Full-time transfer case with synchronized single planetary gear reduction unit

A power transfer system for a four-wheel drive motor vehicle having a power source and front and rear drivelines, comprising:

• a transfer case including a housing;
• an input shaft rotatably supported in said housing and driven by the power source;
• a front output shaft rotatably supported in said housing and coupled to the front driveline;
• a rear output shaft rotatably supported in said housing and coupled to the rear driveline;
• a mainshaft;
• a planetary gear assembly operable for selectively coupling said input shaft to said mainshaft to define a high-range drive mode whereat said mainshaft is driven at a direct speed ratio relative to said input shaft and a low-range drive mode whereat said mainshaft is driven at a reduced speed ratio relative to said input shaft, said planetary gear assembly having a first member driven by said input shaft, a second member, and a third member driving said mainshaft and interconnecting said first member to said second member;
• a clutch apparatus including a range sleeve supported for rotation with said second member of said planetary gear assembly and movement between a first range position whereat said range sleeve couples said second member to said third member for establishing said high-range drive mode, a second range position whereat said range sleeve couples said second member to said housing for establishing said low-range drive mode, and a third range position whereat said range sleeve uncouples said second member from said third member and said housing for establishing a non-driven mode, and synchronizer means for causing speed synchronization between said second member and said third member in response to movement of said range sleeve to said first range position, said synchronizer means further operable for causing speed synchronization between said second member and said housing in response to movement of said range sleeve to said second range position;
• an interaxle differential interconnecting said mainshaft to said front and rear output shafts for permitting speed differentiation therebetween, said interaxle differential including an input driven by said mainshaft, a first output interconnecting said input to said front output shaft, and a second output interconnecting said input to said rear output shaft;
• a transfer clutch operable for controlling speed differentiation across said interaxle differential, said transfer clutch including a set of first clutch plates supported for rotation with said first output of said interaxle differential, a set of second clutch plates supported for rotation with said second output of said interaxle differential and which are alternately interleaved with said first clutch plates, and a thrust mechanism movable between a first mode position whereat a minimum clutch engagement force is exerted on said clutch plates for permitting unrestricted speed differentiation between said front and rear output shafts, and a second mode position whereat a maximum clutch engagement force is exerted on said clutch plates for inhibiting speed differentiation;
• a drive mechanism interconnected to said range sleeve and said thrust mechanism for controlling coordinated movement thereof, said drive mechanism being movable between a PT-H position whereat said range sleeve is located in said first range position and said thrust mechanism is located in said second mode position, a FT-H position whereat said range sleeve is located in said first range position and said thrust mechanism is located in said first mode position, a N position whereat said range sleeve is located in said third range position and said thrust mechanism is located in either of said first and second mode positions, and a PT-L position whereat said range sleeve is located in said second range position and said thrust mechanism is located in said second mode position;
• and an actuator for selectively moving said drive mechanism;
• sensor means for detecting dynamic and operational characteristics of the motor vehicle and generating sensor input signals indicative thereof;
• a mode select mechanism for enabling a vehicle operator to select one of a part-time four-wheel high-range drive mode, a full-time four-wheel high-range drive mode, a neutral mode, and a part-time four-wheel low-range drive mode, said mode select mechanism generating a mode signal indicative of the particular mode selected;
• and
• a controller for controlling actuation of said actuator in response to said mode signal and said sensor input signals, said controller operable for causing said actuator to move said drive mechanism to said PT-H position when said mode signal indicates selection of said part-time four-wheel high-range drive mode, said controller operable for causing said actuator to move said drive mechanism between said FT-H and PT-H positions as a function of said sensor input signals when said mode signal indicates selection of said full-time four-wheel high-range drive mode, said controller causing said actuator to move said drive mechanism to said N position when said mode signal indicates selection of said neutral mode, and said controller causing said actuator to move said drive mechanism to said PT-L position when said mode signal indicates selection of said part-time four-wheel low-range drive mode.

A transfer case for use in a four-wheel drive motor vehicle having a power source, front and rear drivelines, sensors for detecting dynamic characteristics of the motor vehicle, and an electronic controller for generating control signals in response to the sensor signals, said transfer case comprising:

• a housing;
• an input shaft rotatably supported in said housing and driven by the power source;
• a front output shaft rotatably supported in said housing and coupled to the front driveline;
• a rear output shaft rotatably supported in said housing and coupled to the rear driveline;
• a mainshaft;
• a planetary gear assembly operable for selectively coupling said input shaft to said mainshaft to define a high-range drive mode whereat said mainshaft is driven at a direct speed ratio relative to said input shaft and a low-range drive mode whereat said mainshaft is driven at a reduced speed ratio relative to said input shaft, said planetary gear assembly having a sun gear driven by said input shaft, a ring gear, and a carrier assembly driving said mainshaft and having pinion gears journally supported therefrom that are meshed with said sun gear and ring gear;
• a clutch apparatus including a range sleeve supported for rotation with said ring gear and movement between a first range position whereat said range sleeve couples said ring gear to said carrier assembly for establishing said high-range drive mode and a second range position whereat said range sleeve couples said ring to said housing for establishing said low-range drive mode, and synchronizer means for causing speed synchronization between said ring gear and said carrier assembly in response to movement of said range sleeve to said first range position, said synchronizer means further operable for causing speed synchronization between said ring gear and said housing in response to movement of said range sleeve to said second range position;
• an interaxle differential interconnecting said mainshaft to said front and rear output shafts for permitting speed differentiation therebetween, said interaxle differential including an input driven by said mainshaft, a first output interconnecting said input to said front output shaft, and a second output interconnecting said input to said rear output shaft;
• a transfer clutch operable for controlling speed differentiation across said interaxle differential, said transfer clutch including a set of first clutch plates supported for rotation with said first output of said interaxle differential, a set of second clutch plates supported for rotation with said second output and alternately interleaved with said first clutch plates, and a thrust mechanism movable between a first mode position whereat a minimum clutch engagement force is generated and said transfer clutch is in a non-actuated state for permitting unrestricted speed differentiation between said front and rear output shafts, and a second mode position whereat a maximum clutch engagement force is generated and said transfer clutch is in a fully-actuated state for inhibiting speed differentiation;
• a drive mechanism interconnected to said range sleeve and said thrust mechanism for controlling coordinated movement thereof, said drive mechanism being movable between a FT-H position whereat said range sleeve is located in said first range position and said thrust mechanism is located in said first mode position, a PT-H position whereat said range sleeve is located in said first range position and said thrust mechanism is in said second mode position, and a PT-L position whereat said range sleeve is located in said second range position and said thrust mechanism is located in said second mode position;
• an actuator for selectively moving said drive mechanism;
• and
• a mode select mechanism for enabling a vehicle operator to select one of a full-time four-wheel high-range drive mode and a part-time four-wheel low-range drive mode and generating a mode signal indicative of the particular mode selected;
• whereby the controller actuates said actuator in response to said mode signal and the sensor signals, the controller being operable for causing said actuator to move said drive mechanism between said FT-H and PT-H positions as a function of the sensor signals when said full-time four-wheel high-range drive mode is selected for automatically controlling speed differentiation across said interaxle differential, and the controller being operable for causing said actuator to move said drive mechanism to said PT-L position when said part-time four-wheel low-range drive mode is selected.