FR2752401A1 - MULTI-CIRCUIT BRAKING SYSTEM FOR VEHICLES - Google Patents

Abstract

The invention relates to a braking system (2) with multiple circuits, provided with: a first circuit (I) comprising a master cylinder (4), front wheel brakes (5, 6), and first means of 'corresponding actuation (7, 8); a second braking circuit (II) comprising actuating means (24, 25, 28, 29) of the front wheel brakes (5, 6) and of the rear wheel brakes (26, 27); and a control apparatus (44). According to the invention, the second brake circuit is a hydraulic circuit (II) supplied by a pump (38), at least one arrangement of valves (16 to 23) being arranged between the pump (38) and the actuating means. (24, 25, 28, 29) hydraulic for the purpose of adjusting the brake pressure.

Description

Multi-circuit braking system for vehicles State of the

  The invention relates to a multi-circuit braking installation, in which the first circuit comprises a single-circuit master cylinder controlled by a brake pedal,

  front wheel brakes of the separate type connected to said circuit with first means of action-

  second actuation means, in which the braking circuit supplements

  be silent at least one includes the second means for actuating the front wheel brakes and additional actuating means for the rear wheel brakes and which is equipped with a control device, the control device being connected to at least

  a sensor serving as a setpoint generator which is at least interactively coupled

  directly to the brake pedal or to the brake master cylinder and is used to send energy taken from an energy source indirectly into the second actuation means of the front wheel brakes and into the actuation means rear wheel brakes. Document US 4,658,939 discloses a two-circuit braking system intended for vehicles, in which the first braking circuit which acts exclusively on the brakes

  of the front wheels is in the form of a hydraulic braking circuit with a master

  brake cylinder for single circuit which is actuated by the brake pedal and in which the

  second circuit, at least one in number, produced in the form of an electric braking circuit

  independent energy stick, for this purpose comprises a current source, electric motors

  as well as screw transmissions as actuating means for the rear wheel brakes and for the front wheel brakes, the latter being dual circuit. It is intended to control and distribute independent energy to electric motors an electric control device which is coupled to the brake pedal via a potentiometer or the like. A disadvantage of this system is for example the weight of electric motors and screw transmissions, in particular because these elements are arranged on the wheel brake and thus form part of the unsprung masses of the vehicle. Another disadvantage is that to quickly apply wheel brakes using electric motors, high currents

  are necessary, so that the cost of the electrical network of a vehicle equipped with such an in-

  braking stallation is relatively high. We can still consider it a drawback

  deny the fact that when suddenly released wheel brakes actuated in this way

  electro-mechanical track, the play can increase more quickly than in hydraulic brakes

  currents, which can lead to longer brake reaction times.

  Document US 3,799,300 discloses a hydraulic braking installation with a three-circuit

  ple for vehicles which has, in the case of the front wheel brakes, so-called "split" brakes for dual circuit braking and, in the case of the rear wheels, brakes

  single circuit wheels, the rear wheel brakes being combined with a

  working bre of a double circuit brake master cylinder, first front wheel brake cylinders being associated with a second working chamber of said brake master cylinder and

  a hydraulic brake force amplifier which is controlled by an active brake pedal

  operating the master cylinder and also providing pressure for the second brake cylinders of the front wheel brakes. One drawback here is the technical complexity of the dual-circuit brake master cylinder; a second drawback is the design of the braking force amplifier. This resides in the fact that in operation with amplification of the -2 - braking force a push rod coupled to the brake pedal moves with a shorter stroke than a neighboring piston of the master cylinder of the master cylinder with double circuit. Therefore, in the event of a fault in the tightness of the linings of the master cylinder pistons, a shift of said pistons

  master cylinder cannot be detected at the brake pedal.

  In document US 5,000,295, one starts from a hydraulic braking installation for vehicles

  cules, in which the brake pressure increases for the actuating means

  associated with the wheel brakes are controlled by acting on the supply voltage of a mo-

  electric drive driving a pump, depending on the position occupied by a brake pedal. A braking system of this type is perfectly suited to limit braking slip, when the supply voltage of the electric motor can be controlled by

  depending on the value of the brake slip. It is planned to associate in terms of cons-

  own production of a pump and consequently an electric motor at each wheel brake. Thus, in the event of a breakdown of the electric motor or the pump, the wheel brake being actuated by the

  muscular strength of the driver of the vehicle, a total loss of braking force is avoided.

  However, since there is not between the muscular force braking circuit and the circuit

  brake operated by a pump that a sliding seal in contact with the piston and that a

  failure at this joint is practically not detectable in normal braking mode, such a braking installation contains certain safety risks. Another drawback is that a driver of the vehicle during a panic-type actuation of the brake pedal urges the annular surface of the piston with a braking pressure which alone can be sufficient to block a wheel on ice. In such a situation, it is not enough to prevent a brake pressure produced by the pump from acting on the associated piston of the brake.

  wheel or lower it by means of a valve controlled by electric means.

  An additional disadvantage is that the pump and the electric motor increase

  lie about the weight of the wheel brake which, as mentioned above in connection with document US Pat. No. 4,658,939, has harmful repercussions on the running characteristics of a vehicle. Another disadvantage is that for a four-wheeled vehicle, a technical expense relating to four pumps and four electric motors is necessary instead of for example a pump and

an electric motor.

  Document DE 40 29 793 A1 discloses a braking installation for vehicles with

  a double circuit brake master cylinder and two 2/2 distributors.

  The object of the invention is to propose a braking installation free from at least some

  problems and limitations encountered in the previously mentioned known devices.

  To this end, the braking installation of the invention is essentially characterized by the fact

  that the second means for actuating the front wheel brakes and the means for actuating

  rear wheel brakes are arranged in the form of means of action-

  hydraulic, by the fact that the energy source is arranged in the form of a hydraulic energy source with at least one supply tank and a pump, by the fact that at

  least one valve arrangement that can be controlled by a control device is available

  placed between the energy source and the second actuation means and the actuation means

  additional, by the fact that wheel rotation detectors are associated with the wheels which can be braked using the front wheel brakes and rear wheel brakes, 3 - by the fact that the control unit is connected to the wheel rotation detectors and is arranged so as to detect the braking slip of braked wheels and to control at least one of the valve arrangements in order to modify the braking pressure in at least one of the actuation means in the direction a limitation of the braking slip and by the fact that a distributor open in normal position is disposed between the brake master cylinder and the first actuation means supplied by the latter with the front wheel brakes, which distributor can be closed by the control unit when said control unit

  controls at least one of the valve arrangements to limit brake slip

ge. Advantages of the invention

  The braking installation for vehicles according to the invention thus has the advantage that the

  properties of the first prior hydraulic brake circuit which acts on separate front wheel brakes are retained and which can be used as a brake for the rear wheels of the standard hydraulic wheel brakes, which can be used for the wheel brakes before known type of hydraulic wheel brakes, common elements of hydraulic braking systems can be used for hydraulic braking systems with independent braking energy. We see that by replacing the wheel brakes activated by

  electro-mechanical track by means of hydraulically actuated wheels it is possible to

  reduce the unsprung masses which is advantageous in terms of the rolling characteristics of a vehicle equipped in this way. The advantage also lies in the fact that, to quickly apply wheel brakes with an independent braking force, a hydraulic accumulator can be used here; so the hydraulic pump drive motor can

  be relatively light and a relatively inexpensive on-board electrical network is sufficient for

  lie while running the drive motor. The advantage is still that with the brake circuit,

  service age, at least one, actuated by an external force, the braking forces

  ge produced can be reduced automatically when the control device arranged accordingly detects an unacceptable increase in brake slip or a risk of wheel lock, any further increase in brake slip

  following an increase in the pressure in the brake master cylinder possibly

  triggered by the driver of the vehicle being stopped in the case of at least one increase

  braking slip of the front wheels is not admissible.

  Additional arrangements may be made to improve the brake installation.

  age of the invention and derive other advantages from it.

  For example, one can provide a bypass line comprising a non-return valve

  bypassing the distributor, this non-return valve being able to open in the direction of the master cylinder

brake dre.

  This characteristic makes it possible, in a manner known per se, by abruptly releasing the brake pedal, to rapidly lower the pressure in the wheel brake cylinders of the first circuit

braking.

  It is also possible to provide that a distributor closed in the normal position is connected to the first means for actuating the front wheel brakes, that a spring accumulation chamber is indirectly connected to the first means of actuation by this distri -4-

  and the spring storage chamber is connected indirectly to the housing.

  brake tre-cylinder by a non-return valve which opens in the direction of said master cylinder.

  These characteristics improve the braking installation defined previously in the sense that in addition to preventing an annoying rise in pressure in the first braking circuit, in the wheel brake cylinders of the front wheels, it is possible to lower the pressure of

  braking in said wheel brake cylinders. The pressure fluid flowing in an ac-

  accumulator each time the brake pressure is lowered is brought back from the accumulator into the brake master cylinder when the brake pedal is released. The battery may have

  a capacity which, for example, corresponds substantially to the pumping capacity of the master

brake cylinder.

  It is also possible to provide for a return pump to be mounted in the first brake circuit.

  stroke connected to the brake master cylinder, in the bypass line leading to the distributor

  which pump pumps the fluid towards the brake master cylinder.

  These features provide the advantage that in the first hy-

  hydraulics also, that is to say in the so-called auxiliary braking circuit, it is also possible to lower

  as often as necessary and at a value as low as necessary the pressure in the cylinders

  dres front wheel brakes and that it can be increased to the level of the pressure prevailing in the brake master cylinder It can also be provided that the return pump is driven by a motor driving the

  independent power source pump.

  These features provide the advantage that economically the return pump can

  be driven by an electric motor from the hydraulic pump of the braking circuit to be

  independent company. It is indeed advantageous for the return pump to do its main work.

  cipal when the brake pressure is lowered, while the pump of the independent energy braking circuit, at least one in number, must normally or essentially supply

  its work during increases in brake pressure.

  It is also possible to provide that at least one arrangement of valves of the braking circuit supplied

  ted by the energy source is arranged in the form of proportional distributor.

  These characteristics provide the advantage known per se that, using the valve arrangements claimed, it is possible to trigger essentially smoothly, therefore smoothly and without noise, an increase in braking pressures and also a reduction in pressures.

braking.

  It can also be provided that the setpoint generator is arranged in the form

  a brake master cylinder pressure sensor connected to said brake master cylinder.

  This feature provides the advantage that, despite the application of features

  previously mentioned, the control unit receives a set value for a pressure

  braking sion selected by the driver by actuating the brake pedal, even when operating in brake slip limiting mode, when the brake master cylinder is isolated from the brake cylinders of wheels or that the return pump

  attempts to bring the brake pedal back against the driver's action.

  It is also possible to provide a sensor which serves as a set value generator and which is

  linked at least indirectly to the brake pedal or the brake master cylinder.

  This characteristic offers a possibility of realization in the case where the vehicle's braking system is not fitted out with a device for limiting braking slip. It would be

  In itself possible to remove the previously mentioned pressure sensor, but it is above all

  geux, for safety reasons, to have two sensors which detect an actuation

  of the brake pedal by the driver and transform it each time into a set value

  gne. Considering that in normal service brake operation with no tendency to block

  wheel age, the set values delivered by the pressure sensor and by the

  must match from the point of view of the trend during a stronger action on the

  brake pad, the control unit can, with suitable programming, trigger

  an acoustic and / or optical alarm signal in the event of failure of one of the mentioned sensors

born.

  One can also provide that the sensor is arranged in the form of a stroke sensor.

  This characteristic constitutes an example of an implementation which is technically simple, for the

  which one can use for example a rheostat with cursor.

  Finally, it can be provided that to regulate the sliding slip of the drive wheels

  created using the wheel brakes, the control device connected to the wheel rotation detectors is arranged so as to detect the slipping of the driving wheels on

  the basis of the signals from the wheel rotation detectors and to control at least one of the agents

  valve cements for sending energy from the energy source into at least one of the actuating means in order to at least partially compensate for the excess torque by a braking torque

  These characteristics provide the advantage that by using elements suitable for the function-

  independent braking energy, such as the hydraulic pump,

  With electrically controlled valves and wheel brakes for the drive wheels, it is possible to at least partially compensate by braking the excess engine torque at these drive wheels, so that the tendency of the drive wheels to slip

  counteracted in the sense of limiting the propulsion slip.

  Drawings Three embodiments are represented on the drawings and described in detail.

  in the following. FIG. 1 represents a circuit plan for a simple embodiment

  ple of the braking system for a vehicle according to the invention; Figure 2 shows a per-

  brake system installation for a vehicle brake system and figure

  3 shows another mode of arrangement for a braking circuit of the braking system.

age for vehicle.

-6 -

  Description of the exemplary embodiments

  A braking installation 2 for vehicles according to the invention shown in FIG. 1

  comprises a first hydraulic brake circuit I and a second hydraulic brake circuit II

  hydraulics. The hydraulic braking circuit I comprises a master brake cylinder 4 actuated using a brake pedal 3, two brakes 5, 6 of front wheels, of the so-called separate type, with each of the first actuation means 7 and 8 , a main brake line 9 as well as wheel brake lines 10 and 11. Between the brake master cylinder 4 and the brake pedal 3 is a pedal rod 12. A stroke sensor 13 is coupled to the pedal rod 12 for the purpose of measuring the displacement stroke of the pedal rod 12 when the brake pedal is actuated 3. The stroke sensor 13 is preferably in the form of a sensor

  electric analog, for example which delivers voltages according to the travel of displacement

  cementation of the pedal rod 12 and as a result of the displacement of the pedal 3, but also of a

  tone not shown of a brake master cylinder 4. In the embodiment, the stroke sensor 13 is therefore used to indirectly measure the stroke of the brake pedal 3 and / or of said piston

brake master cylinder.

  The braking circuit II comprises an energy source 15, arrangements of electrically controlled valves 16 to 23, second actuation means 24, 25 on the front wheel brakes 5 and 6 as well as rear wheel brakes 26 and 27 with actuating means 28

  and 29 correspondents in the form each time of at least one wheel brake cylinder. The cir-

  braking system II also includes braking pressure sensors 30, 31, 32 and 33 which are connected to lines 34, 35, 36 and 37 of wheel brakes which lead to the second

  actuation means 24 and 25 and actuation means 28 and 29. The pressure sensors

  Braking may include, for example, membranes based on pressure sensitive semiconductors with extensometers. For example, it is also possible to use pressure sensors of a different type with a capacitor or a piezoelectric element as a measuring element. Since sensors of this type are part of the state of the art, there is no need to describe them specifically here. It is only important here that a brake pressure

  wheel is transformed into an electrical quantity preferably analog, such as a tension

  if we. The energy source 15 comprises a pump 38, a supply tank 39 for pressure fluid sucked by the pump 38, a motor 40 for example electrically driven for the pump 38, a pressure accumulator 41 supplied by the pump 38 , a non-return valve 42

  which is arranged on the suction side of the pump 38 and opens in the direction of the di-

  rection of the pressure accumulator 41, as well as a pressure limiting valve 43 which is connected to the pressure accumulator 41 and opens in the direction of the supply tank 39. The braking circuit II also comprises a control device 44 for setting

  runs the motor 40 and to control the arrangement of valves 16 to 23. The

  demand 44 is connected to a pressure sensor 45 which, in turn, is connected to the accumulator

  41 and the stroke sensor 13 as well as a master cylinder pressure sensor 14

  dre redundant with the first. The control device 44 is also connected to the brake pressure sensors 30 to 33. The control device 44 is produced, in a manner known per se, in the form of a brake pressure regulator to which signals are transmitted from the stroke sensor 13 or / and from the master cylinder pressure sensor 14 as the set values and from the signals from the brake pressure sensors 30 to 33 as the actual values and which, depending deviations between setpoints and actual values, controls the arrangements of electrically controlled valves 16 to 23 in the direction of bringing the actual values closer to the setpoints. This is among other things

  of the state of the art set out in the introductory part of the description and it is not necessary

  Please describe it in more detail here. This is why we will only indicate that the agencies-

  elements of electrically controlled valves 16 to 23 can be distributors with two inputs of the type with progressive adjustment, which in accordance with the symbols provided by standard ISO 1219 is represented by two parallel lines at the top and at the bottom of two squares respectively and by an arrow symbolizing an electromagnet. One of these valve arrangements 16, 18, 20, 22 is a valve which is closed in the normal position while the other

  valve arrangement 17, 19, 21, 23 is a valve which is open in the normal position.

  The valves 17, 19, 21, 23 open in the normal position are arranged between the actuating means 24, 25, 28, 29 and the supply tank 39, so that, as can be seen, when the arrangements of valves 17, 19, 21, 23 are in their basic position, the

  actuating means 24, 25, 28, 29 are placed in communication with the reservoir 39

  flying at atmospheric pressure, so that there is no braking. The val-

  ves 16, 18, 20 and 22 which in the normal position are closed, prevent a flow of fluid

  pressure from the pressure accumulator 41 to the actuating means 24, 25, 28 and 29.

  We will also indicate that the valve arrangements represented 16 to 23 are interchange-

  able with, for example, 2-input / 2-position distributors that cannot be brought in

  in intermediate throttling positions. It is also possible to use instead of combinations

  sounds of two distributors 2/2 distributors with three positions and three inputs.

  Operation of the brake system 2: An actuation of the brake pedal 3 causes, via the pedal rod 12 and the piston, not shown, of the brake master cylinder 4 to discharge pressure fluid to

  through the main brake line 9 and the wheel brake lines 10 and 11 in the pre-

  better actuation means 7 and 8 with the consequence that a braking pressure builds up

  blit in said actuating means 7 and 8. This braking pressure causes the establishment

  braking forces in the front wheel brakes 5 and 6. Simultaneously with the establishment-

  As a result of the braking pressure in the braking circuit I, increasing tendency signals are generated at the stroke sensor 13 and the brake master pressure sensor 14. If the control unit 44 is in service and in perfect working order, it detects, as described above, deviations between the actual values delivered by the

  brake pressure sensors 30 to 33 which are not initially used

  cited by a pressure and set values supplied by sensors 13 and 14. In order to

  blir in the actuating means 24, 25, 28, and 29 a braking pressure which does not yet exist, the control device 44 firstly brings the valve arrangements 17, 19, 21 and 23 into the blocking positions then adjusts the valve arrangements 16, 18, 20 and 22 at

  less in partial opening positions. Thus pressure fluid flows from the accumulator.

  pressure regulator in the actuating means 24, 25 and 28, 29 with the consequence

  that signals from the brake pressure sensors 30 to 33 are transmitted to the device

  control command 44 which, when the actual values are sufficiently close to the values

  their setpoint, let the valve arrangements 16, 18, 20, 22 return to their original position with the effect that the brake pedal 3 being left at rest, the braking pressures -8- ge in the means of actuation 24, 25, 28, 29 remain constant. If for example following a

  heating of the pressure fluid enclosed in the actuating means 24 to 29 the pressure

  pressure tends to increase, the pressure increase is signaled to the control unit 44 by higher effective values supplied by the brake pressure sensors 30

  to 33, so that said control device, by opening at least partially and momentarily

  especially the arrangements of valves 17 and 18 and 20 and 22, again causes convergence

  between the actual values and the set values. On the other hand, if a vehicle driver

  let the brake pedal 3 return at least partially to its starting position, the

  their setpoints decrease and the control device 44 intervenes through the

  valve arrangements 17 and 19 and 21 and 23 in the direction of reducing the brake pressure

  swim. The described operation corresponds to normal braking operation for which, the ISO 611 standard gives the vehicle brake installation described the name of service braking installation. If the brake circuit II does not deliver any braking force

  for service braking, whether due to a leak in the lines

  you belong to the brake circuit II, because the pump 38 is not driven by the motor

  40 or because the control unit 44 fails to start the motor 40

  che, it is possible as indicated in the introduction, to produce a brake pressure in ac-

  actuating the brake master cylinder 4 by muscular force via the brake pedal 3 and the pedal rod 12, which brake pressure acts in the first means

  actuation 7 and 8 of the front wheel brakes 5 and 6. Thus, a vehicle equipped with the output

  te can only be restrained by muscular force, which the ISO 611 standard designates by

  term "auxiliary braking"; the braking circuit I thus constitutes an auxiliary braking circuit

  re. It is noted with regard to the braking circuit I that it is not necessary to have

  an arrangement of electrically controlled valves when switching from service braking mode

  normal defect in the auxiliary braking mode.

  Since the braking circuit II, which is an independent energy braking circuit

  dante, is equipped with the described arrangements of electrically operated valves, it offers the possibility

  bility, as already taught by the state of the art of placing on the wheels which are associated with the front wheel brakes 5 and 6 or even with the rear wheel brakes rotation detectors of

  wheel 46 to 49 and to improve the control device 44 in order to detect an increase

  non-permissible braking slip and to arrange the said device so that in the event of an inadmissible or annoying increase in the braking slip of the wheels, it does not matter whether only one wheel or all the wheels are concerned, mode switch

  adaptation of the actual value to the set value in regulation or limit mode

  wheel slip; note that as is known to the technical specialist

  braking, the permissible braking pressures possibly being appreciably lower

  braking pressures preselected by the driver of the vehicle through

the brake pedal.

  Since, as indicated above, the braking circuit I constitutes an installation

  tion of auxiliary braking, it is quite naturally desirable that said circuit I be sufficient at least to produce a minimum deceleration prescribed by law of a vehicle equipped with such a braking circuit. However, during normal service braking on snow or 9-ice, it may happen that a decrease in the braking pressure as indicated above does not result in a sufficient reduction of the braking slip at braked wheel level

  by the front wheel brakes 5 and 6. This is the reason why a 2/2 50 distributor is

  tee in the main brake line, which valve can be brought in by a

  electric control from its normal open position to a closed position. To bring the dis-

  timer 2/2 from its normal open position to the closed position, the control device 44 is arranged so that it monitors the way in which the braking slip increases when the braking pressure increases and, if necessary, puts an end to an increase in the braking pressure in the first actuation means 7 and 8 by bringing the distributor

  2/2 50 in its closed position. Since a hydraulic column is then formed, rela-

  tively rigid, which starts at the level of the master cylinder of firein and extends to the distributor 2/2 50 closed, the brake pedal 3 urged by a greater muscular force

  practically no longer moves but produces an increase in pressure at the level of the cap

  pressure master 14 of the brake master cylinder which then delivers to the control unit 44 the

  set pressure to be observed. To a certain extent, the master pressure sensor 14

  brake brake cylinder is more important than stroke sensor 13.

  So that in a manner known per se, the braking pressure can be lowered quickly by releasing the brake pedal 3, although the distributor 2/2 50 has been brought into position.

  closed by the control device 44, a bypass line 51 provided with a check valve

  return 52 bypasses the 2/2 distributor 50.

  Note also that thanks to the arrangements of valves 16 to 23 electrically controlled and

  thanks to wheel rotation detectors 46 to 49, wheel rotation detectors being

  associated at least with the driving wheels and a greater number of wheel rotation detectors being used if necessary to obtain reference quantities, the braking circuit II

  can be improved to form a device for regulating the slip of the drive.

  Such a drive slip regulation device belongs to the category of devices

  sitives which have the function of compensating at least partially by braking the driving wheel concerned an excess of engine torque compared to the torque that can be transmitted

by a wheel to the roadway.

  When the braking system described is installed for example in a relative vehicle

  light part, the part of the braking circuit I, as an auxiliary braking circuit, in the ra-

  the vehicle slowing down during service braking can be relatively high, so that it is desirable not only to put an end to a pressure increase in the first actuating means 7 and 8 using the 2/2 distributor, but still to lower once to

  minus the braking pressure too high in the first braking means 7 and 8. For this-

  1a, FIG. 2 shows an improvement of a braking installation 2a which additionally comprises an accumulation chamber 53 with spring and an additional distributor 2/2 54

  closed in the normal position which is placed between said accumulation chamber and the pre-

  better actuation means 7 and 8. In the case of too high a braking pressure in the first actuation means 7 and 8, the control device 44 has improved, after having closed the normally open distributor 2/2 50 , opens at least a short time the 2/2 valve 54 normally closed so that pressure fluid flows at least

  partially actuating means 7 and 8 in the spring-loaded accumulation chamber 53.

- 10-

  The drop in braking pressure in the first braking means 7 and 8 eliminates a risk.

  that blocking. So that the spring-loaded accumulation chamber 53 can be drained after

  a braking action, this can be connected to the brake master cylinder 4 through the line

  main brake te 9 via a non-return valve 54. A more detailed description is not

  necessary here since the arrangement of 2/2 distributors 50 and 54 as well as the spring-loaded accumulation chamber 53 and the non-return valve 54 are part of the state of the art such

  that it is established by the documents DE-PS-1 555 600 and US-PS3,556,610.

  It can be seen that, thanks to the principle used, the braking installation for vehicles 2a according to FIG. 2 allows, at least by significant reductions in the braking pressure by bleeding the

* pressure fluid from the actuating means 7 and 8 to the accumulation chamber 53 to be

  goes out, to empty the brake master cylinder 4. In this case the braking circuit II will be arranged so that it is sufficiently efficient for a braking pressure in the

  actuation means 7 and 8 relatively low compared to the pressure in the master cylinder

  brake dre 4 is compensated by an increase in the braking pressure for the second braking means 24 and 25. For this one can arrange the control device 44a so that by a single opening or by multiple openings of the distributor 2/2 54, the actual values measured by the brake pressure sensors 30 and 31 are

  modified in the direction of a lowering of the signal level and that, when the risk of blocking

  cage is moved aside or when the braking slip is sufficiently reduced, higher braking pressures, corresponding to a pressure established in the brake master cylinder,

  are available in the second actuation means 24 and 25.

  If one wishes to avoid an arrangement of this type of the control device 44a and if one does not

  do not want to size the pump 38 and the pressure accumulator 41 for an insufficient pressure

  dependent so high, it is possible, in accordance with FIG. 3, to provide a braking installation 2b with independent energy in accordance with the invention with a return pump 54 in addition to the arrangement of the distributor 2/2 50. This then removes the accumulator chamber

  tion 53 with spring as well as the non-return valve shown in figure 2. The brake circuit

  ge I then comprises an ABS device called exhaustion, which device is known in principle and is widely used in various embodiments such as Bosch ABS2 and

Bosch ABS5.

  The front wheel brakes 5 and 6 of the "separate brake" type can for example be chosen in the state of the art. The specialist can choose between wheel brakes with first wheel brake cylinders and second wheel brake cylinders arranged in parallel with the first or with first wheel brake cylinders and second wheel brake cylinders combined in axial direction, for example according to American patents

3,750,857 and 3,752,273.

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Claims (10)

  1. Multi-circuit braking installation (2, 2a, 2b), in which the first circuit (I) comprises a single-circuit master cylinder (4) controlled by a brake pedal (3), brakes (5, 6) separate type front wheels connected to said circuit with first actuation means (7, 8) and second actuation means (24, 25), in which the circuit   braking system (Il) additional to the number of at least one comprises the second means of ac-   actuation (24, 25) of the front wheel brakes (5, 6) and additional actuation means (28, 29) for the rear wheel brakes 26, 27) which is equipped with a control device (44 , 44a, 44b), the control device (44, 44a, 44b) being connected to at least one sensor (13, 14) serving as a set point generator which is coupled at least indirectly to the brake pedal (3) or to the brake master cylinder (4) and is used to indirectly send energy taken from an energy source (15) into the second actuation means (24, 25) of the brakes (5 , 6) of front wheels and in the actuating means (28,   29) additional brakes (26, 27) rear wheels, characterized in that the   conds means for actuating (24, 25) the brakes (5, 6) of the front wheels and the means of action   nement (28, 29) of the brakes (26, 27) rear wheels are arranged in the form of hydraulic actuating means, by the fact that the power source (15) is arranged in the form of a source d hydraulic power with at least one supply tank (39) and a pump, in that at least one arrangement of valves (16, 17, 18, 19, 20, 21, 22, 23) which can be controlled by a control device (44, 44a, 44b) is arranged between the   energy source (15) and the second actuation means (24, 25) and the actuation means   ment (28, 29) additional, by the fact that wheel rotation detectors (46, 47, 48, 49) are associated with the wheels which can be braked using the brakes (5, 6) of front wheels and rear wheel brakes (26, 27), in that the control unit (44, 44a, 44b) is   connected to the wheel rotation detectors (44, 47, 48, 49) and is arranged to detect   ter the brake slip of braked wheels and to order at least one of the agencies-   valve parts (16, 17, 18, 19, 20, 21, 22, 23) to change the brake pressure in   at least one of the actuating means (24, 25, 28, 29) in the direction of limiting the sliding   braking and by the fact that a distributor (50) open in the normal position is disposed between the brake master cylinder (4) and the first actuation means (7, 8) supplied by the latter with brakes ( 5, 6) of front wheels, which distributor can be closed by the control device (44, 44a, 44b) when said control device (44, 44a, 44b) controls the   minus one of the valve arrangements (16 to 23) for the purpose of limiting braking slip.   2. Multiple circuit braking installation according to claim 1, characterized in that   that a bypass line (51) comprising a non-return valve (52) bypasses the dispenser   tor (50), the non-return valve (52) being able to open in the direction of the brake master cylinder (4). 3. A multi-circuit braking installation according to claim 1 or 2, characterized in that a distributor (54) closed in the normal position is connected to the first means   actuation (7, 8) of the brakes (5, 6) of the front wheels, by the fact that a storage chamber   tion (53) with spring can be connected indirectly to the first actuating means.   ment (7, 8) by this distributor (54) and by the fact that the spring storage chamber (53) is indirectly connected to the brake master cylinder (4) by a non-return valve (54)   which opens in the direction of said master cylinder.   -12 - 4. Multi-circuit braking installation according to claim 1, characterized in that a return pump (54) is mounted in the first braking circuit (I) connected to the   brake master cylinder (4), in the bypass line leading to the distributor (50), which   the pump delivers the liquid towards the brake master cylinder (4).   5. Multiple circuit braking installation according to claim 4, characterized in that the return pump (54) can be driven by a motor (40) driving the pump (30)   from the independent power source (15).   6. Multiple circuit braking installation according to claim 1, characterized in that   that at least one arrangement of valves (16 to 23) of the braking circuit (II) supplied by the source   this energy (15) is arranged in the form of a proportional distributor.   7. A multi-circuit braking installation according to claim 1, characterized in that the setpoint generator is arranged in the form of a pressure sensor of   brake master cylinder (4) connected to said brake master cylinder (4).   8. Multiple circuit braking installation according to claim 1 or 7, characterized in that there is provided a sensor (13) serving as a set point generator which is linked to the   less indirectly to the brake pedal (3) or to the brake master cylinder (4).   9. Multi-circuit braking installation according to claim 8, characterized in that   that the sensor is arranged in the form of a stroke sensor (13).   10. A multi-circuit braking installation according to claim 1, characterized in that, in order to regulate the sliding of the drive wheels braked with the wheel brakes (5, 6 or / and 26, 27), l control device (40, 40a, 40b) connected to the   rotation of wheels (46, 47, 48, 49) is arranged so as to detect the sliding of the drive   driving wheels based on signals from the wheel rotation detectors (46, 47, 48,   49) and to order at least one of the valve arrangements (16 to 23) to send energy   gie from the energy source (15) in at least one of the actuation means (24,, 28, 29) for the purpose of at least partially compensating the excess torque by a couple braking.