Abstract: In the case of the on setting of an eco switch signal ESW, when a torque demand Tr* is less than a good fuel consumption-assuring minimum torque Temin, the hybrid vehicle of the invention stops the operation of an engine and controls a motor MG2 to output a required torque for constant speed drive. When the torque demand Tr* is not less than the good fuel consumption-assuring minimum torque Temin, on the other hand, the engine is driven at a drive point in a good fuel consumption range among drive points on an optimum fuel consumption operation curve to ensure output of the required torque for the constant speed drive. Such control enhances the fuel efficiency for the constant speed drive.

Abstract: In a constant speed drive (in an auto cruise), the procedure of the invention executes proportional control to set an accelerator opening Acc corresponding to an observed vehicle speed and a target vehicle speed. When the accelerator opening Acc is less than a preset opening A2 included in a dead zone where a torque demand Tr* is kept equal to 0, the procedure corrects the accelerator opening Acc to have a corresponding torque demand Tr* included in a negative zone where the torque demand Tr* takes negative values and linearly increases. This arrangement heightens the linearity of the graph of the torque demand Tr* against the accelerator opening Acc in the constant speed drive, compared with the linearity in a standard drive.

Abstract: In the case of the on setting of an eco switch signal ESW, when a torque demand Tr* is less than a good fuel consumption-assuring minimum torque Temin, the hybrid vehicle of the invention stops the operation of an engine and controls a motor MG2 to output a required torque for constant speed drive. When the torque demand Tr* is not less than the good fuel consumption-assuring minimum torque Temin, on the other hand, the engine is driven at a drive point in a good fuel consumption range among drive points on an optimum fuel consumption operation curve to ensure output of the required torque for the constant speed drive. Such control enhances the fuel efficiency for the constant speed drive.

Abstract: In a constant speed drive (in an auto cruise), the procedure of the invention executes proportional control to set an accelerator opening Acc corresponding to an observed vehicle speed and a target vehicle speed. When the accelerator opening Acc is less than a preset opening A2 included in a dead zone where a torque demand Tr* is kept equal to 0, the procedure corrects the accelerator opening Acc to have a corresponding torque demand Tr* included in a negative zone where the torque demand Tr* takes negative values and linearly increases. This arrangement heightens the linearity of the graph of the torque demand Tr* against the accelerator opening Acc in the constant speed drive, compared with the linearity in a standard drive.