HYDRAULIC DRIVE CIRCUIT DEVICE FOR WORKING VEHICLE

• Main Author: IWAI TETSUO
• Format: Patent
• Language: English
• Published: 24.12.1999
• Edition: 6
• Subjects: BLASTING; CONVEYING; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR; FLUID-PRESSURE ACTUATORS; FLUID-PRESSURE ACTUATORS, e.g. SERVO-MOTORS; GATHERING OR REMOVAL OF DOMESTIC OR LIKE REFUSE; HANDLING THIN OR FILAMENTARY MATERIAL; HEATING; HYDRAULICS OR PNEUMATICS IN GENERAL; LIGHTING; MECHANICAL ENGINEERING; PACKING; PERFORMING OPERATIONS; STORING; SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; TRANSPORTING; WEAPONS

PROBLEM TO BE SOLVED: To provide a hydraulic drive circuit device for a working vehicle which reduces the discharge quantity of a variable displacement hydraulic pump directly coupled with an engine for traveling a vehicle without generating, any pressure loss of discharge fluid, and can be manufactured lightweight at a low cost. SOLUTION: In a hydraulic drive circuit device in which an orifice 5 and a hydraulic pilot operation type center bypass control valve 6 are interposed in a discharge circuit 3 continuous to a tank 4 from a variable displacement hydraulic pump 2 directly coupled with an engine 1 for traveling, the pressure before and behind the orifice 5 is lead to a discharge quantity control device 8 of the hydraulic pump through a signal line to control the increase/decrease of the discharge quantity of the pump, a sequence valve 14 is provided in the discharge circuit, and a pressure reducing valve 16 is interposed in the hydraulic pilot circuit, a solenoid control valve 19 to selectively introduce the pressure in the downstream or the tank pressure to a signal line 7b is provided. A second solenoid control valve to lead the secondary pressure of the pressure reducing valve 16 to a spring chamber of the sequence valve 14 may be provided.