FI126488B - Exhaust system for multi-cylinder gas and diesel engines - Google Patents

Description

Exhaust system for multi-cylinder gas and diesel engines

The invention relates to an exhaust pipe for multi-cylinder gas and diesel engines according to claim 1 of a plurality of substantially similarly constructed pipe fittings.

DE 38 15 406 A1 discloses an exhaust pipe system in which the exhaust pipe formed of the pipe pieces is lined with, for example, an external thermal insulation in the form of insulating mats generally made of fiberglass material. However, since the exhaust pipe is subjected to relatively large thermal expansions, which are known to cause over-stresses or even disturbances inside the cylinder head, the individual pipe pieces are interconnected by means of plug-in connections so that relative axial movements of the pipe pieces are possible. This exhaust system is expensive to install and disassemble because the exhaust pipe is molded into the cylinder head.

In the exhaust systems of the Applicant, the individual pipe pieces are also connected by more reliable stretch pieces, i.e. axial and / or radial expansion joints, than the already described plug connections, so that they can be stretched freely upon heating. The individual pipe pieces and the stretch pieces are insulated, whereby the insulation consists of, for example, mineral wool, a layer of aluminum foil and possibly an asbestos fabric covered with a support fabric. Outwardly, the exhaust pipe is covered by a cover in the form of a cladding. Such an exhaust system naturally goes against the requirement of the compact design of an internal combustion engine. Admittedly, exhaust pipe insulation is effective, yet expensive and unfortunately short-lived. In addition, the expansion pieces, so-called expansion joints, represent a significant cost factor for the exhaust system.

Another known exhaust system is disclosed in US 540 4716 A. Radial and / or axial compensators, i.e. exhaust gas compensators, have already been described, for example, in DE 10 2004 021 799 B3.

The drawbacks of the exhaust system described above are obvious. It requires a large number of parts, there are several thermal bridges, at least due to the relatively complicated geometry of the pipeline connections.

In addition, it is always possible to blow out hot air at the intersections of the outer lining of the sheet metal. Also, the insulating material of fiberglass material is not long-lived, the fiberglass material is easily degraded.

In contrast, there are certain requirements for thermal insulation. Thus, the outdoor temperature in the exhaust system should not exceed 220 ° C. In addition, the insulation must be oil and fuel tight in the event of a leak through the exhaust pipe. Despite the isolation, the exhaust pipe must be demountable. Aiming at a multi-year life span, and including all components. joints must be vibration resistant. In addition, for large engines, it is desirable that the exhaust pipe be step-proof and that it is possible to attach the exhaust pipe when disassembling the cylinder head.

It is therefore an object of the invention to provide an exhaust system of the aforementioned kind in such a way that hot exhaust gases are extensively shielded prior to energy loss so that there are no damaging effects of the components of the exhaust system so that the cost-effective manufacture of the exhaust system defective pipe parts and sealing problems can be easily replaced. This object is solved according to the invention by the features of claim 1. Other embodiments of the invention will be apparent from the features of the dependent claims.

Advantages achieved by the invention are that the proposed exhaust system, despite providing reliable connections and seals through heat-resistant pipe connections that absorb axial and radial movements, can dispense with relatively expensive axial expansion joints .

A very special advantage is that the life of the exhaust pipe insulation, depending on the construction, achieves the life of the exhaust pipe system and, unlike the previous isolations, is maintenance-free. In addition, advantages over prior art include shorter installation times, a more compact design, and not least a cleaner engine view.

An insulating layer of ceramic foam integrated in the pipe sections reduces the surface temperature of the outer wall of the exhaust system to below 200 ° C.

Further, because the exhaust system is very advantageously suppressed by a thin-plate contact guard, a lowering to about 60 ° C in the traffic area is further achieved.

In order to close the insulating longitudinal chamber, integrated closures are preferably used in the pipe joints and in the axial expansion joints to absorb deformations and consequent stresses, preferably between the plugs of the pipeline part molded in the form of single piece casting walls.

An embodiment of the invention is illustrated schematically in the drawing and will be described in more detail below.

The sole figure shows a partial view of the exhaust system for a multi-cylinder internal combustion engine according to the invention, in which the insulating chambers are closed by simple axial expansion joints.

The figure shows a part of an exhaust system for multi-cylinder gas and diesel engines consisting of a plurality of substantially similarly formed pipeline sections 1 or 2. Each pipeline section 1,2 comprises a pipeline connection portion 3,4 for the cylinder.

The double-walled pipeline sections 1, 2 are manufactured as single-piece castings, which in each case may be connected by a commercially available pipe coupling not shown here.

Each pipeline section 1, 2 comprises a centrally extending pipeline section 6, which is sheathed by forming a longitudinal chamber 7 approximately coaxially with the external pipeline section 12.

Each of the longitudinal chambers 7 has a filling 8 of insulating material in the form of a ceramic foam.

The ceramic foam is preferably composed of a mixture of metal oxide compounds, in particular alumina and / or silica in the form of inorganic, foamable and curable molding compounds. Advantageously, such ceramic foam may be combined with 99% alumina and silica and 1% various metal oxides.

However, it is also possible to granulate a product which has produced a mixture of various metal oxides into a granulated product. Such materials are known, for example, from DE 101 50 057 A1 as fire protection material.

Advantageously, the conduit parts 1, 2 are sheathed with a thin-plate contact shield 9. In addition, the outer conduit body 12 is provided with support means for the exhaust system on which the contact shield 9 rests and thus represents the support of the exhaust system itself.

The sealing chamber 7 is closed by means of a sealing plate 13 integrated in the axial compensator 11. However, it is also conceivable to use the exhaust pipe system according to the invention in which the conduit parts 1, 2 are connected and sealed by a pipe connection.

Furthermore, it would be conceivable for the exhaust system of the invention to be based on the above difference with the only difference being that only one pipe coupling or axial compensator is fitted between the two insulating chambers 7 of the pipeline sections 1, 2. thermal expansion.

In the illustrated embodiment, the pipeline part 2 is formed as an end piece which is closed at the end side by a double wall. Each part 1, 2 is made as a unit in the form of a one-piece molding part and provided with a centrally extending tube 6 for the exhaust gas, forming an annular longitudinal chamber 7 with in the form of a part attached to the cylinder 30.

In the axial direction, exhaust gases and passageways for insulation are made available in this manner. Circular tubular connections or axial expansion joints 11 and / or transverse transverse walls 20 are disposed between the axially adjacent end faces of the pipeline sections 1, 2 so that space is available at these points for thermal expansion of the casting walls in the axial and radial direction.

Claims (4)

An exhaust pipe system consisting of several substantially similar tubing parts (1, 2) for multi-cylinder gas and diesel engines, each part (1, 2) of the pipeline comprising a pipe joint (3, 4) for a cylinder (30) and a thermal insulation provided for each part (1, 2) of the pipe, so that each part (1,2) of the pipe is realized as double-walled in such a way that a centrally running pipe piece (6) is formed by forming a longitudinal chamber (7). roughly coaxial with an outer piping piece (12), the longitudinal chamber (7) is molded by ceramic foam and the individual sections (1, 2) of the pipeline are joined by heat-resistant pipe couplings, which also allow closing of the longitudinal chamber (7) by heat expansion; the longitudinal chamber (7) is realized with a locking plate (13) which is integrated in the pipe coupling or in a compensator (11). 2. Exhaust pipe system according to claim 1, characterized in that the double-walled parts (1,2) of the pipeline are made as one-piece castings. 3. Exhaust pipe system according to claim 1, characterized in that the chemical composition of the ceramic foam is alumina and / or silica possibly supplied with inorganic fillers. Exhaust pipe system according to one of the preceding claims, characterized in that the exhaust pipe system is sheathed with a sheet metal damping protection (9).