AU2006352370A1

AU2006352370A1 - Brake device especially for a utility vehicle

Info

Publication number: AU2006352370A1
Application number: AU2006352370A
Authority: AU
Inventors: Christian Rollin
Original assignee: Renault Trucks SAS
Current assignee: Renault Trucks SAS
Priority date: 2006-12-13
Filing date: 2006-12-13
Publication date: 2008-07-03
Anticipated expiration: 2026-12-13
Also published as: WO2008078006A1; AU2006352370B2; JP2010513110A; EP2620337A2; EP2121398A1; JP5191995B2; BRPI0622199A2

Description

WO 2008/078006 PCT/FR2006/002724 Brake device especially for a utility vehicle Technical field of the invention 5 The present invention relates to a braking device for a utility vehicle, particularly for a utility vehicle with multiple front and rear axles. Technical background 10 Conventionally, utility vehicles, notably trucks (what is generally meant by a truck is any motorized vehicle intended to carry or tow a load) are equipped with a braking system that operates using a pressurized fluid 15 which may be a hydraulic fluid but is usually a pneumatic fluid. As a safety precaution, any utility vehicle has two braking circuits. One braking circuit may operate the 20 brakes of the front axle or axles while the second braking circuit may operate the brakes of the rear axle or axles. Each braking circuit has its own compressed air reservoir and so if one of the circuits should fail, it still remains possible to brake the vehicle 25 using the braking circuit that remains intact. During homologation of a utility vehicle, a braking test may be carried out during which the front braking circuit is neutralized to simulate a failure. In order 30 to be issued with a homologation certificate, the truck has nonetheless to be able to retain a certain deceleration capability and in order for it to do so it is necessary that a braking capability be re established on the front axle of the vehicle. The rear 35 braking circuit alone is generally not sufficient to slow the vehicle.

WO 2008/078006 - 2 - PCT/FR2006/002724 Re-establishing braking capability in the front braking circuit may be done using a device like the one disclosed in document WO 2006/067283. 5 However, in the case of a multi-axle vehicle, particularly that of a vehicle that has several front axles, a device like the one disclosed in document WO 2006/06283 may prove unsuitable. In the case, for example, of site vehicles, there are generally two 10 front axles, but in the case of special vehicles or military vehicles, the number of front axles may exceed two. These front axles, which may also be steered, are each equipped with at least two pneumatic braking actuators which act on each of the two wheels of an 15 axle respectively. The braking actuator is the component which converts a fluidic signal - generally a pneumatic signal in utility vehicles - into a mechanical action on a braking means associated with a wheel, namely a disk or a drum. 20 It will be appreciated that, if the front braking circuit is deactivated, either as part of a homologation test or as the result of damage sustained during vehicle operation, it then becomes necessary to 25 regain substantial pneumatic power if sufficient braking capability to bring the vehicle to a halt is to be re-established. Indeed it is necessary to take the capability of the numerous pneumatic actuators into consideration. 30 It would therefore seem that managing the braking operation in a multi-axle vehicle in a defective mode involves special considerations that are not currently afforded sufficient weight. 35 Summary of the invention WO 2008/078006 - 3 - PCT/FR2006/002724 It is one object of the invention to propose a braking device for a utility vehicle with one or more front axles and one or more rear axles, an emergency function that allows a defective braking circuit to regain a 5 certain braking capability. It is another object of the invention to propose a braking device that has an emergency function the operation of which is reliable. 10 It is another object of the invention to propose a braking device with an emergency function the on-cost of which remains modest. 15 The subject of the invention is, essentially, a braking device particularly for a utility vehicle, comprising a first pneumatic braking circuit capable of acting on one or more first braking actuators of the vehicle and operating at a nominal pneumatic operating pressure and 20 a second pneumatic braking circuit capable of acting on one or more second braking actuators of the vehicle and operating under a nominal operating pressure; further, the braking device comprises means of connecting the second pneumatic braking circuit to the first pneumatic 25 braking circuit that prevent the passage of pneumatic fluid from the second circuit to the first circuit when the first braking circuit is operating at its nominal operating pressure and which allow the passage of pneumatic fluid from the second to the first braking 30 circuit when the first braking circuit is operating at a pressure below its nominal operating pressure. The invention thus proposes to make a permanent connection between the first braking circuit and the 35 second braking circuit and to use the pneumatic pressure of the second braking circuit to feed the first braking circuit in the event of pneumatic failure of the latter, that is to say in the event of a drop in WO 2008/078006 - 4 - PCT/FR2006/002724 pneumatic pressure in this circuit. Thus, the invention makes it possible to re-establish a braking capability that is significant, because it comes from another braking circuit, on the first braking actuator or 5 actuators which, as a result of the failure of the first braking circuit, would otherwise have no pneumatic braking resource. According to one advantageous embodiment, the braking 10 device comprises a distribution valve connecting the second braking circuit to the first braking circuit; said distribution valve has a first inlet connected to the first braking circuit, a second inlet connected to the second braking circuit, and an outlet connected to 15 a first control module for controlling the first braking circuit. The connection between the first braking circuit and the second braking circuit is put to good use in the 20 event of pneumatic failure of the first braking circuit which leads to a complete or partial drop in the pneumatic pressure in the first braking circuit; this drop in pressure in the first braking circuit is manifested by a switching of the distribution valve 25 which allows pneumatic pressure from the second braking circuit to feed the first braking module EBS. According to one possibility, the distribution valve may be a three-port two-position 3/2 directional 30 control valve having a first inlet connected to the first braking circuit, a second inlet connected to the second braking circuit and an outlet connected to the first control module and a spool which, in the rest position, shuts off the second inlet. 35 For preference, the directional control valve may be pneumatically operated and, when the pressure at the first inlet is above a threshold pressure, places said WO 2008/078006 - 5 - PCT/FR2006/002724 first inlet in communication with the outlet and, when the pressure at the first inlet is below a threshold pressure, places the second inlet in communication with the outlet. 5 According to another option, the distribution valve may be a double cutoff valve having a first inlet connected to the first braking circuit, a second inlet connected to the second braking circuit, an outlet connected to 10 said first control module and a shutter which moves between the first inlet and the second inlet so as to direct the air from that one of the inlets and that may be subject to the higher pressure toward the outlet; the device may further comprise, in series with the 15 distribution valve, means of offsetting the pressurizing of the two inlets of the double cutoff valve in favor of the first inlet connected to the first braking circuit. 20 Inserting a double cutoff valve between the first braking circuit and the second braking circuit allows these two circuits to be connected using a standard, inexpensive component the operation of which is reliable. Combined with the means for offsetting the 25 pneumatic pressure applied (i) to the first inlet of the double cutoff valve connected to the first braking circuit and (ii) to the second inlet of the double cutoff valve connected to the second braking circuit, the double cutoff valve allows there to be a permanent 30 pneumatic connection between the first braking circuit and the second braking circuit. According to one advantageous arrangement, the braking device according to the invention further comprises a 35 sectional valve positioned upstream of the distribution - valve and having an inlet connected to the second braking circuit and an outlet connected to the second inlet of the distribution valve, the sectional valve WO 2008/078006 - 6 - PCT/FR2006/002724 allowing fluid to pass between its inlet and its outlet when the pneumatic pressure in the second braking circuit exceeds a predetermined pressure equal to the cutoff pressure. 5 In practice, the function of offsetting the pneumatic pressure applied (i) to the inlet of the double cutoff valve connected to the first braking circuit and (ii) to the inlet of the double cutoff valve connected to 10 the second braking circuit may be performed by a sectional valve which, like the double cutoff valve, is a standard inexpensive component the operation of which is reliable. 15 In concrete terms, it is envisioned that the first braking circuit be a front braking circuit of a vehicle and that the second braking circuit be a rear braking circuit of this vehicle. This is because failure of the front braking circuit proves to be more critical than 20 failure of the rear braking circuit. In the case of a utility vehicle, the mass of the vehicle is very unevenly distributed and is mainly concentrated in the forward part of the vehicle. When such a vehicle is unladened, there is a substantial risk that the rear 25 axle assembly or assemblies will be unloaded such that any braking applied only to the rear axle assembly or axle assemblies could prove ineffective. For preference, the distribution valve and the 30 sectional valve are directly attached to the first control module. This arrangement makes it possible to set aside any potential damage that could be caused by any elements that may be interposed between the double cutoff valve or the sectional valve and the control 35 module. It may be envisioned for the first control module to be an electronified control module.

WO 2008/078006 - 7 - PCT/FR2006/002724 In practice, the first control module may be electrically operated. As a preference, the first control module may additionally comprise redundant 5 pneumatic operation and is known by the name of an electronic braking system EBS module. According to another aspect of the invention, the braking device comprises a first pneumatic operating 10 circuit capable of acting on the first control module and a second pneumatic operating circuit capable of acting on a second control module that controls the second braking circuit, the braking device comprising means of connecting the second pneumatic operating 15 circuit to the first pneumatic operating circuit that prevent pneumatic fluid from passing from the second operating circuit to the first operating circuit when the first operating circuit is at its nominal operating pressure and which allow pneumatic fluid to pass from 20 the second to the first operating circuit when the first operating circuit is operating at a pressure below its nominal operating pressure. In concrete terms, the device may comprise a 25 distribution valve connecting the second pneumatic operating circuit to the first pneumatic operating circuit, said valve having a second inlet connected to the second operating circuit, a first inlet connected to the first operating circuit, and an outlet connected 30 to the first control module. According to one option, the distribution valve is a double cutoff valve having a first inlet connected to the first pneumatic operating circuit, a second inlet 35 connected to the second pneumatic operating circuit, an outlet connected to an operating orifice of the first control module and a shutter which moves between the first inlet and the second inlet in such a way as to WO 2008/078006 - 8 - PCT/FR2006/002724 direct the air from that one of the inlets that is subjected to the higher pressure toward the outlet. According to another possibility, the distribution 5 valve may be a 3/2 directional control valve with three ports and two positions having a first inlet connected to the first pneumatic operating circuit, a second inlet connected to the second pneumatic operating circuit and an outlet connected to an operating port of 10 the first control module and a spool which, in the rest position, shuts off the second inlet. In one embodiment which, for example, may correspond to a conventional site vehicle, the- first braking circuit 15 may have at least four braking actuators capable of acting on at least two first axles, and the second braking circuit may have at least four actuators capable of acting on at least two second axles. 20 Brief description of the drawings To make it easier to understand, the invention is described with reference to the appended drawing which, by way of nonlimiting example, depicts a number of 25 embodiments of the utility vehicle braking device according to this invention. Figure 1 is a diagram depicting a braking device according to the prior art; 30 Figures 2 and 3 are diagrams depicting one embodiment of a braking device in a normal mode of operation and in a defective mode of operation, respectively; 35 Figures 4 and 5 are diagrams depicting another embodiment of a braking device in a normal mode of operation and in a defective mode of operation, respectively; WO 2008/078006 - 9 - PCT/FR2006/002724 Figures 6 and 7 are diagrams depicting another embodiment of a braking device in a normal mode of operation and in a defective mode of operation, 5 respectively. Detailed description of the invention Figure 1 schematically shows the design of a braking 10 device for a utility vehicle according to the prior art. The vehicle illustrated has four axles divided into two front axles and two rear axles; the multitude of axles, particularly at the front of a vehicle, presents a particular set of problems in the event of 15 the failure of a braking circuit and more particularly of the front braking circuit. In general, the braking of a utility vehicle, for example a truck carrying a load or towing a load, is 20 provided pneumatically. To do this, as can be seen in figure 1, there is an air compressor 2 which supplies an air directional control valve 3. The function of the air directional control valve 3 is to filter and regulate the pressure of the air from the air 25 compressor 2. Downstream of the air directional control valve 3 there may be two reservoirs 4, 5 which feed respectively into (i) a first, front pneumatic braking circuit 6 intended 30 to supply the braking energy to the front axles and (ii) a rear pneumatic braking circuit 7 intended to supply the braking energy to the rear axles. The front braking circuit 6 is connected to four 35 braking actuators 8a, 8b and 9a, 9b which convert the pneumatic energy into a mechanical action on a means of braking a wheel, that is to say a disk or drum as the WO 2008/078006 - 10 - PCT/FR2006/002724 case may be. The braking means have not been depicted in the figures because their features are widely known. Symmetrically, the rear braking circuit 7 is connected 5 to four braking actuators 10a, 10b and 11a, 11b which convert the pneumatic energy into a mechanical action on a wheel braking means, that is to say a disk or a drum as the case may be. The braking means have not been depicted in the figures because their features are 10 widely known. In the usual way, the rear brake actuators 10a, 10b and 11a, 11b which incorporate the parking brake function may have springs 12a, 12b and 13a, 13b which keep the braking means applied, the pneumatic pressure coming to release the - said braking 15 means as the vehicle drives along. The pneumatic pressure applied to the front actuators 8a, 8b and 9a, 9b and rear actuators 10a, 10b and 11a, 11b is fixed by, respectively, a front control module 20 which may be a front electronic braking system EBS 15 and a rear control module which may be a rear electronic braking system EBS 16, which fix the datum value for the pneumatic pressure to be applied to the front actuators 8a, 8b and 9a, 9b and to the rear 25 braking actuators 10a, 10b and 11a, 11b under braking. Schematically, the electronic braking system EBS sets the datum value to be applied to a braking actuator on the basis of the demand for braking by the driver by incorporating one or more parameters control of which 30 may be stored in an electronic control unit ECU not depicted in the drawing; these parameters may, nonlimitingly, include the grip or the speed or an unloading of a wheel, the angle of turn of a steered wheel, a distribution factor relating to the braking 35 split to be applied to a towing vehicle and to a trailer, etc.

WO 2008/078006 - 11 - PCT/FR2006/002724 Braking is initiated by a driver of the vehicle who, generally using his foot, depresses a pedal 18 of an operating device 19. In the normal mode of operation of the vehicle, the front 15 and rear 16 electronic 5 braking systems EBS are controlled by an electrical signal (possibly weighted by one or more of the aforementioned parameters) which is proportional to the travel applied to the pedal 18. Electric wire connections which have not been depicted in the drawing 10 may provide the connection between the control device 19 and each. of the front 15 and rear 16 electronic braking systems EBS. In the event of an electrical failure, a pneumatic 15 control system may take over in order to provide control of the front 15 and rear 16 electronic systems EBS. Depending on the travel applied to the pedal 18, a pneumatic signal is transmitted via a front pneumatic operating circuit 20 to the front electronic braking 20 system EBS 15 in order to set a datum value to be applied to the four front braking actuators 8a, 8b and 9a, 9b and a pneumatic signal is transmitted through a rear pneumatic operating circuit 21 to the rear electronic braking system EBS 16 to set a datum value 25 to be applied to the four rear braking actuators 10a, 10b and 11a, 11b. The front 20 and rear 21 pneumatic operating circuits, by convention, have been depicted in broken line while 30 the pneumatic power circuits, namely the front braking circuit 6 and the rear braking circuit 7 have, by convention, been depicted in continuous line. It can therefore be seen that failure of one of the 35 front 6 or rear 7 braking circuits results in a complete loss of braking on the axles concerned. In the case of a multiple-axle vehicle, given the number of braking actuators, it is appropriate to re-establish a WO 2008/078006 - 12 - PCT/PR2006/002724 significant amount of pneumatic energy in order to allow these actuators, of which there are at least four, to act to good effect on the braking means of the disk or drum type. 5 In one embodiment of the invention which has been schematically represented in figure 2 it can be seen that a first braking circuit (in this instance the front braking circuit 6) is pneumatically connected to 10 the second braking circuit (in this instance the rear braking circuit 7). Connection between the front 6 and rear 7 braking circuits may be by way of two standard components, 15 namely a sectional valve 23 positioned in series with a double cutoff valve 24. In practice, it is envisioned that a tapping be made on the rear braking circuit 7 and that the inlet of the 20 sectional valve 23 be connected to the rear braking circuit 7. Functionally, the sectional valve 23 behaves like a shutter the operation of which is automatic; the sectional valve 23 is open and therefore allows fluid to pass in the downstream direction if the pressure 25 applied upstream at its inlet cannot be sustained at a sufficiently high predetermined level. In concrete terms, the sectional valve 23 may have a flexible diaphragm pressed against the seat; the diaphragm is kept pressed against a seat under the action of a 30 spring the tension of which can be adjusted by an adjusting screw. The sectional valve therefore allows a pneumatic circuit to be fed when the pressure upstream of the valve has at least reached a so-called cutoff pressure that corresponds to the pressure needed to 35 oppose the action of the spring. When the set opening pressure is exceeded, it lifts the diaphragm off its seat and against the force exerted by the spring. The sectional valve is then open and the air is directed WO 2008/078006 - 13 - PCT/FR2006/002724 towards the downstream circuit. As soon as this condition is no longer met, the spring pushes the diaphragm back against its seat, which causes the diaphragm to close and prevents the pressures in the 5 upstream and downstream circuits from equalizing. The double cutoff valve 24 is a pneumatic component which has a first inlet 25 and a second inlet 26 and an outlet 27 together with a shutter 29 which moves 10 between the first and second inlets 25 and 26 and shuts off the inlet that is at the lower pressure. As figure 2 shows, the double cutoff valve 24 provides the connection between the front braking circuit 6 and 15 the rear braking circuit 7 because the inlet 26 of the double cutoff valve 24 is connected to the outlet of the sectional valve 23 and the inlet 25 of the double cutoff valve 24 is connected to the front braking circuit 6. The outlet 27 of the double cutoff valve 24 20 goes to the front electronic braking system EBS 15. In concrete terms, the sectional valve 23 and the double cutoff valve 24 are directly fixed to the front electronic braking system EBS 15. The sectional valve 25 23 and the double cutoff valve 24 form part of an emergency system and it is therefore important that no element liable in itself to experience a malfunction or a failure be interposed between the sectional valve 23 or the double cutoff valve 24 and the front electronic 30 braking system EBS 15. The braking circuit 1, when in a normal mode of operation illustrated in figure 2, operates with a front braking circuit 6 and a rear braking circuit 7 35 which act independently of one another. Action on the control device 11 results in braking by the four front actuators 8a, 8b and 9a, 9b and braking by the four rear actuators 10a, 10b and 11a, 11b.

WO 2008/078006 - 14 - PCT/FR2006/002724 It is important to emphasize that, when the vehicle starts, as the pneumatic pressure in the front 6 and rear 7 braking circuits increases to a nominal 5 operating pressure, the sectional valve 23 provides control over the position of the shutter 29 of the double cutoff valve 24. Under normal operating conditions of the braking device 10 1, in order to ensure the independence of the front 6 and rear 7 braking circuits from one another so that each of the front 6 and rear 7 braking circuits operates independently, it is important for the shutter 29 of the double cutoff valve 24 to shut off the second 15 inlet 26 thereof which is connected to the rear braking circuit 7. In the exemplary embodiment illustrated, this function is assigned to the sectional valve 23; the increase in 20 pressure occurs simultaneously in the front braking circuit 6 and in the rear braking circuit 7; however, at the double cutoff valve 24, there is an offset observed in the application of nominal pneumatic pressure to the first inlet 25 of the double cutoff 25 valve 24 that is connected to the front braking circuit 6 by comparison with the application of the pneumatic pressure to the second inlet 26 of the double cutoff valve 24 connected to the rear braking circuit 7. This offset, which is important for correct operation of the 30 braking device 1, is achieved, in the example illustrated, by the sectional valve 23 which allows fluid to pass only when a pneumatic pressure that exceeds a predetermined value is applied to its inlet. The action of the sectional valve 23 means that as the 35 pneumatic pressure in the front 6 and rear 7 braking circuits increases, the shutter 29 of the double cutoff valve 24 is immediately subjected to a pneumatic pressure from the second inlet 25 of the double cutoff WO 2008/078006 - 15 - PCT/FR2006/002724 valve 24 connected to the front circuit 6 and therefore positions itself in the position in which the shutter 29 shuts off the second inlet 26 of the double cutoff valve 24 which is connected to the rear circuit 7. In 5 this mode of operation which corresponds to the normal mode of operation of the braking device 1, the front braking circuit 6 and the rear braking circuit 7 are permanently connected but the sectional valve 23 defines an order of priority in the application of the 10 pneumatic pressures which are applied to each of the inlets 25 and 26 of the double cutoff valve 24 so as to control the position of the shutter 29 thereof. It, m'ay be emphasized that the sectional valve 23 has 15 the additional function of isolating the front braking circuit 6 from the rear braking circuit 7 in the event of a partial or total loss of pneumatic pressure in the rear braking circuit 7. In this particular instance, the sectional valve 23 cannot allow fluid to pass 20 because, by construction, it prevents fluid from passing toward the front braking circuit 6 if the pressure in the rear braking circuit 7 is not kept at a sufficiently high predetermined level. 25 In the event of pneumatic failure of the front braking circuit 6, which represents the scenario that it is the most critical to manage, the braking device 1 in its embodiment depicted allows significant pneumatic braking power to be re-established on the two front 30 axles. Pneumatic failure of the front braking circuit means that no pneumatic pressure either for powering or for operating the front braking circuit reaches the front 35 electronic braking system EBS 15. This state of the braking device 1 in which the front braking circuit 6 is inoperative is depicted in figure WO 2008/078006 - 16 - PCT/FR2006/002724 3 where, to illustrate this state, the front braking circuit 6 and the front pneumatic operating circuit have been partially effaced. 5 The consequence of a partial or complete drop in pressure below the nominal braking pressure in the front braking circuit 6, causes the shutter 29 of the double cutoff valve 24 to move toward the inlet 26 of the double cutoff valve 24 which is connected to the 10 front braking circuit 6. The front braking system EBS 15 is then pneumatically supplied via the rear braking circuit 7; significant braking capability is therefore re-established on the four front braking actuators 8a, 8b and 9a, 9b. By way of example, if the nominal 15 pneumatic pressure of the rear braking circuit is of the order of 12 to 14 bar, the emergency pneumatic pressure that can be transferred to the four front actuators 8a, 8b and 9a, 9b is of the order of 6 to 7 bar, allowing significant deceleration. 20 Figures 4 and 5 illustrate another form of embodiment of the invention which offers an additional degree of incorporation of pneumatic and electrical problems. Specifically, as can be seen from these figures, 25 provision is made for the front braking circuit 6 to be connected to the rear braking circuit 7 in arrangements similar to those described in figures 2 and 3 but provision is also made for the front pneumatic operating circuit 20 to be connected to the rear 30 pneumatic operating circuit 21. In the embodiment shown in figures 4 and 5, it is envisioned for the way in which the front and rear braking circuits are connected to be applied also to the front and rear pneumatic operating circuits. 35 The connecting of the front 20 and rear 21 pneumatic operating circuits may be assigned to a double cutoff valve 30. This double cutoff valve 30 has a first inlet WO 2008/078006 - 17 - PCT/FR2006/002724 31 which is connected to the front pneumatic operating circuit 20, a second inlet 32 which is connected to the rear pneumatic operating circuit 21, and an outlet 33 which is connected to a front control module which may 5 be a front electronic braking system EBS 15; the double cutoff valve 30 incorporates a shutter 34 which moves between the first and second inlet 31 and 32 according to the pressure applied to each of the two inlets in the knowledge that the shutter 30 allows pressurized 10 air from that one of the first and second inlets 31 and 32 which is at the higher pressure to pass. Provision may be made for a sectional valve to be positioned in series with the double cutoff valve 30. 15 During normal operation of the braking device as shown in figure 4, the front braking circuit 6 acts independently of the rear braking circuit 7 as was explained hereinabove and the front pneumatic operating circuit 20 acts independently of the rear pneumatic 20 operating circuit 21. Specifically, during normal operation of the braking device, the shutter 34 of the double cutoff valve 30 is pressed against the second inlet 32; the shutter 32 is placed in this position as the pneumatic pressure in the front and rear pneumatic 25 operating circuits 20 and 21 increases. Priority is given to the front pneumatic operating circuit 20 over the rear pneumatic operating circuit 22 in terms of the order in which the pneumatic pressures are applied to the shutter 34 of the double cutoff valve 30 from the 30 first inlet 30 and from the second inlet 32. A sectional valve may make it possible to produce an offset in the application of the pneumatic pressure to the first inlet 31 and to the second inlet 32 respectively in the double cutoff valve 30; it may also 35 be envisioned for the nominal pressure of the front pneumatic operating circuit 20 to be slightly higher than the nominal pressure of the rear pneumatic WO 2008/078006 - 18 - PCT/FR2006/002724 operating circuit 21 in order to observe the order of priority on the double cutoff valve 30. It may be recalled that the front and rear pneumatic 5 operating circuits 20 and 21 pneumatically control the front and rear electronic braking systems 15 and 16 in redundancy with electrical control circuits of the electronic braking systems EBS. The front and rear pneumatic operating circuits 20 and 21 have the 10 function of taking over in the event of an electrical failure that renders the electrical control circuits inoperative. Figure 5 shows how the braking device behaves in the 15 event of an electrical problem and in the event of a problem with the pneumatic supply to the front portion of the vehicle which is manifested in the fact that the front braking circuit 6 and the front pneumatic operating circuit 20 become inoperative; to illustrate 20 this problem, the front braking circuit 6 and the front pneumatic operating circuit 20 do not feature in figure 5. As far as the emergency supply of compressed air for 25 power is concerned, the front electronic braking system EBS 15 is supplied by the rear braking circuit 7 according to the principle explained hereinabove in relation to figure 3. 30 As far as the emergency supply of compressed air for operation is concerned, the front electronic braking system EBS 15 is supplied by the rear operating circuit 21. In the event of a partial or complete drop in pressure in the front pneumatic operating circuit 20, 35 the first inlet 31 finds itself at a pressure lower than the pressure applied at the second inlet 32 of the double cutoff valve 30; as a result, the shutter 34 positions itself against the first inlet 31. The double WO 2008/078006 - 19 - PCT/FR2006/002724 cutoff valve 30 therefore directs the flow of compressed air toward the front electronic braking system EBS 15 operating port. 5 It would therefore appear that the invention makes it possible to re-establish all the pneumatic power and operating functions on the front braking actuator or actuators. 10 It may be added that the invention may find an application on a vehicle equipped with a conventional braking system, that is to say a vehicle that has no electronic braking systems EBS. 15 As figure 6 demonstrates, in a conventional configuration, there may be a front braking circuit 6 which supplies compressed air as a power to several front braking actuators 8a, 8b, 9a, 9b; the front braking circuit 6 incorporates a front control module 20 which may, for example, be a relay valve 38 which controls the pressure to be applied to the front braking actuators 8a, 8b, 9a, 9b as a function of a control pressure delivered by the control device 19 which, in this instance, may be a pneumatic operated 25 valve. A front pneumatic operating circuit 20 connects the control device 19 to an operating port of the relay valve 38. For the rear part of the vehicle, there is a rear 30 braking circuit 7 which supplies compressed air for power to several rear braking actuators 10a, 10b, 11a, 11b; the rear braking circuit 7 incorporates a rear control module which may, for example, be a brake regulator 39 or an apportioner which controls and 35 possibly corrects on the basis of certain parameters, the pressure that has to be applied to the rear brake actuators 10a, 10b, 11a, 11b. A pneumatic rear operating circuit 21 connects the control device 19 to WO 2008/078006 - 20 - PCT/FR2006/002724 an operating port of the regulator 39; as a safety precaution, the pneumatic operating circuit is additionally connected to an operating port of the relay valve 38. 5 The braking device shown in figure 6 differs from those shown in figures 2 and 4 in that the front and rear control modules are, in the case of the device of figure 6, exclusively pneumatically controlled whereas, 10 in the case of the devices of figures 2 and 4, the control modules are electronically operated and, redundantly, pneumatically operated also. In normal operation, the braking device shown in figure 15 6 behaves as if the front braking circuit 6 were independent of the rear braking circuit 7. The front braking circuit 6 is connected to the rear braking circuit 7 by a double cutoff valve 24 in series with which there may be a sectional valve 23 just as in the 20 implementation of the invention illustrated by figures 2 and 4. Thus, there is an offset in the pressurizing of the first and second inlets 25 and 26 of the double cutoff valve 24 with priority accorded to the pressurizing of the first inlet 25 such that the 25 shutter 29 shuts off the second inlet of the double cutoff valve 24. In the event of a problem with the pneumatic supply of power and operation of the front part of the vehicle, 30 something which is illustrated in figure 7 by the absence of a front braking circuit 6 and of the front pneumatic operating circuit 20, the double cutoff valve 24 places the rear braking circuit 7 in communication with the front braking circuit 6. The shutter 29 comes 35 to press against the first inlet 26 of the double cutoff valve 24 and this makes it possible, in an emergency mode of operation, to supply compressed air for power to the front braking actuators 8a, 8b, 9a, WO 2008/078006 - 21 - PCT/FR2006/002724 9b. Operation of the relay valve 38 is achieved through the rear pneumatic operating circuit 21 which is connected to an operating port of the relay valve 38. 5 The invention notably makes it possible to offer a braking device which is particularly well suited to managing malfunctions of a braking circuit or a vehicle that has multiple front and rear axles. 10 Of course, the invention is not restricted to the embodiment described hereinabove but on the contrary encompasses all alternative forms of embodiment thereof. The invention could notably be implemented in the context of a hydraulic braking device. 15 It is emphasized that the invention can be implemented via a system which takes account of the management of a failure of the rear braking circuit; for that, the orientation of the sectional valve 23 and of the double 20 cutoff valve 24 would have to be reversed with respect to the way in which they are oriented in the exemplary embodiment shown in figures 2 and 3. The invention could equally be implemented in the 25 context of a symmetric system, that is to say of a system capable of taking account of a failure on the front braking circuit or on the rear braking circuit. For that, the arrangements (double cutoff valve 24 and sectional valve 23) found in the exemplary embodiment 30 of figure 2 and which relate to the front braking circuit could be found symmetrically in the rear braking circuit. It may equally be envisioned for the arrangements of 35 the present invention to be transposed onto a vehicle the two braking circuits of which are not divided into a front circuit and a rear circuit but to a vehicle that has two braking circuits employing an X-split, WO 2008/078006 - 22 - PCT/FR2006/002724 namely a first braking circuit that acts on one or more braking actuators situated front right and on one or more rear left braking actuators, and a second braking circuit acting on one or more braking actuators 5 situated front left and on one or more rear right braking actuators. It may also be envisioned for the connection between the front braking circuit 6 and the rear braking 10 circuit 7 to be achieved via a 3/2 pneumatic directional control valve with a- spool used as a circuit selector. In this possible implementation of the invention, the front braking circuit 6 and the rear braking circuit 7 are respectively connected to a first 15 inlet and to a second inlet of the directional control valve whereas the outlet from the directional control valve is connected to a front control module of the electronic and/or pneumatic type. In the normal mode of operation of the braking device, the spool of the 20 directional control valve is positioned in such a way as to shut off the inlet connected to the rear braking circuit; the directional control valve is therefore open from the front braking circuit to the front control module. 25 In the emergency mode of operation, the spool of the directional control valve pivots to shut off the inlet connected to the front braking circuit such that the front control module is fed via the rear braking 30 circuit. Operation of the 3/2 directional control valve may preferably be pneumatic operation; provision may also be made for the directional control valve to be operated using the compressed air from the front braking circuit which keeps the spool in its position 35 in which it shuts off the inlet connected to the rear braking circuit. In the event of a partial or complete drop in pressure of the front braking circuit, the spool pivots, thus placing the inlet of the spool WO 2008/078006 - 23 - PCT/FR2006/002724 connected to the rear braking circuit in communication with the outlet from the directional control valve.

Claims

1. A braking device (1) particularly for a utility vehicle, comprising a first pneumatic braking circuit 5 capable of acting on one or more first braking actuators of the vehicle and operating at a nominal pneumatic operating pressure and a second pneumatic braking circuit capable of acting on one or more second braking actuators of the vehicle and operating under a 10 nominal operating pressure, characterized in that the braking device comprises means of connecting the second pneumatic braking circuit to the first pneumatic braking circuit that prevent the passage of pneumatic flfid from the second braking circuit to the first 15 braking circuit when the first braking circuit is operating at its nominal operating pressure and which allow the passage of pneumatic fluid from the second to the first braking circuit when the first braking circuit is operating at a pressure below its nominal 20 operating pressure.

2. The braking device as claimed in claim 1, characterized in that it comprises a distribution valve connecting the second braking circuit to the first 25 braking circuit, said distribution valve having a first inlet connected to the first braking circuit, a second inlet connected to the second braking circuit, and an outlet connected to a first control module (15) for controlling the first braking circuit. 30

3. The braking device as claimed in claim 2, characterized in that the distribution valve is a three-port two-position directional control valve having a first inlet connected to the first braking 35 circuit, a second inlet connected to the second braking circuit and an outlet connected to the first control module and a spool which, in the rest position, shuts off the second inlet. WO 2008/078006 - 25 - PCT/FR2006/002724

4. The braking device as claimed in claim 3, characterized in that the directional control valve is pneumatically operated and, when the pressure at the 5 first inlet (26) is above a threshold pressure, places said first inlet (26) in communication with the outlet (27) and, when the pressure at the first inlet (26) is below a threshold pressure, places the second inlet (26) in communication with the outlet (27). 10

5. The braking device as claimed in claim 2 or claim 3, characterized in that the distribution valve has a double cutoff valve (24) having a first inlet (26) connected to the. first braking circuit, a second inlet 15 connected to the second braking circuit, an outlet (27) connected to said first control module and a shutter (29) which moves between the first inlet (26) and the second inlet (25) so as to direct the air and that one of the inlets (25) and (26) that is subject to the 20 higher pressure toward the outlet (27) and, in series with the double cutoff valve, means of offsetting the pressurizing of the two inlets of the double cutoff valve in favor of the first inlet connected to the first braking circuit. 25

6. The braking device as claimed in one of claims 2 to 5, characterized in that it comprises a sectional valve (23) positioned upstream of the distribution valve and having an inlet connected to the second 30 braking circuit and an outlet connected to the second inlet (25) of the distribution valve, the sectional valve allowing fluid to pass between its inlet and its outlet when the pneumatic pressure in the second braking circuit exceeds a predetermined pressure equal 35 to the cutoff pressure.

7. The braking device as claimed in one of claims 1 to 6, characterized in that the first braking circuit WO 2008/078006 - 26 - PCT/FR2006/002724 is a front braking circuit (6) of a vehicle and the second braking circuit is a rear braking circuit (7) of said vehicle. 5

8. The braking device as claimed in claim 6 or claim 7, characterized in that the distribution valve and the sectional valve (23) are directly attached to the first control module (15). 10

9. The braking device as claimed in one of claims 2 to 8, characterized in that the first control module is an electronified control module.

10. The braking device as. claimed in claim 9, 15 characterized in that the first control module is electrically operated.

11. The braking device as claimed in claim 9 or claim 10, characterized in that the first control module has 20 redundant pneumatic operation.

12. A braking device, characterized in that it comprises a first pneumatic operating circuit (20) capable of acting on the first control module and a 25 second pneumatic operating circuit (21) capable of acting on a second control module that controls the second braking circuit, the braking device comprising means of connecting the second pneumatic operating circuit to the first pneumatic operating circuit that 30 prevent pneumatic fluid from passing from the second operating circuit to the first operating circuit when the first operating circuit is operating correctly and which allow pneumatic fluid to pass from the second to the first operating circuit when the first operating 35 circuit is defective.

13. The braking device as claimed in claim 12, characterized in that it comprises a distribution valve WO 2008/078006 - 27 - PCT/FR2006/002724 connecting the second pneumatic operating circuit (21) to the first pneumatic operating circuit (20), said valve having a second inlet connected to the second operating circuit, a first inlet connected to the first 5 operating circuit, and an outlet connected to the first control module (15).

14. The braking device as claimed in claim 13, characterized in that the distribution valve is a 10 double cutoff valve (30) having a first inlet (31) connected to the first pneumatic operating circuit (20), a second inlet (32) connected to the second pneumatic operating circuit (21), an outlet (33) connected to said first control module and a shutter 15 (34) which moves between the first inlet (31) and the second inlet (32) in such a way as to direct the air from that one of the inlets (31) and (32) that is subjected to the higher pressure toward the outlet (33). 20

15. The braking device as claimed in claim 14, characterized in that the distribution valve is a 3/2 directional control valve. 25

16. The braking device as claimed in one of claims 1 to 15, characterized in that the first braking circuit has at least four braking actuators (8a, 8b, 9a, 9b) capable of acting on at least two first axles, and the second braking circuit has at least four actuators 30 (10a, 10b, Ila, 1ib) capable of acting on at least two second axles.