초록 ▼

A power take-off (PTO) transmission unit transfers power between an input shaft and an output shaft. A gear set selectively couples the input shaft to the output shaft. A shift device includes a shift rail with ends forming inner pistons within chambers. The shift rail is configured to translate bet

A power take-off (PTO) transmission unit transfers power between an input shaft and an output shaft. A gear set selectively couples the input shaft to the output shaft. A shift device includes a shift rail with ends forming inner pistons within chambers. The shift rail is configured to translate between first, second, and third positions based on the pressures of the chambers. Inner pistons nest within the outer pistons in the chambers. A shift fork and shift collar translate with the shift rail to, in the first position, engage the gear set such that power is transferred at a first speed ratio; in the second position, engage the gear set such that power is transferred at a second speed ratio; and in the third position, engage the gear set to provide a neutral mode in which the output shaft is free to rotate relative to the input shaft.

대표청구항 ▼

1. A power take-off (PTO) transmission unit for transferring power between an input shaft coupled to a work vehicle and an output shaft coupled to an implement, the PTO transmission unit comprising: a housing at least partially defining a first chamber and a second chamber configured to be coupled t

1. A power take-off (PTO) transmission unit for transferring power between an input shaft coupled to a work vehicle and an output shaft coupled to an implement, the PTO transmission unit comprising: a housing at least partially defining a first chamber and a second chamber configured to be coupled to a fluid source for selectively pressurizing the first chamber and the second chamber;a gear set positioned within the housing and selectively coupling the input shaft to the output shaft; anda shift device positioned within the housing and comprising: a shift rail with a first end forming a first inner piston within the first chamber and a second end forming a second inner piston within the second chamber, the shift rail configured to translate between a first position, a second position, and a third position based on the pressures of the first and second chambers;a first outer piston arranged within the first chamber such that the first inner piston nests within the first outer piston and a second outer piston arranged within the second chamber such that the second inner piston nests within the second outer piston;a shift fork coupled to and translating with the shift rail; anda shift collar coupled to and translating with the shift fork to, in the first position, engage the gear set such that power is transferred from the input shaft to the output shaft at a first speed ratio,in the second position, engage the gear set such that power is transferred from the input shaft to the output shaft at a second speed ratio, andin the third position, engage the gear set to provide a neutral mode in which the output shaft is free to rotate relative to the input shaft. 2. The PTO transmission unit of claim 1, further comprising a clutch device arranged within the housing and coupled to the gear set, the clutch device having an engaged condition in which power is transferred from the output shaft to the gear set and a disengaged condition in which the output shaft is rotationally decoupled relative to the gear set. 3. The PTO transmission unit of claim 2, further comprising a brake device arranged within the housing and coupled to the gear set, the brake device configured to, upon engagement, restrict movement of at least a portion of the gear set. 4. The PTO transmission unit of claim 3, further a controller coupled to the clutch, the brake, and the fluid source to selectively operate in at least a first mode, a second mode, and a third mode; wherein, in the first mode, the clutch is engaged, the brake is disengaged, and the shift rail is in the first position;wherein, in the second mode, the clutch is engaged, the brake is disengaged, and the shift rail is in the second position; andwherein, in the third mode, the clutch is disengaged, the brake is engaged, and the shift rail is in the third position. 5. The PTO transmission unit of claim 4, wherein the gear set is a planetary gear set comprising a sun gear, planet gears engaging the sun gear, a planet carrier supporting the planet gears and rotationally fixed to the output shaft; and a ring gear engaging the planet gears; and wherein, in the first position, the shift collar fixes the sun gear to the planet carrier;wherein, in the second position, the shift collar fixes the sun gear to the housing; andwherein, in the third position, the shift collar disengages the sun gear from the planet carrier and from the housing. 6. The PTO transmission unit of claim 5, wherein the planet carrier, the input shaft, and the output shaft have coincident longitudinal axes. 7. The PTO transmission unit of claim 1, wherein the shift rail is translated into the first position by pressurizing the second chamber and venting the first chamber and into the second position by pressurizing the first chamber and venting the second chamber. 8. The PTO transmission unit of claim 7, wherein the shift rail is translated into the third position by pressurizing the first chamber and second chamber. 9. The PTO transmission unit of claim 8, wherein the first chamber is at least partially formed by a first end cap and a first stop and the second chamber is at least partially formed by a second end cap and a second stop; and wherein, in the first position, the first outer piston engages the first end cap, the first inner piston engages the first outer piston, the second outer piston engages the second stop, and the second inner piston separates the second outer piston;wherein, in the second position, the first outer piston engages the first stop, the first inner piston separates from the first outer piston, the second outer piston engages the second end cap, and the second inner piston engages the second outer piston; andwherein the third position, the first outer piston engages the first stop, the first inner piston engages the first outer piston, the second outer piston engages the second end stop, and the second inner piston engages the second outer piston. 10. A power take-off (PTO) arrangement for transferring power between a work vehicle and an implement, comprising: a housing at least partially defining a first chamber and a second chamber;a fluid source configured to selectively supply fluid to pressurize the first chamber and the second chamber;an input shaft at least partially extending into the housing and configured to be driven by the work vehicle;an output shaft at least partially extending into the housing;a PTO shaft coupled to the output shaft and configured to be rotationally coupled to the implement;a gear set positioned within the housing and selectively coupling the input shaft to the output shaft;a clutch device coupled to the gear set and configured to, upon engagement, transfer power from the output shaft to the gear set;a brake device coupled to the gear set and configured to, upon engagement, restrict movement of the at least a portion of the gear set;a shift device comprising: a shift rail with a first end forming a first inner piston within the first chamber and a second end forming a second inner piston within the second chamber, the shift rail configured to translate between a first position, a second position, and a third position based on the pressures of the first and second chambers;a first outer piston arranged within the first chamber such that the first inner piston nests within the first outer piston and a second outer piston arranged within the second chamber such that the second inner piston nests within the second outer piston;a shift fork coupled to, and translating with, the shift rail; anda shift collar coupled to, and translating with the shift fork to selectively engage the gear set based on the first, second, and third positions of the shift rail; anda controller coupled to the clutch, the brake, and the fluid source to selectively operate in at least a first mode, a second mode, and a third mode;wherein, in the first mode, the clutch is engaged, the brake is disengaged, and the shift rail is in the first position such that power is transferred from the work vehicle to the implement at a first speed ratio;wherein, in the second mode, the clutch is engaged, the brake is disengaged, and the shift rail is in the second position such that power is transferred from the work vehicle to the implement at a second speed ratio; andwherein, in the third mode, the clutch is disengaged, the brake is engaged, and the shift rail is in the third position such that the output shaft is free to rotate relative to the input shaft and the brake. 11. The PTO arrangement of claim 10, wherein the clutch is integrated into the housing. 12. The PTO arrangement of claim 11, wherein the brake device is integrated into the housing. 13. The PTO arrangement of claim 10, wherein the gear set is a planetary gear set comprising a sun gear, planet gears engaging the sun gear, a planet carrier supporting the planet gears and rotationally fixed to the output shaft, and a ring gear engaging the planet gears, and wherein, in the first position, the shift collar fixes the sun gear to the planet carrier;wherein, in the second position, the shift collar fixes the sun gear to the housing; andwherein, in the third position, the shift collar disengages the sun gear from the planet carrier and from the housing. 14. The PTO arrangement of claim 13, wherein the planet carrier, the input shaft, and the output shaft have coincident longitudinal axes. 15. The PTO arrangement of claim 10, wherein the shift rail is translated into the first position by pressurizing the second chamber and venting the first chamber and into the second position by pressurizing the first chamber and venting the second chamber. 16. The PTO transmission unit of claim 10, wherein the shift rail is translated into the third position by pressurizing the first chamber and second chamber. 17. The PTO arrangement of claim 16, wherein the first chamber is at least partially formed by a first end cap and a first stop and the second chamber is at least partially formed by a second end cap and a second stop; and wherein, in the first position, the first outer piston engages the first end cap, the first inner piston engages the first outer piston, the second outer piston engages the second stop, and the second inner piston separates the second outer piston;wherein, in the second position, the first outer piston engages the first stop, the first inner piston separates from the first outer piston, the second outer piston engages the second end cap, and the second inner piston engages the second outer piston; andwherein the third position, the first outer piston engages the first stop, the first inner piston engages the first outer piston, the second outer piston engages the second end stop, and the second inner piston engages the second outer piston. 18. A work vehicle, comprising: a power system;a propulsion system driven by the power system to move the work vehicle;a power take-off (PTO) arrangement driven by the power system and configured to provide power to an implement attached to the work vehicle, the PTO arrangement comprising: a housing at least partially defining a first chamber and a second chamber;a fluid source configured to selectively supply fluid to pressurize the first chamber and the second chamber;an input shaft at least partially extending into the housing and configured to be driven by the work vehicle;an output shaft at least partially extending into the housing;a PTO shaft coupled to the output shaft and configured to be rotationally coupled to the implement;a gear set positioned within the housing and selectively coupling the input shaft to the output shaft;a clutch device coupled to the gear set and configured to, upon engagement, transfer power from the output shaft to the gear set;a brake device coupled to the gear set and configured to, upon engagement, restrict movement of at least a portion of the gear set;a shift device comprising: a shift rail with a first end forming a first inner piston within the first chamber and a second end forming a second inner piston within the second chamber, the shift rail configured to translate between a first position, a second position, and a third position based on the pressures of the first and second chambers;a first outer piston arranged within the first chamber such that the first inner piston nests within the first outer piston and a second outer piston arranged within the second chamber such that the second inner piston nests within the second outer piston;a shift fork coupled to, and translating with, the shift rail; anda shift collar coupled to, and translating with the shift fork to selectively engage the gear set based on the first, second, and third positions of the shift rail; anda controller coupled to the clutch, the brake, and the fluid source to selectively operate in at least a first mode, a second mode, and a third mode;wherein, in the first mode, the clutch is engaged, the brake is disengaged, and the shift rail is in the first position such that power is transferred from the work vehicle to the implement at a first speed ratio;wherein, in the second mode, the clutch is engaged, the brake is disengaged, and the shift rail is in the second position such that power is transferred from the work vehicle to the implement at a second speed ratio; andwherein, in the third mode, the clutch is disengaged, the brake is engaged, and the shift rail is in the third position such that the output shaft is free to rotate relative to the input shaft and the brake. 19. The work vehicle of claim 18, wherein the clutch and the brake device are integrated into the housing. 20. The work vehicle of claim 18, wherein the gear set is a planetary gear set comprising a sun gear, planet gears engaging the sun gear, a planet carrier supporting the planet gears and rotationally fixed to the output shaft, and a ring gear engaging the planet gears; and wherein, in the first position, the shift collar fixes the sun gear to the planet carrier;wherein, in the second position, the shift collar fixes the sun gear to the housing; andwherein, in the third position, the shift collar disengages the sun gear from the planet carrier and from the housing.