Calibrating an Adaptive Pivoting Vane Pump to Deliver a Stepped Pressure Profile 2013-01-1729
This paper presents a process for the selection of spring rate and pre-load for an adaptively controlled pivoting vane oil pump. The pivoting vane pump has two modes: high and low speed. A spring within the pump is installed to induce a torque that causes an adaptive displacement mechanism within the pump to move toward maximum oil chamber size. In low speed mode, two feedback regions are pressurized that produce torques that counter the spring generated torque. Together, both regions being pressurized by main oil gallery pressure tend to reduce pump displacement more at lower speeds than if only a single chamber is pressurized. At higher speeds, a solenoid switch turns off pressure to one of the feedback pressure chambers, thereby reducing feedback torque that counters spring torque. This enables higher pressure calibrations in this speed mode. In this paper, we identify a process for choosing the spring rate and pre-load that calibrates the adaptive displacement mechanism. For a fixed pump geometry, the objective is to choose a spring rate and installed pre-load that causes the pivoting vane pump to generate just enough oil flow to produce a stepped target oil pressure profile. Higher pressure than required is a waste of energy, whereas lower pressure than required may damage the engine.
The basic inputs to the process are a speed threshold that separates all engine speeds into two groups, a high speed category and a low speed category. Also required are target flow and pressures for each speed category. For each mode (i.e., high or low speed), the lowest permissible functioning flow and pressures are identified by the engine design requirements as inputs to this process. These targets are utilized to produce a physically realizable solution for a spring rate and pre-load selection when possible. The process will, if required, adjust input parameters (flow and pressure targets) to produce revised inputs that lead to a feasible solution. Care is taken to make only adjustments to the input parameters that maintain pressure targets and minimize pressure overshoot. If, for a given pump geometry, a spring calibration is not feasible, alternative pump geometries are suggested by our analysis.