kV or less. Further, between one end 822 of the secondary coil L2 and the spark plug 113, a stray capacitance Cs consisting of a capacitance component of about 15 to 20 pH is formed.

In the second embodiment, first, as charge control, when a primary current is passed through the primary coil L1 (when ON), a voltage (for example, 960 V) is applied at both ends 821 and 822 of the secondary coil L2 when ON. occurs. The maximum value of the voltage applied to one end 822 of the secondary coil L2 is a positive value (for example, about +480V), and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is a negative value (for example, about -480V). ). On the other hand, at this time, the voltage applied to the power supply line 150 is, for example, 12V.

Therefore, a current flows from the power supply device 102 side to the secondary coil L2 side via the power supply line 150 and the first connection line 122. Here, a second resistor 132 is inserted into the second connection line 121b that connects one end 822 of the secondary coil L2 and the spark plug 113. The resistance value of the second resistor 132 is 1 MΩ or more. Thereby, when a current flows through the second connection line 121b, a voltage is applied at the second resistor 132, and as a result, the ON voltage and secondary voltage generated in the secondary coil L2 can be reduced. . As a result, it is possible to suppress discharge from occurring in the spark plug 113 when it is turned on, that is, at abnormal timing.

Furthermore, as discharge control, when the switching element 70 is switched from the closed state to the open state and the primary current flowing from the power supply device 102 to the primary coil L1 is cut off, one end 822 of the secondary coil L2 is applied with a voltage of minus several thousand V to A high negative voltage of tens of thousands of volts is induced. This causes dielectric breakdown in the gap d of the spark plug 113. A second connection is connected from the ground point (ground) to the center electrode 141 of the spark plug 113 via the ground electrode 142 of the spark plug 113 (see FIG. 5), and in which the second backflow prevention diode 131 is inserted. A current is generated that flows in the forward direction through the wire 121a, or through the second connection wire 121b in which the second resistor 132 is inserted, and further flows toward the secondary coil L2. As a result, a discharge occurs in the gap d of the spark plug 113, thereby generating a spark and igniting the fuel filled in the internal combustion engine.

Further, after the discharge ends, a current (secondary current) flows from the power supply device 102 side to the vicinity of one end 822 of the secondary coil L2, the second connection line 121b, and the first connection line 122. It flows toward the vicinity of the center electrode 141 of the spark plug 113 and the like. As a result, the electric charge remaining near one end 822 of the secondary coil L2, the second connection wire 121b, or the vicinity of the center electrode 141 of the spark plug 113 is canceled out, and the voltage applied to the one end 822 of the secondary coil L2 (secondary voltage ), and the residual energy remaining at these locations can be reduced. That is, the absolute value of the secondary voltage can be reduced in a short time without causing discharge to occur again in the spark plug 113. As a result, even if a pressure change occurs in the internal combustion engine thereafter, it is possible to suppress discharge from occurring in the gap d of the spark plug 113 at an abnormal timing. As a result, even in internal combustion engines that use fuel containing hydrogen, which is easy to burn even at relatively low temperatures and has a high burning rate, this will prevent the fuel from igniting at abnormal timing, leading to reduced damage to the engine, etc. .

Further, as described above, the resistance value of the second resistor 132 is 10 MΩ or less. In this way, by reducing the resistance value of the second resistor 132 to a certain extent, the current flowing from the power supply device 102 side to the vicinity of the center electrode 141 of the spark plug 113 via the second connection wire 121b after discharge is completed. can be maintained above a certain level. Thereby, the residual energy remaining in the vicinity of the center electrode 141 of the spark plug 113 can be further reduced.

Note that the second limiting diode 134 does not necessarily have to be provided. FIG. 6 is a block diagram schematically showing the operating environment of the ignition device 1 according to the second modification. In the second modification of FIG. 6, a second connection wire 121a is one of two second connection wires 121a and 121b wired in parallel between one end 822 of the secondary coil L2 and the spark plug 113. , a second backflow prevention diode 131 is inserted. The second backflow prevention diode 131 is a diode that has a forward direction in the direction from one end 822 of the secondary coil L2 to the other end 821. Further, only the second resistor 132 is inserted in the second connection line 121b, which is the other of the two second connection lines 121a and 121b.

In the second modification, first, as charge control, when a primary current is passed through the primary coil L1 (when ON), a current (secondary current) flows from the power supply device 102 side to the power line 150 and 1 connection line 122 to the secondary coil L2 side. At this time, a current flows through the second resistor 132 and a voltage is applied thereto, thereby making it possible to reduce the ON voltage generated in the secondary coil L2. As a result, it is possible to suppress discharge from occurring in the spark plug 113 when it is turned on, that is, at abnormal timing.

Furthermore, as discharge control, when the switching element 70 is switched from the closed state to the open state and the primary current flowing from the power supply device 102 to the primary coil L1 is cut off, one end 822 of the secondary coil L2 is applied with a voltage of minus several thousand V to A high negative voltage of tens of thousands of volts is induced. This causes dielectric breakdown in the gap d of the spark plug 113. A second connection is connected from the ground point (ground) to the center electrode 141 of the spark plug 113 via the ground electrode 142 of the spark plug 113 (see FIG. 6), and in which the second backflow prevention diode 131 is inserted. A current is generated that flows in the forward direction through the wire 121a, or through the second connection wire 121b in which the second resistor 132 is inserted, and further flows toward the secondary coil L2. As a result, a discharge occurs in the gap d of the spark plug 113, thereby generating a spark and igniting the fuel filled in the internal combustion engine.

Further, after the discharge ends, the current (secondary current) is transmitted from the power supply device 102 side to the second connection line 150 and the first connection line 122 in a short time without causing discharge again in the spark plug 113. It flows toward the vicinity of one end 822 of the secondary coil L2, the second connection line 121b, and the vicinity of the center electrode 141 of the spark plug 113. As a result, the electric charge remaining near one end 822 of the secondary coil L2, the second connection wire 121b, or the vicinity of the center electrode 141 of the spark plug 113 is canceled out, and the voltage applied to the one end 822 of the secondary coil L2 (secondary voltage ), and the residual energy remaining at these locations can be reduced. As a result, even if a pressure change within the internal combustion engine occurs thereafter, it is possible to further suppress discharge from occurring at abnormal timing in the gap d of the spark plug 113.

<3. Modified example>
Although the exemplary embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

In the above embodiments and modified examples, the charging control is configured such that the voltage applied to one end 822 of the secondary coil L2 has a positive value, and the voltage applied to the other end 821 of the secondary coil L2 has a negative value. was. Further, in the discharge control, the configuration was such that a negative high voltage ranging from minus several thousand volts to tens of thousands of volts was induced at one end 822 of the secondary coil L2. However, by changing the winding direction of the primary conductor 81 in the primary coil L1 and the winding direction of the secondary conductor 82 in the secondary coil L2, the voltage appearing at both ends 821, 822 of the secondary coil L2 can be changed. The sign of the value may be reversed. In this case, the first backflow prevention diode 111 inserted in the first connection line 122a in the first embodiment, the first restriction diode 114 inserted in the first connection line 122b, and the second connection line 121a in the second embodiment The forward direction and reverse direction of the inserted second backflow prevention diode 131 and the second restriction diode 134 inserted into the second connection line 121b may be reversed.

In the first embodiment described above, the cathode side of the first backflow prevention diode 111, the cathode side of the first limiting diode 114, and the other end 821 of the secondary coil L2 were each connected to the positive side of the power supply device 102. . However, as shown in the third variant of FIG. 7, these may be connected to a ground point (ground). That is, the first backflow prevention diode 111 is inserted in one of the two first connection wires 122a and 122b wired in parallel between the other end 821 of the secondary coil L2 and the ground point (ground). The first limiting diode 114 is a diode that is inserted in the other of the first connecting lines 122a and 122b, and has a forward direction in the direction from one end 822 of the secondary coil L2 to the other end 821, respectively. Good too. Further, in the second embodiment described above, the cathode side of the second backflow prevention diode 131 and the cathode side of the second limiting diode 134 were each connected to the positive side of the power supply device 102. However, as shown in the fourth variant of FIG. 8, these may be connected to a ground point (ground).

In the third modification and the fourth modification, first, when the primary current is passed through the primary coil L1 as charge control (when ON), the voltage at both ends 821 and 822 of the secondary coil L2 when ON is (for example, 960V) is generated. The maximum value of the voltage applied to one end 822 of the secondary coil L2 is a positive value (for example, about +480V), and the minimum value of the voltage applied to the other end 821 of the secondary coil L2 is a negative value (for example, about -480V). ).

Here, in the third modification, the first backflow prevention diode 111 and the first restriction diode 114 are inserted in the first connection lines 122a and 122b. Furthermore, in the fourth modification, a second backflow prevention diode 131 and a second restriction diode 134 are inserted in the second connection lines 121a and 121b. The forward direction is the direction from one end 822 of the secondary coil L2 to the other end 821, respectively. Therefore, the current flows from one end 822 of the secondary coil L2 to the other end 821 and further to the ground point, thereby reducing the ON voltage and secondary voltage generated in the secondary coil L2. . As a result, it is possible to suppress discharge from occurring in the spark plug 113 when it is turned on, that is, at abnormal timing.

Furthermore, as discharge control, when the switching element 70 is switched from the closed state to the open state and the primary current flowing from the power supply device 102 to the primary coil L1 is cut off, one end 822 of the secondary coil L2 is applied with a voltage of minus several thousand V to A high negative voltage of tens of thousands of volts is induced. This causes dielectric breakdown in the gap d of the spark plug 113. In the third modification, from the ground point (ground) to the center electrode 141 of the spark plug 113 via the ground electrode 142 of the spark plug 113 (see FIG. 7), from one end 822 of the secondary coil L2 to the other end. 821, and flows in the forward direction through the first connection line 122a in which the first backflow prevention diode 111 is inserted, or flows in the forward direction through the first connection line 122b in which the first restriction diode 114 is inserted, Further, a current (secondary current) flowing toward the ground point (ground) is generated.

Further, in the fourth modification, the flow is directed from the ground point (ground) to the center electrode 141 of the spark plug 113 via the ground electrode 142 of the spark plug 113 (see FIG. 8), and the second backflow prevention diode 131 is connected. Flows in the forward direction through the inserted second connection wire 121a, or flows in the forward direction through the second connection wire 121b in which the second limiting diode 134 is inserted, from one end 822 of the secondary coil L2 to the other end 821, Further, a current (secondary current) flowing toward the ground point (ground) is generated. As a result, a discharge occurs in the gap d of the spark plug 113, thereby generating a spark and igniting the fuel filled in the internal combustion engine.

In addition, after the discharge ends, in the third modification, the current (secondary current) is transmitted from the ground point (ground) to the vicinity of one end 822 of the secondary coil L2 via the first connection wires 122a and 122b, and to the second connection. It flows toward the wire 121 and the vicinity of the center electrode 141 of the spark plug 113 . In the fourth modification, the current (secondary current) is transmitted from the ground point (ground) via the first connection wire 122 to the vicinity of one end 822 of the secondary coil L2, the second connection wires 121a, 121b, and It flows toward the vicinity of the center electrode 141 of the spark plug 113 and the like.

This makes it possible to reduce residual energy remaining in these locations. That is, the absolute value of the voltage (secondary voltage) applied to one end 822 of the secondary coil L2 can be reduced in a short time without causing discharge in the spark plug 113 again. As a result, even if a pressure change occurs in the internal combustion engine thereafter, it is possible to suppress discharge from occurring in the gap d of the spark plug 113 at an abnormal timing. As a result, even in internal combustion engines that use fuel containing hydrogen, which has the characteristics of being easy to burn even at relatively low temperatures and having a high burning rate, this will prevent the fuel from igniting at abnormal timing, leading to less damage to the engine, etc. .

The ignition device of the present invention is installed not only in vehicles such as automobiles, but also in various devices such as generators and industrial machines, and is used to generate electric sparks in the spark plugs of internal combustion engines to ignite fuel. It is fine as long as it is suitable.

The detailed shape and structure of the above-mentioned ignition device may be changed as appropriate without departing from the spirit of the present invention. Furthermore, the elements appearing in the above-described embodiments and modifications may be combined as appropriate to the extent that no contradiction occurs.

1 Ignition device 60 Iron core 70 Switching element 81 Primary conductor 82 Secondary conductor 102 Power supply device 103 Ignition coil 104 Igniter 105 ECU
111 First backflow prevention diode 112 First resistor 113 Spark plug 114 First limiting diode 121, 121a, 121b Second connection line 122, 122a, 122b First connection line 131 Second backflow prevention diode 132 Second resistor 134 Second restriction Diode 150 Power line 811 One end of primary coil 812 Other end of primary coil 821 Other end of secondary coil 822 One end of secondary coil Cs Stray capacitance 71 Drive IC (control unit)
L1 Primary coil L2 Secondary coil Rv Residual voltage value d (Spark plug) gap

Claims (9)

An ignition device for an internal combustion engine using fuel containing at least hydrogen,
an ignition coil formed by electromagnetically coupling a primary coil and a secondary coil to each other;
a power supply device that applies a DC voltage to one end of the primary coil via a power line;
a switching element that is inserted between the other end of the primary coil and a ground point and can switch between energization and interruption of the primary current flowing from the power supply device to the primary coil;
a spark plug that ignites the fuel by discharging in a gap based on a high voltage induced at one end of the secondary coil;
It is inserted in one of two first connection wires wired in parallel between the other end of the secondary coil and the power supply device or the ground point, and runs from one end of the secondary coil to the other end. a first backflow prevention diode that is a forward diode in the direction;
a first resistor inserted in the other of the two first connection lines;
has
The ignition device, wherein the first resistor has a resistance value of 1 MΩ or more. The ignition device according to claim 1,
The other of the two first connection lines is a Zener diode or an avalanche diode that is inserted in series with the first resistor and has a forward direction in the direction from one end of the secondary coil to the other end. further comprising a first limiting diode;
The ignition device, wherein the breakdown voltage of the first limiting diode is less than the breakdown voltage at the gap of the spark plug. The ignition device according to claim 1,
The ignition device, wherein the first resistor has a resistance value of 10 MΩ or less. An ignition device for an internal combustion engine using fuel containing at least hydrogen,
an ignition coil formed by electromagnetically coupling a primary coil and a secondary coil to each other;
a power supply device that applies a DC voltage to one end of the primary coil via a power line;
a switching element that is inserted between the other end of the primary coil and a ground point and can switch between energization and interruption of the primary current flowing from the power supply device to the primary coil;
a spark plug that ignites the fuel by discharging in a gap based on a high voltage induced at one end of the secondary coil;
inserted in one of two second connection wires wired in parallel between one end of the secondary coil and the spark plug, and forward in the direction from one end of the secondary coil to the other end. A second backflow prevention diode, which is a diode,
a second resistor inserted in the other of the two second connection lines;
has
The ignition device, wherein the second resistor has a resistance value of 1 MΩ or more. The ignition device according to claim 4,
The other of the two second connection lines is a Zener diode or an avalanche diode that is inserted in series with the second resistor and has a forward direction in the direction from one end of the secondary coil to the other end. further comprising a second limiting diode;
The ignition device, wherein the breakdown voltage of the second limiting diode is less than the breakdown voltage at the gap of the spark plug. The ignition device according to claim 4,
The ignition device, wherein the second resistor has a resistance value of 10 MΩ or less. The ignition device according to any one of claims 1 to 6,
further comprising a control unit that controls switching of the switching element,
The control unit includes:
Charging control that charges the primary coil by causing a primary current to flow through the primary coil by bringing the switching element into a closed state;
After performing the charging control, the switching element is switched to an open state to induce a high voltage at one end of the secondary coil, thereby discharging the spark plug in the gap;
The ignition device. The ignition device according to any one of claims 1 to 6,
An ignition device having a stray capacitance formed between one end of the secondary coil and the spark plug. The ignition device according to claim 2 or claim 5,
The ignition device, wherein the breakdown voltage is 2 kV or less.

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