JP2013161523A - Ignition method, ignition device, and engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition method, an ignition device, and an engine such that an air-fuel mixture can be stably ignited even under a hard-to-burn condition.SOLUTION: A flow of gas flowing from a primary discharge gap to a secondary discharge gap is generated. Primary discharge is generated in a primary discharge gap while the flow of the gas is generated. Primary plasma is generated in the primary discharge gap by the primary discharge. The primary plasma is propagated to the secondary discharge gap through the flow of the gas. When the primary plasma is present in the secondary discharge gap, secondary discharge is generated in the secondary discharge gap. Secondary plasma is generated in the secondary discharge gap by the secondary discharge. Simultaneously with or after the generation of the secondary plasma, an air-fuel mixture is burnt into flames.

Description

  The present invention relates to an ignition method for igniting an air-fuel mixture, an ignition device for igniting an air-fuel mixture, and an engine.

  A typical spark plug includes a center electrode and side electrodes. A discharge gap is formed between the center electrode and the side electrode. The gap length of the discharge gap depends on the pulse voltage waveform, the composition of the gas mixture, the pressure, the temperature, and the like, but is typically about 1 mm. A pulse voltage is applied between the center electrode and the side electrodes, and a discharge is generated in the discharge gap. The mixture is ignited by the discharge, and a flame is generated in the discharge gap.

  Patent Document 1 describes a plug in which two or more discharge gaps are formed.

JP 2004-79458 A

  In a general spark plug, it is difficult to increase the gap length of the discharge gap, and the flame is difficult to spread. Under difficult combustion conditions such as when lean combustion is performed, the fact that the flame is difficult to spread impairs ignition stability.

  The present invention is made to solve this problem. An object of the present invention is to provide an ignition method, an ignition device, and an engine that can ignite the air-fuel mixture stably even under flame-resistant conditions even under difficult combustion conditions.

  The first aspect of the present invention is directed to an ignition method for igniting an air-fuel mixture.

  In the first aspect of the present invention, a gas flow is generated in the combustion chamber where the electrode structure is exposed. Assume that n is a natural number of 2 or more. An n−1 primary discharge gap and an n order discharge gap are formed in the electrode structure. The gap length of the n-th order discharge gap is longer than the gap length of the n-th order discharge gap. The gas flows from the n-1 primary discharge gap to the n primary discharge gap.

  In a state where a gas flow is generated, n-1 primary discharge is generated in the n-1 primary discharge gap, and n-1 primary plasma is generated in the n-1 primary discharge gap.

  The n-1 primary plasma is propagated to the n order discharge gap on the gas flow.

  When n-1 primary plasma is present in the n order discharge gap, n order discharge is generated in the n order discharge gap, and n order plasma is generated in the n order discharge gap. A flame is induced in the air-fuel mixture simultaneously with or after the generation of the n-th order plasma.

  The second to eighth aspects of the present invention are directed to an ignition device that ignites an air-fuel mixture.

  In the second aspect of the present invention, a plug and a pulse voltage application mechanism are provided.

  The plug includes an electrode structure. Assume that n is a natural number of 2 or more. An n−1 primary discharge gap and an n order discharge gap are formed in the electrode structure. The gap length of the n-th order discharge gap is longer than the gap length of the n-th order discharge gap. The n-th order discharge gap is disposed downstream of the n-1 primary discharge gap in the gas flow.

  The pulse voltage application mechanism is configured to apply the n-th order pulse voltage to the plug after the n-1st order pulse voltage. The n-1 primary pulse voltage generates an n-1 primary discharge in the n-1 primary discharge gap. The nth order pulse voltage generates an nth order discharge in the nth order discharge gap. The n−1 primary plasma is generated in the n−1 primary discharge gap by the n−1 primary discharge. The n-1 primary plasma propagates along the gas flow to the nth discharge gap. The pulse voltage application mechanism is configured to apply the n-th order pulse voltage to the plug when the n−1 primary plasma exists in the n-th order discharge gap.

  The third aspect of the present invention adds further matters to the second aspect of the present invention. In the third aspect of the present invention, the electrode structure includes a center electrode, a first side electrode, and a second side electrode. An n−1 primary discharge gap is formed between the discharge end of the center electrode and the discharge end of the first side electrode. An n-th order discharge gap is formed between the discharge end of the center electrode and the discharge end of the second side electrode.

  The fourth aspect of the present invention adds further matters to the second aspect of the present invention. In the fourth aspect of the present invention, the electrode structure includes a center electrode, a first side electrode, and a second side electrode. An n−1 primary discharge gap is formed between one discharge end of the center electrode and the discharge end of the first side electrode. An n-th order discharge gap is formed between the other discharge end of the center electrode and the discharge end of the second side electrode.

  The fifth aspect of the present invention adds further matters to the third or fourth aspect of the present invention. In the fifth aspect of the present invention, the first side electrode is disposed so as not to overlap the n−1 primary discharge gap when viewed from the downstream side of the gas flow. The second side electrode is disposed so as not to overlap the n-th order discharge gap when viewed from the downstream side of the gas flow.

  The sixth aspect of the present invention adds further matters to any one of the second to fifth aspects of the present invention. In the sixth aspect of the present invention, an n-secondary discharge gap is further formed in the electrode structure. The gap length of the n-1 primary discharge gap is longer than the gap length of the n-2 secondary discharge gap. The n-1 primary discharge gap is disposed downstream of the n-2 secondary discharge gap in the gas flow.

  The pulse voltage application mechanism is configured to apply an n-2 secondary pulse voltage to the plug before the n-1 primary pulse voltage. The n-2 secondary pulse voltage generates an n-2 secondary discharge in the n-2 secondary discharge gap. An n-2 secondary discharge generates n-2 secondary plasma in the n-2 secondary discharge gap. The n-2 secondary plasma propagates along the gas flow to the n-1 primary discharge gap. The pulse voltage application mechanism is configured to apply an n−1 primary pulse voltage to the plug when the n−2 secondary plasma exists in the n−1 primary discharge gap.

  The seventh aspect of the present invention adds further matters to any one of the second to sixth aspects of the present invention. In the seventh aspect of the present invention, at least two or both of the n−1 primary discharge gap and the n primary discharge gap are formed.

  The eighth aspect of the present invention adds a further matter to any one of the second to seventh aspects of the present invention. In the eighth aspect of the present invention, the pulse voltage application mechanism is configured such that the power input by the n-th order pulse voltage is less than the power input by the n-th order pulse voltage.

  The ninth aspect of the present invention is directed to an engine. In a ninth aspect of the present invention, a combustion chamber, a flow generation mechanism, a plug, and a pulse voltage application mechanism are provided.

  The plug includes an electrode structure that is exposed to the combustion chamber. Assuming that n is a natural number of 2 or more, an n−1 order discharge gap and an nth order discharge gap are formed in the electrode structure. The gap length of the n-th order discharge gap is longer than the gap length of the n-th order discharge gap. The n-th order discharge gap is disposed downstream of the n-1 primary discharge gap in the gas flow.

  The pulse voltage application mechanism is configured to apply the n-th order pulse voltage to the plug after the n-1st order pulse voltage. The n-1 primary pulse voltage generates an n-1 primary discharge in the n-1 primary discharge gap. The nth order pulse voltage generates an nth order discharge in the nth order discharge gap. The n−1 primary plasma is generated in the n−1 primary discharge gap by the n−1 primary discharge. The n-1 primary plasma propagates along the gas flow to the nth discharge gap. The pulse voltage application mechanism is configured to apply the n-th order pulse voltage to the plug when the n−1 primary plasma exists in the n-th order discharge gap.

  According to the present invention, discharge is generated in the discharge gap having a long gap length, and the flame is greatly spread. Even under difficult combustion conditions, the air-fuel mixture can be ignited stably.

  In particular, according to the fifth aspect of the present invention, the side electrode does not hinder the propagation of the plasma, and the flame further spreads.

  In particular, according to the sixth aspect of the present invention, the flame further spreads.

  In particular, according to the eighth aspect of the present invention, power consumption is reduced.

  These and other objects, features, aspects and advantages of the invention will become more apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

It is a schematic diagram of the engine of 1st Embodiment. It is a perspective view of the plug of 1st Embodiment. It is a top view of the plug of 1st Embodiment. It is a side view of the plug of 1st Embodiment. It is a schematic diagram which shows the flow of ignition to the air-fuel mixture of the first embodiment. It is a schematic diagram which shows the flow of ignition to the air-fuel mixture of the first embodiment. It is a schematic diagram which shows the flow of ignition to the air-fuel mixture of the first embodiment. It is a schematic diagram which shows the flow of ignition to the air-fuel mixture of the first embodiment. It is a schematic diagram which shows the waveform of the pulse voltage of 1st Embodiment. It is a perspective view of the plug of the modification of 1st Embodiment. It is a perspective view of the plug of 2nd Embodiment. It is a top view of the plug of 2nd Embodiment. It is a side view of the plug of 2nd Embodiment. It is a schematic diagram which shows the flow of ignition to the air-fuel mixture of the second embodiment. It is a schematic diagram which shows the flow of ignition to the air-fuel mixture of the second embodiment. It is a schematic diagram which shows the waveform of the pulse voltage of 2nd Embodiment. It is a perspective view of the plug of 3rd Embodiment. It is a top view of the plug of 3rd Embodiment. It is a side view of the plug of 3rd Embodiment. It is a perspective view of the center electrode of 3rd Embodiment. It is a perspective view of the plug of 4th Embodiment. It is a top view of the plug of 4th Embodiment. It is a side view of the plug of 4th Embodiment. It is a perspective view of the plug of 5th Embodiment. It is a top view of the plug of 5th Embodiment.

{First embodiment}
(Outline)
The first embodiment relates to an ignition method for igniting an air-fuel mixture, an ignition device for igniting an air-fuel mixture, and an engine.

(Engine components)
The schematic diagram of FIG. 1 shows the engine of the first embodiment.

  As shown in FIG. 1, the engine 1000 includes a combustion container 1020, an intake mechanism 1022, an exhaust mechanism 1024, and an ignition device 1026. The ignition device 1026 includes a plug 1040 and a pulse voltage application mechanism 1042. The combustion container 1020 includes a main body 1060 and a piston 1062. A combustion chamber 1080 is formed in the combustion container 1020. The pulse voltage application mechanism 1042 includes a pulse generation circuit 1100 and a cable 1102.

(Plug component)
The schematic diagrams from FIG. 2 to FIG. 4 are a perspective view, a plan view, and a side view, respectively, of the plug of the first embodiment.

  As shown in FIGS. 2 to 4, the plug 1040 includes an electrode structure 1140, an insulator 1142, and a metal shell 1144. The electrode structure 1140 includes a center electrode 1160, a first side electrode 1162, and a second side electrode 1164. A primary discharge gap 1200 is formed between the discharge end 1180 of the center electrode 1160 and the discharge end 1182 of the first side electrode 1162 (see FIGS. 3 and 4). A secondary discharge gap 1202 is formed between the discharge end 1180 of the center electrode 1160 and the discharge end 1184 of the second side electrode 1164 (see FIGS. 3 and 4).

(Engine operation)
When engine 1000 is operated, the air-fuel mixture is sucked into combustion chamber 1080 by intake mechanism 1022, and combustion chamber 1080 is filled with the air-fuel mixture. The air-fuel mixture filling the combustion chamber 1080 is compressed by the piston 1062 toward the top dead center. The ignition device 1026 ignites the compressed air-fuel mixture, the air-fuel mixture burns, an explosive force is generated, and the piston 1062 moves toward the bottom dead center. Exhaust from the combustion chamber 1080 is performed by the exhaust mechanism 1024. When engine 1000 is a direct injection engine, air is sucked into combustion chamber 1080 by intake mechanism 1022 and fuel oil is injected into combustion chamber 1080.

(Gap length)
The center electrode 1160, the first side electrode 1162, and the second side electrode 1164 are arranged so that the gap length of the secondary discharge gap 1202 is longer than the gap length of the primary discharge gap 1200.

(Disposition of discharge gap)
When intake is performed by the intake mechanism 1022, a mixture flow such as tumble, swirl, squish, or the like is generated in the combustion chamber 1080. The plug 1040 is attached to the combustion vessel 1020 so that the secondary discharge gap 1202 is disposed downstream of the primary discharge gap 1200 in the flow of the air-fuel mixture. Therefore, when intake is performed by the intake mechanism 1022, a flow of air-fuel mixture that flows from the primary discharge gap 1200 to the secondary discharge gap 1202 is generated.

(Flow generation mechanism)
Instead of using the intake mechanism 1022 as a flow generation mechanism for generating a mixture flow in the combustion chamber 1080, a flow generation mechanism provided separately from the intake mechanism 1022 or provided separately from the intake mechanism 1022 is provided. The flow generation mechanism may be configured by the cooperation of the mechanism and the intake mechanism 1022, and the flow of the air-fuel mixture may be generated.

(Ignition flow to mixture)
The schematic diagrams from FIG. 5 to FIG. 8 show the flow of ignition to the air-fuel mixture.

  As shown in FIG. 5, when intake is performed by the intake mechanism 1022, an air-fuel mixture flow 1210 flowing from the primary discharge gap 1200 to the secondary discharge gap 1202 is generated in the combustion chamber 1080.

  As shown in FIG. 6, the primary discharge 1220 is generated in the primary discharge gap 1200 in the state where the mixture flow 1210 is generated. Primary plasma 1240 is generated in the primary discharge gap 1200 by the primary discharge 1220. The primary plasma 1240 may be a flame or may not be a flame. A portion that is in flame and a portion that is not in flame may coexist in the primary plasma 1240.

  As shown in FIG. 7, the primary plasma 1240 propagates to the secondary discharge gap 1202 along the mixture flow 1210. When the primary plasma 1240 that is not in flame is propagated to the secondary discharge gap 1202, when the primary discharge 1220 is generated, the air-fuel mixture may not exist in the primary discharge gap 1200. The primary plasma 1240 may propagate to the primary discharge gap 1200 along a gas flow that is not.

  As shown in FIG. 8, when the primary plasma 1240 exists in the secondary discharge gap 1202, the secondary discharge 1222 is generated in the secondary discharge gap 1202. In the case where a portion that is in flame and a portion that is not in flame coexist in the primary plasma 1240, the secondary discharge 1222 is generated when the portion that is in flame exists in the secondary discharge gap 1202. Alternatively, the secondary discharge 1222 may be generated when a portion that is not in the flame exists in the secondary discharge gap 1202. Secondary plasma 1242 is generated in the secondary discharge gap 1202 by the secondary discharge 1222. A flame is induced simultaneously with the generation of the secondary plasma 1242 or after the generation of the secondary plasma 1242, and the mixture is ignited. In the case where a flame is induced with a delay from the generation of the secondary plasma 1242, the air-fuel mixture may not exist in the secondary discharge gap 1202 when the secondary discharge 1222 is generated. It is sufficient that the air-fuel mixture exists at the position where the flame is triggered when the flame is finally triggered.

  When plasma is present in the secondary discharge gap 1202, the impedance of the secondary discharge gap 1202 is lowered, and discharge is likely to occur in the secondary discharge gap 1202. For this reason, even if the gap length of the secondary discharge gap 1202 is increased, discharge can be generated in the secondary discharge gap 1202. As a result, discharge occurs in the discharge gap having a long gap length, and the flame spreads greatly. The air-fuel mixture can be ignited stably even under difficult combustion conditions such as when lean combustion is performed due to a flame that spreads greatly.

(Pulse voltage application mechanism)
Center electrode 1160 and positive electrode 1120 of pulse generation circuit 1100 are electrically connected by a cable 1102. The metal shell 1144 and the negative electrode 1122 of the pulse generation circuit 1100 are grounded.

  When the pulse generation circuit 1100 generates a pulse voltage between the positive electrode 1120 and the negative electrode 1122, the pulse voltage is applied between the center electrode 1160 of the plug 1040 and the metal shell 1144, and the center electrode 1160 and the first electrode A pulse voltage is applied between the side electrode 1162 and a pulse voltage is applied between the center electrode 1160 and the second side electrode 1164.

  The cable 1102 may be omitted, and the positive electrode 1120 of the pulse generation circuit 1100 may be directly attached to the center electrode 1160.

  The type of pulse generation circuit 1100 is preferably an inductive energy storage type. However, the form of the pulse generation circuit 1100 may be other than the induction energy storage type.

(Pulse voltage waveform)
The schematic diagram of FIG. 9 shows the waveform of the pulse voltage of the first embodiment.

  As shown in FIG. 9, the pulse generation circuit 1100 is configured to generate a secondary pulse voltage 1262 between the positive electrode 1120 and the negative electrode 1122 after the primary pulse voltage 1260. The primary pulse voltage 1260 generates a primary discharge 1220 in the primary discharge gap 1200. The secondary pulse voltage 1262 generates a secondary discharge 1222 in the secondary discharge gap 1202. The pulse generation circuit 1100 is configured to generate a secondary pulse voltage 1262 when the primary plasma 1240 is present in the secondary discharge gap 1202. In the pulse generation circuit 1100, circuit constants are selected so that a pulse voltage having the waveform shown in FIG. 9 can be generated. Alternatively, the pulse generation circuit 1100 is controlled by the controller so that a pulse voltage having the waveform shown in FIG. 9 can be generated.

  The primary pulse voltage 1260 may be one single pulse as shown in FIG. 9, or may be a repetition of two or more single pulses. The secondary pulse voltage 1262 may be one single pulse as shown in FIG. 9, or may be a repetition of two or more single pulses. The waveform of each single pulse constituting the repetition of two or more single pulses may be different.

  Desirably, the pulse generation circuit 1100 is configured such that the power input by the secondary pulse voltage 1262 is less than the power input by the primary pulse voltage 1260. This reduces power consumption. Since the secondary discharge 1222 is generated when the secondary discharge 1222 is likely to occur, the power input by the secondary pulse voltage 1262 is at least 2 less than the power input by the primary pulse voltage 1260. The next discharge 1222 occurs without any problem.

  The peak voltage of the primary pulse voltage 1260 is 5 to 40 kV, and the half width is 100 ns to 10 μs. When two or more single pulses are repeated, the repetition frequency is 5 to 100 kpps.

  The peak voltage of the secondary pulse voltage 1262 is 50 V to 30 kV, and the half width is 5 to 10 μs. When two or more single pulses are repeated, the repetition frequency is 10 to 200 kpps.

  Typically, primary pulse voltage 1260 and secondary pulse voltage 1262 are unipolar positive pulses, with center electrode 1160 being the anode and first side electrode 1162 and second side electrode 1164 being the cathode. become. However, the primary pulse voltage 1260 and the secondary pulse voltage 1262 are unipolar negative pulses, the center electrode 1160 is a cathode, and the first side electrode 1162 and the second side electrode 1164 are anodes. Is also allowed. The primary pulse voltage 1260 and the secondary pulse voltage 1262 may be bipolar.

(Electrode structure)
As shown in FIGS. 2 to 4, the electrode structure 1140 is disposed at the tip of the plug 1040. When the plug 1040 is attached to the combustion vessel 1020, the electrode structure 1140 is exposed to the combustion chamber 1080. As a result, the primary discharge gap 1200 and the secondary discharge gap 1202 are arranged in the combustion chamber 1080, and the air-fuel mixture can be ignited by the primary discharge 1220 and the secondary discharge 1222.

(Center electrode)
The center electrode 1160 has a bar shape. The center electrode 1160 is electrically insulated from the metallic shell 1144 by the insulator 1142, and is mechanically fixed on the central axis of the metallic shell 1144 by the insulator 1142. The distal end side of the center electrode 1160 protrudes from the opening of the metal shell 1144 toward the distal end side in the axial direction. The vicinity of the tip of the center electrode 1160 is a discharge end 1180 that becomes the start point or end point of discharge.

(Side electrode)
The first side electrode 1162 and the second side electrode 1164 have a bent bar shape. The first side electrode 1162 and the second side electrode 1164 are electrically connected to the metallic shell 1144 and mechanically fixed to the outer edge of the opening of the metallic shell 1144. The first side electrode 1162 and the second side electrode 1164 extend to the axial front end side, bend in the middle, and extend to the radial center side. The gap lengths of the primary discharge gap 1200 and the secondary discharge gap 1202 are adjusted according to the length, shape, and the like of the first side electrode 1162 and the second side electrode 1164. The vicinity of the tips of the first side electrode 1162 and the second side electrode 1164 is a discharge end 1182 and a discharge end 1184 that are the start point or end point of discharge, respectively.

(Preferred arrangement of side electrodes)
The first side electrode 1162 is disposed so as not to overlap the primary discharge gap 1200 when viewed from the downstream side of the air-fuel mixture flow 1210. Further, the second side electrode 1164 is disposed so as not to overlap the secondary discharge gap 1202 when viewed from the downstream side of the air-fuel mixture flow 1210. As a result, the first side electrode 1162 and the second side electrode 1164 do not hinder the propagation of plasma, and the flame spreads greatly.

  However, as shown in the schematic diagram (perspective view) of FIG. 10, the first side electrode 1162a overlaps the first discharge gap when viewed from the downstream side of the mixture flow 1210a, and the downstream of the mixture flow 1210a. Even when the second side electrode 1164a is overlapped with the second discharge gap when viewed from the side, the effect that the flame spreads is not completely lost.

(Deformation of electrode structure)
As long as the gap length of the secondary discharge gap 1202 is longer than the gap length of the primary discharge gap 1200, the center electrode 1160 is disposed as long as the secondary discharge gap 1202 is disposed downstream of the primary discharge gap 1200. The structure, arrangement, number, and the like of the first side electrode 1162 and the second side electrode 1164 may be changed.

(Metal fitting)
A round hole is formed in the metal shell 1144. A center electrode 1160, an insulator 1142, and the like are accommodated inside the round hole. The metal shell 1144 may be replaced with a shape that is difficult to call the “metal metal fitting”. For example, the metallic shell 1144 may be replaced with a three-dimensional object such as a plate, a rod, or a rectangular parallelepiped having a round hole. The round hole may be replaced with a hole having another shape.

(Material)
The insulator 1142 is made of ceramic, resin, or the like. As the ceramic, alumina, zirconia or the like is employed. As the resin, vinyl chloride resin, fluororesin or the like is employed.

  The center electrode 1160, the first side electrode 1162, the second side electrode 1164, and the metal shell 1144 are made of a conductor. As the conductor, a metal such as platinum may be employed, an alloy such as stainless steel or nickel alloy may be employed, or conductive ceramics may be employed.

(engine)
The engine 1000 is preferably a reciprocating engine. The reciprocating engine may be either a 4-cycle engine or a 2-cycle engine. However, the engine 1000 may be other than the reciprocating engine. For example, the engine 1000 may be a rotary engine. The engine 1000 may be a gas engine.

  Engine 1000 is typically incorporated into a vehicle. However, the engine 1000 may be incorporated in a transport machine other than an automobile. For example, the engine 1000 may be incorporated in a railway vehicle, an industrial vehicle, a ship, an aircraft, a spacecraft, or the like. The engine 1000 may be incorporated in a machine other than the transport machine. For example, the engine 1000 may be incorporated in a tool, a farm tool, an engine generator, or the like.

(Mixture)
The air-fuel mixture is a mixture of air and fuel oil. The air-fuel mixture may be a mixture of air and combustible gas. For example, the air-fuel mixture may be a mixture of air and hydrogen gas, propane gas, butane gas, or the like. The combustible gas may be a mixture.

  Air may be replaced with other types of flammable gases. For example, air may be replaced with oxygen. The fuel oil may be replaced with other types of flammable liquids. For example, the fuel oil may be replaced with methanol.

  The air-fuel mixture is typically depressurized, but may be pressurized. The pressure of the air-fuel mixture may be atmospheric pressure.

{Second Embodiment}
(Outline)
The second embodiment relates to a plug that replaces the plug of the first embodiment. In the first embodiment, the gap length of the discharge gap is expanded in two stages. In the second embodiment, the gap length of the discharge gap is expanded in three stages. The configuration of the other embodiment may be adopted in the second embodiment as it is or after being modified.

(Plug component)
The schematic diagrams from FIG. 11 to FIG. 13 are a perspective view, a plan view, and a side view of the plug of the second embodiment, respectively.

  As shown in FIGS. 11 to 13, the plug 2040 includes an electrode structure 2140, an insulator 2142, and a metal shell 2144. The electrode structure 2140 includes a center electrode 2160, a first side electrode 2162, a second side electrode 2164, and a third side electrode 2166. A primary discharge gap 2200 is formed between the discharge end 2180 of the center electrode 2160 and the discharge end 2182 of the first side electrode 2162 (see FIGS. 12 and 13). A secondary discharge gap 2202 is formed between the discharge end 2180 of the center electrode 2160 and the discharge end 2184 of the second side electrode 2164. A tertiary discharge gap 2204 is formed between the discharge end 2180 of the center electrode 2160 and the discharge end 2186 of the third side electrode 2166.

(Gap length)
The center electrode 2160, the first discharge electrode 2202, the first discharge gap 2202 have a gap length longer than the primary discharge gap 2200, and the tertiary discharge gap 2204 has a gap length longer than the secondary discharge gap 2202. The side electrode 2162, the second side electrode 2164, and the third side electrode 2166 are arranged.

(Disposition of discharge gap)
In the plug 2040, the secondary discharge gap 2202 is arranged downstream of the primary discharge gap 2200 in the mixture flow 1210, and the tertiary discharge gap 2204 is arranged downstream of the secondary discharge gap 2202 in the mixture flow 1210. To the combustion vessel 1020. Therefore, when intake is performed by the intake mechanism 1022, a mixture flow 1210 flows from the primary discharge gap 2200 to the secondary discharge gap 2202 and then flows from the secondary discharge gap 2202 to the tertiary discharge gap 2204. .

(Ignition flow to mixture)
As in the case of the first embodiment, primary discharge is generated in the primary discharge gap 2200 in a state where the air-fuel mixture flow 1210 is generated. Primary plasma is generated in the primary discharge gap 2200 by the primary discharge. The primary plasma may be a flame or may not be a flame. A portion that is in flame and a portion that is not in flame may coexist in the primary plasma. The primary plasma propagates along the mixture flow 1210 to the secondary discharge gap 2202. When the primary plasma that is not in flame is propagated to the secondary discharge gap 2202, when the primary discharge occurs, the air-fuel mixture does not have to exist in the primary discharge gap 2200, and the gas is not air-fuel mixture such as air. The primary plasma may propagate up to the primary discharge gap 2200 along the flow of. When primary plasma is present in the secondary discharge gap 2202, secondary discharge is generated in the secondary discharge gap 2202. In the case where a portion that is in flame and a portion that is not in flame coexist in the primary plasma, secondary discharge may occur when the portion that is in flame exists in the secondary discharge gap 2202. In addition, secondary discharge may occur when a portion that is not flame exists in the secondary discharge gap 2202. Secondary plasma is generated in the secondary discharge gap 2202 by the secondary discharge. The secondary plasma may be a flame or may not be a flame. A portion that is in flame and a portion that is not in flame may coexist in the secondary plasma.

  Further, as shown in the schematic diagram (plan view) of FIG. 14, the secondary plasma 2242 propagates to the tertiary discharge gap 2204 along the mixture flow 1210.

  As shown in FIG. 15, when the secondary plasma 2242 exists in the tertiary discharge gap 2204, the tertiary discharge 2224 is generated in the tertiary discharge gap 2204. A tertiary plasma 2244 is generated in the tertiary discharge gap 2204 by the tertiary discharge 2224. A flame is induced simultaneously with the generation of the tertiary plasma 2244 or after the generation of the tertiary plasma 2244, and the mixture is ignited. In the case where the flame is induced with a delay from the generation of the tertiary plasma 2244, the air-fuel mixture may not exist in the tertiary discharge gap 2204 when the tertiary discharge 2224 is generated. It is sufficient that the air-fuel mixture exists at the position where the flame is triggered when the flame is finally triggered.

  As a result, discharge occurs in the discharge gap having a long gap length, and the flame spreads greatly. The discharge gap may be expanded in four or more stages.

(Pulse voltage waveform)
The schematic diagram of FIG. 16 shows the waveform of the pulse voltage applied when the air-fuel mixture is ignited by the plug of the second embodiment.

  As shown in FIG. 16, the secondary pulse voltage 2262 is applied to the plug 2040 after the primary pulse voltage 2260, and the tertiary pulse voltage 2264 is applied to the plug 2040 after the secondary pulse voltage 2262. Primary pulse voltage 2260 generates a primary discharge in primary discharge gap 2200. The secondary pulse voltage 2262 generates a secondary discharge in the secondary discharge gap 2202. The tertiary pulse voltage 2264 generates a tertiary discharge 2224 in the tertiary discharge gap 2204. A secondary pulse voltage 2262 is applied to the plug 2040 when the primary plasma is present in the secondary discharge gap 2202. A tertiary pulse voltage 2264 is applied to the plug 2040 when secondary plasma is present in the tertiary discharge gap 2204.

(Preferred arrangement of side electrodes)
The first side electrode 2162 is disposed so as not to overlap the primary discharge gap 2200 when viewed from the downstream side of the air-fuel mixture flow 1210. Further, the second side electrode 2164 is arranged so as not to overlap the secondary discharge gap 2202 when viewed from the downstream side of the air-fuel mixture flow 1210. Further, the third side electrode 2166 is arranged so as not to overlap the tertiary discharge gap 2204 when viewed from the downstream side of the air-fuel mixture flow 1210. As a result, the first side electrode 2162, the second side electrode 2164, and the third side electrode 2166 do not hinder the propagation of the plasma, and the flame spreads greatly.

{Third embodiment}
(Outline)
The third embodiment relates to a plug that replaces the plug of the first embodiment. In the first embodiment, one discharge end is provided on the center electrode, but in the third embodiment, two discharge ends are provided on the center electrode. The configuration of the other embodiment may be adopted in the third embodiment as it is or after being modified.

(Plug component)
The schematic diagrams from FIG. 17 to FIG. 19 are a perspective view, a plan view, and a side view of the plug of the third embodiment, respectively.

  As shown in FIGS. 17 to 19, the plug 3040 includes an electrode structure 3140, an insulator 3142, and a metal shell 3144. The electrode structure 3140 includes a center electrode 3160, a first side electrode 3162, and a second side electrode 3164. A primary discharge gap 3200 is formed between the first discharge end 3180 of the center electrode 3160 and the discharge end 3182 of the first side electrode 3162 (see FIGS. 18 and 19). A secondary discharge gap 3202 is formed between the second discharge end 3186 of the center electrode 3160 and the discharge end 3184 of the second side electrode 3164 (see FIGS. 18 and 19).

(Gap length)
The center electrode 3160, the first side electrode 3162, and the second side electrode 3164 are disposed so that the gap length of the secondary discharge gap 3202 is longer than the gap length of the primary discharge gap 3200.

(Disposition of discharge gap)
The plug 3040 is attached to the combustion vessel 1020 so that the secondary discharge gap 3202 is disposed downstream of the primary discharge gap 3200 in the flow of the air-fuel mixture. Therefore, when intake is performed by the intake mechanism 1022, a flow of air-fuel mixture that flows from the primary discharge gap 3200 to the secondary discharge gap 3202 is generated.

(Ignition flow to mixture)
As in the case of the first embodiment, primary discharge is generated in the primary discharge gap 3200 in a state where the air-fuel mixture flow 1210 is generated. Primary plasma is generated in the primary discharge gap 3200 by the primary discharge. The primary plasma propagates to the secondary discharge gap 3202 along the mixture flow 1210. When the primary plasma is present in the secondary discharge gap 3202, secondary discharge is generated in the secondary discharge gap 3202. Secondary plasma is generated in the secondary discharge gap 3202 by the secondary discharge. A flame is induced simultaneously with the generation of the secondary plasma or after the generation of the secondary plasma, and the mixture is ignited.

  As a result, discharge occurs in the discharge gap having a long gap length, and the flame spreads greatly.

(Center electrode)
The schematic diagram of FIG. 20 is a perspective view of the center electrode of the third embodiment.

  As shown in FIG. 20, the center electrode 3160 of the third embodiment has a structure in which a first semi-cylindrical body 3280 and a second semi-cylindrical body 3282 are joined. The flat side surface of the first semi-cylindrical body 3280 and the flat side surface of the second semi-cylindrical body 3282 are joined. The vicinity of the upper surface of the first semi-cylindrical body 3280 becomes the first discharge end 3180, and the vicinity of the upper surface of the second semi-cylindrical body 3282 becomes the second discharge end 3186. The first discharge end 3180 protrudes from the second discharge end 3186 to the front end side in the axial direction. The central electrode 3160 is formed with a step in the axial direction by a combination of columns having different heights, and two or more discharge ends are formed. The column is not limited to a semi-cylindrical body. Further, the curved side surface 3200 of the first semi-cylindrical body 3280 is directed to the first side electrode 3162 side, and the curved side surface 3202 of the second semi-cylindrical body 3282 is directed to the second side electrode 3164 side. It is done. Accordingly, the gap length of the secondary discharge gap 3202 becomes longer than the gap length of the primary discharge gap 3200.

{Fourth embodiment}
(Outline)
The fourth embodiment relates to a plug that replaces the plug of the first embodiment. In the first embodiment, one primary discharge gap and one secondary discharge gap are formed. In the fourth embodiment, one primary discharge gap is formed and two secondary discharge gaps are formed. . The configuration of the other embodiment may be employed in the fourth embodiment as it is or after being modified.

(Plug component)
The schematic diagrams from FIG. 21 to FIG. 23 are a perspective view, a plan view, and a side view of the plug of the fourth embodiment, respectively.

  As shown in FIGS. 21 to 23, the plug 4040 includes an electrode structure 4140, an insulator 4142, and a metal shell 4144. The electrode structure 4140 includes a center electrode 4160, a first side electrode 4162, a second side electrode 4164, and a third side electrode 4166. A primary discharge gap 4200 is formed between the discharge end 4180 of the center electrode 4160 and the discharge end 4182 of the first side electrode 4162 (see FIG. 22). A first secondary discharge gap 4202 is formed between the discharge end 4180 of the center electrode 4160 and the discharge end 4184 of the second side electrode 4164 (see FIG. 22). A second secondary discharge gap 4204 is formed between the discharge end 4180 of the center electrode 4160 and the discharge end 4186 of the third side electrode 4166 (see FIG. 22).

(Gap length)
The center electrode 4160, the first side electrode 4162, and the second electrode are so arranged that the gap length of the first secondary discharge gap 4202 and the second secondary discharge gap 4204 is longer than the gap length of the primary discharge gap 4200. Side electrode 4164 and third side electrode 4166 are arranged. The gap length of the first secondary discharge gap 4202 and the gap length of the second secondary discharge gap 4204 are the same.

(Disposition of discharge gap)
The plug 4040 is attached to the combustion vessel 1020 such that the first secondary discharge gap 4202 and the second secondary discharge gap 4204 are arranged downstream of the primary discharge gap 4200 in the air-fuel mixture flow 1210. Therefore, when intake is performed by the intake mechanism 1022, an air-fuel mixture flow 1210 flows from the primary discharge gap 4200 to the first secondary discharge gap 4202 and the second secondary discharge gap 4204.

(Ignition flow to mixture)
As in the case of the first embodiment, primary discharge is generated in the primary discharge gap 4200 in a state where the air-fuel mixture flow 1210 is generated. Primary plasma is generated in the primary discharge gap 4200 by the primary discharge. The primary plasma propagates along the mixture flow 1210 to the first secondary discharge gap 4202 and the second secondary discharge gap 4204. When primary plasma is present in the first secondary discharge gap 4202 and the second secondary discharge gap 4204, secondary discharge is generated in the first secondary discharge gap 4202 and the second secondary discharge gap 4204. Then, secondary plasma is generated in the first secondary discharge gap 4202 and the second secondary discharge gap 4204 by the secondary discharge. A flame is induced simultaneously with the generation of the secondary plasma or after the generation of the secondary plasma, and the mixture is ignited.

  Thereby, it becomes easy to generate | occur | produce discharge in the discharge gap with a long gap length, and a flame spreads large.

  The number of primary discharge gaps is one, and the number of secondary discharge gaps is two. The number of primary discharge gaps may be two or more. The number of secondary discharge gaps may be three or more. Generally speaking, two or more primary discharge gaps and / or secondary discharge gaps may be formed.

{Fifth embodiment}
The fifth embodiment relates to a plug that replaces the plug of the first embodiment. In the first embodiment, the side electrode is a ground electrode, but in the fifth embodiment, the side electrode is a floating electrode. The configuration of the other embodiment may be employed in the fifth embodiment as it is or after being modified.

(Plug component)
The schematic views of FIGS. 24 and 25 are a perspective view and a plan view, respectively, of the plug of the fifth embodiment.

  As shown in FIGS. 24 and 25, the plug 5040 includes an electrode structure 5140, an insulator 5142, and a metal shell 5144. The electrode structure 5140 includes a center electrode 5160, a first side electrode 5162, and a second side electrode 5164. A primary discharge gap 5200 is formed between the discharge end 5180 of the center electrode 5160 and the discharge end 5182 of the first side electrode 5162 (see FIG. 25). A secondary discharge gap 5202 is formed between the discharge end 5180 of the center electrode 5160 and the discharge end 5184 of the second side electrode 5164 (see FIG. 25).

(Gap length)
The center electrode 5160, the first side electrode 5162, and the second side electrode 5164 are arranged so that the gap length of the secondary discharge gap 5202 is longer than the gap length of the primary discharge gap 5200.

(Disposition of discharge gap)
Plug 5040 is attached to combustion vessel 1020 such that secondary discharge gap 5202 is arranged downstream of primary discharge gap 5200 in mixture flow 1210. Therefore, when intake is performed by the intake mechanism 1022, an air-fuel mixture flow 1210 flowing from the primary discharge gap 5200 to the secondary discharge gap 5202 is generated.

(Floating electrode)
The first side electrode 5162 and the second side electrode 5164 are electrically insulated from the metal shell 5144 and the center electrode 5160. In this case, when the pulse generation circuit 1100 generates a pulse voltage between the positive electrode 1120 and the negative electrode 1122, the pulse voltage is applied between the center electrode 5160 of the plug 5040 and the metal shell 5144, and the center electrode 5160 A pulse voltage is induced between the first side electrode 5162 and the first side electrode 5162, and a pulse voltage is induced between the center electrode 5160 and the second side electrode 5164. The induced pulse voltage generates a primary discharge in the primary discharge gap 5200 and a secondary discharge in the secondary discharge gap 5202.

  Desirably, the first side electrode 5162 and the second side electrode 5164 are electrically insulated. Accordingly, the potential of the first side electrode 5162 and the potential of the second side electrode 5164 are independent, and the generation of the primary discharge and the secondary discharge can be easily controlled. However, the first side electrode 5162 and the second side electrode 5164 may be electrically connected.

(Ignition flow to mixture)
As in the case of the first embodiment, primary discharge is generated in the primary discharge gap 5200 in a state where the air-fuel mixture flow 1210 is generated. Primary plasma is generated in the primary discharge gap 5200 by the primary discharge. The primary plasma propagates to the secondary discharge gap 5202 along the mixture flow 1210. When the primary plasma is present in the secondary discharge gap 5202, secondary discharge is generated in the secondary discharge gap 5202. Secondary plasma is generated in the secondary discharge gap 5202 by the secondary discharge. A flame is induced simultaneously with the generation of the secondary plasma or after the generation of the secondary plasma, and the mixture is ignited.

  While the invention has been shown and described in detail, the above description is illustrative in all aspects and not restrictive. Thus, it will be appreciated that numerous modifications and variations can be devised without departing from the scope of the invention.

1000 Engine 1020 Combustion vessel 1022 Intake mechanism 1026 Pulse voltage application mechanism 1080 Combustion chamber 1140, 2140, 3140, 4140, 5140 Electrode structure 1200, 2200, 3200, 4200, 5200 Primary discharge gap 1202, 2202, 3202, 4202, 4204 5202 Secondary discharge gap 2204 Tertiary discharge gap

Claims (9)

An ignition method for igniting an air-fuel mixture,
(a) An electrode structure in which an n-1 primary discharge gap and an n primary discharge gap are formed, and the gap length of the n primary discharge gap is longer than the gap length of the n-1 primary discharge gap, assuming that n is a natural number of 2 or more. Generating a flow of gas flowing from the n-1 primary discharge gap to the n order discharge gap in the combustion chamber where
(b) generating n-1 primary plasma in the n-1 primary discharge gap and generating n-1 primary plasma in the n-1 primary discharge gap in a state where the gas flow is generated; ,
(c) propagating the n−1 primary plasma to the n order discharge gap on the gas flow;
(d) generating an n-order discharge in the n-order discharge gap and generating an n-order plasma in the n-order discharge gap when the n-first order plasma is present in the n-order discharge gap;
(e) inducing a flame in the mixture simultaneously with the step (d) or after the step (d);
An ignition method comprising: An ignition device for igniting an air-fuel mixture,
Provided with an electrode structure, assuming that n is a natural number greater than or equal to 2, an n-1 primary discharge gap and an n primary discharge gap are formed in the electrode structure, and a gap length of the n primary discharge gap is the n-1 primary discharge gap. A plug that is longer than the gap length of the gas flow, and the n-th order discharge gap is disposed downstream of the n-first order discharge gap in the gas flow;
An n-th order pulse voltage for generating an n-th order discharge in the n-th order discharge gap is applied to the plug after an n-first order pulse voltage for generating an n-th order discharge in the n-first order discharge gap, and the n- When the n-1 primary plasma generated in the n-1 primary discharge gap by the primary discharge and propagated to the n primary discharge gap along the gas flow exists in the n primary discharge gap, the n primary pulse is generated. A pulse voltage application mechanism configured to apply a voltage to the plug;
An ignition device comprising: The ignition device of claim 2,
The electrode structure is
A center electrode having a first discharge end;
A first side electrode having a second discharge end, wherein the n-1 primary discharge gap is formed between the first discharge end and the second discharge end;
A second side electrode having a third discharge end, wherein the n-th order discharge gap is formed between the first discharge end and the third discharge end;
An ignition device comprising: The ignition device of claim 2,
The electrode structure is
A center electrode having a first discharge end and a second discharge end;
A first side electrode having a third discharge end, wherein the n-1 primary discharge gap is formed between the first discharge end and the third discharge end;
A second side electrode having a fourth discharge end, wherein the n-th order discharge gap is formed between the second discharge end and the fourth discharge end;
An ignition device comprising: The ignition device according to claim 3 or claim 4,
The first side electrode is
Arranged so as not to overlap the n-1 primary discharge gap when viewed from the downstream side of the gas flow,
The second side electrode is
An ignition device disposed so as not to overlap the n-th order discharge gap when viewed from the downstream side of the gas flow. The ignition device according to any one of claims 2 to 5,
An n-2 secondary discharge gap is further formed in the electrode structure, a gap length of the n-1 primary discharge gap is longer than a gap length of the n-2 secondary discharge gap, and the n-1 primary discharge gap is the n- It is arranged downstream of the gas flow with respect to the secondary discharge gap,
The pulse voltage application mechanism is:
An n-2 secondary pulse voltage for generating an n-2 secondary discharge in the n-2 secondary discharge gap is applied to the plug before the n-1 secondary pulse voltage, and the n-2 secondary discharge causes the n-2 secondary discharge to occur. When the n-2nd plasma generated in the secondary discharge gap and propagating to the n-1 primary discharge gap along the gas flow is present in the n-1 primary discharge gap, the n-1 primary pulse is generated. An igniter configured to apply a voltage to the plug. The ignition device according to any one of claims 2 to 6,
An ignition device in which at least two or more of the n−1 primary discharge gap and the n primary discharge gap are formed. The ignition device according to any one of claims 2 to 7,
An ignition device in which the pulse voltage application mechanism is configured such that the power supplied by the n-th order pulse voltage is less than the power supplied by the n-1 order pulse voltage. An engine,
A combustion vessel in which a combustion chamber is formed;
A flow generating mechanism for generating a gas flow in the combustion chamber;
Provided with an electrode structure exposed to the combustion chamber, and n is a natural number of 2 or more, an n−1 primary discharge gap and an n order discharge gap are formed in the electrode structure, and a gap length of the n order discharge gap is n A plug that is longer than a gap length of a primary discharge gap, and the n-th order discharge gap is disposed downstream of the n-first order discharge gap in the gas flow;
An n-th order pulse voltage for generating an n-th order discharge in the n-th order discharge gap is applied to the plug after an n-first order pulse voltage for generating an n-th order discharge in the n-first order discharge gap, and the n- When the n-1 primary plasma generated in the n-1 primary discharge gap by the primary discharge and propagated to the n primary discharge gap along the gas flow exists in the n primary discharge gap, the n primary pulse is generated. A pulse voltage application mechanism configured to apply a voltage to the plug;
An engine with

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