HYBRID VEHICLE DRIVE SYSTEM

A drive system of a hybrid vehicle including an internal combustion engine, a first motor-generator, a first power transmission path and a second power transmission path, a power division mechanism, a second motor-generator, a clutch portion provided at the power transmission path to make or break the first power transmission path, and a microprocessor. The microprocessor is configured to determine whether a drive in a region exceeding a characteristic curve of a driving force defined by a sum of a driving force output through the first power transmission path and a driving force of the second motor-generator at a low vehicle speed is necessary, and to control the clutch portion to a half-clutch state when determining that the drive in the region is necessary, while connecting or disconnecting the clutch portion when determining that the drive in the region is not necessary.