JP4692459B2 - Intake port shape of internal combustion engine - Google Patents

Description

  The present invention relates to an intake port shape of an internal combustion engine, and more particularly to an intake port shape of an internal combustion engine capable of enhancing a swirling airflow generated in a combustion chamber even when the valve lift amount of the intake valve is in a small and medium region. About.

  Conventionally, various intake port shapes have been proposed to improve the flow of intake air flowing into the combustion chamber. For example, Patent Document 1 proposes a structure of an in-cylinder injection internal combustion engine having intake ports that are inclined inward toward each other downward so that the distance between two intake ports gradually decreases toward the combustion chamber. Has been. According to the structure of the cylinder injection internal combustion engine, the two tumble flows merge to form a strong turbulent flow near the spark plug and the air-fuel ratio near the spark plug becomes rich. Burn can be realized. Patent Document 2 proposes a cylinder head of an internal combustion engine having an upright port that is curved in the axial direction of the camshaft in order to ensure a distance from the inner pivot. According to the cylinder head of this internal combustion engine, the deterioration of the intake efficiency is suppressed as much as possible even when there is a large space limitation when forming an upright port, such as using an inner pivot type swing arm and an upright port together. Can do.

JP-A-10-169453 JP 09-236043 A

  By the way, when generating a strong swirl airflow in the cylinder, it is necessary to design the intake port so as to realize an optimum shape according to such a request. However, in general, the swirling airflow is strengthened when the valve lift amount of the intake valve is mainly in the middle-high range. FIG. 7 is a diagram schematically showing general intake ports 10X and 10Y together with a combustion chamber 54, an intake valve 55, and an exhaust valve 56. As shown in FIG. 7 is a projection view (horizontal projection view) of the intake ports 10X and 10Y when the cylinder head is viewed from above, and the intersection of the streamline of the intake port 10 and the inlet-side opening surface of the intake port. Is defined as a start point P1, and a point obtained by projecting the intersection of the streamline of the intake port and the central axis of the intake valve 55 on the horizontal plane S is defined as an end point P2. A straight line including the start point P1 and extending in the direction orthogonal to the crank axis on the horizontal plane S is defined as a straight line L1, and a straight line including the end point P2 and extending in the direction orthogonal to the crank axis on the horizontal plane S is defined as a straight line L2.

  In FIG. 7A, the straight line connecting the start point P1 and the end point P2 and the streamline F of the intake port projected on the horizontal plane S (hereinafter also simply referred to as the projected streamline of the intake port) F are substantially the same, and The intake port 10X having a shape in which the distance between the two intake ports 10Xa and 10Xb gradually increases from P1 toward the end point P2 is illustrated. Also, in FIG. 7B, the intake port when the projected streamline F of the intake port is not on the combustion chamber 54 center side (hereinafter also simply referred to as the inner side) than the straight line L1 (hereinafter also simply referred to as the outer side). 10Y is illustrated. In these intake ports 10X and 10Y, since the intake air tends to flow into the combustion chamber 54 from the entire downstream opening of the intake port 10, the swirling airflow is preferable when the valve lift amount is in the small and medium regions. Not strengthened.

  In other words, focusing on the small and medium range of the valve lift amount of the intake valve, the main valve of the intake generally does not have a favorable directivity, so the valve stem portion of the intake valve is a major obstacle, and the valve lift amount is not always small. The swirling airflow was not suitably strengthened in the middle region. For this reason, it can be used to reduce the emissions of HC and CO and to suppress the deterioration of fuel consumption, to the mixing characteristics of the air-fuel mixture, to the flame propagation necessary to improve the combustion during cold and lean combustion, and to suppress knocking. There was room for improvement in the required burning rate. Conventionally, there has not been a design guideline for an intake port that can suitably enhance the swirling airflow even in a small and medium valve lift range.

  Accordingly, the present invention has been made in view of the above problems, and an internal combustion engine capable of enhancing the swirling airflow generated in the combustion chamber even when the valve lift amount of the intake valve is in the small and middle region. The purpose is to provide an intake port shape.

In order to solve the above problems, the present invention, when viewed in communication with the combustion chamber of an internal combustion engine, the combustion chamber 2 of the cylinder head intake port is formed for generating a tumble flow in from above, each of the intake The point at which the intersection of the streamline of the port and the inlet-side opening surface of the intake port is projected on the horizontal plane, and the intersection of the streamline of each intake port and the central axis of the intake valve is projected onto the horizontal plane Each of the intake ports is located on the combustion chamber center side with respect to a straight line including the end point and extending in a direction perpendicular to the crank axis on the horizontal plane. water with streamlines of the intake ports of each of the projections, including the end point after bending on the combustion chamber center side than a straight line extending in a direction perpendicular to the crank axis in the horizontal plane with including the start point Characterized in that it reached the end point without than the straight line extending in a direction perpendicular to the crank axis on the surface located outside the combustion chamber.

  Here, when the starting point and the ending point are positioned as described above, the intake air flowing through the intake port generally flows into the combustion chamber generally outward as shown in FIG. 7A, for example. However, according to the present invention in which the intake port is curved as described above, when the main flow of intake air drifted by the airflow control valve or the like flows into the combustion chamber, it is more than the valve stem portion of the intake valve. It can be oriented to circulate inside. Thus, according to the present invention in which the main flow of the intake air can be prevented from interfering with the valve stem portion, the swirl airflow generated in the combustion chamber can be enhanced even when the valve lift amount of the intake valve is in the small and medium regions. Can be achieved.

The present invention is in communication with the combustion chamber of an internal combustion engine, said watching two cylinder heads that intake port is formed for generating a tumble flow in the combustion chamber from the top, and stream line of each said intake port, said When the point of projection of the intersection with the inlet side opening surface of the intake port on the horizontal plane is the starting point, and when the point of projection of the intersection of the streamline of each intake port and the central axis of the intake valve is the horizontal plane, each said intake port, the starting point is, each said intake port is located so as to be contained on a straight line extending in a direction perpendicular to the crank axis on a horizontal plane, which and projected on a horizontal plane and with including the end point The stream line is curved toward the center of the combustion chamber with respect to the straight line and then reaches the end point without being positioned outside the combustion chamber with respect to the straight line . In addition, when the start point and the end point are positioned as described above, the intake air flowing through the intake port generally tends to flow straight into the combustion chamber as a whole, but the intake port is curved as described above. According to the present invention, the main flow of the intake air can be directed as described above, so that the swirl airflow generated in the combustion chamber can be strengthened even when the valve lift amount of the intake valve is in the small and medium regions. Can be achieved.

  ADVANTAGE OF THE INVENTION According to this invention, even when the valve lift amount of an intake valve exists in a small / medium area | region, it can provide the intake port shape of the internal combustion engine which can aim at reinforcement | strengthening of the swirl | vortex airflow produced | generated in a combustion chamber.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a view schematically showing an intake port 10A having an intake port shape (hereinafter simply referred to as an intake port shape) of the internal combustion engine according to the present embodiment together with a main part of the internal combustion engine 50A. The internal combustion engine 50A is an in-cylinder direct fuel injection gasoline engine. However, the present invention is not limited to this, and any other internal combustion engine may be applied instead of the direct injecting gasoline engine as long as the present invention is applicable. The internal combustion engine 50A has an in-line four-cylinder cylinder arrangement structure, but is not limited to this, and may have an appropriate cylinder arrangement and number of cylinders. In the present embodiment, regarding the internal combustion engine 50A, the main part of the cylinder 51a is shown as a representative of each cylinder, but the other cylinders have the same structure.

  The internal combustion engine 50A includes a cylinder block 51, a cylinder head 52A, a piston 53, and the like. The cylinder block 51 is formed with a substantially cylindrical cylinder 51a. A piston 53 is accommodated in the cylinder 51a. A cavity 53 a for guiding the tumble flow T is formed on the top surface of the piston 53. A cylinder head 52 </ b> A is fixed to the upper surface of the cylinder block 51. The combustion chamber 54 is formed as a space surrounded by the cylinder block 51, the cylinder head 52 </ b> A, and the cylinder 53. The cylinder head 52 </ b> A is formed with exhaust ports 20 a and 20 b for exhausting the combusted gas from the combustion chamber 54 in addition to the intake port 10 </ b> A for guiding intake air to the combustion chamber 54. The cylinder head 52A is provided with an intake valve 55 for opening and closing the flow path of the intake port 10A and an exhaust valve 56 for opening and closing the flow path of the exhaust port. In addition, the cylinder head 52A is provided with a spark plug, a fuel injection valve, and the like (not shown).

  The intake air is deviated by an airflow control valve (not shown) and flows into the combustion chamber 54 from the intake port 10A, and is generated into a strong tumble flow T in the combustion chamber 54. In this embodiment, the inlet side opening of the intake port 10A is formed on the side surface of the cylinder head 52A, but the intake port 10A is an upright port having an inlet side opening formed on the upper surface of the cylinder head 52A. Also good. Further, the swirling airflow generated in the combustion chamber 54 is not limited to the tumble flow T. For example, a reverse tumble flow swirling in a direction opposite to the tumble flow T shown in FIG. 1 or a tumble flow T and a swirl flow are synthesized. Such an oblique tumble flow may be used.

  FIG. 2 is a schematic diagram of the intake port 10A shown in a three-dimensional manner. As shown in FIG. 2, the direction parallel to the extending direction of the cylinder 51a is defined as the vertical direction, and the direction orthogonal thereto is defined as the horizontal direction. When the intake port 10A is viewed from the upper surface of the cylinder head 52A, the intake port 10A is projected onto the horizontal plane S shown in FIG. Further, the vertical plane G perpendicular to the crank axis line divides the inner side and the outer side on the horizontal plane S. FIG. 2 shows a vertical plane G1 including the start point P1 and a vertical plane G2 including the end point P2. In the present embodiment, the vertical axis G2 includes the central axis of the intake valve 55. From FIG. 2, it can be seen that the starting point P1 is located inside the vertical plane G2. It can also be seen that the projected streamline F of the intake port 10A projected onto the horizontal plane S is curved inward from the vertical plane G1. A straight line formed by intersecting the horizontal plane S and the vertical plane G1 is a straight line L1, and a straight line formed by intersecting the horizontal plane S and the vertical plane G2 is a straight line L2.

  FIG. 3 is a diagram schematically showing the intake port 10A viewed in a horizontal projection. FIG. 3 shows the combustion chamber 54 and intake / exhaust valves 55 and 56 together with the intake port 10A. As shown in FIG. 3, the starting point P1 is located inside the straight line L2. The projected streamline F of the intake port 10A is curved inward from the straight line L1. As a result, the main flow biased by the air flow control valve is directed to flow into the combustion chamber 54 from between the valve stem portion of the intake valve 55 and the inner wall surface of the intake port 10A mainly in the first half of the curved portion. That is, even if the positions of the start point P1 and the end point P2 are designed to have a positional relationship as shown in FIG. 3, according to the intake port 10A having the curved intake port shape as described above, the directivity as described above is mainly used. Can be given. The curved portion may be designed with an appropriate position, length, and degree of curvature according to specifications such as the inclination angle of the intake port 10A.

  FIG. 4 is a graph showing the relationship between the valve lift amount and the tumble strength for the intake port 10A having the intake port shape according to the present embodiment and the general intake port 10X. The shape of the intake port 10X is as shown in FIG. In the intake port 10A, by collecting the main flow inside the intake port 10A, a flow along the umbrella shape of the intake valve 55 is formed in the small and middle region of the valve lift amount, and the intake air flows most smoothly into the combustion chamber 54. . Thereby, compared with the intake port 10X, the tumble strength can be increased particularly in a region where the valve lift is small and medium. As described above, the intake port shape of the internal combustion engine that can enhance the swirling airflow generated in the combustion chamber can be realized by the intake port 10A even when the valve lift amount of the intake valve 55 is in the small and middle region.

  The intake port 10B having the intake port shape according to the present embodiment is located so that the start point P1 includes the end point P2 and is included on the straight line L3 extending in the direction perpendicular to the crank axis on the horizontal plane S, and The projected streamline F of the intake port 10B projected onto the horizontal plane S is different from the intake port 10A having the intake port shape according to the first embodiment in that it is curved inward from the straight line L3. FIG. 5 is a schematic view of the intake port 10B viewed in a horizontal projection. FIG. 5 also shows the combustion chamber 54 and intake / exhaust valves 55 and 56 together with the intake port 10B. As shown in FIG. 5, it can be seen that the start point P1 is located on the straight line L3 in the intake port 10B. It can also be seen that the projected streamline F of the intake port 10B is curved inward from the straight line L3.

  Thus, the main flow is directed to flow into the combustion chamber 54 from between the valve stem portion of the intake valve 55 and the inner wall surface of the intake port 10B, mainly before passing through the curved portion. That is, even if the positions of the start point P1 and the end point P2 are in the positional relationship shown in FIG. 5 by design, the intake port 10B having the curved intake port shape as described above is mainly directed as described above. Can have sex. As described above, the intake port 10B can realize the intake port shape of the internal combustion engine that can enhance the swirling airflow generated in the combustion chamber even when the valve lift amount of the intake valve 55 is in the small and middle region.

  In the intake port 10C having the intake port shape according to the present embodiment, the start point P1 is not located on the inner side (that is, located outside) the straight line L2, and the projected streamline of the intake port 10 projected onto the horizontal plane S The point that F is curved inward from the straight line L2 is different from the intake port 10A having the intake port shape according to the first embodiment. FIG. 6 is a diagram schematically showing the intake port 10C viewed in a horizontal projection. FIG. 6 also shows the combustion chamber 54 and intake / exhaust valves 55 and 56 together with the intake port 10C. As shown in FIG. 6, it can be seen that the starting point P1 is located outside the straight line L2. It can also be seen that the projected streamline F of the intake port 10C is curved inward from the straight line L2.

  As a result, the main flow is directed to flow into the combustion chamber 54 mainly between the valve stem portion of the intake valve 55 and the inner wall surface of the intake port 10C just before passing through the curved portion. That is, even if the positions of the start point P1 and the end point P2 are designed to have the positional relationship shown in FIG. 6, the intake port 10C having the curved intake port shape as described above is mainly used in the directivity as described above. Can be given. When the start point P1 is located outside the straight line L2, for example, the intake air is formed as a whole by forming the intake port so that the projected streamline F is substantially the same as the straight line connecting the viewpoint P1 and the end point P2. It is also possible to flow into the combustion chamber 54 inward. However, according to the intake port 10C having the intake port shape according to the present embodiment, the mainstream directivity can be further improved. Further, for example, when the position of the starting point P1 is relatively close to the straight line L2 by design, the intake port 10C is particularly effective. As described above, the intake port shape of the internal combustion engine that can enhance the swirling airflow generated in the combustion chamber can be realized by the intake port 10C even when the valve lift amount of the intake valve 55 is in the small and middle region.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, although the intake ports 10A, 10B, and 10C are independent ports in the above-described embodiment, the present invention is not limited to this, and the intake passage may be a siamese port that branches on the downstream side and merges into one on the upstream side. Good.

It is a figure which shows typically 10 A of intake ports with the principal part of 50 A of internal combustion engines. It is the schematic diagram of 10 A of intake ports shown in three dimensions. It is a figure which shows typically 10 A of intake ports which looked at horizontal projection. It is a figure which contrasts and shows the relationship between valve lift amount and tumble strength about intake port 10A and general intake port 10X. FIG. 5 is a diagram schematically showing an intake port 10B viewed in a horizontal projection. It is a figure which shows typically 10 C of intake ports seen by horizontal projection. 2 is a view schematically showing general intake ports 10X and 10Y together with a combustion chamber 54, an intake valve 55, and an exhaust valve 56. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Intake port 50 Internal combustion engine 51 Cylinder block 52 Cylinder head 53 Piston 54 Combustion chamber 55 Intake valve 56 Exhaust valve

Claims (2)

When viewed from above, a cylinder head that communicates with a combustion chamber of an internal combustion engine and has two intake ports that generate a tumble flow in the combustion chamber, the streamlines of each of the intake ports and the inlet side of the intake port When the point of projection of the intersection with the opening surface on the horizontal plane is the starting point, and the point of projection of the intersection of the streamline of each intake port and the central axis of the intake valve on the horizontal plane is the end point,
Each of the intake ports has the start point that is located on the combustion chamber center side with respect to a straight line that includes the end point and extends in a direction perpendicular to the crank axis on the horizontal plane, and that is projected on the horizontal plane. A direction in which the streamline of the port includes the start point and includes the end point after being curved toward the center of the combustion chamber from a straight line extending in a direction orthogonal to the crank axis on the horizontal plane and orthogonal to the crank axis on the horizontal plane An intake port shape of an internal combustion engine, wherein the end point is reached without being positioned outside the combustion chamber with respect to the straight line extending in a straight line. When viewed from above, a cylinder head that communicates with a combustion chamber of an internal combustion engine and has two intake ports that generate a tumble flow in the combustion chamber, the streamlines of each of the intake ports and the inlet side of the intake port When the point of projection of the intersection with the opening surface on the horizontal plane is the starting point, and the point of projection of the intersection of the streamline of each intake port and the central axis of the intake valve on the horizontal plane is the end point,
Each of the intake ports is located such that the start point is included on a straight line including the end point and extending in a direction perpendicular to the crank axis on the horizontal plane and projected onto the horizontal plane The shape of the intake port of the internal combustion engine is characterized in that the streamline is curved toward the center of the combustion chamber from the straight line and then reaches the end point without being positioned outside the combustion chamber from the straight line.

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