JP5434296B2 - Plasma ignition device - Google Patents

Description

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

In recent years, in combustion engines such as automobiles, 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. .
As an engine capable of simultaneously improving the combustion efficiency of the engine and reducing the environmental load, it is impossible to propagate the flame with a spark plug using a conventional spark discharge by injecting gas in a high-temperature and high-pressure plasma state into the engine combustion chamber. A method for efficiently burning a lean air-fuel mixture has attracted attention.

As such a plasma ignition device, Patent Literature 1 has a center electrode and an axial hole extending in the axial direction, and the distal end surface of the central electrode is accommodated on the distal end side in the axial hole, and the central electrode is An insulator to be held; a cavity formed in a concave shape with the inner peripheral surface of the shaft hole and the tip surface of the central electrode at the tip of the insulator; and the axial direction of the insulator A metal shell that surrounds and holds a vertical radial periphery, and is disposed closer to the distal end side in the axial direction than the distal end portion of the insulator, and is in an annular contact with the distal end portion of the insulator, in the axial direction When viewed from above, the cavity has a contact portion in which the opening of the cavity is inside, and a ground electrode having a communication portion that communicates the inside of the cavity with outside air, and the ground electrode is in the axial direction. The subject The plasma is characterized in that it is in non-contact with the tool, and is in contact with the metal shell in the radial direction, and its outer edge is joined to the metal shell and electrically connected to the metal shell. A jet spark plug is disclosed.
In the plasma jet ignition plug of Patent Document 1, the contact portion of the ground electrode is joined to the metal shell in a state of being in contact with the tip portion of the insulator, and between the ground electrode and the tip portion of the insulator or between the insulator and the main body. By setting a gap that may occur between the metal fittings to be closed, energy leakage is prevented and reduction in ignitability is suppressed.

However, when the conventional plasma ignition device as in Patent Document 1 is applied to a combustion engine in which fuel spray such as a gasoline direct injection engine is directly injected into the combustion chamber and the fuel spray easily adheres to the tip of the spark plug, It has been found that the following problems may occur.
That is, when the entire engine is cold, such as at a low temperature start or immediately after the first explosion, water vapor generated by the combustion explosion of the mist-like fuel or air-fuel mixture injected into the fuel chamber is applied to the ground electrode of the spark plug. It may be cooled and condensed by touching it to become liquid.
When such a liquid material enters the cavity including the opening of the ground electrode that opens toward the combustion chamber together with the gas in the combustion chamber during the compression process of the internal combustion engine, the liquid material insulates oil droplets or the like. In the case where the liquid is a liquid, the dielectric strength between the center electrode and the ground electrode is increased to increase the required voltage, or when the liquid is a conductive material such as water droplets. It has been found that the insulation between the ground electrode and the center electrode is short-circuited through the liquid material, and it is difficult for a discharge to occur between the center electrode and the ground electrode, resulting in a misfire. did.

  Therefore, in view of such a situation, the present invention may cause misfire even if the fuel injected into the combustion chamber or the water vapor existing in the combustion chamber is cooled and condensed to enter the discharge space. It is an object of the present invention to provide a highly reliable plasma ignition device without any problems.

In the first invention, a center electrode formed in a substantially long axis shape, an insulator formed in a substantially cylindrical shape covering the center electrode and extending downward from the lower end surface of the center electrode, and the insulator A plasma ignition plug configured by a substantially cylindrical housing covering the ground electrode formed in a substantially annular shape extending to the housing; and a high energy power source for supplying high energy to the plasma ignition plug. Then, high energy is given to the discharge space defined between the center electrode and the ground electrode, and the gas in the discharge space is injected into the engine combustion chamber as a high-temperature and high-pressure plasma state to In the plasma ignition device that performs ignition, the liquid space that has entered the discharge space and the opening space defined inside the opening portion of the ground electrode that opens toward the combustion chamber is discharged from the discharge space. Comprising a liquid material discharge means, a liquid material reservoir means for temporarily storing the discharged liquid material, and as the liquid substance reservoir means, airtight with the outside between the insulator and the housing holding A ground electrode discharge portion formed in a substantially annular shape in close contact between the lower end surface of the insulator and the ground electrode, and as the liquid material discharge means, The communication path that communicates with the discharge space includes a surface of the insulator at a boundary between the insulator and the ground electrode discharge portion, a surface of the ground electrode discharge portion at a boundary between the insulator and the ground electrode discharge portion, At least one of the positions inside the ground electrode discharge part, the surface of the ground electrode discharge part at the boundary between the ground electrode discharge part and the ground electrode, and the surface of the ground electrode at the boundary between the ground electrode discharge part and the ground electrode Provided (claim 1).

In a second aspect of the present invention, the communication passage forms a cross-sectional area per one above 0.1 mm @ 2 (claim 2).

In the third invention, the volume of the void portion is formed over an equal times the volume of the space combined with the discharge space and the open space (claim 3).

According to the first invention, at the time of low temperature starting or the like, the grounding in which a mist-like fuel injected into the combustion chamber, water vapor generated by explosion, etc. is cooled and liquefied is opened toward the combustion chamber. Even if it enters the discharge space defined in the plasma ignition plug from the opening of the electrode, the liquid material that has entered the discharge space and the opening space is discharged by the liquid material discharge means, and the liquid material storage means. Therefore, when liquid fuel adheres between the center electrode and the ground electrode, the required voltage for destroying the insulation of the discharge space increases or the center electrode and the ground electrode There is no risk of short circuiting between the two.
Specifically, even if liquid fuel enters the open space and the discharge space, liquid matter such as liquefied fuel or condensed water is discharged in the discharge path when the pressure in the combustion chamber rises rapidly during the compression stroke of the combustion engine. If the discharge space is blocked by the liquid material, it may be difficult to form a discharge path.
However, by providing the communication path as in the present invention, the liquid material is sucked into the gap, and a discharge path between the center electrode and the ground electrode is secured, and plasma ignition exhibiting stable ignitability. It has been clarified by the inventors' intensive studies that the apparatus can be realized.
In addition, when the gap is formed between the insulator and the housing by the present inventors' earnest test, the liquid material that has entered the discharge space is discharged into the gap to discharge the discharge path. It has been found that the effect of the present invention that achieves stable ignition while ensuring the above can be exhibited.
Further, the communication path includes the insulator surface at the boundary between the insulator and the ground electrode discharge portion, the ground electrode discharge portion surface at the boundary between the insulator and the ground electrode discharge portion, and the ground electrode discharge portion. Internally, the ground electrode discharge part surface at the boundary between the ground electrode discharge part and the ground electrode, the ground electrode surface at the boundary between the ground electrode discharge part and the ground electrode can be formed at any position. The liquid material that has entered the discharge space is discharged from the communication path into the gap, and the effect of the present invention is ensured to secure a discharge path between the center electrode and the ground electrode discharge part.
Therefore, when a high voltage is applied from the high energy power source, a discharge occurs between the center electrode and the ground electrode at a stable voltage, and a large current is released into the discharge space as a trigger, A gas in the discharge space becomes a high-temperature and high-pressure plasma state and is injected into the combustion chamber, thereby realizing a plasma ignition device exhibiting stable ignitability.

By forming the communication path within the scope of the second invention, even if the liquid material enters the discharge space when the pressure in the combustion chamber rises, the liquid material is quickly put into the gap. It has been revealed by the inventors' diligent tests that it can be discharged easily.
In addition, when the cross-sectional area per said communication path is smaller than 0.1 mm < ² >, it is guessed that pipe resistance becomes large and it becomes difficult to discharge | emit liquid substance in the said space | gap part.

The inventors of the present inventors have conducted intensive tests to form the gap within the scope of the third invention, thereby discharging the liquid material that has entered the discharge space into the gap, and the center electrode and the above-mentioned It was confirmed that a discharge path could be secured between the ground electrode discharge part.

1 is a half sectional view showing an outline of a plasma ignition device in a first embodiment of the present invention. (A) is principal part sectional drawing of the plasma ignition apparatus in the 1st Embodiment of this invention, (b) is a partially notched perspective view which shows the detail of the ground electrode discharge part which is the principal part of this invention. The effect of the plasma ignition apparatus in the 1st Embodiment of this invention is shown, (a) is principal part sectional drawing in the state to which the fuel droplet adhered, (b) is principal part sectional drawing in a compression stroke. The simulation test result for confirming the effect of this invention is shown, (a) is drawing substitute photograph which shows the state which the droplet adhered, (b) is drawing substitute photograph at the time of pressurization. The problem of the conventional plasma ignition device is shown, (a) is the principal part sectional view in the state where the fuel droplet adhered, (b) is the principal part sectional view in the compression stroke. The simulation test result for confirming the conventional problem is shown, (a) is a drawing substitute photograph showing a state where droplets are attached, and (b) is a drawing substitute photograph at the time of pressurization. The characteristic view which shows the relationship between the discharge space volume with respect to the effect of this invention, and a space | gap part volume. The outline | summary of the ground electrode discharge part used for the plasma ignition apparatus in the 2nd Embodiment of this invention is shown, (a) is a top view, (b) is sectional drawing, (c) is a bottom view, (d). These are principal part sectional drawings in an assembly state. Sectional drawing of the principal part of the plasma ignition apparatus in the 3rd Embodiment of this invention.

  The present invention relates to a plasma ignition device that gives high energy to a gas in a discharge space and injects it into a combustion chamber as a high-temperature and high-pressure plasma to ignite an air-fuel mixture in the engine combustion chamber. Liquid material that discharges liquid fuel from the discharge space when the fuel injected into the chamber adheres to the tip of the plasma spark plug, cools, and enters into the discharge space partitioned by the plasma spark plug. Discharge means and liquid material storage means for temporarily storing the discharged liquid fuel are provided to prevent an increase in insulation withstand voltage and short circuit between the center electrode and the ground electrode, thereby realizing stable ignition. It is a plasma ignition device.

An outline of the plasma ignition device 1 according to the first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the plasma ignition device 1 according to the present embodiment has a high voltage applied to a plasma ignition 10 and a plasma ignition plug 10 that are mounted so that a tip is exposed in a combustion chamber 300 of a combustion engine 30 (not shown). The high-energy power source 20 is configured to apply and supply a large current.

  The plasma ignition plug 10 includes a center electrode 11 formed in a substantially long axis shape, an insulator 12 formed in a substantially cylindrical shape covering the center electrode 11, a housing 13 formed in a substantially cylindrical shape covering the insulator 12, and a housing 13, a ground electrode 130 formed in a substantially annular shape and having an opening 131 that opens toward the combustion chamber 300, a discharge chip 150, a discharge space 140 partitioned inside the insulator 12, In the discharge space 140, the gap 160 formed between the insulator 12 and the housing 13 as a liquid material storage means for temporarily storing the fuel adhering to the surface of the ground electrode 130. As a liquid material discharging means for discharging the invading fuel, a gap 160 formed in the discharge chip 150 and a communication path 161 that connects the discharge space 140 are configured.

The center electrode 11 has a center electrode discharge portion 110 formed on the distal end side and a center electrode terminal portion 112 connected to the external high energy power source 20 on the proximal end side. The center electrode discharge portion 110 and the center electrode terminal portion 112 is integrally connected through a central electrode middle shaft 111.
The center electrode discharge part 110 is formed of a highly heat-resistant conductive material containing a noble metal such as iridium or an iridium alloy.
The center electrode middle shaft 111 is formed of a nickel alloy or the like having excellent corrosion resistance, and a metal material having good electrical conductivity and high thermal conductivity such as copper is enclosed therein.
The center electrode terminal portion 112 is made of a highly conductive metal material such as iron or aluminum.

The insulator 12 is formed in a substantially cylindrical shape so as to cover the center electrode 11 using an insulating ceramic such as high-purity alumina excellent in mechanical strength, heat resistance, thermal conductivity, and dielectric strength at high temperatures. Yes.
A substantially cylindrical discharge space forming portion 120 extending downward from the lower end surface of the center electrode discharge portion 110 is formed on the distal end side of the insulator 12. Inside the discharge space forming part 120, a discharge space 140 is partitioned by the lower end surface of the center electrode discharge part 110 and the ground electrode opening 131.
An insulator locking portion 121 having a large diameter is formed in the middle of the insulator 12, and is fixed by a substantially cylindrical housing 13 so as to cover the insulator locking portion 121.
A corrugated insulator head 122 is formed on the base end side of the insulator 12 exposed from the housing 13, and an insulation leak is caused between the center electrode terminal portion 112 exposed from the insulator head 122 and the housing 13. It does not occur.

The ground electrode 130 covers the lower end surface of the discharge space forming part 120 and communicates with the lower end opening of the discharge space forming part 120, opens toward the combustion chamber 300, and opens the ground electrode with the opening space 141 defined inside. It is formed in a substantially annular shape having a portion 131.
A substantially cylindrical side electrode 132 is formed so as to continue to the base end side of the ground electrode 130 and cover the outer periphery of the discharge space forming portion 120.
The housing 13 is formed so as to be connected to the base end side of the side electrode 132 and cover the insulator locking portion 121, and further, a screw portion 133 to be screwed to the combustion engine 60 is formed on the outer periphery of the distal end side of the housing 13. A hexagonal portion 135 for tightening the screw portion 133 is formed on the outer periphery of the base end side of the housing 13. Further, the insulator locking portion 121 is fixed by crimping to the end face of the housing 13 on the base end side. A caulking portion 134 is formed.
The ground electrode 130, the side electrode 132, and the housing 13 are made of a metal material such as nickel, a nickel alloy, or iron.

A substantially cylindrical void 160 is formed between the side electrode 132 and the insulator 12.
On the proximal end side of the gap 160, a contact portion where the insulator locking portion 121 and the housing 13 are in contact is formed, and a metal seal is used as a confidentiality holding member between the insulator locking portion 121 and the housing 13. Since the member 170 (packing), the insulating powder seal member 171, the sealing member 172 and the like are inserted, the airtightness is maintained, and the gas in the gap 160 and the discharge space 140 is prevented from leaking to the outside. Yes.
In the present invention, the gap 160 constitutes a discharged fuel storage means that discharges fuel droplets adhering to the surface of the plasma spark plug 10 from the discharge space 140 and temporarily stores them.
Further, the gap 160 facilitates the insertion of the discharge space forming part 120 into the side electrode 132 during the manufacture of the plasma spark plug 10 and is formed between the side electrode 132 and the center electrode discharge part 110. The stray capacitance is reduced to suppress discharge noise.

As shown in FIG. 2A, a discharge chip 150 is interposed as a ground electrode discharge portion at the boundary between the ground electrode 130 and the lower end surface of the discharge space forming portion 120.
The discharge chip 150 is made of a metal material excellent in heat resistance and sputtering resistance, and is formed in a substantially annular shape as shown in FIG.
The upper surface of the discharge chip 150 is in airtight contact with the lower end surface of the insulator 12. The inner peripheral surface of the discharge chip 150 is connected to the discharge space 140, the outer peripheral surface of the discharge chip 150 is exposed to the substantially cylindrical gap portion 160, penetrates the inner peripheral surface and the outer peripheral surface, and the discharge space 140 and the gap portion 160 A communication passage 161 that communicates with each other is formed.
It is sufficient that at least one communication passage 161 is formed, but a plurality of communication passages 161 may be formed as shown in the figure.
Further, when the cross-sectional area S per one of the communication passages 161 is smaller than 0.1 mm ² , the pipe resistance of the communication passage 161 is large, and a liquid material such as liquid fuel does not easily flow into the gap 160. Become. Therefore, it is desirable that the cross-sectional area S per one communication path 161 is at least 0.1 mm ² or more.
In the present embodiment, the discharge space 140 has a volume of about 4 mm ³ , the gap 160 has a volume of about 20 mm ³ , and the discharge space 140 is also five times or more the volume.

The effects of the present invention will be described with reference to FIGS.
As shown in FIG. 3 (a), the fuel injected into the combustion chamber 300 during the low temperature start is cooled and the fuel droplets _DFL are formed so as to cover the opening 131 of the ground electrode 130. However, as shown in FIG. 4B, when the pressure P _CYL in the combustion chamber 300 is increased to, for example, 1.0 MPa in the compression step of the combustion cycle, the fuel droplet D _FL is The gas in the discharge space 140 enters while pressing the gas in the discharge space 140 from the opening 131. However, since the communication passage 161 is formed in the discharge chip 150, the fuel liquid enters the gap 160 through the communication passage 161 due to the capillary effect. Drop D _FL is inhaled.

At this time, the pressure in the combustion chamber 300 increases rapidly through the fuel droplets D _FL spike pressure in the discharge space 140, closed aperture of the discharge space 140 side of the communication passage 161 by the fuel droplets D _FL If it is a state, the pressure _{P 160} in the gap 160 is lower than the pressure _{P 140} relatively discharge space 140, and since the volume of the void portion 160 is much larger than the volume of the discharge space 140 When the pressure P _CYL in the combustion chamber 300 increases due to compression, the pressure P140 in the discharge space 140 immediately becomes equal to the pressure P _CYL in the combustion chamber 300, and the pressure P ₁₆₀ in the gap ₁₆₀ is relatively low, fuel droplets D _FL is instantaneously sucked into the gap portion 160, the opening 131 of the ground electrode 130 and the inner peripheral surface of the lower end surface and the discharge tip 150 of the center electrode discharge portion 110 The surface is exposed to the discharge space 140 and the opening space 141 without being covered with the liquid fuel, and the discharge is possible between the lower end surface of the center electrode discharge portion 110 and the inner peripheral surface of the discharge chip 150. Inferred.

In this state, when a high voltage is applied between the center electrode discharge unit 110 and the discharge chip 150 from the term energy power source 20 in accordance with an ignition signal transmitted from an electronic control device (not shown), the inside of the discharge space 140 As a trigger, a large current flows from the high energy power source 20 and the gas in the discharge space 140 and the open space 141 is injected in a high temperature / high pressure plasma state.
At this time, the liquid fuel temporarily sucked into the gap 160 is heated by the gas in a plasma state and burns. Alternatively, even if it remains in the gap 160, when the pressure P _CYL in the discharge space 140 and the opening space 141 is reduced after ignition, the pressure P 160 in the gap ₁₆₀ causes the discharge space 140 and the opening space 141 to _enter the gap 160. It is discharged and burned at the next ignition.
The lower end portion of the insulator 12, the discharge tip 150, and the ground electrode 130 are kept in close contact with each other, and the gas has poor wettability compared to the liquid, has a large coefficient of friction, and the inner diameter φD of the communication path 161 is Since it is sufficiently small, there is no possibility that the gas in the discharge space 140 and the opening space 141 will leak into the gap 160 through the communication path 161 when the gas in the discharge space 140 and the opening space 141 is in a high-temperature and high-pressure plasma state.

FIG. 4 shows the results of a simulation test conducted to confirm the effect of the present invention. As shown in the figure (a), atmospheric pressure, or, to keep the pressure vessel to 0.1 MPa, to expose the tip of the plasma ignition plug 10 of the present invention, the fuel droplets D _FL to simulate water droplets D _W (0.08 ml) is attached to the tip of the plasma spark plug 10 and the pressure vessel is raised to 1.0 MPa in a manner similar to the compression process of the combustion engine 30 as shown in FIG. The water droplet _DW was sucked into the discharge space 140 and the opening space 141 from the ground electrode opening 131, and it was confirmed that discharge was possible when a high voltage was applied between the center electrode 11 and the housing 13. .
(Comparative example)

Here, with reference to FIG. 5, FIG. 6, the problem at the time of using the conventional plasma ignition plug 10z as a comparative example is demonstrated.
In the conventional plasma plug 10z, the discharge chip 150z and the lower end surface of the insulator 12 are in close contact so that the pressure in the discharge space 140z does not leak into the gap 160z.
As shown in FIG. 5 (a), when adhering fuel droplets _{D FL} so as to cover the ground electrode opening 131Z, as shown in FIG. 5 (b), the pressure _{P CYL} in the combustion chamber 300 rises , the discharge portion of the fuel droplets enters the space 140Z, the gas in the discharge spaces 140Z until it equals the pressure _{P CYL} pressure _{P 140} z combustion chamber 300 within the discharge space 140Z via a fuel compression Is done.
At this time, since the liquid fuel has no escape, it stays in the discharge space 140z and the opening space 141z, covers the surface of the discharge chip 150z, and the withstand voltage between the center electrode discharge part 110 and the discharge chip 150z becomes extremely high. It became clear that it became impossible to discharge.

FIG. 6 shows the result of a simulation test conducted to confirm such a problem. As shown in FIG. 5A, the tip of a conventional plasma ignition plug 10z is exposed in a pressure vessel maintained at atmospheric pressure or 0.1 MPa, and a water droplet D _W is imitated by a fuel droplet D _FL. z (0.8 ml) is attached to the tip of the plasma spark plug 10z, and the pressure vessel is raised to 1.0 MPa in a manner similar to the compression process of the combustion engine 30 as shown in FIG. The water droplet D _W z was not sucked into the discharge space 140 z from the ground electrode opening 131 z, and almost no change was observed in the water droplet D _W z.
Further, when a high voltage was applied between the center electrode 11z and the housing 13z, it was confirmed that the center electrode 11z and the housing 13z were short-circuited and could not be discharged.

Referring to FIG. 7, the volume of discharge space 140 and opening space 141 with respect to the effect of the present invention and the center electrode gap 160 obtained by the inventors' diligent tests performed by changing the volume of gap 160. The relationship with the volume of will be described.
To a discharge space 140 and open space 141 and the combined volume _V C (mm ^3), where changing the volume _V V of the gap portion 160 (mm ^3), as shown in FIG. 7, the volume of the void portion 160 In the comparative example in which the volume ratio (V _V / V _C ) to the volume of the discharge space 140 and the opening space 141 is 0.7 or less, the discharge space 140 and the discharge space 140 and the opening space 141 are penetrated by the penetration of the liquid material into the discharge space 140 and the opening space 141. The dielectric strength of the open space 141 increased, and at 35 kV, which is the upper limit of the applied voltage of the test apparatus, discharge was not possible, and an open waveform was obtained as shown as a comparative example in FIG.
Volume to volume ratio of the discharge space 140 and the opening space 141 of the volume of the cavity portion 160 _(V V / V _C) is 1.0 or more, that is, the more equal volumes of _{V C} of the discharge space 140 and open space 141 As described above, when the volume V _V of the gap 160 and the opening space 141 is set, the liquid material that has entered the discharge space 140 and the opening space 141 is discharged into the gap 160, and FIG. 7 shows an embodiment. Thus, it was found that the discharge voltage can be discharged at a stable voltage of 35 kV or less. It has also been found that the cross-sectional area S of the communication passage 161 is desirably 0.1 mm ² or more.

  Further, in the above embodiment, the effect is described using the results of the test using the amount of water droplets such that the liquid material entering the discharge space 140 and the opening space 141 fills the discharge space 140 and the opening space 141. However, not only when such a large amount of liquid material enters the discharge space 140 and the opening space 141, but many fine granular droplets existing in the combustion chamber 400 enter the compression stroke. Even in the case where it is scattered between the center electrode discharge part 110 and the discharge chip 150, it is sucked into the gap part 160 due to the capillary effect of the communication path 161, so that the amount of liquid substances attached in the middle of the discharge path is reduced. In addition, it is possible to suppress an increase in the withstand voltage and to discharge with a stable discharge voltage.

Plasma ignition devices 1a to 1d in which the formation position of the passage 161 is changed in the second embodiment of the present invention will be described with reference to FIGS. 8 (a) to (d).
As in the above embodiment, the communication path 161 may be formed in the discharge chip 150 so as to penetrate the side surface from the inner peripheral surface to the outer peripheral surface. However, as shown in FIG. A part of the lower end surface of 150a and a part of the outer peripheral side surface may be recessed in a groove shape to form a communication path 161a that is formed in a substantially L shape. With such a configuration, the discharge space 140 and the gap portion 160 are in communication with each other, and the fuel droplets that have entered the discharge space 140 and the opening space 141 are temporarily inserted into the gap portion 160 as in the above embodiment. And a stable discharge path is formed between the center electrode discharge part 110 and the discharge tip 150a, and ignition is reliably caused.
Further, as shown in this figure (b), the communication path 161b may be formed in a groove shape on the surface of the discharge chip 150a, or as shown in this figure (c), the ground electrode 130c and the discharge chip 150c. The communication path 161c may be formed in the shape of a groove on the surface on the ground electrode 130c side at the boundary between the insulating discharge space forming portion 120d and the discharge chip 150d as shown in FIG. In this case, the communication path 161d may be formed in a groove shape on the surface on the insulator discharge space forming portion 120 side.
In any of the embodiments, the liquid material that has entered the discharge space 140 and the opening space 141 is discharged from the communication paths 161a, 161b, 161c, and 161d to the gap portion 160, and the center electrode discharge portion 110, the ground electrode discharge portion 130, and the like. An effect similar to that of the above-described embodiment for securing a discharge path between the two can be expected.

With reference to FIG. 9, the plasma ignition apparatus 1e in the 3rd Embodiment of this invention is demonstrated. In the above embodiment, the gap 160 is formed between the insulator 12 and the housing 13 as the liquid material storing means, and the communication passage 161 that communicates the gap 160 and the discharge space 140 is provided as the liquid discharge means. In the present embodiment, the gap GAP of 0.02 mm or more and 0.15 mm or less is provided between the center electrode 11 and the insulator 12, and the liquid material storage means (gap part) 160e and the liquid material are described. The difference is that the discharge means (communication path) 161e is used. In the present embodiment, if the communication passage 161e has a shape in which the gap portion 160e and the discharge space 140 communicate with each other, the diameter of the center electrode 110e is reduced so that the inner peripheral wall of the insulator 120e has a smaller diameter. The same pore shape or groove as in the above embodiment at either the center electrode 110e side or the insulator 120e side at the boundary between the tip of the center electrode 110e and the diameter changing portion of the insulator 120e. Alternatively, as shown in FIG. 9, a gap may be provided so as not to contact the tip of the center electrode 110e and the diameter changing portion of the insulator 120e.
With this configuration, the liquid material that has entered the discharge space 140 and the opening space 141 during the compression stroke is sucked into the gap 160e from the communication path 161e, and the center electrode discharge portion 110d and the ground electrode discharge portion 130 are sucked. And a plasma ignition device 1e capable of realizing stable ignition can be realized.
In the present embodiment, even in the test were carried out by varying the size of the gap portion 160e, results similar to the results shown in FIG. 7 is obtained, equal volume V _C of the discharge space 140 and open space 141 It has been found that the effect of the present invention can be obtained by providing the gap portion 160e with a volume that is twice or more.
Further, in the present embodiment, the gap 160e and the communication path 161e may be provided only between the center electrode 11 and the insulator 12, and in addition to this, A space 160 may be provided between the housing 13 and the communication path 161 may be formed at the boundary between the tip of the insulator 120e and the ground electrode 130 or the ground electrode discharge part 131.

  Further, the gap portion 160, 160a, 160b, 160c, 160d and the combustion chamber 400 are communicated with the ground electrode 130 or the side electrode 132, and a communication hole having a predetermined flow path resistance is formed, thereby forming the gap portion. It is presumed that it is possible to adopt a configuration in which the liquid material that has entered the 160, 160a, 160b, 160c, and 160d can be discharged into the combustion chamber 400.

  In the present invention, the high energy power source 20 is not particularly limited, and the insulation between the center electrode discharge part 110 and the ground electrode 130 is broken, and a large current is discharged into the discharge space 140 to discharge. Any configuration can be used as long as the gas in the space 140 can be ejected in a high-temperature and high-pressure plasma state, and a known high-energy power source used in a plasma ignition device can be appropriately employed.

DESCRIPTION OF SYMBOLS 1 Plasma ignition apparatus 10 Plasma ignition plug 11 Center electrode 110 Center electrode discharge part 12 Insulator 13 Housing 130 Ground electrode 131 Ground electrode opening part 140 Discharge space 150 Ground electrode discharge part (discharge chip)
160 Cavity (Liquid material storage means)
161 communication path (liquid discharge means)
170 Confidentiality retaining member (packing)
20 High energy power source 30 Combustion engine

JP 2008-277257 A JP 2007-255374 A

Claims (3)

A center electrode formed in a substantially long axis shape, an insulator formed in a substantially cylindrical shape covering the center electrode and extending downward from the lower end surface of the center electrode, and formed in a substantially cylindrical shape covering the insulator A plasma ignition plug configured to extend to the housing and a ground electrode formed in a substantially annular shape, and a high energy power source for supplying high energy to the plasma ignition plug, A plasma ignition device for igniting a combustion engine by applying high energy to a discharge space partitioned between the ground electrode and injecting the gas in the discharge space into a high temperature / high pressure plasma state into an engine combustion chamber In
An opening space partitioned inside the opening of the ground electrode that opens toward the combustion chamber, a liquid material discharging means for discharging the liquid material that has entered the discharge space from the discharge space, and the discharged liquid material A liquid storage means for temporarily storing
As the liquid material storing means, a gap portion is provided between the insulator and the housing to maintain airtightness with the outside,
While interposing a ground electrode discharge portion formed in a substantially annular shape closely between the lower end surface of the insulator and the ground electrode,
As the liquid material discharge means, a communication path that communicates the gap and the discharge space,
The insulator surface at the boundary between the insulator and the ground electrode discharge part;
The ground electrode discharge portion surface at the boundary between the insulator and the ground electrode discharge portion;
Inside the ground electrode discharge part,
The surface of the ground electrode discharge part at the boundary between the ground electrode discharge part and the ground electrode;
The surface of the ground electrode at the boundary between the ground electrode discharge section and the ground electrode;
A plasma ignition device provided at at least one of the positions. ^2. The plasma ignition device according to claim 1, wherein each of the communication passages has a cross-sectional area of 0.1 mm ² or more . 3. The plasma ignition device according to claim 1, wherein a volume of the gap is formed to be equal to or greater than a volume of a space obtained by combining the discharge space and the opening space .