JPH0319362B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in compression internal heat engines.

In order to cope with the rise in fuel prices since oil shocks, efforts are being made to improve the thermal efficiency of internal combustion engines and to use cheap, inferior fuel. Generally, an improvement in the thermal efficiency of an internal combustion engine results in an increase in the heat load on the combustion chamber, leading to an increase in the temperature of the exhaust valve. In addition, inferior fuel has an increased content of vanadium, sodium, sulfur, ash, etc., and sometimes contains vanadium pentoxide (V ₂ O ₅
The amount of Na ₂ SO ₄ ) deposited on the exhaust valve increases, which, together with the rise in valve temperature, promotes high-temperature corrosion. Furthermore, inferior fuel generally produces a large amount of hard combustion residue, and some fuels inherently contain hard catalyst particles. When exhaust gas flows out through the exhaust valve after combustion in the cylinder, foreign substances such as deposits, hard combustion residue, and hard catalyst particles that cause the above-mentioned high-temperature corrosion first adhere to the valve seat. Then, when the exhaust valve closes, it gets caught in the valve seat. With these foreign objects still stuck in the exhaust valve, new air is supplied from the air supply valve, and after being compressed, the foreign objects caught in the valve seat during explosion work inside the cylinder are removed by compression pressure and explosion pressure. Then, it bites into the valve seat even more and is crushed and press-fitted, creating a concave mark on the valve seat. As these impressions gradually increase, a channel connecting them is formed, leading to a blow-through.

In order to prevent the above-mentioned foreign matter from being crushed and press-fitted into the valve seat part due to compression pressure and explosion pressure, the present invention slightly opens the exhaust valve during the compression stroke of the supply air to clean the air during the compression stroke. The purpose is to cool the valve by blowing out air, and also to blow away the foreign matter and prevent the formation of dents. In order to achieve this objective, the method of the present invention provides an internal combustion engine having an exhaust valve at the top of the cylinder, in which the ratio of the cylinder internal pressure to the exhaust pipe internal pressure is approximately equal to the critical pressure ratio, and in consideration of engine performance, the amount of air ejected is In the middle of the compression stroke of the supply air, when the mass is at its minimum, the exhaust valve is temporarily slightly opened to allow the supply air to blow through, thereby blowing away foreign matter attached to the valve seat of the exhaust valve. Features.

The present invention can be applied to both two-cycle engines and four-cycle engines. Further, the present invention can be applied to any other drive method such as a camshaft drive method of an exhaust valve, an electronically controlled hydraulic drive method, and the like. The present invention will be explained using an embodiment of a camshaft-driven four-cycle engine.

In FIG. 1, a piston 2 moves up and down within a cylinder 1, and combustion exhaust gas is discharged by the up and down movement of an exhaust valve 3. 4 is a fuel injection valve. The exhaust valve 3 opens only when exhausting the combustion exhaust gas after burning the fuel, and is closed during air supply to the cylinder 1 and during compression, and when the combustion exhaust gas is discharged, the cam 5 is activated as the engine rotates. When the connecting rod 7 is pushed up via the roller 6, the rocker arm 8 rotates about the pin 9, pushing down the valve stem 10 and opening the exhaust valve 3. In an engine that repeats such operations, FIG. 2 shows an example of changes in cylinder pressure P and opening/closing timing of the intake valve and exhaust valve in the case of a four-cycle engine. 1 cycle (720°)
In the middle, the exhaust valve opens at θ ₁ degree before the bottom dead center (BDC) of the piston, and closes at θ ₂ degrees after the top dead center (TDC) after the exhaust extrusion stroke (E), but after entering the compression stroke and after BDC. At θ ₃ degrees, the auxiliary cam according to the present invention opens the exhaust valve again for a period of Δθ degrees to blow out compressed air. On the other hand, the air supply valve opens at θ ₄ degrees before TDC and closes at θ ₅ degrees after BDC after air supply stroke 1.

Fig. 3 corresponds to Fig. 2 and shows the positions of the cams added, with the exhaust cam 5 at the above timing,
It is a diagram showing the air supply cams 5' superimposed on each other. In a four-stroke engine, the exhaust cam 5 and the intake cam 5' each rotate only once every two revolutions of the engine, so the circumference in FIG. 3 represents 720 degrees. In the present invention, in order to open the exhaust valve and release air during the compression stroke, an auxiliary cam 1 for air release shown in FIG.
1 will be provided. In order to minimize the stress generated in the auxiliary cam 11 by the compression pressure, it is better to set the auxiliary cam at a location where the cylinder internal pressure is as low as possible, that is, at a location as close as possible to the starting point of the compression stroke. On the other hand, the higher the air jetting speed is, the greater the effect is on blowing off foreign objects, so the auxiliary cam should be positioned at a position where the ratio of the cylinder internal pressure to the exhaust pipe internal pressure is approximately equal to the critical pressure ratio, that is, the exhaust pipe internal pressure is approximately For 3ata, set it to a position where the cylinder pressure is approximately 6ata. Furthermore, in terms of engine performance, the mass of the ejected air should be minimized, and the size and opening period of the auxiliary cam 11 are determined taking the above points into consideration. In addition, the lift height of the auxiliary cam and the valve opening period Δθ are determined so that the minimum amount of air necessary to blow away the foreign matter flows out.
Choose a cam profile so that the lift height changes as gradually as possible.

With electronic control and hydraulic drive systems, valve opening/closing timing,
All aspects such as lift size are controlled by electronic circuits and a hydraulic drive system.

As is clear from the above description, the present invention provides an internal combustion engine having an exhaust valve at the top of the cylinder, in which the exhaust valve is slightly opened around the middle of the compression stroke of the charge air to allow the air being recontracted to blow through into the exhaust pipe. This prevents oxides such as vanadium, sodium, sulfur, and ash in the exhaust gas, especially vanadium pentoxide, from accumulating on the valve seat, and blows away combustion residues with fresh air. Since the fresh air has the function of cleaning the exhaust valve and the function of cooling the valve, it is possible to operate the engine without damaging the valve seat of the exhaust valve of the internal combustion engine due to pressure injection of combustion residue. Because it has the effect of being able to
It becomes possible to use inferior fuel containing hard catalyst particles.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view for explaining the exhaust valve operating mechanism of an internal combustion engine, Fig. 2 is a diagram showing the opening/closing timing of the supply and exhaust valves and changes in cylinder pressure, and Fig. 3
The figure shows a timing diagram with the supply and exhaust cams superimposed. 1... Cylinder, 2... Piston, 3... Exhaust valve, 4... Fuel injection valve, 5... Exhaust cam, 5'...
...Air supply cam, 6...Roller, 7...Connecting rod, 8...
...Rotzker arm, 9...pin, 10...valve stem.

Claims (1)

[Claims] 1. In an internal combustion engine having an exhaust valve at the top of the cylinder, the ratio of the cylinder internal pressure to the exhaust pipe internal pressure is approximately equal to the critical pressure ratio, and the air supply is such that the mass of the ejected air is minimized in consideration of engine performance. An exhaust valve for an internal combustion engine, characterized in that the exhaust valve is temporarily slightly opened in the middle of a compression process to allow supply air to blow through and blow away foreign matter attached to a valve seat of the exhaust valve. Method for preventing the occurrence of dents.