JP5537494B2 - Ignition device and ignition system - Google Patents

Description

  The present invention relates to an ignition device for a plasma jet ignition plug that generates plasma and ignites an air-fuel mixture or the like.

  Conventionally, in a combustion apparatus such as an internal combustion engine, an ignition plug that ignites an air-fuel mixture by spark discharge is used. In recent years, in order to meet the demand for higher output and lower fuel consumption of combustion devices, as a spark plug that spreads quickly and can be ignited more reliably even with a lean mixture with a higher ignition limit air-fuel ratio, Plasma jet spark plugs have been proposed.

  Generally, a plasma jet ignition plug is disposed on a cylindrical insulator having a shaft hole, a center electrode inserted into the shaft hole with the tip surface being more immersed than the tip surface of the insulator, and an outer periphery of the insulator. And a ring-shaped ground electrode joined to the tip of the metal shell. Further, the plasma jet ignition plug has a space (cavity portion) formed by the front end surface of the center electrode and the inner peripheral surface of the shaft hole, and the cavity portion passes through a through hole formed in the ground electrode. It is designed to communicate with the outside.

  In such a plasma jet ignition plug, the air-fuel mixture is ignited as follows. First, a voltage is applied to the gap formed between the center electrode and the ground electrode, and a spark discharge is generated in the gap to cause dielectric breakdown. After that, by supplying electric power to the gap, the gas in the cavity is turned into plasma, and plasma is generated inside the cavity. Then, the air-fuel mixture is ignited by ejecting the generated plasma from the opening of the cavity.

  In general, an ignition device for a plasma jet spark plug includes a voltage application unit for applying a voltage to the gap to generate a spark discharge, and a power input unit for supplying power to the gap with a capacitor. (For example, see Patent Document 1). In addition, diodes are provided between the plasma jet ignition plug and the voltage application unit and between the plasma jet ignition plug and the power input unit (capacitor), respectively, and one of the voltage application unit and the power input unit is connected to the other. Inflow of current can be prevented. Furthermore, an inductor may be provided between the plasma jet ignition plug and the power input unit (capacitor). By providing the inductor, it is possible to prolong the power application time from the power input unit to the plasma jet ignition plug and reduce the current peak value, thereby improving ignitability and suppressing noise.

JP 2010-218768 A

  By the way, when an inductor is provided, energy is generated in the inductor when power is supplied from the power input unit (capacitor) to the plasma jet ignition plug. However, the direction of current flow is limited to one direction by the diode disposed between the plasma jet ignition plug and the power input unit (capacitor). Therefore, the reverse current due to the energy generated in the inductor does not flow, and the generated energy may be consumed as it is. That is, only a part of the energy output from the power input unit can be input to the plasma jet ignition plug, which may reduce the energy efficiency.

  The present invention has been made in view of the above circumstances, and an object thereof is to recharge a capacitor with a reverse current by an inductor, thereby improving energy efficiency and improving ignitability, and It is to provide an ignition system.

  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. The ignition device of this configuration is used for a plasma jet ignition plug having a center electrode, a ground electrode, and a cavity that surrounds at least a part of a gap formed between the electrodes and forms a discharge space. An ignition device to be used,
A voltage application unit for applying a voltage to the gap;
A capacitor, and a power supply unit that charges the capacitor, and a power input unit that supplies power to the gap;
An inflow prevention diode connected in series between the plasma jet ignition plug and the power input unit, and preventing current inflow from the voltage application unit to the power input unit,
The inflow prevention diode and the inductor connected in series between the power input unit,
A voltage is applied to the gap from the voltage application unit to generate a spark discharge in the gap, and a plasma is generated in the cavity unit by supplying power charged in the capacitor to the gap through the inductor. Can be generated,
A recharging unit is provided that recharges the capacitor by a reverse current caused by the inductor generated when power is supplied from the capacitor to the spark plug.

  According to the above configuration 1, the recharge unit is provided, and the capacitor is caused by the reverse current generated by the inductor that is generated when power is supplied from the capacitor to the plasma jet spark plug (hereinafter also simply referred to as “ignition plug”). Can be recharged. Then, power can be reapplied from the recharged capacitor to the spark plug, and the capacitor can be recharged by the reverse current generated when this power is applied. That is, according to the above configuration 1, the energy generated in the inductor that has been wasted in the past can be used effectively, and power can be supplied from the capacitor to the spark plug a plurality of times. (In other words, energy efficiency can be improved and ignitability can be improved).

  Configuration 2. The ignition device of this configuration is characterized in that, in the above configuration 1, the recharging unit is a recharging diode having one end connected between the inflow prevention diode and the inductor and the other end grounded. .

  According to the configuration 2, the recharging unit can be easily realized, and the device can be downsized and the manufacturing cost can be reduced.

Configuration 3. In the ignition device of this configuration, in the above configuration 1 or 2, the power supply device generates a negative voltage,
One end of the capacitor is connected between the power supply device and the inductor, and the other end of the capacitor is grounded.

  According to the configuration 3, plasma can be generated using the central electrode as the negative electrode, and the ignitability and electrode wear resistance can be improved.

Configuration 4. In the ignition device of this configuration, in the configuration 1 or 2, the power supply device generates a positive voltage,
The capacitor is connected in series between the power supply device and the inductor,
One end of itself is connected between the power supply device and the capacitor, and the other end of the device is grounded, and is turned off when the capacitor is charged by the power supply device, while the electric power charged in the capacitor is A semiconductor switch that is turned on when the gap is inserted;
A switch protection diode connected in parallel with the semiconductor switch and through which a reverse current due to the inductor flows is provided.

  In general, it is relatively difficult to generate a negative high voltage, and the configuration of monitoring means for confirming the generation of a negative voltage tends to be complicated. Therefore, if a power supply device that generates a negative voltage is used, the manufacturing cost may increase and the device may be complicated.

  In this respect, according to the above-described configuration 4, the power supply device generates a positive voltage, so that the manufacturing cost can be suppressed and the device can be more reliably prevented from being complicated.

  Further, since the capacitor is connected in series between the power supply device and the inductor, in the charged capacitor, the side connected to the power supply device is positive, and the side connected to the spark plug is negative. Therefore, when power is supplied from the capacitor to the spark plug, a current flows from the spark plug to the capacitor side (that is, plasma is generated with the center electrode as the negative electrode). Therefore, ignitability and electrode wear resistance can be improved.

  Furthermore, the capacitor can be charged by turning off the semiconductor switch when the capacitor is charged by the power supply device, and the power to the spark plug is turned on by turning on the semiconductor switch when the capacitor is charged. Can be input.

  In addition, since the reverse current caused by the inductor flows through the switch protection diode connected in parallel with the semiconductor switch, it is possible to more reliably prevent the semiconductor switch from being damaged due to the occurrence of the reverse current.

  Configuration 5. The ignition device of this configuration is the charge in which the one end of itself is connected between the capacitor and the inductor and the other end of the ignition device of the present configuration is grounded, and a current flows when the capacitor is charged by the power supply device A diode is provided.

  According to the configuration 5, when the capacitor is charged, a current flows through the charging diode arranged on the upstream side of the inductor, so that almost no current flows through the inductor. Therefore, it is possible to more reliably prevent energy from being generated in the inductor when charging the capacitor. As a result, energy loss during charging of the capacitor can be suppressed, and energy efficiency can be further improved.

Configuration 6. The ignition system of this configuration includes the ignition device according to any one of the above configurations 1 to 5,
And a plasma jet ignition plug to which electric power is supplied from the ignition device.

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

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. This is an equivalent circuit when attention is paid to capacitors and inductors. (A) is a waveform diagram of a current value when no inflow preventing diode is present in the equivalent circuit, and (b) is a waveform diagram of a current value in the equivalent circuit. (A) is a wave form diagram which shows the voltage of a gap | interval, (b) is a wave form diagram which shows the electric current of a gap | interval. It is a block diagram which shows schematic structure, such as an ignition device in 2nd Embodiment. It is a block diagram which shows schematic structure, such as an ignition device in 3rd Embodiment.

Hereinafter, embodiments will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of an ignition system 101 including a plasma jet ignition plug (hereinafter referred to as “ignition plug”) 1 and an ignition device 71 including a voltage application unit 31 and a power input unit 41. It is. In FIG. 1, only one spark plug 1 is shown, but the internal combustion engine EN is provided with a plurality of cylinders, and the spark plugs 1 are provided corresponding to the respective cylinders. A voltage application unit 31 and a power input unit 41 are provided for each spark plug 1.

  First, prior to the description of the ignition system 101, a schematic configuration of the spark plug 1 will be described.

  FIG. 2 is a partially cutaway front view showing the spark plug 1. 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.

  The spark plug 1 is composed of a cylindrical insulator 2, a cylindrical metal shell 3 that holds the insulator 2, and the like.

  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 the leg long portion 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 penetrating along the axis CL1, and a center electrode 5 is inserted and fixed to the tip end side of the shaft hole 4. The center electrode 5 includes an inner layer 5A made of copper, a copper alloy or the like having excellent thermal conductivity, and an outer layer made of a Ni alloy containing nickel (Ni) as a main component (for example, Inconel (trade name) 600 or 601). 5B is provided. Furthermore, the center electrode 5 has a rod shape (cylindrical shape) as a whole, and the tip thereof is disposed on the rear end side in the axis line CL1 direction with respect to the tip surface of the insulator 2. In addition, tungsten (W), iridium (Ir), platinum (Pt), nickel (Ni), or a portion of the center electrode 5 that is at least 0.3 mm from the tip to the rear end in the direction of the axis CL1 An electrode tip 5C formed of an alloy containing at least one of these metals as a main component is provided.

  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 glass seal layer 9 electrically connects the center electrode 5 and the terminal electrode 6, 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 spark plug 1 is attached to the outer peripheral surface of the metal shell 3 (for example, an internal combustion engine or a fuel cell reformer). A threaded portion (male threaded portion) 15 for attachment to the hole is formed. In addition, a seat portion 16 is formed on the outer peripheral surface on the rear end side of the screw portion 15, and a ring-shaped gasket 18 is fitted on the screw neck 17 on the rear end of the screw portion 15. Further, on the rear end side of the metal shell 3, 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. 1 is provided with a caulking portion 20 for holding the insulator 2. In addition, an annular engagement portion 21 is formed on the outer periphery of the distal end portion of the metal shell 3 so as to protrude toward the distal end side in the axis CL1 direction. The ground electrode 27 is joined.

  A tapered step portion 22 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 rear end of the metal shell 3 is engaged with the step 14 of the metal shell 3. It is fixed to the metal shell 3 by caulking the opening on the side inward in the radial direction, that is, by forming the caulking portion 20. An annular plate packing 23 is interposed between the step portions 14 and 22 of both the insulator 2 and the metal shell 3. As a result, the airtightness in the combustion chamber is maintained, and the fuel gas that enters the gap between the long leg portion 13 of the insulator 2 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 24 and 25 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 24. , 25 is filled with powder of talc (talc) 26. That is, the metal shell 3 holds the insulator 2 via the plate packing 23, the ring members 24 and 25, and the talc 26.

  A disc-shaped ground electrode 27 is joined to the front end of the metal shell 3 so as to be positioned on the front side of the insulator 2 in the direction of the axis CL1. The ground electrode 27 is joined to the metal shell 3 by welding its outer peripheral portion to the engagement portion 21 while being engaged with the engagement portion 21 of the metal shell 3. In the present embodiment, the ground electrode 27 is made of W, Ir, Pt, Ni, or an alloy containing at least one of these metals as a main component.

  In addition, the ground electrode 27 has a through hole 27H penetrating in the thickness direction at the center thereof. A cavity 28, which is a cylindrical space formed by the inner peripheral surface of the shaft hole 4 and the tip surface of the center electrode 5 and opens toward the tip side, communicates with the outside via the through hole 27H. Has been.

  In the spark plug 1 described above, spark discharge is generated by applying a high voltage to the gap 29 formed between the center electrode 5 and the ground electrode 27, and then electric power is supplied to the gap 29 to discharge the gap. Plasma is generated in the cavity portion 28 by changing the state. Then, next, the structure of the voltage application part 31 for applying a high voltage to the said gap | interval 29 of the spark plug 1 and the power input part 41 for supplying electric power to the gap | interval 29 is demonstrated.

  As shown in FIG. 1, the voltage application unit 31 is electrically connected to the spark plug 1 via a diode 36 for preventing current from flowing from the power input unit 41 and a resistor 37 for noise suppression. It is connected to the. The voltage application unit 31 includes a primary coil 32, a secondary coil 33, a core 34, and an igniter 35.

  The primary coil 32 is wound around the core 34, one end of which is connected to the battery VA for power supply, and the other end is connected to the igniter 35. The secondary coil 33 is wound around the core 34, and one end thereof is connected between the primary coil 32 and the battery VA, and the other end is connected to the terminal electrode 6 of the spark plug 1. Yes.

  In addition, the igniter 35 is formed of a predetermined transistor, and switches between supply and stop of power supply from the battery VA to the primary coil 32 in accordance with an energization signal input from a predetermined ECU (electronic control unit) 61. . When applying a high voltage to the spark plug 1, a current is passed from the battery VA to the primary coil 32, a magnetic field is formed around the core 34, and the energization signal from the ECU 61 is switched from on to off. Then, energization of the primary coil 32 from the battery VA is stopped. When the energization is stopped, the magnetic field of the core 34 is changed, and a negative high voltage (for example, 5 kV to 30 kV) is generated in the secondary coil 33. By applying this high voltage to the spark plug 1 (terminal electrode 6), a spark discharge can be generated in the gap 29.

  In addition, the power input unit 41 is electrically connected to the spark plug 1 and includes a power supply device PS and a capacitor 42.

  The power supply device PS is a power supply circuit capable of generating a negative high voltage (for example, 500 V to 1500 V), and is electrically connected to the spark plug 1 and the capacitor 42. Further, the ECU 61 controls the charging timing of the capacitor 42 from the power supply device PS, and charging of the capacitor 42 is performed before power is supplied from the capacitor 42 to the spark plug 1 (before spark discharge in the spark plug 1). It is like that.

  In addition, one end of the capacitor 42 is connected between the power supply device PS and an inductor 44 described later, and the other end of the capacitor 42 is grounded. When a spark discharge occurs in the gap 29 and the dielectric breakdown occurs between the electrodes 5 and 27, the electric power stored in the capacitor 42 is ignited via an inflow prevention diode 43 and an inductor 44 described later, and the spark plug 1. Plasma is generated. During plasma generation, the current flowing through the gap 29 is relatively large, and the resistance value R of the spark plug 1 (gap 29) is very small.

  In addition, an inflow prevention diode 43 that prevents current from flowing from the voltage application unit 31 to the power input unit 41 is connected in series between the power input unit 41 and the spark plug 1.

  In addition, an inductor 44 is connected in series between the inflow prevention diode 43 and the power input unit 41. Due to the presence of the inductor 44, it is possible to continue the ejection of plasma from the cavity portion 28 for a certain period of time, reduce the peak value of current when power is turned on, and the like.

  By the way, when attention is paid to the capacitor 42, the inflow prevention diode 43, the inductor 44, and the spark plug 1, the circuit configuration at the time of plasma generation of the spark plug 1 is the same as the equivalent circuit shown in FIG. In the ignition device 71, the capacitance of the capacitor 42 is C (μF), the inductance L (μH) of the inductor 44, and the resistance value R (Ω) of the ignition plug 1 (gap 29) at the time of plasma generation. 4L / C-R> 0 (in addition, since the resistance value R is very small, in a general plasma jet ignition plug ignition device, 4L / C-R> 0 is likely to be satisfied). Therefore, when it is assumed that the inflow prevention diode 43 does not exist in the equivalent circuit, as shown in FIG. 4A, as power is supplied from the power input unit 41 (capacitor 42) to the spark plug 1, Since a reverse current is generated in the inductor 44, energy flows back and forth between the capacitor 42 and the inductor 44, and the current flowing through the spark plug 1 oscillates damped. However, when the inflow prevention diode 43 is present as in the present embodiment, the current flows only in one direction. Therefore, as shown in FIG. Only the current due to the electric power first input from the (capacitor 42) flows. That is, due to the presence of the inflow prevention diode 43, the reverse current due to the energy generated in the inductor 44 does not flow, and the generated energy may be consumed as it is.

  In consideration of this point, in the present embodiment, as shown in FIG. 1, a recharging diode 51 is provided as a recharging unit that recharges the capacitor 42 by the reverse current generated by the inductor 44. The recharging diode 51 has its anode connected between the inflow prevention diode 43 and the inductor 44 and its cathode is grounded. Therefore, the reverse current by the inductor 44 flows into the capacitor 42 as shown by the arrow in FIG. 1, and as a result, the capacitor 42 is charged. Then, as shown in FIGS. 5 (a) and 5 (b), power is supplied from the charged capacitor 42 to the spark plug 1 and the reverse current of the inductor 44 generated by the power supply is caused. Recharging the capacitor 42 is repeated. As a result, electric power is supplied to the spark plug 1 a plurality of times.

  As described above in detail, according to the present embodiment, the recharging diode 51 is provided, and the capacitor 42 is recharged by the reverse current caused by the inductor 44 generated when the power is supplied from the capacitor 42 to the spark plug 1. can do. Then, power can be supplied again from the recharged capacitor 42 to the spark plug 1, and the capacitor 42 can be charged again by the reverse current generated when the power is supplied. That is, according to the present embodiment, the energy generated in the inductor 44 that has been wasted in the past can be used effectively, and power is supplied from the capacitor 42 to the spark plug 1 a plurality of times. (That is, energy efficiency can be improved and ignitability can be improved).

Further, spark discharge and plasma generation can be performed using the center electrode 5 as a negative electrode, and the ignitability and electrode wear resistance can be improved.
[Second Embodiment]
Next, the second embodiment will be described focusing on differences from the first embodiment. In the first embodiment, a power supply circuit capable of generating a negative high voltage is used as the power supply PS. However, in the second embodiment, as shown in FIG. A power supply circuit capable of generating a positive high voltage is used.

  The ignition device 171 in the second embodiment includes a power input unit 141 (capacitor 142), an inflow prevention diode 143, an inductor 144, a recharging diode 151, and the like, as in the first embodiment. However, with the change of the power supply device PS2, the arrangement position of the capacitor 142 is changed.

  More specifically, the capacitor 142 is connected in series between the inductor 144 and the power supply device PS2, and an FET (field effect transistor) 145 as a semiconductor switch is electrically connected to the capacitor 142.

  The FET 145 has its source grounded and its drain connected between the capacitor 142 and the power supply device PS2. A gate voltage based on an output signal from the ECU 61 is applied to the gate of the FET 145. The gate voltage is normally turned off (that is, when the capacitor 142 is charged from the power supply device PS2), but is turned on in accordance with the voltage application start timing from the voltage application unit 31 to the spark plug 1. The on-time is equal to the time when power is supplied from the capacitor 142 to the spark plug 1. That is, the FET 145 is turned on when the electric power charged in the capacitor 142 is supplied to the spark plug 1 (gap 29), and is turned off when the capacitor 142 is charged by the power supply device PS2. In the present embodiment, the rising timing of the gate voltage is set to substantially coincide with the timing (the falling timing of the energization signal) when the energization signal from the ECU 61 to the igniter 35 is switched from on to off.

  Note that the power-on time from the capacitor 142 to the spark plug 1 varies depending on the configuration of the capacitor 142, the inductor 144, and the like, but can be set to 10 μs to 50 μs, for example. Further, when the capacitor 142 is charged by the power supply device PS2, a current flows through the inductor 144 and the recharging diode 151.

  Furthermore, in the second embodiment, a switch protection diode 146 connected in parallel with the FET 145 is provided. The switch protection diode 146 has its anode connected between the capacitor 142 and the FET 145, and its cathode is grounded, so that a reverse current from the inductor 144 can pass therethrough.

  As described above, according to the second embodiment, the same operational effects as those of the first embodiment are basically obtained. That is, the reverse current caused by the inductor 144 can be recharged to the capacitor 142, and power can be reapplied from the recharged capacitor 142 to the spark plug 1.

  Furthermore, since the power supply device PS2 generates a positive voltage, it can suppress the manufacturing cost and more reliably prevent the device from becoming complicated.

In addition, since the reverse current caused by the inductor 144 flows through the switch protection diode 146, damage to the FET 145 due to the generation of the reverse current can be prevented more reliably.
[Third Embodiment]
Next, the third embodiment will be described focusing on the differences from the second embodiment. In the third embodiment, as shown in FIG. 7, a charging diode 147 is provided upstream of the inductor 144 (on the power input unit 141 side). The charging diode 147 has its anode connected between the capacitor 142 and the inductor 144, and its cathode is grounded. In the second embodiment, the capacitor 142 is charged by the power supply device PS2, and the current flows through the inductor 144 and the recharging diode 151. However, in the third embodiment, the charging diode 147 is provided. Thus, when the capacitor 142 is charged by the power supply device PS2, a current flows through the charging diode 147, and a current hardly flows through the inductor 144.

  As described above, according to the third embodiment, the same functions and effects as those of the second embodiment are basically obtained.

  In addition, since it is configured such that almost no current flows through the inductor 144 when charging the capacitor 142, it is possible to more reliably prevent energy from being generated in the inductor 144 during charging. As a result, energy loss during charging of the capacitor 142 can be suppressed, and energy efficiency can be further improved.

  Next, an input efficiency evaluation test was performed in order to confirm the operational effects achieved by the above embodiment. The outline of the input efficiency evaluation test is as follows. That is, a sample A of an ignition device having a recharging unit (recharging diode) and a sample B of an ignition device configured without providing a recharging unit (recharging diode) are manufactured, and a capacitor of each sample Was charged, and the electric energy (charge energy) charged in the capacitor was measured. Then, power is supplied from the power input portion of each sample to the spark plug, and the discharge current of the gap is measured, and the discharge current and the resistance of the gap at the time of discharge (note that the resistance of the gap is not strictly constant) However, since it is generally about 1Ω, the power energy input to the spark plug was calculated based on 1Ω in this test). Then, energy input efficiency was obtained by multiplying the value obtained by dividing the calculated power energy by the charging energy by 100. Table 1 shows the test results of the test. In each sample, the output voltage from the power supply device was set to 600V or 1500V. In addition, the sample in which the output voltage of the power supply device is 600 V is set to 0.68 μF or 3.3 μF in the capacitance of the capacitor, and the sample in which the output voltage of the power supply device is 1500 V is set to 0.1 μF in the capacitor. Or 0.5 μF. Furthermore, the inductance of the inductor was set to 5 μH or 50 μH.

  As shown in Table 1, it was clarified that Sample A provided with the recharging unit has an energy efficiency higher than that of Sample B, and has an excellent energy efficiency. This is considered to be because the capacitor is recharged by the reverse current generated by the inductor and the charging energy is supplied to the spark plug by providing the recharge unit.

  From the above results, it can be said that it is preferable to provide a recharging unit that recharges the capacitor with a reverse current by the inductor from the viewpoint of improving energy efficiency and improving ignitability.

  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 recharging diode 51 is used as the recharging unit. However, as the recharging unit, the recharging unit is turned on when a reverse current flows through the inductors 44 and 144, and the power input units 41 and 141. A semiconductor switch such as a transistor, FET, or thyristor that is turned off when power is supplied from the (capacitors 42 and 142) to the spark plug 1 may be used. That is, the recharging unit can pass a reverse current through the inductors 44 and 144, while the passage of current flowing when power is supplied from the power input units 41 and 141 (capacitors 42 and 142) to the spark plug 1 is restricted. Anything can be used.

  (B) In the above embodiment, the FET 145 is cited as the semiconductor switch, but the available semiconductor switch is not limited to this. Therefore, a transistor or a thyristor may be used as the semiconductor switch.

  (C) In the above embodiment, the voltage application unit 31 and the power input unit 41 are provided for each spark plug 1, but without providing the voltage application unit 31 and the power input unit 41 for each spark plug 1, It is good also as supplying the electric power from the voltage application part 31 or the electric power input part 41 to each spark plug 1 via a distributor.

  (D) The configuration of the spark plug 1 in the above embodiment is an exemplification, and the configuration of the available plasma jet spark plug is not particularly limited. Therefore, for example, only the inner peripheral side portion of the ground electrode 27 that is consumed by spark discharge may be formed of a metal such as W or Ir, or the center electrode 5 may be configured without providing the electrode tip 5C. It is good to do.

  DESCRIPTION OF SYMBOLS 1 ... Spark plug (plasma jet spark plug), 5 ... Center electrode, 27 ... Ground electrode, 28 ... Cavity part, 29 ... Gap, 31 ... Voltage application part, 41 ... Power supply part, 42 ... Capacitor, 43 ... Inflow prevention Diode 44, Inductor 51 ... Recharging diode (recharging unit) 71 ... Ignition device 101 ... Ignition system 145 ... FET (semiconductor switch) 146 ... Switch protection diode 147 ... Charging diode, PS: Power supply device.

Claims (6)

An ignition device used for a plasma jet ignition plug having a center electrode, a ground electrode, and a cavity that surrounds at least a part of a gap formed between the electrodes and forms a discharge space,
A voltage application unit for applying a voltage to the gap;
A capacitor, and a power supply unit that charges the capacitor, and a power input unit that supplies power to the gap;
An inflow prevention diode connected in series between the plasma jet ignition plug and the power input unit, and preventing current inflow from the voltage application unit to the power input unit,
The inflow prevention diode and the inductor connected in series between the power input unit,
A voltage is applied to the gap from the voltage application unit to generate a spark discharge in the gap, and a plasma is generated in the cavity unit by supplying power charged in the capacitor to the gap through the inductor. Can be generated,
An ignition device comprising: a recharging unit that recharges the capacitor by a reverse current caused by the inductor generated when power is supplied from the capacitor to the ignition plug.   2. The ignition device according to claim 1, wherein the recharging unit is a recharging diode having one end connected between the inflow prevention diode and the inductor and the other end grounded. The power supply device generates a negative voltage,
The ignition device according to claim 1, wherein one end of the capacitor is connected between the power supply device and the inductor, and the other end of the capacitor is grounded. The power supply device generates a positive voltage,
The capacitor is connected in series between the power supply device and the inductor,
One end of itself is connected between the power supply device and the capacitor, and the other end of the device is grounded, and is turned off when the capacitor is charged by the power supply device, while the electric power charged in the capacitor is A semiconductor switch that is turned on when the gap is inserted;
The ignition device according to claim 1, further comprising: a switch protection diode connected in parallel with the semiconductor switch and through which a reverse current from the inductor flows.   5. A charging diode having one end connected to the capacitor and the inductor, the other end connected to the ground, and a current flowing when the capacitor is charged by the power supply device. Ignition device according to. The ignition device according to any one of claims 1 to 5,
An ignition system comprising: a plasma jet ignition plug to which electric power is supplied from the ignition device.

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