Differences and Similarities between Hydraulic Motors and Hydraulic Pumps

From the perspective of working principle, hydraulic pumps can be used as hydraulic motors; The reverse is also true. However, due to their different functions, there are also different performance requirements for them. The structural differences between hydraulic pumps and hydraulic motors of the same type are mainly manifested in:

1. As the inlet of the hydraulic motor is pressure oil, which is higher than the atmospheric pressure, there is no difference in the structural size of the inlet and outlet ports. However, the working pressure of the hydraulic pump suction chamber is generally lower than the atmospheric pressure. To improve the oil suction capacity and avoid cavitation, the suction port is usually made larger than the outlet port.

2. The hydraulic motor directly drives the working mechanism, requiring forward and reverse bidirectional rotation, so the internal structure should have symmetry. Hydraulic pumps generally rotate in one direction, and in order to improve overall performance, their internal structure is sometimes designed to be asymmetrical.

3. The working range of the hydraulic motor is relatively wide to meet the requirements of the working mechanism. The bearing structure and lubrication method of the hydraulic motor need to consider the factors of speed changes in design to ensure normal operation within a wide speed range. However, the hydraulic pump has a high speed and little change, so there is no such requirement.

4. Hydraulic motors are usually started under load, requiring a large starting torque and high starting efficiency.

Due to the above reasons, many hydraulic pumps and motors of the same type cannot be used in reverse.