EP1330381A1

EP1330381A1 - Vacuum brake booster comprising a mechanical emergency braking auxiliary system

Info

Publication number: EP1330381A1
Application number: EP01945026A
Authority: EP
Inventors: Ludwig Friedsam; Heinrich Plewnia; Gerd Puscher; Peter SCHÜLTER
Original assignee: Lucas Automotive GmbH
Current assignee: ZF Active Safety GmbH
Priority date: 2000-11-02
Filing date: 2001-04-20
Publication date: 2003-07-30
Also published as: KR20030045161A; AU2001267363A1; US20030188632A1; DE10054252A1; BR0113880A; JP2004513817A; US6672198B2; DE10054252B4; WO2002036403A1

Abstract

The invention relates to a vacuum brake booster (10) comprising a vacuum chamber (16), a working chamber (18) which is separated from said vacuum chamber by a moveable wall, and a control valve (20) comprising a housing (12) which is coupled to the moveable wall in a force-transmitting manner (14). Said control valve is able to control the supply of atmospheric pressure or vacuum to the working chamber (18) according to the displacement of an actuating piston (28), in order to obtain a pressure difference on the moveable wall (14). The inventive vacuum brake booster (10) comprises an emergency braking auxiliary system having a permanent magnet (38) and an armature (36) which interacts with the permanent magnet (38). Said armature is elastically pre-stressed against the actuating direction and is pulled by the permanent magnet (38) in the event of emergency braking in the system, in such a way that the control valve (20) is held open for the supply of atmospheric pressure to the working chamber (18). The vacuum brake booster (10) comprises a coupling device (90) for detachably coupling the armature (36) to the actuating piston (28).

Description

Vacuum brake booster with mechanical emergency brake aid

The invention relates to a vacuum brake booster with a vacuum chamber and a working chamber separated from it by a movable wall, a control valve which has a housing which is coupled to the movable wall in a force-transmitting manner and which, in order to achieve a pressure difference on the movable wall, the supply of atmospheric pressure or Overpressure to

Working chamber can control depending on the displacement of an actuating piston, and an emergency braking aid with a permanent magnet and an armature interacting with the permanent magnet, which is resiliently biased against the actuating direction and is pulled into contact with the permanent magnet during emergency braking, whereby the control valve is kept open for the supply of atmospheric pressure to the working chamber.

Vacuum brake boosters have been known for a long time and are used millions of times to support the actuation forces of a hydraulic vehicle brake system and thereby to keep them at a level that is comfortable for the driver of a vehicle. So-called emergency braking aids are also known, which are often also referred to as "braking assistants".

These are devices which provide a driver with increased braking power in the event of an emergency stop with essentially the same actuation force.

Emergency braking aids can be divided into electromagnetically actuated and mechanically actuated systems. The use of a mechanical system is often sought for reasons of cost.

A vacuum brake booster with such a mechanical emergency brake aid is known for example from WO 00/07862. This vacuum brake booster has a vacuum chamber and a work chamber separated from it by a movable wall. A control valve, which a housing having a force-transmitting coupling to the movable wall comprises an atmosphere valve seat which, in order to achieve a pressure difference on the movable wall, can control the supply of atmospheric pressure to the working chamber as a function of the displacement of an actuating piston coupled to an input element of the brake booster.

A mechanical emergency brake aid is arranged in the housing of the control valve for better braking force support during emergency braking. The emergency braking aid comprises an armature which interacts with a permanent magnet and can be rigidly coupled to the actuating piston in the actuating direction by means of a stop formed on the actuating piston. The armature is resiliently biased against the actuation direction of the brake booster against the stop formed on the actuation piston and is held at a first distance from the permanent magnet in the starting position of the control valve. In the course of an approach to the permanent magnet, the armature becomes less than a predetermined second distance, which is smaller than the first distance, from the permanent magnet against the resilient pretensioning force acting on the armature and by removing its rigid coupling in the direction of actuation with the actuating piston in Attachment to the permanent magnet. As a result, the atmosphere valve, the valve seat of which is formed in one piece with a sleeve-shaped extension rigidly coupled to the armature, is kept open to the maximum. The maximum possible pressure difference then builds up, as a result of which the maximum possible boosting force of the brake booster is achieved.

After an emergency stop, the armature must be removed from the permanent magnet. This is done by means of a bolt which is rigidly connected to the actuating piston and extends at right angles to a longitudinal axis of the actuating piston and projects through a recess in the sleeve-shaped extension of the armature which extends counter to the actuating direction. Upon a return stroke of the input member of the brake booster, the actuating piston also moves against the actuating supply direction. The bolt coupled to the actuating piston comes into contact with an end face of the recess of the sleeve-shaped extension facing the vacuum chamber, so that the forces displacing the actuating piston against the direction of actuation are introduced into the sleeve-shaped extension coupled to the armature. Since these forces exceed the force required to detach the armature from the permanent magnet, the displacement of the actuating piston against the actuation direction, which is accompanied by a reduction in the actuating force applied by the driver, finally leads to detachment of the armature from the permanent magnet.

Due to the displacement of the actuating piston against the actuation direction required for the detachment of the armature from the permanent magnet, the stop for the armature formed on the actuating piston has also moved away from the armature by the displacement path of the actuating piston. After the armature has been detached from the permanent magnet, the armature is consequently along the displacement path of the biasing force acting on the armature counter to the actuation direction of the brake booster

Actuating piston accelerates. The armature therefore hits the stop formed on the actuating piston at high speed. This impact of the armature on the stop provided for the armature produces a clearly perceptible and annoying switch-off noise.

In addition, operating positions of the brake booster are possible in which, before the armature hits the stop formed on the actuating piston, the valve seat formed on the free end of the sleeve-shaped extension of the armature collides with the associated valve sealing member of the control valve and tears it open suddenly. The result is that the connection between the working chamber and the vacuum chamber is opened and the braking force support provided by the brake booster is abruptly reduced, which is noticeable to the driver by a force strike on the brake pedal which is perceived as unpleasant. The invention has for its object to provide a vacuum brake booster with mechanical emergency brake aid, which has an improved operating behavior.

Starting from a vacuum brake booster of the type described at the outset, this object is achieved according to the invention in that a coupling device is provided which permits detachable coupling of the armature to the actuating piston.

By means of the coupling device according to the invention, influence can be exerted on the movement of the armature against the actuating direction relative to the actuating piston in order to avoid an uncontrolled relative movement between the armature and the actuating piston as a result of the armature detaching from the permanent magnet. The coupling device makes it possible, after the armature has been detached from the permanent magnet, to prevent the armature from accelerating counter to the actuation direction or at least to reduce it in such a way that the switch-off problems observed in the prior art vacuum brake boosters no longer occur in the vacuum brake boosters according to the invention.

The coupling preferably takes place as a result of a return stroke movement of the actuating piston, i.e. the coupling device can be activated by a return stroke movement. The coupling can take place before or after the armature is torn off the permanent magnet.

The armature and the actuating piston can be coupled, for example, by means of frictional engagement, frictional engagement or positive engagement. The coupling device is preferably designed such that coupling takes place only after a certain return stroke of the input member of the vacuum brake booster, but before the armature is detached from the permanent magnet. Armature and actuating piston can be coupled to one another both directly and indirectly. An indirect coupling of the actuating piston and armature is possible, for example, in that the actuating piston is coupled to a further component of an armature assembly which also includes the armature. So the actuator supply piston, for example, can be coupled to a sleeve-shaped extension of the armature which extends counter to the actuating direction.

According to a first embodiment of the invention

Coupling device designed as a locking device which allows coupling of armature and actuating piston by means of a locking connection. The latching device preferably comprises a first latching element and a complementary second latching element, which cooperate to couple the armature and the actuating piston. The latching connection is preferably formed and released by moving the first latching element in the radial direction with respect to a longitudinal axis of the vacuum brake booster. The first locking element is expediently in the radial direction, i. H. biased either radially inward or radially outward.

According to a first variant of the first exemplary embodiment, the first latching element is designed as a snap hook or snap ring which interacts with a second latching element, for example in the form of a depression or opening. The snap hook is advantageously arranged at the end of a pivot arm extending essentially in the axial direction, so that the snap hook can be moved in the radial direction by means of a pivoting movement. The snap hook can be formed in one piece with the swivel arm. For example, it is possible to manufacture the snap hook by bending the swivel arm in certain areas.

The swivel arm can be rigidly coupled to a further arm which allows the swivel arm to be deflected. The further arm consequently enables the swivel arm to be actuated, since deflection of the further arm is transmitted to the swivel arm. The further arm is preferably deflected as a result of an interaction of the further arm with a stop movable relative to the further arm. The stop can be formed, for example, in a housing of the vacuum brake booster. In order to simplify the manufacture of the coupling device and to avoid complex bending processes, the swivel arm and the further arm can be manufactured separately and connected to one another by means of welding, for example. With such a

Coupling device, it is advantageous to pivotally attach the swivel arm, and not the other arm, to the actuating piston. Such a configuration allows an improved introduction of force into the actuating piston, since the holding forces applied by the swivel arm in the coupled position can be transmitted directly to the actuating piston.

The snap hook, i.e. the first locking element can have an inclined surface which is delimited by the corresponding opening, i.e. of the complementary locking element cooperates. In an extreme case, the snap hook can be formed by this inclined surface. Dimensional tolerances can be compensated for by means of the inclined surface, since the inclined surface always allows the snap hook to interact with the opening provided for the snap hook without play.

According to a second variant of the first exemplary embodiment, the first catch element has a spherical or annular shape and interacts with a second catch element in the form of a bevel in such a way that, depending on the axial position of the first catch element, the armature also contributes to the bevel the actuating piston is coupled or the coupling is released.

In the two variants of the first exemplary embodiment described above, the first latching element and the second latching element can each be provided both in the region of the armature and in the region of the actuating piston. However, the first latching element is preferably arranged in the region of the actuating piston and the second latching element is formed in a sleeve-shaped extension of the armature.

According to a second embodiment of the invention, the coupling device is designed as a clamping device. The second Embodiment, the coupling of the armature with the actuating piston is consequently carried out by a clamp connection.

The clamping device can comprise a clamping element, which is able in the radial direction, i. H. to generate a clamping force radially inward or radially outward with respect to a longitudinal axis of the vacuum brake booster. The clamping element preferably has asymmetrical clamping properties with respect to axial relative movements between the armature and the actuating piston in and against the direction of actuation. With others

Words, depending on the direction of the axial relative movement between the armature and the actuating piston, the clamping element generates a differently high clamping force. The clamping element is expediently designed such that it generates a clamping force at least when the armature moves relative to the actuating piston against the actuating direction.

According to a first variant of the second embodiment according to the invention, the asymmetrical clamping properties are realized by means of a slope which interacts with the clamping element. It is thus possible to design the clamping element in such a way that it runs on the bevel in the axial direction as a result of a relative movement between the armature and the actuating piston and thereby generates a clamping force acting in the radial direction. Advantageously ¹ is the clamping element as a rolling element, for. B. designed as a ball or ring. The slope can be formed both in the area of the armature, for example radially on the inside of a sleeve-shaped extension of the armature, and in the area of the actuating piston.

According to a second variant of the second embodiment of the invention, a clamping arm, which extends obliquely to the longitudinal axis of the brake booster and is preferably biased in the radial direction, is provided for realizing asymmetrical clamping properties. The clamping arm is preferably rigidly connected either to the actuating piston or to the armature or a component of the armature assembly and has either the armature or the armature assembly or the actuating arm. piston on the end section contacting under prestress. The asymmetrical clamping properties of the

Clamp arms are on its inclined position, i.e. H. the application of force at a certain angle z. B. from the anchor in the actuating piston or vice versa.

Both in the first and in the second embodiment of the invention, an opening sleeve movable in the axial direction can be provided, which allows the coupling between the armature and the actuating piston to be released. The opening sleeve is preferably arranged radially on the inside with respect to a sleeve-shaped extension of the arm that extends counter to the actuation direction and is freely movable in the axial direction with respect to the sleeve-shaped extension. A latching coupling between armature and actuating piston can be released, for example, by the opening sleeve interacting with at least one of two complementary latching elements in such a way that the latching connection is canceled. A clamp connection can be released in that the opening sleeve is moved in the axial direction with respect to a pretensioned clamping arm that a pretensioned. End section of the Kle marms in plant - is brought to the freely movable opening sleeve.

^* According to a third embodiment of the invention is the Koppe- leinrichtung formed as a supporting device which for

Coupling the armature with the actuating piston allows the armature to be supported against the actuating direction on the actuating piston. The support device preferably comprises a pivotable support element which is pivoted into a support position for coupling the armature and the actuating piston.

Irrespective of the specific design of the coupling device, at least one stop can be formed on the actuating piston, which stop is arranged in front of the armature in the actuating direction and which interacts with the armature in the opposite direction to the actuating direction. The armature is then no longer detached from the permanent magnet, as in the prior art, by means of a bolt, but by means of the one formed on the actuating piston Attack. The bolt is thus released from its function with regard to the detachment of the armature from the permanent magnet, so that the design requirements for the bolt are reduced. The bolt can therefore perform additional functions or, in extreme cases, can even be completely omitted without the detaching process of the armature being impaired by the permanent magnet.

The stop formed on the actuating piston preferably interacts directly with the armature counter to the actuating direction. For example, the stop can interact with an end face of the armature, which faces the vacuum chamber of the brake booster. The end face of the armature interacting with the stop is preferably not identical to that end face of the armature which comes into contact with the permanent magnet. The end face of the armature cooperating with the stop can be arranged, for example, axially offset in or against the actuating direction with respect to the end face of the armature interacting with the permanent magnet.

The vacuum brake booster expediently has an actuating piston on which, on the one hand, the abovementioned stop for the armature is formed and, on the other hand, which is additionally coupled to a bolt which extends at right angles to the longitudinal axis of the actuating piston. The bolt can perform different functions. It is conceivable to limit the mobility of the actuating piston in the axial direction by means of the bolt. For this purpose, the bolt can interact with a stop for the bolt, which is formed, for example, on the brake booster housing. The mobility of the actuating piston is expediently limited, at least counter to the actuating direction, by the interaction of the bolt coupled to the actuating piston with the stop provided for the bolt. Preferred exemplary embodiments of the invention are explained in more detail with further details and advantages on the basis of the attached schematic figures. Show it:

Fig. La - ld longitudinal sections through the control valve of a first embodiment of a vacuum brake booster according to the invention;

2 shows a longitudinal section through the control valve of a second exemplary embodiment of a vacuum brake booster according to the invention in its starting position;

3a-3d show longitudinal sections through the control valve of a third exemplary embodiment of a vacuum brake booster according to the invention;

4a shows a longitudinal section through the control valve of a fourth exemplary embodiment of a vacuum brake booster according to the invention in its starting position;

4b and 4c longitudinal sections through the control valve of building on the fourth embodiment

Embodiments of further vacuum braking force according to the invention;

4d shows a cross section through the control valve of the vacuum brake booster according to the invention according to FIG. 4c;

4e and 4f the manufacture of the in the invention

Vacuum brake booster according to FIGS. 4c and 4d used

Snap hook; 5a and 5b are longitudinal sections through the control valve of a fifth exemplary embodiment of a vacuum brake booster according to the invention;

6a and 6b are longitudinal sections through the control valve of a sixth embodiment of a vacuum brake booster according to the invention;

7 - 9 are longitudinal sections through the control valve of a seventh, eighth and ninth exemplary embodiment of a vacuum brake booster according to the invention in its initial position;

10 shows a longitudinal section through the control valve of a tenth exemplary embodiment of a vacuum brake booster according to the invention in an operating position; and

11a and 11b longitudinal sections through the control valve of an eleventh embodiment of a vacuum brake booster according to the invention.

1 a shows a first exemplary embodiment of a vacuum brake booster 10 according to the invention with a housing 12 in which a movable wall 14 separates a vacuum chamber 16 from a working chamber 18 in a pressure-tight manner.

When the brake booster 10 is operating, the vacuum chamber 16 is constantly connected to a vacuum source, for example to the intake tract of an internal combustion engine or to a vacuum pump. A control valve 20 with a housing 22 can either connect the working chamber 18 to the vacuum chamber 16 in order to evacuate the working chamber 18, or connect the evacuated working chamber 18 to the ambient atmosphere, ie the ambient pressure, or with overpressure to create a pressure to generate difference on the movable wall 14. The movable wall 14 is coupled to the control valve housing 22 in a force-transmitting manner.

The brake booster 10 is actuated by means of a rod-shaped input member 26, which is biased into its initial position by a spring 24 and which projects into the control valve housing 22 along an axis A and is fastened in its actuating piston 28 by means of fastening means (not shown) with its one spherical end ,

The end of the actuating piston 28 opposite the spherical end of the input member 20 is in contact with a sensing disk 30 which transmits an actuating force introduced into the brake booster 10 via the input member 26 via a reaction disk 32 made of elastomer material to a reaction piston 34 of a functionally downstream of the brake booster 10. Master cylinder not shown here transmits a hydraulic vehicle brake system.

The actuating piston 28 passes through an annular armature 36 which is arranged concentrically to it and an annular permanent magnet 38 which is likewise arranged concentrically with the actuating piston 28 and is received in a cup-shaped component 40. The permanent magnet 38 and the pot-shaped component 40 are movably guided in the axial direction within the control valve housing 22. For this purpose, a screw connection is provided between the pot-shaped component 40 and a restraining sleeve 42 projecting into the interior of the pot-shaped component 40. The restraining sleeve 42 is pressed against an actuation direction of the vacuum brake booster 10 against an abutment 46 formed on the control valve housing 22 by an insert 44, which closes one end of the control valve housing 22 facing the vacuum chamber 16, between the insert 44 and the restraining sleeve 42 an elastic element 45 made of an elastomer material is additionally arranged. The vacuum brake booster 10 shown in Fig. La comprises an armature assembly which is composed of the annular armature 36 and a sleeve-shaped extension 48 which is rigidly coupled to the armature 36 and extends counter to the actuation direction. As can be seen in FIG. 1 a, the annular armature 36 has a neck 50 extending radially on the inside counter to the actuation direction. At its end facing the input member 26, the neck 50 opens into a radially inwardly extending ring collar 52, the vacuum chamber 16 facing end face cooperates with a return spring 58. The prestressed return spring 58 is supported with its end facing the vacuum chamber 16 on the insert 44 of the control valve 20 and with its end facing the input member 26 on the annular collar 52 of the armature 36 -Brake booster 10 biased against a stop 53 formed on the actuating piston 28 and interacting with the armature 36 in the actuating direction.

In front of the stop 53 for the armature 36 in the actuating direction, a further stop 70 is formed on the actuating piston 28, which interacts with the armature 36 against the actuating direction. This further stop is designed as a ring 70, which is arranged immovably in the axial direction within a circumferential receiving groove 72 formed radially on the outside of the actuating piston 28.

A latch 80, which extends perpendicular to the longitudinal axis A of the vacuum brake booster 10, is displaceable in the axial direction within a further receiving groove 82 formed radially on the outside on the actuating piston 28. The mobility of the latch 80 relative to the actuating piston 28 in and against the actuating direction is limited by the two end faces of the receiving groove 82 facing the latch 80. The latch 80 extends in the radial direction through an opening in the sleeve-shaped extension 48. hJ t> -

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Sections, i.e. the snap hook 99 together with the opening sleeve 96 such that the opening sleeve 96 is displaced relative to the actuating piston 28 against the actuating direction. From this displacement of the opening sleeve 96 against the actuation direction, the bolt 80 extending through the opening 100 of the opening sleeve 96 is also detected. The bolt 80 is consequently displaced from the front side 102 of the opening sleeve 96 which delimits the opening 100 and faces the input member 26, counter to the actuation direction. The bolt 80 is shifted relative to the actuating piston 28 until the axial play of the bolt 80 predetermined by the receiving groove 82 is almost used up.

FIG. 1b shows the functional position of the vacuum brake booster 10 according to the invention during normal braking. When the input member 26 is actuated quickly and with a relatively large stroke, as is typical for emergency braking, the operating position of the vacuum brake booster 10 shown in FIG. 1c results. In the event of emergency braking, the armature 36 approaches the permanent magnet 38 as far as possible that the force of the return spring 58 is no longer sufficient to keep the armature 36 away from the permanent magnet 38. The force exerted by the permanent magnet 38 on the armature 36 then predominates. The latter therefore decouples from the input member 26 and comes into contact with the permanent magnet 38. The first valve seat 54 is thus maximally open and ambient air flows into the working chamber 18 until the maximum possible differential pressure on the movable wall 14 and thus the maximum possible Reinforcing force of the brake booster 10 is reached.

As a result of the coupling of the armature 36 with the permanent magnet 38, the sleeve-shaped extension 48 moves relative to the actuating piston 28 and relative to the opening sleeve 96, which is held back by the snap hooks 99, in the actuating direction, ie to the left in FIG. 1c. If the actuating force applied by the driver is reduced after the coupling of armature 36 and permanent magnet 38, the actuating piston 28 moves counterclockwise. towards the direction of actuation, ie n figure lc to the right. As shown in FIG. 1c, the actuating piston decouples from the sensing disk 30, and the snap hooks 99 can snap into the openings 98 of the sleeve-shaped extension 48. The armature assembly and consequently also the armature 36 are thus coupled to the actuating piston 28 even before the armature 36 is detached from the permanent magnet 38.

As a result of the displacement of the actuating piston 28 against the actuating direction, the stop ring 70 comes into contact with the end face of the annular collar 52 of the armature 36 facing the vacuum chamber 16, so that the forces acting against the actuating piston 28 against the actuating direction by means of the stop ring 70 in the anchor 36 are initiated. Those from the actuating piston 28 into the armature counter to the actuating direction

Finally, 36 forces are sufficient to release the coupling between permanent magnet 38 and armature 36 and to tear armature 36 off permanent magnet 38.

As a result of the activated coupling device 90, that is to say as a result of the engagement of the latching hooks 99 in the openings 98 of the sleeve-shaped extension 48, the armature assembly comprising the armature 36 can no longer move relative to the actuating piston 28 after the armature 36 has been torn off by the permanent magnet 38. This consequently precludes the armature assembly from picking up speed in an uncontrolled manner after the armature 36 has been torn off the permanent magnet 38.

The operating position of the vacuum brake booster 10 after the armature 36 has been torn off by the permanent magnet 38 while simultaneously coupling the sleeve-shaped extension 48 and thus the armature 36 to the actuating piston 28 is shown in FIG. 1d.

Only after the brake pedal has been fully released does the vacuum brake booster 10 return from the operating position shown in FIG. 1d to its initial position shown in FIG. During the rewind the Bolt 80 retained at stop 84. As a result of this interaction between the stop 84 and the latch 80, the latch 80 is displaced within the receiving groove 82 of the actuating piston 28 in the actuating direction, ie to the left in FIG. 1d, until the latch 80 again abuts the end face of the receiving groove 82 facing the input member 26 arrives and the axial play of the bolt 80 within the receiving groove 82 is used up.

The axial displacement of the latch 80 within the groove 82 relative to the actuating piston 28 is transmitted to the opening sleeve 96, the end face 102 of which faces the input member 26 and delimits the opening 100 and is still in contact with the latch 80. As a result, the opening sleeve 96 moves relative to the sleeve-shaped extension 48 and the actuating piston 28 in the actuating direction. The snap hooks 99 are therefore pushed out of the openings 98 of the sleeve-shaped extension 48 by the opening sleeve 96 and the coupling between the actuating piston 28 and the sleeve-shaped extension 48 and thus also the armature 36 is released. This corresponds to the starting position of the vacuum brake booster 10 shown in FIG.

FIG. 2 shows a second exemplary embodiment of a vacuum brake booster 10 according to the invention. The function and structure of the second exemplary embodiment are essentially the same as the first exemplary embodiment. As in the first exemplary embodiment, the coupling device 90 is designed as a latching device, with a snap hook 99 latching into an opening 98 provided in the sleeve-shaped extension 48 to form a latching connection between the actuating piston 28 and the sleeve-shaped extension 48 of the armature 36. As in the first exemplary embodiment, the snap hook 99, which is biased radially outward, is formed by a radially outer end of a swivel arm 94, which is designed in one piece with a sleeve 92 rigidly coupled to the actuating piston 28. C5

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110 designed. The stop body 110 is arranged on a surface facing the input member 26 of a spring plate 112 extending perpendicular to the longitudinal axis of the actuating piston 98. The spring plate 112 is fastened in the middle between two legs of the bolt 80 and, like the bolt 80, is rigidly coupled to the actuating piston 28.

In the starting position of the vacuum brake booster 10 shown in FIG. 3a, the spring plate 112, which is under tension, is clamped together with the latch 80 in a groove 82 of the actuating piston 28 such that the spring plate 112 after a separation of the stop body 110 from a in the housing 12 of the vacuum brake booster 10 designed stop 84 can perform a pivoting movement against the actuating direction. In Fig. 3a, this pivoting movement is prevented due to the engagement of the snap hook 99 on a radially outer surface of the sleeve-shaped extension 48.

After an emergency braking, the operating position of the vacuum brake booster 10 shown in FIG. 3b results, in which the armature 36 comes into contact with the permanent magnet 38. The control valve housing 22 moves with respect to the housing 12 of the vacuum brake booster 10 in the actuating direction, i. H. 3b to the left. The stop body 110 of the spring plate 112 then releases from the stop 84 formed in the housing 12 of the vacuum brake booster 10 and the swivel arm 94 continues to tension the snap hook 99 against a radially outer surface of the sleeve-shaped extension 48.

If the driver ends the emergency braking by withdrawing the brake pedal, the input member 26 shifts relative to the sleeve-shaped extension 48 against the actuation direction, ie to the right in FIG. 3b. As a result of the return stroke of the input member 26, due to restoring forces of the return springs 24 and 58, the actuating piston 28 and the swivel arm 94 rigidly coupled to the actuating piston 28 are displaced relative to the armature 36 and the sleeve-shaped extension 48

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th end of the swivel arm 94 is formed and has a leg 99A extending obliquely to the longitudinal axis A of the vacuum brake booster 10.

In the activated position of the emergency brake aid shown in Fig. 4b, i.e. when permanent magnet 38 and armature 36 are coupled, the snap hook 99 engages in the corresponding opening 98 of the sleeve-shaped extension 48. The coupling device 90 is thus activated and the armature 36 is coupled to the actuating piston 28. Due to the leg 99A, which runs obliquely to the longitudinal axis A, of the U-shaped profile forming the snap hook 99, it is ensured that the snap hook 99 always completely, i.e. filled in without play. Different dimensions of the opening 98 due to dimensional tolerances can thus be compensated for. Of course, instead of an essentially U-shaped profile, the snap hook 99 could also be formed by an essentially V-shaped profile and have two legs which extend obliquely to one another and to the longitudinal axis A.

In order to move the coupling device 90 into its decoupled position according to FIG. 4b, the spring plate 112, as already described above, interacts with the stop 84 formed on the housing 12 of the vacuum brake booster 10. Because of this interaction, the swivel arm 94 is elastically bent radially outward and the snap hook 99 is finally pulled out of the opening 98 of the sleeve-shaped extension 48. In the starting position (rest position) of the vacuum brake booster 10, the snap hook 99 then rests under prestress on the sleeve-shaped extension 48.

4c shows a further exemplary embodiment of a vacuum brake booster 10 according to the invention. It is somewhat modified compared to the fourth exemplary embodiment according to FIG. 4a and the exemplary embodiment according to FIG. 4b.

Again, the swivel arm 94 and the arm formed by the spring plate 112 are formed as separate components and are one The region 112a of the spring plate 112 which extends parallel to the swivel arm is connected to the swivel arm 94 by means of welding. The section of the spring plate 112 which extends perpendicular to the swivel arm 94 has a bead 112b at its end facing the swivel arm 94, which bead surrounds this section of the

Swivel arms 112 stiffened locally. The associated reduction in the elasticity of the spring plate 112 increases the switch-off safety of the coupling device 90.

The manufacture of the snap hook 99 of the vacuum brake booster according to FIG. 4c is explained in more detail below with reference to FIGS. 4d to 4f.

As can be seen from FIG. 4e, the swivel arm 94 is designed as a strip-shaped spring plate. At its end facing the input member 26, the swivel arm 94 has a T-shaped end section which is formed, for example, by punching. The areas 94a and 94b projecting over the width of the swivel arm 94 are bent downwards after punching, as shown in FIG. 4f. Each of the two bent areas 94a, 94b forms a snap hook 99b, 99c. As shown in cross section in FIG. 4d, the two snap hooks 99b, 99c engage in the coupled position of the coupling device 90 in the opening 98 of the sleeve-shaped extension 48.

The production of the snap hooks 99b, 99c described with reference to FIGS. 4d and 4f improves their dimensional accuracy, since the shape of the snap hooks 99b, 99c is defined by the punching out and not the bending process. at

The dimensional accuracy is usually low due to spring-back effects. Bending back due to spring-back effects does not, however, influence the dimensional accuracy of the coupling sought according to the invention. This is because the bending in Fig. 4d is to the left and right and thus the dimensional accuracy in directions perpendicular to the plane of the drawing is not affected. The vacuum brake booster according to the third (Fig. 3a - 3d) and the fourth (Fig. 4a - 4f) embodiment can be modified such that, as in the first embodiment, an actuator 36 upstream of the armature 36 and trained on the actuating piston 28 Stop for detaching the armature 36 from the permanent magnet 38 is provided.

5a and 5b show a fifth exemplary embodiment of a brake booster 10 according to the invention in an initial position and in an operating position of the vacuum brake booster 10. The vacuum brake booster 10 according to the fifth exemplary embodiment is similar in construction and mode of operation to the vacuum brake booster 10 according to the previous exemplary embodiments.

As in the previous exemplary embodiments, the coupling device 90 is designed as a latching device. The coupling device 90 comprises a first locking element in the form of an expansion ring 122 and a complementary, second locking element in the form of a bevel 124 formed in the cylindrical extension 48. The expansion ring 122 is arranged axially immovably in a circumferential annular groove 126 formed in the actuating piston 28 and extends radially externally biased against a radially inner surface of the sleeve-shaped extension 48.

In the initial position of the vacuum brake booster 10 shown in FIG. 5 a, the expansion ring 122 contacts a cylindrical section 128 of the sleeve-shaped extension 48 which follows the bevel 124 in the actuating direction and which has a smaller inner diameter than the cylindrical section 130 which has the bevel 124 precedes in the direction of actuation.

In the case of emergency braking, the operating position of the vacuum brake booster 10 shown in FIG. 5b results, in which the armature 36 is in contact with the permanent magnet 38. As a result of the coupling of the armature 36 with the Permanent magnet 38 associated displacement of the sleeve-shaped extension 48, the slope 124 moves so far in the actuating direction that the expansion ring 122 can expand radially outward in the region of the slope 124. The widening of the expansion ring 122 in the area of the slope 124 causes the sleeve-shaped extension 48 and thus also the armature 36 to be coupled to the actuating piston 28, so that a displacement of the sleeve-shaped extension 48 relative to the actuating piston 28 is excluded. This is due to the fact that the axial forces acting on the armature 36 against the actuating direction after the armature 36 has been detached from the permanent magnet are not sufficient to press the expansion ring 122 back into the annular groove 126 by means of the bevel 124.

Only after the brake pedal has been withdrawn and the associated return stroke of the input member 26 can the expansion ring 122 be compressed by the bevel 124 by means of the return spring forces introduced into the sleeve-shaped extension 48 to such an extent that the diameter of the expansion ring 122 corresponds to the inside diameter of the bevel 124 in Direction of actuation corresponds to the following cylindrical section 128 of the sleeve-shaped extension 48 and the starting position of the vacuum brake booster 10 shown in FIG. 5a results.

6a and 6b show a sixth exemplary embodiment of a vacuum brake booster 10 according to the invention. The vacuum brake booster 10 according to the embodiment shown in FIGS. 6a and 6b essentially corresponds in structure and function to the vacuum brake booster of the previous embodiments.

The vacuum brake booster 10 according to the sixth exemplary embodiment also comprises a coupling device 90 in the form of a latching device. The latching device is composed of a first latching element in the form of a spring ring 132 and a complementary, second rascele ent in the form of a recess 134 formed as a groove. The spring ring 132 is on an end face 136 of the armature 36 which faces the input member 26 and has a radially inner section which is designed as a snap ring 138 and which is designed to engage in the recess 134 formed in the actuating piston 28.

6a shows the operating position of the vacuum brake booster 10 during emergency braking. As a result of the emergency braking, the anchor 36 was pulled into contact with the permanent magnet 38. The snap ring 138 has jumped out of the recess 134. If the driver now ends the emergency braking, the armature 36 is torn off by the permanent magnet 38. The armature 36 then moves against the direction of actuation until it comes into contact with the stop 53 formed on the actuating piston 28 (FIG. 1b). Before the armature 36 can come into contact with the stop 53, however, deformation work must be carried out for the expansion of the snap ring 138, which is necessary for the snap ring 138 to snap into the recess 134. The deformation work is performed by the armature 36, which accelerates against the actuation direction after tearing off, as a result of which the impact of the armature 36 against the stop 53 is damped.

7 shows a seventh exemplary embodiment of a vacuum brake booster 10 according to the invention. The

Vacuum brake booster according to FIG. 7 essentially corresponds in structure and function to the previous exemplary embodiments. Different from the previous ones

Exemplary embodiments, however, the coupling device 90 is not designed as a latching device, but rather as a clamping device. The clamping device 90 comprises a sleeve 140 rigidly coupled to the actuating piston 28 and fastened radially on the outside to the actuating piston 28, which sleeve is formed in one piece with a plurality of clamping elements 142 in the form of radially outwardly projecting clamping arms 142. The clamping arms 142 rest against the sleeve-shaped extension 48 radially on the inside under pretension. The clamping arms 142 consequently generate a clamping force radially outwards. The clamping arms 142 open obliquely into the sleeve-shaped extension 48. With this inclined position of the clamping arms 142, asymmetrical clamping properties are associated. While the clamping force of the clamping arms 142 is relatively small when the sleeve-shaped extension 48 moves relative to the actuating piston in the actuating direction, the clamping arms 142 generate a relatively high clamping force when the sleeve-shaped extension 48 is displaced in the opposite direction.

The asymmetrical clamping forces generated by the clamping arms 142 are dimensioned such that, in the event of emergency braking, the armature 36 can decouple from the actuating piston 28 and come into contact with the permanent magnet 38, but the clamping forces, on the other hand, are sufficient by one after the armature 36 has been torn off the permanent magnet 38 Displacement of the armature 36 relative to the actuating piston 28 against the actuation direction and in particular strongly dampening an impact of the armature 36 against the stop 53 formed on the actuating piston 28.

8 shows an eighth exemplary embodiment of a vacuum brake booster 10 according to the invention. The vacuum brake booster according to FIG. 8 essentially corresponds in function and structure to the vacuum brake booster of the seventh exemplary embodiment. As in the seventh exemplary embodiment, the coupling device 90 is designed as a clamping device with a plurality of clamping arms 142.

In a departure from the seventh exemplary embodiment, the clamping device 90 according to the eighth exemplary embodiment additionally comprises an opening sleeve 96 with the functionality known from the first exemplary embodiment. The opening sleeve 96 allows the coupling of the radially outwardly biased arms 142 to the sleeve-shaped extension 48 to be released after the vehicle brake has been completely released. o rH 1 XJ Φ .. 54

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10 shows a tenth exemplary embodiment of a vacuum brake booster 10 according to the invention. The vacuum brake booster 10 according to the tenth exemplary embodiment essentially corresponds in function and structure to the vacuum brake booster of the ninth embodiment. In a departure from the ninth exemplary embodiment, the coupling device 90 designed as a clamping device does not include a solid carrier ring, but instead, for cost reasons, a bent sheet metal part 158 which is arranged within a groove 152 of the actuating piston 28 and which defines a slope 154. The rolling element 156 corresponds to the rolling element of the ninth exemplary embodiment.

11a and 11b show an eleventh embodiment of a vacuum brake booster 10 according to the invention. The vacuum brake booster 10 according to the eleventh embodiment is similar in function and structure to the vacuum brake booster of the previous exemplary embodiments. In a departure from the previous exemplary embodiments, the coupling device 90 is designed as a supporting device which allows the armature 36 to be supported against the actuating direction on the actuating piston 28.

The support device 90 comprises a support element 160 which can be pivoted into a support position for coupling the armature 36 and the actuating piston 28. The support element 160 extends in the starting position of the vacuum brake booster 10 shown in FIG opening 162 of armature 36 extending in the direction of actuation. The support element 160 is rigidly coupled to the actuating piston 28 and is biased radially outward. An arm 164 is formed in one piece with the support element 160, which extends radially outward and which, in the starting position shown in FIG. 11 a, is in contact with a stop 84 formed on the housing 12 of the vacuum brake booster 10. det. In the starting position according to FIG. 11 a, the support element 160 is snapped into the opening 162 of the armature 36, but without performing a support function.

In the event of emergency braking, the armature 36 moves relative to the actuating piston 28 in the actuating direction, i. H. 11a to the left. The armature 36 moves so far in the axial direction from the actuating piston 28 that the support element 160 detaches from the associated opening 162 and, due to the prestress, swings radially outward until the end of the support element 160 facing the vacuum chamber 16 is at one of the input member 26 facing end face of the armature 36 formed bevel 166 contacted.

During a return stroke of the input member 26, the armature 36 is torn off from the permanent magnet 38 and the operating position of the vacuum brake booster 10 shown in FIG. 11b is established. The support element 160 fulfills its support function and prevents the armature 36 from colliding against the stop 53 formed on the actuating piston 28.

Only after the brake pedal has been fully released does the arm 184 again run against the stop 84 on the housing 12 of the vacuum brake booster 10, whereupon the support element 160 is pivoted radially inward and can again dip into the opening 162 formed in the armature 36. The support element 160 is then released from its support function and the initial position of the vacuum brake booster 10 shown in FIG. 11a is established.

Claims

claims

1. Vacuum brake booster (10), with

- a vacuum chamber (16) and a working chamber (18) separated from it by a movable wall (14),

- A control valve (20) which has a housing (22) which is coupled to the movable wall (14) in a force-transmitting manner and which, in order to achieve a pressure difference on the movable wall (14), supplies atmospheric pressure or excess pressure to the working chamber (18) as a function of the displacement of an actuating piston (28) can control, and

- An emergency braking aid with a permanent magnet (38) and one with the permanent magnet (38) cooperating armature (36) which is resiliently biased against the direction of actuation of the brake booster and is pulled in an emergency braking in contact with the permanent magnet (38), whereby the control valve (20) is kept open for the supply of atmospheric pressure to the working chamber (18), characterized in that a coupling device (90) for releasably coupling the armature (36) to the actuating piston (28) is provided.

2. Vacuum brake booster according to claim 1, characterized in that the coupling device (90) is a latching device.

3. Vacuum brake booster according to claim 2, characterized in that the latching device (90) comprises a first latching element (99, 122, 138) and a complementary, second latching element (98, 124, 134) which interact to the armature (36) to couple with the actuating piston (28).

4. Vacuum brake booster according to claim 3, characterized in that the first latching element (99, 122, 138) is movable in the radial direction.

5. Vacuum brake booster according to claim 4, characterized in that the first latching element (99, 122, 138) is biased in the radial direction.

6. Vacuum brake booster according to one of claims 3 to 5, characterized in that the first latching element is designed as a snap hook (99) or as a ring (122, 138).

7. Vacuum brake booster according to claim 6, characterized in that the snap hook (99) is arranged in the region of a pivot arm (94) extending substantially in the axial direction.

8. Vacuum brake booster according to claim 7, characterized in that the snap hook (99b, 99c) is formed by folding one or more areas of the swivel arm (94).

9. Vacuum brake booster according to claim 7 or 8, characterized in that the swivel arm (94) with a further arm (110, 112), which allows a deflection of the swivel arm (94), is rigidly coupled.

10. Vacuum brake booster according to one of claims 7 to 9, characterized in that the pivot arm (94) is pivotally attached to the actuating piston (28).

li. Vacuum brake booster according to one of claims 3 to 10, characterized in that the second latching element is designed as an opening (98), depression (134) or bevel (124).

12. Vacuum brake booster according to claim 11, characterized in that the snap hook (99) has a sloping surface (99a) which interacts with a boundary (98a) of the openings (98).

13. Vacuum brake booster according to claim 1, characterized in that the coupling device (90) is a clamping device.

14. Vacuum brake booster according to claim 13, characterized in that the clamping device (90) comprises a clamping element (142, 156) generating a clamping force in the radial direction.

15. Vacuum brake booster according to claim 14, characterized in that the clamping element (142, 156) has asymmetrical clamping properties with respect to an axial relative movement in and against the actuating direction between the armature (36) and the actuating piston (28).

16. Vacuum brake booster according to claim 14 or 15, characterized in that the clamping device (90) comprises a slope (154) with which the clamping element (156) interacts.

17. Vacuum brake booster according to one of claims 14 to 16, characterized in that the clamping element is designed as a rolling element, in particular as a ring or ball (156).

18. Vacuum brake booster according to one of claims 14 or 15, • characterized in that the clamping element is an obliquely to the longitudinal axis of the vacuum brake booster (10) extending clamping arm (142).

19. Vacuum brake booster according to one of claims 1 to 18, characterized in that the coupling device (90) has an axially movable opening sleeve (96) for canceling the coupling between armature (36) and actuating piston (28).

20. Vacuum brake booster according to claim 1, characterized in that the coupling device (90) is a support device.

21. Vacuum brake booster according to claim 20, characterized in that the support device (90) comprises a support element (160) which can be pivoted into a support position for coupling the armature (36) and actuating piston (28).

22. Vacuum brake booster according to one of claims 1 to 21, characterized in that a stop (70) is provided on the actuating piston (28), which is upstream of the armature (36) in the actuating direction and which is opposite to the actuating direction with the armature (36) interacts.

23. Vacuum brake booster according to one of claims 1 to 22, characterized in that a bolt (80) is provided which extends essentially perpendicular to the actuating piston (28) and is coupled to the actuating piston (28).