Arrangement And A Method For Controlling A Work Vehicle

Abstract

An arrangement for controlling a work vehicle including a hydraulic system that includes at least one pump and at least one actuator operatively driven by hydraulic fluid delivered from the pump is provided. At least a first pump is a variable displacement pump. The system is of load-sensing type in that the pump displacement is controlled by a pilot pressure representing a load exerted on the system. The arrangement includes an arrangement for reducing the pilot pressure delivered to the first pump so that the first pump displacement is regulated down when there is a need for limiting hydraulic power consumption.

1 . An arrangement for controlling a work vehicle ( 1 ) comprising a hydraulic system ( 22 ), which comprises at least one pump ( 18 , 180 ) and at least one actuator ( 4 , 5 , 8 , 9 , 10 ) operatively driven by hydraulic fluid delivered from said pump, wherein at least a first pump ( 18 ) is a variable displacement pump, the system ( 22 ) being of load-sensing type in that the pump displacement is controlled by a pilot pressure representing a load exerted on the system, characterized in that the arrangement comprises means ( 63 ) for reducing the pilot pressure delivered to the first pump ( 18 ) so that the first pump displacement is regulated down when there is a need for limiting hydraulic power consumption.  
   
   
       2 . An arrangement according to  claim 1 , characterized in that said means ( 63 ) for reducing the pilot pressure to the first pump ( 18 ) is adapted to reduce the pilot pressure to the first pump to such an extent that the first pump does not deliver any hydraulic fluid flow.  
   
   
       3 . An arrangement according to  claim 1  or  2 , characterized in that the hydraulic system ( 22 ) comprises at least two variable displacement pumps ( 18 , 180 ) for delivering hydraulic fluid to said actuator ( 4 , 5 , 8 , 9 , 10 ).  
   
   
       4 . An arrangement to  claim 3  characterized in that the displacement of a second pump ( 180 ) is controlled by a pilot pressure representing the load exerted on the system in a non-manipulated form.  
   
   
       5 . An arrangement to  claim 3  or  4  characterized in that conduits ( 48 , 59 ) for the pilot pressure are connected both to an input pilot port ( 47 ) of the first pump ( 18 ) and to an input pilot port ( 45 ) of a second pump ( 180 ), that a flow restrictor ( 66 ) is arranged on the conduit ( 48 ) to the input pilot port ( 47 ) of the first pump ( 18 ) and that the flow restrictor is arranged upstream of said means ( 63 ) for reducing the pilot pressure to said first pump.  
   
   
       6 . An arrangement according to any of the preceding claims, characterized in that said means ( 63 ) for reducing the pressure to said first pump ( 18 ) is formed by a valve, and that the valve in an activated state is adapted to at least partly route the pilot pressure in a conduit ( 65 ) bypassing the first pump.  
   
   
       7 . An arrangement according to any of the preceding claims characterized in that each pump ( 18 , 180 ) has an associated hydraulically controlled arrangement ( 43 , 44 ) for controlling the displacement of the pump and that the displacement control arrangement controls the pump displacement depending on the input pilot pressure.  
   
   
       8 . An arrangement according to any of the preceding claims characterized in that said pump ( 18 , 180 ) is operatively driven by an engine ( 14 ) arranged for propelling the vehicle.  
   
   
       9 . An arrangement according to  claim 8  characterized in that the arrangement comprises means ( 60 , 61 , 70 ) for detecting an operation state of a driveline ( 13 ) of the work vehicle and means ( 62 ) connected to the detection means for evaluating the detected operation state and generating an operation state signal.  
   
   
       10 . An arrangement according to  claim 9  characterized in that said evaluating means ( 62 ) is connected to said means ( 63 ) for reducing the pilot pressure to the first pump ( 18 ) for controlling the displacement reduction depending on the operation state of the driveline.  
   
   
       11 . An arrangement according to  claim 9  or  10  characterized in that said detection means comprises means ( 60 ) for detecting an engine speed.  
   
   
       12 . An arrangement according to any of claims  9 - 11  characterized in that said detection means comprises means for detecting a turbocharger pressure.  
   
   
       13 . An arrangement according to any of claims  9 - 12  characterized in that said detection means comprises means for detecting an engine torque or output power.  
   
   
       14 . An arrangement according to any of claims  9 - 13  characterized in that said detection means comprises means ( 61 ) for detecting a gear state in a vehicle gear box ( 15 ).  
   
   
       15 . An arrangement according to any of claims  9 - 14  characterized in that said detection means comprises means ( 70 ) for detecting a position of an accelerator pedal ( 71 ).  
   
   
       16 . An arrangement according to claim any of claims, characterized in that at least one of said actuators is arranged to move an implement of the work vehicle.  
   
   
       17 . A method of controlling a work vehicle with a hydraulic system for operating at least one actuator, comprising the steps of sensing a load exerted on the system and controlling a displacement of a first pump with variable displacement by means of a pilot pressure representing the load, the pump operatively driving the actuator by delivering hydraulic fluid to it, and reducing the pilot pressure to the first pump in case the hydraulic power needs to be limited.  
   
   
       18 . A method according to  claim 17 , wherein the pilot pressure to the first pump is reduced to such an extent that the first pump does not deliver any hydraulic fluid flow.  
   
   
       19 . A method according to  claim 17  or  18 , wherein said pump is operatively driven by an engine arranged for propelling the vehicle.  
   
   
       20 . A method according to any of claims  17 - 19 , wherein an operation state of a driveline of the work vehicle is detected, the detected operation state is evaluated and an operation state signal generated for controlling the pump displacement reduction depending on the operation state of the driveline.  
   
   
       21 . A method according to  claim 20 , wherein an engine speed is detected.  
   
   
       22 . A method according to  claim 20  or  21 , wherein a turbocharger pressure is detected.  
   
   
       23 . A method according to any of claims  20 - 22 , wherein an engine torque or output power is detected.  
   
   
       24 . A method according to any of claims  20 - 23 , wherein a position of an accelerator pedal ( 71 ) is detected.  
   
   
       25 . A method according to any of claims  20 - 24 , wherein a gear state in a vehicle gear box ( 15 ) is detected.  
   
   
       26 . A computer program comprising code means for performing all the method steps described in any of claims  17 - 25  when said program is run on a computer.  
   
   
       27 . A computer program product comprising program code means stored on a computer readable medium for performing the method described in any of claims  17 - 25  when said program product is run on a computer.