A drive force transfer device is mounted on a four-wheel-drive vehicle having main drive wheels and auxiliary drive wheels. A cam mechanism presses a main clutch in the axial direction. An electromagnetic clutch mechanism actuates the cam mechanism and has an electromagnetic coil and a pilot clutch. When the electromagnetic coil is not energized, the pressing force of the cam mechanism, which is generated because of drag torque of the pilot clutch in the case where a output rotary member rotates faster than a input rotary member, is smaller than that generated because of drag torque of the pilot clutch in the case where the input rotary member rotates faster than the output rotary member.

Methods and systems are provided for operating an electromagnetic pulse disconnect assembly for selectively engaging two rotating components of a vehicle drivetrain. A disconnect assembly is needed that is not powered by vacuum diverted from an engine of the vehicle, as modern engines are being developed to reduce vacuum production and remove vacuum lines for powering peripheral devices such as disconnects. An electromagnetic pulse disconnect assembly is provided that operates via pulses of electrical current and includes an electromagnetic coil for translating a clutch ring assembly and a latching ring assembly to selectively couple two rotating components.

A drive switching mechanism of a utility vehicle includes: a two-wheel drive and four-wheel drive switching device that switches between two-wheel drive and four-wheel drive of the utility vehicle; and a control unit that controls the drive switching mechanism. The two-wheel drive and four-wheel drive switching device switches between two-wheel drive and four-wheel drive by using a first clutch. The control unit permits the two-wheel drive and four-wheel drive switching device to switch from two- wheel drive to four-wheel drive when a rotation difference of the first clutch becomes equal to or smaller than a predetermined value.

A power transfer assembly for a motor vehicle includes a clutch protection system to prevent damage to an actively-controlled multi-plate mode clutch of the power transfer assembly. The clutch protection system includes a transfer case control module (TCCM) and an engine control module (ECM) configured to regulate the distribution of torque applied from an engine to front and rear output shafts of the power transfer assembly. The TCCM is in operable communication with the engine control module ECM, wherein TCCM is configured to detect slip in the actively-controlled multi-plate friction clutch and to communicate with the ECM to selectively reduce the output torque of the engine in response to detected slip.

A mechanical front wheel drive roller wedging control system includes a 4WD switch in a vehicle operator station, a roller cage drag mechanism electrically activated by the 4WD switch and providing a drag on a roller cage if the 4WD switch is in an on position, and a throttle pedal switch actuated by the throttle pedal and that deactivates the roller cage drag mechanism when the throttle pedal is released. In an alternative embodiment, a controller may deactivate the roller cage drag mechanism when a throttle position sensor or engine speed sensor is below a minimum value.

A four-wheel drive vehicle comprises: main drive wheels and sub-drive wheels; a first input rotating member; a first output rotating member; a second input rotating member; a second output rotating member; a first dog clutch; a second dog clutch; a synchromesh mechanism. In the case of canceling a disconnect state in which the power transmitting member interrupts power transmission from the drive power source and the sub-drive wheels, the control device controls an engagement torque of the coupling to a preset first torque and operates the synchromesh mechanism to engage the first dog clutch when it is determined that the rotation speeds are synchronized between the second input rotating member and the second output rotating member, and controls the engagement torque of the coupling to a second torque smaller than the first torque to engage the second dog clutch when it is determined that the first dog clutch is engaged.

A driving force transmission control apparatus includes: a driving force transmission device that includes an electromagnetic clutch mechanism configured to generate a frictional force between clutch plates by energization of an electromagnetic coil and transmits a driving force by actuating the electromagnetic clutch mechanism; and a control device that controls the driving force transmission device. The control device includes a storage unit storing a hysteresis value representing the difference between a current value required to transmit a predetermined torque when an energization current to the electromagnetic coil is gradually increased and a current value required to transmit the predetermined torque when the energization current is gradually reduced, a torque command value calculator that calculates a torque command value, and a current command value calculator that calculates a current command value representing a target value of a current to be supplied to the electromagnetic coil based on the torque command value and the hysteresis value.

Methods and systems are provided for operating an electromagnetic coil assembly. As one example, a method comprises responsive to energization of an electromagnetic coil of an electromagnetic coil assembly, translating the electromagnetic coil along a central axis of the electromagnetic coil assembly toward a magnetic armature while maintaining the armature fixed along the central axis. The electromagnetic coil assembly may be utilized within various clutching, braking, or lever applications.

A clutch control method is provided for a four-wheel-drive vehicle in which the main drive wheels are connected to a drive source, and the auxiliary drive wheels are connected via a friction clutch to the drive source. When the vehicle starts off due to an accelerator depressing operation, the friction clutch is engaged to distribute, a drive torque from the drive source to the main drive wheels and the auxiliary drive wheels. In this clutch control method, when the vehicle switches from a traveling state to a stopped state while maintaining in a travel shift position, a control is preformed to apply initial torque as an engagement torque control of the friction clutch while the vehicle is stopped. A magnitude of the initial torque is set to a magnitude that maintains a drive-system torsion state by transmitting torque to an auxiliary-drive-wheel drive system before the vehicle is stopped.

A control device of a four-wheel-drive vehicle having an electronic control coupling changing a transmission torque, and a connecting/disconnecting mechanism connecting/disconnecting an input to the input-side rotating member of the coupling, comprising: a storage portion storing a relationship between the drive current to the coupling and the transmission torque of the coupling; a control portion controlling the drive current based on the relationship; and a learning portion performing correction for the relationship through learning by applying a braking torque to the input-side rotating member by an electromagnetic actuator. The learning portion performs the correction for the relationship by using the drive current supplied to the coupling and the braking torque at the time of determination that the transmission torque is balanced with the braking torque based on rotational speeds of the input-side rotating member and the output-side rotating member while the rotational speed of the input-side rotating member is increased.