DE4017744A1 - Antilock protected hydraulic braking system for motor vehicle - has synchronised pistons in chambers of tandem master cylinder with controlled connections to front wheel brakes - Google Patents

Abstract

The master cylinder (2) coupled to a vacuum servo amplifier (1) contains two pressure chambers (7, 8) bounded by separate pistons (9, 10), which move in synchronism at constant axial spacing. The hydraulic line (13) connecting the second chamber (8) to the front wheel brake cylinders (20, 21) is closed in antilock conditions by two blocking valves (44, 45) under central electronic control (33). Their outlets are connected to the first chamber (7) by a pressure-equalising arrangement (15) of two hydraulic spaces (17, 18) with springs opposing movement of their separator (16). ADVANTAGE - Simplified structure with shortened master cylinder can be mfd. at esp. low cost.

Description

The invention relates to an anti-lock motor vehicle brake system, with an actuating unit consisting of a pressure spaces limited by two master cylinder pistons facing master brake cylinder, preferably a tandem master cylinder and one upstream of it, by means of a Vacuum brake booster that can be actuated in the input member there is, to the pressure chambers of the master brake cylinder via hydraulic lines wheel brake cylinder with attached are connected with central control electronics whose inputs output signals from the rotational behavior of the braking sensors are fed and whose control signals in a blocking rule in hydrau inserted lines, the wheel brake cylinders pre control switched pressure medium valves, the primary piston of the tandem master cylinder is formed in two parts and from an outer bulb and one guided therein, with the one gear link in a force-transmitting connection inside piston exists and one in the housing of the vacuum brake a booster that can be ventilated in a blocking rule Vacuum chamber separating a working chamber Liche wall is movable independently of the input member and with is connected to the outer bulb, and wherein by the Input member interacting with the inner piston Valve piston of a control valve is actuated by the actuation of which the working chamber is ventilated.

Such a brake system is such. B. from the earlier application the applicant P 40 05 584.1 known.  

The subject of this application is to order in a Blocking rule case counteracting the actuating force Retaining force, one with the input member of the Vacuum brake booster in operative connection hydraulic chamber provided, its connection with a unpressurized pressure medium reservoir by means of an electro solenoid-operated shut-off valve can be shut off. The Chamber is through a between the surface of the Master brake cylinder and one coaxial to the master cylinder Ordered intermediate piece formed annulus and through one of the movable wall of the vacuum brake power amplifier removable locking piston limited. The Both pressure chambers of the master brake cylinder are released position in connection with the pressure medium reservoir, the connections when actuated by means of central valves be cordoned off.

Is particularly disadvantageous in the known actuation unity to see their complicated structure, the considerable Manufacturing and assembly costs caused. Another Disadvantage is the considerable axial length of the Master cylinder seen in particular on the stroke of the first safety distance contained in the first piston which is necessary to the in the second pressure chamber reduce the prevailing hydraulic pressure at any time can. That is also very complicated and labor-intensive Setting of all  Functionally important dimensions or the adaptation of the existing ones coaxial dimensions (diameter of the master cylinder, inner and Outside diameter of the locking piston or inside diameter of the Intermediate piece). With a relatively high cost too the use of the central valves mentioned. As those that occur in a normal case also become negative Pulsations felt that can be felt on the operating pedal.

It is therefore an object of the present invention anti-lock motor vehicle brake system of the beginning Specify the type mentioned, which is particularly expensive saving way can be produced. Furthermore should all functional dimensions can be easily adjusted. A Another subtask is the axial length of the Shorten the master cylinder and ver its structure simple.

This object is achieved in that the second pressure space limited by the second piston in one Blocking rule case can be shut off by means of a valve arrangement is and that the two master cylinder pistons at the actuation at a constant axial distance from each other which are moved synchronously.

To ensure that in all of the individual pressure spaces of the master brake cylinder connected wheel brake cylinder relieve the same pressures, one advantageous further training provided that between the Exit of the second pressure chamber  Valve arrangement and that limited by the first piston a hydraulic arrangement is connected in the first pressure chamber, which equalize pressure while separating the enables two pressure rooms.

The valve arrangement is preferably by two parallel, electromagnetically operated shut-off valves formed.

So that the driver opens one of the shut-off valves can recognize occurring functional error that an opening of the Prevents valve after the end of the control process, is in another embodiment of the subject of the invention provided that each shut-off valve one wheel brake each is arranged and that between the first pressure chamber and the Output of the first shut-off valve or second shut-off valve tils a first or second hydraulic arrangement ge is switched, which enables pressure equalization.

To the synchronous movement of the two master cylinder pistons To ensure actuation applies to the hydraulic active areas of the first and second pistons, respectively, the following Equation:

in which

A₁ the hydraulically effective area of the first piston,
A₂ the hydraulically effective area of the second piston,
V₁ the displaced from the first pressure chamber pressure medium volume and
V₂ the volume displaced from the second pressure chamber

mean.

A hydraulic transmission in the event of a failure of the two Get master cylinder pressure chambers, with the first piston through an outer bulb of larger diameter and a Guided inside piston is formed in a advantageous development of the invention provided that the second piston by two coaxially arranged Piston parts is formed, with radially inner pistons partly by an axial extension of the inner piston det, the cross-sectional area (hydraulic effective Area) is smaller than the total area of the inner piston.

Another advantageous embodiment of the invention counter standes, especially for an emergency translation when off case of the first pressure chamber, provides that the second Piston at its end facing away from the first piston Has cylindrical recess in which an elastic Reaction disc is arranged on which the inner piston directly and the outer bulb via a power transmission sleeve supports.  

Further features and advantages of the invention emerge from the Subclaims and the following description of two Aus examples based on the attached drawing. The drawing shows:

Fig. 1 is a schematic representation of a first design variant from an anti-lock automotive vehicle brake system according to the invention,

Fig. 2 is a schematic representation of a second embodiment of the anti-lock Kraftfahrzugbremsanlage according to the invention,

Fig. 3 shows a first embodiment of a ver used in the inventive motor vehicle brake system actuator, and

Fig. 4 shows another embodiment of the master cylinder used in the actuation unit of FIG. 3.

In the figures of the drawing are corresponding to each other Components with the same reference numerals.

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 side facing away from the input member 4 of the vacuum brake booster 1 , a master brake cylinder 2 is provided, the pressure spaces 7 , 8 with a pressure medium reservoir 5 are in Ver connection.

A first hydraulic line 11 connects the first pressure chamber 7 with the wheel brake cylinders of only schematically shown, possibly associated with the rear axle, two wheel brakes 22 , 23 via two solenoid valves 14 , 24 formed as 2/2-way valves, which are usually accommodated in a valve block .

At the second pressure chamber 8 are connected by means of a second hydraulic line 13 with the interposition of two preferably electromagnetically actuated shut-off valves 44 , 45 wheel brake cylinders of the only schematically illustrated two wheel brakes 20 , 21 , which are connected upstream of two further solenoid valves 47 , 48 and which, for example, the front axle are assigned to the motor vehicle.

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 , 37 and 38 with the solenoid valves 47 , 48 , 14 , 24 and the two shut-off valves 44 , 45 to actuate them in dependence on the sensor signals.

At the master cylinder-side working chamber of the vacuum brake booster 1 , a pneumatic 3/2-way valve 42 , which can be controlled by the central control electronics 33, is connected via a pneumatic line 43, said working chamber optionally (via a check valve 41 ) with a vacuum source 12 or the Atmosphere connects.

In order to be able to apply the same hydraulic pressures to the wheel brake cylinders connected to the individual pressure chambers 7 , 8 of the master cylinder 2 , a hydraulic arrangement 15 is finally provided which enables pressure equalization between the two pressure chambers 7 , 8 . As can be seen in FIG. 1, the arrangement 15 consists of two hydraulic spaces 17 , 18 , which are separated from one another by a piston 16 that can be displaced to a limited extent and by means of hydraulic lines 39 , 40 to the outlet side of the shut-off valves 44 , 45 or the hydraulic line 11 are connected. In the context of the inventive concept, it is quite conceivable to accommodate the shut-off valves 44 , 45 in the valve block mentioned Ven. The same also applies to the hydraulic arrangement 15 , which can also be integrated in the housing of the master cylinder 2 .

In the embodiment of the motor vehicle brake system according to the invention shown in FIG. 2, the two wheel brakes 20 , 21 of the front axle wheels are individually connected to the two shut-off valves 45 , 44 with the interposition of the solenoid valves 47 , 48 , with the line section 49 between the shut-off valve 45 and the Solenoid valve 47 of the first hydraulic chamber 17 is connected to the hydraulic arrangement 15 mentioned in connection with FIG. 1, the second hydraulic chamber 18 of which is connected to the first hydraulic line 11 . A second structurally identical hydraulic arrangement 50 is connected between the hydraulic line 11 and the line section 51 leading from the shut-off valve 44 to the wheel brake 21 in such a way that its first hydraulic chamber 77 is subjected to the pressure supplied to the wheel brake 21 during normal braking, while in the second hydraulic chamber 78 which is supplied with hydraulic pressure to the wheel brakes 22 , 23 .

The vacuum brake booster 1 of the ge shown in Fig. 3 assembly has two shell-shaped, with its open sides assembled housing parts 148 , 149 , which form an amplifier housing 100 . The left drawn in Fig. 1, provided with an unspecified pneumatic connection housing part 148 is firmly connected to the tandem master cylinder 2 , while in the right housing part 149 a control valve 101 taking control housing 102 is sliding and sealed GE leads. The control valve 101 is actuated by a valve piston 124 connected to the input member 4 .

As can be seen in the drawing without further ado, the vacuum brake force amplifier 1 shown is a brake booster in tandem configuration, the housing 100 of which is divided by a partition 141 into two pneumatic spaces 142 and 143 . The shown in the drawing right pneumatic chamber 142 is disposed therein by a pressure chamber 105, and a first working chamber 106 divided from a diaphragm plate 108 and an adjacent thereto rolling diaphragm 109 existing first movable wall 107 into a first, while pneumatic one on the left Space 143 defines a second movable wall provided with the reference numeral 144 , a second vacuum chamber 145, which is connected to the first vacuum chamber 105, and a second working chamber 146 , which is connected to the first working chamber 106, which can be ventilated during normal braking by means of the control valve 101 .

The input member-side housing part 149 is preferably provided with radial webs 58 which limit the two working chambers 106 , 146 connecting ventilation channels. On these webs 58 , the partition 141 is supported and is held axially by a retaining ring 52 which is clamped in the connection area of the two housing parts 148 , 149 at its edge.

The transmission of the reinforcing force applied by the second movable wall 144 to the control housing 102 takes place by means of a metallic sleeve 147 which is sealed and passed through the partition wall 141 .

Inside the amplifier housing 100 there is a first metallic sleeve 125 , which has an axial section 53 of smaller diameter at its end facing the control housing 102 . The section 53 is provided with two radially opposite slots 150 which receive a force transmission element - transverse pin 123 - which extends through an axial extension 60 of the valve piston 124 and which simultaneously has a relaxation sleeve 110 arranged coaxially to the extension 60 within the cylindrical section 53 holds, whose task is explained in the following text.

The length of the slots 150 is preferably larger than the distance between the end of the section 53 and a support plate 126 resting on the control housing 102 , so that a limited movement of the valve piston 124 in the actuating direction is possible before the first sleeve 125 through the movable wall 107 is moved. A relative movement of the valve piston 124 relative to the expansion sleeve 110 is made possible by two radially opposite slots 104 formed in the expansion sleeve 110 .

The first sleeve 125 is guided telescopically at its end facing away from the control housing 102 in a second metallic sleeve 116 , which is connected in a form-fitting manner, for example by means of reeving 151 , to an axial tubular extension 61 formed on the housing part 148 on the master cylinder side and projecting into the interior of the amplifier housing 100 is. Since the first sleeve 125 bears under the action of a valve piston return spring 62 on a formed on the second sleeve 116 radial annular surface 55 under bias, the valve piston 124 ge on the master cylinder-side housing part 148 ge and thereby positioned relative to the control housing 102 . The annular surface 55 also serves as an abutment for a return spring 117 , which is provided for resetting the two movable walls 107 , 144 and, on the other hand, is supported on the support plate 126 . The support plate 126 prevents displacement of a seal sealing the valve piston 124 from the control housing 102 , in the example shown a sealing sleeve 59 .

The also axially adjacent to the support plate 126 relaxation sleeve 110 is in engagement with the radially outer part (outer piston) 121 of the first pressure chamber 7 of the tandem master cylinder 2 delimiting, two-part first piston 9 , so that when actuating a direct transmission of the moving from the Walls 107 , 144 applied reinforcing force on the outer bulb 121 . For this purpose, the Ent tension sleeve 110 at its end facing the master cylinder 2 has a convexly curved support surface 56 , the shape of which corresponds to a concave curved support surface 57 formed at the end of the outer bulb 21 .

The outer part 121 , which guides the second part (inner piston) 120 of the first piston 8, is provided at its end facing the tension sleeve 110 with a cylindrical recess 63 , the diameter of which is larger than the diameter of the inner piston 120 . This recess 63 receives a force transmission sleeve 140 , which is provided with a radial annular surface 64 , which rests on the bottom of the recess 63 in the release position and which, when actuated, allows the inner piston 120 to be carried along by the outer piston 121 . The inner piston 120 is provided on its end facing away from the first pressure chamber 7 with a dome-shaped recess 69 which is initially located at a small axial distance from the end of the extension 60 of the valve piston 124 . Reaches the hydraulic pressure built up in the first pressure chamber 7 a predetermined value, the inner piston 120 is pushed ver against the actuation direction, so that there is contact between the end of the extension 60 and the inner piston 120 . At the same time, the force transmission sleeve 140 is moved in the same direction against the action of a preload the spring 118 , the other end of which is supported on the outer bulb 121 , preferably by means of a securing ring 65 . The fixed positioning of the spring 118 in the recess 63 enables an exact setting of the "spring height" of the response characteristic by changing the installation length or the spring rate of the spring 118 .

In order to ensure that the two master cylinders 9, 10 move synchronously when actuated at a distance a from one another, the following condition must be met for their hydraulically active cross-sectional areas A ₁ and A ₂ :

A₁ the hydraulically active surface of the first piston 9 ,
A₂ the hydraulically active surface of the second piston 10 ,
V₁ from the first pressure chamber 7 displaced pressure medium volume and
V₂ the medium volume displaced from the second pressure chamber 7

mean.

As can also be seen in FIG. 3, the second piston 10 delimiting the second pressure chamber 8 is formed in two parts and preferably consists of a sleeve-shaped first radially outer piston part 119 , in which a second piston part 130 is guided in a sealed manner. The second piston part 130 is formed by an axial extension 131 of the inner piston 120 , the diameter of which is smaller than that of the inner piston 120 . This creates an annular surface in the transition area on the inner piston 120 , the meaning of which is explained in the text below. In the first pressure chamber 7 , two return springs 111 , 113 are arranged which bias the two pistons 9 , 10 against the direction of actuation or hold them at stops formed in the master cylinder housing, the radially outer return spring with the outer piston 121 and the radially inner return spring 113 cooperates with the sleeve-shaped part 119 of the second piston 10 . In order to allow the pressure medium to continue to flow from the storage container (not shown) into the pressure chambers 7 and 8 , radial bores 114 are provided in the outer piston 120 or the sleeve-shaped piston part 119 , each of which is arranged in the release position at an axial distance in front of the sealing lip of the sealing sleeve 115 are. The radially inner surface of the sealing sleeve 115 is stiffened by a support ring 122 , which engages around the outer piston 121 or the piston part 119 with radial play, so that the pressure medium can flow through the resulting annular gap. The axial distance between the bores 114 and the sealing lip mentioned represents the closing path of the valve arrangement designed in this way, after its replacement in the two pressure chambers 7 , 8 a hydraulic pressure can be built up.

The mode of operation of the motor vehicle brake system according to the invention shown in FIG. 1 is described below in connection with FIG. 3:

During normal braking, in which the two shut-off valves 44 , 45 remain open and the pneumatic 3/2-way valve 42 connects the working cylinder 145 ( FIG. 3) on the master cylinder side of the vacuum brake booster to the vacuum source 12 , the pressure is built up and released as in one Known, consisting of a master cylinder and a pre-connected vacuum brake booster existing actuation unit.

The hydraulic arrangement 15 enables pressure compensation between the two pressure spaces 7 and 8 of the master cylinder 2 .

If, during a braking operation, one of the sensors 25 to 28 blocks one of the wheels festge, the central control electronics 33 generate switching signals which cause a simultaneous switching of the shut-off valves 44 , 45 , so that the second pressure chamber 8 is shut off and the inner piston 120 or the brake pedal 3 remains in the activated position. At the same time, the pneumatic 3/2-way valve 42 is switched by the control technology, so that the movable wall 6 (or 107 and 144 ) of the vacuum brake booster 1 becomes powerless and the pressure prevailing in the wheel brakes due to the return movement of the first piston 9 or its outer bulb 120 can be dismantled. The reduction of the pressure applied to the wheel brakes 22 , 23 can take place directly via the hydraulic line 11 , while the pressure prevailing in the wheel brakes 20 , 21 is built by moving the piston 16 of the hydraulic compensation arrangement 15 .

As can be seen in particular from FIG. 3, the end of the piston part 119 partially guided in the outer piston 121 facing the inner piston 120 is at a small axial distance b from the annular surface formed on the inner piston 120 . Since the sleeve-shaped piston part 119 should not be shifted from the inner piston 120 during normal braking, the distance b must be chosen larger than the axial distance a was between the outer piston 121 and the radially outer piston part 119 of the second piston 10 .

In a blocking rule case, in which the piston part 119 stops and the inner piston 120 comes to rest on this part, the distance b must be covered. This causes the pedal 3 to fall through by this amount. In the control, it is also conceivable that the outer piston 121 is retracted to the stop so that the holes 114 provided in it drive the sealing sleeve 115 over and the connection between the first pressure chamber 7 and the reservoir 5 is released, so that the in System prevailing residual pressure can be reduced to zero.

If, when actuated, the first pressure chamber 7 or the brake circuit connected to it fails, for example due to a leak, both the annular surfaces formed on the outer piston 121 and on the inner piston 120 become ineffective. Through the contact between the outer piston 121 and the radially outer piston part 119 of the second piston 10 , the amplifying force is transmitted to the piston part 119 , while the actuating force acting on the pedal 3 acts on the inner piston 120 and thus the radially inner piston part 130 of the second piston 10 shifts. Since the hydraulically effective area of the piston part 130 is smaller than the hydraulically effective total area of the inner piston 120 , a step change occurs when the force is transmitted from the first pressure chamber 7, which results in a larger transmission ratio.

In the event of failure of the second pressure chamber 8 , the hydraulic ratio of the actuation unit shown in FIG. 3 corresponds to the ratio between the total area of the first piston 9 and the mentioned annular surface formed on the inner piston 120 . The described design of the two master cylinder pistons 9, 10 ensures that a hydraulic transmission in the other (intact) circuit is constantly available in the event of a hydraulic circuit.

In the second embodiment shown in FIG. 4 of the tandem master cylinder 2 which can be connected upstream of the vacuum brake booster, the second piston 10 is formed in one piece and is biased by means of a return spring 132 arranged in the second pressure chamber 8 . The return spring 132 is preferably tied to the bottom of the master cylinder bore.

At its end facing the first piston 9 , the second piston 10 has a partially slightly conical cylindrical recess 127 which receives an elastic reaction disk 128 , on the one hand the inner piston 120 and on the other hand, by means of a force transmission sleeve 129 , the outer piston 121 axially support. A formed on the power transmission sleeve 129 , facing away from the outer piston 121 annular surface 133 is at a small axial distance a 'from the end of the second piston 20 , the distance a' corresponds to the distance a mentioned in connection with FIG. 3. This measure achieves an emergency translation in the event of failure of the first pressure chamber 7 , which is defined as the ratio of the area of the reaction disk 128 to the area of the end of the inner piston 120 abutting it.

Reference symbol list

1 vacuum brake booster
2 master brake cylinders
3 brake pedal
4 input link
5 pressure medium reservoir
6 movable wall
7 first pressure chamber
8 second pressure chamber
9 first piston
10 second pistons
11 first line
12 vacuum source
13 second line
14 hydraulic 2/2-way valve
15 hydraulic arrangement
16 pistons
17 hydraulic room
18 hydraulic room
20 wheel brake
21 wheel brake
22 wheel brake
23 wheel brake
24 hydraulic 2/2-way valve
25 sensor
26 sensor
27 sensor
28 sensor
29 signal line
30 signal line
31 signal line
32 signal line
33 central control electronics
34 control line
35 control line
36 control line
37 control line
38 control line
39 Management
40 line
41 check valve
42 3/2-way valve
43 pneumatic line
44 shut-off valve
45 shut-off valve
46 pistons
47 valves
48 valves
49 line section
50 hydraulic arrangement
51 line section
52 retaining ring
53 section
55 ring surface
56 contact surface
57 contact surface
58 footbridge
59 seal
60 extension
61 continuation
62 piston return spring
63 recess
64 ring surface
65 circlip
69 dome-shaped recess
77 hydraulic room
78 hydraulic room
100 amplifier housings
101 control valve
102 control housing
103 poppet valve
104 recess
105 first working chamber
106 second working chamber
107 movable wall
108 membrane plates
109 rolling membrane
110 relaxation sleeve
111 return spring
112 poppet valve holder
113 return spring
114 hole
115 sealing sleeve
116 sleeve
117 return spring
118 compression spring
119 piston part
120 inner pistons
121 outer bulb
122 support ring
123 cross pin
124 valve piston
125 sleeve
126 support plate
127 recess
128 reaction disc
129 power transmission sleeve
130 piston part
131 extension
132 return spring
133 ring surface
140 power transmission sleeve
141 partition
142 pneumatic room
143 pneumatic room
144 second movable wall
145 third working chamber
146 fourth chamber of labor
147 sleeve
148 housing part
149 housing part
150 slot
151 reeving

Claims (11)

1. An anti-lock motor vehicle brake system, with an actuating unit, which consists of a master brake cylinder having two pressure chambers delimited by two master cylinder pistons, preferably a tandem master cylinder and a vacuum brake power supply connected upstream of it, which can be actuated by means of an input member, with the pressure chambers of the master brake cylinder via hydraulic lines Wheel brake cylinders are connected, with central control electronics, at the inputs of which output signals from the sensors detecting the rotational behavior of the wheels to be braked are fed and whose control signals control hydraulic pressure inserted in hydraulic lines upstream of the wheel brake cylinders, the primary piston of the tandem master cylinder being formed in two parts is and consists of an outer bulb and an inner bulb guided therein, which is in force-transmitting connection with the input member, and an i In the housing of the vacuum brake booster, a vacuum chamber which can be ventilated in a blocking control case and which is separable from a working chamber can be moved independently of the input member and is connected to the outer piston, and a valve valve of a control valve which interacts with the inner piston can be actuated by the actuation thereof by the input member the working chamber is ventilated, characterized in that the second pressure chamber ( 8 ) delimited by the second piston ( 10 ) can be shut off by means of a valve arrangement ( 44 , 45 ) in the event of a blockage and that the two master cylinder pistons ( 9 , 10 ) are actuated in a constant axial distance from each other can be moved synchronously. 2. An anti-lock motor vehicle brake system according to claim 1, characterized in that between the output of the second pressure chamber ( 8 ) shutting off valve arrangement ( 44 , 45 ) and the first pressure chamber ( 7 ) delimited by the first piston ( 9 ), a hydraulic arrangement ( 15 ) is switched, which enables pressure equalization with simultaneous separation of the two pressure chambers ( 7 , 8 ). 3. An anti-lock motor vehicle brake system according to claim 1, characterized in that the valve arrangement is formed by two parallel, electromagnetically actuated shut-off valves ( 44 , 45 ). 4. An anti-lock motor vehicle brake system according to claim 3, characterized in that each shut-off valve ( 44 or 45 ) is assigned a wheel brake ( 20 or 21 ) and that between the first pressure chamber ( 7 ) and the outlet of the first shut-off valve ( 44 ) or second shut-off valve ( 45 ) a first or second hydraulic arrangement ( 15 , 50 ) is connected, which enables pressure equalization. 5. Anti-lock motor vehicle brake system according to claim 4, characterized in that the hydraulic arrangements ( 15 and 50 ) by two by means of an intermediate piston ( 16 and 46 ) separate hydraulic spaces ( 17 , 18 and 47 , 48 ) are formed. 6. An anti-lock motor vehicle brake system according to claim 1, characterized in that the following equation applies to the surfaces (A ₁ or A ₂ ) of the first or second piston ( 9 or 10 ): whereinV₁ - the volume of pressure medium displaced from the first pressure chamber ( 7 ) and
V₂ - from the second pressure chamber ( 8 ) displaced volume mean. 7. An anti-lock motor vehicle brake system according to one of the preceding claims, wherein the two master cylinder pistons are held by means of return springs in the release position on stops formed in the master cylinder housing, characterized in that both return springs ( 111 , 113 ) are arranged in the first pressure chamber ( 7 ) and are supported on the master cylinder housing . 8. An anti-lock automotive vehicle brake system according to any one of the preceding claims, wherein the pressure chambers of the master cylinder to stand closable trailing spaces with a pressure fluid supply reservoir in communication, characterized in that the Verbin dung several formed by one or in the master cylinder piston (9, 10) provided radial holes (114) is, which are arranged in the release position at an axial distance from the sealing lip of a standing sealing sleeve ( 115 ). 9. An anti-lock motor vehicle brake system according to claim 8, characterized in that the sealing sleeve ( 115 ) has a support ring ( 122 ) which engages around the master cylinder piston ( 9 , 10 ) with radial play. 10. An anti-lock motor vehicle brake system according to one of the preceding claims, characterized in that the second piston ( 10 ) has at its end facing the first piston ( 9 ) a cylindrical recess ( 127 ) in which an elastic reaction disc ( 128 ) is arranged, on which the inner piston ( 120 ) is supported directly and the outer piston ( 121 ) via a force transmission sleeve ( 129 ). 11. An anti-lock motor vehicle brake system according to one of claims 1 to 9, characterized in that the second piston ( 10 ) by two coaxially arranged piston parts ( 119 , 130 ) is formed, the radially inner piston part ( 130 ) by an axial extension ( 131 ) of the inner piston ( 120 ) is formed, the cross-sectional area (hydraulic effective area) of which is smaller than the total area of the inner piston ( 120 ).