FR2772708A1 - SERVO BRAKE - Google Patents

Abstract

The invention relates to a brake booster (10) comprising a housing (12) having a front wall (14) and a rear wall (16), an inner diaphragm (18) defining first and second chambers (20, 22), a piston (24) slidably and tightly mounted in the rear wall, and at least one link bar (30) extending between the front and rear walls through openings (34, 36) thereof. The connecting bar is fixed at a first end (38) on one (16) of the walls of the housing, and at the other end (40) on the other wall (14) by a nut (42). The nut has a main body (52) abutting this other wall, inside the housing, around the edge (50) of the respective opening, and an annular extension (44) extending through it. 'opening and folded down to crimp the edge of the opening between the main body and the folded-down extension. Use in motor vehicle braking systems.

Description

The present invention relates to a brake booster or

  a brake system servomotor of a motor vehicle

  tor. A known brake booster comprises a housing having a front wall and a rear wall, a membrane fixed inside the housing to define two chambers inside the housing, and one or more bars of

  link extending between the front and rear walls.

  Each link bar is normally crimped to a pre-

  first end on one of the walls, and is fixed at the other end on the other wall by a nut screwed on the connecting bar, a flat or other annular seal being located between the nut and the wall. Such an arrangement presents risks of leakage around the joint until

  the brake booster is installed in a vehicle with

  tor, requires testing and a special design of the nut to ensure that a seal is actually present,

  and requires that the two walls of the housing be tightened

ties together.

  It is an object of the present invention to sur-

  mount one or more of the problems mentioned above

above.

  A brake booster according to the present invention comprises

  carries a housing having a front wall and a rear wall

  a membrane mounted inside the housing to

  define a first and a second chamber in the box

  tier, a piston assembly slidably and sealingly mounted in the rear wall, and at least one connecting bar extending between the front wall and the rear wall and through openings in the front and rear walls, and is characterized in what the link bar

  is fixed at a first end to a first of the parts

  kings of the case, and the link bar is attached to the

  be end to the other wall by a nut, the nut having a main body which abuts against this other

  wall inside the housing around the edge of the opening

  respective ture, and an annular extension which extends through the opening and is folded down to grip the edge

  of the opening between the main body and the extension

  folded down. In the present invention, the crimping of the nut of the connecting bar to said other wall of the

  housing eliminates the need for an additional seal

  shut up, remove the need to crimp the walls together

  of the housing, and reduces the risk of leakage before installation

  the brake booster in a motor vehicle.

  The present invention will now be described.

  written, by way of example only, with reference to the accompanying drawings, in which:

  - Figure 1 is a sectional view of a servo

  brake according to the present invention, - Figure 2 is a sectional view of a nut, a connecting bar and the front wall of the brake booster housing of Figure 1, before crimping the nut to the front wall , and - Figure 3 is a view similar to that of Figure 2, after crimping the nut to the front wall. Referring to Figure 1, the brake booster 10

  according to the present invention comprises a housing 12

  carrying a front wall 14 and a rear wall 16. A membrane 18 is positioned inside the housing 12 to define a front chamber 20 and a rear chamber 22 inside the housing. The front chamber 20 can be connected to a vacuum source (not shown) and the

  rear chamber 22 can be connected to air at the pressure

  atmospheric or above. A piston assembly 24 is sealingly and slidingly mounted in the wall

  rear 16. A push bar 26 is connected to the assembly

  piston 24 and can be connected to the brake pedal

  (not shown) of a motor vehicle. An action bar

  28 is connected to the piston assembly 24 and can be connected to a master cylinder piston

  (not shown) of the vehicle's braking system

  tor. Two connecting bars 30 extend between the

  front and rear walls 14, 16 of the housing 12 for reinforcing

  cer the case. Each link bar 30 has a threaded portion 32 at each end, which extends through a

  opening 34, 36 of the front and rear walls 14, 16 res-

  pectively. The threaded portions 32 which extend through the rear wall 16 can be used to mount the brake booster 10 in the motor vehicle. The threaded portions 32 which extend through the wall

  before 14 can be used to mount the master

  tre-cylinder on the brake booster 10. A flange 39 is formed at a first end 38 of each

  connecting bar 30. The flange 39 is located at the inside

  inside of the housing 12 against one of the walls (which in this example is the rear wall 16) and the connecting bar

  is crimped or fixed in position by folding down a part

  tie 41 of the connecting bar against the external surface

  rear of the rear wall 16. Other arrangements suitable

  tees to fix the first end 38 of the connecting bars 30- can be used. The arrangement described so far is known to those skilled in the art and does not

  will not be described in more detail.

  According to the present invention, the other end

  of each connecting bar 30 is fixed to the wall ad-

  adjacent 14 (front) by a nut 42. The nut 42 is screwed

  on the threaded part 32 of the connecting bar, inside

  inside of the housing 12, and abuts against the wall

  before 14 (see figures 2 and 3). Nut 42 has an extension

  annular axial annular 44 which extends through the opening 34 of the front wall 14. During assembly, a tool 46 is screwed onto the threaded end 32 of the connecting bar 30 to bring the tool into abutment against the nut 42. The tool 46 has a shaped end face 48 which projects inside the extension 44 of the nut 42. An additional screwing of the tool 46 up to a torque predetermined causes the shaped end face 48 to deform and fold down the extension 44 around the edge 50 of the opening 34 of the front wall

  14 to crimp the edge of the opening between the extension

  folded down 44 and the main body 52 of the nut 42.

  An annular groove 54 is preferably formed in the main body 52 of the nut 42 while being adjacent to the

  extension 44 and radially outward thereof

  this. The edge 50 of the opening 34 of the front wall 14 is preferably folded so as to be offset in the

  groove 54 during the folding of the extension 44.

  Means may be provided to resist the rotation of each nut 42 relative to the connecting bar 30 when each nut is in contact

  with the front wall 14 of the housing 12. For example, the

  groove 34 of the front wall 14 can be hexagonal or

  have another non-circular shape and the radial shape-

  The outer edge of the flange 44 (which projects through the opening) may have a similar shape. Alternatively, the surface of the nut 42 in contact with the front wall 14, or the surface of the groove 54, when it exists, can be knurled or provided with grooves to grip the

front wall.

  With this arrangement, the connecting bars 30

  can be attached and sealed at both ends

  tees on the walls 14, 16 of the housing 12. It was not born

  stop having an additional seal, and there is no need to crimp the walls 14, 16 of the housing 12 together. By permanently fixing the connecting bars at each end, the brake booster 10 is made watertight

  before installation in the motor vehicle.

  Although the embodiments described above

  above represent the nuts 42 adjacent to the front wall 14 of the housing 12, it will be noted that the nuts may

  may alternatively or additionally be used

  located at the rear wall 16 of the housing. Also,

  crimping the nuts 42 against the front or rear wall

  14, 16 can be obtained by other means than the tool 46 screwed onto the threaded end 32 of the bars

  link 30. For example, extension 44 can be shortened

  beaten by simply pushing the nut with a load.

Claims (5)

  1. Brake booster (10) comprising a housing (12) having a front wall (14) and a rear wall (16), a   membrane (18) mounted inside the housing for   nir a first and a second chamber (20, 22) in the   housing, a piston assembly (24) so mounted   smoothing and waterproof in the rear wall, and at least one connecting bar (30) extending between the front wall and the rear wall and through openings (34, 36) of the front and rear walls, characterized in that the connecting bar is fixed at one end (38) to a first (16) of the walls of the housing, and in that the connecting bar is fixed at the other end (40) to the other wall (14) by a nut (42), the nut having a   main body (52) which abuts against this au-   be wall, inside the housing, around the edge (50) of the respective opening, and an annular extension (44) which extends through the opening and is folded down   to crimp the edge of the opening between the main body pal and the extension folded down.   2. Brake booster (10) according to claim 1, characterized in that an annular groove (54) is formed   in the main body (52) of the nut (42) being ad-   adjacent to and radially outward from the annular extension (44), the edge of the opening of   said other wall being offset in the groove (54).   3. Brake booster (10) according to claim 1 or 2, characterized in that it further comprises means   located on said other wall and / or the nut (42) for   sister the rotation of the nut (42) relative to the link bar (30).   4. Brake booster (10) according to any one of   Claims 1 to 3, characterized in that it comprises   two connecting bars (30), each having a nut (42)   crimped to said other wall of the housing (12).   5. Brake booster (10) according to any one of   claims 1 to 4, characterized in that said further   wall is the front wall (14) of the housing (12).