Patent ID: 8903585

Claim:
A control system for controlling a hybrid vehicle including an internal combustion engine and a motor/generator as power sources, a friction engagement element interposed between the power sources and drive wheels, the transmission interposed between the power sources and drive wheels, and a rotation speed detection unit to detect either input rotation speed or output rotation speed of the transmission, comprising: a start request unit to request a start of the internal combustion engine; a slip determination unit to determine whether or not the friction engagement element is allowed to slip; a start determination unit to determine whether or not to allow the internal combustion engine to start, wherein the start determination unit that, responsive to receipt of the start request of the internal combustion engine from the start request unit: issues a command to reduce torque capacity of the friction engagement element; prevents the internal combustion engine from starting when the slip determination unit determines that the friction engagement element is not allowed to slip, and within a predetermined time after the command issues while a rotation speed of the transmission is below a predetermined value; allows the internal combustion engine to start by permitting a start control unit to execute a normal start control process to start the internal combustion engine with the friction engagement element in a slipped state when the slip determination unit determines that the friction engagement element is allowed to slip within the predetermined time after the command issues while the rotation speed of the transmission is below the predetermined value; allows the internal combustion engine to start by permitting the start control unit to execute a back-up start control process to start the internal combustion engine with the friction engagement element engaged when the slip determination unit determines that the friction engagement element is not allowed to slip responsive to the command and the rotation speed of the transmission is at or above the predetermined value; and permits, during the back-up start control process, the start control unit to switch to the normal start control process to start the internal combustion engine while maintaining the friction engagement element in the slipped state when the slip determination unit determines that the friction engagement element is allowed to slip.