Hydraulic control device of a forklift truck

• Main Authors: Uno, Takashi, Yokomachi, Naoya, Ueda, Yuki, Matsuo, Tsutomu, Kanna, Takanori, Goto, Tetsuya
• Format: Patent
• Language: English
• Published: 23.10.2018
• Subjects: BLASTING; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR; FLUID-PRESSURE ACTUATORS; FLUID-PRESSURE ACTUATORS, e.g. SERVO-MOTORS; HAULING; HEATING; HOISTING; HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDEDFOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCEDIRECTLY TO THE SURFACE OF A LOAD; HYDRAULICS OR PNEUMATICS IN GENERAL; LIFTING; LIGHTING; MECHANICAL ENGINEERING; PERFORMING OPERATIONS; SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; TRANSPORTING; WEAPONS

A hydraulic control device of a forklift truck includes a first hydraulic cylinder, a first instruction member, a second hydraulic cylinder, a second instruction member, a hydraulic pump, an electric motor, a first passage which has a drain passage, a lowering control valve that controls flow of hydraulic oil, a flow rate control valve, and a controller. When a lowering operation of forks and an operation of a hydraulically-operated unit are performed simultaneously, when a required rotation speed of the hydraulic pump that is required for operating the hydraulically-operated unit at an instruction speed based on an operation of the second instruction member is a specified rotation speed or lower, the controller controls an instruction rotation speed of the electric motor so as to operate the hydraulic pump at the required rotation speed to thereby restrict the operation of the hydraulic pump.