Travel control device for work vehicle and work vehicle

Abstract

A travel control device for a work vehicle includes: a hydraulic pump; a plurality of hydraulic motors connected to the hydraulic pump in parallel through a closed-circuit connection, that drive different wheels with pressure oil delivered from the hydraulic pump; a slip detection device that detects a slip occurring at each of the wheels; and a flow control device that reduces, upon detection of a slip occurring at any of the wheels by the slip detection device, a quantity of pressure oil supplied to a hydraulic motor for driving the wheel at which the slip has been detected, among the plurality of hydraulic motors.

1 . A travel control device for a work vehicle, comprising:
 a hydraulic pump;   a hydraulic motor for driving front wheels and a hydraulic motor for driving rear wheels with pressure oil delivered from the hydraulic pump, connected to the hydraulic pump in parallel through a closed-circuit connection;   a slip detection device that detects a slip occurring at any of the front wheels and the rear wheels; and   a flow control device that reduces, upon detection of a slip occurring at any of the front wheels and the rear wheels by the slip detection device, a quantity of pressure oil supplied to a hydraulic motor for driving the wheel at which the slip has been detected, among the hydraulic motor for driving the front wheels and the hydraulic motor for driving the rear wheels.   
     
     
         2 . A travel control device for a work vehicle according to  claim 1 , wherein:
 the flow control device reduces the quantity of pressure oil supplied to the hydraulic motor by a greater extent as an extent of slippage detected by the slip detection device becomes larger.   
     
     
         3 . A travel control device for a work vehicle according to  claim 1 , wherein:
 the flow control device comprises a restoring device that gradually restores the quantity of pressure oil supplied to the hydraulic motor to a value before reduction as the slip detection device determines that a slip is eliminated after the quantity of pressure oil supplied to the hydraulic motor is reduced upon the detection of a slip by the slip detection device.   
     
     
         4 . A travel control device for a work vehicle according to  claim 1 , wherein:
 the slip detection device comprises a speed detection device that detects a rotational velocity at each of the front wheels and the rear wheels, estimates a vehicle speed based upon the rotational velocities detected by the speed detection device and detects a slip based upon deviations of the rotational velocities detected by the speed detection device relative to the estimated vehicle speed.   
     
     
         5 . A travel control device for a work vehicle according to  claim 1 , wherein:
 the flow control device comprises flow control valves each disposed in a pipeline between the hydraulic pump and one of the hydraulic motor for driving the front wheels and the hydraulic motor for driving the rear wheels and electromagnetic switching valves via which a pilot pressure is applied to the flow control valves.   
     
     
         6 . A travel control device for a work vehicle according to  claim 3 , wherein:
 the flow control device comprises flow control valves each disposed in a pipeline between the hydraulic pump and one of the hydraulic motor for driving the front wheels and the hydraulic motor for driving the rear wheels and electromagnetic switching valves via which a pilot pressure is applied to the flow control valves; and   the restoring device is constituted with slow return valves that slowly restores the pilot pressure applied to the flow control valves via the electromagnetic switching valves.   
     
     
         7 . A travel control device for a work vehicle according to  claim 3 , wherein:
 the flow control device comprises flow control valves each disposed in a pipeline between the hydraulic pump and one of the hydraulic motor for driving the front wheels and the hydraulic motor for driving the rear wheels and electromagnetic switching valves via which a pilot pressure is applied to the flow control valves; and   the restoring device is constituted with a delay processing circuit that executes delay processing on control signals provided to the electromagnetic switching valves.   
     
     
         8 . A work vehicle comprising:
 a drive control device for a work vehicle according to  claim 1 .   
     
     
         9 . A travel control device for a work vehicle according to  claim 2 , wherein:
 the flow control device comprises a restoring device that gradually restores the quantity of pressure oil supplied to the hydraulic motor to a value before reduction as the slip detection device determines that a slip is eliminated after the quantity of pressure oil supplied to the hydraulic motor is reduced upon the detection of a slip by the slip detection device.   
     
     
         10 . A travel control device for a work vehicle according to  claim 2 , wherein:
 the slip detection device comprises a speed detection device that detects a rotational velocity at each of the front wheels and the rear wheels, estimates a vehicle speed based upon the rotational velocities detected by the speed detection device and detects a slip based upon deviations of the rotational velocities detected by the speed detection device relative to the estimated vehicle speed.   
     
     
         11 . A travel control device for a work vehicle according to  claim 3 , wherein:
 the slip detection device comprises a speed detection device that detects a rotational velocity at each of the front wheels and the rear wheels, estimates a vehicle speed based upon the rotational velocities detected by the speed detection device and detects a slip based upon deviations of the rotational velocities detected by the speed detection device relative to the estimated vehicle speed.