FR2508115A1 - PNEUMATIC SERVO-SURPRESSOR - Google Patents

Abstract

THE INVENTION CONCERNS A PNEUMATIC SERVO-BOOSTER, INCLUDING A BOX WHOSE INTERIOR IS SEPARATED IN FRONT AND REAR CHAMBERS BY A PISTON, A REACTION DISC IN A DEFORMABLE MATERIAL, AN OUTPUT SHAFT IN THE FRONT OF THE DISC, RECEIVING THE OUTPUT FORCE OF THE SERVO-BOOSTER THROUGH THE PISTON AND THE DISC, AN INPUT SHAFT PLACED TOWARDS THE REAR OF THE DISK AND RECEIVING THE REACTION FORCE OF THE OUTPUT SHAFT THROUGH THE DISC, AND A VALVE INCORPORATED IN THE PISTON AND CONTROLLED BY THE INPUT SHAFT TO PRODUCE A PRESSURE DIFFERENCE BETWEEN THE FRONT AND REAR CHAMBERS. ACCORDING TO THE INVENTION, A CLEARANCE IS FORMED BETWEEN THE REACTION DISC 17 AND THE INPUT SHAFT 7, 8, FORWARD AND BACKWARD AND WITH THE INACTIVE CONDITION OF THE SERVO-BOOSTER. THE INVENTION APPLIES IN PARTICULAR TO THE BRAKING SYSTEMS OF MOTOR VEHICLES.

Description

The present invention relates to a servo-overpressure

  pneumatic tire for use in a braking system

  of a vehicle, and more particularly, to a servo-overpressure

  in that way having a housing, a piston separating the interior of the housing into front and rear chambers, an output shaft placed in the front chamber and receiving the output of the servo-booster by the piston, a valve mechanism incorporated in the piston, an input shaft

  passing through the rear end of the servo-booster and

  actuating the valve mechanism to produce a pressure difference between the front and rear chambers, and a reaction disc made of a deformable material and received in the piston, with a surface in engagement with the shaft

  output to transmit the output force, the other

  face of the disk being in engagement with the piston and with

  the front end of the input shaft.

  In the above-mentioned servo-booster, the overpressure ratio or the ratio between the output force and the input force is determined by the ratio of the pressure receiving surface of the output shaft to the output shaft. the reaction disk and the pressure receiving surface of the input shaft against the reaction disk Usually, the reaction disk is received in a recess formed in the front surface of the piston, the front surface of the engaging reaction disk the rear end of the output shaft and the rear surface of the disk engaging the bottom of the recess and facing the front end of the input shaft; With the inactivated condition of the servo-booster, the end front of the input shaft is spaced from the rear surface of the disc of

  reaction The space between the front end of the drive shaft

  trea (usually the front end of a plunger which is integrally connected to the input shaft and which is slidably disposed in the piston) serves to enhance the feel

to the pedal.

  However, the servo-booster according to the prior art has a problem because part of the trailing end of the reaction disk protrudes towards the input shaft to fill the space between them each time the the brake is applied and consequently the disc has

  tend to age relatively quickly.

  The present invention aims to solve the problem

  above and, according to the invention, a space or clearance is formed between the reaction disk and the output shaft in a forward-to-back direction or in an axial direction and

  with the inactivated condition of the servo-booster.

  Preferably, another deformable member, deforming more easily than the disc, is interposed between the piston and the output shaft to maintain the space or clearance between

  this shaft and the disc with the inactivated condition of the servo

  booster. When the output force does not exceed a predetermined level, it is simply transmitted by the other deformable member, from the piston to the output shaft and no

  reaction force is transmitted to the input shaft.

  According to the invention, it is possible to obtain a desired characteristic and to reduce the deterioration

  Moreover, the present invention can easily

  apply to existing servo-compressors, according to

the prior art.

  The invention will be better understood and other purposes,

  characteristics, details and advantages of it

  more clearly in the explanatory description

  which will follow made with reference to the schematic drawings

  annexed given solely as an example illustrating

  embodiments of the invention and in which: Figure 1 is a longitudinal sectional view of a pneumatic servo-booster according to the invention; FIG. 2 gives a curve of the servo-booster according to the invention, the input force being indicated on the abscissa and the output force on the ordinate; and FIG. 3 is a partial sectional view of another

  embodiment of the invention.

  The pneumatic booster-booster illustrated in FIG. 1 comprises a casing 1 consisting of a front casing 1A and a rear casing 1B, and a piston 3 consisting of a flexible membrane 2, a main body 4, a piston plate 5 and a retaining disk 6 The outer circumference of the membrane 2 is tightly sealed between the front and rear casings 1A and 1B, and the main body 4 extends sealingly and slidably through the rear casing 1B Thus, the piston 3 separates the interior of the casing 1 into front and rear chambers A and B In this embodiment, the main body 4 and the retaining disk 6 are formed of a synthetic resin and are held by clamping bolts. (only one is dashed) The piston plate is formed

  sheet metal and is glued to the flexible membrane.

ble 2.

  The front chamber A is connected to a vacuum source such as the intake manifold of an engine

of an automobile.

  An input shaft consisting of a rod 7 and a plunger 8 connected to the front end (left end in the drawing) of the rod 7, passes through the rear end of the main body 4. The rear end of the rod 7 is connected, for example, to a brake pedal and the plunger 8 fits slidably in a bore 3 formed in the main body 4 When the brake pedal is depressed, the input shaft moves to the left or in The direction

  the output force of the servo-booster.

  Valve seats 3b and 8a are formed at the rear ends of the bore 3a and the plunger 8 which, with the inactivated condition shown in the drawing, respectively engage

  an annular valve with a needle 9 formed of an elastic material

  A spring 10 acts on the valve 9 to the left and when the plunger 8 moves to the left, from the position shown in Figure 1, the valve seat

8 a separates from the valve 9.

  Furthermore, an annular recess 3 e is provided in the retaining disk 6 of the piston 3, which opens towards the

  front chamber A, and the recess 3 e communicates with the

  The recess 3 e receives a reaction disc 17 made of a deformable material such as rubber. The disc 17 abuts against an annular shoulder 3 g formed between the recess 3 e and the recess 3 e. the opening 3 f so that the movement of the disc 17

  backward is prevented The forward end of the plunge

  8 slidably crosses the opening 3 f and comes into

  Against the rear end of the disk 17 A rear end of larger diameter 12a of an output shaft 12 is slidably received in the recess 3e and, in the inactivated condition, there is a gap or clearance S between the front surface of the disk 17 and the rear surface of the

  rear end portion 12a of the outlet rod 12.

  A cap member 13 is attached to the front end of the retaining disc 6 and has a central bore through or freely passes a portion 12b of reduced diameter of the output shaft 12, which diameter is smaller than that of the rear end portion 12a of the output shaft, so the rear end portion 12a of the shaft of

  outlet 12 is retained in the recess 3 e.

  A retaining ring 14 is mounted on the reduced diameter portion 12b of the output shaft 12 to support a spring retainer 15 A coil spring 16, acting as another deformable member according to the invention, extends between the retaining means 15 and the cap member 13 The spring 16 normally biases the

  exit 12 forward The spring force 16 is preferably

  low frequency, so that the spring can easily deform

sea in comparison to the disc 17.

  The servo-booster also comprises a return spring 11 which extends between the front casing 1A and the cap member 13 to urge the piston 3 rearwards, three circumferentially spaced reinforcing rods (one being shown in FIG. 1) extending between the front and rear envelopes 1A and 1B, a restriction plate 18 mounted on the plunger 8 to restrict

  relative movement between the plunger 8 and the main body

  pal 4 and to restrict the return position of the input shaft relative to the casing to the inactivated condition of the servo-booster The main body 4 is crossed by an axial passage 3 c and a radial passage 3 d for put the front and rear chambers A and B in communication when the valve seat 3b is separated from the valve 9 with the seat 8a engaging the valve 9 The radial passage 3d is also used to introduce atmospheric air into the rear chamber B when the valve seat 8a is separated from the valve

  9 with the seat 3b in engagement with the valve 9.

  In operation, when the rod 7 is pushed forward by depressing the brake pedal, the plunger 8 moves forward with respect to the piston 3 and the seat

  8 a on the plunger 8 separates from the valve 9 The atmospheric air

  is introduced into the rear chamber B and a pressure difference is produced between the front and rear chambers A and B The piston 3 moves to the left, however, at the initial condition, the force acting on the piston 3 is transmitted to the output shaft 12 by the coil spring 16, the retaining means 15 and the retaining ring

  14 When the spring 16 is deflected according to the game & initial-

  formed between the rear end of the output shaft 12 and the disk 17, the rear end of the output shaft

  12 abuts against the reaction disk 17.

  Then, the force acting on the piston 3 is mainly

  transmitted to the output shaft 12 by the disk 17, and the reaction force is transmitted to the diver 8 of the shaft

  In this way, we obtain a characteris-

  desired tension between the entry force and the force of

output as shown in Figure 2.

  FIG. 3 shows another embodiment of the invention or parts corresponding to the first embodiment.

  are represented by the same benchmarks and their description

  In this embodiment, the cap member 13, the retaining ring 14, the spring retainer 15 and the coil spring 16 of the first embodiment are replaced by a retaining means and a spring. Belleville 21 The retaining means 20 is of complicated configuration with a portion of a first diameter which is interposed between the inner circumference of the recess 3 e and the outer circumference of the larger diameter rear end portion of the spindle. output 12 The retaining means 20 further has an annular flange for receiving the force of the Belleville spring 21 which is interposed between the annular flange and the piston 3 The retaining means 20 defines an axial clearance S between the piston 3 and the set S is bigger than the game that is

  defined between the disc 17 and the retaining means 20.

  In the embodiment of FIG. 3, the force of the pressure difference acting on the piston 3 is initially transmitted to the output shaft 12 by the retaining means 20 and the Belleville spring 21 When the spring 21 is deflected according to the set S, the reaction disc 17 serves to transmit the output force to the output shaft

  and transmitting the reaction force to the input shaft.

  The retaining means 20 allows a slight defect of alignment.

  between the output shaft 12 and the piston 3 to prevent

  expensive as well as the inner circumference of the recess 3 e

  does not stick to the output shaft 12.

  It will be understood that the coil spring 16 and the Belleville spring 21 in the embodiments may be

  replaced by, for example, rubber or the like.

  On the other hand, it has been pointed out that the coil spring 16 is easily deformable in comparison with the disc 17 however, if desired, the spring 16 or spring 21 may have

an important force.

  As has been described, according to the invention, the disk 17 does not protrude rearwards in the opening 3 f of

  diameter, it is therefore possible to prevent the deterioration

  ration of the reaction disc and to guarantee a long duration of use.

Claims (2)

R E V E N D I C A T IO N S   1 pneumatic servo-booster, of the type comprising a casing, a piston separating the interior of the casing in front and rear chambers, a reaction disc made of a deformable material and received in the piston, an output shaft placed in front of the reaction disk and receiving the output force of the servo-booster by the piston and by the reaction disk, an input shaft placed towards the rear of the disk and receiving the reaction force of the output shaft by the disk , and a valve mechanism incorporated in the piston and controlled by the input shaft to produce a pressure difference between the front and rear chambers, characterized in that a set   formed between the reaction disk (17) and the drive shaft   (7, 8) forward and backward and under the condition   inactivated servo-booster.   2 pneumatic servo-booster according to claim   1, characterized in that another pressure-depressable member (16; 21), which can be deformed more easily than the aforesaid disk (17), is interposed between the piston (3) and the output shaft (12). ), and when the output force is less than a predetermined level, the output force is only transmitted from the piston to the output shaft by the other deformable member.