Patent Application
20140271234
This application relates to turbocharger systems within internal combustion engines, more particularly, to exhaust-driven turbochargers having a magnetic brake.
Internal combustion engines, its mechanisms, refinements and iterations are used in a variety of moving and non-moving vehicles or housings. Today, for example, internal combustion engines are found in terrestrial passenger and industrial vehicles, marine, stationary, and aerospace applications. There are generally two dominant ignition cycles commonly referred to as gas and diesel, or more formally as spark ignited and compression ignition, respectively. More recently, exhaust-driven turbochargers have been incorporated into the system connected to the internal combustion engine to improve the power output and overall efficiency of engine.
Turbochargers are generally incorporated to increase engine performance. In such applications, turbochargers often require control of their speed (the RPMs at which the turbine or compressor wheel rotates) so that either compressor surge or over speed does not occur. Typically, turbo speed control is accomplished by valves, levers and/or actuated devices that bypass exhaust gas around the turbine housed in the turbine section of the turbocharger. These types of controls include several moving parts that can wear over the life of the turbocharger and ultimately wear out.
There is a need to continue to improve the exhaust-driven turbochargers, including the efficiency, power, and control thereof, in particular the turbo speed control.
In one aspect, turbochargers are disclosed herein that can replace or augment the turbo speed control previously existing, such as that accomplished by valves, levers, and actuated devices, by including a braking system for the compressor wheel utilizing Lenz's law. Here, a non-contacting, non-friction brake system is disclosed that includes one or more electromagnets positioned proximate to the compressor wheel, which is electrically conductive, and a control circuit electrically coupled to the one or more electromagnets to turn the one or more electromagnets on or off to provide braking action to the compressor wheel. When the electromagnet(s) are activated the magnetic field generated thereby brakes the compressor wheel and as a result reduces the turbo speed of the turbocharger.
In another aspect, a system is disclosed that includes the turbocharger described in the preceding paragraphs and an internal combustion engine in fluid communication therewith. The system may also include an engine control unit that communicates with the control circuit of the brake system to turn the electromagnet(s) on or off as needed. In one embodiment, the control circuit receives commands from the engine control unit to activate the electromagnet(s) to brake the compressor wheel in coordination with at least one engine function to avoid a surge in the compressor section of the turbocharger or over revving of the turbine.
In another aspect, methods for controlling the rotational speed of a turbocharger are disclosed. The method may include providing a turbocharger such as those described herein having electromagnet(s) and a control circuit, and operating the control circuit to allow electric current to flow to the one or more electromagnets to create a magnetic field to slow the rotations of the compressor wheel.
The following detailed description will illustrate the general principles of the invention, examples of which are additionally illustrated in the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.
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In one embodiment, the electromagnets 128 may be composed of an iron core with coils of wire wound around the core. The electromagnets provide the ability to control the strength of the magnetic flux density, the polarity of the field, and the shape of the field. The strength of the magnetic flux density is controlled by the magnitude of the current flowing in the coil, the polarity of the field is determined by the direction of the current flow, and the shape of the field is determined by the shape of the iron core around which the coil is wound. Additionally, the braking system may be controlled and/or adjusted by changing the number of electromagnets, their spacing, orientation, and location relative to the compressor wheel.
The braking system in the turbocharger 102 has many benefits over conventional methods of turbine speed control, especially over by-pass systems using valves, levers and actuators. One benefit is the utilization of the magnetic fields created by the electromagnets in that the electromagnets act very fast to provide braking, which reduces response time and allow increased turbo performance. Accordingly, the turbo speed (surge) safety margins can be reduced due to the instantaneous turbo speed braking action. Another benefit is that the braking system has no moving parts other than the compressor wheel, which was already present. The electromagnetic braking system provides the additional benefit of being a variable controlled system by electronically controlling the strength of the magnetic field. This proportional braking provides greater turbo speed control by applying only the minimum braking required to maintain proper turbine/compressor wheel speed.
As discussed above, the braking system can avoid surge or over revving, which could result in catastrophic failure of the turbocharger. This in turn would prevent engine catastrophic damage from the engine ingesting debris from the turbocharger failure.
Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention which is defined in the appended claims.
