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
  • B60T13/57—Vacuum systems indirect, i.e. vacuum booster units characterised by constructional features of control valves

Definitions

• the present invention relates, in general, to the technical field of braking systems for motor vehicles.
• the invention relates to a servo brake assist tire comprising: a rigid casing; a movable partition sealingly delimiting a front chamber and a rear chamber inside the rigid envelope, the front chamber being connected in operational position to a pressure source delivering a first pressure, and the rear chamber being selectively connected to the front chamber or subjected to a controlled pressure by selective communication with a second pressure higher than the 'first; a pneumatic piston moving with the movable partition; a control rod adopting in the piston, a relative position depending at least on an actuating force selectively applied to the control rod in an axial actuation direction oriented towards the front chamber, and on an opposing restoring force oriented in an axial return direction; a plunger housed in the piston and driven by the control rod; a three-way valve controlling the pressure in the rear chamber, this valve connecting - selectively the rear chamber to the front chamber, or to the second pressure, depending on whether the control rod adopts with respect to the piston a relative position of rest under the
• the present invention aims to provide a servomotor distinguished from known servomotors, in terms of its performance or its size, at least either by a reduced dead stroke, or by a time of shorter response, either by a reduced difference between the attack force and the return force, or by a restricted diameter of the piston tail, and possibly by several of these parameters.
• the booster according to the invention is essentially characterized in that the valve comprises a lever mounted tilting relative to the control rod and having on either side of the control rod the first and second lever arms -respectively terminated by first and second ends, first and second valve seats defined in the piston, first and second valves articulated on the first and second respective ends of the lever and being applied selectively to the first and second respective seats by relative movements respectively oriented in the axial direction of actuation and in the axial direction of return, a first communication path connecting the rear and front chambers through the first valve seat, a second communication path connecting the rear chamber second pressure through the second valve seat, a spring biasing at least the first lever arm in the axial return direction, and a stop stopping the movement - • of the first lever arm in the axial return direction to the rest position of the control rod -
• the valves are articulated on the lever by means of respective rods, and the stop is formed
• the previously mentioned spring may consist of a helical spring constrained in compression and disposed between the piston and the lever.
• the piston may have a piston tail passing in leaktight manner through an opening made in the casing, for the control rod to be integral with a sleeve having two ends by which this sleeve is slidably mounted in the piston tail, that a ring is pivotally mounted on a median external surface of the sleeve, and that the two lever arms of the lever are fixed to the ring and pass through Respective axial ports, made in the piston tail and arranged in the rear chamber.
• the ring is for example formed of two halves of rings threaded on pivots projecting from the median external surface of the sleeve, and joined to one another by means of two connections by which the lever arms are fixed to the ring.
• FIG. 1 is an axial sectional view of a known booster, shown with the master cylinder which it allows to actuate;
• Figure 2 is a partial schematic axial sectional view of a booster according to the invention, shown in the rest position;
• Figure 3 is a partial schematic axial sectional view of the booster of Figure 2, -represented in the actuation phase;
• Figure 4 is a partial schematic axial sectional view of the booster of Figure 2, shown in the return phase;
• - Figure 5 is a partial cross-sectional view of a particular embodiment of a booster according to the invention, the section being made in the plane of the lever; and
• FIG. 6 is a partial axial section view of the booster illustrated in FIG. 5, this booster being observed according to the incidence defined by the arrows VI-VI of FIG. 5.
• the invention relates to a pneumatic brake booster.
• a pneumatic brake booster essentially comprises a rigid casing 1, a movable partition 2, a front chamber 3, a rear chamber 4, a pneumatic piston 5, a control rod 7, a plunger 8, a three-way valve 9, and a reaction member 13, for example a rubber reaction disc.
• the front 3 and rear 4 chambers are delimited in a sealed manner, inside the rigid envelope 1, by the movable partition 2, these chambers therefore having respective variable and complementary volumes.
• the control rod 7 is slidably mounted in the piston 5, and adopts with respect to this piston a position which depends in particular on an actuation force Fe which can be applied to the control rod 7 in an axial actuation direction X +, and an opposing return force Fr, exerted by a spring 98, and oriented in an axial return direction
• the plunger 8 which is housed in the piston 5, is driven by the control rod 7 and controls the three-way valve 9, the latter controlling the pressure in the rear chamber 4.
• valve 9 connects the rear chamber 4 either to the front chamber 3 or to the second pressure Pa, depending on whether the control rod 7 adopts relative to the piston 5 a relative position of rest under the effect of the force Fr, or an actuation position under the effect of the actuation force
• the front chamber 3 When the booster is placed in its operational environment, the front chamber 3 is permanently connected to a source of pneumatic vacuum, such as the intake inlet of a heat engine or a vacuum pump, delivering a low pressure Pd.
• a source of pneumatic vacuum such as the intake inlet of a heat engine or a vacuum pump, delivering a low pressure Pd.
• the rear chamber 4 When the booster is at rest, the rear chamber 4 is connected to the front chamber 3, and therefore subjected to the vacuum Pd which prevails in the front chamber.
• the rear chamber 4 When the servomotor is actuated by application of the actuating force Fe, the rear chamber 4 is subjected to a pressure controlled by communication with a second pressure Pa greater than the first Pd, for example with the atmosphere, the difference between the pressures Pa and Pd then making it possible to reveal an assistance force Fa, which is exerted on the movable partition 2, and which is applied to the disc 13 by the pneumatic piston 5, which moves with the movable partition 2.
• the valve 9 essentially comprises a lever 90, two valve seats 51 and 52, two valves 61 and 62, two communication channels 11 and 12, a spring 93, and a stop 611.
• the lever 90 is mounted tilting relative to the control rod 7 and has, on either side of the control rod, identical and opposite lever arms 91 and 92, the ends of which form the ends 901 and 902 of the lever 90.
• the valves 61 and 62 are articulated on the respective ends 901 and 902 of the lever 90 and can be applied to the respective seats 51 and 52, which are both formed in the pneumatic piston 5.
• valve 61 can be applied to the seat 51 by a movement oriented in the axial direction of actuation X +, while the valve
• the communication path 11 connects the rear 4 and front 3 chambers through the valve seat 51, while the communication path 12 connects the rear chamber 4 at the second pressure Pa through the second valve seat 52.
• the function of the spring 93 is to urge the lever arm 91 in the axial return direction X-, this spring being for example constituted by a helical spring constrained in compression and disposed between the piston 5 and the lever 90.
• the stop 611 has the function of stopping the movement of the lever arm 91 in the axial return direction X- for the rest position of the control rod 7.
• FIGS. 2 to 4 The operation of the booster of the invention is illustrated in FIGS. 2 to 4.
• the spring 98 pushes the piston 5 in the return direction X- -
• the lever arm 91 blocked by the stopper 611, pushes the valve 61 against the seat 51, the arm 'of lever 92 symmetrically pulling the valve 62 toward the seat 52.
• a force for actuating Fe is exerted on the rod 7 (FIG. 3)
• this rod moves in the piston 5 in the direction of actuation X +.
• the communication channel 12 is then open, and the atmospheric air, available outside the rigid envelope 1, is admitted into the rear chamber 4 through this second communication channel.
• this relative displacement of the rod 7 relative to the piston 5 produces the application of the valve 62 on the valve seat 52, the communication channel 12 being thus cut, and the rear chamber 4 being therefore isolated atmospheric air.
• the communication channel 11 is then open, and the rear chamber 4 is subjected to the pressure Pd prevailing in the front chamber 3.
• the restoring force Fr exerted by the spring 98 makes it possible to return the piston 5 to its rest position by moving it in the return direction X-.
• valves 61, 62 are for example articulated on the lever 90 by means of respective rods 610 and 620.
• the stop 611 can then for example be formed by an extension of the rod 610 of the valve 61, which comes into contact with the rigid casing 1 for the rest position of the control rod 7.
• FIGS. 5 and 6 An example of a practical embodiment of the invention is illustrated by FIGS. 5 and 6, in the traditional case -where the piston 5 has a piston tail 50 slidably mounted sealingly in an opening 10 made in the rigid casing .
• control rod 7 is integral with a hollow sleeve 14, which is slidably mounted in a sealed manner in the piston tail 50 by its two ends 141 and 142. Between its ends 141 and 142, the sleeve 14 has a median external surface 140 which is essentially cylindrical, continuous, of restricted diameter, and from which two pivots, 143 and 144, project mutually aligned in the median plane of the sleeve 14 and turned opposite one another.
• the halves of rings 151 and 152 are joined together to the other by means of respective links 16 and 17, by which the lever arms 91 and 92 of the lever 90 are respectively fixed to the ring 15.
• lever arms 91 and 92 pass through respective axial slots 501 and 502, which are formed in the piston tail 50 and which are arranged in the rear chamber 4.
• the seal provided between each of the ends 141 and 142 of the sleeve 14 and the internal surface of the piston tail 50 makes it possible to obtain that the only possible communication channel between the rear chamber 4 and the atmosphere Pa is that which constitutes the communication channel 12 which passes between the seat 52 and the valve 62.

Landscapes

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

Applications Claiming Priority (3)

Publications (1)

Family

ID=8866395

Family Applications (1)

Country Status (5)

Family Cites Families (2)

• 2001
  • 2001-08-08 FR FR0110617A patent/FR2828467B1/fr not_active Expired - Fee Related
• 2002
  • 2002-07-30 EP EP02774860A patent/EP1420990A1/de not_active Withdrawn
  • 2002-07-30 US US10/486,431 patent/US20040195912A1/en not_active Abandoned
  • 2002-07-30 JP JP2003518892A patent/JP2004537468A/ja not_active Withdrawn
  • 2002-07-30 WO PCT/FR2002/002727 patent/WO2003013928A1/fr not_active Application Discontinuation

Non-Patent Citations (1)

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