What are the functions of hydraulic pumps and hydraulic motors respectively

We all know that the function of hydraulic pumps is to convert mechanical energy into hydraulic energy of liquids, while hydraulic motors convert hydraulic energy of liquids into mechanical energy. Both hydraulic system components play a role in energy conversion. So what are the similarities or differences between them?

The similarities between hydraulic pumps and hydraulic motors:

1) In principle, hydraulic motors and pumps are reversible. If driven by a motor, the output is hydraulic energy (pressure and flow), which is a hydraulic pump; If the input pressure oil outputs mechanical energy (torque and speed), it becomes a hydraulic motor.

2) From a structural perspective, the two are similar.

3) From the perspective of working principle, both use changes in sealing working volume for oil suction and drainage. For hydraulic pumps, when the working volume increases, oil is sucked in, and when the working volume decreases, high-pressure oil is discharged. For hydraulic motors, when the working volume increases, high-pressure oil enters, and when the working volume decreases, low-pressure oil is discharged.

Differences between hydraulic pumps and hydraulic motors:

1) Hydraulic pump is a conversion device that converts the mechanical energy of the motor into hydraulic energy, outputting flow and pressure, hoping for high volumetric efficiency; A hydraulic motor is a device that converts the pressure energy of a liquid into mechanical energy, outputting torque and speed, hoping for high mechanical efficiency. Therefore, hydraulic pumps are energy devices, while hydraulic motors are executive components.

2) The steering of the output shaft of the hydraulic motor must be able to rotate forward and reverse, so its structure is symmetrical; Some hydraulic pumps (such as gear pumps, vane pumps, etc.) have clear regulations for steering, and can only rotate in one direction and cannot change the direction of rotation at will.

3) In addition to the inlet and outlet ports, hydraulic motors also have separate leakage ports; Hydraulic pumps generally only have inlet and outlet ports (excluding axial piston pumps), and their internal leakage liquid is connected to the inlet port.

4) The volumetric efficiency of hydraulic motors is lower than that of hydraulic pumps.

In addition, the working speed of hydraulic pumps is usually higher, while the output speed of hydraulic motors is lower. In addition, the oil suction port of the gear pump is large and the oil discharge port is small, while the oil suction and discharge ports of the gear hydraulic motor are of the same size.