In the late 1850s, the original low-speed large torque hydraulic motor was developed by a fixed rotor part of the pump, which consisted of an inner ring and a gear or rotor matched to it. The inner ring and the shell can be connected together, and the oil entering from the oil inlet pushes the rotor around a central point. This slowly rotating rotor is driven by a spline shaft to become a cycloid hydraulic motor.
After the advent of this initial cycloid motor, the motor of another concept began to form after several decades of evolution. The motor is fitted with rollers in a built-in gear ring. Motors with rollers can provide higher start-up and running torque, and rollers reduce friction, thus increasing efficiency, even at very low speeds the output shaft can produce stable output. By changing the direction of the input and output flow, the motor quickly reversing, and in two directions to generate equal value torque. Each series of motor has a variety of displacement of the election to meet a variety of speed and torque requirements.