JP2015158164A - Ignition device for internal combustion engine - Google Patents

Abstract

An ignition device capable of igniting a wider range by forming plasma in a wider range in a combustion chamber.
An electromagnetic wave generating power source generates microwaves that can resonate within a combustion chamber. The microwave radiator 20 is disposed so as to face the combustion chamber 108, and radiates the microwave generated by the electromagnetic wave generation power source 60 toward the combustion chamber 108. The charge supply device 30 supplies charge into the combustion chamber 108 so as to cross the electric field vector of the electric field formed by the microwave radiated from the microwave radiator 20. As a result, the electric charge moves by the action of the electromagnetic force of the microwave, so that microwave plasma is formed in a wider range, and the lean air-fuel mixture is ignited over a wider range.
[Selection] Figure 1

Description

  The present invention relates to an ignition device for an internal combustion engine, and more particularly to an ignition device for igniting an air-fuel mixture in a combustion chamber by using electromagnetic waves.

  As an ignition device for an internal combustion engine, an ignition device that ignites an air-fuel mixture in a combustion chamber by using an electromagnetic wave such as a microwave having a frequency of several GHz is known.

  Patent Document 1 discloses an ignition device in which a microwave radiation antenna is provided at a position facing the top surface of a piston. By radiating microwaves from the microwave radiation antenna into the combustion chamber, the air-fuel mixture in the combustion chamber is ignited.

  Patent Document 2 discloses an internal combustion engine that uses an engine combustion chamber as a microwave resonator.

  Patent Document 3 discloses an apparatus that expands plasma by irradiating laser-induced plasma with microwaves.

JP 2007-113570 A JP 2000-230426 A JP 2009-70586 A

  By the way, in an internal combustion engine, improvement in combustion efficiency is desired. In order to improve the combustion efficiency, it is conceivable to ignite the air-fuel mixture in a wide range by forming plasma in a wide range in the combustion chamber. In any of Patent Documents 1 to 3, it is difficult to form plasma over a wide range in the combustion chamber.

  An object of the present invention is to provide an ignition device capable of forming a plasma in a wider range in a combustion chamber and performing a wider range of ignition.

  The invention according to claim 1 is an ignition device for an internal combustion engine that ignites an air-fuel mixture in a combustion chamber, and is disposed in a state facing the combustion chamber, electromagnetic wave generating means for generating an electromagnetic wave that can resonate in the combustion chamber, An electromagnetic wave radiator that radiates an electromagnetic wave generated by the electromagnetic wave generation means toward the combustion chamber, and an electric charge in the combustion chamber so as to cross an electric field vector of an electric field formed by the electromagnetic wave radiated from the electromagnetic wave radiator. An internal combustion engine ignition device.

  According to a second aspect of the present invention, in the ignition device for an internal combustion engine according to the first aspect, the charge supply means supplies a charge by laser light.

  According to a third aspect of the present invention, in the ignition device for an internal combustion engine according to the second aspect, a tip portion of the electromagnetic wave radiator protrudes into the combustion chamber, and the charge supply means is connected to the electromagnetic wave radiator. Charge is generated in the combustion chamber by irradiating the tip with laser light.

  The invention according to claim 4 is the ignition device for an internal combustion engine according to claim 2, wherein an electric field concentration electrode for locally increasing the electric field strength in the combustion chamber is provided in the combustion chamber, The charge supply means generates a charge in the combustion chamber by irradiating a tip of the electric field concentration electrode with a laser beam.

  According to a fifth aspect of the present invention, in the ignition device for an internal combustion engine according to the first aspect, the charge supply means supplies a charge into the combustion chamber by a torch-like plasma.

  According to a sixth aspect of the present invention, in the ignition device for an internal combustion engine according to the first aspect, the charge supply means supplies a charge into the combustion chamber by spark discharge.

  According to the present invention, by supplying a charge into the combustion chamber so as to cross the electric field vector, the charge moves along the electric field vector and is distributed so as to cross the electric field vector, so that plasma can be formed in a wide range. It becomes possible. As a result, the air-fuel mixture can be ignited over a wider range.

1 is a diagram showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. It is a schematic diagram which shows electric field distribution in a combustion chamber. It is a graph which shows the frequency and reflectance of a microwave. It is a schematic diagram which shows electric field distribution in a combustion chamber. It is a schematic diagram for demonstrating the effect | action which an electric field exerts on an electric charge. 1 is a diagram illustrating a schematic configuration of a charge supply device according to a first embodiment. It is a graph for demonstrating the supply timing of a microwave and a laser beam. It is a schematic diagram which shows the behavior of an electric charge. It is a schematic diagram which shows the behavior of an electric charge. It is a schematic diagram which shows the plasma formed in the combustion chamber. FIG. 3 is a diagram illustrating a schematic configuration of an internal combustion engine according to a second embodiment. 6 is a schematic diagram showing an electric field distribution according to Example 2. FIG. It is a schematic diagram which shows the plasma formed in the combustion chamber. It is a graph which shows the relationship between a laser energy and the light emission area of a plasma. FIG. 6 is a diagram illustrating a schematic configuration of a charge supply device according to a third embodiment. FIG. 10 is a diagram illustrating a schematic configuration of a charge supply device according to a fourth embodiment. FIG. 10 is a diagram illustrating a schematic configuration of a charge supply device according to a fifth embodiment. FIG. 10 is a diagram illustrating a schematic configuration of a charge supply device according to a sixth embodiment.

  FIG. 1 shows an example of an internal combustion engine according to an embodiment of the present invention. In the internal combustion engine 100 according to the present embodiment, the air-fuel mixture in the combustion chamber 108 is ignited using electromagnetic waves such as microwaves.

  The internal combustion engine 100 includes a cylinder head 102, a cylinder 104, a combustion chamber 108 formed by the cylinder 104 and the piston 106, an intake valve 112 that opens and closes an intake port 110 provided in the cylinder head 102, and a cylinder head 102. An exhaust valve 116 that opens and closes the provided exhaust port 114 and a fuel injection valve 118 are included. In the intake process, the intake valve 112 is opened and the piston 106 is lowered to introduce intake gas into the combustion chamber 108 from the intake port 110. By disposing the fuel injection valve 118 so as to face the intake port 110, fuel is injected into the intake port 110, so that the air-fuel mixture is introduced into the combustion chamber 108. In the compression process, the intake valve 112 is closed, and the air-fuel mixture is compressed by raising the piston 106. The ignition device 10 ignites the air-fuel mixture in the combustion chamber 108 by radiating electromagnetic waves such as microwaves into the combustion chamber 108. The gas after combustion is discharged to the exhaust port 114 when the exhaust valve 116 is opened in the exhaust process.

  The ignition device 10 includes a microwave radiator 20 as an electromagnetic wave propagation means, a charge supply device 30, an electromagnetic wave generation power source 60, a control device 62, and an electromagnetic wave transmission path 64. The electromagnetic wave generation power source 60 is configured by, for example, a magnetron, a traveling wave amplifier tube, a solid oscillation element, or the like, and generates an electromagnetic wave such as a microwave. The control device 62 controls the output (electric power) by controlling at least one of the height and width of the microwave pulse generated by the electromagnetic wave generating power source 60. The electromagnetic wave generation power source 60 outputs a microwave pulse at the timing of igniting the air-fuel mixture in the combustion chamber 108, and the output microwave pulse propagates through the electromagnetic wave transmission path 64. The electromagnetic wave transmission path 64 is configured by, for example, a coaxial cable or a waveguide. A microwave radiator 20 is provided at the end of the electromagnetic wave transmission path 64 so as to face the combustion chamber 108. As an example, the microwave radiator 20 is disposed at the center of the upper surface of the combustion chamber 108. The microwave radiator 20 radiates the microwave generated by the electromagnetic wave generation power source 60 and propagated through the electromagnetic wave transmission path 64 into the combustion chamber 108. The charge supply device 30 is disposed in the vicinity of the microwave radiator 20 on the upper surface of the combustion chamber 108 and generates charges in the combustion chamber 108. In addition, although the electromagnetic waves used for ignition of the air-fuel mixture are not limited to microwaves, an example using microwaves will be described below as an example.

  FIG. 2 shows an example of the microwave radiator 20. In FIG. 2, the charge supply device 30 is omitted. The microwave radiator 20 has a coaxial structure constituted by an outer conductor 22 and an inner conductor 24. The outer conductor 22 has a cylindrical shape and is grounded. The inner conductor 24 has a columnar shape and is disposed in the outer conductor 22 along the central axis of the outer conductor 22. A dielectric 26 is disposed between the outer conductor 22 and the inner conductor 24. The dielectric 26 may be air or a solid substance. The microwave radiator 20 is disposed in the cylinder head 102 with the open end of the outer conductor 22 facing the combustion chamber 108. As shown in FIGS. 1 and 2, the tip 24a of the inner conductor 24 protrudes into the combustion chamber 108, and the inner conductor 24 functions as an antenna electrode. An electromagnetic wave such as a microwave supplied to the microwave radiator 20 via the electromagnetic wave transmission path 64 propagates between the outer conductor 22 and the inner conductor 24 and is radiated into the combustion chamber 108.

  In the combustion chamber 108, a microwave having a predetermined frequency resonates in a predetermined resonance mode. The electromagnetic wave generating power source 60 generates a microwave having a frequency that resonates in the combustion chamber 108 based on the control of the control device 62. In a state where the microwave is resonating in the combustion chamber 108, the reflection of the microwave energy is small, and most of the microwave energy is stored in the combustion chamber 108.

FIG. 3 shows the relationship between the microwave frequency and the reflectance. As an example, TM ₀₁₀ mode resonance will be described. When a microwave having a frequency (for example, resonance frequency: 2.48 GHz) at which the reflectance of the microwave is lowest in the combustion chamber 108 is supplied into the combustion chamber 108, a high electric field region is formed in the combustion chamber 108. The reflectance indicates an index of microwave incident energy into the combustion chamber 108, and the lower the reflectance level, the greater the microwave incident energy into the combustion chamber 108. Note that the resonance frequency of the microwave in the combustion chamber 108 varies depending on the shape, size, conductivity, resonator Q value, and the like of the combustion chamber 108. In the present embodiment, as an example, the combustion chamber 108 has a cylindrical shape.

  FIG. 2 shows the distribution of the electric field formed in the combustion chamber 108 by the supply of microwaves. The central portion is highest in the radial direction (lateral direction) of the combustion chamber 108, gradually decreases toward the peripheral portion (outside in the radial direction), and is lowest at a certain position.

  FIG. 4 shows the electric field vector in the combustion chamber 108. The direction of the electric field vector is basically perpendicular to the upper and lower surfaces of the combustion chamber 108, but on the side surface of the front end portion 24a of the inner conductor 24 (the front end portion of the antenna electrode), the radial direction (lateral direction) of the combustion chamber 108 ) Component is added, so that it tilts in the radial direction from the vertical direction. Note that the magnitude of the electric field vector changes depending on the phase of the microwave, but the gradient (angle) of the electric field vector does not change. When the phase is shifted 180 degrees, the direction of the electric field vector is reversed.

  In this embodiment, an electric field is formed in the combustion chamber 108 by supplying microwaves into the combustion chamber 108, and charges are generated in the combustion chamber 108 by the charge supply device 30 so as to cross the electric field vector of the electric field. . Thereby, in the combustion chamber 108, plasma is formed in a wider area, and the air-fuel mixture can be ignited over a wider area.

  This phenomenon will be described in detail with reference to FIG. Assume that an electric field E is formed between the electrodes as shown in FIGS. As shown in FIG. 5A, when a charge q is supplied under the electric field E, the charge q receives a force F proportional to the electric field E (F = q · E) and moves along the electric field vector. A plasma is formed along the direction of movement. Then, as shown in FIG. 5B, when the charge q is supplied so as to cross the electric field vector, the charge q moves in parallel on the electric field vector, so that the plasma formation range is expanded. On the other hand, as shown in FIG. 5C, when the charge q is supplied along the electric field vector, the charge q moves in series on the electric field vector, so that the spread of the plasma is restricted. In the present embodiment, as shown in FIG. 5B, it is possible to form plasma in a wider area in the combustion chamber 108 by supplying electric charge into the combustion chamber 108 so as to cross the electric field vector. It becomes.

  FIG. 6 shows a charge supply device 30 according to the first embodiment. The charge supply device 30 according to the first embodiment is a laser spark plug that emits laser light. In the first embodiment, laser light is radiated from the charge supply device 30 to the tip 24 a of the inner conductor 24 (tip of the antenna electrode).

  With reference to FIG. 7, the supply timing of the microwave and the laser beam will be described. As an example, a microwave pulse having a peak power of 220 W is supplied from the microwave radiator 20 into the combustion chamber 108 at a desired ignition timing. In synchronization with the supply timing of the microwave pulse, a laser beam having an energy of 10 mJ is irradiated from the charge supply device 30 to the tip 24 a of the inner conductor 24. As an example, after supplying the microwave pulse, the laser beam is irradiated while the microwave pulse is being supplied. The tip 24a of the inner conductor 24 (the tip of the antenna electrode) is locally heated by the irradiation of the laser light, so that charges are released from the tip 24a toward the surrounding space as shown in FIG. . The electric charges (initial electrons) generated by the laser light irradiation exist so as to cross the electric field vector as shown in FIG. Since these charges move by the action of the electromagnetic force of the microwave, as shown in FIG. 10, as an example, a microwave plasma 200 having a width of about 5 mm is formed radially along the electric field vector. Thus, the lean air-fuel mixture is ignited over a wider range by the microwave plasma 200 formed in a wide area. As a result, it is possible to promote the initial combustion at the time of lean fuel and improve the engine fuel efficiency. As shown in FIG. 7, when laser light is applied, the reflection of microwaves increases, which is a phenomenon associated with the formation of plasma.

  Next, Example 2 will be described with reference to FIG. In the second embodiment, the protrusion 40 functioning as an electric field concentration electrode is provided at a position facing the microwave radiator 20 at the center of the top surface of the piston 106 facing the combustion chamber 108. The protrusion 40 has a function of locally increasing the electric field strength in the combustion chamber 108 in the vicinity of the protrusion 40. In the vicinity of the protrusion 40, a high electric field of several tens to several hundred times the average electric field of the microwave in the combustion chamber 108 can be obtained. That is, the electric lines of force are perpendicularly incident on the metal surface, and the electric field strength increases at the metal edge having a small curvature, and the electric field strength increases as the curvature decreases. As shown in FIG. 11, the electric field distribution is highest in the central portion where the protrusions 40 are arranged, and becomes lower toward the peripheral portion (outside in the radial direction). Note that, by changing the width of the protrusion 40, the magnitude of the maximum electric field strength and the width of the high electric field region change. The maximum electric field strength increases as the width of the protrusion 40 decreases, and the maximum electric field strength decreases as the width of the protrusion 40 increases, but a high electric field is formed in a wider range in the radial direction of the combustion chamber 108.

  FIG. 12 shows an electric field vector in the combustion chamber 108. The direction of the electric field vector between the tip 24a of the inner conductor 24 and the protrusion 40 is perpendicular to the lower surface of the tip 24a. However, the combustion chamber is formed on each side surface of the tip 24a and the protrusion 40. Since 108 radial (lateral) components are added, it tilts in the radial direction from the vertical direction.

  In the second embodiment, as shown in FIG. 12, the tip of the protrusion 40 is irradiated with laser light from a charge supply device 30 (not shown). For example, as shown in FIG. 7, a microwave pulse having a peak power of 220 W is supplied from the microwave radiator 20 into the combustion chamber 108 at a desired ignition timing. In synchronization with the supply timing of the microwave pulse, a laser beam with an energy of 10 mJ is irradiated from the charge supply device 30 to the tip of the protrusion 40. Since the tip of the protrusion 40 is locally heated by the laser light irradiation, electric charges are discharged from the tip of the protrusion 40 toward the surrounding space. Charges (initial electrons) generated by laser light irradiation exist so as to cross the electric field vector. Since these electric charges move by the action of the electromagnetic force of the microwave, as shown in FIG. 13, for example, a microwave plasma 210 having a width of about 5 mm is formed in a curved shape along the electric field vector. Thus, the lean air-fuel mixture is ignited over a wider range by the microwave plasma 210 formed in a wide area. In the second embodiment as well, the laser beam may be applied to the tip 24a of the inner conductor 24 without irradiating the tip of the protrusion 40 with the laser beam.

  FIG. 14 shows the light emission area of the plasma formed by Example 2. FIG. 14 shows, as a comparative example, a light emission area of plasma formed by a spark ignition plug having a gap between electrodes of 1 mm. According to Example 2, the light emission area of plasma is larger than that of the comparative example. That is, according to Example 2, it is possible to form plasma in a wider range than in the comparative example. Note that as the energy of the irradiated laser beam increases, the amount of charge generated in the combustion chamber 108 increases, so that the area of the plasma to be formed increases accordingly.

  Next, Example 3 will be described with reference to FIG. In the third embodiment, a laser beam is irradiated from the charge supply device 30 to a high electric field portion formed in the vicinity of the front end portion 24 a of the inner conductor 24. As an example, a microwave pulse with a specified power is supplied from the microwave radiator 20 into the combustion chamber 108 at a desired ignition timing. In synchronism with the supply timing of the microwave pulse, a laser beam having an energy of about 50 mJ is irradiated from the charge supply device 30 to the vicinity (high electric field portion) of the front end portion 24 a of the inner conductor 24. Laser plasma is formed by this laser beam. The laser plasma is extended along the optical axis by extending the focal length of the laser light and irradiating the laser light so as to cross the electric field vector. That is, the laser beam is condensed linearly. The focal length is 150 mm or more as an example. The charge generated by the laser plasma exists across the electric field vector. Since these electric charges move by the action of the electromagnetic force of the microwave, a microwave plasma larger than the laser plasma is formed. Thus, the lean air-fuel mixture is ignited over a wider range by the microwave plasma formed in a wide area.

  Next, Example 4 will be described with reference to FIG. In the fourth embodiment, a charge supply device 30a is provided instead of the charge supply device 30 according to the first to third embodiments. The charge supply device 30 a is a plasma ignition plug, and forms a torch-like plasma in the combustion chamber 108. As an example, a microwave pulse with a specified power is supplied from the microwave radiator 20 into the combustion chamber 108 at a desired ignition timing. In synchronism with the supply timing of the microwave pulse, a torch-like plasma is formed in the vicinity of the front end portion 24a of the inner conductor 24 by the charge supply device 30a. Charges are generated across the electric field vector by a torch-like plasma. Since these charges move by the action of the electromagnetic force of the microwave, microwave plasma is formed in a wide area. The lean air-fuel mixture is ignited over a wider range by the microwave plasma thus formed.

  Next, Example 5 will be described with reference to FIG. In the fifth embodiment, a charge supply device 30b is provided instead of the charge supply devices 30 and 30a according to the first to fourth embodiments. The charge supply device 30b is a spark ignition plug that generates a DC discharge. The spark spark plug has a center electrode 32 and a ground electrode 34. The gap formed between the center electrode 32 and the ground electrode 34 is disposed in the vicinity of the tip 24a of the inner conductor 24 so as to be orthogonal to the electric field vector formed by the microwave.

  First, at a desired ignition timing, a microwave pulse with a specified power is supplied from the microwave radiator 20 into the combustion chamber 108. In synchronization with the supply timing of the microwave pulse, the charge supply device 30b generates a spark discharge between the center electrode 32 and the ground electrode 34 to generate charges. The electric charge generated by the spark discharge exists so as to cross the electric field vector. Since these charges move by the action of the electromagnetic force of the microwave, microwave plasma is formed in a wide area. The lean air-fuel mixture is ignited over a wider range by the microwave plasma thus formed.

  Next, Example 6 will be described with reference to FIG. In the sixth embodiment, a charge supply device 30b as a spark ignition plug is used. The gap formed between the center electrode 32 and the ground electrode 34 of the spark spark plug is disposed in the vicinity of the tip 24a of the inner conductor 24 along the direction of the electric field vector formed by the microwave.

  In the sixth embodiment, the electric charge supplied from the spark spark plug is distributed across the electric field vector by using the airflow flowing in the direction orthogonal to the electric field vector (the radial direction of the combustion chamber 108). For example, the electric charge is distributed across the electric field vector by flowing the airflow of the intake air of the engine in the radial direction of the combustion chamber 108.

  First, at a desired ignition timing, a microwave pulse with a specified power is supplied from the microwave radiator 20 into the combustion chamber 108. Synchronizing the supply timing of the microwave pulses, the charge supply device 30b generates a spark discharge between the center electrode 32 and the ground electrode 34 to generate charges. The spark discharge is extended in the radial direction by the airflow flowing in the radial direction (lateral direction) of the combustion chamber 108. Thereby, the electric charge generated by the spark discharge exists so as to cross the electric field vector. Since these charges move by the action of the electromagnetic force of the microwave, microwave plasma is formed in a wide area. The lean air-fuel mixture is ignited over a wider range by the microwave plasma thus formed.

  DESCRIPTION OF SYMBOLS 10 Ignition device, 20 Microwave radiator, 30, 30a, 30b Charge supply device, 22 Outer conductor, 24 Inner conductor, 24a Tip, 26 Dielectric, 32 Center electrode, 34 Ground electrode, 60 Electromagnetic wave generation power source, 62 Control Device, 64 Electromagnetic wave transmission path, 100 Internal combustion engine, 102 Cylinder head, 104 Cylinder, 106 Piston, 108 Combustion chamber, 110 Intake port, 112 Intake valve, 114 Exhaust port, 116 Exhaust valve, 118 Fuel injection valve

Claims (6)

In an ignition device for an internal combustion engine that ignites an air-fuel mixture in a combustion chamber,
Electromagnetic wave generating means for generating an electromagnetic wave that can resonate in the combustion chamber;
An electromagnetic wave emitter disposed in a state facing the combustion chamber, and radiating an electromagnetic wave generated by the electromagnetic wave generation means toward the combustion chamber;
Charge supply means for supplying charge into the combustion chamber so as to cross an electric field vector of an electric field formed by the electromagnetic wave radiated from the electromagnetic wave emitter;
An ignition device for an internal combustion engine, comprising: The ignition device for an internal combustion engine according to claim 1,
The charge supply means supplies charges by laser light;
An ignition device for an internal combustion engine. The internal combustion engine ignition device according to claim 2,
The tip of the electromagnetic wave emitter protrudes into the combustion chamber,
The charge supply means generates a charge in the combustion chamber by irradiating the tip of the electromagnetic wave radiator with a laser beam.
An ignition device for an internal combustion engine. The internal combustion engine ignition device according to claim 2,
An electric field concentration electrode for locally increasing the strength of the electric field in the combustion chamber is provided in the combustion chamber,
The charge supply means generates a charge in the combustion chamber by irradiating a laser beam to a tip of the electric field concentration electrode.
An ignition device for an internal combustion engine. The ignition device for an internal combustion engine according to claim 1,
The charge supply means supplies charge into the combustion chamber by torch-like plasma.
An ignition device for an internal combustion engine. The ignition device for an internal combustion engine according to claim 1,
The charge supply means supplies charge into the combustion chamber by spark discharge.
An ignition device for an internal combustion engine.

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