A novel method to design pressure compensator for variable displacement axial piston pump

Abstract

An innovative design procedure has been formulated by developing a mathematical model for the pressure compensator of an axial piston pump. The compensator provides energy saving by making the pump variable displacement type depending on the system load, thereby providing energy saving by better resource management. The procedure involves simple static design steps to ensure a balanced swiveling torque on the swash plate for specified cut-in and cut-off pressure limits. Adopting the basic pump model from the earlier works, the dynamic model of the pump has been updated by including the compensator dynamics. A design sensitivity analysis through dynamic simulation has been performed that corroborates the need of the design through torque balancing. Also, through dynamic simulation, tolerances of some critical dimensions have been identified. The pressure compensator model has been validated against experimental result obtained from a reference pump.

A Single Stage Spool Valve for the Pressure Compensator of a Variable Displacement Pump – Design, Dynamic Simulation and Comparative Study With A Real Pump

“…(2) Table 1 lists the parameters some of which has been chosen from the earlier experience [14], while others are obtained from the above conditions. As shown in Fig.…”

Energy-saving design of variable-displacement bi-directional pump-controlled electrohydraulic system

“…A compensator in a VDP establishes flow matching by adjusting the pump stroking through a swash mechanism, whose inclination λ is guided by the piston in the stroking cylinder and a spring-loaded bias cylinder. 27–29 These cylinders are shown in Figure 1 as SC and BC, respectively. The change in inclination from λ max to λ min causes the stroking to vary from the maximum for the rated pump flow at a cut-in pressure to near zero at the cut-off pressure yielding no outflow from the pump.…”

“…A careful design of the clearance was found to contribute adequate damping to the stroking mechanism about any equilibrium position between the cut-in and cut-off orientations. 27,28 The loss of energy in any compensator valve for a VDP is insignificant, since it draws only a small amount of pilot flow from the pump delivery.…”

“…Hence, the net thrust on the former becomes much lower. A cut-off pressure above the cut-in value only by a close margin is achieved in a good design of each valve, 27 as the movement of the spool over a close range allows the complete switching of the connection across the metered port from the tank to pump ports. This requires the spring stiffness of the LSV actuated by a lower differential pressure to be much higher than that in the COV actuated by only the delivery pressure.…”

“…A careful design of the spool valve is also crucial, since the ensuing dynamics should lead to a new equilibrium quickly in response to a change of actuation flow fed as a change in the pressure feedback thrusting the spool. 27,28 In some EHLS designs, the power limiting option is also integrated to the controller on the basis of the sensor feedback of the pump speed for handling a situation of possible power saturation. 29 Such saturation could arise in a mobile system, if the installed power capacity of the pump falls below the total demand to all the serving actuators over some period.…”