METHOD FOR CONTROLLING A WASTE-HEAT UTILIZATION SYSTEM FOR A MOTOR VEHICLE

摘要

The invention relates to a method for controlling a waste-heat utilization system (20) for a motor vehicle driven by an internal combustion engine (10) by means of a drive train (13), wherein the waste-heat utilization system (20) has at least one expander (22), at least one evaporator (21), and at least one pump (24) for an operating medium, in particular ethanol. At least the evaporator (21) is arranged in the region of the exhaust gas system (11) of the internal combustion engine (10). The expander (22), which can be operated in several operating modes, performs work in at least one operating mode. One operating mode of at least two operating modes (1, 2, 4, 5) of the expander (22) is selected by a control device (30) on the basis of at least one input variable from the group of expander rotational speed (n), gear information (GI), coasting information (CI), and pressure (p1, p2) and temperature (T1, T2) of the operating medium upstream or downstream of the expander (22) and the expander (22) is operated in said operating mode. A first operating mode (1) is associated with a warm-up phase of the expander (22) and a second operating mode (2) is associated with a normal operating phase of the expander (22). The bypass valve (26) is opened in the first operating mode (1) and closed in the second operating mode. The second operating mode (2) is selected if the pressure (p2) and/or the temperature (T2) of the operating medium downstream of the expander (22) exceeds a defined value.