Method of slowing a hydrostatic drive work machine

• US 20060150809A1
• Filed: 01/12/2005
• Published: 07/13/2006
• Est. Priority Date: 01/12/2005
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Shah, Vaibhav H.
• Granted Patent: US 7,296,496 B2
• Time in Patent Office: Days
• US Class Current: 91/472
• CPC Class Codes: F16H 61/061 using electric control means
• CPC Class Codes: F16H 61/4157 Control of braking, e.g. preventing pump over-speeding when motor acts as a pump
• CPC Class Codes: F16H 61/421 Motor capacity control by electro-hydraulic control means, e.g. using solenoid valves
• CPC Class Codes: F16H 61/423 Motor capacity control by fluid pressure control means
• CPC Class Codes: F16H 61/431 Pump capacity control by electro-hydraulic control means, e.g. using solenoid valves
• CPC Class Codes: F16H 61/46 Automatic regulation in accordance with output requirements
• CPC Class Codes: F16H 61/462 for achieving a target speed ratio
• CPC Class Codes: Y10T 74/19163 with interrelated controls

Abstract

A method of reducing speed in a hydrostatic drive work machine, and a hydrostatic drive work machine are provided. The method includes the steps of retarding the work machine by at least one of, upstroking a variable displacement hydraulic motor thereof, and downstroking a variable displacement pump coupled with the motor. An offgoing clutch pressure is dropped after each of the motor and pump displacements reaches a predetermined point. The steps of slowing the work machine are carried out by adjusting the respective displacements at rates based on a predetermined acceleration limit and/or a predetermined jerk limit of the work machine. The hydrostatic drive work machine further includes an electronic control module having a control algorithm recorded thereon for to neutral.

Claims

1. A method of reducing speed in a hydrostatic drive work machine comprising the step of:

retarding the work machine by at least one of, downstroking a variable displacement pump and upstroking a variable displacement motor in a work machine hydrostatic drive that includes a transmission having at least two gears.

2. The method of claim 1 wherein the step of retarding the work machine comprises:

downstroking the pump toward a decreased displacement at a first rate;

upstroking the motor toward an increased displacement at a second rate;

wherein each of the first and second rates is based at least in part on one or both of a predetermined acceleration limit and a predetermined jerk limit of the work machine.

3. The method of claim 2 further comprising the step of:

dropping an offgoing clutch pressure after each of the motor displacement and pump displacement reaches the increased displacement and decreased displacement, respectively;

4. The method of claim 1 wherein the step of retarding the work machine comprises the steps of:

initially slowing the work machine by upstroking the variable displacement motor, prior to dropping the offgoing clutch pressure; and

further slowing the work machine by downstroking the variable displacement pump, prior to dropping the offgoing clutch pressure.

5. The method of claim 4 wherein:

the step of initially slowing the work machine comprises slowing the work machine at an initial deceleration rate; and

the step of further slowing the work machine comprises slowing the work machine at a subsequent deceleration rate that is greater than the initial deceleration rate.

6. The method of claim 5 wherein the step of slowing the work machine by upstroking the variable displacement motor comprises, prior to initiating downstroking of the pump, verifying that the motor has reached a point at or close to the increased displacement.

7. The method of claim 6 wherein the step of dropping the offgoing clutch pressure comprises initiating dropping the same only if the motor displacement is at or close to a maximum motor displacement, and the pump displacement is at or close to a zero pump displacement.

8. The method of claim 7 wherein upstroking the motor, downstroking the pump, and dropping the clutch pressure are all effected with an electronic control module operable to send a control signal to actuators associated one with each of the motor, pump and a clutch.

9. The method of claim 2 wherein the first rate and the second rate are rates of change in relative displacement of the motor and the pump, respectively, each being at least partially linear and the first rate being relatively faster than the second rate.

10. An article comprising:

a computer readable medium having a control algorithm recorded thereon, said control algorithm including means for slowing a hydrostatic drive work machine having at least two gears, said means for slowing including means for slowing said work machine by at least one of;

upstroking a variable displacement motor of the work machine toward an increased displacement; and

downstroking a variable displacement pump fluidly connected with said variable displacement motor toward a decreased displacement.

11. The article of claim 10 wherein:

said means for slowing includes, means for slowing said work machine at a first rate with said motor, and means for slowing said work machine at a second rate with said pump;

wherein each of said first and second rates is based at least in part on one or both of an acceleration limit and a jerk limit of said work machine.

12. The article of claim 11 wherein said means for slowing further includes means for determining a displacement of said motor, and means for initiating downstroking of said pump at a time based at least in part on the displacement of said motor.

13. The article of claim 12 wherein said means for slowing further includes means for determining a displacement of said pump and means for dropping an offgoing clutch pressure at a time based on the displacement of said pump.

14. The article of claim 13 wherein said means for slowing further includes:

means for activating a motor actuator to adjust a relative position of said motor at said first rate and a corresponding displacement thereof; and

means for activating a pump actuator to adjust a relative position of said pump at said second rate and a corresponding displacement thereof.

15. A hydrostatic drive work machine comprising:

a variable displacement motor;

a variable displacement pump fluidly connected with said variable displacement motor;

a transmission operably coupled with said motor and having at least two gears;

an electronic control module in control communication with said motor, said pump and said transmission, said electronic control module including an article having a computer readable medium with a control algorithm recorded thereon, said control algorithm including;

means for adjusting a displacement of each of said motor and said pump; and

means for slowing said work machine with at least one of said motor and said pump.

16. The hydrostatic drive work machine of claim 15 wherein said control algorithm further includes means for selectively disengaging one of said at least two gears when a displacement of said motor is at or close to an elevated displacement and a displacement of said pump is at or close to a decreased displacement.

17. The hydrostatic drive work machine of claim 16 wherein said means for adjusting a displacement of each of said motor and said pump includes means for adjusting each of the same at rates based at least in part on one or both of a predetermined acceleration limit and a predetermined jerk limit of said work machine to slow said work machine.

18. The hydrostatic drive work machine of claim 17 wherein said means for adjusting a displacement of each of said motor and said pump further includes means for initiating an upstroking of said pump at a time based at least in part on a displacement of said motor.

19. The hydrostatic drive work machine of claim 18 wherein:

said motor includes a rotatable motor drive plate operable to reciprocate a plurality of motor pistons and disposed at an adjustable angle relative thereto;

said pump includes a rotatable pump drive plate operable to reciprocate a plurality of pump pistons and disposed at an adjustable angle relative thereto;

said transmission further including at least two clutches operably coupled one with each of said at least two gears, wherein said means for selectively disengaging includes means for dropping a clutch pressure of one of said clutches at a time based at least in part on one or both of an angle of the motor drive plate relative to the motor pistons and the angle of the pump drive plate relative to the pump pistons.

20. The hydrostatic drive work machine of claim 18, further comprising:

a motor actuator coupled with said motor and operable to adjust a displacement thereof;

a pump actuator coupled with said motor and operable to adjust a displacement thereof;

at least one clutch actuator operable to drop a clutch pressure in said transmission to selectively disengage said at least two gears;

each of said motor actuator, said pump actuator and said at least two clutch actuators being operably coupled with said electronic control module;

said means for slowing including means for initiating dropping said clutch pressure only if a displacement of said motor is at a maximum displacement and a displacement of said pump is at a zero displacement.