The primary criterion for selecting a hydraulic pump is […]
The primary criterion for selecting a hydraulic pump is the condition demand of the centering system, and on this basis, the output, operating pressure and structural type of the pump are determined.
To determine the flow of the extra flow pump of the pump, the highest speed demand of the element shall be implemented satisfactorily. Therefore, the output flow QP of the pump shall be determined according to the maximum flow and the leakage required by the system, that is, QP ≥ kqmax, QP
The output flow of a pump (L / min) k the disclosure coefficient of a system, usually k = 1.1 ~ 1.3 (the pipeline length takes the large value, the pipeline short takes the small value); Qmax implements the maximum flow required by component practice one by one (L / min).
According to the calculated flow, there are the following conditions for selecting pump:
① Assuming that the system is supplied with one actuator by a single pump, the hydraulic pump is selected according to the highest speed of the actuator.
② If the system is supplied by one hydraulic pump to several implementing elements, the flow required by each implementing element in each period shall be calculated, the flow circulation diagram shall be made, and the flow of the pump shall be selected according to the maximum flow.
③ Assuming that the system is supplied by two pumps, the small flow pump is selected according to the demand of the maximum working speed of the working feed; the active feed is supplied by two pumps together, and the oil demand of the active feed is calculated according to the demand of the active feed speed, from which the flow of the small flow pump fed by the working feed is subtracted, that is, the flow of the large flow pump.
④ When multiple actuating elements act together, the flow of the pump shall be determined according to the sum of the maximum flow of the actuating elements acting together.
⑤ Assuming that there is accumulator in the system as the power compensation of the implementing element, the flow specification of the pump can be smaller.
⑥ As for the system of regulating speed by saving valve in operation process, the minimum overflow flow of overflow valve (usually 3L / min) should be added when judging the flow of pump. After calculating the output flow of the pump, select the additional flow equal to or slightly greater than the calculated pump flow QP according to the commodity sample.
It should be noted that:
First, the extra flow of the selected pump should not be too much larger than the flow of the internship operation to prevent excessive overflow of the pump
, forming a larger power throw away.
Second, because the influence of disclosure is taken into account when determining the extra flow of the pump, the extra flow is larger than the flow required by the accounting, so the practice speed may be slightly larger.
The operating pressure of the additional pressure pump of the pump shall be determined according to the maximum operating pressure of the hydraulic cylinder, i.e
In the formula of PP ≥ Pmax + ∑Δ P or PP ≥ kpmax, the operating pressure of PP-1 pump (PA); the maximum operating pressure of pmax-1 actuator (PA) ∑Δ P-1 total pressure of oil inlet and return circuits (PA). In the initial calculation, 0.2-0.5 MPA can be taken for economical speed regulation and simpler oil circuit; 0.5-1.5 MPA can be taken for the system with speed regulating valve and disordered pipeline in the oil inlet circuit. K - coefficient, considering the pressure from the hydraulic pump to the pipeline of the implementing element, k = 1.3 ~ 1.5 is taken. In the commercial sample of hydraulic pump, the additional pressure and the maximum pressure value of the pump are indicated. After calculating PP, the pump shall be selected according to the extra pressure, and the extra pressure of the selected pump shall be equal to or higher than the calculated value. In use, only a short time overload place, or the scheme specially described in the commodity specification, is allowed to select the hydraulic pump according to the high pressure.
When the output flow and working pressure of the hydraulic pump are determined, the detailed structure of the pump can be selected. Compare the determined PP and QP values with the additional pressure and flow on the nameplate of the hydraulic pump to be selected, so that the value on the nameplate is equal to or slightly greater than PP
And the QP value is enough. In general, gear pump should be selected when the extra pressure is 2.5MPa; vane pump should be selected when the extra pressure is 6.3MPa; plunger pump should be selected when the working pressure is higher; if the load of the machine tool is large and there are active and slow working strokes, limited variable vane pump or double vane pump can be selected; when it is applied to the auxiliary equipment of the machine tool, such as feeding and clamping and other unimportant places, price can be selected Low cost gear pump; quantitative pump can be selected when frugal speed regulation is selected; variable pump shall be selected when high-power place is assumed, volume speed regulation or volume frugal speed regulation is adopted; vane variable pump shall be selected for medium and low-pressure system; plunger variable pump shall be selected for medium and high-pressure system; screw pump can be selected in extremely precise place, such as mirror grinding machine, etc., which requires little oil supply pulsation.
Determine the speed of the hydraulic pump when the type and specification of the hydraulic pump are determined, the speed of the hydraulic pump shall be selected according to the speed specified in the commodity sample.