JPH0330695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in an intake system for an engine.

(Prior Art) Conventionally, there have been known engines in which a combustion chamber is formed in the cylinder head of an engine, such as those described in, for example, Japanese Patent Application Laid-Open Nos. 50-107309 and 1982-65207. This is done by providing a recess in the area surrounding the intake port or exhaust port and the ignition plug in the cylinder head.
A combustion chamber is formed by the recess between the inner wall surface of the cylinder head and the upper surface of the piston when the piston is at top dead center, and a squish zone with a minute gap is formed adjacent to the recess. It is.

In this structure, the combustion chamber has a compact, almost spherical shape, and the flame propagation distance is shortened, which is very advantageous against knocking, and it becomes possible to set the ignition timing close to the optimum value. In addition, since the knocking resistance is good, by increasing the compression ratio to a level higher than that of conventional ones, lean combustion can be performed using a lean air-fuel mixture, thereby improving fuel efficiency.

On the other hand, when introducing intake air into the combustion chamber of an engine, the inflow of intake air is given directionality to generate a swirl in the combustion chamber, thereby increasing the combustion speed.
Techniques for improving combustion efficiency are known. In an engine equipped with a combustion chamber structure having a compact combustion chamber and a squeezing zone, unburned gas is more likely to be discharged than in a normal engine, and therefore, countermeasures against this are required. In other words, since the flame does not enter the squish zone smoothly, it essentially becomes a quench zone, and for this reason, the air-fuel mixture existing in this zone is not fully combusted during the combustion explosion process and remains unburned. It is emitted as a gas. Therefore, if the above-mentioned swirl is used to make it easier for the flame to spread to this squish zone near the compression top dead center, the amount of unburned gas can be significantly reduced. In this way, the intake swirl has an important meaning in the engine having the above structure.

When this swirl generation function is combined with the above-mentioned compact combustion chamber and high compression ratio combustion chamber with a squeeze zone, the advantages of both are combined to further increase the combustion speed at low engine loads. This improves combustion efficiency and improves combustion conditions. On the other hand, when the engine is under high load as the filling amount increases, the combustion speed becomes too fast and the combustion pressure rises rapidly, leading to an increase in combustion noise, so it is necessary to improve this point.

(Purpose of the Invention) This invention was made to solve such conventional problems, and it improves combustion efficiency by generating swirl at low loads, and suppresses swirl at high loads to improve combustion efficiency. To provide an engine intake device that reduces noise.

(Structure of the Invention) This invention provides a partial recess in the inner wall of the cylinder head facing the upper surface of the piston to include an exhaust port, and a gap between the inner wall surface of the cylinder head and the upper surface of the piston when the piston is at the top dead center. A combustion chamber formed by the recessed portion and a squishing zone with a minute gap are formed, the squishing zone is communicated with the squishing zone, and intake air is introduced to swirl in the circumferential direction within the cylinder for low-load use for swirl generation. an intake passage;
A high-load intake for suppressing swirl, which is equipped with an on-off valve that communicates with the squeezing zone and closes when the engine is under low load, and supplies intake air to the squeezing zone in the piston sliding direction so as to suppress the swirl. The intake passage constitutes an intake passage. As a method for suppressing the swirl, the intake passage may be configured to introduce intake air in a direction substantially parallel to the center line of the cylinder, or the intake passage may be configured to introduce intake air in a direction opposite to the swirl. You may.

Embodiment 1 In FIGS. 1 to 3, 1 indicates a cylinder block, 2 indicates a cylinder head, and 3 indicates a piston.
A recess 4 is partially provided in the inner wall of the cylinder head 2 facing the upper surface of the piston 3, and a recess 4 is formed between the inner wall surface of the cylinder head 2 and the upper surface of the piston 3 when the piston 3 is at the top dead center. A combustion chamber 5 is formed, and a squish zone 6 with a minute gap is formed adjacent to the recess 4.

Reference numeral 7 indicates an intake port that opens to the squish zone 6, 8 indicates an exhaust port that opens to the recess 4, the intake port 7 is connected to an intake passage 9 that opens to one side of the cylinder head 2, and the exhaust port 8 is connected to the cylinder head. The exhaust passages 10 open on the other side of the 2 are connected to each other. Further, an intake valve 11 and an exhaust valve 12 are arranged in the intake port 7 and the exhaust port 8, which contact and seal the respective valves. Further, a spark plug 13 is attached to the cylinder head 2 so as to face the recess 4.

The intake passage 9 is divided by a partition wall 14 near the intake port 7, and consists of a low-load intake passage 9a and a high-load intake passage 9b, and an on-off valve 15 is disposed in the high-load intake passage 9b. , this on-off valve 1
5 is closed by an actuator (not shown) when the engine is under low load, and when the load is low, it closes the high load intake passage 9b and closes the low load intake passage 9a.
It is configured to supply intake air by.

The low-load intake passage 9a is formed with a relatively small passage area to improve the flow velocity of the intake air flowing through the low-load intake passage 9a, and to increase the flow rate in the circumferential direction of the cylinder (direction of arrow S in FIG. 1). The opening is configured to introduce intake air into the cylinder in a circumferential direction to generate a swirl.

On the other hand, the high-load intake passage 9b opens in a direction substantially parallel to the center line of the cylinder, that is, toward the top surface of the piston 3, and is configured to introduce intake air while suppressing the generation of swirl without imparting a swirling flow to the intake air. has been done.

In the above configuration, during low-load operation, the on-off valve 15 is closed to introduce intake air from the low-load intake passage 9a to the intake port 7, increasing the intake air flow velocity and introducing the intake air in the circumferential direction. The intake air introduced into the squish zone 6 becomes a swirling flow without being obstructed and generates a swirl. That is, when introduced into the recess 4, the flow is obstructed by the side wall thereof, resulting in poor swirl generation efficiency, but when introduced into the squish zone as described above, swirl is generated throughout the cylinder. Therefore, vaporization and atomization of the fuel are promoted, flame propagation to the squish zone 6 is also improved, and combustibility and combustion efficiency are improved.

Furthermore, by forming a compact combustion chamber, a high compression ratio can be achieved, further improving combustion efficiency. Furthermore, at the end of the compression process, the squishing flow generated in the squishing zone 6, which is a minute gap formed between the inner wall surface of the cylinder head 2 and the upper surface of the piston 3, is pushed toward the combustion chamber 5. The combustion efficiency is improved by actively generating turbulence in the air-fuel mixture in the chamber 5.

On the other hand, when the load is high, the on-off valve 15 opens and intake air is also supplied from the high-load intake passage 9b.
The filling efficiency of intake air is improved and high output can be obtained. At this time, since the intake air supplied from the high-load intake passage 9b is introduced in a direction substantially parallel to the center line of the cylinder, the generation of swirl is suppressed, thereby preventing the combustion speed from becoming too large. Reduce combustion noise.

(Effects of the Invention) As explained above, the present invention has a compact combustion chamber formed in the cylinder head of an engine, in which a low-load intake passage is opened in the squish zone to generate a swirl, and a high-speed The load intake passage is configured to suppress the above-mentioned swirl, and at low loads, the synergistic effect of the squish flow and swirl improves combustibility. is generated throughout the cylinder, which greatly improves combustibility, and also suppresses the combustion speed and reduces combustion noise at high loads.

[Brief explanation of the drawing]

FIG. 1 is a plan view of essential parts of an engine showing an embodiment of the present invention, and FIGS. 2 and 3 are cross-sectional views taken along the line - and -, respectively, of FIG. 1. 1... Cylinder block, 2... Cylinder head, 3... Piston, 4... Recess, 5... Combustion chamber, 6... Squeeze zone, 7... Intake boat, 8... Exhaust port, 9... Intake passage, 9a...
...Intake passage for low load, 9b...Intake passage for high load, 15...Opening/closing valve.

Claims (1)

[Claims] 1. A recess is partially provided in the inner wall of the cylinder head facing the top surface of the piston to include an exhaust port,
When the piston is at top dead center, a combustion chamber formed by the recess and a slight squish zone are formed between the inner wall surface of the cylinder head and the top surface of the piston, and communicate with the squish zone and allow intake air to flow through the combustion chamber. The swirl is suppressed by providing a low-load intake passage for swirl generation that is introduced in a circumferential direction inside the cylinder, and an on-off valve that communicates with the squish zone and closes when the engine is under low load. An intake system for an engine, characterized in that an intake passage is constituted by a high-load intake passage for suppressing swirl and supplying intake air in a piston sliding direction to a squish zone.