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EP-4143389-B1 - METHODS FOR PREVENTING PRIME MOVER STALL

EP4143389B1EP 4143389 B1EP4143389 B1EP 4143389B1EP-4143389-B1

Inventors

  • JADHAV, MAHESH K
  • RUGGE, Kedar

Dates

Publication Date
20260513
Application Date
20210430

Claims (7)

  1. A method for preventing prime mover stall for a work machine including a hydraulic system, the method comprising: receiving, at a control system, a prime mover speed setting (1102) and a hydraulic system inlet pressure value (1104) associated with one or more control valves of the hydraulic circuit; calculating (1106), at the control system, an actual required flow rate value of the hydraulic circuit; referencing a map (1108), with the control system, using the prime mover speed setting the actual required flow rate, and the inlet pressure value to return a maximum flow rate setting; continuously or repeatedly monitoring an actual prime mover speed (1110) and updating the maximum flow rate setting based on the actual prime mover speed; operating the one or more control valves (1114) with the control system, such that the lesser of the actual required flow rate and the maximum flow rate setting is not exceeded (1112); and indirectly controlling a pump of the hydraulic system (1116) with a load-sense control to de-stroke the pump to meet the maximum flow rate setting to prevent stalling of the prime mover.
  2. The method of claim 1, wherein the map includes multiple curves for different prime mover speed settings.
  3. The method of claim 1, wherein the map is generated by the control system from a prime mover curve map.
  4. The method of claim 1, wherein the map includes curves for a power mode operational setting of the prime mover and for an economy mode operational setting of the prime mover.
  5. The method of claim 1, wherein the step of operating the one or more control valves includes reducing the opening area of the one or more valves such that the lesser of the actual required flow rate and the maximum flow rate setting is not exceeded to prevent stalling of the prime mover
  6. The method of claim 1, further including the step of defining a maximum flow demand setting by selecting the lower of the actual required flow rate and the maximum flow rate setting, wherein the step of operating the one or more control valves includes operating the one or more valves to not exceed the maximum flow demand setting.
  7. The method of claim 1, wherein the pump is operated without a torque limiter.

Description

BACKGROUND Hydraulic systems are commonly used to power various functions of work machines, such as the propulsion of the work machine and various work circuits. For example, a hydraulic system in an excavator application could be configured to power one or more hydraulic actuators to drive the work machine and to power boom, arm, bucket, swing and travel functions. In some circumstances, the combined power required to simultaneously service all of the power requirements of the work machine can be enough to stall the prime mover powering the hydraulic system. In some implementations, prime mover stall is controlled by utilizing a mechanical torque controller directly mounted on the pump. In some implementations, the torque controller is controlled through software by monitoring the prime mover speed drop, wherein the rate of change in prime mover speed is used to control flow from the pump through a separate control valve to prevent prime mover stall. In some cases, electronic displacement control pump is used to prevent prime mover stall. Although these approaches operate to prevent prime mover stall, additional costs are incurred, and additional components are required with respect to pump torque control, an electronic displacement control, etc. US 2012/221212 A1 discloses a hydraulic control system for a wheel loader with a pump, a plurality of actuators, and a plurality of valve arrangements configured to meter pressurized fluid. In the control system, a controller is configured to receive a pump torque limit, determine a maximum pump flow capacity, and determine desired flow rates for each of the plurality of valve arrangements based on the signals. The controller is further configured to make a first reduction of the desired flow rates based on the maximum pump flow capacity, to make a second reduction of the desired flow rates based on the pump torque limit, and to command the plurality of valve arrangements to meter the desired flow rates after the second reduction. SUMMARY In general terms, the present disclosure is directed to improved control approach for preventing prime mover stall for a work machine without requiring the incorporation of additional control equipment. Such work machines include, for example, an excavator, wheel loader, backhoe loader, tractor, telehandler, etc. In examples, the prime mover can be an internal combustion engine. In examples, the prime mover can be an electric motor. From the prime mover speed-torque/power curve a flow vs pressure map is generated for different prime mover speed and fed to the supervisory controller or alternatively the control system in the supervisory controller itself can generate the flow vs pressure map utilizing the prime mover speed- torque/power curve which is provided as an input. The actual set prime mover speed is communicated to the supervisory controller along with the pump inlet pressure. Based on these 2 inputs the control system determines the max flow that can be generated w/o stalling the prime mover at that particular prime mover speed and pump pressure from the map. This is referenced to 'max available flow'. The control system also estimates the 'total pump flow' required based on the joysticks input command. The flow sharing control block compares the 'total required flow' with the 'max available flow' and when the 'total required flow' is greater than 'max available flow' the block commands reduced flow demand based on the priority setting to different control valve spools to meet the max available flow. Based on the reduced flow demand the spool openings are reduced and the load sense pump accordingly de-strokes to maintain the LS margin thereby reducing the pump output flow and prevent the prime mover from stalling. The flow sharing block can reside in the supervisory controller or in the control valve controller like Eaton CMA twin spool control valve. According to the present invention, a method for preventing prime mover stall for a work machine including a hydraulic system includes the steps of receiving, at a control system, a prime mover speed requirement and a hydraulic system inlet pressure value associated with one or more control valves of the hydraulic circuit; calculating, at the control system, an actual required flow rate value of the hydraulic circuit; referencing a map, with the control system, using the prime mover speed setting the actual required flow rate, and the inlet pressure value to return a maximum flow rate setting; and continuously or repeatedly monitoring an actual prime mover speed and inlet pressure and updating the maximum flow rate setting based on the actual prime mover speed and the inlet pressure; operating the one or more control valves, with the control system, such that the lesser of the actual required flow rate and the maximum flow rate setting is not exceeded; and controlling a pump of the hydraulic system with a load-sense control to de-stroke the pump to meet the maximum flow rat