JP6145759B2 - Antenna structure, high-frequency radiation plug, and internal combustion engine - Google Patents

Description

  The present invention relates to an antenna structure in which a radiating antenna for radiating a high frequency is covered with an insulator, a high frequency radiation plug including the antenna structure, and an internal combustion engine including the high frequency radiation plug.

  Conventionally, an antenna structure in which a radiating antenna for radiating a high frequency is covered with an insulator is known. For example, Japanese Patent Laid-Open No. 2010-96128 discloses an internal combustion engine provided with this type of antenna structure.

  In the internal combustion engine described in Japanese Patent Application Laid-Open No. 2010-96128, 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. This radiating antenna is covered with a dielectric.

JP 2010-96128 A

  By the way, when an antenna structure is provided in a structure having a large installation place restriction such as an internal combustion engine, it is difficult to secure a large radiation surface from which an electromagnetic wave from a radiation antenna is radiated in an insulator of the antenna structure. . For this reason, the radiation efficiency decreases as the high-frequency power radiated from the radiation antenna is increased.

  The present invention has been made in view of such a point, and an object thereof is to improve high-frequency radiation efficiency in an antenna structure in which a radiation antenna for radiating high-frequency waves is embedded in an insulator.

  A first invention includes a radiation antenna for radiating a high frequency, and an insulator in which the radiation antenna is embedded. The insulator is exposed to a radiation space that radiates a high frequency, and is An antenna structure in which a main radiation surface for radiating high-frequency radiation to the radiation space is formed, wherein the radiation antenna is formed in a rod shape and bends along the main radiation surface inside the insulator. In the radiation antenna, the installation positions of adjacent portions adjacent to each other in the radiation antenna are shifted in the direction perpendicular to the main radiation surface.

  In the first invention, the radiation antenna is a rod-like antenna that extends while bending along the main radiation surface. In the radiation antenna, the installation positions of adjacent portions adjacent to each other in the radiation antenna are shifted in the direction perpendicular to the main radiation surface.

  Here, in the antenna structure, in order to improve high-frequency radiation efficiency, it is desirable that the radiation antenna area (hereinafter referred to as “transparent antenna area”) when the main radiation surface is seen through from the front is larger. For example, when providing such a rod-shaped radiating antenna along only one cross section parallel to the main radiating surface in an insulator, install the radiating antenna so that dielectric breakdown does not occur between adjacent parts that are not in contact with each other. In the cross section, it is necessary to secure a certain distance between adjacent portions. Therefore, in order to ensure the space | interval of the adjacent parts in the installation cross section of a radiation antenna, a see-through antenna area is restrict | limited.

  On the other hand, in the first invention, the installation positions of the proximity portions are shifted from each other in the direction perpendicular to the main radiation surface. Therefore, when the main radiation surface is seen through from the front, the interval between adjacent portions can be reduced or eliminated. As a result, the limitation of the fluoroscopic antenna area is relaxed.

  In a second aspect based on the first aspect, the radiation antenna extends spirally along the radiation surface.

  In a third aspect based on the first aspect, in the radiating antenna, when the main radiating surface is seen through from the front, the adjacent portions abut or overlap each other.

  A fourth invention is constituted by the antenna structure of any one of the first to third inventions, a transmission line for transmitting a high frequency radiated from the radiation antenna, and a cylindrical conductor, and the radiation antenna is provided at one end. And a casing for accommodating the transmission line extending from the radiation antenna to the other end side.

  A fifth invention includes the high-frequency radiation plug according to the fourth invention, and an internal combustion engine main body in which a combustion chamber is formed and the high-frequency radiation plug is attached to the combustion chamber so as to radiate a high frequency. It is an internal combustion engine.

  In the present invention, in the radiating antenna, the positions of the adjacent portions in the direction perpendicular to the main radiating surface are shifted from each other, whereby the interval between the adjacent portions when the main radiating surface is seen through from the front can be reduced or eliminated. . Therefore, the limitation of the fluoroscopic antenna area is relaxed and the fluoroscopic antenna area can be increased, so that high-frequency radiation efficiency can be improved.

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. 1 is a longitudinal sectional view of a high-frequency radiation plug according to an embodiment. It is the perspective view which saw through the antenna structure which concerns on embodiment. It is the front view which saw through the antenna structure which concerns on embodiment from the main radiation surface.

  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. The electromagnetic wave generator 31 outputs a microwave with an output value (for example, 500 watts) of 100 to 1000 watts. 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.

  As shown in FIG. 1, the high-frequency radiation plug 34 is formed in a substantially cylindrical shape as a whole. As shown in FIG. 4, the high-frequency radiation plug 34 includes a ceramic structure 36 in which a conductor is embedded in a ceramic 63 (electrical insulator), and a casing 37 that houses the ceramic structure 36.

  The ceramic structure 36 is formed in a prismatic shape. The cross-sectional shape of the ceramic structure 36 is uniform over the length direction. The cross-sectional shape of the ceramic structure 36 is, for example, a square. The ceramic structure 36 has the same length of one side in any cross section, and the length of one side is, for example, 1.5 to 5 mm (for example, 3 mm).

  The ceramic structure 36 includes a transmission unit 38 in which a microwave transmission line 60 is embedded, and a radiation unit 39 in which the radiation antenna 16 is embedded. The transmission unit 38 and the radiation unit 39 are integrated. In the ceramic structure 36, the transmission part 38 occupies most. In the ceramic structure 36, one end portion constitutes a radiating portion 39 and the remaining portion constitutes a transmission portion 38.

  In the transmission unit 38, a central conductor 61 and an outer conductor 62 constituting a microwave transmission line 60 are embedded in a ceramic 63. The center conductor 61 is a linear conductor. The center conductor 61 is provided on the axial center of the ceramic structure 36 over the entire length of the transmission portion 38. On the other hand, the outer conductor 62 is, for example, a rectangular cylindrical conductor. The outer conductor 62 surrounds the central conductor 61 with the ceramic 63 interposed therebetween. The outer conductor 62 is provided at a certain distance from the center conductor 61 over its entire length. Only one end of the outer conductor 62 is exposed at the end face of the ceramic structure 36. In the high-frequency radiation plug 34, one end of the transmission unit 38 is a microwave input terminal. In the transmission unit 38, the microwave input from the input terminal is transmitted to the radiation unit 39 without leaking outside the outer conductor 62.

  When the ceramic structure 36 is manufactured by using the lamination technique described in JP-A-10-75108, the outer conductor 62 is configured by combining a conductor layer and a cylindrical conductor (via hole). Also good. In that case, the distance between the cylindrical conductors adjacent to each other in the microwave transmission direction is set in the outer conductor 62 so that the microwave does not leak outside the outer conductor 62.

  The radiating unit 39 constitutes an antenna structure including a radiating antenna 16 for radiating microwaves and a ceramic 63 (insulator) in which the radiating antenna 16 is embedded. The radiation antenna 16 is embedded in the radiation part 39 so that the radiation antenna 16 is not exposed to the outer surface of the ceramic structure 36. That is, the entire surface of the radiation antenna 16 is covered with the ceramic 63. The radiation antenna 16 is integrated with the central conductor 61 of the transmission unit 38 at the input end.

  In the radiation part 39, as shown in FIG. 4, the end surface 65 and a part of side surface of the ceramic structure 36 become an exposed surface exposed to the combustion chamber 20 (radiation space). Of these exposed surfaces, the end surface 65 of the ceramic structure 36 from which most of the microwave radiated from the radiation antenna 16 is radiated to the combustion chamber 20 constitutes the main radiation surface 65. The main radiation surface 65 is a surface where the area of the radiation antenna 16 when viewed from the front is the largest among the exposed surfaces.

  The radiating antenna 16 is formed in a rod shape and is bent along the main radiating surface 65 inside the ceramic 63. Specifically, as shown in FIG. 5, the radiating antenna 16 is a spiral conductor that turns in a rectangular shape around the axis of the center conductor 61. As shown in FIGS. 5 and 6, in the radiation antenna 16, the installation positions of adjacent portions 66 and 67 adjacent to each other in the radiation antenna 16 are shifted in the direction perpendicular to the main radiation surface 65. In the radiation antenna 16, when the main radiation surface 65 is seen through from the front, the flange portions of the proximity portions 66 and 67 are in contact with each other. When the main radiation surface 65 is seen through from the front, the proximity portions 66 and 67 may overlap each other.

  Specifically, the radiating antenna 16 includes a central portion 100 that is in contact with the central conductor 61 and configured by a single cylindrical conductor, and a central portion 100 that is provided outside the central portion 100 and configured by a plurality of cylindrical conductors. The first intermediate portion 101 and the second intermediate portion 102, and the outer peripheral portion 103 provided on the outermost side and configured by a plurality of cylindrical conductors. In the radiating antenna 16, the center portion 100, the first intermediate portion 101, the second intermediate portion 102, and the outer peripheral portion 103 are provided in this order from the inside, and the ends of those adjacent to each other are connected by the connection conductor 104. The first intermediate portion 101 and the second intermediate portion 102 constitute adjacent portions 66 and 67. The second intermediate portion 102 and the outer peripheral portion 103 constitute adjacent portions 66 and 67. In the radiating antenna 16, only the second intermediate portion 192 of the central portion 100, the first intermediate portion 101, the second intermediate portion 102, and the outer peripheral portion 103 is installed in the direction perpendicular to the main radiating surface 65. It is shifted to the side. As a result, the installation positions of the first intermediate portion 101 and the second intermediate portion 102 are shifted in the direction perpendicular to the main radiation surface 65. The installation positions of the second intermediate portion 102 and the outer peripheral portion 103 are shifted in the direction perpendicular to the main radiation surface 65.

  The casing 37 is formed in a cylindrical shape having a circular outer peripheral shape and a rectangular inner peripheral shape in cross-sectional view. In sectional view, the inner peripheral shape of the casing 37 and the side length of the inner periphery are the same as the outer peripheral shape of the ceramic structure 36 and the side length of the outer periphery. A ceramic structure 36 is fitted into the casing 37 so that the end face of the radiation part 39 is exposed at one end and the end face of the transmission part 38 is exposed at the other end. From one end of the casing 37, a part of the radiating portion 39 protrudes so that a part of the radiating antenna 16 is located outside the casing 37.

  The outer diameter of the casing 37 changes at one place in the axial direction of the casing 37. A step is formed on the outer peripheral surface of the casing 37 only at one location. In the casing 37, the outer diameter on the distal end side where the radiation part 39 is exposed is smaller than the outer diameter on the proximal end side where the transmission part 38 is exposed.

  The high frequency radiation plug 34 is attached to the cylinder head 22 so that the radiation portion 39 is exposed to the combustion chamber 20. The high frequency radiation plug 34 is screwed into the mounting hole of the cylinder head 22. As for the high frequency radiation plug 34, the input terminal of the transmission part 38 is connected to the output terminal of the electromagnetic wave switch 32 via a coaxial cable (not shown). In the high frequency radiation plug 34, when a microwave is input from the input terminal of the transmission unit 38, the microwave passes through the inside of the outer conductor 62 of the transmission unit 38. The microwaves that have passed through the transmission unit 38 are radiated from the radiation antenna 16 to the combustion chamber 20.

Further, in the internal combustion engine body 11, a plurality of receiving antennas 52 that resonate with microwaves radiated from the radiation antenna 16 to the combustion chamber 20 are provided on the partition member that partitions the combustion chamber 20. Each receiving antenna 52 is formed in an annular shape. As shown in FIG. 1, two receiving antennas 52 are provided on the top of the piston 23. Each receiving antenna 52 is electrically insulated from the piston 23 by an insulating layer 56 formed on the top surface of the piston 23, and is provided in an electrically floating state.
-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. Note that the output timing and pulse width of the electromagnetic wave drive signal may be set so that the microwave is emitted over a period in which the flame passes through the region where the two receiving antennas 52 are provided.

  In each receiving antenna 52, the microwave resonates. In the vicinity of the two receiving antennas 52, a strong electric field region having a relatively strong electric field strength is formed in the combustion chamber 20 throughout the second half period of the flame propagation. 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.
-Effect of the embodiment-

In the present embodiment, in the radiating antenna 16, the adjacent portions 66 and 67 in the case where the main radiating surface 65 is seen through from the front side are shifted by shifting the installation positions of the adjacent portions 66 and 67 in the direction perpendicular to the main radiating surface 65. Can be reduced or eliminated. Therefore, the limitation of the fluoroscopic antenna area is relaxed and the fluoroscopic antenna area can be increased, so that the microwave radiation efficiency can be improved.
<< Other Embodiments >>

  The embodiment may be configured as follows.

  In the embodiment, the radiating antenna 16 is formed in a spiral shape turning in a rectangular shape, but the radiating antenna 16 may be formed in a spiral shape turning in a circular shape. Further, the radiation antenna 16 may be a rod-shaped antenna bent into a rectangular wave shape that reciprocates a plurality of times when the main radiation surface 65 is seen through from the front.

  In the embodiment, the center conductor 61 is in contact with the radiating antenna 16, but the center conductor 61 may be capacitively coupled to the radiating antenna 16.

  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 outer conductor 62 of the transmission unit 38 may be omitted. In that case, the transmission unit 38 transmits microwaves between the outer peripheral surface of the center conductor 61 and the inner peripheral surface of the casing 37.

  In the embodiment, the central conductor 61 of the transmission unit 38 may be omitted, and the transmission unit 38 may be a waveguide.

  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 an insulator, a high frequency radiation plug including the antenna structure, and an internal combustion engine including the high frequency radiation plug. Useful for.

16 Radiating antenna
36 Ceramic structure
39 Radiation section (antenna structure)
61 Center conductor
63 Ceramic (insulator)
67 Proximity
68 Proximity

Claims (5)

A radiating antenna for radiating high frequencies;
An insulator with the radiating antenna embedded therein;
The insulator has an antenna structure that is exposed to a radiation space that radiates a high frequency, and that has a main radiation surface on which a high frequency radiated from the radiation antenna is radiated to the radiation space,
A transmission unit in which a high-frequency transmission line is embedded and a radiation unit in which the radiation antenna is embedded constitute an integrated ceramic structure,
The radiating antenna includes a central portion configured by a single rod-shaped cylindrical conductor that is in contact with a central conductor constituting a microwave transmission line, and a plurality of rod-shaped cylindrical shapes that are parallel to the central portion and have different lengths. The inside of the insulator is bent along the main radiation surface so that the conductor turns in a rectangular shape around the center conductor by the plate-like connection conductor ,
The rod-shaped cylindrical conductors are arranged in three rows outside the center portion, and only the cylindrical conductors in the second row are shifted in the direction perpendicular to the main radiation surface and toward the transmission portion. Antenna structure. In claim 1,
The antenna structure is characterized in that the radiation antenna extends spirally along the radiation surface. In claim 1 or 2,
In the radiating antenna, when the main radiating surface is seen through from the front, the adjacent portions abut or overlap each other. The antenna structure according to any one of claims 1 to 3,
A transmission line for transmitting a high frequency radiated from the radiation antenna;
A high-frequency radiation plug comprising a cylindrical conductor, the radiation antenna being provided at one end, and a casing for accommodating the transmission line extending from the radiation antenna to the other end side. A high-frequency radiation plug according to claim 4,
An internal combustion engine comprising a combustion chamber and an internal combustion engine body to which the high frequency radiation plug is attached so as to radiate a high frequency to the combustion chamber.