CONTROL UNIT FOR UPPER SWIVEL BODY OF HYDRAULIC EXCAVATOR.

摘要

This invention relates to a control unit for an upper swivel body of a hydraulic excavator which is used in order to prevent an abrupt pressure rise in a hydraulic line and to make a smooth swivel control when the upper swivel body equipped with a driver's cabin and a working machine and having a large inertia is accelerated or decelerated. To this end, pressure control valves (10), (11) controlled together with proportional solenoid valves (8), (8a) by a controller (7) are connected to a discharge line and return line of a hydraulic pump (1) so as to control an input pressure and an output pressure of an upper swivel body driving motor (3) when the motor rotates. Particularly, one of the pressure control valves (10) controls and increases the driving pressure of the driving motor (3) in accordance with a speed increase signal outputted from the controller (7) and the other pressure control valve (11) controls and decrease the braking pressure of the driving motor (3) in accordance with a speed decrease signal outputted from the controller (7).