JP2016183624A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of forming a heat insulation film on a wall surface of a cylinder head near an opening portion of an intake port for a combustion chamber while improving a relation between a swirl ratio and a flow coefficient of the intake port.SOLUTION: An internal combustion engine comprises a tangential port 22 and a helical port 24 connected to a common combustion chamber 12 for forming a swirl flow. A wall surface around an opening portion 34 of the tangential port 22 includes a first cutter part 42 in a region downstream, in an intake flow direction, of a first valve seat section 36. A wall surface around an opening portion 38 of the helical port 24 includes a second cutter part 44 in a region downstream, in the intake flow direction, of a second valve seat section 40. Heat insulation films are formed on respective surfaces of the first cutter part 42 and the second cutter part 44. A surface roughness of the heat insulation film formed on the surface of the first cutter part 42 is lower than that of the heat insulation film formed on the surface of the second cutter part 44.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine including a tangential port and a helical port as intake ports for generating a swirl flow in a combustion chamber.

  Patent Document 1 discloses an internal combustion engine in which a heat shielding film (heat insulating film) is formed on a part or all of a wall surface constituting a combustion chamber.

JP 2013-024143 A JP 2002-195044 A JP 2000-310125 A

  There is known an internal combustion engine that includes an intake port including a tangential port and a helical port connected to a common combustion chamber and generates a swirl flow in the combustion chamber. In the internal combustion engine having such a configuration, if a heat insulating film is formed on the wall surface of the cylinder head in the vicinity of the opening portion of the intake port with respect to the combustion chamber, there are the following problems. That is, since the heat insulating film basically has a large surface roughness, it can affect the flow of intake air flowing into the cylinder. As a result, there is a possibility that the flow coefficient of the intake port is lowered or the swirl ratio is lowered.

  The present invention has been made to solve the above-described problems, and improves the relationship between the swirl ratio and the flow rate coefficient of the intake port, while the cylinder head wall surface near the opening of the intake port with respect to the combustion chamber. An object of the present invention is to provide an internal combustion engine capable of forming a heat insulating film.

  The internal combustion engine according to the present invention includes an intake port including a tangential port and a helical port connected to a common combustion chamber in a cylinder head. A swirl flow is generated in the combustion chamber of the internal combustion engine. The wall surface around the opening of the tangential port with respect to the combustion chamber is located on the downstream side of the flow of intake air with respect to the first valve seat portion that contacts the intake valve that opens and closes the tangential port when the valve is closed. A combustion chamber wall surface formed in the cylinder head includes a first groove portion formed so as to cover the first valve seat portion when viewed from the axial direction of the cylinder. The wall surface around the opening of the helical port with respect to the combustion chamber is located at a portion downstream of the flow of the intake air with respect to the second valve seat portion that contacts the intake valve that opens and closes the helical port when the valve is closed. The combustion chamber wall surface formed in a cylinder is viewed from the axial direction of the cylinder, and includes a second groove portion formed so as to cover the second valve seat portion. Thermal insulation films are formed on the surfaces of the first groove and the second groove, respectively. The surface roughness of the heat insulation film formed on the surface of the first groove is smaller than the surface roughness of the heat insulation film formed on the surface of the second groove.

  According to the present invention, the surface roughness of the heat insulating film formed on the surface of the first groove portion on the tangential port side is greater than the surface roughness of the heat insulating film formed on the surface of the second groove portion on the helical port side. By making it smaller, it becomes possible to form a heat insulating film on the wall surface of the cylinder head near the opening of the intake port with respect to the combustion chamber while improving the relationship between the swirl ratio and the flow coefficient of the intake port.

1 is a diagram schematically illustrating the overall configuration of an internal combustion engine according to Embodiment 1 of the present invention. FIG. 2 is a perspective view for explaining a specific configuration of an intake port provided in the intake passage shown in FIG. 1. It is the figure which looked at the combustion chamber shown in Drawing 2 from the lower part side in the direction of an axis of a cylinder. It is sectional drawing showing the structure around each opening part of the tangential port and helical port with respect to a combustion chamber. It is a figure for demonstrating the effect by providing the difference in the surface roughness of the heat insulation film | membrane between a tangential port and a helical port. It is a figure showing the relationship (trade off-line) between the flow coefficient of an intake port, and a swirl ratio.

Embodiment 1 FIG.
FIG. 1 is a diagram schematically showing the overall configuration of an internal combustion engine 10 according to Embodiment 1 of the present invention. An internal combustion engine 10 shown in FIG. 1 is a compression ignition engine (a diesel engine as an example). An intake passage 14 and an exhaust passage 16 communicate with the combustion chamber 12 of each cylinder of the internal combustion engine 10.

  Each cylinder is provided with a fuel injection valve 18 that injects fuel into the combustion chamber 12. An actuator for controlling the operation of the internal combustion engine 10 such as the fuel injection valve 18 is electrically connected to an electronic control unit (ECU) 20 and is driven according to a command from the ECU 20.

  FIG. 2 is a perspective view for explaining a specific configuration of the intake port provided in the intake passage 14 shown in FIG. As shown in FIG. 2, the intake passage 14 includes a tangential port 22 and a helical port 24 as intake ports connected to the common combustion chamber 12.

  The tangential port 22 is formed so that the intake air can be guided so that the intake air flows into the combustion chamber 12 in a direction along the cylinder inner peripheral surface 26. According to the tangential port 22 formed in this way, the swirl flow generated in the combustion chamber 12 can be strengthened as the flow rate of the intake air supplied from the tangential port 22 increases.

  On the other hand, the helical port 24 positively flows toward the lower side (piston side) in the axial direction of the cylinder with respect to the intake air flowing into the combustion chamber 12 from the helical port 24 as indicated by a broken arrow in FIG. In order to produce, it is formed in a spiral shape. The generation of the swirl flow in the internal combustion engine 10 is mainly performed by the tangential port 22, and the other helical port 24 has the above-described shape so as not to inhibit the flow of the generated swirl.

  Next, with reference to FIG. 3 and FIG. 4, configurations around the respective openings of the tangential port 22 and the helical port 24 with respect to the combustion chamber 12 will be described.

  FIG. 3 is a view of the combustion chamber 12 shown in FIG. 2 as viewed from below in the axial direction of the cylinder. FIG. 4 is a cross-sectional view showing a configuration around the respective openings of the tangential port 22 and the helical port 24 with respect to the combustion chamber 12. 3 and 4, reference numeral 28 denotes an intake valve, reference numeral 30 denotes an exhaust valve 30, and reference numeral 32 denotes a spark plug.

  4A schematically shows a cross section of the configuration around the opening 34 of the tangential port 22 taken along the line AA (see FIG. 3) passing through the axial center of the intake valve 28 that opens and closes the tangential port 22. It expresses. A wall surface around the opening 34 is formed with a first valve seat portion 36 that contacts the umbrella portion 28a of the intake valve 28 when the valve is closed. On the other hand, FIG. 4B schematically shows a cross section of the configuration around the opening 38 of the helical port 24 taken along the line BB (see FIG. 3) passing through the axial center of the intake valve 28 that opens and closes the helical port 24. It expresses. A wall surface around the opening 38 is formed with a second valve seat portion 40 that contacts the umbrella portion 28a of the intake valve 28 when the valve is closed.

  Further, the opening 34 of the tangential port 22 has a groove in a downstream portion of the intake flow (intake flow flowing into the combustion chamber 12 from the tangential port 22) with respect to the first valve seat portion 36. A first cutter part 42 having a shape is formed. On the other hand, the opening 38 of the helical port 24 has a groove-like shape at a downstream side of the intake air flow (intake air flowing into the combustion chamber 12 from the helical port 24) with respect to the second valve seat 40. A second cutter portion 44 is formed.

  The 1st cutter part 42 and the 2nd cutter part 44 are parts formed together when forming the 1st valve seat part 36 and the 2nd valve seat part 40 with a processing tool (valve seat cutter). As shown in FIG. 3 (that is, the combustion chamber wall surface formed in the cylinder head is viewed from the axial direction of the cylinder), the first cutter portion 42 and the second cutter portion 44 are each a first valve seat portion. 36 and the second valve seat portion 40 are formed so as to cover the entire circumference. In addition, the first cutter portion 42 is formed to extend in the swirling direction of the swirl flow in the combustion chamber 12.

  In the internal combustion engine 10 of the present embodiment, a heat insulating film is formed on the wall surface of the cylinder head 46 constituting the combustion chamber 12 in order to improve fuel efficiency by reducing cooling loss. In order to enhance the fuel efficiency improvement effect due to the application of the heat insulating film, it is desirable to increase the number of portions to which the heat insulating film is applied. Therefore, in the present embodiment, a heat insulating film is also formed on the first cutter part 42 and the second cutter part 44 near the outlets of the tangential port 22 and the helical port 24. As a method for applying the heat insulating film, for example, a method of forming an anodized film (anodized film) by anodizing the aluminum alloy that is a base material of the cylinder head 46, or zirconia is applied to the application target part. A technique of forming a zirconia film by thermal spraying can be used.

  In addition, the internal combustion engine 10 of the present embodiment has a surface roughness between the heat insulating film formed on the surface of the first cutter unit 42 and the heat insulating film formed on the surface of the second cutter unit 44. It is characterized in that a difference is provided.

  More specifically, the surface roughness of the heat insulating film formed on the surface of the first cutter unit 42 is smaller than the surface roughness of the heat insulating film formed on the surface of the second cutter unit 44. A heat insulating film is provided. Such a relative difference in surface roughness can be given as an example by the following method. That is, with respect to the formation of the heat insulating film of the first cutter portion 42 that is the side that relatively reduces the surface roughness, a step of polishing the heat insulating film is added, and the heat insulation of the other second cutter portion 44 is added. Do not polish the film.

  Next, with reference to FIG. 5, the effect by providing a difference in the surface roughness of the heat insulation film between the tangential port 22 and the helical port 24 will be described. As described above, the surface roughness of the heat insulating film of the first cutter portion 42 on the tangential port 22 side is relatively small. When the surface roughness of the first cutter portion 42 is large, the flow of intake air from the tangential port 22 is changed to the cylinder head as indicated by the arrow marked “large roughness” in FIG. It becomes easy to peel from 46 wall surfaces. On the other hand, when the surface roughness of the first cutter portion 42 is small (that is, the surface is smooth), the tangential is indicated by an arrow denoted as “low roughness” in FIG. The flow of intake air from the port 22 can easily flow along the wall surface of the cylinder head 46. As a result, the intake air flowing into the combustion chamber 12 from the tangential port 22 easily flows toward the tangential direction of the cylinder inner peripheral surface 26 (see FIG. 3), so that a strong swirl flow can be easily generated. Further, since the surface roughness is small, it is possible to suppress the occurrence of turbulence in the boundary layer between the first cutter portion 42 and the air passing therearound, and to increase the flow coefficient of the tangential port 22.

  On the other hand, the surface roughness of the heat insulating film of the second cutter portion 44 on the helical port 24 side is relatively increased. When the surface roughness of the second cutter portion 44 is small, the flow of the intake air from the helical port 24 is changed to the cylinder head 46 as shown by the arrow indicated as “small roughness” in FIG. It becomes easy to flow along the wall surface. On the other hand, when the surface roughness of the second cutter portion 44 is small, the flow of the intake air from the helical port 24 is changed to the cylinder head as indicated by the arrow indicated as “large roughness” in FIG. It becomes easy to peel on the wall surface of 46. As a result, the flow of the intake air flowing into the combustion chamber 12 from the helical port 24 can be made more fully directed downward (piston side) in the axial direction of the cylinder. More specifically, as can be seen by looking at the shapes of the left side of the first cutter part 42 and the second cutter part 44 in FIGS. 5 (A) and 5 (B), the second cutter part 44 As compared with the first cutter part 42, a steep inclination is given. For this reason, when the surface roughness is large, the intake air flows into the combustion chamber 12 in a manner concentrated on the umbrella portion 28 a side of the intake valve 28 without following the inclination of the second cutter portion 44. Thereby, the flow of the swirl generated in the combustion chamber 12 can be made difficult to be inhibited by the intake air from the helical port 24.

  FIG. 6 is a diagram illustrating the relationship (trade off-line) between the flow coefficient of the intake port and the swirl ratio. In addition, the flow coefficient of the intake port here indicates a flow coefficient when the tangential port 22 and the helical port 24 are comprehensively captured.

  As shown in FIG. 6, there is a trade-off relationship between the flow coefficient of the intake port and the swirl ratio (swirling strength of swirl flow). That is, when the flow coefficient is increased, the swirl ratio is decreased, and conversely, when the swirl ratio is increased, the flow coefficient is decreased. By adopting the above-described configuration of the present embodiment, that is, by making the surface roughness of the heat insulating film of the first cutter portion 42 smaller than the surface roughness of the heat insulating film of the second cutter portion 44, the intake port The swirl ratio can be increased while increasing the flow coefficient as a whole. As a result, as shown in FIG. 6 as an example, the swirl ratio under the same flow coefficient can be increased from a black circle mark to a star mark in the same figure.

  As described above, according to the configuration of this embodiment, the cylinder head 46 near the openings 34 and 38 of the tangential port 22 and the helical port 24 is improved while improving the trade-off relationship between the flow coefficient and the swirl ratio. A heat insulating film can be formed on the wall surface.

  By the way, in Embodiment 1 mentioned above, it employ | adopts the technique of grind | polishing about the heat insulation film | membrane of the 1st cutter part 42, and not grind | polishing about the heat insulation film | membrane of the 2nd cutter part 44. The surface roughness of the heat insulating film formed on the surface of the first cutter unit 42 is made smaller than the surface roughness of the heat insulating film formed on the surface of the second cutter unit 44. However, the method of giving the relative difference in surface roughness is not limited to the above example, and may be as follows, for example. That is, the heat-insulating film of the second cutter portion 44 on the side where the surface roughness is to be relatively reduced is subjected to shot blasting in order to increase the surface roughness, and the surface roughness is to be relatively reduced. Such a process is not performed on the heat insulating film of the first cutter unit 42 on the side. Or you may vary the provision method of a heat insulation film between ports. Specifically, for example, the heat insulating film of the first cutter unit 42 on the side where the surface roughness is desired to be relatively reduced is an anodized film, and the second cutter unit 44 on the side where the surface roughness is desired to be relatively increased. The heat insulating film may be a zirconia film formed by zirconia spraying.

  Further, in the first embodiment described above, the internal combustion engine 10 in which one tangential port 22 and one helical port 24 are connected to the common combustion chamber 12 is taken as an example. However, in the present invention, one or both of the tangential port and the helical port connected to the common combustion chamber may be plural. The present invention may be applied not only to the compression ignition type internal combustion engine 10 but also to a spark ignition type internal combustion engine (for example, a gasoline engine).

  In the first embodiment described above, the first cutter portion 42 corresponds to the “first groove portion” in the present invention, and the second cutter portion 44 corresponds to the “second groove portion” in the present invention. ing.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Combustion chamber 14 Intake passage 22 Tangential port 24 Helical port 26 Cylinder inner peripheral surface 28 Intake valve 28a Intake valve umbrella part 34 Tangential port opening part 36 First valve seat part 38 Helical port opening part 40 2nd valve seat part 42 1st cutter part 44 2nd cutter part 46 Cylinder head

Claims (1)

An internal combustion engine comprising a cylinder head having an intake port including a tangential port and a helical port connected to a common combustion chamber, wherein a swirl flow is generated in the combustion chamber,
The wall surface around the opening of the tangential port with respect to the combustion chamber is located on the downstream side of the flow of intake air with respect to the first valve seat portion that contacts the intake valve that opens and closes the tangential port when the valve is closed. Including a first groove portion formed to cover the first valve seat portion when the combustion chamber wall surface formed in the cylinder head is viewed from the axial direction of the cylinder;
The wall surface around the opening of the helical port with respect to the combustion chamber is located at a portion downstream of the flow of the intake air with respect to the second valve seat portion that contacts the intake valve that opens and closes the helical port when the valve is closed. A second groove portion formed so as to cover the second valve seat portion when the combustion chamber wall surface formed in the above is viewed from the axial direction of the cylinder,
Heat insulation films are formed on the surfaces of the first groove and the second groove, respectively.
An internal combustion engine characterized in that a surface roughness of the heat insulating film formed on the surface of the first groove is smaller than a surface roughness of the heat insulating film formed on the surface of the second groove.

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