Hydraulic Power Source with Variable Displacement Pump
The most efficient hydraulic power source is a variable displacement pump. Figure 1 shows a diagrammatic arrangement of a pressure compensated variable displacement pump which supplies fluid to the system at constant pressure and varying flow. In a variable displacement pump the rate of flow is controlled by operating the delivery control lever which in turn varies the displacement of the pump from nominal zero to its maximum rating. Different methods are used to obtain variable displacement, but most designs use either the principle of variable swash plate angle or provide means for varying the angular position of the cylinder block assembly in relation to the drive shaft axis.
Fig 1. Pressure-compensated variable displacement pump.
The pre-load of the bias spring in the pressure control unit determines the supply pressure. If the pump delivers fluid in excess of that required by the system supply pressure will momentarily rise unbalancing the load acting on the piston of the delivery control actuator which will then reduce the displacement of the pump until flow equilibrium is restored. If the delivery control lever overshoots the equilibrium position, supply pressure-will drop below the nominal setting. unbalancing the control piston and thereby increasing pump flow until equilibrium is regained. Typical pressure flow characteristics of a pressure compensated variable delivery pump are shown in Fig. 2. Unless the pump is allowed to saturate. working pressure is always within the cut-off pressure band. the design of the pressure control unit determining pressure flow characteristics. Normally supply pressure at maximum flow is 90% or more of the pressure at zero flow.
Fig 2. Pressure-flow characteristics of a pressure-compensated variable displacement pump.
flow control in a variable displacement pump,hydraulic pump characteristic,hydraulic pump pressure flow,variable displacement pump flow pressure chart,variable hydraulic pump working principle,working principle of variable displacement pumpRelated posts:
- Hydraulic Power Supply with Accumulator A more efficient supply system employing some additional components, is...
- Hydraulic Constant Pressure Supply Typical arrangements of a constant pressure supply are shown in...