FI122851B - Device for exhaust gas recirculation - Google Patents

Description

Device for exhaust gas recirculation

The invention relates to an apparatus for recirculating exhaust gas for a piston-internal combustion engine.

It is an object of the invention to provide a device of the type mentioned initially so that, regardless of the pressure of the fresh air in the cylinder, a guaranteed, sufficient supply of exhaust gas can take place.

This is achieved, in accordance with the invention, by providing in each cylinder an open and closed control valve for the line leading to the exhaust manifold.

These measures provide a simple structure for recirculating a portion of the exhaust gas to fresh air without using a compressor. Since the exhaust gas will never come into contact with cold components, lowering the dew point temperature can be avoided.

Preferably, the valve control times are selected such that the valve is open during the stroke for a period of time greater than the pressure of the fresh air introduced into the cylinder and further for the period of fresh air being supplied to the cylinder. Thus, a portion of the exhaust gas, which is under relatively high pressure, is available for the next 20 additions to fresh air.

The invention can be particularly advantageously used in heavy-duty four-stroke piston engines with one or more exhaust gas engines because it does not require connection to the control of the intake and exhaust valves and consequently permits simultaneous opening of the valves, which is necessary for too high component temperatures.

Further features and advantages will be apparent from the dependent claims and from the description of an exemplary embodiment suitable for a four-stroke reciprocating piston engine engine supercharged by means of an exhaust gas engine.

00 ^ 30 Here is the presentation: | Fig. 1 is a schematic section through the cylinder; and Fig. 2 is two diagrams with valve stroke and pressure curves in a simplified view.

Figure 1 shows the cylinder as a whole with 1, the cylinder with cover 2 and the piston with 3. The cylinder head 2 has a suction valve 4 and an exhaust valve 5 disposed in a manner known per se. However, there may be two inlet and exhaust valves 2. Further, the cylinder head 2 is provided with a hole 7 which pierces the cylinder head in the vertical direction. The hole 7 can be closed inwardly of the cylinder 1 by means of a valve 8. The bore 7 is joined only by the conduit 9 shown in abbreviated form in Fig. 1, which of course can also be implemented as an integral part 5, depending on the embodiment of the cylinder head.

The hole 7 and the tube 9 together form a conduit that leads to the exhaust manifold 10. In this case, several cylinders can also be connected to each other through a single conduit into one common exhaust manifold, but the individual cylinders can also produce the exhaust gas. A cooling device 11 is provided in the exhaust cavity 10, which increases the efficiency of the exhaust gas recirculation. In this case, adjust the cooling power so that the dew point of the sulfuric acid does not fall.

Figure 2 shows the valve movements and, depending on them, the pressures prevailing in the cylinder 1. Here, the upper diagram shows the movements of the valve 15 of interest, with the Y axis indicating the valve height and the X axis the rotation angle of the impact shaft. The lower diagram again shows the angle of rotation of the palm on the X-axis and the pressures on the Y-axis depending on the movements of the valve.

When the piston 3 goes upwards from its lower dead center in a work stroke 20, the exhaust valve 5 opens. Conveniently, at the beginning of the work stroke, valve 8 also opens so that a portion of the exhaust gas passes through conduit 7, 9 to the exhaust gas reservoir 10.

Figure 2 shows that, in the selected embodiment, the valve 8, marked with a stroke of 12, opens approximately at the same time as the exhaust valve 5, marked with a stroke of 13. Since, after opening the exhaust valve 5, the pressure in the cylinder drops sharply, as shown by curve 14, the valve 8 closes after a short time. The exhaust manifold container 10 has

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therefore, the exhaust gas is under relatively high pressure, as shown by curve 15. Before the piston 3 reaches the upper dead center, while the exhaust valve ^ 30 5 is still open, the suction valve 4 with a stroke of 16 is opened.

£ As soon as the exhaust valve 5 closes, the valve 8 opens, whereupon the o high-pressure exhaust portion in the exhaust manifold

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Section 10 can move to cylinder 1 in fresh air. As a result, the pressure of the exhaust gas collected in the exhaust manifold 10 is reduced as can be seen in curve 15.

When the pressure of this part of the exhaust gas is still greater than the internal pressure of the cylinder, shown by curve 14, valve 8 closes. Thus, it is achieved that the major part of the exhaust gas contained in the exhaust gas accumulator 10 is transferred to the cylinder 1. Conveniently, the valve 8 is adjusted to close before the pressure of the exhaust portion reaches the charge air pressure schematically represented by line 17.

The valve adjustment shown in the diagram of Figure 2 is not absolute, only individual cylinders can produce exhaust gas. It would also be possible to combine the AGR system with the starter system. It is only necessary to ensure that the exhaust gas pressure in the exhaust manifold container 10 is greater than the pressure in the cylinder 1 with the valve 8 open. Thus, for example, valve 8 may also open during the stroke before the exhaust valve opens.

The adjustment of the valve 8 may be effected in a manner known per se, mechanically by means of cams or electronically.

The valve 8 is mounted according to the respective configuration of the inlet and exhaust valves, not in the center, as shown in Fig. 1 for illustrative purposes, but conveniently at the edge of the cylinder head.

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Claims (4)

An apparatus for recirculating exhaust gas adapted for a supercharged four-stroke piston engine driven by a heavy-duty oil engine, which permits overlapping adjustment times for the suction valve (4) and the exhaust valve (5), wherein each cylinder (1) is provided in open and close adjusting valve (8), characterized in that the adjustment times of the valve (8) are selected such that the valve (8) is open during the working stroke for a period when the exhaust gas pressure is higher than the sy-10 cylinder (1) the pressure of the fresh air to be supplied, and further for a period of time providing fresh air to the cylinder (1), wherein the valve (8) is opened at approximately the same time as the exhaust valve (5) so that some of the exhaust gases enter the exhaust reopen after the exhaust valve (5) is closed so that the exhaust-15 gas the high pressure part of the exhaust gas in the fuel tank (10) can be introduced into the cylinder (1) as fresh air, whereby the stroke curve of the valve (8) is adjusted such that the valve (8) is closed so that the exhaust pressure is always higher than the cylinder pressure (14). Device according to Claim 1, characterized in that the pressure of the stripping air is the supercharging pressure produced by the exhaust gas compressor. Device according to Claim 1 or 2, characterized in that the pipes (7, 9) of the plurality of cylinders (1) are connected to one common exhaust manifold. Device according to one of the preceding claims, characterized in that a cooling device (11) is mounted in the exhaust manifold (10). CM δ CM ιό o 00 CM X cc CL o 00 CD o sfr o o CM