Working Vehicle Travel Control Apparatus

Abstract

A working vehicle travel control apparatus, comprising: a variable displacement hydraulic pump; a variable displacement hydraulic motor connected in a closed circuit to the hydraulic pump and driven upon pressure oil from the hydraulic pump; a first control unit controls a motor displacement angle of the hydraulic motor by an electrical signal; a constant mesh transmission includes a clutch device that includes a High clutch section transmits power at a first transmission gear ratio and a Low clutch section that transmits power at a second transmission gear ratio, which is greater than the first transmission gear ratio, the constant mesh transmission transmits or interrupts power from the hydraulic motor; and a second control unit controls the first control unit so as to reduce the motor displacement angle to a predetermined value when the transmission is switched from the first transmission gear ratio to the second transmission gear ratio.

1 . A working vehicle travel control apparatus, comprising:
 a variable displacement hydraulic pump that is driven by an engine;   a variable displacement hydraulic motor that is connected in a closed circuit to the hydraulic pump and driven upon pressure oil from the hydraulic pump;   a first control unit that controls a motor displacement angle of the hydraulic motor by an electrical signal;   a constant mesh transmission that includes a clutch device that includes a High clutch section that transmits power at a first transmission gear ratio and a Low clutch section that transmits power at a second transmission gear ratio, which is greater than the first transmission gear ratio, the constant mesh transmission that transmits or interrupts power from the hydraulic motor; and   a second control unit that controls the first control unit so as to reduce the motor displacement angle to a predetermined value when the transmission is switched from the first transmission gear ratio to the second transmission gear ratio.   
     
     
         2 . A working vehicle travel control apparatus according to  claim 1 , wherein:
 the predetermined value of the motor displacement angle is set to be greater than a minimum displacement angle of the hydraulic motor and a minimal motor displacement angle at which the working vehicle can be driven by the hydraulic motor.   
     
     
         3 . A working vehicle travel control apparatus according to  claim 1 , wherein:
 the second control unit controls the first control unit so that when the transmission is switched from the first transmission gear ratio to the second transmission gear ratio, after the motor displacement angle is reduced to the predetermined value and fixed to the predetermined value for a predetermined period of time, and then the motor displacement angle is recovered.   
     
     
         4 . A wheel loader, comprising a travel control apparatus according to  claim 1 .