The Difference Between Hydraulic Pump And Hydraulic Motor

First: different emphasis points: hydraulic pumps provide pressure and flow, emphasizing volumetric efficiency; Hydraulic motors are designed to generate torque to drive loads, emphasizing mechanical efficiency.
Second: different speed conditions: hydraulic pumps usually operate under relatively constant high speed conditions; The speed range of hydraulic motors is relatively large, some requirements are very low, and some require operation at very high speed.
Third: the operation direction is different: the hydraulic pump shaft usually runs in one direction, but the flow direction and pressure may change; Most hydraulic motors require positive and negative operation in both directions, and some hydraulic motors also require that they can operate in a pump mode (pump condition) to achieve the purpose of braking load.
Fourth, the temperature change of the working fluid is different: the hydraulic pump in most systems are continuous operation, the temperature change of the working fluid is relatively small; Hydraulic motor according to the working conditions, the operation may be intermittent, will be subjected to frequent temperature shock.
Fifth: the bearing capacity of the main shaft is different: most hydraulic pumps are installed with the prime mover, and the main shaft generally does not bear additional load; Many hydraulic motors are mounted directly in the wheel or interlinked with belt wheels, sprockets or gears, and sometimes the spindle will bear a high radial load.
In addition to these five points, there are also differences in parameters:
1, the hydraulic motor is usually allowed to exceed the rated pressure of 20%-50% in a short period of time under pressure, but the instantaneous maximum pressure can not appear at the same time as the maximum speed. The back pressure of the oil return circuit of the hydraulic motor has a certain limit, and the leakage pipe must be set when the back pressure is large.
2, usually should not make the maximum torque and maximum speed of the hydraulic motor appear at the same time. The actual speed should not be lower than the minimum speed of the motor to avoid crawling. When the speed required by the system is low, and the performance parameters of the motor such as speed and torque are not easy to meet the working requirements, a deceleration mechanism can be added between the motor and the main engine driven by it. In order to operate smoothly at very low speeds, the leakage from the motor must be constant, with a certain oil return back pressure and an oil clearance of at least 35mm2/s. For motors that need to operate at low speeds, check their minimum stable speed.
3. In order to prevent cavitation or loss of braking ability of the brake motor working as a pump, it should be ensured that the oil suction port of the motor has enough oil pressure at this time, which can be achieved by the oil pump in the closed circuit or the back pressure valve in the open circuit; When the hydraulic motor drives a large inertia load, a bypass check valve in parallel with the motor should be set up in the hydraulic system to replenish oil, so as to avoid the lack of oil in the inertial motor during the shutdown process.
4, for the hydraulic motor can not bear additional axial and radial force, or the hydraulic motor can bear additional axial and radial force, but the actual axial and radial force of the load is greater than the axial force or radial force allowed by the hydraulic motor, should consider the use of elastic coupling to connect the motor output shaft and the working mechanism.
5. When the motor needs to be locked for a long time to prevent load movement, the hydraulic release mechanical brake on the motor shaft should be used.