Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Patent
1995-09-08
1997-12-30
Koczo, Michael
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
F02B 3712
Patent
active
057017417
DESCRIPTION:
BRIEF SUMMARY
This invention relates to turbochargers for internal combustion engines and relates more particularly to the control of the exhaust gas driven turbine of a turbocharger.
With the increase in popularity of compression ignition engines, particularly in passenger cars and light commercial vehicles, there is an incentive to provide small turbochargers for such engines to enhance their power output. With a well designed turbocharger a compression ignition engine can produce a power output which is similar to an engine of much larger capacity. Moreover the environmental cleanliness and fuel consumption may even show improvements relative to petrol engines. Again, a turbocharger employed on a petrol engine can greatly increase its power output.
A typical exhaust gas driven turbocharger comprises a bearing housing assembly supporting a rotatable shaft, one end of which carries an air compressor wheel enclosed by a compressor housing and the other end of which carries a turbine wheel enclosed by a turbine housing and which is subjected to exhaust gas flow to drive the compressor.
In order to constrain the boost pressure which such a turbocharger can produce at the air induction manifold of the engine, it has been proposed to provide a so-called "wastegate" including a controllable exhaust gas by-pass valve. Typically, such a wastegate valve has comprised a spring biased poppet valve having a valve stem connected to a pressure responsive diaphragm subject, in a valve opening direction, to a control pressure derived from the output of the turbocharger compressor. By providing such a wastegate it is possible to prevent a turbocharger from overboosting and advantageously to improve the matching of the operation of the turbocharger to the demands of the engine. However, the control thereby achieved is only approximate because the system is pneumatic and is dependent not only upon the boost pressure but also upon the value of a spring bias, the effective control areas and the exhaust gas pressure acting on the valve. In practice such control is only a compromise consistent with providing reasonable engine performance whilst preventing possible damage to the engine due to overboosting.
An alternative form of turbocharger control has also been proposed in which the input nozzle geometry of a drive turbine of a turbocharger is variable. One form of such a variable input nozzle is described in EP-A-0 571 205 published on 24 Nov. 1993, the disclosure of which is incorporated herein by way of reference. In such a proposal the turbine housing of the turbocharger has an inlet nozzle for receiving exhaust gases from an engine and is shaped to conduct such gases to impinge upstream edges of blades of a turbine wheel. The nozzle has axially spaced side walls extending about said upstream edges of the turbine wheel and axially extending spaced and angled vanes traverse the space defined between the side walls and are carried by one side wall and are receivable in slots in the other side wall. One side wall is formed by one end of an axially movable sleeve slidably carried in a bore of the housing downstream of the turbine wheel and means are provided axially to move the sleeve to thereby vary the geometry of said nozzle in response to air pressure derived from the output of the turbocharger compressor. Again, as in the case of a wastegated turbocharger, pneumatic control of the variable nozzle geometry is dependent upon fixed and variable parameters and these may be less than ideal for all operating conditions of the engine.
An object of the invention is to provide a turbocharger for an internal combustion engine with an improved control mechanism which better lends itself to respond to the requirements of the respective internal combustion engine.
According to one aspect of the present invention there is provided a turbocharger comprising a drive-shaft mounted in bearing means in a housing, the drive-shaft drivably connecting an exhaust gas driven turbine wheel to the impeller of a compressor, a gas flow control device positioned u
REFERENCES:
patent: 2354573 (1944-07-01), Brock
patent: 2477668 (1949-08-01), Sparrow
patent: 4097786 (1978-06-01), Lund
patent: 4174617 (1979-11-01), Karchay
patent: 4280680 (1981-07-01), Payne
patent: 5174119 (1992-12-01), Hanauer et al.
Allied-Signal Inc.
Fischer Felix L.
Koczo Michael
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