JP2006294257A - Ignition device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition device for an internal combustion engine which can ignite a fuel even if the fuel is unevenly distributed. <P>SOLUTION: The ignition device for the internal combustion engine is composed of a housing 2 zoning a chamber 3, an outer electrode 5 with a outer electrode hole 50 connecting the chamber 3 through the outside of the housing, and a center electrode 4. Plasma is generated in the chamber 3 by impressing a voltage between the center electrode 4 and the outer electrode 5, and then, plasma jets are injected. A capacity of the chamber 3 is 10mm<SP>3</SP>or less and a ratio of a length in an axis direction to an inner diameter of the chamber 3 shall be 2 or more. In this internal combustion engine ignition device, injected plasma jets will reach fuel through a mixture gas, even if there is no fuel in the mixture gas near an ignition unit. This device has an excellent ignition capability. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ignition device for an internal combustion engine that ignites an air-fuel mixture in an internal combustion engine, and more particularly to an ignition device for an internal combustion engine that performs ignition by injecting plasma.

  The internal combustion engine supplies an air-fuel mixture containing fuel into a cylinder, generates a force for expanding by igniting the fuel in the air-fuel mixture, and obtains energy by moving a piston with the expanding force. As a method of igniting an air-fuel mixture in an internal combustion engine, a method of injecting a plasma jet and igniting the air-fuel mixture has been developed.

  An ignition device that performs ignition with a plasma jet is disclosed in Patent Document 1, for example. Patent Document 1 discloses a substantially cylindrical housing that divides a chamber, a center electrode that is fitted into an end portion of the chamber of the substantially cylindrical housing, and an external chamber that is provided at the other end portion of the cylindrical housing. And an external electrode having an external electrode hole communicating therewith is disclosed. In this ignition device, a high voltage is applied between the center electrode and the external electrode to generate plasma in the chamber, and this plasma is ejected through the external electrode hole to ignite the air-fuel mixture. With the same input energy, the ignition device having such a configuration tends to eject a larger plasma jet because the gas in the chamber is warmed and expanded as the volume in the chamber is small and the volume in the chamber is small.

However, although the ignition device disclosed in Patent Document 1 has a small chamber volume of about 3.14 mm ³ , there is a problem that the jet length of the plasma jet is short. When the jet length of the plasma jet is shortened, there is a problem that misfire occurs.

  Specifically, an internal combustion engine such as a vehicle engine introduces an air-fuel mixture into a cylinder and ignites fuel in the air-fuel mixture. The air-fuel mixture introduced into the cylinder is unevenly distributed in the cylinder. That is, there is a portion in the cylinder where there is not a sufficient mixture (no fuel in the mixture). When the portion where the fuel does not exist is present in the vicinity of the ignition device, the plasma jet does not reach the fuel in the air-fuel mixture and cannot be ignited even when the ignition device ejects the plasma jet.

In particular, in recent years, fuel in the air-fuel mixture has been reduced by techniques such as lean burn, and an ignition device for an internal combustion engine having excellent ignition performance has been demanded.
US Pat. No. 2,874,321

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an ignition device for an internal combustion engine that can ignite fuel even when the fuel is unevenly distributed in an ignition device that emits a plasma jet and ignites an air-fuel mixture. And

  In order to solve the above-mentioned problems, the present inventors have studied the ignition device for an internal combustion engine. As a result, the length between a pair of electrodes to which a voltage is applied in order to reduce the volume of the chamber and generate plasma. It has been found that the above-mentioned problem can be solved by lengthening the length. Moreover, it discovered that the said subject could be solved by controlling the shape of a chamber.

That is, the first ignition device for an internal combustion engine according to the present invention includes a housing that has an opening and a bottom surface facing the opening, and that defines a chamber having a circular cross section extending in the axial direction. An external electrode having an external electrode hole that communicates the opening and the outside, and a center electrode disposed on the bottom surface of the chamber. A voltage is applied between the center electrode and the external electrode to generate plasma in the chamber. Is an internal combustion engine ignition device that emits a plasma jet from an opening of a chamber, the volume of the chamber is 10 mm ³ or less, and the ratio of the length in the axial direction of the chamber to the length of the inner diameter is 2 or more It is characterized by being.

  A second ignition device for an internal combustion engine according to the present invention includes a housing that defines an axially extending chamber having an opening and a bottom surface facing the opening, and is provided on the surface of the housing and communicates with the chamber. An external electrode having an external electrode hole in which the opening on the surface opposite to the chamber and the opening of the chamber on the surface of the housing coincide with each other, and a center electrode disposed on the bottom surface of the chamber. An ignition device for an internal combustion engine that generates a plasma in a chamber by applying a voltage between the electrodes and injects a plasma jet from an opening of the chamber. The chamber has a cross-sectional shape in a plane perpendicular to the axial direction. It has a circular shape and is characterized in that the inner diameter at the bottom of the chamber is different from the inner diameter at the opening.

  In the first ignition device for an internal combustion engine of the present invention, the injection length of the plasma jet injected from the chamber is long. As a result, even if the fuel in the air-fuel mixture does not exist in the vicinity of the ignition device, the ejected plasma jet penetrates through the portion where the fuel in the air-fuel mixture does not exist and reaches the fuel. The first internal combustion engine ignition device of the present invention has excellent ignition performance.

  The second ignition device for an internal combustion engine of the present invention can eject a plasma jet having a desired shape by adjusting the cross-sectional shape of the chamber. That is, it is possible to lengthen the jet length of the plasma jet and to jet the plasma jet over a wide range. The plasma jet easily reaches the fuel in the air-fuel mixture. The second internal combustion engine ignition device of the present invention has excellent ignition performance.

(First ignition device)
A first internal combustion engine ignition device according to the present invention includes a housing having an opening and a bottom surface facing the opening, and defining a chamber having a circular cross section extending in the axial direction, and an opening of the chamber provided on the surface of the housing. An external electrode having an external electrode hole that communicates with the outside, and a central electrode disposed on the bottom surface of the chamber, and a voltage is applied between the central electrode and the external electrode to generate plasma in the chamber An ignition device for an internal combustion engine that injects a plasma jet from an opening of a chamber, wherein the chamber has a volume of 10 mm ³ or less, and a ratio of an axial length of the chamber to a length of an inner diameter is 2 or more .

  Thus, in the ignition device that ejects the plasma jet, the ejection length of the plasma jet ejected from the chamber can be increased by reducing the chamber volume. When a high voltage is applied between the center electrode and the external electrode, plasma is generated in the chamber, and the generated plasma heats the chamber (gas such as air). When the chamber volume is small, the generated plasma can heat the inside of the chamber to a higher temperature. Thereby, since the inside of a chamber becomes a state of higher energy (high temperature), the ejection length of the plasma jet ejected from a chamber becomes long.

  Further, by setting the ratio of the axial length and the inner diameter of the chamber to 2 or more, the chamber becomes a shape that is long in the axial direction. As the axial length of the chamber increases, the distance between the center electrode and the external electrode increases. An increase in the distance between the electrodes with a constant chamber volume indicates a decrease in the inner diameter of the chamber. Even if the volume is the same, if the distance between the electrodes becomes longer and the discharge distance increases, the gas inside the chamber becomes warmer. That is, when a high voltage is applied between the two electrodes to generate plasma, the generated long plasma raises the temperature in the chamber. Furthermore, since the inner diameter of the chamber is shortened, the speed at which plasma is ejected from the chamber is increased. As a result, the ejection length of the plasma jet ejected from the chamber becomes longer. In the present invention, the length in the axial direction of the chamber is the distance between the opening of the chamber and the bottom surface in the axial direction of the chamber, and the inner diameter of the chamber is the inner diameter at the bottom surface of the chamber. In the ignition device of the present invention, the bottom surface of the chamber is preferably formed perpendicular to the axial direction.

  If the distance between the center electrode and the external electrode is large, the discharge distance is increased and the gas inside the chamber can be further warmed. However, when the discharge distance is increased, the applied voltage increases and the burden on the plasma power source increases. When the distance between the two electrodes is 3 mm or less, the voltage applied between the two electrodes in order to generate plasma can be lowered. When the distance between the two electrodes exceeds 3 mm, the voltage required to generate plasma between the two electrodes increases. That is, an excessive voltage is required for one ignition. Since an excessive voltage is required at the time of ignition, this excessive voltage also damages the electrodes. Furthermore, not only the cost required for ignition increases, but also a mechanism for preventing high-voltage leakage is required, which increases the cost of the mechanism for ignition.

  In the ignition device of the present invention, the center electrode is disposed on the bottom surface of the chamber. The state of being disposed on the bottom surface of the chamber of the ignition device is a state in which the center electrode is present on the bottom surface portion of the chamber. That is, the center electrode may be formed such that the columnar center electrode protrudes from the bottom surface, forms a part of the bottom surface, or forms the entire bottom surface. Since the inside of the chamber becomes a plasma generation space, it is preferable that the bottom surface of the chamber is partitioned by the center electrode. The center electrode having such a configuration can be formed by fitting a columnar center electrode into a cylindrical housing having a hollow portion formed in the axial direction. The shape of the housing is preferably a shape having no step portion around the end face of the center electrode in order to avoid local stress concentration.

  It is preferable that the opening of the external electrode hole on the surface of the external electrode facing the housing matches the opening of the chamber on the surface of the housing. That is, in the ignition device of the present invention, the external electrode is provided on the outer peripheral surface of the opening of the chamber. The plasma jet generated in the chamber is ejected from the opening of the external electrode hole through the external electrode hole. By matching the opening of the chamber and the opening of the connection portion of the external electrode hole, the plasma flow path defined by the chamber and the external electrode hole has a smooth shape. Thereby, the plasma flow is not hindered at the interface between the housing and the external electrode, and a plasma jet having a long ejection length can be ejected.

  The external electrode hole preferably has an inner diameter of the opening on the surface facing the housing and an inner diameter of the opening on the surface facing away from the housing. That is, it is preferable that the diameter of the external electrode hole is changed in the axial direction of the chamber. By changing the inner diameter of the external electrode hole, the ejection width of the ejected plasma jet can be adjusted. That is, when the external electrode hole has a shape that is reduced in diameter as it advances in the axial tip direction (direction from the bottom surface of the chamber toward the opening), the diameter of the plasma jet to be ejected becomes small. As the diameter decreases, the jet length of the plasma jet becomes longer. Further, when the external electrode hole has a shape whose diameter is increased as it advances in the axial direction, the plasma jet can be ejected at a wider angle.

(Second ignition device)
A second internal combustion engine ignition device according to the present invention includes a housing that defines an axially extending chamber having an opening and a bottom surface facing the opening, and is provided on the surface of the housing and communicates with the chamber so as to face the housing. An external electrode having an external electrode hole in which the opening on the surface and the opening of the chamber on the surface of the housing coincide with each other, and a center electrode disposed on the bottom surface of the chamber. An ignition device for an internal combustion engine that generates a plasma in a chamber by applying a voltage between them and injects a plasma jet from an opening of the chamber. The chamber has a circular cross-sectional shape in a plane perpendicular to the axial direction. And the inner diameter at the bottom of the chamber is different from the inner diameter at the opening. In the ignition device of the present invention, the bottom surface of the chamber is preferably formed perpendicular to the axial direction.

  Thus, in the ignition device for ejecting the plasma jet, the ejection width of the ejected plasma jet can be adjusted by changing the inner diameter of the chamber. Plasma generated in the chamber flows along the side wall surface defining the chamber and is ejected from the opening. By changing the inner diameter of the chamber, the side wall surface becomes tapered, and a plasma jet is ejected in a direction along the side wall surface. Thereby, the jet width of the plasma jet can be controlled. The change in the inner diameter of the chamber is not particularly limited, but it is preferable that the change in the diameter between the inner diameter of the bottom surface and the inner diameter of the opening is smooth.

  The inner diameter at the bottom of the chamber is preferably smaller than the inner diameter at the opening. That is, when the chamber has a shape whose diameter increases as it advances in the axial tip direction (direction from the bottom surface of the chamber toward the opening), the plasma jet can be ejected at a wider angle.

  The inner diameter at the bottom of the chamber is preferably larger than the inner diameter at the opening. That is, when the chamber has a shape that is reduced in diameter in the axial direction, the diameter of the plasma jet that is ejected is reduced. As the diameter decreases, the jet length of the plasma jet becomes longer.

  In the ignition device of the present invention, the center electrode is disposed on the bottom surface of the chamber. The state of being disposed on the bottom surface of the chamber of the ignition device is a state in which the center electrode is present on the bottom surface portion of the chamber. That is, the center electrode may be formed such that the columnar center electrode protrudes from the bottom surface, forms a part of the bottom surface, or forms the entire bottom surface. Since the inside of the chamber becomes a plasma generation space, it is preferable that the bottom surface of the chamber is partitioned by the center electrode. The center electrode having such a configuration can be formed by fitting a columnar center electrode into a cylindrical housing having a hollow portion formed in the axial direction.

  It is preferable that the opening of the external electrode hole on the surface of the external electrode facing the housing matches the opening of the chamber on the surface of the housing. That is, in the ignition device of the present invention, the external electrode is provided on the outer peripheral surface of the opening of the chamber. The plasma jet generated in the chamber is ejected from the opening of the external electrode hole through the external electrode hole. By matching the opening of the chamber and the opening of the connection portion of the external electrode hole, the plasma flow path defined by the chamber and the external electrode hole has a smooth shape. Thereby, the plasma flow is not hindered at the interface between the housing and the external electrode, and a plasma jet having a long ejection length can be ejected.

  In the ignition device of the present invention, it is preferable that the inner diameter of the external electrode hole communicating with the chamber also changes in the axial direction of the chamber. By changing the inner diameter of the external electrode hole, the same effect as when the inner diameter of the chamber is changed is exhibited. That is, in the external electrode hole, it is preferable that the inner diameter of the opening on the surface facing the housing is different from the inner diameter of the opening on the surface facing away from the housing.

  The external electrode hole preferably has an inner diameter of the opening on the surface facing the housing smaller than the inner diameter of the opening on the surface facing away from the housing. That is, when the external electrode hole has a shape whose diameter increases as it advances in the axial direction, the plasma jet can be ejected at a wider angle.

  The external electrode hole preferably has an inner diameter of the opening on the surface facing the housing larger than the inner diameter of the opening on the surface facing away from the housing. That is, when the external electrode hole has a shape that is reduced in diameter in the axial direction, the diameter of the jetted plasma jet is reduced. As the diameter decreases, the jet length of the plasma jet becomes longer.

  In the ignition device of the present invention, the external electrode hole may not be expanded or contracted. That is, the external electrode hole may have a shape with a constant cross section.

  When the chamber has a reduced diameter, the external electrode hole preferably has a reduced diameter or a constant cross-sectional shape. Further, when the chamber is expanded in diameter, it is preferable that the external electrode hole has an expanded diameter or a shape having a constant cross section.

  In the first ignition device and the second ignition device of the present invention, the housing is preferably made of ceramics. Generally, ceramics have low thermal conductivity (hard to transfer heat). For this reason, by forming the housing with ceramics, the heat of the plasma generated in the chamber heats the inside of the chamber before heating the housing, and a plasma jet having a longer ejection length can be ejected. Furthermore, since the energy of the electric power applied between the electrodes is ejected as a plasma jet without loss, an effect that the electric energy for generating plasma can be reduced is also shown.

  The ceramic constituting the housing is not particularly limited as long as it is a material that is difficult to transmit the heat of plasma generated in the cavity. Moreover, it is preferable not to melt | dissolve with the high temperature of the generated plasma. As the ceramic constituting the housing, alumina ceramic is preferably used.

  The center electrode and the external electrode can be formed of a material having heat resistance and high conductivity. Examples of such a material include iron-based metals such as stainless steel, nickel-based metals, and iridium-based metals. The center electrode and the external electrode are preferably members having a surface made of an iridium metal. The center electrode and the external electrode are electrodes that generate plasma in the cavity when electric power is applied between the two electrodes. Since each electrode is made of an iridium-based metal, it is possible to prevent the electrodes from being damaged by the applied high energy power or generated plasma. The iridium-based metal refers to iridium or an alloy containing iridium.

  The first ignition device and the second ignition device of the present invention generate a plasma in the chamber by applying a pulsed voltage between the center electrode and the external electrode. The pulse width of the pulse voltage is preferably as short as possible. More preferably, it is 0.1 msec or less. More preferably, it is 0.01-0.1 ms. Moreover, it is preferable that the discharge current of a pulsed voltage is 10 A or more and 100 A or less.

  In an ignition device that ignites by injecting a plasma jet, the discharge voltage was set to −20 kV, the plasma ejection length was measured when the application time and the peak power were changed, and the measurement results are shown in FIG.

  As shown in FIG. 12, if the application time of the applied power is shortened, the plasma blowing length is shortened, and if the peak current of the applied power is increased, the plasma blowing length is lengthened. It can be seen that a larger peak current needs to be applied in order to blow out plasma having a desired length in a short time. For example, substantially the same plasma blowing length is obtained for plasma with an applied power of 1 A and 1 msec and for plasma with an applied power of 10 A and 0.01 msec. The energy per pulse of the pulse power is expressed by the following equation (1). As shown in Equation 1, even if the discharge voltage is increased, the energy amount per pulse is greatly reduced if the application time is significantly shortened. Specifically, FIG. 13 shows energy at an applied power of 1 A and 1 msec and energy at an applied power of 10 A and 0.01 msec. Thus, by shortening the application time of the applied power, the energy required for plasma generation can be reduced, and as a result, the ignition device for an internal combustion engine of the present invention can inject a plasma jet with a small energy.

E: pulse energy, V: discharge voltage (V), I: peak current (A), t: application time (sec)
The first ignition device and the second ignition device of the present invention are preferably ignition plugs that ignite the fuel in the combustion chamber of the engine.

  Hereinafter, the present invention will be described using examples.

(First embodiment)
FIG. 1 is a schematic cross-sectional view in the axial direction of a spark plug that is an ignition device for an internal combustion engine of the present embodiment.

  The spark plug 1 has a housing 2 having a substantially cylindrical structure made of alumina ceramic having electrical insulation. The housing 2 is formed such that the shaft center portion 20 is hollow. The hollow shaft portion 20 includes a small diameter portion 21 provided on the distal end side where the chamber 3 is formed, a large diameter portion 22 provided on the proximal end side and having a larger diameter than the small diameter portion 21, and the small diameter portion 21 and the large diameter portion. 22 and a tapered portion 23 whose inner peripheral surface is inclined is formed so as to be coaxial. FIG. 2 shows a schematic cross section of the housing 2 in the axial direction.

  The center electrode 4 is fitted in the shaft center portion 20. The center electrode 4 is a member made of cylindrical iridium having the same outer diameter as the inner diameter of the small diameter portion 21 of the shaft center portion 20. An end face 4a on the front end side of the center electrode 4 is located inside from the end face 2a on the front end side of the housing 2, and the chamber 3 is defined by the end face 4a. Further, the end face 4a on the front end side of the center electrode 4 exists on a plane perpendicular to the axial direction.

  A cylindrical middle shaft 40 made of nickel and having the same outer diameter as the inner diameter of the large diameter portion 22 is fitted into the large diameter portion 22 of the shaft center portion 20. An end portion 400 on the proximal end side of the middle shaft 40 protrudes from the housing 2 and is formed in a shape that can be connected to an external power supply device. Then, a conductive adhesive 41 was filled in the center portion 20 and between the center electrode 4 and the center shaft 40, and the center electrode 4 and the center shaft 40 were electrically connected.

  The housing 2 is inserted into the outer electrode 5 having a substantially bottomed cylindrical shape at the tip. The external electrode 5 is provided with an external electrode hole 50 communicating with the chamber 3 in a bottomed cylindrical bottom portion. The external electrode 5 includes an annular electrode portion 51 made of iridium that defines the external electrode hole 50, and a conductive portion 52 made of stainless steel that holds the electrode portion 51 and forms a substantially bottomed cylindrical shape of the external electrode 5. The inside of the substantially bottomed cylindrical shape is formed in a shape that matches the outer peripheral shape of the housing 2. That is, the housing 2 and the external electrode 5 are provided in close contact with each other.

The chamber 3 of the spark plug 1 of the present embodiment is formed to be a cylindrical space having an inner diameter of 1.3 mm, an axial length of 3 mm, and a volume of 4 mm ³ . The external electrode hole 50 opened to the external electrode 5 is formed to be a cylindrical space having an inner diameter of 1.3 mm. Note that the thickness of the external electrode 5 is, for example, 0.1 to 1.0 mm. Here, the lower limit of the thickness of the external electrode 5 is set to 0.1 mm is a limit value in which the shape of the external electrode 5 can be maintained and the external electrode 5 is not deformed. On the other hand, the upper limit of the thickness of the external electrode 5 is set to 1.0 mm because heat conduction of the external electrode 5 is improved when the external electrode 5 is thick, and heat is transferred by discharge through the external electrode 5. This is to prevent it. An outline of an axial cross section in the vicinity of the chamber 3 of the spark plug 1 of the present embodiment is shown in FIG.

  For example, as shown in FIG. 4, the spark plug 1 of the present embodiment is connected to a pulse power source 6 and attached to an engine for use. The ignition plug 1 can be attached to the engine by forming a screw portion (not shown) on the outer peripheral surface of the ignition plug 1 and screwing this screw portion into the cylinder head 7 of the engine.

  The operation of the spark plug 1 will be described.

  First, a pulse voltage applied to the spark plug 1 by the pulse power source 6 is created. FIG. 5 is a diagram showing an applied voltage pulse and a discharge current pulse. As shown in FIG. 5, the applied voltage pulse created by the pulse power supply 6 in this embodiment has a voltage value of −20 kV and a pulse width of 0.01 ms.

  When such a pulse application voltage is generated, the pulse signal is input from the pulse power source 6 to the center electrode 4 of the spark plug 1. Specifically, when a pulse signal is input to the spark plug 1, the pulse signal is applied to the center electrode 4 via the central shaft 40 and the conductive adhesive 41.

  When a pulse voltage is applied to the center electrode 4, a discharge current flows between the center electrode 4 and the electrode part 51 that partitions the external electrode hole 50 of the external electrode 5 through the chamber 3, and discharge occurs. In the present embodiment, a discharge current of 10 A flows through the chamber 3. This discharge current flows to the cylinder head via the conductive portion 52 of the external electrode 5.

  When a discharge occurs as described above, the air in the chamber 3 is warmed by the heat of the discharge, causing ionization. Along with this, plasma is generated in the chamber 3. Moreover, the inside of the chamber 3 becomes a high pressure state by the air heated by the discharge. As a result, the inside of the chamber 3 becomes a high temperature / high pressure plasma state, and the plasma is injected from the opening of the chamber 3 into the combustion chamber through the external electrode hole 50 as a plasma jet.

The spark plug 1 is formed so that the volume of the chamber ³ is as small as 4 mm ³ . Not only is the air in the chamber 3 heated quickly, but the inside of the chamber 3 can be heated with a small amount of energy. And if discharge is performed and a high voltage is applied to the air in the chamber 3, the air in the chamber 3 can be heated to a higher temperature. That is, the chamber 3 has higher energy.

  Furthermore, the ratio of the distance between the electrodes 4 and 5 (the axial length of the chamber 3) and the inner diameter of the chamber 3 in the chamber 3 is 2.3. That is, the chamber 3 is formed in a shape that is long in the axial direction. This shape is a state in which the inside of the chamber 3 is more easily heated (high-energy plasma is likely to be generated). Furthermore, since the inner diameter of the chamber 3 is short, the speed at which plasma is ejected from the opening of the chamber 3 increases. As a result, the ejection length of the plasma jet ejected from the chamber 3 is increased.

  In the spark plug 1, the chamber 3 is partitioned into a housing 2 made of alumina ceramics having low thermal conductivity. For this reason, it is difficult for heat generated by the discharge to be transferred from the chamber 3 to the outside of the spark plug 1 via the housing 2.

  As described above, since heat loss of discharge can be prevented, it is possible to reliably warm up to a temperature at which plasma is generated in the chamber 3. Since heat loss can be prevented in this way, the number of discharges for warming the air in the chamber 3 can be reduced, and power saving can be achieved.

  As described above, the spark plug 1 of the present embodiment can eject a plasma jet having a long ejection length from the external electrode hole 50 of the external electrode 5. Since it is injected from the spark plug 1 to a far position in the combustion chamber, it is possible to spread the flame kernels in the combustion chamber and to exert an effect of promoting combustion.

  When the plasma jet is thus injected into the combustion chamber, the air-fuel mixture in the combustion chamber is ignited by the plasma jet. Thereby, combustion of the air-fuel mixture occurs in the combustion chamber.

  As described above, the piston in the combustion chamber of the engine is driven by the internal combustion engine ignition device to generate a driving force in the engine.

(Second embodiment)
This embodiment is a spark plug having a configuration in which the diameter of the external electrode hole 50 is increased as it advances in the distal direction, and the vicinity of the chamber 3 is shown in FIG. Note that the configuration is the same as that of the first embodiment except that the external electrode hole 50 has a configuration in which the diameter is increased, and is not particularly described.

  The external electrode 5 of the spark plug 1 of the present embodiment has a configuration in which the electrode portion 51 and the conductive portion 52 of the first embodiment are integrated, and is formed of stainless steel. In addition, the spark plug 1 of the present embodiment has a shape in which the diameter of the chamber 3 and the external electrode hole 50 is increased as the chamber 3 and the external electrode hole 50 progress from the proximal end side to the distal end direction.

Specifically, the chamber 3 of the spark plug 1 is formed to be a cylindrical space having an inner diameter of 1.3 mm, an axial length of 3 mm, and a volume of 4 mm ³ , similar to the spark plug of the first embodiment. ing.

  The external electrode hole 50 has an opening on the surface side facing the housing 2 of 1.7 mm so that the opening on the surface side of the external electrode 5 facing the housing 2 has a circular shape with an inner diameter of 1.3 mm. It is formed to be circular. The length of the external electrode hole 50 in the axial direction was 2 mm. That is, the side wall surface 500 that defines the external electrode hole 50 is formed to be inclined with respect to the axial direction.

  Further, in the spark plug 1 of the present embodiment, the side wall surface 210 that defines the chamber 3 and the side wall surface 500 that defines the external electrode hole 50 are smoothly connected without causing a step at the connection portion between them. It has a shape that does not hinder the progress of the plasma jet when it is ejected.

  The spark plug 1 of the present embodiment can be operated in the same manner as the spark plug of the first embodiment.

  In the spark plug 1 of the present embodiment, the plasma generated in the chamber 3 advances in the tip direction in the axial direction of the chamber 3 and is ejected from the opening of the chamber 3. The plasma jet ejected from the opening of the chamber 3 advances in the external electrode hole 50 in the axial direction. The side wall surface 500 of the external electrode hole 50 is inclined so as to expand in diameter, and the plasma jet also expands in the radial direction as it proceeds through the external electrode hole 50. And it ejects from the opening part of the external electrode hole 50. FIG. That is, the plasma jet ejected from the external electrode hole 50 is ejected at a wide angle along the side wall surface 500 of the external electrode hole 50. Since the plasma jet is injected from the spark plug 1 to a wide range in the combustion chamber, the flame kernel can be spread over a wide range in the combustion chamber, and the effect of promoting the combustion is exhibited.

(Third embodiment)
The present embodiment is a spark plug having a configuration in which the diameter of the external electrode hole 50 is reduced as it advances in the distal direction, and the vicinity of the chamber 3 is shown in FIG. The configuration is the same as that in the first embodiment except that the external electrode hole 50 has a smaller diameter, and will not be described in particular.

  The external electrode 5 of the spark plug 1 of the present embodiment has a configuration in which the electrode portion 51 and the conductive portion 52 of the first embodiment are integrated, and is formed of stainless steel. In addition, the spark plug 1 of the present embodiment has a shape in which the diameter of the chamber 3 and the external electrode hole 50 is reduced as it advances from the proximal end side toward the distal end direction.

Specifically, the chamber 3 of the spark plug 1 is formed to be a cylindrical space having an inner diameter of 1.3 mm, an axial length of 3 mm, and a volume of 4 mm ³ , similar to the spark plug of the first embodiment. ing.

  The external electrode hole 50 has a 0.9 mm opening on the surface facing away from the housing 2 so that the opening on the surface facing the housing 2 of the external electrode 5 is a circle having an inner diameter of 1.3 mm. It is formed to be circular. The length of the external electrode hole 50 in the axial direction was 2 mm. That is, the side wall surface 500 that defines the external electrode hole 50 is formed to be inclined with respect to the axial direction.

  Further, in the spark plug 1 of the present embodiment, the side wall surface 210 that defines the chamber 3 and the side wall surface 500 that defines the external electrode hole 50 are smoothly connected without causing a step at the connection portion between them. It has a shape that does not hinder the progress of the plasma jet when it is ejected.

  The spark plug 1 of the present embodiment can be operated in the same manner as the spark plug of the first embodiment.

  In the spark plug 1 of the present embodiment, plasma generated in the chamber 3 is ejected from the opening of the chamber 3. The plasma jet ejected from the opening of the chamber 3 advances in the external electrode hole 50 in the axial direction. At this time, the plasma jet ejected from the opening of the chamber 3 proceeds along the side wall surface 500 of the external electrode hole 50. When proceeding along the side wall surface 500 of the external electrode hole 50, the plasma jet concentrates in the vicinity of the axial center and proceeds in the axial direction. And it ejects from the opening part of the external electrode hole 50 at a faster speed. As a result, since the plasma jet is ejected from the spark plug 1 into the combustion chamber for a long time, the flame kernel can be spread over a wide area in the combustion chamber, and the combustion can be promoted.

(Fourth embodiment)
In the present embodiment, the spark plug having the configuration shown in FIG. The configuration other than the vicinity of the chamber 3 shown in the figure is the same as that in the first embodiment and will not be described in particular.

  In the spark plug 1 of the present embodiment, the electrode portion 51 and the conductive portion 52 of the external electrode 5 are integrally formed of stainless steel. In addition, the spark plug 1 of the present embodiment has a shape in which the diameter of the chamber 3 and the external electrode hole 50 is increased as the chamber 3 and the external electrode hole 50 progress from the proximal end side to the distal end direction. That is, the chamber 3 and the external electrode hole 50 form an integral frustoconical space.

Specifically, the bottom surface on the proximal end side of the chamber 3 is formed by the end surface of the distal end of the center electrode 4 and has a circular shape with an inner diameter of 1.3 mm. The opening of the chamber 3 is formed to be a circle having an inner diameter of 2.1 mm. The axial length of the chamber 3 is 3 mm. The central electrode 4 is opened at a position 3 mm perpendicularly from the end face of the tip. The volume of the chamber 3 was 7 mm ³ . The side wall surface 210 of the housing 2 that defines the chamber 3 is formed to be inclined with respect to the axial direction.

  The external electrode 5 defines a frustoconical external electrode hole 50. The external electrode hole 50 has a surface side opening facing the housing 2 having a circular shape of 2.1 mm, and a surface side opening facing the housing 2 has a circular shape of 2.6 mm. It is formed as follows. The length of the external electrode hole 50 in the axial direction was 2 mm. The side wall surface 500 that defines the external electrode hole 50 is formed to be inclined with respect to the axial direction. The angle formed by the side wall surface 500 defining the external electrode hole 50 with respect to the axial direction is the same as the angle formed by the side wall surface 210 of the housing 2 defining the chamber 3 with respect to the axial direction.

  Further, in the spark plug 1 of the present embodiment, the side wall surface 210 that defines the chamber 3 and the side wall surface 500 that defines the external electrode hole 50 are smoothly formed without forming a step at the connecting portion between them. It is connected and has a shape that does not hinder the progress of the plasma jet when the plasma jet is ejected.

  The spark plug 1 of the present embodiment can be operated in the same manner as the spark plug of the first embodiment.

  In the spark plug 1 of the present embodiment, plasma generated in the chamber 3 travels along the side wall surface 210 in the chamber 3 and is ejected from the opening of the chamber 3. The plasma that has traveled along the side wall surface in the chamber 3 is ejected in a direction along the side wall surface. Since the side wall surface of the external electrode hole 50 is located on the same straight line as the side wall surface of the chamber 3, the plasma traveling along the side wall surface of the chamber 3 proceeds along the side wall surface of the external electrode hole 50. The liquid is ejected from the opening of the external electrode hole 50. That is, the plasma jet ejected from the external electrode hole 50 is ejected at a wide angle along the side wall surface of the external electrode hole 50. Since the plasma jet is injected from the spark plug 1 to a wide range in the combustion chamber, the flame kernel can be spread over a wide range in the combustion chamber, and the effect of promoting the combustion is exhibited.

(Fifth embodiment)
This embodiment is a spark plug having a configuration in which the opening of the external electrode hole 50 has a larger diameter, and the vicinity of the chamber 3 is shown in FIG. The configuration is the same as that of the third embodiment except that the external electrode hole 50 has a larger diameter, and is not particularly described.

  The spark plug 1 has a housing 2 that defines a chamber 3 having the same shape as that of the fourth embodiment. That is, the side wall surface 210 of the housing 2 that defines the chamber 3 is formed to be inclined with respect to the axial direction.

  The external electrode hole 50 has a circular opening of 3.1 mm on the surface side facing away from the housing 2 so that the opening of the external electrode 5 facing the housing 2 has a circular shape of 2.1 mm. It is formed as follows. The length of the external electrode hole 50 in the axial direction was 2 mm. The side wall surface 500 that defines the external electrode hole 50 is formed to be inclined with respect to the axial direction. The angle formed by the side wall surface 500 defining the external electrode hole 50 with respect to the axial direction is larger than the angle formed by the side wall surface 210 of the housing 2 defining the chamber 3 with respect to the axial direction.

  Further, in the spark plug 1 of the present embodiment, the side wall surface 210 that defines the chamber 3 and the side wall surface 500 that defines the external electrode hole 50 are smoothly connected without causing a step at the connection portion between them. It has a shape that does not hinder the progress of the plasma jet when it is ejected.

  The spark plug 1 of the present embodiment has a shape in which the outer electrode hole 50 has a diameter expanded on the tip side. That is, the plasma jet ejected from the opening of the chamber 3 spreads over a wide angle along the side wall surface of the external electrode hole 50 and is ejected from the opening of the external electrode hole 50. Since the plasma jet is injected from the spark plug 1 to a wide range in the combustion chamber, the flame kernel can be spread over a wide range in the combustion chamber, and the effect of promoting the combustion is exhibited.

(Sixth embodiment)
In the present embodiment, the spark plug having the configuration shown in FIG. The configuration other than the vicinity of the chamber 3 shown in the figure is the same as that in the first embodiment and will not be described in particular.

Specifically, the bottom surface on the proximal end side of the chamber 3 is formed by the end surface of the distal end of the center electrode 4 and has a circular shape with an inner diameter of 1.3 mm. The opening of the chamber 3 is formed in a circular shape having an inner diameter of 0.78 mm. The axial length of the chamber 3 is 3 mm. The central electrode 4 is opened at a position 3 mm perpendicularly from the end face of the tip. The volume of the chamber 3 was 2.6 mm ³ . That is, the chamber 3 is formed in a shape that is reduced in diameter as it advances in the axial tip direction. The side wall surface 210 of the housing 2 that defines the chamber 3 is formed to be inclined with respect to the axial direction.

  The external electrode 5 defines external electrode holes 50 having a constant cross section. The external electrode hole 50 is formed to have a circular shape with an inner diameter of 0.78 mm in a cross section perpendicular to the axial direction. The length of the external electrode hole 50 in the axial direction was 2 mm.

  In the spark plug 1 of the present embodiment, the side wall surface 210 that defines the chamber 3 and the side wall surface 500 that defines the external electrode hole 50 are smoothly connected to each other without causing a step at the connection portion therebetween. It has a shape that does not impede the progress of the plasma jet when it is ejected.

  The spark plug 1 of the present embodiment can be operated in the same manner as the spark plug of the first embodiment.

  In the spark plug 1 of the present embodiment, plasma generated in the chamber 3 travels along the side wall surface 210 in the chamber 3 and is ejected from the opening of the chamber 3. At this time, since the side wall surface 210 is formed to be inclined, the plasma is concentrated in the axial center portion, and the plasma jet is ejected at a higher speed from the opening. The plasma jet passes through the external electrode hole 50 and is ejected from the opening of the external electrode hole 50 at a high speed. As a result, since the plasma jet is ejected from the spark plug 1 into the combustion chamber for a long time, the flame kernel can be spread over a wide area in the combustion chamber, and the combustion can be promoted.

(Seventh embodiment)
This embodiment is a spark plug having a configuration in which the opening of the external electrode hole 50 has a smaller diameter, and the vicinity of the chamber 3 is shown in FIG. The configuration is the same as that of the sixth embodiment except that the external electrode hole 50 has a smaller diameter, and is not specifically described.

  The spark plug 1 has a housing 2 that defines a chamber 3 having the same shape as that of the sixth embodiment. That is, the side wall surface 210 of the housing 2 that defines the chamber 3 is formed to be inclined with respect to the axial direction.

  The external electrode hole 50 is formed so that the opening on the surface side facing the housing 2 of the external electrode 5 has a circular shape of 1 mm, and the opening on the surface side facing the housing 2 has a circular shape of 0.8 mm. Is formed. The length of the external electrode hole 50 in the axial direction was 2 mm. The side wall surface 500 that defines the external electrode hole 50 is formed to be inclined with respect to the axial direction. The angle formed by the side wall surface 500 defining the external electrode hole 50 with respect to the axial direction is the same as the angle formed by the side wall surface 210 of the housing 2 defining the chamber 3 with respect to the axial direction.

  In the spark plug 1 of the present embodiment, the side wall surface 210 that defines the chamber 3 and the side wall surface 500 that defines the external electrode hole 50 are smoothly connected to each other without causing a step at the connection portion therebetween. It has a shape that does not impede the progress of the plasma jet when it is ejected.

  The spark plug 1 of the present embodiment can be operated in the same manner as the spark plug of the first embodiment.

  In the spark plug 1 of the present embodiment, plasma generated in the chamber 3 travels along the side wall surface 210 in the chamber 3 and is ejected from the opening of the chamber 3. At this time, since the side wall surface 210 is formed to be inclined, the plasma is concentrated in the axial center portion, and the plasma jet is ejected at a higher speed from the opening. This plasma jet is also concentrated in the axial center portion of the external electrode hole 50 and ejected from the opening of the external electrode hole 50 at a high speed. As a result, since the plasma jet is ejected from the spark plug 1 into the combustion chamber for a long time, the flame kernel can be spread over a wide area in the combustion chamber, and the combustion can be promoted.

It is sectional drawing of the axial direction of the ignition plug of 1st embodiment. It is sectional drawing of the axial direction of the housing of the spark plug of 1st embodiment. It is sectional drawing of the axial direction vicinity of the chamber of the ignition plug of 1st embodiment. It is the figure which showed the structure of the state which assembled | attached the ignition plug of 1st embodiment to the engine. It is the figure which showed the waveform of the applied voltage pulse applied to the ignition plug of 1st embodiment, and the discharge current pulse. It is sectional drawing of the axial direction vicinity of the chamber of the ignition plug of 2nd embodiment. It is sectional drawing of the axial direction vicinity of the chamber of the ignition plug of 3rd embodiment. It is sectional drawing of the axial direction of the chamber vicinity of the ignition plug of 4th embodiment. It is sectional drawing of the axial direction vicinity of the chamber of the spark plug of 5th embodiment. It is sectional drawing of the axial direction of the chamber vicinity of the spark plug of 6th embodiment. It is sectional drawing of the axial direction vicinity of the chamber of the spark plug of 7th embodiment. It is the figure which showed the relationship between the pulse width of an applied voltage, and plasma ejection length. It is the figure which showed the difference of the pulse energy of the spark plug of this invention, and the conventional spark plug.

Explanation of symbols

1: Spark plug 2: Housing 20: Shaft center portion 21: Small diameter portion 210: Side wall surface 22: Large diameter portion 23: Tapered portion 3: Chamber 4: Center electrode 40: Middle shaft 400: End portion 41: Conductive adhesive 5 : External electrode 50: External electrode hole 500: Side wall surface 51: Electrode part 52: Conductive part 6: Pulse power supply 7: Cylinder head

Claims (12)

A housing having an opening and a bottom surface facing the opening and defining a chamber having a circular cross section extending in the axial direction;
An external electrode provided on the surface of the housing and having an external electrode hole communicating the opening of the chamber and the outside;
A central electrode disposed on the bottom surface of the chamber;
An ignition device for an internal combustion engine that generates a plasma in the chamber by applying a voltage between the central electrode and the external electrode, and injects a plasma jet from an opening of the chamber,
An ignition device for an internal combustion engine, wherein the chamber has a volume of 10 mm ³ or less, and a ratio of an axial length to an inner diameter length of the chamber is 2 or more.   The internal combustion engine ignition device according to claim 1, wherein a distance between the center electrode and the external electrode is 3 mm or less.   The internal combustion engine ignition device according to claim 1, wherein the bottom surface of the chamber is partitioned by the center electrode.   2. The ignition device for an internal combustion engine according to claim 1, wherein an opening of the external electrode hole on a surface of the external electrode facing the housing coincides with an opening of the chamber on the surface of the housing.   2. The internal combustion engine ignition device according to claim 1, wherein the outer electrode hole has an inner diameter of an opening portion on a surface facing the housing and an inner diameter of an opening portion on a surface facing the housing. A housing that defines an axially extending chamber having an opening and a bottom surface facing the opening;
An external electrode provided on a surface of the housing, in communication with the chamber, and having an external electrode hole in which an opening on a surface facing the housing and an opening of the chamber on the surface of the housing coincide with each other;
A central electrode disposed on the bottom surface of the chamber;
An ignition device for an internal combustion engine that generates a plasma in the chamber by applying a voltage between the central electrode and the external electrode, and injects a plasma jet from an opening of the chamber,
An ignition device for an internal combustion engine, wherein the chamber has a circular cross-sectional shape in a plane perpendicular to the axial direction, and an inner diameter at a bottom surface of the chamber is different from an inner diameter at an opening.   The internal combustion engine ignition device according to claim 6, wherein an inner diameter at the bottom surface of the chamber is smaller than an inner diameter at the opening.   The internal combustion engine ignition device according to claim 6, wherein an inner diameter at the bottom surface of the chamber is larger than an inner diameter at the opening.   The ignition device for an internal combustion engine according to claim 6, wherein the outer electrode hole has an inner diameter of an opening portion on a surface facing the housing and an inner diameter of an opening portion on a surface facing the housing.   10. The internal combustion engine ignition device according to claim 9, wherein the outer electrode hole has an inner diameter of the opening at a surface facing the housing smaller than an inner diameter of the opening at a surface facing the housing.   10. The internal combustion engine ignition device according to claim 9, wherein the outer electrode hole has an inner diameter of the opening at a surface facing the housing larger than an inner diameter of the opening at a surface facing the housing.   The internal combustion engine ignition device according to claim 6, wherein the bottom surface of the chamber is partitioned by the center electrode.

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