Vehicle power transmission device and control system for power transmission

A power transmission control system for a vehicle comprising:

• a power transmission device including (a) a power split device which includes a first, a second, and a third rotor which rotate in conjunction with each other to split power among an electric rotating machine, an internal combustion engine, and a driven wheel of the vehicle, the first, the second, and the third rotor being so linked as to have rotational speeds that are arrayed on a straight line when graphically displayed in a nomographic chart, (b) a torque transmission control mechanism which selectively establishes and blocks transmission of torque between the first rotor and the internal combustion engine, (c) a first connecting mechanism which establishes a mechanical connection between the second rotor and the third rotor, (d) a second connecting mechanism which establishes a mechanical connection between the first rotor and the second rotor, and (d) a speed variator which has a variable input-to-output speed ratio, wherein when the torque transmission control mechanism establishes the transmission of torque between the first rotor and the internal combustion engine, powers of the second and third rotors are opposite in sign to each other;
• and
• a controller configured to control operations of the first and second connecting mechanism to switch between a first and a second operation mode, the first operation mode being to establish the mechanical connection between the second and third rotors through the first connecting mechanism and block the mechanical connection between the first and second rotors through the second connecting mechanism, the second operation mode being to block the mechanical connection between the second and third rotors through the first connecting mechanism and establish the mechanical connection between the first and second rotors through the second connecting mechanism, the controller also configured to control the input-to-output speed ratio of the speed variator so that a total input-to-output speed ratio of a power transmission path extending from one of the internal combustion engine and the electric rotating machine to the driven wheel has values different between the first and second operation modes, the controller configured to establish the mechanical connections through the first and second connecting mechanisms when a travel permission switch for the vehicle is turned off.