JPH04314915A - Internal combustion engine - Google Patents

Abstract

PURPOSE:To exhaust residual gas in the corner of the vicinity of a top face of a piston, and reduce a rate of residual gas in a cylinder. CONSTITUTION:An intake valve 1 and a plurality of exhaust valves 2 are arranged in a cylinder head 3. A scavenging port 14 is formed on an intake side of a side wall 7a of a cylinder block 7. Air discharged from a supercharger 10 is supercharged into a cylinder 12 from the intake valve 1 and the scavenging port 14. The scavenging port 14 is opened in a direction along a top face 4a of a piston 4. An air system intake passage 15 communicated with the scavenging port 14 is formed on an upper portion than the scavenging port 14. Air inside the air system intake passage 15 flows from an upper to a lower portion, and introduced into the cylinder 12 from the scavenging port 14. A part of the air flows on the side of the top face 4a of the piston 4, to push out residual gas in a corner on an opposite side of the scavenging port 14. Emission and the like can be improved, and fuel consumption can be reduced.

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. That is, in such a device, as shown in the prior art of the present invention, for example, as shown in Japanese Utility Model Application Publication No. 55-23436, the air-fuel mixture pressurized in the crank chamber is introduced into the cylinder through the scavenging hole, and the Since residual gas in the cylinder is scavenged using the air-fuel mixture, the above-mentioned problems are likely to occur.

In order to solve this problem, recently, intake and exhaust valves are installed in the cylinder head, and the intake and exhaust valves are driven to open and close in synchronization with changes in the crank angle, and the supercharging action of the supercharger is also controlled. Two-stroke engines have been developed that are configured to perform gas exchange using The cylinder block is provided with a scavenging hole that communicates with the air passage, and only air is supplied through the scavenging hole to push out residual gas in 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. Furthermore, since gas exchange can be performed using only 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]

[Problems to be Solved by the Invention] However, it is difficult to sufficiently exhaust the residual gas in the cylinder simply by opening the scavenging holes in the cylinder block. In scavenging the inside of the cylinder, it is first assumed that the exhaust valve is open. For this reason, when the scavenging hole opens, the air introduced through the scavenging hole, even though it is pressurized,
There is a possibility that the gas may diagonally cross the inside of the cylinder toward the exhaust valve and blow through the exhaust valve. In particular, when the air passage is located below the scavenging hole, air is introduced upward into the cylinder from below. As a result, the corner near the top surface of the piston on the opposite side of the scavenging hole tends to become a snowdrift area, and there is a high possibility that combustion gas will remain in that area. Such problems tend to occur even in low speed and light load ranges where a sufficient supercharging effect cannot be obtained by the supercharging means.

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 the cylinder head, and has a scavenging hole on the intake side of the side wall of the cylinder block. The intake air discharged from the supercharging means is communicated into the cylinder through the scavenging hole and a mixture system intake passage which has a fuel supply means in the middle and communicates into the cylinder through the intake valve. The piston is configured so that it can be introduced into both the air system intake passage and the air system intake passage, and the air system intake passage is provided above the scavenging hole, and the scavenging hole is opened in a direction along the top surface of the piston. do.

Although the intake valve and the exhaust valve may be of the single-valve type, in order to improve the exhaust efficiency, it is preferable to adopt the multiple-valve type of the exhaust valve.

In the case of a multi-cylinder engine, the mixture system intake passage and the air system intake passage are usually branched in the middle and connected to each cylinder. that time,
The fuel supply means may be provided at an upstream portion of the air-fuel mixture system intake passage where it is not branched, or may be provided at each branch passage portion after branching.

[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 such a structure, if the scavenging hole is opened before introducing the air-fuel mixture into the cylinder, only the air that has passed through the air system intake passage is introduced into the cylinder. The air system intake passage is located above the scavenging hole, and the scavenging hole is opened in the direction along the top surface of the piston, so the air in the air system intake passage flows from the top to the bottom and flows from the scavenging hole into the cylinder. is discharged. Then, after a part of it flows along the top surface of the piston within the cylinder, it heads toward the exhaust valve side. At this time, residual gas near the top surface of the piston is forced out through the exhaust valve.

When the intake valve opens, the air-fuel mixture is introduced into the cylinder from the air-fuel mixture system intake passage. At this time, the residual gas below the intake valve is pushed toward the exhaust valve or the scavenging hole, and is discharged through the exhaust valve. After the exhaust valve closes,
The air-fuel mixture is forced into the cylinder by the supercharging action of the supercharging means. At this time, only air continues to be supercharged from the air system intake passage, so the air-fuel mixture and air collide violently as they are introduced into the cylinder, making the air and fuel more even. mixed with When the air-fuel mixture is ignited, the piston is pushed down by the explosive combustion pressure, and the exhaust valve opens at a predetermined crank angle to end the explosion stroke, causing the exhaust gas in the cylinder to flow out violently. .

[0014]

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.

[0016] Also, a supercharger 1 serving as supercharging means
0 is supplied to the cylinder 12 via the intake valve 1, which has an injector 11 as a fuel supply means in the middle.
The air-fuel mixture system intake passage 13 communicates with the cylinder 1 through a scavenging hole 14 provided in the side wall 7a of the cylinder block 7.
2 and an air system intake passage 15 that communicates with the air system.

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 vicinity of the intake valve 1. It is designed to spray. The mixture system intake passage 13 and the air system intake passage 15 are
As shown in FIG. 1, they have a common air inlet 16 through which air pressurized by the supercharger 10 is introduced. The air system intake passage 15 includes a scavenging surge tank 17 and a scavenging manifold 18 provided above the scavenging hole 14.
It is composed of: The scavenging hole 14 is located on the intake side of the side wall 7a of the cylinder block 7, near the bottom dead center of the piston 4, and is opened and closed by the piston 4. As shown in FIG. 1, the scavenging hole 14 is open in the direction along the top surface 4a of the piston 4, and has a large cross-sectional area at its upstream portion. The intake valve 1, exhaust valve 2, and scavenging hole 14 are opened and closed at the following timings in synchronization with changes 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 holes 14 are opened to start scavenging. The intake valve 1 begins to open just before the piston 4 reaches the bottom dead center. Around this time, fuel is started to be supplied from the injector 11, and the exhaust valve 2 is closed. Air system intake passage 15 for a certain period of time
After supercharging the air mixture into the cylinder 12 from the air mixture system intake passage 13, the scavenging hole 14 and the intake valve 1 are sequentially closed to proceed to the compression stroke. 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 this configuration, when the scavenging hole 14 is opened after a certain blowdown period, only the air that has passed through the air system intake passage 15 is introduced into the cylinder 12. The air system intake passage 15 is located above the scavenging hole 14, and the scavenging hole 14 is opened in the direction along the top surface 4a of the piston 4, so the air in the air system intake passage 15 flows from above to below. Then, the air is turned horizontally and introduced into the cylinder 12 through the scavenging hole 14. A part of the introduced air flows along the top surface 4a of the piston 4 and then heads toward the exhaust valve 2 side. At that time, push the residual gas G near the top surface 4 of the piston 4 toward the exhaust valve 2 side,
It will be forcibly pushed out through the exhaust valve 2.

When the intake valve 1 opens, the air-fuel mixture that has passed through the air-fuel mixture system intake passage 13 flows from the cylinder head 3 side to the recess 8.
be introduced within. At this time, the residual gas in the recess 8 is pushed toward the exhaust valve 2 side and the scavenging hole 14 side to be discharged to the outside. After the exhaust valve 2 is closed, the air-fuel mixture is forced into the cylinder 12 by the supercharging action of the supercharger 10. At that time, since supercharging of only air continues from the air system intake passage 15, the air-fuel mixture and air will be introduced into the cylinder 12 while violently colliding with each other. It is evenly mixed. When the air-fuel mixture is ignited by the two spark plugs 9 at a predetermined crank angle, a 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 at which the explosion stroke is to be completed is reached, the two exhaust valves 2 are opened, and the exhaust gas in the cylinder is forced to flow out through these exhaust valves 2. Therefore, according to the above configuration, during gas exchange, pressurized air that does not contain fuel can be introduced along the top surface 4a of the piston 4, so that the air near the top surface 4a of the piston 4 is Not only the combustion gas on the side opposite to the scavenging hole 14 but also the residual gas in the entire cylinder 12 can be forcibly pushed out to the outside. Therefore, the residual gas in the cylinder 12 can be reliably reduced, and asymmetric combustion, misfire, etc. due to the influence of the residual gas can be effectively prevented. As a result, deterioration in emissions can be prevented and drivability can be stabilized.

According to this embodiment, 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 within the recess 8.
They are driven to open and close on the a side. Therefore, when the intake valve 1 opens and the mixture is introduced into the cylinder 12,
First, the air-fuel mixture is introduced into the recess 8. 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-fuel mixture introduced through the intake valve 1 at the time of overlap immediately flows through the exhaust valve 2. This prevents the gas from blowing through to the outside, and it is also possible to suppress the discharge of unburned gas containing HC and the like to the outside. Further, when the piston 4 reaches the top dead center from the bottom dead center, a squish area 19 is formed between the bottom surface 3a of the cylinder head 3 and the top surface 4a of the piston 4 on the exhaust valve 2 side, as shown in FIG. On the intake valve 1 side, a compact combustion chamber 5 is formed between the recess 8 and the top surface 4a of the piston 4. In this case, the air-fuel mixture pushed out from the squish area 19 is forced into the combustion chamber 5, so that the air and fuel are further stirred within the combustion chamber 5. As a result, the combustion speed of the air-fuel mixture can be increased, and the compression ratio can be increased without difficulty, making it possible to improve thermal efficiency and achieve low fuel consumption. Furthermore, since the ignition plug 9 can be placed 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 guided to the ignition plug 9. 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.

The combustion chamber is not limited to the shape shown in the above embodiments, but may have other shapes. 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,
When the intake valve 1 is opened, a necessary amount of fuel is injected from the injector 11 and combustion is performed. On the other hand, when the engine is under low load, the air cycle in which only air is introduced into the cylinder 12 at the time of intake, and the combustion cycle in which the air-fuel mixture is supplied to the cylinder 12 and combusted are performed every revolution of the crankshaft. Do this alternately. In this case, it is preferable that the fuel injection be completed before the intake valve 1 closes, so that the fuel adhering to the intake valve 1 etc. can be forced into the cylinder 12 using compressed air. In the air cycle, when the intake valve 1 is opened, 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, the combustion cycle described above again starts.

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, it is possible to further reduce the amount of residual gas. After that, the air-fuel mixture is introduced into the cylinder 12, so that asymmetric combustion due to the influence of residual gas can be 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.

[0024]

[Effects of the Invention] Since the present invention has the above-described configuration, it is possible to effectively suppress combustion gas from remaining in the corner on the opposite side of the scavenging hole in the vicinity of the top surface of the piston, and
Residual gas in the cylinder can be forced out by pressurized air. Therefore, it is possible to effectively suppress asymmetric combustion and misfires caused by residual gas.
Deterioration of emissions can be prevented and drivability can be stabilized.

[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: III in FIG. 1 showing an embodiment of the present invention.
-III Line arrow diagram.

FIG. 4 is an explanatory diagram showing an embodiment of the present invention.

[Explanation of symbols]

1... Intake valve 2... Exhaust valve 3... Cylinder head 4... Piston 4a... Top surface 7a... Side wall of cylinder block 10... Supercharging means (supercharger) 11... Fuel supply means (injector) 12... Cylinder 13...Mixture system intake passage 14...Scavenging hole 15...Air system intake passage

Claims (1)

[Claims] Claim 1: An internal combustion engine comprising an intake valve and an exhaust valve in a cylinder head, and a scavenging hole on the intake side of a side wall of a cylinder block, wherein the intake air discharged from a supercharging means is transferred to an intermediate position. The fuel is configured to have a fuel supply means and can be introduced into both a mixture system intake passage that communicates with the cylinder via the intake valve and an air system intake passage that communicates with the cylinder via the scavenging hole. An internal combustion engine characterized in that the air system intake passage is provided above the scavenging hole, and the scavenging hole is opened in a direction along the top surface of the piston.