A hybrid vehicle system comprises an engine (1), a gearbox (4),
a
clutch (3) for engaging or disengaging the gearbox (4) with or from
the engine (1), a rotating machine (2), a power transmission mechanism
(5) for transmitting the rotation of the rotating machine (2) to
the gearbox, and a capacitor (7) for storing electric power supplied from
the rotating machine (2). A control unit (20) computes the drive
force required by the vehicle, and determines the portion of output to be produced
by the rotating machine (2) according to the stored energy in the capacitor
(7) and the portion of output to be produced by the engine (1) so
that the drive force requirement may be satisfied. The outputs from the rotating
machine (2) and the engine (1) are controlled to obtain the determined
portions of output, and a clutch (3) is then engaged.
