JP2011247270A - Port structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge exhaust smoothly without complicating a structure, in a port structure of an internal combustion engine.SOLUTION: An upstream part of an exhaust port 41 is substantially formed with a square cross section having two planes parallel to each other, while a throat portion 41a continuing from a combustion chamber 12 is formed with a circular cross section. As a result, the upstream part of the exhaust port 41 and the throat portion 41a are continuously formed with a smooth plane, which prevents separation of exhaust stream to increase an intake flow.

Description

  The present invention relates to a port structure of an internal combustion engine applied to an exhaust port that discharges combustion gas from a combustion chamber when an exhaust valve is opened.

  FIG. 9 is a schematic view showing an intake port structure of a general internal combustion engine, FIGS. 10-1 to 11-2 are schematic views showing a design concept of the intake port structure of the internal combustion engine, and FIG. It is the schematic showing the intake port structure of an engine.

  In a general internal combustion engine intake port structure, as shown in FIG. 9, a downstream end of the intake port communicates with an upper portion of the combustion chamber 101, and an intake valve 103 is provided there. Therefore, the intake flow of the intake port 102 can be introduced into the combustion chamber 101 by opening and closing the intake valve 103. In such a design concept of the intake port 103, achieving both a high tumble ratio and a high flow coefficient achieves highly efficient engine performance.

  That is, the intake flow of the intake port 102 is introduced into the combustion chamber 101 when the intake valve 103 is opened. At this time, the intake flow 104 flowing on the upper surface side of the intake port 102 must flow linearly into the combustion chamber 101 to form a strong tumble flow 105. On the other hand, the intake air flow 106 flowing on the lower surface side of the intake port 102 needs to flow along the wall surface to the combustion chamber 101 so as not to interfere with the tumble flow. That is, the throat portion 107 of the intake port 102 can have a high tumble ratio by forming the upper surface portion in a gentle curved shape, and can have a high flow coefficient by setting its bending angle θ large on the lower surface portion side. It becomes.

  By the way, when forming the throat part connected with a combustion chamber in the downstream end part with respect to the intake port formed in the cylinder head, this throat part is formed using the throat cutter from the lower surface of a cylinder head. As illustrated in FIG. 10A, a throat portion 205 is formed by cutting along the axis 204 of the intake valve inclined at a predetermined angle with respect to the axis 203 of the intake port 202 using a throat cutter 201 having a bowl shape. . Also, as shown in FIG. 10-2, a throat cutter 211 having a chevron shape is used to cut the throat portion 215 by cutting along the axis 214 of the intake valve inclined at a predetermined angle with respect to the axis 213 of the intake port 212. Form.

  However, as shown in FIG. 10A, when the throat portion 205 is formed using the bowl-shaped throat cutter 201, a dead volume is formed on the upper surface portion of the throat portion 205 in the intake port 202, and the intake flow is disturbed. The tumble flow is weakened. On the other hand, as shown in FIG. 10-2, when the throat portion 215 is formed by using the throat cutter 211 having a chevron shape, the bending angle θ of the lower surface portion of the throat portion 215 in the intake port 212 becomes small, and the intake air flow becomes the wall surface. And the flow rate will drop.

  As a method for increasing the flow rate of the intake air flowing into the combustion chamber from the intake port, it is known to increase the diameter of the intake port. However, as shown in FIG. 11A, when the intake port 301 having a circular cross section is thickened and moved upward, the intake flow 303 flowing on the upper surface side of the intake port 302 is linearly moved downward into the combustion chamber. As a result, the formation position of the tumble flow is lowered and the flow rate is lowered. Also, as shown in FIG. 11-2, when the intake port 311 having a circular cross section is made thicker and moved downward, the bending angle of the lower surface portion of the intake port 312 becomes smaller, and the intake flow 313 flowing here is separated from the wall surface. As a result, the flow rate decreases.

  From such a design concept of the intake port, a technique for increasing the strength of the tumble flow without reducing the maximum flow rate is described in each Patent Document 1. In the intake port structure of the internal combustion engine described in Patent Document 1, as shown in FIG. 12, the intake port 401 and the combustion chamber 402 can be opened and closed by an intake valve 403, and the tumble flow side half of the intake port 401 is opened. 401a has a substantially triangular cross-sectional shape wider than the other half 401b so that the intake air flow from the intake port 401 promotes tumble.

Japanese Utility Model Publication No. 04-137224

  However, in the intake port structure of the conventional internal combustion engine described in Patent Document 1 described above, since the intake port 401 has a substantially triangular cross-sectional shape, the cross-sectional area substantially decreases with respect to the circular cross-sectional shape. As a result, the flow rate introduced into the combustion chamber 402 decreases. In order to ensure a predetermined flow rate, it is necessary to increase the width or height of the intake port 401. However, if the shape of the intake port is changed, as described above, the intake flow is disturbed and the flow rate cannot be prevented from decreasing.

  Further, the intake port 401 needs to have a circular cross-sectional shape in accordance with the shape of the intake valve 403 so that the downstream end can be closed by the intake valve 403. Therefore, the shape of the intake port 401 must be changed from a triangular cross-sectional shape to a circular cross-sectional shape on the way. However, since the other half portion 401a of the intake port 401 having a triangular cross-sectional shape has an acute angle shape, it is difficult to smoothly continue the circular cross-sectional shape. For this reason, the intake port 401 is twisted at the connecting portion from the triangular cross-sectional shape portion to the circular cross-sectional shape portion, and the intake air flow that flows into the combustion chamber 402 cannot be smoothly flown by the corner portion or the step portion. The flow rate will drop.

  An object of the present invention is to solve such a problem, and an object of the present invention is to provide a port structure of an internal combustion engine that can smoothly discharge exhaust gas without causing a complicated structure.

  In order to solve the above-described problems and achieve the object, the port structure of the internal combustion engine of the present invention is an internal combustion engine port structure capable of communicating with a combustion chamber via an open / close valve. The throat portion to the combustion chamber has a circular cross-sectional shape, and the exhaust port and the throat portion are continuous with a smooth surface.

  The port structure of the internal combustion engine of the present invention is characterized in that the exhaust port and the throat portion are formed to have substantially the same width.

  In the port structure of the internal combustion engine of the present invention, the exhaust port is set to have a width larger than a height.

  In the port structure of the internal combustion engine of the present invention, the exhaust port has an upper surface portion, a lower surface portion, and left and right side portions, and at least two surfaces of the left and right side portions are parallel, and the upper surface portion and the left and right side portions are Are continuous by the left and right upper curved surface portions, the lower surface portion and the left and right side surface portions are continuous by the left and right lower curved surface portions, and the curvature radius of the upper curved surface portion is set smaller than the curvature radius of the lower curved surface portion. It is characterized by.

  According to the port structure of the internal combustion engine of the present invention, the exhaust port has a substantially square cross-sectional shape having two parallel surfaces, while the throat portion has a circular cross-sectional shape, and the exhaust port and the throat portion are continuously connected by a smooth surface. As a result, it is possible to discharge the exhaust gas smoothly from the combustion chamber without complicating the structure.

FIG. 1 is a schematic cross-sectional view in which a port structure of an internal combustion engine according to Reference Example 1 of the present invention is applied to an intake port. FIG. 2 is a schematic diagram illustrating an intake port of Reference Example 1. FIG. 3 is a cross-sectional view illustrating a method of processing the intake port of Reference Example 1. FIG. 4 is a graph showing the relationship between the tumble ratio and the flow rate in the intake port of Reference Example 1. FIG. 5 is a schematic cross-sectional view in which the port structure of the internal combustion engine according to the first embodiment of the present invention is applied to an exhaust port. FIG. 6 is a plan view in which the port structure of the internal combustion engine according to Reference Example 2 of the present invention is applied to an intake port. 7 is a sectional view taken along line VII-VII in FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. FIG. 9 is a schematic view showing an intake port structure of a general internal combustion engine. FIG. 10A is a schematic diagram illustrating a design concept of an intake port structure of an internal combustion engine. FIG. 10-2 is a schematic diagram illustrating a design concept of the intake port structure of the internal combustion engine. FIG. 11A is a schematic diagram illustrating a design concept of an intake port structure of an internal combustion engine. FIG. 11-2 is a schematic diagram illustrating a design concept of the intake port structure of the internal combustion engine. FIG. 12 is a schematic diagram showing an intake port structure of a conventional internal combustion engine.

  Hereinafter, an embodiment of a port structure of an internal combustion engine according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Reference example 1

  FIG. 1 is a schematic cross-sectional view in which a port structure of an internal combustion engine according to Reference Example 1 of the present invention is applied to an intake port, FIG. 2 is a schematic view showing an intake port of Reference Example 1, and FIG. FIG. 4 is a graph showing the relationship between the tumble ratio and the flow rate in the intake port of Reference Example 1. FIG.

  In Reference Example 1, the port structure of the internal combustion engine of the present invention will be described as applied to an intake port. In the intake port structure of the internal combustion engine of Reference Example 1, as shown in FIGS. 1 and 2, the intake port 11 has a cylinder head whose center line C1 is inclined at a predetermined angle with respect to the center line C2 of the combustion chamber 12. 13 is provided. The intake valve 14 is supported by the cylinder head 13 so as to be movable in the axial direction along a center line C3 having a predetermined angle with respect to the center line C1 of the intake port 11. An annular seat ring 15 on which the intake valve 14 is seated is attached to the end edge of the intake port 11 facing the combustion chamber 12.

  In addition, the intake port 11 has an approximately square cross section (rectangular cross section) at the upstream portion thereof. That is, in the cross-sectional shape of the intake port 11, the two surfaces of the upper surface portion 21 and the lower surface portion 22 are parallel, and the two surfaces of the left side surface portion 23 and the right side surface portion 24 are parallel. Then, both end portions of the upper surface portion 21 and upper end portions of the left and right side surface portions 23 and 24 are continuous by the left and right upper curved surface portions 25 and 26, and both end portions of the lower surface portion 22 and lower ends of the left and right side surface portions 23 and 24. Are continuous by the left and right lower curved surface portions 27, 28. In this case, the curvature radius R1 of the upper curved surface portions 25, 26 is set to be smaller than the curvature radius R2 of the lower curved surface portions 27, 28.

  On the other hand, the intake port 11 has a downstream portion thereof, that is, a throat portion 11a having a substantially circular cross-sectional shape. The intake port 11 is continuously changed from the upstream portion to the downstream throat portion 11a so that the square cross-sectional shape is gradually changed to a circular cross-sectional shape and the cross-sectional shape is smoothly changed. In this case, since the line of the lower surface portion 22 of the intake port 11 is shorter than the line of the upper surface portion 21 with respect to the throat portion 11a, the surface becomes wrinkled when the curvature radius of the cross section changes greatly, and the edge portion becomes Will be formed. In this reference example, as described above, the intake port 11 has the curvature radius R2 of the lower curved surface portions 27 and 28 on the lower surface portion 22 side rather than the curvature radius R1 of the upper curved surface portions 25 and 26 on the upper surface portion 21 side. Is set larger. For this reason, it is easy to change the lower curved surface portions 27 and 28 of the large curvature radius R2 to the circular cross section, and the intake port 11 can be continued on a smooth surface from the upstream portion to the downstream throat portion 11a.

  Further, it is desirable that the upstream portion of the intake port 11 and the throat portion 11a are set so that the widths thereof are substantially equal. Thereby, the intake air flow of the intake port 11 can smoothly flow into the combustion chamber 12 through the throat portion 11a. Further, it is desirable that the upstream portion of the intake port is set to be rectangular so that the width W is larger than the height H. Thus, while ensuring a predetermined cross-sectional area of the flow path, the upper surface position of the intake port 11 can be set low to ensure a strong tumble flow, and the lower surface position of the intake port 11 can be set high. Thus, by increasing the bending angle θ of the wall surface leading to the combustion chamber 12, separation of the intake flow can be suppressed and the intake flow rate can be increased. In addition, since the curvature radius R1 of the upper curved surface portions 25 and 26 on the upper surface portion 21 side is set smaller than the curvature radius R2 of the lower curved surface portions 27 and 28 on the lower surface portion 22 side, the intake port 11 has a larger planar area. In this respect, the tumble can be efficiently increased by increasing the intake air flow rate.

  In the seat ring 15, an inner peripheral surface 16 a in a region near the center of the combustion chamber 12 is inclined along the flow path of the intake port 11, and an inner peripheral surface 16 b in a region near the outer peripheral portion of the combustion chamber 12 is in the combustion chamber. It is formed so as to expand toward 12. In other words, the throat portion 11a of the intake port 11 and the inner peripheral surface 16a of the seat ring 15 are smoothly connected, and the energy loss of the intake flow is minimized and the tumble flow is not weakened. On the other hand, the inner peripheral surface 16b of the seat ring 15 is smoothly connected from the throat portion 11a of the intake port 11, so that separation of the intake air flow in the vicinity of this connection portion is reduced and energy loss is minimized. It is expanded toward the combustion chamber 12 with a predetermined radius of curvature R3 so that the bending angle θ increases. The curvature radius R3 is preferably set within a range of D / 10 or more and D / 2 or less, for example, where D is the representative inner diameter of the intake port 11.

  The throat portion 11a and the seat ring 15 of the intake port 11 thus configured have inner peripheral surfaces 16a and 16b formed as approximate curved surfaces by a plurality of taper processes. The processing method will be described below.

  As shown in FIG. 3, in the first step, the seat cutter 31 is advanced by a predetermined amount along the center line C3 of the intake valve 14, and the inner peripheral surfaces 16a and 16b of the seat ring 15 are cut. In the second step, the throat cutter 32 is advanced by a predetermined amount along a center line C4 inclined by a predetermined angle α toward the center line C1 side of the intake port 11 with respect to the center line C3 of the intake valve 14, The peripheral surfaces 16a and 16b and the throat portion 11a of the intake port 11 are processed.

  The seat cutter 31 is machined so that the inner peripheral surface 16a is inclined toward the central portion of the combustion chamber 12 by cutting the inner peripheral surfaces 16a and 16b of the seat ring 15 into a conical shape. The surface 16b is processed so as to expand toward the outer peripheral portion of the combustion chamber 12 at a bending angle θ. The throat cutter 32 is cut so that the boundary portions between the inner peripheral surfaces 16a and 16b of the seat ring 15 and the throat portions 1a and 16b are smoothly continuous, so that the inner peripheral surface 16b has a predetermined radius of curvature R3. The radius of curvature R3 is formed as an approximate curved surface by a plurality of taper processes.

Here, the operation of the intake port structure of the internal combustion engine of the present reference example will be described. As shown in FIG. 1, when the intake valve 14 is opened, a negative pressure is generated in the combustion chamber 12 by the lowering operation of the piston, and the intake air passes through the intake port 11 and is introduced into the combustion chamber 12 through the valve seat 15. Is done.

  In this reference example, the intake port 11 has a square cross-sectional shape and is smoothly connected to a throat portion 11a having a circular cross-sectional shape. Therefore, it is possible to ensure a large flow path cross-sectional area without changing the positions of the port upper line and the port lower line, and the intake air flow near the upper surface portion 21 of the intake port 11 smoothly flows into the combustion chamber 12. Therefore, a predetermined flow rate can be secured without reducing strong tumble.

  The intake port 11 having a square cross-sectional shape has a large radius of curvature R2 on the lower surface portion 22 side, and is smoothly connected to the throat portion 11a having a circular cross-sectional shape, and the inner peripheral surface 16b of the seat ring 15 is predetermined. And a curvature radius R3. Therefore, wrinkles are not generated at the connection portion between the lower surface portion 22 of the intake port 11 and the throat portion 11a, and the intake air flow flowing in the vicinity of the lower surface portion 22 of the intake port 11 is smoothly separated from the wall surface without causing separation. 12, the flow rate can be increased.

  In the intake port structure of this reference example, a high-efficiency intake port structure that achieves both high tumble and a high flow coefficient can be realized by the square cross-sectional shape of the intake port 11 and the oblique throat. That is, as shown in the graph of FIG. 4, the small black circles are data obtained by measuring the tumble ratio and the flow rate by changing the port angle, the port diameter, the port height, etc. in the conventional intake port having a circular cross-sectional shape. The flow rate decreases as the tumble ratio increases. In this case, conventionally, an intake port structure in which the tumble ratio and the flow rate are compatible at the intermediate position (large black circle) is employed. On the other hand, in the intake port structure of this reference example, the energy loss of the tumble component is reduced as compared with the conventional intake port structure and the separation of the intake flow can be suppressed. Therefore, as shown by white circles in FIG. Both tumble flow and high flow rate can be achieved, and a highly efficient intake port can be realized.

  Thus, in the intake port structure of the internal combustion engine of Reference Example 1, the upstream portion of the intake port 11 has a substantially square cross-sectional shape having two parallel surfaces, while the throat portion 11a to the combustion chamber 12 has a circular cross-section. The upstream portion of the intake port 11 and the throat portion 11a are made continuous with a smooth surface.

  Therefore, a flow path cross-sectional area of a predetermined size can be secured by the intake port 11 having a substantially square cross-sectional shape. Thereby, the intake flow flowing in the vicinity of the upper surface portion 21 of the intake port 11 flows into the combustion chamber 12 through the throat portion 11a, and a strong tumble flow can be formed. Further, the intake air flow that flows in the vicinity of the lower surface portion 22 of the intake port 11 flows into the combustion chamber 12 through the throat portion 11a. By increasing the bend angle θ of the wall surface, the separation of the intake air flow is suppressed and the intake air flow is reduced. The flow rate can be increased.

  The tumble flow can be strengthened without reducing the intake flow rate introduced into the combustion chamber 12, the mixing of fuel and air in the combustion chamber 12 is improved, and the combustion of the air-fuel mixture is promoted to increase the combustion efficiency. it can. And by improving this combustion efficiency, low and medium speed torque can be improved, and the output of the internal combustion engine can be improved.

  Further, the upper surface portion 21 and the lower surface portion 22 and the left and right side surface portions 23 and 24 in the intake port 11 are parallel to each other, and the upper surface portion 21 and the left and right side surface portions 23 and 24 are made continuous by the left and right upper curved surface portions 25 and 26. 22 and the left and right side surfaces 23 and 24 are made continuous by the left and right lower curved surface portions 27 and 28, and the curvature radius R of the upper curved surface portions 25 and 26 is set smaller than the curvature radius R2 of the lower curved surface portions 27 and 28.

  Therefore, by securing a large plane area on the upper surface portion 21 side of the intake port 11, it is possible to efficiently increase the tumble by increasing the intake flow rate, and on the lower surface portion 22 side, the throat portion 11a having a circular cross-sectional shape It can be easily and smoothly continued without a step, and the intake air flow rate can be increased to improve combustion.

  Furthermore, from the throat portion 11 a of the intake port 11 to the seat ring 15, processing is performed by the seat cutter 31 from the combustion chamber 12 side along the center line C 3 of the intake valve 14, and the intake port with respect to the center line C 2 of the intake valve 14 is processed. 11 is processed by the slow cutter 32 along an axis C4 inclined at a predetermined angle α toward the center line C1 side. Therefore, the inner peripheral surface 16b of the seat ring 15 can be formed with a radius of curvature R3 that is as large as possible, and the intake air flow that flows in the vicinity of the lower surface portion 22 of the intake port 11 smoothly enters the combustion chamber 12 without being separated from the wall surface. It will flow in and the flow rate can be increased.

  FIG. 5 is a schematic cross-sectional view in which the port structure of the internal combustion engine according to the first embodiment of the present invention is applied to an exhaust port. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated by the reference example mentioned above, and the overlapping description is abbreviate | omitted.

  In the first embodiment, the port structure of the internal combustion engine of the present invention will be described as applied to an exhaust port. In the exhaust port structure of the internal combustion engine of the first embodiment, as shown in FIG. 5, the exhaust port 41 is provided such that its center line C5 is inclined at a predetermined angle with respect to the center line C2 of the combustion chamber 12. The exhaust valve 42 is supported so as to be axially movable along a center line C6 having a predetermined angle with respect to the center line C5 of the exhaust port 41, and an end portion of the exhaust port 41 facing the combustion chamber 12 is supported. A seat ring 43 on which the exhaust valve 42 is seated is seated.

  The upstream portion of the exhaust port 41 has a substantially square cross-sectional shape. Two surfaces of the upper surface portion 51 and the lower surface portion 52 are parallel to each other, and two surfaces of the left side surface portion 53 and the right side surface portion 54 are parallel to each other. Yes. The upper surface portion 51 and the left and right side surface portions 53 and 54 are continuous by the left and right upper curved surface portions 55 and 56, and the lower surface portion 52 and the left and right side surface portions 53 and 54 are continuous by the left and right lower curved surface portions 57 and 58. In this case, the curvature radii of the upper curved surface portions 55 and 56 are set smaller than the curvature radii of the lower curved surface portions 57 and 58.

  On the other hand, as for the exhaust port 41, the downstream part, ie, the throat part 41a, has comprised the substantially circular cross-sectional shape. The exhaust port 41 is continuously changed from the upstream portion to the downstream throat portion 41a so that the square cross-sectional shape is gradually changed to a circular cross-sectional shape and the cross-sectional shape is smoothly changed.

  Further, the seat ring 43 has an inner peripheral surface 44 a in a region near the center of the combustion chamber 12 inclined along the flow path of the exhaust port 41, and an inner peripheral surface 44 b in a region near the outer peripheral portion of the combustion chamber 12. It is formed so as to expand toward the combustion chamber 12. That is, the throat portion 41a of the exhaust port 41 is cut by a sheet cutter and a throat cutter, similarly to the throat portion 11a of the intake port 11 described above.

  Therefore, when the exhaust valve 42 is opened, the combustion gas in the combustion chamber 12 is discharged to the exhaust port 41 through the valve seat 43 by the upward movement of the piston. In the present embodiment, since the inner curvature radius R5 is set large at the throat portion 41a of the exhaust port 41, the exhaust flow flowing from the combustion chamber 12 to the lower surface portion 52 of the exhaust port 41 smoothly flows from the combustion chamber 12. It can be discharged and the exhaust flow rate can be increased.

  As described above, in the exhaust port structure of the internal combustion engine of the first embodiment, the upstream portion of the exhaust port 41 has a substantially square cross-sectional shape having two parallel surfaces, while the throat portion 41a continuing from the combustion chamber 12 has a circular cross-section. The upstream portion of the exhaust port 41 and the throat portion 41a are continuous with a smooth surface. Therefore, the exhaust port 41 having a substantially square cross-sectional shape can secure a flow passage cross-sectional area of a predetermined size, and can set the radius of curvature R5 of the throat portion 41a to be large, thereby suppressing exhaust gas separation. Thus, the intake flow rate can be increased.

Reference example 2

  6 is a plan view in which the port structure of the internal combustion engine according to Reference Example 2 of the present invention is applied to an intake port, FIG. 7 is a sectional view taken along line VII-VII in FIG. 6, and FIG. 8 is a sectional view taken along line VIII-VIII in FIG. FIG.

  Reference Example 2 will be described by applying the port structure of the internal combustion engine of the present invention to a branched intake port. In the intake port structure of the internal combustion engine of the reference example 2, as shown in FIGS. 6 to 8, the intake port 61 is a branch type, so-called siamese type port shape, and is a collective portion with respect to one inlet portion 62. 63 is formed, and is divided into two from the middle of the collective portion 63 to form branch portions 64a and 64b, and two throat portions 65a and 65b are formed in the branch portions 64a and 64b. The intake port 61 is provided in the cylinder head 67 so that its center line C1 is inclined at a predetermined angle with respect to the center line C2 of the combustion chamber 66. The intake valve 68 provided in the branch portions 64a and 64b is supported so as to be axially movable along a center line C3 having a predetermined angle with respect to the center line C1 of the intake port 61. An annular seat ring 69 on which each intake valve 68 is seated and released is press-fitted into an end edge portion of each branch portion 64a, 64b of the intake port 61 facing the combustion chamber 12.

  Further, in the intake port 61, the collecting portion 63 and the branch portions 64a and 64b have a substantially square cross section (rectangular cross section). That is, in the cross-sectional shape of the intake port 11, the collective portion 63 has a shape in which two square cross sections are integrally continuous at opposite sides, and the branch portions 64 a and 64 b are independent of each square cross section of the collective portion 63. It has a branched shape. In each square cross-sectional shape, two surfaces of the upper surface portions 71a and 71b and the lower surface portions 72a and 72b are parallel to each other, and two surfaces of the left side surface portions 73a and 73b and the right side surface portions 74a and 74b are parallel to each other. The both end portions of the upper surface portions 71a and 71b and the upper end portions of the left and right side surface portions 73a, 73b, 74a and 74b are continuous by the left and right upper curved surface portions 75a, 75b, 76a and 76b, and the lower surface portions 72a and 72b Both end portions and the lower end portions of the left and right side surface portions 73a, 73b, 74a, and 74b are continuous by left and right lower curved surface portions 77a, 77b, 78a, and 78b. In this case, the curvature radius R1 of the upper curved surface portions 75a, 75b, 76a, 76b is set smaller than the curvature radius R2 of the lower curved surface portions 77a, 77b, 78a, 78b.

  In the intake port 61, the throat portions 65a and 65b have a substantially circular cross-sectional shape, and the square cross-sectional shape is gradually changed to a circular cross-sectional shape from the branch portions 64a and 64b to the throat portions 65a and 65b. Both are continuous so that the transition is smooth. In this case, in the intake port 61, the curvature radius R2 on the lower surface portion 72a, 72b side is set larger than the curvature radius R1 on the upper surface portion 71a, 71b side. It is easy, and the intake port 61 can be continued on a smooth surface from the branch portions 64a and 64b to the throat portions 65a and 65b.

  On the other hand, the seat ring 69 has an inner peripheral surface 70 a in a region near the center of the combustion chamber 66 inclined along the flow path of the intake port 61 and an inner peripheral surface 70 b in a region near the outer peripheral portion of the combustion chamber 66. It is formed so as to expand toward the combustion chamber 66. In other words, the throat portions 65a and 65b and the seat ring 69 of the intake port 61 have inner peripheral surfaces 70a and 70b formed as approximate curved surfaces by a plurality of taper processes, as in Reference Example 1 described above.

  As described above, in the intake port structure of the internal combustion engine of Reference Example 2, the intake port 61 includes the branch portions 64a and 64b that are divided into two from the middle of the collective portion 63, and the branch portions 64a and 64b are provided. On the other hand, the throat portions 65a and 65b have a circular cross-sectional shape, and the two are made continuous by a smooth surface.

  Therefore, a flow passage cross-sectional area of a predetermined size can be secured by the intake port 61 having a substantially square cross-sectional shape. Thereby, the intake flow flowing in the vicinity of the upper surface portions 71a and 71b of the intake port 61 flows into the combustion chamber 66 through the throat portions 65a and 65b, and a strong tumble flow can be formed. In addition, the intake flow flowing in the vicinity of the lower surface portions 72a and 72b of the intake port 61 flows into the combustion chamber 12 through the throat portions 65a and 65b. By increasing the bending angle θ of the wall surface 70b, the intake flow is separated. The intake flow rate can be increased while suppressing the above. As a result, the tumble flow can be strengthened without reducing the intake flow rate introduced into the combustion chamber 66, the mixing of fuel and air in the combustion chamber 66 is improved, the combustion of the air-fuel mixture is promoted, and the combustion efficiency is improved. Can be increased. And by improving this combustion efficiency, low and medium speed torque can be improved, and the output of the internal combustion engine can be improved.

  In the above description, the upstream portion of each port 11, 41, 61 has a substantially square cross-sectional shape, and the upper surface portions 21, 51, 71a, 71b and the lower surface portions 22, 52, 72a, 72b are parallel to the left side. Although the surface portions 23, 53, 73a, 73b and the right side surface portions 24, 54, 74a, 74b are parallel, at least two surfaces of the left side surface portions 23, 53, 73a, 73b and the right side surface portions 24, 54, 74a, 74b are parallel. The upper and lower surface portions 21, 22, 51, 5271a, 71b, 72a, 72b may not be parallel.

  In the above description, the exhaust port structure of the internal combustion engine does not depend on the form of the internal combustion engine, and may be applied to each port without branching of the 2-valve engine as in Reference Example 1, As in Reference Example 2, the present invention may be applied to an exhaust port branched into two branches of a 4-valve engine. Further, the present invention may be applied to a port injection engine that injects fuel into an intake port or a direct injection engine that injects fuel directly into a combustion chamber.

  As described above, the port structure of the internal combustion engine according to the present invention is such that it continues from a substantially square cross-sectional shape to a circular cross-sectional shape with a smooth surface, and can be applied to an exhaust port.

DESCRIPTION OF SYMBOLS 11 Intake port 11a Throat part 12 Combustion chamber 13 Cylinder head 14 Intake valve 15 Seat ring 16a, 16b Inner peripheral surface 21 Upper surface part 22 Lower surface part 23 Left side surface part 24 Right side part 25, 26 Upper curved surface part 27, 28 Lower curved surface part 31 Seat Cutter 32 Throat cutter 41 Exhaust port 42 Exhaust valve 43 Seat ring 61 Intake port 63 Collecting part 64a, 64b Branch part 65a, 65b Throat part 66 Combustion chamber 67 Cylinder head 68 Intake valve 69 Seat ring 70a, 70b Inner peripheral surface 71a, 71b Upper surface portion 72a, 72b Lower surface portion 73a, 74b Left side surface portion 74a, 74b Right side surface portion 75a, 75b, 76a, 76b Upper curved surface portion 77a, 77b, 78a, 78b Lower curved surface portion

Claims (4)

  In a port structure of an internal combustion engine that can communicate with a combustion chamber via an open / close valve, the exhaust port has a substantially square cross-sectional shape having two parallel surfaces, and the throat portion to the combustion chamber has a circular cross-sectional shape, and the exhaust port And a port structure for an internal combustion engine, characterized in that the throat portion is continuous with a smooth surface.   2. The port structure for an internal combustion engine according to claim 1, wherein the exhaust port and the throat portion are formed to have substantially the same width.   3. The port structure for an internal combustion engine according to claim 1 or 2, wherein the exhaust port is set to have a width larger than a height.   The port structure of the internal combustion engine according to any one of claims 1 to 3, wherein the exhaust port has an upper surface portion, a lower surface portion, and left and right side portions, and at least two surfaces of the left and right side portions are parallel to each other. None, the upper surface portion and the left and right side surface portions are continuous by the left and right upper curved surface portions, and the lower surface portion and the left and right side surface portions are continuous by the left and right lower curved surface portions, and the curvature radius of the upper curved surface portion is the lower curved surface portion A port structure of an internal combustion engine characterized by being set smaller than the radius of curvature of the internal combustion engine.

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