FR2839693A1 - BRAKING DEVICE OF AN INDUSTRIAL VEHICLE AXLE - Google Patents

Abstract

Braking device for an industrial vehicle axle, comprising: - a brake circuit (1) specific to the axle, including a pneumatic compressed air tank (2), a braking control system (3) and brake actuators (4), - an electronic control unit (6), regulating the supply of the pneumatic tank (2) from a source of compressed air (5), characterized in that l the control-command unit (6) is capable of regulating the pneumatic reservoir with compressed air according to a variable setpoint as a function of information produced within the control-command unit, said setpoint being variable between two thresholds, namely a high threshold corresponding to a nominal pressure value, and a low threshold making it possible to limit the pneumatic energy available at the level of the braking circuit considered.

Description

disengaged. BRAKING DEVICE OF AN INDUSTRIAL VEHICLE AXLE Domain

  The invention relates to the field of the industrial vehicle industry, the braking of which uses pneumatic means. The invention relates more particularly to a braking device equipping this type of vehicle, and which provides an improvement in driving safety, in particular with regard to stability problems observed in certain circumstances, during braking.

strongly brands.

  Previous techniques: Generally, trucks or more generally industrial vehicles have a braking system which uses pneumatic energy. The braking system of the towing vehicle is decoupled from the trailer braking system, which operates almost autonomously. Within the towing vehicle, the braking system is itself separated axle by axle, in order to increase

  the ability and braking ability.

  The braking device of the motor vehicle therefore comprises a braking circuit specific to each axle. Each braking circuit has a pneumatic compressed air reservoir, acting as a pneumatic energy source, to which is connected a braking control circuit associated with brake actuators. Generally, industrial vehicles include one or more electronic control control units. Among these, one may be more particularly dedicated to the management of braking and associated functions. Among these functions, one of the control units ensures the regulation of the supply of pneumatic tanks from a source of compressed air,

  which is generally a pneumatic compressor.

  However, it has been observed that the braking systems could cause certain undesired phenomena, depending on the configuration of the vehicle, or on the correct operating capacity of certain devices ideally designed for

increase security.

  s Thus, many vehicles are fitted with anti-lock braking systems (ABS) whose objective is to take advantage of the best grip conditions

  by acting on the braking actuators as soon as a wheel cage is established.

  When these ABS systems are integrated into a traditional brake system, there is a problem when a failure of the ABS system occurs. In fact, in this case, the forces exerted on the axles can be such that the wheels lock, with the associated consequences. If it is the rear axle of the towing vehicle, it is frequent to observe in this case a crossing across the trailer, commonly called "wallet". These phenomena appear when the anti-lock braking function is inoperative. This ABS function can be provided by an independent module, associated with the actuators of the braking circuit, or even by a specific command and control unit, ensuring overall management of the braking, device

  also known as the Electronic Braking System (EBS).

  In the latter case, the braking management is globalized, which simplifies the braking operation, in normal mode, when the set of devices interacting with the EBS, or the EBS itself, is operational. However, a problem arises when this overall management system is no longer able to provide all of the functions, for example because it is partially faulty, or it cannot receive the information necessary for its good functioning, due to faulty sensors. In other words, the functioning of this type of globalized system is complex in degraded mode, since the braking circuit must then be duplicated by an emergency braking circuit which, although

  Obviously, the overall braking circuit becomes more complex and the cost increases.

  A problem which the invention proposes to solve is that of enabling management of degraded modes of the various devices ensuring braking safety, without complicating the braking circuit itself, while ensuring

  the same level of security as existing systems.

  s In addition, there are also certain problems during braking, when the towed load is particularly low, or even when the towing vehicle is operating alone, and without a trailer. In fact, the application of a very strong braking force at the level of the front axle of the towing vehicle can cause the latter to tilt forwards, with the risk of lifting the rear wheels of the towing vehicle, and adverse consequences with regard to handling, in particular. This is why braking systems include

  generally a correction mechanism taking into account the load of the vehicle.

  These correction mechanisms can be implemented on conventional braking systems, and take the form of reduction valves which are generally installed in the control circuit of the front axle. These valves reduce the braking forces applied to the front axle

  when the vehicle is lightly loaded, or even in the form of a tractor-

  alone. The use of these additional valves complicates the braking circuit, all the more since it is necessary that these valves are controlled in a way

  appropriate, by a specific control circuit.

  It has also been proposed to provide braking correction as a function of the load by integrating it into account in global braking systems of the EBS type as mentioned above. The same drawbacks are observed with regard to the management of the degraded modes of these global EBS type managements, since it is necessary to double the main braking control circuit by

  an auxiliary brake control circuit.

  Another problem which the invention proposes to solve is that of ensuring; a correction of the braking force as a function of the load of the vehicle, and by extension to the particular case where the tractor operates alone .; Disclosure of the Invention: The invention therefore relates to a pneumatic braking device for an axle of an industrial vehicle. In known manner, such a device comprises a brake system specific to the axle, including a pneumatic compressed air reservoir, a brake control system and brake actuators. This device also includes an electronic control unit ensuring the regulation of the supply of the pneumatic reservoir from a source of compressed air. In accordance with the invention, this device is characterized in that the command control unit is capable of regulating the compressed air of the pneumatic reservoir according to a variable set point as a function of information developed within the command control unit. , this setpoint being variable between two thresholds, namely a high threshold corresponding to a nominal pressure value, and a teas threshold, making it possible to limit the pneumatic energy available at the level of the

  deinage circuit considered in certain circumstances.

  In other words, the invention consists in reducing the pressure prevailing within the reservoir of the braking circuit when the configuration of the vehicle is such that it is preferable to reduce the braking force to be applied to the axle in question. The device according to the invention therefore does not act in a specific way on the brake actuators, but more generally on the braking circuit by limiting the quantity of energy available by reducing the pressure of the compressed air. . This solution has the advantage of not requiring additional components to complicate the braking circuit, since the air pressure can be regulated with the components used to ensure the

regulation at nominal level.

  In practice, the information produced by the control unit, and which determines the use of either the nominal threshold or the teas threshold, can be representative either of the vehicle load or of the presence of the trailer or the tractor operation alone, or even reflect the

  correct or faulty operation of the anti-lock braking system.

  In practice, the specific braking of the front axle will be ensured, taking into account, first of all, the information representing the load of the vehicle, and by extension the presence of a trailer. This management can also take into account independently, the fact that the anti-blocking system of

  wheels may be faulty at the front axle.

  Similarly, the rear axle braking management can take into account in the first place the information that the anti-lock braking system is faulty, to reduce the pressure in the rear braking circuit, and thus limit the risks of "portfolio". The load information on the rear axle can also be taken into account in a

optimization goal.

  In practice, different strategies can be considered to determine the set value applied to the pressure regulation system in the pneumatic tank. Thus, the set values can adopt only two values, corresponding to the high and teas thresholds. However, it is possible that this setpoint also adopts discrete intermediate values between these two thresholds, or even be continuously variable between these two thresholds, in particular when

  this setpoint depends on the value of the load.

  In a particular embodiment, the pneumatic compressed air reservoir can be supplied by means of a valve, which is itself controlled by the control unit. This valve is suitable, as the case may be, for supplying either the reservoir from the source of compressed air, or the partial emptying of said reservoir. This valve can advantageously be incorporated into a global compressed air distribution system disposed at the outlet of the

  air compressor driven by the engine.

  This or these valves can also be integrated into a circuit

supply exist.

Brief description of the hours

  The way of carrying out the invention as well as the advantages which flow from it

  will emerge clearly from the description of the embodiment which follows, in support of

  attached figures in which: - Figure 1 is a block diagram illustrating the pneumatic braking device of an axle, - Figure 2 is a curve illustrating the variation of the pressure setpoint

  in the pneumatic tank depending on the vehicle load.

  Method of carrying out the invention Figure 1 illustrates an example of architecture of a braking device according to the invention in which the actual braking circuit (1) is observed comprising a compressed air reservoir (2) supplying a braking control system (3) acting on braking actuators (4) mechanically cooperating with the axle to be braked (not shown). The reservoir (2) is supplied with compressed air from a source of compressed air which can typically be a compressor (5). This supply takes place through a valve (10) whose r81e will be explained further. The braking device also comprises a control control unit (6) itself interfaced with a communication bus (7) allowing it to communicate with other control control units or computers, or generally with other systems present.

on the vehicle.

  This control unit (6) receives information from a pressure sensor (11) for determining the pressure prevailing inside

of the tank (2).

  Depending on this pressure, the control unit can regulate the supply of compressed air to the reservoir (2) from the

compressor (5).

  In accordance with the invention, this regulation is carried out with respect to a set point which may vary as a function of different information relating to the

  operation of certain organs or devices present on the vehicle.

  Among this information, there may be mentioned in particular an indicator of the correct functioning of the anti-lock system (8) of the wheels which can, for example, be connected by a wire connection (9) to the control unit (6). Additional information, such as in particular from the vehicle load sensor,

  can kansiter via the bus (7) from other computers.

  1S As evoked, the invention can be applied to the regulation of the device

  braking of the front axle or the rear axle of the vehicle.

  Thus, in the case where it is a question of regulating the braking of the front axle, the set pressure of the reservoir can be managed as illustrated in FIG. 2, depending on the load of the vehicle. More precisely, beyond a certain axle load (C2), the setpoint pressure can be chosen at a nominal value, of the order of 10 to 12 bars. This pressure makes it possible to obtain a reserve of sufficient energy to ensure effective braking of the vehicle, when the load is relatively large, and the braking forces must therefore be sustained,

and relatively high.

  Conversely, when the load is low, typically below a certain threshold (C1), the pressure setpoint can be set at a low value, or safety pressure, and typically of the order of 2 to 5 bars. In this case, the power of a tire stored in the tank (2) is lower, but largely

  sufficient to ensure effective braking of the lightly loaded vehicle.

  The value of the safety pressure is determined in particular as a function

  different regulatory requirements relating to braking performance.

  These wind values are adapted for each vehicle silhouette.

  In the particular case where the kactor vehicle is alone, this safety pressure is determined so that when the braking demand is maximum, the braking torque applied to the front wheels is limited so as to

  avoid load transfer by tilting the vehicle at the front.

  In both load thresholds ((: 1, C2), the pressure setpoint can either be continuously variable as illustrated in figure 2, or adopt different intermediate values. The two load thresholds (C1, C2) can also be

  combined, so that the pressure value adopts only two values.

  As already mentioned, this regulation of the tank pressure setpoint may be subject to the monitoring of another parameter, corresponding to the fact that the vehicle is operating as a sen-kactor, or else coupled by a trailer. In this case, the pressure setpoint adopts either the nominal pressure value or the

safety pressure value.

  This set pressure can also change as a function of other parameters that wind for example an indicator of the correct functioning of the anti-lock braking system (8). In this case, and particularly with regard to the rear axle, the pressure setpoint is reduced in the case where the anti-lock braking system is faulty, to avoid in the event of sustained braking demand, that the wheels do not lock automatically, due to the non-functioning of the ABS system. On the other hand, when the ABS system works correctly, this can ensure a limitation of the braking torque provided to the axle, without it being necessary to restrict the power of the

  braking associated with the axle in question.

  Of course, the different information on load, operation in a senl tractor, or fault mode of the ABS system can be combined with appropriate logic to regulate the pressure of the brake reservoir. s In practice, this regulation can be carried out automatically as illustrated in FIG. 1 by the combination of the two valves (10, 15). The first valve (10) makes it possible to supply the reservoir (2) in the illustrated position from the compressor (5) or more generally from the source of compressed air including various safety devices or a desiccator. In the position opposite to that illustrated in FIG. 1, the valve (10) ensures the connection of the reservoir (2) with the second valve (1 S). In the illustrated form, the second valve (l S) insulates the reservoir (2), so that the pressure in the latter decreases only when consumption of the braking system. In the position opposite that of FIG. 1, the second valve (15) allows the emptying of the reservoir (2), in particular in the case where the set pressure changes from the nominal value to the value of

safety pressure.

  As already mentioned, the various valves (10, 15) can be integrated into a compressed air distribution device such as that described in patent applications No. FR 01.09590 and FR 01.09589 of the Applicant, not yet

  published on the filing date of this application.

  It follows from the foregoing that the braking device in accordance with the invention has multiple advantages, and in particular that of making it possible to avoid tilting around the front axle of the vehicle, during braking, when the latter is in configuration of the tractor alone, and all the more so if it has a strong front overhang, or else is in a carrying configuration, in particular

  when it is short wheelbase, vice or low load.

  The same device also makes it possible to avoid blocking of the wheels of the vehicle in order to ensure its stability and its directibility, even in the case where an anti-locking device of the wheels is faulty. This braking device has a particularly simple structure, since it requires only very little, or even no additional pneumatic component, than those which already make it possible to assure

  the configuration brake circuit supply.

Claims (6)

  1 / Braking device for an axle of an industrial vehicle, comprising: - a braking circuit (1) specific to the axle, including a pneumatic compressed air reservoir (2), a braking control system (3) and brake actuators (4), - an electronic control unit (6), regulating the supply of the pneumatic reservoir (2) from a source of compressed air (5), characterized in that that the control unit (6) is capable of ensuring the regulation of the compressed air of the pneumatic reservoir according to a variable setpoint as a function of information developed within the control unit, said setpoint being variable between two thresholds, namely a high threshold corresponding to a nominal pressure value, and a teas threshold allowing to   limit the pneumatic energy available at the braking circuit in question.   2 / Braking device according to claim 1, characterized in that the   setpoint can adopt two values, namely the high and teas thresholds.   3 / braking device according to claim 1, characterized in that the set value can adopt intermediate values between the two thresholds high and teas.   4 / Braking device according to claim 1, characterized in that the information produced by ['control unit command (6) representative wind   of the vehicle load and in particular of its trailer.   / Braking device according to claim 1, characterized in that the information produced by the control unit (6) representative wind the presence of a trailer.   r 6 / braking device according to claim 1, characterized in that the information produced by ['control unit command (6) wind representative of the operating state of the anti-lock system of the wheels of ltessieu considered. 7 / Braking device of the front axle of a vehicle according to the claims 4 or 5.   8 / Braking device of the rear axle of a vehicle according to the lO claim 6.   9 / Apparatus according to claim 1, characterized in that the pneumatic compressed air reservoir (2) is supplied by means of a valve (10) controlled by ['control unit command (6), and adapted according if necessary, supply the reservoir (2) from the compressed air source (5) or the drain partial to said reservoir (2). Depositor: RENAULT V.I.   Agent: Cabinet LAURENT ET CHARRAS