JP2013060869A - Ignition system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently enhance contamination resistance of an ignition plug without applying constitution change for suppressing contamination to the ignition plug.SOLUTION: An ignition system 31 has the ignition plug 1, a power source 41 for electric discharge for applying voltage to the ignition plug 1, and an alternate current power source 51 for supplying alternate current power to the ignition plug 1. The ignition plug 1 has an insulator 2, a center electrode 5, a main fitting 3, a grounding electrode 27 for forming a gap 28 with a distal end part of the center electrode 5 and is attached to an internal combustion engine EN. The ignition system 31 has a control section 71 for controlling a power source 41 for electric discharge and the alternate current power source 51, the control section 71 can set an operation mode of the power source 41 for the electric discharge and the alternate current power source 51 to a gap plasma generating mode for supplying the alternate current power to a spark generated by an application of the voltage to the ignition plug 1 from the power source 41 for the electric discharge from the alternate current power source 51 and generating an alternate current plasma in a gap 28.

Description

  The present invention relates to an ignition system used for an internal combustion engine or the like.

  An ignition plug used in a combustion apparatus such as an internal combustion engine includes, for example, a center electrode extending in the axial direction, an insulator provided on the outer periphery of the center electrode, a cylindrical metal shell provided on the outer periphery of the insulator, A ground electrode fixed to the tip of the metal fitting. Then, by applying a high voltage to the gap formed between the center electrode and the ground electrode, a spark discharge is generated in the gap, and as a result, the fuel gas (air mixture) is ignited. ing.

  By the way, carbon is generated in the combustion chamber due to incomplete combustion of the fuel gas, and the generated carbon is deposited on the surface of the insulator exposed to the combustion chamber (that is, the spark plug is soiled). ) If the insulator is contaminated, current flows easily through the surface of the insulator (carbon), so spark discharge occurs at a location different from the gap, and the combustion state deteriorates, such as a reduction in combustion efficiency and output. May be invited. Further, when the contamination further progresses, the current leaks between the center electrode and the metal shell through the surface of the insulator (carbon), and there is a possibility that the spark discharge itself cannot be performed. Therefore, it is important to improve the resistance to fouling (fouling resistance) from the viewpoint of realizing a good combustion state.

  The technique for improving the fouling resistance is to increase the surface area of the leg part by increasing the length of the part of the insulator exposed to the combustion chamber (leg part), so that some carbon adheres to the leg part. In addition, a method for ensuring insulation between the center electrode and the metal shell is conceivable. There has also been proposed a method of maintaining insulation between the center electrode and the metal shell by providing insulating oil between the long leg portion and the metal shell (see, for example, Patent Document 1).

JP 2001-135457 A

  However, in the method of increasing the length of the leg length part, the leg length part is likely to be overheated, which may cause problems such as pre-ignition (early ignition). Further, in the method described in Patent Document 1, since the insulating oil is dripped with the operation of the internal combustion engine, a bridge connecting the center electrode and the ground electrode is formed by the insulating oil, and a spark discharge is caused. May cause trouble. In other words, when the contamination is to be suppressed by changing the configuration of the spark plug, the contamination may be suppressed, but there may be disadvantages in other aspects.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to effectively improve the antifouling property of the spark plug without subjecting the spark plug to a configuration change for suppressing fouling. 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 system of the present configuration includes an insulator having an axial hole extending in the axial direction, a center electrode inserted at a tip end side of the axial hole, a metal shell disposed on an outer periphery of the insulator, and the metal shell A spark plug attached to the internal combustion engine, and a ground electrode that forms a gap with the tip of the center electrode.
A discharge power source for applying a voltage to the spark plug;
An AC power supply for supplying AC power to the spark plug;
An ignition system comprising:
A controller for controlling the discharge power supply and the AC power supply;
The control unit sets the operation mode of the discharge power source and the AC power source at a timing other than a normal ignition timing by the spark plug to the spark generated by applying a voltage from the discharge power source to the spark plug. A gap plasma generation mode in which AC power is supplied from a power source and AC plasma is generated in the gap can be set.

  The “regular ignition timing” refers to the timing at which the fuel gas is ignited to operate the internal combustion engine (hereinafter the same).

  According to the configuration 1, the control unit can generate the AC plasma in the gap by setting the operation mode of the discharge power source and the AC power source to the gap plasma generation mode. And the carbon adhering to the surface (tip surface of an insulator) located in the vicinity of the gap among the insulators can be effectively burned out by the generated high-temperature AC plasma. Accordingly, excellent antifouling properties can be realized.

  Further, it is not necessary to make a configuration change for suppressing the contamination on the spark plug, and the conventional spark plug can be used as it is. Therefore, it is possible to prevent the occurrence of problems associated with the configuration change of the spark plug.

  Configuration 2. The ignition system of the present configuration is the above-described configuration 1, wherein the control unit sets the operation mode at a timing other than a normal ignition timing by the spark plug until a predetermined period elapses after the start of the internal combustion engine. The gap plasma generation mode can be set.

  During the predetermined period from the start of the internal combustion engine, the temperature in the combustion chamber is low, so the fuel gas may not be sufficiently atomized. For this reason, carbon is likely to be generated, and the spark plug is particularly likely to be stained.

  In this regard, according to the above-described configuration 2, the operation mode of the discharge power source and the AC power source can be set to the gap plasma generation mode from the time when the internal combustion engine is started until a predetermined period elapses. Therefore, even during a period in which the spark plug is particularly susceptible to contamination, the contamination can be more reliably prevented.

Configuration 3. The ignition system of the present configuration includes a misfire detection unit that detects misfire of the internal combustion engine in the above configuration 1 or 2,
The control unit is capable of setting the operation mode to the gap plasma generation mode at a timing other than a normal ignition timing by the spark plug when the misfire is detected by the misfire detection unit. To do.

  Note that “misfire of the internal combustion engine” refers to a spark plug caused by fouling, and includes spark discharge mistakes and fuel gas ignition mistakes associated with the fouling (the same applies hereinafter).

  According to the configuration 3, when the misfire detection unit detects misfire of the internal combustion engine, the operation mode can be set to the gap plasma generation mode. Therefore, the internal combustion engine can be recovered from a misfire state caused by fouling.

  Configuration 4. In the ignition system of this configuration, in any one of the above configurations 1 to 3, the control unit can set the operation mode to the gap plasma generation mode in the intake stroke, the exhaust stroke, or the combustion stroke of the internal combustion engine. It is characterized by that.

  According to the configuration 4, the AC plasma can be generated in the gap during the intake stroke, the exhaust stroke, and the combustion stroke of the internal combustion engine. Accordingly, it is possible to more reliably prevent the operation of the internal combustion engine from being hindered due to the generation of AC plasma for burning out carbon.

Configuration 5. The ignition system of the present configuration includes an insulator having an axial hole extending in the axial direction, a center electrode inserted on a tip side of the axial hole, a metal shell disposed on an outer periphery of the insulator, and the insulator A spark plug attached to the internal combustion engine, and a space formed between the outer peripheral surface of the metal shell and the inner peripheral surface of the metal shell,
An AC power supply for supplying AC power to the spark plug;
An ignition system comprising:
A control unit for controlling the AC power supply;
The control unit supplies an AC power from the AC power source to the ignition plug at a timing other than a normal ignition timing by the ignition plug, and generates an AC plasma in the space. The generation mode can be set.

  According to the configuration 5, the control unit sets the operation mode of the AC power supply to the spatial plasma generation mode, so that the space formed between the outer peripheral surface on the tip end side of the insulator and the inner peripheral surface of the metal shell is formed. AC plasma can be generated. More specifically, the space located between the center electrode whose outer periphery is covered with an insulator (dielectric material) and the metal shell facing the outer peripheral surface of the center electrode by applying AC power to the spark plug. Thus, dielectric barrier discharge (that is, AC plasma) can be generated. Therefore, the carbon adhering to the surface forming the space in the insulator can be effectively burned out, and excellent antifouling resistance can be realized.

  In addition, since it is not necessary to change the configuration of the spark plug in order to suppress contamination, it is possible to prevent the occurrence of problems associated with the configuration change of the spark plug.

  Configuration 6. The ignition system of the present configuration is the above-described configuration 5, wherein the control unit sets the operation mode at a timing other than a normal ignition timing by the spark plug until a predetermined period elapses after the start of the internal combustion engine. The spatial plasma generation mode can be set.

  According to the said structure 6, the effect similar to the said structure 2 will be show | played fundamentally.

Configuration 7. The ignition system of the present configuration includes a misfire detection unit that detects misfire of the internal combustion engine in the configuration 5 or 6,
The control unit is capable of setting the operation mode to the spatial plasma generation mode at a timing other than a normal ignition timing by the spark plug when the misfire is detected by the misfire detection unit. To do.

  According to the said structure 7, the effect similar to the said structure 3 will be show | played fundamentally.

  Configuration 8. In the ignition system of this configuration, in any of the above configurations 5 to 7, the control unit can set the operation mode to the spatial plasma generation mode in the intake stroke, the exhaust stroke, or the combustion stroke of the internal combustion engine. It is characterized by that.

  According to the said structure 8, the effect similar to the said structure 4 will be show | played fundamentally.

  Configuration 9 The ignition system of this configuration is characterized in that, in any of the above configurations 5 to 8, the control unit can set the operation mode to the spatial plasma generation mode in the intake stroke of the internal combustion engine.

  The lower the pressure in the combustion chamber, the more reliably the AC plasma can be generated in the space (without increasing the supply power). Accordingly, in the intake stroke in which the pressure in the combustion chamber is the lowest in one combustion cycle as in the above configuration 9, AC plasma can be easily generated by setting the operation mode to the AC plasma generation mode.

Configuration 10 The ignition system according to this configuration is the ignition system according to any one of the above configurations 5 to 9, wherein a step portion that is directly or indirectly locked to the metal shell is provided on an outer periphery of the insulator, and a rear end of the step portion. A large-diameter portion formed on the side and bulging radially outward,
The inner periphery of the insulator is provided with a locked portion to which the center electrode is locked,
At least the surface located between the rear end of the large-diameter portion and the rear end of the stepped portion of the outer peripheral surface of the insulator, and the locked portion from the rear end of the inner peripheral surface of the insulator The surface located between the rear ends is covered with a metal layer.

  From the standpoint of enhancing the ease of insertion of the insulator into the metal shell and the ease of insertion of the center electrode, etc. into the insulator, the metal shell disposed on the insulator and its outer periphery, the center electrode disposed on the inner periphery, etc. There may be a gap (air layer) between the two. When such an air layer is present, when AC power is supplied to the spark plug, AC plasma is generated in the air layer, which may hinder the generation of AC plasma in the space. There is a fear.

  In this regard, the configuration 10 is configured such that a portion of the insulator corresponding to the air layer is covered with the metal layer. Therefore, generation of AC plasma in the air layer can be prevented more reliably, and AC plasma can be generated more reliably in the space. As a result, the above-described effect of improving the fouling resistance can be more reliably exhibited.

Configuration 11 The ignition system of the present configuration includes an insulator having an axial hole extending in the axial direction, a center electrode inserted at a tip end side of the axial hole, a metal shell disposed on an outer periphery of the insulator, and the metal shell An internal combustion engine having a ground electrode fixed to the tip of the center electrode and forming a gap between the center electrode and a space formed between an outer peripheral surface of the insulator and an inner peripheral surface of the metal shell. With spark plug mounted,
A discharge power source for applying a voltage to the spark plug;
An AC power supply for supplying AC power to the spark plug;
An ignition system comprising:
A controller for controlling the discharge power supply and the AC power supply;
The control unit sets the operation mode of the discharge power source and the AC power source at a timing other than a normal ignition timing by the spark plug to the spark generated by applying a voltage from the discharge power source to the spark plug. A gap plasma generation mode in which AC power is supplied from a power source to generate AC plasma in the gap, or a space plasma generation mode in which AC power is supplied from the AC power source to the spark plug to generate AC plasma in the space. It can be set.

  According to the above configuration 11, both the gap plasma generation mode and the spatial plasma generation mode can be selected as the operation mode, and the control unit can set any one mode as the operation mode. . Therefore, both the carbon adhering to the surface of the insulator located near the gap (the front end surface of the insulator) and the carbon adhering to the surface of the insulator forming the space are effectively burned out. Can do. As a result, the stain resistance can be dramatically improved.

  In addition, since it is not necessary to change the configuration of the spark plug in order to suppress contamination, it is possible to prevent the occurrence of problems associated with the configuration change of the spark plug.

  Configuration 12. The ignition system of this configuration is the above-described configuration 11, wherein the control unit sets the operation mode at a timing other than a normal ignition timing by the ignition plug until a predetermined period elapses after the start of the internal combustion engine. The gap plasma generation mode or the spatial plasma generation mode can be set.

  According to the above-described configuration 12, even when the spark plug is particularly susceptible to contamination, the contamination can be extremely effectively prevented.

Configuration 13 The ignition system of the present configuration includes a misfire detection unit that detects misfire of the internal combustion engine in the above configuration 11 or 12,
The control unit can set the operation mode to the gap plasma generation mode or the spatial plasma generation mode at a timing other than a normal ignition timing by the spark plug when the misfire is detected by the misfire detection unit. It is characterized by being.

  According to the configuration 13, the internal combustion engine can be more reliably recovered from the misfire state caused by the fouling.

  Configuration 14 In the ignition system of this configuration, in any of the above configurations 11 to 13, the control unit sets the operation mode to the gap plasma generation mode or the spatial plasma generation in the intake stroke, the exhaust stroke, or the combustion stroke of the internal combustion engine. The mode can be set.

  According to the said structure 14, the effect similar to the said structure 4 is show | played fundamentally.

  Configuration 15 The ignition system of this configuration is characterized in that, in any of the above configurations 11 to 14, the control unit can set the operation mode to the spatial plasma generation mode in the intake stroke of the internal combustion engine.

  According to the said structure 15, the effect similar to the said structure 9 is show | played fundamentally.

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 explanatory drawing which shows the timing etc. which make an operation mode a gap | interval plasma generation mode. It is a partially broken front view which shows the structure of the ignition plug in 2nd Embodiment. In 2nd Embodiment, it is explanatory drawing which shows the timing etc. which make an operation mode a space plasma generation mode. In 3rd Embodiment, it is explanatory drawing which shows the timing etc. which make an operation mode a gap | interval plasma generation mode or a space plasma generation mode.

Embodiments will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of the ignition system 31. As shown in FIG. 1, the ignition system 31 includes an ignition plug 1 attached to the internal combustion engine EN, a discharge power supply 41, an AC power supply 51, a mixing circuit 61, a control unit 71, a misfire detection unit 81, and the like. It has. 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. And the electric power from the power supply 41 for discharge and the alternating current power supply 51 is supplied to each spark plug 1 via the distributor which is not shown in figure.

  First, the configuration of the spark plug 1 will be described.

  As shown in FIG. 2, the spark plug 1 includes an insulator 2 as a cylindrical insulator, 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 bulging radially outward on the side, a middle body portion 12 having a smaller diameter on the distal side than the large-diameter portion 11, and a distal end 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 length portions 13 are accommodated in the metal shell 3, and the rear end side trunk portion 10 is formed of the metal shell. 3 is exposed from the rear end. In addition, a tapered step portion 14 is formed at a 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, a shaft hole 4 is formed through the insulator 2 along the axis CL <b> 1, and a center electrode 5 is inserted on the tip side of the shaft hole 4. The center electrode 5 has a rod shape as a whole, and its tip protrudes from the tip of the insulator 2 toward the tip in the direction of the axis CL1. The center electrode 5 is made of a Ni alloy containing nickel (Ni) as a main component. Furthermore, a hook-like portion 5F protruding radially outward is provided at the rear end portion of the center electrode 5, and the hook-like portion 5F is a tapered locked engagement provided on the inner periphery of the insulator 2. The center electrode 5 is inserted into the shaft hole 4 while being locked to the portion 4A. Note that an inner layer made of copper or copper alloy having excellent thermal conductivity may be provided inside the center electrode 5. In this case, heat extraction of the center electrode 5 is improved, and durability can be improved.

  Furthermore, on the rear end side of the shaft hole 4, a terminal electrode 6 having a rod shape and made of metal such as carbon steel is inserted. Further, a connecting portion 6A bulging radially outward is provided at the rear end portion of the terminal electrode 6, and the connecting portion 6A protrudes from the rear end of the insulator 2 and is output from the mixing circuit 61. (Transmission path 32C described later) is electrically connected.

  Further, a cylindrical glass seal portion 7 is disposed between the center electrode 5 and the terminal electrode 6. The glass seal portion 7 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.

  The metal shell 3 is formed in a cylindrical shape from a metal such as low carbon steel, and a screw portion (male screw portion) 15 for attaching the spark plug 1 to the mounting hole of the internal combustion engine is formed on the outer peripheral surface thereof. Yes. A flange-like seat portion 16 is formed on the outer peripheral surface of the screw portion 15 on the rear end side, 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 internal combustion engine is provided. A caulking portion 20 for holding the insulator 2 is provided.

  Further, on the inner peripheral surface of the metal shell 3, an annular protrusion 21 is provided that protrudes radially inward. The insulator 2 is inserted from the rear end side to the front end side of the metal shell 3, and the rear end side of the metal shell 3 with its stepped portion 14 locked to the protrusion 21. Are fixed to the metal shell 3 by caulking the opening in the radial direction, that is, by forming the caulking portion 20. An annular plate packing 22 is interposed between the stepped portion 14 and the protruding portion 21. As a result, the gas tightness in the combustion chamber is maintained, and the fuel gas (air mixture) entering the gap between the leg length 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. It has become.

  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 powder of talc (talc) 25. 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.

  In addition, a ground electrode 27 formed of an alloy containing Ni as a main component and bent back at a substantially middle portion is joined to the distal end portion 26 of the metal shell 3. The ground electrode 27 has a side surface facing the tip of the center electrode 5, and a gap 28 is formed between the tip of the center electrode 5 and the ground electrode 27.

  Next, the configuration of the discharge power supply 41 and the like will be described with reference to FIG.

  The discharge power supply 41 applies a high voltage to the spark plug 1 and causes a spark discharge in the gap 28. In the present embodiment, the discharge power supply 41 includes a primary coil 42, a secondary coil 43, a core 44, and an igniter 45.

  The primary coil 42 is wound around the core 44. One end of the primary coil 42 is connected to the battery VA for power supply, and the other end is connected to the igniter 45. The secondary coil 43 is wound around the core 44, one end of which is connected between the primary coil 42 and the battery VA, and the other end is connected to the terminal of the spark plug 1 via the mixing circuit 61. It is connected to the electrode 6.

  In addition, the igniter 45 is formed by a predetermined transistor, and switches between supply and stop of power supply from the battery VA to the primary coil 42 according to the energization signal input from the control unit 71. When a high voltage is applied to the spark plug 1, a current is passed from the battery VA to the primary coil 42 to form a magnetic field around the core 44, and the energization signal from the control unit 71 is switched from on to off. As a result, energization of the primary coil 42 from the battery VA is stopped. When the energization is stopped, the magnetic field of the core 44 changes, and a negative high voltage (for example, 5 kV to 30 kV) is generated in the secondary coil 43. By applying this high voltage to the spark plug 1, a spark discharge can be generated in the gap 28.

  The AC power source 51 supplies AC power having a relatively high frequency (for example, 50 kHz to 100 MHz) to the spark plug 1. Further, an impedance matching circuit (matching unit) 33 is provided between the AC power supply 51 and the mixing circuit 61. The impedance matching circuit 33 is configured so that the output impedance on the AC power source 51 side matches the input impedance on the mixing circuit 61 and the spark plug 1 (load) side, and is supplied to the spark plug 1 side. Attenuation of AC power is prevented. The AC power transmission path from the AC power source 51 to the spark plug 1 is constituted by a coaxial cable having an inner conductor and an outer conductor disposed on the outer periphery of the inner conductor. As a result, the reflection of power is prevented. Is planned.

  The mixing circuit 61 converts the high voltage transmission path 32A output from the discharge power supply 41 and the AC power transmission path 32B output from the AC power supply 51 into one transmission path 32C connected to the spark plug 1. In summary, a coil 62 and a capacitor 63 are provided. In the coil 62, a relatively low-frequency current output from the discharge power supply 41 is allowed to pass, while a relatively high-frequency current output from the AC power supply 51 is not allowed to pass. Inflow of the current output from the power supply 51 to the discharge power supply 41 side is suppressed. On the other hand, in the capacitor 63, a relatively high frequency current output from the AC power supply 51 can pass, while a relatively low frequency current output from the discharge power supply 41 cannot pass. Thus, inflow of the current output from the discharge power supply 41 to the AC power supply 51 side is suppressed. The secondary coil 43 may be used in place of the coil 62 and the coil 62 may be omitted.

  In the present embodiment, an AC plasma is generated in the gap 28 by supplying AC power from the AC power supply 51 to the spark generated in the gap 28 by the voltage from the discharge power supply 41. Has been. Then, by the control unit 71 (in the present embodiment, constituted by a predetermined electronic control unit (ECU) 91), the voltage application timing from the discharge power source 41 to the spark plug 1 or the AC power source 51 from the spark plug 1 is set. The supply timing of AC power to (i.e., the generation timing of AC plasma) is controlled.

  The misfire detection unit 81 is configured by the ECU 91, and after the AC plasma is generated in the gap 28 (when it is considered that the fuel gas is combusted), a predetermined voltage (for example, 100V) is applied to the gap 28. ˜300 V) is applied, and the current flowing through the gap 28 is detected. Here, when combustion occurs normally, ions are generated along with the combustion. Therefore, an ion current flows through the gap 28 by applying the predetermined voltage to the gap 28. Using this point, the misfire detection unit 81 detects misfire of the internal combustion engine EN based on the detected current (ion current). Specifically, the misfire of the internal combustion engine EN is detected by comparing the detected current peak value or integral value with a predetermined criterion value. In addition, in the case where combustion did not occur normally due to contamination of the insulator 2 due to adhesion of carbon or the like (for example, when spark discharge did not occur due to the contamination or the fuel gas was not ignited), A misfire of the internal combustion engine EN will be detected.

  Next, control of the discharge power supply 41 and the AC power supply 51 by the control unit 71 will be described.

  As shown in FIG. 3, the control unit 71 controls the discharge power supply 41 and the AC power supply 51 at regular ignition timing (ignition timing for operating the internal combustion engine EN) during the compression stroke or immediately after the compression stroke. Thus, AC plasma is generated in the gap 28 to ignite the fuel gas. The control unit 71 applies only the voltage from the discharge power supply 41 to the gap 28 to cause a spark discharge, and the discharge power supply 41 and the like are set so that the fuel gas is ignited by the spark discharge. It is also possible to control.

  Further, the control unit 71 generates AC plasma in the gap 28 by controlling the discharge power source 41 and the AC power source 51 at timings other than the regular ignition timing. That is, the operation mode of the discharge power supply 41 and the AC power supply 51 is a gap plasma generation mode in which AC plasma is generated in the gap 28. In the present embodiment, in the intake stroke, the exhaust stroke, or the combustion stroke, the operation mode of both the power sources 41 and 51 is set to the gap plasma generation mode every predetermined cycle of the internal combustion engine EN. In the present embodiment, the AC plasma is generated in the region surrounded by the virtual circle VC1 (see FIG. 2) and in the vicinity thereof, and the ignition is performed so that the AC plasma reaches at least the front end surface of the insulator 2. The output power of the AC power source 51 for the plug 1 and the supply time of the AC power for the spark plug 1 are set.

  Further, the control unit 71 sets the operation mode to the gap plasma generation mode in the intake stroke, the exhaust stroke, or the combustion stroke until a predetermined period (for example, 3 minutes) elapses from the start of the internal combustion engine EN. It is configured.

  Further, when misfire of the internal combustion engine EN is detected by the misfire detection unit 81, the control unit 71 sets the operation mode to the gap plasma generation mode in the exhaust stroke or the combustion stroke.

  As described above in detail, according to the present embodiment, the controller 72 can generate the AC plasma in the gap 28 by setting the operation mode to the gap plasma generation mode. The AC plasma can effectively burn off the carbon adhering to the surface of the insulator 2 located in the vicinity of the gap 28 (the front end surface of the insulator 2). Accordingly, excellent antifouling properties can be realized.

  Moreover, it is not necessary to change the configuration for suppressing the contamination on the spark plug, and the conventional spark plug 1 can be used as it is. Therefore, it is possible to prevent the occurrence of problems associated with the configuration change of the spark plug.

  Further, the operation mode is set to the gap plasma generation mode from when the internal combustion engine EN is started until a predetermined period elapses. Therefore, even during a period in which the spark plug 1 is particularly susceptible to contamination, the contamination can be more reliably prevented.

  In addition, when the misfire detection unit 81 detects misfire of the internal combustion engine EN, the operation mode is set to the gap plasma generation mode. Therefore, the internal combustion engine EN can be recovered from a misfire state caused by fouling.

In addition, in the present embodiment, the operation mode is the gap plasma generation mode in the intake stroke, the exhaust stroke, or the combustion stroke of the internal combustion engine. Accordingly, it is possible to more reliably prevent the operation of the internal combustion engine EN from being hindered due to the generation of AC plasma for burning out carbon.
[Second Embodiment]
Next, the second embodiment will be described focusing on differences from the first embodiment. In the second embodiment, as shown in FIG. 4, a predetermined portion of the insulator 2 is a metal layer 29 made of a predetermined metal material (in FIG. 4, the metal layer 29 is shown to be thicker than actual). Covered with. Specifically, a surface located between the rear end side of the outer peripheral surface of the insulator 2 and the rear end of the stepped portion 14 slightly from a portion located inside the caulking portion 20, and the insulator 2 The inner peripheral surface is covered with a metal layer 29. That is, from the viewpoint of enhancing the ease of insertion of the insulator 2 into the metal shell 3 and the ease of insertion of the center electrode 5 and the terminal electrode 6 into the insulator 2, the outer peripheral surface of the insulator 2 and the inner periphery of the metal shell 3. A slight gap is formed between the insulator 2 and the outer peripheral surface of the center electrode 5 or the like, and between the insulator 2 and the metal shell 3 or the center electrode 5 or the like. There may be an air layer. In the present embodiment, the insulator 2 is configured such that a portion corresponding to the air layer is covered with the metal layer 29. In addition, between the outer peripheral surface of the portion of the insulator 2 that is located on the rear end side with respect to the rear end of the large-diameter portion 11 and inserted through the metal shell 3, and the inner peripheral surface of the metal shell 3, talc Since 25 is filled, there may be no air layer. Therefore, it is good also as not providing the metal layer 29 in the outer peripheral surface of the site | part which contacts the talc 25 among the insulators 2. FIG.

  Further, in the second embodiment, as shown in FIG. 5, the control unit 71 controls the AC power source 51 at a timing other than the regular ignition timing, so that the outer peripheral surface of the leg long portion 13 and the metal shell 3 An annular AC plasma is generated in an annular space 30 (see FIG. 4) formed between the inner peripheral surface and exposed in the combustion chamber. That is, the operation mode of the AC power supply 51 is set to a space plasma generation mode in which AC plasma is generated in the space 30. Specifically, by supplying only AC power from the AC power source 51 to the spark plug 1, the center electrode 5 whose outer periphery is covered with the insulator 2 and the metal shell 3 facing the outer peripheral surface of the center electrode 5 are provided. A dielectric barrier discharge (alternating current plasma) is generated in the space 30 therebetween. That is, in the second embodiment, AC plasma is generated in the region surrounded by the virtual ellipse VC2 (see FIG. 4) and in the vicinity thereof.

  Further, the control unit 71 sets the operation mode of the AC power supply 51 to the spatial plasma generation mode until a predetermined period (for example, 3 minutes) elapses from the start of the internal combustion engine EN.

  In addition, when misfire of the internal combustion engine EN is detected by the misfire detection unit 81, the control unit 71 sets the operation mode to the spatial plasma generation mode in the exhaust stroke or the combustion stroke.

  In consideration of the fact that the lower the pressure in the combustion chamber is, the more reliably the AC plasma can be generated, it is preferable that the operation mode is the spatial plasma generation mode in the intake stroke, the exhaust stroke, or the combustion stroke, In the intake stroke, the operation mode is more preferably a spatial plasma generation mode.

  As described in detail above, according to the second embodiment, by generating AC plasma in the space 30, the carbon adhering to the surface of the insulator 2 that forms the space 30 is effectively removed. Can be burned out. As a result, excellent antifouling properties can be realized.

Moreover, since the site | part corresponding to the said air layer among the insulators 2 is covered with the metal layer 29, generation | occurrence | production of the alternating current plasma in an air layer can be prevented more reliably. As a result, AC plasma can be more reliably generated in the space 30, and the above-described effect of improving the stain resistance can be more reliably exhibited.
[Third Embodiment]
Next, the third embodiment will be described focusing on differences from the first and second embodiments. In the first and second embodiments, the operation mode is only one of the gap plasma generation mode and the spatial plasma generation mode. In contrast, in the third embodiment, both the gap plasma generation mode and the spatial plasma generation mode can be selected as the operation mode, and the control unit 71 sets one of the modes as the operation mode. [For example, as shown in FIG. 6, the control unit 71 changes the operation mode to a gap plasma generation mode, a spatial plasma generation mode for each predetermined cycle (for example, one cycle) of the internal combustion engine EN. It is possible to alternately switch to the gap plasma generation mode.

  As described above in detail, according to the third embodiment, AC plasma can be generated in both the gap 28 and the space 30. Therefore, both the carbon adhering to the surface of the insulator 2 near the gap 28 (the front end surface of the insulator 2) and the carbon adhering to the surface of the insulator 2 forming the space 30 are effective. Can be burned down. As a result, the stain resistance can be dramatically improved.

  Next, in order to confirm the effect achieved by the above-described embodiment, when the fuel gas is ignited by spark discharge and neither the gap plasma generation mode nor the spatial plasma generation mode is used (condition 1), When the operation mode of the discharge power source and the AC power source is the gap plasma generation mode (Condition 2), and when the operation mode of the AC power source is the AC plasma generation mode (Condition 3) in the exhaust stroke, A fouling resistance evaluation test based on JIS D1606 was conducted.

  The outline of the fouling resistance evaluation test is as follows. That is, a test vehicle having a 4-cylinder DOHC engine with a displacement of 1.6 L is placed on a chassis dynamometer in a low temperature test chamber (−10 ° C.), and a spark plug is assembled to the engine of the test vehicle. After performing idling three times, the vehicle travels for 40 seconds at a third speed of 35 km / h, and again travels for 40 seconds at a third speed of 35 km / h with an idling of 90 seconds. Then stop and cool the engine once. Next, after performing idling three times, traveling for 20 seconds at a speed of 15 km / h is performed a total of three times, with the engine stopped for 30 seconds, and then the engine is stopped. With this series of test patterns as one cycle, the insulation resistance value of the spark plug was measured for each cycle, and the number of cycles required until the insulation resistance value decreased to 10 MΩ or less was measured. Table 1 shows the test results of the test. The AC power supply has an oscillation frequency of 13 MHz, an output power (average value of the input electric power per second) of 500 W, and when generating AC plasma, the AC power supply generates 1 ms from the ignition plug to the spark plug. AC power was supplied. In addition, the test is performed with 20 cycles as the upper limit. When the insulation resistance value of the spark plug exceeds 10 MΩ at the end of the 20 cycles, “over 20” is displayed in the “number of cycles” column of Table 1. did.

  As shown in Table 1, it became clear that the conditions 2 and 3 using the gap plasma generation mode and the spatial plasma generation mode are excellent in antifouling property. This is because the gap plasma generation mode can be used to burn off carbon adhering to the tip of the insulator due to AC plasma, and the spatial plasma mode can be used to cause the surface of the leg length to be This is probably because the carbon adhering to (the surface forming the space) could be burned out.

  From the results of the above test, it can be said that the operation mode of the AC power supply or the like is preferably the gap plasma generation mode or the spatial plasma generation mode in order to improve the stain resistance.

  Further, as described above, carbon adhering to different sites is burned out when the operation mode is the gap plasma generation mode and when the operation mode is the spatial plasma generation mode. Therefore, it can be said that the use of both the gap plasma generation mode and the spatial plasma generation mode can dramatically improve the fouling resistance.

  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 said 2nd Embodiment, although the inner peripheral surface of the insulator 2 is covered with the metal layer 29, it is from the rear end among the inner peripheral surfaces of the insulation insulator 2 to the rear end of the to-be-latched part 4F. Only the surface located between the two may be covered with the metal layer 29. That is, the metal layer 29 may be provided only in a portion of the insulator 2 corresponding to the air layer that is particularly likely to cause trouble in the generation of AC plasma in the space 30.

  (B) In the above embodiment, the control unit 71 and the misfire detection unit 81 are configured by the ECU 91. However, the control unit 71 and the misfire detection unit 81 are configured by, for example, a microcomputer without configuring the ECU 91. May be. Alternatively, the discharge power supply 41 may be controlled by an ECU or the like, and the AC power supply 51 may be controlled by a control unit including a microcomputer or the like.

  (C) In the above embodiment, the power from the discharge power supply 41 or the AC power supply 51 is supplied to each spark plug 1 via the distributor. A power source 51 may be provided.

  (D) 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 thereto.

1 ... Spark plug 2 ... Insulator (insulator)
DESCRIPTION OF SYMBOLS 3 ... Metal shell 4 ... Shaft hole 4A ... Locked part 5 ... Center electrode 11 ... Large diameter part 14 ... Step part 27 ... Ground electrode 28 ... Gap 29 ... Metal layer 30 ... Space 31 ... Ignition system 41 ... Power supply for discharge DESCRIPTION OF SYMBOLS 51 ... AC power supply 71 ... Control part 81 ... Misfire detection part CL1 ... Axis EN ... Internal combustion engine

Claims (15)

An insulator having an axial hole extending in the axial direction; a center electrode inserted on the tip end side of the axial hole; a metal shell disposed on the outer periphery of the insulator; A spark plug that is attached to the internal combustion engine, and includes a ground electrode that forms a gap with the tip portion;
A discharge power source for applying a voltage to the spark plug;
An AC power supply for supplying AC power to the spark plug;
An ignition system comprising:
A controller for controlling the discharge power supply and the AC power supply;
The control unit sets the operation mode of the discharge power source and the AC power source at a timing other than a normal ignition timing by the spark plug to the spark generated by applying a voltage from the discharge power source to the spark plug. An ignition system characterized in that it can be set to a gap plasma generation mode in which AC power is supplied from a power source and AC plasma is generated in the gap.   The control unit is capable of setting the operation mode to the gap plasma generation mode at a timing other than a normal ignition timing by the spark plug until a predetermined period has elapsed since the start of the internal combustion engine. The ignition system according to claim 1, wherein A misfire detection unit for detecting misfire of the internal combustion engine,
The control unit is capable of setting the operation mode to the gap plasma generation mode at a timing other than a normal ignition timing by the spark plug when the misfire is detected by the misfire detection unit. The ignition system according to claim 1 or 2.   4. The control unit according to claim 1, wherein the control unit can set the operation mode to the gap plasma generation mode in an intake stroke, an exhaust stroke, or a combustion stroke of the internal combustion engine. 5. Ignition system. An insulator having an axial hole extending in the axial direction, a center electrode inserted on the distal end side of the axial hole, a metal shell disposed on the outer periphery of the insulator, an outer peripheral surface of the insulator, and the metal shell A spark plug attached to the internal combustion engine, and a space formed between the inner peripheral surface of
An AC power supply for supplying AC power to the spark plug;
An ignition system comprising:
A control unit for controlling the AC power supply;
The control unit supplies an AC power from the AC power source to the ignition plug at a timing other than a normal ignition timing by the ignition plug, and generates an AC plasma in the space. An ignition system that can be set to a generation mode.   The control unit is capable of setting the operation mode to the spatial plasma generation mode at a timing other than a normal ignition timing by the spark plug until a predetermined period has elapsed since the start of the internal combustion engine. 6. Ignition system according to claim 5, characterized in that A misfire detection unit for detecting misfire of the internal combustion engine,
The control unit is capable of setting the operation mode to the spatial plasma generation mode at a timing other than a normal ignition timing by the spark plug when the misfire is detected by the misfire detection unit. The ignition system according to claim 5 or 6.   8. The control unit according to claim 5, wherein the control unit can set the operation mode to the spatial plasma generation mode in an intake stroke, an exhaust stroke, or a combustion stroke of the internal combustion engine. 9. Ignition system.   The ignition system according to any one of claims 5 to 8, wherein the control unit is capable of setting the operation mode to the spatial plasma generation mode in an intake stroke of the internal combustion engine. On the outer periphery of the insulator, a step portion that is directly or indirectly locked to the metal shell and a large-diameter portion that is formed on the rear end side of the step portion and bulges outward in the radial direction are provided. And
The inner periphery of the insulator is provided with a locked portion to which the center electrode is locked,
At least the surface located between the rear end of the large-diameter portion and the rear end of the stepped portion of the outer peripheral surface of the insulator, and the locked portion from the rear end of the inner peripheral surface of the insulator The ignition system according to any one of claims 5 to 9, wherein a surface located between the rear ends is covered with a metal layer. An insulator having an axial hole extending in the axial direction; a center electrode inserted on the tip end side of the axial hole; a metal shell disposed on the outer periphery of the insulator; A spark plug that is attached to the internal combustion engine, and includes a ground electrode that forms a gap with the tip, and a space formed between the outer peripheral surface of the insulator and the inner peripheral surface of the metal shell,
A discharge power source for applying a voltage to the spark plug;
An AC power supply for supplying AC power to the spark plug;
An ignition system comprising:
A controller for controlling the discharge power supply and the AC power supply;
The control unit sets the operation mode of the discharge power source and the AC power source at a timing other than a normal ignition timing by the spark plug to the spark generated by applying a voltage from the discharge power source to the spark plug. A gap plasma generation mode in which AC power is supplied from a power source to generate AC plasma in the gap, or a space plasma generation mode in which AC power is supplied from the AC power source to the spark plug to generate AC plasma in the space. An ignition system characterized by being configurable.   The control unit switches the operation mode to the gap plasma generation mode or the spatial plasma generation mode at a timing other than a normal ignition timing by the spark plug until a predetermined period has elapsed since the start of the internal combustion engine. The ignition system according to claim 11, wherein the ignition system is configurable. A misfire detection unit for detecting misfire of the internal combustion engine,
The control unit can set the operation mode to the gap plasma generation mode or the spatial plasma generation mode at a timing other than a normal ignition timing by the spark plug when the misfire is detected by the misfire detection unit. The ignition system according to claim 11 or 12, characterized in that:   14. The control unit according to claim 11, wherein the operation mode can be set to the gap plasma generation mode or the spatial plasma generation mode in an intake stroke, an exhaust stroke, or a combustion stroke of the internal combustion engine. The ignition system according to any one of the preceding claims.   The ignition system according to any one of claims 11 to 14, wherein the control unit can set the operation mode to the spatial plasma generation mode in an intake stroke of the internal combustion engine.

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