DE2613607A1 - MULTICYLINDER ENGINE EXHAUST SYSTEM WITH TWO SEPARATE EXHAUST PIPES - Google Patents

Description

Dr D. Thomsen PATE N ANWALTS OFFICE

& Telephone (089) 530211 OP 1 O r Π Π

530 212 I OIO υ U /

W. We! Π kaUf f telegram address J

I expertia

Cable address J.

PATENT LAWYERS Munich: Frankfurt / M .:

Dr. rer. nat. O. Thomsen Dipl.-Ing. W. Weinkauff

(Fuchshohl 71)

Dresdner Bank AQ, Munich, account 5574237

8000 Munich 2

Kaiser-Ludwig-Platz 6 3 _{O #} March 1976

Nissan Motor Company, Limited Yokohama City, Japan

Multi-cylinder engine exhaust system with two separate exhaust lines

The present invention relates to an exhaust system for a multi-cylinder internal combustion engine two or more separate exhaust pipe systems in which catalytic converter units are provided.

The main object of the present invention is to provide an improved exhaust system of the type described in the opening paragraph To find the type that has a maximum service life and maximum efficiency of the catalytic converter can accomplish. In addition, the interference between each other through the relevant separate exhaust lines flowing exhaust gases and thereby the exhaust noise

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OFUGlNAL INSPECTEq

of the engine can be contained. Finally, a reinforced and stiffened, easy-to-assemble exhaust system should be of the genus mentioned at the outset can be obtained.

According to the invention, an exhaust system for a multi-cylinder internal combustion engine proposed in which the multiple cylinders are divided into at least two groups and which at least two separate exhaust lines leading away from the cylinder groups concerned, at least two in the separate ones Exhaust lines appropriately arranged catalytic converter and at least one connecting pipe which connects the two exhaust lines fluidly connects to one another in the area above the catalytic converter.

Further features, problems and a number of advantages that characterize the invention are evident from the following detailed description in conjunction with the appended claims and drawings very easy to understand. In the drawings show:

Fig. 1 is a schematic plan view of a multiple

cylinder internal combustion engine with an exhaust system, as is known from the prior art;

Fig. 2 is a graph showing the operating characteristics of the engine and exhaust system shown in Fig. 1;

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Pig. 3 is a schematic plan view of a multi-cylinder internal combustion engine having an exhaust system which is a preferred embodiment of the present invention Invention represents;

Fig. 4 is a perspective detailed view of parts of the exhaust system shown in Fig. 3;

FIG. 5 is a graphical representation of an operating characteristic which is derived from the embodiment of FIG present invention in comparison with an embodiment known from the prior art was obtained; and

Fig. 6 is a graph showing another operational characteristic obtained by the embodiment of the present invention in comparison with an embodiment known from the prior art was obtained.

In some engines, such as V-engines or engines with cylinders arranged flat against each other, it is common that the cylinders are divided into two groups, which accordingly connected to separate exhaust pipes or ducts. Fig. 1 shows an example of a motor 1o with Cylinders, which are identified by the accompanying reference numerals, each group of 4 cylinders in succession is connected to an exhaust duct 12a or 12b, which then

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merges into an exhaust line 13a or 13b. In the two exhaust lines 13a and 13b there are catalytic converters 14a and 14b respectively. The two exhaust lines are direct downstream of the catalytic converter 14a or 14b connected with each other.

The above-described design of an exhaust system has various disadvantages, which are explained below should.

In the eight-cylinder engine shown, the engine firing order is, for example, 1, 8, 4, 3, 6, 5, 7, 2, but also different other firing sequences are conceivable. However, with each firing order that may be used, the firing intervals are between the cylinders in question in a group of an eight-cylinder engine are no longer equal to one another. As a result it shows then that the intervals at which the exhaust gases are expelled from the respective group of cylinders, in undesirable Way can be irregular.

This is recognized far more clearly with reference to FIG. 2. Fig. 2 (A) shows the intermittent change in pressure of the Exhaust gases when using a four-cylinder engine. It is can be seen that in such a Mo.tor the exhaust gases a Sequence of regular intermittent curves with each ignition of the individual cylinders. That's the reason why the firing interval between the four cylinders is essentially constant for each possible firing order.

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In contrast, in an eight-cylinder engine, the intermittent exhaust gas pressure is changed irregularly, as shown in Fig. 2 (B) depending on the irregular firing order as mentioned above.

In the case of an eight-cylinder engine, the catalytic converters in the exhaust pipes must therefore be fast and withstand abrupt changes in the pressure of the exhaust gases, resulting in a reduction in catalyst efficiency and results in a rapid drop in converter life.

In addition, there is an interference phenomenon between the exhaust gases flowing through the separate exhaust lines on what increases the exhaust noise of the engine.

A preferred embodiment of the invention is now described with reference to FIGS. 3 and 4. As can be seen from these illustrations, the two separate exhaust lines are through a connecting pipe 15 located upstream of the catalytic converters 14a and 14b is connected.

Each exhaust pipe 13a or 13b and one adjacent one The ends of the connecting pipe 15 are connected to one another via a socket connection as shown in FIG. It is on each end of the connecting tube 15 has a slotted sleeve 17 formed in which a short arm 18a or 18b of the associated Exhaust line 13a or 13b is inserted. The socket

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17 and the arm 18a or 18b are suitable with the aid of a trained clamp 19 and a ü-bolt 2o (as shown) bracketed together. The above-described type of connection of the exhaust lines with the connecting pipe can recognize some of the advantages, which will be more clearly expressed in the following description.

Fig. 5 is a graph showing a change in intermittent exhaust pressure within the catalytic Converter, plotted on the ordinate, as a function of the vehicle speed, which is plotted on the abscissa is. From this illustration it can be seen that the pressure change according to the present invention (by a solid line Line shown) is relatively stable compared to that according to the known system (shown by a dashed line).

The reduction in the exhaust noise according to the present invention can be seen very clearly from the two representations in FIG. 6, in which the noise level in dB and the engine speed are plotted on the ordinate and the abscissa, respectively. The noise level was measured in the vicinity of the catalytic converter, essentially at a distance of 150 ram from it. The illustration (A) shows the result of the measurement at a relatively high frequency, while the illustration (B) shows this measurement result at a relatively low frequency. It should be noted that in both representations the noise level according to the invention, represented by

*
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a solid line, are significantly lower than the noise level in the known system, represented by a dashed line.

As described, in the present invention, the exhaust pipes and those connected to them constitute Connecting pipe a base frame construction. When the connecting pipe would be rigidly connected to the exhaust lines, for example by welding, would reduce the stresses caused by the uneven heat distribution in the exhaust system, locally on the connection areas between the exhaust pipes and the connecting pipe, and shorten the life of the exhaust system. A sleeve-like connection construction according to the present invention can compensate for the heat expansion of the exhaust pipes. Because besides that Exhaust system consists of different parts, not only is it extremely easy to assemble the parts, but it is also possible to eliminate excessive voltages by adjusting the length of the connection areas, those at the joints of this composite system due to the manufacturing inaccuracies of the individual parts develop.

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Claims (3)

Claims ■ 1.) Exhaust system for a multi-cylinder internal combustion engine, in which the plurality of cylinders are divided into at least two groups, characterized in that the at least two groups, in turn, at least two separate exhaust lines (13a, 13b), which are from the groups concerned lead away the cylinder; at least two catalytic converters (14a, 14b), which are in the respective separate exhaust lines (13a, 13b) are arranged; and at least one connecting pipe (15), which in a region downstream of the catalytic converters (14a, 14b) a fluid connection between the two exhaust lines (13a, 13b) creates (Fig. 3). 2. Exhaust system according to claim 1, characterized in that that the connecting pipe (15) at its respective end has a sleeve (17) for receiving the exhaust line (13a or 13b) and a bracket (19) which. surrounds the sleeve (17) and thereby presses sealingly against the exhaust lines (13a, 13b) (Fig. 4). 3. Exhaust system for an internal combustion engine with two Groups of four cylinders each, characterized by two separate exhaust ducts (12a, 12b), each of which is connected to the lead away two cylinder groups; two separate, longitudinally and parallel extending exhaust lines (13a, 13b), which 609841/0798 are connected to the exhaust passages (12a, 12b), respectively; two catalytic converters (14a, 14b) arranged in the two exhaust pipes (13a, 13b); and one Connection pipe (15), which is located at one point upstream of the catalytic converters (14a, 14b) across between the two exhaust lines (13a, 13b) extends and this Lines fluidly connects (Fig. 3). 609841/0798 L e rse I te