JP2008184964A - Plasma ignition device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma ignition device stabilizing an ignition direction of plasma gas and having excellent ignitability. <P>SOLUTION: The plasma ignition device 1 is installed on an internal combustion engine, and is provided with: a plasma ignition plug 10 provided with an insulation member 120 insulating a center electrode 110 and a ground electrode 131; and high voltage power sources 20, 30 applying high voltage on the plasma ignition plug 10. Gas in an electric discharge space 140 with an inner wall part 126 provided in the insulation member 120 is put into a high temperature and high voltage plasma condition by high voltage applied between the center electrode 110 and the ground electrode 131, the gas is injected into the internal combustion engine 40 and is ignited. A turn imparting mechanism part 160 is provided on the inner wall part 126 of the electric discharge space 140 to inject gas under the plasma condition while imparting turning. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to stabilization of plasma state gas injection in a plasma ignition device used for ignition of an internal combustion engine.

In an internal combustion engine such as an automobile engine, in a plasma ignition device 1i as shown in FIG. 8, a discharge power source 20 is provided between a center electrode 110 and a ground electrode 131i of a plasma ignition plug 10i attached to the engine head 40. When a high voltage is applied and a discharge is started in the discharge space 140i formed by the center electrode 110, the ground electrode 131i, and the insulating member 120i, a large current is supplied from the plasma generating power source 30 to discharge the discharge space. The gas in 140i can be made into a high-temperature and high-pressure plasma state, and can be ignited by being injected from the tip opening 132i of the plasma spark plug 10i.
The plasma state gas injected from the plasma ignition device 1i is rich in directivity and has a very high temperature range of several thousand to several tens of thousands K in a large volumetric range, so that it is rare in combustion of a direct injection engine. In order to burn the air-fuel mixture, it is expected to be applied to stratified combustion that makes combustion easy by aiming at a portion having a high fuel concentration in the air-fuel mixture.

As such a plasma ignition device, Patent Document 1 discloses an insulating member provided with an insertion hole extending vertically and holding the center electrode at the center in order to prevent contamination of the center electrode and the insulating member. A surface gap type spark plug is disclosed which is constituted by a ground electrode provided with an opening communicating with the insertion hole at the lower end of the cover, and in which a discharge gap is formed in the insertion hole.
US Pat. No. 3,581,141

By the way, in the conventional plasma ignition device 1i, as shown in FIGS. 7A, 7B, and 7C, the discharge paths A, B, and C differ depending on the degree of ignition, so that they are discharged into the discharge space 140i. Distribution occurs in the concentration of the generated electrons 51, and distribution occurs in the concentration of the generated cations 50.
Further, it is assumed that the amount of gas remaining in the discharge space 140i after injection is not constant.
For this reason, the injection directions A, B, and C of the plasma state gas also vary with the degree of ignition, which may affect the ignitability of the internal combustion engine.

  Therefore, in view of such circumstances, the present invention has an object to provide a plasma ignition device that stabilizes the injection direction of the plasma state gas and has excellent ignitability in the plasma ignition device.

  According to the first aspect of the present invention, a high voltage is applied between the center electrode and the ground electrode, and the plasma ignition plug mounted on the internal combustion engine and provided with an insulating member that insulates between the center electrode and the ground electrode. A high-voltage power supply, and by applying a high voltage, the gas in the discharge space formed with the inner wall portion in the insulating member is turned into a high-temperature and high-pressure plasma state and injected into the internal combustion engine for ignition. In the plasma ignition device, the surface portion of the inner wall portion includes a turning imparting mechanism portion that is formed so that a gas in a plasma state ejected from the discharge space is ejected while swirling.

  According to the first aspect of the present invention, since the plasma state gas generated in the discharge space is jetted while turning, the straightness in the injection direction is improved by the gyro effect by the turning. Therefore, in the stratified combustion of the lean air-fuel mixture, it is possible to accurately aim at the plasma flame nucleus serving as the ignition source, and the ignition by the plasma ignition device can be stabilized.

  In the invention of claim 2, the swivel imparting mechanism portion is provided to be inclined at a predetermined angle with respect to the ejection direction of the gas in a plasma state ejecting from the center electrode side toward the ground electrode side in the discharge space. Or at least one of a ridge formed in a convex shape on the surface portion.

According to the invention of claim 2, when the plasma state gas is injected from the inside of the discharge space, the plasma state gas is injected along the protruding strip portion or the recessed strip portion formed on the inner wall portion. Rectified.
Further, since the ridge portion or the ridge portion is formed to be inclined at a predetermined angle with respect to the axial direction of the inner wall surface of the insulating member, the ridge portion or the ridge portion is swirled without greatly reducing the plasma state gas injection force. It becomes possible to give power.

  In the invention of claim 3, the concave strip portion or the convex strip portion is formed in a single or multiple spiral form.

According to the invention of claim 3, since the injection direction of the plasma state gas rectifies more smoothly, a strong turning force can be applied without significantly reducing the injection force of the plasma state gas.
Therefore, the straightness of the plasma state gas injection is further improved, and the ignition stability of the plasma ignition device can be further improved.

  In the invention of claim 4, the recess or protrusion is formed with respect to the formation area in the inner circumferential direction of the discharge space, and the non-formation area other than the formation area as the formation area is not formed. The formation area is set.

The gas in the plasma state is rectified by the turning imparting mechanism, but the jet power is weakened.
Therefore, as in the invention of claim 4, by providing the formation region and the non-formation region separately, the balance between the jet power and the turning force of the gas in the plasma state can be adjusted.
Therefore, it is possible to set an optimal injection condition according to the characteristics of the internal combustion engine, and the ignition stability of the plasma ignition device can be further improved.

  In the invention of claim 5, the non-formation region is formed on the surface portion of the inner wall portion so that only the non-formation region continues from the center electrode side to the ground electrode side.

According to the invention of claim 5, since the non-formation region is configured such that only the non-formation region is provided continuously in the axial direction from the center electrode side to the ground electrode side, the swirl force of the plasma state gas is controlled. While ensuring the fixed quantity, it is possible to enhance the jet power of the gas in the plasma state that is jetted from the center electrode side toward the ground electrode side.
Therefore, the aiming accuracy is further improved in the plasma ignition device.

  In a sixth aspect of the present invention, the swivel imparting mechanism section is a region where the formation area of the swivel imparting mechanism section with respect to the axial direction of the discharge space is defined as an area where the formation area is not formed, and the formation area is formed. Are set separately on the ground electrode side.

According to the invention of claim 6, since the gas converted into plasma on the center electrode side does not receive resistance, the injection force toward the ground electrode is ensured, and the turning force is secured on the ground electrode side by the turning imparting mechanism section. Can do.
Therefore, the aiming accuracy is further improved in the plasma ignition device.

  According to a seventh aspect of the invention, the insulating member is formed in a cylindrical shape that covers the outer periphery of the central electrode formed in the shape of a shaft and extends downward from the tip surface of the central electrode, and the ground electrode is the outer periphery of the insulating member And the tip is bent toward the center of the discharge space, and is formed in a bottomed cylindrical shape having a ground electrode opening communicating with the inner diameter of the insulating member.

  According to the invention of claim 7, it is possible to realize a plasma ignition device in which a discharge space is formed in the insulating member.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a configuration of a plasma ignition device 1 according to a first embodiment of the present invention.
2A and 2B are circuit diagrams applied to the present invention.
As shown in FIG. 1, the plasma ignition device 1 includes a plasma ignition plug 10 and a discharge power source 20 and a plasma generation power source 30 as a high voltage power source.
The plasma spark plug 10 includes an axial center electrode 110, a cylindrical insulating member 120 that insulates and holds the center electrode 110, a bottomed cylindrical metal housing 130 that covers the insulating member 120, and a distal end of the housing 130. The inner wall 126 of the insulating member 120 is spirally grooved as a turning imparting mechanism to be described later to form a concave portion 160.

  The distal end side of the center electrode 110 is formed of a conductive material having a high melting point, and a central electrode middle shaft 111 made of a metal material having good electrical conductivity and high thermal conductivity such as a steel material is formed inside, and an insulation is formed on the proximal end side. A center electrode terminal portion 112 exposed from the member 120 and connected to the external discharge power source 20 and the plasma generation power source 30 is formed.

The insulating member 120 is made of high-purity alumina or the like excellent in heat resistance, mechanical strength, high-temperature dielectric strength, thermal conductivity, and the like, and is formed in a substantially cylindrical shape.
The distal end side of the insulating member 120 forms a cylindrical discharge space 140 extending downward from the distal end surface of the central electrode 110, and the proximal end side insulates the central electrode 120 and the housing 130, so that a high voltage escapes to other than the above electrodes. An insulating member head 121 is formed to prevent this.

An annular ground electrode 131 that covers the insulating member 120 and is bent toward the inside is formed at the tip of the housing 130.
A ground electrode opening 132 is formed in the ground electrode 131, and a taper 133 having a diameter increasing toward the tip is formed at the tip of the ground electrode opening 132.

The housing 130 is made of a conductive metal material, and the ground electrode 131 is made of a conductive metal material or a conductive ceramic material having a high melting point, high hardness, and high thermal conductivity.
The housing 130 is fixed to the engine block 40 of the internal combustion engine so that the ground electrode 131 is exposed in the internal combustion engine (not shown), and the housing 130 and the engine block 40 are electrically grounded. The housing screw portion 134 is formed.
A housing hexagonal portion 135 for tightening the screw portion 134 is formed on the outer peripheral portion on the proximal end side of the housing 130.

  On the surface of the inner wall portion 126 of the insulating member 120 constituting the discharge space 140, a groove that is recessed facing the discharge space as a turning imparting mechanism portion extends in a spiral shape extending from the central electrode side 110 side toward the ground electrode 131. A concave line portion 160 formed in the above is provided.

  2A shows a circuit for applying a high voltage using the center electrode 110 of the plasma spark plug 10 as a cathode and the ground electrode 131 as an anode, and FIG. 2B shows the center electrode 110 of the plasma spark plug 10. Is a positive electrode and a ground electrode 131 is a negative electrode to apply a high voltage, and the present invention can be applied to any circuit.

  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 unit 25, and is connected to the plasma ignition plug 10 via a rectifying element 26. The first battery 21 is grounded on the cathode side.

  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 anode side.

When the ignition switch 22 is turned on, a low positive 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 the switching of the igniter 24. The magnetic field in the ignition coil 23 changes, and a negative secondary voltage of −10 to −30 kV 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).
When the applied secondary voltage exceeds the discharge voltage between the center electrode 110 and the ground electrode 131, a discharge is started between both electrodes, and 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. . This plasma state gas becomes high temperature and high pressure and is injected into the combustion chamber of the internal combustion engine.

The effect of the present invention on the injection of the high-temperature and high-pressure plasma state gas 142 generated at this time will be described with reference to FIG.
The gas in the discharge space 140 formed by the center electrode 110, the insulating member 120, and the ground electrode 131 becomes a plasma state due to the discharge of a large current from the plasma generating power source 30, and the volume rapidly expands.
Since the proximal end side of the discharge space 140 is sealed by the center electrode 110, a flow in the direction of the opening 132 provided in the ground electrode 131 is formed.
At this time, the flow of the plasma state gas is rectified along the concave groove 160 formed in a spiral shape on the surface of the inner wall 126 of the insulating member 120.
This flow becomes a swirl force and jets while rotating the high temperature / high pressure plasma state gas 142.
Since the plasma state gas 142 injected from the plasma type spark plug 10 is rotating, a gyro effect is produced and it goes straight.
Since the discharge path changes with each ignition, the distribution of ionized gas in the discharge space 140 changes. However, by rotating in the discharge space 140, it is always possible to inject in a certain direction.
Further, immediately after the injection, air is exchanged in the discharge space 140 while rotating, so that stable plasma state gas injection can be obtained each time.

FIG. 4 shows a cross section of the main part in the second embodiment of the present invention. The basic structure in this embodiment is the same as that of the first embodiment, and the same components are denoted by the same reference numerals, and the description thereof will be omitted (the same applies hereinafter).
In the present embodiment, as the swivel imparting mechanism portion, a ridge that extends spirally from the center electrode 110 side toward the ground electrode 131 side on the surface of the inner wall portion 126 of the insulating member 120 and projects toward the discharge space 140. 160b was provided.
The ridge 160b serves as a barrier, a flow path is formed in the space sandwiched between the ridges 160b, and a swirling force is generated in the plasma state gas generated in the discharge space 140, and plasma is generated as in the first embodiment. The state gas 142 is injected while rotating.

FIGS. 5 (a), (b), (c) and (d) show third, fourth, fifth and sixth embodiments of the present invention, respectively.
In the third embodiment, as shown in FIG. 5A, the spiral ridge 160c is provided not only on the inner wall 126 of the insulating member 120 but also on the inner wall 132 of the ground electrode 131. . It is considered that the rotation imparting mechanism is provided on the entire inner wall of the discharge space 140, thereby increasing the rotational force of the plasma jet and further stabilizing the straightness.
Moreover, in this embodiment, you may comprise a rotation provision mechanism part with a concave-line part.

In the fourth embodiment, as shown in FIG. 5 (b), the ridge 160 d is provided so as to be partially interrupted as a non-formed region with respect to the circumferential direction of the inner wall of the discharge space 140.
By providing a region that does not impart turning to the circumferential direction of the inner wall of the discharge space 140, the turning force is reduced as compared to the third embodiment, but the injection pressure can be increased and the reach distance can be increased. Conceivable.
Accordingly, it is possible to expect an optimal balance between the turning force and the injection force in accordance with conditions such as the capacity of the internal combustion engine to be applied and the generation position of stratified combustion.
In the present embodiment, as a matter of course, the turning imparting mechanism portion may be constituted by a concave portion.

In the fifth embodiment, as shown in FIG. 5C, the non-formation region with respect to the circumferential direction of the inner wall of the discharge space 140 is formed on the surface portion of the inner wall portion from the center electrode side 110 to the ground electrode side 131. A convex strip 160d is provided by being partially interrupted so that only the region (non-formed region) continues.
It is considered that the reduction of the injection pressure can be further suppressed and the reach distance can be lengthened by providing the region where the rotation is not imparted with respect to the circumferential direction of the inner wall of the discharge space 140 so as to be continuous in the axial direction.
Therefore, it is possible to expect the injection of plasma gas with higher aiming accuracy.
In the present embodiment, as a matter of course, the turning imparting mechanism portion may be constituted by a concave portion.

In the sixth embodiment, the non-formation region is set with respect to the axial direction of the inner wall portion 126 of the discharge space 140, and the ridge 160e is provided.
By providing a region where no turning is provided at a position close to the center electrode 110 with respect to the axial direction of the inner wall of the discharge space 140, it is possible to prevent a reduction in the jet driving force in the axial direction.
Further, by providing a region where no turning is provided at a position close to the ground electrode 131, resistance at the ground electrode opening 132 can be reduced, and disturbance during injection can be prevented.
Therefore, by providing the protruding portion 160e so as to be partially interrupted with respect to the axial direction of the inner wall of the discharge space 140, the swirl force and It is considered that the balance with the injection force can be adjusted as appropriate.
Moreover, in this embodiment, you may comprise a rotation provision mechanism part with a concave-line part.

FIGS. 6 (a), (b), and (c) show seventh, eighth, and ninth embodiments of the present invention, respectively.
In the seventh embodiment, a semiconductor portion 150f made of, for example, tin oxide and hafnium is provided at the boundary between the insulating member 120 and the ground electrode 131, and the turning imparting mechanism portion is directed from the center electrode 110 side toward the ground electrode 131 side. A protruding strip 160 f extending in a spiral shape is provided across the surface of the inner wall 126 of the insulating member 120, the surface of the semiconductor portion 150 f, and the surface of the opening 132 of the ground electrode 131.
Similar to the second embodiment, the swirl imparting effect is great and the straightness of the jet is improved. In addition, the semiconductor part 150f easily emits electrons, and the discharge path is lifted from the inner wall of the insulating member 120, thereby forming channeling. It becomes difficult and the stability of plasma injection is further improved.
In the present embodiment, it is more preferable to use the circuit shown in FIG. The ground electrode 131 side becomes a cathode, and electrons can be easily emitted from the semiconductor portion 150f in contact with the ground electrode 131.
Accordingly, the discharge voltage is stabilized, and the gas injection performance of the plasma state is further stabilized.
Further, in the present embodiment, the turning imparting mechanism part may be constituted by a concave line part.

In the eighth embodiment, a semiconductor portion 150g made of, for example, tin oxide and hafnium is provided at the boundary between the insulating member 120 and the ground electrode 131, and the turning imparting mechanism portion is directed from the center electrode 110 side to the ground electrode 131 side. The protrusions 160 f extending in a spiral shape are provided only on the inner wall surface of the insulating member 120.
As in the third and fourth embodiments, in addition to suppressing the decrease in the jet power and increasing the reachable distance, the semiconductor portion 150f is easy to emit electrons, and the discharge path extends from the inner wall of the insulating member 120. Since it floats, it becomes difficult to form channeling, and the stability of plasma injection is further improved.
In the present embodiment, as in the seventh embodiment, it is more preferable to use the circuit shown in FIG.
Further, in the present embodiment, the turning imparting mechanism part may be constituted by a concave line part.

In the ninth embodiment, the inner diameter of the insulating member 120h is tapered so as to increase toward the tip, and a semiconductor portion made of, for example, tin oxide and hafnium is formed at the boundary between the insulating member 120h and the ground electrode 131. 150 h is provided, and as the turning imparting mechanism portion, a protruding portion 160 f that spirally extends from the center electrode 110 side toward the ground electrode 131 side is provided on the insulating member 120 h and the inner wall surface of the semiconductor portion 150 h.
Since the discharge space 140 becomes larger in diameter toward the tip, the gas in the discharge space 140 before and after the injection can be quickly replaced, and the semiconductor portion 150f easily emits electrons, and the discharge path becomes the insulating member 120. Since it floats from the inner wall, channeling becomes difficult to form, and the stability of plasma injection is further improved.
In the present embodiment, as in the seventh embodiment, it is more preferable to use the circuit shown in FIG.
Moreover, in this embodiment, you may comprise a rotation provision mechanism part with a concave-line part.

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, the plasma ignition device including one plasma ignition plug has been described. However, it goes without saying that the present invention can also be applied to a multi-cylinder engine including a large number of ignition plugs. Yes.
Further, in the above embodiment, the case where the high voltage power source is constituted by the two power sources of the discharge power source 20 and the plasma generating power source 30 has been described. However, different voltages are supplied from one power source via a Dc-Dc converter or the like. The discharge power supply 20 and the plasma generation power supply 30 may be adjusted to a high voltage and a high current.

The partial cross section figure which shows the structure of the plasma type ignition device in 1st Embodiment of this invention. (A) is the 1st circuit diagram used for this invention, (b) is the 2nd circuit diagram used for this invention. The principal part sectional view showing the effect in a 1st embodiment of the present invention. The principal part sectional drawing which shows the effect in the 2nd Embodiment of this invention. (A) is principal part sectional drawing in 3rd Embodiment of this invention, (b) is principal part sectional drawing in 4th Embodiment of this invention, (c) is principal part sectional drawing in 5th Embodiment of this invention. (D) is principal part sectional drawing in the 6th Embodiment of this invention. (A) is principal part sectional drawing in 7th Embodiment of this invention, (b) is principal part sectional drawing in 8th Embodiment of this invention, (c) is principal part sectional drawing in 9th Embodiment of this invention. . The principal part sectional drawing which shows the change of the injection direction which is a problem of the conventional plasma ignition device to (a)-(c). The partial cross section figure which shows the structure of the conventional plasma ignition device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma type ignition device 10 Plasma type spark plug 110 Center electrode 120 Insulating member 126 Inner wall part 131 Ground electrode 132 Ground electrode opening part 140 Discharge space 160 Turning imparting mechanism part 20 Power supply for discharge (high voltage power supply)
30 Power supply for plasma generation (high voltage power supply)
40 Engine block (internal combustion engine)

Claims (7)

A plasma ignition plug mounted on an internal combustion engine and provided with an insulating member that insulates between a center electrode and a ground electrode; and a high-voltage power source that applies a high voltage between the center electrode and the ground electrode , And
In the plasma ignition device for igniting by injecting the gas in the discharge space formed with the inner wall portion in the insulating member into a high-temperature and high-pressure plasma state into the internal combustion engine by applying the high voltage,
A plasma ignition device characterized in that the surface portion of the inner wall portion is provided with a turning imparting mechanism portion formed such that a gas in a plasma state ejected from the discharge space is ejected while swirling.   The swivel imparting mechanism portion is provided to be inclined at a predetermined angle with respect to the direction of the gas in a plasma state that is ejected from the center electrode side toward the ground electrode side toward the ground electrode side, and has a concave shape on the surface portion. 2. The plasma ignition device according to claim 1, wherein the plasma ignition device is at least one of a ridge formed on the surface and a ridge formed in a convex shape on the surface portion.   The plasma igniter according to claim 2, wherein the concave stripe portion or the convex stripe portion is formed in a single or multiple spiral shape.   The concave stripe or the convex stripe is formed with respect to a formation area in the inner circumferential direction of the discharge space, and a non-formation area other than the formation area as a non-formation area. The plasma ignition device according to any one of claims 2 to 3, wherein is set.   The said non-formation area | region is formed so that only this non-formation area | region may be continued from the said center electrode side toward the said ground electrode side at the said surface site | part of the said inner wall part. Plasma ignition device.   The swivel imparting mechanism section has a region where the swivel imparting mechanism section is formed with respect to the axial direction of the discharge space, a region where the formation region is not formed as the center electrode side, and a region where the formation region is formed as the ground electrode side. The plasma ignition device according to any one of claims 1 to 3, wherein the plasma ignition device is set separately. The insulating member is formed in a cylindrical shape that covers the outer periphery of the central electrode formed in a shaft shape and extends downward from the front end surface of the central electrode,
The ground electrode is formed in a bottomed cylindrical shape that covers the outer periphery of the insulating member, has a tip bent toward the center of the discharge space, and has a ground electrode opening that communicates with the inner diameter of the insulating member. The plasma ignition device according to any one of claims 1 to 6, characterized in that: