Load control device for engine of work vehicle

Abstract

A load control device for an engine of a work vehicle that purposes to render the work vehicle, such as a wheel loader or the like, capable of raising a vehicle speed in a short period of time by providing a sufficient traction force when a high traveling load is imposed, without causing degradation of a vehicle body performance, waste of energy, and other problems. The load control device is provided with variable displacement hydraulic pumps ( 7, 8, 9 ) being provided with absorption torque changing means ( 19, 22 ) for changing absorption torque. A controller ( 18 ) determines whether a traveling load is in a high state, and when it has been determined that the traveling load is in the high state, control for lowering the absorption torque for the hydraulic pumps ( 7, 8, 9 ) is carried out. This control is carried out, provided, for example, that a “power mode” is selected with the power mode switch ( 31 ). The determination that the traveling load is in the high state can be made by determining that the wheel loader ( 100 ) is in an acceleration state.

1 . A load control device for an engine of a work vehicle in which an output of the engine is transmitted to a drive wheel, and the output of the engine is transmitted to a work machine through a variable displacement hydraulic pump, comprising:
 absorption torque changing means for changing absorption torque for the variable displacement hydraulic pump;   traveling load state determination means for determining whether a traveling load is in a high state;   deceleration state detecting means for detecting whether the work vehicle is in a deceleration state; and   control means for, when it is determined by the traveling load state determination means that the traveling load is in the high state, providing a control to lower the absorption torque for the variable displacement hydraulic pump, and when it is detected by the deceleration state detection means that the work vehicle is in the deceleration state, canceling the control for lowering the absorption torque for the variable displacement hydraulic pump.   
   
   
       2 . (canceled) 
   
   
       3 . The load control device for an engine of a work vehicle of  claim 1 , wherein the traveling load state determination means comprises:
 acceleration detection means for detecting acceleration of the work vehicle; and   means for determining whether the acceleration of the work vehicle detected by the acceleration detection means is a prescribed threshold value or over.   
   
   
       4 . The load control device for an engine of a work vehicle of  claim 1 , wherein the traveling load state determination means comprises:
 operation amount detection means for detecting an amount of operation of a running operation element; and   means for determining whether the amount of the operation of the running operation element detected by the operation amount detection means is a prescribed threshold value or over.   
   
   
       5 . The load control device for an engine of a work vehicle of  claim 1 , wherein the traveling load state determination means comprises:
 revolution difference computing means for computing a difference between a target revolution and an actual engine revolution for the engine; and   means for determining whether the revolution difference computed by the revolution difference computing means is a prescribed threshold value or over.   
   
   
       6 . (canceled) 
   
   
       7 . The load control device for an engine of a work vehicle of  claim 1 , wherein the output of the engine is transmitted to the drive wheel through a torque converter and a transmission, and
 the traveling load state determination means computes the traveling load on the basis of an input shaft revolution of the torque converter, an output shaft revolution of the transmission, and a speed stage being currently selected in the transmission.   
   
   
       8 - 12 . (canceled)