FR2837449A1 - Master brake cylinder e.g. for motor vehicle electro-hydraulic braking system has intermediate piece accommodating spherical end of control rod and axial screw for adjusting axial play between the sphere and intermediate piece - Google Patents

Abstract

The brake master cylinder includes a piston having a hollow piston rod (13) connected to a control rod (14), axially actuated along an axis of the piston by a brake pedal connected to the end of the control rod. A spherical end (16) of the control rod includes an intermediate piece (19) on its exterior having a hollow for receiving the sphere, and an axial screw (20) adjusts the axial play between the sphere and intermediate piece. The screw is fixed to the intermediate piece and the sphere, intermediate piece and the screw are fixed to the piston rod. An Independent claim is included for a process for mounting the above motor vehicle brake system master cylinder.

Description

,,, I, f

  FIXING THE CONTROL ROD IN A MASTER CYLINDER

  FOR A BRAKING SYSTEM OF A MOTOR VEHICLE AND ITS

ASSEMBLY PROCESS

  The present invention relates to a fixing of the control rod in a master cylinder for braking installation of an automobile, more particularly for electro braking installation

  hydraulic, and its mounting method.

  Electro-hydraulic braking systems are known which comprise a service braking system with an external energy source and an emergency braking system with a muscular energy source, these two braking systems being controlled by a ma ^ tre- brake cylinder, the actuation pedal of which is located in the passenger compartment of the vehicle. Such an installation is described among others in

  document FR-A-2 772 706 by the applicant.

  In these known electro-hydraulic braking systems, the vehicle braking system is actuated using the brake pedal which actuates a control rod of the master cylinder, itself actuating a primary piston sliding in a bore formed at

  Inside the brake master cylinder.

  The control rod is fixed in the primary piston rod by a quick metal fastener by elastic fitting of a sphere

  end of the control rod entering the metal fastener.

  Such a ball joint attachment is shown in Figure 1 of a master

  cylinder of the prior art, in cross section.

  There are also known pneumatic braking systems comprising a pneumatic brake booster. Such a pneumatic booster is described for example in documents FR-A-2,532,084 and FR-A-2,658,466 of the applicant. It comprises a front shell and a rear shell which together form a rigid envelope. A movable partition sealingly separates the interior of this

2 2837449

  rigid envelope and delimits there a front chamber and a rear chamber.

  At rest the chamber is connected to a source of vacuum which delivers a low pressure Pd relative to atmospheric pressure. The rear chamber is in communication with the front chamber. A pneumatic piston moves with the movable partition. The actuator is controlled by a movable control rod between a rest position and an actuation position. When a force is exerted on the control rod by the brake pedal, this force greater than the return force of a spring causes the rear chamber to communicate with an environment at atmospheric pressure and pushes the movable partition towards the forward and generates an assist force used to

operate a master cylinder.

  In these pneumatic installations, the control rod actuated by the brake pedal is connected to the master cylinder by means of a pneumatic system. On the contrary, in a hydraulic braking device, the control rod is connected to the brake pedal at one end and is connected at the other end to the primary piston of the three-cylinder. There is therefore no pneumatic system between the two. Currently, in hydraulic systems, the attachment of the control rod to the piston rod in the primary piston is such that it allows axial play between the rod and the primary piston. Such an axial clearance is at least 0.1 mm. However, the current rod-piston attachment comprising a

  axial play has certain drawbacks.

  Indeed, after braking, when the driver releases the brake pedal, the inertia of the brake pedal tends to want to tear off the rod, that is to say that there is a directed restoring force of the rod towards the tax. Such a return face causes the pedal to recede from its initial rest position. A small noise is produced which is bothersome to the driver and cannot be tolerated in high-end cars.

3 2837449

  Another drawback of the retraction of the brake pedal is that if a posterior braking is carried out, the driver must first compensate for this retraction before performing the actual braking. Braking is therefore delayed. Yet another disadvantage of receding the brake pedal is that it

  delays the triggering of a self-adjusting brake light switch.

  Such a brake switch is a device which enables the brake lights to be switched on when the brake pedal is depressed. These highly sensitive devices are designed to minimize the time it takes to turn on the brake lights from the moment the driver presses the

brake pedal.

  A first aim of the invention is therefore to make the axial clearance between the control rod of a piston and the piston of a master cylinder in a braking system as low as possible, preferably zero.

  hydraulic, preferably electro-hydraulic.

  Furthermore, it is desired that the control rod and the piston

  primary have an angular movement.

  In addition, good tensile strength is desired.

  A problem which arises is that it is impossible to secure the control rod to the pneumatic piston from the outside. Indeed, it is ": impossible to insert a tool inside the piston rod to" <, remove the axial clearance between the control rod and the piston rod. In addition, the distance between the yoke on which the brake pedal is attached and the end of the piston rod is too short to introduce a

  \ <outii which would allow fixation.

  In order to solve the problems and achieve the objectives mentioned above, the invention relates to a master cylinder for a brake installation of a vehicle which comprises a sliding piston / in a bore, said piston comprising a hollow piston rod connecting a control rod axially actuated along the longitudinal axis XX / of the piston by a brake pedal connected to the external end of the control rod, the opposite end of said control rod being constituted by a sphere allowing an angular movement between the control rod and the piston rod is such that: The sphere of the control rod comprises at its external part an intermediate part provided with a hollow housing intended to receive the sphere and d an axial screw for adjusting the axial clearance of the sphere with respect to the intermediate piece, the screw being fixed to the intermediate piece, and

  the sphere, screw and intermediate piece assembly being fixed to the piston rod.

  The intermediate piece is crimped onto the sphere, the screw being glued or crimped-after adjustment, and the sphere, screw, intermediate piece assembly

stuck in the piston rod.

  Optionally, the sphere, screw, intermediate piece assembly is

snapped into the piston rod.

  Provision may be made for screwing the intermediate piece into the piston rod so as to secure the sphere, screw, intermediate piece assembly. However, the distance between the yoke on which the brake pedal is fixed and the piston rod is too short to introduce a tool which would allow the fixing of the sphere, screw, intermediate piece assembly. In addition, the intermediate piece cannot be screwed in by rotating the control rod since its end comprises a ball of ball joint and therefore there can be no rotational entrainment of the intermediate part by the control rod. According to another embodiment, two small diametrically opposite rods are therefore provided on the sphere which stop the control rod in rotation. We

  can in this way screw the intermediate piece into the piston rod.

  By tightening, we arrive at a breaking torque, the rods breaking.

  Thus, the intermediate piece is crimped onto the sphere, the screw is glued or crimped after adjustment, and the sphere, screw, intermediate piece assembly is screwed into the piston rod by means of two diametrically opposite rods on the sphere which block it in rotation, these

2837449

  rods breaking at the end of screwing when a breaking torque is reached. The front face of the axial adjustment screw, directed towards the

  control and directed towards the sphere is a hollow spherical caJotte.

  The invention further relates to a method for mounting a master.

cylinder mentioned above.

  This mounting method is such that the intermediate piece is crimped onto the sphere, the axial clearance of the control rod relative to the piston rod is adjusted by means of the adjustment screw, the adhesive is glued or crimped after adjustment, we introduce the sphere, screw, intermediate piece assembly into the piston rod and we glue the sphere, screw, piece ... ntermedare assembly. Optionally, the intermediate piece is crimped onto the sphere, the axial clearance of the control rod relative to the piston rod is adjusted by means of the adjustment screw, the adhesive is glued or crimped after adjustment, the sphere, screw, intermediate piece in the piston rod and

  crimps the sphere, screw and intermediate piece assembly.

  According to another embodiment of the mounting method, the intermediate piece is crimped onto the sphere, the axial clearance of the control rod relative to the piston rod is adjusted by means of the adjusting screw, glued or crimped the screw after adjustment, the sphere, screw and intermediate piece assembly is introduced into the piston rod and the sphere, screw and intermediate piece assembly is screwed into the piston rod by means of two diametrically opposite rods on the sphere which block it in rotation, these rods breaking at the end of screwing when we reach a

breaking torque.

  The invention will be better understood using the description below

  below with reference to the appended drawings in which: FIG. 1 is a view in longitudinal section of a master cylinder

  an installation of hydraulic braking of the prior art.

6 2837449

  Figure 2 is a longitudinal sectional view of a control rod and a piston rod secured in a first embodiment

  realization of the present invention.

  Figure 3 is a longitudinal sectional view of a control rod and a piston rod secured according to a second mode of

  realization of the present invention.

  Figure 4 is a longitudinal sectional view of a control rod and a piston rod secured in a third mode

  of the present invention.

  FIG. 1 shows a master cylinder equipping an electro-hydraulic braking installation of the prior art which comprises a braking system with an electrical energy source and an emergency system with a muscular energy source. These two systems are controlled by a master cylinder 10. The latter comprises a piston 11 sliding in a bore 12. The piston 11 comprises a piston rod 13 which is connected to a control rod 14 itself actuated axially along the longitudinal axis XX of the piston 11 by the brake peJale (not shown) connected to the outer end 15 of the control rod 14. The opposite end 16 of the control rod is constituted by a sphere. The control rod 14 is fixed in the piston rod 13 by a metal clip 17 by elastic fitting of the sphere 16 of the end of the rod penetrating into the metal clip 17. In this system of the prior art, the control rod 14 and piston rod 13 have an angular movement, that is to say that they are movable relative to one another thanks to the ball joint formed. The fixing of such a system allows axial play along the axis XX of the control rod 14 relative to the piston rod 13, due to the elastic interlocking of the

  ball in the mechanical part 17.

  According to the invention, it is desired to keep the angular travel of the control rod relative to the piston rod, but on the other hand

7 2837449

  wishes to reduce as much as possible, preferably cancel, the axial play of

  the control rod relative to the piston rod.

  A problem which arises when it is desired to remove the axial play of the control rod 14 relative to the piston rod 13 in a hydraulic braking system is that it is impossible to disassemble the rod 13 piston-rod assembly. 14. In fact, the piston rod 13 has a cavity 18 in the form of a truncated cone flared towards the control rod 14 and there is not enough clearance between the control rod 14 and the piston rod 13 . This movement does not allow the introduction of a tool between the control rod 14 and the piston rod 13. However, according to the invention, in order to be able to eliminate the axial play between the control rod 14 and the piston rod 13, an intermediate piece 19 is introduced which is housed at the bottom of the cavity 18 and which receives the sphere 16 of the control rod 14. This intermediate part has the function of reducing the clearance between the sphere 16 of the control rod 14 and the cavity 18. However, this clearance if it is reduced is not thereby canceled. To effect the maximum reduction in axial play, or even its cancellation, a screw is provided according to the invention.

  adjustment 20 of the axial clearance between the sphere 16 and the intermediate piece 19.

  However, as mentioned above, this adjustment of the axial clearance cannot be carried out using a tool penetrating into the cavity 18 when the control rod 14 is housed in the intermediate piece 19.

  therefore performs the adjustment of the axial clearance before mounting.

  According to the embodiment shown in FIG. 2, after adjusting the axial clearance of the sphere 16 relative to the intermediate piece 19, and therefore relative to the piston rod 13, the sphere 16 is crimped into the intermediate piece 19 by crimping points 21_. The screw 20 is crimped in the intermediate piece 19 by the crimping points 21b on the periphery of the intermediate piece 19. This gives a control rod 14, screw 20, intermediate piece 19 assembly which is introduced into

8 2837449

  the cavity 18 o it is glued by a deposit of glue 22 on the periphery

  external of the intermediate piece 19.

  According to the embodiment shown in Figure 3, after adjusting the axial clearance of the sphere 16 relative to the intermediate piece 19, the screw 20 is bonded with the intermediate piece by a deposit of glue 23 on the outer periphery of the screw 20 The control rod 14, screw 20, intermediate piece 19 assembly is introduced into the cavity 18 where it is snapped in thanks to the snap-on lugs 24 placed at the periphery of the piece.

  intermediate 19, on the side opposite to the adjusting screw 20.

  Thus, the control rod 14, screw 20, intermediate piece 19 assembly can be secured by crimping or snap-fastening and this assembly

  can be secured to the piston rod by gluing or snap-fastening.

  According to a third embodiment of the present invention shown in FIG. 4, two small diametrically opposed rods 25 are provided on the sphere 16 which stop the control rod 14 in rotation. After adjusting the axial clearance using the screw 20 and after securing the sphere, screw, intermediate piece by crimping and / or bonding, the control rod is rotated around the axis XX in the direction of the arrow F1, so as to fix the sphere, screw, intermediate piece assembly in the cavity 18. For this purpose, a thread 26 is provided on the external periphery of the intermediate piece and a thread 27 on the internal periphery of the cavity 18. By tightening, one arrives at a cup of "rupture, the rods then break, and the whole is also fixed by screwing

\ <in force in the cavity.

  \: The master cylinder and its mounting method according to the invention \ can be the master cylinder of a hydraulic braking installation or

  electro-hydraulic, possibly pneumatic.

+ ..

9 2837449

Claims (8)

  1. Master cylinder for a braking installation of a vehicle comprising a piston (11) sliding in a bore (12), said piston (11) comprising a hollow piston rod (13) connected to a control rod (14 ) axially actuated along the longitudinal axis XX of the piston (11) by a brake pedal connected to the external end of the control rod (14), the opposite end of said control rod being constituted by a sphere allowing angular movement between the control rod (14) and the piston rod (13), characterized in that the sphere (16) of the control rod (14) has at its external part an intermediate part (19) provided with a hollow housing intended to receive the sphere and an axial screw (20) for adjusting the axial clearance of the sphere (16) relative to the intermediate piece (19), the screw (20) being fixed to the intermediate piece ( 19), and the sphere, intermediate piece and screw assembly   (16, 19, 20) being fixed to the piston rod (13).   2. Master cylinder for a brake installation of a vehicle according to claim 1, characterized in that the intermediate piece (19) is crimped onto the sphere (16), the screw (20) being glued or crimped after adjustment, and the sphere assembly, intermediate piece, screws (16, 19, 20) being glued in the piston rod (13).   3. My ^ 'tre-cylinder for a vehicle braking installation according to claim 1, characterized in that the intermediate piece is crimped onto the sphere, the screw being glued or crimped after adjustment, and the sphere assembly, intermediate piece, screw (16, 19, 20) being snapped into the piston rod (13). 1 0 2837449   4. My master cylinder for a braking installation of a vehicle according to claim 1, characterized in that the intermediate piece (16) is crimped onto the sphere (19), i8 screws (20) being glued or crimped after adjustment, and the sphere assembly, intermediate piece, screw (16, 19, 20) being screwed into the piston rod by means of two diametrically opposed rods on the sphere which block it in rotation, these rods breaking in end of   screwing when a breaking torque is reached.   5. Master cylinder for a vehicle brake installation according to   Any of the preceding claims, characterized in that   the face towards the control rod (14) of the axial screw (20) of   adjustment directed towards the sphere (19) is a hollow spherical shell.   6. A method of mounting a master cylinder for a brake installation of a vehicle according to claim 1 or 2, characterized in that crimped ia intermediate piece (19) on the sphere (16), adjusts the axial clearance of the control rod relative to the piston rod by means of the control screw (20), we glue or crimp the screw (20) after adjustment, we introduce the sphere assembly, intermediate piece, screws (16, 19, 20) in the piston rod and we glue the sphere assembly, intermediate piece, screws (16, 19, 20).   7. A method of mounting a master cylinder for a braking installation of a vehicle according to claim 1 carErcté: risé en - that one crimps the intermediate piece (16) on the sphere, one adjusts the axial clearance of the control rod relative to the piston rod by means of the adjusting screw (20), glue or crimp the screw (20) after adjustment, the sphere assembly, intermediate piece, screw ( 16, 19, 20) in the rod   piston and the sphere assembly is crimped, intermediate screw part (16, 19, 20).   8. A method of mounting a master cylinder for a vehicle braking installation according to claim 1 or 4, characterized in that the intermediate piece (16) is crimped onto the sphere (19), adjusts the axial clearance of the control rod relative to the piston rod by means of the adjustment screw (20), we glue or crimp the screw (20) after adjustment, we introduce the sphere assembly, intermediate piece, screw (16, 19, 20) in the piston rod and screw the sphere assembly, intermediate piece, screw (16, 19, 20) in the piston rod by means of two diametrically opposite rods on the sphere which block it in rotation, these rods breaking at the end of screwing when a couple of