JP2013194717A - Antenna structure, high-frequency radiation plug, and internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce costs by separating a high-frequency transmission channel from a radiation antenna and by respectively improving the versatility of insertion holes, high-frequency transmission channels, and antenna structures to increase the amount of high-frequency radiation energy while preventing an antenna conductor from melting.SOLUTION: An antenna structure to radiate high frequency into the combustion chamber of an internal combustion engine includes: an end cap part that blocks the inside opening of a through-hole provided in an internal combustion engine for guiding high frequency into the combustion chamber of the internal combustion engine; a radiation antenna provided at the end cap part to radiate electromagnetic waves into the combustion chamber of the internal combustion engine; and a power feeding part which connects the radiation antenna with a high-frequency transmission channel provided inside the through-hole to supply the high frequency from the high-frequency transmission channel to the radiation antenna. The high-frequency transmission channel is detachably provided on the power feeding part to enable transmission of the high frequency.

Description

  The present invention relates to an antenna structure for radiating high frequency, a high frequency radiation plug including the antenna structure, and an internal combustion engine including the high frequency radiation plug.

  Conventionally, an antenna structure for radiating a high frequency is known. For example, Patent Document 1 discloses an internal combustion engine provided with this type of antenna structure.

  In the internal combustion engine described in Patent Document 1, an electromagnetic wave supply path is embedded in the cylinder head, and an end surface on the combustion chamber side of the electromagnetic wave supply path is a radiation antenna. The radiating antenna is covered with a dielectric.

JP 2010-96128 A

  By the way, in this kind of antenna structure, the insertion hole opened for the high-frequency transmission path must be adapted to the shape of the antenna structure integrated with the high-frequency transmission path, and there is a limit in versatility. Therefore, the cost has been increased.

  In addition, in the conventional antenna structure, when there is no multiple reflection of radio waves reflected from the cylinder of the internal combustion engine, the peak value of the electric field is lowered, so the plasma generation region is local, and the flame propagation promoting effect is achieved. It does not appear in the acupressure waveform and heat generation rate. There was a case that the flame propagation promoting effect was not seen. Thus, due to the lack of the peak electric field strength, the plasma expansion was unstable, and the radiation efficiency from the antenna was low.

  In the conventional antenna structure, the antenna conductor may be melted.

  The present invention has been made in view of such points, and the object thereof is to separate the high-frequency transmission path and the radiating antenna and improve the versatility of the insertion hole, the high-frequency transmission path, and the antenna structure. It is to reduce the cost.

  Another object is to increase the amount of high-frequency radiation energy while preventing the antenna conductor from being melted.

  1st invention is an antenna structure which radiates | emits a high frequency to the combustion chamber of an internal combustion engine, Comprising: The end cap part which plugs up the inner side opening of the insertion hole provided in the internal combustion engine in order to guide a high frequency to the combustion chamber of an internal combustion engine; The radiation antenna that radiates electromagnetic waves to the combustion chamber of the internal combustion engine, and the high-frequency transmission path provided inside the insertion hole and the radiation antenna are connected to each other, and a high frequency is supplied from the high-frequency transmission path to the radiation antenna. The high-frequency transmission line is provided so as to be detachable and capable of high-frequency transmission with respect to the power supply unit.

  According to the first invention, since the high-frequency transmission path is provided so as to be detachable and capable of high-frequency transmission with respect to the power feeding portion, the high-frequency transmission path and the radiation antenna can be separated, and the insertion hole, high-frequency transmission The cost can be reduced by improving the versatility of the road and the antenna structure.

1 is a longitudinal sectional view of an internal combustion engine according to an embodiment. It is a front view of the ceiling surface of the combustion chamber of the internal combustion engine which concerns on embodiment. It is a block diagram of the ignition device and electromagnetic wave radiation device concerning an embodiment. It is a conceptual diagram of the plug for high frequency radiation which concerns on embodiment. It is a front view of the radiation antenna concerning an embodiment. It is sectional drawing of the antenna structure which concerns on embodiment. It is sectional drawing of the antenna structure which concerns on other embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

The present embodiment is an internal combustion engine 10 according to the present invention. The internal combustion engine 10 is a reciprocating type internal combustion engine in which a piston 23 reciprocates. The internal combustion engine 10 includes an internal combustion engine body 11, an ignition device 12, an electromagnetic wave emission device 13, and a control device 35. In the internal combustion engine 10, a combustion cycle in which the air-fuel mixture is ignited by the ignition device 12 and the air-fuel mixture is combusted is repeatedly performed.
-Internal combustion engine body-

  As shown in FIG. 1, the internal combustion engine body 11 includes a cylinder block 21, a cylinder head 22, and a piston 23. A plurality of cylinders 24 having a circular cross section are formed in the cylinder block 21. A piston 23 is provided in each cylinder 24 so as to reciprocate. The piston 23 is connected to the crankshaft via a connecting rod (not shown). The crankshaft is rotatably supported by the cylinder block 21. When the piston 23 reciprocates in the axial direction of the cylinder 24 in each cylinder 24, the connecting rod converts the reciprocating motion of the piston 23 into the rotational motion of the crankshaft.

  The cylinder head 22 is placed on the cylinder block 21 with the gasket 18 interposed therebetween. The cylinder head 22, together with the cylinder 24, the piston 23, and the gasket 18, constitutes a partition member that partitions the combustion chamber 20 having a circular cross section. The diameter of the combustion chamber 20 is, for example, about half the wavelength of the microwave that the electromagnetic wave emission device 13 radiates to the combustion chamber 20.

  The cylinder head 22 is provided with one spark plug 40 that constitutes a part of the ignition device 12 for each cylinder 24. As shown in FIG. 2, in the spark plug 40, the tip exposed to the combustion chamber 20 is positioned at the center of the ceiling surface 51 of the combustion chamber 20 (the surface exposed to the combustion chamber 20 in the cylinder head 22). . The outer periphery of the distal end portion of the spark plug 40 is circular as viewed from the axial direction. A center electrode 40 a and a ground electrode 40 b are provided at the tip of the spark plug 40. A discharge gap is formed between the tip of the center electrode 40a and the tip of the ground electrode 40b.

An intake port 25 and an exhaust port 26 are formed in the cylinder head 22 for each cylinder 24. The intake port 25 is provided with an intake valve 27 that opens and closes an intake side opening 25a of the intake port 25, and an injector 29 that injects fuel. On the other hand, the exhaust port 26 is provided with an exhaust valve 28 for opening and closing the exhaust side opening 26 a of the exhaust port 26.
-Ignition device-

  The ignition device 12 is provided for each combustion chamber 20. As shown in FIG. 3, each ignition device 12 includes an ignition coil 14 that outputs a high voltage pulse, and an ignition plug 40 that is supplied with the high voltage pulse output from the ignition coil 14.

  The ignition coil 14 is connected to a DC power source (not shown). When the ignition coil 14 receives the ignition signal from the control device 35, the ignition coil 14 boosts the voltage applied from the DC power supply, and outputs the boosted high voltage pulse to the center electrode 40 a of the spark plug 40. In the spark plug 40, when a high voltage pulse is applied to the center electrode 40a, dielectric breakdown occurs in the discharge gap and spark discharge occurs. A discharge plasma is generated in the discharge path of the spark discharge. A negative voltage is applied to the center electrode 40a as a high voltage pulse.

The ignition device 12 may include a plasma expansion unit that supplies electric energy to the discharge plasma to expand the discharge plasma. A plasma expansion part expands a spark discharge by supplying high frequency (for example, microwave) energy to discharge plasma, for example. According to the plasma expansion part, it is possible to improve the stability of ignition with respect to a lean air-fuel mixture. The electromagnetic wave emission device 13 may be used as the plasma expansion unit.
-Electromagnetic radiation device-

  As shown in FIG. 3, the electromagnetic wave radiation device 13 includes an electromagnetic wave generator 31, an electromagnetic wave switch 32, and a high frequency radiation plug 34. In the electromagnetic wave radiation device 13, one electromagnetic wave generator 31 and one electromagnetic wave switch 32 are provided, and a high frequency radiation plug 34 is provided for each combustion chamber 20.

  When receiving the electromagnetic wave drive signal (pulse signal) from the control device 35, the electromagnetic wave generator 31 continuously outputs the microwave over the time of the pulse width of the electromagnetic wave drive signal. In the electromagnetic wave generator 31, a semiconductor oscillator generates microwaves. In place of the semiconductor oscillator, another oscillator such as a magnetron may be used.

  The electromagnetic wave switch 32 includes one input terminal and a plurality of output terminals provided for each high frequency radiation plug 34. The input terminal is electrically connected to the electromagnetic wave generator 31. Each output terminal is electrically connected to the input terminal of the corresponding high-frequency radiation plug 34. The electromagnetic wave switch 32 is controlled by the control device 35 and sequentially switches the supply destination of the microwaves output from the electromagnetic wave generator 31 between the plurality of high-frequency radiation plugs 34.

  The high frequency radiation plug 34 is an antenna structure that radiates high frequency to the combustion chamber of the internal combustion engine. As shown in FIG. 6, the high frequency radiation plug 34 has an insertion hole provided in the internal combustion engine for guiding the high frequency to the combustion chamber of the internal combustion engine. An end cap portion 51 that closes the inner opening, a radiation antenna 16 that is provided in the end cap portion 51 and radiates electromagnetic waves to the combustion chamber of the internal combustion engine, and a high-frequency transmission path 60 and a radiation antenna 16 that are provided inside the insertion hole are connected. The high-frequency transmission path 60 is provided so as to be detachable and capable of high-frequency transmission with respect to the power supply section 52.

  The power feeding unit 52 includes a power feeding conductor 52 a whose one end is end-welded to one end of the radiation antenna 16. The other end of the power feeding conductor 52 a is a locking portion provided at the end of the internal conductor of the high-frequency transmission path 60. The high-frequency transmission path 60 is detachably connected to the power supply unit 52 and capable of high-frequency transmission by the engagement between the engaging part and the engagement part of the power supply conductor 52a.

  According to this structure, since the high-frequency transmission path 60 is provided so as to be detachable and capable of high-frequency transmission with respect to the power supply unit 52, the high-frequency transmission path 60 and the radiation antenna 16 can be separated, The versatility of the high-frequency transmission line 60 and the antenna structure can be improved and the cost can be reduced.

  The end cap portion 51 has a base ceramic made of ceramic, and a screw portion that can be screwed with a screw portion provided in the through hole. The end cap portion 51 is screwed with the screw portion of the through hole, thereby forming the through hole. Seal.

  In this manner, the end cap portion 51 is screwed to the internal combustion engine wall surface.

  The base ceramic and the fitting portion of the fitting nut portion and the saddle-shaped center conductor of the power supply conductor 52a are insert-molded.

  As shown in FIG. 4, the high-frequency transmission line 60 is a coaxial transmission line, and the high-frequency transmission line 60 is provided with a center conductor 61 and an outer conductor 62 as high-frequency transmission conductors. The center conductor 61 is a linear conductor. The center conductor 61 is provided on the axial center of the electrical insulator 36 over the entire length of the high-frequency transmission path 60. On the other hand, the outer conductor 62 is composed of a cylindrical conductor.

The radiating antenna 16 is formed in a spiral shape and provided on the end cap portion 51.
Here, the radiation antenna 16 is obtained by joining φ0.3 refractory metal springs with end caps.

  -Control device operation-

  The operation of the control device 35 will be described. The control device 35 performs a first operation for instructing the ignition device 12 to ignite the air-fuel mixture in one combustion cycle for each combustion chamber 20, and a microwave is applied to the electromagnetic wave emission device 13 after the ignition of the air-fuel mixture. A second operation for instructing radiation is performed.

  Specifically, the control device 35 performs the first operation at the ignition timing at which the piston 23 is positioned before the compression top dead center. The control device 35 outputs an ignition signal as the first operation.

  When the ignition device 12 receives the ignition signal, spark discharge occurs in the discharge gap of the spark plug 40 as described above. The air-fuel mixture is ignited by spark discharge. When the air-fuel mixture is ignited, the flame spreads from the ignition position at the center of the combustion chamber 20 toward the wall surface of the cylinder 24.

  After the air-fuel mixture has ignited, the control device 35 performs the second operation, for example, at the start timing of the second half period of flame propagation. The control device 35 outputs an electromagnetic wave drive signal as the second operation.

  When receiving the electromagnetic wave drive signal, the electromagnetic wave radiation device 13 radiates a microwave continuous wave (CW) from the radiation antenna 16 as described above. Microwaves are emitted over the second half of the flame propagation.

  In the vicinity of the antenna 16, a strong electric field region having a relatively strong electric field strength is formed in the combustion chamber 20 throughout the latter half of the flame propagation period. The propagation speed of the flame is increased by receiving microwave energy when the flame passes through the strong electric field region.

When the microwave energy is large, microwave plasma is generated in the strong electric field region. Active species (for example, OH radicals) are generated in the generation region of the microwave plasma. The propagation speed of the flame passing through the strong electric field region is increased by the active species.
<< Other Embodiments >>

  The embodiment may be configured as follows.

  The power supply unit 52 includes a power supply conductor 52 a whose one end is end-welded to one end of the radiation antenna 16, and a coaxial adapter ferrule 53 provided between the other end of the power supply conductor 52 a and the high-frequency transmission path 60. 60 is connected to the power feeding section 52 via a coaxial adapter ferrule 53 so as to be detachable and capable of high frequency transmission.

  The coaxial adapter ferrule 53 includes a heat insulator 54, and the power feeding portion 52 of the radiating antenna 16 transmits a high frequency by connecting to a central conductor extending from the high frequency transmission path 60 through the center of the heat insulator 54.

  In the present embodiment, a buffer matching circuit is provided between the feeder line and the antenna in order to improve the radiation efficiency of the antenna. This improves the effect of plasma flame propagation and reduces power.

  In this embodiment, the isolator of the semiconductor amplifier is eliminated in order to increase the electric field strength in the engine cylinder.

  In this way, the coaxial tube penetrating the engine interior is slidably joined in the axial direction with the saddle-shaped central conductor at the tip to obtain electrical conduction.

  In order to improve the radiation efficiency of the antenna, a buffer matching circuit may be provided between the feed line and the antenna.

  Thus, in this embodiment, the amount of high-frequency radiation energy can be increased while preventing the antenna conductor from being melted.

  In addition, the electric field peak value is increased and the plasma generation region is expanded. In addition, the flame propagation promoting effect can be enhanced in the finger pressure waveform, the heat generation rate, and the like. Further, the plasma expansion can be made stable, and the radiation efficiency from the antenna can be improved.

  Further, the melting loss of the antenna conductor can be reduced.

  The embodiment may be configured as follows.

  The coaxial adapter ferrule 53 is provided between the antenna side electrode connected to the other end of the power supply conductor 52a, the high frequency transmission path side electrode that receives a high frequency from the high frequency transmission path 60, the antenna side electrode, and the high frequency transmission path side electrode. The coaxial adapter ferrule 53 includes a dielectric 55, and transmits a high frequency from the high frequency transmission path 60 to the feeding portion 52 of the antenna via the dielectric 55 through a capacitive junction.

  As described above, in the embodiment, the center conductor 61 is in contact with the radiation antenna 16, but the center conductor 61 may be capacitively coupled to the radiation antenna 16.

  Also in this case, in this embodiment, the amount of high-frequency radiation energy can be increased while preventing the antenna conductor from being melted.

  In addition, the electric field peak value is increased and the plasma generation region is expanded. In addition, the flame propagation promoting effect can be enhanced in the finger pressure waveform, the heat generation rate, and the like. Further, the plasma expansion can be made stable, and the radiation efficiency from the antenna can be improved.

  Further, the melting loss of the antenna conductor can be reduced.

  Moreover, in the said embodiment, although the radiation antenna 16 was formed in the spiral shape which turns in a rectangle, the radiation antenna 16 may be formed in the spiral shape which turns in a circle. Further, the radiation antenna 16 may be a rod-shaped antenna that is bent so as to reciprocate a plurality of times.

  In the embodiment, a plurality of high-frequency radiation plugs 34 may be provided in the internal combustion engine body 11.

  In the embodiment, the internal combustion engine 10 may be of another type (diesel engine, ethanol engine, gas turbine, etc.). Further, when the internal combustion engine 10 is an aircraft engine, when the engine misfires, the ignition device 12 and the electromagnetic wave radiation device 13 are used to generate a microwave plasma obtained by expanding the spark discharge plasma using a microwave, and reignition is performed. You may go.

  As described above, the present invention relates to an antenna structure in which a radiating antenna for radiating a high frequency is covered with a dielectric, a high-frequency radiating plug including the antenna structure, and an internal combustion engine including the high-frequency radiating plug. It is useful for an engine and a method for manufacturing an antenna structure.

16 Radiating antenna
34 Antenna structure
60 High-frequency transmission line
61 Center conductor (conductor for high-frequency transmission)
62 Outer conductor (conductor for high-frequency transmission)
51 End cap
52 Power supply unit
52a Feeding conductor
53 Coaxial adapter ferrule
54 Thermal insulation

Claims (10)

An antenna structure that radiates high frequency into a combustion chamber of an internal combustion engine,
An end cap portion that closes an inner opening of an insertion hole provided in the internal combustion engine in order to guide the high frequency to the combustion chamber of the internal combustion engine;
A radiation antenna that is provided in the end cap portion and radiates electromagnetic waves to the combustion chamber of the internal combustion engine;
A high-frequency transmission line provided inside the insertion hole and a radiation antenna are connected, and a power supply unit that supplies high frequency from the high-frequency transmission line to the radiation antenna is provided
The antenna structure characterized in that the high-frequency transmission path is provided so as to be detachable and capable of high-frequency transmission with respect to the power feeding section. In claim 1,
The power supply unit includes a power supply conductor whose one end is end-welded to one end of the radiation antenna,
The other end of the power supply conductor is provided with an engaging portion that can be engaged with the engaging portion provided at the end of the inner conductor of the high-frequency transmission path,
An antenna structure characterized in that the high-frequency transmission line is detachably connected to the power feeding portion and capable of high-frequency transmission by engagement of the locking portion and the engaging portion of the power feeding conductor. In claim 1,
The power supply unit has a power supply conductor whose one end is end-welded to one end of the radiation antenna;
A coaxial adapter ferrule provided between the other end of the feeding conductor and the high-frequency transmission path;
An antenna structure characterized in that the high-frequency transmission path is detachably connected to the power feeding portion and capable of high-frequency transmission via a coaxial adapter ferrule. In claim 3,
The coaxial adapter ferrule has a thermal insulator,
An antenna structure characterized in that a feeding portion of a radiating antenna is connected to a central conductor extending from a high-frequency transmission path through the center of a heat insulator to transmit a high frequency. In claim 3,
The coaxial adapter ferrule includes an antenna side electrode connected to the other end of the power supply conductor, a high frequency transmission path side electrode that receives a high frequency from the high frequency transmission path,
A dielectric provided between the antenna side electrode and the high frequency transmission line side electrode;
The coaxial adapter ferrule transmits a high frequency from a high frequency transmission line to a power feeding portion of the antenna through a dielectric through a capacitive junction. In any one of claims 1 to 5,
The end cap portion includes a screw portion that can be screwed with a screw portion provided in the through hole, and the through hole is sealed by screwing with the screw portion of the through hole. . In any one of Claims 1 thru | or 6,
A radiation antenna is formed in a spiral shape and provided in an end cap portion. In any one of Claims 1 thru | or 7,
An antenna structure, wherein the high-frequency transmission line is a coaxial transmission line. The antenna structure according to any one of claims 1 to 8,
A high frequency radiation plug comprising a casing for holding an antenna structure. A high-frequency radiation plug according to claim 9,
An internal combustion engine having an internal combustion engine body in which a combustion chamber is formed and a high frequency radiation plug is attached to the combustion chamber so as to radiate a high frequency.

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