The hydraulic pump and the hydraulic motor are reversible hydraulic components. Input any working fluid to any hydraulic pump, it can be turned into a hydraulic motor. Otherwise, when the main shaft of the hydraulic motor is driven by the external torque, it can also be changed into a hydraulic pump.Because they have the same basic structural elements---closed and periodically variable volume and corresponding oil distribution mechanism.
However, the different working conditions between hydraulic motor and hydraulic pump, their performance requirements are different, so there are still many differences between the same type of hydraulic motor and hydraulic pump. First of all, the hydraulic motor is able to be positive and reversed, so its internal structure should be symmetrical;Hydraulic motor speed range needs to be large enough, especially for its minimum steady speed has certain requirements;therefore, it usually adopts rolling bearings or hydrostatic sliding bearings. Secondly, the hydraulic motor does not have the ability of self suction because it operates under the condition of input pressure oil, but it needs a certain initial sealing to provide the necessary starting torque. Because of these differences, the hydraulic motor and hydraulic pump are similar in structure, but can not be reversible.
According to their structural types,hydraulic motors can be divided into gear type, vane type, plunger type and other types ; According to the rated speed of hydraulic motor, it is divided into two categories: high speed and low speed. Rated speed is higher than 500r/min belongs to high-speed hydraulic motor, rated speed of less than 500r/min belongs to low-speed hydraulic motor. The basic types of high speed hydraulic motors are gear type, screw type, vane type and axial plunger type, etc. Their main characteristics are high speed, small inertia, easy to start and brake, adjust (speed and reverse) high sensitivity. Usually high-speed hydraulic motor output torque is not large, so it is also called high-speed small torque hydraulic motor. The basic type of low speed hydraulic motor is radial plunger type. In addition, the axial piston type, vane type and gear type also have low speed structure type. Low speed hydraulic motor is characterized by large displacement, large volume, low speed (sometimes up to a few revolutions per minute or even a few zeros). Therefore, the utility model can be directly connected with a working mechanism, and a speed reduction device is not needed, so that the driving mechanism is greatly simplified. Usually low-speed hydraulic motor output torque is larger, so it is also called low-speed large torque hydraulic motor.