This invention relates to brake systems for vehicles, and more particularly to brake boosters for such systems.
A typical brake system for a vehicle includes a device known as a brake booster, which is used to amplify the force applied directly to a brake pedal by an operator of the vehicle. The booster is typically mounted outside of the passenger compartment in the engine compartment on a firewall, or dashboard, forming the front wall of the passenger compartment. A push rod extends from the booster through an opening in the front wall for connection with a brake pedal assembly located within the passenger compartment. A flexible boot or a sliding seal is provided around the push rod for environmentally sealing the hole in the front wall while allowing movement of the push rod by the brake pedal.
The booster is mounted in this fashion because it must draw in and expel a volume of air through a breather port surrounding the push rod, as the brake pedal is depressed and released. This drawing in and expulsion of air through the breather port unavoidably generates noise that would be objectionable to passengers in the vehicle, if the booster were mounted within the passenger compartment.
Because the breather port surrounding the push rod is located on the side of the booster closest to the front wall of the passenger compartment, some provision must be made to allow air to flow between the booster and the front wall, in order for the air around the booster to reach the breather port.
In some prior booster mounting arrangements, a mounting adapter is provided between the booster and the front wall of the passenger compartment. The adapter includes a ventilation port open to the engine compartment to provide airflow through the adapter to and from the breather port of the booster. U.S. Pat. No. 4,932,275 to Bischoff, et al, illustrates this approach.
Providing an adapter, as taught by Bischoff, significantly increases the distance that booster protrudes into the engine compartment, however, thereby consuming space could be used for other components. The adapter also undesirably increases fabrication and installation cost. Using an adapter also cantilevers the booster farther away from the front wall, which often requires that the front wall be reinforced, adding even more undesirable cost and weight to the vehicle.
In another prior approach, the housing of the booster, on the side of the booster adjacent the front wall of the passenger compartment is formed to provide an air channel, such that when the booster is mounted on the wall, air can flow through the channel from the engine compartment to the booster breather port. This approach solves some of the problems associated with using an adapter, as described above, but the length of the booster is undesirably increased to allow room for the channel. German patent application DE 195 23 309 A1 discloses this approach.
What is needed, therefore, is an improved apparatus and method for mounting a brake booster in a manner that provides a solution to one or more of the problems described above.
Our invention provides such an improved method and apparatus for mounting a brake booster on a wall, by adapting the wall to provide an air passage for fluid communication from a breather port of the booster to air surrounding the booster, when the rear surface of the booster is bearing against the wall.
One form of our invention provides an apparatus for mounting a brake booster on a wall, where the booster has a push rod extending from a rear surface of the booster through a hole in the wall, and a breather port surrounding the push rod. The apparatus includes a mounting surface of the wall, disposed about the hole in the wall, and adapted for receiving the rear surface of the booster. The wall further includes an air passage in the wall adapted for providing fluid communication from the breather port to air surrounding the booster, when the rear surface of the booster is bearing against the mounting surface. The apparatus may also include a seal disposed between the push rod and the wall for resisting airflow through the wall via either the hole or the air passage.
In one form of our invention, the wall includes a front and a rear surface thereof, with the mounting surface comprising a portion of the front side of the wall and the air passage comprising a channel in the wall. The channel has an inside surface thereof extending below and contiguous with the front surface of the wall. The channel may be provided by deforming a portion of the wall in a direction away from where the booster would be mounted, if the booster were mounted on the mounting surface.
The wall may include a tubular recessed segment thereof recessed below the front surface and contiguously connected thereto, with the hole disposed in the recessed segment. The recessed area may be adapted to receive a seal between the push rod and wall for resisting airflow through the hole. The seal may a lip seal adapted for sliding movement of the pushrod through the seal.
In another form of an apparatus according to our invention, the wall includes a front and a rear surface thereof, with the mounting surface comprising a first portion of the front side of the wall, including the hole, and raised above a second portion of the front side of the wall. The first portion and second portions of the front side of the wall are connected contiguously by a tubular portion of the wall, and the air passage is defined by a breather hole extending through the tubular section of the wall. The apparatus may also include a seal between the rear surface of the wall and the pushrod. The seal may be a lip seal around the push rod, with the wall including a lip seal support having a surface thereof extending from and contiguous with the rear surface of the wall, and having a second hole for passage of the push rod.
Our invention also provides a method for mounting a brake booster on a wall, where the booster has a push rod extending from a rear surface of the booster through a hole in the wall, and the booster also has a breather port surrounding the push rod. The wall is adapted to provide a mounting surface of the wall disposed about the hole in the wall for receiving the rear surface of the booster, and to provide an air passage for fluid communication from the breather port to air surrounding the booster, when the rear surface of the booster is bearing against the mounting surface. The method may further include sealing the push rod to the wall, in a manner resisting airflow through the wall via either the hole or the air passage.
The wall may be further adapted to include a front and a rear surface thereof, with the mounting surface comprising a portion of the front side of the wall and the air passage comprising a channel in the wall, with the channel having an inside surface thereof extending below and contiguous with the front surface of the wall. The channel may be formed by deforming a portion of the wall in a direction away from the booster, if the booster were mounted on the mounting surface. The wall may also be adapted to include a tubular recessed segment thereof recessed below the front surface and contiguously connected thereto with the hole disposed in the recessed segment. The recessed area may be further adapted to receive a seal between the push rod and wall for resisting airflow through the hole. The seal may be a lip seal adapted for sliding movement of the pushrod through the seal.
In another form of a method according to our invention, the wall includes a front and a rear surface thereof, and is adapted such that the mounting surface comprises a first portion of the front side of the wall including the hole and raised above a second portion of the front side of the wall. The first portion and second portions of the front side of the wall are connected contiguously by a tubular portion of the wall, and the air passage is defined by a hole extending through the tubular section of the wall. The method may further include providing a seal between the rear surface of the wall and the pushrod. The seal may include a lip seal around the push rod, with the wall being adapted to include a lip seal support having a surface thereof extending from and contiguous with the rear surface of the wall, and having a second hole for passage of the push rod.
Our invention may be readily adapted for use with prior brake boosters. Our invention does not require an adapter, or special adaptations of the booster housing, as was the case in prior booster mounting approaches. Cost and weight are therefore reduced. Because our invention does not rely on adapters or special configurations of the booster, which may be proprietary to a particular booster manufacturer, a vehicle manufacturer using our invention can utilize boosters from a variety of manufacturers, without fear of being locked in to a particular booster supplier.
The foregoing and other features and advantages of the invention are apparent from the following detailed description of exemplary embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being. defined by the appended claims and equivalents thereof.