WO2003099625A1

WO2003099625A1 - Low-pressure brake booster and brake booster/master cylinder unit

Info

Publication number: WO2003099625A1
Application number: PCT/EP2003/005369
Authority: WO
Inventors: Peter Schlüter; Gerd Puscher; Monika Matthei
Original assignee: Lucas Automotive Gmbh
Priority date: 2002-05-23
Filing date: 2003-05-22
Publication date: 2003-12-04
Also published as: AU2003250818A1; DE10222866A1

Abstract

Disclosed is a low-pressure brake booster (10) comprising a booster housing (58), the interior space of which is separated into a low pressure chamber (78) and a working chamber (80) by means of at least one movable wall (76), and a control valve (82) which extends into the booster housing (58) and controls a difference in pressure that acts on the movable wall (76). Said control valve (82) is actuated by an entering member (32) and is provided with a housing (84) which is connected to the movable wall (76) so as to transmit power and can be axially displaced relative to the booster housing (58). A gap (96) which is located between an exterior surface (92) surrounding the control valve housing (84) and the booster housing (58) is sealed from the ambient atmosphere by means of a first, elastically deformable bellows-type element (98).

Description

Vacuum brake booster and brake booster / master cylinder unit

The invention relates to a vacuum brake booster with an booster housing, the interior of which is divided by at least one movable wall into a vacuum chamber and a working chamber, and a control valve projecting into the booster housing for controlling a pressure difference acting on the movable wall, which can be actuated by an input member and a Control valve housing connected to the movable wall in a force-transmitting manner. The invention further relates to a brake booster / master cylinder unit with such a vacuum brake booster and a master cylinder which has a master cylinder housing which delimits a bore in which a first piston is sealingly guided and axially displaceable to form a first pressure chamber.

Such vacuum brake booster and brake booster / master cylinder units, which are known in various embodiments from the prior art, are usually either mechanically, for example by stepping on a brake pedal connected to the input member, or electronically, for example by means of a controlled by an electronic control unit Electromagnet arrangement actuated. When the brake booster is actuated, a control valve opens a connection between a working chamber and the ambient atmosphere, so that air can flow into the working chamber, whereupon a differential pressure builds up on a movable wall. This

Differential pressure shifts the movable wall and a control valve housing connected to the movable wall axially in the direction of actuation, which results in a corresponding servo force which is transmitted to a master cylinder which is functionally connected to the brake booster. When the brake application is terminated, the control valve closes the connection between the working chamber and the ambient atmosphere and instead opens a connection between a vacuum chamber and the working chamber. Since the vacuum chamber of the brake booster is constantly connected to a vacuum source, for example the intake tract of an internal combustion engine or a vacuum pump, this leads to a reduction in the differential pressure on the movable wall, so that the movable wall and the control valve housing are moved back to their starting position. With such vacuum brake boosters, a booster kergehäuse on its force input side usually has a hollow cylindrical collar with a sealing and bearing bush fixed therein, in which the control valve housing is sealed and axially displaceably guided. Sealing elements, which have to be lubricated with a silicone grease in order to reduce friction, are usually used in such a sealing and bearing bush for the sealed guidance of the control valve housing.

In the case of a brake booster equipped with such a sealing and bearing bush, the lubricant used to reduce friction can evaporate, in particular at high outside temperatures, so that the friction between the sealing elements and the control valve housing can increase in the course of the operating time of the booster. In addition, the evaporation of the lubricating grease can contaminate the interior of the brake booster and in particular electronic components arranged in the interior of the booster housing. Finally, such an arrangement requires a relatively high outlay on assembly and production.

The invention has for its object to provide a vacuum brake booster and a brake booster / master cylinder unit, in which the disadvantages described above can be avoided.

To achieve this object, in the vacuum brake booster according to the invention there is a gap between an outer surface surrounding the control valve housing and the booster housing, which gap is sealed from the ambient atmosphere by a first, elastically deformable bellows. In this way, the arrangement according to the invention enables a friction-free displacement of the control valve housing relative to the booster housing; the use of a lubricant is unnecessary. The elastically deformable bellows can, for example, be designed as a rolling bellows and ensures a reliable seal of the booster housing against the ambient atmosphere. The bellows has a size and shape that is designed so that the axial displacement of the control valve relative to the booster housing is not hindered. In a structurally simple embodiment of the brake booster according to the invention, the gap between the outer surface of the essentially hollow cylindrical control valve housing and an opposite inner surface of a section of the booster housing which extends coaxially to the control valve housing is formed, ie a conventional booster housing can be used in a cost-saving manner. Preferably, a first end of the first bellows is attached to an outer surface of the booster housing and a second end of the first bellows is attached to the outer surface of the control valve housing. The first end of the bellows, which is preferably designed as a rolling bellows, can cooperate, for example, for securely fastening the bellows to the booster housing with a projection formed on the outer surface of the booster housing, while the second end of the bellows can be fixed in a groove formed in the outer surface of the control valve housing.

The control valve housing advantageously consists of a deep-drawn sheet metal part. Alternatively, the control valve housing is made of plastic and is designed as an injection molded part. The control valve housing can be easily and inexpensively manufactured in the above-mentioned ways and at the same time has a low weight.

The control valve housing is preferably attached to a membrane plate connected to the movable wall by means of a crimp connection. Such a crimp connection is particularly simple and inexpensive to manufacture and ensures a secure connection of the control valve housing to the diaphragm plate. As a result, the movement of the movable wall can be reliably transmitted to the control valve housing which can be displaced axially relative to the booster housing, so that when the brake booster is actuated, the control housing moves together with the movable wall and the diaphragm plate relative to the booster housing.

In a preferred embodiment of the brake booster according to the invention, a first and a second valve member are arranged in the control valve housing so as to be displaceable in the axial direction relative to one another, the first valve member being resiliently biased in the opposite direction of actuation. Preferably, the first and the second valve member each have a hollow cylindrical first section, a second section projecting radially outward from the first section and a third section extending in the axial direction from the second section, at least part of the hollow cylindrical first section of the first Valve member is axially displaceably guided in the hollow cylindrical first section of the second valve member. A control valve constructed in this way is structurally simple and therefore inexpensive to manufacture. Since the second valve member takes over the leadership of the first valve member, an additional component for fulfilling this function can be dispensed with. Preferably, a second, elastically deformable bellows, for example in the form of a rolling bellows, extends over outer surfaces of the third sections of the first and second valve members and over an end face of the third section of the first valve member facing the force input side of the brake booster. The first and the second valve member are thus connected to one another via the second bellows, the bellows having a size and a shape which is designed such that the axial displacement of the first and second valve members relative to one another is not impeded.

In an advantageous embodiment of the vacuum brake booster according to the invention, the end face of the third section of the first valve member encompassed by the second bellows interacts with a first valve seat formed on an end wall of the control valve housing in order to establish or interrupt a connection between the ambient atmosphere and the working chamber. In this particularly simple arrangement, the elastically deformable material of the second bellows, which covers the end face of the third section of the first valve member, ensures that the first valve member gently lies against the first valve seat when the first valve seat is closed.

A flange formed on the input member and projecting radially outwards for opening the first valve seat preferably interacts with the hollow cylindrical first section of the first valve member. If the flange present on the input member abuts an end face of the first section of the first valve member when the input member is actuated, the first valve member is axially displaced relative to the second valve member against its resilient bias.

As a result, the end face of the third section of the first valve member which is encompassed by the second bellows lifts off the first valve seat, as a result of which the connection between the ambient atmosphere and the working chamber of the brake booster is opened. The flange present on the input member is preferably spherical in order to compensate for a deflection of a brake pedal connected to the input member when the brake booster is installed.

In a preferred embodiment of the invention Bremskraftverstär- kers a projection formed on the second bellows sealing bead for the production and interruption of a connection between the vacuum chamber and the working chamber ^¬ with a second valve seat together, which at a radially inwardly projecting flange of the membrane plate is formed. Since the second bellows consists of an elastically deformable material, the sealing bead is softly applied to the second valve seat when the second valve seat is closed. The sealing bead is preferably formed on a section of the second bellows, which extends at least over an end face of the third section of the second valve member facing away from the force input side of the brake booster. Alternatively, the connection between the vacuum chamber and the working chamber can also be opened or closed by the interaction of the end face of the third section of the second valve member facing away from the force input side of the brake booster and covered by a section of the second bellows with the second valve seat.

The first and the second valve seat are preferably each annular and have the same diameter in order to avoid the occurrence of reaction forces resulting from pressure differences.

The resilient bias of the first valve member is preferably generated by means of a return spring, the opposite ends of which are supported on the first valve member and the second valve member. As a result, the force of the return spring urges the first and the second valve member in opposite directions, so that the second valve member is biased in the actuating direction on the second valve seat. To open the second valve seat, the force exerted by the return spring on the second valve member must therefore be overcome.

In an alternative embodiment of the brake booster according to the invention, the opposite ends of the return spring, which biases the first valve member in the opposite actuation direction, are supported on the first valve member and on a support element arranged in the control valve housing. The support element can be pushed by the force of the return spring either against the radially inwardly projecting flange of the diaphragm plate or against an end face of a first piston which is arranged axially displaceably in a housing of a master cylinder functionally connected to the vacuum brake booster. This arrangement has the advantage that when the brake pedal is released to establish the connection between the working chamber and the vacuum chamber, the force of the return spring no longer has to be overcome. This can, for. B. a spring, which is a component of the vehicle brake system which is used to open the vacuum sealing seat with the second valve member. acts, moves back to its rest position when releasing the brake, be designed accordingly weaker.

Preferably, an end of the second bellows facing the force input side of the brake booster is attached to the input member. In this embodiment of simple construction, the end of the bellows can be fixed, for example, in a groove formed on a peripheral surface of the input member.

In an alternative embodiment of the brake booster according to the invention, the second bellows instead has a sealing surface which interacts with a peripheral surface of the input member. The input member then protrudes sealed into the second bellows and is axially displaceable relative to the second bellows. An end of the second bellows facing the force input side of the brake booster is then preferably attached to a holding element connected to the control valve housing. To fix the second bellows to the holding element, the end of the second bellows facing the force input side of the brake booster can have, for example, a radially outwardly projecting flange which interacts with a radially inwardly projecting flange of the holding element. In the release position of the brake, a negative pressure prevails in the interior of the control valve housing when the first and second valve seats are closed. This creates a pressure difference between the atmospheric pressure prevailing outside the control valve and the underpressure present inside the control valve housing on an end face of the second bellows facing the force input side of the brake booster. If the second bellows is connected to the input member in a force-transmitting manner, this differential pressure acting in the actuating direction is transferred to the input member, so that, for example, a restoring force of a spring that biases the input member in the actuating opposite direction must be increased by the amount of force exerted by the differential pressure in the actuating direction in order for an automatic To prevent actuation of the brake booster from the rest position. If the end of the second bellows is fastened to a holding element connected to the control valve housing, there is no force-transmitting connection between the second bellows and the input member, so that the differential pressure force acting on the end face of the second bellows via the holding element into the control valve housing and not into the Input element is initiated. Thereby, the input member actuation in the opposite direction bias ^¬ de spring by the amount of differential pressure force can be designed to be weaker, so that a response force of a brake booster / master cylinder unit determined by the spring force of this spring can be reduced accordingly.

A brake booster / master cylinder unit according to the invention comprises a vacuum brake booster according to the invention and a master cylinder which has a master cylinder housing which delimits a bore, in which a first piston is sealingly and axially displaceably guided to form a first pressure chamber, the bore being in the direction of its free one End-extending, substantially hollow cylindrical extension of the master cylinder housing axially guides the first piston. With such an arrangement, no further components serving to guide the first piston in the master cylinder or in the brake booster are required. If the master cylinder is assembled with a brake booster to form a master cylinder / brake booster unit according to the invention, the hollow cylindrical extension is preferably arranged completely inside the brake booster housing.

The first piston is preferably hollow-cylindrical and, in the normal case, can only be actuated indirectly by a force output member of the brake booster upstream of the master brake cylinder. By "normal case" it is meant here that the first piston is actuated exclusively by the brake booster upstream of the master brake cylinder if the latter works properly and is not fully controlled during braking, i.e. does not provide his maximum assistant. For direct actuation of the first piston, an actuating piston is preferably guided axially displaceably in the first piston. In this embodiment, the master cylinder according to the invention is designed as a master cylinder with a purely hydraulic reaction, the actuation of which takes place without an interposed, rubber-elastic reaction disk.

In a preferred embodiment of the brake booster / master cylinder unit according to the invention, the radially inwardly projecting flange formed on the diaphragm plate of the brake booster is connected to a radially outwardly projecting flange of the first piston. As a result, the force generated by the build-up of the pressure difference on the movable wall for actuating the first piston can be transmitted directly to the flange formed on the first piston via the flange formed on the diaphragm plate. The hollow cylindrical first section of the second valve member of the control valve is preferably axially displaceably guided on the actuating piston. This makes it possible to dispense with an additional component for fulfilling a guiding function for the first valve member.

In a particularly preferred embodiment of the brake booster / master cylinder unit according to the invention, an end face of the actuating piston facing the force input side of the brake booster for opening the second valve seat interacts with a projection that projects radially inward on the hollow cylindrical first section of the second valve member. If the end face of the actuating piston abuts against the projection formed on the second valve element when the brake is released and the return movement of the actuating piston into its rest position, the second valve member is displaced axially in the actuating opposite direction relative to the first valve member. As a result, the sealing bead formed on the second bellows or the end face of the second or third sections of the second valve member lifts off from the second valve seat, whereby the connection between the vacuum chamber and the working chamber of the brake booster is opened.

In an alternative embodiment of the brake booster / master cylinder unit according to the invention, the hollow cylindrical first section of the second valve member and the hollow cylindrical first section of the first valve member are axially displaceable on an extension section of the actuating piston which extends in the direction of the force input side of the brake booster. This configuration is structurally particularly simple since a telescopic guide of the hollow cylindrical first section of the first valve member can be dispensed with in the hollow cylindrical first section of the second valve member.

As an alternative to this, the hollow cylindrical first section of the second valve member and the hollow cylindrical first section of the first valve member can also be guided axially displaceably on an outer surface of a sleeve which is fixedly connected to the actuating piston. For a firm connection of the sleeve to the actuating piston, the sleeve is preferably pressed onto an end section of the actuating piston facing the force input side of the brake booster. Since relatively high forces are required when the sleeve is mounted on the actuating piston and in particular when the sleeve is displaced relative to the actuating piston, the actuating piston should be brought into a position before the sleeve is pushed on are in which the forces acting on the actuating piston during assembly of the sleeve do not act on the return springs biasing the actuating piston into its rest position, but can be absorbed by the master cylinder housing.

Preferably, an actuating element, which is arranged in a groove formed in the extension section of the actuating piston or in the sleeve fixedly connected to the actuating piston, cooperates with an end face of the second section of the first valve member facing the force input side of the brake booster in order to open the first valve seat. This will be the first

Together with the actuating piston, the valve member is axially displaced relative to the second valve member, so that the end face of the third section of the first valve member encompassed by the second bellows loses sealing contact with the first valve seat and the connection between the atmospheric pressure and the working chamber of the brake booster is opened. The actuating element can be, for example, a simple spring ring or the like. This structurally particularly simple configuration has the additional advantage that the first valve element is sealed by means of a simple O-ring seal with respect to the extension section of the actuating piston or the sleeve which is fixedly connected to the actuating piston, and thus a sealing attachment of the second rolling bellows to the input member is dispensed with can. This makes it possible to attach an end section of the second bellows directly to the first valve element, thereby shortening the bellows and the first valve element and thus reducing the installation space requirement.

In a preferred embodiment of the brake booster / master cylinder unit according to the invention, a radially outwardly projecting projection formed on the actuating piston or on the sleeve firmly connected to the actuating piston acts to open the second valve seat with an end face of the hollow cylindrical one facing away from the force input side of the brake booster first portion of the second valve member together. If the radially outwardly projecting projection formed on the actuating piston or on the sleeve firmly connected to the actuating piston when releasing the brake and the subsequent return movement of the actuating piston into its rest position against the end face of the hollow cylindrical first section of the second facing away from the force input side of the brake booster Stops valve member, the second valve member axially displaced in the opposite direction of actuation relative to the first valve member. As a result, the sealing bead formed on the second bellows or the end face of the second or third sections of the second valve member lifts off the second valve seat, as a result of which the connection between the vacuum chamber and the working chamber of the brake booster is opened.

The sleeve preferably has a radially inwardly projecting projection, with an end face of the projection formed on the sleeve facing the force input side of the brake booster in the assembled state of the sleeve on an end face facing away from the force input side of the brake booster of a radially outwardly projecting one formed on the actuating piston Projection is present. In this embodiment, it is prevented in a simple manner that the sleeve pushed onto an end section of the actuating piston can become detached from the actuating piston.

In a particularly preferred embodiment of the brake booster / master cylinder unit according to the invention, the rest position of the actuating piston is defined by a shoulder formed in the longitudinal bore, which in the rest position of the actuating piston interacts with a stop element present on the actuating piston. The shoulder can be formed, for example, on the master cylinder housing, while the stop element can be designed in the form of a stop disk projecting radially outward from the actuating piston. By determining the rest position of the actuating piston, the rest position of the control valve housing of the brake booster upstream of the master cylinder is also defined. By suitably positioning the protrusion formed on the master cylinder housing, the control valve housing can be brought into a so-called "lost travel free" position in its rest position, whereby an almost loss-free activation of the brake booster and thus a quick response of the brake system can be achieved.

The configuration according to the invention thus makes it possible to dispense with a previously used crossbar, which was used to set the "lost travel free" position of the control valve housing, which was arranged on the control valve housing and cooperated with a stop formed on a wall of a brake booster housing. The use of such a crossbar had the disadvantage that the shells of the brake booster housing had to be positioned very precisely, since the positioning of the shells due to the stop formed on them for the determination of the "lost travel free" position of the control valve housing and thus for the proper functioning of the brake booster was of crucial importance. In the commonly used two-part brake booster housings, it was therefore imperative to staple the housing shells together in a complex manner in order to ensure the correct positioning of the housing. By determining the "lost travel free" position of the control / valve housing by means of a projection formed in the master cylinder housing, this complex and costly assembly step can be dispensed with and the housing shells of the brake booster can instead be connected to one another, for example, by means of a pull bolt.

In a preferred embodiment of the brake booster, at least one bolt is sealed and guided through the booster housing, the diaphragm plate and the movable wall. The bolt has a key surface on its end facing away from the force input side of the brake booster and protruding from the booster housing and a thread on its end facing the force input side of the brake booster and also protruding from the booster housing. By turning the bolt, the brake booster can then be screwed into a receptacle in a simple manner, which can be provided, for example, in a bulkhead arranged in the engine compartment of a motor vehicle. Furthermore, a radially outwardly projecting contact flange can be formed on the bolt, which is supported in the assembled state of the bolt on an inner surface of a shell of the booster housing facing the force input side of the brake booster. For particularly secure fastening of the brake booster, there are preferably two bolts which each pass through the booster housing parallel to its longitudinal axis. These features and the features described below can be implemented in connection with the other features of the brake booster according to the invention. However, it is also possible to equip a conventional or differently designed brake booster with the bolts described above or to design it with the features described below.

In an alternative embodiment of the brake booster, at least one bolt is sealed through a shell of the booster housing facing the force input side of the booster, into the booster housing and through the diaphragm plate and through the movable wall. On End of the bolt facing away from the force input side of the brake booster is screwed into a receptacle which is formed in a radially outwardly projecting flange of a section of the master cylinder housing arranged inside the booster housing. With this arrangement, the bolt is capable of absorbing the tensile forces acting on the master brake cylinder during a brake application, which would otherwise have to be absorbed by the shells of the booster housing. As a result, the shells of the amplifier housing can be designed correspondingly weaker, which results in a significant reduction in the weight of the amplifier housing. Because the bolt is arranged with the radially outwardly projecting flange of the inside of the amplifier housing

Section of the master cylinder housing is screwed, the bolt on the side of the booster housing facing away from the force input side of the brake booster no longer has to be guided out of the booster housing, so that an additional sealing point to the ambient atmosphere can be dispensed with.

At its end facing the force input side of the brake booster and protruding from the booster housing, the bolt preferably has a thread. As a result, the brake booster can be fastened, for example with the aid of a nut, to a bulkhead arranged in the engine compartment of a motor vehicle. Furthermore, a radially outwardly projecting contact flange can be formed on the bolt, which is supported in the assembled state of the bolt on an inner surface of the shell of the booster housing facing the force input side of the brake booster.

In a particularly preferred embodiment, the radially outwardly projecting contact flange formed on the bolt is not supported in the assembled state of the bolt on the inner surface of the shell of the booster housing facing the force input side of the brake booster, but on a bulkhead or a holding element or holding element arranged in the engine compartment of a motor vehicle from a sealing element, which seals an opening formed in the amplifier housing and penetrated by the bolt against the ambient atmosphere. As an alternative to this, the contact flange can also be supported on the bulkhead or the holding element or directly on the booster housing. The bolt can be fastened to the bulkhead or the holding element in such a way that the booster housing lies against the bulkhead and is supported on it. In a further preferred embodiment, the bolt is fastened to the bulkhead or the holding element in such a way that there is a gap between the booster housing and the bulkhead or the holding element, as a result of which the booster housing can move freely as a result of the pressure difference between the booster shells prevailing negative pressure and the atmospheric pressure inside the housing is made possible. Radially outwardly projecting sealing lips are preferably arranged on a sealing bead formed on the movable wall and fixed between end sections of the booster housing shells, so that despite the movement of the booster housing shells described above, a reliable sealing of the booster housing from the ambient atmosphere is ensured. In particular if the control valve housing is in a "lost travel free" position by the above-described interaction of a stop element present on the actuating piston of the master cylinder with a projection formed on the master cylinder housing, caulking of the booster housing shells can be dispensed with. Since with such an arrangement the previously common crossbar attached to the booster housing and thus the very exact positioning of the shells of the brake booster housing that was previously required can be dispensed with, the production and assembly effort and thus the costs can be considerably reduced. There are preferably two such bolts, each of which penetrate the amplifier housing parallel to its longitudinal axis.

In a further alternative embodiment of the brake booster, at least one bolt is sealed through the booster housing, the diaphragm plate, the movable wall and through the radially outwardly projecting flange of the section of the master cylinder housing arranged in the interior of the booster housing. The bolt has a key surface on its end facing away from the force input side of the brake booster and protruding from the booster housing, and a thread on its end facing the force input side of the brake booster and also protruding from the booster housing. By turning the bolt, the brake booster can then be easily screwed into a receptacle, which can be provided, for example, in the bulkhead arranged in the engine compartment. The radially outwardly projecting flange of the master cylinder housing and a shell of the booster housing facing away from the force input side of the brake booster are preferably clamped together by means of a first and a second fastening means arranged on the bolt. This allows the bolt to absorb tensile forces acting on the master brake cylinder during a brake application, so that the shells of the booster housing can be made correspondingly weaker and thus lighter. The first fastening means can be, for example, a nut which is screwed onto the end of the bolt which faces away from the force input side of the brake booster and protrudes from the booster housing, while the second fastening means can be an adjusting nut which is connected to the bolt in a rotationally fixed manner and which is in the assembled state of the bolt is arranged in the interior of the booster housing and is supported on the flange of the master cylinder housing. There are preferably two bolts of this type, which penetrate the amplifier housing, the diaphragm plate, the movable wall and the radially outwardly projecting flange of the master cylinder housing, each parallel to the longitudinal axis of the amplifier housing.

In a particularly preferred, alternative embodiment of the brake booster, at least one bolt is sealed through the shell of the booster housing facing away from the force input side of the booster, the radially outwardly projecting flange of the section of the master cylinder housing arranged inside the booster housing, and through a sleeve. which in turn seals the diaphragm plate, the movable wall and a shell of the booster housing facing the force input side of the brake booster. At its end facing the force input side of the brake booster and protruding from the booster housing, the bolt preferably has a thread. By turning the bolt, the brake booster can then be screwed in a particularly simple manner in a receptacle, which can be provided, for example, in the bulkhead arranged in the engine compartment of a motor vehicle. At the same time, the bolt is able to absorb the tensile forces acting on the master brake cylinder during a brake application, so that the shells of the booster housing can be made correspondingly weaker and thus lighter.

An end of the sleeve facing away from the force input side of the brake booster preferably protrudes into a recess which is formed in the flange of the master cylinder housing. The end of the sleeve can be provided with a thread, for example, so that the sleeve can be screwed into the recess formed in the flange of the master cylinder housing. The external thread of the sleeve and / or an internal thread formed in the recess can be covered with a sealing compound consisting of a plastic material. alternative for this purpose, the sleeve can also be clamped airtight in the recess formed in the flange of the master cylinder housing by inserting the bolt into the sleeve.

For a particularly secure connection of the sleeve to the booster housing, the sleeve on its end facing the force input side of the brake booster preferably has a radially outwardly projecting flange which bears on the booster housing or on a sealing element which is formed in the booster housing and penetrated by the sleeve Seals the opening against the ambient atmosphere.

Various embodiments of the invention are explained in more detail below with reference to the attached schematic drawings. It shows:

Fig. 1 shows a longitudinal section of a first embodiment of a with

Master cylinder connected vacuum brake booster,

2 shows a detailed view of a control valve of the vacuum brake booster shown in FIG. 1,

3 shows a detailed view of a control valve of a second exemplary embodiment of a vacuum brake booster connected to a master cylinder,

4 shows a detailed view of a control valve of a third exemplary embodiment of a vacuum brake booster connected to a master cylinder,

5 shows a detailed view of a control valve of a fourth exemplary embodiment of a vacuum brake booster connected to a master cylinder,

Fig. 6 shows a longitudinal section of a fifth embodiment of a with

Master cylinder connected vacuum brake booster,

7 is a longitudinal section of a vacuum equipped with the control valve shown in FIG. 6 and connected to a master cylinder. brake booster, wherein an actuating piston of the master cylinder is in a position for mounting a sleeve to be fixed on the actuating piston,

Fig. 8 shows a longitudinal section of a sixth embodiment of a with a

Master cylinder connected vacuum brake booster,

Fig. 9 shows a longitudinal section of a seventh embodiment of a with

Master cylinder connected vacuum brake booster,

Fig. 10 is a longitudinal section of an eighth embodiment of a with

Master cylinder connected vacuum brake booster,

11 shows a detail of a ninth exemplary embodiment of a vacuum brake booster connected to a master cylinder, in longitudinal section,

Fig. 12 shows a section of a tenth embodiment of a with a

Master cylinder connected vacuum brake booster in longitudinal section,

Fig. 13 is a longitudinal section of an eleventh embodiment of a with

Master cylinder connected vacuum brake booster, and

Fig. 14 is a longitudinal section of a twelfth embodiment of a with

Master cylinder connected vacuum brake booster.

In Fig. 1, a vacuum brake booster 10 for a vehicle brake system is shown in its rest position. The brake booster 10 is functionally connected to a master cylinder 12.

The master cylinder 12 has a housing 14 with a longitudinal bore 16, in which a hollow cylindrical first piston 18 is axially displaceably and sealingly guided. The first piston 18 acts on a first pressure chamber 20, which is also referred to as Primärdruckkam- mer and is delimited in the bore 16 of the master cylinder housing 14 axially between the first piston 18 and a floating in the bore 16 angeord ^¬ Neten second piston 22nd The second piston 22 is also opposite sealed the master cylinder housing 14 and acts on a between the second piston 22 and an end wall 24 of the master cylinder housing 14, also referred to as a secondary pressure chamber second pressure chamber 26. In the installed state of the master cylinder 12, the first pressure chamber 20 is connected to a first brake circuit of the vehicle brake system, while the second pressure chamber 26 is connected to a second brake circuit of the vehicle brake system.

An actuating piston 28 passes through the first piston 18 and is guided axially displaceably in the first piston 18 by means of a radially outwardly extending annular collar 30. The master cylinder 12 and the brake booster 10 are actuated by means of a rod-shaped input member 32 which is fastened in the actuating piston 28 with its spherical end 34. At its other end, the input member 32 is connected to an actuator, not shown, of the vehicle brake system, for example a brake pedal, via which an axial force can be exerted on the input member 32.

At its end facing away from the input member 32 and on the left in the figure, the actuating piston 28 has a rod-shaped extension 36 of reduced diameter that projects into the first pressure chamber 20. A hollow cylindrical sleeve 38 is arranged axially displaceably on this rod-shaped extension 36 of the actuating piston 28 and has a flange 40 which projects radially outwards at its end facing the input member 32, which is on the right in the figure. The sleeve 38 is sealed both from the actuating piston 28 and from the first piston 18, the actuating piston 28 being guided in the sleeve 38. The flange 40 formed on the sleeve 38 is pressed by a helical spring 42, the ends of which are supported on the flange 40 or on the annular collar 30 of the actuating piston 28, in the actuating direction against a step 44 formed on the first piston 18 and projecting radially inwards.

In the first pressure chamber 20, on the rod-shaped extension 36 of the actuating piston 28 projecting into the first pressure chamber 20, a first stop element 46, which is resiliently biased in the actuating direction, is axially displaceably guided. The second piston 22 acting on the second pressure chamber 26 is resiliently biased into its rest position. At its end facing away from the input member 32 and on the left in the figure, the second piston 22 has a radially outwardly extending flange 48. The master cylinder housing 14 is divided transversely with respect to the longitudinal bore 16 into three sections 50, 52, 54, which are clamped together by two screws passing through them in the longitudinal direction, not shown in the figure, between the first section 50 shown on the right in the figure and the a shell 56 of a brake booster housing 58 is clamped to the second section 52 adjacent to the first section 50 of the master cylinder housing 14. The thickness of the shell 56 defines an axial distance between the first section 50 and the second section 52 of the master cylinder housing 14. On the first section 50, a hollow cylindrical extension 60 protruding into the brake booster 10 for guiding the first main piston 18 in the master cylinder housing 14 is formed.

A first valve 62 is arranged in the first section 50 of the master cylinder housing 14 radially outside of the longitudinal bore 16. There is a radially inwardly projecting second stop element 64 on the valve 62, which cooperates with the first stop element 46 in the rest position of the master brake cylinder 12 in order to hold the first valve 62, which is resiliently biased into its closed position, in its open position. The first stop element 46 arranged on the rod-shaped extension 36 of the actuating piston 28 also rests in the rest position of the master brake cylinder 12 against a step-shaped shoulder 66 which is formed on the first section 50 of the master cylinder housing 14.

In its closed position, the first valve 62 closes a first trailing bore 68 which is formed in the second section 52 of the master cylinder housing 14 and is connected in a fluid-conducting manner to a hydraulic fluid container, not shown. The distance between the first and second sections 50, 52 of the master cylinder housing, which is determined by the thickness of the booster housing shell 56, is sealed by means of a first sealing element 72 vulcanized onto an end face of the first housing section 50. Furthermore, a hydraulic fluid passage 74 is formed in the first stop element 64.

Arranged in the second section 52 of the master cylinder housing 14 is a second valve 62 'which is resiliently biased into its firing position and has a radially inwardly projecting third stop element 64'. In the rest position of the master brake cylinder 12, the third stop element 64 'interacts with the radially outwardly projecting flange 48 of the second piston 22 in order to hold the second valve 62' in its open position. In its closed position, the second valve 62 'closes one formed in the third section 54 of the master cylinder housing 14 second trailing bore 68 ', which, like the first trailing bore 68, is connected in a fluid-conducting manner to the hydraulic fluid reservoir, not shown. A second sealing element 72 'is vulcanized onto an end face of the third housing section 54.

The interior of the brake booster housing 58 is divided by a movable wall 76 into a vacuum chamber 78 and a working chamber 80. When the brake booster 10 is operating, the vacuum chamber 78 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 82 for controlling a pressure difference acting on the movable wall 76 projects into the amplifier housing 58 along an axis L.

As can best be seen in FIG. 2, the control valve 82 has a hollow cylindrical control valve housing 84 consisting of a deep-drawn sheet metal part, which is connected to a diaphragm plate 88 by a crimp connection 86. The control valve housing 84 projects into a hollow cylindrical section 90 of the booster housing 58, which extends coaxially with the control valve housing 84. Between an outer surface 92 of the control valve housing 84 and an inner surface 94 of the hollow cylindrical section 90 of the booster housing 58, an annular gap 96 extends, which is pressed against it by a first, elastically deformable rolling bellows 98

Ambient atmosphere is sealed. A first end 100 of the first bellows 98 is attached to an outer surface 102 of the hollow cylindrical portion 90 of the booster housing 58, while a second end 104 of the first bellows 98 is fixed in a groove 106 formed in the outer surface 92 of the control valve housing 84.

In the control valve housing 84, a first and a second valve member 108, 110 are arranged to be axially displaceable relative to one another, the first valve member 108 being driven by the force of a return spring 112, the opposite ends of which rest on the first and the second valve member 108, 110, respectively a direction opposite to the actuation direction is biased, while the second valve member 110 is biased in the actuation direction by the force of the return spring 112. The first valve member 108 comprises an axially extending, hollow cylindrical first section 114, a second section 116 projecting radially outward from the first section 114 and a third section 118 extending in the axial direction from the second section 116. The second valve member 110 also comprises an axially extending, hollow cylindrical first section 120, a second section 122 projecting radially outward from the first section 120 and a third section 124 extending in the axial direction from the second section 122. The hollow cylindrical first section 120 of the second valve member 110 is guided on the actuating piston 28 so as to be axially displaceable the hollow cylindrical first section 114 of the first valve member 108 is axially displaceably guided in the hollow cylindrical first section 120 of the second valve member 110.

A second, elastically deformable rolling bellows 126 extends over outer surfaces 128, 130 of the third sections 118, 124 of the first and second valve members 108, 110 and encompasses an end face 132 of the third section 118 of the first valve member 108 facing the force input side of the brake booster. One of the force input side End 134 of the second bellows 126 facing the brake booster is received in an annular groove 136 formed on the input member 32. To establish or interrupt a connection between the ambient atmosphere and the working chamber 80 of the brake booster 10, the end face 132 of the third section 118 of the first valve member 108 encompassed by the second bellows 126 interacts with a first valve seat 138 which is connected to an end wall 140 of the control valve housing 84 is trained. A connection between the vacuum chamber 78 and the working chamber 80 is established or interrupted by the interaction of a sealing bead 142 formed on the second bellows 126 with a second valve seat 144, which is formed on a radially inwardly projecting flange 146 of the diaphragm plate 88. The first and second valve seats 138, 144 each have the same diameter in order to avoid the occurrence of reaction forces resulting from pressure differences.

On the outside of the end wall 140 of the control valve housing 84, a hollow cylindrical air filter element 150, which is axially penetrated by the input member 32, is fastened by means of a first adhesive disc 152. On an outer end face 154 of the

A further adhesive disc 155 is attached to filter element 150 and essentially covers the entire outer end face 154 of filter element 150. In an alternative embodiment, not shown, the further adhesive disc 155 extends only over partial areas of the outer end face 154 of the filter element 150.

The function of the brake booster / master cylinder unit is explained in more detail below. If via the actuator, not shown, of the vehicle brake system a force is applied to the input member 32, the input member 32 transmits this force to the actuating piston 28, whereby it moves against the force of the coil spring 42 relative to the first piston 18 and the sleeve 38 in FIG. 1 to the left. The rod-shaped extension 36 of the actuating piston 28 is immersed in the first pressure chamber 20.

At the same time, the displacement of the actuating piston 26 to the left means that a radially outwardly projecting, spherical flange 156 of the input member 32 cooperates with an end face 157 of the first section 114 of the first valve member 108, so that the first valve member 108 counteracts the force of the spring 112 is axially displaced relative to the second valve member 110 in the actuating direction. As a result, the end face 132 of the third section 118 of the first valve member 108 encompassed by the second bellows 126 loses the sealing contact with the first valve seat 138, so that the connection between the atmospheric pressure and the working chamber 80 is opened. Since the further adhesive disc 155 essentially covers the entire outer end face 154 of the filter element 150, air flows first in the radial and then in the axial direction through the filter element 150 into the control valve housing 84 and from there through an opening 158 formed in the control valve housing 84 into the working chamber 80. If the further adhesive disc 155 only covers partial areas of the outer end face 154 of the filter element 150, the air can flow through the filter element 150 both radially and axially, as a result of which an increased air throughput through the air filter element 150 is achieved. Due to the inflow of air into the working chamber 80, a differential pressure builds up on the movable wall 76, which causes the movable wall 76 to be shifted to the left, so that the control valve housing 84 connected to the movable wall 76 via the diaphragm plate 88 also moves to the left shifts. The force generated by the brake booster 10 is transmitted via a force output surface 160 formed on the diaphragm plate 88 to an opposite end face 162 of a flange 164 formed on the first piston 18 and projecting radially outward, so that the first piston 18 begins to also move to the left and thus to move into the first pressure chamber 20.

By moving the actuating piston 28 to the left, the first valve 62 is moved into its closed position due to its resilient bias, in which it closes the first trailing bore 68. The first and the second stop element 46, 64 initially shift to the left together until the closing ^{path of} the first valve 62 is overcome, whereupon the first stop element 46 releases from the second stop element 64 of the first valve 62. When the fluid connection between the hydraulic fluid container and the first pressure chamber 20 is interrupted, hydraulic pressure builds up in the first pressure chamber 20. Due to the pressure building up in the first pressure chamber 20, the second piston 22 also shifts to the left, as a result of which the second valve 62 'is displaced into its closed position due to its resilient bias. The flange 48 formed on the second piston 22 and the third stop element 64 'initially shift to the left together until the closing path of the second valve 62' is overcome, whereupon the flange 48 of the second piston 22 moves away from the third stop element 64 'of the second valve 62 'releases. If that too

If the fluid connection between the second follow-up bore 68 ′, which is in fluid communication with the hydraulic fluid container, and the second pressure chamber 26 is interrupted, a hydraulic pressure likewise builds up in the second pressure chamber 26.

The hydraulic pressure building up in the course of the displacement of the actuating piston 28 and of the first piston 18 to the left in the first pressure chamber 20 acts both on the hydraulically effective surface of the actuating piston 28 and on the hydraulically active surface of the sleeve 38 Piston 18 acting reaction force via the diaphragm plate 88 and the control valve housing 84 is introduced into the brake booster 10 and is therefore not noticeable on the brake pedal, are the hydraulically effective for feedback of the hydraulic pressure building up in the first pressure chamber 20 to the brake pedal and thus to the vehicle driver Surfaces of the actuating piston 28 and the sleeve 38 are decisive. Several phases can be distinguished with regard to the reaction force felt by the driver when the brake is actuated on the brake pedal. At the beginning of the brake application, the fluid connection between the first pressure chamber 20 and the hydraulic fluid container is still open, so that the reaction force corresponds to the spring force of the coil spring 42 (phase 1).

As soon as the fluid connection between the first pressure chamber 20 and the hydraulic fluid container is interrupted and consequently a hydraulic pressure builds up in the first pressure chamber 20, a hydraulic reaction force is additionally generated, which reacts on the brake pedal via an end face of the rod-shaped extension 36 of the actuating piston 28. As a result, the reaction force felt on the brake pedal is then composed of the hydraulic force acting on the end face of the rod-shaped extension 36 and the spring force of the helical spring 42 together (phase 2). Since the hydraulically effective diameter of the end face of the rod-shaped extension 36 is relatively small, the hydraulic pressure in the first and second pressure chambers 20, 26 can be increased rapidly in this phase of braking.

If the pressure in the first pressure chamber 20 continues to rise during the braking process and exceeds a predetermined value, the sleeve 38 is displaced to the right relative to the first piston 18 and the actuating piston 28 against the force of the spring 42 until the flange 40 of the sleeve 38 comes into contact with a projection 168 formed on the actuating piston 28. This creates a mechanical coupling between the sleeve 38 and the actuating piston 28, so that the sleeve 38 is displaced together with the actuating piston 28 when the actuating piston 28 is moved further to the left. The sum of the hydraulically effective surfaces of the actuating piston 28 and the sleeve 40 is then decisive for the hydraulic portion of the reaction force felt on the brake pedal (phase 3). In this phase of the braking process, the driver receives stronger feedback about the pressure actually prevailing in the first pressure chamber 20.

The ratio in which a vehicle driver feels the increase in hydraulic pressure in the first pressure chamber 20 as an increase in the counterforce to be overcome at the brake pedal is referred to as the transmission ratio. With a large transmission ratio, the actuating piston 28 can move further to the left relative to the control valve housing 84 with the same actuation force than with a smaller transmission ratio. At the same time, a larger transmission ratio leads to a larger opening stroke of the control valve 82 of the brake booster 10 and thus to a stronger response of the brake booster 10.

When the braking process is ended by releasing the brake pedal, the actuating piston 28 is displaced to the right by the force of the spring 42, so that the phases described above are carried out in reverse order. As a result of the backward displacement of the second piston 22 to the right, the flange 48 formed on the second piston 22 again comes into contact with the third stop element 64 'formed on the second valve 62', so that the second valve 62 'establishes the fluid connection between the second pressure chamber 26 and the second trailing bore 68 'releases. The first valve 62 is also opened again when the first The abutment element 46 abuts the second abutment element 64 formed on the first valve 62 due to the backward displacement of the actuating piston 28 to the right.

In the control valve 82 of the brake booster 10, when the actuating piston 28 moves back to the right, the end face 132 of the third section 118 of the first valve member 108, which is surrounded by the second bellows 126, again comes into sealing contact with the first valve seat 138 due to the force of the spring 112, so that the connection between the atmospheric pressure and the working chamber 80 is broken. An end face 170 of the actuating piston 28 then abuts a radially inwardly projecting projection 172, which is formed on the hollow cylindrical first section 120 of the second valve member 110. As a result, the sealing bead 142 is raised against the force of the spring 112 from the second valve seat 144, so that the connection between the vacuum chamber 78 and the working chamber 80 is opened. Since the vacuum chamber 78 is constantly connected to a vacuum source, this leads to a decrease in the differential pressure acting on the movable wall 76, so that the movable wall 76, the first piston 18 and the control valve housing 84 move back into their rest position. When an equilibrium position is reached, the second valve seat 144 again seals against the sealing bead 142.

The backward movement of the actuating piston 28 to the right is limited by the first stop element 46 abutting the shoulder 66 formed on the first section 50 of the master cylinder housing 14. Paragraph 66 defines the rest position of the actuating piston 28 and thus the rest position of the control valve housing 84 of the brake booster 10 upstream of the master cylinder 12 in a so-called “lost travel free” position, which enables the brake booster 10 to be activated almost without loss from its release position.

An alternative embodiment of the control valve 82 is shown in FIG. 3, the function of which corresponds to the function explained in connection with the first embodiment. In contrast to the first embodiment, however, an end of the spring 112 facing away from the force input side of the brake booster 10 is not supported on the second valve member 110 but on a support element 174. The support element 174 has a hollow cylindrical body 176 and a radially outwardly projecting flange 178 and is pressed by the force of the spring 112 against the end face 162 of the flange 164 formed on the first piston 18. The control valve 82 shown in FIG. 3 has the advantage that the force of the spring 112 is no longer overcome when the brake pedal is released and the actuating piston 28 is moved back to the right to establish the connection between the working chamber 80 and the vacuum chamber 78 got to. As a result, the spring 42, which shifts the actuating piston 28 back into its rest position when the brake is released and its spring force due to the interaction of the end face 170 of the actuating piston 28 with the radially inwardly projecting projection formed on the hollow cylindrical first section 120 of the second valve member 110 172 also causes the sealing bead 142 to be raised by the second valve seat 144, so that it is designed to be correspondingly weaker. As a result, the response force of the brake booster / master cylinder unit, which results in the embodiment shown in FIGS. 1 and 2 from the sum of the spring forces of the two springs 42, 112, in the embodiment shown in FIG. 3 by the force the spring 112 can be reduced. The response behavior of the brake system can then be set in the desired manner by a suitable choice of the spring stiffness of the spring 42.

4 shows a further embodiment of the control valve 82, the function of which also corresponds to the function explained in connection with the first embodiment. However, in the embodiment shown in FIG. 4, the end 134 of the second bellows 126 facing the force input side of the brake booster is not fastened to the input member 32 inside the control valve housing 84 as in the embodiments shown in FIGS. 1 to 3. Instead, the end 134 of the second bellows 126 facing the force input side of the brake booster projects out of the control valve housing 84 and has a sealing surface 182 which interacts with a peripheral surface 180 of the input member 32 in order to seal the interior of the control valve housing 84 through which the input member 32 is sealed against the ambient atmosphere , The input member 32 is axially displaceable relative to the second bellows 126. At the end 134 of the bellows 126, a radially outwardly projecting flange 184 is formed, which is fastened to a holding element 186, which is attached to an outer surface of the end wall 140 of the control valve housing 84.

Since the interior of the control valve housing 84 is connected via the opening 158 to the working chamber 80 which is subjected to a negative pressure in the release position of the brake, when the first and second valve seats 138, 144 are closed, the control valve 82 also resides in the interior of the control valve housing. ses 84 a negative pressure. This creates a pressure difference between the atmospheric pressure prevailing outside the control valve 82 and the negative pressure present in the interior of the control valve housing 84 on an annular end face 188 of the second bellows 126 facing the force input side of the brake booster. In the embodiments of the control valve 82 shown in FIGS. 1 to 3, this differential pressure acting in the actuating direction is transmitted to the input member 32, since the second bellows 126 is connected to the input member 32 in a force-transmitting manner. As a result, the restoring force of the spring 42, which prestresses the actuating piston 28 and the input member 32 connected to the actuating piston 28 in the opposite direction of actuation, must be increased by the amount of force exerted by the differential pressure in the actuating direction in order to activate the brake booster 10 automatically from the rest position prevent. In the control valve 82 shown in FIG. 4, there is no force-transmitting connection between the second bellows 126 and the input member 32. Rather, the end face 188 of the second

Roller bellows 126 acting differential pressure force is introduced via the holding element 186 into the control valve housing 84, so that the spring 42 is designed to be weaker by the amount of the differential pressure force and the response force of the brake booster / master cylinder unit determined by the spring force of the spring 42 can be reduced accordingly.

FIG. 5 shows a further alternative embodiment of the control valve 82. In contrast to the exemplary embodiments shown in FIGS. 3 and 4, however, the hollow cylindrical first section 114 of the first valve member 108 is not axially displaceably guided in the hollow cylindrical first section 120 of the second valve member 110 , Instead, the actuating piston 28 is provided with an extension section 28 ′ which extends coaxially to the input member 32 and which projects so far in the direction of the force input side of the brake booster 10 that both the hollow cylindrical first section 120 of the second valve member 110 and the hollow cylindrical first section 114 of the first valve member 108 can be guided on the extension section 28 '.

As already explained, the actuating piston 28 moves in the actuating direction when the input member 32 is actuated, i. H. 5 to the left. The actuating force acting on the actuating piston 28 is determined by means of a

Spring washers 238, which is arranged in a groove 240 formed on the outer circumference of the extension section 28 'of the actuating piston 28 and on one of the Force input side of the brake booster 10 facing the end face 242 of the second section 116 of the first valve member 108 is applied to the first valve member 108. As a result, the first valve member 108 together with the actuating piston 28 is displaced axially relative to the second valve member 110 in the actuating direction against the force of the spring 112. As a result, the end face 132 of the third section 118 of the first valve member 108 encompassed by the second rolling bellows 126 loses the sealing contact with the first valve seat 138 and the connection between the atmospheric pressure and the working chamber 80 of the brake booster 10 is opened.

When the actuating piston 28 is moved back in the opposite actuation direction, i. H. 5 to the right, a projection 244, which is formed on the extension section 28 'of the actuating piston 28 and protrudes radially outward, comes into contact with an end face 246 of the hollow cylindrical first section 120 of the second valve member 110 facing away from the force input side of the brake booster 10 the sealing bead 142 is lifted off the second valve seat 144 and the connection between the vacuum chamber 78 and the working chamber 80 of the brake booster 10 is opened, wherein, as explained in connection with the exemplary embodiment shown in FIG. 3, the actuating piston 28 is displaced when it is moved back it is not necessary to overcome the force exerted by the spring 112.

The embodiment of a control valve 82 shown in FIG. 5 also differs from the exemplary embodiments shown in FIGS. 3 and 4 in that the first valve member 108 is sealed off from the extension section 28 ′ of the actuating piston 28 by means of a sealing ring 248. As a result, the sealing fastening of the second bellows 126 to the input member 32 can be dispensed with and the second bellows 126 can be fixed to the first valve member 108 instead.

In the embodiment shown in FIG. 6 of a vacuum brake booster 10 connected to a master cylinder 12, the hollow cylindrical first sections 114, 120 of the first and second valve members 108, 110 are not on an extension section 28 'as in the embodiment shown in FIG. 5 of the actuating piston 28, but guided on an outer surface of a sleeve 250. The sleeve 250 is fixedly connected with one of the power input side of the Bremskraftver ^¬ stärkers facing end portion 252 of the actuating piston 28 and guided axially displaceably in the first piston 18 together with the actuating piston 28 by means of a radially outwardly extending annular collar 254. On its right-hand side facing the force input side of the brake booster in FIG. 6, the sleeve extends coaxially with the input member 32. The spring ring 238 for transmitting the actuating force acting on the actuating piston 28 to the first valve member 108 is the same as that in FIG. 6 Control valve 82 shown arranged in a groove 240 'formed on the outer circumference of the sleeve 250.

When the sleeve 250 moves together with the actuating piston 28 in the actuating direction, the actuating force acting on the actuating piston 28 is transmitted via the sleeve 250 and the spring ring 238 to the end face 242 of the second section 116 of the first valve member 108 facing the force input side of the brake booster 10 transferred so that the first valve member 108, as explained in connection with the configuration of a control valve 82 shown in FIG. 5, together with the actuating piston 28 against the force of the spring 112 in the actuating direction axially relative to the second valve member 110 and the connection releases between the atmospheric pressure and the working chamber 80 of the brake booster 10.

When the actuating piston 28 is moved back in the opposite actuation direction, i. H. 6 to the right, a protrusion 258 formed on the sleeve 250 and projecting radially outwards comes into contact with the end face 246 of the hollow cylindrical first section 120 of the second valve member 110 facing away from the force input side of the brake booster 10, so that the sealing bead 142 is lifted from the second valve seat 144 and the connection between the vacuum chamber 78 and the working chamber 80 of the brake booster 10 is opened. Also in the control valve 82 shown in FIG. 6, when the actuating piston 28 is moved back, as explained in connection with the control valve 82 shown in FIG. 3, it is not necessary to overcome the force applied by the spring 112.

The first valve member 108 of the control valve shown in FIG. 6 is sealed off from the sleeve 250 by means of a sealing ring 248 '. As a result, as with the control valve shown in FIG. 5, the sealing fastening of the second bellows 126 to the input member 32 can be dispensed with and the second bellows 126 can be fixed to the first valve member 108 instead. The position of the first valve member 108 in its rest position relative to the actuating piston 28 influences the position of the actuating piston 28 in its “lost travel free” position, which is caused by the interaction of the shoulder 66 formed on the main cylinder housing 14 with the axially on the rod-shaped extension 36 of the actuating piston 28 guided stop element 46 is set. Since the rest position of the first valve member 108 is determined by the spring ring 238, which is arranged in the groove 240 'formed on the outer circumference of the sleeve 250, the position of the sleeve 250 and the spring ring 238 connected to it can position the rest of the actuating piston 28 First valve member 108 and thus the "lost travel free" position of the actuating piston 28 can be set, which enables an almost loss-free activation of the brake booster 10 from its rest position.

In order to ensure a secure fit of the sleeve 250 on the end section 252 of the actuating piston 28 facing the force input side of the brake booster, the sleeve 250 must be fixed on the end section 252 of the actuating piston 28 with a relatively large excess. As a result, relatively high forces are required for mounting the sleeve 250 on the end section 252 of the actuating piston 28 and in particular for displacing the sleeve 250 relative to the actuating piston 28 in order to set the “lost travel free” position. For this reason, the actuating piston 28 is moved into its position shown in FIG. 7 before the sleeve 250 is pushed onto its end section 252, in which the forces acting on the actuating piston 28 during assembly of the sleeve 250 can be absorbed by the master cylinder housing 14. It can thereby be avoided that the spring force of the return spring 42 has to be designed to absorb the forces occurring during the assembly of the sleeve 250 on the end section 252 of the actuating piston 28, which leads to an inadmissible increase in the actuating force to be applied by a vehicle driver for actuating the braking system would.

The further embodiment shown in FIG. 8 of a vacuum brake booster 10 connected to a master cylinder 12, like the embodiment shown in FIG. 7, has a sleeve 250 fixed on an end section 252 of the actuating piston 28 for guiding the hollow cylindrical first sections 114, 120 of the first and second valve members 108, 110. In order to ensure a particularly secure fastening of the sleeve 250 on the end section 252 of the actuating piston 28, the sleeve 250 has a step-shaped projection which projects radially inwards Projection 260. In the assembled state of the sleeve 250, an end face of the protrusion 260 formed on the sleeve 250 faces the force input side of the brake booster against an end face of a protrusion 262 formed on the actuating piston 28 and projecting radially outward, facing away from the force input side of the brake booster that a release of the sleeve 250 from the actuating piston 28 is reliably prevented.

In the embodiment of a vacuum brake booster 10 connected to a master cylinder 12 shown in FIG. 9, two bolts 190, 190 ′ are guided parallel to the longitudinal axis L through the booster housing 58, the diaphragm plate 88 and the movable wall 76. First and second openings 192, 192 ', 194, 194' formed in shells 56, 56 'of the amplifier housing 58 and penetrated by the bolts 190, 190' are against the by means of first and second sealing elements 196, 196 ', 198, 198' Sealed ambient atmosphere. The bolts 190, 190 'have a key surface 202, 202' on their end 200, 200 'facing away from the force input side of the brake booster 10 and protruding from the booster housing 58 and on their end facing the force input side of the brake booster 10 and also projecting out of the booster housing 58 204, 204 'a thread 206, 206'. A radially outwardly projecting contact flange 208, 208 'is also formed on the bolts 190, 190' and is supported on the inner surface 210 of the shell 56 'of the amplifier housing 58 when the bolts 190, 190' are in the assembled state. To mount the brake booster 10 in the engine compartment of a motor vehicle, the bolts 190, 190 'can be screwed into receptacles by means of the thread 206, 206', which are provided in a bulkhead, not shown, arranged in the engine compartment of a motor vehicle.

10 shows a further exemplary embodiment of a vacuum brake booster 10 connected to a master cylinder 12. Two bolts 190, 190 'arranged parallel to the longitudinal axis L are through the shell 56' of the booster housing 58 into the interior of the booster housing 58 and through the diaphragm plate 88 and through the movable wall 76 passed through. Openings 192, 192 'formed in the shell 56' of the amplifier housing 58 and penetrated by the bolts 190, 190 'are sealed off from the ambient atmosphere by the sealing elements 196, 196'. The end 204, 204 'of the bolts 190, 190' facing away from the force input side of the brake booster 10 is screwed into receptacles 214, 214 'by means of a thread 212, 212', which in a radially outwardly projecting flange 216 one inside of the amplifier housing 58 arranged section 50 of the master cylinder housing 14 are formed. With this arrangement, the bolts 190, 190 'are capable of absorbing the tensile forces acting on the master brake cylinder 12 during a brake application, which would otherwise have to be absorbed by the shells 56, 56' of the booster housing 58. At their ends 204, 204 'facing the force input side of the brake booster 10 and protruding from the booster housing 58, the bolts 190, 190' have a further thread 206, 206 '. As a result, the brake booster 10 can be attached, for example with the aid of a nut, to a bulkhead, not shown, arranged in the engine compartment of a motor vehicle. Furthermore, a radially outwardly projecting contact flange 208, 208 'is formed on the bolts 190, 190', which in the assembled state of the bolts 190, 190 'is supported on an inner surface 210 of the shell 56' of the booster housing 58 which faces the force input side of the brake booster 10 ,

In the exemplary embodiment shown in FIG. 11 of the brake booster 10 connected to a master cylinder 12, the radially outwardly projecting flange 208 formed on the bolt 190 is not supported on the inner surface 210 of the shell facing the force input side of the brake booster 10 in the assembled state of the bolt 190 56 'of the booster housing 58, but on a bulkhead 218 or a sealing element 196 which is arranged in the engine compartment of a motor vehicle and which seals an opening 192 formed in the booster housing shell 56' and penetrated by the bolt 190 against the ambient atmosphere. The half of the brake booster 10, which is not shown in FIG. 11 and is arranged below the longitudinal axis L, is constructed in the same way as the half of the brake booster 10 which is arranged and arranged above the longitudinal axis L onto the screw 220 formed on the end 204 of the bolt 190. In FIG. 11, the bolt 190 is fastened to the bulkhead 218 in such a way that the booster housing 58 bears against the bulkhead 218 and is supported on it. A recess 222 is formed in the bulkhead 218 for receiving the contact flange 208 formed on the bolt 190.

In the embodiment shown in FIG. 12, the bolt 190 is attached to the bulkhead 218 such that a gap S is present between the booster housing 58 and the bulkhead 218. This results in a free movement of the amplifier housing 58 as a result of the pressure difference acting on the amplifier housing shells 56, 56 'between the negative pressure prevailing inside the housing and allows atmospheric pressure. Radially outwardly projecting sealing lips 227 are preferably arranged on a sealing bead 225 formed on the movable wall 76 and fixed between end sections 223, 223 'of the booster housing shells 56, 56', so that despite the movement of the booster housing shells 56, 56 'described above, a reliable seal of the amplifier housing 58 against the ambient atmosphere is ensured. In particular, if the rest position of the control valve housing 58 in a “lost travel free” position is determined by the interaction of the stop element 46 present on the actuating piston 28 of the master cylinder 12 with the shoulder 66 formed on the first section 50 of the master cylinder housing 14, caulking is possible the amplifier housing shells 56, 56 'are dispensed with. Since with such an arrangement the previously common crossbar attached to the booster housing 58 and thus the very exact positioning of the shells 56, 56 ′ of the brake booster housing 58 that was previously required can be dispensed with, the manufacturing and assembly outlay and thus the costs of the brake booster 10 can be considerable be reduced.

In the further exemplary embodiment shown in FIG. 13 of a vacuum brake booster 10 connected to a master cylinder 12, two bolts 190, 190 'are parallel to the longitudinal axis L through the shells 56, 56' of the booster housing 58, the diaphragm plate 88, the movable wall 76 and the radially outwardly projecting flange 216 of the section 50 of the master cylinder housing 14 arranged inside the booster housing 58 is passed through. The bolts 190, 190 'have a key surface 202, 202' on their end 200, 200 'facing away from the force input side of the brake booster 10 and protruding from the booster housing 58 and on their end facing the force input side of the brake booster 10 and also out of the booster housing 58 protruding end 204, 204 'a thread 206, 206'. By turning the bolts 190, 190 ', the brake booster 10 can be screwed into receptacles which are provided in the bulkhead, not shown, arranged in the engine compartment of a motor vehicle. The radially outwardly projecting flange 216 of the master cylinder housing 14 and the shell 56 of the booster housing 58 are by means of a nut 224, 224 ', which is screwed onto the end 200, 200' of the bolts 190, 190 ', and a non-rotatable with the bolts 190 , 190 'connected adjusting nut 226, 226' clamped together. The adjusting nut 226, 226 'is supported on the flange 216 of the master cylinder housing 14. The bolts 190, 190 'are able to absorb the tensile forces acting on the master brake cylinder 12 during a brake application FIG. 14 shows another exemplary embodiment of a brake booster 10 connected to a master cylinder 12. The half of the brake booster 10, which is not shown in FIG. 14 and is arranged below the longitudinal axis L, is constructed in the same way as the half of the brake booster 10 which is arranged and arranged above the longitudinal axis L. A bolt 190 is sealed by means of the sealing element 198 through the shell 56 of the booster housing 58, the radially outwardly projecting flange 216 of the section 50 of the master cylinder housing 14 arranged inside the booster housing 58 and through a sleeve 228. The sleeve 228 in turn passes through the diaphragm plate 88, the movable wall 76 and the shell 56 'of the amplifier housing 58. The opening 192 formed in the shell 56' of the amplifier housing 58 and penetrated by the sleeve 228 is sealed by means of the sealing element 196 against the ambient atmosphere. At its end 204 facing the force input side of the brake booster 10 and protruding from the booster housing 58, the bolt 190 has a thread 206, so that the brake booster 10 can be screwed into a receptacle by rotating the bolt 190 in the engine compartment, which is not shown in FIG of a motor vehicle arranged bulkhead is provided. At the same time, the bolt 190 is able to absorb the tensile forces acting on the master brake cylinder 12 during a brake application.

An end 230 of the sleeve 228 which faces away from the force input side of the brake booster 10 projects into a recess 232 which is formed in the flange 216 of the main cylinder housing 14. The end 230 of the sleeve is threaded so that the sleeve 228 can be screwed into the recess 232 formed in the flange 216 of the master cylinder housing 14. The external thread of the sleeve 228 is covered with a sealing compound consisting of a plastic material. At its end 234 facing the force input side of the brake booster 10, the sleeve 228 has a radially outwardly projecting flange 236 which bears on the sealing element 196 which seals the opening 192.

Claims

claims

1. Vacuum brake booster (10) with

- An amplifier housing (58), the interior of which is divided by at least one movable wall (76) into a vacuum chamber (78) and a working chamber (80), and

- In the amplifier housing (58) projecting control valve (82) for controlling a pressure difference acting on the movable wall (76), which can be actuated by an input member (32) and a force-transmitting connected to the movable wall (76), axially relative to Booster housing (58) has displaceable control valve housing (84), a gap (96) being present between an outer surface (92) surrounding the control valve housing (84) and the booster housing (58), which gap is opposed by a first, elastically deformable bellows (98) the surrounding atmosphere is sealed.

2. Vacuum brake booster according to claim 1, characterized in that the gap (96) between the outer surface (92) of the substantially hollow cylindrical control valve housing (84) and an opposite inner surface (94) of a section (90) extending coaxially to the control valve housing (84) of the amplifier housing (58) is formed.

3. Vacuum brake booster according to claim 1 or 2, characterized in that a first end (100) of the first bellows (98) on an outer surface (102) of the booster housing (58) and a second end (104) of the first bellows (98) the outer surface (92) of the control valve housing (84) is attached.

4. Vacuum brake booster according to one of claims 1 to 3, characterized in that the control valve housing (84) consists of a deep-drawn sheet metal part.

5. Vacuum brake booster according to one of claims 1 to 4, characterized in that the control valve housing (84) is fastened by a crimp connection (86) to a membrane plate (88) connected to the movable wall (76).

6. Vacuum brake booster according to one of claims 1 to 5, characterized in that a first and a second valve member (108, 110) are arranged in the axial direction relative to each other in the control valve housing (84), the first valve member (108) resilient in the opposite direction of actuation is biased.

7. Vacuum brake booster according to claim 6, characterized in that the first and the second valve member (108, 110) each have a hollow cylindrical first section (114, 120), a radially outwardly projecting from the first section and second section (116, 122) have a third section (118, 124) extending in the axial direction from the second section (116, 122), at least part of the hollow cylindrical first section (114) of the first valve member (108) being axially displaceable in the hollow cylindrical first section (120 ) of the second valve member (110) is guided.

8. Vacuum brake booster according to claim 7, characterized in that a second, elastically deformable bellows (126) over outer surfaces (128, 130) of the third sections (118, 124) of the first and second valve members (108, 110) and one the end face (132) of the third section (124) of the first valve member (108) facing the force input side of the brake booster (10).

9. Vacuum brake booster according to claim 8, characterized in that the end face (132) of the third section (118) of the first valve member (108) encompassed by the second bellows (126) for establishing or interrupting a connection between the ambient atmosphere and the working chamber ( 78) cooperates with a first valve seat (138) formed on an end wall (140) of the control valve housing (84).

10. Vacuum brake booster according to claim 9, characterized in that a on the input member (32) formed, radially outwardly projecting flange (156) for opening the first valve seat (138) with the hollow cylindrical first section (114) of the first valve member (108) interacts.

11. Vacuum brake booster according to claim 5 and one of claims 8, 9 or 10, characterized in that a sealing bead (142) formed on the second bellows (126) for establishing or interrupting a connection between the vacuum chamber (78) and the working chamber ( 80) cooperates with a second valve seat (144) which is formed on a radially inwardly projecting flange (146) of the diaphragm plate (88).

12. Vacuum brake booster according to claims 10 and 11, characterized in that the first and the second valve seat (138, 144) each have the same diameter.

13. Vacuum brake booster according to one of claims 6 to 12, characterized in that opposite ends of a return spring (112), which biases the first valve member (108) in the opposite actuation direction, are supported on the first valve member (108) and the second valve member (110) ,

14. Vacuum brake booster according to one of claims 6 to 12, characterized in that opposite ends of a return spring (112), which biases the first valve member (108) in the opposite actuation direction, on the first valve member (108) and on one in the control valve housing (84) support the arranged support element (174).

15. Vacuum brake booster according to one of claims 8 to 14, characterized in that one of the force input side of the brake booster (10) facing end (134) of the second bellows (126) is attached to the input member (32).

16. Vacuum brake booster according to one of claims 8 to 14, characterized in that the second bellows (126) has a sealing surface (182) which cooperates with a peripheral surface (180) of the input member (32), and that one of the force input side of the brake booster (10) facing end (134) of the second bellows (126) is attached to a holding element (186) connected to the control valve housing (84).

17. Brake booster / master cylinder unit (10, 12), with

- a vacuum brake booster (10) according to one of claims 1 to 16, and

- A master cylinder (12) having a master cylinder housing (14) which delimits a bore (16) in which a first piston (18) is sealingly and axially displaceably guided to form a first pressure chamber (20), wherein the bore (16) in the direction of its free end, essentially hollow cylindrical extension (60) of the master cylinder housing (14) axially guides the first piston (18).

18. Brake booster / master cylinder unit according to claim 17, characterized in that the first piston (18) is hollow-cylindrical and, in the normal case, can only be actuated indirectly by a force output member (88) of the brake booster (10) connected upstream of the master brake cylinder (12), and in that For direct actuation of the first piston (18), an actuating piston (28) is guided axially displaceably in the first piston (18).

19. Brake booster / master cylinder unit according to claim 11 and one of claims 17 or 18, characterized in that the formed on the diaphragm plate (88) of the brake booster (10), radially inwardly projecting flange (146) with a radially outwardly projecting flange (164) of the first piston (18) is connected.

20. Brake booster / master cylinder unit according to claim 7 and one of claims 18 or 19, characterized in that the hollow cylindrical first section (120) of the second valve member (110) is axially displaceably guided on the actuating piston (28).

21. Brake booster / master cylinder unit according to claim 7 and one of claims 18, 19 or 20, characterized in that one of the force input side of the brake booster facing end face (170) of the actuating piston (28) for opening the second valve seat (144) with one cooperates with the hollow cylindrical first section (114) of the second valve member (110) and protrudes radially inwards (172).

22. Brake booster / master cylinder unit according to claim 7 and one of claims 18 or 19, characterized in that the hollow cylindrical first section (120) of the second The valve member (110) and the hollow cylindrical first section (114) of the first valve member (108) are axially displaceable on an extension section (28 ') of the actuating piston (28) extending in the direction of the force input side of the brake booster (10).

23. Brake booster / master cylinder unit according to claim 7 and one of claims 18 or 19, characterized in that the hollow cylindrical first section (120) of the second valve member (110) and the hollow cylindrical first section (114) of the first valve member (108 ) are axially displaceable on an outer surface of a sleeve (250) fixedly connected to the actuating piston (28).

24. Brake booster / master cylinder unit according to claim 22 or 23, characterized in that an actuating element (238) in a in the extension portion (28 ') of the actuating piston (28) or in the sleeve fixedly connected to the actuating piston (28) (250) formed groove (240; 240 ') is arranged, for opening the first valve seat (138) cooperates with an end face (242) of the second section (116) of the first valve member (108) facing the force input side of the brake booster (10).

25. Brake booster / master cylinder unit according to one of claims 22 to 24, characterized in that a radially outwardly projecting projection (244) is formed on the actuating piston (28) or on the sleeve (250) fixedly connected to the actuating piston (28) ; 258) for opening the second valve seat (144) cooperates with an end face (246) of the hollow cylindrical first section (120) of the second valve member (110) facing away from the force input side of the brake booster (10).

26. Brake booster / master cylinder unit according to one of claims 23 to 25, characterized in that the sleeve (250) has a radially inwardly projecting projection (260), wherein one of the force input side of the brake booster facing the face of the sleeve (250) trained projection (260) in the assembled state of the sleeve (250) on one of the force input side of the

End face facing away from the brake booster of a radially outwardly projecting projection (262) formed on the actuating piston (28).

27. Brake booster / master cylinder unit according to one of claims 18 to 26, characterized in that the rest position of the actuating piston (28) is defined by a shoulder (66) formed in the longitudinal bore (16), which in the rest position of the actuating piston (28 ) interacts with a stop element (46) provided on the actuating piston (28).

28. Brake booster / master cylinder unit according to claim 27, characterized in that the shoulder (66) is formed on the master cylinder housing (14).