Created on:2021-06-16 09:46

Main parameters and common problems of hydraulic pump

Main parameters and common problems of hydraulic pump

1.6.10 variable method and variable control mode

(1) The basic principle and common methods of variable can be seen from the theoretical flow calculation formula of hydraulic pump [see formula (1-1)]. The flow of hydraulic pump can be adjusted by changing the speed of pump, 2 or displacement V (geometric parameter).

① The flow rate is adjusted by changing the speed n of the hydraulic pump. This kind of adjustment method has two schemes: throttle adjustment and frequency conversion adjustment because of different driving prime mover of hydraulic pump.

a. The throttle adjustment scheme is mainly used for the hydraulic pump with the internal combustion engine as the prime mover. By adjusting the throttle size of the internal combustion engine and changing the engine speed (that is, the speed of the hydraulic pump), the output flow of the hydraulic pump can be changed. However, the adjustment range of this scheme is limited by the lowest engine speed.

b. The frequency conversion regulation scheme is used for the hydraulic pump with the AC asynchronous motor controlled by the frequency converter as the prime mover. The output flow of the pump can be changed by changing the speed of the motor or the pump. This kind of adjustment scheme has good dynamic and static characteristics of the hydraulic pump, and has significant practical significance for the flow adjustment of the quantitative pump whose displacement can not be changed. With the reduction of the price of frequency converter, this kind of regulation scheme is increasingly valued and widely used.

② The flow rate is adjusted by changing the displacement V (geometric parameter) of the hydraulic pump. According to this principle, both vane pump and plunger pump can be made into variable displacement pump: single acting vane pump adopts the method of changing eccentricity, axial plunger pump adopts the method of changing swash plate inclination angle to adjust flow, which belongs to the scope of changing displacement. This kind of adjustment method has the remarkable characteristics of small loss and high efficiency, and is widely used.

(2) Variable control mode and its characteristics by changing the displacement of the hydraulic pump V (geometric parameters) to adjust the flow, when the speed of the pump is constant, the discharge flow of the pump changes, which can form a flow control pump. As there is always resistance load at the pump outlet, the change of pump outlet flow will affect the pump outlet pressure. Sometimes control the displacement of the pump can also control the working pressure of the pump, forming a pressure control variable pump. It can be seen that there are many kinds of variable control methods. In engineering practice, the axial piston pump is most suitable to install various variable control mechanisms in structure, so the variable control mode is the most. Vane pump can also be installed with a number of variable control mechanisms. Some typical variable control methods are shown in the table below.

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