Brake booster with recessed shell receiving master cylinder flange

The invention relates to a braking device for a motor vehicle having a bulkhead (1) separating the passenger compartment (5) from the engine compartment (3). The device comprises a master cylinder (7) having a flange (13), via which it is fastened by means of a screw/nut assembly (15) to the front wall of a pneumatic brake booster (9) controlled as a result of the action on a tappet (11) passing through the rear wall of a brake booster, and a mechanism for fastening the device to the bulkhead (1) such that the brake booster (9) is arranged on the same side as the passenger compartment (5). The master cylinder (7) is partially arranged in the passenger compartment (5) and passes through an opening made in the bulkhead (1) for this purpose.

BACKGROUND OF THE INVENTION 
The present invention relates to a braking device for a motor vehicle, 
comprising a master cylinder and a pneumatic brake booster. It is known 
that motor vehicles using have a bulkhead separating the passenger 
compartment from the engine compartment. For the sake of greater 
compactness, there is increasingly less room available in the engine 
compartment and a braking device comprising a pneumatic brake booster and 
a master cylinder in line takes up a considerable amount of space. 
It was therefore proposed, particularly in U.S. Pat. No. 4,455,829, to 
arrange the brake booster in the passenger compartment of the vehicle. 
According to the teaching of this document, sheet-metal lugs are welded to 
the periphery of the brake booster and are fastened to the bulkhead by 
means of screws and nuts. 
Such a solution, although making it possible to save a little space in the 
engine compartment, is not entirely satisfactory because it makes the 
operation of mounting the device in the vehicle more difficult. 
Furthermore, it does not make it possible to avoid tearing forces at the 
fastening of the master cylinder to the brake booster. The sheet metal of 
the front part of the brake booster must therefore have an appreciable 
thickness, and reinforcements must be provided inside the brake booster, 
to prevent any elongation of the brake booster, this being contrary to the 
manufacturers' requirement to make the components lighter, and increasing 
its cost. 
SUMMARY OF THE INVENTION 
It is an object of the invention to overcome these disadvantages. 
The invention therefore relates to a braking device for a motor vehicle 
having a bulkhead separating the passenger compartment from the engine 
compartment, this device comprising a master cylinder having a flange, via 
which it is fastened by means of a screw/nut assembly to the front wall of 
a pneumatic brake booster controlled as a result of the action of a tappet 
passing through the rear wall of the brake booster, and a means for 
fastening the device to the bulkhead such that the brake booster is 
arranged on the same side as the passenger compartment. 
According to the invention, the master cylinder is partially arranged in 
the passenger compartment and passes through an opening made in the 
bulkhead for this purpose. 
Preferably, a recess is formed in the front wall of the brake booster, so 
as to receive the flange of the master cylinder. 
Also preferably, the bulkhead is in contact with that face of the flange 
opposite the brake booster. It is formed by the screw/nut assembly for 
fastening the master cylinder to the front wall of the brake booster.

DETAILED DESCRIPTION OF THE INVENTION 
A person skilled in the art will have realized that the terms "front" and 
"rear" used herein refer to the direction of the vehicle. In the Figures, 
the front is therefore on the right, towards the engine compartment, while 
the rear is on the left, towards the passenger compartment of the vehicle. 
Moreover, a person skilled in the art knows the functioning of pneumatic 
or vacuum-type brake boosters and of master cylinders, and this 
functioning will not be described herein. 
Referring now to the Figures, the bulkhead 1 separates the engine 
compartment 3 and the passenger compartment 5 of the motor vehicle. The 
braking device comprises a master cylinder 7 and a pneumatic brake booster 
9 which is controlled as a result of the action of a tappet 11 usually 
connected to the brake pedal of the vehicle. The master cylinder 7 
possesses a flange 13 making it possible to fasten it to the front wall of 
the brake booster 9 by means of screws and nuts. 
In general terms, a rear part of the master cylinder projects slightly into 
the brake booster 9, so as to ensure a good coaxial positioning of the 
components of the assembly and to reduce its length. 
According to the embodiment illustrated in FIGS. 1 and 3, the means for 
fastening the device to the bulkhead consists of the screw/nut assembly 15 
for fastening the master cylinder to the front wall of the brake booster 
9, the bulkhead 1 being retained between that face of the flange 13 
opposite the brake booster and at least one nut provided for this purpose. 
The master cylinder 7 is thus partially arranged in the passenger 
compartment 5 and passes through an opening 18 made in the bulkhead 1 for 
this purpose. 
The main objects sought after, namely the reduction in the overall size of 
that part of the device located in the engine compartment, are thus 
achieved. 
Furthermore, the brake booster 9 is now subjected only to the force exerted 
on the tappet 11 by the driver of the vehicle and no longer tends to be 
elongated, since its part subjected the most to the tearing forces bears 
on the bulkhead. It is therefore no longer necessary to provide 
reinforcements inside the brake booster which can thus be made 
considerably lighter and even be produced from plastic or superfine sheet 
metal. Finally, since the brake booster is no longer liable to elongation, 
the travel of the actuating pedal decreases in proportion. 
To reduce the overall size of that part of the device located in the 
passenger compartment, according to FIG. 2 a recess is formed in the front 
wall of the brake booster, so as to receive the flange 13 of the master 
cylinder 7. In fact, a person skilled in the art knows that the stroke of 
the piston arranged inside the brake booster 9 is limited by the presence 
of a restoring spring resting on the inner face of the wall of the brake 
booster. Such a recess provides, within the brake booster, an annular zone 
which allows the restoring spring to perform its function appropriately 
inside the brake booster, the stroke of the inner piston of the brake 
booster not being impeded if a maximum brake force is applied to the 
tappet of the brake booster by the driver. 
If the shape of the master cylinder makes it impossible for the opening 18 
made in the bulkhead to allow the device to pass through and be 
sufficiently small so that the device can be fastened to the bulkhead by 
means of screws and nuts fastening the master cylinder to the front wall 
of the brake booster, according to an alternative version of the invention 
the means for fastening the device can consist of another screw/nut 
assembly arranged at a suitable distance from the axis of the device, at 
the periphery of the above-mentioned opening made in the bulkhead. 
In order to reduce the overall size of the part projecting into the engine 
compartment, the fastening means can comprise a spacer making it possible 
to distance the front wall of the brake booster from the bulkhead, or a 
protuberance can be formed on the front wall of the brake booster. In this 
case, the spacer will have a length or the protuberance a height which is 
at least equal to the thickness of the flange 13. 
Of course, a person skilled in the art will be able to make many 
modifications to the present invention, without departing from the scope 
of the invention. 
For example, since the braking device according to the invention is no 
longer subjected to tearing forces at its fastening point, the means for 
fastening the device can comprise matching fastening members capable of 
fitting into one another irreversibly, such as a rod supported by the 
device and an opposite hole made in the bulkhead and the edge of which is 
notched and bent partially away from the rod, and this rod can be formed 
by an extension of the screw of the assembly for fastening the master 
cylinder to the front wall of the brake booster.