Motor-assisted variable geometry turbocharging system

Abstract

The motor-assisted variable geometry turbocharging system has a motor to add power to the turbocharging shaft, especially at low exhaust gas volume. Additionally, the turbocharger has control over compressor air inlet direction and / or control of exhaust gas to a two-volute expander. These are individually controlled directly or indirectly from an engine controller to enhance turbocharger performance. In a preferred embodiment, the motor is an electric motor, mounted directly on the turbocharger shaft intermediate the turbo expander and turbo compressor and within the main housing.

Description

FIELD OF THE INVENTIONThe present invention relates generally to variable geometry components used in turbochargers applied to internal combustion engines that operate over a broad range of speed and load.BACKGROUND OF THE INVENTIONFixed geometry turbochargers can be designed to operate efficiently at a particular engine load and speed. However, when operated over a broad range of engine speed and load, the compressor and turbine components are forced to function off their design points and consequently suffer losses in efficiency that affects engine performance adversely. If the turbocharger is matched to an engine at the engine's rated speed, it will run considerably off its maximum efficiency where the engine is "torqued down" to low engine operating speeds. Conversely, if the turbocharger is matched to an engine's low speed range, the turbocharger will have a tendency to "overspeed" when the engine is operated at maximum speed and load.To prevent overspeeding in turbochargers th...

AI Technical Summary

Benefits of technology

In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed to a motor-assisted variable geometry turbocharging system. The variable geometry is provided by the exhaust gas flow configuration into the exhaust gas turbine and / or the air inlet flow into the air compressor, together with a motor drive for both the turbine and compressor to enhance performance of a variable geometry turbocharging system.

It is thus a purpose and advantage of this invention to provide a motor drive for the turbo expander shaft to supply power into the turbocharger system in addition to that which can be achieved by extraction from the exhaust gas, even with a two-volute turbo expander to enhance performance, especially at low exhaust gas flow rates.

It is a further purpose and advantage of this invention to provide a motor for adding power to a turbocharger which also includes control of the air inlet to the turbo compressor, to enhance performance of the turbocharger even when it is equipped with prewhirl vanes upstream of the compressor wheel which controls the rotation of the air as it enters the inducer of the compressor wheel, to enhance performance of such systems by providing the power necessary to provide adequate pre-whirl even at low exhaust gas flow rates.

It is a further purpose and advantage of this invention to supply power to a turbocharger which is driven by exhaust gas expansion by including a motor to supply torque to aid in rotating the shaft in the same direction as exhaust gas expansion, and to include such a turbocharging motor together with control of air flow into the turbo compressor to enhance vehicle performance.

It is a further purpose and advantage of this invention to provide a motor connected to a turbo compressor shaft and control the motor in addition to controlling exhaust gas flow to the turbine and / or air flow into the turbo compressor to enhance engine performance.

Problems solved by technology

However, when operated over a broad range of engine speed and load, the compressor and turbine components are forced to function off their design points and consequently suffer losses in efficiency that affects engine performance adversely.

Conversely, if the turbocharger is matched to an engine's low speed range, the turbocharger will have a tendency to "overspeed" when the engine is operated at maximum speed and load.

The waste gate, however, allows the escape of exhaust gas energy, which could be better utilized by the turbocharger turbine and results in a substantial loss in system efficiency.

The various movable devices that have been employed in the turbocharger turbine have been complicated, expensive, and subject to questionable durability.

Consequently, they have met with limited commercial success.

However, this causes a movement of the compressor efficiency islands and choke area to lower flow and can result in lowering the compressor efficiency when the engine is operating at high speed and load.

Variable diffuser vanes is one type of variable geometry compressor that could be employed, but the movable vanes cause significant mechanical complication internally in the construction of the turbocharger and must be precisely positioned by a rather elaborate control system.

Positive pre-whirl moves the compressor operating vane to lower flow and usually lowers compressor efficiency somewhat.

Both the flapper valve and the pre-whirl vanes are external from the turbocharger construction, resulting in much lower overall cost than other devices that must be built into the internal construction of the turbocharger.

At very low engine speed, for example, at low idle, there is insufficient exhaust gas energy to drive turbocharger fast enough to produce significant levels of boost.

Consequently, there is an appreciable lag time between opening of the engine throttle and when the turbocharger is running fast enough to produce enough boost pressure to eliminate smoke on acceleration, for example.

These fuel limiting devices cause slower response to throttle opening and a sluggishness in engine and vehicle response.

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