Drive control system for vehicle

A drive control system for a vehicle, the drive control system comprising:

• an engine;
• an electric motor;
• a selectable one-way clutch including an annular fixed plate on which engaging pieces are mounted, an annular rotating plate engaged with the engaging pieces, and an annular selector plate provided between the fixed plate and the rotating plate, the selectable one-way clutch being configured to selectively switch between an engaged state and a non-engaged state, the engaged state being a state in which the selector plate is in an open state such that the engaging pieces engage with the rotating plate to restrict a rotational direction of the rotating plate to one direction, the non-engaged state being a state in which the selector plate is in a closed state such that the engaging pieces cannot engage with the rotating plate, and the non-engaged state being a state in which the rotating plate can rotate in both directions;
• a planetary gear mechanism including an input element coupled to the engine, an output element that transmits power toward drive wheels, and a reaction-force element, as at least three rotating elements, the reaction-force element being configured to rotate integrally with the rotating plate and to be selectively non-rotatably fixed by the selectable one-way clutch, the planetary gear mechanism being configured to distribute power generated from the engine to the electric motor side and the drive wheels side when the selectable one-way clutch is in the non-engaged state;
• an actuator including a movable member coupled to the selector plate, the actuator being configured to switch the selector plate between the open state and the closed state;
• a sensor configured to detect a position of the movable member, and output a signal corresponding to the position;
• and
• an electronic control unit configured to:
• (i) determine whether a malfunction occurs due to a first failure or a second failure, the malfunction being detection of the open state of the selector plate while the vehicle is traveling with the selectable one-way clutch controlled to be in the non-engaged state, the first failure being a condition where the selector plate is actually placed in the open state, the second failure being a condition where the sensor outputs the signal indicating the open state of the selector plate, even though the selector plate is actually in the closed state;
• (ii) execute a first limp-home traveling mode in which the vehicle travels while causing the electric motor to keep a rotational direction of the reaction-force element equal to said one direction, when the malfunction is caused by the first failure;
• and
• (iii) execute a second limp-home traveling mode in which the drive wheels are driven by the engine while the selectable one-way clutch is kept in the non-engaged state, and the electric motor generates electric power, using power distributed to the electric motor side by the planetary gear mechanism, when the malfunction is caused by the second failure.