JP2019116878A - Internal combustion engine - Google Patents

Abstract

To provide an internal combustion engine capable of suppressing generation of smoke by enhancing premixing of a fuel, in a compression self-ignition type internal combustion engine.SOLUTION: A compression self-ignition type internal combustion engine has a fuel injection nozzle disposed in a state that an injection hole for injecting a fuel is exposed to a combustion chamber from a cylinder head of the internal combustion engine, and a duct support fixed to a top face of the cylinder head and provided with a hollow duct inside so that fuel spray injected from the injection hole of the fuel injection nozzle passes therethrough. The duct support is constituted to expose an inlet and an outlet of the duct to the combustion chamber. At least a part of an outer surface exposed to the combustion chamber, of the duct support is provided with a heat-shielding film. The heat-shielding film has heat conductivity lower than that of the duct support.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an internal combustion engine, and more particularly, to a compression self-ignition internal combustion engine that performs combustion by directly injecting fuel into a compressed combustion chamber.

  BACKGROUND ART Conventionally, for example, Patent Document 1 discloses a technique for promoting premixing of a fuel and a charging air in a combustion chamber in a compression self-ignition internal combustion engine. In this technique, a duct constituted by a hollow pipe is provided in the vicinity of the opening of the tip of the fuel injection device exposed to the combustion chamber. The fuel injected from the opening is injected into the combustion chamber through the hollow tube. Inside the hollow tube, in the process of passing the injected fuel, premixing with the charge air is promoted. As a result, the distribution of rich fuel in the combustion chamber is reduced, and the generation of smoke is reduced.

Japanese Patent Application Publication No. 2017-530298 JP, 2013-92103, A

  However, in the above-mentioned prior art, the duct is suspended from the combustion chamber. In such a configuration, if the combustion in the combustion chamber is continuously performed, the duct may be overheated. In this case, evaporation of fuel may be promoted in the process of passing through the duct, and combustion may be induced before the premixing with the charged air proceeds.

  The present invention has been made in view of the above problems, and provides an internal combustion engine capable of promoting fuel premixing and suppressing smoke generation in a compression self-ignition internal combustion engine. To aim.

  The first invention is directed to a compression self-ignition internal combustion engine that performs combustion by injecting fuel into a compressed combustion chamber in order to achieve the above object. The internal combustion engine has an injection hole for injecting fuel, and is fixed to a fuel injection nozzle provided so that the injection hole is exposed from the cylinder head of the internal combustion engine to the combustion chamber, and fixed to the top surface of the cylinder head And a duct support internally formed with a hollow duct through which the fuel spray injected from the injection hole of the nozzle is formed. The duct support is configured such that the inlet and the outlet of the duct are exposed to the combustion chamber. The internal combustion engine is provided with a heat shielding film formed on at least a part of the outer surface of the duct support exposed to the combustion chamber. And, the heat shielding film has a thermal conductivity lower than the thermal conductivity of the duct support.

The second invention has the following features in the first invention.
The duct support is made of a material having a thermal conductivity higher than that of the material of the cylinder head.

The third invention has the following features in the first or second invention.
Inside the cylinder head, a cooling water flow passage for circulating the cooling water is formed. The duct support is configured to include an exposed portion exposed to the inside of the cooling water flow path.

The fourth invention has the following features in the third invention.
The duct support is configured such that the exposed portion extends along the flow direction of the cooling water flow path.

The fifth invention has the following features in any one of the first to fourth inventions.
The duct is configured such that the direction from the inlet to the outlet coincides with the direction of the fuel spray injected from the injection hole.

The sixth invention has the following features in any one of the first to fifth inventions.
The fuel injection nozzle has a plurality of injection holes having different injection directions. A plurality of ducts are provided corresponding to each of the plurality of injection holes.

The seventh invention has the following features in any one of the first to sixth inventions.
The fuel injection nozzle is configured such that the injection direction of the injection hole is in the range of 45 ° to 90 ° with respect to the cylinder center axis.

  According to the first aspect of the present invention, at least a part of the outer surface exposed to the combustion chamber is covered with the heat shield film. According to such a configuration, since heat transfer from the combustion chamber to the duct support is suppressed, overheating of the duct can be prevented. As a result, pre-mixing with the charge air is advanced while suppressing self-ignition of the fuel spray, so that it is possible to prevent the combustion of rich fuel. As described above, according to the first aspect of the invention, it is possible to reduce the smoke and improve the thermal efficiency by shortening the afterburning period.

  According to the second invention, the duct support is made of a material having higher thermal conductivity than the cylinder head. According to such a configuration, the cooling effect of the fuel spray by the duct can be further enhanced.

  According to the third aspect of the invention, the cooling water flow path through which the cooling water flows is formed inside the cylinder head. The exposed portion of the duct support is exposed to the inside of the cooling water flow path. According to such a configuration, the cooling efficiency of the duct provided inside the duct support can be further enhanced.

  According to the fourth invention, the duct support is configured such that the exposed portion extends along the flow direction of the cooling water flow path. According to such a configuration, the heat radiation from the exposed portion to the cooling water can be promoted, so that the cooling efficiency of the duct can be further enhanced.

  According to the fifth invention, the fuel injected from the injection hole can pass smoothly from the inlet to the outlet of the duct.

  According to the sixth aspect of the invention, even in the case of having a plurality of injection holes, it is possible to promote the premixing of the fuel injected from each injection hole.

  According to the seventh invention, the fuel spray passing through the duct becomes less susceptible to the influence of the air flow in the combustion chamber due to the rise of the piston. Thereby, it is possible to suppress the decrease in the spray penetration force of the fuel spray passing through the duct.

FIG. 2 is a view schematically showing the internal structure of a combustion chamber of the internal combustion engine according to Embodiment 1 from the lower surface side. It is the figure which cut | disconnected the internal combustion engine in FIG. 1 by the AA line, and transparently penetrated the internal structure from the side side typically. FIG. 3 schematically shows a duct support of the engine according to Embodiment 1 from the lower surface side. FIG. 4: is a figure which shows typically the cross section which cut | disconnected the duct support body in FIG. 3 by the BB line. It is the figure which cut | disconnected the engine which concerns on Embodiment 2 at the same position as the AA line in FIG. 1, and has transparently penetrated the internal structure from the side side typically. It is a figure which shows typically the cross section which cut | disconnected the engine in FIG. 5 by CC line.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, when the number of the number, the number, the quantity, the range, etc. of each element is mentioned in the embodiment shown below, the mention is made unless otherwise specified or the number clearly specified in principle. The present invention is not limited to the above numbers. Further, the structures described in the embodiments described below are not necessarily essential to the present invention, unless otherwise specified or clearly specified in principle.

Embodiment 1
The first embodiment will be described with reference to the drawings.

[Configuration of Embodiment 1]
FIG. 1 is a view schematically showing an internal structure of a combustion chamber of an internal combustion engine according to a first embodiment from the lower surface side. Moreover, FIG. 2 is the figure which cut | disconnected the internal combustion engine in FIG. 1 by the AA, and has seen through the internal structure typically from the side side. The internal combustion engine 2 of the first embodiment is a compression self-ignition internal combustion engine (hereinafter simply referred to as "engine") having a plurality of cylinders. FIGS. 1 and 2 show the internal structure of one of the plurality of cylinders provided in the engine 2.

  As shown in FIGS. 1 and 2, the engine 2 includes a cylinder head 4 and a cylinder block 6. A cylinder bore 62 is formed in the cylinder block 6. A piston (not shown) is disposed inside the cylinder bore 62. A combustion chamber 8 is formed in a space surrounded by the cylinder head 4, the cylinder bore 62 and the top surface of the piston.

  Two intake valves 12 and two exhaust valves 14 are disposed on the top surface portion 42 of the cylinder head 4 forming the combustion chamber 8. At the center of the top surface portion 42, a fuel injection nozzle 16 is disposed. More specifically, a mounting hole 44 for fixing the fuel injection nozzle 16 penetrates at the center of the top surface portion 42 of the cylinder head 4 forming the combustion chamber 8. The fuel injection nozzle 16 is fixed to the mounting hole 44 such that the injection hole 18 at the tip is exposed into the combustion chamber 8.

  The engine 2 according to the first embodiment is provided with a duct support 30 in which a duct 20 is formed as a characteristic configuration. The duct support 30 is an annular member configured in a convex shape so as to surround the periphery of the injection hole 18 of the fuel injection nozzle 16. The duct support 30 has an upper surface 32 in contact with the top surface portion 42 of the cylinder head 4, an inner side surface 34 forming the inner peripheral side of the annular ring, an outer side surface 36 forming the outer peripheral side of the annular ring It is comprised by the lower surface 38 which faces a piston side inside. The duct support 30 is fixed by a bolt (not shown) so that the upper surface 32 is in close contact with the top surface portion 42 of the cylinder head 4 at a position where the center axis of the annular ring coincides with the cylinder center axis L1.

  The duct 20 is constituted by a straight hollow tube penetrating the inside of the duct support 30 from the inlet 202 provided on the inner side surface 34 of the duct support 30 to the outlet 204 provided on the outer side surface 36. .

  The fuel injection nozzle 16 according to the first embodiment is provided with eight injection holes 18 which are uniformly and radially injected toward the cylinder bore 62. Each injection hole 18 is configured such that an angle θ1 formed by an injection hole axis L2 indicating the fuel injection direction and the cylinder center axis L1 is in the range of 45 ° to 90 °. In the engine 2 of the first embodiment, the ducts 20 are provided for the injection hole axis L2 of the eight injection holes 18, respectively. The duct 20 is configured such that the central axis of the hollow tube coincides with the injection hole axis L2.

  For the duct support 30 of the first embodiment, a material with high thermal conductivity is selected. As such a material, for example, metal materials such as silver, copper, gold, and aluminum, alloy materials such as beryllium copper and copper-chromium zinc, STC (Super Thermal Conductive) materials, and the like can be used. The duct support 30 is preferably made of a material having a thermal conductivity higher than that of the cylinder head 4. For example, when the cylinder head 4 is aluminum, it is desirable for the duct support 30 to use a material such as copper having a thermal conductivity higher than that of aluminum.

  Further, the duct support 30 of the first embodiment is provided with the heat shielding film 40 as its characteristic configuration. FIG. 3 is a view schematically showing the duct support of the engine according to the first embodiment from the lower surface side. Moreover, FIG. 4 is a figure which shows typically the cross section which cut | disconnected the duct support body in FIG. 3 by the BB line. As shown in these figures, in the duct support 30 of the first embodiment, the heat shield film 40 is formed on the inner side surface 34, the outer side surface 36, and the lower surface 38 which are the outer surfaces exposed to the combustion chamber 8. ing. The heat shielding film 40 is formed, for example, by the following procedure. First, nickel chromium-based ceramic particles are sprayed on the entire inner side surface 34, outer side surface 36 and lower surface 38 of the duct support 30. Next, zirconia particles are sprayed on the entire surface of the nickel chromium film. According to such two-stage thermal spraying, it is possible to form a thermal spray film provided with a nickel chromium-based intermediate layer and a surface layer of zirconia as a thermal barrier film. The thermal spray coating has a porous structure derived from internal bubbles formed in the process of thermal spraying. Therefore, this thermal spray coating functions as a heat shielding film having a thermal conductivity lower than that of the material of the duct support 30. In addition, the formation procedure of a heat shielding film is not specifically limited. Also, as the thermal spraying method, various methods such as flame spraying, high speed flame spraying, arc spraying, plasma spraying, laser spraying, etc. can be adopted.

[Operation of Embodiment 1]
In the compression self-ignition engine 2, fuel is injected from the fuel injection nozzle 16 in a state where the air filled in the combustion chamber 8 is compressed. Preferably, the injected fuel is mixed with the charge air to promote homogenization of the fuel concentration, and then self-ignition combustion is performed. However, for example, in the configuration not provided with the duct 20, the fuel injected from the fuel injection nozzle 16 receives heat of the combustion chamber 8 and overheats quickly, and is self-ignited before being sufficiently mixed with the filling air There is a risk of In this case, the generation of smoke due to the combustion of the rich fuel and the reduction of the thermal efficiency due to the prolongation of the afterburning period become problems.

  In the engine 2 of the first embodiment, the duct 20 is provided in the combustion chamber 8 as a means for solving the above problem. The fuel spray injected from the fuel injection nozzle 16 is introduced into the inside of the duct 20 from the inlet 202. Further, since the inlet 202 of the duct 20 is exposed in the combustion chamber 8, the charge air in the combustion chamber 8 is also guided from the inlet 202 of the duct 20 to the inside. In the duct 20, the fuel spray and the charging air are mixed while being cooled, so that the fuel concentration can be homogenized without prematurely igniting. The fully premixed mixture is injected from the outlet 204 of the duct 20. The injected air-fuel mixture receives heat from the combustion chamber 8 and is self-ignited to burn.

  Here, the material of the duct support 30 constituting the duct 20 is made of a material having high thermal conductivity. According to such a configuration, it is possible to enhance the cooling performance for cooling the fuel spray led to the duct 20 and the charged air, so suppressing self-ignition and promoting the premixing of the fuel spray and the charged air. Is possible.

  Further, in the duct support 30 of the first embodiment, the heat shield film 40 covers the inner side surface 34, the outer side surface 36, and the lower surface 38 exposed to the combustion chamber 8. According to such a configuration, heat transfer from the combustion chamber 8 to the duct support 30 can be suppressed, so overheating of the duct 20 can be prevented.

  As described above, according to the engine 2 of the first embodiment, it is possible to promote the premixing of the fuel spray and the filling air while suppressing the self-ignition while the injected fuel spray passes through the duct 20. . This makes it possible to suppress the generation of smoke due to the self-ignition of the rich fuel before it is homogenized.

  Further, according to the engine 2 of the first embodiment, since the self-ignition while passing through the duct 20 is suppressed, the self-ignition timing can be delayed. As a result, since the afterburning period is shortened, the thermal efficiency can be improved.

  Further, in the engine 2 of the first embodiment, since the duct support 30 is in contact with the cylinder head 4, heat transfer from the duct support 30 to the cylinder head 4 can be promoted. This makes it possible to prevent overheating of the mixture in the duct 20 and to promote premixing.

  Further, in the engine 2 of the first embodiment, the central axis of the duct 20 coincides with the injection hole axis L2. According to such a configuration, the interference between the fuel spray and the wall surface of the duct 20 can be prevented, so that the fuel concentration can be efficiently homogenized.

  Further, in the engine 2 of the first embodiment, the angle θ1 formed by the central axis of the duct 20 with the cylinder central axis L1 is set in the range of 45 ° to 90 °. According to such a configuration, it is possible to suppress the decrease in the spray penetration force due to the air flow in the duct 20.

[Modification of Embodiment 1]
The engine 2 of the first embodiment may adopt a form modified as follows.

  The shape of the duct support 30 is not limited to an annular shape. That is, the duct support 30 may be fixed to the top surface portion 42 of the cylinder head 4 and may have a shape that allows the inlet 202 and the outlet 204 of the duct 20 to communicate with the combustion chamber 8. The larger the contact area between the upper surface 32 of the duct support 30 and the top surface portion 42 of the cylinder head 4, the better the heat transfer from the duct support 30 to the cylinder head 4. Therefore, as for the shape of the duct support 30, it is preferable to adopt a shape such that the contact area with the cylinder head 4 becomes as large as possible.

  The configuration of the duct 20 is not limited to the shape, the number, and the like as long as the fuel injected from the injection hole 18 of the fuel injection nozzle 16 passes from the inlet 202 to the outlet 204.

  As long as the heat shield film 40 is a film having a thermal conductivity lower than that of the material of the duct support 30, the material, the shape, the film thickness, and the formation method are not limited. For example, the heat shield film 40 is not limited to the configuration of the thermal spray film, and a material having a thermal conductivity lower than that of the material of the duct support 30 may be closely adhered to the outer surface of the duct support 30 as the heat shield film 40. Although the heat shield film 40 is preferably formed on the entire outer surface of the duct support 30 exposed to the combustion chamber 8, the heat shield film 40 is formed on a part of the outer surface exposed to the combustion chamber 8. May be.

Second Embodiment
The second embodiment will be described with reference to the drawings.

[Features of Embodiment 2]
FIG. 5 is a schematic perspective view of the internal structure taken from the side of the engine according to the second embodiment at the same position as the line A-A in FIG. Moreover, FIG. 6 is a figure which shows typically the cross section which cut | disconnected the engine in FIG. 5 by CC line. In FIGS. 5 and 6, the elements shared with FIG. 2 are assigned the same reference numerals and detailed explanations thereof will be omitted.

  As shown in FIGS. 5 and 6, the engine 2 of the second embodiment is characterized in that a part of the duct support 30 is exposed to the cooling water flow path 46 in the cylinder head 4. More specifically, the upper surface 32 of the duct support 30 is provided with an exposed portion 50 penetrating from the side of the top surface portion 42 of the cylinder head 4 to the cooling water flow path 46. The exposed portion 50 has a shape extending along the flow direction of the cooling water inside the cooling water flow path 46. According to such a shape of the exposed portion 50, the fuel spray passing through the duct 20 and the heat transmitted from the filling air to the duct support 30 are transferred to the cooling water in the cooling water flow path 46 through the exposed portion 50. Heat is dissipated. As a result, the cooling performance of the duct 20 can be further improved, so it is possible to prevent self-ignition due to evaporation of the fuel spray inside the duct 20 and to promote premixing.

[Modification of Embodiment 2]
The engine 2 of the second embodiment may adopt a form modified as follows.

  As long as the exposed portion 50 is configured to be exposed to the cooling water flow path 46 formed in the cylinder head 4, the shape thereof is not limited. The exposed portion 50 preferably has a shape that can increase the contact area with the cooling water without interrupting the flow of the cooling water inside the cooling water flow path 46. As such a structure, for example, a structure in which a plurality of slits along the flow direction of the cooling water are provided on the surface of the exposed portion 50 in the cooling water flow channel 46 or a structure in which the surface of the exposed portion 50 is corrugated be able to.

2 Internal combustion engine (engine)
4 cylinder head 6 cylinder block 8 combustion chamber 12 intake valve 14 exhaust valve 16 fuel injection nozzle 18 injection hole 20 duct 30 duct support 32 upper surface 34 inner side surface 36 outer surface 38 lower surface 40 heat shield film 42 top surface portion 44 mounting hole 46 cooling Water channel 50 Exposed section 62 Cylinder bore 202 Inlet 204 Outlet

Claims (7)

In a compression self-ignition internal combustion engine that performs combustion by injecting fuel into a compressed combustion chamber,
A fuel injection nozzle having an injection hole for injecting fuel, the injection hole being exposed from a cylinder head of the internal combustion engine to the combustion chamber;
A hollow duct fixed to a top surface of the cylinder head and through which a fuel spray injected from the injection hole of the fuel injection nozzle passes is formed inside the duct support;
The duct support is configured such that the inlet and the outlet of the duct are exposed to the combustion chamber,
A heat shielding film formed on at least a part of the outer surface of the duct support exposed to the combustion chamber;
The internal combustion engine, wherein the heat shielding film has a thermal conductivity lower than the thermal conductivity of the duct support.   The internal combustion engine according to claim 1, wherein the duct support is made of a material having a thermal conductivity higher than that of the material of the cylinder head. Inside the cylinder head, a cooling water flow path for circulating the cooling water is formed;
The internal combustion engine according to claim 1, wherein the duct support includes an exposed portion exposed to the inside of the cooling water flow path.   The internal combustion engine according to claim 3, wherein the duct support body is configured such that the exposed portion extends along the flow direction of the cooling water flow path.   The duct according to any one of claims 1 to 4, wherein a direction from the inlet to the outlet matches a direction of fuel spray injected from the injection hole. Internal combustion engine as described. The fuel injection nozzle has a plurality of injection holes having different injection directions,
The internal combustion engine according to any one of claims 1 to 5, wherein a plurality of the ducts are provided corresponding to each of the plurality of injection holes.   7. The fuel injection nozzle according to any one of claims 1 to 6, wherein an injection direction of the injection hole is in a range of 45 ° to 90 ° with respect to a cylinder center axis. Internal combustion engine as described.

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