Control device for a hydraulic pump of construction machinery

A hydraulic pump control device for a construction machine including an engine, a variable displacement hydraulic pump connected to the engine, an operation lever generating a secondary signal pressure in proportion to an operation amount, a control valve installed in a bypass path of the hydraulic pump to control a flow rate discharged from the hydraulic pump in accordance with an operation of the operation lever, a hydraulic actuator driven by hydraulic fluid supplied when the control valve is shifted, an orifice installed on a downstream side of the bypass path to form a negative signal pressure, and a regulator controlling a discharge flow rate by controlling an inclination angle of a swash plate of the hydraulic pump, the hydraulic pump control device comprising:

• an accumulator storing a signal pressure of pump control;
• a solenoid valve movable between a first position and a second position, in the first position the solenoid valve directs through the solenoid valve signal pressure from the accumulator to the regulator, in the second position the solenoid valve directs through the solenoid valve the negative signal pressure generated by the orifice to the regulator;
• and
• a safety lever configured to be manually actuated by an operator to apply a solenoid control signal to the solenoid valve for moving the solenoid valve between the first position and the second position,
• wherein movement of the solenoid valve manually by the operator during engine start to the first position to direct signal pressure from the accumulator to the regulator results in the regulator maintaining the inclination angle of the swash plate of the hydraulic pump at minimum capacity by compensating for the negative signal pressure;
• and
• the safety lever comprises a switch which is switched on to supply the solenoid control signal to the solenoid valve so that the solenoid valve is shifted when the safety lever is shifted to a locking position.