Method for operating a braking system of a vehicle, control unit for a vehicle, vehicle, and vehicle combination

Abstract

The invention relates to a method for operating a braking system (10) of a vehicle (50), in particular a commercial vehicle, the braking system having a friction brake (11) and a regenerative brake (12), wherein a braking scenario is determined based on a deceleration parameter in response to a requested deceleration of the vehicle (50), and wherein the vehicle (50) is decelerated depending on the determined braking scenario by means of the friction brake (11) and / or the regenerative brake (12), wherein a conditioning criterion is used to check whether a predefined conditioning effect for conditioning the friction brake (11) can be achieved with the determined braking scenario, and, if the conditioning criterion is satisfied, the vehicle (50) is decelerated by means of the friction brake (11). The invention also relates to a control unit (20), to a vehicle (50), and to a vehicle combination (70) for carrying out the method.

Description

[0001] Method for operating a braking system of a vehicle, control unit for a

[0002] Vehicle, vehicle and vehicle combination

[0003] The invention relates to a method for operating a braking system of a vehicle, in particular a commercial vehicle, comprising a friction brake and a regenerative braking system. The invention further relates to a control unit for a vehicle with a braking system, as well as to a vehicle and a vehicle combination.

[0004] The braking system operated by the method has a friction brake and a regenerative brake. A friction brake is understood to be a mechanical brake with a brake pad by means of which the vehicle can be decelerated through a friction effect, with kinetic energy being converted into heat during the braking process. A regenerative brake, also called a regenerative brake, is understood to be an electromechanical brake implemented by means of an electric drive, by means of which the vehicle can be decelerated by an electric motor, with kinetic energy being converted into electrical energy during the braking process. Accordingly, it is provided that, in addition to a friction brake, the vehicle has an electric drive designed for regenerative deceleration of the vehicle for selective acceleration and deceleration of the vehicle, which is simply referred to below as a regenerative brake.

[0005] In principle, it is already known to decelerate a vehicle using a regenerative brake, a friction brake, or a combination of the regenerative brake and the friction brake. Such combined braking using both types of brakes is referred to in technical circles as brake blending. Due to the ability of the regenerative brake to convert kinetic energy into electrical energy, which can be fed into a vehicle's energy storage system, for example, conventional methods for operating braking systems in vehicles that feature a regenerative brake and a friction brake prioritize the use of the regenerative brake. The friction brake is used as a support in less frequent braking situations, such as emergency braking, where maximum deceleration power must be provided as quickly as possible.Due to the significantly reduced use of the friction brake in such conventional processes with prioritized regenerative braking, a reduction in the friction coefficient of the friction brake pad can occur, for example, due to a so-called sleepiness of the brake pad due to a lack of thermal activation, which can lead to a reduced braking effect when the friction brake is deployed. It has already been recognized that regular activation of the friction brake can help to reduce or prevent such a sleepy effect. Activating the friction brake to restore a desired friction coefficient of the brake pad can be referred to as conditioning, since it actively influences the condition of the friction brake in terms of its braking effectiveness. Conditioning can therefore serve to maintain or restore the braking capability of the friction brake and can be achieved through its activation.Conditioning can be carried out according to known methods, for example cyclically using a braking operation counter or taking into account predetermined conditions, for example with regard to a measurable condition of the brake pad of the friction brake.

[0006] WO 2013 / 182480 A1 describes a method for ensuring the braking effect of a brake in ferry operation, wherein the brake comprises a braking surface and a brake pad. According to the described method, the braking effect of the brake is detected, a friction characteristic of the friction surface is assigned to the braking effect, and this value is compared with a limit value. If the limit value is exceeded, the brake is activated in such a way that material removal and / or heat input to the braking surface and / or friction surface is / are caused.

[0007] DE 10 2021 131 753 A1 relates to a method for actuating a friction brake device for an electrically driven vehicle with an electric drive capable of regenerative braking. According to the described method, it is determined whether braking by the friction brake device is required for lining maintenance, and braking is initiated by the friction brake device based on a braking parameter. In addition, drive information relating to the electric drive is determined, and the braking parameter and a drive parameter are modified depending on the drive information to achieve lining maintenance, with the drive parameter initiating operation of the electric drive depending on the braking.

[0008] An efficient design of the method for operating the braking system to maximize the usable recuperation energy on the one hand and to effectively prevent the friction brake from falling asleep as an opposing requirement on the other hand continues to represent a technical challenge. At the same time, it is desirable to provide an economical and technically feasible solution, since the known methods can be associated with increased measurement and control technology expenditure and a high level of technical complexity.

[0009] Against this background, the object of the invention is to provide a method and devices for operating a braking system of a vehicle comprising a friction brake and a recuperation brake, with which a high proportion of usable recuperation energy can still be achieved with deceleration processes of the vehicle and yet the braking effect of the friction brake can be effectively maintained in a simple and efficient manner.

[0010] This object is achieved by a method for operating a braking system of a vehicle according to claim 1, as well as by a control unit, a vehicle, and a vehicle combination according to the independent claims. Advantageous embodiments are disclosed in the dependent claims, the description, and the figures.

[0011] According to the features of independent claim 1, a method is proposed for operating a braking system of a vehicle, in particular a commercial vehicle, having a friction brake and a recuperation brake, wherein in response to a requested deceleration of the vehicle, a braking scenario is determined on the basis of a deceleration parameter, and wherein the vehicle is decelerated by means of the friction brake and / or the recuperation brake as a function of the determined braking scenario, wherein a conditioning criterion is used to check whether a predetermined conditioning effect for conditioning the friction brake can be achieved with the determined braking scenario, and if the conditioning criterion is met, the vehicle is decelerated by means of the friction brake.In other words, the proposed method includes a check to determine whether, in the context of a current or expected braking situation, a sufficient conditioning effect can be achieved by activating the friction brake to decelerate the vehicle, so that the friction coefficient of the friction brake pad can be effectively and efficiently increased again. In particular, if the conditioning criterion is not met, a decision can be made to decelerate the vehicle with the recuperation brake or with a combination of the recuperation brake and the friction brake, depending on the determined braking scenario, so that electrical energy can be recovered. In particular, if the conditioning criterion is met, it can be provided that the vehicle is decelerated exclusively using the friction brake, so that the entire requested deceleration power is implemented by means of the friction brake in order to maximize the conditioning effect.If the vehicle's braking system has a plurality of friction brakes, the described method can refer to several or all of the plurality of friction brakes. Accordingly, if the conditioning criterion is met, the vehicle can be decelerated using one, several, or all of the plurality of friction brakes, depending on the selected embodiment.

[0012] The proposed method has the advantage that, when the vehicle is decelerated by the friction brake for conditioning purposes, a sufficient conditioning effect can be ensured, for example, with regard to the desired material removal from and / or heat input into the brake pad to maintain the braking effect of the friction brake. This reliably prevents the friction brake from falling asleep, while any unnecessary braking operations performed using the friction brake, which would, for example, be associated with an inadequate conditioning effect, are avoided in favor of using the regenerative braking system. Accordingly, not only is the maintenance or restoration of the braking capacity of the friction brake ensured, but the increased usability of the regenerative braking system associated with the conditional conditioning also leads to an increase in the efficiency of the braking system.The vehicle can in particular be a commercial vehicle, in particular a trailer such as a semi-trailer. In principle, however, the method is also applicable to passenger cars. The vehicle has in particular an electric drive designed for recuperative deceleration of the vehicle for selectively accelerating and decelerating the vehicle. Depending on the embodiment, the vehicle can, for example, be a purely electrically powered electric vehicle or a hybrid vehicle with an electric drive and a combustion engine. The vehicle's electric drive can be operated in motor mode and in generator mode. In generator mode, the electric drive has the effect of a recuperation brake. Braking using the recuperation brake, in which kinetic energy is converted into electrical energy, is also referred to as regenerative braking.

[0013] The vehicle's braking system can be controlled by a control unit to control the braking functions of the braking system. The braking system can, in particular, have a brake control unit configured to implement the proposed method. Depending on the embodiment, the braking system can have one or more regenerative brakes and one or more friction brakes. The friction brake can be controlled by the control unit via an electropneumatic braking system. Depending on the embodiment, the regenerative brake can be controlled, for example, by the brake control unit or by a drive control unit of the vehicle assigned to the electric drive.The control unit can be configured to determine a braking scenario based on a deceleration parameter in response to a requested deceleration of the vehicle and to decelerate the vehicle using the friction brake and / or the regenerative brake depending on the determined braking scenario. The control unit can further be configured to check, based on a conditioning criterion, whether a predetermined conditioning effect for conditioning the friction brake can be achieved with the determined braking scenario, and to decelerate the vehicle using the friction brake if the conditioning criterion is met.

[0014] A requested deceleration of the vehicle can be transmitted to the control unit, for example, as a deceleration request signal. A deceleration request signal can be generated, for example, based on an accelerator pedal signal when a driver depresses a brake pedal of the vehicle and transmitted to the control unit. Alternatively or additionally, a deceleration request signal can be generated, for example, by another control device of the vehicle, such as a driver assistance system, and transmitted to the control unit.

[0015] A braking scenario is determined based on a deceleration parameter, which may include, for example, a signal parameter of the deceleration request signal such as the accelerator pedal signal strength, a dynamic vehicle parameter such as its current speed, a static vehicle parameter such as its load, and / or an environmental parameter such as the condition or gradient of the road surface, weather conditions, or a traffic situation. In particular, the braking scenario can be determined based on a combination of deceleration parameters. In other words, the deceleration parameters can take into account static or dynamic vehicle status information and variables that can affect the deceleration performance to be provided by the braking system or are directly related to this. Determining a braking scenario can be accompanied by a parameter analysis of a current or expected braking situation.Such a parameter analysis can, for example, include a classification of a deceleration parameter value, for example, by assigning the parameter value or a combination of parameter values ​​to predefined braking scenarios based on specified criteria regarding the deceleration parameters. For example, a deceleration parameter value can be compared with a limit value. Braking scenarios can be defined in various levels of detail, for example, in a particularly simple way through dual assignments such as "light braking" and "hard braking" or through fine-grained multi-factor scenarios such as "light braking in urban traffic on dry roads" or "hard braking on a downhill gradient."Based on the determined braking scenario, the vehicle can be decelerated using the friction brake and / or the regenerative braking system by applying appropriate control specifications in order to individually and appropriately optimize the deceleration effect and / or utilize recuperation energy. To check whether a specified conditioning effect for conditioning the friction brake can be achieved with the determined braking scenario, corresponding conditioning effect information can be assigned to specified braking scenarios, one of the deceleration parameters, or a combination of deceleration parameters, for example, or a conditioning property can be specified as a condition that is, for example, algorithmically comparable to properties of the determined braking scenario.If the test result regarding fulfillment of the conditioning criterion is positive, deceleration of the vehicle can be initiated immediately using the friction brake, in particular exclusively using the friction brake. This ensures that the friction brake is conditioned under favorable conditions, for example, ensuring sufficient energy input into the friction brake pad. On the other hand, testing the conditioning criterion can ensure that no unnecessary friction braking is performed for conditioning purposes if the intended conditioning cannot achieve the desired braking force-maintaining effect under the given circumstances, or only insufficiently.

[0016] In principle, it is also conceivable to make a conditioning process of the friction brake dependent on additional factors, such as user-defined or temporal factors, or on a measurable condition of the brake pad by activating it. For example, the conditioning criterion can be checked depending on a check of a temporal precondition, such as the expiration of a minimum period since the last conditioning. Furthermore, it is conceivable, for example, to carry out conditioning after the expiration of a predefined maximum period regardless of whether the conditioning criterion is met, or, for example, to carry out a power-enhancing measure to actively influence the conditioning criterion, as explained below, or, for example, to initiate a time-limited activation of the friction brake during constant travel or acceleration of the vehicle, as explained below.According to one embodiment, the conditioning criterion can be considered met if a predetermined minimum deceleration performance of the friction brake can be achieved with the determined braking scenario. This allows a predetermined conditioning effect to be easily implemented using a brake-related comparison criterion. Due to a direct relationship between the deceleration performance and an energy input into the brake lining of the friction brake, a sufficient energy input into the friction lining of the friction brake can be reliably ensured when the predetermined minimum deceleration performance is reached. The deceleration performance of the friction brake can be a braking performance in the sense of a product of braking force and the relative speed of the friction bodies. The deceleration performance of the friction brake correlates with an energy input into the brake lining, part of which is converted into heat and mechanical work for the conditioning of the friction brake.A minimum deceleration power can be defined as a limit value above which a specified conditioning effect, such as a desired minimum heat input, can be achieved. It is conceivable, for example, that predefined braking scenarios are assigned different representative values ​​or value ranges of deceleration power, which are compared with the specified minimum deceleration power when testing the conditioning criterion. Alternatively or additionally, it is possible to estimate or calculate a current or expected deceleration power for the braking scenario based on one or more deceleration parameters to determine the braking scenario.

[0017] According to one embodiment, the conditioning criterion can be considered met if one of the following predefined minimum values ​​can be achieved with the determined braking scenario: a predefined minimum brake pressure, a predefined minimum speed, a predefined minimum axle load, and / or a predefined minimum control pressure. These are easily measured deceleration parameters that have a direct impact on the achievable deceleration performance and can therefore be representative of the achievable energy input into the brake pad to achieve a corresponding conditioning effect. According to one embodiment, fulfillment of the conditioning criterion can depend on whether at least two of the aforementioned minimum values ​​can be achieved, thus providing increased certainty regarding the achievable conditioning effect.

[0018] In modern vehicles, the majority of braking events during vehicle operation occur in a lower brake pressure range. In such a lower brake pressure range, it may be advantageous to use the regenerative braking or a combination of the regenerative braking with the friction brake after a predefined brake blending to decelerate the vehicle. Infrequent, more severe braking events above a predefined minimum brake pressure can, however, be used to condition the friction brake by activating it, in particular by activating it alone. The minimum brake pressure can be specified by the control system depending on the vehicle. According to one non-limiting embodiment, a brake pressure between two and three bar can be specified as the minimum brake pressure for a commercial vehicle such as a semi-trailer.The brake pressure as a deceleration parameter can be easily derived from a deceleration request signal, enabling rapid processing, for example by comparing the derived brake pressure with the minimum brake pressure.

[0019] The higher the vehicle speed, the greater the energy input into the friction brake pad for the same braking force. Friction brake conditioning can therefore be more efficient at higher speeds and result in a greater conditioning effect. By specifying a minimum speed as the conditioning criterion, the vehicle's current speed can be used as an easily recorded deceleration parameter and compared with the specified minimum speed. The minimum speed can be specified by the control system, particularly depending on the vehicle and optionally depending on national speed regulations.According to a non-limiting exemplary embodiment, a speed of 50 km / h or higher, in particular a value between 50 and 80 km / h, for example 60 km / h, can be specified as the minimum speed for a commercial vehicle such as a semi-trailer. If the vehicle's axle load is low, it may under certain circumstances be the case that only an inadequate conditioning effect can be achieved when the vehicle is decelerated using the friction brake for conditioning purposes. In addition, the risk of wheel locking and the associated intervention of a vehicle's ABS system may increase when the vehicle is decelerated using the friction brake with a low axle load. It may therefore be advantageous to specify a minimum axle load for deceleration using the friction brake for conditioning purposes in the control system.The minimum axle load can be specified by the control system, particularly depending on the vehicle and optionally depending on national regulations regarding permissible axle loads. According to a non-limiting exemplary embodiment, an axle load of, for example, four tonnes or more can be specified as the minimum axle load for a commercial vehicle such as a semi-trailer. One advantage of a specified minimum axle load as a conditioning criterion is that fulfillment of an axle load-related conditioning criterion can be determined at the start of the journey. Thus, for example, deceleration of the vehicle using the friction brake for conditioning purposes can be generally permitted or not for the duration of the journey. This can reduce the load on the control unit when processing deceleration request signals.

[0020] For example, if the vehicle is designed as a trailer and is connected or connectable to a towing vehicle to form a vehicle combination, a deceleration requested in the towing vehicle can be signaled to the trailer vehicle by means of a control pressure. The level of the control pressure can be dependent on a desired target deceleration, so that a braking system of the trailer vehicle derives the required brake pressure to implement the requested deceleration from the level of the control pressure. Accordingly, a specified minimum control pressure can advantageously be used as an indirect parameter of a minimum brake pressure as a minimum value to fulfill the conditioning criterion.

[0021] According to one embodiment, predictive route data of the vehicle can be taken into account when determining the braking scenario and / or when checking the conditioning criterion. For example, one or more braking scenarios along the vehicle's intended route can be determined based on topology data. This allows the braking scenario to be determined and / or an assessment of whether a sufficient conditioning effect can be achieved with friction braking in a current or expected braking situation to be carried out with a forward-looking approach. In particular, route sections along the vehicle's intended route can be identified that could be associated with an increased conditioning effect upon activation of the friction brake, for example, upon detection of an impending longer downhill stretch.Activation of the friction brake for conditioning purposes can therefore be proactively planned and carried out more efficiently for such identified route sections.

[0022] Depending on the embodiment, the described conditioning criteria can be evaluated individually, partially with each other, or all together in combination, for example by linking the individual test results using Boolean operators and assigning an overall test result to the combined test results. Furthermore, with regard to the specified minimum values, several minimum values ​​can also be stored in the control system, which can be selected depending on different driving or environmental conditions. For example, in winter weather conditions, higher minimum deceleration performances may be required to activate the friction brake for conditioning purposes. Accordingly, according to one embodiment, the conditioning criteria can be flexibly selected, for example, through stored control system instructions or through manual user input.

[0023] According to one embodiment, the deceleration performance achievable with the determined braking scenario can be increased to a predetermined minimum deceleration performance by means of a performance-enhancing measure. A performance-enhancing measure can be an active influencing of a conditioning criterion. For example, a deceleration parameter can be influenced in such a way that a braking scenario with an achievable, predetermined conditioning effect is actively brought about. A performance-enhancing measure can ensure sufficient conditioning of the friction brake, for example, in cases where the conditioning criterion has not been met, for example, due to a particularly proactive driving style or slow-moving traffic over an extended period of time.

[0024] According to one embodiment, the power-enhancing measure can comprise a predefined distribution of a deceleration power to be provided in response to the requested deceleration across one or more of a plurality of vehicle axles of the vehicle. This enables an effective and easily implemented power increase to ensure the conditioning effect. With the described power-enhancing measure, the required deceleration power for decelerating the vehicle can be specifically distributed among one or more of a total number of vehicle axles of the vehicle as required in order to bundle the provided deceleration power according to a specific distribution scheme, for example, individually or in pairs.For example, when the friction brakes of several vehicle axles are activated for deceleration purposes, the vehicle's friction brakes are controlled with at least approximately evenly distributed power requirements. When one friction brake of the vehicle is activated for conditioning purposes, one or more friction brakes can be controlled with a higher power requirement than the other friction brakes. This makes it possible to specifically achieve a predetermined conditioning effect if the friction brake on the vehicle axle is activated for conditioning to provide the predefined distributed deceleration power. In this way, for example, the friction brakes of several vehicle axles of the vehicle can also be specifically conditioned one after the other on a scheduled basis. Depending on the embodiment, the power increase measure can be carried out depending on deceleration parameters or the determined braking scenario.For example, in braking scenarios that involve an increased risk of wheel locking, the deceleration power to be provided may be distributed across several vehicle axles or the implementation of the power increase measure may not be permitted for such braking scenarios.

[0025] According to one embodiment, conditioning of the friction brake can be carried out by means of a temporary activation of the friction brake during constant travel or acceleration of the vehicle if fulfillment of the conditioning criterion for a requested deceleration has not been determined over a predefined period of time. In other words, in such a case, in addition to activating the friction brake in response to a requested deceleration when the conditioning criterion is fulfilled, it is also possible to specifically activate the friction brake without a requested deceleration being present. This can additionally ensure sufficient conditioning of the friction brake, for example in cases where the conditioning criterion has not been met for an extended period of time, for example due to a particularly proactive driving style or slow-moving traffic.To perform the conditioning, a brake pressure above the brake application pressure, for example, just above 0.4 bar, can be applied during constant travel or acceleration of the vehicle. The time-limited activation can, for example, have an activation duration of up to two minutes. According to one non-limiting embodiment, the predefined period can be a period of more than 10 hours of driving time.

[0026] According to one embodiment, a condition of the friction brake can be checked or continuously monitored by detecting or estimating a braking parameter related to an energy input into a brake pad of the friction brake. A braking parameter can, for example, be a deceleration power or braking force provided at the friction brake. The braking parameter can be derived from one of the deceleration parameters described above. For example, a brake pressure or a speed of the vehicle at the time of the requested deceleration can be taken into account during the detection or estimation. Based on the braking parameter, for example, an expected energy input can be modeled. The estimated energy input can be a statistical reference value with which a condition of the friction brake can be indirectly monitored.Alternatively or additionally, it is possible to consider sensor-detected variables on the brake pad, such as heating of the brake pad monitored by a temperature sensor. Accordingly, the temperature of the brake pad can also be considered a braking parameter. Through accompanying assessment or sensor-supported monitoring of the condition of the friction brake, appropriate active conditioning can be ensured, while still achieving a high proportion of usable recuperation energy during vehicle deceleration. Furthermore, it is conceivable that the tested or monitored condition of the friction brake could be used as a condition for decelerating the vehicle using the friction brake for conditioning purposes.Accordingly, depending on the determined or estimated condition of the friction brake, a conditioning braking action can be performed by decelerating the vehicle using the friction brake. The condition of the friction brake can thus be used, for example, as a precondition for checking the determined braking scenario for compliance with the conditioning criterion.

[0027] According to one embodiment, the vehicle can be designed as an electrically powered trailer. The trailer can, for example, be purely electrically powered or have a combination of an electric drive and a combustion engine. Different trailer types can be selected as the trailer, for example, semi-trailers, caravans, or car trailers. Due to powerful electric drives for fulfilling the trailer's transport tasks, increasingly improved recuperation processes in practice, and the increasing performance of continuous braking systems, electrically powered trailers can be more susceptible to decreasing braking effects on the friction brakes due to falling asleep. Accordingly, the proposed method can have increased advantages for vehicles designed as electrically powered trailers.

[0028] According to one embodiment, the vehicle configured as an electrically powered trailer can be connected to a towing vehicle to form a vehicle combination, wherein, to condition the friction brake in response to a requested deceleration, a higher deceleration power is provided to the vehicle configured as an electrically powered trailer than to the towing vehicle as a performance-enhancing measure. In other words, the trailer can be deliberately braked more strongly than the towing vehicle in order to also brake the towing vehicle mechanically connected to the trailer, thereby increasing the energy input into the friction brake of the trailer. The vehicle combination remains stretched, which is advantageous for safety reasons.By deliberately redistributing the deceleration power to be provided to the vehicle combination, with a power focus on the trailer, an effective and easy-to-implement power increase measure is provided to ensure the conditioning effect of the deceleration process on the trailer's friction brake. The towing vehicle can be equipped with a continuous braking system. Increased deceleration power can be requested from the trailer as soon as the continuous braking system in the towing vehicle is activated.

[0029] According to one embodiment, the deceleration performance of the vehicle configured as an electrically powered trailer can be temporarily increased to a maximum permissible deceleration performance corresponding to a brake cable adjustment of the vehicle combination. This allows for a temporary maximization of the deceleration performance within specified permissible limits. By limiting the time for the increase, excessive wear of the brake pad can be avoided outside of a conditioning process. According to a non-limiting exemplary embodiment, a temporary shift of the deceleration performance of the trailer can occur from a mid-range to an upper range limit of a compatibility band defined for brake cable adjustment, for example, the so-called EG band.The temporary increase in the maximum permissible deceleration power in accordance with the brake cable coordination of the vehicle combination can occur in particular if, in order to condition the friction brake in response to a requested deceleration power, a higher deceleration power is provided to the trailer vehicle than to the towing vehicle as a power increase measure.

[0030] The object underlying the invention is further achieved with a control unit for a vehicle for carrying out the method according to one of the features described above, wherein the control unit is configured to receive a deceleration request signal, to determine a braking scenario based on a deceleration parameter and to control a recuperation brake and / or a friction brake of a braking system of the vehicle depending on the determined braking scenario in order to decelerate the vehicle, wherein the control unit is configured to check, based on a conditioning criterion, whether a predetermined conditioning effect for conditioning the friction brake can be achieved with the determined braking scenario, and to control the friction brake of the braking system in order to decelerate the vehicle if the conditioning criterion is met.The proposed control unit can also achieve the aforementioned advantages of efficient and effective conditioning of the friction brake of the braking system, while still allowing a high proportion of usable recuperation energy to be achieved during vehicle deceleration. The control unit can be designed, for example, as a brake control unit of the braking system. The deceleration request signal can be generated, for example, based on an accelerator pedal signal when a driver actuates a brake pedal of the vehicle and transmitted to the control unit. Alternatively or additionally, a deceleration request signal can be generated, for example, by another control device of the vehicle, for example, by a driver assistance device, and transmitted to the control unit. If the vehicle is designed as a trailer, the control unit can, for example, be a brake control unit of the trailer.In principle, it is also possible for a towing vehicle connected to the trailer vehicle to have the control unit or for a towing vehicle control to be signal-connected to the control unit of the trailer vehicle, so that the deceleration power to be provided can be coordinated and distributed between the towing vehicle and the trailer vehicle in accordance with the previously described embodiments of the method.

[0031] The object underlying the invention is further achieved with a vehicle, in particular a commercial vehicle, for carrying out the method according to one of the features described above, wherein the vehicle has a braking system with a friction brake and a regenerative brake and a control unit according to one of the features described above. The vehicle has an electric drive designed for regenerative deceleration of the vehicle for selectively accelerating and decelerating the vehicle. Depending on the embodiment, the vehicle can be, for example, a purely electrically powered electric vehicle or a hybrid vehicle with an electric drive and a combustion engine. The electric drive of the vehicle can be operated in motor mode and in generator mode. In generator mode, the electric drive has the effect of a regenerative brake.

[0032] According to one embodiment, the vehicle can be designed as an electrically powered trailer. Different trailer types can be selected as trailers, for example, semi-trailers, caravans, or car trailers. Due to powerful electric drives for fulfilling the trailer's transport tasks, increasingly improved recuperation processes, and the increasing performance of continuous braking systems, electrically powered trailers can be more susceptible to reduced braking performance of the friction brakes due to slackening. This problem can be advantageously overcome with the described vehicle designed as an electrically powered trailer.

[0033] The object underlying the invention is further achieved with a vehicle combination comprising a towing vehicle and a vehicle designed as an electrically powered trailer according to the features described above. With a vehicle combination, for example, as part of a power increase measure, the deceleration power to be provided can be dynamically distributed in such a way that a conditioning effect for a friction brake to be conditioned of the vehicle combination, in particular of the electrically powered trailer, can be optimized. It is also conceivable in principle for the vehicle combination to comprise a towing vehicle and several trailers. Such a vehicle combination is also called a road train. Depending on the embodiment, one, several or all trailers of the road train can be electrically powered.

[0034] In general, unless explicitly defined otherwise, the words “ein / eine” are not to be understood as numbers, but as indefinite articles with the literal meaning of “at least one”.

[0035] The invention permits various embodiments and is explained in more detail below using an exemplary embodiment with the accompanying drawings. They show schematically: Fig. 1 is a schematic diagram of a vehicle combination with a vehicle having a braking system, in a side view;

[0036] Fig. 2 is a simplified flow diagram of a method for operating the braking system; and

[0037] Fig. 3 is a schematic diagram of a vehicle control unit for controlling the braking system.

[0038] Fig. 1 shows a schematic diagram of a vehicle combination 70 with a towing vehicle 60 and a vehicle 50 configured as a trailer 50a. According to the exemplary embodiment shown, the vehicle combination 70 is configured as a semitrailer, with the towing vehicle 60 being formed by a tractor unit and the trailer 50a by a semitrailer. The towing vehicle 60 and the trailer 50a can be regarded as commercial vehicles. The trailer 50a is electrically powered and accordingly has an electric drive operable in motor mode and in generator mode, which is configured to generate an accelerating or decelerating torque on a vehicle axle 51 of the trailer 50a and is referred to below as the regenerative brake 12.

[0039] As can be seen from Fig. 1, the trailer vehicle 50a has a braking system 10 with friction brakes 11, a regenerative brake 12, and a control unit 20, exemplified as a brake control unit. The friction brakes 11 are arranged on different vehicle axles 51 of the trailer vehicle 50a and each have a brake pad 11a for transmitting a braking force to the respective vehicle axle 51. The regenerative brake 12 is schematically illustrated on one of the vehicle axles 51 shown. The control unit 20 can be configured to control the friction brakes 11 via a braking system (not shown in detail), for example an electropneumatic one. The control unit 20 can also be configured to control the regenerative brake 12 or can be connected via signaling to a separate drive control unit for controlling the regenerative brake 12.The towing vehicle 60 has a towing vehicle control 61, to which, for example, a deceleration request signal 21, shown schematically in Fig. 3 and generated, for example, by an accelerator pedal signal, can be input. According to the exemplary embodiment shown, the towing vehicle 60 is also electrically driven and therefore, in addition to a friction brake 11, additionally has a recuperation brake 12. The recuperation brake 12 and the friction brake 11 can be controlled, in particular, via a braking system of the towing vehicle 60 by means of the towing vehicle control 61 or a supplementary brake control unit and / or drive control unit of the towing vehicle 60. To simplify the illustration of the technical operative connection, signal connections 73 between the towing vehicle control 61 and the friction brake 11 as well as the recuperation brake 12 of the towing vehicle 60 are shown.The towing vehicle control 61 is also signal-coupled to the trailer vehicle 50a via a trailer interface 72 and can communicate with the control unit 20 via a corresponding signal connection 73, in particular forwarding the deceleration request signal 21 to the latter.

[0040] The control unit 20, the vehicle 50 designed as a trailer vehicle 50a and the described vehicle combination 70 are designed according to the illustrated embodiment to carry out the method 100 for operating the braking system 10 of the vehicle 50, which is described below with reference to Fig. 2 in conjunction with Fig. 3.

[0041] For this purpose, Fig. 2 shows a simplified flow diagram of the method 100 for operating the braking system 10. Fig. 3 shows a schematic diagram of the control unit 20 of the vehicle 50 for controlling the braking system 10. The control unit 20 has, for example, a processor-based data processing unit 40, a memory unit 41, a plurality of signal inputs 20a and a plurality of signal outputs 20b.

[0042] The method 100 begins, as illustrated in Fig. 2, with the start 101 of the method 100. From the start 101 of the method 100, it can be monitored, for example by means of the control unit 20 shown in Fig. 3, whether a deceleration of the vehicle 50 is requested. To provide information about a requested deceleration, a deceleration request signal 21 can be transmitted, for example, as shown in Fig. 3, from the towing vehicle control 61 to the control unit 20 of the vehicle 50. If a requested deceleration of the vehicle 50 is present in a first step 110 of the method 100, a braking scenario 22, schematically illustrated in Fig. 3, is determined in a second step 120 in response to the requested deceleration. Depending on the determined braking scenario 22, the control unit 20 causes the vehicle 50 to be decelerated by means of the friction brakes 11 and / or by means of the regenerative brake 12.For this purpose, a third step 130 is used to check, based on a conditioning criterion 23, whether a predetermined conditioning effect for conditioning the friction brakes 11 can be achieved with the determined braking scenario 22. If the check shows that the conditioning criterion 23 is considered to be met, the vehicle 50 is decelerated by means of the friction brakes 11 in a fourth step 140a. If the check shows that the conditioning criterion 23 is not considered to be met, the vehicle 50 is decelerated in an alternative step 140b by means of the recuperation brake 12 or by means of the recuperation brake 12 and the friction brakes 11 in combination. This allows a high proportion of usable recuperation energy to continue to be achieved with deceleration processes of the vehicle 50, while still maintaining the braking effect of the friction brakes 11 in a simple and efficient manner.

[0043] According to the exemplary embodiment illustrated in Fig. 2, if the test result indicates that the conditioning criterion 23 is not met, a follow-up test can be performed according to a further step 150. During the follow-up test, it can be determined whether the conditioning criterion 23 can be met by a power increase measure 29 visualized in Fig. 3, for example by increasing a deceleration power 24' achievable with the determined braking scenario 22 to a predetermined minimum deceleration power 24 by means of the power increase measure 29. If the result of the follow-up test is positive, the power increase measure 29 is carried out in a further step 160, and the vehicle 50 is decelerated by means of the friction brakes 11 according to step 140a.If the result of the follow-up test is negative, the vehicle 50 can be decelerated according to the alternative step 140b using the regenerative braking system 12 or using the regenerative braking system 12 and the friction brakes 11 in combination. After the vehicle 50 has been decelerated using the friction brakes according to step 140a or alternatively using the regenerative braking system 12 or using the regenerative braking system 12 and the friction brakes 11 in combination according to the alternative step 140b, the previously described sequence of the method 100 can be repeated, optionally beginning with the first step 110 to determine a deceleration request, or can be concluded with an end 170 of the method 100, signaled, for example, by the end of the journey.

[0044] As can be seen in Fig. 3, the control unit 20 has a signal input 20a, via which the control unit 20 is signal-coupled to the vehicle control system 61 of the towing vehicle 60, wherein the trailer interface 72 interposed according to Fig. 1 is not shown in detail in Fig. 3 for reasons of clarity. Via the signal connection 73 shown in Fig. 1, the control unit 20 receives a deceleration request signal 21 at the signal input 20a, which is analyzed in the data processing unit 40 with regard to existing deceleration parameters 21a, if necessary in conjunction with further provided sensor signals, in order to determine a braking scenario 22. Based on a conditioning criterion 23, a check is carried out to determine whether a predetermined conditioning effect for conditioning the friction brakes 11 can be achieved with the determined braking scenario.According to the exemplary embodiment shown, a predetermined minimum deceleration power 24, a predetermined minimum brake pressure 25, a predetermined minimum speed 26, a predetermined minimum axle load 27, and / or a predetermined minimum control pressure 25a can be used as conditioning criteria 23. These minimum values ​​can be stored, for example, in the memory unit 41 and compared with current values ​​of the deceleration power 24', the brake pressure 25', the speed 26', the axle load 27', and / or the brake pressure 25a' of the vehicle 50 available to the control unit 20, either individually or in combination. In addition, predictive route data 28 can be analyzed, for example, in order to include anticipated braking scenarios 22 along a planned route of the vehicle 50 in the evaluation.If it is determined that the conditioning criterion 23 is met with the currently requested braking scenario 22 or with a predicted braking scenario 22 along the planned route, the vehicle 50 is decelerated using the friction brakes 11 in accordance with the braking scenario 22. For this purpose, the control unit 20 transmits a braking signal 31a to the friction brakes 11 of the vehicle 50 via a signal output 20b of the control unit 20. According to the illustration in Figs. 1 and 3, the vehicle 50 has, for example, two friction brakes 11, which are assigned to different vehicle axles 51 and can each be controlled via a separate signal output 20b of the control unit 20. An electropneumatic braking system provided for implementing the braking signal 31a is not shown in detail in Figs. 1 to 3.If it is determined that the conditioning criterion 23 is not met with the currently requested braking scenario 22 or with a predicted braking scenario 22 along the planned route, the vehicle 50 is decelerated according to the braking scenario 22 using the regenerative brake 12 or with a combination of the regenerative brake 12 and the friction brakes 11. For this purpose, a braking signal 31b for the regenerative brake 12 can be output at a further signal output 20b of the control unit 20.

[0045] Furthermore, Fig. 3 schematically indicates that the conditioning criterion 23 can also be met with the aid of a power increase measure 29, for example, by increasing a deceleration power 24' achievable with the determined braking scenario 22 to a predetermined minimum deceleration power 24 by means of the power increase measure 29. For this purpose, for example, a predefined distribution 30 of a deceleration power 24' to be provided in response to the requested deceleration can be carried out across several vehicle axles 51 of the vehicle 50 as a power increase measure 29. Accordingly, the braking signals 31a used to activate the friction brakes 11 can be output with a predefined, in particular variably selectable, power ratio, indicated in Fig. 3 by a percentage symbol.

[0046] As can further be seen in Fig. 3, a sensor-detected braking parameter 11d can be transmitted to the control unit 20, for example, via a further signal input 20a. The braking parameter 11d can, for example, be a temperature signal representing a temperature of the brake pad 11a of a friction brake 11 and can be detected by a temperature sensor 11c arranged on the brake pad 11a. This allows a condition 11b of the friction brake 11 to be estimated and monitored. Using the monitored condition 11b of the friction brake 11, the previously described method 100 can be made even more efficient, for example by assuming a deteriorated condition 11b of the friction brake 11 as a precondition for testing a braking scenario 22 for fulfillment of the conditioning criterion 23.

[0047] From Fig. 3, it can further be seen that, starting from the towing vehicle control 61, a brake cable adjustment 71 between the trailer vehicle 50a and the towing vehicle 60 can be specified. Based on the brake cable adjustment 71, a maximum permissible deceleration power 24max can be determined and stored, for example, in the memory unit 41 of the control unit 20. To implement a further power increase measure 29, which includes the towing vehicle 60 and the trailer vehicle 50a as a common unit and in which, in response to a requested deceleration, a higher deceleration power 24* is provided to the trailer vehicle 50a than to the towing vehicle 60, in particular the deceleration power 24' of the trailer vehicle 50a can be increased for a limited time to the maximum permissible deceleration power 24max in accordance with the brake cable adjustment 71.

[0048] With the control unit 20 shown in Fig. 3, it is further possible, although not shown in detail, for conditioning of the friction brakes 11 to be carried out by means of a time-limited activation of the friction brakes 11 during constant travel or acceleration of the vehicle 50. Such deceleration-independent conditioning can, for example, be linked to a time condition and can occur, for example, if no fulfillment of the conditioning criterion 23 has been determined during a requested deceleration over a predefined period of time or if the friction brakes 11 have not been activated in principle over a predefined period of time.

[0049] With the above-described method 100, the vehicle 50, the vehicle combination 70, and the control unit 20, a high proportion of usable recuperation energy can still be achieved with deceleration processes of the vehicle 50, while still maintaining the braking effect of the friction brakes 11 in a simple and efficient manner. The described means enable an efficient and safe method 100 for operating the braking system 10 of the vehicle 10. Reference symbol (part of the description)

[0050] 10 Braking system

[0051] 11 Friction brake

[0052] 11a brake pad

[0053] 11 b Condition of the friction brake

[0054] 11c Temperature sensor

[0055] 11d Brake parameters

[0056] 12 Regenerative braking

[0057] 20 Control unit

[0058] 20a Signal input

[0059] 20b Signal output

[0060] 21 Delay request signal

[0061] 21a Delay parameters

[0062] 22 Braking scenario

[0063] 23 Conditioning criterion

[0064] 24 Minimum deceleration power

[0065] 24' deceleration power

[0066] 24max max. permissible deceleration power

[0067] 25 Minimum brake pressure

[0068] 25' brake pressure

[0069] 25a Minimum control pressure

[0070] 25a' control pressure

[0071] 26 Minimum speed

[0072] 26' speed

[0073] 27 Minimum axle load

[0074] 27' axle load

[0075] 28 predictive route data

[0076] 29 Performance increase measure

[0077] 30 Distribution of deceleration power

[0078] 31a Brake signal friction brake

[0079] 31b Brake signal regenerative brake

[0080] 40 Data processing unit

[0081] 41 Storage unit vehicle a trailer vehicle

[0082] Vehicle axle

[0083] towing vehicle

[0084] Towing vehicle control

[0085] vehicle combination

[0086] Brake cable adjustment

[0087] Trailer interface

[0088] Signal connection 0 Procedure for operating a braking system 1 Start 0 Deceleration request 0 Determination of braking scenario 0 Check of the conditioning criterion 0a Deceleration of the vehicle using the friction brake 0b Deceleration of the vehicle using the regenerative brake 0 Check for fulfillment with performance increase measure 0 Performance increase measure 0 End

Claims

Patent claims 1. Method (100) for operating a braking system (10) of a vehicle (50), in particular a commercial vehicle, comprising a friction brake (11) and a recuperation brake (12), wherein in response to a requested deceleration (110) of the vehicle (50) a braking scenario (22) is determined (120) on the basis of a deceleration parameter (21), and wherein the vehicle (50) is decelerated (140a, 140b) by means of the friction brake (11) and / or the recuperation brake (12) as a function of the determined braking scenario (22), characterized in that a conditioning criterion (23) is used to check (130) whether a predetermined conditioning effect for conditioning the friction brake (11) can be achieved with the determined braking scenario (22), and if the conditioning criterion (23) is met, the vehicle (50) is decelerated by means of the friction brake (11) is delayed (140a).

2. Method (100) according to claim 1, characterized in that the conditioning criterion (23) is considered to be fulfilled if a predetermined minimum deceleration performance (24) of the friction brake (11) can be achieved with the determined braking scenario (22).

3. Method (100) according to claim 1 or 2, characterized in that the conditioning criterion (23) is considered to be fulfilled if one of the following predetermined minimum values ​​can be achieved with the determined braking scenario (22): - a specified minimum brake pressure (25); - a specified minimum speed (26); - a specified minimum axle load (27) and / or - a specified minimum control pressure (25a).

4. Method (100) according to one of the preceding claims, characterized in that predictive route data (28) of the vehicle (50) are taken into account in the determination (120) of the braking scenario (22) and / or in the testing (130) of the conditioning criterion (23).

5. Method (100) according to one of the preceding claims, characterized in that an achievable with the determined braking scenario (22) Deceleration power (24') is increased to a predetermined minimum deceleration power (24) by means of a power increase measure (29).

6. The method (100) according to claim 5, characterized in that the power increase measure (29) comprises a predefined distribution (30) of a deceleration power (24') to be provided in response to the requested deceleration (110) to one or more of a plurality of vehicle axles (51) of the vehicle (50).

7. Method (100) according to one of the preceding claims, characterized in that conditioning of the friction brake (11) is carried out by means of a time-limited activation of the friction brake (11) during constant travel or acceleration of the vehicle (50) if no fulfillment of the conditioning criterion (23) has been determined during a requested deceleration (110) over a predefined period of time.

8. Method (100) according to one of the preceding claims, characterized in that a condition (11b) of the friction brake (11) is checked or continuously monitored by detecting or estimating a braking parameter (11d) associated with an energy input into a brake pad (11a) of the friction brake (11).

9. Method (100) according to one of the preceding claims, characterized in that the vehicle (50) is designed as an electrically driven trailer vehicle (50a).

10. Method (100) according to claim 9, characterized in that the vehicle (50) designed as an electrically driven trailer vehicle (50a) is connected to a towing vehicle (60) to form a vehicle combination (70), and in that, in order to condition the friction brake (11) in response to a requested deceleration (110), as a power increase measure (29), a higher deceleration power (24') is provided to the vehicle (50) designed as a trailer vehicle (50a) than to the towing vehicle (60).

11. Method (100) according to claim 10, characterized in that the deceleration power (24') of the vehicle (50) designed as an electrically driven trailer vehicle (50a) is increased for a limited time to a maximum permissible deceleration power (24max) in accordance with a brake cable adjustment (71) of the vehicle combination (70).

12. Control unit (20) for a vehicle (50) for carrying out the method (100) according to one of claims 1 to 11, wherein the control unit (20) is configured to receive a deceleration request signal (21a), to determine (120) a braking scenario (22) based on a deceleration parameter (21), and to control a recuperation brake (12) and / or a friction brake (11) of a braking system (10) of the vehicle (50) depending on the determined braking scenario (22) for decelerating (140a, 140b) the vehicle (50), characterized in that the control unit (20) is configured to check (130) based on a conditioning criterion (23) whether a predetermined conditioning effect for conditioning the friction brake (11) can be achieved with the determined braking scenario (22), and if the conditioning criterion is met (23) to control the friction brake (11) of the braking system (10) to decelerate (140a) the vehicle (50).

13. Vehicle (50), in particular a commercial vehicle, for carrying out the method (100) according to one of claims 1 to 11, wherein the vehicle (50) has a braking system (10) with a friction brake (11) and a recuperation brake (12) and a control unit (20) according to claim 12.

14. Vehicle (50) according to claim 13, wherein the vehicle (50) is designed as an electrically powered trailer vehicle (50a).

15. Vehicle combination (70) comprising a towing vehicle (60) and a vehicle (50) designed as an electrically driven trailer vehicle (50a) according to claim 14.

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