Method for operating a brake system of a motor vehicle, control device and motor vehicle

Abstract

The invention relates to a method for operating a brake system of a motor vehicle, the brake system having a friction brake device and a recuperation brake device, in which method a cleaning requirement (V1) of the respective wheel brakes of the friction brake device of the motor vehicle is determined, a deceleration of the motor vehicle desired by the driver is determined from a brake pedal mechanically decoupled from the friction brake device and a brake force required for the desired deceleration of the motor vehicle is determined (V2), wherein a predefined first portion of the brake force is allocated to the recuperation brake device and the remaining portion of the required brake force is allocated to the wheel brakes of the friction brake device (V3), wherein the brake force to be provided by the friction brake device is allocated to the wheel brakes in accordance with the determined cleaning requirement of the respective wheel brake.

Description

Technical Field

[0001] This invention relates to a method for a braking system used in operating a motor vehicle. Background Technology

[0002] A method for controlling a braking system for a vehicle is known from US 2010 / 0276240 A1. In this method, a master brake cylinder is separated from the wheel brake cylinders by means of a release valve. The master brake cylinder is configured to detect the operation of the brake input element. The inflow of brake medium from a reservoir to the wheel brake cylinders is controlled by a control valve, thereby adjusting the braking pressure at the associated wheel. Summary of the Invention

[0003] The purpose of this invention is to provide a solution that achieves particularly good cleaning of the corresponding wheel brakes of a motor vehicle under conditions of particularly high energy recovery of braking energy, wherein the driver's brake pedal feel is minimally affected.

[0004] This objective is achieved by a method according to the invention for a braking system for operating a motor vehicle. Other possible embodiments of the invention are disclosed in the specification and drawings.

[0005] This invention relates to a method for a braking system for operating a motor vehicle. The braking system of the motor vehicle includes a friction braking device and a regenerative braking device. The friction braking device is configured to convert the kinetic energy of the motor vehicle into heat energy via friction. The friction braking device includes wheel brakes configured as corresponding friction brakes for each wheel of the motor vehicle. Here, the corresponding wheel brakes may be configured as, for example, disc brakes or drum brakes. The regenerative braking device is configured to convert the kinetic energy of the motor vehicle into electrical energy. For this purpose, the regenerative braking device may have a generator. Compared to vehicles that decelerate solely via friction brakes, especially in vehicles with regenerative braking, the corresponding friction brakes are used for deceleration to a significantly lower degree. This can quickly and often result in a suboptimal friction ratio at the wheel brakes, which, especially through signs of corrosion, can lead to negative effects on braking characteristics, including the vehicle's acoustics. Consequently, the friction brakes should be replaced particularly frequently if necessary. If the regenerative braking share is reduced to increase the hydraulic braking share, this results in increased vehicle wear and tear.

[0006] To overcome these drawbacks, the method is configured to determine the cleaning requirements of the corresponding wheel brakes of the vehicle's friction braking system. This cleaning requirement can be derived, for example, from corrosion of the corresponding wheel brakes. This means that if a wheel brake shows signs of corrosion, it should be cleaned. Furthermore, the method is configured to determine the driver's desired deceleration of the vehicle based on the brake pedal position, which is mechanically decoupled from the friction braking system, and to determine the braking force required for that desired deceleration. The brake pedal position can be determined, for example, by means of a sensor device. Therefore, the driver can preset how forcefully the vehicle should be braked by adjusting the brake pedal. The mechanical decoupling of the brake pedal from the friction braking system should be understood as the brake pedal not being directly coupled to the corresponding wheel brake via hydraulic pressure. This means that no direct displacement of brake fluid via the brake pedal occurs in the hydraulic braking circuit connected to the wheel brakes. Instead, a control signal is generated based on the brake pedal position, which presets the hydraulic pressure to be applied to the wheel brakes. This hydraulic pressure is adjusted by means of an actuator upon receiving the control signal.

[0007] A predetermined first portion of the braking force required for the desired deceleration of the motor vehicle is allocated to the regenerative braking device, and the remaining portion of the required braking force is allocated to the friction braking device. The motor vehicle is thus decelerated not only by the regenerative braking device but also by the friction braking device. Here, the braking force provided by the friction braking device is distributed to the wheel brakes according to the determined cleaning requirements of the respective wheel brakes. The friction braking device may, for example, include corresponding hydraulic brakes, wherein each wheel of the motor vehicle is associated with a hydraulic brake. To distribute the braking force to the wheel brakes, the corresponding braking pressure at the wheel brakes can be adjusted via hydraulic fluid. The higher the corresponding cleaning requirement of the corresponding wheel brake, the higher the share of the remaining portion of the required braking force at that wheel brake, so as to clean the wheel brake by applying braking force, especially to prevent signs of corrosion. In particular, the braking system can operate in a cleaning mode, in which the cleaning requirement of the corresponding wheel brake is determined and the remaining portion of the required braking force is distributed to the wheel brakes of the friction braking device according to the determined cleaning requirement. This method thus enables the recovery and reuse of a particularly large portion of braking energy via regenerative braking, thereby allowing the vehicle to operate with exceptional efficiency and exceptionally low energy demand. Furthermore, it achieves targeted cleaning of the corresponding wheel brakes through the distribution of braking force. Pedal feel defects, particularly those arising from the different distribution of braking force to the corresponding wheel brakes based on their respective cleaning requirements, can be avoided through mechanical decoupling of the brake pedal from the friction braking device. Therefore, independent of the distribution of braking force to the regenerative braking device and, or to, the corresponding wheel brakes of the friction braking device, the ride comfort for vehicle passengers can be exceptionally high.

[0008] In one possible improvement of this method, the hydraulic braking pressure to be applied to the corresponding wheel brake for adjusting the braking force is determined via a stored association rule based on the braking force allocated to the corresponding wheel brake, and this determined braking pressure is applied to the associated wheel brake. As an association rule, a characteristic curve can be stored for each wheel brake, pre-setting the relationship between the hydraulic braking pressure applied to the corresponding wheel brake and the braking force generated at the corresponding wheel brake in the form of braking torque. Therefore, it is determined what portion of the braking force required for the desired deceleration should be applied based on the allocation at the corresponding wheel brake. The association rule determines what hydraulic braking pressure should be applied to that wheel brake to cause the determined portion of the braking force to act at that wheel brake. Subsequently, the determined hydraulic braking pressure is applied to the associated wheel brake. For the required braking force setting for the remaining portion of the friction braking device allocated to the wheel brakes, the corresponding wheel brake is selected according to the corresponding cleaning requirements, and its corresponding portion of the braking force is assigned to the selected wheel brake. The sum of the braking force share of all selected wheel brakes and the required braking force distributed to the first part of the regenerative braking device corresponds to the total braking force required for the desired deceleration of the vehicle. Through correlation rules, it can be determined with particular precision what hydraulic braking pressure should be applied to the corresponding wheel brake to cause the preset braking force share for that wheel brake to act at that wheel brake. This hydraulic braking pressure can be adjusted by means of an actuator at the corresponding wheel brake. This achieves mechanical decoupling of the brake pedal from the adjustment of the hydraulic braking pressure at the corresponding wheel brake. Therefore, for a fixed required braking force, the brake pedal position and brake pedal resistance are independent of the distribution of braking force between the friction braking device and the regenerative braking device, and independent of the distribution of braking force among the corresponding wheel brakes. Therefore, the driver cannot perceive any difference in the corresponding distribution of the required braking force at the brake pedal. Thus, there is no pedal feel defect.

[0009] In another possible design of the invention, the braking force distributed to the wheel brakes of the friction braking device is allocated to the wheel brakes according to at least one preset stability criterion to be followed. Here, the preset stability criterion can be a predetermined range for the ratio of the braking force share applied to the respective wheel brakes when comparing them to each other. This means that, by presetting the stability criterion, the braking force shares applied to different wheel brakes are allowed to differ from each other. Here, the maximum difference can be preset absolutely or relatively. By adhering to the preset stability criterion, it is ensured that loss of control of the vehicle during deceleration is avoided. This results in the vehicle's stability being negatively affected particularly little during deceleration, and the vehicle's stability being particularly high.

[0010] In this regard, one possible improvement to the method is to follow at least one stability criterion when the corresponding braking force associated with a wheel brake is at most the maximum braking force of the corresponding wheel brake and / or when the braking force ratio between the corresponding wheel brakes is within the allowable range of that braking force ratio. In other words, application parameters can be preset, which preset limit values ​​or key data for the distribution of braking force to the wheel brakes. A separate maximum braking force can be preset for each wheel brake, or a maximum braking force that should be followed for each of the wheel brakes can be preset. Regarding the allowable range of the braking force ratio between the corresponding wheel brakes, a preset amount of difference is allowed between the respective braking force shares of each wheel brake. Excessive differences between the respective braking force shares applied to the wheel brakes can negatively impact the vehicle's driving dynamics. This impact on driving dynamics can cause the vehicle to veer off course or deviate from its trajectory. By following the stability criterion, particularly reliable operation of the vehicle is achieved.

[0011] In another possible design of the invention, when the anti-lock braking system (ABS) and / or electronic stability control system intervene in the vehicle's driving dynamics as a driving dynamics adjustment system, the distribution of braking force between the regenerative braking device and the friction braking device and / or between the wheel brakes is preset by the driving dynamics adjustment system. This means that the corresponding driving dynamics adjustment system has a higher priority than the required braking force distribution based on cleanliness requirements. Once the corresponding driving dynamics adjustment system intervenes in the vehicle's braking for stabilization, the distribution of braking force between the regenerative braking device and the friction braking device and / or between the wheel brakes is preset by the driving dynamics adjustment system. Here, the driving dynamics system may preset the absolute value of the corresponding braking force share and / or preset the limit value or main data for the distribution of braking force. The anti-lock braking system (ABS) resists possible wheel lock-up during vehicle braking by reducing braking pressure. Thus, the vehicle's maneuverability and trajectory holding are achieved during braking. With the help of ABS, complete wheel lock-up of the vehicle is avoided. Slip can be adjusted here, the slip being preset by how much the corresponding wheel speed deviates from the total distance traveled. This means that ABS can be pre-set during braking to determine how far the wheels roll and the distance at which they lock completely. Additionally, ABS can be configured to distribute braking force between the front and rear axle wheels. Electronic Stability Control (ESC) is an electronically controlled driving assistance system for motor vehicles that counteracts vehicle drift by applying targeted braking to each wheel via its corresponding associated wheel brakes. ECS counteracts vehicle slippage during oversteer and understeer within the limits of cornering by applying targeted braking to each wheel, thereby ensuring driver control. Oversteer is corrected by braking the front wheels outside the corner, and understeer by braking the rear wheels inside the corner. Therefore, ESC pre-sets corresponding braking force shares for the wheel brakes to stabilize the vehicle. If, for example, ESC detects vehicle drift, the braking force distribution determined based on the wheel brake cleanup requirements is discarded, and the braking force is instead distributed to the wheel brakes by ESC. For this purpose, ESC can pre-set the distribution of braking force between regenerative braking devices and friction braking devices and / or between the wheel brakes. In this case, it is possible that the ESC distributes the required braking force based on the brake pedal position, or that the ESC presets the braking force to be achieved, which deviates from the required braking force determined based on the brake pedal position. By presetting the braking force distribution through an activated ride dynamics adjustment system, exceptionally high stability of the vehicle's ride dynamics can be achieved.

[0012] In an improved embodiment of the invention, when it is determined that there is no need for cleaning, the braking force allocated to the wheel brakes is evenly distributed across all wheel brakes. In other words, a corresponding share of braking force is assigned to each wheel brake, and this share of braking force is the same for all wheel brakes. This achieves particularly uniform deceleration of the vehicle and keeps the risk of deformation of the vehicle during braking particularly low.

[0013] In another possible design of the invention, the maximum possible regenerative braking power of the regenerative braking device is selected as a preset first part of the braking force. This allows for the recovery of a particularly large amount of energy during vehicle deceleration, thereby enabling particularly efficient and low-energy operation of the vehicle. Thus, the regenerative braking capacity is fully utilized to invoke the maximum possible regenerative braking power.

[0014] In this regard, in one possible improvement of the invention, it can be configured such that if the braking force required for the preset deceleration of the vehicle is less than or equal to the maximum possible regenerative braking power of the regenerative braking device and a cleaning requirement is determined, a regenerative power lower than the maximum possible regenerative braking power of the regenerative braking device is selected as the first portion of the preset braking force, and the remaining portion of the required braking force is allocated to the friction braking device. If the braking force required for the preset deceleration of the vehicle is less than or equal to the maximum possible regenerative braking power of the regenerative braking device and the maximum possible regenerative braking power of the regenerative braking device is selected as the first portion of the preset braking force, then the braking force available for the friction braking device is 0. Therefore, cleaning of the wheel brakes of the friction braking device is not required. For this reason, once a cleaning requirement is determined, a regenerative power lower than the maximum possible regenerative braking power of the regenerative braking device is selected as the first portion of the preset braking force, provided that the braking force required for the preset deceleration of the vehicle is less than or equal to the maximum possible regenerative braking power. If the braking force required for the preset deceleration of the vehicle is greater than the maximum possible regenerative braking power of the regenerative braking device, then the maximum possible regenerative braking power of the regenerative braking device can be selected as the first portion of the preset braking force. In other words, depending on the situation, if it is determined that regenerative braking alone is sufficient for the vehicle's preset deceleration, but at least one of the wheel brakes is contaminated and therefore requires cleaning, then the vehicle may decelerate less via regenerative braking than the maximum possible regenerative braking power, wherein the vehicle is additionally decelerated via hydraulic braking by means of friction braking. In the second case, regenerative braking is insufficient to achieve the vehicle's preset deceleration, wherein the remaining required braking force is provided by friction braking, wherein the braking force is distributed to the wheel brakes according to the respective cleaning requirements of the wheel brakes. The purpose of this method is to recover a particularly large portion of the braking force via regenerative braking power. To achieve this purpose, braking force is distributed between friction braking and regenerative braking, wherein as much braking force as possible should be recovered via regenerative braking, in addition to cleaning at least one wheel brake. This allows for particularly energy-efficient operation of the vehicle.

[0015] In another possible design of the invention, a larger share of the braking force of the friction braking device is distributed to all the rear wheel brakes of the motor vehicle compared to the front wheel brakes. If the motor vehicle is a motorcycle, then it is possible that a larger share of the braking force of the friction braking device is distributed to the rear wheel brakes of the motorcycle compared to the front wheel brakes. However, if the motor vehicle is a car, then it is configured that a larger share of the braking force of the friction braking device is distributed to the two rear wheel brakes of the motor vehicle compared to the front wheel brakes. In particular, disc brakes at the rear axle of a motor vehicle have a particularly high cleaning requirement because they experience lower energy input compared to the front wheel brakes during normal customer operation. By distributing a larger share of the braking force of the friction braking device to all the rear wheel brakes of the motor vehicle compared to the front wheel brakes, reliable cleaning of the corresponding rear wheel brakes of the motor vehicle can be achieved.

[0016] In another possible design of the invention, the cleaning requirements of the respective wheel brakes are determined via a model based on the braking pressure and braking frequency applied to the respective wheel brakes, particularly based on the braking pressure and braking frequency applied to the respective wheel brakes over their service life. The model can therefore be a type of energy calculator that can calculate, over the operating time of the respective wheel brakes, when and for how long braking occurred at which wheel brakes due to the corresponding braking force input, and accordingly how corrosion development occurred at the respective wheel brakes. The model can therefore provide a particularly good estimate of how the corresponding cleaning requirements of the respective wheel brakes develop over their service life. Therefore, it is advantageously unnecessary to use additional sensors to determine the corresponding cleaning requirements of the respective wheel brakes. In this model, the corresponding braking process at the wheel brakes can be stored with precise resolution in terms of duration and / or braking pressure, thereby allowing the cleaning requirements to be determined with particularly high accuracy via a model specific to the respective wheel brakes.

[0017] In another possible design of the invention, the higher the specific cleaning requirement for the wheel brake, the higher the braking force to be applied to the corresponding wheel brake by means of a friction braking device. The wheel brake can be polished by the braking force applied to it, wherein the higher the braking force applied, the greater the polishing effect. This means that, for example, to achieve particularly good polishing of corrosion signs, a particularly high braking force is applied to the wheel brake to be cleaned. Therefore, a particularly good cleaning effect can be achieved by applying braking force to the corresponding wheel brake.

[0018] Further features of the invention can be derived from the following description and from the accompanying drawings. The features and combinations of features mentioned in the description above, as well as the features and combinations of features shown separately in the following description and / or in the drawings, can be used not only in the combinations described herein, but also in other combinations or individually, without departing from the scope of the invention. Attached Figure Description

[0019] The attached figure, the only one shown, is a schematic diagram of a method for operating a braking system for a motor vehicle. Detailed Implementation

[0020] exist Figure 1 The accompanying diagram illustrates a method for operating a braking system for a motor vehicle, wherein the braking system includes a friction braking device and a regenerative braking device. The friction braking device is configured to decelerate the motor vehicle via corresponding friction brakes (which are associated with corresponding wheels of the motor vehicle and are hereinafter referred to as wheel brakes). The regenerative braking device is configured to decelerate the motor vehicle, wherein the kinetic energy of the motor vehicle is converted into electrical energy during deceleration via the regenerative braking device, and this electrical energy can be stored in the motor vehicle's battery. Thus, the energy stored back in the motor vehicle's battery by means of the regenerative braking device can be used to efficiently drive the motor vehicle.

[0021] In this method, the first method step V1 is set to determine the cleaning requirements of the corresponding wheel brakes of the vehicle's friction braking system. Here, the cleaning requirements of the corresponding wheel brakes can be determined, in particular, by means of a model based on the braking pressure and braking frequency applied to the corresponding wheel brakes during the corresponding braking events, especially during the service life of the wheel brakes.

[0022] In the second method step V2, the method is configured to determine the braking force required for the deceleration of the motor vehicle as desired by the driver. To this end, the brake pedal position, which is mechanically decoupled from the friction braking device, is analyzed, and the desired deceleration is determined based on the determined brake pedal position. The driver can thus preset how strongly the motor vehicle should decelerate by pressing the brake pedal to different positions. This method therefore determines how strongly the motor vehicle should decelerate according to the driver's desire and what braking force is required to induce this deceleration. By decoupling the brake pedal from the friction braking device, the driver can feel the distribution of braking force to the corresponding wheel brakes of the friction braking device through the resistance of the brake pedal. Due to the decoupling of the brake pedal from the friction braking device, the brake pedal resistance is the same for each distribution of braking force when the driver performs the desired deceleration characterized by the brake pedal position. Therefore, there is no so-called pedal feel disadvantage.

[0023] In the third method step V3, the method is configured to allocate a predetermined first portion of the braking force required for the desired deceleration of the motor vehicle to the regenerative braking device and allocate the remaining portion of the required braking force to the friction braking device. Here, the portion of the braking force provided by the friction braking device is allocated to the wheel brakes according to the determined cleanliness requirements of the respective wheel brakes.

[0024] As a first part of the preset braking force, the maximum possible regenerative braking power of the regenerative braking device is selected to recover a particularly large amount of braking energy, thereby enabling the vehicle to operate efficiently with this particularly high energy. If the braking force required for the preset deceleration of the vehicle is less than or equal to the maximum possible regenerative braking power of the regenerative braking device, and a cleaning requirement is further determined for at least one wheel brake of the friction braking device, then a regenerative braking power lower than the maximum possible regenerative braking power of the regenerative braking device is selected as the first part of the preset braking force, and the remaining portion of the required braking force is distributed to the corresponding wheel brake of the friction braking device. Here, the higher the corresponding determined cleaning requirement for the corresponding wheel brake, the more braking force can be applied to that wheel brake to allow it to abrade its contaminants. In order not to compromise the stability of the vehicle during braking, the remaining portion of the braking force to be distributed to the wheel brakes is distributed to the wheel brakes according to a preset stability criterion. Here, it can be set such that the stability criterion is followed when the corresponding braking force associated with the wheel brake is at most the maximum braking force for the corresponding wheel brake and / or when the braking force ratio between the corresponding wheel brakes is within the allowable range for that braking force ratio. Furthermore, it can be configured such that when the anti-lock braking system and / or electronic stability control system intervene in the driving dynamics of the motor vehicle as a driving dynamics adjustment system, the distribution of braking force between the regenerative braking device and the friction braking device and / or between the wheel brakes is preset by the driving dynamics adjustment system.

[0025] Compared to the corresponding front wheel brakes of a motor vehicle, a larger share of the braking force from a friction braking system can be distributed to all rear wheel brakes. If it is determined that there is no need for cleaning of the corresponding wheel brakes, then the braking force to be distributed to the wheel brakes can be evenly distributed to all wheel brakes.

[0026] In this method, in manual braking where the driver of the motor vehicle pre-sets the desired deceleration of the vehicle via the corresponding brake pedal position, the hydraulic portion of the braking torque required for the desired deceleration is specifically distributed to the axle or specifically to the individual wheels of the vehicle, particularly the wheel brakes associated with those wheels, within the vehicle's stability limits. This increases the energy input and thus the grinding effect at the wheel brakes to be ground. It is possible that a lower hydraulic braking torque portion, especially in braking with a regenerative portion, is also placed independently of the structural braking force distribution target at the axle or at the defined wheels of the vehicle. Negative impacts on pedal feel can be avoided by using a decoupled braking system, where the brake pedal is mechanically decoupled from the friction braking device. This decoupled braking system can be a simulator system including a stroke simulator, which can be constructed, for example, as a 1-Box-System. The name 1-Box-System describes the structure of the braking system in which all components of the braking system are housed in a common housing and therefore within a box. Here, the brake pedal can be directly connected to this box. Within a common housing, an electromechanical brake booster, an electronic stability control system, and a brake fluid reservoir can be arranged. The simulator system describes a possible form of mechanical decoupling between the brake pedal and the friction braking system. Brake fluid displaced by the brake pedal can be transferred to the brake fluid reservoir, which can also be called a simulator. This avoids the direct transfer of brake fluid to the wheel brakes via the brake pedal. Instead, the braking pressure in the respective wheel brakes is built up by a separate motor via corresponding hydraulic lines.

[0027] In coupled braking systems with vacuum brake boosters or electromechanical brake boosters, the brake pedal feel is drastically altered by the distribution of braking force to the selected wheels. Brake pedal feel is determined by the ratio of brake pedal travel or brake pedal force to the vehicle's deceleration. By disengaging the individual wheels from the coupled braking system's hydraulic pressure during braking, the driver must displace a smaller volume of brake fluid to generate a preset pressure in the brakes of the remaining wheels, resulting in a steeper travel-pressure characteristic curve in this case. On the other hand, the preset deceleration is not achieved in this case because the corresponding braking torque acts generally on fewer wheels.

[0028] In a decoupled braking system (particularly a brake-by-wire system), the stroke and force curves can be preset by mechanical design independently of the hydraulic ratio in the friction braking device when the brake pedal is operated. Deceleration for a given brake pedal position is triggered by a pressure regulator in the friction braking device that is decoupled from the brake pedal and can be preset by software functions applicable to the braking system.

[0029] This method achieves a brake pedal feel and thus brake pedal travel-deceleration behavior that corresponds to the normal deceleration behavior expected by the driver, which corresponds to deceleration without active braking torque distribution to individual wheels or braking of all wheels of the vehicle. To this end, a characteristic curve and / or a composite characteristic curve is stored in the controller of the braking system for each wheel brake, depicting the braking torque at the wheel adjusted to a set braking pressure. A function in the controller reads in the brake pedal position representing the driver's desired position and determines the desired total wheel braking torque. This desired total wheel braking torque is derived from the deceleration behavior of the vehicle via braking of all wheels from the applied standard brake pedal travel, i.e., in the case of functional intervention. If, during this braking process, individual wheels or axles are now hydraulically separated, the function determines the corresponding braking pressure to be applied based on the stored characteristic curve for each wheel brake, from which the desired total wheel braking torque is generated at the active wheel brake. This braking pressure to be applied is adjusted at the corresponding wheel brake by means of a pressure adjuster of the friction braking device. Therefore, the deceleration behavior of the brake pedal travel is equal to that of the standard brake pedal travel, and the active function is imperceptible or almost imperceptible to the driver.

[0030] In this method, the braking pressure in the friction braking device is measured or calculated. Application parameters can be preset for the function, defining which wheel brakes and / or axles are allowed to disengage and / or allow disengagement of the corresponding wheel brakes and / or axles up to what deceleration. The described function should impair vehicle stability and safety to a particularly small extent. For this reason, vehicle stability or vehicle safety functions have higher priority. If the function should be terminated and braking is again performed via all wheel brakes, then the corresponding wheel brakes are released via the appropriate valves, and the braking pressure is adjusted via a pressure adjuster to match the desired total wheel braking torque to all wheels of the vehicle. The function can be activated as needed and therefore depends on the estimated state of the wheel brakes.

[0031] Because the hydraulic braking torque share, especially during braking with a recovery share, is specifically distributed to each axle or wheel, and particularly to the wheel brakes associated with these axles or wheels, disadvantages can be avoided. Furthermore, pedal feel disadvantages can be avoided by using this function during manual braking. An algorithm can be considered to determine and distribute the hydraulic braking torque. This algorithm is used for deceleration of the vehicle based on the driver's braking expectation and the adaptation of the corresponding active wheel brakes, so that the driver's brake pedal feel for a given driver braking expectation remains the same independently of the corresponding active wheel brakes.

[0032] In the brake regulation system controller and thus the control equipment of the vehicle's braking system, the driver's desired braking torque can be divided into a generator share and a hydraulic share based on the available hydraulic generator torque. The hydraulic share can then be allocated to the wheel brakes associated with the axle or wheels, which potentially have the highest cleaning requirements and therefore the highest polishing requirements. In this method, the desired total wheel braking torque equivalent to braking through all wheels is determined based on the driver's braking expectations, and the braking pressure corresponding to braking through the selected wheels or axle is calculated based on stored characteristic curves. This braking pressure is adjusted via a pressure adjustment unit in the friction braking device. In particular, the distribution of the remaining required braking force to the wheel brakes of the friction braking device is imperceptible to the driver of the vehicle, wherein the stability of the vehicle is minimally, and especially completely, unaffected. The cleaning requirements of the corresponding wheel brakes can be determined according to an algorithm that sums the input energy of each wheel brake. In principle, disc brakes on the rear axle have a higher need to be cleaned of dirt, especially signs of corrosion, because they experience lower energy input than front axle brakes during normal customer operation.

[0033] In general, the present invention demonstrates how to achieve a function for improving the frictional properties of the corresponding wheel brakes in a vehicle with a decoupled braking system.

[0034] List of reference numerals

[0035] The corresponding method steps from V1 to V3

Claims

1. A method for operating a braking system of a motor vehicle, the braking system including a friction braking device and a regenerative braking device, wherein the method determines the cleaning requirements (V1) of the corresponding wheel brakes of the friction braking device of the motor vehicle, determines the driver-desired deceleration of the motor vehicle based on the brake pedal position of a brake pedal mechanically decoupled from the friction braking device, and determines the braking force (V2) required for the desired deceleration of the motor vehicle, wherein, The first portion of the predetermined braking force is allocated to the regenerative braking device, and the remaining portion of the required braking force is allocated to the wheel brakes (V3) of the friction braking device. The braking force to be provided by the friction braking device is allocated to the wheel brakes according to the determined cleaning requirements of the respective wheel brakes. - Distribute the braking force to the wheel brakes of the friction braking device according to at least one preset stability criterion to be followed, and / or - When the anti-lock braking system and / or electronic stability control intervene in the vehicle's driving dynamics as a driving dynamics adjustment system, the distribution of braking force between the wheel brakes is preset by the driving dynamics adjustment system, and / or - Select the maximum possible regenerative braking power of the regenerative braking device as the first part of the preset braking force.

2. The method according to claim 1, wherein, The hydraulic braking pressure to be applied to the corresponding wheel brake to adjust the braking force is determined via stored association rules based on the braking force assigned to the corresponding wheel brake, and the determined braking pressure is applied to the associated wheel brake.

3. The method according to claim 1 or 2, wherein, The at least one stability criterion is followed when the corresponding braking force associated with the wheel brake is at most the maximum braking force for the corresponding wheel brake and / or the braking force ratio between the corresponding wheel brakes is within the allowable range for the braking force ratio.

4. The method according to claim 1 or 2, wherein, When the anti-lock braking system and / or the electronic stability controller intervene in the driving dynamics of the motor vehicle as a driving dynamics adjustment system, the distribution of braking force between the regenerative braking device and the friction braking device is preset by the driving dynamics adjustment system.

5. The method according to claim 1 or 2, wherein, When it is determined that there is no need for cleaning, the braking force allocated to the wheel brakes is evenly distributed to all wheel brakes.

6. The method according to claim 1 or 2, wherein, If the braking force required for the preset deceleration of the motor vehicle is less than or equal to the maximum possible regenerative braking power of the regenerative braking device and the cleaning requirement is determined, a regenerative power lower than the maximum possible regenerative braking power of the regenerative braking device is selected as the preset first part of the braking force, and the remaining part of the required braking force is distributed to the friction braking device.

7. The method according to claim 1 or 2, wherein, Compared to the wheel brakes of all the front wheels, a larger share of the braking force of the friction braking device is distributed to the wheel brakes of all the rear wheels of the motor vehicle.

8. The method according to claim 1 or 2, wherein, The cleaning requirements of the corresponding wheel brakes are determined by the model based on the braking pressure and braking frequency applied to the corresponding wheel brakes.

9. The method according to claim 1 or 2, wherein, The higher the specific cleaning requirement for the wheel brake, the higher the braking force to be applied to the corresponding wheel brake by means of the friction braking device.

10. The method according to claim 8, wherein, The cleaning requirements of the corresponding wheel brakes are determined by a model based on the braking pressure and braking frequency applied to the corresponding wheel brakes during their service life.

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