When an engine start command is generated to an engine that is in a stopped state, engine start control for cranking the engine and starting fuel combustion after increasing the engine speed is performed. In the engine start control, one of a first start pattern in which an initial combustion speed is higher than a resonance speed of the engine, and a second start pattern in which the initial combustion speed is lower than the resonance speed of the engine is selected according to the speed ratio (gear position) of a transmission. Cranking torque in the second start pattern is lower than the cranking torque in the first start pattern.

A power transmission device for a hybrid vehicle has a first clutch device (1a) disposed in a drivetrain between an engine (E) and a driving wheel (D). A second clutch device (1b) disposed in a drivetrain extends from a motor (M) to the driving wheel (D). The oil pump (P), connected to the motor (M), supplies oil to a predetermined moving component disposed in the vehicle by using driving power of the motor (M). A transmission (A) is disposed in a drivetrain between the engine (E) and the motor (M) and the driving wheel (D). The transmission adjusts rotation speed of the motor (M). The power transmission device supplying oil by causing the motor (M) to rotate the oil pump (P) at an appropriate rotation speed.

A vehicle transmission apparatus having a starting engagement friction element, which has friction plates and a hydraulic servo including a piston that is moved according to a supplied oil pressure to press the friction plates, which is controlled to be engaged when a vehicle is started by using at least a driving force of the internal combustion engine, and which transfers creep torque. A control device capable of receiving an accelerator operation amount signal and capable of outputting a command value that controls the oil pressure. The control device executes temporary increase control of temporarily increasing the command value, when the accelerator operation amount signal is turned on from a state where the accelerator operation amount signal is off and the command value is output so that the starting engagement friction element transfers the creep torque.

A vehicle transmission apparatus having a starting engagement friction element, which has friction plates and a hydraulic servo including a piston that is moved according to a supplied oil pressure to press the friction plates, which is controlled to be engaged when a vehicle is started by using at least a driving force of the internal combustion engine, and which transfers creep torque. A control device capable of receiving an accelerator operation amount signal and capable of outputting a command value that controls the oil pressure. The control device executes temporary increase control of temporarily increasing the command value, when the accelerator operation amount signal is turned on from a state where the accelerator operation amount signal is off and the command value is output so that the starting engagement friction element transfers the creep torque.

An electronic control unit starts shift initial oil pressure control after the completion of lockup initial oil pressure control when shift control is performed during the performance of lockup control, the electronic control unit starts shift initial oil pressure control after the completion of lockup initial oil pressure control. Besides, the electronic control unit places priority on the shift control and starts the lockup initial oil pressure control after the completion of the shift initial oil pressure control, when the lockup control is performed during the performance of the shift control. Therefore, the shift initial oil pressure control and the lockup initial oil pressure control are prevented from occurring at the same time when the shift control and the lockup control are performed at the same time.

An electronic control unit starts shift initial oil pressure control after the completion of lockup initial oil pressure control when shift control is performed during the performance of lockup control, the electronic control unit starts shift initial oil pressure control after the completion of lockup initial oil pressure control. Besides, the electronic control unit places priority on the shift control and starts the lockup initial oil pressure control after the completion of the shift initial oil pressure control, when the lockup control is performed during the performance of the shift control. Therefore, the shift initial oil pressure control and the lockup initial oil pressure control are prevented from occurring at the same time when the shift control and the lockup control are performed at the same time.

In the case where the lockup clutch is in the complete engagement state when a changeover between shift stages is made with the second shift mode selected, an electronic control unit holds the lockup clutch in the complete engagement state. Meanwhile, in the case where the lockup clutch is in the slip engagement state, the electronic control unit holds the lockup clutch in the slip engagement state based on a slip amount of the torque converter, or switches the lockup clutch to the complete engagement state.

In the case where the lockup clutch is in the complete engagement state when a changeover between shift stages is made with the second shift mode selected, an electronic control unit holds the lockup clutch in the complete engagement state. Meanwhile, in the case where the lockup clutch is in the slip engagement state, the electronic control unit holds the lockup clutch in the slip engagement state based on a slip amount of the torque converter, or switches the lockup clutch to the complete engagement state.

Based on a determination result by a nitrogen concentration determination section, an electronic control unit changes a switching line used to switch between a differential state and a non-differential state of a differential mechanism and a gear shift line used to switch a gear stage of an automatic transmission mechanism. In conjunction with a change of an engine operation point to a high-speed side in a nitrogen-enriched state of intake air, a first motor rotational speed in the differential state of the differential mechanism becomes higher than that in a non-enriched state of the intake air. Thus, corresponding to the above, the differential mechanism is appropriately switched between the differential state and the non-differential state, and the gear stage of the automatic transmission mechanism is appropriately switched.

Based on a determination result by a nitrogen concentration determination section, an electronic control unit changes a switching line used to switch between a differential state and a non-differential state of a differential mechanism and a gear shift line used to switch a gear stage of an automatic transmission mechanism. In conjunction with a change of an engine operation point to a high-speed side in a nitrogen-enriched state of intake air, a first motor rotational speed in the differential state of the differential mechanism becomes higher than that in a non-enriched state of the intake air. Thus, corresponding to the above, the differential mechanism is appropriately switched between the differential state and the non-differential state, and the gear stage of the automatic transmission mechanism is appropriately switched.