Method and device for engine braking

摘要

A method for engine braking of an engine which has at least one exhaust-gas turbocharger with an exhaust-gas turbine acted on by an exhaust-gas flow and a charge air compressor. A device for throttling exhaust-gas flow is arranged between exhaust outlet valves and the exhaust-gas turbocharger, and a bypass line conducts the exhaust-gas flow past the throttling device, the exhaust-gas flow being conducted through the at least one bypass line to a turbine wheel of the exhaust-gas turbine. An exhaust gas counter-pressure and a charge air pressure are measured. Based on the measurement, an optimum position of the throttling device to obtain a predetermined braking action is determined. The exhaust-gas counter-pressure and the charge air pressure are subsequently controlled by adjusting the throttling device corresponding to the determination of the optimum position of the throttling device.

主权项

1. A method for engine braking of an engine, the engine having:
at least one exhaust-gas turbocharger with an exhaust-gas turbine acted on by an exhaust-gas flow and a charge air compressor, the exhaust-gas turbine and the charge air compressor being commonly mounted on a common shaft; an exhaust gas manifold disposed to conduct the exhaust-gas flow from outlet valves of the engine to the exhaust-gas turbocharger; a throttling device for throttling the exhaust-gas flow between the outlet valves and the at least one exhaust-gas turbocharger; and at least one bypass line for conducting the exhaust-gas flow past the throttling device; the method which comprises: conducting the exhaust-gas flow through the at least one bypass line to a turbine wheel of the exhaust-gas turbine, throttling the exhaust-gas flow and thus generating a pressure increase in the exhaust gas upstream of the throttling device for throttling the exhaust-gas flow, and taking a measurement of an exhaust-gas counter-pressure and of a charge air pressure; determining, based on the measurement of the exhaust-gas counter-pressure and of the charge air pressure, a position of the throttling device to obtain a predetermined braking action; and controlling the exhaust-gas counter-pressure and the charge air pressure by way of the throttling device in accordance with the determined position of the throttling device for throttling the exhaust-gas flow; wherein the controlling step includes performing a determination that a current exhaust-gas counter-pressure lies below a desired exhaust-gas counter-pressure and the charge air pressure corresponds to a desired value, and in response to the determination, closing the position of the throttling device further; and wherein the controlling step includes performing a further determination that the current exhaust-gas counter-pressure lies below the desired exhaust-gas counter-pressure and the charge air pressure lies below the desired value, and in response to the further determination, opening the position of the throttling device further.