DE4404334A1 - Brake booster for vehicle ABS braking system - Google Patents

Abstract

A vehicle braking system has a brake booster combined with the master cylinder. The booster housing is divided into a vacuum chamber and a working chamber by a moving wall (66) carrying a control valve for the pressure difference. The moving wall is formed by a diaphragm with a flexible outer rim (71). The diaphragm is sealed to the valve housing (73) by a flexible inner rim (98). The moving wall is located on a sleeve that can slide on the control valve housing. The sleeve has a radial collar (78) that lies on a guide ring (91) with a bayonet connection to the valve housing. Between the collar and the guide ring is an elastic ring (88).

Description

The invention relates to an actuating unit for a anti-lock motor vehicle brake system consisting from a pneumatic brake booster preferably a vacuum brake booster as well as a master brake cylinder connected downstream, with an amplifier housing that is movable by a Wall into a vacuum chamber as well as a work chamber is divided, as well as one, one on the movable Pneumatic pressure difference acting on the wall Control valve that in one with the movable wall in power-transmitting connection standing control housing is arranged, the movable wall by a Membrane plate and an adjoining one, in the radial outer edge area having a roll fold Membrane is formed opposite the control housing sealed and separated from the brake pressure control mode Control housing by one inside the Pneumatic amplifier housing Pressure equalization against the direction of actuation is movable.

Such an actuation unit is, for example from the earlier application of the applicant P 43 01 336 known. Is less advantageous with the previously known Actuator especially the type of seal between the control housing and one the movable  Wall-bearing, movable separately from the control housing Force transmission sleeve to be viewed by means of a a circumferential groove formed in the control housing arranged sealing ring takes place. The use of the mentioned sealing ring is, however, with considerable Manufacturing and assembly costs connected. The Transfer of a portion of the moving wall of the vacuum brake booster applied Reinforcing force on the control housing takes place in the the area of the brake cylinder facing away from the Control housing via a on the power transmission sleeve molded radial collar from which the timing case is taken along when actuated.

It is therefore an object of the present invention to Actuating unit for anti-lock Motor vehicle brake systems of the aforementioned Specify genus in which the seal between the Control box and moving wall using of inexpensive components is feasible and enables compensation of larger tolerances.

This object is achieved in that the seal between the movable wall and the Control housing by means of a radially inner Edge area of the membrane formed second roll fold he follows.

In an advantageous development of the invention finds the power transmission from the movable wall  on the control housing in the master brake cylinder facing area of the control housing instead. By these measures will increase the stability of the Control unit of the vacuum brake booster reached.

A particularly precise guidance of the one on the Control housing slidably guided, a radial Collar with power transmission sleeve arranged, movable wall is another Design of the subject of the invention thereby achieved that the collar on one with the timing case positively connected centering ring rests.

Effective noise reduction, especially at Pressure modulation, is after another Invention feature achieved in that between the Collar and the centering ring an elastic ring is arranged.

In a particularly easy to install version of the The subject of the invention is between the centering ring and the control housing a bayonet connection intended.

Good guidance or a slight deflection of one one of the sealing seats of the control valve, preferably actuated by an electromagnet Sleeve in the control housing is at another advantageous embodiment of the subject of the invention thereby achieved that the control housing in Movement range of the sleeve has guide ribs.  

Another advantageous embodiment of the invention provides that the sleeve is formed in two parts and from a first sleeve part carrying the sealing seat as well as one at the armature of the electromagnet supporting second sleeve part, which are telescoped so that one Power transmission from the second sleeve part to the first Sleeve part takes place. Through these measures, a considerable ease of assembly achieved.

For vacuum brake booster, its control housing consist of plastic and have vacuum channels, which is a connection between the vacuum chamber and the Allow work chamber, it is special advantageous if the vacuum channels through axially extending grooves are formed, which are opposite to the Working chamber through the radially inner area the membrane are sealed.

To pinch the movable wall in particular to prevent a pressure drop in a normal case, the membrane plate has a preferably conical Recess on, particularly at a relative Backward movement of the movable wall against the Control housing receives the second roller fold.

Another significant simplification of assembly, especially in embodiments of the invention Actuator unit, one with the movable wall of the brake booster in power transmission  Have connected modulator pistons and at which the power transmission between the movable Wall and the modulator piston by means of one with the Power transmission sleeve in operative connection Power transmission plate takes place at a another embodiment of the invention achieved that the power transmission plate with the Power transmission sleeve by means of a snap connection connected is. This measure will make the use of different thickness power transmission plates for Tolerance narrowed.

To realize different Facilitating gain factors looks different feature essential to the invention, in particular in Vacuum brake boosters, their control valve by means of one connected to the input member Actuator is actuated, the one Transfer of the actuating force to a share the output force of the vacuum brake booster transmitting, elastic reaction disk enables before that between the actuator and the Reaction disk arranged a translation disk is.

Further advantageous features of the invention are especially important for executions where the modulator piston has an (outer) part of the delimiting the first pressure chamber of the master brake cylinder, at least two-part first (primary) Piston forms, the other part (inner piston) with  one the actuating force of the brake booster transmitting input member cooperates. So at an advantageous development of the invention effective centering in power transmission between Control housing and inner piston achieved in that the the end of the inner piston facing the control housing is spherical segment-shaped and with a dome-like recess having pressure plate interacts, which rests on the reaction disc.

Another advantageous embodiment of the invention is characterized in that in the master cylinder housing a hydraulic chamber is provided, the Connection to the modulator room via in one Extension of the inner piston formed bores he follows. This measure will be significant Manufacturing advantages achieved, in particular the Connection of a connection of the hydraulic chamber with the modulator room blocking or releasing Allows solenoid valve in grid size.

An increase in functional reliability in particular a failure of the first or primary pressure chamber achieved according to a further feature of the invention, that the hydraulic chamber through a partition is limited, in the axial extension Intermediate piston is guided, both with the Inner piston as well as with the second (secondary) piston can be brought into engagement.

A shortening of the axial length is particularly for master brake cylinders where the connection  between the modulator room and the first (primary) Pressure chamber through a through the modulator piston actuable central valve takes place, thereby achieved that the central valve is coaxial with the first (primary) Piston is formed and one on the inner piston slidably guided closing body and a Has sealing seat, which by a in one Modulating piston guide sleeve immovable arranged ring is formed.

To guide the first or primary piston finally see the present invention before that the guide sleeve can be taken away from the inner piston is.

Further features and advantages of the invention are based the following description of an embodiment from the attached drawing. In the Drawing shows:

Fig. 1 is a schematic representation of an anti-lock automotive vehicle brake system having an operating unit according to the invention,

Fig. 2 is a supply unit used in the actuation unit according to the invention shown in FIG. 1 in an axial sectional view and

Fig. 3 a vacuum brake booster upstream of the master cylinder of Fig. 2 according to the invention in the release position, partially broken away.

In the figures of the drawing, one another is ent speaking components with the same reference numerals designated.

Fig. 1 shows an anti-lock motor vehicle brake system with a vacuum brake booster 1 , which is connected via an input member 4 in a known manner with a brake pedal 3 . On the one input member 4 facing away from the vacuum brake booster 1 , a master cylinder 2 is seen before, the pressure chambers 6 , 8 with a pressure medium reservoir 5 are in communication.

A first hydraulic line 11 connects the first, by a first master cylinder piston (primary piston) 9 limited (primary) pressure chamber 6 with the wheel brake cylinders of only schematically shown Darge, possibly assigned to the rear axle two wheel brakes 22 , 23 via two as 2/2 -Way valves formed wheel valves 14 , 24 , which are usually housed in a valve block.

To the second (secondary) piston 10 limited by a second master cylinder (secondary) pressure chamber 8 , the wheel brake cylinders of the only schematically shown two wheel brakes 20 , 21 are connected by means of a second hydraulic line 13 , to which two further wheel valves 47 , 48 are connected upstream and which are assigned to the front axle of the vehicle, for example.

The front and rear wheel brakes 20 , 21 , 22 and 23 are each assigned a sensor 25 , 26 , 27 and 28 , which are connected to central control electronics 33 via corresponding signal lines 29 , 30 , 31 and 32 .

The control electronics 33 is connected via control lines 34 , 35 , 36 and 37 to the wheel valves 47 , 48 , 14 , 24 , in order to actuate them as a function of the sensor signals.

The main cylinder-side working or vacuum chamber of the vacuum brake booster 1 is continuously connected to a vacuum source 12 via a check valve 41 .

As can be seen in particular in FIG. 2, the first (primary) piston 9 delimiting the first (primary) pressure chamber 6 is of three parts and consists of an inner part or piston 15 of smaller diameter, which is connected to the input member 4 of the brake booster 1 ( Fig. 1) is in force-transmitting connection, an outer part or pistons 16 of larger diameter which forms a co-operates with a movable wall of the vacuum brake booster 1 modulator piston, and a fixed to the inner piston 15 guide sleeve 17 a along with the Modulatokolben 16 annular modulator space 7 , which forms part of the first pressure space 6 in the normal braking mode and can be connected to the wheel brakes 22 , 23 in the braking pressure control mode (see FIG. 1).

A spring plate 45 axially bears against the guide sleeve 17 in its fastening area on the inner piston 15 , on which a piston return spring 18, which prestresses the primary piston 9 against the direction of actuation, is axially supported. A sealing of the primary piston 9 is provided by two sealing sleeves 38 and 39, which are arranged one behind the other in the master cylinder housing 19 so as to be immovable.

As already mentioned, the modulator chamber is about 7 in the guide sleeve 17 and the spring plate 45 formed passages 51 and 52 with the first pressure chamber 6 in connection. The connection is established through a preferably coaxially arranged in the guide sleeve 17 to the inner piston 15 central valve 54 which is operable by the modulator piston sixteenth For this purpose, a plurality of rod-shaped actuating elements 57 are supported on the end face of the modulator piston 16 , which extend through a ring 56 forming a sealing seat 60 of the central valve 54 and having a plurality of axial bores, and interact with an annular closing body 55 preloaded by a valve spring 65 , which thereby acts is held at a distance from the sealing seat 60 so that the connection remains open. The sealing collar 39 , which seals the primary piston 6 to the outside, is arranged in an annular recess of a closure part 40 guiding the guide sleeve 17 , which is secured in the master cylinder housing 19, for example by means of a snap ring 49 .

As can further be seen from FIG. 2, the first pressure chamber 6 is delimited by a partition 42 arranged immovably in the master cylinder housing 19 , on the axial extension 53 of which the second (secondary) piston 10 delimiting the second (secondary) pressure chamber 8 axially supports. The second (secondary) piston 10 has a cylindrical recess 46 which receives the axial extension 53 . The partition 42 delimits in the master cylinder housing 19, on the other hand, a hydraulic chamber 43 which is connected to the modulator chamber 7 . For this purpose, the inner piston 15 has an axial extension 44 which extends into the partition wall 42 and is sealed off from the partition wall 42 by means of a sealing sleeve 50 and is provided with a bore 58 which, on the one hand, with the chamber 43 and, on the other hand, with a second, vertically to the bore 59 formed in the inner piston 15 , which opens into the modulator chamber 7 .

In order to enable transmission of the actuating force to the second (secondary) piston 10 in the event of a failure of the first (primary) pressure chamber 6, an intermediate piston 61 guided in the axial extension 53 of the partition 42 is provided, which is preloaded on the second (secondary) -) Piston 10 supporting compression spring 62 rests against a step formed within the partition 42 and can be brought into a force-transmitting connection with the front end of the inner piston 15 . The second (secondary) piston 10 interacts with a further sealing collar 63 which is arranged standing in the master cylinder housing 19 and is secured against axial displacement by means of a spacer sleeve 64 supported on the partition wall 42 .

The structure of the vacuum brake booster 1 of the actuating unit according to the invention shown in the drawing is shown in FIG. 3. The amplifier housing 111 is divided by an axially movable wall 66 into a vacuum chamber 67 and a working chamber 68 . The axially movable wall 66 consists of a metallic diaphragm plate 69 and an adjoining flexible diaphragm 70 , which has a roller fold 71 between the outer periphery of the diaphragm plate 69 and the booster housing 111 and is clamped on the circumference of the booster housing 111 for sealing. In order to detect movements of the movable wall 66 which occur during the actuation, a displacement sensor 109 is provided which is arranged on the booster housing 65 on the master cylinder side and whose actuating member 110 bears axially against the diaphragm plate 69 .

A control valve 72, which can be actuated by the input member or an actuating rod 4, is accommodated in a control housing 73, which is sealed in the booster housing 111 in a sliding sealing ring 74 , and consists of a first or vacuum sealing seat 75 formed on the control housing 73 , one on a cylindrical cylinder biased by a spring 77 sleeve 80 formed second and atmospheric sealing seat 76 and a cooperating with both sealing seats 75, 76, valve body 79 which is pressed by means of a bearing against a retainer ring 83 valve spring 84 against the sealing seats 75, 76th The sleeve 80 is preferably formed in two parts and consists of a first sleeve part 81 which carries the atmospheric sealing seat 76 and a second sleeve part 82 which are telescopically pushed into one another in such a way that a power transmission from the second sleeve part 82 to the first sleeve part 81 can take place. In the range of movement of the sleeve 80 , the control housing 73 has ribs, not shown, which serve to guide the sleeve 80 . The front sleeve member 81 abuts against a part connected to the actuating rod 4 actuating element 90, which is biased counter to actuating direction by means of a second compression spring 89, the force of which provides a bias of the atmospheric sealing seat 76 against the valve body 79th A return spring 107 , which is supported on the vacuum-side end wall of the booster housing 111 , holds the movable wall 66 in the starting position shown. The movable wall 66 is arranged separately from the control housing 73 on a power transmission sleeve 86 which is axially displaceably guided on the control housing 73 and which, by means of a radial collar 78 with the interposition of an elastic ring 88, enables the amplification force to be transmitted to the control housing 73 . The power transmission, which preferably takes place in the area of the control housing 73 facing the master brake cylinder 2 , takes place by means of a centering ring 91 guiding the front end of the actuating element 90 , which is connected to the control housing 73 in a form-fitting manner, preferably by means of a bayonet connection. In its end face facing the master brake cylinder 2 , the centering ring 91 has a cylindrical recess 92 which receives a rubber-elastic reaction disk 93 which transmits a portion of the output force of the vacuum brake booster 1 and a pressure plate 95 which is guided in a guide ring 94 and on which the inner piston 15 of the master brake cylinder connected 2 supports. A transmission of a significantly greater proportion of the boost force to the outer or modulator piston 16 is effected by means of an axially applied to the force transmitting sleeve 86 force-transmitting plate 87 which is positively connected with it, for example by means of a snap connection. The power transmission plate 87 has in its center a bore 97 through which the inner part 15 of the primary piston 9 extends.

The radially inner edge region of the membrane 70 designed according to the invention ensures an effective, smooth sealing of the movable wall 66 with respect to the control housing 73 . The aforementioned edge region is formed as a spanned on the control housing 73 sealing bead 98 which is received in a recess provided in the control housing 73 annular groove 96th The subsequent therein, preferably conically shaped surface of the diaphragm 70 forms a second rolling fold 99 which rolls in particular at a relative backward movement of the movable wall 66 on the control housing 73rd An unimpeded rolling movement of the second roller fold 99 is made possible by a conical recess 100 in the area of the diaphragm plate 69 encompassing the control housing 73 .

Of FIG. 3 can be seen finally that the working chamber 68 is connectable to the vacuum chamber 67 via laterally extending channels in the control housing 73 85th In order to be able to connect the working chamber 68 to the atmosphere when the control valve 72 is actuated, an approximately radially extending channel 101 is finally formed in the control housing 73 . The return movement of the input member 4 at the end of a braking process is limited by a cross member 102 which, in the release position of the vacuum brake booster 1 shown in the drawing, bears against the mechanical seal 74 forming a stop.

In order to realize a low maintenance required during a control operation, pressure hold phase in the actuation of the actuating unit according to the invention, in an opening into the vacuum chamber 67 the cylindrical recess 103 of the control housing 73 is arranged a solenoid 104, whose armature is in force-transmitting connection with the sleeve 80 105th The electromagnet 104 , which is preferably arranged coaxially to the input member or the actuating element 90 , is held in the recess 103 by means of the aforementioned centering ring 91 with the interposition of an elastic sealing ring 106 .

In an anti-lock control case, two pressure phases or actuation states of the control valve 72 must be realized. It is assumed that an actuating force F _{E is} introduced at the input member 4 , which results in a displacement of the input member 4 or an opening of the atmospheric sealing seat 76 (with the vacuum sealing seat 75 closed). By the action of a resultant of the pressure prevailing in the brake master cylinder 2 is press-reaction force is contact between a fitted onto the front end of the actuating element 90 transforming disk 108 and the reaction disk 93, wherein the transmission disc 108 is partially immersed in the reaction disc 93 and biases it. If a tendency to lock is now recognized in one of the motor vehicle wheels, at which the pressure introduced in the modulator chamber 7 is to be kept constant (pressure holding phase), the electromagnet 104 is energized with a first current level, which displaces its armature 105 or the sleeve 80 or sleeve 80 lying thereon . until contact of the atmospheric sealing seat 76 has on the valve body 79 to the sequence 82, so that both of the control valve sealing seats 75, 76 are closed. The force applied by the electromagnet 104 only has to overcome the force of the spring 77 which prestresses the sleeve 80 and the friction of the sealing point between the actuating element 90 and the sleeve 80 or 81 .

If the central control electronics 33 detects in a blocking control case that a pressure reduction phase in the modulator chamber 7 is required, then a pneumatic pressure equalization within the vacuum brake booster 1 must be initiated. For this purpose, the electromagnet 104 is loaded with a second current level, so that the force of the valve body 79 against the vacuum seal seat 75 pressing valve spring 84 is overcome and the vacuum seal seat 75 is opened and a quick evacuation of the working chamber 68 can take place Movable wall 66 of the brake booster 1 without power and can be retracted counter to the direction of actuation, while the control housing 73 remains, so that the voltage in the modulator chamber 7 is released.

During normal braking, the pressure build-up and reduction takes place as in a known actuator unit consisting of a master brake cylinder and a vacuum brake booster connected upstream of it. The inner part 15 of the primary piston 9 moves in synchronism with the modulator or outer piston 16 when the vacuum brake booster 1 is actuated, so that there is no change in the relative position of the two parts 15 , 16 with respect to one another and the central valve 54 remains open. The pressure build-up in the first pressure chamber 6 , 7 of the master brake cylinder 2 accordingly takes place through the action of the modulator piston 16 together with the inner piston 15 .

A hydraulic pressure medium connection, not shown, enables pressure equalization between the two pressure spaces 6 and 8 of the master brake cylinder 2 .

If, during a braking operation, one of the sensors 25 to 28 detects that one of the wheels is blocking, the central control electronics 33 generate switchover signals which result in the vacuum brake booster 1 being reversed, the movable wall 66 of which becomes powerless and the modulator piston 16 is pushed back . Through the return movement of the modulator piston 16, which allows a reduction of the pressure prevailing in the wheel brakes 20, 21, 22, 23 pressure, the closing body is relieved 55 of the central valve 54 so that it closes the sealing seat and the modulator chamber 7 is isolated from the primary pressure chamber 6 . The primary pressure chamber 6 is now blocked and the inner part 15 of the primary piston 9 and the input member 4 with the coupled brake pedal 3 remain, so that the driver's foot force is supported on the volume locked in the first pressure chamber 6 and no further pressure increase in the wheel brakes by Driver is possible. The pressure supplied to the wheel brakes 20 , 21 , 22 , 23 can be reduced via the above-mentioned pressure medium connection between the pressure chambers 6, 8 . Since the modulator chamber 7 is permanently connected to the hydraulic chamber 43 , the pressure prevailing in the system can be changed by changing the position of the modulator piston 16 . The normal case is ended by bringing the modulator piston 16 back into its original position and opening the central valve 54 .

It is very clear from the above description that the behavior of the central valve 54 separating the modulator chamber 7 from the primary pressure chamber 6 is determined only by the relative movement of the modulator piston 16 with respect to the inner part 15 of the primary piston 9 . In order to increase the functional reliability of the brake system according to the invention or to secure the brake function in the event of a vacuum failure, a second hydraulic pressure medium connection is conceivable between the first (primary) pressure chamber 6 and the hydraulic chamber 43 , which can be shut off by means of an electromagnetically actuated, preferably normally open, first valve would. In the normal braking mode, this second pressure medium connection would remain open, although it would normally be closed during the entire regulation.

In order to ensure an effective increase in brake pressure above the control point of the vacuum brake booster I, an electromagnetically actuated, preferably normally closed second valve can be inserted in the first hydraulic pressure medium connection between the modulator chamber 7 and the hydraulic chamber 43 , which remains closed in the normal braking mode and in a normal case is opened to release the pressure medium connection mentioned.

It is self-ver within the scope of the present invention of course, the functions of the previous he mentioned valves by a single electromagnetic realizable 3/2-way valve.

Reference list

1 vacuum brake booster
2 master brake cylinders
3 brake pedal
4 input link
5 pressure medium reservoir
6 pressure room
7 modulator room
8 pressure chamber
9 pistons
10 pistons
11 line
12 vacuum source
13 line
14 wheel valve
15 inner pistons
16 outer pistons, modulator pistons
17 intermediate pistons
18 piston return spring
19 master cylinder housing
20 wheel brake
21 wheel brake
22 wheel brake
23 wheel brake
24 wheel valve
25 sensor
26 sensor
27 sensor
28 sensor
29 signal line
30 signal line
31 signal line
32 signal line
33 Control electronics
34 control line
35 control line
36 control line
37 control line
38 sealing sleeve
39 sealing sleeve
40 closure part
41 check valve
42 partition
43 chamber
44 extension
45 spring plates
46 recess
47 wheel valve
48 wheel valve
49 snap ring
50 sealing sleeve
51 passage
52 passage
53 continuation
54 central valve
55 closing body
56 ring
57 actuator
58 hole
59 hole
60 sealing seat
61 intermediate piston
62 compression spring
63 sealing sleeve
64 spacer sleeve
65 valve spring
66 wall
67 vacuum chamber
68 Chamber of Labor
69 membrane plates
70 membrane
71 roll fold
72 control valve
73 control housing
74 mechanical seal
75 sealing seat
76 sealing seat
77 spring
78 collar
79 valve body
80 sleeve
81 sleeve part
82 sleeve part
83 retaining ring
84 valve spring
85 vacuum channel
86 transmission sleeve
87 Power transmission plate
88 ring
89 compression spring
90 actuator
91 centering ring
92 recess
93 reaction disc
94 guide ring
95 printing plate
96 ring groove
97 hole
98 sealing bead
99 roll fold
100 recess
101 channel
102 cross member
103 recess
104 electromagnet
105 anchors
106 sealing ring
107 return spring
108 transmission disc
109 displacement sensor
110 actuator
111 amplifier housing

Claims (16)

1.Actuating unit for an anti-lock motor vehicle brake system, consisting of a pneumatic brake booster, preferably a vacuum brake booster, and a master brake cylinder connected downstream, with an booster housing, which is divided by a movable wall into a vacuum chamber and a working chamber, and one acting on the movable wall Pneumatic pressure difference controlling control valve, which is arranged in a control housing with the movable wall in force-transmitting connection, the movable wall is formed by a membrane plate and an adjacent, in the radially outer edge area having a roller fold ', sealed to the control housing and in Brake pressure control mode can be moved separately from the control housing against the actuation direction by pneumatic pressure equalization introduced within the booster housing , so that ch characterized in that the sealing between the movable wall ( 66 ) and the control housing ( 73 ) takes place by means of a second roller fold ( 98 ) formed in the radially inner edge region of the membrane ( 70 ). 2. Actuating unit according to claim 1, characterized in that the power transmission from the movable wall ( 66 ) to the control housing ( 73 ) takes place in the area of the control housing ( 73 ) facing the master cylinder ( 2 ). 3. Actuator according to claim 2, wherein the movable wall is arranged on a displaceably guided on the control housing power transmission sleeve, which is provided with a radial collar, characterized in that the collar ( 78 ) on a with the control housing ( 73 ) positively connected centering ring ( 91 ) is present. 4. Actuating unit according to claim 3, characterized in that an elastic ring ( 88 ) is provided between the collar ( 78 ) and the centering ring ( 91 ). 5. Actuating unit according to claim 3, characterized in that a bayonet connection is provided between the centering ring ( 91 ) and the control housing ( 73 ). 6. Actuating unit according to one of the preceding claims, wherein the control valve has two sealing seats and one of the sealing seats is formed on a sleeve displaceable by an electromagnet, characterized in that the control housing ( 73 ) in the range of motion of the sleeve ( 80 ) or ( 81 , 82 ) has guide ribs. 7. Actuating unit according to claim 6, characterized in that the sleeve ( 80 ) is formed in two parts and from a sealing seat ( 76 ) carrying the first sleeve part ( 81 ) and one on the armature ( 105 ) of the electromagnet ( 104 ) supporting second sleeve part ( 82 ), which are telescopically pushed into one another in such a way that a power transmission from the second sleeve part ( 82 ) to the first sleeve part ( 81 ) takes place. 8. Actuating unit according to one of the preceding claims, wherein the vacuum chamber can be connected to the working chamber via vacuum channels formed in the control housing, characterized in that the vacuum channels ( 85 ) are formed by axially extending grooves which are opposite to the working chamber ( 68 ) by the radial inner area of the membrane ( 70 ) are sealed. 9. Actuating unit according to claim 1, characterized in that the diaphragm plate ( 69 ) has a preferably conical recess ( 100 ) which receives the second roller fold ( 99 ) in particular with a relative backward movement of the movable wall ( 66 ) relative to the control housing ( 73 ) . 10. Actuating unit according to one of the preceding claims, wherein two pressure spaces delimited by at least two pistons and a modulator space are formed in the master cylinder, which forms part of the first pressure space in normal braking mode, can be connected to the wheel brakes of the motor vehicle separately from the first pressure space in braking pressure control mode and by a modulator piston, which is connected to the movable wall of the brake booster in a force-transmitting connection, is bounded, which forms an (outer) part of the first (primary) piston, which at least in two parts defines the first pressure chamber, the other part (inner piston) of which the actuating force of the Brake power amplifier transmitting input member cooperates and the power transmission between the movable wall and the modulator piston takes place by means of a power transmission plate in operative connection with the power transmission sleeve, characterized in that the Power transmission plate ( 87 ) is connected to the power transmission sleeve ( 86 ) by means of a snap-in connection. 11. Actuating unit according to one of the preceding claims, wherein the control valve can be actuated by means of an actuating element connected to the input member, which enables a transmission of the actuating force to an elastic reaction disk transmitting a portion of the output force of the vacuum brake booster, characterized in that between the actuating element ( 90 ) and the reaction disk ( 93 ) a transmission disk ( 108 ) is arranged. 12. Actuating unit according to claim 10 or 11, characterized in that the end of the inner piston ( 15 ) facing the control housing ( 73 ) is formed in the shape of a spherical segment and cooperates with a pressure plate ( 95 ) which has a dome-like recess and which bears on the reaction disk ( 93 ) . 13. Actuating unit according to one of the preceding claims 10 to 12, characterized in that in the master cylinder housing ( 19 ) a hydraulic chamber ( 43 ) is provided, the connection to the modulator chamber ( 7 ) via in an extension ( 44 ) of the inner piston ( 15 ) trained bores ( 58 , 59 ). 14. Actuating unit according to claim 13, characterized in that the hydraulic chamber ( 43 ) is delimited by a partition ( 42 ), in the axial extension ( 53 ) of which an intermediate piston ( 61 ) is guided, which in the event of failure of the first (primary ) Pressure chamber ( 6 ) can be brought into engagement with both the inner piston ( 15 or 44 ) and with the second (secondary) piston ( 10 ). 15. Actuating unit according to one of the preceding claims 10 to 14, wherein the connection between the modulator chamber and the first (primary) pressure chamber takes place via a central valve which can be actuated by the modulator piston, characterized in that the central valve ( 54 ) is coaxial with the first (primary) ) Piston ( 9 ) is formed and has a closing body ( 55 ) which is displaceably guided on the inner piston ( 15 ) and a sealing seat which is formed by a ring ( 56 ) immovably arranged in a guide sleeve ( 17 ) guiding the modulator piston ( 16 ). 16. Actuating unit according to claim 17, characterized in that the guide sleeve ( 17 ) from the inner piston ( 15 ) is arranged so that it can be taken along.