Control system

1. A control system that performs a control of a hybrid vehicle drive system that includes an input member that is drivingly connected to a rotary electric machine; a clutch that selectively and drivingly connects the input member to an internal combustion engine; an output member that is drivingly connected to a wheel; and a speed change mechanism that includes a plurality of engagement elements, has a plurality of shift speeds selectively formed by controlling the engagement and disengagement of the plurality of engagement elements, and changes a rotational speed of the input member by a speed ratio of the respective shift speeds and transmits the changed rotational speed to the output member, wherein

the speed change mechanism includes a one-way transmission speed as one of the plurality of shift speeds, the one-way transmission speed being a shift speed at which a rotary driving force is transmitted from the input member to the output member and a rotary driving force is not transmitted from the output member to the input member, and

when starting combustion in the internal combustion engine under a combustion-stopped vehicle running condition in which the clutch is disengaged, combustion in the internal combustion engine is stopped, the speed change mechanism forms the one-way transmission speed, and the output member rotates, a rotational speed feedback control is executed that sets a value that multiplies a rotational speed of the output member by a speed ratio of the one-way transmission speed as a reference rotational speed of the input member, sets a starting rotational speed that is lower than the reference rotational speed as a target rotational speed, and controls the rotary electric machine such that the rotational speed of the input member matches the target rotational speed, and during execution of the rotational speed feedback control a start control is performed that increases an engagement pressure of the clutch to increase a rotational speed of the internal combustion engine and start combustion in the internal combustion engine.

2. The control system according to claim 1 , wherein

at least one of the plurality of engagement elements is a one-way clutch, and

the one-way transmission speed is formed by the one-way clutch and engagement of at least one of the plurality of engagement elements other than the one-way clutch.

3. The control system according to claim 1 , wherein

once the internal combustion engine starts combustion and the clutch completes engagement, the target rotational speed is changed and set to a rotational speed that matches the reference rotational speed, and execution of the rotational speed feedback control is continued, with the rotational speed feedback control being terminated following synchronization of the rotational speed of the input member and the reference rotational speed.

4. The control system according to claim 1 , wherein

the combustion-stopped vehicle running condition is further a condition in which transmission of a driving force to the output member is not required.

5. The control system according to claim 1 , wherein

an amplitude of the rotational speed of the input member during execution of the rotational speed feedback control is a feedback control amplitude, and

the starting rotational speed is set to a rotational speed that is lower than the reference rotational speed by a rotational speed that adds a predetermined margin to the feedback control amplitude.