Work machine including hydrostatic ground drive which automatically provides increased propulsion torque when the mechanical transmission is in a high gear
View Patent ↗A work machine having a mechanical transmission in combination with a hydrostatic ground drive including a primary drive and a secondary drive engageable for providing additional propulsion torque in a power assist mode, the hydrostatic drive automatically providing an increased torque capability when the transmission is engaged in a high speed range, thereby allowing the work machine to accelerate from a complete stop to a high speed range with the transmission in a high speed range without the need to stop to shift the mechanical transmission to accommodate an increased propulsion torque requirement.
1. A self-propelled agricultural work machine, comprising:
a set of primary movers supporting a portion of the machine and operable for propelling the machine over the ground at a ground speed;
a set of secondary movers supporting another portion of the machine and operable by at least one secondary fluid motor connected in driving relation thereto for driving the secondary movers for assisting the primary movers for propelling the machine;
a mechanical transmission connected in driving relation directly to the set of primary movers, the transmission being selectably engageable in a plurality of speed ranges, including at least one road speed range for propelling the work machine between a zero ground speed and a predetermined high ground speed suitable for travel over public roads, and at least one low speed range within the road speed range for propelling the work machine between the zero ground speed and a predetermined low ground speed suitable for performing work functions in agricultural fields and slower than the predetermined high ground speed, the transmission being configured and operable for transitioning between the plurality of speed ranges only at the zero ground speed;
a hydrostatic drive including a pump connected in a fluid loop with a primary fluid motor and operable for directing a flow of pressurized fluid through the loop at a fluid pressure to the primary fluid motor for controllably driving the primary fluid motor, the primary fluid motor being connected in driving relation to the mechanical transmission;
a valve connected to the fluid loop and to the at least one secondary fluid motor and selectably operable in a power assist mode for diverting a portion of the flow of fluid in the loop from the primary fluid motor to the at least one secondary motor for controllably driving the at least one secondary fluid motor;
a controller configured and operable for monitoring the speed range of the transmission, the fluid pressure in the loop, and the ground speed of the machine, the controller connected in operative control of the valve and programmed for automatically operating the valve in the power assist mode when the transmission is engaged in the at least one road speed range and the ground speed is below a predetermined transition speed less than the predetermined high ground speed.
2. The work machine of claim 1 , wherein the controller is programmed for automatically operating the valve to produce gradual changes in the fluid pressure in the loop.
3. The work machine of claim 1 , wherein the controller is further programmed for automatically operating the valve in the power assist mode when the mechanical transmission is engaged in the at least one road speed range and the fluid pressure exceeds a predetermined maximum fluid pressure and remains greater than a predetermined lower, transition fluid pressure.
4. The work machine of claim 1 , wherein the plurality of speed ranges comprises a first speed range for propelling the machine between the zero ground speed and a predetermined first ground speed, a second speed range including the first speed range for propelling the machine between the zero ground speed and a predetermined second ground speed, a third speed range including the second speed range for propelling the machine between the zero ground speed and a predetermined third ground speed, and a fourth speed range including the third speed range for propelling the machine between the zero ground speed and a predetermined fourth ground speed, and the controller is further programmed for automatically operating the valve in the power assist mode when the mechanical transmission is engaged in the third speed range or the fourth speed range and the ground speed is below a predetermined transition speed less than the predetermined third ground speed.
5. The work machine of claim 2 , wherein the power assist mode includes a first sub mode for diverting a first portion of the flow of fluid in the loop from the primary motor to the at least one secondary motor and a second sub mode for diverting a second smaller portion of the flow of fluid in the loop from the primary motor to the at least one secondary motor, and the controller is further programmed for automatically operating the valve in the first sub mode when the transmission is engaged in the at least one road speed range and the ground speed is below a predetermined first transition speed and operating the valve in the second sub mode when the transmission is engaged in the at least one road speed range and the ground speed is between the predetermined first transition speed and a predetermined second transition speed, the predetermined second transition speed being between the predetermined first transition speed and the predetermined high ground speed.
6. The work machine of claim 1 , wherein the predetermined high ground speed is about twenty miles per hour, the predetermined low ground speed is between about five and ten miles per hour, and the predetermined transition speed is about five miles per hour.
7. The work machine of claim 4 , wherein the predetermined first ground speed is about five miles per hour, the predetermined second ground speed is about ten miles per hour, the predetermined third ground speed is about fifteen miles per hour, the predetermined fourth ground speed is about twenty miles per hour, and the predetermined transition speed is about five miles per hour.
8. The work machine of claim 5 , wherein the predetermined first transition speed is about five miles per hour, the predetermined second transition speed is about ten miles per hour and the predetermined high ground speed is about twenty miles per hour.
9. The work machine of claim 4 , wherein the controller is further programmed for automatically operating the valve in the power assist mode when the mechanical transmission is engaged in the third speed range or the fourth speed range and the fluid pressure exceeds a predetermined maximum fluid pressure and remains greater than a predetermined lower, transition fluid pressure.
10. The work machine of claim 5 , wherein the controller is further programmed for automatically operating the valve in the second sub mode when the transmission is engaged in the at least one road speed range and the fluid pressure exceeds a predetermined second maximum fluid pressure and remains greater than a second predetermined transition fluid pressure lower than the second maximum fluid pressure and operating the valve in the first sub mode when the transmission is engaged in the at least one road speed range and the fluid pressure exceeds a first maximum pressure higher than the second maximum pressure and remains greater than a predetermined first transition fluid pressure.
11. A self-propelled agricultural work machine, comprising:
a set of primary movers supporting a portion of the machine and operable by a primary fluid motor for propelling the machine over the ground at a ground speed;
a set of secondary movers supporting another portion of the machine and operable by at least one secondary fluid motor connected in driving relation thereto for driving the secondary movers for assisting the primary movers for propelling the machine;
a mechanical transmission connected in driven relation to the primary fluid motor and in driving relation directly to the set of primary movers, the transmission configured and operable for shifting between a plurality of speed ranges only when the machine is stationary, the plurality of speed ranges including at least one road speed range for propelling the work machine between a zero ground speed and a predetermined high ground speed suitable for travel over public roads, and at least one low speed range within the road speed range for propelling the work machine between the zero ground speed and a predetermined low ground speed slower than the predetermined high speed;
a hydrostatic drive including a pump connected in a fluid loop with the primary fluid motor and operable for directing a flow of pressurized fluid through the loop at a fluid pressure to the primary fluid motor for controllably driving the primary fluid motor;
a valve connected to the fluid loop and to the at least one secondary fluid motor and selectably operable in a power assist mode for diverting a portion of the flow of fluid in the loop from the primary fluid motor to the at least one secondary fluid motor for controllably driving the at least one secondary fluid motor;
a controller configured and operable for monitoring the speed range of the transmission, the fluid pressure in the loop, and the ground speed of the machine, the controller connected in operative control of the valve and programmed for automatically operating the valve in the power assist mode when the transmission is in the at least one road speed range and the ground speed is less than a predetermined transition speed which is less than the predetermined high ground speed.
12. The work machine of claim 11 , wherein the controller is programmed for automatically operating the valve to produce gradual changes in the fluid pressure in the loop.
13. The work machine of claim 11 , wherein the plurality of speed ranges comprise a first speed range for propelling the machine between the zero ground speed and a predetermined first ground speed, a second speed range including the first speed range for propelling the machine between the zero ground speed and a predetermined second ground speed, a third speed range including the second speed range for propelling the machine between the zero ground speed and a predetermined third ground speed, and a fourth speed range including the third speed range for propelling the machine between the zero ground speed and a predetermined fourth ground speed, and the controller is further programmed for automatically operating the valve in the power assist mode when the mechanical transmission is engaged in the third speed range or the fourth speed range and the ground speed is less than the predetermined transition speed which is less then the predetermined third ground speed.
14. The work machine of claim 12 , wherein the power assist mode includes a first sub mode for diverting a first portion of the flow of fluid in the loop from the primary motor to the at least one secondary motor and a second sub mode for diverting a second smaller portion of the flow of fluid in the loop from the primary motor to the at least one secondary motor, and the controller is further programmed for automatically operating the valve in the first sub mode when the transmission is engaged in the at least one road speed range and the ground speed is less than a predetermined first transition speed and operating the valve in the second sub mode when the transmission is engaged in the at least one road speed range and the ground speed is between the predetermined first transition speed and a predetermined second transition speed, the predetermined second transition speed being between the predetermined first transition speed and the predetermined high ground speed.
15. The work machine of claim 11 , wherein the predetermined high ground speed is about twenty miles per hour, the predetermined low ground speed is between about five and ten miles per hour, and the predetermined transition speed is about five miles per hour.
16. The work machine of claim 13 , wherein the predetermined first ground speed is about five miles per hour, the predetermined second ground speed is about ten miles per hour, the predetermined third ground speed is about fifteen miles per hour, the predetermined fourth ground speed is about twenty miles per hour, and the predetermined transition speed is about five miles per hour.
17. The work machine of claim 14 , wherein the predetermined first transition speed is about five miles per hour, the predetermined second transition speed is about ten miles per hour and the predetermined high ground speed is about twenty miles per hour.
18. The work machine of claim 11 , wherein the controller is further programmed for automatically operating the valve in the power assist mode when the mechanical transmission is engaged in the at least one road speed range and the fluid pressure exceeds a predetermined maximum fluid pressure and remains greater than a predetermined lower, transition fluid pressure.
19. The work machine of claim 13 , wherein the controller is further programmed for automatically operating the valve in the power assist mode when the mechanical transmission is engaged in the third speed range or the fourth speed range and the fluid pressure exceeds a predetermined maximum fluid pressure and remains greater than a predetermined lower, transition fluid pressure.
20. The work machine of claim 14 , wherein the controller is further programmed for automatically operating the valve in the second sub mode when the transmission is engaged in the at least one road speed range and the fluid pressure exceeds a predetermined second maximum fluid pressure and remains greater than a second predetermined transition fluid pressure lower than the second maximum fluid pressure and operating the valve in the first sub mode when the transmission is engaged in the at least one road speed range and the fluid pressure exceeds a first maximum pressure higher than the second maximum pressure and remains greater than a predetermined first transition fluid pressure.