Internal-combustion engines – Intake manifold – Manifold tuning – balancing or pressure regulating means
Reexamination Certificate
2000-05-30
2001-12-11
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Intake manifold
Manifold tuning, balancing or pressure regulating means
Reexamination Certificate
active
06328011
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a suction pipe for the intake air of internal combustion engines, which has a pressure-relieving site in the suction pipe for pressure waves coming from the cylinder.
Such pressure-relieving sites for suction pipes are generally known. The pressure-relieving sites are intended for the controlled dissipation of the energy contained in pressure waves due to so-called backfiring. Backfirings are flame reactions which, starting out from the cylinder-side inlets of the suction pipe, extend into the air-guiding ducts of the suction pipe. The danger that this phenomenon will occur exists particularly when the internal combustion engine is operating with a large timing overlap of the valves. The backfiring then consists of an already ignited portion of the fuel-air mixture in the cylinder. Backfiring can lead to destruction of the suction pipe structure, especially when plastic suction pipes are used. By these means, the functioning of the internal combustion engine is seriously endangered, since unfiltered supplementary air can be drawn in through the destroyed suction pipe. In this case, neither the supplying of the internal combustion engine with intake air of the required degree of purity nor the maintaining of limiting values with regard to the emission of pollutants by the internal combustion engine can be assured.
In order to eliminate this problem and thereby assure the emergency running properties of the internal combustion engine in the event of backfiring, a valve, for example, may be installed in the wall of the suction pipe. This comprises a rubber mushroom head, which assumes the function of a valve and is closed in the normal operating state of the internal combustion engine. In the event of backfiring, the pressure wave expands in the suction pipe and opens up the rubber mushroom head, which in this case functions as a pressure-relief valve. In this way, the overpressure in the surroundings of the internal combustion engine can be reduced, so that a component failure becomes less likely.
However, for reliable operation of the pressure-relieving site, an adequate cross section for the passage of the pressure wave is required. This cannot be provided by a rubber mushroom head valve, since the reliable operation of the valve cannot be assured when the dimensions of the component exceed a certain size. It would be possible to provide several valves. However, this represents an additional expense.
A further disadvantage of the pressure-relief valve has to do with flow properties. The geometry of the rubber mushroom head and of the associated outlet opening interferes with the internal contour of the suction pipe, as a result of which there is turbulence, which increases the flow losses of the intake air. Especially in the vicinity of the outlets of the suction pipe adjacent the cylinders, i.e. at the location where the backfiring originates, interference with the flow of the intake air is not acceptable, if a concerted production of turbulence in the combustion spaces of the cylinder is to be achieved. In other words, the rubber mushroom head must be mounted away from the location where the backfiring originates, as a result of which its effect is reduced.
A further disadvantage arises due to the use of a resilient or elastic material for producing a reasonably priced pressure-relief valve. The resilient or elastic properties are very dependent on the temperature, so that a constant functioning of the rubber mushroom head, independently of the operating temperature of the engine and of the external temperature, cannot be assured.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a relief for pressure waves in a suction pipe, which ensures that the emergency running properties of the internal combustion engine function reliably and effectively.
This and other objects of the invention are achieved by the invention described and claimed hereinafter.
The inventive suction pipe, which enables the passage of intake air in a known manner, has a bursting geometry, which is accommodated in a wall section of the suction pipe, as a pressure-relieving site. This bursting geometry discharges into a buffer volume. In the event of backfiring and the destruction of the bursting geometry, the buffer volume is used for dissipating the energy of the pressure wave. The overall structure of the suction pipe therefore remains unchanged, the buffer volume representing a space, which is closed off to the outside, so that the total system represents a closed system even after the bursting geometry has been broken open. In this way, the emergency running properties of the internal combustion engine are maintained even if the incident becomes noticeable due to a changed gas exchange of the internal combustion engine. In any event, the vehicle with the damaged suction pipe can be moved under its own power to the next service station.
The bursting geometry can be an integral component of the walls of the suction pipe or it can be a separate part connected to the suction pipe. It is, for example, possible to construct the bursting geometry from a lid, which is glued into an associated opening in the wall of the suction pipe. The glued connection is then constructed as a predetermined breaking site, so that backfiring would cause the lid to be detached from the opening and flung into the buffer volume.
The buffer volume can be mounted at any place in the suction pipe. Particularly appropriate sites, however, are those which are close to the location where backfiring originates. The bursting geometry can then be built into the wall of the intake ducts leading to the cylinders. It is also possible to dispose the buffer volume in the collection space opposite the outlets from the collection space into the intake ducts of the suction pipe. A backfire spreading out is then conducted along the comparatively stable intake ducts and, in the collection space, strikes the bursting geometry, which is destroyed thereby.
If the wall section is formed by a glued-in lid, then it is advantageous to construct this, as well as the associated installed opening, in a conical shape, so that the lid can be inserted only from the side of the buffer volume. By these means, the blow-out direction of the lid into the buffer volume is clearly defined. If the lid is circular, it is furthermore ensured that, after it is blown out, it cannot leave the buffer volume and reach the suction pipe, where it could interfere with the passage of air.
In a further embodiment of the invention, the wall section is formed by a concerted weakening in relation to the wall surrounding it. It can then be produced in one piece with the suction pipe, for example, as a casting. The weakening of the wall then leads to a failure of the suction pipe at precisely this place in the event of backfiring. Advantageously, the weakening of the wall section is formed by a groove, which extends along a fracture edge of the bursting geometry. If the groove is ring-shaped, it forms a lid-like structure, which can be blown out by the backfiring.
In one embodiment of the invention, which is particularly advantageous from a flow point of view, the groove is on the side of the wall, remote from the interior of the suction pipe, that is, on the side of the buffer volume. The internal contour of the suction pipe can remain totally unaffected by the provision of the bursting geometry, so that the flow properties of the suction pipe are the same as those of a suction pipe without bursting geometry.
In order to ensure that the suction pipe functions reliably after the bursting geometry is destroyed, the wall section desirably may have a reinforced connecting region to the wall surrounding the suction pipe. Whereas the wall section along the fracture edge is pulled out of the suction pipe wall, the reinforced region remains in existence and can be constructed like a hinge. The wall section then remains hanging at this hinge and cannot pass to the suction pipe, where it would have an adverse effect on the
Jessberger Thomas
Pham Kinh Toai
Pietrowski Herbert
Crowell & Moring LLP
Filterwek Mann & Hummel GmbH
Huynh Hai
Wolfe Willis R.
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