Thread Content
Due to their poor sealing performance, low volumetric efficiency, the limitation on the input oil pressure, and the inability to generate high torque, gear hydraulic motors also experience changes in instantaneous speed and torque as the position of the meshing points changes. Therefore, they are suitable only for applications that require high speed and low torque. In this article, Xingdiyuan Machinery explains the structural features and working principles of hydraulic motors. I. Structural features and working principle of high-speed external gear motors: 1) The working principle of high-speed external gear motors is shown in Figure 3-58. http://www.yeyajichangjia.com/uploads/200310/1-200310141Z2136.jpg Figure 3-58 External gear motor 2) Structural features of the gear motor compared to gear pumps a. To meet the requirements for forward and reverse rotation, the gear motor has equal inlet and outlet ports, showing symmetry; it also has a separate drain port to carry the oil that leaks from the bearing area outside the housing. b. To reduce the starting friction torque, rolling bearings are used. c. To reduce torque pulsation, the gear ratio of the gear motor is higher than that of the pump. 3) Applications of gear motors Due to their poor sealing properties, low volumetric efficiency, the limitation on the input oil pressure, and the inability to generate high torque, as well as the fact that their speed and torque change depending on the position of the meshing points, gear hydraulic motors are suitable only for applications requiring high speed and low torque. They are generally used in construction machinery, agricultural machinery, and mechanical devices where high torque consistency is not required. II. Structural features and working principle of low-speed hydraulic motors: 1) Working principle of radial piston motors The basic type of low-speed hydraulic motor is the radial piston type, as shown in Figure 3-59. http://www.yeyajichangjia.com/uploads/200310/1-20031014192U91.jpg Figure 3-59: Principle of the rod-type radial piston motor 2) Characteristics of radial piston motors 1. Features: High input oil pressure and large displacement; it can operate stably at motor shaft speeds of less than 10 r/min, with good stability at low speeds; high output torque, ranging from several hundred to several thousand newton-meters ； 2. Advantages: Simple structure, reliable operation ； 3. Disadvantages: Large size and weight, as well as significant torque fluctuations.