JPH09144547A - Suction and exhaust device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of combustion being attendant on inner EGR by forming the swirl of intake in a cylinder through an intake port, and providing an exhaust port having such shape as the swirl of exhaust is formed in the same direction as the swirl of intake in the case of mixing exhaust gas with the intake. SOLUTION: Each one pair of an intake port 21 and an exhaust port 22, which are provided in a cylinder head 20, are formed in a herical shape, and their shapes are set up so that the swirls of intake and of exhaust may be the same in direction. An exhaust valve is opened in an exhaust stroke and also partially opened in an intake stroke, and inner EGR is therefore carried out in the intake stroke. When such inner EGR is carried out, the swirl of exhaust being the same in direction as the swirl of intake is caused in the cylinder 11, and the strength of the swirl of intake can be thereby increased to quicken the mixing of the intake and the jetted fuel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake / exhaust system for an engine, and more particularly to an internal EG in which an exhaust valve is partially opened in an intake stroke so that a part of exhaust gas is mixed with intake air.
R (Exhaust gas recirculation Exhaust Gas Rec
The present invention relates to an intake / exhaust device for an engine, which is adapted to perform iculation.

[0002]

2. Description of the Related Art EGR has been attempted as a countermeasure for exhaust gas, particularly for suppressing the production of nitrogen oxides. The EGR is intended to return a part of the exhaust gas to the intake side, thereby increasing the specific heat capacity of the intake air, lowering the oxygen concentration in the intake air, and suppressing combustion.

When EGR is performed, combustion is suppressed, the temperature rise in the cylinder is suppressed, and the amount of nitrogen oxides in the exhaust gas is reduced.

The above-mentioned EGR is designed to return a part of the exhaust gas from the outside to the intake side. However, by partially opening the exhaust valve in the intake stroke, a part of the exhaust gas is converted into the intake air. Internal EGR that has been set back is also being attempted. The internal EGR is achieved by devising the shape of the exhaust valve, which does not require a special conduit for returning exhaust gas from the outside to the intake side, and the intake system of the engine is polluted or corroded by the exhaust gas. Can be prevented.

[0005]

FIG. 7 shows a conventional four-valve engine using such internal EGR, and a pair of helical intake ports 2 formed in a cylinder head 1 swirl the intake air. At the same time, part of the exhaust gas is returned from the exhaust manifold 3 to the cylinder side.

However, the conventional exhaust port 3 has a shape in which a pair of ports are simply assembled in the cylinder head 1. Therefore, according to such a shape, the exhaust gas blown back into the cylinder during the intake stroke does not have directionality and hinders the swirl of intake air to weaken the swirl of intake air. It was supposed to prevent good mixing with the intake air. Therefore, according to such a conventional internal EGR, there is a problem that combustion is deteriorated and smoke is generated in the exhaust gas.

The present invention has been made in view of the above problems, and even if the internal EGR is performed, the swirl of the intake air is not reduced, so that the combustion is prevented from being deteriorated. It is an object of the present invention to provide an intake / exhaust device for an engine.

[0008]

SUMMARY OF THE INVENTION The present invention relates to an intake / exhaust device for an engine, in which an exhaust valve is partially opened in an intake stroke to mix a part of exhaust gas with intake air. In addition to forming an intake air swirl in the cylinder, an exhaust port having a shape that causes an exhaust gas swirl in the same direction as the intake air swirl when the exhaust gas is mixed with the intake air is provided. The present invention relates to an intake / exhaust device for an engine.

Therefore, when performing the internal EGR in which the exhaust valve is partially opened in the intake stroke to mix a part of the exhaust gas to the intake side, an exhaust swirl in the same direction as the intake swirl is formed in the cylinder, This not only reduces the intake air swirl, but also increases the intake air swirl, which promotes mixing of the intake air and fuel and improves combustion. Therefore, the combustion is improved while suppressing the generation of nitrogen oxides, and the deterioration of smoke in the exhaust gas is prevented.

[0010]

1 shows an engine equipped with an intake / exhaust device according to an embodiment of the present invention. The engine includes a cylinder block 10. The cylinder block 10 is provided with a cylinder 11 formed of a through hole that penetrates vertically. Piston 1 in cylinder 11
2 is slidably held. The piston 12 is provided with a combustion chamber 13 having a concave portion on the upper portion thereof, and is connected to a connecting rod 15 by a piston pin 14. The lower end side of the connecting rod 15 is connected to the crank pin of the crank shaft.

The upper part of the cylinder 11 is a cylinder head 20.
Is blocked by An intake port 21 and an exhaust port 22 are formed in the cylinder head 20, respectively. These ports 21 and 22 are the intake valves 2 respectively.
3 and the exhaust valve 24 are adapted to open and close. Intake port 21 and exhaust port 2
An intake manifold 25 and an exhaust manifold 26 are attached to both side surfaces of the cylinder head 20 so as to communicate with the cylinder 2.

FIG. 2 shows the intake port 21 and the exhaust port 22 provided in the cylinder head 20 in cross section. Here, each of the intake port 21 and the exhaust port 22 is provided as a pair, and the ports 21 and 22 are both formed in a helical shape so as to generate an intake swirl and an exhaust swirl. Moreover, the shapes of the intake port 21 and the exhaust port 22 are set so that the intake swirl and the exhaust swirl are in the same direction.

FIG. 3 particularly shows an exhaust valve opening / closing cam 30 for opening / closing the exhaust valve 24. This cam 30 is provided with a first cam 31 for discharging combustion gas and a second cam 3 for performing internal EGR in the intake stroke.
2 is provided. With such a cam 30, the exhaust valve 23 can be opened and closed as shown in FIG. That is, the exhaust valve 23 is opened in the exhaust stroke and is also partially opened in the intake stroke, so that the internal EGR is performed by the partial opening in the intake stroke.

Therefore, when the internal EGR as shown in FIG. 4 is performed by the second cam 32 of the exhaust valve opening / closing cam 30 as shown in FIG. 3, as shown in FIG. 2, exhaust gas in the same direction as the intake swirl is exhausted. Swirl is generated in this cylinder by blowing back exhaust gas from the other cylinder. That is, the exhaust swirl does not reduce the intake swirl, but rather the exhaust gas flows in a direction of increasing the strength of the intake swirl. Therefore, the mixing of intake air and fuel spray in the case of internal EGR is promoted more, which improves combustion. Therefore, the fuel efficiency is improved and the deterioration of smoke in the exhaust gas is prevented. Moreover, by performing the internal EGR, the heat capacity of the intake air in the cylinder is increased and the oxygen concentration is relatively decreased, so that the combustion temperature is suppressed, and thereby the nitrogen oxides are reduced. That is, by performing such internal EGR, it is possible to suppress the generation of nitrogen oxides and prevent deterioration of fuel consumption and smoke.

Although the above embodiment relates to the intake / exhaust device for a four-valve engine, it can be applied to a three-valve engine as shown in FIG. That is, even in an engine intake / exhaust device including a pair of helical intake ports 21 and a single helical exhaust port 22, the exhaust port 22 has a shape in which the exhaust swirl is in the same direction as the intake swirl when performing internal EGR. The shape may be such that the flow of

Furthermore, as shown in FIG. 6, it is also applicable to a two-valve engine having a single intake port 21 and a single exhaust port 22. Even in this case,
When the internal EGR is performed by making both the intake port 21 and the exhaust port 22 into a helical shape and causing the intake swirl and the exhaust swirl generated in such a shape to flow in the same direction. In addition to promoting the mixing of intake air and fuel spray in, thereby improving fuel efficiency and preventing smoke deterioration,
It becomes possible to reduce nitrogen oxides.

[0017]

INDUSTRIAL APPLICABILITY As described above, the present invention forms an intake swirl in a cylinder by means of a helical intake port, and, when mixing exhaust gas with intake air, an exhaust swirl in the same direction as the intake swirl. An exhaust port having a shape that causes the above is provided.

Therefore, according to the present invention, when the internal EGR is performed in which the exhaust valve is partially opened in the intake stroke to mix a part of the exhaust gas with the intake air, the swirl of the exhaust gas hinders the effect of the swirl of the intake air. Rather, it promotes mixing of intake air and fuel spray to improve fuel efficiency and prevent smoke from worsening. Therefore, it becomes possible to provide an intake / exhaust device for an engine capable of improving combustion while suppressing generation of nitrogen oxides.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a main part of an engine.

FIG. 2 is a cross-sectional view of a cylinder head.

FIG. 3 is a front view of an exhaust valve opening / closing cam.

FIG. 4 is a graph showing opening / closing of an exhaust valve.

FIG. 5 is a cross-sectional view of a cylinder head of another embodiment.

FIG. 6 is a cross-sectional view of a cylinder head of yet another embodiment.

FIG. 7 is a cross-sectional view of a cylinder head of a conventional engine.

[Explanation of symbols]

 10 Cylinder Block 11 Cylinder (Through Hole) 12 Piston 13 Combustion Chamber (Recess) 14 Piston Pin 15 Connecting Rod 20 Cylinder Head 21 Intake Port 22 Exhaust Port 23 Intake Valve 24 Exhaust Valve 25 Intake Manifold 26 Exhaust Manifold 30 Exhaust Valve Open / Close Cam 31 First cam 32 Second cam

Claims (1)

[Claims] 1. An intake / exhaust device for an engine, wherein an exhaust valve is partially opened during an intake stroke to mix a part of exhaust gas with intake air, and a swirl of intake air is introduced into a cylinder by a helical intake port. An intake / exhaust device for an engine, which is formed and is provided with an exhaust port shaped so as to generate an exhaust swirl in the same direction as the intake swirl when the exhaust gas is mixed with the intake air.