JPH089375Y2 - Air-fuel mixture generator for 2-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a two-stroke gasoline engine, and more particularly to a device for forming a rich air-fuel mixture in the vicinity of a spark plug.

[Conventional technology]

Conventionally, as a structure for forming a rich air-fuel mixture in the vicinity of a spark plug, there is one disclosed in Japanese Utility Model Laid-Open No. 60-15966. In this configuration, the fuel injection valve is arranged substantially horizontally at the outlet of the intake port and injects fuel toward the spark plug when the intake valve is opened.

[Problems to be Solved by the Invention] The above-described conventional configuration has a problem in that the fuel injected from the fuel injection valve directly hits the spark plug, so that carbon is likely to be deposited on the spark plug, resulting in misfire. . Further, when such a fuel injection valve is used in a two-cycle engine in which the supply and exhaust ports are opened and closed by the supply and exhaust valves, as will be described below, fuel blow-through causes deterioration of fuel consumption and exhaust gas emission, and particularly idle During an extremely light load operation such as operation, there is a problem of increasing the fluctuation between combustion cycles due to the flow of the rich mixture.

In a two-cycle engine, if fuel injection is performed after the exhaust valve is closed and before the intake valve is closed,
A rich mixture can be formed in the upper part of the combustion chamber. However, at this time, since the piston is in the ascending process, part of this rich air-fuel mixture is once pushed back to the air supply port side and does not burn while the air supply / exhaust valves are open in the next cycle. It will blow through to the exhaust port. Further, liquid fuel adhering to the air supply port or the air supply valve umbrella portion may be carried by fresh air immediately after the air supply valve is opened, and may blow through to the exhaust port as it is. If the fuel that does not burn in this way blows through to the exhaust port, the amount of fuel consumed will increase by this amount, and the amount of gas in the exhaust gas will increase.

In addition, when the air-fuel ratio (= fresh air volume / stroke volume) is about 0.1 and the load is light, when the piston is near top dead center, the relatively rich air-fuel mixture is flattened and the combustion chamber and each port are crushed. The air flows in the combustion chamber due to the turbulence of the air flow in the combustion chamber caused by the pressure difference between the two. As a result, the air-fuel mixture in the vicinity of the spark plug repeats rich and lean states, which causes very large combustion fluctuations, that is, extremely light load operation such as idle operation becomes unstable.

The present invention prevents carbon contamination of the spark plug, improves fuel efficiency and exhaust gas emission, and forms a stable rich mixture layer in the vicinity of the spark plug to suppress combustion fluctuations especially at extremely light loads. The purpose is to enable extremely light load operation.

[Means for solving the problem]

According to the present invention, in view of the above problems, there is provided a two-cycle engine in which a supply / exhaust port is opened / closed by a supply / exhaust valve, and a concave electrode chamber provided on a cylinder head surface and an ignition plug arranged in the electrode chamber. And a fuel injection valve for injecting fuel near the air supply valve in the air supply port in the latter half of the air supply valve opening period, and provided between the electrode chamber and the cylinder head opening of the air supply port. A shutoff wall that closes the electrode chamber side portion of the air supply valve at least during an initial period of opening the air supply valve;
A communication passage opening to the shut-off wall and communicating with the electrode chamber; both the air supply valve and the exhaust valve are opened while the piston is descending, and closed while the piston is rising; A two-cycle engine air-fuel mixture generating device is provided, wherein the opening of the passage is arranged at a position where the communication passage communicates with the inside of the air supply port during opening of the air supply valve.

[Action]

The atomized fuel injected from the fuel injection valve rides on fresh air flowing into the combustion chamber from the air supply port and mixes with this fresh air.
As a result, a rich mixture is formed in the upper part of the combustion chamber, and this rich mixture is pushed into the electrode chamber by the rise of the piston.

〔Example〕

 The present invention will be described below with reference to illustrated embodiments.

1 and 2 show a second embodiment to which the present invention is applied.
3 shows a cycle engine. A piston 13 is slidably provided in a cylinder bore 12 formed in the cylinder block 11, and a combustion chamber 15 is formed by the cylinder head 14, the cylinder bore 12 and the top surface of the piston 13. The air supply port 16 and the exhaust port 19 formed in the cylinder head 14 are
It is opened and closed by an air supply valve 17 and an exhaust valve 18, respectively.

A central portion of the cylinder head surface 21 that faces the combustion chamber 15, that is, a portion of the ignition plug 22 that faces the electrode 23 is recessed more than other portions to form an electrode chamber 24. That is, the electrode 23 is located in the electrode chamber 24 and does not project into the combustion chamber 15. Electrode chamber
24 is a substantially columnar space, which is provided near the outlet of the air supply port.

A fuel injection valve 32 is arranged facing the air supply valve 17 in a horizontal hole 31 formed in the cylinder head 14 below the air supply port 16. The fuel injection valve 32 is a so-called wide-angle injection type injection valve having a conventionally known configuration, and in the present embodiment, it is designed to operate only when the engine load is smaller than a certain value, and to the outlet of the air supply port 16. The atomized fuel A is injected toward the target. On the other hand, when the engine load is larger than a certain value, another fuel injection valve (not shown) provided above the air supply port 16 injects fuel.

A blocking wall 33 is provided between the electrode chamber 24 and the air supply port 16. As can be seen from FIG. 2, the blocking wall 33 is raised between the air supply port 16 and the electrode chamber 24 and the exhaust port 19 toward the combustion chamber 15 (FIG. 1) side with respect to other portions. To do. The wall surface 34 of the shutoff wall 33 on the air supply port 16 side is formed in a cylindrical shape along the edge of the valve umbrella 17a of the air supply valve 17 to be opened and closed. A communication passage 35 extending from the center of the end of the air supply port 16 toward the electrode 23 of the ignition plug 22 is bored in the blocking wall 33. As shown in FIG. 1, the communication passage 35 is inclined so that the electrode 23 side is located above and faces the combustion chamber 15 when the air supply valve 17 is closed, and the air supply valve 17 is opened. Facing the end of port 16.

The supply / exhaust valve opens and closes at the timing shown in FIG. That is, the exhaust valve first opens about 80 ° before bottom dead center, and then the air supply valve opens about 50 ° before bottom dead center. Then, after the exhaust valve closes at about 40 ° after bottom dead center, the air supply valve closes at about 70 ° after bottom dead center. The symbols a to e correspond to the symbols (a) to (e) in FIG. 4, respectively.

No. 4 for extremely light load operation such as idle operation
A description will be given with reference to FIGS.

In FIG. 4 (a), when the exhaust valve 18 is opened, the pressure of the combustion chamber 15 causes so-called blowdown in the exhaust port, and the residual gas G is discharged to the exhaust port as shown by arrow B.

Next, when the air supply valve 17 is opened, fresh air is supplied from the air supply port 16 to the combustion chamber 15 as indicated by an arrow C in FIG. 4 (b).
Flows into. The fresh air flows into the combustion chamber 15 from the cylinder bore 12 side of the air supply valve 17 because the shutoff wall 33 is provided. Further, at this time, since the communication passage 35 faces the air supply port 16, a part of the fresh air flows into the electrode chamber 24 through the communication passage 35 and flows toward the combustion chamber 15 side as shown by an arrow D. As a result, the residual gas in the electrode chamber 24 is scavenged. On the other hand, in the exhaust port, a negative pressure wave is generated due to the exhaust pressure pulsation, whereby the residual gas G near the exhaust valve 18 is sucked into the exhaust port. Then, so-called transverse scavenging occurs, and the fresh air becomes the combustion chamber.
The residual gas G in 15 is extruded to the exhaust port side.

In the latter half of the opening period of the air supply valve 17 and before the exhaust valve 18 is closed, the fuel injection valve 32 injects the atomized fuel A as shown in FIG. 4 (c). This atomized fuel A is supplied to the air supply port
The fresh air flowing into the fuel chamber 15 from 16 is mixed, and the air is mixed appropriately. At this time the piston 13 is starting to rise,
For this reason, the inflow velocity of the air-fuel mixture into the combustion chamber 15 is smaller than the inflow velocity of fresh air immediately after the intake valve 17 shown in FIG. 4B is opened. Therefore, the air-fuel mixture does not reach the lower portion of the combustion chamber 15, and the vortex E generated on the back surface of the air supply valve 17 forms a rich air-fuel mixture in the upper portion of the combustion chamber 15. On the other hand, even after the fuel injection is completed, while the exhaust valve 18 is open, the residual gas and part of the fresh air are pushed to the exhaust port side by the fresh air flowing from the air supply port 16.

Therefore, the rich mixture formed in the upper part of the combustion chamber 15 is promoted to be vaporized by a large amount of radiant heat of the high temperature residual gas in the combustion chamber 15. Also, as the piston 13 rises, FIG. 4 (d)
As indicated by arrows H and I, a part of the fresh air F flowing into the combustion chamber 15 passes through the communication passage 35 and the gap between the intake valve 17 and the valve seat,
The air supply port 16 is caused to flow backward, whereby the rich air-fuel mixture A is further pushed to the upper part of the combustion chamber 15.

After closing the air supply valve 17, as shown in FIG. 4 (e), the rich mixture A, the fresh air F, and the residual gas G were respectively compressed by the rise of the piston 13 and formed in the upper part of the combustion chamber 15. The rich mixture A is pushed into the vicinity of the electrode chamber 24 and the blocking wall 33. Then, the rich air-fuel mixture in the electrode chamber 24 is ignited by the ignition plug 22, and this becomes the ignition source, and the air-fuel mixture outside the electrode chamber 24 burns.

As described above, in the present embodiment, the electrode 23 of the spark plug 22 is disposed in the electrode chamber 24 recessed from the cylinder head surface 21, and the atomized fuel is injected in the latter half of the opening period of the air supply valve 17. Is configured. Therefore, the fuel does not directly contact the electrode 23 of the spark plug, and carbon contamination of the spark plug is prevented. On the other hand, at the time of fuel injection, the inflow velocity of the air-fuel mixture into the combustion chamber 15 is relatively small, so that a rich air-fuel mixture is formed in the upper part of the combustion chamber 15, and this rich air-fuel mixture is held in the electrode chamber 24 and cuts off the wall. Since it is blocked by 33, it will not be pushed back to the air supply port 16. Further, since a part of the valve umbrella portion 17a of the air supply valve 17 is close to the shutoff wall 33, fresh air flows into the combustion chamber 15 through the side of the fuel injection valve 32, and therefore, in the vicinity of the fuel injection valve 32. The flow velocity is high, and the fuel is guided to the combustion chamber 15 without adhering to the valve head portion 17a. Therefore, when the air supply / exhaust valves 17, 18 are opened, fuel does not blow from the air supply port 16 to the exhaust port. As a result, not only the fuel efficiency is improved and the exhaust gas emission is improved, but it is possible to prevent the output from being reduced particularly during high load operation. Further, during the light load operation, the rich air-fuel mixture is formed in the electrode chamber 24 and is stably maintained in the vicinity of the spark plug 22, so that the combustion state becomes extremely stable. Therefore, extremely light load operation such as idle operation can be performed in a stable state without causing engine stall, and engine vibration can be suppressed.

Although the communication passage 35 is a hole penetrating the blocking wall 33 in the above embodiment, it may be a notch opening downward instead of this.

[Effect of device]

As described above, according to the present invention, it is possible to improve fuel efficiency and exhaust gas emission without causing carbon contamination of the spark plug. Further, particularly during extremely light load operation such as idle operation, combustion fluctuation is suppressed and stable operation can be performed.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, a sectional view taken along the line I--I of FIG. 2, FIG. 2 is a plan view of the cylinder head surface seen from below, and FIG. FIG. 4 (a) is a sectional view showing the engine immediately after the exhaust valve is opened, and FIG. 4 (b) is a sectional view showing the engine immediately after the air supply valve is opened. FIG. 4 (c) is a sectional view showing the engine in a state where fuel injection is being performed, FIG. 4 (d) is a sectional view showing the engine immediately before the air supply valve is closed, and FIG. 4 (e) is air supply. It is sectional drawing which shows the engine immediately after a valve closed. 16 ... Air supply port, 17 ... Air supply valve, 18 ... Exhaust valve, 19 ... Exhaust port, 21 ... Cylinder head surface, 22 ... Spark plug, 23 ... Electrode, 24 ... Electrode chamber, 32 ... Fuel injection valve, 33 ... Blocking wall, 35 ... Communication passage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toyokazu Umebana, Toyota City, Toyota City, Aichi Prefecture, Toyota, Ltd. (72) Takao Tate, Toyotacho, Toyota City, Aichi Prefecture, Toyota City, Toyota (72) Inventor Hiroaki Nihei 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (56) Reference JP 53-1310 (JP, A) JP 51-2808 (JP, A) JP JP-A-51-54110 (JP, A) JP-A-63-223316 (JP, A) JP-A-47-7003 (JP, A) JP-A-58-85319 (JP, A) Actual development JP-A-60-15966 (JP , U) Actual development Sho 60-97373 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A supply / exhaust port which is opened / closed by a supply / exhaust valve.
In a cycle engine, a concave electrode chamber provided on a cylinder head surface, a spark plug arranged in the electrode chamber, and in the vicinity of the air supply valve in the air supply port in the latter half of the air supply valve opening period. Is provided between the electrode chamber and the cylinder head opening of the air supply port, and closes the electrode chamber side portion of the air supply valve at least during the initial opening period of the air supply valve. A shut-off wall and a communication passage that opens into the shut-off wall and communicates with the electrode chamber.The air supply valve and the exhaust valve both open when the piston descends and closes when the piston rises. The mixture forming device for a two-cycle engine, wherein the opening of the communication passage is arranged at a position where the communication passage communicates with the air supply port during opening of the air supply valve. .