JP2016188624A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine that is inhibited in a blow-by phenomenon in an overlap period and is improved in scavenging efficiency.SOLUTION: In an internal combustion engine, a valve contact surface, to which the head part of an exhaust valve abuts when the exhaust valve is closed, is formed on an opening part of an exhaust port into a combustion chamber. A connection space, that is a part of the exhaust port positioned above the valve contact surface and through which the exhaust port is connected to the combustion chamber, includes an intake side connection space positioned on the intake port side and an exhaust side connection space positioned on a bore wall surface side of the exhaust port side that is on the opposite side from the intake side connection space across the exhaust valve. A communication passage is provided for providing communication between a downstream side predetermined part of the exhaust port positioned on the downstream side of the connection space and the exhaust side connection space.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an internal combustion engine.

  In an internal combustion engine, in order to improve the intake efficiency from the intake port and the scavenging efficiency to the exhaust port, the opening area of the intake / exhaust valve is maximized and the opening position thereof is improved. Further, in the operating state of the internal combustion engine, there may be an overlap period in which the valve opening timing of the intake valve and the valve opening timing of the exhaust valve overlap. In such an overlap period, a blow-through phenomenon in which fresh air or air-fuel mixture flowing into the combustion chamber from the intake port flows out to the exhaust port is likely to occur. When this blow-through phenomenon occurs, problems such as a deterioration in the emission performance of the internal combustion engine and a decrease in the output of the internal combustion engine occur.

  Therefore, as shown in Patent Document 1, a protruding wall that protrudes toward the combustion chamber is provided along the peripheral portion on the intake port side that is the opening of the exhaust port, and the protruding margin of the protruding wall is smaller than a predetermined amount. In addition, a technique is disclosed in which the gap between the protruding wall and the umbrella portion of the exhaust valve is set to be smaller than the protruding margin of the protruding wall. With such a configuration, it is said that the blow-through phenomenon is suppressed and the reduction of the scavenging efficiency due to the protruding wall is suppressed.

JP-A-4-303118 JP 2013-72390 A

  According to the above prior art, in order to suppress the blow-through phenomenon during the overlap period in the internal combustion engine, the protruding wall is formed at the peripheral edge of the opening of the exhaust port. The protruding wall is formed so as to protrude into the combustion chamber, and the flow of fresh air to the exhaust port is suppressed by the height (protrusion margin) of the protruding wall. However, in order to efficiently lead the combustion gas in the combustion chamber to the exhaust port side and improve the scavenging efficiency, a configuration that suppresses the blow-through phenomenon and ensures a smooth flow of the combustion gas in the exhaust port is required. The above prior art has not been devised from such a viewpoint.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an internal combustion engine that suppresses the blow-through phenomenon in the overlap period and improves the scavenging efficiency.

  In the present invention, in order to solve the above-described problem, a predetermined space of the exhaust port located above the valve contact surface with which the exhaust valve abuts, the space on the bore wall surface side on the exhaust valve side, and further in the exhaust port The structure which provided the communicating path which connects the space of a downstream side was employ | adopted. Thereby, in the gas flow from the combustion chamber to the intake port, the gas flow on the bore wall surface side on the exhaust valve side can be made stronger than the gas flow on the intake port side, thereby suppressing the blow-through phenomenon. The scavenging efficiency can be improved.

Specifically, according to the present invention, an intake port side ceiling surface where an intake port is opened in a cylinder head and an exhaust port side ceiling surface where an exhaust port is opened in the cylinder head are perpendicular to the center axis of the cylinder. In an internal combustion engine having a pent roof type combustion chamber inclined with respect to an intersecting plane, a valve contact surface is formed at the opening to the combustion chamber of the exhaust port when the exhaust valve is closed when the exhaust valve is closed. An exhaust side connection space located on the intake port side in a partial space of the exhaust port where the exhaust port is connected to the combustion chamber and located above the valve contact surface. And an exhaust side connection space located on the bore wall surface side on the exhaust port side opposite to the intake side connection space across the exhaust valve. And the said internal combustion engine is provided with the communicating path which connects the downstream downstream predetermined part of the said exhaust port located in the downstream of the said connection space, and the said exhaust side connection space.

  According to the present invention, an internal combustion engine that suppresses a blow-through phenomenon in an overlap period and improves scavenging efficiency is provided.

1 is a diagram showing a schematic configuration of an internal combustion engine according to the present invention. It is a figure which shows schematic structure regarding the intake port and exhaust port in the internal combustion engine shown in FIG.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine according to the present embodiment. The internal combustion engine 1 includes a cylinder head 20 and a cylinder block 30 and is a gasoline engine for driving a vehicle (spark ignition internal combustion engine) having four cylinders 2 therein. However, the present invention can be applied not only to gasoline engines but also to other engines. In FIG. 1, only one cylinder 2 is shown for convenience. In this specification, the cylinder head 20 side with respect to the cylinder block 30 is defined as the upper side, and the cylinder block 30 side with respect to the cylinder head 20 is defined as the lower side.

  A piston 3 is slidably provided in the cylinder 2. An intake port 4 and an exhaust port 5 provided in the cylinder head 20 are connected to the combustion chamber 8 of the cylinder 2. Note that two intake ports 4 and two exhaust ports 5 are connected to each cylinder 2, but only one intake port 4 and exhaust port 5 are shown in FIG. 1 for convenience. The combustion chamber 8 is inclined with respect to a plane in which an intake port side ceiling surface 22 in which the intake port 4 is opened and an exhaust port side ceiling surface 21 in which the exhaust port 5 is opened are perpendicular to the central axis of the cylinder 2. It is a pent roof type combustion chamber.

  The opening of the intake port 4 to the combustion chamber 8 is opened and closed by the intake valve 6. An opening of the exhaust port 5 to the combustion chamber 8 is opened and closed by an exhaust valve 7. Further, the cylinder 2 is provided with a fuel injection valve 11 that directly injects fuel into the combustion chamber 8 and a spark plug 12 that ignites an air-fuel mixture formed in the combustion chamber 8.

The arrows in FIG. 1 represent the flow of gas (intake air) in the combustion chamber 8. As indicated by this arrow, in the present embodiment, in the combustion chamber 8, the swirl flow swirls in the axial direction of the cylinder 2, and in the vicinity of the bore wall surface on the exhaust port side, the piston port 3 A gas flows in a direction toward the top surface, and a tumble flow is formed in the vicinity of the bore wall surface on the intake port side in which the gas flows in a direction from the top surface of the piston 3 toward the intake port side ceiling surface 22. Since such a tumble flow is formed, the mixing of fuel and air is promoted.
The flammability is improved.

  In the internal combustion engine 1, in order to suitably realize intake air introduction into the combustion chamber 8 and discharge of combustion gas from the combustion chamber 8, a predetermined range from the exhaust stroke in the cylinder 2 to the intake stroke in accordance with the operating conditions of the internal combustion engine 1. There may be a valve overlap in which the opening of the intake valve 6 and the opening of the exhaust valve 7 overlap each other during the period. Here, when a tumble flow is formed in the combustion chamber 8 as described above, the direction of the swirl flow is the direction in which the intake air introduced from the intake port 4 into the combustion chamber immediately faces the exhaust port side ceiling surface 21. become. Therefore, when a valve overlap occurs, a blow-through phenomenon in which the intake air introduced into the combustion chamber 8 is directly discharged to the exhaust port 5 side is likely to occur.

  Therefore, in the following, a configuration for suppressing the blow-through phenomenon in the internal combustion engine 1 will be described with reference to FIG. FIG. 2 is a cross-sectional view showing a schematic configuration of the intake port 4 and the exhaust port 5 in the internal combustion engine 1. In the cross-sectional view, a cross section including the central axis 7a of the exhaust valve 7 and parallel to the central axis of the cylinder 2 is shown. The schematic structure of the exhaust port 5 is shown. FIG. 2 shows a valve overlap state in which both the intake valve 6 and the exhaust valve 7 are opened. In the present embodiment, since the structure of the intake port 4 is the same as that in the prior art, the detailed description thereof is omitted. The notations [IN] and [EX] shown in FIG. 2 are symbols that relatively represent the position on the intake port 4 side and the position on the exhaust bore wall surface (that is, the bore wall surface on the exhaust port 5 side). is there.

  Here, the structure of the exhaust port 5 in the vicinity of the opening where the exhaust port 5 opens to the exhaust port side ceiling surface 21 will be described. In the vicinity of the opening, a valve contact surface 24 with which the umbrella portion 7b of the exhaust valve 7 abuts when the exhaust valve 7 is closed is formed. In the intake port 5, a space connecting the intake port 5 to the combustion chamber 8 and having a certain length along the flow direction of the exhaust gas from a position immediately upstream of the valve contact surface 24. It is defined as In FIG. 2, the connection space 23 is a hatched area.

  When the valve overlap between the exhaust valve 7 and the intake valve 6 occurs, the exhaust valve 7 is placed in a minute lift state in which the lift amount is relatively small. In such a minute lift state, the gas flows into the exhaust port 7 with respect to the inner wall surface of the exhaust port 5 and the exhaust gas in the vicinity of the opening including the valve contact surface 24 rather than the specific shape of the exhaust port 5. The size of the gap formed between the valve 7 and the umbrella 7b has a dominant influence. Therefore, the connection space 23 is a space that serves as a flow path for the gas flowing from the combustion chamber 8 to the exhaust port 5 when the exhaust valve 7 is in a minute lift state. As a result, the ease greatly influences the ease of gas flow from the combustion chamber 8 to the exhaust port 7 when the exhaust valve 7 is placed in a minute lift state.

  Here, in this embodiment, the space on the intake port side in the connection space 23 corresponds to the intake side connection space of the present invention. The intake side connection space is a space on the right side of the connection space 23 in the state shown in FIG. The space on the bore wall surface side (exhaust bore wall surface side) on the exhaust port side in the connection space 23 corresponds to the exhaust side connection space of the present invention. The exhaust side connection space is a space on the left side of the connection space 23 in the state shown in FIG. Considering the characteristics relating to the ease of gas flow in the connection space 23 described above, the ease of gas flow in the intake side connection space is determined from the combustion chamber 8 to the exhaust port 7 when the exhaust valve 7 is placed in a minute lift state. This is considered to affect the ease of gas flow in the region on the intake port side (region R1 shown in FIG. 2). In addition, the ease of gas flow in the exhaust side connection space is determined based on the region on the exhaust bore wall surface side (of the gas flow from the combustion chamber 8 to the exhaust port 7 when the exhaust valve 7 is in a minute lift state) This is considered to affect the ease of gas flow in the region R2) shown in FIG.

  In view of this point, in the internal combustion engine 1, the connection space 23 is opened to the exhaust side connection space by the opening 25 a, and the exhaust port 5 is opened to the predetermined portion further downstream from the connection space 23 by the opening 25 b. A communication path 25 is provided. By providing the communication path 25 in this way, when the exhaust valve 7 is placed in a minute lift state, the gas flowing into the exhaust side connection space is added to the communication path 25 in addition to the flow path of the main body portion of the exhaust port 5. It is possible to flow. This means that gas easily flows in the exhaust side connection space by the communication passage 25. Therefore, when the exhaust valve 7 is placed in a minute lift state, the communication passage 25 causes gas to flow relatively easily from the combustion chamber 8 to the inside of the exhaust port 5 on the exhaust bore wall surface side compared to the intake port side. Become. As a result, it is possible to improve the scavenging efficiency according to the gas flow on the exhaust bore wall side while effectively suppressing the blow-by phenomenon caused by the gas flow from the intake port side at the time of valve overlap in the minute lift state It becomes.

  In order to make the gas flow in the communication passage 25 smooth, a predetermined portion where the opening 25b is opened is a portion where the gas pressure is relatively low in the exhaust port 5, for example, the flow path cross-sectional area of the exhaust port 5 is It is preferable to set the area to be wide.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Piston 4 ... Intake port 5 ... Exhaust port 6 ... Intake valve 7 ... Exhaust valve 7b ... Umbrella part 8 ... Combustion chamber 20 ... Cylinder head 21 ... Exhaust port side ceiling surface 22 ... Intake port side ceiling surface 23 ... Connection space 24 ... Valve contact surface 25 ... Communication passage 30 ... Cylinder block

Claims (1)

The intake port side ceiling surface where the intake port is opened in the cylinder head and the exhaust port side ceiling surface where the exhaust port is opened in the cylinder head are inclined with respect to a plane perpendicular to the central axis of the cylinder. In an internal combustion engine having a pent roof type combustion chamber,
A valve contact surface is formed at the opening to the combustion chamber of the exhaust port where the umbrella portion of the exhaust valve abuts when the exhaust valve is closed,
The exhaust port is connected to the combustion chamber, and is a partial space of the exhaust port, the connection space located above the valve contact surface, the intake side connection space located on the intake port side, and An exhaust side connection space located on the side of the bore wall surface on the exhaust port side opposite to the intake side connection space across the exhaust valve, and
A communication path that is located downstream of the connection space and communicates with the predetermined portion on the downstream side of the exhaust port and the exhaust side connection space is provided.
Internal combustion engine.

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