Secondary air system for an internal combustion engine

Details Secondary air system for an internal combustion engine Secondary air system for an internal combustion engine

1998-12-15

2000-08-01

Denion, Thomas

Power plants

Internal combustion engine with treatment or handling of...

Having auxiliary device mechanically driven by exhaust gas

60289, 60307, 60397, F01N 504

Patent

active

060949090

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a secondary air system for an internal combustion engine. It is known that to improve the oxidation of hydrocarbons and carbon monoxides so-called secondary air, that is, additional air, can be blown into the exhaust gas end of the internal combustion engine.
German Patent Application DE-A-42 19267 describes a system for blowing secondary air for internal combustion engines in which a compressor is driven by an air-flow machine acting as a motor. The air-flow machine is connected parallel to a duct section with a throttle, the duct section being disposed upstream from a throttle connection to increase the power. The aspirated air is guided by a switch valve either through the throttle or through the air-flow machine.
A disadvantage of the known system is that the aspirated air fed to the motor is reduced by the additional throttle. Also, an additional element exists in the aspirated air train which has to be regulated according to the load on the motor.
It is also known to use a diaphragm pump for the injection of secondary air into internal combustion engines. A disadvantage of this system is the need to provide a pressure reservoir, which thus makes the system less economical.


SUMMARY OF THE INVENTION

The invention is addressed to the problem of improving the known systems.
This problem is solved, setting out from the preamble of the independent claim 1, by its distinctive characteristics.
The important advantage of the invention is that an additional throttle system is not needed for driving a turbine. Instead, unused energy, already present, is used for driving the turbine.
In one embodiment of the invention it is proposed to use as the drive means a turbine powered by the aspirated air. The pressure drop between the pressure of the aspirated air of the internal combustion engine ahead of the throttle valve and the pressure of the intake air following the throttle valve is used such that the turbine is disposed in a bypass line which is arranged to extend around the throttle valve. This turbine directly drives a pump for the secondary air. In an alternative embodiment of the invention the secondary air can also be produced by an electric motor serving as a pump.
Another embodiment of the invention envisions using filtered intake air for the secondary air injection. This has the advantage of reducing the degree of contamination of the drive for the secondary air.
In accordance with one advantageous embodiment of the invention it is proposed to provide an apparatus for preparing the secondary air. This is, for example, an additional filter element which is designed for the requirements of the pump. The clean air for driving the turbine of the secondary air charger cools very greatly upon expansion in the turbine. Consequently, water can condense out of the intake air or possibly freeze.
To prevent an accumulation of moisture, in a further embodiment of the invention it is proposed to install a water separator, as for example a baffle plate or a nonwoven web, on the low-pressure side of the turbine in the line carrying the expanded air to the plenum. It is also possible to provide an ice separator in the form of a baffle plate or a nonwoven web on the low-pressure side of the turbine.
In an additional embodiment of the invention it is proposed to mount the secondary air charger with the engine's air intake tube to form a single unit. Alternatively, it is also possible to integrate the secondary air charger with the throttle valve connection in a single module. Other variants are the integration of the secondary air charger into the clean air duct, in the air filter housing or in the cylinder head cover of the engine.
It is also possible, of course, to assemble the secondary air charger with some other selected component into one unit or configure it as a module.
In another embodiment of the invention it is proposed to regulate both the engine power and the secondary air charger power by the mass air flow fed to the secondary air charger. An alternat

REFERENCES:
patent: 3299629 (1967-01-01), Bouchard
patent: 4146986 (1979-04-01), Kohama et al.
patent: 4463554 (1984-08-01), Sudbeck et al.
patent: 4534173 (1985-08-01), Tsukamoto
patent: 4674283 (1987-06-01), Ishida et al.
patent: 5400597 (1995-03-01), Mirabile

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