FR2539368A1 - ASSISTED ACTUATOR DEVICE WITH AUXILIARY FORCE, FOR MASTER CYLINDER OF MOTOR VEHICLE BRAKING SYSTEM - Google Patents

Abstract

THE INVENTION CONCERNS AN ASSISTED BRAKING SYSTEM INCLUDING, BETWEEN THE BRAKE PEDAL AND A BRAKING MASTER CYLINDER 3, A VACUUM SERVO MOTOR 5 AND A FORCE TRANSMISSION LINKAGE 6, 7, 8, 12. THE ORGAN OUTPUT 9 OF THE SERVO MOTOR 5 IS ARTICULATED ON THE FIRST ARM 6 OF A LEVER WITH TWO ARMS 6, 12 MOUNTED TO PIVOT AROUND A MOVABLE BEARING 8, OF WHICH THE SECOND ARM 12 IS CONNECTED TO THE ROD 7 OF THE MASTER CYLINDER PISTON 3. THE MOBILE BEARING 8 IS MOVED BY AN AUXILIARY CYLINDER 11 EXPOSED TO DEPRESSION.

Description

2539368:

  The invention relates to an auxiliary force-assisted actuator device for a motor vehicle brake system master cylinder comprising a vacuum servo motor controlled by the brake pedal and a force transmission linkage acting on the piston. of the master cylinder.

  The "pedal ratio" suitable for actuating the master

  cylinder under normal service conditions may, in the event of assistance failure, be inappropriate because the driver is unable to provide the necessary force for actuation

  This is why it is known to take

  positions according to which the "pedal ratio" is modified in the event of a disturbance of the assistance, so that the driver can supply the master cylinder with the force necessary for the actuation of

  this, however, at the cost of a greater race pedal.

  Thus, it is already known a pedal assisted system comprising (German patent application DE-OS 2549194) a brake pedal linked by a hinge to a lever pivotable about a fixed point and attached, in one located between its ends, to an actuating member of a maler-cylinder, in order to

  to apply an actuating force to this organ, this system of

  dale being equipped with an auxiliary force assistance device,

  which allows, when moving the pedal, to apply to the

  an auxiliary force ("assistance force") This assistive

  tance has a force transmission device separate from the

  Actuator During operation of the brake assist device, the brake pedal and the lever pivot about the fixed point and, if the brake assist device fails, the brake pedal pivots about a point. located between the fixed point and the point of connection between the lever and the actuating member, on or near the line of action of the force applied by the brake pedal to the actuating member that the force transmission device

attack the lever.

  Also known is an assisted actuation device for a master cylinder of motor vehicle braking systems (US Patent No. 2,229,247) in which a two-armed lever pivotally mounted about a fixed trunnion is articulated by its first arm, via a pull rod, on a

  lever with one arm operated by the brake pedal By its second

  arm, this lever with two arms acts directly on the piston rod of the master cylinder, the lever connected to the brake pedal acting, by its free end, on the valve system of a servo motor of which

  the piston is supported on the piston rod of the master cylinder.

  These known devices have the disadvantage that the assistance forces acting on the piston rod of the master cylinder, variable because of the pressure fluctuations in the ducts connected to the booster, certainly assist the efforts to be provided to the pedal, but this however, the transmission ratio of the

  pedal lever lever acting on the piston rod of the master-

  cylinder is adapted to the circumstances.

  The object of the present invention is to provide an actuating device of the type in question, in which, in the event of reduced negative pressure, the transmission ratio of the transfer linkage

  efforts will be increased, counterbalancing the reduction in

  this assistance provided by the vacuum servo motor In case of

  total failure of the source of depression, the trans-

  The mission must then be set at such a value that the fall of the assistance force is approximately compensated for by the variation of the transmission ratio, and that the force required for the pedal to

  braking is not significantly increased Finally, this arrangement

  It must also have an architecture such that the enclosure or housing of the vacuum servo motor does not support any of the forces

  support generated by the force transmission linkage.

  According to the invention, these objects are attained by the fact that the output member of the vacuum servomotor is articulated on the first arm of a two-armed lever mounted so as to pivot about a movable bearing for pivoting and sliding, the second arm of this lever being connected to the piston rod of the master cylinder, and said movable bearing being held and guided by the actuating rod of the

  piston of an auxiliary cylinder exposed to a pressure difference.

  Preferably, the vacuum chamber of the servo motor to

2539368.

  depression and the chamber in front of the auxiliary cylinder piston

  are constantly connected to the same source of depression by

picks, soft or rigid.

  In order to achieve as simple a construction as possible and to prevent the vacuum servo motor housing from being heavy and expensive, the piston rod of the master cylinder and the output member of the vacuum servomotor are mutually parallel, the movement of the actuating rod of the auxiliary cylinder being effected in a plane located perpendicularly to the plane of the piston rod and the plane of the output member It is advantageous that in case of decline of the pressure in the lines connected to the vacuum chamber of the vacuum servomotor and to the chamber situated in front of the piston of the auxiliary cylinder, a spring arranged in the auxiliary cylinder

  moves towards the latter, the actuating rod equipped with the modular bearing

  bile for pivoting and sliding arranged on it, to lengthen the first lever arm, that is to say the arm articulated on'the organ

  output of the vacuum servo motor.

  The different objects and characteristics of the invention

  will now be detailed in the description that follows, made

  by way of nonlimiting example, with reference to the single figure of the accompanying drawing which shows a vacuum servomotor (for example a brake force amplifier operating by depression)

  mounted, as well as the master cylinder, on a wall, the cylinder

  xiliary being attached by clamping at the end of the master-cylin-

dre located on the piston side.

  Essentially, the auxiliary force-assisted actuator device comprises: the vacuum assist or servo motor 5, which "assists" with the force supplied to the pedal and uses> as a source of force, the difference of pressure between

  atmospheric pressure and the depression generated in the tubing of

  drawing of a four-stroke internal combustion engine; the cylinder

  emitter or master cylinder 3 arranged on the base plate 18

  with the vacuum servo motor 5; the auxiliary cylinder 11

  held by Box 19; the force transmission linkage, 6, 8 and 12, this linkage being interposed between the output member 9 of the

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  vacuum servomotor 5 and the piston rod 7 of the master cylinder 3; and the lines 15 and 16 connected to the suction line

(not shown) of the engine.

  The actuating device operates as follows when depressing the brake pedal 4, the output member 9 moves in the direction of the arrow and pivots the lever with two arms, 6 and 12, around the movable bearing 8 arranged on the actuating rod 13 of the auxiliary cylinder 11 During the pivoting of the lever 6, 12, the

  piston rod 7 is moved to the right, and the brake pressure

  in the working chamber of the master cylinder 3 If the pressure decreases in the lines 15 and 16, thus also in the chamber 14 of the auxiliary member 11, the compression spring 17 then pushes the piston 10 back, that is to say towards the position shown in the drawing The recoil of the actuating rod 13 has the effect of also displacing the movable bearing for pivoting and sliding, 8, so that the ratio of the lengths of the arms 6 and 12 of the lever varies For the position shown in the drawing, the transmission ratio of the arms 6 and 12 of the lever is of the order of 2/5, that is to say that a relatively large stroke of the output member 9 of the vacuum servomotor corresponds to a relatively short stroke of the piston rod 7. Therefore, if the vacuum source is faulty, and thus also the assistance provided by the vacuum servo motor, the force relatively important that should be provided to the pedal to ensure braking is

  reduced to an allowable value by varying the transmission ratio

  lever mission: the report "pedal stroke / stroke of the

  7 "piston rod is set to the most favorable value for this case.

  If the assistance is only partially available, the mobile bearing 8 then comes to an intermediate position. If the assistance is total, the mobile bearing is then in its indicated upper position.

  in continuous line, in 8 'on the drawing.

  It is obvious that the foregoing descriptions have

  given as a non-limitative example and that many variants can be envisaged without departing from the scope

of the invention.

Claims (4)

  1 actuator device assisted by an auxiliary force,   for master cylinder (3) of an automotive vehicle braking system   bile, comprising a vacuum servomotor (5) controlled by the brake pedal (4), and a force transmission linkage (6, 7, 8, 12) acting on the piston of the master cylinder (3), characterized in that the output member (9) of the vacuum servomotor (5) is hinged to the first arm (6) of a two-armed lever (6, 12) mounted   pivoting about a movable bearing for pivoting and   lissement (8), the second arm (12) of this lever being connected to the rod (7) of the piston of the master cylinder (3), and said movable bearing (8) being held and guided by the actuating rod ( 13) of the piston   (10) an auxiliary cylinder exposed to a pressure difference.   2 Devices according to claim 1, characterized in that the vacuum chamber of the vacuum servomotor (5) and the chamber (14) in front of the piston (10) of the auxiliary cylinder (11) are constantly connected to the same source of depression by pipes (15, 16), flexible or rigid.   3 Device according to claim 1, characterized in that the piston rod (7) of the master cylinder (3) and the output member (9) of the vacuum servomotor (5) are mutually parallel, and in that the movement of the actuating rod (13) of the auxiliary cylinder (11) takes place in a plane situated perpendicular to the   plane of the piston rod (7) and the plane of the output member (9).   4 Device according to any one of the claims   previous, characterized in that in the event of a decrease in the depression in the lines (15, 16) connected to the vacuum chamber of the vacuum servomotor and the chamber (14) in front of the piston   (10) of the auxiliary cylinder 11), a spring (17) arranged in the cy-   the auxiliary rod (11) moves the rod (11)   (13) provided with the movable bearing for pivoting and sliding (8) arranged on it, in order to lengthen the first lever arm (6), that is to say that articulated on the output member (9) of the servo -engine to depression.