JP4760780B2 - Plasma ignition device - Google Patents

Description

  The present invention relates to improvement in durability and stabilization of ignitability of a plasma ignition device used for ignition of an internal combustion engine.

In recent years, from the standpoint of environmental protection, in order to reduce emissions in combustion exhaust gas and improve fuel efficiency, internal combustion engines require lean mixed combustion, supercharged mixed combustion, etc., and ignition conditions have become stricter, making ignition difficult. There is a demand for an ignition device that can achieve stable ignition even in an internal combustion engine.
In the plasma ignition device 1z ignition as shown in FIG. 12 (a), when the ignition switch 22z is turned on, a low primary voltage is applied from the discharge battery 21z to the primary coil 231 of the ignition coil 23z, and the electronic control device ( ECU) The primary voltage is cut off by switching of the igniter (transistor) 24z controlled by 25z, the magnetic field in the ignition coil 23z is changed, and a secondary voltage of −10 to −30 zV is applied to the secondary coil 232z of the ignition coil 23z. When this secondary voltage reaches a discharge voltage proportional to the discharge gap 141z in the discharge space 140z formed between the center electrode 110z and the ground electrode 130z, discharge starts, and at the same time, the discharge battery 21z The plasma energy supply battery 31z provided separately from the capacitor 33 The energy (for example, −450V, 120A) stored in the discharge space 140z is released into the discharge space 140z at a stretch, and the gas in the discharge space 140z becomes a high-temperature and high-pressure plasma state, and the opening 132z provided at the tip of the discharge space 140z. Since it is injected, it is rich in directivity and generates an extremely high temperature range of several thousand to several tens of thousands of degrees in a large volume range.
Therefore, such a plasma ignition device is expected to be applied to an ignition device in a low-ignition internal combustion engine such as lean mixed combustion or supercharged mixed combustion.

  In Patent Document 1, in order to prevent contamination of the center electrode, an insulating member provided with an insertion hole that holds the center electrode in the center and extends vertically and that extends vertically, covers the insulating member, and communicates with the insertion hole at the lower end. The surface gap type spark plug is disclosed in which a discharge gap is formed in the insertion hole.

By the way, in such a conventional plasma ignition device 1z, the high voltage is normally applied by rectification by the rectifying elements 26z and 34z so that the center electrode 110z becomes a cathode.
Therefore, as shown in FIG. 12B, cations 50 such as nitrogen ions having a large mass collide with the surface of the center electrode 110z, and the surface of the center electrode 110z is decomposed. Cathode sputtering occurs.
The surface of the center electrode 110z is gradually eroded by the cathode sputtering, and the distance between the center electrode 110z and the ground electrode 130z, that is, the discharge distance 141z gradually increases, and the discharge voltage gradually increases in proportion to the discharge distance 141z. Therefore, there is a possibility that the internal combustion engine may be misfired due to the long-term use, and the electric discharge becomes impossible.

Therefore, the inventors of the present invention filed earlier in Japanese Patent Application No. 2007-046725 applied the high voltage power supplies 20, 30 with the center electrode 110x as the anode and the ground electrode 130x as the cathode as shown in FIG. By connecting, the plasma ignition device 1x having excellent durability by suppressing the consumption of the ground electrode 130x due to cathode sputtering was proposed.
In the plasma ignition device 1x using the center electrode 110x side as an anode, as shown in FIG. 11B, the flow of electrons due to discharge is directed from the ground electrode 130x to the center electrode 110x, and only the electrons 51 having a small mass are center electrodes. The positive ions 50 such as nitrogen ions having a large mass collide with the surface of 110x and repel due to the electric repulsive force with the central electrode 110x as the anode, and the surface of the central electrode 110x is eroded by the cathode sputtering. There is nothing to do.

In addition, since the ground electrode 130x is a cathode, there is a possibility that the cation 50 having a large mass collides to cause cathode sputtering and the surface thereof is eroded.
However, the surface of the ground electrode 130x that is in contact with the discharge space is disposed so as to be substantially orthogonal to the direction in which the plasma gas is ejected, and the cation 50 strikes the surface of the ground electrode 130x obliquely. Thus, since the impact force of cations is weakened, the degree of erosion due to cathode sputtering is greatly reduced compared to the conventional plasma igniter 1z using the central electrode as a cathode, and the durability of the plasma igniter 1x having high durability is reduced. Realization is possible.
US Pat. No. 3,581,141

By the way, in the plasma ignition device 1x using the center electrode 110x as an anode, the discharge space 140x is formed inside a cylindrical insulating member 120x extending to the injection side while holding the center electrode 110x. An electron discharge path from the ground electrode 130x to the center electrode 110x is formed along the inner peripheral wall of the insulating member 120x.
For this reason, when the ionized gas in a high-temperature and high-pressure plasma state is injected from the discharge space 140x, a part of the thermal energy of the ionized gas is transferred to the engine block 40 via the insulating member 120x and the ground electrode 130x. In addition to being discharged, it travels in the discharge space 140 and is consumed as kinetic energy until it is ejected from the ground electrode opening 132.
In addition, the extended surface discharge path is formed so as to cover the inner peripheral wall of the insulating member 120x, and the gas in the discharge space 140 is frequently ionized in the vicinity of the extended surface discharge path. It was found that the distribution density of the gas in the plasma state is biased.

Therefore, in the plasma ignition device 1x having the anode on the center electrode 110x side, a high-temperature region having a large volume is generated in comparison with a spark discharge by a normal spark plug. There is a possibility that the effect of improving the ignitability of a hardly ignitable internal combustion engine that performs combustion, supercharged mixed combustion, or the like cannot be obtained sufficiently.
In addition, the plasma ignition device 1x having the anode on the center electrode 110x side as compared with the conventional plasma ignition device as disclosed in Patent Document 1 has much improved durability, but the gas in a plasma state is improved. Since the cathode ground electrode 130x is disposed on the jetting direction side, the occurrence of cathode sputtering cannot be completely suppressed, and there is a limit to the improvement in durability.

  Therefore, in view of such circumstances, the present invention aims to further improve the durability of the plasma ignition device and provide a plasma ignition device excellent in ignitability.

In the invention of claim 1, a plasma ignition plug comprising a center electrode, an insulating member holding the center electrode, and a ground electrode disposed outside the center electrode via the insulating member, A high voltage power source for supplying a high voltage and a large current to the plasma spark plug is formed, and a high voltage and a large current are applied from the high voltage power source to form between the center electrode and the ground electrode. In a plasma ignition device that ignites a gas in the discharge space in a high-temperature and high-pressure plasma state and injects it into an internal combustion engine, and connects the high-voltage power source with the center electrode as an anode and the ground electrode as a cathode In addition, the discharge space is formed by recessing the lower surface of the insulating member in a groove shape with a width equal to or smaller than the diameter of the center electrode, and a part of the center electrode and a part of the ground electrode are formed in the groove part. Opposite and release between both electrodes Possible to be.

According to the first aspect of the present invention, when a high voltage and a large current are applied to the plasma ignition device from the high voltage power source, along the lower surface of the groove portion in which the specific range of the insulating member is defined. An extended surface discharge path of electrons from the ground electrode to the central electrode is formed, and the gas on the internal combustion engine side of the extended surface path becomes a plasma state and is injected into the internal combustion engine.
At this time, since the groove portion is opened over the entire surface of the groove portion with respect to the internal combustion engine, the gas in a plasma state is quickly released into the internal combustion engine, so that heat energy is not lost. It can be used for ignition of internal combustion engines .
Furthermore, in the gas in a plasma state, cations having a large mass such as nitrogen ions are generated outside the surface discharge path of electrons from the cathode side to the anode side and are quickly released from the discharge space. Thus, the collision frequency of cations to the cathode is reduced, and consumption of the cathode due to cathode sputtering can be suppressed.
In addition, the ground electrode is electrically grounded to the internal combustion engine and is also thermally coupled, and is quickly cooled even when high-temperature cations collide. It is further suppressed.
If the groove is formed within the range shown in the first aspect of the invention, even when a plurality of discharge spaces are formed, discharge spaces that are almost independent from each other can be formed, so that discharge can be performed at a specific position. It becomes possible to further stabilize the ignitability.
Further, the width of the groove portion can be appropriately changed according to the characteristics of the internal combustion engine as long as it is within the range shown in the invention of this claim.
Accordingly, it is possible to realize a plasma ignition device that is extremely excellent in ignitability and excellent in durability.

Specifically, as in the invention of claim 2 , the insulating member is formed in a substantially cylindrical shape covering the central electrode formed in a shaft shape, and the ground electrode is formed in a substantially annular shape covering the insulating member. and, the groove is formed Article 1 or the bottom surface of the insulating member.

According to the second aspect of the present invention, the discharge space is provided on the lower surface of the insulating member, not inside the insulating member as in the conventional plasma ignition device, so that the gas in the plasma state in the discharge space has the gas. Thermal energy is significantly less spent on kinetic energy for movement in the discharge space.
Accordingly, a plasma ignition device with good energy efficiency and extremely excellent ignitability can be realized.

According to a third aspect of the present invention, the groove is formed with a substantially constant depth along the shape of the lower surface of the insulating member.

According to the invention of claim 3 , since the discharge space is formed at a substantially constant depth regardless of the shape of the lower surface of the insulating member, a plasma state is formed in the discharge space. Gas will be generated with a substantially uniform density.
Therefore, gas in a plasma state can always be generated in a constant state, and the reliability as an ignition device is improved.

According to a fourth aspect of the present invention, the center electrode protrudes toward the combustion chamber side of the internal combustion engine with respect to the ground electrode, and the lower surface of the insulating member includes a tip edge of the center electrode and a tip edge of the ground electrode. to Do an inclined surface connecting.

According to invention of Claim 4 , the physique of the said plasma type spark plug for ensuring the predetermined extended surface discharge distance can be made small. Alternatively, the surface discharge distance can be increased in a plasma ignition plug having a predetermined physique. Accordingly, since the density in the high temperature region is increased, the loss of heat energy can be further reduced, and the plasma ignition device can be used for ignition of an internal combustion engine and further excellent in ignitability.
In addition, since the ground electrode serving as the cathode is on the downstream side with respect to the gas ejection direction in the plasma state, the cation collision frequency is reduced and the durability is further improved.

According to a fifth aspect of the present invention, the center electrode protrudes toward the combustion chamber of the internal combustion engine with respect to the ground electrode, and the lower surface of the insulating member has a tip edge of the center electrode and the ground electrode. It is also possible to form a substantially spherical curved surface that is connected to the leading edge of the cylinder and protrudes toward the combustion chamber.

  When the extended surface discharge path is curved, the size of the plasma ignition plug for securing a predetermined extended surface discharge distance can be further reduced. Alternatively, the surface discharge distance can be increased in a plasma ignition plug having a predetermined physique. Accordingly, since the density in the high temperature region is further increased, the loss of heat energy can be reduced and the plasma ignition device can be used for ignition of the internal combustion engine and further excellent in ignitability. In addition, since the ground electrode serving as the cathode is on the downstream side with respect to the gas ejection direction in the plasma state, the cation collision frequency is reduced and the durability is further improved.

According to a sixth aspect of the present invention, the ground electrode includes a protrusion that extends toward the discharge space at a portion exposed to the discharge space.

According to invention of Claim 6 , the electric field density in the said projection part of the said ground electrode becomes high, and it becomes easy to discharge. Therefore, the consumption of the electrode can be further suppressed and the ignitability is improved.

In the invention of claim 7, said center electrode, corresponding to the number of threads of the groove is divided into a plurality and allowed independently of one another via an insulating member.

According to the seventh aspect of the present invention, it is possible to control the discharge between the center electrode and the ground electrode at an arbitrary position, and the discharge position can be changed according to the state of the internal combustion engine, or the electrode can be consumed uniformly. Therefore, the discharge position can be changed to further stabilize the ignitability. Accordingly, it is possible to realize a plasma ignition device having extremely excellent durability and ignitability.

Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
1A is a partial cross-sectional view showing an outline of the plasma ignition device 1 according to the first embodiment of the present invention, FIG. 1B is a cross-sectional view taken along the line BB in FIG. 1, and FIG. AA arrow directional view in the figure.
As shown in FIG. 1A, the plasma ignition device 1 in this embodiment includes a plasma ignition plug 10, a discharge power source 20 and a plasma generation power source 30 as a high voltage power source, and an internal combustion engine (not shown). It is mounted on the engine block 40 of the engine.
The plasma spark plug 10 includes a center insulator 110 and a cylindrical insulator 120 as an insulating member for insulating and holding the center electrode 110 so as to cover the center electrode 110 and a metal ground electrode 130 formed in a substantially annular shape covering the insulator 120. It is configured.
The distal end side of the center electrode 110 is formed in a long axis shape by a conductive material such as iridium, an iridium alloy, and copper, for example, and a central electrode central shaft 111 made of a metal material having good electrical conductivity and high thermal conductivity such as a steel material is contained therein. A center electrode terminal portion 112 exposed from the insulator head 122 and connected to the external discharge power source 20 and the plasma generating power source 30 is formed on the base end side. The tip of the center electrode 110 protrudes closer to the combustion chamber side of the internal combustion engine than the tip of the ground electrode 130.

  The ground electrode 130 constitutes a housing 135 that holds the insulator 120 on its proximal end side, and fixes the plasma ignition plug 1 to the engine block 40 so that the ground electrode 130 is exposed in a combustion chamber (not shown). A screw portion 132 for electrically grounding 130 and the engine block 40 is formed, and a housing hexagonal portion 133 for tightening the screw portion 132 is formed on the outer peripheral side of the proximal end. The housing 135 including the ground electrode 130 is formed of a metal material such as nickel or iron.

The insulator 120 will be described in detail with reference to FIGS. 1 (a), (b), and (c).
The insulator 120 is made of high-purity alumina or the like excellent in heat resistance, mechanical strength, dielectric strength at high temperature, thermal conductivity, etc., and is formed in a substantially cylindrical shape (inner diameter φD1 outer diameter φD2) that holds the center electrode 110. The outer diameter (φD3) is increased so as to cover a part of the lower end surface of the ground electrode 130, and is in contact with the lower surface of the ground electrode 130 at the locking portion 125.

The lower surface of the insulating member 120 connects the tip edge of the center electrode 110 and the tip edge of the ground electrode 130 to form a curved surface that protrudes toward the combustion chamber.
Further, as a main part of the present invention, the lower surface 126 of the insulating member 120 is formed with a groove 121 that forms a discharge space 140 by recessing the surface into a groove with a certain depth H and a certain width W. Yes.

A part of the side surface of the center electrode 110 is exposed in the range of width W × depth H in the groove 121 to form a center electrode discharge part, and a part of the ground electrode 130 is width W × length L (≈H). The ground electrode discharge part 131 is configured to be exposed in the range of, and discharge is possible between the center electrode discharge part and the ground electrode discharge part 131.
Specifically, the diameter φD1 of the center electrode 110 is 0.5 mm to 3 mm, the inner diameter (or outer diameter of the insulating member) φD2 of the ground electrode is 5 mm to 15 mm, the groove width W is 0.5 mm to 3 mm, and the groove 121 The depth H is 0.5 to 3 mm, the number of grooves 121 is 1 to 6, and the height difference between the position of the lower end surface of the center electrode 110 and the position of the lower end surface of the ground electrode is 0.5 mm to 5 mm. Each selected.

  In the middle of the insulator 120, there is formed a center electrode locking portion that is locked to the housing 135 via a seal member or the like that maintains the airtightness of the insulator 120 and the housing 135 (not shown). An insulator head 122 is formed that insulates the electrode 120 from the housing 130 and prevents a high voltage from escaping other than the electrode.

Hereinafter, with reference to FIG. 2 (a), the discharge power source 20 and the plasma generating power source 30 which are high voltage power sources in the first embodiment of the present invention will be described in detail and with reference to FIG. 2 (b). Then, the effect of this embodiment will be described.
The discharge power source 20 includes a first battery 21, an ignition key 22, an ignition coil 23, an igniter 24 including a transistor, and an electronic control device 25, and is connected to the plasma ignition plug 10 via a rectifying element 26. .
In the present embodiment, the first battery 21 is grounded on the anode side and rectified by the rectifying element 26 so that the center electrode 110 becomes the anode.

The plasma generating power source 30 includes a second battery 31, a resistor 32, and a plasma generating capacitor 33, and is connected to the plasma ignition plug 10 via a rectifying element 34.
The second battery 31 is grounded on the cathode side and rectified by the rectifying element 34 so that the center electrode 110 becomes an anode.

The ignition switch 22 is turned on, and a low voltage negative primary voltage is applied from the first battery 21 to the primary coil 231 of the ignition coil 23 by the ignition signal from the ECU 25, and the primary voltage is cut off by switching of the igniter 24. Then, the magnetic field in the ignition coil 23 changes, and a positive secondary voltage of 10 to 30 zV is induced in the secondary coil 232 of the ignition coil 23 by the self-induction action.
On the other hand, the plasma generating capacitor 33 is charged by the second battery 31 (for example, 450 V, 120 A).

As shown in FIG. 2B, when the applied secondary voltage exceeds a discharge voltage proportional to the total surface discharge distance between the center electrode 110 and the ground electrode 130, a discharge is started between the two electrodes. The gas in the discharge space 140 becomes a plasma state in a small region.
The gas in the plasma state has electrical conductivity, causes discharge of electric charges stored between both electrodes of the plasma generating capacitor 33, induces further gas state of the gas in the discharge space 140, and expands the region. .
At this time, the extended surface discharge path is formed so as to crawl the bottom surface of the groove 121, the electrons 51 are directed from the surface of the ground electrode discharge part 131 to the side surface of the center electrode 110, and the cation 50 such as nitrogen ion having a large mass is formed. The outer surface (combustion chamber side) of the extended surface discharge path is generated from the center electrode 110 toward the ground electrode 130.
Since the discharge space 140 has a larger area opening toward the combustion chamber than the volume, the plasma state gas becomes high temperature and high pressure and is immediately injected from the discharge space 140 into the combustion chamber.
Therefore, according to the present embodiment, the gas in a plasma state having a very high temperature and a large volume is injected into the internal combustion engine with almost no energy loss, so that ignition is quickly induced in the internal combustion engine.

Furthermore, since the cation 50 is generated from the discharge space 140 in addition to being generated outside the extended discharge path of the electrons 51, the collision frequency with the ground electrode discharge part 131 is low, and grounding by cathode sputtering is performed. It becomes possible to suppress consumption of the electrode 130. Further, since the ground electrode 130 is directly screwed to the engine block 40 by the screw portion 132, it is easy to dissipate heat and the consumption of the electrode can be suppressed.
The discharge power source 20 and the plasma generating power source 30 shown in the present embodiment can also be applied to the second to eleventh embodiments of the present invention described later.

In the first embodiment of the present invention, three grooves 121 are formed at equal intervals, but the number of grooves 121 and the width of the grooves 121 can be appropriately changed according to the combustion conditions of the internal combustion engine.
For example, as shown in FIGS. 3A to 3C, the grooves formed on the lower surfaces of the insulating members 120a, 120b, and 120c of the plasma spark plugs 10a, 10b, and 10c are shown in FIG. As described above, six grooves 121a may be formed on the lower surface of the insulating member 120, or the grooves 121b may be formed so as to increase in width toward the ground electrode 130b as shown in FIG. However, as shown in (c), the groove 121c may be formed so as to increase in width toward the center electrode.

As shown in FIG. 3A, the durability of the plasma spark plug can be further improved by increasing the number of grooves.
As shown in FIG. 3B, when the width of the groove 121b is gradually increased toward the ground electrode discharge part 131b, the density of the plasma state gas on the ground electrode discharge part 131 side in the discharge space 140b is increased. Since it falls, the injection direction of the plasma state gas can be biased toward the center electrode 110 side.
If the width of the groove 121c is gradually increased toward the center electrode 110 as shown in FIG. 3C, the plasma state gas density on the center electrode 110 side decreases in the discharge space 140c. The gas injection direction can be biased toward the ground electrode 130 side.

  4B to 4G show examples of the cross-sectional shape of the groove 121 in the AA cross section in FIG. As shown in (a), the bottom surface of the groove 121 may be formed in a curved surface that is convex toward the discharge space 140, or as shown in (c), the bottom of the groove 121d is formed into a flat cross-sectional shape. It may be formed in a letter shape, or as shown in (d), the wall surface of the groove 121e may be widened outward, or as shown in (e), the bottom surface of the groove 121d It may be formed in a substantially U-shaped cross section with an R provided at the corner with the wall surface, or may be formed in a U-shaped cross section with the bottom surface of the groove 121g rounded as shown in (f). As shown, the groove 121h may be formed in a V-shaped cross section.

A plasma spark plug 10i according to a second embodiment of the present invention will be described with reference to FIG.
FIG. 5A is a cross-sectional view of the main part in the present embodiment, FIG. 5B is a cross-sectional view taken along the line BB in the figure, and FIG.
In the present embodiment, the configuration is basically the same as that of the first embodiment, but only the shapes of the insulating member 120i and the ground electrode 130i are different.
In the first embodiment, as described above, the bottom surface of the annular ground electrode 130 is covered with the engaging portion 125 having the enlarged diameter of the insulating member 120, and the groove 121 is notched in the portion of the ground electrode 130. Although the ground electrode discharge portion 131 is formed by partially exposing the discharge space 140, in this embodiment, the insulating member 120i is formed in a cylindrical shape inscribed in the inner diameter of the ground electrode 130i to form the discharge space 140i. A cutout portion that is recessed toward the center of the shaft is provided at a position where the protrusion is formed, and a protrusion 131 i that protrudes toward the center of the shaft is formed in the ground electrode 130 so as to fit into the cutout. With such a structure, when a high voltage is applied between the center electrode 110i and the ground electrode 130i, the electric field density at the protrusion 131i increases, and discharge becomes easy.
Therefore, according to this embodiment, in addition to further improving the ignitability, it can be expected to improve the durability of the electrode. In this embodiment, the changes shown in FIGS. 3 and 4 can be applied.

  Further, as shown in FIGS. 6A and 6B, the diameter φD3 of the enlarged diameter portion of the insulating member 120j is made the same as the outer diameter φD4 of the ground electrode 130 to completely cover the lower surface of the ground electrode 130, and the groove portion It is good also as a shape exposed to the discharge space 140i only in 121i. Since the lower surface of the ground electrode 130 other than the ground electrode discharge part 131i is covered with the insulating member 120i, the insulating member 120i serves as a protective member to block heat from the internal combustion engine and further improve the durability of the ground electrode 130i. .

Further, as shown in FIGS. 7A and 7B, only the portion exposed to the groove 121k of the ground electrode 130 is protruded by the depth Y toward the combustion chamber to form the ground electrode discharge portion 131k. Also good. By adopting such a shape, the electric field density in the ground electrode discharge part 131k increases, and discharge becomes easy.
Therefore, according to this embodiment, in addition to further improving the ignitability, it can be expected to improve the durability of the electrode.

Fig.8 (a) is principal part sectional drawing in the 3rd Embodiment of this invention, (b) is an AA arrow line view in this figure.
In this embodiment, the basic configuration is the same as that of the first embodiment, but only the shape of the lower bottom surface of the insulating member 120m and the shape of the groove 121m are different.
The center electrode 110m protrudes closer to the combustion chamber of the internal combustion engine than the ground electrode 130m, and the lower surface 126 of the insulating member 120m forms an inclined surface 126m that connects the leading edge of the middle electrode 110 and the leading edge of the ground electrode 130. In addition, a groove 121m whose surface is recessed at a substantially constant depth is formed.
The physique of the plasma type spark plug 10m for ensuring a predetermined extended surface discharge distance can be reduced. Alternatively, the total surface discharge distance can be increased in the plasma-type spark plug 10m having a predetermined physique. Therefore, since the density in the high temperature region is increased, the loss of heat energy can be further reduced and used for ignition of the internal combustion engine.

Fig.9 (a) is principal part sectional drawing in the 4th Embodiment of this invention, (b) is an AA arrow line view in this figure. In this embodiment, the basic configuration is the same as that of the first embodiment, but only the shape of the bottom surface of the insulating member 120n and the shape of the groove 121n are different.
In the present embodiment, the lower surface 126n of the insulating member 120n is formed in a horizontal plane substantially orthogonal to the central axis, and the outer diameter of the ground electrode 130n is increased in order to take a predetermined extended surface discharge distance. .
By adopting such a configuration, the amount of projection of the plasma plug 10n into the combustion chamber can be made extremely small, so that the influence on the air flow in the combustion chamber can be extremely reduced.
Further, since the discharge space 140n is formed so as to be substantially orthogonal to the axial center of the plasma plug 10n, the gas in the plasma state is injected substantially parallel to the axis of the plasma plug 10n. Become.
Therefore, extremely stable ignition can be expected.

FIG. 10 shows an outline of a plasma ignition plug 10p according to the fifth embodiment of the present invention. (A) is a top view of the head, (b) is a cross-sectional view of the head, (c) is a cross-sectional view of the main part, and (d) is a bottom view of the main part.
As shown in FIG. 10, it is divided into a plurality of center electrodes 110a, 110b, 110c corresponding to the number of grooves 121, and is electrically independent from each other via an insulating member. In the present embodiment, it is possible to control so as to discharge between the center electrodes 110a, 110b, 110c and the ground electrode discharge portions 131a, 131b, 131c at arbitrary positions, and the discharge position according to the state of the internal combustion engine. And the discharge position can be changed in order to make the electrode wear uniform, and the ignitability can be further stabilized. Accordingly, it is possible to realize a plasma ignition device having extremely excellent durability and ignitability.

As a matter of course, the present invention is not limited to the above embodiment, and can be appropriately changed without departing from the gist of the present invention.
For example, in the above-described embodiment, a plasma ignition device including one plasma ignition plug has been described. However, the present invention can also be applied to a multi-cylinder engine including a large number of ignition plugs.

(A) is a partial cross-sectional view showing an outline of the plasma ignition device 1 according to the first embodiment of the present invention, (b) is a cross-sectional view taken along the line BB in this figure, and (c) is in this figure. AA arrow view. (A) is a block diagram containing the circuit of the plasma ignition device 1 in the 1st Embodiment of this invention, (b) is principal part sectional drawing which shows the effect in this embodiment. (A), (b), (c) is a principal part top view which shows the example of a change which can be applied to this invention. (A) is principal part top view in the 1st Embodiment of this invention, (b)-(g) is AA sectional drawing in this figure which shows the example of a change which changed the shape of the groove part. The principal part sectional view showing the effect in a 1st embodiment of the present invention. (A) is principal part sectional drawing of the plasma type spark plug used for the 2nd Embodiment of this invention, (b) is BB sectional drawing in this figure, (c) is AA in this figure. Arrow view. The modification which can be applied to this invention is shown, (a) is principal part sectional drawing, (b) is an AA arrow line view in this figure. The modification which can be applied to this invention is shown, (a) is principal part sectional drawing, (b) is an AA arrow line view in this figure. (A) is principal part sectional drawing of the plasma type spark plug used for the 3rd Embodiment of this invention, (b) is an AA arrow directional view in this figure. (A) is principal part sectional drawing of the plasma ignition plug used for the 4th Embodiment of this invention, (b) is an AA arrow directional view in this figure. The outline | summary of the plasma type spark plug 10p in the 5th Embodiment of this invention is shown, (a) is a head top view, (b) is head sectional drawing, (c) is principal part sectional drawing, (D) is a main part bottom view. (A) is a block diagram which shows the conventional plasma ignition device which improved durability, (b) is principal part sectional drawing which shows the effect and problem in this figure structure. (A) is a block diagram which shows the conventional plasma type ignition device, (b) is principal part sectional drawing which shows the problem in this figure structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma type ignition device 10 Plasma type spark plug 110 Center electrode 120 Insulator (insulating member)
121 Groove portion 130 Ground electrode 131 Ground electrode discharge portion 140 Discharge space 20 Discharge power source (high voltage power source)
30 Power supply for plasma generation (high voltage power supply)
40 Engine block (internal combustion engine)

Claims (7)

A plasma spark plug comprising a center electrode, an insulating member for holding the center electrode, and a ground electrode disposed outside the center electrode via the insulating member, and a high voltage applied to the plasma spark plug And a high voltage power supply for supplying a large current,
A high voltage and a large current are applied from the high voltage power source, and the gas in the discharge space formed between the center electrode and the ground electrode is changed into a high temperature and high pressure plasma state and injected into the internal combustion engine. In a plasma ignition device that ignites,
With the center electrode as an anode and the ground electrode as a cathode, the high voltage power supply is connected,
The discharge space is formed by recessing the lower surface of the insulating member in a groove shape with a width equal to or smaller than the diameter of the center electrode, and a part of the center electrode and a part of the ground electrode are opposed to the groove. A plasma ignition device characterized in that discharge is possible between both electrodes. The insulating member is formed in a substantially cylindrical shape covering the central electrode formed in a shaft shape,
The ground electrode is formed in a substantially annular shape covering the insulating member,
The plasma-type ignition device according to claim 1, wherein at least one groove is formed on the lower surface of the insulating member . The plasma ignition device according to claim 1 or 2, wherein the groove is formed at a substantially constant depth along the shape of the lower surface of the insulating member . The center electrode protrudes to the combustion chamber side of the internal combustion engine from the ground electrode, and the lower surface of the insulating member is an inclined surface connecting the tip edge of the center electrode and the tip edge of the ground electrode. The plasma ignition device according to any one of claims 1 to 3. The center electrode protrudes to the combustion chamber side of the internal combustion engine from the ground electrode, and the lower surface of the insulating member connects the tip edge of the center electrode and the tip edge of the ground electrode to the combustion chamber side. The plasma ignition device according to any one of claims 1 to 3, wherein the plasma ignition device has a curved surface that is convex toward the surface . The plasma ignition device according to any one of claims 1 to 5, wherein the ground electrode includes a protrusion that extends toward the discharge space at a portion exposed to the discharge space . The plasma ignition device according to any one of claims 1 to 6, wherein the center electrode is divided into a plurality of parts corresponding to the number of the grooves and made independent from each other via an insulating member .