Hydraulic pumps and hydraulic motors are essential hydraulic components on every excavator. The structure and working principle are also very similar. Some people outside the industry sometimes confuse these two things. Some people say that the hydraulic pump and the hydraulic motor are like a pair of lovers, each attacking the other; some people say that the hydraulic pump and the hydraulic motor are like a generator and an electric motor. Is this description correct? What is the difference between the two?
Similarities between hydraulic motors and hydraulic pumps:
(1) In principle, hydraulic motors and hydraulic pumps are reversible. If driven by a motor, the output is hydraulic energy (pressure and flow), which is a hydraulic pump; if pressure oil is input, the output is mechanical energy (turn Torque and speed), it becomes a hydraulic motor.
Hydraulic pump
(2) From the structural point of view, the two are similar.
Hydraulic motor
(3) In terms of working principle, both of them use the change of the sealed working volume to absorb and discharge oil. For hydraulic pumps, oil is sucked when the working volume increases, and high-pressure oil is discharged when the working volume decreases. For hydraulic motors, high-pressure oil enters when the working volume increases, and low-pressure oil is discharged when the working volume decreases.
The difference between hydraulic motor and hydraulic pump:
(1) The hydraulic pump is an energy device, and the hydraulic motor is an actuator. A hydraulic pump is a conversion device that converts the mechanical energy of a motor into hydraulic energy. It outputs flow and pressure and hopes to have high volumetric efficiency; a hydraulic motor is a device that converts the pressure energy of a liquid into mechanical energy and outputs torque and speed. It is hoped that the mechanical efficiency is high.
Komatsu excavator hydraulic pump
(2) The steering of the output shaft of the hydraulic motor must be able to rotate forward and reverse, so its structure is symmetrical; and some hydraulic pumps (such as gear pumps, vane pumps, etc.) have clear regulations for steering, and they can only rotate in one direction. The direction of rotation cannot be changed at will.
Hydraulic motor
(3) In addition to the oil inlet and outlet ports, hydraulic motors have separate oil leakage ports; hydraulic pumps generally have only oil inlet and outlet ports (except for axial piston pumps), and the internal leakage oil is communicated with the oil inlet.
(4) The volumetric efficiency of hydraulic motors is lower than that of hydraulic pumps.
(5) Generally, the working speed of hydraulic pumps is relatively high, while the output speed of hydraulic motors is relatively low. 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 the same size.
