Power split and variable creep drive system for street sweeper or like specialty vehicle

1. A single engine street sweeper comprising:

a. a truck chassis including a drive wheel axle;

b. a variable transmission supported by the truck chassis and operably connected to the drive wheel axle;

c. a power split drive system located between the variable transmission and drive wheel axle, the power split drive system including:

i. a first power input shaft operably connected to the variable transmission;

ii. a first power output shaft operably connected to a hydraulic motor/pump;

iii. a second power output shaft operably connected to the drive wheel axle;

iv. a third power output shaft operably connected to a hydraulic pump and to the first power input shaft;

v. a planetary gear set interconnecting the first power input shaft with the first and second power output shafts;

vi. a hydraulic work circuit including the hydraulic motor/pump and the hydraulic pump;

d. wherein the single engine street sweeper is operable between:

i. a transport mode in which the power split drive system is disengaged such that all power from the variable transmission is directed to the drive wheel axle; and

ii. a work mode in which the power split drive system is engaged such that power can be selectively distributed from the variable transmission to the drive wheel axle and to the hydraulic motor/pump operating as a hydraulic pump, wherein the work mode includes a reverse drive mode in which the hydraulic motor/pump operates as a hydraulic motor driven by the hydraulic pump associated with the third power output shaft.

2. The single engine street sweeper of claim 1 , wherein the first power input shaft is connected to a ring gear of the planetary gear set, the first power output shaft is connected to a sun gear of the planetary gear set, and the second power output shaft is connected to a planet gear carrier of the planetary gear set.

3. The single engine street sweeper of claim 1 , further including a coupler assembly that operates the single engine street machine between the transport and work modes.

4. The single engine street sweeper of claim 1 , wherein the hydraulic motor/pump is a variable displacement device.

5. The single engine street sweeper of claim 4 , wherein the relative proportion of power delivered to the drive wheel axle and the hydraulic pump/motor is controlled by varying the displacement of the hydraulic motor/pump.

6. A power split drive system for converting a single engine over-the-highway vehicle to a specialty work vehicle with work functions powered by the single engine, the power split drive system comprising:

a. a first power input shaft configured for operable connection to the single engine;

b. a first power output shaft operably connected to a hydraulic motor/pump;

c. a second power output shaft configured for operable connection to a drive wheel axle of the vehicle;

d. a third power output shaft operably connected to a hydraulic work circuit or power take-off unit;

e. a planetary gear set interconnecting the first power input shaft with the first and second power output shafts;

f. wherein the power split drive system is operable between:

i. a transport mode in which the power split drive system is disengaged such that all power from the first power input shaft is directed to the second power output shaft; and

ii. a work mode in which the power split drive system is engaged such that power can be selectively distributed from the first power input shaft to the first power output shaft such that the hydraulic motor/pump operates as a hydraulic pump and to the second power output shaft, wherein the work mode includes a reverse drive mode in which the hydraulic motor/pump operates as a hydraulic motor driven by a hydraulic pump associated with the third power output shaft.

7. The power split drive system of claim 6 , wherein the first power input shaft is connected to a ring gear of the planetary gear set, the first power output shaft is connected to a sun gear of the planetary gear set, and the second power output shaft is connected to a planet gear carrier of the planetary gear set.

8. The power split drive system of claim 6 , further including a coupler assembly that operates the power split drive system between the transport and work modes.

9. The power split drive system of claim 6 , wherein the third power output shaft is operably connected to the hydraulic work circuit or power take-off unit and to the first power input shaft.

10. The power split drive system of claim 6 , wherein the hydraulic motor/pump is a variable displacement device.

11. The power split drive system of claim 10 , wherein the relative proportion of power delivered to the first and second output shafts is controlled by varying the displacement of the hydraulic motor/pump.

12. A single engine vehicle converted from a highway truck chassis comprising:

a. a vehicle including a chassis, a cab, a single engine, and a driveline including axles and wheels;

b. a work system to perform work functions, the work system including a variable displacement hydraulic machine;

c. a power split device with a variable transmission mechanically connecting the chassis single engine to the work system and the driveline, the power split device including:

i. an input component with a shaft joining to the chassis engine;

ii. a hydraulic work circuit port or power-take-off port to provide power for work equipment;

iii. at least one planetary gear set, in which:

1. a first output component with a shaft connecting to the variable-displacement hydraulic machine, which is able to provide power to the work system from the input component;

2. a second output component with a shaft connecting and providing power to the vehicle driveline from the input component; and

d. a control system to manage the hydraulic machine, wherein power from the single engine can be selectively distributed between the work system and the vehicle driveline, and wherein the variable displacement hydraulic machine operates as a hydraulic pump in a ‘work (sweep)’ mode during forward propulsion of the vehicle such that pressurized fluid is provided by the hydraulic machine to drive the work equipment, and wherein the hydraulic machine operates as a hydraulic motor in reverse propulsion of the vehicle to drive the vehicle.

13. The power split drive system of claim 12 , wherein a speed of the second output component is variable such that a vehicle propulsion speed is variable.

14. The power split drive system of claim 13 , wherein the vehicle can creep from 0 to 20 miles per hour in a work mode of the power split device.

15. The power split drive system of claim 13 , wherein the vehicle can creep from 0 to 5 miles per hour in the work mode.

16. The power split drive system of claim 13 , wherein the variable displacement hydraulic machine operates as a pressure-compensated variable displacement pump.

17. The power split drive system of claim 13 , wherein there is at least one coupler to engage the input component with the power-take-off port and planetary gear set to switch the vehicle between the ‘work (sweep)’ mode and a ‘transport’ mode.

18. The power split drive system of claim 12 , wherein the work system includes at least one hydraulic pump, connected to the hydraulic work circuit port or power take-off port.

19. The power split drive system of claim 12 , wherein the planetary gear set includes a ring gear serving as an input component, a sun gear connected to the first output component and a planet gear carrier connected to the second output component.

20. The power split drive system of claim 12 , wherein the control system communicates with chassis engine control modules and controls the displacement of the hydraulic machine to vary a torque of the variable displacement machine in response to an acceleration pedal signal inside the vehicle cab.

21. The power split drive system of claim 12 , wherein the hydraulic machine is switched between operating as a pump and a motor by operation of directional control valves.

22. The power split drive system of claim 17 , wherein the coupler connects the input component to second output component directly in the transport mode, such that an on-highway chassis original driveline arrangement is restored.

23. A power split device with a variable transmission for mechanically connecting a chassis single engine to a work system and to a vehicle driveline, the power split device comprising:

a. an input component with a shaft for joining to the chassis engine;

b. a hydraulic work circuit port or a power-take-off port to provide power for work equipment;

c. a variable displacement hydraulic work machine;

d. at least one planetary gear set, in which:

i. a first output component with a shaft for connecting to the hydraulic work machine, which is able to provide power to a work system from the input component;

ii. a second output component with a shaft for connecting and providing power to the vehicle driveline from the input component; and

e. a control system to manage the hydraulic work machine, wherein power from the single engine can be selectively distributed between the work system and the vehicle driveline system, wherein the variable displacement hydraulic machine operates as a hydraulic pump in a ‘work (sweep)’ mode during forward propulsion of the vehicle such that pressurized fluid is provided by the hydraulic machine to drive work equipment, and wherein the hydraulic machine operates as a hydraulic motor in reverse propulsion of the vehicle to drive the vehicle.

24. The power split device of claim 23 , wherein a speed of the second output component is variable such that a vehicle propulsion speed is variable.

25. The power split device of claim 24 , wherein the variable displacement hydraulic machine operates as a pressure-compensated variable displacement pump.

26. The power device system of claim 23 , wherein the planetary gear set includes a ring gear serving as an input component, a sun gear connected to the first output component and a planet gear carrier connected to the second output component.

27. The power split device of claim 23 , wherein the control system is configured to communicate with a chassis engine control module and controls the displacement of the hydraulic machine to vary a torque of the variable displacement machine in response to an acceleration pedal signal inside a vehicle cab.

28. The power split device of claim 23 , wherein the hydraulic machine is switched between operating as a pump and a motor by operation of directional control valves.

29. The power split device of claim 23 , wherein there is at least one coupler to engage the input component with the power-take-off port and planetary gear set to switch the vehicle between the ‘work (sweep)’ mode and a ‘transport’ mode.

30. The power split device of claim 29 , wherein the coupler connects the input component to second output component directly in the transport mode, such that an on-highway chassis original driveline arrangement is restored.