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
• • 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
  • B60T13/569—Vacuum systems indirect, i.e. vacuum booster units characterised by piston details, e.g. construction, mounting of diaphragm
• • 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
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
  • B60T8/321—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration deceleration
  • B60T8/3255—Systems in which the braking action is dependent on brake pedal data
  • B60T8/3275—Systems with a braking assistant function, i.e. automatic full braking initiation in dependence of brake pedal velocity

Definitions

• the invention relates to a pneumatic actuator for actuating a motor vehicle braking master cylinder.
• the invention relates more particularly to a pneumatic servomotor for actuating a master cylinder for braking a motor vehicle, of the type which comprises a rigid envelope inside which a transverse partition movable delimiting a front chamber, subjected to a first pressure of engine depression, and a rear chamber subjected to a second pressure varying between engine depression and atmospheric pressure, of the type which comprises a movable piston, integral with the movable partition, one front face of which is liable to stress a master cylinder actuating rod, of the type which comprises a servomotor control rod moving in the piston selectively as a function of an axial input force exerted towards the front against a return force exerted on the rod by a return spring, of the type which comprises a plunger which is arranged at the front of the control rod in the piston and which c has at its rear end at least one rear annular seat of a three-
• the distance separating the first probe from the reaction disc is called "jump distance" and it corresponds to the theoretical distance that the first probe must travel before the driver of the vehicle feels the reaction force of the master cylinder.
• the first probe of the reaction disc corresponds to the stroke according to which the first probe is capable of compressing the reaction disc until the latter is fully compressed.
• the action of the control rod causes the displacement of the plunger comprising the first feeler, which causes the maximum opening three-way valve and put it at atmospheric pressure in the rear chamber. I t follows a displacement towards the front of the movable partition, and the extrem ity of the plunger forming the first feeler enters the reaction disc of elastomeric material which is integral with the rear face of the movable piston by compressing it .
• the force exerted on the actuating rod of the master cylinder when the control rod is at the end of the stroke results from the assistance force which is caused by the pressure difference on each side of the movable wall and of the force exerted by the feeler plunger on the reaction disc.
• the driver of the vehicle also feels the braking reaction force, which is transmitted from the master cylinder to the plunger via the reaction disc.
• the plunger can come into contact with the reaction disc and transmit to the driver a feeling of maximum braking even before the difference in pressure is maximum between the front and rear pressure chambers, which i can lead the driver to release his effort, even if he should be maintained to benefit from the maximum braking effort.
• a servomotor which comprises a first feeler which is slidably mounted relative to the plunger to penetrate the reaction disc and which can, when the actuator control rod is actuated at a determined speed, be locked relative to the movable piston so as to maintain a maximum braking force on the actuating rod of the master cylinder via the reaction disc even if the driver would have partially released his force.
• This design has the drawback of requiring a significant effort from the driver, since in order for the probe to penetrate the reaction disc at the end of its travel, the actuating force must be exerted against the reaction force of the master- cylinder re.
• the invention overcomes the drawbacks of the two aforementioned designs by proposing a booster according to the first design to which is added a second feeler which, during rapid application, can be pushed by the plunger and locked axially with respect to the piston, then be pushed by the piston in the reaction disc so that the rapid application of a braking force can be carried out, according to a new jump distance of value greater than the initial value, by meeting only a reduced antagonistic force transmitted by the reaction disc, so that the application of the braking force can be carried out more quickly.
• the invention provides a servomotor as described above, characterized in that it comprises a tubular sleeve, which is slidably mounted on the plunger, which comprises a front section which crosses the piston and one end of which comprises a second probe, and which is capable, when the control rod is actuated at a speed greater than a determined speed, of being pushed by the plunger and blocked by a one-way clutch device according to a determined axial position relative to the piston, then to be driven by the piston to drive the second probe to penetrate the reaction disc so as to allow the first probe to apply a rapid braking force against an antagonistic reaction force of the master cylinder which is reduced along a second determined jump distance, greater than the first jump distance.
• the bush includes a rear tubular section which is slidably mounted in a rear bore complementary to the piston,
• the nidirectional clutch device comprises a key, which is mounted in a recess of the piston passing through the piston perpendicularly to its axis, and of which a substantially annular intermediate part surrounds with play the sleeve and is likely, when the input force is exerted on the control rod at a speed greater than the determined speed, to be driven by the mobile piston to tilt around a generally transverse axis so as to cooperate with the periphery of the rear tubular section of the sleeve to block said sleeve in a determined axial position,
• the rear tubular section of the sleeve has at least one transverse locking face which is turned axially towards the rear to form a stop for a lug which is carried by an upper part of the key and which extends radially towards the bush, so as to axially index the determined locking position of the bush and of the second probe,
• the rear section of the sleeve has a groove of substantially frustoconical profile, a front shoulder face forming the transverse locking face,
• the lug of the key is, in section through an axial plane, shaped according to an angular sector complementary to the frustoconical profile of the groove of the sleeve, - the key has a lower part substantially in the shape of an "L", diametrically opposite to the lug, which extends radially from its annular part and which is resiliently biased against an abutment face of the casing of the booster by means of a return spring interposed between a front face of the recess of the piston and a front face of said lower part,
• the second probe has an outside diameter greater than that of the rear section of the socket
• the reaction disc is received in a cup, coaxial with the piston, which is integral with the rear end of the actuating rod and of which a rear tubular part is slidably mounted in an annular groove coaxial with the front face of the piston, -
• the key has substantially, in section through an axial plane, the shape of a "T” whose vertical branch of substantially radial orientation comprises the annular intermediate part and the lower part substantially in the shape of "L”, and whose upper horizontal branch is received with clearance between the two opposite walls of the recess and comprises projecting from its end before the lug.
• FIG. 1 is an overall view in axial section of a pneumatic brake booster produced in accordance with the invention
• - Figure 2 is a detail view in axial pe pe of the booster of Figure 1 shown in a rest position of the control rod
• FIG. 3 is a detail view in axial section of the booster of FIG. 1 shown in a position of application at slow speed of a braking force on the control rod,
• FIG. 4 is a detail view in axial section of the booster of Figure 1 shown during application at high speed of a braking force on the control rod according to a first step of start of actuation the control rod,
• FIG. 5 is a detail view in axial section of the booster of Figure 1 shown during application at high speed of a braking force on the control rod according to a second intermediate step of action the control rod.
• FIG. 1 the set of a servomotor
• the pneumatic servomotor 10 comprises a rigid casing 1 2 inside which is movably mounted a transverse partition 14 which delimitably a front chamber 1 6, subjected to a first pressure "P -i" whose value is equal to the value of the depression of the vehicle engine, and a rear chamber 1 8 sou put at a second pressure "P 2 ".
• the second pressure "P 2 " is likely, as will be described later, to vary between the value of engine vacuum "P" and the value of atmospheric pressure "P a ".
• the front chamber 1 6 is supplied with pressure "P,” via a vacuum duct 20 which is connected for example to an intake manifold (not shown) of a vehicle engine.
• the pneumatic booster 10 comprises a movable piston 22 which is integral with the movable partition 14. Inside the casing 12, the movable partition 14 is biased elastically towards the rear by a return spring 24 which bears on the casing 12 and on a front face 26 of the movable piston 22.
• the servomotor 1 0 is coupled to a brake master cylinder 28 which is moreover connected to a vehicle braking circuit by means of hydraulic conduits 30 and 32.
• the front face 26 of the piston m obi le 22 is coupled to an actuating rod 34 of the master cylinder 28 by means of a cup 36, coaxial with the piston 22, which is integral with the rear end 38 of the actuating rod 34 and one of which rear tubular part 40 is slidably mounted in an annular coaxial groove 42 arranged in the front face 26 of the piston 22.
• the cup 36 receives a reaction disc 44 of elastomeric material, the function of which will be described later.
• the piston 22 comprises a control rod 46, which is for example connected to a brake pedal (not shown) of the vehicle by means of a coupling sleeve 48 which is arranged at its rear free end.
• the rod 46 is capable of moving in the movable piston 22, selectively as a function of an axial input force exerted forward on the control rod 46.
• the actuating force is exerted against a return force which is exerted on the rod 46 by a return spring 50 which is interposed between the movable piston 22 and the control rod 46. Sealing against dust and foreign bodies from the rear end of the movable piston 22 is ensured by a bellows 51, which is mounted on the rear end 53 of the casing 12, and which is crossed by the control rod 46.
• control rod 46 is in the form of a ball joint 52 which is received in a complementary housing 54 of a substantially cylindrical plunger 56 which is slidably mounted in the movable piston 22.
• the plunger 56 has at its rear end at least one annular seat 58 rear of a three-way valve 60 which is gradually movable between a position in which, the control rod 46 being at rest, the front chamber 1 6 and the chamber rear 18 are in communication, and a position in which, the control rod 46 being actuated, the second pressure "P 2 " prevailing in the rear chamber 1 8 increases, the valve 60 putting the rear chamber 1 8 in communication with the pressure atmospheric "P a ".
• the servomotor 1 0 comprises a first feeler 62, forming the front end of the plunger 56 and passing through the piston 22. More particularly, the first feeler
• the plunger 56 therefore comprises a front section 61 whose end forms the first feeler 62, an intermediate section 63 with a diameter greater than the front section, and a rear section 65 whose rear end forms the seat 58 of the valve.
• the first probe 62 is arranged at a first determined distance "d 1" from the reaction disc 44.
• the first probe 62 is capable, as will be seen later, of accompanying the piston 22 according to the first jump distance "d 1" up to that, the piston 22 having completely compressed the reaction disc 44 in the cup 36, the latter comes into contact with the first probe 62 and transmits the reaction force of the master cylinder 28 to the control rod 46 as shown in Figure 3.
• the booster 1 0 comprises a tubular sleeve 64, which is slidably mounted on the plunger 56, which comprises a front section 66 which passes through the piston and whose end 68 comprises a second feeler, and which is capable of, when the control rod 46 is actuated at a speed greater than the determined speed, to be pushed by the plunger 56 and blocked by a one-way clutch device 70 in a determined axial position relative to the piston 22, then to be driven by the piston 22 to drive the second feeler 68 to penetrate the reaction disc 44 as illustrated in FIG. 4, so as to allow the first feeler 62 to apply a rapid braking force against a force reaction antagonist of the master cylinder 28 that i is reduced along a determined second jump distance "d2", greater than the jump distance "d 1", as shown in FIG. 5.
• the sleeve 64 is slidably mounted in the piston 22, and it is, in the preferred embodiment of the invention, fully coaxial with the plunger 56.
• the sleeve 64 comprises a rear tubular section 72 which is slidably mounted in a rear bore 74 complementary to the piston 22.
• the second probe 68 is coaxial with the plunger 56. This arrangement is not limiting of the invention, and the second feeler 68 may not be coaxial with plunger 56, provided that the front section 66 of sleeve 64, which carries the second feeler 68, is coaxial with plunger 56.
• the second probe 68 came integrally with the section 66 of the sleeve 64. This arrangement is not limiting of the invention, and the second probe 68 could, alternatively (not shown), be attached to the front section 66 of the sleeve 64.
• the second probe 68 has an outside diameter which is greater than that of the rear section 72 of the sleeve and which is substantially intermediate between that of the reaction disc 44 and that of the first probe 62.
• the rear section 72 of the sleeve 64 has a bore 76 which has a diameter corresponding to that of the intermediate section 63 of the plunger 56.
• the unidirectional clutch device 70 comprises a key 78, which is mounted in a recess 80 of the piston 22 passing through the piston 22 perpendicularly to its axis A, and of which a substantially annular intermediate portion 82 surrounds the socket 64 with play.
• key 78 has a bottom portion 84 substantially in the shape of an "L" which extends radially from the annular part 82 and which is resiliently biased against a stop face 86 of the casing 1 2 of the booster 1 0 by means of a return spring 88 interposed between a front face 90 of the recess 80 of the piston 22 and a front face 92 of the lower part 84.
• the spring 88 is interposed between the front face 90 of the recess 80 and a vertical branch 94 of the lower part 84 in the shape of an "L".
• a horizontal branch 96 of the lower part 84 in the shape of an "L” is more particularly intended to come into abutment against a stop face 86 of the casing 12 of the booster 10.
• the abutment face 86 of the casing 1 2 is for example carried by a ring 98 which is received in the cylindrical casing 1 2 of the booster 1 0.
• the ring 98 is for example mounted tight in the rear end of envelope 12.
• the key 78 is likely, when the input force is exerted on the rod , control 46 at a speed greater than the determined speed, to be driven by the movable piston 22 to tilt around a generally transverse axis so as to cooperate with the periphery of the rear tubular section 72 of the sleeve 64 to block said sleeve 64 relative to the piston 22 according to a determined axial position.
• the rear tubular section 72 of the sleeve 64 has at least one transverse blocking face 1 00, which is turned axially towards the rear to form a stop for a lug 1 02 which is carried by an upper part of the key 78 and which extends radially towards the socket 64, so as to axially index the determined locking position of the socket 64 and of the second probe 68.
• the key 78 therefore has substantially, in section through an axial plane, the shape of a "T", the vertical branch of substantially radial orientation comprises the annular intermediate portion 82 and the lower portion 84 substantially in the form of "L”, and whose upper horizontal branch 83, forming the upper part, is received with clearance between the two opposite walls 90, 91 of the recess 80 and comprises projecting from its end before the lug 1 02.
• the rear section 72 of the socket 64 has a groove 104 of substantially frustoconical profile, a front shoulder face forms the transverse face 1 00 of blocking.
• the transverse blocking face 1 00 is annular, but it could consist of an angular portion or sector of annular element, or alternatively of a flange projecting from the socket 64, without modifying the properties and advantages of the invention.
• the frustoconical groove 1 04 is of a profile which progressively joins the cylindrical periphery of the rear section 72 of the sleeve 64.
• the lug 1 02 of the key 78 is, in section through an axial plane, shaped according to an angular sector which is complementary to the frustoconical profile of the groove 104 of the socket 64.
• the frustoconical profiles of the lug 1 02 and the groove 1 04 of the socket 64 are particularly advantageous because they allow, during the tilting of the key 78, to guide the lug 1 02 of the key 78 to its position abutment against the front shoulder face 1 00 of the sleeve 64.
• the actuator 1 0 is capable of operating in different configurations which have been shown in FIGS. 2 to 5.
• the horizontal branch 96 of the lower part 84 of the key 78 bears on the abutment face 86 of the ring 98 secured to the casing 12 of the booster 10.
• a transverse pin 1 06 which passes through a lumen (not shown) of the sleeve 64 and the plunger 56, is, in the rest position of the rod 46, bearing on a front face 1 07 of the annular intermediate portion 82 of the key 78 to define the rest position of the plunger 56, the first feeler 62 of which forms with the reaction disc 44 the first jump distance "d 1".
• the plunger 46 and the piston 22 advance at substantially the same speed.
• the lug 102 of the key 78 falls on the periphery of the front section 66 of the sleeve 64 without blocking it.
• the piston 22 compresses the reaction disc 44 and the latter deforms to fill the cavity formed in the socket 64 by the jump distance "d 1".
• the distance "d 1" is completely covered when the reaction disc 44 can no longer compress on contact with the first feeler 62.
• the plunger 56 which slides forward relative to the piston 22 initially stationary, first pushes the sleeve 64 by through its rear section 65, and the two feelers 62 and 64 advance simultaneously.
• the piston 22 moves in turn and as soon as the lower part 84 of the key 78 leaves its support on the abutment face 86, the lug 1 02 of the key 78 falls back into the groove 1 04 of the socket that it locks with respect to the piston 22 by resting on its transverse shoulder face 1 00.
• the jump distance being characterized by the distance which separates the rest position of the first probe 62 from the position of the probe 62 in which it compresses the reaction disc 44, the probe 62 can therefore still travel, a second distance of jump "d2", which is greater than the jump distance "d 1" previously mentioned.
• the first probe 62 can therefore locally recompress the reaction disc 44 along the distance "d2" until said disc 44 is no longer compressible.
• the booster therefore presents itself in a configuration similar to that which has been represented in FIG. 4, with the exception of the fact that the piston 22 has advanced into the casing 12 of the booster 10 .
• this second distance "d2" corresponds substantially to the distance separating the first probe 62 from the second probe 68, but it would be possible for the first probe 62 to compress the reaction disc 44 only when it has crossed the second probe 68, this depending on the mechanical characteristics of the elastomeric material from which the reaction disc 44 is made.
• This configuration therefore allows the driver to apply a braking force very quickly without having to provide excessive force to oppose the opposing reaction force of the master cylinder.
• the servomotor 1 0 is therefore characterized by two differentiated jump distances, namely a first jump distance "d 1" reserved for the application of a braking force at slow speed, and a second distance from its ut "d2" reserved for the application of a braking force at high speed.

Landscapes

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

Applications Claiming Priority (3)

Publications (1)

Family

ID=8863745

Family Applications (1)

Country Status (5)

Families Citing this family (2)

Family Cites Families (3)

• 2001
  • 2001-05-25 FR FR0107019A patent/FR2825059B1/fr not_active Expired - Fee Related
• 2002
  • 2002-05-23 WO PCT/EP2002/007460 patent/WO2002094627A1/fr not_active Ceased
  • 2002-05-23 RU RU2003136075/11A patent/RU2003136075A/ru not_active Application Discontinuation
  • 2002-05-23 EP EP02745426A patent/EP1406801A1/de not_active Withdrawn
  • 2002-05-23 JP JP2002591318A patent/JP2004525033A/ja active Pending

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events