JP6312242B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine. In particular, the present invention relates to the structure of a combustion chamber of an internal combustion engine that directly injects fuel into the combustion chamber.

  Up to now, for example, in a direct injection type diesel engine (a diesel engine that directly injects fuel into a combustion chamber and burns it), not only the penetration of fuel spray (penetration) is increased, but also swirl (swirl flow) and squish Air flow such as (longitudinal flow) has been used to control the spatial distribution of the mixture of fuel and air in the combustion chamber to improve the air utilization rate and to improve combustion.

  More specifically, in a conventional reentrant combustion chamber (see FIG. 8) in a diesel combustion engine, the fuel injection pressure is increased to increase the atomization and penetration of the fuel spray and to the fuel spray by swirl. Air introduction was promoted, and the air-fuel ratio was improved by squishing the air-fuel mixture outside the combustion chamber. However, since the strength of the airflow changes depending on the operating conditions such as the engine speed and load, the spray colliding with the combustion chamber wall surface stays, soot generation and heat loss increase.

  Here, for example, in Patent Document 1, as shown in FIG. 9, the top surface of the piston 9 includes a cavity 10 that is recessed so as to form most of the combustion chamber, and a cylinder ceiling portion is formed on the inner peripheral surface of the cavity 10. In relation to the combustion chamber structure of a direct injection type diesel engine in which fuel is injected radially from the center of the cylinder and self-ignited, a peripheral portion of the opening of the cavity 10 is recessed by a required depth with respect to the top surface of the piston 9 ( The outer peripheral portion of the bottom surface of the turned portion 24 rises so as to draw a gently curved surface as it goes outward in the radial direction, reaches the top surface of the piston 9 and is within the bottom surface of the turned portion 24. There is a combustion chamber (two-stage lip structure) configured such that the inlet lip portion 11 is formed at a position one step down from the top surface of the piston 9 by the peripheral portion and the combustion chamber wall surface portion 12 rising from the bottom surface of the cavity 10. Piston is described.

JP 2007-21644 A

  According to the piston provided with the combustion chamber described in Patent Document 1, mixing of fuel spray and air is improved in the combustion chamber, and better combustion can be performed. Can be improved.

  However, in response to the demand for further reduction of NOx emissions, the EGR rate is further increased to lower the combustion temperature, and the combustion chamber (in-cylinder; in-cylinder) is controlled to an even lower oxygen concentration atmosphere. Is needed.

  In such an atmosphere having a low oxygen concentration, combustion is worsened due to insufficient intake of oxygen into the fuel spray injected from the injection hole of the fuel injector (fuel injection valve) opened toward the combustion chamber. There is an actual situation that an increase in the emission of black smoke (soot) and HC (hydrocarbon) is inevitable.

  The present invention has been made in view of such circumstances, and is capable of effectively incorporating oxygen into the fuel spray even when the combustion chamber is in a low oxygen concentration atmosphere while having a relatively simple and low-cost configuration. Therefore, an object of the present invention is to provide an internal combustion engine that can reduce the emission of black smoke (soot) and HC (hydrocarbon).

Therefore, the internal combustion engine according to the present invention is
An internal combustion engine comprising a combustion chamber surrounded by a piston top surface of the internal combustion engine, a cylinder head lower surface, and an inner wall of a cylinder in which the piston is slidably accommodated,
A fuel injection nozzle that is attached to the cylinder head and injects fuel from the lower surface of the cylinder head to the approximate center of the combustion chamber,
An outer peripheral side opening that is opened on the lower surface of the cylinder head on the outer peripheral side of the combustion chamber;
A central opening that is opened in the lower surface of the cylinder head on the fuel injection nozzle side of the combustion chamber;
A passage provided inside the cylinder head and communicating the outer peripheral side opening and the central side opening;
It includes a communication unit configured to include a,
When viewed from a direction along the reciprocating direction of the piston, the outer periphery of the outer peripheral opening is disposed at an inscribed position in contact with the inlet diameter of the combustion chamber recessed in the top surface of the piston. It is characterized by that.

  In this invention, the opening area of the said outer peripheral side opening part may be larger than the opening area of the said center side opening part.

  In the present invention, the center side opening part of the adjacent communication part may be configured to be continuous in the circumferential direction of the combustion chamber.

  In the present invention, the communication portion may be an opening concentric with the fuel injection nozzle formed with a predetermined gap from the outer periphery of the fuel injection nozzle.

  According to the present invention, although it is a relatively simple and low-cost configuration, even if the combustion chamber has a low oxygen concentration atmosphere, oxygen can be effectively taken into the fuel spray, and thus black smoke ( It is possible to provide an internal combustion engine capable of reducing the soot and HC (hydrocarbon) emissions.

1 is a cross-sectional view (cross-sectional view cut along a plane substantially orthogonal to a crankshaft) schematically representing the vicinity of a combustion chamber of an internal combustion engine according to an embodiment of the present invention. It is the figure which looked at the combustion chamber of FIG. 1 from the cylinder head lower surface side. It is sectional drawing (sectional drawing cut | disconnected by the plane substantially orthogonal to a crankshaft) which represented typically another example of the combustion chamber vicinity of the internal combustion engine which concerns on embodiment same as the above. It is the figure which looked at the combustion chamber of FIG. 3 from the cylinder head lower surface side. FIG. 4 is a view of the combustion chamber of the internal combustion engine viewed from above the cylinder head in order to explain the positional relationship (minimum radius position) between the outer opening and the piston combustion chamber in the combustion chamber of the internal combustion engine of FIG. 1 or FIG. 3. FIG. 4 is a view of the combustion chamber of the internal combustion engine viewed from above the cylinder head in order to explain the positional relationship (maximum radius position) between the outer opening and the piston combustion chamber in the combustion chamber of the internal combustion engine of FIG. 1 or FIG. 3. FIG. 2 is a cross-sectional view (a cross-sectional view cut along a plane substantially orthogonal to a crankshaft) for explaining an example for forming the communication portion 200 in the combustion chamber of the internal combustion engine of FIG. 1. It is sectional drawing which shows an example of the combustion chamber (reentrant type) of the conventional internal combustion engine. It is sectional drawing which shows an example of the combustion chamber (two-stage lip structure) of the conventional internal combustion engine.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

  As shown in FIG. 1, an internal combustion engine 100 according to an embodiment of the present invention includes a lower surface of a cylinder head 110, a top surface (upper surface) of a piston 120, and a cylinder liner 140 fitted into a cylinder block 130. A fuel injector 160 is attached to the cylinder head 110 so that the fuel injection nozzle 161 at the tip thereof faces the combustion chamber 150 defined by the peripheral wall surface.

  The fuel injector 160 is provided in the cylinder head 110 for each cylinder (combustion chamber), and the fuel injection nozzle 161 at the tip of the fuel injector 160 is substantially at the center of the combustion chamber 150 when viewed from the direction along the reciprocating motion of the piston 120. It arrange | positions so that it may become.

At the tip of the fuel injection nozzle 161 facing the combustion chamber 150, for example, a plurality of 6 to 10 injection holes are provided at predetermined intervals in the circumferential direction, and the top surface of the piston 120 is recessed from the plurality of injection holes. To the provided piston combustion chamber (cavity) 121, fuel is injected and supplied at a predetermined timing with a fuel injection amount set according to the operating state (rotational speed, load, etc.) of the internal combustion engine 100. It has become.
Reference numeral 170 denotes an intake valve, and reference numeral 180 denotes an exhaust valve.

  Here, in general, in a diesel engine, as the piston approaches compression top dead center, the air sucked into the combustion chamber becomes high temperature and high pressure, and combustion is performed by self-ignition by injecting high pressure fuel into the atmosphere. Then, diffusion combustion is performed while forming a mixture of fuel and air with kinetic energy or the like of the fuel spray.

  Recent research has gradually elucidated the structure of the fuel spray, and the fuel spray takes air into the fuel spray by exchanging momentum with the surrounding air, and when combustion starts, the air intake is mainly the uppermost flame of the fuel spray. Occurs in the part that is not covered by the fuel (relatively immediately after the injection from the fuel injection nozzle), the momentum of the fuel spray decreases rapidly with the end of the fuel injection, and the mixture of fuel and air remains slow and the It has been understood that a lot of black smoke (soot) and HC (hydrocarbon) are generated by interfering with the fuel gas.

  If mixing with the air of the fuel spray used for combustion after the end of fuel injection can be promoted in a state where the amount of momentum is injected in the latter part of such a fuel injection period, combustion in the latter part of the combustion period (late stage) (Combustion) can be activated, and it can be expected to contribute to improving fuel efficiency and reducing black smoke (soot) and HC (hydrocarbon).

  For this reason, in the present embodiment, as shown in FIG. 1, a configuration in which the communication portion 200 is provided on the lower surface side of the cylinder head 110 is employed.

  The communication portion 200 includes an outer peripheral side opening 201 that opens toward the outer peripheral side (near) of the cylinder (combustion chamber) on the lower surface of the cylinder head 110, and a central side that opens toward the fuel injection nozzle 161 side (near). The opening 202 is configured to include a passage 203 that communicates the outer peripheral opening 201 and the central opening 202.

  As shown in FIG. 2, the communication part 200 (outer peripheral side opening 201, central side opening 202, passage 203) avoids interference with the intake valve 170, the exhaust valve 180, the intake port, the exhaust port, and the like. However, a plurality of layouts can be arranged in the circumferential direction of the combustion chamber.

  According to the cylinder (combustion chamber) provided with such a communication part 200, the fuel spray injected into the combustion chamber from the nozzle hole of the fuel injection nozzle 161 ignites, and the flame is directed toward the outer periphery of the cylinder (combustion chamber). When grown, along with the upward movement of the piston 120 and the like, unused air (oxygen) existing on the outer peripheral side of the cylinder (combustion chamber) passes through the outer peripheral opening 201 provided on the lower surface of the cylinder head 110. Then, it is guided into the passage 203.

  As a result, unused air (oxygen) including unused air (oxygen) stored in the passage 203 from the central side opening 202 on the opposite side of the outer peripheral side opening 201 becomes cylinder (combustion). Will be ejected to the room.

  Here, since the center side opening 202 is provided near the injection hole of the fuel injection nozzle 161, unused air (oxygen) ejected from the center side opening 202 is the root of the fuel spray ( The introduction of air in the vicinity of the base end (such as a portion in which the momentum is reduced in the later period of the fuel injection period) is promoted, so that the combustion can be activated as a whole including the later period of the fuel.

  Conventionally, the fuel spray ejected from the nozzle hole of the fuel injection nozzle 161 and the surrounding gas of the fuel spray are mixed with the kinetic energy of the fuel spray, the shape of the piston combustion chamber (cavity) 121, swirl, and squish. However, according to the present embodiment, unused on the outer peripheral side of the combustion chamber (cylinder) where reaction with the flame is difficult (difficult to use in combustion) The air (oxygen) of the fuel can be moved via the communication portion 200 by the action of the combustion pressure and temperature, and can be ejected near the injection hole of the fuel injection nozzle 161, so that the air into the fuel spray (Oxygen) introduction can be promoted more than before, the EGR rate is further increased in order to lower the combustion temperature and reduce NOx emissions, and the combustion chamber (cylinder) is controlled to a lower oxygen concentration atmosphere. Ah Also, it is possible to suppress the emission of black smoke and improve combustion (soot) and HC (hydrocarbons).

  As shown in FIG. 3, the opening area (passage cross-sectional area) of the outer peripheral opening 201 can be set to be larger than the opening area (passage cross-sectional area) of the central opening 202. As a result, the pressure difference between the outer opening 201 on the inlet side of the air into the communication passage 203 and the central opening 202 on the outlet side can be increased. This air (oxygen) can be ejected to a cylinder (combustion chamber) near the injection hole of the fuel injection nozzle 161.

  Here, for example, as shown in FIG. 4, the central opening 202 may be configured to be continuous in the circumferential direction of the combustion chamber. Even in such a case, the total opening area (passage cross-sectional area) of the outer peripheral opening 201 can be set to be larger than the total opening area (passage cross-sectional area) of the central opening 202.

  Further, as shown in FIG. 5, the outer circumferential side opening 201 has an outer diameter of the outer circumferential side opening 201 that is the inlet diameter (lip) of the piston combustion chamber 121 when viewed from the direction along the reciprocating direction of the piston 120. (Inner diameter) 122 and can be disposed at an inscribed position in contact with the inside.

  Such a position is obtained by effectively using the unused air on the outer peripheral side of the combustion chamber (cylinder) and the air flow by the outlet portion (lip portion) of the piston combustion chamber 121 to extend the outer peripheral side opening 201 and the passage 203. Is the minimum radius position (the minimum radius position of the pitch circle passing through the centers of the plurality of outer peripheral openings 201).

  On the other hand, as shown in FIG. 6, the outer peripheral side opening 201 has an outer periphery of the outer peripheral side opening 201 that is the inlet diameter (lip) of the piston combustion chamber 121 when viewed from the direction along the reciprocating direction of the piston 120. (Inner diameter) and can be disposed at a circumscribed position that contacts the outside.

  Such a position is obtained by effectively using the unused air on the outer peripheral side of the combustion chamber (cylinder) and the air flow by the outlet portion (lip portion) of the piston combustion chamber 121 to extend the outer peripheral side opening 201 and the passage 203. Is the maximum radial position (the maximum radial position of the pitch circle passing through the centers of the plurality of outer peripheral openings 201).

  That is, the outer peripheral side opening 201 according to the present embodiment is disposed within the range from the minimum radius position to the maximum radius position of the pitch circle, so that unused air on the outer peripheral side of the combustion chamber (cylinder) is removed. It is preferable in that the air flow at the outlet portion (lip portion) of the piston combustion chamber 121 can be effectively utilized and the outer peripheral side opening 201 can be extended to the passage 203 effectively.

  By the way, the communication part 200 (the outer peripheral side opening part 201, the center side opening part 202, the channel | path 203) can be formed by using a lost mold, for example in the case of casting of the cylinder head 111.

  Further, after the cylinder head 110 is formed by casting, it can be formed by machining such as drilling. At this time, the passage 203 can be formed by using a plug as shown in FIG. 7 after drilling the passage 203 extending in the lateral direction of the cylinder head.

  By the way, the piston combustion chamber 121 according to the present embodiment can have a two-stage lip structure as described in Patent Document 1, but is not limited to this, and a toroidal combustion chamber. , Reentrant combustion chambers and other shapes.

  In the present embodiment, the diesel engine has been described as an example. However, the present invention is not limited to this, and even a fuel other than light oil such as gasoline, natural gas, alcohol, biofuel, or the like is directly combusted. The present invention can be applied to any internal combustion engine that injects fuel into the chamber and is included in the technical scope of the present invention.

  The present invention is not limited to the embodiments of the invention described above, and various modifications can be made without departing from the gist of the present invention.

100 Internal combustion engine
110 Cylinder head 120 Piston 121 Piston combustion chamber (cavity)
DESCRIPTION OF SYMBOLS 150 Combustion chamber 160 Fuel injector 161 Fuel injection nozzle 200 Communication part 201 Outer opening part 202 Center side opening part 203 Passage

Claims (3)

An internal combustion engine comprising a combustion chamber surrounded by a piston top surface of the internal combustion engine, a cylinder head lower surface, and an inner wall of a cylinder in which the piston is slidably accommodated,
A fuel injection nozzle that is attached to the cylinder head and injects fuel from the lower surface of the cylinder head to the approximate center of the combustion chamber,
An outer peripheral side opening that is opened on the lower surface of the cylinder head on the outer peripheral side of the combustion chamber;
A central opening that is opened in the lower surface of the cylinder head on the fuel injection nozzle side of the combustion chamber;
A passage provided inside the cylinder head and communicating the outer peripheral side opening and the central side opening;
It includes a communication unit configured to include a,
When viewed from a direction along the reciprocating direction of the piston, the outer periphery of the outer peripheral opening is disposed at an inscribed position in contact with the inlet diameter of the combustion chamber recessed in the top surface of the piston. An internal combustion engine characterized by that.   2. The internal combustion engine according to claim 1, wherein an opening area of the outer peripheral opening is larger than an opening area of the central opening. 3. The internal combustion engine according to claim 1, wherein a central opening of adjacent communication portions is configured to be continuous in a circumferential direction of the combustion chamber.

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