Pre-energization for power operated disconnect systems

A method of controlling a secondary drivetrain, the method comprising the steps of:

• receiving a connect request from a control system to connect a disconnect mechanism of the secondary drivetrain, the disconnect mechanism operatively disposed between an electric motor and ground engaging wheels of the secondary drivetrain;
• in response to receiving the connect request, increasing electric motor speed to reduce a speed difference between a first clutch member and a second clutch member of the disconnect mechanism when the first and second clutch members are in a disconnected state;
• during the increasing of the electric motor speed, applying a current, at an initial level for pre-energization, to an electromagnetic actuator of the disconnect mechanism;
• during the increasing of the electric motor speed, detecting a decreasing speed difference between the first clutch member and the second clutch member of the disconnect mechanism;
• confirming the speed difference between the first clutch member and second clutch member is below a threshold level;
• in response thereto, applying the current, at a second level of the current that is higher than the initial level of the current, to the electromagnetic actuator and, in response thereto, providing movement of a plunger operatively coupled to the second clutch member in a direction toward the first clutch member and engaging the second clutch member with the first clutch member and reaching a connected state;
• in response to engaging the first and second clutch members, transferring torque between the electric motor and the ground-engaging wheels via the disconnect mechanism;
• wherein a common connect request signal causes the motor speed to increase and the initial level of the current to be applied during the same period;
• wherein the time to increase the current to the second level of the current following the connect request signal is unknown at the time of the connect request signal and is dependent on detection of the speed difference reaching the threshold level, wherein the time to reach the threshold level is unknown.

An electrically powered drivetrain of a vehicle, wherein the electrically powered drivetrain comprises:

• an electric motor drivingly coupled to a differential mechanism having a disconnect mechanism including a first clutch member and a second clutch member moveable from a disconnected state into a connected state with the first clutch member;
• wherein, in the connected state, torque is transferred from the electric motor to ground engaging wheels of the drivetrain, and, in the disconnected state, torque output from the electric motor is operationally decoupled from the ground engaging wheels;
• wherein, in response to receiving a connect request from a control system of the vehicle, an actuator of the disconnect device applies a current, at an initial level of the current, to a plunger that applies a force on the second clutch member toward the first clutch member, wherein the initial level of the current is below a level that overcomes a bias on the second clutch member, and the second clutch member remains in the disconnected state during application of the initial level of the current;
• wherein the first clutch member rotates independent of the second clutch member in the disconnected state;
• wherein actuation of the electric motor in response to the connect request reduces a speed difference between the first clutch member and the second clutch member;
• wherein the control system detects and confirms that the speed difference is below a threshold level, and the control system increases the current applied to the actuator to a second level of the current that is higher than the initial level of the current, wherein the second level of the current applies a force that overcomes the bias on the second clutch member, and the second clutch member moves to the connected state and torque transfers from the electric motor to the ground engaging wheels via the differential mechanism;
• wherein a biasing mechanism is disposed operatively between the plunger and the first clutch member, wherein the biasing mechanism exerts the bias and biases the second clutch member away from the first clutch member toward the disconnected state;
• wherein the initial level of the current causes the plunger to exert a force against the biasing member, wherein the biasing force is greater than the force exerted by the plunger against the biasing member, wherein the plunger remains stationary during provision of the initial level of the current.