DE2617245C2 - Exhaust gas cleaning system for a four-stroke internal combustion engine - Google Patents

Description

The invention relates to an exhaust gas purification system for a four-stroke internal combustion engine according to the preamble of claim 1.

Such an exhaust gas cleaning system is known (DE-OS 19 26 041, in particular the embodiment according to Fig. 1! and 12). In this known exhaust gas cleaning system, all exhaust ducts, d. H. the exhaust ducts both the first group of cylinders and the exhaust ducts of the second group of Cylinders fed with additional air. The valve device consists of two check valves, one of which Check valve the exhaust channels of the first group and the other check valve the exhaust channels are connected to the second group. The disadvantage of the known exhaust gas cleaning system is that it is made relatively complicated in particular by the two valves in the air line.

The invention is based on the object of designing a generic exhaust gas purification system in such a way that that a more comprehensive exhaust gas cleaning effect with as little as possible a greater structural effort is achieved.

According to the invention, this object is achieved by the features in the characterizing part of patent claim 1 solved.

In the exhaust gas cleaning system according to the invention, only some of the exhaust gas ducts are supplied with additional air fed, which can be done without disadvantage from a single valve, and it is also provided that in on The exhaust gas ducts of the second group connected to the exhaust manifold are not mixed with additional air is available, which is returned to the intake system in order to achieve a further reduction through exhaust gas recirculation to achieve the pollutant content. Exhaust gas recirculation

ίο for the purpose of reducing the pollutant content in internal combustion engines is known per se (DE-AS 20 22 911).

One advantage of the invention is that the valve device has only a single valve.

As a result, a structural simplification is achieved. It has been shown that even if only the Exhaust ducts of the cylinders of the first group are fed with additional air, a sufficient amount of additional Juft is fed in. Another benefit of the

zo invention is that in the second exhaust manifold

■ 'isoxygenless or at least low-oxygen exhaust gas is present, which can be returned to the intake system, so that exhaust gas cleaning by additional air injection

, solution in the exhaust system is combined with exhaust gas cleaning by exhaust gas recirculation to the intake system, ; which results in a higher exhaust gas cleaning effect than the sole supply of additional air into the exhaust system.

Advantageous refinements of the invention are characterized in the subclaims.

μ Embodiments of the invention are in the Drawings shown it shows

F i g. 1 shows a schematic plan view of an internal combustion engine with an exhaust gas cleaning system according to the invention;

F i g. FIG. 2 shows a sectional illustration according to FIG. 11-11 in FIG. 1; Fig.3 is a control diagram showing the inlet and Shows exhaust timing;

F i g. 4 is a control diagram that shows the valve lifts of the intake valves as a function of the crank angle Shows exhaust valves of all cylinders of a four cylinder engine;

5 shows a schematic top view of an embodiment of the invention, wherein a possible combination of the cylinders is shown with corresponding Branch lines are connected; and

6 shows a plan view corresponding to FIG further embodiment.

F i g. 1 shows a schematic plan view of an internal combustion engine with an exhaust gas cleaning system according to the invention, of which, however, not all of the features in FIG. 1 are shown. F i g. 2 shows a cross section by part of the in F i g. 1 internal combustion engine shown. In the following, reference is first made to this FIG. 1 and 2 received. The internal combustion engine comprises a cylinder block 1, a piston 3, which is in an im Cylinder block 1 trained cylinder 2 back and forth

• is movably seated, a cylinder head 4 attached to the cylinder block 1, an inlet valve (not shown) Exhaust valve 6 which can open and close an exhaust port 5, an exhaust manifold 7 and a Intake manifolds 8, which are attached to the cylinder head 4, an air filter 9, which is mounted on the intake manifold 8 is attached, and a catalytic converter 1.0. The exhaust gas to be emitted, which is produced by combustion in the

i> 5 combustion chamber 11 is created by the exhaust manifold 7 passed into the catalytic converter 10, after which the purified in the catalytic converter 10 Exhaust gas is released into the surrounding atmosphere.

Fig. 3 shows a timing chart of the intake and exhaust timing. In a conventional internal combustion engine having an intake valve and an exhaust valve, the intake timing and the exhaust timing overlap. During this overlapping time, both the inlet valve and the outlet valve are open until the outlet valve closes. Like F i g. 3 shows, for example, the exhaust valve A opens 50 ° before BDC (bottom dead center), and it closes 16 ° after TDC (top dead center). The inlet valve B opens 16 ° before TDC and closes 50 ° after BDC. As a result, an overlap time C occurs during which both the exhaust valve A and the intake valve B are open.

It is assumed that in FIG. 2 cylinder shown is run through an exhaust stroke. Meanwhile, the exhaust valve 6 is open and the exhaust gas is passed from the combustion chamber 11 through the exhaust port 5, an exhaust duct 12 and the exhaust manifold 7 in the catalytic converter OK, while the piston 3 in cylinder 2 moves upwards to this 'time, the pressure in the outlet passage 12 and in the ^ corresponding branch line of the exhaust manifold 7 is greater than the atmospheric pressure then, when the, inlet valve opens and the piston 3 is further -bewegt upward so that it reaches at the top dead center of its uppermost position , There is practically atmospheric pressure in the outlet channel 12 "and in the branch line of the exhaust manifold 7. When the piston 3 then begins its downward movement, combustible mixture is sucked into the 'combustion chamber 11 via an inlet opening (not shown). At this point in time, the' outlet valve 6 is still Therefore, part of the exhaust gas in the exhaust port 12 is moved back into the combustion chamber 11, so that the pressure in the exhaust port 12 and becomes slightly lower than atmospheric pressure in the branch pipe of the exhaust manifold 7. While (the piston has a position close to top dead center and thus both the inlet valve and the outlet valve 6 are open, the pressure in the outlet channel 12 and in the branch line of the exhaust gas collector 7 therefore has a value close to the suction negative pressure. The internal combustion engine is provided with an automatically opening and closing valve 13, known per se, which is designed as a tongue valve and is supplied via the additional air that supports the oxidation of unburned gases in the outlet duct 12, this using the negative pressure or using the Fluctuations in the exhaust gas pressure takes place, which are generated by the opening and closing of the outlet valve 6 and the inlet valve. Valve 13 is via a line 14, an (air filter 15 for filtering the additional air, a noise damper 16 for suppressing the intake noise of the additional air and a line 17 connected to the suction side of the air filter at a point that is the air inlet ■ opening of the air filter 9 is opposite. Furthermore, the valve is connected via a distribution line 18 for additional air drawn in, branch lines 19, air suction nozzles 20 at the engine-side ends of the branch lines 19 and channels 21 in the cylinder head 4 to a certain number of outlet channels 12 to be explained. The lines 14 and 17 and the distribution line 18 form an air line for the additional air. The valve 13 opens when the pressure in the branch lines 19 is slightly lower than in the line 17, ie lower than atmospheric pressure, or when the pressure drops in the Branch lines 19 exceeds a certain value. If the pressure in the outlet channel 12 becomes negative pressure or if there is a pressure drop in the outlet channel 12, the line 17, the noise damper 16, the air filter 15, the line 14,

ι the valve 13, the distribution line 18, the branch lines 19, the air outlet nozzles 20 and the channels 21, air is sucked from the air filter 9 into the outlet channel 12. One Internal combustion engine, which drives a motor vehicle, for example, usually has four, six or eight

in cylinder on. It has been found that it is too when additional air in the exhaust ducts, d. H. the outlet duct 12 or the branch pipe of the exhaust manifold 7, initiated by only two of the four cylinders, is possible, the exhaust gas is such a sufficient

i) To supply the amount of air necessary to carry it out effectively the oxidation in the catalytic converter is required.

In the following, the F i g. 4 to 6 received. It is assumed that an internal combustion engine has four

Λ) cylinder, namely a No. 1 cylinder, a No. 2 cylinder, a No. 3 cylinder and a No. 4 cylinder, and that the firing order in this engine is 1-3-4-2. and exhaust timing of each cylinder is shown in FIG. 4 shown. In Fig. 4, the abscissa is the crank angle θ, and the ordinate is the valve lift of the intake valves and the exhaust valves of each cylinder. The curves A, under which the area is shown hatched, each show the lifts of the exhaust valves

No. 1 to No. 4 cylinders and curves B show the lifts of the intake valves of No. 1 to No. 4 cylinders, respectively. The overlap time between the exhaust valve and the intake valve is indicated by arrow C, respectively.

It is assumed that the branch pipes 19 connected to the single valve 13 and the air cleaner 15 are connected to the No. 1 and No. 2 cylinders. Like F i g. 4 shows, in this case, the exhaust valve A of cylinder No. 1 is open, while the intake valve and the exhaust valve of cylinder No.? are opened simultaneously during their overlap time, so that the pressure in the exhaust port 12 of the No. 2 cylinder is negative. However, since the exhaust valve A of the No. 1 cylinder is open, the pressure in the exhaust passage 12 thereof is greater than atmospheric pressure. This has the consequence that the valve 13 from the pressure in the Auslaßkana! of cylinder # 1 is kept closed. Therefore, in spite of the negative pressure and a pressure drop in the exhaust port of the No. 2 cylinder, additional air cannot be fed into the exhaust port of the No. 2 cylinder. In other words, when the branch lines 19 are connected to said two cylinders, the exhaust valve of one of the two cylinders is open,

while the opening times of the intake valve and the exhaust valve of the other cylinder overlap. So if it applies to the two cylinders that the opening times of the exhaust valves of the two Cylinder overlap, no additional air can enter the cylinder due to the influence of one of the two cylinders the other of the two cylinders.

Since two cylinders with additional air are fed in "- 1, the branch lines 19 must therefore be connected to two such cylinders that the

The opening times of the exhaust valves of these cylinders do not overlap or overlap. These cylinders form a first group, while a second group consists of the remaining cylinders that do not have branch lines

17 245

19 are connected. It is also provided that the exhaust collector 7 is divided into two separate exhaust gas generators T and 7 ″, one of which is assigned to the two cylinders mentioned and the other is assigned to the other cylinders

Taking into account these basic principles, the following Korhbinatiorismoglicnkeiien exist for two cylinders, which are connected with a single valve Ϊ3: Either the cylinder Ni ^- . 1 and cylinder no. 4 are combined to form the first group, as shown in FIG. 5, or cylinder no. 2 and cylinder Nf >> 3 are combined to form the first group, as shown in F 5 g. 6 is shown. In both cases, the exhaust manifold 7 is divided into the two separate exhaust manifolds T and 7 ″, as shown in FIG. 1 and as indicated by dashed lines in FIG.

In the embodiment shown in FIGS the channel 21 connected to the branch line 19 opens into the outlet channel 12 Branch line 19 can, however, also directly into one. Line branch of the Abgässämmiers 7 open out.

As the F i g. 5 and 6 show is of the cylinders of the second group that is not connected to valve 13 Are connected, exhaust gas supplied into the intake system 28, for example the intake divider 8, via a Control valve 26 for controlling the flow of recirculated exhaust gas and an exhaust line 27 recirculated, this exhaust gas containing no additional air. In other words, this means that the gas is inert is returned to the AnsaiJgverteiier, whereby a significant reduction in the content of toxic nitrogen oxides in the exhaust gas is achieved. Furthermore, if the

. Overlap of the opening times of the inlet valve and the exhaust valve of each cylinder connected to the valve 13 compared to the

ίο *.! Overlap times of the cylinders of the second Group is extended; is thereby the amount of den

h / first-named cylinders increased additional air

\ Bert, whereby the cleaning efficiency and also the operating behavior of the internal combustion engine improve

I5 $ ert can be.

The atmospheric side of the valve 13 is preferably connected via the air filter 15 and the noise damper 16 to the suction side of the air filter 9 at a point which is opposite the air inlet opening into the air filter 9. This ensures that if, due to a fault in the valve 13 , exhaust gas flows back into the air filter 9 via the branch lines i9, the distributor line 18 and the line 17, this exhaust gas cannot be released into the atmosphere. Rather, this exhaust gas is sucked back into the combustion chamber.

For this purpose 4 sheets of drawings

Claims (3)

Patent claims: 1. Exhaust gas cleaning system for a four-stroke internal combustion engine with an intake system, several Cylinders, each of which has an exhaust valve and, downstream thereof, an exhaust duct, an exhaust manifold into which the exhaust ducts open, an air line through which the Ambient additional air is introduced into the exhaust gas ducts, and a valve device in the air line, which opens automatically when the pressure in the exhaust gas ducts falls below a certain level, whereby the Cylinders are combined into a first group and a second group and the first group comprises at least two cylinders and the exhaust valve opening times of the first group do not overlap, characterized in that only the exhaust ducts (12) of the cylinders (2) of the first Group are connected to the air line (14,17,18) that the valve device is a single valve (13) is that all of the exhaust ducts fed with additional air are supplied to the exhaust manifold (7) in one first exhaust manifold (7 ') assigned to the exhaust ducts of the first group and a second, the exhaust gas ducts of the second group associated exhaust manifold (7 ") is divided and that to the second exhaust collector an exhaust gas recirculation line (27) is connected through the exhaust gas to Suction system (28) is returned. 2. Exhaust gas cleaning system according to claim 1, characterized by a control valve (26) for Control of the exhaust gas recirculation through the exhaust gas recirculation line (27). 3. Exhaust gas cleaning system according to claim 1 or 2, characterized in that the respective overlap time of the inlet valve and the outlet valve (P) of the individual cylinders (2) of the first Group is longer than the overlap time for the cylinders of the second group.