Drive system for hybrid vehicle

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

• an engine configured to start by itself by starting rotating of the engine with combustion energy of a fuel generated in a cylinder from a condition in which rotation is stopped, and increasing a rotational speed to complete starting;
• a first differential mechanism connected to the engine, the first differential mechanism being to transmit rotation of the engine;
• a second differential mechanism to connect the first differential mechanism with drive wheels,
• the second differential mechanism including a first rotational element, a second rotational element, and a third rotational element, the first rotational element connected to an output element of the first differential mechanism, the second rotational element connected to a first rotating machine, and the third rotational element connected to a second rotating machine and the drive wheels;
• a switching device to change a speed ratio of the first differential mechanism;
• and
• an electronic control unit configured to selectively establish a first running condition and a second running condition, the first running condition being a running condition in which the hybrid vehicle runs using the second rotating machine as a power source, in a condition in which the switching device allows differential operation of the first differential mechanism,
• the second running condition being a running condition in which the hybrid vehicle runs using the second rotating machine as a power source, in a condition in which the switching device inhibits operation of the first differential mechanism, and
• a running region in which the hybrid vehicle runs in the second running condition in a case where the engine cannot start by itself, is larger than a running region in which the hybrid vehicle runs in the second running condition in a case where the engine can start by itself.