JP2013108465A - Igniter and ignition system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure sufficient durability of a spark plug, while improving ignitability.SOLUTION: An igniter 31 includes: an ignition coil 41 having a primary coil 42 and a secondary coil 43 connected to the spark plug 1 and generating secondary voltage in the secondary coil 43 by cutting off a primary current flowing to the primary coil 42; and a capacitor 61 connected in parallel to the spark plug 1 between the secondary coil 43 and the spark plug 1, charged by impressing the secondary voltage and generating spark discharge by the spark plug 1 by discharge of itself. The igniter 31 generates a plurality of times of spark discharge by the spark plug 1 in response to repetition of charge and discharge in the capacitor 61. A current-carrying control part 51 corresponding to a spark discharge stopping part can stop the plurality of times of spark discharge in the middle in the spark plug 1 by passing an electric current again to the primary coil 42.

Description

  The present invention relates to an ignition device and an ignition system for generating a spark discharge in a spark plug.

  The spark plug is attached to, for example, an internal combustion engine (engine) and used for igniting an air-fuel mixture in the combustion chamber. In general, a spark plug includes an insulator having a shaft hole, a center electrode inserted through the tip end of the shaft hole, a metal shell provided on the outer periphery of the insulator, and a ground electrode joined to the tip of the metal shell. A spark discharge gap is formed between the ground electrode and the center electrode. In addition, by applying a voltage to the spark plug, electric charge is stored in the spark plug, the energizing cable, etc., and the spark discharge gap is dielectrically broken as the voltage is applied, so that the stored charge is sparked. It flows into the discharge gap and spark discharge occurs in the spark discharge gap.

  As an ignition device for an ignition plug, one having an ignition coil is generally known. When a voltage is applied to a spark plug from a general ignition device having such an ignition coil, the spark plug (spark discharge gap) has a minute induction following a capacity current whose current value fluctuates rapidly. Current flows. Here, paying attention to the fact that increasing the capacity current contributes to the improvement of ignitability, a capacitor is connected in parallel with the spark plug between the spark plug and the ignition coil, and stored in the capacitor immediately after the spark discharge. There has been proposed a technique for increasing the capacity current and improving the ignitability by discharging the generated charge (see, for example, Patent Document 1).

JP-A-9-68149

  By the way, in the above technique, when the capacitance of the capacitor and the spark plug is relatively small, an induced current flows following the capacity current, as in the general ignition device described above. On the other hand, when the electrostatic capacity of the capacitor or the like is relatively large, the induced current does not flow after the capacitive discharge, and the spark discharge is temporarily stopped. And a capacitor etc. will be charged again by the electrical energy for an induction current, and a spark discharge will occur again by discharge of the charged capacitor etc. That is, by connecting a capacitor in parallel with the spark plug, spark discharge can be generated a plurality of times, and ignitability can be improved.

  However, if the spark discharge is always generated a plurality of times, the center electrode and the ground electrode forming the spark discharge gap are rapidly consumed, and the durability of the spark plug may be insufficient.

  The present invention has been made in view of the above circumstances, and the object thereof is to generate a plurality of spark discharges, while it is possible to stop a plurality of spark discharges on the way and to improve the ignitability. It is an object of the present invention to provide an ignition device and an ignition system capable of ensuring sufficient durability in an ignition plug while achieving the above.

  Hereinafter, each configuration suitable for solving the above-described object will be described in terms of items. In addition, the effect specific to the corresponding structure is added as needed.

Configuration 1. An ignition device of this configuration includes a primary coil and a secondary coil connected to an ignition plug, and an ignition coil that generates a secondary voltage in the secondary coil by interrupting a primary current flowing through the primary coil When,
A capacitor connected in parallel with the spark plug between the secondary coil and the spark plug, charged by applying the secondary voltage, and causing a spark discharge in the spark plug by its own discharge; Prepared,
With the repetition of charging and discharging in the capacitor, an ignition device that causes multiple spark discharges in the spark plug,
A spark discharge stop unit is provided that stops a plurality of times of spark discharge in the spark plug by re-energizing the primary coil.

  According to the configuration 1, the capacitor connected in parallel with the spark plug is provided between the secondary coil and the spark plug. In the capacitor, charging by the secondary voltage applied from the ignition coil (secondary coil) and discharging of the stored charge are repeatedly generated, so that a plurality of spark discharges can be generated in the spark plug. it can. As a result, ignitability can be improved.

  On the other hand, as described above, in the case where spark discharge is always generated a plurality of times, the durability of the spark plug may be insufficient. By re-energizing the coil, a plurality of spark discharges in the spark plug can be stopped halfway. Therefore, the durability of the spark plug can be dramatically improved as compared with the case where spark discharge is always generated a plurality of times.

  As described above, according to the above-described configuration 1, by causing a spark discharge a plurality of times, for example, even when ignition of the air-fuel mixture is relatively difficult, the air-fuel mixture is more reliably ignited. On the other hand, for example, when ignition of the air-fuel mixture is relatively easy, the durability of the spark plug can be improved by stopping the spark discharge halfway. That is, according to the said structure 1, sufficient durability can be ensured in a spark plug, improving ignitability.

Configuration 2. The ignition device of the present configuration includes a discharge frequency measuring unit that measures the number of spark discharges in the spark plug in the configuration 1,
The spark discharge stop timing by the spark discharge stop unit is determined based on the number of spark discharges measured by the discharge number measuring unit.

  According to the said structure 2, it can prevent more reliably that spark discharge generate | occur | produces too much, and can improve durability more reliably.

Configuration 3. The ignition device of the present configuration includes an integrated value measuring unit that measures at least one of an integrated value of electric energy input to the ignition plug and an integrated value of a value corresponding to the electric energy in the above-described configuration 1,
The spark discharge stop timing by the spark discharge stop unit is determined based on the integrated value measured by the integrated value measuring unit.

  Note that “the integrated value of the values corresponding to the electric energy” means that the maximum value of the current flowing through the spark plug in each spark discharge is integrated or the maximum value of the voltage applied to the spark plug in each spark discharge is integrated. And those obtained by integrating the area surrounded by the current chart in each spark discharge.

  According to the configuration 3, it is possible to more reliably prevent the input energy to the spark plug from becoming excessively large. As a result, the durability can be improved more reliably.

  Configuration 4. The ignition device of this configuration is characterized in that, in any one of the above configurations 1 to 3, the capacitance of the capacitor is 50 pF or more and 200 pF or less.

  According to the configuration 4, the capacitance of the capacitor is 50 pF or more. Therefore, it takes time to charge the capacitor, and the spark discharge can be easily interrupted until the capacitor is completely charged (that is, an induced current flows through the spark plug and the spark discharge continues). Can be prevented more reliably).

  Furthermore, according to the configuration 4, the capacitance of the capacitor is set to 200 pF or less. Therefore, the capacitor can be more reliably charged a plurality of times by the energy supplied from the ignition coil. As a result, the capacitance is 50 pF or less, and coupled with the ability to prevent the continuation of the spark discharge, a plurality of spark discharges can be generated more reliably.

  Configuration 5. The ignition device of this configuration is characterized in that, in any one of the above configurations 1 to 4, the spark discharge stop timing by the spark discharge stop unit is after 100 μs or more has elapsed since the interruption of the primary current.

  According to the configuration 5, the spark discharge stop timing is after 100 μs or more has elapsed since the primary current was cut off (that is, the application of the secondary voltage to the spark plug). Therefore, it is possible to sufficiently ensure the voltage application time to the spark plug, and it is possible to more reliably generate spark discharge.

Configuration 6. The ignition system of this configuration includes the ignition device according to any one of the above configurations 1 to 5,
An ignition system comprising: an ignition plug connected to the ignition device.

  According to the configuration 6, the same operational effects as the configuration 1 and the like are achieved.

  Configuration 7. The ignition system of this configuration is characterized in that, in the above configuration 6, the sum of the resistance of the conductive wire connecting the capacitor and the spark plug and the internal resistance of the spark plug is 1Ω or less.

  According to the configuration 7, the sum of the resistance of the conductive wire connecting the capacitor and the spark plug and the internal resistance of the spark plug, that is, the resistance value of the current input path from the capacitor to the spark discharge gap is 1Ω or less. Yes. Therefore, it is possible to more reliably prevent energy loss when a current is supplied from the capacitor to the spark discharge gap, and it is possible to more reliably generate the spark discharge a plurality of times.

It is a block diagram which shows schematic structure of an ignition system. It is a partially broken front view which shows the structure of a spark plug. It is a timing chart which shows the correlation with electricity supply signal S1, S2, a primary current, a discharge voltage, and a discharge current. It is a graph which shows the example of the relationship between the rotation speed and load in an internal combustion engine, and the frequency | count threshold value set. It is a block diagram which shows schematic structure, such as an electricity supply control part, in 2nd Embodiment. It is a timing chart which shows correlation with energization signals S1 and S2, a primary current, a discharge voltage, and a discharge current in a 2nd embodiment. It is a block diagram which shows schematic structure, such as an electricity supply control part in 3rd Embodiment. It is a timing chart which shows correlation with energization signals S1 and S2, a primary current, a discharge voltage, and a discharge current in a 3rd embodiment. It is a block diagram which shows schematic structure of the ignition system in another embodiment. It is a block diagram which shows schematic structure of the ignition system in another embodiment.

Hereinafter, embodiments will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of the ignition system 101. As shown in FIG. 1, the ignition system 101 includes an ignition plug 1 attached to the internal combustion engine EN, and an ignition device 31 that is connected to the ignition plug 1 and supplies electric power to the ignition plug 1. Although only one spark plug 1 is shown in FIG. 1, the actual internal combustion engine EN is provided with a plurality of cylinders, and the spark plug 1 is provided corresponding to each cylinder. An ignition device 31 is provided for each ignition plug 1.

  First, prior to the description of the ignition device 31, the configuration of the spark plug 1 will be described.

  As shown in FIG. 2, the spark plug 1 includes a cylindrical insulator 2, a cylindrical metal shell 3 that holds the insulator 2, and the like. In FIG. 2, the direction of the axis CL1 of the spark plug 1 is the vertical direction in the drawing, the lower side is the front end side of the spark plug 1, and the upper side is the rear end side.

  As is well known, the insulator 2 is formed by firing alumina or the like, and in its outer portion, a rear end side body portion 10 formed on the rear end side, and a front end than the rear end side body portion 10. A large-diameter portion 11 that protrudes radially outward on the side, a middle body portion 12 that is smaller in diameter than the large-diameter portion 11, and a tip portion that is more distal than the middle body portion 12. The leg length part 13 formed in diameter smaller than this on the side is provided. In addition, of the insulator 2, the large diameter portion 11, the middle trunk portion 12, and most of the leg long portions 13 are accommodated inside the metal shell 3. A tapered step portion 14 is formed at the connecting portion between the middle body portion 12 and the long leg portion 13, and the insulator 2 is locked to the metal shell 3 at the step portion 14.

  Further, the insulator 2 is formed with a shaft hole 4 extending along the axis CL <b> 1, and a center electrode 5 is inserted and fixed to the tip side of the shaft hole 4. The center electrode 5 includes an inner layer 5A made of copper or a copper alloy and an outer layer 5B made of a Ni alloy containing nickel (Ni) as a main component. The center electrode 5 has a rod shape (cylindrical shape) as a whole, and a tip portion of the center electrode 5 projects from the tip of the insulator 2.

  In addition, a terminal electrode 6 is inserted and fixed on the rear end side of the shaft hole 4 in a state of protruding from the rear end of the insulator 2.

  Further, a cylindrical glass seal layer 9 is disposed between the center electrode 5 and the terminal electrode 6. The center electrode 5 and the terminal electrode 6 are electrically connected by the glass seal layer 9, and the center electrode 5 and the terminal electrode 6 are fixed to the insulator 2.

  In addition, the metal shell 3 is formed in a cylindrical shape from a metal such as low carbon steel, and a screw for attaching the spark plug 1 to a combustion device such as an internal combustion engine or a fuel cell reformer on the outer peripheral surface thereof. A portion (male screw portion) 15 is formed. Further, a seat portion 16 is formed on the rear end side of the screw portion 15 so as to protrude toward the outer peripheral side, and a ring-shaped gasket 18 is fitted into the screw neck 17 at the rear end of the screw portion 15. Further, a tool engaging portion 19 having a hexagonal cross section for engaging a tool such as a wrench when the metal shell 3 is attached to the combustion device is provided on the rear end side of the metal shell 3. A caulking portion 20 that bends inward in the radial direction is provided at the rear end portion of the metal shell 3.

  In addition, a tapered step portion 21 for locking the insulator 2 is provided on the inner peripheral surface of the metal shell 3. The insulator 2 is inserted from the rear end side to the front end side of the metal shell 3, and the step 14 of the metal shell 3 is locked to the step 21 of the metal shell 3. It is fixed to the metal shell 3 by caulking the opening on the rear end side in the radial direction, that is, by forming the caulking portion 20. An annular plate packing 22 is interposed between the step portions 14 and 21. Thereby, the airtightness in the combustion chamber is maintained, and the fuel gas entering the gap between the leg long portion 13 of the insulator 2 exposed to the combustion chamber and the inner peripheral surface of the metal shell 3 is prevented from leaking outside.

  Further, in order to make the sealing by caulking more complete, annular ring members 23 and 24 are interposed between the metal shell 3 and the insulator 2 on the rear end side of the metal shell 3, and the ring member 23 , 24 is filled with talc 25 powder. That is, the metal shell 3 holds the insulator 2 via the plate packing 22, the ring members 23 and 24, and the talc 25.

  A ground electrode 27 is joined to the tip portion 26 of the metal shell 3 so as to be bent back at a substantially middle portion of the metal shell 3 and the tip side surface thereof faces the tip portion of the center electrode 5. A spark discharge gap 28 is formed between the tip of the center electrode 5 and the tip side surface of the ground electrode 27, and spark discharge is generated in the spark discharge gap 28 in a direction substantially along the axis CL1. To be done.

  Next, the configuration of the ignition device 31 will be described with reference to FIG.

  The ignition device 31 includes an ignition coil 41, an energization control unit 51, a capacitor 61, and a discharge number measurement unit 72.

  The ignition coil 41 includes a primary coil 42, a secondary coil 43, and a core 44.

  The primary coil 42 is wound around the core 44. One end of the primary coil 42 is connected to the power supply battery VA via the energization control unit 51, and the other end switches between energization and energization stop for itself. Therefore, it is connected to the collector of a transistor 56 to be described later. The secondary coil 43 is wound around the core 44, and one end thereof is connected between the primary coil 42 and the energization control unit 51, and the other end is connected to the terminal electrode 6 of the spark plug 1. Has been.

  The energization control unit 51 is provided between the ignition coil 41 and the battery VA, and includes a transistor 52 (NPN type), a transistor 53 (PNP type), a diode 54, a diode 55, and a transistor 56 (NPN type). It has.

  The transistor 52 has an emitter grounded and a collector connected to the base of the transistor 53. In addition, an energization signal S2 from a predetermined ECU (electronic control unit) 71 is input to the base of the transistor 52 via a resistor 58. By switching between high and low of the energization signal S2, the transistor 52 is turned on.・ Off can be switched.

  The transistor 53 is arranged in series with respect to the conductive wire connecting the battery VA and the ignition coil 41, the emitter is connected to the battery VA, and the collector is connected to the ignition coil 41. The transistor 53 is turned on when the energization signal S2 input to the transistor 52 is High, and is turned off when the energization signal S2 input to the transistor 52 is Low. Yes. That is, on / off of the transistor 53 is switched via the transistor 52 by switching High / Low of the energization signal S2.

  The diode 54 is connected in parallel with the transistor 53, the anode is connected to the collector side of the transistor 53, and the cathode is connected to the emitter side of the transistor 53. The diode 55 is connected in parallel with the primary coil 42, the anode is grounded, and the cathode is connected between the transistor 53 and the ignition coil 41 (primary coil 42).

  The transistor 56 is grounded at the emitter, and receives an energization signal S1 from the ECU 71 via a drive circuit 57 for driving itself with respect to the base. The transistor 56 is turned on when the energization signal S1 is High, and is turned off when the energization signal S1 is Low.

  The energization control unit 51 applies a high voltage (secondary voltage) from the ignition coil 41 to the spark plug 1 to cause spark discharge in the spark discharge gap 28 of the spark plug 1 as follows. To work. That is, as shown in FIG. 3, by setting both energization signals S1 and S2 to High (time t1) and turning on both transistors 53 and 56, a primary current flows from the battery VA to the primary coil 42, and the core A magnetic field is formed around 44. After that, both the energization signals S1 and S2 are set to Low (time t2), and the transistors 53 and 56 are turned off to cut off the primary current and change the magnetic field of the core 44. Thereby, a negative secondary voltage (for example, 5 kV to 30 kV) is generated in the secondary coil 43, and this secondary voltage is applied to the spark plug 1. Then, along with the application of the secondary voltage to the spark plug 1, spark discharge occurs in the spark discharge gap 28. In the present embodiment, the electrical energy supplied from the ignition coil 41 to the spark plug 1 side is set to a predetermined value (for example, 30 mJ or more and 100 mJ or less) with the interruption of the primary current.

  Returning to FIG. 1, the capacitor 61 is connected in parallel with the spark plug 1 between the ignition coil 41 and the spark plug 1. The capacitor 61 is charged with the electric power supplied from the ignition coil 41 (secondary coil 43) and discharges the stored charge, thereby causing a spark discharge in the spark discharge gap 28. That is, with the repeated charging and discharging of the capacitor 61, the spark plug 1 generates a plurality of spark discharges (specifically, capacitive discharge in which a large current flows in a short time).

  In the present embodiment, the capacitance of the capacitor 61 is set to 50 pF or more and 200 pF or less.

  The number-of-discharges measurement unit 72 is configured by the ECU 71, and the number-of-discharges measurement unit 72 (ECU 71) includes a current flowing through the spark plug 1 by the discharge of the capacitor 61 measured by a predetermined current sensor (not shown). Information on the current value of is input. And the discharge frequency measurement part 72 measures the frequency | count of the spark discharge in the spark plug 1 based on the information regarding the input electric current value. Specifically, the discharge frequency measuring unit 72 determines that a spark discharge has occurred when the current value of the current flowing through the spark plug 1 exceeds a predetermined current threshold value set in advance. And the frequency | count of discharge is measured by integrating | accumulating the frequency | count of having determined with the spark discharge having arisen.

  Further, the energization control unit 51 re-energizes the primary coil 42 at a stop timing determined based on the number of spark discharges measured by the discharge number measurement unit 72, thereby performing a plurality of times in the spark plug 1. The spark discharge can be stopped halfway.

  Specifically, as shown in FIG. 3, when the energization signals S1 and S2 are switched from High to Low (time t2) and electric power is supplied from the ignition coil 41 to the spark plug 1 side, the discharge frequency measurement unit When the number of spark discharges measured by 72 exceeds a preset predetermined number of times threshold, the energization signal S1 is switched from Low to High while keeping the energization signal S2 Low (time t3). As a result, a current flows through the primary coil 42 through the diode 55 and the transistor 56. Then, when the primary current gradually increases and the current value reaches a current value that can be generated by the magnetic flux remaining in the core 44 (time t4), the high current generated in the secondary coil 43 is increased. A voltage having a polarity opposite to the voltage is generated in the secondary coil 43. As a result, the spark discharge in the spark plug 1 is forcibly stopped halfway. That is, in the present embodiment, the energization control unit 51 corresponds to a “spark discharge stop unit”. Note that the primary current at the time of re-energization gradually decreases after the increase due to the influence of internal resistance and the like, and finally stops flowing. Further, in the present embodiment, when the spark discharge stop timing cuts off the energization of the primary coil 42 and generates the secondary voltage in the secondary coil 43 in order to generate the spark discharge more reliably (time t2). It is set when 100 μs or more has passed.

  In addition, in the present embodiment, the ECU 71 is input with information regarding the rotational speed and load of the internal combustion engine EN acquired by a sensor (not shown), and the ECU 71 sets the threshold value based on the information. It is configured as follows. Specifically, as shown in FIG. 4, the number-of-times threshold is set to a smaller value as the rotational speed or load of the internal combustion engine EN increases, and the number of times increases as the rotational speed or load of the internal combustion engine EN decreases. The threshold is set to a large value. In other words, under conditions where the air-fuel mixture can be ignited relatively easily, durability is improved by reducing the number of discharges. On the other hand, conditions under which the air-fuel mixture is relatively difficult to ignite (prone to misfire) (Condition), the ignition probability is increased by increasing the number of discharges, and the ignitability is improved.

  Further, the ECU 71 is configured to set the number-of-times threshold to a maximum value that can be set immediately after the internal combustion engine EN is started and until the internal combustion engine EN is sufficiently warmed up. That is, under conditions where the occurrence of misfire is a particular concern, the ignitability can be improved to the maximum without stopping the spark discharge. Instead of setting the number threshold to the maximum value that can be set, the spark discharge halfway stop function is temporarily stopped immediately after the internal combustion engine EN is started until the internal combustion engine EN is sufficiently warmed up. It is also possible to make it.

  Further, in the present embodiment, the resistance of the lead wire 62 (see FIG. 1) connecting the capacitor 61 and the spark plug 1 and the internal resistance of the spark plug 1 (more specifically, from the rear end of the terminal electrode 6 to the center electrode 5). The resistance to the tip) is 1Ω or less.

  As described in detail above, according to the present embodiment, the capacitor 61 connected in parallel with the spark plug 1 is provided between the secondary coil 43 and the spark plug 1. And in the capacitor | condenser 61, charging by the secondary voltage applied from the ignition coil 41 (secondary coil 43) and the discharge of the stored electric charge are repeatedly generated, so that the spark plug 1 causes a plurality of spark discharges. Can be generated. As a result, ignitability can be improved.

  Further, in the present embodiment, the energization controller 51 can re-energize the primary coil 42, thereby stopping a plurality of spark discharges in the spark plug 1 halfway. Therefore, the durability of the spark plug 1 can be dramatically improved as compared with the case where spark discharge is always generated a plurality of times.

  In addition, in the present embodiment, the spark discharge stop timing is determined based on the number of spark discharges measured by the discharge number measuring unit 72. Therefore, it is possible to more reliably prevent an excessive number of spark discharges from occurring, and the durability of the spark plug 1 can be improved more reliably.

  Furthermore, since the capacitance of the capacitor 61 is 50 pF or more, it takes time to charge the capacitor 61, and the spark discharge can be easily interrupted before the charging of the capacitor is completed. Further, since the capacitance of the capacitor 61 is set to 200 pF or less, the capacitor 61 can be more reliably charged a plurality of times by the energy supplied from the ignition coil 41. As a result, combined with the ability to prevent the continuation of spark discharge, multiple spark discharges can be generated more reliably.

  In addition, the stop timing of the spark discharge is after 100 μs or more has elapsed since the primary current was cut off. Therefore, it is possible to sufficiently ensure the voltage application time to the spark plug 1 and to generate spark discharge more reliably.

In the present embodiment, the sum of the resistance of the conducting wire 62 and the internal resistance of the spark plug 1, that is, the resistance value of the current input path from the capacitor 61 to the spark discharge gap 28 is 1Ω or less. Therefore, it is possible to more reliably prevent energy loss at the time of supplying current from the capacitor 61 to the spark discharge gap 28, and it is possible to more reliably generate spark discharge a plurality of times.
[Second Embodiment]
Next, the second embodiment will be described focusing on differences from the first embodiment. In the second embodiment, as shown in FIG. 5, the energization control unit 81 includes a thyristor 82 having an anode connected between the primary coil 42 and the transistor 88 and a cathode connected between the primary coil 42 and the battery VA. ing. An energization signal S2 from the ECU 71 is input to the gate of the thyristor 82 via the drive circuit 83 for driving the thyristor, the resistor 84, and the capacitor 85. Furthermore, the conducting wire between the primary coil 42 and the battery VA is electrically connected to the gate of the thyristor 82 through a resistor 86 and a capacitor 87 connected in parallel. The transistor 88 and the drive circuit 89 for driving the transistor 88 have the same configuration as the transistor 56 and the drive circuit 57 in the first embodiment.

  When applying a high voltage (secondary voltage) from the ignition coil 41 to the ignition plug 1 in the energization control unit 81, the energization signal S1 is changed with the energization signal S2 kept low as shown in FIG. By switching from High to Low (time t2), a secondary voltage is generated in the secondary coil 43. When the spark discharge is stopped halfway, the energization signal S2 is switched from Low to High (time t3), the thyristor 82 is turned on, and the primary current is applied to the closed loop formed by the primary coil 42 and the thyristor 82. Flows (the primary coil 42 is energized again). When the primary current gradually increases and reaches a current value that can be generated by the magnetic flux remaining in the core 44 (time t4), the high voltage generated in the secondary coil 43 is increased. A voltage with a polarity opposite to that is induced in the secondary coil 43. As a result, the spark discharge in the spark plug 1 is forcibly stopped halfway. That is, in the second embodiment, the energization control unit 81 corresponds to a “spark discharge stop unit”. The primary current at the time of re-energization gradually decreases after the increase due to the influence of internal resistance and the thyristor 82 is turned off when the primary current stops flowing.

As described above, according to the second embodiment, the same operational effects as those of the first embodiment can be obtained.
[Third Embodiment]
Next, a third embodiment will be described focusing on differences from the first and second embodiments. In the third embodiment, the energization control unit 91 includes a transistor 92 (NPN type), a diode 93, a resistor 94, a diode 95, and a capacitor 96, as shown in FIG.

  The transistor 92 is supplied with an energization signal S1 from the ECU 71 via a drive circuit 97 for driving the transistor 92, and by switching between High and Low of the energization signal S1, It can be switched off. The diode 93 is connected in parallel with the transistor 92, the anode is grounded, and the cathode is connected between the transistor 92 and the capacitor 96.

  The resistor 94 and the diode 95 are respectively connected in parallel, provided in series with the capacitor 96, and connected between the primary coil 42 and the transistor 98. The diode 95 has an anode connected between the primary coil 42 and the transistor 98, and a cathode connected to the capacitor 96. Note that the transistor 98 and the drive circuit 99 for driving the transistor 98 have the same configuration as the transistor 56 and the drive circuit 57 in the first embodiment.

  When applying a high voltage (secondary voltage) from the ignition coil 41 to the ignition plug 1 in the energization control unit 91, as shown in FIG. 8, the energization signal S1 is changed with the energization signal S2 kept low. By switching from High to Low (time t2), a secondary voltage is generated in the secondary coil. When the spark discharge is stopped halfway, by switching the energization signal S2 from Low to High while keeping the energization signal S1 Low (time t3), the transistor 92 is turned on, and the diode 95 and the capacitor A primary current flows through the primary coil 42 via 96 (the primary coil 42 is energized again). When the primary current gradually increases and reaches a current value that can be generated by the magnetic flux remaining in the core 44 (time t4), the high voltage generated in the secondary coil 43 is increased. A voltage with a polarity opposite to that is induced in the secondary coil 43. As a result, the spark discharge in the spark plug 1 is forcibly stopped halfway. That is, in the third embodiment, the energization control unit 91 corresponds to a “spark discharge stop unit”. When a predetermined amount of charge is stored in the capacitor 96, no current flows through the capacitor 96 and the primary current is cut off. The electric charge stored in the capacitor 96 is discharged through the diode 93 and the resistor 94 when the transistor 98 is turned on.

  As described above, according to the third embodiment, the same functions and effects as those of the first and second embodiments are achieved.

  In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

  (A) In the above embodiment, the timing for stopping the spark discharge in the middle is determined based on the number of discharges measured by the discharge number measuring unit 72. On the other hand, as shown in FIG. 9, an integrated value measuring unit 112 configured by the ECU 71 and measuring the integrated value of the electric energy input to the spark plug 1 is provided and measured by the integrated value measuring unit 112. The stop timing of the spark discharge may be determined based on the integrated value of electric energy. Specifically, a sensor (not shown) capable of measuring the current flowing through the spark plug 1 is provided, and the electric energy input from the ignition coil 41 to the spark plug 1 is determined based on the current value measured by the sensor. Find the integrated value. For example, when the obtained integrated value exceeds a predetermined integrated value threshold value, the spark discharge is stopped halfway. In this case, it can prevent more reliably that the input energy with respect to the spark plug 1 becomes large too much, and can improve durability more reliably. The integrated value measuring unit 112 may be provided together with the discharge number measuring unit 72. Then, when the integrated value of electrical energy measured by the integrated value measuring unit 112 exceeds the integrated value threshold value, or when the number of discharges measured by the discharge number measuring unit 72 exceeds the frequency threshold value, a spark is generated. You may stop discharge on the way.

  Further, together with the integrated value of the electric energy or instead of the integrated value of the electric energy, the integrated value measuring unit 112 has a value corresponding to the electric energy (for example, the maximum current flowing through the spark plug in each spark discharge). Value, the maximum value of the voltage applied to the spark plug in each spark discharge, the integrated value of each spark discharge in the area surrounded by the current chart, and the like, and based on this integrated value (for example, the integrated value is a predetermined value). The spark discharge may be stopped halfway when the threshold value is exceeded. In this case, compared to the case where the integrated value of electrical energy is used as a measurement target, measurement becomes easier, and the processing load on the integrated value measuring unit 112 can be reduced.

  (B) In the above embodiment, the discharge count measuring unit 72 and the integrated value measuring unit 112 are configured by the ECU 71. However, the discharge count measuring unit 72 and the integrated value measuring unit 112 are provided separately from the ECU 71. Also good. For example, the discharge count measuring unit 72 and the integrated value measuring unit 112 may be configured by a microcomputer.

  (C) The configuration of the spark plug 1 in the above embodiment is an exemplification, and the configuration of the spark plug to which the technical idea of the present invention can be applied is not limited to this. Therefore, for example, a plasma jet ignition plug having a cavity (space) at the tip of the insulator and capable of generating plasma in the cavity may be used as the ignition plug.

  (D) Although not particularly described in the above embodiment, when the misfire in the spark plug 1 is detected, the number of discharges may be increased by relatively increasing the number-of-times threshold. Specifically, for example, the current value of the current flowing through the spark plug 1 by the ECU 71 or the like within a predetermined time (that is, within a period for which a spark discharge is to be generated) within a predetermined time from the start timing of energization of the spark plug 1. Is compared with the current threshold value to determine whether or not a spark discharge has occurred. When it is determined that no spark discharge has occurred (that is, misfiring has occurred and it is difficult to ignite the air-fuel mixture), it is possible to increase the number of times threshold and increase the number of discharges. Good. In this case, the ignition probability is increased, and the air-fuel mixture can be more reliably ignited even under difficult conditions. In addition, when misfiring has occurred due to adhesion of carbon or the like to the insulator 2, by increasing the number of discharges, carbon or the like can be effectively burned out, and the spark plug 1 is restored to a normal state. Can be made.

  (E) In the above embodiment, the discharge count measuring unit 72 is configured to measure the number of spark discharges of the spark plug 1 based on the current flowing through the spark plug 1 due to the discharge of the capacitor 61. On the other hand, as shown in FIG. 10, the discharge number measuring unit 72 may measure the number of spark discharges in the spark plug 1 based on the current and voltage flowing through the spark plug 1.

  DESCRIPTION OF SYMBOLS 1 ... Spark plug, 31 ... Ignition device, 51 ... Current supply control part (spark discharge stop part), 41 ... Ignition coil, 42 ... Primary coil, 43 ... Secondary coil, 61 ... Capacitor, 62 ... Conductor, 72 ... Number of discharges Measuring unit, 101... Ignition system, 112... Integrated value measuring unit.

Claims (7)

An ignition coil that has a primary coil and a secondary coil connected to the spark plug, and generates a secondary voltage in the secondary coil by blocking a primary current flowing through the primary coil;
A capacitor connected in parallel with the spark plug between the secondary coil and the spark plug, charged by applying the secondary voltage, and causing a spark discharge in the spark plug by its own discharge; Prepared,
With the repetition of charging and discharging in the capacitor, an ignition device that causes multiple spark discharges in the spark plug,
An ignition device comprising: a spark discharge stopping section that stops a plurality of times of spark discharge in the spark plug by re-energizing the primary coil. A discharge number measuring unit for measuring the number of spark discharges in the spark plug;
2. The ignition device according to claim 1, wherein the spark discharge stop timing by the spark discharge stop unit is determined based on the number of spark discharges measured by the discharge frequency measurement unit. An integrated value measuring unit that measures at least one of an integrated value of electric energy input to the spark plug and an integrated value of a value corresponding to the electric energy;
2. The ignition device according to claim 1, wherein the spark discharge stop timing by the spark discharge stop unit is determined based on the integrated value measured by the integrated value measuring unit.   4. The ignition device according to claim 1, wherein the capacitor has a capacitance of 50 pF or more and 200 pF or less. 5.   5. The ignition device according to claim 1, wherein the spark discharge stop timing by the spark discharge stop unit is after 100 μs or more has elapsed from the interruption of the primary current. 6. The ignition device according to any one of claims 1 to 5,
An ignition system comprising: an ignition plug connected to the ignition device.   The ignition system according to claim 6, wherein a sum of a resistance of a conductive wire connecting the capacitor and the spark plug and an internal resistance of the spark plug is 1Ω or less.

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