Altitude compensated vacuum supply system and control

摘要

An altitude compensating control system for a vacuum pump supplying a vehicle accessory vacuum supply system comprising, in a preferred embodiment, a dual diaphragm pressure switch spring biased in a closing direction to actuate the pump and having an ambient pressure exposed diaphragm acting in a switch-opening direction opposed by a controlled vacuum pressure exposed diaphragm of larger area acting in a switch closing direction to provide a controlled vacuum pressure range that declines from a desired operational vacuum pressure range at sea level to a lower satisfactory vacuum level for efficient operation at higher altitudes. Other features and advantages are also disclosed.