US Patent 10392005 Hybrid electric vehiclecapable of switching driving modes based on gradient

A hybrid electric vehicle including a gradient acquiring portion which acquires a gradient of a road surface on which the vehicle is running, and a control portion which determines whether the vehicle runs on a first driving by means of power from the motor by releasing the engagement and disengagement portion, or on a second driving by means of power from at least the internal combustion engine by applying the engagement and disengagement portion. The control portion restricts a switch from the second driving to the first driving when the gradient of the downward slope is equal to or greater than a threshold value. The control portion holds the second driving when the switch from the second driving to the first driving is restricted, even though the control portion obtains a request for a switch to the first driving while the vehicle runs the downward slope on the second driving.