Magnetic powder torque transfer clutch for controlling slip across a differential mechanism

A method for controlling wheel slip across a differential mechanism of a motor vehicle having a steering angle and a steering direction, the differential mechanism driven by a driveshaft and having first and second rotating output shafts driveably connected to the wheels and connectable by a clutch that is activated by a magnetic field of variable strength to change a torque capacity of the clutch, the method comprising the steps of:

• determining the steering angle and the direction of the steering angle;
• determining a target speed of the output shafts that corresponds to the current driveshaft speed, steering angle and steering direction;
• determining the speeds of the output shafts;
• reducing the magnitude of torque to be transmitted by the clutch in comparison to the magnitude of torque carried by the first and second output shafts;
• comparing the speeds of the output shafts and the target speeds to determine whether wheel slip is present;
• and
• in response to the comparison, adjusting the magnitude of the field strength to increase the torque capacity of the clutch and control the speed of the output shafts such that the wheel slip is reduced.

A system for controlling wheel slip of a motor vehicle having wheels, a steering angle and a steering direction, comprising:

• a differential mechanism driven by a driveshaft, and including two rotating output shafts driveably connected to the wheels;
• a clutch including a first element driveably connected to the first output shaft, a second element driveably connected to the second output shaft, a chamber at least partially bounded by the first element and second element, magnetic powder located in the chamber, an electromagnetic coil producing a magnetic field of variable strength passing through the chamber and magnetic powder and changing a capacity of the clutch to transmit torque between the first and second output shafts as the field strength changes;
• sensors producing signals representing the speed of the output shafts, the steering angle, and the direction of the steering angle;
• and
• a controller receiving as input the signals produced by the sensors, determining a target speed of the output shafts that corresponds to a driveshaft speed, steering angle and steering direction, comparing the speed of the output shafts and the target speeds to determine whether wheel slip is present, and adjusting the magnitude of the field strength to control the speed of the output shafts and reduce wheel slip.

A clutch for changing a magnitude of transmitted torque, comprising:

• first and second rotating control shafts;
• a first element driveably connected to a first control shaft;
• a second element driveably connected to the second output shaft;
• a chamber at least partially bounded by the first element and second element;
• magnetic powder located in the chamber;
• and
• an elecromagnetic coil producing a magnetic field of variable strength passing through the chamber and magnetic powder and changing a capacity of the clutch to transmit torque between the first and second control shafts as the field strength changes.