Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2001-01-19
2002-07-16
Nguyen, Hoang (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S600000
Reexamination Certificate
active
06418719
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to control systems for turbochargers. More particularly, this invention relates to control systems that sense the exhaust gas pressure to control variable geometry turbochargers on internal combustion engines.
BACKGROUND OF THE INVENTION
Many internal combustion engines use turbochargers to improve engine performance. A turbocharger increases the density of the intake air into the engine. The higher density air increases the amount of fuel the engine may combust. As a result, the power output of the engine increases.
Turbochargers typically have a turbine and a compressor connected by a common shaft. The turbine has blades attached to a wheel, which is mounted on the shaft. A turbine housing encloses the turbine and connects to the exhaust gas manifold of the engine. The turbine housing has vanes for directing the exhaust gases against the turbine blades. The compressor has blades attached to another wheel, which also is mounted on the shaft. A compressor housing encloses the compressor and connects to the intake air manifold of the engine. The compressor housing has vanes for assisting the compressor to pressurize intake air. The compressor housing is isolated from the turbine housing.
In operation, exhaust gases pass through the exhaust gas manifold into the turbine housing. The vanes in the turbine housing direct the exhaust gases against the turbine blades. The exhaust gas pressure causes the turbine to spin, which causes the compressor to spin. The spinning compressor pressurizes the intake air. As a result, higher density air is provided to the intake air manifold.
In a turbocharger, the exhaust gas pressure has a direct effect on the intake air pressure. As the exhaust gas pressure increases, the turbine and consequently the compressor spin faster. A faster spinning compressor increases the intake air pressure. The opposite effect occurs as the exhaust gas pressure decreases.
Many turbochargers have a fixed geometry. The vanes in the turbine and compressor housings are stationery. By design, a fixed-geometry turbocharger operates efficiently at a particular engine speed and load. Conversely, it operates less efficiently at engine speeds and loads for which it is not designed.
At low engine speeds, the exhaust gas pressure is low. It may be below the minimum necessary for operating the turbine. As the engine accelerates from idle or slow speeds, there is a delay from the time when the engine load increases to the time when there is sufficient exhaust gas pressure to spin the turbine. Even when the turbine spins, the exhaust gas pressure may not reach a high enough pressure fast enough to spin the turbine as fast as it is necessary for the compressor to produce the desired intake air pressure.
The exhaust gas pressure increases as engine speed increases. At some point, the pressure becomes high enough to overpower the turbocharger. An overpowered turbocharger reduces engine performance. Additionally, the high exhaust pressure associated with an overpowered turbocharger may cause the turbocharger to fail from fatigue, broken seals, and similar problems.
To improve efficiency, fixed-geometry turbochargers are sized to provide high compressor speeds at low engine speeds. The vanes in the turbine housing usually narrow to increase the exhaust gas pressure. The vanes also direct the exhaust gas flow toward a portion of the turbine blades. While these changes improve the performance of the turbocharger at low engine speeds, they adversely affect the performance of the turbocharger at high engine speeds. The narrowing of the vanes lowers the exhaust gas pressure at which the turbocharger becomes overdriven.
To avoid overdriving, fixed-geometry turbochargers have a waste gate or similar valve positioned between the turbine and the exhaust gas manifold. When the exhaust gas pressure reaches a certain level, the waste gate opens to divert exhaust gases away from the turbine. This approach responds and corrects for an overdriving condition. However, it waits for the condition to occur before responding. It also wastes energy and requires additional equipment.
New turbocharger designs have a variable geometry. The turbine and/or compressor housings have variable nozzles, which move to change the flow area and flow direction. In many designs, only the turbine has variable nozzles.
A variable nozzle turbine (VNT) turbocharger typically has curvilinear nozzles, which rotate between open and closed positions about a pivot. In some designs, the closed position leaves a small gap between the nozzles. In other designs, the nozzles touch when they are closed, which essentially stops the flow of exhaust gas to the turbine. The nozzles connect to each other by a ring or similar apparatus to move in unison. An electronic control module sends an electronic signal to activate a solenoid, pneumatic valve, or similar device.
When the exhaust gas pressure is low, the nozzles close to create a narrower area for the exhaust gases to flow. The narrower area restricts gas flow through the turbine housing, thus increasing exhaust gas pressure. The nozzles also direct the exhaust gases optimally at the tips of the turbine blades. The directed flow and higher pressure enables the turbine to start spinning sooner and at a faster rate. As a result, a VNT turbocharger provides the high compressor speeds desired at low engine speeds.
As the exhaust gas pressure increases, the nozzles open to reduce the restriction to the gas flow. The gas flow also is directed toward the entire length of the turbine blades. With less restriction and broader gas flow, the turbine and consequently the compressor spins slower than if the nozzles were closed under these conditions. As a result, the turbocharger is able to respond and correct for overdriven conditions.
Proper nozzle control is necessary to optimize performance of a VNT turbocharger. Internal combustion engines, especially those in vehicles, have constantly changing demands. One moment, the engine is at low speed. The next moment, the engine is at high speed. Engine load and other parameters change almost constantly. Accordingly, the nozzles must adjust to new operating conditions quickly. If the nozzles delay closing, such as when the engine goes from high to low speeds, the turbocharger will not provide the desired intake air pressure. If the nozzles delay opening, such as when the engine goes from low to high speeds, the turbocharger will be overdriven.
In most designs, VNT turbochargers are controlled by the intake air pressure. The measured intake air pressure is compared to a desired intake air pressure. A sensor is located in the intake air manifold to determine the measured intake air pressure. The engine's electronic control module (ECM) or other microprocessor determines the desired intake air pressure based on engine operating parameters such as engine speed, engine load, ambient air pressure, etc. If the measured intake pressure is higher then the desired intake pressure, the ECM opens the nozzles until the measured and desired intake pressures are equal. Conversely, if the measured intake pressure is lower than the desired intake pressure, the ECM closes the nozzles until the intake pressures are equal.
To open or close nozzles, the ECM sends an electric signal to the solenoid, pneumatic valve, or other device controlling the nozzles. The strength of the electric signal or duty cycle determines the position of the nozzles. The duty cycle is a percentage of the total electrical signal necessary to move the nozzles into their closed position. While the duty cycle is indicative of the nozzle position, the duty cycle for a particular nozzle position varies from turbocharger to turbocharger.
Intake air pressure is not suitable for optimizing the performance of a VNT turbocharger. Generally, the intake air pressure increases as the nozzles close. However, there is position where the intake air pressure reaches a maximum level and then decreases if the nozzles close further.
FIG. 1
shows the relati
Murphy Brian J.
Seiberlich Mathew J.
Terry Wesley J.
Calfa Jeffrey P.
International Engine Intellectual Property Company, L.L.C.
Nguyen Hoang
Powell Neil T.
Sullivan Dennis Kelly
LandOfFree
Control of a variable geometry turbocharger by sensing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control of a variable geometry turbocharger by sensing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control of a variable geometry turbocharger by sensing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2843084