The rotary motor is the core hydraulic component of the excavator's on-board rotating mechanism,commonly known as a rotary motor.It is mostly a high-speed plunger motor and is usually combined with a rotary gearbox(planetary gearbox)to form a rotary assembly.It converts the hydraulic energy output by the main pump into mechanical energy and drives the cab,boom,and counterweight to achieve a 360°rotation of the entire vehicle.Internally integrated wet multi disc parking brake,rotary relief valve,oil replenishment valve,and buffer valve,with multiple functions of driving,buffering,and brake locking.

　　High pressure hydraulic oil enters the motor,pushing the plunger and sliding shoe to act on the inclined plate.The cylinder body rotates and outputs power,which is then reduced in speed and amplified in torque through the planetary gearbox,driving the small gear to mesh and rotate the large gear ring to complete the rotation of the vehicle.When the joystick is returned to the center position,the wet brake presses the friction plate under the action of the spring to lock the motor output shaft,achieving parking and preventing the car from slipping on the slope during operation;Operate the rotary handle again,and the pressure oil pushes open the brake piston to release the brake,so that the motor can rotate.The overflow valve is responsible for rotation overload protection;The oil replenishment valve prevents internal components from being damaged by suction and cavitation caused by rotational inertia.

　　The entire assembly includes the motor body,port plate,plunger shoe assembly,brake friction plate,valve group,reduction planetary gear,and output small gear.The motor friction pair relies entirely on hydraulic oil lubrication;Add gear oil separately for lubrication inside the gearbox,and do not mix hydraulic oil.Heavy loading and slope loading conditions in mines result in significant impact on turning start stop,high loads on motors and gearboxes,and accelerated wear and tear;The workload of earthwork leveling operations is relatively gentle.

　　The fault of the rotary motor will not trigger a separate alarm.Typical symptoms include weak or slow rotation,sliding on a slope,shaking and abnormal noise during rotation,heating of the motor housing,and excessive oil return from the drain port.Many repairs can easily confuse motor body,gearbox,and main valve faults,and blindly replace parts.Rotary motors belong to high-value precision hydraulic components,and the plunger and distribution plate are often scratched and worn,requiring professional hydraulic test benches for maintenance.Familiarity with the working logic of rotary motors and proper maintenance of hydraulic oil and gearbox gear oil can reduce early damage and avoid safety hazards and construction site shutdowns caused by rotary failure.