JP2874426B2 - Direct injection spark ignition engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a direct injection spark ignition engine.

[0002]

2. Description of the Related Art In a premixed spark ignition engine having a carburetor and a fuel injection valve in an intake pipe, there is a problem of delay in fuel transport especially during a transient operation. A direct injection spark ignition engine in which a fuel injection valve faces a combustion chamber has been considered.

A direct injection type spark ignition engine disclosed in, for example, Japanese Patent Application Laid-Open No. 57-62915 has been disclosed.
In addition to injecting fuel into the combustion chamber during the intake stroke, intake swirl is generated in the combustion chamber to promote mixing of fuel and air.

[0004] The uniform mixing of fuel and air contributes to the stability of combustion. However, in the case of combustion using an ultra-lean mixture, smooth ignition with a spark plug becomes extremely difficult with such a uniform mixing system. To stabilize the ignition performance, it is effective to stratify the air-fuel mixture to increase the air-fuel ratio in the vicinity of the spark plug.However, in such an engine where fuel and air are mixed from the intake stroke, the vicinity of the spark plug However, it is difficult to collect fuel at a low temperature, and there is a problem that stable ignition performance cannot be obtained when performing ultra-lean combustion with an air-fuel mixture considerably smaller than the stoichiometric air-fuel ratio.

The present invention has been made in view of the above problems, and has as its object to improve the shape of a combustion chamber of a direct injection spark ignition engine in order to enable lean combustion.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a direct injection type spark ignition engine in which an ignition plug and a fuel injection valve are made to face a combustion chamber. The fuel injection valve faces the side of the intake valve, and a slope is formed on the top surface of the piston to reflect and diffuse the fuel spray injected from the fuel injection valve in the direction of the exhaust valve. A squish area for generating a gas flow facing the diffusion fuel is formed on a side of the valve, and a fuel injection timing of the fuel injection valve is set during a compression stroke.

[0007] In the above structure, two intake valves are provided.
And set the intake port connected to each intake valve to operating conditions.
A swirl control valve for opening and closing depending provided, before
Bypassing the serial swirl control valve to form a secondary port leading to the intake immediately before the one of the intake valve.

[0008]

The fuel spray injected during the compression stroke hits the inclined surface and diffuses toward each exhaust valve. As a result, the fuel spray hits the piston top surface and the exhaust valve, which are relatively hot, and promotes atomization and vaporization.

[0009] A squish is generated from the side of the exhaust valve near the top dead center of the piston, and the squish transports a large amount of fuel distributed near the exhaust valve to the vicinity of the spark plug. The stratification of the mixture mixture is realized. Since the fuel injection is in the compression stroke, the stratified state of the air-fuel mixture is maintained even at the time of ignition, thereby ensuring stable ignition performance even when the air-fuel mixture is diluted, reducing fuel consumption, reducing emissions, High output is measured.

[0010] In the region far from the combustion chamber of the spark plug, the air-fuel ratio becomes ultra lean, autoignition reaction is suppressed leading to knocking, resulting to increase the compression ratio as the thermal efficiency, the improvement in output can be achieved.

In addition, immediately before one of the two intake valves,
Secondary port that guides intake air around the swirl control valve
In the configuration provided with a swirl control valve, each intake port is closed by the swirl control valve, and a strong swirl is generated in the combustion chamber by the intake air flow guided from the auxiliary port, thereby increasing the flame propagation speed and further stabilizing the flame. Lean combustion can be realized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a direct injection spark ignition type 4-stroke engine will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, the combustion chamber ceiling wall 11 of the cylinder head 1 is inclined in a pent roof type, and an ignition plug 8 faces a central portion thereof.
Two intake valves 9 and two exhaust valves 10 are provided to face each other.

As means for generating a swirl in the combustion chamber 5, a swirl control valve 7 for opening and closing both intake ports 13 branching in a siamese shape is provided, and the swirl control valve 7 is bypassed at the bottom of one intake port 13. A sub port 15 for guiding intake air is provided.

The inlet 15a of the sub port 15 opens right upstream of the swirl control valve 7 at the fully closed position, and the outlet 15b of the sub port 12 opens right upstream of the valve seat 6. Swirl control valve 7
When the valve is fully closed, most of the intake air passes through the auxiliary port 15 and is sucked into the combustion chamber 5 through one of the intake valves 9 at a low inflow angle. As shown by an arrow S in FIG. 2, a strong swirl is generated in the combustion chamber 5.

The swirl control valve 7 is rotated about a shaft 19 by a driving device (not shown), and is fully closed during a partial load operation and fully opened during a high load operation.

A fuel injection valve 3 is provided on the ceiling wall 11 of the combustion chamber, beside the intake valve 9 and between the intake valves 9 in this embodiment. The fuel injection timing should be as close as possible to the ignition timing during the compression stroke (for example, 30 degrees before top dead center).
, And the fuel injection direction is directed somewhat obliquely downward from the horizontal so that the fuel spray hits the center of the piston 4 at a predetermined stroke position near the compression top dead center.

As shown in FIG. 3, the top surface 2 of the piston 4
A diffusion table 20 is formed at the approximate center of 1 so as to protrude, and an inclined surface 22 facing the fuel spray from the fuel injection valve 3 is formed on the diffusion table 20. The inclination angle of the inclined surface 22 is determined at a predetermined angle with respect to the direction of the fuel spray from the fuel injection valve 3, and the fuel spray reflected on the inclined surface 22 is applied to each exhaust valve as shown by a two-dot chain line in FIGS. The light is diffused toward the head portion 10a of the ten.

On the ceiling wall 11 of the combustion chamber, a squish area 12 is provided on the side of both exhaust valves 10, while
A squish area 24 is formed on the top surface 21 of the piston 4 to the side of the diffusion table 20. Both are formed parallel to each other, and generate a squish (gas flow) facing the center of the combustion chamber 5 near the top dead center of the piston 4, in other words, facing the fuel spray.

The diffusion table 20 protrudes from the top surface 21 of the piston 4 in a triangular pyramid shape, and behind the inclined surface 22, a pair of inclined surfaces 23 facing the squish areas 12, 24 are formed.
The inclination angle and the inclination direction of each inclined surface 23 are determined so that the squish is reflected on each inclined surface 23 and guided to the vicinity of the ignition plug 8.

Next, the operation will be described.

FIG. 4A shows a state in which the piston 4 has reached a crank angle of 90 ° before the compression top dead center.
Here, fuel injection has not yet been performed.

FIG. 4B shows a state in which the piston 4 has reached 30 ° before the compression top dead center, where fuel injection is performed. Most of the fuel spray from the fuel injection valve 3 is reflected on the inclined surface 22 and guided toward the head 10 a of each exhaust valve 10. By colliding or diffusing the fuel spray with the diffusion table 20 and the exhaust valve 10, which are relatively high in temperature, the atomization and vaporization of the fuel spray are promoted. On the other hand, the piston 4 and the exhaust valve 10 having a high thermal load are cooled by the fuel spray.

On the other hand, a squish heading toward the center of the combustion chamber 5 is generated with the rise of the piston 4 as shown by a white arrow in FIG. B, and this squish is reflected and diverted to each inclined surface 23 of the diffusion table 20. By pushing the fuel toward the spark plug 8, fuel distributed in the vicinity of each exhaust valve 10 is pushed back to the vicinity of the spark plug 8 at the center of the combustion chamber.

FIG. 4C shows a state in which the piston 4 has reached the compression top dead center. In this case, most of the fuel is collected near the spark plug 8 and the mixture near the spark plug 8 is stratified. Become The rich mixture layer formed in the vicinity of the spark plug 8 is pushed in toward the combustion chamber ceiling wall 11 by the injection of fuel during the compression stroke and the rise of the piston 4 in the subsequent stroke until ignition. The mixture layer does not diffuse, and a good ignition atmosphere is generated and maintained in the vicinity of the spark plug 8, and the ignition is reliably ignited to generate an initial flame kernel.

During the partial load operation, the swirl control valve 7 is closed, and the intake air introduced from one of the intake valves 9 through the sub-port 15 during the intake stroke forms a strong swirl (swirl flow) along the inner circumference of the cylinder. Since the swirl increases the flame propagation speed, stable lean combustion is realized, and fuel consumption is reduced, emissions are reduced, and high output is achieved.

At the time of high load operation in which the swirl control valve 7 is opened, the intake air is uniformly introduced from each intake port 13 and no swirl is generated in the combustion chamber 5, but the fuel injection amount is increased, so that sufficient ignition performance is obtained. And reliable flame propagation is maintained.

Further, by stratifying the air-fuel mixture, the air-fuel ratio is relatively large in a region far from the spark plug 8 of the combustion chamber 5, that is, by making the air-fuel ratio ultra-lean, knocking that tends to occur at the end of the combustion chamber is caused. hardly occurs autoignition reaction, Thus it is possible to increase the substantial compression ratio, thermal efficiency, improvement in output can be achieved.

[0029]

As described above, according to the present invention, in a direct injection type spark ignition engine, an intake valve and an exhaust valve are provided opposite to each other with an ignition plug interposed therebetween on a ceiling wall of a combustion chamber, and fuel is provided beside the intake valve. With the injection valve facing, an inclined surface for reflecting and diffusing fuel spray in the direction of the exhaust valve was formed on the piston top surface, and a squish area for generating a gas flow facing the diffused fuel was formed on the side of the exhaust valve. In addition, fuel is collected near the ignition plug immediately before ignition, and even if the mixture is lean, stable ignitability can be ensured by stratification, and fuel economy and exhaust emission can be improved based on lean combustion.

Also, two intake valves are connected to each of the intake valves.
Swirlco that opens and closes the intake port to open and close according to operating conditions
Control valve, and the swirl control valve
Guides intake just before one of the intake valves, bypassing the lube
According to the configuration in which the auxiliary port is formed, a swirl is generated at the time of partial load, so that the flame propagation speed is increased, and the stability of lean combustion can be further improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view of a ceiling wall of the combustion chamber.

FIG. 3 is a plan view of the piston.

FIG. 4 is a diagram showing fuel and gas flows.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 fuel injection valve 4 piston 5 combustion chamber 7 swirl control valve 8 spark plug 9 intake valve 10 exhaust valve 11 combustion chamber ceiling wall 12 squish area 13 intake port 15 subport 20 diffusion table 22 inclined surface 23 inclined surface 24 squish area

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-215817 (JP, A) JP-A-58-25513 (JP, A) JP-A-3-105017 (JP, A) 156801 (JP, U) Japanese Utility Model Application Hei 3-116766 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02B 1/00-23/10

Claims (2)

(57) [Claims] In a direct injection type spark ignition engine having an ignition plug and a fuel injection valve facing a combustion chamber, an intake valve and an exhaust valve are provided on a ceiling wall of the combustion chamber with an ignition plug interposed therebetween so as to face each other. With the fuel injection valve facing the side, an inclined surface for reflecting and diffusing the fuel spray injected from the fuel injection valve in the direction of the exhaust valve is formed on the top surface of the piston, and the diffusion fuel is formed on the side of the exhaust valve. A squish area for generating a gas flow facing the fuel injection valve, wherein a fuel injection timing of the fuel injection valve is set during a compression stroke. 2. An intake valve connected to two intake valves.
A swirl control valve for opening and closing in accordance with the intake port to the operating conditions provided, according to claim 1, characterized in that the formation of the secondary port leading to the intake immediately before the one of the intake valves to bypass the swirl control valve Direct injection spark ignition engine.