JPS6218731B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In the intake stroke of an engine, the present invention generates a strong swirling flow in the burnt gas flowing back into the combustion chamber from the exhaust passage, and also generates a strong swirling flow in the burned gas flowing back into the combustion chamber from the intake passage. By promoting the swirling flow of fuel gas, it increases combustion efficiency and improves engine performance across the entire range from high-load to low-load operation, while also minimizing the generation of unburned harmful components such as HC and CO. This invention relates to an apparatus for improving the combustion of air-fuel mixture in a four-stroke internal combustion engine with a simple configuration, which can reduce the amount of air-fuel mixture.

In four-stroke internal combustion engines for automobiles, as a means of obtaining high output during high-load operation, the opening timings of the intake and exhaust valves are generally overlapped to increase intake efficiency, that is, the intake valves are opened immediately before the end of the exhaust stroke in which the piston rises. The exhaust valve is kept open until the middle of the suction stroke when the next piston descends, but if the opening timings of the intake and exhaust valves overlap in this way, the absolute amount of intake air will be large. In the engine's high-load operating range, the amount of intake air is large, so there is no problem with the combustion of the intake air-fuel mixture, and it is possible to increase the intake efficiency and obtain the desired high output.
On the other hand, in the engine's low-load operating range, the throttle valve opening of the carburetor is naturally small and the absolute amount of intake air is small. The ratio is high (20 to 40% of the new air mixture to the cylinder volume), which not only makes ignition unstable, but also reduces turbulence and swirling of the intake air mixture caused by piston reciprocation and squishing. The propagation of the combustion flame may also be slowed down, leading to a decrease in combustion efficiency, resulting in the inconvenience of increasing the amount of unburned harmful components such as HC and CO in the exhaust gas. Naturally, this phenomenon tends to become more pronounced as the overlapping period of the intake and exhaust valves becomes longer and the higher the output type becomes. Therefore, if the engine is made to be a high-output type, the combustion efficiency in the low-load operating range will be lowered, and the amount of exhaust gas will be reduced.
A problem arises in that a large amount of unburned harmful components such as HC and CO are generated.

In order to solve this problem, measures such as forming the intake passage in a spiral shape, forming blades on the intake valve, and forming a guide wall around the intake valve have been taken. Various technical means have been proposed to improve combustion by creating swirl and turbulence in the air-fuel mixture in the combustion chamber. The amount of fresh air-fuel mixture sucked into the cylinder becomes extremely small, and the ratio of residual gas to the new air-fuel mixture in the cylinder becomes extremely high. It is difficult to achieve a satisfactory improvement in combustion by simply taking measures that cause combustion to occur. Furthermore, in order to improve combustion in the deceleration range of the engine, it has been proposed to attach a throttle opener or dart pot to the intake system to temporarily increase the throttle valve opening of the carburetor. Although this method is effective in improving combustion by increasing the intake amount of fresh air-fuel mixture in the deceleration operating range of the engine and increasing the amount of new air-fuel mixture relative to the amount of residual gas in the cylinder, on the other hand, it In this case, more new air-fuel mixture than necessary is supplied, and combustion is excessively promoted, leading to a decrease in engine braking performance and another problem in that deceleration drivability deteriorates.

In view of the above points, the main object of the present invention is to provide a means for generating a swirling flow by backflowing burnt gas in the combustion chamber in the exhaust system of an engine, and to encourage the swirling flow of backflowing burnt gas in the intake system. by applying the means of
Improves combustion in all operating ranges of the engine, especially in low-load operating ranges, and reduces the amount of harmful unburned components such as HC and CO as much as possible without adversely affecting high-load, high-output engine operation. The goal is to reduce the

Another object of the present invention is to improve the fuel consumption rate by enabling good engine operation with a lean mixture as a whole.

Yet another object of the present invention is to always provide good engine operating performance regardless of operating conditions.

In order to achieve the above object, the present invention provides an intake valve opening communicating with an intake passage and an exhaust valve opening communicating with an exhaust passage on the wall surface of a combustion chamber formed at the upper part of a cylinder in which a piston is slidably fitted. an intake valve is provided at the intake valve port, an exhaust valve is provided at the exhaust valve port, and a fuel supply means is connected to the intake passage for supplying an air-fuel mixture thereto. In a four-stroke internal combustion engine, the combustion chamber is defined by a four-stroke internal combustion engine, in which a part of the burnt gas in the exhaust passage flows back into the combustion chamber by not closing the exhaust valve during the intake stroke in which the piston descends. A swirling flow generation guide wall is provided around the exhaust valve port of the combustion chamber wall to cause the burnt gas flowing back into the combustion chamber to collide with it to generate a swirling flow. At the same time, a portion of the intake passage connected to the intake valve port is meandered in an S-shape so that the intake air drawn into the combustion chamber from inside the intake passage promotes a swirling flow of the backflow burnt gas. It is characterized by

Embodiments of the present invention will be described below with reference to the drawings.

In Figures 1 to 3, a combustion chamber 4 is formed in the cylinder head 3 above the piston 1 into which the piston 2 is slidably fitted, and valve seats 7 and 8 are provided on the upper wall of the combustion chamber 4, respectively. The installed intake valve port 5 and exhaust valve port 6 are opened eccentrically from the center of the combustion chamber 4, and the intake valve port 5 has an intake passage 9 formed in the cylinder head 3 and meandering in an S-shape. In addition, an exhaust passage 10 formed in the cylinder head 3 is formed in the exhaust valve port 6 . An air-fuel mixture supply device 11 such as a carburetor is connected to the intake passage 9 as usual.
The intake valve port 5 is provided with an intake valve 12 that opens and closes the port 5, and the exhaust valve port 6 is provided with an exhaust valve 13 that opens and closes the port 6. The direction of the outlet of the intake passage 9 toward the intake valve port 5 and the direction of the exhaust passage 10 toward the exhaust valve port 6 are each biased toward one side from the center of the cylinder 1, and as will be described later, combustion is The intake air drawn into the chamber 4 and the burned gas flowing back from the exhaust passage 10 into the combustion chamber 4 flow along the outer circumferential wall inside the cylinder 1, respectively.

The intake and exhaust valves 12 and 13 are opened and closed according to a desired opening and closing cycle by a conventionally known valve operating mechanism. In addition, in this engine, in order to obtain high output in a high-load operating range, the opening timings of the intake and exhaust valves 12 and 13 are made to overlap, so that the intake valve 12 is opened before the end of the exhaust stroke, and the opening timing of the The negative pressure generated in the exhaust passage 10 due to exhaust inertia causes new air-fuel mixture to be sucked into the combustion chamber from the intake passage, thereby increasing intake efficiency and improving engine performance.

As mentioned above, there are intake and exhaust valves 12 on the combustion chamber 4 wall.
A swirling flow generation guide wall 14 is provided to generate a swirling flow in the burnt gas flowing back from the exhaust passage 10 into the combustion chamber 4 due to the overlap of the valve opening timings 13.

Therefore, this swirling flow generation guide wall 1 in the present invention
4 generates a more powerful unidirectional swirling flow of burned gas in the combustion chamber 4 to increase the flame propagation velocity of the unburnt mixture (the algebra between the flow velocity of the unburned mixture just before the flame front and the combustion velocity). The swirl flow generation guide wall 14 has a special configuration to increase the combustion efficiency by increasing the combustion efficiency.The configuration of the swirl flow generation guide wall 14 will be explained below. It extends from the outer peripheral wall of the combustion chamber 4 toward the center of the combustion chamber 4 in an arc shape along the outer periphery of the exhaust valve port 6 . As clearly shown in FIG. 4, its vertical cross-sectional shape is formed into a substantially U-shape, with the inner circumferential surface 15 facing the exhaust valve port 6 being substantially vertical, and the outer circumferential surface facing the outer circumferential wall of the combustion chamber 4. The surface 16 is formed into a concave arc upward and downward, and the inner and outer peripheral surfaces 15,
A bottom surface 17 connecting the lower ends of the holes 16 is formed as a substantially horizontal flat surface. and a connecting corner between the inner circumferential surface 15 and the bottom surface 17 and a connecting corner between the inner circumferential surface 15 and the bottom surface 17 and the outer circumferential surface 16 and the bottom surface 1
The connecting corners with 7 are rounded r ₁ and r ₂ , respectively.

The swirling flow generation guide wall 1 is provided on the upper wall of the combustion chamber 4.
4, an ignition plug 18 is provided close to the outer wall surface on the side away from the exhaust valve port 6, that is, the outer circumferential surface 16.

In the engine of the present invention, the exhaust valve 13
is still open, so part of the burned gas that flowed into the exhaust passage 10 at the beginning of this intake stroke flows back into the combustion chamber 4 (in this case, when the engine is in a low load operating range, the throttle valve is opened). Since the temperature is small, the amount of burned gas flowing back into the combustion chamber 4 is large). By the way, when the exhaust valve 13 is still open during the suction stroke, the swirling flow generation guide wall 14 exists in the gap between the exhaust valve port 6 and the outer periphery of the exhaust valve 13, as shown in FIG. However, the fluid resistance is large, and the fluid resistance is small where the swirling flow generation guide wall 14 is not present. Therefore, an imbalance occurs in the burnt gas flowing back from the exhaust passage 10 to the combustion chamber 4 through the exhaust valve port 6, and as a result, the backflow burnt gas generates a swirling flow and flows into the combustion chamber 4. . Moreover, the reflected flow of the backflowing burnt gas that collides with the arcuate inner circumferential surface 15 of the swirling flow generation guide wall 14 from the exhaust passage 10 is converged and becomes a strong swirling flow that gathers in the same direction and forms the inside of the combustion chamber 4. flows. The intake air drawn into the combustion chamber from inside the intake passage is drawn into the combustion chamber through the intake passage, which has an S-shaped meandering portion that connects to the intake valve port so as to promote a swirling flow of backflow burnt gas. This intake air further effectively promotes the swirling flow of the backflowing burnt gas generated as described above, and as a result, the total airflow of the backflowing burnt gas and the new mixture becomes a strong swirling flow, which flows into the combustion chamber. Flows within 4.

Then, when the spark plug 18 ignites a spark near the top dead center of the piston 2 immediately before the end of the compression stroke, the flow velocity of the air-fuel mixture increased by the swirling flow, the swirling flow, and the swirling flow. The flame in the combustion chamber 4 grows powerfully and rapidly due to the small mixture turbulence caused by the combustion and the increased combustion speed. Therefore, without changing the air-fuel ratio, the flame grows strongly and reliably, and combustion is significantly improved. Even the HC in the exfoliated quenching layer can be combusted without difficulty. The entire intake air-fuel mixture can be reliably combusted even under load and deceleration operating ranges.

As described above, according to the present invention, in a four-cycle internal combustion engine, a swirling flow generation guide wall is provided around the exhaust valve port of the combustion chamber wall defining the combustion chamber, protruding toward the combustion chamber side, and Since the burnt gas flowing back into the combustion chamber collides with the swirling flow generation guide wall to generate a swirling flow, it is effective especially when the amount of intake air is small, such as in the low load and deceleration operating range of the engine. Even if there is a problem, a strong swirling flow is generated in the overall air flow in the combustion chamber, and the combustion flame obtained by the spark ignition of the ignition plug grows powerfully and rapidly, increasing the flame propagation speed, reducing load and deceleration. Even in the operating range, the intake air-fuel mixture can be combusted evenly to significantly improve combustion efficiency, and the generation of unburned harmful components such as HC and CO can be reduced as much as possible.

In addition, the swirling flow generation guide wall converges the backflowing burnt gas that collides with it and causes it to flow into the combustion chamber as a unidirectional collective swirling flow, thereby generating a stronger swirling flow inside the combustion chamber. is possible.

Furthermore, according to the present invention, the portion of the intake passage connected to the intake valve port is formed by meandering in an S-shape so that the intake air drawn into the combustion chamber from the intake passage is encouraged to flow back and swirl the burned gas. As a result, the swirling flow of the backflowing burnt gas is effectively promoted and becomes more powerful, and the combustion flame grows more powerfully and rapidly, increasing the flame propagation speed, and as a result, the combustion efficiency is further improved. The generation of unburned harmful components can be further reduced.

[Brief explanation of the drawing]

Fig. 1 is a bottom view of the cylinder head of an engine equipped with the device of the present invention, Fig. 2 is a sectional view taken along the line - Fig. 3 is a perspective view of the swirling flow generation guide wall, and Fig. 4 is an enlarged view of the exhaust valve portion. FIG. 1... Cylinder, 2... Piston, 4... Combustion chamber, 5... Intake valve port, 6... Exhaust valve port, 9... Intake passage, 10... Exhaust passage, 11... Air-fuel mixture Supply device, 12... Intake valve, 13... Exhaust valve, 14... Swirling flow generation guide wall.

Claims (1)

[Claims] 1. An intake valve port communicating with the intake passage and an exhaust valve port communicating with the exhaust passage are opened in the wall surface of the combustion chamber formed at the upper part of the cylinder into which the piston is slidably fitted, respectively, and the intake valve An intake valve in the mouth,
Each of the exhaust valve ports is provided with an exhaust valve, and the intake passage is connected with a fuel supply means for supplying an air-fuel mixture thereto, so that when the piston is on the downward intake stroke, the exhaust valve is not closed. In a four-stroke internal combustion engine in which a part of the burnt gas in the exhaust passage is caused to flow back into the combustion chamber, a portion of the combustion chamber wall defining the combustion chamber is formed around the exhaust valve port. A swirling flow generation guide wall is provided that protrudes toward the combustion chamber to cause the burnt gas flowing back into the combustion chamber to collide with the burned gas to generate a swirling flow. A combustion improvement device for an air-fuel mixture in a four-stroke internal combustion engine, wherein a portion of the intake passage connected to the intake valve port is meandered in an S-shape so as to promote a swirling flow of backflowing burned gas.