Tie rod apparatus and method for assembling a vacuum booster

An apparatus and method are provided for adjusting the axial distance between the front and rear walls (120,124) of a vacuum booster (110), from outside of the booster (110), after the booster (110) has been assembled. The booster (110) includes a housing (122) having a front housing (114) and a rear housing (116) joined together and defining a longitudinal axis (118) of the booster (110). The front housing (114) defines a front wall (120) of the housing and an inner surface (122) of the front wall (120). The rear housing (116) defines a rear wall (124) of the housing (110) and includes a captive nut (129) having threads adapted for threaded engagement with a threaded end (130) of a tie rod (128). The front and rear walls (120,124) are spaced an axial distance from one another along the longitudinal axis (118). A tie rod (128) extends axially through the housing (112) and has a first end (130) engaging the rear wall (129) of the housing (112) and a second end (132) engaging the front wall (120) of the housing (112). The first end (130) of the tie rod (128) has threads for engaging the threads of the captive nut (129) in the rear wall (124) of the housing (112). The second end (132) of the tie rod (128) has an axially facing surface (137) thereof for applying an axially directed force against the inner surface (122) of the front wall (120) of the housing (112). The axial distance of the housing (112) between the front and rear walls (120,124) of the housing (112) is adjusted by turning the tie rod (128), to thread the first end (130) of the tie rod (128) farther in or out of the captive nut (129). The captive nut (129) may include a tube (156) extending axially therefrom along a part of the tie rod (128) into the interior of the housing (112), through one or more separate fluid chambers (150,152) within the booster (110), to provide a sealed passageway precluding leakage between the fluid chambers (150,152) along the tie rod (128).