JPH04318221A - Internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent unburnt gas from being discharged to the outside, and reduce a residual gas amount in a cylinder. CONSTITUTION:There is provided a recessed part 8 which constitutes a combustion chamber 5 on the intake side at the bottom surface 3a of a cylinder head 3, an intake valve 1 and an injector 11 are disposed at the recessed part 8, and an exhaust valve 2 is provided at the bottom surface 3a. Air which is discharged from a supercharger 10 is supercharged in a cylinder 12 through the intake valve 1 and a scavenge port 14. Residual gas in a cylinder 11 is pushed out forcingly only with air. Air which is introduced from the recessed part 8 does not blow by immediately from the exhaust valve 2 due to a wall surface 8b, thus improving scavenge ability. Besides, fuel is supplied from the injector 11 after the exhaust valve 2 is closed, so it is possible to prevent unburnt gas from being discharged to the outside. It is, thus possible to improve emission and so forth, and reduce fuel consumption.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides suction and
The present invention relates to an internal combustion engine having an exhaust valve, and particularly relates to an improvement in gas exchange performance thereof.

0002

[Prior Art] Conventionally popular two-stroke engines employing the so-called crank chamber compression scavenging system cannot have a separate lubrication system within the crank chamber, making it difficult to effectively prevent piston seizure. . Furthermore, since lubricating oil is mixed into the air-fuel mixture, oil consumption is large and white exhaust smoke is likely to occur. Moreover, there is a large amount of residual gas mixed in with the fresh air supplied into the cylinder, and
Since there is a lot of fresh air blowing through, it is easy to cause deterioration of emissions, and there are problems with starting performance and stability at low speeds and light loads.

In order to solve this problem, as a prior art of the present invention, for example, as shown in Japanese Utility Model Application Laid-Open No. 62-95136, intake and exhaust valves are provided in the cylinder head, and the cylinder head is provided with intake and exhaust valves, and the cylinder head is provided with an intake/exhaust valve. A two-stroke engine has been developed that is configured to synchronize the opening and closing of intake and exhaust valves and to perform gas exchange using the supercharging action of a supercharger. The tip of the injector faces inside the cylinder.

[0004] With this kind of engine, the fuel system and the lubrication system can be separated as in a four-stroke engine, so piston seizure can be effectively prevented. Furthermore, various problems caused by the mixing of oil into the air-fuel mixture can also be eliminated. Moreover, since scavenging can be performed only with air that does not contain fuel, it is possible to suppress asymmetric combustion due to the influence of residual gas and deterioration of emissions due to air-fuel mixture blow-through. Furthermore, since each revolution of the crankshaft has a combustion stroke, the output per unit cylinder volume (specific output) is greater than that of a four-stroke engine, and there is less vibration. Therefore, it is convenient for achieving reduction in size and weight.

[0005]

However, in an internal combustion engine in which the cylinder head is provided with intake and exhaust valves, the intake valve and the exhaust valve must be disposed close to each other. Moreover, in such a combustion chamber, in order to efficiently fill the combustion chamber with air, the intake valve is usually opened before the exhaust valve is closed. Therefore, when the intake and exhaust valves overlap, a portion of the air introduced into the cylinder through the intake valve immediately blows out from the exhaust valve side. If the air blows through on the top side of the combustion chamber in this way, it becomes difficult to sufficiently exhaust the residual gas on the top side of the piston. As a result, asymmetric combustion and misfire due to the influence of residual gas are likely to occur, resulting in worsening of emissions and the like. If fuel is injected into the intake port, which is located upstream of the intake valve, not only will scavenging be insufficient, but the air-fuel mixture will blow through, causing unburned gas containing HC, etc. to be discharged to the outside. The problem arises that

The present invention aims to solve these problems all at once.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention takes the following measures.

That is, the internal combustion engine according to the present invention includes an intake valve and an exhaust valve in a cylinder head. Also,
A recess is provided on the intake valve side of the bottom surface of the cylinder head, and the intake valve and the injector are respectively disposed in the recess, and supply air discharged from the supercharging means is transferred to the cylinder via the intake valve. It is configured so that it can be introduced into an intake passage communicating with the inside. The fuel injection device is characterized in that fuel is supplied from the injector after the exhaust valve is closed.

[0009] Although a plurality of intake valves may be used, it is preferable to adopt a single-valve type, since this makes it easier to arrange spark plugs on both sides of the intake valve, which improves ignition performance and shortens combustion time.

[0010] For the exhaust valve, it is preferable to adopt a multiple valve type in order to improve exhaust efficiency.

[0011] As the supercharging means, a mechanical type such as a supercharger that can exert a supercharging effect from a low rotational speed range may be used, or other types may be used as necessary. It can be used as

0012

[Operation] According to this structure, the intake valve is driven to open and close within the recess, and the exhaust valve is driven to open and close on the bottom side of the cylinder head. Therefore, the air introduced into the recess when the intake valve opens is guided toward the top surface of the piston while pushing the residual gas near the recess. In other words, sucking
A part of the air introduced into the cylinder through the intake valve when the exhaust valves overlap does not immediately blow through the exhaust valve to the outside. Moreover, since the air is pressurized by the supercharging means, it is forced into the cylinder from the concave side toward the top surface of the piston, and the residual gas in the cylinder is forced out through the exhaust valve. It will be pushed out.

When the exhaust valve is closed, the injector starts supplying fuel into the recess. Even at this time, supercharging with only air from the intake passage continues. For this reason,
The fuel and air are agitated within the cylinder while violently colliding with each other, and the air and fuel are mixed.

Furthermore, when the piston reaches the top dead center, a compact combustion chamber can be formed between the recess and the top surface of the piston on the intake valve side. As the piston approaches top dead center, the air-fuel mixture pushed out from the exhaust valve side is pushed into the combustion chamber, so that air and fuel are mixed more evenly within the combustion chamber. Then, when the air-fuel mixture is ignited by the ignition plug disposed in the recess, a flame spreads within the combustion chamber. When the piston is pushed down from the top dead center to the bottom dead center by the explosive combustion pressure at that time, the flame will rapidly propagate from the recess side to the end gas on the exhaust valve side. When a predetermined crank angle at which the explosion stroke is to be completed is reached, the exhaust valve opens, and the exhaust gas in the cylinder flows out violently.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A case in which an embodiment of the present invention is applied to an automobile engine will be described below with reference to the drawings.

The engine shown in FIG. 1 includes an intake valve 1 and a plurality of exhaust valves 2 in a cylinder head 3, and the top surface 4a of the piston 4 approaches the bottom surface 3a of the cylinder head 3 at top dead center. At the same time, a combustion chamber 5 is formed on the intake valve 1 side. The intake valve 1 is driven to open and close in the direction of operation of the piston 4 by a valve operating mechanism 6 provided in the cylinder head 3, and as shown in FIG.
One is arranged for one cylinder. The exhaust valves 2 are driven to open and close in the direction of operation of the piston 4 by the valve operating mechanism 6, and as shown in FIG. 2, two exhaust valves are arranged for one cylinder. It is set larger than 1. The cylinder head 3 is fixed on the cylinder block 7 and has a flat bottom surface 3a. The piston 4 has a flat top surface 4a. The combustion chamber 5 is formed by the top surface 4a of the piston 4 and the recess 8 provided in the bottom surface 3a of the cylinder head 3. As shown in FIGS. 1 and 2, the recess 8 is a half-moon-shaped recess provided on the side of the intake valve 1, and the intake valve 1 is disposed in the center of the upper surface 8a. As shown in FIG. 2, spark plugs 9 are arranged on both sides of the intake valve 1, respectively. The tip of the injector 11 faces the center of the corner of the recess 8, as shown in FIGS. 1 and 2.

[0017] Also, a supercharger 1 serving as supercharging means
0 is supplied to the cylinder 12 through an intake passage 13 that communicates with the inside of the cylinder 12 via the intake valve 1 and a scavenging hole 14 provided in the side wall 7a of the cylinder block 7.
The air is introduced into both the scavenging passage 15 and the scavenging passage 15 communicating therewith.

The injector 11 has a built-in electromagnetic coil, and when a pulse voltage is applied to the electromagnetic coil from an electronic control device (not shown), an amount of fuel corresponding to the application time of the pulse voltage is injected into the recess 8. It is supposed to be done. As shown in FIG. 1, the intake passage 13 and the scavenging passage 15 are
It has a common air inlet 16, and the air inlet 1
Air pressurized by a supercharger 10 is introduced into the supercharger 6. As schematically shown in FIG. 3, the scavenging hole 14 is located near the bottom dead center of the piston 4 on the intake side of the side wall 7a of the cylinder block 7, and is opened and closed by the piston 4. There is.

The intake valve 1, the exhaust valve 2, and the scavenging hole 14 are opened and closed at the timing shown in FIG. 4 in synchronization with the change in crank angle. When the piston 4 is moving from the top dead center to the bottom dead center, the exhaust valve 2 is opened to start blowdown. After a certain blowdown period, the scavenging hole 14 begins to open to start scavenging, and the intake valve 1 begins to open just before the piston 4 reaches the bottom dead center. After a certain scavenging period, the exhaust valve 2 is closed. While only air is supercharged from the scavenging passage 15 and intake passage 13 for a certain period of time, the scavenging hole 14 is closed first and the injector 1 is
Start fuel injection from 1. After supercharging air from the intake passage 13 for a certain period of time, the intake valve 1 is closed, and then fuel injection is ended. Then, just before the piston 4 reaches the top dead center, the two spark plugs 9 ignite the air-fuel mixture, and the explosion stroke begins.

According to such a configuration, when the scavenging hole 14 and the intake valve 1 are opened one after another after a certain blowdown period, only the air that has passed through the scavenging passage 15 and the intake passage 13 enters the cylinder 12. The air is introduced into the air and scavenged. This air is forced into the cylinder 12 from above and below by the supercharging action of the supercharger 10, so the residual gas in the cylinder 12 is removed by the two exhaust valves 2.
It will be forcibly pushed out through the

Further, the intake valve 1 is driven to open and close within the recess 8, and the exhaust valve 2 is driven to open and close on the bottom surface 3a side of the cylinder head 3, respectively. Since the wall surface 8b of the recess 8 exists between the intake valve 1 and the exhaust valve 2, a portion of the air introduced through the intake valve 1 at the time of overlap immediately flows into the exhaust valve 2.
There is no possibility of blowing through to the outside. Moreover, the recess 8
When the air introduced into the recess 8 is guided to the top surface 4a side of the piston 4, it pushes the residual gas on the recess 8 side and cooperates with the air introduced through the scavenging hole 14 to close the exhaust valve. 2 and forcefully extrude it to the outside.

When the exhaust valve 2 and the scavenging hole 14 are closed, fuel is supplied from the injector 11 into the recess 8. At this time, since only air continues to be supercharged from the intake passage 13, the fuel and air violently collide with each other and are agitated within the cylinder 12, resulting in a mixture of air and fuel. .

When the piston 4 reaches the top dead center from the bottom dead center, as shown in FIG.
A squish area 17 is formed between the bottom surface 3a of the piston 4 and the top surface 4a of the piston 4, and a combustion chamber 5 is formed between the recess 8 and the top surface 4a of the piston 4 on the intake valve 1 side. In this case, since the air-fuel mixture pushed out from the squish area 17 is forced into the combustion chamber 5, the air and fuel are further stirred within the combustion chamber 5. Then, when the air-fuel mixture is ignited by the two spark plugs 9 at a predetermined crank angle,
Flame spreads within the combustion chamber 5. When the piston 4 is pushed down from the top dead center toward the bottom dead center by the explosion combustion pressure at that time, the flame will rapidly propagate from the recess 8 side to the end gas on the exhaust valve 2 side. When a predetermined crank angle is reached to end the explosion stroke, the two exhaust valves 2 open,
Exhaust gas in the cylinder will violently flow out through these exhaust valves 2.

[0024] Therefore, according to the above configuration,
Air introduced through the intake valve 1 during overlap can be prevented from immediately blowing through the exhaust valve 2. Moreover, during gas exchange, the residual gas in the cylinder 12 is forcibly discharged to the outside by only the air introduced into the cylinder 12 through the intake valve 1 and the scavenging hole 14. It hardly remains, and it is possible to effectively prevent asymmetric combustion, misfire, etc. due to the influence of residual gas. As a result, deterioration of emissions can be prevented, and
Drivability can be stabilized.

Moreover, since the inside of the cylinder 12 is scavenged only with air that does not contain fuel, and the fuel is directly supplied from the injector 11 into the cylinder 12 after the exhaust valve 2 is closed, there is no air-fuel mixture blow-through. External discharge of unburned gas containing , HC, etc. can be effectively suppressed.

The combustion chamber 5 is compact and is formed on the intake valve 1 side. Moreover, since the air-fuel mixture is forcibly forced into the combustion chamber 5 from the exhaust valve 2 side as a hot squish, the air and fuel are further agitated. When the air-fuel mixture burns explosively in the combustion chamber 5 and the piston 4 is pushed down from top dead center to bottom dead center, the flame rapidly flows from the recess 8 side to the end gas on the exhaust valve 2 side. As a result, unburned gas and spontaneous ignition are less likely to occur on the exhaust valve 2 side. With such a fuel, the combustion speed of the air-fuel mixture can be increased, and the compression ratio can be increased without difficulty, so that thermal efficiency can be increased and fuel efficiency can be reduced at the same time. In particular, if the intake valve 1 is made single and the ignition plugs 9 are arranged on both sides as in the above embodiment, the ignition performance is improved. Moreover, since the distance from the spark plug 9 to the end of the combustion chamber 5 can be shortened,
Together with the compact combustion chamber 5, the combustion period can be further shortened and rapid combustion can be achieved.

Furthermore, if the intake valve 1 and the ignition plug 9 are arranged in the recess 8, the ignition plug 9 can be effectively cooled by fresh air, and at the same time, fresh air can always be introduced to the ignition plug 9. be able to. Therefore, pre-ignition can be prevented and ignition performance can be improved.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above embodiment. For example, the spark plug may be placed on the side of the recess. In that case, the ignition plug can be placed in the middle of the combustion chamber in the thickness direction, which has the advantage of further increasing the combustion speed. Alternatively, one spark plug may be arranged in the middle of the side surface of the recess, and two intake valves may be arranged on the upper surface of the recess.

Next, a mode in which the engine is used as a variable cycle engine will be schematically explained. In the following description, the same reference numerals will be used for the same parts as in the above embodiment, and the description will be omitted. Here, a variable cycle engine means that, for example, when the engine is under high load, there is a combustion stroke every time the crankshaft rotates once, and when the engine is under low load, there is a combustion stroke during multiple revolutions of the crankshaft. refers to an engine with a combustion stroke of When the engine is under high load, combustion and gas exchange occur in the same way as in the two-stroke engine described above. That is, fuel is injected from the injector 11 at a predetermined fuel injection timing, and combustion is performed. On the other hand, when the engine is under low load, an air cycle in which no combustion occurs and a combustion cycle in which fuel is injected from the injector 11 to cause combustion are performed alternately every time the crankshaft rotates once. In the air cycle, no fuel is injected from the injector 11, and only air compressed by the supercharger 10 is supercharged into the cylinder 12. Then, only the air is compressed and expanded, and the inside of the cylinder 12 is scavenged with the air. After that, again
Shift to the combustion cycle described above.

According to such a variable cycle engine, when the load is low, the cylinder 1 is heated only by air.
Since the inside of 2 is cleaned, residual gas can be further reduced than in the case described above. After that,
Since the air-fuel mixture is introduced into the cylinder 12, asymmetric combustion due to the influence of residual gas can be more reliably prevented, and
Emissions etc. can be improved. Furthermore, like a four-stroke engine, fuel needs to be supplied once during two revolutions of the crankshaft, so fuel consumption can be reasonably suppressed. When the load is high, combustion occurs every time the crankshaft rotates once, similar to a two-cycle engine, and energy is output each time, making it possible to increase engine output.

[0031]

[Effects of the Invention] Since the present invention has the above-described configuration, it is possible to effectively suppress part of the air introduced into the cylinder when the intake and exhaust valves overlap from immediately blowing outside through the exhaust valve. At the same time, the inside of the cylinder can be effectively scavenged using only air. Therefore, it is possible to effectively suppress asymmetric combustion, misfire, etc. due to the influence of residual gas, prevent deterioration of emissions, and stabilize drivability.

Moreover, since the inside of the cylinder is scavenged only with air that does not contain fuel, and the fuel is directly supplied from the injector into the cylinder after the exhaust valve closes, there is no blow-through of the air-fuel mixture, and HC, etc. It is possible to reliably reduce the external discharge of unburned gas contained therein. Furthermore, according to the present invention,
A compact combustion chamber can be formed on the intake valve side, and the air-fuel mixture can be forced into the combustion chamber by squish or the supercharging action of the supercharging means, effectively increasing the combustion speed and compression ratio of the air-fuel mixture. be able to. For this reason, combustion efficiency is increased and at the same time low fuel consumption is possible.

Furthermore, the ignition plug can be placed close to the intake valve and away from the exhaust valve, allowing the ignition plug to be effectively cooled by fresh air and at the same time allowing fresh air to be constantly guided to the ignition plug. can. Therefore, pre-ignition can be prevented and ignition performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIG. 2 is a bottom view of a cylinder head showing one embodiment of the present invention.

FIG. 3: IV- in FIG. 1 showing an embodiment of the present invention;
IV line arrow diagram.

FIG. 4 is a valve diagram showing one embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an embodiment of the present invention.

[Explanation of symbols]

1... Intake valve 2... Exhaust valve 3... Cylinder head 3a... Bottom surface 5... Combustion chamber 8... Recessed portion 10... Supercharging means (supercharger) 11... Injector 12... Cylinder 13... Intake passage

Claims (1)

[Claims] 1. An internal combustion engine including an intake valve and an exhaust valve in a cylinder head, wherein a recess is provided on the bottom surface of the cylinder head on the intake valve side, and the intake valve and the injector are respectively disposed in the recess. The air supply system is configured such that supply air discharged from the supercharging means can be introduced into an intake passage communicating with the inside of the cylinder via the intake valve, and fuel is supplied from the injector after the exhaust valve is closed. An internal combustion engine characterized by: