EP4775826A1

EP4775826A1 - Exhaust port structure for internal combustion engine

Info

Publication number: EP4775826A1
Application number: EP25220927.5A
Authority: EP
Inventors: Takuya Kanai; Ayumi OISHI
Original assignee: Suzuki Motor Corp
Current assignee: Suzuki Motor Corp
Priority date: 2025-01-09
Filing date: 2025-12-04
Publication date: 2026-07-15
Also published as: JP2026120310A

Abstract

Object

Provided is an exhaust port structure for an internal combustion engine capable of facilitating exhaust from an exhaust port and increasing the output of the internal combustion engine even in a structure in which a lower surface of a boss portion supporting an exhaust valve guide projects into the exhaust port.

Solution

An exhaust port 3A of an exhaust port structure of an internal combustion engine 1 includes a cylindrical portion 3D, an exhaust passage portion 3E, and a connecting portion 3F connecting the cylindrical portion 3D and the exhaust passage portion 3E. The connecting portion 3F includes a recessed portion 3G formed by making an inner wall of a cylinder head 3 upstream of a boss portion 3B in a flow direction of exhaust gas swell in a direction away from the exhaust passage portion 3E. The recessed portion 3G includes a first curved surface 3c extending from the cylindrical portion 3D toward the boss portion 3B, and a second curved surface 3d having a curvature radius R2 larger than a curvature radius R1 of the first curved surface 3c and being curved from the first curved surface 3c toward a lower surface 3b of the boss portion 3B.

Description

Technical Field

The present invention relates to an exhaust port structure for an internal combustion engine.

Background Art

An exhaust port structure for an internal combustion engine that increases the flow rate at an exhaust port by rectifying the flow of exhaust gas generated around a valve stem supporting an exhaust valve is described (see JP10-110650 A ).
The exhaust port structure for an internal combustion engine described in Patent Document 1 ( JP10-110650A ) is formed at a cylinder head, and includes therein a boss of a valve guide that supports the valve stem of the exhaust valve. In the exhaust port structure, a projection that extends from the boss of the valve guide toward a port opening and projects into the exhaust port is provided at an exhaust port wall surface on an opposite side of an exhaust port outlet with the valve stem interposed therebetween.
With such a configuration, the exhaust port structure for an internal combustion engine in the related art can divide the exhaust gas into two by the projection to cause the exhaust gas to flow on both sides of the exhaust valve, thereby suppressing stagnation upstream of the valve stem and occurrence of a vortex downstream of the valve stem. As a result, the flow rate of the exhaust gas at the exhaust port can be increased.

Citation List

Patent Literature

Patent Document 1: JP 10-110650 A

Summary of Invention

Technical Problem

However, in the exhaust port structure for an internal combustion engine in the related art, in a case where the boss supporting the exhaust valve guide projects from an upper surface of the exhaust port into the exhaust port, the exhaust gas may collide with the boss portion and the flow of the exhaust gas may be blocked by the boss portion.
That is, the exhaust gas may collide with an outer peripheral surface of the boss above a lower surface of the boss, and the flow of the exhaust gas may be blocked by the boss portion. As a result, there is a possibility that exhaust from the exhaust port cannot be facilitated and the output of the internal combustion engine cannot be increased.
The present invention has been made in view of the above circumstances, and an object thereof is to provide an exhaust port structure for an internal combustion engine capable of facilitating exhaust from an exhaust port and increasing the output of the internal combustion engine even in a structure in which a lower surface of a boss portion supporting an exhaust valve guide projects into the exhaust port.

Solution to Problem

According to the present invention, an exhaust port structure for an internal combustion engine includes: an exhaust port formed at a cylinder head and including an opening communicating with a combustion chamber; an exhaust valve guide supported by the cylinder head so as to be opposed to the opening; and an exhaust valve reciprocatively supported by the exhaust valve guide so as to open and close the opening. The exhaust port includes: a cylindrical portion continuous with the opening; an exhaust passage portion extending in an oblique direction with respect to the cylindrical portion; a connecting portion connecting the cylindrical portion and the exhaust passage portion; and a boss portion projecting from an upper surface of the exhaust passage portion into the exhaust port and supporting an lower end portion of the exhaust valve guide. The connecting portion includes a recessed portion formed by making an inner wall of the cylinder head upstream of the boss portion in a flow direction of exhaust gas swell in a direction away from the exhaust passage portion with respect to the boss portion. The recessed portion includes a first curved surface extending outward from the cylindrical portion and a second curved surface having a curvature radius larger than a curvature radius of the first curved surface and being curved from the first curved surface toward a lower surface of the boss portion.

Advantageous Effects of Invention

As described above, according to the present invention, even in a structure in which the lower surface of the boss portion supporting the exhaust valve guide projects into the exhaust port, the exhaust from the exhaust port can be facilitated, and the output of the internal combustion engine can be increased.

Brief Description of Drawings

FIG. 1 is a diagram illustrating an exhaust port structure for an internal combustion engine according to an example of the present invention, and is a cross-sectional view of an exhaust port and a cylinder head around the exhaust port.
FIG. 2 is a diagram illustrating the exhaust port structure for an internal combustion engine according to the example of the present invention, and is an enlarged cross-sectional view of the exhaust port.
FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2.
FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2.
FIG. 5 is a diagram illustrating the exhaust port structure for an internal combustion engine according to the example of the present invention, and is a diagram illustrating a flow of exhaust gas in the exhaust port.

Description of Embodiments

According to an embodiment of the present invention, an exhaust port structure for an internal combustion engine includes: an exhaust port formed at a cylinder head and including an opening communicating with a combustion chamber; an exhaust valve guide supported by the cylinder head so as to be opposed to the opening; and an exhaust valve reciprocatively supported by the exhaust valve guide so as to open and close the opening. The exhaust port includes: a cylindrical portion continuous with the opening; an exhaust passage portion extending in an oblique direction with respect to the cylindrical portion; a connecting portion connecting the cylindrical portion and the exhaust passage portion; and a boss portion projecting from an upper surface of the exhaust passage portion into the exhaust port and supporting an lower end portion of the exhaust valve guide. The connecting portion includes a recessed portion formed by making an inner wall of the cylinder head upstream of the boss portion in a flow direction of exhaust gas swell in a direction away from the exhaust passage portion with respect to the boss portion. The recessed portion includes a first curved surface extending outward from the cylindrical portion and a second curved surface having a curvature radius larger than a curvature radius of the first curved surface and being curved from the first curved surface toward a lower surface of the boss portion.
Accordingly, with the exhaust port structure for an internal combustion engine according to the embodiment of the present invention, even in a structure in which the lower surface of the boss portion supporting the exhaust valve guide projects into the exhaust port, the exhaust from the exhaust port can be facilitated, and the output of the internal combustion engine can be increased.

Examples

Hereinafter, an exhaust port structure for an internal combustion engine according to an example of the present invention will be described with reference to the drawings.
FIGS. 1 to 5 are diagrams each illustrating an exhaust port structure for an internal combustion engine according to an example of the present invention.
First, the configuration will be described.
In FIGS. 1 to 5, up, down, front, rear, left, and right directions are defined with reference to an internal combustion engine mounted on a vehicle. The front-rear direction of the vehicle is a front-rear direction, the left-right direction of the vehicle (vehicle width direction) is a left-right direction, and the vertical direction of the vehicle (height direction) is an up-down direction.
As illustrated in FIG. 1, an internal combustion engine 1 is mounted on a vehicle. The internal combustion engine 1 includes a cylinder block 2, a cylinder head 3 provided at an upper part of the cylinder block 2, a cylinder head cover (not illustrated) provided at an upper part of the cylinder head 3, and an oil pan (not illustrated) provided at a lower part of the cylinder block 2, converts thermal energy into mechanical energy by combusting fuel, and transmits power to a transmission (not illustrated).
The cylinder block 2 is formed with a cylinder 2B at which a piston 2A is reciprocatively provided, and a combustion chamber 4 is formed at a bottom surface of the cylinder head 3.
The combustion chamber 4 is a space surrounded by an upper surface of the piston 2A located at a top dead center, an inner wall surface of the cylinder 2B, and the bottom surface of the cylinder head 3, and the fuel is combusted in the space.
The cylinder head 3 is formed with an exhaust port 3A. A pair of exhaust ports 3A is provided at each cylinder 2B and, for example, in the case of the internal combustion engine 1 having four cylinders, eight exhaust ports 3A are provided at the cylinder head 3.
An opening 3a is formed at a lower surface of the cylinder head 3, and the opening 3a communicates with the combustion chamber 4 and the exhaust port 3A. Exhaust gas combusted in the combustion chamber 4 is discharged to the exhaust port 3A through the opening 3a.
The cylinder head 3 is provided with an exhaust valve 5. The exhaust valve 5 includes a valve stem 5A and a valve body 5B having an umbrella shape and provided at a lower part of the valve stem 5A.
An exhaust valve guide 7 having a tubular shape is provided at the cylinder head 3 along the up-down direction. The exhaust valve guide 7 is supported by an upper wall 3C of the exhaust port 3A, and is disposed above the exhaust port 3A so as to be opposed to the opening 3a.
The valve stem 5A of the exhaust valve 5 is slidably supported at the exhaust valve guide 7. That is, the exhaust valve 5 is slidably supported at the upper wall 3C of the exhaust port 3A via the exhaust valve guide 7.
The cylinder head 3 is provided with a valve seat 6 having an annular shape, and the valve body 5B is contactable with a lower surface of the valve seat 6. The opening 3a of the cylinder head 3 is formed by an inner peripheral surface of the valve seat 6.
The exhaust valve 5 is moved downward by being pressed against a cam surface of an exhaust valve (not illustrated), and is moved upward by a valve spring (not illustrated) when the pressing of the exhaust valve is released.
When the exhaust valve 5 is moved downward by being pressed against the cam surface of the exhaust valve, the exhaust valve 5 is separated from the valve seat 6 to open the opening 3a, thereby causing the combustion chamber 4 and the exhaust port 3A to communicate with each other.
When the pressing of the exhaust valve is released, the exhaust valve 5 is biased by the valve spring to move upward and come into contact with the lower surface of the valve seat 6, thereby closing the opening 3a and blocking the communication between the combustion chamber 4 and the exhaust port 3A.
In this way, the exhaust valve 5 is attached to the exhaust valve guide 7 so as to open and close the opening 3a. In addition, the exhaust valve 5 is reciprocatively supported by the exhaust valve guide 7 having a long dimension in the up-down direction, so that the exhaust valve 5 is prevented from being inclined and the occurrence of wear is suppressed.
The exhaust port 3A includes a cylindrical portion 3D, an exhaust passage portion 3E, and a connecting portion 3F.
The cylindrical portion 3D is continuous with the opening 3a. The cylindrical portion 3D has an opening area smaller than that of the valve body 5B of the exhaust valve 5, and is disposed above the valve body 5B.
The exhaust passage portion 3E extends obliquely upward to the left with respect to the cylindrical portion 3D, and communicates, at a downstream end thereof, with an exhaust collection portion 8.
The exhaust collection portion 8 communicates with the downstream end of the exhaust passage portion 3E provided at each cylinder 2B, and collects the exhaust gas discharged from the exhaust passage portion 3E provided at each cylinder 2B and discharges the collected exhaust gas to the outside of the cylinder head 3. In FIG. 1, the range of the exhaust collection portion 8 is indicated by an arrow.
As illustrated in FIGS. 1 and 2, the cylinder head 3 is provided with a boss portion 3B (see FIGS. 3 and 4). The boss portion 3B projects into the exhaust port 3A from an upper surface 3u of the exhaust passage portion 3E which is opposed to the opening 3a in the axial direction of the exhaust valve 5.
That is, a lower surface 3b of the boss portion 3B is located below the upper surface 3u of the exhaust passage portion 3E. The upper surface 3u of the exhaust port 3A is a lower surface of the upper wall 3C.
The boss portion 3B supports a lower end portion 7a of the exhaust valve guide 7, and the exhaust valve guide 7 extends downward from the upper surface 3u of the exhaust port 3A by an amount corresponding to the length of the boss portion 3B in the up-down direction.
That is, the exhaust valve guide 7 is formed to have a dimension in the up-down direction elongated by the length of the boss portion 3B in the up-down direction. Accordingly, the exhaust valve 5 is supported by the exhaust valve guide 7 in a long range in the up-down direction of the valve stem 5A, and thus the exhaust valve 5 can be more effectively prevented from falling.
The connecting portion 3F is disposed between the cylindrical portion 3D and the exhaust passage portion 3E in a flow direction of the exhaust gas, and connects the cylindrical portion 3D and the exhaust passage portion 3E.
As illustrated in FIGS. 1 and 2, the connecting portion 3F is formed with a recessed portion 3G. The recessed portion 3G is formed at an inner wall of the cylinder head 3 upstream of the boss portion 3B, and swells in a direction away from the exhaust passage portion 3E with respect to the boss portion 3B.
As illustrated in FIG. 1, the recessed portion 3G includes a first curved surface 3c extending outward from the cylindrical portion 3D and having a curvature radius R1, and a second curved surface 3d having a curvature radius R2 larger than the curvature radius R1 of the first curved surface 3c and being curved from the first curved surface 3c toward the lower surface 3b of the boss portion 3B.
As illustrated in FIG. 2, when an imaginary extension curve 11 having the curvature radius R2 which is the same as the curvature radius of the second curved surface 3d and extending from the second curved surface 3d toward the boss portion 3B side is set, the imaginary extension curve 11 is in contact with the lower surface 3b of the boss portion 3B.
The upper surface 3u of the exhaust port 3A includes the upper surface 3u of the exhaust passage portion 3E. As illustrated in FIG. 1, the second curved surface 3d is disposed in a direction away from the opening 3a with respect to an imaginary extension surface 10A extending from an imaginary plane 10 along the upper surface 3u of the exhaust passage portion 3E to the connecting portion 3F.
That is, the opening 3a is disposed below the imaginary extension surface 10A, and the second curved surface 3d is disposed above the imaginary extension surface 10A.
As illustrated in FIG. 4, the upper surface 3u of the exhaust passage portion 3E is formed with groove portions 3e and 3f. The groove portions 3e and 3f are formed on both side portions in the width direction of the boss portion 3B, respectively, and are recessed in a direction away from the opening 3a with respect to the lower surface 3b of the boss portion 3B. That is, the groove portions 3e and 3f are recessed upward with respect to the lower surface 3b of the boss portion 3B.
Width-direction both side portions 3m and 3n of the second curved surface 3d are connected to the groove portions 3e and 3f, respectively, and the width-direction both side portions 3m and 3n of the second curved surface 3d are connected to the exhaust passage portion 3E via the groove portions 3e and 3f.
Next, the effects of the exhaust port structure for the internal combustion engine 1 of this example will be described.
The exhaust port structure for the internal combustion engine 1 of the present example includes the exhaust port 3A formed at the cylinder head 3 and including the opening 3a communicating with the combustion chamber 4, the exhaust valve guide 7 supported by the cylinder head 3 so as to be opposed to the opening 3a, and the exhaust valve 5 reciprocatively supported by the exhaust valve guide 7 so as to open and close the opening 3a.
The exhaust port 3A includes the cylindrical portion 3D continuous with the opening 3a, the exhaust passage portion 3E extending in an oblique direction with respect to the cylindrical portion 3D, the connecting portion 3F connecting the cylindrical portion 3D and the exhaust passage portion 3E, and the boss portion 3B projecting from the upper surface 3u of the exhaust passage portion 3E into the exhaust port 3A and supporting the lower end portion 7a of the exhaust valve guide 7.
The connecting portion 3F includes the recessed portion 3G formed by making an inner wall of the cylinder head 3 upstream of the boss portion 3B in a flow direction of exhaust gas swell in a direction away from the exhaust passage portion 3E with respect to the boss portion 3B.
The recessed portion 3G includes the first curved surface 3c having the curvature radius R1 and extending outward from the cylindrical portion 3D, and the second curved surface 3d having the curvature radius R2 larger than the curvature radius R1 of the first curved surface 3c and being curved from the first curved surface 3c toward the lower surface 3b of the boss portion 3B.
Accordingly, the exhaust port 3A is expanded by the first curved surface 3c of the recessed portion 3G, so that the volume of the exhaust port 3A can be increased.
In addition, the exhaust gas having flowed into the exhaust port 3A from the opening 3a can be guided to the lower surface 3b of the boss portion 3B by the second curved surface 3d having the curvature radius R2 larger than the curvature radius R1 of the first curved surface 3c and being curved toward the lower surface 3b of the boss portion 3B.
Therefore, the exhaust gas guided to the lower surface 3b of the boss portion 3B can smoothly flow to the exhaust passage portion 3E along the lower surface 3b of the boss portion 3B.
That is, the exhaust gas is prevented from colliding with the outer peripheral surface of the boss portion 3B above the lower surface 3b of the boss portion 3B, and the flow of the exhaust gas can be suppressed from being blocked by the boss portion 3B. As a result, the ventilation resistance of the exhaust port 3A can be reduced, and the output of the internal combustion engine 1 can be increased.
According to the exhaust port structure for the internal combustion engine 1 of the present example, when the imaginary extension curve 11 having the curvature radius R2 which is the same as the curvature radius of the second curved surface 3d and extending from the second curved surface 3d toward the boss portion 3B side is set, the imaginary extension curve 11 is in contact with the lower surface 3b of the boss portion 3B.
Accordingly, the exhaust gas flowing along the second curved surface 3d can be reliably guided to the lower surface 3b of the boss portion 3B, and the exhaust gas guided to the lower surface 3b of the boss portion 3B can smoothly flow to the exhaust passage portion 3E along the lower surface 3b of the boss portion 3B. As a result, the ventilation resistance of the exhaust port 3A can be more effectively reduced, and the output of the internal combustion engine 1 can be more effectively increased.
According to the exhaust port structure for the internal combustion engine 1 of the present example, the second curved surface 3d is disposed in a direction away from the opening 3a with respect to the imaginary extension surface 10A extending from the imaginary plane 10 along the upper surface 3u of the exhaust passage portion 3E to the connecting portion 3F.
Accordingly, the curvature radius R2 of the second curved surface 3d can be increased, and the exhaust gas discharged from the opening 3a to the exhaust port 3A can be curved along the second curved surface 3d.
Therefore, the exhaust gas can be prevented from being disturbed and can smoothly flow to the exhaust passage portion 3E while avoiding the boss portion 3B. As a result, the ventilation resistance of the exhaust port 3A can be more effectively reduced, and the output of the internal combustion engine 1 can be more effectively increased.
According to the exhaust port structure for the internal combustion engine 1 of the present example, in the upper surface 3u of the exhaust port 3A, the upper surface 3u of the exhaust passage portion 3E includes the groove portions 3e and 3f at both side portions in the width direction of the boss portion 3B.
In addition, the groove portions 3e and 3f are recessed in a direction away from the opening 3a with respect to the lower surface 3b of the boss portion 3B, and the width-direction both side portions 3m and 3n of the second curved surface 3d are connected to the groove portions 3e and 3f.
In this way, the upper surface 3u of the exhaust passage portion 3E includes the groove portions 3e and 3f at both side portions in the width direction of the boss portion 3B, so that the cross-sectional area of the exhaust port 3A can be prevented from being decreased around the boss portion 3B. In other words, the cross-sectional area of the exhaust port 3A can be increased around the boss portion 3B.
By connecting the width-direction both side portions 3m and 3n of the second curved surface 3d to the groove portions 3e and 3f, the exhaust gas discharged from the opening 3a to the exhaust port 3A can be discharged from a central portion in the width direction of the second curved surface 3d to the exhaust passage portion 3E through the lower surface 3b of the boss portion 3B, and can be discharged from width-direction both side portions 3m and 3n of the second curved surface 3d to the exhaust passage portion 3E through the groove portions 3e and 3f.
Accordingly, the discharge of the exhaust gas from the second curved surface 3d to the exhaust passage portion 3E can be facilitated, and thus the output of the internal combustion engine 1 can be increased.
FIG. 5 illustrates a state in which exhaust gas G1 discharged from the opening 3a to the exhaust port 3A (the exhaust gas G1 in an upper region out of the exhaust gas G1 indicated by solid lines) is discharged from the central portion in the width direction of the second curved surface 3d to the exhaust passage portion 3E through the lower surface 3b of the boss portion 3B.
FIG. 5 also illustrates a state in which exhaust gas G2 discharged from the opening 3a to the exhaust port 3A (indicated by solid lines in FIG. 3 and indicated by dotted lines in FIG. 5) is discharged from the width-direction both side portions 3m and 3n of the second curved surface 3d to the exhaust passage portion 3E through the groove portions 3e and 3f.
While the example of the present invention has been disclosed, it will be apparent to those skilled in the art that modifications may be made without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

Reference Signs List

1 Internal combustion engine
3 Cylinder head
3A Exhaust port
3a Opening
3b Lower surface (lower surface of boss portion)
3B Boss portion
3c First curved surface
3D Cylindrical portion
3d Second curved surface
3E Exhaust passage portion
3e Groove portion
3F Connecting portion
3f Groove portion
3G Recessed portion
3m Width-direction both side portions (width-direction both side portions of second curved surface)
3u Upper surface (upper surface of exhaust port, upper surface of exhaust passage portion)
4 Combustion chamber
5 Exhaust valve
7 Exhaust valve guide
7a Lower end portion (lower end portion of exhaust valve guide)
10 Imaginary plane
10A Imaginary extension surface
11 Imaginary extension curve

Claims

An exhaust port structure for an internal combustion engine, comprising:
an exhaust port formed at a cylinder head and including an opening communicating with a combustion chamber;

an exhaust valve guide supported by the cylinder head so as to be opposed to the opening; and

an exhaust valve reciprocatively supported by the exhaust valve guide so as to open and close the opening,

the exhaust port including

a cylindrical portion continuous with the opening,

an exhaust passage portion extending in an oblique direction with respect to the cylindrical portion,

a connecting portion connecting the cylindrical portion and the exhaust passage portion, and

a boss portion projecting from an upper surface of the exhaust passage portion into the exhaust port and supporting a lower end portion of the exhaust valve guide,

the connecting portion including a recessed portion formed by making an inner wall of the cylinder head upstream of the boss portion in a flow direction of exhaust gas swell in a direction away from the exhaust passage portion with respect to the boss portion, and

the recessed portion including a first curved surface extending outward from the cylindrical portion and a second curved surface having a curvature radius larger than a curvature radius of the first curved surface and being curved from the first curved surface toward a lower surface of the boss portion.
The exhaust port structure for an internal combustion engine according to claim 1, wherein
when an imaginary extension curve having a same curvature radius as the curvature radius of the second curved surface and extending from the second curved surface toward the boss portion side is set, the imaginary extension curve is in contact with the lower surface of the boss portion.
The exhaust port structure for an internal combustion engine according to claim 1 or 2, wherein
the second curved surface is disposed in a direction away from the opening with respect to an imaginary extension surface extending from an imaginary plane along an upper surface of the exhaust passage portion to the connecting portion.
The exhaust port structure for an internal combustion engine according to claim 1 or 2, wherein
an upper surface of the exhaust port is formed with groove portions disposed at both side portions in a width direction of the boss portion,

the groove portions are recessed in a direction away from the opening with respect to the lower surface of the boss portion, and

both side portions in a width direction of the second curved surface are connected to the groove portions.
The exhaust port structure for an internal combustion engine according to claim 3, wherein
an upper surface of the exhaust port is formed with groove portions disposed at both side portions in a width direction of the boss portion,

the groove portions are recessed in a direction away from the opening with respect to the lower surface of the boss portion, and

both side portions in a width direction of the second curved surface are connected to the groove portions.