This invention relates in general to vehicle braking systems, and in particular to a method of mounting a vacuum brake booster and master cylinder assembly onto a vehicle panel.
Most passenger vehicles include brake booster assemblies having a master cylinder and an accompanying brake booster. The master cylinder includes a housing having a bore formed therein. One or more pistons are slidably disposed in the bore. The pistons and the walls of the bore define pressure chambers having outlet ports connected to brake conduits. The other end of the brake conduits are connected to wheel brakes at the wheels of the vehicle. The master cylinder further includes an input rod. One end of the input rod is connected to one of the pistons, and the other end of the input rod is operatively connected to a brake pedal mounted in the interior of the vehicle. To apply a braking force to the wheel brakes, the driver of the vehicle depresses the brake pedal which causes movement of the input rod and the pistons to pressurize the chambers within the bore of the master cylinder. The fluid pressure within the chambers is transmitted to the wheel brakes via the conduits, thereby applying a braking force to the wheel brakes.
Brake systems also commonly include brake boosters operatively connected to the master cylinder to provide an assisting force in addition to the input force provided by the driver. Vacuum brake boosters and hydraulic brake boosters are two common types of boosters for passenger vehicles. Hydraulic brake boosters generally provide the assisting force by generating pressurized fluid to either impart a force on the input piston or introduce the pressurized fluid into the pressure chambers of the master cylinder or the fluid conduits connected to the wheel brakes.
Vacuum or pneumatic brake boosters provide an assisting force with the aid of the vacuum source of an engine manifold. Commonly, vacuum brake boosters include a hollow shell housing generally formed from stamped metal. A movable wall is disposed in the housing for movement in the forward and rearward directions with respect to the housing. The wall divides the interior of the housing into a front chamber to be connected to a vacuum source of the automobile, and a rear chamber which is selectively pneumatically connected to the front chamber and atmospheric pressure. A power piston is connected to the movable wall. An input member is disposed in the power piston and is movable in the forward and rearward direction with respect to the power piston by the operation of a brake pedal. A valve mechanism includes a vacuum pressure valve and selectively connects the rear chamber with the front chamber in response to the operation of the input member, and an atmospheric pressure valve selectively connects the rear chamber with atmospheric pressure in response to the operation of the input member. An output member is movable in the forward direction in response to the movement of the power piston with the movable wall for outputting the forward movement force of the power piston to the master cylinder.
Typically, brake booster assemblies include the vacuum booster which is attached to the master cylinder prior to installation in the vehicle. A fluid reservoir may also be attached to the master cylinder and selectively in fluid communication with the pressure chambers of the master cylinder. The brake booster, master cylinder, the input rod, and the reservoir generally are combined and attached to one another to form the brake booster assembly. The booster assembly is commonly installed into the vehicle as a single unit. The assembly is installed in the engine compartment and attached to the fire wall or dash panel separating the engine compartment from the passenger compartment. The assembly is attached such that the input rod extends through an opening formed through the panel. Commonly, the vacuum brake booster includes a plurality of mounting bolts extending outwardly from the shell. The mounting bolts extend through a plurality of corresponding apertures formed in the panel. After the input rod and mounting bolts are extended through their corresponding openings and apertures of the panel, the input rod is connected to a pedal assembly located on the opposing side of the panel from the brake booster assembly within the passenger compartment of the vehicle. Mounting fasteners or nuts are then threadably engaged with the mounting bolts of the brake booster assembly to secure the brake booster assembly to the panel. The pedal assembly may be connected to the input rod assembly prior to or subsequently to threadably fastening the threaded nuts to the mounting bolts. Since the brake booster assembly is located on the opposed side the of panel from the pedal assembly, this installation generally requires two workers or installers to prevent the brake booster assembly from tilting or falling out of its mounting location on the panel prior to installation. One installer holds the brake booster assembly in its mounting position, while the other installer holds the pedal assembly and mounts the threaded nuts to the mounting bolts of the booster. This type of installation is time consuming.