Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
  • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
  • B60T13/24—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release the fluid being gaseous
  • B60T13/46—Vacuum systems
  • B60T13/52—Vacuum systems indirect, i.e. vacuum booster units
  • B60T13/573—Vacuum systems indirect, i.e. vacuum booster units characterised by reaction devices
  • B60T13/575—Vacuum systems indirect, i.e. vacuum booster units characterised by reaction devices using resilient discs or pads

Definitions

• the present invention relates to a pneumatic brake booster with enhanced assistance.
• the object of the invention is in particular to provide more powerful assistance in the event of strong braking. It concerns pneumatic brake assist servomotors whose braking law has an inflection when going from normal braking, for which assistance is normal, to strong braking for which assistance must be stronger, with moreover, more assistance.
• a pneumatic brake booster comprises in principle a front chamber with variable volume separated from a rear chamber also with variable volume by a partition formed by a tight and flexible membrane and by a rigid skirt plate.
• the rigid skirt drives a pneumatic piston bearing, via a push rod, on a primary piston of a master cylinder of a hydraulic braking circuit, typically a tandem master cylinder.
• the front chamber located on the side of the master cylinder, is pneumatically connected to a vacuum source.
• the rear chamber opposite the front chamber and placed on the side of a brake pedal, is pneumatically connected, in a controlled manner by a valve, to a source of propellant, typically air under atmospheric pressure.
• the front and rear chambers are connected together by a first valve while the rear chamber is isolated from atmospheric pressure by a second valve.
• the front chamber is first isolated from the rear chamber by closing the first valve, then air is admitted into the rear chamber by opening the second valve. This air intake has the effect of propelling the partition and implementing the pneumatic braking assistance.
• the effort of a driver, transmitted by a brake pedal, and the effort of the braking assistance combine together in the pneumatic brake booster on a reaction disc.
• these two forces are applied to two adjacent surfaces, generally concentric, in fixed proportions (thus fixing a ratio constant braking assistance).
• the disc is also in reaction, in particular by a cup which contains it, with a reaction force exerted by a hydraulic braking circuit located downstream of the transmission of the forces.
• a proportion between a (significant) force applied by a driver and the force applied in correspondence by a pneumatic brake booster on a hydraulic brake control must then have a high value, for example greater than ten.
• a high value for example greater than ten.
• the braking assistance is modified, in particular by additional hydraulic assistance, in order to give the braking, from a certain braking force, a proportionality of the assistance which is higher than that which prevails when the effort is low.
• an assistance curve showing the force applied to a downstream hydraulic braking circuit, as a function of the force of a driver follows an inflection from a certain value of this force of the driver: its slope becomes higher.
• This curve then undergoes a known effect of saturation of the assistance which is encountered when the movable partition is carried as far as possible in the front chamber and or when the rear chamber is brought to the highest available pressure (that of air ambient).
• the second solution has the drawback of requiring the development of pneumatic brake booster motors of new design and of not being able to adapt to the pneumatic brake booster motors already produced.
• the complexity of the new solution can in itself be a factor of significant additional costs.
• a principle of the invention may include the use of the compressible nature of the reaction disc. Indeed, in conventional assistance braking, the reaction disc deforms under the effect of braking. The crushing of the different surfaces of the disc leads to opening and closing one or the other of the valves so that the balance of forces is achieved in the desired proportion.
• the disc plays the role of a fluid subjected to equal pressures on its surfaces (which fixes the proportionality ratio), it does not need to be made of an incompressible material. And in reality it is not: it is made of a compressible material, for example rubber.
• the movable partition then acts in two ways on the movable assembly. And these two actions add their efforts. On the one hand, in a conventional manner, the reaction disc drives the moving assembly. On the other hand, the resumption of effort completes the push.
• the invention therefore relates to a pneumatic booster. brake assist comprising
• this moving part being carried on the one hand, by means of a first reaction device, by the movable partition and by the brake rod, and being in reaction on the other hand, by the first reaction device, with the hydraulic braking circuit, and - a device for admitting a high pressure fluid into the rear chamber at the time of braking, characterized in that it comprises
• FIG. 1 a general sectional view of a pneumatic brake booster according to the invention
• FIG. 2a and 2b curves representative of the forces of braking with conventional pneumatic assistance and in the invention respectively;
• FIG. 3a and 3b sections of a preferred embodiment of the pneumatic brake booster of the invention, in two orientations perpendicular to each other.
• FIG. 1 shows a pneumatic brake booster with enhanced assistance according to the invention.
• This pneumatic brake booster comprises a front chamber 1 connectable by a socket 2 to a vacuum source not shown.
• the vacuum source can be constituted by an intake gas intake from a gasoline engine of a vehicle.
• an external vacuum source would be used.
• the pneumatic brake booster also includes a rear chamber 3 which can be connected, for example by a valve 4, to a high pressure inlet 5: typically air at ambient pressure.
• the pneumatic brake booster also comprises a movable partition 6 usually provided with a rigid skirt and a waterproof membrane.
• the membrane prevents pneumatic communication between the two chambers.
• the partition 6 is pierced with a sealed orifice 7 to allow a mobile assembly 8 to pass.
• the assembly 8 is mechanically connected on the one hand by a brake rod 9 to a brake pedal, and on the other hand to a circuit 10 brake hydraulics.
• the principle of the assistance provided by such a pneumatic brake booster is as follows. Under the action of the rod 9, the moving element 8 plunges into the rear chamber by releasing the valve 4 by which the ambient air is introduced into the rear chamber 3. The ambient air then exerts pressure on the partition 6 which drives, in addition to a support 11 integral with the rod 9, the movable assembly 8 so that one end 12 of the latter actuates the hydraulic braking circuit 10.
• the saturation force must be placed beyond a force Fb applied to the hydraulic circuit for which a locking of the wheels of the vehicle is caused.
• the value of the force Fs is fixed by choices corresponding to driver comfort, notably allowing him to put his foot on the brake pedal without braking.
• the slope of the assistance 14 for a conventional pneumatic brake booster is linear and essentially depends on the respective bearing surfaces of the brake rod and the movable partition on a reaction disc.
• FIG. 2b shows the improvement brought by the invention.
• the correspondence curve between the force applied by the driver and the force applied to the hydraulic circuit undergoes a first evolution 16 comparable to the evolution 14 of the curve 13.
• the mechanism of the invention causes additional assistance so that the slope of the assistance includes a much higher segment 17. Therefore, the saturation force FS 'encountered with the device of the invention is much lower than the saturation force FS of the conventional solution. Beyond the saturation force FS ′, the correspondence curve includes a segment 18 similar to segment 15. We will see below how it is possible to adjust the value of the intermediate force Fi.
• This adjustment leads to creating a segment 16 and a segment 17 or, in certain cases, for example for sports cars, to offer, from the start, assistance whose slope 19 is the same as that of segment 17. At the When segments 16 and 17 meet, there is an inflection point 20 at which the assistance force increases proportionally much more rapidly.
• FIG. 3a shows in detail a first known reaction device and, according to the invention, a second reaction device.
• the movable element 8 is carried by the movable partition 6 by the effect 22 of air at atmospheric pressure admitted by the valve 4.
• the partition 6 is supported, by means of a hollow pneumatic piston 23 against a disc flexible 24.
• the disc 24 is contained in a cup 25 perfectly adapted to its shape.
• the piston 23 generally has the shape of a bell.
• the partition 6 presses on the outer base of the bell, and the top of the piston 23 is pierced and has an inner peripheral ring 26 which presses on the disc 24 at the inner periphery of the cup 25.
• Inside the ring 26 exactly, applies one end 27 of the brake rod 9.
• the end 27 forms the support 11.
• the ring 26 and the end 27 are such that they occupy the whole space between them. inside the cup 25.
• the disk 24 playing as a fluid makes it possible to organize the relative displacement (very minimal) of the end 27 relative to the base of the ring 26.
• the end 27 first enters the disc 24 which is flexible.
• the valve 4 at the rear of the pneumatic brake booster opens, the air enters the rear chamber 3.
• the piston 23 then in turn presses on the disc 24. This phenomenon occurs until the balance of support is again reached.
• the disc is flat.
• the valve 4 remains open and assistance occurs.
• a balance of the forces applied by the end 27 and the ring 26 is established due to the plasticity of the disc 24.
• a second reaction device is created which will allow another balance between additional assistance (much stronger) and the forces applied to the braking rod ( in this case also assisted by the first reaction device).
• the piston 23 has, inside the bell a circular support 28 forming a ledge.
• the movable element 8 then comprises, in the preferred embodiment, a slide 29 formed by a plunger 30 and an envelope 31.
• the plunger 30 is fixedly attached to the base of the cup 25. It extends from this cup towards the hydraulic circuit 10.
• the casing 31 envelops the plunger, drives the moving equipment downstream, and has at its base a saucer 32 whose peripheral ends 33 can come to bear on the ledge 28.
• the helical spring 34 is compressed between the saucer 32 and the cup 25 with a force Fc ( Figure 2b) corresponding to the intermediate force Fi for which we want to adjust the intervention of the additional pneumatic assistance.
• Fc Figure 2b
• the plunger assembly 30 - casing 31 and spring 34 behaves rigidly. The driver's effort and the assistance's effort are then transmitted to the hydraulic circuit according to segment 16.
• the spring 34 As soon as the force applied by the driver becomes greater than the force Fi, the spring 34 is no longer maintained by the pin 35 in the slot 36 but is on the contrary compressed by the braking force on the one hand and by the reaction of the hydraulic circuit on the other hand. Being compressed beyond the force Fc, the spring 34 contracts and the periphery 33 of the saucer 32 comes to bear on the ledge 28. In doing so, the assistance contribution occurs on the one hand by the ring 26 (as before) but also through the saucer 32 by the support of the ledge 28 ..
• the saucer 32 is slightly flexible and behaves, interposed between the envelope 31 and the turn 28, like a spring.
• the slope of the segment 17 is then equal to the ratio of the stiffness of the spring equivalent to the saucer 32 and the stiffness of the spring 34 (or of the spring 34 and of a spring equivalent to the compressibility of the disc 34).
• the effort Fi applied by a conductor is of the order of one hundred kilos.
• the assistance caused by the ring 26 alone is of the order of 3000 DaN leading to a force applied to the master cylinder Fc of the order of 4000 DaN.
• saucers such as 32 were already provided in the state of the art. But they were only used to retain substantially in alignment the different parts of the moving assembly.
• the invention now provides that the clearances between the saucer 32 and the turn 28, and the supports 11 of the end 27 of the rod 9 on the mobile assembly are not no longer left independent of each other. They are planned so that the recovery of forces can take place.
• the invention may consist in replacing an upstream end of the movable assembly 8 by the slide 29 supported by the spring 34 on the back of the cup 25.
• Such modifications are entirely in accordance with the known embodiments and do not entail fine-tuning or delicate approvals.
• the spring 34 and the spring formed by the saucer 32 are interposed in series between the movable partition 6 and the first reaction device constituted by the cup 25.
• the second reaction device formed by the casing 31 is connected by on the one hand at the midpoint of the two springs in series and on the other hand exerts its force on the hydraulic braking circuit.

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• Engineering & Computer Science (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Braking Systems And Boosters (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=8857044

Family Applications (1)

Country Status (10)

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Family Cites Families (5)

• 2000
  • 2000-11-28 FR FR0015466A patent/FR2817223B1/fr not_active Expired - Fee Related
• 2001
  • 2001-11-26 WO PCT/FR2001/003736 patent/WO2002044001A1/fr not_active Application Discontinuation
  • 2001-11-26 EP EP01998467A patent/EP1347909A1/fr not_active Withdrawn
  • 2001-11-26 JP JP2002545955A patent/JP2004514594A/ja not_active Withdrawn
  • 2001-11-26 US US10/433,631 patent/US6901843B2/en not_active Expired - Fee Related
  • 2001-11-26 KR KR10-2003-7007162A patent/KR20030055325A/ko not_active Application Discontinuation
  • 2001-11-26 BR BR0115884-8A patent/BR0115884A/pt not_active Application Discontinuation
  • 2001-11-26 AU AU2002216143A patent/AU2002216143A1/en not_active Abandoned
  • 2001-11-26 RU RU2003119446/11A patent/RU2274568C2/ru not_active IP Right Cessation
  • 2001-11-26 CN CNB018216366A patent/CN1256254C/zh not_active Expired - Fee Related

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