System for limiting turbocharger rotational speed

#The present invention relates generally to systems for limiting turbocharger rotational speed, and more specifically to systems for preventing turbocharger overspeed conditions without requiring a turbocharger rotational speed sensor.

#Turbochargers are well known devices for pressurizing intake air entering the combustion chambers of an internal combustion engine to thereby increase the efficiency and power output of the engine. In general, pressurizing the intake air increases the quantity of air entering the engine cylinders during the intake stroke, and this allows more fuel to be utilized in establishing a desired air-to-fuel ratio. Increased available engine output torque and power is thereby realized. In a turbocharged engine, the exhaust manifold of the engine is fluidly coupled to a turbine of the turbocharger, and the exhaust gas flowing to the turbine causes a turbine wheel to rotate at a speed determined by the pressure and flow rate of exhaust gas. A compressor wheel within a compressor of the turbocharger is mechanically coupled to the turbine wheel, and is therefore rotatably driven by the turbine wheel. An inlet of the compressor receives fresh ambient air, and an outlet of the compressor is fluidly coupled to the intake manifold of the engine. The rotatably driven action of the compressor wheel increases the amount of intake air supplied to the intake conduit, thereby resulting in an increased, or so-called “boost”, pressure therein. In such systems it may be desirable to limit the rotational speed of the turbocharger to avoid turbocharger overspeed conditions.

#The present invention may comprise one or more of the following features and combinations thereof. A system for limiting turbocharger rotational speed may comprise a turbocharger having a compressor defining a compressor outlet fluidly coupled to an intake manifold of an internal combustion engine and a compressor inlet, and having a turbine defining an exhaust gas inlet fluidly coupled to an exhaust manifold of the engine and an exhaust gas outlet. A first pressure sensor may produce a first pressure signal indicative of pressure at the compressor inlet. A first temperature sensor may produce a first temperature signal indicative of temperature at the compressor inlet. Means may be provided for determining an operating condition other than the pressure and the temperature at the compressor inlet, and producing a corresponding operating condition indicator. A control mechanism may be provided for controlling a swallowing capacity or efficiency of the turbine. A control computer may be configured to determine a maximum compressor outlet pressure value as a function of the first pressure signal, the first temperature signal, the operating condition indicator and a maximum turbocharger speed value, and to control the control mechanism in a manner that limits compressor outlet pressure to the maximum compressor outlet pressure value to thereby limit rotational speed of the turbocharger to the maximum turbocharger speed value.

#FIG. 1 is a schematic and block diagram of one illustrative embodiment of a system for limiting turbocharger rotational speed.

#FIG. 2A is a schematic and block diagram of one illustrative mechanism for controlling the swallowing capacity or efficiency of the turbocharger of FIG. 1.

#FIG. 2B is a schematic and block diagram of another illustrative mechanism for controlling the swallowing capacity or efficiency of the turbocharger of FIG. 1.

#For the purposes of promoting an understanding of the principles of the invention, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.

#Referring now to FIG. 1, one illustrative embodiment of a system 10 for limiting turbocharger rotational speed is shown. System 10 includes an internal combustion engine 12 having an intake manifold 14 fluidly coupled to an outlet of a compressor 16 of a turbocharger 18 via an intake conduit 20, wherein the compressor 16 also includes a compressor inlet coupled to an intake conduit 22 for receiving fresh ambient air. The turbocharger compressor 16 is mechanically coupled to a turbine 24 via a drive shaft 25, wherein turbine 24 includes a turbine inlet fluidly coupled to an exhaust manifold 26 of engine 12 via an exhaust conduit 28, and further includes a turbine outlet fluidly coupled to ambient via an exhaust conduit 30.

#System 10 includes a control computer 32 that is illustratively microprocessor-based and is generally operable to control and manage the overall operation of engine 12. Control computer 32 includes a memory unit 35 as well as a number of inputs and outputs for interfacing with various sensors and systems coupled to engine 12. Control computer 32, in one embodiment, may be a known control unit sometimes referred to as an electronic or engine control module (ECM), electronic or engine control unit (ECU) or the like, or may alternatively be a general purpose control circuit capable of operation as will be described hereinafter. In any case, control computer 32 includes one or more control algorithms, as will be described in greater detail hereinafter, for limiting turbocharger rotational speed based on input signals provided by a number of engine and/or turbocharger operating condition sensors.