Vacuum pump is a device which gets the drive from the engine camshaft. In some designs, it is driven by the alternator shaft. The main function of the vacuum pump is to evacuate the air from the brake booster tank, thus creating vacuum, which can be used for brake application. In addition to this, in new generation engines, to meet the Euro V emission targets, vacuum pump also has to create vacuum in the auxiliary tank which will be used to actuate the turbocharger wastegate actuation mechanism and EGR valve.
The vacuum pump used for brake application when modified to perform the additional function of turbocharger may deteriorate the primary application performance. The tapping position and the size of the vacuum port for the auxiliary tank will influence the primary braking performance of the pump. The work described in this paper involves the systematic analysis of layout study of vacuum pumps to meet the performance of the vehicle for brake and turbocharger applications.
Steady state bench test conditions were framed to simulate the actual vehicle condition of braking and turbocharger actuation as individual and simultaneous conditions. Design of experiments by Taguchi's method was adapted to arrive at the number of optimum trials for experimental verification. Proto samples were made and evaluated for the experiments designed. Final design included provision/opening position of additional boss for connection with turbocharger wastegate, optimization of secondary nipple diameter and location, for target performance. Based on the test results the design was finalized to the specific engine requirements.
Finally the pump was fitted in the vehicle and validated for performance for brake application and turbocharger wastegate actuation for the entire engine operating conditions.