Electric starter system with latch mechanism for pinion pre-engagement control

A powertrain comprising:

• an internal combustion engine having an engine speed and a flywheel;
• a transmission connected to the engine;
• a load coupled to the transmission;
• and
• an electric starter system for use with the engine, the electric starter system having:
• a pinion gear;
• a solenoid device coupled to the pinion gear, the solenoid device movable between a pre-engaged position wherein the pinion gear is moved into engagement with the flywheel and a disengaged position wherein the pinion gear is disengaged from the flywheel;
• a brushless starter motor that is selectively connectable to the flywheel of the engine via the pinion gear during a requested engine start event;
• and
• a latch mechanism selectively engageable with the solenoid device, the latch mechanism moveable between a latched position wherein the solenoid device is mechanically held in the pre-engaged position and an unlatched position wherein the solenoid device is released for movement to the disengaged position whereby when the latch mechanism is in the latched position, the solenoid device is mechanically held in the pre-engaged position with the pinion gear engaging the flywheel and ready to start the engine.

A method for controlling an electric starter system for an internal combustion engine having an engine speed and a flywheel, the method comprising:

• responsive to a requested start of the engine determining, via a controller, when the engine speed is less than a threshold speed;
• responsive to the engine speed being less than the threshold speed, commanding delivery of a control current to a solenoid device via the controller at a current level sufficient for moving the solenoid device to a pre-engaged position wherein a pinion gear operatively connected to the solenoid device moves into engagement with the flywheel;
• commanding rotation of a brushless starter motor by a predetermined angle to thereby fully engage the pinion gear with the flywheel;
• commanding movement of a latch mechanism into a latched position whereby the latch mechanism is engaged with the solenoid device such that the solenoid device is mechanically held in the pre-engaged position for operative connection with the pinion gear translated for continued contact with the flywheel;
• and
• ending delivery of current to the solenoid device after the latch mechanism is in the latched position whereby when the current is ended, the latch mechanism mechanically holds the solenoid device in the pre-engaged position wherein the pinion gear is in contact with the flywheel without continued delivery of current.