JP5691662B2 - Non-thermal equilibrium plasma ignition device - Google Patents

Description

  The present invention relates to a non-thermal equilibrium plasma ignition device that is mounted on a hardly ignitable combustion engine and ignites the combustion engine.

Recently, from the viewpoint of CO ₂ reduction, high supercharging to achieve high output in a small, high compression automobile engines, and high efficiency, the development of the engine such as to achieve low NO _X is promoted.
In the case of a high-supercharged, high-compression automobile engine, the in-cylinder pressure before ignition is high, and therefore, when igniting with a spark ignition plug, it is necessary to increase the energy supplied to the ignition plug several times that of the prior art. Further, in the case of a generator engine for a cogeneration system, the cylinder bore diameter is large and the air-fuel mixture concentration is also lean. In order to burn such an inflammable internal combustion engine with high efficiency, an ignition device having a high combustion speed and excellent ignitability is desired.

  Patent Literature 1 discloses a plasma ignition device as an ignition device that exhibits excellent ignitability even in a difficult-ignition internal combustion engine or the like.

  However, although the conventional plasma ignition device as disclosed in Patent Document 1 is excellent in ignitability, since thermal equilibrium plasma with a high molecular temperature is generated, the consumption of the electrodes is severe, impeding practical use. .

On the other hand, Patent Document 2 discloses a barrier in order to assist the ignition of a self-igniting internal combustion engine by generating radicals in a cylinder without causing electrode melting due to generation of non-thermal equilibrium plasma (low temperature plasma). An internal combustion engine provided with a discharge part is disclosed.
In the conventional barrier discharge part as disclosed in Patent Document 2, the entire circumference of the rod-shaped center electrode is covered with a dielectric, and the outer circumference thereof is covered with a tubular electrode. A high-frequency alternating current is formed between the center electrode and the annular electrode. By applying a voltage, streamer discharge is generated at a plurality of locations between the side surface of the center electrode and the inner periphery of the annular electrode, and ignition is attempted by generating a large amount of radicals in the discharge chamber.

However, in the barrier discharge as disclosed in Patent Document 2, the non-thermal equilibrium plasma spreads radially from the dielectric side surface toward the tubular electrode. Therefore, even if the energy density is high on the dielectric surface, the energy density gradually decreases. To do.
Moreover, the energy of the non-thermal equilibrium plasma is absorbed by the air-fuel mixture that exists in a wide range from the outer peripheral surface of the dielectric to the inner peripheral surface of the tubular electrode, and volume ignition is performed, as in the case of performing streamer discharge by projecting the electrode into the combustion chamber. In order to generate a large amount of energy, it is necessary to input enormous energy.
Further, since the generation of thermal plasma is prevented by applying a voltage equal to or lower than the dielectric withstand voltage of the dielectric, as shown in FIG. 3B of Patent Document 2, four times in one cycle. Although there is an opportunity to generate non-thermal equilibrium plasma, the time is limited to a very short time, and much of the applied energy may cause a loss such as a rise in temperature of the dielectric.
Furthermore, in order to increase the applied energy, when the AC applied voltage is increased, the application time is increased, or the frequency is increased, the energy accumulated between the center electrode and the tubular electrode is reduced. When a body dielectric breakdown occurs and a streamer discharge extending from the dielectric surface toward the tubular electrode reaches the tubular electrode, a discharge path is formed, and the energy stored between the central electrode and the tubular electrode is released at once. Further, arc discharge, which is thermal plasma, is generated, and there is a possibility that the electrodes are consumed.

On the other hand, in the structure of the barrier discharge part as in Patent Document 2, since discharge occurs at an arbitrary position between the side surface of the center electrode and the annular electrode, the discharge position cannot be specified, and the difference in the discharge position As a result, the amount of non-thermal equilibrium plasma generated with respect to the supplied energy may change, and ignition may become unstable.
For this reason, the amount of non-thermal equilibrium plasma generated due to the ignition condition cannot be made constant, causing a deviation in ignition timing, or the energy accumulated between the center electrode and the tubular electrode being a low pressure such as an intake stroke. There is also a risk of unexpected ignition, such as being discharged occasionally.
In particular, in a multi-cylinder engine, when preignition occurs due to such unauthorized discharge, there is a risk of causing serious trouble such as engine breakage.

  Therefore, in view of such circumstances, the present invention generates a non-thermal equilibrium plasma having a high electron temperature and a low molecular temperature by applying a high frequency within a specific range and an application time, thereby igniting an air-fuel mixture by radicals. An object of the present invention is to provide a non-thermal equilibrium plasma ignition device capable of suppressing energy loss and realizing stable ignition.

In the invention of claim 1, a spark plug mounted on an internal combustion engine and having a center electrode and a ground electrode, which are covered with an insulator or an insulator made of a dielectric, facing each other through a predetermined discharge space; An engine control device that transmits an ignition signal in accordance with the operating state of the internal combustion engine, an AC power source that applies a high-frequency AC voltage to the ignition plug at a predetermined voltage according to the ignition signal, or a plurality of high-speed pulses at a high speed A non-thermal equilibrium plasma is generated in the discharge space and introduced into the combustion chamber of the internal combustion engine by applying a high-voltage power source composed of any one of the high-speed pulse power sources that oscillate twice and a high voltage of 10 kV or more from the high-voltage power source. In a non-thermal equilibrium plasma ignition device that performs ignition by reacting a highly reactive radical with a mixture of a combustible substance and a combustion-supporting gas, the oscillation frequency of the high-voltage power source is It is 00 kHz or more and 500 MHz or less, or the voltage application time per cycle of the voltage power source is 1 ns or more and 1 μs or less, and is approximately annular on the surface of either the center electrode or the ground electrode, or both Provided with a formed electric field concentration portion, provided with a discharge inducing portion serving as a starting point of streamer discharge in a part of the electric field concentration portion ,
The spark plug
A center electrode formed of a conductive material in a substantially long axis shape, an insulator, or a dielectric, and an insulator portion formed in a substantially bottomed cylindrical shape so as to cover the outer periphery and the tip surface of the center electrode;
A housing in which a metal material is formed in a substantially cylindrical shape to hold the lever portion;
The grounding electrode is formed by extending to a part of the housing and extending toward the combustion chamber side, and having a front end side opposed to the center electrode and formed in a substantially L shape.

In the invention of claim 2, a spark plug mounted on an internal combustion engine and having a center electrode and a ground electrode, which are covered with an insulator or a dielectric part made of a dielectric, facing each other through a predetermined discharge space; An engine control device that transmits an ignition signal in accordance with the operating state of the internal combustion engine, an AC power source that applies a high-frequency AC voltage to the ignition plug at a predetermined voltage according to the ignition signal, or a plurality of high-speed pulses at a high speed A non-thermal equilibrium plasma is generated in the discharge space and introduced into the combustion chamber of the internal combustion engine by applying a high-voltage power source composed of any one of the high-speed pulse power sources that oscillate twice and a high voltage of 10 kV or more from the high-voltage power source. In a non-thermal equilibrium plasma ignition device that performs ignition by reacting a highly reactive radical with a mixture of a combustible substance and a combustion-supporting gas, the oscillation frequency of the high-voltage power source is It is 00 kHz or more and 500 MHz or less, or the voltage application time per cycle of the voltage power source is 1 ns or more and 1 μs or less, and is approximately annular on the surface of either the center electrode or the ground electrode, or both Provided with a formed electric field concentration portion, provided with a discharge inducing portion serving as a starting point of streamer discharge in a part of the electric field concentration portion,
The spark plug
A central electrode formed of a conductive material in a substantially long axis shape;
An insulator made of an insulator or a dielectric, covering the outer periphery and the tip surface of the center electrode, and further forming a constant volume discharge space on the tip side; and
A housing in which a metal material is formed in a substantially cylindrical shape to hold the lever portion;
The housing is stretched to cover the tip of the insulator part, and has an opening communicating with the inner diameter of the insulator part constituting the inner peripheral wall of the discharge space, and is constituted by a substantially annular ground electrode.

In a third aspect of the present invention, a plurality of times of application of a high voltage to a single ignition signal transmitted from the engine control device is performed within a certain period of time, and then a plurality of times of high voltage are applied again after a certain period of time. Multiple ignition is performed by repeating the application.

  According to a fourth aspect of the present invention, a through hole penetrating the ground electrode is provided at a position facing the center electrode.

According to a fifth aspect of the present invention, the electric field concentrating portion projects substantially annularly at either or both of the front end surface of the center electrode and the surface of the ground electrode facing the center electrode.

According to a sixth aspect of the present invention, the electric field concentration portion has a tapered shape with a tapered tip.

According to a seventh aspect of the invention, the discharge inducing portion has a slit shape in which a part of the electric field concentration portion is cut out.

In the invention of claim 8, the electric field concentration part has a notch part that is notched at a predetermined width at a plurality of locations, and the width of one notch part is different from the width of the other notch part. The discharge inducing part is used.

In the invention of claim 9 , columnar protrusions that are protruded in a substantially columnar shape at a plurality of locations on either or both of the front end surface of the center electrode and the surface of the ground electrode facing the center electrode. The electric field concentration portion is arranged in a substantially annular shape.

In a tenth aspect of the present invention, the discharge inducing portion is formed by making the outer diameter of one columnar protrusion out of the plurality of columnar protrusions different from the outer diameter of the other columnar protrusion.

According to an eleventh aspect of the present invention, a part of the interval at which the plurality of columnar protrusions are arranged is different from other intervals to form the discharge inducing portion.

According to the present invention, by forming the electric field concentration portion on the surface facing the center electrode or / and the ground electrode, it is possible to reduce the required voltage required for causing the streamer discharge. In addition, by forming the discharge inducing portion, a trigger for starting a streamer discharge is generated at a specific position of the electric field concentration portion, and more stable and lower voltage than when only the electric field concentration portion is formed. It becomes possible to discharge at.
In addition, while maintaining a constant energy density between the center electrode and the ground electrode, non-thermal equilibrium plasma that spreads in a cylindrical shape is generated, and ignition and flame propagation occur on the inner and outer surfaces thereof, so the reactivity is high The reaction area with radicals is dramatically expanded, and extremely excellent ignitability can be realized.
Further, the non-thermal equilibrium plasma generates highly reactive radicals, induces a combustion reaction of the air-fuel mixture existing in the discharge space, and can ignite the internal combustion engine.

Further, the high voltage power source has a high voltage application time limited to 1 ns or more and 1 μs or less, and further, high voltage application and stop are repeated at an oscillation cycle of 500 kHz to 500 MHz, and from streamer discharge to arc discharge. Since the emission of electrons is interrupted before the change to, the generation of streamer discharge is repeated one after another, and the streamer discharge does not arc even if the pressure in the combustion chamber or the air-fuel ratio of the mixture changes. Without transitioning to discharge, non-thermal equilibrium plasma can be generated efficiently and the mixture can be ignited.
On the other hand, regardless of the present invention, when the high voltage application time is long, electrons continue to be emitted after the streamer discharge has occurred, so there is no current path between the center electrode and the ground electrode. There is a risk that arcing will occur due to the formation of thermal equilibrium.

  In addition to the fact that the tip of the center electrode is covered with the insulator, the non-thermal equilibrium plasma has a high electron temperature but a low molecular temperature, so that the electrode is hardly consumed. Therefore, in conventional spark plugs that generate thermal plasma, it is not necessary to use expensive and heat-resistant materials such as iridium and iridium alloys, which are used to suppress electrode consumption. Reduction can also be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the outline | summary of the non thermal equilibrium plasma ignition apparatus in the 1st Embodiment of this invention. The detail of the principal part of the non-thermal equilibrium plasma ignition apparatus of FIG. 1 is shown, (a) is a perspective view, (b) is a cross-sectional schematic diagram which shows the effect. The outline | summary of the non-thermal equilibrium plasma ignition apparatus in the 2nd Embodiment of this invention is shown, (a) is a perspective view, (b) is a cross-sectional schematic diagram which shows the effect. The perspective view which shows the modification of the non-thermal equilibrium plasma ignition device in the 2nd Embodiment of this invention. (A) is principal part sectional drawing which shows the modification of the non-thermal equilibrium plasma ignition apparatus in the 1st Embodiment of this invention, (b) is the other modification of the non-thermal equilibrium plasma ignition apparatus in 2nd Embodiment. FIG. The modification which can be applied to the non-thermal equilibrium plasma ignition apparatus of this invention is shown, (a-1)-(d-1) is a perspective view, (a-2)-(d-2) is a top view. The outline | summary of the non-thermal equilibrium plasma ignition apparatus in the 3rd Embodiment of this invention is shown, (a) is principal part sectional drawing, (b) is a top view of the center electrode front-end | tip part, (c) is the earthing | grounding The top view of an electrode.

The present invention shows excellent ignitability and durability used for a highly ignitable internal combustion engine such as an engine that achieves high efficiency and low NOx by high supercharging, high compression, high EGR, extremely low lean combustion, etc. It is a non-thermal equilibrium plasma ignition device.
With reference to FIG. 1 and FIG. 2, the non-thermal equilibrium plasma ignition apparatus 4 in the 1st Embodiment of this invention is demonstrated. In the following description, the upper side of the figure is referred to as the proximal end side, and the lower side is referred to as the distal end side.
FIG. 1 shows an overall outline of a non-thermal equilibrium plasma ignition device 4 in the present embodiment, and FIG. 2 shows details of a main part of the non-thermal equilibrium plasma ignition device 4 in the present embodiment.

The non-thermal equilibrium plasma ignition device 4 of the present invention is mounted on the engine head 50 of the internal combustion engine 5 not described in detail, the tip is exposed in the combustion chamber 500, and a high voltage is applied at a predetermined application time or frequency. Sometimes an ignition signal IGt is transmitted to drive the high voltage power source 2 according to the operating status of the internal combustion engine 5 according to the operating condition of the ignition plug 1 that generates 40 non-thermal equilibrium plasmas, the high voltage power source 2 that generates a predetermined high voltage, and the internal combustion engine 5. And an engine control unit (ECU) 3 that performs the operation.
In the present embodiment, the spark plug 1 includes a substantially long central electrode 10, an insulator portion 11 formed in a substantially bottomed cylindrical shape covering the outer periphery and tip thereof, and a combustion chamber 50 of the internal combustion engine 5 while covering these. And a substantially L-shaped ground electrode 13 extending at the tip of the housing 12, and the tip surface 101 of the center electrode 10 and / or the center electrode of the ground electrode 13. On the surface facing 10, substantially annular electric field concentration portions 102 and 132, which are essential parts of the present invention, are formed, and discharge induction portions 103 and 133 are formed in the electric field concentration portions 102 and 132.

  The center electrode 10 has a center electrode electric field concentration portion 102 extending to the outer peripheral edge of the tip surface 101 of the center electrode shaft portion 100 formed in a long axis shape and projecting in a substantially cylindrical shape toward the tip direction. Further, a central electrode discharge inducing portion 103 is formed by locally cutting out a part of the central electrode electric field concentration portion 102 in a slit shape, and a central electrode stem 104 and an external portion are formed on the base end side. A center electrode terminal 105 connected to the high voltage power source 2 is formed.

In the present invention, the material constituting the spark plug 1 is not particularly limited, and a material widely used for a spark-type spark plug used for ignition of a general internal combustion engine or the like may be appropriately used. it can.
For example, the center electrode 10 can be made of a conductive material such as nickel, nickel alloy, or iron. In addition, a material having high conductivity such as copper is used for the relatively low temperature portion of the center electrode 10 as in the case of a normal spark ignition plug.
In the present embodiment, in addition to the tip of the center electrode 10 being covered with the insulator 11, the non-thermal equilibrium plasma has a high electron temperature but a low molecular temperature, so that the electrode is hardly consumed. Therefore, an expensive and heat-resistant material such as iridium or an iridium alloy that is used for suppressing electrode consumption in the spark plug that generates thermal plasma need not be used.

The insulator portion 11 is formed in a substantially bottomed cylindrical shape using a heat-resistant ceramic material such as alumina, spinel or zirconia, which is also an insulator and a dielectric.
The insulator cylindrical portion 110 constituting the insulator portion 11 is formed in a bottomed cylindrical shape in which one end on the base end side is open and the other end on the combustion chamber side is closed, and the center electrode shaft portion 100 and the center are formed inside. The electrode middle shaft portion 104 is held.
A blocking partition 111 is formed on the distal end side of the insulator cylindrical portion 110, and the partition 111 covers the distal end surface 101 of the center electrode 10 and the central electrode electric field concentration portion 102.
An insulator locking portion 112 that is caulked and fixed to the housing 12 is formed in the middle of the insulator portion 11, and a substantially cylindrical shape is provided on the base end side in order to ensure insulation between the center electrode terminal portion 105 and the housing 12. The insulator head 113 is formed in a corrugated shape with irregularities on its surface.

The housing 12 holds the insulator 11 inside a housing body 120 in which a metal material such as SUS or carbon steel is formed in a substantially cylindrical shape, and a proximal end side of the housing body 120 via a sealing member that is not described in detail. It is fixed by caulking by a housing caulking portion 122 provided in the housing.
A housing cylindrical portion 123 that extends in a cylindrical shape so as to cover the outer periphery of the distal end of the insulator 11 is formed on the distal end side of the housing body portion 120, and a screw portion 124 is formed on the outer periphery thereof. An annular housing tip 125 that is exposed to the combustion chamber 500 is formed.
A housing hexagonal portion 121 for screwing a screw portion 124 to the cylinder head 50 is formed on the outer periphery of the base end side of the housing body portion 120.
A substantially L-shaped ground electrode 13 is formed extending to the housing front end portion 124.

The ground electrode 13 is made of a heat-resistant metal material similar to that used for a normal spark-ignition plug such as nickel, nickel alloy, or iron.
The ground electrode 13 is connected to the housing front end portion 124 and extends from the ground electrode extending portion 130 extending toward the combustion chamber 500 and the ground electrode extending portion 130 so as to face the front end surface 101 of the center electrode 10. A ground electrode facing part 131 is formed by bending in an approximately L shape toward the axial center of the spark plug 1.
A ground electrode electric field concentration portion 132 that protrudes in a substantially annular shape toward the center electrode 10 is formed at a position facing the center electrode electric field concentration portion 102 of the ground electrode facing portion 131.
Similarly to the central electrode electric field concentration portion 102, a ground electrode discharge inducing portion 133 may be formed in the ground electrode electric field concentration portion 132 by partially cutting it out in a slit shape.

The electric field concentration portions (102, 132) and the discharge inducing portions (103, 133) may be formed on either the center electrode 10 or the ground electrode 13, but the streamer is more formed on both. Electric discharge easily occurs, and the plasma generation region is stably formed in a cylindrical shape.
The central electrode electric field concentration part 102 covered with the partition wall part 111 of the insulator 11 and the ground electrode electric field concentration part 132 are opposed to each other with a predetermined gap therebetween to form the discharge space 14.

In the present embodiment, the high voltage power supply 2 applies a high voltage of 10 kV or higher for a very short time of 1 ns or more and 1 μs or less by applying and closing the semiconductor switching element. , A high-speed pulse power source that converts and applies a high-speed pulse that is repeatedly applied and stopped at an oscillation cycle of 500 kHz to 500 MHz.
Further, the high voltage power supply 2 oscillates a high-speed pulse a plurality of times (for example, about 10 pulses) in response to the ignition signal IGt transmitted from the ECU 3 according to the operation state of the internal combustion engine 5, and further, a time interval of about 500 μs. Can be used as a burst cycle, and a plurality of high-speed pulse oscillations can be repeated again within a fixed time after a fixed time has elapsed to perform a high-speed multiple pulse oscillation to perform multiple ignition (see FIG. 1).
When a high-speed pulse is applied from the high voltage power supply 2 between the center electrode 10 and the ground electrode 13, the position facing the center electrode discharge inducing portion 103 of the insulator partition wall 111 or the ground electrode discharge inducing portion 133 is applied. An extremely short streamer discharge that triggers the streamer discharge is started from the opposite position, and spreads in a cylindrical shape along the center electrode electric field concentration portion 101 and the ground electrode electric field concentration portion 132 formed in an annular shape, A non-thermal equilibrium plasma generation region having a high energy density and a large surface area is formed (see FIG. 2B).

Further, in the high voltage power supply 2 of the present invention, the high voltage application time τ per cycle is limited to 1 ns or more and 1 μs or less, and the high voltage is repeatedly applied and stopped at an oscillation cycle of 500 kHz to 500 MHz. Since the emission of electrons is interrupted before the streamer discharge changes to the arc discharge, the streamer discharge is repeatedly generated one after another, and even if there is a pressure fluctuation in the combustion chamber 500, the streamer discharge Does not transition to arc discharge.
On the other hand, regardless of the present invention, when the high voltage application time is long, electrons continue to be emitted after the streamer discharge has occurred, so there is no current path between the center electrode and the ground electrode. As a result, thermal equilibrium is reached and arc discharge occurs.

Neutral radicals are formed by the streamer discharge generated so as to spread in a substantially cylindrical shape, and highly reactive radicals locally react with the surrounding air-fuel mixture to cause a self-ignition reaction.
At this time, according to the present invention, since the streamer discharge is formed so as to spread in a cylindrical shape, the probability that the non-thermal equilibrium plasma having an extremely high electron temperature of 10 eV or higher and the air-fuel mixture react with each other is increased, and the ignitability is increased. improves.
In addition, electrons generated by streamer discharges are extremely high in temperature and low in mass, so they do not consume the electrodes even when they collide with the electrodes, and are extremely durable compared to the case where thermal equilibrium plasma is generated. Will show gender.
The collisional dissociation reaction and collisional excitation reaction when non-thermal equilibrium plasma is generated are assumed to be as follows.
RH (flammable substance) + e ^{− *} (high-speed electron) → R ・ + H ・ + e−
O ₂ + e ^{− *} → O · + O · + e ⁻
N ₂ + e ^{− *} → N ₂ ^*
O. radicals are extremely reactive, and it is considered that local auto-ignition reaction occurs using this as a trigger.

On the other hand, when a high voltage is applied between the center electrode 10 and the ground electrode 13, an electric field is generated between the side surface of the center electrode 10 and the housing body 120, but the thickness of the insulator cylindrical portion 110 is as follows. Since the electric field concentration portions 102 and 132 are formed on the tip surface 101 of the center electrode 10 and / or the surface of the ground electrode 13, which is much thicker than the wall thickness of the partition wall portion 111, Streamer discharge is generated between the electrode 10 and the ground electrode 13, and streamer discharge is less likely to occur between the side surface of the center electrode 10 and the housing body 120.
Therefore, according to the non-thermal equilibrium plasma ignition device 4 of the present invention, since ignition can be started at a specific position in the combustion chamber 500, it can be applied to both a homogeneous mixed combustion engine and a stratified combustion engine.

Moreover, as a switching element used for generating a high-speed pulse of the high-voltage power supply 2, for example, a power semiconductor such as a power MOSFET or IGBT including a semiconductor such as GaAs (please list current conceivable elements). A device is preferred.
When a currently available semiconductor device is used, the semiconductor temperature rises due to about 10 pulses of switching, making stable switching control difficult, and it takes about 500 μs to recover normally. For this reason, in the above embodiment, it is difficult to restart a plurality of high-speed pulses at short intervals of 500 μs or less, but the present invention does not eliminate burst periods of 500 μs or less.

Furthermore, in the present embodiment, the high-voltage power supply 2 has been described by taking a high-speed pulse power supply as an example. An AC power supply may be used.
When a high-frequency AC power supply is used, streamer discharge is generated every time the direction of current is changed, and the same effect as in the above embodiment can be exhibited.
On the other hand, regardless of the present invention, when an AC power source that oscillates at a frequency lower than 500 kHz or higher than 500 MHz is used, a streamer discharge cannot be generated or an arc discharge may occur. is there.

The non-thermal equilibrium plasma ignition device 4 of the present invention is required to cause streamer discharge by forming the electric field concentration portions 102 and 132 on the opposing surfaces of the center electrode 10 and / or the ground electrode 13. In addition to the effect of reducing the required voltage, by forming the discharge inducing portions 103 and 133, a trigger to start streamer discharge is generated at a specific position of the electric field concentration portions 102 and 132, and only the electric field concentration portions 102 and 132 are provided. It is possible to discharge at a lower voltage more stably than when formed.
In addition, non-thermal equilibrium plasma that spreads in a cylindrical shape is generated while maintaining a constant energy density between the central electrode electric field concentration portion 102 and the ground electrode electric field concentration portion 132, and ignition and flame propagation occur on the inner and outer surfaces. The reaction area with highly reactive radicals is greatly expanded, and extremely excellent ignitability can be realized.
Therefore, if the non-thermal equilibrium plasma ignition device 4 of the present invention is an internal combustion engine that uses energy generated by combustion or explosion of a mixture of combustible gas and combustion-supporting gas as a power source, the fuel used is It is not limited, and can be applied as an ignition device for any internal combustion engine such as a gasoline engine, diesel engine, gas fuel engine, etc., and difficult ignition such as high supercharged mixed combustion, extremely lean combustion, high EGR combustion, etc. It can exhibit excellent ignitability even in the condition of the property.

  In this embodiment, the outer diameter of the central electrode shaft portion 100 and the central electrode electric field concentration portion 102 is φ5.0 mm, the inner diameter of the central electrode electric field concentration portion 102 is φ4.6 mm, and from the tip surface of the insulator partition wall portion 111. When the distance to the tip of the ground electrode electric field concentration part 132 is set to 1 mm, the center electrode of the spark ignition plug of the conventional structure in which the discharge gap is 1 mm and the outer diameter of the center electrode is set to φ1 mm is covered with an insulator. The surface area of the cylindrical non-thermal equilibrium plasma generation region can be increased by 2.5 times with an energy density equal to that of the substantially columnar non-thermal equilibrium plasma generated when a high-speed pulse is applied.

With reference to FIG. 3, the spark plug 1a which is the principal part of the non-thermal equilibrium plasma ignition apparatus in the 2nd Embodiment of this invention is demonstrated.
In the spark plug 1 of the specific heat equilibrium plasma ignition device 4 in the above embodiment, the ground electrode facing portion 131 is formed in a substantially flat plate shape, and the position facing the center electrode electric field concentration portion 102 is substantially annular toward the center electrode 10 side. In the present embodiment, the ground electrode concentration portion 132 is formed so as to protrude, but in the present embodiment, the spark plug 1a penetrates the ground electrode facing portion 131a so as to communicate with the inner periphery of the ground electrode electric field concentration portion 132. The difference is that the hole 134 is provided, and the high-voltage power supply 2 and other configurations are the same as those in the first embodiment.
According to the present embodiment, in addition to the same effects as the above embodiment, as shown in FIG. 5B, when the non-thermal equilibrium plasma is generated in a cylindrical shape and the combustion reaction is started, the non-thermal equilibrium plasma is generated. New air is introduced through the through-hole 134 in the generated region, the propagation speed of the combustion flame is improved, and the ignitability can be further improved.

With reference to FIG. 4, the ignition plug 1b which is a modification of the ignition plug 1a which is the principal part of the non-thermal equilibrium plasma ignition device in the 2nd Embodiment of this invention is demonstrated. In the present embodiment, in addition to the configuration similar to that of the spark plug 1a in the second embodiment, the spark plug 1b compensates for a decrease in the heat absorption property of the ground electrode facing portion 131b due to the formation of the through hole 134. Therefore, the difference is that the surface area is increased by extending the periphery of the ground electrode electric field concentration portion 131 in the radial direction.
By adopting such a configuration, in addition to the same effects as described above, it is possible to improve the heat drawability of the ground electrode 13b and prevent the occurrence of preignition.

With reference to FIG. 5, a modification of the non-thermal equilibrium plasma ignition device in the first embodiment of the present invention and another modification of the non-thermal equilibrium plasma ignition device in the second embodiment will be described. In the above embodiment, an example in which the center electrode electric field concentration portion 102 and the ground electrode electric field concentration portion 132 are formed in a cylindrical shape having a constant cross-sectional area is shown. However, as shown in the present embodiment, the center electrode electric field concentration portion 102c is formed. 102d and the ground electrode electric field concentration portions 132c and 132d are different in that the inner peripheral wall or the outer peripheral wall is formed in a tapered shape with a tapered tip which is gradually reduced in shape.
By adopting such a configuration, in addition to the same effects as in the above embodiment, the electric field concentration portion is tapered at the tip, so that the effect of electric field concentration is enhanced and streamer discharge can be generated at a lower required voltage. Can do.

A modification that can be applied to the non-thermal equilibrium plasma ignition device of the present invention will be described with reference to FIG. 6. In the above embodiment, the center electrode electric field concentration portions 102, 102 a, 102 b, 102 c, 102 d are connected to the center electrode tip surface 101. However, the center electrode modifications 10e to 10h shown in the figure can be appropriately employed.
As shown in FIGS. (A-1) and (a-2), as the electric field concentrating portion 102e, columnar protrusions formed in a substantially columnar shape on the center electrode tip surface 101 are arranged in a plurality of places at equal intervals and arranged in an annular shape. In addition, as the discharge inducing portion 103e, the distance between the protrusions is narrowed at only one place. By adopting such a configuration, in the region where non-thermal equilibrium plasma generated when a high voltage is applied is generated, the streamer discharge is triggered by the discharge inducing portion 103e as in the above embodiment, and the electric field concentration portion It spreads along 103e and is formed in a substantially cylindrical shape with a large surface area. As the discharge inducing portion 103e, one of the protrusions formed in a substantially columnar shape may be thinned out.
Further, as shown in FIGS. (B-1) and (b-2), as the electric field concentration portion 102f, a plurality of protrusions formed in a substantially columnar shape on the center electrode tip surface 101 are arranged at equal intervals and arranged in an annular shape. Further, as the discharge inducing portion 103f, the outer diameter of one projecting portion is reduced. On the contrary, the outer diameter of one protrusion may be increased.
Further, as shown in FIGS. (C-1) and (c-2), as the electric field concentration portion 102g, a plurality of slit-shaped cutouts are formed at equal intervals on the protruding portion that protrudes substantially annularly, Further, the width of one notch is widened as the discharge inducing portion 103g.
In addition, as shown in FIGS. (D-1) and (d-2), a plurality of wide slit-shaped notches are bored at equal intervals as the field concentrating portion 102h. In addition, the width of one notch may be narrowed as the discharge inducing portion 103h.
In any case, in the region where the non-thermal equilibrium plasma generated when a high voltage is applied is generated, the streamer discharge is started by using the discharge inducing parts 103f, g, and h as in the above embodiment, and the electric field concentration It extends along the portions 103f, g, and h, and is formed in a substantially cylindrical shape having a large surface area.
In the present embodiment, only the electric field concentration portions 102e to 102h of the center electrodes 10e to 10h are shown, but the same configuration can be applied to the ground electrode 13.

With reference to FIG. 7, the spark plug 10i which is the principal part of the non-thermal equilibrium plasma ignition apparatus in the 3rd Embodiment of this invention is demonstrated.
In the embodiment described above, the ground electrode 13 is formed in a substantially L shape and is opposed to the front end surface 101 of the center electrode 10 covered with the partition wall portion 111 of the insulator portion 11. However, in the present embodiment, The portion below the partition wall 111 of the insulator portion 11i of the spark plug 10i is extended toward the combustion chamber side, and a discharge space 14i formed between the center electrode 10i and the ground electrode 13i is constant. An insulator cylindrical portion 112 that is divided into volumes is formed. Further, the shroud portion 125i at the tip of the housing 12 is extended to cover the outer periphery of the insulator cylinder portion 112. Further, the ground electrode 13i is connected to the shroud portion 125i. Then, the ground electrode facing portion 131i having an opening communicating with the inner diameter of the insulator cylinder portion 112 constituting the inner peripheral wall of the discharge space 14i covers the bottom surface of the insulator cylinder portion 112. In addition, a ground electrode electric field concentration portion 132i is formed so as to protrude substantially annularly toward the base end side in the insulator cylindrical portion 112, and the ground electrode electric field concentration portion 132i, and the ground electrode A discharge inducing portion 133i is formed by cutting away the facing portion 131i.
By adopting such a configuration, the discharge space 14i is formed in a state of being drawn inside the insulator portion 12i, so that a strong in-cylinder airflow is formed in the combustion chamber in addition to the same effects as in the above embodiment. Also in the engine, it is possible to prevent the generated non-thermal equilibrium plasma from being blown off by the in-cylinder airflow and spreading into the combustion chamber without ignition.
Therefore, when the air-fuel mixture introduced into the discharge space 14i partitioned into a limited volume is ignited by non-thermal equilibrium plasma, the pressure in the discharge space 14i suddenly increases, As a result, it is ejected into the combustion chamber 500, and an igniter excellent in ignitability can be realized.
Also in the present embodiment, the above-described modified examples can be appropriately employed for the center electrode electric field concentration portion 102i and the ground electrode electric field concentration portion 132i.

DESCRIPTION OF SYMBOLS 1 Spark plug 10 Center electrode 100 Center electrode shaft part 101 Center electrode front end surface 102 Center electrode electric field concentration part (annular protrusion)
103 Center electrode discharge inducing part 104 Center electrode middle shaft part 105 Center electrode terminal part 11 Insulator part 110 Insulator cylindrical part 111 Insulator partition part (bottom part)
112 Insulator locking part 113 Insulator head part 12 Housing 120 Housing body part 121 Housing nut part 122 Housing caulking part 123 Housing cylindrical part 124 Screw part 125 Housing front end part (shroud part)
DESCRIPTION OF SYMBOLS 13 Ground electrode 130 Ground electrode extending part 131 Ground electrode opposing part 132 Ground electrode electric field concentration part 134 Ground electrode discharge induction part 14 Discharge space 2 High voltage power supply 3 ECU
4 Non-thermal equilibrium plasma ignition device 5 Internal combustion engine 50 Cylinder head 500 Combustion chamber IGt Ignition signal D Drive voltage PLS _NEQ Non-thermal equilibrium plasma τ High voltage application time

US Pat. No. 3,581,141 JP 2009-121406 A

Claims (11)

A spark plug that is mounted on the internal combustion engine and that has at least a center electrode and a ground electrode that are covered with an insulator or a dielectric made of a dielectric and face each other through a predetermined discharge space, and according to the operating status of the internal combustion engine an engine control unit originating an ignition signal Te, according to the ignition signal, a predetermined voltage to the spark plug, the AC power source applies an AC voltage of high frequency, or, the fast pulse power source which oscillates a plurality of times faster pulses at high speed Non-thermal equilibrium plasma is generated in the discharge space by application of a high voltage power source composed of any of these and a high voltage of 10 kV or more from the high voltage power source, and the combustible material introduced into the combustion chamber of the internal combustion engine is supported. In a non-thermal equilibrium plasma ignition device that performs ignition by reacting a highly reactive radical with a gas mixture with a flammable gas,
The oscillation frequency of the high voltage power source is 500 kHz or more and 500 MHz or less,
Or
The voltage application time per cycle of the voltage power source is 1 ns to 1 μs,
Either one of the center electrode and the ground electrode, or an electric field concentration portion formed in a substantially annular shape on both surfaces,
Electric field concentrated portion of the part provided with the discharge inducing portion serving as a starting point for streamer discharge Rutotomoni,
The spark plug is composed of a center electrode formed of a conductive material in a substantially long axis shape and an insulator or a dielectric, and is formed in a substantially bottomed cylindrical shape so as to cover the outer periphery and the tip surface of the center electrode. And a housing in which a metal material is formed in a substantially cylindrical shape so as to hold the insulator, and extends toward a part of the housing and extends toward the combustion chamber, with the tip side facing the center electrode. A non-thermal equilibrium plasma igniter characterized by comprising a ground electrode formed in a substantially L shape at least . A spark plug that is mounted on the internal combustion engine and that has at least a center electrode and a ground electrode that are covered with an insulator or a dielectric made of a dielectric and face each other through a predetermined discharge space, and according to the operating status of the internal combustion engine An engine control device that emits an ignition signal and an AC power source that applies a high-frequency AC voltage to the spark plug at a predetermined voltage according to the ignition signal, or a high-speed pulse power source that oscillates a high-speed pulse multiple times at high speed Non-thermal equilibrium plasma is generated in the discharge space by application of a high voltage power source composed of any of these and a high voltage of 10 kV or more from the high voltage power source, and the combustible material introduced into the combustion chamber of the internal combustion engine is supported. In a non-thermal equilibrium plasma ignition device that performs ignition by reacting a highly reactive radical with a gas mixture with a flammable gas,
The oscillation frequency of the high voltage power source is 500 kHz or more and 500 MHz or less,
Or
The voltage application time per cycle of the voltage power source is 1 ns to 1 μs,
Either one of the center electrode and the ground electrode, or an electric field concentration portion formed in a substantially annular shape on both surfaces,
While providing a discharge inducing portion serving as a starting point of streamer discharge in a part of the electric field concentration portion,
The spark plug is composed of a center electrode formed of a conductive material in a substantially long axis shape, and an insulator or a dielectric. The spark plug covers the outer periphery and the tip surface of the center electrode, and further has a constant volume on the tip side. An insulator formed so as to partition the discharge space, a housing formed of a metal material in a substantially cylindrical shape to hold the insulator, and extending the tip of the housing to cover the tip of the insulator, A non-thermal equilibrium plasma ignition device comprising an opening communicating with an inner diameter of an insulator portion constituting an inner peripheral wall of the discharge space, and a ground electrode formed in a substantially annular shape . For a single ignition signal transmitted from the engine control device, multiple high voltage applications are performed within a certain period of time, and after a certain period of time, multiple high voltage applications are repeated again for multiple ignition. The non-thermal equilibrium plasma ignition device according to claim 1 or 2, wherein: The non-thermal equilibrium plasma ignition device according to claim 1 or 3, further comprising a through hole penetrating the ground electrode at a position facing the center electrode. The electric field concentration portion, and the distal end surface of the center electrode, either one of the surfaces facing the center electrode of the ground electrode, or claims 1 projecting generally annular in both according to any one of 4 Non-thermal equilibrium plasma ignition device. The non-thermal equilibrium plasma ignition device according to claim 5 , wherein the electric field concentration portion has a tapered shape with a tapered tip . The non-thermal equilibrium plasma ignition device according to claim 5 or 6, wherein the discharge inducing portion has a slit shape in which a part of the electric field concentration portion is cut out . The electric field concentration portion has a cutout portion cut out at a predetermined width at a plurality of locations, and the discharge inducing portion is made different from the width of one of the cutout portions, The non-thermal equilibrium plasma ignition device according to claim 5 or 6 . Column-shaped protrusions that protrude in a substantially column shape at a plurality of locations are disposed in a substantially annular shape on either or both of the front end surface of the center electrode and the surface of the ground electrode facing the center electrode. The non-thermal equilibrium plasma ignition device according to any one of claims 1 to 4, wherein the electric field concentration portion is used. The non-thermal equilibrium plasma ignition device according to claim 9 , wherein an outer diameter of one columnar projection portion of the plurality of columnar projection portions is different from an outer diameter of another columnar projection portion to form the discharge inducing portion . The non-thermal equilibrium plasma ignition device according to claim 9 , wherein a part of an interval at which the plurality of columnar protrusions are arranged is different from other intervals to form the discharge inducing portion .

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