DE3721608A1 - Exhaust manifold - Google Patents

Abstract

A description is given of an exhaust manifold for carrying away combustion gases of an engine, this manifold being flanged on between the engine block and the exhaust pipe. The exhaust manifold has a load-bearing outer tube and an inner tube which serves to carry the gas and is provided with an expansion compensating means. The expansion compensator is preferably designed as a sliding-tube compensator. The outer tube and the inner tube are thermally insulated from one another, preferably by sheathing the inner tube in ceramic fibres.

Description

The invention relates to an exhaust manifold for brewing the combustion gases of an engine with one each Connection flange at the pipe ends.

As is well known, they are made from the cylinders of an engine flowing combustion gases into the open via outlet channels derived. The individual channels are switched off puff manifold, also known as an exhaust manifold is flanged. The transition from the individual cylin derköpfchen can over large pipe sockets with outer transition radii. At the exhaust manifold is usually flanged a silencer. Because of the Exhaust manifolds are generally good sound insulation made of gray cast iron.

Due to different thermal expansions of the cylinder head and the exhaust manifold, which is particularly in one Cold starts occur in the exhaust manifold mecha African voltages that wear the collector tube being able to lead. There is also a risk that occurring stresses the seals to the connection places are moved or grated.

The invention has for its object to provide an exhaust Specify manifold of the type mentioned, whose Wear resistance is improved.

This object is achieved in that the exhaust manifold pipe from a gas-carrying inner pipe and one of them  there is thermally insulated load-bearing outer tube and that the gas-carrying inner pipe with at least one pipe section a sliding end to compensate for tem changes in length caused by temperature.

A basic idea of the invention is therefore the tra part of the exhaust manifold and the temperature to separate the critical gas-carrying part. The has the advantage that the inner part essentially finally with regard to gas resistance and external outer part only with regard to the structural strength speed can be formed. Symptoms of instability due to thermal stresses do not occur in the load-bearing part on. In the gas-carrying part you can use special pressure relief or strain relief areas using of an axial compensator can be neutralized.

The invention also has the advantage that the mass of Inner tube can be kept relatively small, since it does not ne has to fulfill a supporting function. So less Heat absorbed by the exhaust gas and stored, which is too high leading gas temperatures. This can result in diesel engines the soot filter is burnt off, so that additional Filters can be saved. When out with catalyst equipped gasoline engines, the higher temperature leads to a earlier starts. Conversely, the lower heat offers capacity of the exhaust manifold the possibility of Encapsulate the motor more tightly because less heat is inside the Capsule is stored.

A preferred development of the invention consists in that the inner tube consists of two pieces of pipe, one of which End is firmly connected to a connecting flange, and the free ends are nested. This out leadership form is easy to manufacture.  

Alternatively, it may be appropriate for the inside Pipe consists of two pieces of pipe that have an expansion balancing sleeve or a joint another, inside lying pipe section are connected to each other.

It can also be used to improve stability prove expedient, the free pipe ends over Bril to connect the axially displaceable lenflanges.

In order to escape combustion gases in the annular space between It is advantageous to prevent the inner and outer tube liable that the separation point between the pipe pieces with is provided with a seal.

A particularly light embodiment of the invention be is that at least the inner tube is made of stainless steel is posed. The weight can further reduce thereby be decorated that the outer tube is made of stainless steel.

These training courses are also with regard to the wün noteworthy low heat capacity and durability advantageous against the corrosive effect of the exhaust gases. Also is the frictional resistance in the sliding tube compensator relatively low.

The thickness of the inner tube is preferably approximately 0.8 mm and the thickness of the outer tube about 2.5 mm.

Another preferred embodiment of the invention be is that the outer tube in the area of the connection flanges tapered to the outer diameter of the inner tube is, and that it together with the inner tube on the An end flanges is attached. This way the Installation conditions, especially the arrangement of the fittings screws, very well taken into account without that changes to the connecting flanges or the Zylin exhaust pipes compared to conventional exhaust Collecting pipes must be made.

A very good thermal insulation between inside and outside pipe and good sound absorption is achieved  that between the inner and outer tubes an insulating agent is arranged. It proves to be particularly suitable that ceramic fiber is used as insulation.

In the following the invention with reference to one in the drawing voltage illustrated embodiment further described ben.

Figs. 1 to 3 show schematically a longitudinal section through an exhaust manifold.

As illustrated in FIG. 1, an exhaust manifold 1 has an outer tube 2 and an inner tube 3 as well as an inlet-side connecting flange 4 and an outlet-side connecting flange 5 . On the input flange 4 to the exhaust manifold 1 is screwed to a cylinder head of an internal combustion engine (not shown). The connection flange 5 on the outlet side serves for connection to an exhaust pipe (not shown).

The outer tube 2 serves as a supporting part and ensures the necessary mechanical strength and stability of the puff manifold 1 . The routing and discharge of combustion gases from the engine into the exhaust pipe takes place exclusively through the inner pipe 3 , which is thermally insulated from the outer pipe 2 . In the example shown here, this is done by a glass wool covering 8 , which completely fills the annular space between the outer tube 2 and the inner tube 3 . Since the inner tube 2 does not perform a tractive function, it can be made correspondingly weaker than the outer tube 3 . For example, the outer tube 3 can be made from 2.5 mm thick stainless steel and the inner tube from 0.8 mm thick stainless steel.

The inner tube 2 consists of two pipe sections 7 , 8 , each of which has a fixed and a slidably mounted end. The two fixed ends are fastened to the connecting flange 4 , 5 on the input and output sides. The two free ends of the pipe sections 7 , 8 are inserted into one another in such a way that they can be moved relative to one another in the axial direction. Preferably, the pipe section 8 lying on the output side has a slightly larger inside diameter for receiving the pipe section 7 on the input side, so that the pipe section 7 on the input side projects beyond the pipe section 8 on the output side. In principle, the pipe section 8 on the aisle side can have a correspondingly larger inside diameter over its entire length than the pipe section 7 on the inlet side. But it is also possible to equip both pipe sections 7 , 8 with the same inner diameter and to perform the plug connection as a socket connection and, if necessary, to provide a sealing ring.

The outer tube 2 is conically tapered at its two ends in such a way that it is connected to the inner tube 3 in a common annular connection 10 with the connecting flange 4 , 5 on the outlet and outlet sides, respectively. This shape of the outer tube 2 also increases the mechanical stability.

Basically, it is not necessary that the outer tube 2 is completely closed, since it only has a supporting function and the exhaust gas is sent via the inner tube 3 . To silencing and securing against under emissions from the plug connection of the inner tube 3 escaping exhaust gases, the annular space is completely closed to the outside. Instead of fibrous insulating materials, powdered insulating materials can also be used for heat and sound insulation.

If hot combustion gases get into the inner tube 3 according to arrow 9 , they cause the longitudinal expansion of the pipe section 7 , 8 on the inlet and outlet sides. These linear expansions are compensated for by the guide tube construction. Due to the relatively small mass of the inner tube 3 , this absorbs little heat. Through the glass wool sheathing 6 , heat transfer to the outer tube 2 is also prevented, so that there are no thermal stresses. Due to the design-related low heat storage, the exhaust manifold 1 ensures particularly good heat dissipation from the engine compartment.

Fig. 2 shows an exhaust manifold 1 'with a T-shaped or V-shaped branch. Here, the inner tube has three thin-walled pipe sections, two pipe pieces 11, 12 opening into a common T or V pipe section 13 , which is formed, for example, from half-shells. The ends of the two pipe sections 11 , 12 are calibrated to size and are precisely matched to the input side of the T or V pipe section 13 . In this way, the two pipe sections 11 and 12 against the T or V pipe section 13 are slidable ver.

An insulating layer 14 made of glass or rock wool, for example approximately 2 to 5 mm thick, is wound around the pipe sections 11 , 12 , 13 for heat insulation of the hot exhaust gases. The entire construction is held by a common thick-walled outer tube 15 . Since it is not exposed to large thermal loads, it can also be made from cheaper types of steel. In the embodiment, the outer tube 15 is preferably made of welded half shells ge. The pipe sections 11 , 12 and 13 are welded in the region of flanges 16, 17 18 , together with the outer pipe 15 .

Fig. 3 shows an embodiment of an exhaust collecting pipe 1 '' by a cross-pipe piece 19 with three inlet nozzles, each two piece record a Bo genrohrstück 20 and 21 in the example shown, while the third stub provided with a flange 20 is. The two bend pipe pieces 20 , 21 and the cross pipe piece 18 are arranged in a common outer tube 22 and welded at the free ends together with the outer tube 22 to the flanges 16 17, 18, 20 . As has already been described in detail in connection with FIGS. 1 and 2, the outer tube 22 is thermally insulated by an insulating layer 14 . The mobility of the pipe sections 19, 20, 21 in heat stress is in turn guaranteed by sliding tube compensators.

Claims (12)

1. Exhaust manifold for discharging the combustion gases of an engine, each with a connecting flange at the pipe ends, characterized in that it consists of a gas-carrying inner tube ( 3 ) and a thermally insulated load-bearing outer tube ( 2 ) be and that the gas-carrying inner tube ( 3rd ) has at least one pipe section ( 7 , 8 ) with a slidably mounted end to compensate for temperature-related changes in length. 2. Exhaust manifold according to claim 1, characterized in that the inner tube ( 3 ) consists of two pieces of pipe ( 7 , 8 ) be, one end of which is permanently connected to a connection flange ( 4 , 5 ), and the free ends are nested. 3. Exhaust manifold according to claim 1 or 2, characterized in that the inner tube ( 3 ) consists of two pipe sections ( 7 , 8 ) be, which are connected to each other via an expansion-compensating sleeve. 4. Exhaust manifold according to claim 1 or 2, characterized in that the inner tube consists of two pipe sections ( 7 , 8 ) which are bridged by a further inner pipe section. 5. Exhaust manifold according to one of claims 2 to 4, characterized in that the separation point between the pipe sections ( 7 , 8 ) is provided with a seal. 6. Exhaust manifold according to one of the preceding claims, characterized in that at least the inner tube ( 3 ) is made of stainless steel. 7. Exhaust manifold according to claim 6, characterized in that the stainless steel of the inner tube ( 3 ) has a thickness of about 0.8 mm. 8. Exhaust manifold according to one of the preceding claims, characterized in that the outer tube ( 2 ) is made of stainless steel. 9. Exhaust manifold according to claim 8, characterized in that the stainless steel of the outer tube ( 2 ) has a thickness of about 2.5 mm. 10. Exhaust manifold according to one of the preceding claims, characterized in that the outer tube ( 2 ) in the area of the connecting flanges ( 4 , 5 ) is tapered to the outer diameter of the inner tube ( 3 ) and that it is together with the inner tube ( 3 ) is attached to the connecting flanges ( 4 , 5 ). 11. Exhaust manifold according to one of the preceding claims, characterized in that a heat insulating material is arranged between the inner tube ( 3 ) and the outer tube ( 2 ). 12. Exhaust manifold according to claim 11, characterized in that ceramic fiber ( 6 ) is used as the insulating material.