An Automotive Vacuum Pump Driven by Exhaust Pressure Pulsations

Many new fuel-efficient automobiles are equipped with vacuum pumps to assist the operation of pneumatically actuated systems such as mode valves for heating and air conditioning. These pumps are driven by the engine through either mechanical or electrical interfaces and, therefore, consume engine power and decrease fuel economy. To eliminate the fuel economy penalty associated with an auxiliary vacuum source, a new vacuum pump that is powered by pressure pulsations in engine exhaust gas has been designed and tested.

Performance tests have revealed that the pump could evacuate a 5.0-L tank from 100 kPa to 67 kPa in less than 2.5 seconds at all engine operating conditions. The minimum tank pressure attained was 21 kPa to 43 kPa, depending on engine speed and load. This performance should permit satisfactory operation of typical pneumatically actuated vehicle systems, but vehicle validation of the pump would be required before it could be considered for production.