Automatic high speed and low speed switching device for large excavator

Disclosed is an automatic high speed and low speed switching device for a large excavator. A working port B of a pilot-operated directional control valve (4) is communicated with a motor high speed and low speed control port X and a working port B of a high speed and low speed control electromagnetic valve (6), a working port A of the pilot-operated directional control valve (4) is communicated with a hydraulic oil tank (1), an oil inlet of the pilot-operated directional control valve (4) is communicated with a control port pipeline of a shuttle valve (3), an oil inlet K1 of the shuttle valve (3) is communicated with a get-on pilot signal Px, an oil inlet K2 of the shuttle valve (3) is communicated with a working port B of an electromagnetic valve (5), and a working port A of an electromagnetic valve (5) is communicated with a working port A of the high speed and low speed control electromagnetic valve (6) and a pilot pump (7). The automatic high speed and low speed switching device for the large excavator has the advantages that when the excavator travels at a high speed, the device is capable of achieving switching from the high speed state to the low speed state automatically under high pressure or get-on conditions, so that safety high-speed traveling of the excavator is guaranteed; the device is simple in structure and has a certain universality.