The walking hydraulic system of Hitachi excavator is composed of constant power series pump, two three position six-way directional valves, left and right walking motors, pedal proportional pilot valve, etc. When the three position six way directional valve 3 is in the left position and the three position six way directional valve 5 is in the left position, the traveling motor rotates and the excavator advances; When the three position six-way directional valve 3 and the three position six-way directional valve 5 are in the middle position, the traveling motor stops rotating, the middle position adopts the y-rod function, and the left and right traveling motors brake under the friction brake pad of the internal mechanical braking device; When the three position six way directional valve 3 is in the right position and the three position six way directional valve 5 is in the right position, the traveling motor rotates and the excavator reverses: when one three position six way directional valve is in the left position (right position) and the other three position six way directional valve is in the middle position, one traveling motor rotates and the other traveling motor brakes, which can realize the local steering of the excavator
The hydraulic system adopts double pumps to supply oil to the left and right traveling motors respectively. Due to the deviation between the oil supply quantity and pressure of the two oil pumps, the leakage of the central swivel joint, the pressure of the motor on one side decreases, the output torque and speed of the hydraulic motor decrease due to the damage or aging of the internal oil seal of the hydraulic motor on one side, and the damage of the travel control valve, resulting in the insufficient oil supply of the traveling motor on one side The travel control pilot valve is damaged or the pressure build-up is insufficient, resulting in insufficient oil supply to a side of the travel motor, the brake braking cannot be released in time due to the jamming of the balance valve of the braking system, the brake braking cannot be released in time due to the wear of the brake sealing ring, the track tensioning mechanism becomes loose, resulting in track slip, etc.
