서강대학교

초록/요약

Diesel cars use a rotary vane vacuum pump in order to create negative pressure inside the brake booster. In designing a vacuum pump, it is critical to reduce the time required to create enough negative pressure for applying brakes at the second time and the torque required to drive the pump. Therefore, in this study, test equipment to measure the driving torque and time to attain the target pressure of the rotary vane vacuum pump of a brake booster was set up. In addition, the effects of the several design variables on these parameters were analyzed: the length and depth of grooves, thickness of an outlet check valve, and number of bypass holes. Moreover, optimal values of the design variables were proposed and verified to minimize the driving torque using the Taguchi method. In addition, a numerical simulation model to predict the performance of a vacuum pump was developed and experimentally validated by comparing the pump’s drive torque and the time required by a 4 L chamber to reach the target pressure. The housing profile was obtained via 3D scanning, while the check valve, bypass hole, and groove, which significantly affect the pump performance, were mathematically described. The model was validated by comparing the vacuum chamber pressure variation and the average torque. Similarly, the pump performance with respect to changes in major design factors, such as check valve and bypass hole shapes, were compared against the experimental data. Moreover, the pump performance was predicted as a function of the housing profile shape, which is difficult to evaluate experimentally, and a new profile shape to improve the performance was proposed.