JP2011018593A - Plasma ignition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma ignition device that has an excellent durability and can perform stable ignition.SOLUTION: The plasma ignition device 1 brings a gas in a discharge space 140 into a high-temperature and high-voltage plasma state and injects the gas in the plasma state into a combustion chamber 400 to cause ignition. An ignition plug 10 comprises a center electrode 11, an insulator 12 that has a nearly cylindrical shape covering the center electrode 11 and has, on the inside, a discharge space forming section 120 zoning the discharge space 140, a nearly cylindrical housing 13 covering the outer periphery of the insulator 12, a grounding electrode 130 that has a nearly annular shape connected to the housing 13 and has zoned, on the inside, a plasma forming space 141 inside the grounding electrode which communicates with the discharge space 140, and a plasma gas injection/separation means 150 that covers a whole or part of the leading end side of the space 141 inside the grounding electrode. The plasma gas injection/separation means 150 has at least two plasma injection holes 151 making communication between the discharge space 140 and the combustion chamber 400, and changing the injection direction of a whole or part of a plasma gas.

Description

  The present invention relates to a plasma ignition device used for ignition of a combustion engine.

In recent years, in combustion engines such as automobile engines, in order to further reduce environmentally hazardous substances such as nitrogen oxides and carbon dioxide contained in combustion exhaust gas, further improvement in fuel consumption and lean combustion are desired. Yes.
As an engine that can improve the combustion efficiency of the engine and reduce the environmental load at the same time, a gas in a high-temperature and high-pressure plasma state is injected into the combustion chamber of the engine so that flames cannot be propagated by a conventional spark discharge spark plug. 2. Description of the Related Art A plasma ignition device that efficiently burns a lean air-fuel mixture has attracted attention (see Patent Document 1).

  The plasma ignition device gives extremely high energy to the air-fuel mixture in a short time, so it has excellent ignitability, but also has the problem of high power consumption and high electrode consumption. However, it has not been put to practical use in a combustion engine such as an automobile engine in which a combustion cycle is repeated periodically.

  In order to solve such a problem, Patent Document 2 discloses a housing made of ceramics that defines a cavity communicating with the outside by one or more orifices, a center electrode that projects from the cavity, and projects from the cavity. An ignition device for an internal combustion engine, characterized in that the discharge space for generating plasma is partitioned by a housing made of ceramics having low thermal conductivity, thereby disposing the interior of the cavity. The energy required for ignition is reduced by suppressing the plasma energy generated at the outside from flowing out through the housing.

However, in the conventional ignition device as disclosed in Patent Document 2, since the center electrode and the ground electrode are disposed so as to protrude inside the insulating ceramics defining the cavity, The discharge when a high voltage is applied during this period is dominated by air discharge, and the voltage required to break the insulation in the discharge space is higher than the creeping discharge formed so as to crawl the surface of the insulator. It turns out that there is a risk of high.
In addition, since the ground electrode is formed so as to protrude into the cavity, there is a possibility that the consumption position of the electrode is concentrated and the electrode is consumed at an early stage.

  Therefore, in view of such circumstances, the present invention aims to provide a plasma ignition device that is excellent in durability and can realize stable ignition.

  According to the first aspect of the present invention, there is provided a spark plug attached to the internal combustion engine, and a high energy power source for supplying high energy to the spark plug, and by applying a high voltage and supplying a large current from the high energy power source. In the plasma ignition device that performs ignition by injecting the gas in the discharge space formed inside the ignition plug as a high-temperature and high-pressure plasma gas into the combustion chamber of the internal combustion engine, the ignition plug has a substantially long axis center. An electrode, a substantially cylindrical insulator extending from the tip of the center electrode toward the combustion chamber while covering the periphery of the center electrode, a substantially cylindrical housing covering the outer periphery of the insulator, A ground electrode extending in the front end side and formed in a substantially annular shape, and the front end surface of the center electrode in a space defined by the front end surface of the center electrode and the inner peripheral wall of the insulator inside the insulator the above A plasma is formed by facing the inner peripheral edge of the ground electrode to form a discharge space, defining a space in the ground electrode that communicates with the discharge space inside the ground electrode, and covering a part or all of the space in the ground electrode Gas injection / separation means is provided, and the plasma gas injection / separation means includes at least two or more plasma injection holes that communicate between the discharge space and the combustion chamber and change part or all of the injection direction of the plasma gas. (Claim 1).

  According to the plasma ignition device of the present invention, when a high voltage is applied between the center electrode and the ground electrode from the energy source, the lower end surface of the discharge space forming portion and the inner periphery of the ground electrode Since electric field concentration occurs at the boundary with the upper end, the trigger discharge that occurs between the lower end surface of the center electrode and the ground electrode is dominated by the creeping discharge that occurs over the inner peripheral wall surface of the discharge space forming portion. Thus, there is no possibility that air discharge that penetrates the discharge space occurs between the center electrode and the inner peripheral edge of the plasma injection hole. An increase in the required voltage can be suppressed by maintaining a creeping discharge that can be discharged at a lower discharge voltage than in the air discharge.

  In addition, even when the plasma gas injection / separation means is made of metal, the ground electrode internal space is formed, so there is no risk of discharge between the center electrode and the plasma gas injection / separation means. The plasma injection holes formed in the plasma gas injection separation means are not consumed by discharge. Therefore, the shape of the plasma injection hole can be maintained over a long period of use, and the plasma injection direction can be kept constant.

Further, when a large current is applied to the spark plug following the application of a high voltage from a high energy power source and discharged into the discharge space, the gas in the discharge space and the space in the ground electrode has a high temperature and a high pressure. When the plasma state enters the plasma injection hole of the plasma gas injection separation means, the plasma gas injection is separated into a plurality of parts and injected into the combustion chamber.
For this reason, even if a concentration distribution is generated in the air-fuel mixture existing in the combustion chamber, compared with the case where the plasma gas is ejected in one lump as in the case of a plasma igniter having a single-hole plasma gas outlet, Since the chance of contact with the air-fuel mixture increases, the ignitability improves.

  In the second invention, the length of the space in the ground electrode from the upper end of the inner edge of the ground electrode to the plasma gas jet separation means is set in a range of 0.5 mm or more.

  As a result of the inventors' diligent tests, by forming the length of the space portion in the ground electrode to be 0.5 m or more, no discharge occurs between the center electrode and the plasma gas jet separation means, and it is ensured. It has been found that consumption of the plasma nozzle can be suppressed.

  In the third invention, the length of the space in the ground electrode from the upper end of the inner periphery of the ground electrode to the plasma gas jet separation means is set in a range of 3.5 mm or less.

  Plasma generated in the discharge space while reliably suppressing consumption of the plasma nozzle hole by forming the length of the space portion in the ground electrode to 3.5 m or less by intensive studies by the present inventors. It has been found that a penetration force that secures a sufficient jumping distance into the combustion chamber necessary for maintaining good ignitability can be maintained without causing a pressure drop until the gas is ejected from the plasma injection hole.

  In a fourth aspect of the invention, the plasma gas injection / separation means includes a pointed protrusion that protrudes toward the space inside the ground electrode and has a tip that is tapered so as to follow the direction in which the plasma injection hole is formed ( Claim 4).

  Since the plasma gas generated in the discharge space and the space in the ground electrode is rectified by the pointed portion and the resistance when passing through the plasma gas injection separation means is reduced, the plasma gas injection speed is reduced. It is suppressed, and further improvement in ignitability can be expected.

  In the fifth invention, the distance from the upper end of the inner peripheral edge of the ground electrode to the tip of the pointed portion is set to a range of 0.5 mm or more.

In general, electric field concentration is likely to occur at the corners of the electrode, and when the pointed protrusion is formed in the plasma gas injection / separation means electrically connected to the ground electrode, electric field concentration on the pointed protrusion causes the above-described concentration of the electric field. There is a possibility that electric discharge is likely to occur between the central electrode.
However, as in the present invention, by setting the distance from the upper end of the inner peripheral edge of the ground electrode to the tip of the pointed portion to be 0.5 mm or more, the distance from the tip of the center electrode to the tip of the pointed portion is set. The withstand voltage is sufficiently higher than the withstand voltage from the tip of the center electrode to the top edge of the inner periphery of the ground electrode, eliminating the influence of such electric field concentration, and reliably And discharge between the center electrode and the pointed portion can be avoided.

(A) is sectional drawing which shows the whole structure of the plasma ignition apparatus in the 1st Embodiment of this invention, (b) is the bottom view. The equivalent circuit diagram which shows the example of the high energy power supply which can be utilized for the plasma ignition apparatus in the 1st Embodiment of this invention. (A) is principal part sectional drawing of the plasma ignition apparatus in the 1st Embodiment of this invention, (b) is a schematic diagram which shows the state at the time of plasma injection. The principal part sectional view which shows the effect of the present invention at the time of electrode consumption. (A) is principal part sectional drawing at the time of forming the separation part consumption discharge suppression space length shown as an Example of this invention in 0.5 mm or more, (b) is the separation part consumption discharge suppression space shown as a comparative example. The principal part sectional drawing at the time of forming length shorter than 0.5 mm. The effect of this invention is shown with a comparative example, (a) is a characteristic diagram which shows the discharge probability to the separation part with respect to the separation part consumption discharge suppression space length, (b) is the misfire with respect to the separation part consumption discharge suppression space length. The characteristic view which shows a limit air fuel ratio. The bottom view which shows the modification of the plasma ignition apparatus in the 1st Embodiment of this invention from (a) to (d). (A) is principal part sectional drawing of the plasma ignition apparatus in the 2nd Embodiment of this invention, (b) is the bottom view. (A) is principal part sectional drawing of the plasma ignition apparatus in the 3rd Embodiment of this invention, (b) is the bottom view. (A) is principal part sectional drawing of the plasma ignition apparatus in the 4th Embodiment of this invention, (b) is the bottom view. (A) is principal part sectional drawing of the plasma ignition apparatus in the 5th Embodiment of this invention, (b) is the bottom view. The principal part of the plasma ignition apparatus in the 6th Embodiment of this invention is shown, (a) is a partially cutaway perspective view, (b) is the bottom view.

With reference to FIG. 1, the outline | summary of the plasma ignition apparatus 1 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.
The plasma ignition device 1 includes a plasma ignition plug 10 attached to the internal combustion engine 40, a high energy power source 20 that applies high energy to the plasma ignition plug 10, and an electron that drives the high energy power source 20 according to the operating state of the internal combustion engine 40. And a control device (ECU) 30.

The plasma spark plug 10 has a discharge space 140 inside the spark plug, covers a part or all of the front end side of the discharge space 140, and burns by changing the ejection direction of part or all of the plasma generated in the discharge space 140. Plasma gas injection / separation means 150 for injecting into the room is provided.
The plasma spark plug 10 is formed in a substantially cylindrical shape extending from the tip of the center electrode 11 toward the combustion chamber 400 while covering the periphery of the center electrode 11 and the center electrode 11 formed in a substantially long axis shape, and discharges inwardly. The insulator 12 in which the space 140 is partitioned, the substantially cylindrical housing 13 that covers the outer periphery of the insulator 12, is formed in a substantially annular shape extending to the distal end side of the housing 13, and communicates with the discharge space 140 inside. A plasma gas injection / separation means 150, which is a main part of the present invention, is provided in the opening 131 of the ground electrode 130. The plasma gas injection / separation means 150 is provided in the opening 131 of the ground electrode 130. 150 is provided with at least two or more plasma injection holes 151 communicating with the discharge space 140 and the combustion chamber 400 of the internal combustion engine 40. It is desirable that the distance from the upper end of the inner peripheral edge of the ground electrode 130 to the plasma gas jet separating means 150, that is, the length A of the ground electrode space 141 is 0.5 mm or more. The length A of the ground electrode space 141 is preferably 3.5 mm or less in consideration of the jet power of the jet gas.

  The center electrode 11 is formed of a conductive metal material, and a center electrode discharge portion 110 formed of a heat-resistant metal material such as iridium, iridium alloy, tungsten, or tungsten alloy is formed on the tip side. A central electrode middle shaft portion 111 made of a highly heat conductive metal material such as copper or steel material is formed on the base end side of 110, and a terminal portion 112 connected to the high energy power source 20 is further formed on the base end side. Is formed.

The insulator 12 is formed in a substantially cylindrical shape from high-purity alumina or the like excellent in heat resistance, mechanical strength, high-temperature dielectric strength, thermal conductivity, and the like.
A discharge space forming portion 120 extending in a substantially cylindrical shape so as to extend below the center electrode discharge portion 110 is formed on the distal end side of the insulator 12, and inside the discharge space forming portion 120, A discharge space 140 in which the front end surface of the center electrode discharge unit 110 and the inner peripheral edge of the ground electrode 130 face each other is defined in a space defined by the front end surface of the center electrode discharge unit 110 and the inner peripheral wall of the insulator 120.
An insulator locking portion 121 is formed in the middle of the insulator 12.
A corrugated insulator head 122 is formed on the base end side of the insulator 12 exposed from the housing 13.

  The housing 13 is formed in a substantially cylindrical shape from a metal material such as a steel material. A side electrode 132 extending in a cylindrical shape is provided on the front end side of the housing 13 so as to cover the outer periphery of the discharge space forming portion 120. A screw part 133 for fixing to the cylinder head 41 of the internal combustion engine 40 is formed on the outer periphery of the side electrode 132. A hexagonal portion 135 for fastening the screw portion 133 is formed on the outer periphery of the housing 13. A caulking portion 136 is formed on the proximal end side of the housing 13, and the insulator locking portion 121 is caulked and fixed inside the housing 13 via a predetermined sealing member.

A substantially ring-shaped ground electrode 13 is formed so as to extend to the front end side of the side electrode 132 and cover the bottom surface of the discharge space forming portion 120 and partition the ground electrode inner space portion 141 communicating with the discharge space 140. Yes. The opening 131 of the ground electrode 130 is covered with a plasma gas injection / separation means 150, which is a main part of the present invention, and the plasma gas injection / separation means 150 is provided with at least two or more plasma injection holes 151. In the present embodiment, the plasma injection hole 151 is formed obliquely with respect to the central axis of the plasma ignition plug 10 so as to expand outwardly toward the tip side.
As shown in FIG. 1, the plasma gas injection / separation means 150 may be formed separately and bonded to the lower end of the ground electrode 130, or the ground electrode 130 is formed in a bottomed cylindrical shape, The ground electrode 130 and the plasma gas injection / separation means 150 may be integrally formed by forming the injection hole 151.
Further, the plasma gas injection / separation means 150 may be formed of an insulator such as alumina and held and fixed to the lower end surface of the ground electrode 130.

A typical example of the high energy power supply 20 used in the plasma ignition device 1 of the present invention will be described with reference to FIG. In the present invention, the high energy power source 20 is not limited to the present embodiment, and can be used in a known plasma ignition device as long as it can apply a high voltage and a large current to the plasma ignition plug 10. The high energy power source to be used can be appropriately selected.
The high energy power source 20 includes a power source 21 such as a battery, a voltage adjusting unit 22 that adjusts a voltage of the power source 21 including a DC-DC converter, an ignition coil 23 that boosts a voltage supplied from the power source 21, and an ECU 30. Applied to the igniter 24 including a switching element for opening and closing the ignition coil 23 according to the ignition signal, a diode 25 for blocking the high voltage of the capacitor 27, a noise absorbing resistor 26 for absorbing ignition noise, and the voltage adjusting means 22. Energy storage means 27 such as a capacitor for storing the generated electric charge and releasing it as a plasma current, and a diode 28 for blocking a high voltage from the coil 23.
When the voltage of the power source 21 is opened and closed by the ignition signal from the ECU 30, a high voltage is generated in the ignition coil 23 and applied to the plasma spark plug 10, and exceeds the insulation withstand voltage in the discharge space 140. An arc discharge is generated between the electrode discharge unit 110 and the ground electrode 130, and using this as a trigger, the electric energy stored in the energy storage unit 27 flows as a large current to the plasma spark plug 10 and is released into the discharge space 140. Then, the gas in the discharge space 140 becomes a high-temperature and high-pressure plasma state and is injected into the combustion chamber 400 of the internal combustion engine 40, and the air-fuel mixture in the combustion chamber 400 is ignited.

With reference to Fig.3 (a), the specific shape of the plasma ignition plug 10 in this embodiment is demonstrated.
In the present embodiment, the distance L (mm) from the tip of the center electrode discharge unit 110 to the upper end of the inner periphery of the ground electrode 130, and the inner space of the ground electrode from the upper end of the inner periphery of the ground electrode 130 to the plasma gas jet separation means 150 When the length A (mm) of 141, the diameter φD (mm) of the center electrode discharge part 110, and the angle θ (degrees) with respect to the central axis of the plasma injection hole 151, in this embodiment, φD = 1.5 mm, L = 2.0 mm, A = 0.8 mm, and θ = 45 degrees are set. The angle θ with respect to the central axis of the plasma injection hole 151 is presumed not to be particularly limited in order to exert the effect of the present invention, but can be set in the range of 20 to 70 degrees. It has been found that the length A of the space portion 141 in the ground electrode is preferably set to 0.5 mm or more and 3.5 mm or less by the inventors' earnest test described later.

  When the plasma ignition device 1 of the present invention having such a configuration is used, when a high voltage is applied between the center electrode 11 and the ground electrode 130 as shown in FIG. Since electric field concentration occurs at the boundary between the lower end surface of the portion 120 and the inner peripheral edge of the ground electrode 130, the trigger discharge TRG generated between the center electrode discharge portion 110 and the ground electrode 130 is generated in the discharge space forming portion 120. The creeping discharge generated so as to crawl the inner peripheral wall surface becomes dominant, and there is no possibility that air discharge that penetrates the discharge space 140 between the center electrode discharge portion 110 and the inner peripheral edge of the plasma injection hole 151 occurs. .

  In addition, even when the plasma gas injection / separation means 150 is formed of a metal, the center electrode discharge part 110 and the plasma gas injection / separation means 150 are formed because the ground electrode inner space 141 is formed with a depth of 0.5 mm or more. There is no risk of discharge occurring between them, so that the plasma injection holes 151 formed in the plasma gas injection / separation means 150 are not consumed by discharge, and the plasma injection direction is kept constant over a long period of use. Can keep.

When the electrical energy stored in the energy storage means 27 following the trigger discharge TRG flows to the plasma spark plug 10 as a large current and is released into the discharge space 140, the gas in the discharge space 140 and the ground electrode internal space 141 is discharged. Becomes a plasma state of high temperature and high pressure, and when this passes through the plasma injection holes 151 of the plasma gas injection separation means 150, it becomes plasma gas injection PLG separated into a plurality of parts and injected into the combustion chamber 400.
For this reason, even if a concentration distribution is generated in the air-fuel mixture existing in the combustion chamber 400, the gas in the combustion chamber 400 is in comparison with the case where the gas in the plasma state is injected in a lump as in the conventional plasma ignition device. Since the chance of contact with the air-fuel mixture increases, the ignitability improves.

Further, even when a strong in-cylinder airflow such as a tumble vortex is generated in the combustion chamber 400, the gas in a high-temperature / high-pressure plasma state is separated and injected, so that it is blown out by the in-cylinder airflow. The probability of being reduced, and more stable ignition can be realized. In addition, flame nuclei generated by a plurality of plasma injections mutually promote combustion growth and spread to a larger flame, so that ignition with a high combustion rate can be realized.
Further, even if the injected fuel adheres to the tip of the plasma spark plug 10 and easily forms a deposit, since the plurality of plasma injection holes 151 are formed, there is a probability that the deposit will cause clogging. Reduced.

As shown in FIG. 4, the ground electrode may be consumed due to the discharge at the boundary between the ground electrode 130 and the discharge space forming unit 120, but the discharge voltage is changed by changing the discharge position over the entire inner periphery of the ground electrode 130. Long-term use is possible without causing a rise.
In addition, although the ground electrode is inevitably consumed at the boundary between the ground electrode 130 and the discharge space forming unit 120 due to long-term use, the volume of the plasma gas generation space (the discharge space 140 and the ground electrode internal space 141) is larger than the volume. Since the length L of the discharge space 140 can be shortened, the discharge voltage can be lowered correspondingly, and the durability can be improved.

As an example of the present invention, as shown in FIG. 5A, in the plasma spark plug 10, the length A of the ground electrode inner space 141 is set to 0.5 mm or more, and as a comparative example, the length A in FIG. As shown, in the plasma ignition plug 10z, the length A of the ground electrode inner space 141z is set to 0.5 mm or less.
In the embodiment of the present invention, as shown in FIG. 5A, the surface of the inner peripheral wall of the insulator 120 is sandwiched between the tip of the center electrode discharge part 110 and the upper end of the inner peripheral edge of the ground electrode 130. Although the discharge TRG _(SF) is generated, as shown in FIG. 5B, in the comparative example 10z, the distance to the plasma gas injection separation means 150z is short, so the surface of the center electrode discharge part 110z and the plasma gas injection There is a possibility that the air discharge TRG ( _AR ) may occur at the shortest distance of the separation means 150z. For this reason, in the comparative example, the plasma gas injection / separation means 150 may be consumed by the discharge, and the air discharge TRG ( _AR ) is dominant over the creeping discharge, which may increase the required voltage. is there.

As shown in FIG. 6 (a), according to the present inventors' earnest test, in the comparative example, the probability of discharge between the center electrode discharge part 110z and the plasma gas injection separation means 150z is 20% to 60%. It is high, and by setting the length A of the ground electrode internal space 141 to 0.5 mm or more as in the embodiment, the discharge between the center electrode discharge part 110 and the plasma gas injection separating means 150 is reliably suppressed. It turns out that you can.
Further, as shown in FIG. 6 (b), it was found from the ignitability evaluation test conducted by the present inventors that A ≧ 3.5 mm is desirable. This is considered to be because if A is larger than 3.5 mm, the plasma gas injection power injected from the tip of the plasma ignition plug 10 into the combustion chamber 400 is weakened and the ignitability is lowered.
In this test, the misfire limit air-fuel ratio A / F was compared under the conditions of an exhaust capacity of 1800 cc, a rotational speed of 1600 rpm, and a rotational torque of 30 Nm.

  In the above embodiment, an example in which two plasma injection holes 151 are drilled has been shown. However, as shown in FIGS. 7A to 7D, drilling is performed at a position equidistant from the central axis of the plasma spark plug 10. The number of plasma injection holes 150 to be changed can be appropriately changed from 3 to 6 according to the combustion characteristics of the internal combustion engine to be used. At this time, as described above, the inner diameter φd of the plasma injection holes can be appropriately changed according to the number n of the plasma injection holes 150.

The plasma ignition device 1e according to the second embodiment of the present invention basically has the same configuration as that of the above embodiment, and the shape of the plasma ignition plug 10e is as shown in FIG. Is formed in the same manner as the discharge space 140, and the opening diameter is increased stepwise from the tip side, and the opening is covered with the plasma gas injection separating means 150e, and the plasma injection hole 151e is connected to the central axis of the plug. However, it is different in that it is formed in parallel.
By forming in this way, in addition to the same effects as in the above embodiment, when high-temperature and high-pressure plasma gas is injected from the plasma gas injection separation means 150e, the jet flow is disturbed, and the combustion chamber 400 It can be expected that the state of agitation with the air-fuel mixture becomes good and that the ignitability can be improved.

  The plasma ignition device 1f according to the third embodiment of the present invention basically has the same configuration as that of the above embodiment, and the shape of the plasma ignition plug 10f is shown in FIG. The plasma gas injection hole 151f is formed by partially covering with the plasma gas injection separation means 150f formed in the above. Even in such a shape, the same effect as in the first embodiment can be expected.

  A plasma ignition device 1g according to the fourth embodiment of the present invention basically has the same configuration as that of the above embodiment, and the shape of the plasma ignition plug 10g is bridged to the ground electrode opening 131g as shown in FIG. It is different in that the plasma injection hole 151g is formed by partially covering with the formed plasma gas injection separation means 150g. Even in such a shape, the same effect as in the first embodiment can be expected.

  A plasma ignition device 1h according to the fifth embodiment of the present invention basically has the same configuration as that of the above embodiment, and the shape of the plasma ignition plug 10h is as shown in FIG. The plasma gas injection / separation means 150h is integrally formed by projecting the bottom portion into a truncated cone shape toward the tip side, and the plasma injection hole 151h is formed, and the ground electrode 10h and the plasma gas injection separation means 150h are formed. Are different from each other. Even in such a shape, the same effect as in the first embodiment can be expected.

The plasma ignition device 1i according to the sixth embodiment of the present invention basically has the same configuration as that of the above embodiment, and the shape of the plasma ignition plug 10i is formed as shown in FIGS. 12 (a) and 12 (b). Is different.
In the present embodiment, the center electrode discharge part 110i is formed in a substantially prismatic shape, the discharge space 140i and the ground electrode inner space part 141i are partitioned into rectangles, the plasma injection holes 151i are formed in a rectangular cross section, and the pointed parts 152i has an inclined surface along the direction in which the plasma injection hole 151i is formed, and is formed in a triangular prism shape that tapers toward the ground electrode space 141i.
By adopting such a shape, when the high-temperature and high-pressure plasma gas generated in the discharge space 140i and the ground electrode internal space 141i is ejected from the plasma injection hole 151i, it is rectified by the inclined surface of the pointed portion 152i. It is expected that the resistance when passing through the plasma gas jet separation means 150i can be further reduced and the ignitability can be improved.
In the present embodiment, an example in which the discharge space 140i is partitioned into rectangles has been shown. However, it is important to form the pointed portion 152i on an inclined surface along the direction in which the plasma injection hole 151i is formed, It is presumed that the rectifying effect of the pointed portion 152i becomes larger by making it rectangular, but the shape of the discharge space 140i is not limited to a rectangle, and it is partitioned and formed in a substantially cylindrical shape as in the above embodiment. Even in this case, it is expected that the resistance when passing through the plasma gas jet separation means 150i using the inclined surface of the pointed portion 152i can be further reduced, and the ignitability can be improved.

DESCRIPTION OF SYMBOLS 1 Plasma ignition apparatus 10 Spark plug 11 Center electrode 110 Center electrode discharge part 12 Insulator 120 Discharge space formation part 13 Housing 130 Ground electrode 131 Ground electrode opening part 140 Discharge space 141 Ground electrode inner space part 150 Plasma gas injection separation means 151 Plasma Injection hole 20 High energy power supply 30 Electronic control unit (ECU)
40 Internal combustion engine 400 Combustion chamber

JP 2006-294257 A JP 2006-244867 A

Claims (5)

An ignition plug mounted on the internal combustion engine and a high energy power source for supplying high energy to the ignition plug are formed inside the ignition plug by application of a high voltage and supply of a large current from the high energy power source. In a plasma ignition device that performs ignition by injecting the gas in the discharge space as a high-temperature, high-pressure plasma gas into the combustion chamber of the internal combustion engine,
The spark plug includes a substantially long axis center electrode, a substantially cylindrical insulator covering the periphery of the center electrode and extending from the tip of the center electrode toward the combustion chamber, and an outer periphery of the insulator. A substantially cylindrical housing that covers the ground electrode, and a ground electrode that extends substantially toward the distal end of the housing and is formed in a substantially annular shape.
A space defined by the front end surface of the center electrode and the inner peripheral wall of the insulator inside the insulator is formed as a discharge space by making the front end surface of the center electrode and the inner peripheral edge of the ground electrode face each other.
A space in the ground electrode that communicates with the discharge space is defined inside the ground electrode,
A plasma gas jet separating means for covering a part or all of the space in the ground electrode is provided;
The plasma gas injection / separating means comprises at least two or more plasma injection holes that communicate the discharge space and the combustion chamber and change the injection direction of a part or all of the plasma gas. apparatus.   2. The plasma ignition device according to claim 1, wherein the length of the space portion in the ground electrode from the upper end of the inner peripheral edge of the ground electrode to the plasma gas jet separation means is set to a range of 0.5 mm or more.   3. The plasma ignition device according to 1 or 2, wherein the length of the space portion in the ground electrode from the upper end of the inner peripheral edge of the ground electrode to the plasma gas jet separation means is set in a range of 3.5 mm or less.   The plasma gas jet separation means includes a pointed protrusion that protrudes toward the inner space portion side of the ground electrode and has a tip tapered so as to follow a direction in which the plasma injection hole is formed. The plasma ignition device according to any one of 1 to 3.   5. The plasma ignition device according to claim 4, wherein the distance from the upper end of the inner peripheral edge of the ground electrode to the tip of the pointed portion is set to a range of 0.5 mm or more.

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