Hydraulic motor is the liquid pressure can be converted into mechanical energy device, from the principle, hydraulic pump can be used as a hydraulic motor, hydraulic motor can also be used as a hydraulic pump. But in fact the same type of hydraulic pump and hydraulic motor although similar in structure, but because of the two different working conditions, making the two in the structure of some differences.

1, hydraulic motors generally need positive and negative rotation, so the internal structure should have symmetry, while the hydraulic pump is generally unidirectional rotation, there is no such requirement.

2, in order to reduce the suction resistance, reduce radial force, the general hydraulic pump suction port is larger than the size of the discharge port. The pressure of the low pressure chamber of the hydraulic motor is slightly higher than the atmospheric pressure, so there is no such requirement.

3, the hydraulic motor is required to be able to work properly in a wide range of speeds, so it should use hydrodynamic bearings or hydrostatic bearings. Because when the motor speed is very low, if the dynamic pressure bearing, it is not easy to form a lubricating film.

4, vane pumps rely on the vane and rotor with high-speed rotation and the centrifugal force generated so that the vane is always close to the inner surface of the stator, the role of sealing oil, the formation of the working volume. If it is used as a motor, must be installed in the hydraulic motor blade root spring to ensure that the blade is always close to the inner surface of the stator, so that the motor can start normally.

5, hydraulic pumps need to ensure that the structure has the ability to self-priming, while the hydraulic motor does not have this requirement.

6, the hydraulic motor must have a large starting torque. The so-called starting torque, that is, the motor from a standstill state start, the motor shaft can output torque, the torque is usually greater than in the same work pressure difference in the operating state of the torque, so in order to make the starting torque as close as possible to the torque of the working state, the requirements of the motor torque of the pulsation of the small, internal friction is small.

Due to the hydraulic motor and hydraulic pump has the above different characteristics, so that many types of hydraulic motors and hydraulic pumps can not be reversed each other.