SE543381C2

SE543381C2 - Method for controlling a braking system, control device, computer program, computer- readable medium and vehicle

Info

Publication number: SE543381C2
Application number: SE1950479A
Authority: SE
Inventors: Alexander Stamp; Andreas Szilassy; Christian Wessel
Original assignee: Scania Cv Ab
Priority date: 2019-04-17
Filing date: 2019-04-17
Publication date: 2020-12-29
Also published as: DE102020000876A1; SE1950479A1

Abstract

A control device (100) and a method for controlling a braking system (30) for a vehicle (1) is provided. The braking system comprises a first auxiliary brake (10) operable by a braking medium, a cooling system (8) configured to cool the first auxiliary brake, and one or more additional brake means (7, 25). The method comprises predicting a future temperature (Tp) of the braking medium, reducing a currently requested braking torque from the first auxiliary brake if the predicted future temperature of the braking medium is above a maximum temperature (Tmax) of the braking medium, and controlling the one or more additional brake means of the braking system so as to compensate for a loss of braking torque from the first auxiliary brake resulting from the reduction of the initially requested braking torque from the first auxiliary brake. A computer program, a computer-readable medium are also disclosed, as well as a vehicle comprising a braking system.

Description

METHOD FOR CONTROLLING A BRAKING SYSTEM, CONTROL DEVICE, COMPUTER PROGRAM, COMPUTER- READABLE MEDIUM AND VEHICLE TECHNICAL FIELD The present disclosure relates in general to a method for controlling a braking system for a vehicle and a control device configured to control a braking system of a vehicle. The present disclosure further relates in general to a computer program and a computer-readable medium. Moreover, the present disclosure relates in general to a vehicle comprising a braking system.

BACKGROUND In heavy vehicles, an automatic braking process may be used that provide the vehicle with a desired downhill speed by activation of one or more auxiliary brakes. A control arrangement may be adapted to estimate the braking effect required for e.g. maintaining the speed which the vehicle was travelling downhill at the time of initiating the process, and to activate one or more auxiliary brakes with the corresponding braking effect. The automatic braking process may also be used in situations other than downhill travel, such as to achieve a faster or smoother braking effect, or for the purpose of reducing the usage of the service brakes to thereby avoid unnecessary wear thereof. These other situations are however not associated with a risk of an undesirable acceleration of the vehicle.

An auxiliary brake may for example be a retarder, an exhaust brake, an engine brake, a compression brake or the like. A retarder comprises a stator, a rotor and a braking medium (such as oil) that flows at high velocity between the stator and the rotor when the retarder is activated. During the braking process, the kinetic energy of the braking medium converts to thermal energy. The cooling system configured to cool the combustion engine may be used to also cool the braking medium of retarder. However, the cooling system of the combustion engine is primarily dimensioned for cooling the combustion engine, and cooling the braking medium of the retarder may sometime require a greater cooling effect than that cooling the vehicle's engine. It is therefore not unusual during for example a steep downhill run that the temperature of the braking medium of the retarder may rise to an unacceptable level.

Current systems are often based on reducing the braking torque in the auxiliary brake when a critical temperature of the coolant is reached. Such a reduction of the torque of the auxiliary brake often has to be compensated by activation of other auxiliary brakes or by usage of the service brakes to avoid undesirable acceleration of the vehicle, for example in a downhill slope. However, the activation of other auxiliary brakes takes some time and this in turn may allow the vehicle to accelerate, which in turn increases the load on the activated other auxiliary brakes when they become activated due to the increased speed of the vehicle. Moreover, if such additional auxiliary brakes are already maximally activated, the service brakes will have to be relied on for keeping an acceptable speed of the vehicle, which in turn increases the wear on the service brakes.

WO 2005/080166 discloses an example of a method and arrangement for braking a vehicle wherein a supplementary brake may be activated only with the braking effect possible to maintain throughout a downhill run without overloading the cooling system of the supplementary brake. The driver may then decide to either accept a higher vehicle speed than desired, or temporarily activate the vehicle's wheel brakes to maintain the desired vehicle speed during the downhill run.

WO 2008/091193 discloses an example of a method for controlling cooling of an auxiliary brake of a vehicle, such as a retarder. A cooling fan is arranged to cool a coolant, which in turn is arranged to cool the braking medium of the auxiliary brake. According to this method, the cooling fan may be activated automatically provided that a downhill slope steepness is within a predetermined interval. The method comprises pre-cooling the auxiliary brake and pre-loading the cooling system such that the cooling system is able to cool the auxiliary brake when the need for cooling the auxiliary brake is increased.

SUMMARY The object of the present invention is to provide an efficient control of a braking system of a vehicle, so as to obtain a desired braking effect when needed, with reduced risk for wear or damage of the constituent components of the braking system.

The object is achieved by the subject-matter of each one of the appended independent claims.

In accordance with the present disclosure, a method for controlling a braking system for a vehicle is provided. The braking system comprises a first auxiliary brake operable by a braking medium, a cooling system configured to cool the first auxiliary brake, and one or more additional brake means. The method comprises a step (a) of, based on a current temperature of the braking medium and a current requested braking torque of the first auxiliary brake, predicting a future temperature of the braking medium. The method further comprises a step (b) of, if the predicted future temperature of the braking medium is above a predetermined maximum temperature of the braking medium, reducing the current requested braking torque of the first auxiliary brake to an adjusted braking torque to be demanded from the first auxiliary brake. The method may also comprise a step of controlling the first auxiliary brake based on the obtained adjusted braking torque to be demanded from the first auxiliary brake. Alternatively, the method may comprise reiterating steps of the method until an appropriate adjusted braking torque to be demanded from the first auxiliary brake, which results in the predicted future temperature of the braking medium being equal to or lower than the predetermined maximum temperature of the braking medium, has been obtained and thereafter controlling the first auxiliary brake on the basis of the obtained appropriate adjusted braking torque to be demanded from the first auxiliary brake. The method further comprises a step (c) of controlling the one or more additional brake means to compensate for the difference in braking torque between said current requested braking torque and the adjusted braking torque (or appropriate adjusted braking torque) to be demanded from the first auxiliary brake. The method is performed by a control device.

By means of the present method, the risk of the first auxiliary brake becoming overheated may be significantly reduced, or even avoided. The reason for this is that the first auxiliary brake may be controlled based on an adjusted braking torque lower than the initially requested braking torque which over time could risk resulting in the temperature of the braking medium becoming higher that the predetermined maximum temperature.

In view of the fact that the present method considers a predicted future temperature for the control of the braking system, the activation time of other auxiliary brakes than the first auxiliary brake may be initiated at an early point in time, if needed. This is turn results in that a compensation of potential loss of desired braking torque from the first auxiliary brake may be achieved quicker. Thereby, the risk of an undesirable acceleration of the vehicle may be minimized. Furthermore, wear of the one or more additional brake means of the braking system may be minimized due to the activation thereof at a lower vehicle speed, the lower vehicle speed resulting from the minimization of the undesired acceleration of the vehicle.

Furthermore, the method according to the present disclosure also has the advantage of not having to rely on information (for example by a positioning system and map data) regarding a present or upcoming inclination. Such data may not always be known, for example, when the vehicle is travelling off road. Thus, the method for controlling a braking system in accordance with the present disclosure may be used for a broader range of driving situations of the vehicle.

The step of predicting the future temperature of the braking medium may comprise also taking into account the current ambient temperature and/or the current cooling capacity of the cooling system. Thereby, the accuracy of the predicted future temperature may be increased, which in turn improves the control of the braking system so as to achieve the above mentioned object.

Step (b) may for example comprise reducing the current requested braking torque by a predetermined fixed amount of torque or a percentage of the current requested braking torque. Thereby, an easy control of the braking system may be achieved without the need of knowing to which extent the first auxiliary brake may be used to avoid overheating.

The method may further comprise, after step (b), repeating step (a) with usage of the adjusted braking torque to be demanded from the first auxiliary brake as the current requested braking torque of the first auxiliary brake in step (a), and iterating steps (a) and (b) until an appropriate adjusted braking torque to be demanded from the first auxiliary brake which results in a predicted future temperature of the braking medium being equal to or lower than the predetermined maximum temperature of the braking medium has been obtained. Thereby, the first auxiliary brake may for example be controlled directly based on an appropriate adjusted braking torque to be demanded which avoids the risk of overheating of the first auxiliary brake. Thus, the control of the braking system may be further improved.

The method may further comprise, after step (a), a step (al) of, if the predicted future temperature of the braking medium is above the predetermined maximum temperature of the braking medium, increasing the cooling of the auxiliary brake by increasing the cooling capacity of the cooling system, if not already at maximum cooling capacity. Moreover, the method may in such a case comprise a step (a2) of, before step (b), repeating step (a) taking into account the increased cooling capacity of the cooling system. Thereby, it may for example be avoided to control the first auxiliary brake to a lower braking demand than desired if an increase of the temperature of the braking medium to above the predetermined maximum temperature can be avoided already by usage of the cooling system. This in turn may avoid an unnecessary usage of the one or more additional brake means as no compensation for a loss of braking torque from the first auxiliary brake will occur. Moreover, the reduction of braking torque from the first auxiliary brake may be lower compared to if the cooling system is not at its maximum cooling capacity, even in cases where the predicted future temperature of the braking medium is above the predetermined maximum temperature thereof.

The method may further comprise determining the current temperature of the braking medium by measuring the temperature of the braking medium. Alternatively, the method may comprise determining the current temperature of the braking medium by measuring the temperature of a circulating cooling medium in the cooling system. Alternatively, the method may further comprise determining the current temperature of the braking medium by measuring both the temperature of the braking medium and measuring the temperature of the cooling medium. The latter alternative may for example increase the accuracy in the determination of the current temperature of the braking medium.

The present disclosure further relates to a computer program, wherein said computer program comprises program code for causing a control device to perform the method for controlling a braking system as described above.

The present disclosure further relates to a computer-readable medium comprising instructions, which when executed by a control device, cause the control device to perform the method for controlling a braking system as described above.

The present disclosure further provides a control device configured to control a braking system of a vehicle. The braking system comprises a first auxiliary brake operable by a braking medium, a cooling system configured to cool the first auxiliary brake, and one or more additional brake means. The control device is configured to predict a future temperature of the braking medium taking into account the current temperature of the braking medium and a current requested braking torque of the first auxiliary brake. The control device is further configured to reducing the current requested braking torque of the first auxiliary brake (10) to an adjusted braking torque, to be demanded from the first auxiliary brake (10), if the predicted future temperature of the braking medium is above a predetermined maximum temperature of the braking medium. The control device is also configured to control the one or more additional brake means so as to compensate for the difference in braking torque between said current requested braking torque and the adjusted braking torque to be demanded from the first auxiliary brake.

The control device may further be configured to take into account a current ambient temperature and/or a current cooling capacity of the cooling system when predicting the future temperature of the braking medium.

Moreover, the control device may further be configured to reduce the current requested braking torque of the first auxiliary brake to the adjusted braking torque to be demanded from the first auxiliary brake by reducing the current requested braking torque by a predetermined fixed amount or a percentage of the current requested braking torque.

The control device may also be configured to control the cooling system so as to increase the cooling capacity thereof, if not already at maximum cooling capacity, if the predicted future temperature of the braking medium is above the predetermined maximum temperature of the braking medium.

The control device may further be configured to determine an appropriate adjusted braking torque to be demanded from the first auxiliary brake, which results in a predicted future temperature of the braking medium being equal to or lower than the predetermined maximum temperature of the braking medium, by iterating steps of predicting a future temperature of the braking medium and reducing a current requested braking torque to an adjusted braking to be demanded from the first auxiliary brake; and controlling the first auxiliary brake based on the obtained appropriate adjusted braking torque to be demanded from the first auxiliary brake.

The control device has the corresponding advantages described above with regard to the method for controlling a braking system.

The present disclosure also relates to a vehicle, comprising a braking system. The braking system comprises a first auxiliary brake operable by a braking medium, a cooling system configured to cool the first auxiliary brake, and one or more additional brake means. The vehicle further comprises a control device as described above.

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 schematically illustrates a side view of an example of a vehicle; Fig. 2 schematically illustrates an exemplifying embodiment of a powertrain of a vehicle; Fig. 3 schematically illustrates an exemplifying embodiment of a cooling system; Fig. 4 schematically illustrates one exemplifying embodiment of a braking system of a vehicle; Fig. 5 represents a flowchart schematically illustrating a method for controlling a braking system for a vehicle in accordance with a first exemplifying embodiment; Fig. 6 represents a flowchart schematically illustrating a method for controlling a braking system for a vehicle in accordance with a second exemplifying embodiment; Fig. 7 schematically illustrates a device that may constitute, comprise or be a part of a control device configured to control a braking system of a vehicle.

DETAILED DESCRIPTION The invention will be described in more detail below with reference to exemplifying embodiments and the accompanying drawings. The invention is however not limited to the exemplifying embodiments discussed and/or shown in the drawings, but may be varied within the scope of the appended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof.

In accordance with the present disclosure, a method for controlling a braking system for a vehicle is provided. The braking system comprises a first auxiliary brake operable by means of a braking medium, and one or more additional brake means. One example of such a first auxiliary brake operable by means of a braking medium is a retarder. Another example of such a first auxiliary brake is a compression brake. The one or more additional brake means may for example be selected from the group consisting of the service brakes of the vehicle, or any other previously known auxiliary brake (other than the above mentioned first auxiliary brake). Examples of other auxiliary brakes, other than the first auxiliary brake, include an exhaust brake, an engine brake, and a compression brake. Thus, the braking system may for example comprise at least the first auxiliary brake and a second auxiliary brake. The service brakes of the vehicle may constitute a part of the above mentioned braking system or may be a part of a constituent arrangement of the vehicle other than the herein discussed braking system. The braking system further comprises a cooling system configured to cool the first auxiliary brake, such as by cooling the braking medium of the first auxiliary brake. A cooling medium is circulated in a first circuit of the cooling system, and cools the braking medium when passing through a heat exchanger. The cooling system may be a constituent arrangement shared with another system of the vehicle. For example, the cooling system may also be configured to cool other components of the vehicle such as a propulsion unit of the vehicle (herein also referred to as a power unit).

The method for controlling a braking system for a vehicle in accordance with the present disclosure comprises the steps of predicting a future temperature of the braking medium, reducing a currently requested braking torque from the first auxiliary brake if the predicted future temperature of the braking medium is above a maximum temperature of the braking medium, and controlling one or more additional brake means of the braking system so as to compensate for a loss of braking torque from the first auxiliary brake resulting from the reduction of the (initially) requested braking torque. These steps will be described in more detail in the following.

In view of the fact that the present method considers a predicted future temperature for the control of the braking system, the risk of the first auxiliary brake becoming overheated may be significantly reduced, or (at least in some embodiments) even avoided. The reason for this is that the first auxiliary brake may be controlled based on an adjusted braking torque lower than the initially requested braking torque which over time could result in the temperature of the braking medium becoming higher that the predetermined maximum temperature thereof.

Moreover, in view of the fact that the present method considers a predicted future temperature for the control of the braking system, the activation time of other auxiliary brakes than the first auxiliary brake may be initiated earlier than in accordance with previously known control systems wherein an already reached temperature is considered. This is turn results in that a compensation of potential loss of desired braking torque from the first auxiliary brake may be achieved quicker. Thereby, the risk of an undesirable acceleration of the vehicle may be minimized. Furthermore, wear of the one or more additional brake means of the braking system may be minimized due to the activation thereof at a lower vehicle speed, the lower vehicle speed resulting from the minimization of the undesired acceleration of the vehicle.

The method for controlling a braking system in accordance with the present disclosure is performed by a control device configured to control the braking system. The control device may thus be configured to perform any one of the below mentioned steps of the method. The control device may comprise one or more control units. In case of a plurality of control units, each control unit may be configured to control a certain function or a certain function may be divided between more than one control units. The control of the braking system, or any constituent component thereof, may be governed by programmed instructions. These programmed instructions typically take the forms of a computer program which, when executed in a control device, causes the control device to effect desired forms of control action.

The method for controlling a braking system as described herein may typically be performed continuously. In other words, the steps of the method may be repeated, for example with a certain preselected frequency. The method may also be performed for example only when the first auxiliary brake has been activated or at least a request for activation of the first auxiliary brake has been generated by an automatic system of the vehicle or by a driver of the vehicle.

As mentioned above, the method comprises a step of predicting a future temperature of the braking medium. The future temperature of the braking medium may be a temperature of the braking medium after a selected period of time has passed. In other words, the prediction may be based on a selected period of time. The selected period of time may for example in the order of a few seconds, such as after 5 seconds, 10 seconds, 15 seconds, 20 seconds or the like. The accuracy of the predicted future temperature of the braking medium may typically increase with smaller periods of time. Therefore, selecting a shorter period of time when predicting the future temperature may also improve the control of the braking system. However, if the prediction of the future temperature is made for a too short period of time, it may not enable a desired control of the braking system. This may lead to insufficient braking of the vehicle, which in turn may cause an undesired acceleration of the vehicle. This is comparable with the problems associated with the prior art control systems relying for example on a measurement of the coolant temperature. Thus, the prediction of the future temperature of the braking medium may be for time which is after at least 3 seconds, preferably at least 5 seconds. Thereby, an efficient control of the braking system may be achieved by enabling sufficient time for activation or increase of additional braking torque from other brake means if needed.

Predicting the future temperature of the braking medium may be made by directly predicting the future temperature of the braking medium. Alternatively, predicting the future temperature of the braking medium may in practice be made by predicting a future temperature of the cooling medium and, based on a model of the cooling system, thereby deriving a corresponding predicted future temperature of the braking medium.

The prediction of the future temperature of the braking medium is made at least based on a current temperature of the braking medium (in general, the current highest temperature of the braking medium within the braking system) and a currently requested braking torque from the first auxiliary brake. The current temperature of the braking medium may for example be either directly or indirectly determined. A directly determined current temperature of the braking medium may constitute a measured temperature of the braking medium. This may be achieved by utilization of a temperature sensor arranged to determine the temperature of the braking system. An indirectly determined current temperature of the braking medium may for example be achieved by determining a cooling medium temperature, such as by a temperature sensor configured to determine said cooling medium temperature. Based on this determined cooling medium temperature, the current temperature of the braking medium may be estimated using a model of the cooling system. Thus, the current temperature of the braking medium may be determined in accordance with any previously known method in the art therefore. The currently requested braking torque from the first auxiliary brake may for example a currently requested braking torque from a cruise control or the like, or a currently requested braking torque from a driver. The driver may request a braking torque from the first auxiliary brake my activation of any known device therefore, such as a lever or a button, as known in the art. The current requested braking torque of the first auxiliary brake, if actuated by the first auxiliary brake, generates predictable amount of heat over time. Thus, my considering the current temperature of the braking medium and a currently requested braking torque from the first auxiliary brake, it is possible to predict a future temperature of the braking medium.

If desired, it is possible to consider further parameters when predicting the future temperature of the braking medium. Considering further parameters when predicting the future temperature of the braking medium may increase the accuracy of the predicted future temperature of the braking medium and therefore improve the control of the braking system. However, the prediction of the future temperature of the braking medium may become more complex with an increasing amount of considered parameters, which in turn may increase the risk of errors in the prediction.

It is however advantageous to make the prediction of a future temperature of the braking medium, not only based on the current temperature of the braking medium and the current requested braking torque of the first auxiliary brake, but also on the current cooling capacity of the cooling system. For example, if the predicted future temperature of the braking medium is above the predetermined maximum temperature it may be derived that the cooling capacity of the cooling system is insufficient. Then, if the cooling capacity of the cooling system is not already at the maximum cooling capacity allowed by its physical constraints, a control of the cooling system so as to increase the cooling capacity thereof may be performed. By way of example, a cooling fan of the cooling system may be activated, if not already activated, and controlled so as to assist in the removal of thermal energy from the cooling medium. Another example is that the flow of the cooling medium may be altered to increase the cooling capacity of the cooling system. Naturally, both the cooling fan and the flow of the cooling medium may be controlled so as to increase the cooling capacity of the cooling system. Thereafter, a second future temperature of the braking medium (at the increased cooling capacity) may be predicted and only if said second predicted future temperature is above the predetermined maximum temperature of the braking medium is the step of controlling the one or more additional brake means so as to compensate for the loss of braking torque from the first auxiliary brake resulting from the reduction of the requested braking torque performed.

Moreover, predicting the future temperature of the braking medium may not only based on the current temperature of the braking medium and the current requested braking torque of the first auxiliary brake, but also on the ambient temperature, i.e. the temperature outside the vehicle. The ambient temperature of the vehicle may be considered when predicting the future temperature of the braking medium in addition to the cooling capacity of the cooling system, or it may be considered even if the cooling capacity of the cooling system would not be considered when predicting the temperature of the braking medium.

Examples of additional parameters that may be considered when predicting the future temperature of the braking medium, if available, include a positioning system in combination with map data (including information regarding inclination of road), experienced current inclination of road determined for example by an inclination sensor of the vehicle, information from look-ahead systems detecting upcoming road properties and/or traffic conditions, possible additional thermal load on the cooling system, etc. The prediction of the future temperature of the braking medium may consider one or more of these parameters in any combination.

As mentioned above, the method for controlling the braking system in accordance with the present disclosure further comprises a step of reducing a currently requested braking torque from the first auxiliary brake if the predicted future temperature of the braking medium is above a maximum temperature of the braking medium. By reducing the current requested braking torque to an adjusted braking torque to be demanded from the first auxiliary brake, it may be possible to avoid an increase of the temperature of the braking medium above the predetermined maximum temperature. In other words, the first auxiliary brake may be activated with a smaller braking torque and thereby not generate as much heat as would have been generated if the originally requested braking torque would have been continuously used.

When having reduced the requested braking torque of the first auxiliary brake to an adjusted braking torque to be demanded from the first auxiliary brake, it is possible to control the first auxiliary brake based on the adjusted braking torque to be demanded from the first auxiliary brake immediately. Thereafter, the step of predicting a future temperature based on the current temperature of the braking medium and a current requested braking torque (which in such a case thus corresponds to the adjusted braking torque to be demanded obtained from the first iteration of the method) may be repeated and the resulting, second, predicted future temperature of the braking medium would then used when repeating the subsequent steps of the method. This would result in the method gradually arriving at an appropriate braking torque from the first auxiliary brake while avoiding overheating, more or less by trial and error.

Alternatively, when having reduced the requested braking torque of the first auxiliary brake to an adjusted braking torque to be demanded from the first auxiliary brake, the adjusted braking torque to be demanded from the first auxiliary brake may be used in a step of predicting a second future temperature of the braking medium based on the current temperature of the braking medium and said adjusted braking torque to be demanded from the first auxiliary brake before the first auxiliary brake is actually controlled to any adjusted braking torque to be demanded from the first auxiliary brake. This alternative allows for obtaining an appropriate adjusted braking torque to be demanded from the first auxiliary brake, which directly results in a temperature of the braking medium that is below the predetermined maximum temperature, by repeating the prediction of a future temperature and comparison thereof with the predetermined maximum temperature until said appropriate adjusted braking torque to be demanded from the first auxiliary brake has been determined. The first auxiliary brake can thereafter be controlled to the appropriate adjusted braking torque.

A reduction of the current requested braking torque from the first auxiliary brake to an adjusted braking torque to be demanded from the first auxiliary brake may be made with a fixed amount of braking torque, for example 50 Nm, 100 Nm or 200 Nm. Alternatively, the reduction may be made by a percentage of the requested braking torque, for example 2.5%, 5% or 7.5%.

As mentioned above, the method for controlling the braking system in accordance with the present disclosure further comprises a step of controlling one or more additional brake means of the braking system so as to compensate for the loss of braking torque from the first auxiliary brake resulting from the reduction of the requested braking torque. The step of controlling the one or more additional brake means so as to compensate for the loss of braking torque may be performed by any previously known process therefore. However, in contrast to previously known controlling methods of a braking system, the step of controlling the one or more additional brake means so as to compensate for the low of braking torque will be initiated at an earlier point in time as described above. Therefore, the risk of undesirable acceleration of the vehicle is further minimized. This also has the beneficial effect that the braking effect of such one or more additional brake means will be effectuated at a lower vehicle speed than if the vehicle has been able to accelerate until the activation thereof has occurred. This also has the advantage of minimizing the damage or wear of such one or more additional brake means.

The step of controlling one or more additional brake means of the braking system so as to compensate for the loss of braking torque from the first auxiliary brake may comprise activation of such one or more additional brake means, if not already activated. If the one or more additional brake means is already activated, the control thereof so as to compensate for the loss of braking torque may comprise increasing the braking torque of said one or more brake means. If the auxiliary brakes of the braking system are not able to provide the desired braking torque for maintaining a vehicle speed, for example in a downhill slope, the method may further comprise automatically activating the service brakes of the vehicle to deliver an appropriate braking effect.

The above discussed method for controlling a braking system according to the present disclosure may naturally be supplemented with other forms of control of the braking system. For example, if it is detected that the current temperature of the braking medium is above the predetermined maximum temperature of the braking medium, the usage of the first auxiliary brake may be reduced immediately to avoid for example damage of the braking medium or constituent components of the first auxiliary brake.

Figure 1 schematically illustrates a side view of an example of a vehicle 1. The vehicle 1 comprises a powertrain 3 comprising a power unit 2, such as a combustion engine, and a gearbox 4. A clutch (not shown) may be arranged between the power unit 2 and the gearbox 4. The gearbox 4 is connected to the driving wheels 5 of the vehicle 1 via an output shaft 6 of the gearbox 4. The gearbox 4 is adapted to provide a plurality of gear ratios. The gearbox 4 may for example be an automated manual gearbox (AMT). Alternatively, the gearbox 4 may be a manual gearbox.

The vehicle 1 may be, but is not limited to, a heavy vehicle, e.g. a truck or a bus. Furthermore, the vehicle may be a hybrid vehicle comprising a second power unit in the form of an electric motor (not shown) in addition to the combustion engine 2.

Figure 2 schematically illustrates an exemplifying embodiment of a vehicle powertrain 3, such as a powertrain of the vehicle 1 shown in Figure 1. The powertrain 3 comprises a power unit 2, such as a combustion engine. The combustion engine may comprise an engine brake. The powertrain further comprises a gearbox 4 connected to the power unit 2 via a clutch 9. The output shaft 6 of the gearbox 4 is connected to the driving wheels 5 via for example a differential 11 and a drive shaft 12. The powertrain 3 further comprises service brakes 7 arranged at the driving wheels 5. The powertrain 3 further comprises an auxiliary brake in the form of a retarder 10. The retarder 10 is connected to the output shaft 6 of the gearbox 4. Moreover, the powertrain 3 comprises a cooling system 8 adapted to cool the power unit 2 and/or the retarder 10.

As shown in Figure 2, the powertrain 3 may further comprise a control device 100. The control device 100 may be configured to control one or more of the constituent components of the vehicle powertrain 3. The control device 100 may comprise one or more control units. The responsibility for a specific function or control may be divided between two or more of the control units. One or more of the control units may be implemented in the form of a computer. The control device 100 may for example be connected to the power unit 2, the gearbox 4, the retarder 10 and optionally the clutch 9, as shown in Figure 2. The control device 100 may also be connected to any other constituent component of the vehicle powertrain 3, even though not illustrated in the figure, if desired. The connections of the control device 100 to any constituent component of the vehicle powertrain 3 may be in the form of physical connection(s) and/or wireless connection(s).

The control of constituent components in the vehicle powertrain 3 may be governed by programmed instructions. These programmed instructions typically take the forms of a computer program which, when executed in a computer or control unit, causes the computer or control unit to effect desired forms of control action, for example the steps of the method disclosed herein. As described above, such a computer or control unit may be or constitute a part of the control device 100.

Figure 3 schematically illustrates one exemplifying embodiment of a cooling system 8, such as the cooling system of the powertrain shown in Figure 2. The cooling system 8 comprises a first circuit 16 in which a cooling medium, such as water, may be circulated. The cooling system further comprises a second circuit 17, in which a braking medium (such as oil) of a retarder 10 may be circulated. The first circuit 16 may comprise a coolant pump 13 arranged to control the circulation of the cooling medium in the first circuit 16. The coolant pump 13 may typically be driven by the combustion engine 2 via a driving belt or the like.

In the first circuit 16, the cooling medium is led to the combustion engine 2 to effectuate cooling thereof. In the combustion engine, the cooling medium may be circulated through cooling ducts, as known in the art, to cause cooling of the combustion engine. After the cooling medium has passed the combustion engine 2, it is led to a heat exchanger 14 in which it may be used to cool the braking medium flowing in the second circuit 17. The cooling medium is, in the first circuit, led from the heat exchanger 14 to a radiator 15 in which it is intended to give off thermal energy absorbed from the combustion engine 2 and the heat exchanger 14. The cooling system may further comprises a fan 18. The fan 18 may for example be driven by the engine. The fan 18 is arranged in the vicinity of the radiator 15 and may thus assist in the removal of thermal energy from the cooling medium in the first circuit. During operation of the cooling system, the fan may typically remain deactivated if the radiator alone is capable of removing a sufficient amount of the thermal energy absorbed by the cooling medium. According to one alternative, the fan may be activated with different rotational speed depending on the need for assistance in the cooling of the cooling medium. Alternatively, it may, for ease of control, be fully activated with a maximum rotational speed as soon as the radiator alone is not sufficient for removal of an intended amount of adsorbed thermal energy of the cooling medium.

The first circuit 16 may comprise one or more temperature sensors adapted to determine the temperature of the cooling medium when circulating in the first circuit 16. As shown in Figure 3, a first temperature sensor 20a may be arranged upstream of the combustion engine. The first sensor 20a is thus able to determine the temperature of the cooling medium entering the combustion engine. Moreover, a second temperature sensor 20b may be arranged downstream of the heat exchanger 14. The second temperature sensor 20b is thus able to determine the temperature of the cooling medium when leaving the heat exchanger 14. If desired, it is also possible to arrange a third temperature sensor 20c downstream of the combustion engine but upstream of the heat exchanger 14. Thereby, it may for example be possible to determine the contribution of the combustion engine and the braking medium, respectively, to the increased temperature of the cooling medium.

Furthermore, the second circuit 17 may comprise one or more temperature sensors adapted to determine the temperature of the braking medium. In Figure 3, a fourth temperature sensor 21a is arranged in the second circuit upstream of the retarder 10. The fourth temperature sensor is thus able to determine the temperature of the braking medium before it enters into the retarder 10. A fifth temperature sensor 21b may be arranged downstream of the retarder 10 (upstream of the heat exchanger 14). The fifth temperature sensor is thus able to determine the temperature of the braking medium after having passed through the retarder, but before the braking medium has been cooled in the heat exchanger 14. Such a fifth temperature sensor 21b may thus be used to determine a highest current temperature of the braking medium in the second circuit 17.

It shall be recognised that although Figure 3 illustrates an alternative wherein the cooling medium and the braking medium flows in opposite directions through the heat exchanger (as shown by the arrows), a configuration wherein the cooling medium and the braking medium flow in substantially the same direction through the heat exchanger is also possible. In the latter case, the flow of the braking medium through the second circuit would thus be in a direction opposite to the direction illustrated by the arrow in the second circuit 17.

Figure 4 schematically illustrates a braking system 30 for a vehicle according to one exemplifying embodiment. The braking system 30 comprises a first auxiliary brake 10 operable by a braking medium. The first auxiliary brake may for example be a retarder. The braking system further comprises a cooling system 8 configured to cool the first auxiliary brake 10. The braking system further comprises a second auxiliary brake 25. The second auxiliary brake 25 may for example be an exhaust brake, an engine brake or the like. The braking system may optionally further comprise the service brakes 7 of the vehicle. The braking system further comprises a control device 100, for example any one of the control devices described herein. The braking system further comprises a first temperature determining device 26 configured to determine a current temperature of the braking medium of the first auxiliary brake 10. The braking system further comprises a first control unit 27, configured to determine or receive data relating to a requested braking torque of the first auxiliary brake. The braking system may further comprise a second temperature determining device 28 configured to determine an ambient temperature. Moreover, the braking system may comprise a second control unit 29, configured to determine or receive data relating to a current cooling capacity of the cooling system 8.

Figure 5 represents a flowchart schematically illustrating a method for controlling a braking system for a vehicle according to a first exemplifying embodiment of the present disclosure. The method comprises a first step S110 of, based on a current temperature of the braking medium and a current requested braking torque of the first auxiliary brake, predicting a future temperature Tp of the braking medium. The method then comprises a step S120 of comparing the predicted future temperature Tp of the braking medium with a predetermined maximum temperature Tmax of the braking medium. If the predicted temperature Tp of the braking medium is not above the predetermined maximum temperature Tmax, the step S110 may be repeated after a preselected time. However, if the predicted temperature Tp of the braking medium is above the predetermined maximum temperature Tmax, the method proceeds to step S130. Step 130 comprises reducing the current requested braking torque of the first auxiliary brake to an adjusted braking torque to be requested from the first auxiliary brake. Thereafter, the method may optionally proceed to step S110, wherein a future temperature of the braking medium is predicted considering the adjusted braking torque to be demanded from the first auxiliary brake instead of the (previously) requested braking torque. Moreover, after step S130, the method proceeds to step S140. Step S140 comprises controlling the one or more additional brake means to compensate for the difference in braking torque between the (initially) requested braking torque and the adjusted braking torque to be demanded from the first auxiliary brake.

Figure 6 represents a flowchart schematically illustrating a method for controlling a braking system for a vehicle according to a second exemplifying embodiment of the present disclosure. The method shown in Figure 6 comprises, a first step S110' of, based on a current temperature of the braking medium, a current requested braking torque of the first auxiliary brake and the cooling capacity of the cooling system, predicting a future temperature Tp of the braking medium. The method illustrated in Figure 6 further comprises the steps S120, S130 and S140 discussed above with reference to Figure 5. However, in contrast to the method illustrated in Figure 5, the present method of Figure 6 also comprises a step S122 following step S120. Step 122 comprises controlling if the cooling capacity of the cooling system is at its maximum. If it is determined in step S122 that the cooling capacity is not at the maximum cooling capacity which the cooling system is able to provide, the method proceeds to step S124. Step S124 comprises controlling the cooling system so as to increase the cooling capacity thereof. This may for example comprise increasing a rotational speed of a fan 18 of the cooling system 8 (compare with Figure 3). The method then proceeds to step S110, wherein a new future temperature of the braking medium is predicted taking into account also the new (increased) cooling capacity of the cooling system. When it is determined in step S130 that the cooling capacity of the cooling system is at its maximum cooling capacity, the method proceeds to step S130.

Figure 7 schematically illustrates an exemplifying embodiment of a device 500. The control device 100 described above may for example comprise the device 500, consist of the device 500, or be comprised in the device 500.

The device 500, shown in the figure, comprises a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer program, e.g. an operating system, is stored for controlling the function of the device 500. The device 500 further comprises a bus controller, a serial communication port, I/O means, an A/D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540.

There is provided a computer program P that comprises routines for controlling a braking system of a vehicle, such as a braking system described above. The computer program comprises routines for predicting a future temperature of the braking medium (of the first auxiliary brake) based on a current temperature of the braking medium and a current requested braking torque of the first auxiliary brake. The computer program further comprises routines for, if the predicted future temperature of the braking medium is above a predetermined maximum temperature of the braking medium, reducing the current requested braking torque of the first auxiliary brake to an adjusted braking torque to be demanded from the first auxiliary brake. The computer program further comprises routines for controlling the one or more additional brake means so as to compensate for the difference in braking torque between said current requested braking torque and the adjusted braking torque to be demanded from the first auxiliary brake. The computer program may further comprise routines for requesting the first auxiliary brake to deliver said adjusted braking torque to be demanded from the first auxiliary brake.

The program P may be stored in an executable form or in a compressed form in a memory 560 and/or in a read/write memory 550.

The data processing unit 510 may perform certain functions. For example, the data processing unit 510 may effect a certain part of the program stored in the memory 560 or a certain part of the program stored in the read/write memory 550.

The data processing device 510 can communicate with a data port 599 via a data bus 515. The nonvolatile memory 520 may be intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 may be intended to communicate with the data processing unit 510 via a data bus 511. The read/write memory 550 may be adapted to communicate with the data processing unit 510 via a data bus 514.

When data are received on the data port 599, they may be stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 may be prepared to effect code execution according to a computer program comprising program code for causing a control device to perform the method (or parts thereof) for controlling a braking system for a vehicle as described herein.

Parts of the methods herein described may be effected by the device 500 by means of the data processing unit 510 which runs the program stored in the memory 560 or the read/write memory 550. When the device 500 runs the program, methods herein described are executed.

Claims

1. A method for controlling a braking system (30) for a vehicle (1), the method performed by a control device (100), the braking system (30) comprising: a first auxiliary brake (10) operable by a braking medium; a cooling system (8) configured to cool the first auxiliary brake (10); and one or more additional brake means (7, 25); the method comprising steps of: (a) based on a current temperature of the braking medium and a current requested braking torque of the first auxiliary brake, predicting a future temperature (Tp) of the braking medium, (S110); (b) if the predicted future temperature (Tp) of the braking medium is above a predetermined maximum temperature (Tmax) of the braking medium, reducing the current requested braking torque of the first auxiliary brake (10) to an adjusted braking torque to be demanded from the first auxiliary brake (10), (S130); and (c) controlling the one or more additional brake means (7, 25) to compensate for the difference in braking torque between said current requested braking torque and the adjusted braking torque to be demanded from the first auxiliary brake (10), (S140). 2. The method according to claim 1, wherein predicting the future temperature (Tp) of the braking medium further comprises taking into account the current ambient temperature and/or the current cooling capacity of the cooling system (8). 3. The method according to any one of claims 1 or 2, wherein step (b) comprises reducing the current requested braking torque by a predetermined fixed amount of torque or a percentage of the current requested braking torque. 4. The method according to any one of the preceding claims, further comprising after step (b), repeating step (a) with usage of the adjusted braking torque to be demanded from the first auxiliary brake (10) as the current requested braking torque of the first auxiliary brake (10) in step (a), and iterating steps (a) and (b) until an appropriate adjusted braking torque to be demanded from the first auxiliary brake (10) which results in a predicted future temperature (Tp) of the braking medium being equal to or lower than the predetermined maximum temperature (Tmax) of the braking medium has been obtained. 5. The method according to any one of the preceding claims, further comprising, after step (a), a step of: (a1) if the predicted future temperature (Tp) of the braking medium is above the predetermined maximum temperature (Tmax) of the braking medium, increasing the cooling of the auxiliary brake (10) by increasing the cooling capacity of the cooling system (8), if not already at maximum cooling capacity; and optionally a step of: (a2) before step (b), repeating step (a) taking into account the increased cooling capacity of the cooling system (8). 6. The method according to any one of the preceding claims, further comprising determining the current temperature of the braking medium by measuring the temperature of the braking medium and/or by measuring the temperature of a circulating cooling medium in the cooling system (8). 7. A computer program (P) comprising program code for causing a control device (100) to perform the method according to any one of the preceding claims. 8. A computer-readable medium comprising instructions, which when executed by a control device (100), cause the control device (100) to perform the method according to any one of claims 1 to 7. 9. A control device (100) configured to control a braking system (30) of a vehicle (1), the braking system (30) comprising: a first auxiliary brake (10) operable by a braking medium; a cooling system (8) configured to cool the first auxiliary brake (10); and one or more additional brake means (7, 25); wherein the control device (100) is configured to predict a future temperature (Tp) of the braking medium taking into account the current temperature of the braking medium and a current requested braking torque of the first auxiliary brake; the control device (100) further configured to reducing the current requested braking torque of the first auxiliary brake (10) to an adjusted braking torque, to be demanded from the first auxiliary brake (10), if the predicted future temperature (Tp) of the braking medium is above a predetermined maximum temperature (Tmax) of the braking medium; the control device (100) further configured to control the one or more additional brake means (7, 25) so as to compensate for the difference in braking torque between said current requested braking torque and the adjusted braking torque to be demanded from the first auxiliary brake (10). 10. The control device (100) according to claim 9, further configured to take into account a current ambient temperature and/or a current cooling capacity of the cooling system (8) when predicting the future temperature (Tp) of the braking medium. 11. The control device (100) according to any one of claims 9 and 10, further configured to reduce the current requested braking torque of the first auxiliary brake to the adjusted braking torque to be demanded from the first auxiliary brake by reducing the current requested braking torque by a predetermined fixed amount or a percentage of the current requested braking torque. 12. The control device (100) according to any one of claim 9 to 11, further configured to control the cooling system (8) so as to increase the cooling capacity thereof, if not already at maximum cooling capacity, if the predicted future temperature (Tp) of the braking medium is above the predetermined maximum temperature (Tmax) of the braking medium. 13. The control device (100) according to any one of claims 9 to 12, further configured to determine an appropriate adjusted braking torque to be demanded from the first auxiliary brake, which results in a predicted future temperature (Tp) of the braking medium being equal to or lower than the predetermined maximum temperature (Tmax) of the braking medium, by iterating steps of predicting a future temperature of the braking medium and reducing a current requested braking torque to an adjusted braking to be demanded from the first auxiliary brake (10); and controlling the first auxiliary brake (10) based on the obtained appropriate adjusted braking torque to be demanded from the first auxiliary brake. 14. A vehicle (1) comprising a braking system (30), the braking system (30) comprising: a first auxiliary brake (10) operable by means of a braking medium; a cooling system (8) configured to cool the first auxiliary brake; and one or more additional brake means (7, 25); the vehicle (1) further comprising a control device (100) according to any one of claims 9 to 14.

1. Förfarande för styrning av ett bromssystem (30) för ett fordon (1), varvid förfarandet utförs av en styranordning (100), varvid bromssystemet (30) omfattar: en första hjälpbroms (10) som fungerar medelst ett bromsmedium; ett kylsystem (8) konfigurerat för att kyla den första hjälpbromsen (10); och ett eller flera ytterligare bromsmedel (7, 25); varvid förfarandet omfattar stegen att: (a) baserat på en aktuell temperatur hos bromsmediet och ett aktuellt begärt bromsmoment för den första hjälpbromsen, förutse en framtida temperatur (Tp) hos bromsmediet, (S110); (b) om den förutsedda framtida temperaturen (Tp) hos bromsmediet är över en förutbestämd maximitemperatur (Tmax) för bromsmediet, reducera det aktuella begärda bromsmomentet för den första hjälpbromsen (10) till ett justerat bromsmoment som ska begäras från den första hjälpbromsen (10), (S130); och (c) styra nämnda ena eller flera ytterligare bromsmedel (7, 25) för att kompensera för skillnaden i bromsmoment mellan nämnda aktuella begärda bromsmoment och det justerade bromsmoment som ska begäras från den första hjälpbromsen (10), (S140).

2. Förfarande enligt krav 1, varvid förutseendet av den framtida temperaturen (Tp) hos bromsmediet vidare omfattar att beakta den aktuella omgivningstemperaturen och/eller den aktuella kylkapaciteten hos kylsystemet (8).

3. Förfarande enligt något av kraven 1 eller 2, varvid steg (b) omfattar att reducera det aktuella begärda bromsmomentet med ett förutbestämt fast momentvärde eller en procentandel av det aktuella bromsmomentet.

4. Förfarande enligt något av de föregående kraven, vidare omfattande att efter steg (b), upprepa steg (a) med användning av det justerade bromsmoment som ska begäras från den första hjälpbromsen (10) som det aktuella begärda bromsmomentet för den första hjälpbromsen (10) i steg (a), och upprepa steg (a) och (b) tills ett lämpligt justerat bromsmoment som ska begäras från den första hjälpbromsen (10) som resulterar i en förutsedd framtida temperatur (Tp) för bromsmediet som är lika med eller lägre än den förutbestämda maximitemperaturen (Tmax) för bromsmediet har erhållits.

5. Förfarande enligt något av de föregående kraven, vidare omfattande, efter steg (a), ett steg bestående av att: (a1) om den förutsedda framtida temperaturen (Tp) hos bromsmediet är över den förbestämda maximitemperaturen (Tmax) för bromsmediet, öka kylningen av hjälpbromsen (10) genom att öka kylkapaciteten hos kylsystemet (8), om det inte redan är vid maximal kylkapacitet; och fakultativt ett steg bestående av att: (a2) före steg (b), upprepa steg (a) med beaktande av kylsystemets ökade kylkapacitet (8).

6. Förfarande enligt något av de föregående kraven, vidare omfattande att fastställa den aktuella temperaturen hos bromsmediet genom att mäta temperaturen hos bromsmediet och/eller genom att mäta temperaturen hos ett cirkulerande kylmedium i kylsystemet (8).

7. Datorprogram (P) omfattande programkod för att bringa en styranordning (100) att utföra förfarandet enligt något av de föregående kraven.

8. Datorläsbart medium omfattande instruktioner, som, när de utförs av en styranordning (100), bringar styranordningen (100) att utföra förfarandet enligt något av kraven 1 till 7.

9. Styranordning (100) konfigurerad för att styra ett bromssystem (30) hos ett fordon (1), varvid bromssystemet (30) omfattar: en första hjälpbroms (10) som fungerar medelst ett bromsmedium; ett kylsystem (8) konfigurerat för att kyla den första hjälpbromsen (10); och ett eller flera ytterligare bromsmedel (7, 25); varvid styranordningen (100) är konfigurerad för att förutse en framtida temperatur (Tp) hos bromsmediet med beaktande av den aktuella temperaturen hos bromsmediet och ett aktuellt begärt bromsmoment för den första hjälpbromsen; styranordningen (100) vidare är konfigurerad för att reducera det aktuella begärda bromsmomentet för den första hjälpbromsen (10) till ett justerat bromsmoment, som ska begäras från den första hjälpbromsen (10), om den förutsedda temperaturen (Tp) hos bromsmediet är över en förutbestämd maximitemperatur (Tmax) för bromssystemet; styranordningen (100) vidare är konfigurerad för att styra nämnda ena eller flera ytterligare bromsmedel (7, 25) för att kompensera för skillnaden i bromsmoment mellan nämnda aktuella begärda bromsmoment och det justerade bromsmoment som ska begäras från den första hjälpbromsen (10).

10. Styranordning (100) enligt krav 9, vidare konfigurerad för att beakta en aktuell omgivningstemperatur och/eller en aktuell kylkapacitet hos kylsystemet (8) när den förutser den framtida temperaturen (Tp) hos bromsmediet.

11. Styranordning (100) enligt något av kraven 9 och 10, vidare konfigurerad för att reducera det aktuella bromsmomentet för den första hjälpbromsen till det justerade bromsmoment som ska begäras från den första hjälpbromsen genom att reducera det aktuella begärda bromsmomentet med ett förutbestämt fast värde eller en procentandel av det aktuella begärda bromsmomentet.

12. Styranordning (100) enligt något av kraven 9 till 11, vidare konfigurerad för att styra kylsystemet (8) för att öka kylkapaciteten därav, om det inte redan är vid maximal kylkapacitet, om den förutsedda framtida temperaturen (Tp) hos bromsmediet ligger över den förutbestämda maximitemperaturen (Tmax) för bromsmediet.

13. Styranordning (100) enligt något av kraven 9 till 12, vidare konfigurerad för att fastställa ett lämpligt justerat bromsmoment som ska begäras från den första hjälpbromsen, vilket resulterar i en förutsedd framtida temperatur (Tp) hos bromsmediet som är lika med eller lägre än den förbestämda maximitemperaturen (Tmax) för bromsmediet, genom att upprepa stegen att förutse en framtida temperatur hos bromsmediet och reducera ett aktuellt begärt bromsmoment till ett justerat bromsmoment som ska begäras från den första hjälpbromsen (10); och styra den första hjälpbromsen (10) baserat på det erhållna lämpliga justerade bromsmoment som ska begäras från den första hjälpbromsen.

14. Fordon (1) omfattande ett bromssystem (30), varvid bromssystemet (30) omfattar: en första hjälpbroms (10) som fungerar medelst ett bromsmedium; ett kylsystem (8) konfigurerat för att kyla den första hjälpbromsen; och ett eller flera ytterligare bromsmedel (7, 25); varvid fordonet (1) vidare omfattar en styranordning (100) enligt något av kraven 9 till 13.