초록 ▼

A torque transfer mechanism is provided for controlling the magnitude of a clutch engagement force exerted on a multi-plate clutch assembly that is operably disposed between a first rotary and a second rotary member. The torque transfer mechanism includes a clutch actuator assembly for generating an

A torque transfer mechanism is provided for controlling the magnitude of a clutch engagement force exerted on a multi-plate clutch assembly that is operably disposed between a first rotary and a second rotary member. The torque transfer mechanism includes a clutch actuator assembly for generating and applying a clutch engagement force on the clutch assembly. The clutch actuator assembly includes an electric motor/brake unit and a torque/force conversion mechanism. The motor/brake unit can be operated in either of a motor mode or a brake mode to cause bi-directional linear movement of an output member of the torque/force conversion mechanism. The thrust force generated by the torque/force conversion mechanism is applied to the clutch assembly. The dual mode feature of the electric motor/brake unit significantly reduces the power requirements.

대표청구항 ▼

1. A transfer case for use in a four-wheel drive vehicle having a powertrain and first and second drivelines comprising:a first shaft driven by the powertrain and adapted for connection to the first driveline;a second shaft adapted for connection to the second driveline;a friction clutch assembly op

1. A transfer case for use in a four-wheel drive vehicle having a powertrain and first and second drivelines comprising:a first shaft driven by the powertrain and adapted for connection to the first driveline;a second shaft adapted for connection to the second driveline;a friction clutch assembly operably disposed between said first and second shafts;a ball screw operator rotatably driven by one of said first and second shafts and having a first component in threaded engagement with a second component, and a third component in threaded engagement with said second component, said first component being axially moveable relative to said second component in response to relative rotation between said second and third components, said first component is adapted to exert a clutch engagement force on said friction clutch assembly the magnitude of which corresponds to the axial position of said first component relative to said second component;an electric motor having a rotor fixed for rotation with said second component of said ball screw operator, said motor is operable in a motor mode wherein said rotor is driven to cause relative rotation between said second and third components, and said motor is operable in a brake mode wherein said rotor is braked to cause relative rotation between said second and third components; anda controller for actuating said motor so as to control the direction and amount of rotation of said rotor which, in turn, controls the direction and amount of axial travel of said first component of said ball screw operator for varying the clutch engagement force exerted on said friction clutch assembly, said controller further operable for switching from said motor mode to said brake mode when the rotary speed of one of said first and second shafts exceeds a predetermined threshold value. 2. The transfer case of claim 1 wherein said friction clutch assembly includes a hub fixed for rotation with one of said first and second shafts a drum fixed for rotation with the other of said first and second shafts, and a clutch pack operably disposed between said hub and drum, and wherein said first component of said ball screw operator is a first screw, said second component is a nut and said third component is a second screw, said second screw fixed for rotation with said first shaft, said rotor of said motor being fixed for rotation with said nut such that actuation of said motor causes said nut to rotate relative to said second screw whereby said first screw moves axially relative to nut for engaging said clutch pack. 3. The transfer case of claim 2 wherein said first screw is caused to move axially between a retracted position and an extended position in response to the direction and magnitude of rotary movement of said nut and said rotor caused by actuation of said motor. 4. The transfer case of claim 3 wherein a minimum clutch engagement force is exerted on said clutch pack when said first screw is located in its retracted position and a maximum clutch engagement force is exerted on said clutch pack when said first screw is located in its extended position. 5. The transfer case of claim 1 wherein said motor includes a coil and said rotor includes magnets that are located in close proximity to said coil, rotation of said rotor with said nut of said ball screw operator causes said magnets to induce a magnetic field in said coil such that energization of said coil causes said rotor to be braked when said motor is operating in its brake mode. 6. The transfer case of claim 1 wherein said first shaft is a first output shaft driving the first driveline, said second shaft is a second output shaft coupled to the second driveline, and wherein said first component of said ball screw operator is moveable between a first position whereat a minimum clutch engagement force is exerted on said friction clutch assembly and a second position whereat a maximum clutch engagement force is exerted on said friction clutch assembly, wherein l ocation of said first component in its first position establishes a two-wheel drive mode, location of said first component in its second position establishes a part-time four-wheel drive made, and wherein said controller is operable in each of its motor and brake modes to vary the position of said first component between its first and second positions for varying the drive torque transferred from said first output shaft to said second output shaft so as to define an on-demand four-wheel drive mode. 7. The transfer case of claim 2 wherein first screw has internal threads having a first lead, said nut has threads on an outer surface which are aligned with said internal threads on said first screw and which have a second lead, said nut further including threads on an inner surface having a third lead, and wherein said second screw has external threads which are aligned with said threads on said inner surface of said nut and which have a fourth lead. 8. The transfer case of claim 7 wherein said first said equals said second lead and said third lead equals said fourth lead. 9. A transfer case for use in a four-wheel drive vehicle having a powertrain and first and second drivelines, comprising:a differential having an input driven by the powertrain and first and second outputs driving the first and second drivelines;a friction clutch assembly operably disposed between any two of said input and said first and second outputs of said differential;a clutch actuator for generating a clutch engagement force to applied to said friction clutch assembly, said clutch actuator including a ball screw operator rotatably having a first threaded component driven by said first output, a second threaded component in threaded engagement with said first threaded component, and a third threaded component in threaded engagement with said second threaded component, said third component being axially moveable relative to said second component in response to relative rotation between said first and second components, said third component adapted to exert a clutch engagement force on said friction clutch assembly the magnitude of which corresponds to the axial position of said third component relative a said second component, and an electric motor having a rotor fixed for rotation with said second component of said ball screw operator, said motor is operable in a motor mode wherein said rotor is driven to cause relative rotation between said first and second components, and said motor is operable in a brake mode wherein said rotor is braked to cause relative rotation between said first and second components; anda controller for actuating said motor so as to control the direction and amount of rotation of said rotor which, in turn, controls the direction and amount of axial travel of said third component of said ball screw operator for varying the clutch engagement force exerted on said friction clutch assembly, said controller further operable for switching from said motor made to said brake mode when the rotary speed of one of said first and second outputs exceeds a predetermined threshold value. 10. The transfer case of claim 9 wherein said friction clutch assembly includes a hub fixed for rotation with one of said first and second outputs, a drum fixed for rotation with the other of said first and second outputs, and a clutch pack operably disposed between said hub and drum, and wherein said first component of said ball screw operator is an inner screw, said second component is a nut, and said third component is an outer screw, said rotor of said motor being fixed for rotation with said nut such that actuation of said motor causes said nut to rotate relative to said inner screw whereby said outer screw moves axially on said nut relative to said clutch pack. 11. The transfer case of claim 10 wherein said outer crew is caused to move axially between a retracted position and an extended position in response to the direction and magnitude of rotary movement of said nut and said rotor caused by actuation of said motor. 12. The transfer case of claim 11 wherein said motor includes a coil and said rotor includes magnets located in close proximity to said coil, rotation of said rotor with said nut causes said magnets to induce a magnetic field in said coil such that energization of said coil causes said rotor to be braked when said motor is operating in its brake mode. 13. The transfer case of claim 9 further comprising first output shaft driving the first driveline, said second shaft is a second output shaft coupled to the second driveline, and wherein said third component of said ball screw operator is moveable between a first position whereat a minimum clutch engagement force is exerted on said friction clutch assembly and a second position whereat a maximum clutch engagement force is exerted on said friction clutch assembly, wherein location of said third component in its first position establishes a full-time four-wheel drive mode, location of said third component in its second position establishes a locked four-wheel drive mode, and wherein said controller is operable in each of its motor and brake modes to vary the position of said third component between its first and second positions for varying the drive torque transferred from said first output shaft to said second output shaft so as to define an adaptive four-wheel drive mode. 14. A power transmission device, comprising:a first rotary member;a second rotary member;a torque transfer mechanism for transferring drive torque from said first rotary member to said second rotary member, said torque transfer mechanism including a friction clutch assembly operably disposed between said first and second rotary members and a clutch actuator assembly for applying a clutch engagement force on said friction clutch assembly, said clutch actuator assembly including an electric motor having a rotor, and a torque/force conversion mechanism having a first component fixed for rotation with said first rotary member, a second component fixed for rotation with said rotor, and a third component supported for movement between a first position and a second position in response to relative rotation between said first and second components, said third component operable to exert a minimum clutch engagement force on said friction clutch assembly when located in its first position and a maximum clutch engagement force when located in its second position, said motor being operable in a motor mode wherein said rotor is driven to cause relative rotation between said first and second components and in a brake mode wherein said rotor is braked to cause such relative rotation; anda controller for switching said electric motor from said motor mode into said brake mode when the rotary speed of one of said first and second rotary members exceeds a predetermined rotary speed value. 15. The power transmission device of claim 14 wherein said controller provides electrical power to drive said rotor when said motor is operating in its motor mode, and wherein electrical power generated by rotation of said rotor is used to brake said rotor when said motor is operating in its brake mode. 16. The power transmission device of claim 14, wherein said friction clutch assembly includes a hub fixed for rotation with one said first and second rotary members, a drum fixed for rotation with the other of said first and second rotary members, and a clutch pack operably disposed between said hub and drum, and wherein said first component of said torque/force conversion mechanism is a first screw, said second component is a nut, and said third component is a second screw, said rotor of said motor being fixed for rotation with said nut such that actuation of said motor causes said nut to rotate relative to said first screw for causing said second screw to move relative to said clutch pack between its first and second and positions. 17. The power transmission device of claim 16 where in said second screw is caused to move linearly between its first position and its second and position in response to the direction and magnitude of rotary movement of said nut and said rotor caused by actuation of said motor. 18. The power transmission device of claim 14 wherein said motor includes a coil and said rotor includes magnets located in close proximity to said coil, rotation of said rotor with said nut cause said magnets to induce a magnetic field in said coil such that energization of said coil causes said rotor to be braked when said motor is operating in its brake mode. 19. The power transmission device of claim 14 herein said first rotary member is a first shaft driving a first driveline of a motor vehicle, said second rotary member is a second shaft coupled to a second driveline of the motor vehicle, and wherein said torque transfer mechanism is operable to transfer drive torque from said first shaft to said second shaft. 20. The power transmission device of claim 19 defining a transfer case wherein said first shaft is a primary output shaft driving the first driveline, said second shaft is a secondary output shaft coupled to the second driveline, and wherein location of said third component in its first position release engagement of said clutch assembly so as to define a two-wheel drive mode, and location of said third component in its second position fully engages said clutch assembly so as to define a part-time four-wheel drive mode, said controller is operable to control said electric motor for varying the position of said third component between its first and second positions to controllably vary the drive torque transferred from said primary output shaft to said secondary output shaft so as to define an on-demand four-wheel drive mode. 21. The power transmission device of claim 20 further comprising sensors to detect a vehicle operating condition, said controller receiving input signals from said sensors and generating electric control signals based on said input signals which are supplied to said electric motor for controlling the direction and amount of rotary movement of said rotor. 22. The power transmission device of claim 19 defining a power take-off unit wherein said first shaft provides drive torque to a first differential associated with the first driveline, and wherein said second shaft is coupled to a second differential associated with the second driveline. 23. The power transmission device of claim 14 wherein said first rotary member is a drive shaft driven by a drivetrain of a motor vehicle, said second rotary member is a pinion shaft driving a differential associated with an axle assembly of the motor vehicle, and wherein said friction clutch assembly is disposed between said drive shaft and said pinion shaft such that actuation of said clutch actuator assembly is operable to transfer drive torque from said drive shaft to said pinion shaft. 24. The power transmission device of claim 14 wherein said first rotary member includes a first differential supplying drive torque to a pair of first wheels in a motor vehicle, and a transfer shaft driven by said first differential, said second member includes a drive shaft coupled to a second differential interconnecting a pair of second wheels in the motor vehicle, and wherein said friction clutch assembly is disposed between said transfer shaft and said drive shaft. 25. The power transmission device of claim 14 herein said first rotary member includes a first shaft supplying drive torque to a second shaft which is coupled to a first differential for driving a pair of first wheels in a motor vehicle, said second rotary member is a third shaft driving a second differential interconnecting a pair of second wheels of the motor vehicle, and wherein said friction clutch assembly is operably disposed between said first and third shafts. 26. The power transmission device of claim 14 further including an interaxle differential driven by said first rotary me mber and having a first output driving a first driveline in a motor vehicle and a second output driving a second driveline in the motor vehicle, and wherein said friction clutch assembly is operably disposed between said first and second outputs of said interaxle differential.