Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-05-03
2001-04-03
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S602000, C060S611000, C123S572000, C123S322000, C415S157000, C415S158000, C415S160000, C415S164000
Reexamination Certificate
active
06209324
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German application 198 19 699.7-13, filed in Germany on May 2, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an exhaust turbocharger for an internal combustion engine and an engine equipped therewith, said exhaust turbocharger being provided with a main compressor for compressing fresh air to be supplied to the engine, an additional compressor for compressing the combustion exhaust gases recycled to engine, a turbine that can be driven by the exhaust gases from the engine and which serves to drive the main compressor and the additional compressor, an exhaust return line by which the exhaust gases to be returned to the engine are supplied to the additional compressor, and a boost air line by which the air compressed in the main compressor is supplied to the engine.
Exhaust turbochargers are regularly used for increasing the performance of vehicle engines, especially in motor vehicles, with reduced fuel consumption being possible at the same time. An exhaust turbocharger of the type recited at the outset is known from German Patent Document DE 43 12 078 A1. In order for exhaust recycling, especially for reduction of NOx emissions, to be feasible in an engine with an exhaust turbocharger, the recycled exhaust gases must have at least the same pressure as the boost air supplied to the engine for combustion and to be mixed with the recycled exhaust gases. Since an exhaust return line removes a portion of the exhaust gases to be recycled for combustion before they enter the turbine of the turbocharger, the required pressure in the recycled exhaust gases in conventional exhaust turbochargers that operate without an additional compressor can be produced by a corresponding buildup of the exhaust gases upstream of the turbine. For this purpose, the turbine guide grid of the exhaust turbocharger turbine is designed to produce appropriate throttling. However, as a result of this throttling, the performance, and especially the efficiency of the turbine is significantly reduced in particular. In distinction to this, the abovementioned known turbocharger for producing the pressure required to recycle the exhaust has an additional compressor that is driven by the turbine together with the main compressor. This feature makes it possible to run the turbine of the exhaust turbocharger with improved efficiency. Then sufficient surplus power is available in order to increase the exhaust to be recycled to the necessary (boost) pressure in the additional compressor.
The quantity of recycled exhaust required for achieving favorable pollutant emission values depends on the individual operating state of the engine (load, rpm). Similarly, the pressure required for boosting the engine is likewise dependent on the operating state of the engine. Deviation from the optimum boost pressure for the individual operating state leads to increased charge changing losses and consequently to power losses and increased fuel consumption by the engine. The known exhaust turbocharger can be designed only for a specific operating point of the engine as regards optimum values both for pollutant emissions and also for engine power and fuel consumption. At all operating points that differ from this, deterioration of at least one of these values can occur.
The present invention is concerned with the problem of designing an exhaust turbocharger of the type recited at the outset so that an internal combustion engine equipped with it is improved as regards pollutant emissions, fuel consumption, and performance.
This problem is solved according to the invention by an exhaust turbocharger of the above described general type, wherein the turbine has a variable geometry and a first control member is located in the exhaust return line to selectively connect the exhaust return line to the intake side of the additional compressor or to the boost air line.
The invention is based on the general idea of designing the turbine used for driving the main compressor and the additional compressor as variable turbines with variable geometry.
Preferably adjustable guide grids, rotatable guide blades, axially displaceable guide grid rings or flaps in the turbine area or the like can be used to vary the throughput geometry of the turbine. A turbine of this kind is basically known for example from German Patent Documents DE 33 22 436 A1, DE 43 03 521 C1, and DE 43 30 487 C1. The use of a variable turbine of this kind in an exhaust turbocharger that has an additional compressor for exhaust recycling permits the exhaust recycling to be influenced by changing the accumulated pressure in the exhaust gases upstream of the turbine. A change of this kind in the accumulated pressure upstream of the turbine firstly has a indirect influence on the exhaust recycling rate and secondly produces a change in the turbine power and consequently a change in the boost pressure that can be produced in the main compressor and in the additional compressor, and thus also exerts an indirect influence on the exhaust recycling rate. Because of these effects that are linked to one another, an improvement in the values for pollutant emissions, engine power, and fuel consumption can be achieved.
The design of the exhaust turbocharger according to the invention permits optimization of engine operation over the entire range of engine operating states as regards fuel consumption, pollutant emissions, and engine performance.
In one preferred embodiment of the exhaust turbocharger according to the invention, a gas line connection can be provided with which the gases compressed in the additional compressor can be fed into a boost air line through which the air compressed in the main compressor is supplied to the engine.
In an improvement on the exhaust turbocharger, a boost air cooler can be provided in the boost air line. The gas line connection coming from the additional compressor is then connected to the boost air line downstream of this boost air cooler and upstream of the engine. This measure prevents contamination of the boost air cooler by materials transported in the exhaust, soot particles for example.
In certain preferred embodiments of the turbocharger according to the invention, a control member can be located in an exhaust return line through which the exhaust gases recycled to the engine can be supplied to the additional compressor, by which control member the quantity of exhaust flowing into the exhaust return line can be controlled. With this measure, the exhaust recycling rate can be additionally influenced in order better to adapt it to the respective operating conditions of the engine and to shut it off as well if necessary.
In accordance with certain preferred embodiments of the exhaust turbocharger according to the invention, an additional control member can be provided in the exhaust return line by which the exhaust return line can be connected either to the intake side of the additional compressor or to the gas line connection to the boost air line or directly to the boost air line. With the aid of this additional control member, it is possible to cause the exhaust stream to be recycled to bypass the additional compressor. This can be advantageous at certain operating points of the engine or of the turbine in which an accumulated pressure builds up in the exhaust upstream of the turbine, said pressure guaranteeing the optimum exhaust recycling rate for this operating point.
In addition, advantages are gained if the exhaust turbocharger according to the invention is used in an internal combustion engine which, in addition to the exhaust turbocharger according to the invention, has an exhaust recycling device and a control device that permits switching engine operation between driving operation and braking operation. The exhaust turbocharger and a control device are designed so that the control device controls or actuates the exhaust turbocharger to regulate the engine braking power during braking operation. An exhaust turboch
Daudel Helmut
Finger Helmut
Sumser Siegfried
Daimler-Chrysler AG
Denion Thomas
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Trieu Thai-Ba
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