Method for operating a braking system for a motor vehicle, corresponding braking system and computer program product

Abstract

Method for operating a braking system (1) for a motor vehicle, wherein the braking system (1) has a control element (9) for specifying a braking force to be set, wherein, depending on a state variable of a drive unit provided for driving the motor vehicle, noise-generating operation of the braking system (1) is carried out at least temporarily independently of the braking force to be set, characterized in that a state variable of an exhaust aftertreatment device of the drive unit is used as the state variable.

Description

The invention relates to a method for operating a brake system for a motor vehicle, wherein the brake system has an operating element, which is displaceable in particular along a displacement path, for presetting a braking force to be set, wherein, as a function of a state variable of a drive device provided for driving the motor vehicle, a noise-generating operation of the brake system is carried out at least temporarily independently of the braking force to be set. The invention further relates to a brake system for a motor vehicle and to a computer program product.The prior art discloses, for example, the publication DE 10 2016 217 144 A1. This describes a method for haptic information feedback to a brake pedal of a motor vehicle. In this case, it is provided that a current stability index describing the current driving situation is compared with a stored critical stability index, wherein a haptic information feedback is impressed on the brake pedal of the motor vehicle if the ratio of current stability index to critical stability index exceeds a predefined limit value.Furthermore, the publication DE 10 2013 213 050 A1 discloses a method for regulating the restoring force of a control unit of motor vehicles. The control unit can be, for example, an accelerator pedal or an accelerator grip, wherein actuation of the control unit by applying an actuating force causes a deflection of the control unit. A restoring force acts on the control unit, wherein the restoring force is directed counter to the actuating force and in the direction of the initial position of the control unit, and wherein the control unit is deflected by a deflection angle. In this case, a setpoint angle of the deflection of the control unit is determined by a control loop, and a current deflection of the control unit. Depending on the difference between the current deflection and the desired angle, the restoring force is modulated onto the control unit.DE 694 18 210 T2 relates to the construction of dampers used to reduce the amplitude of pressure fluctuations in hydraulic fluid lines, and more particularly to the construction of noise dampers used in vehicle anti-lock braking systems and to their use in such systems.Furthermore, the publications CN 2 20 314 976 U and DE 36 03 961 A1 are known from the prior art.It is the object of the invention to propose a method for operating a brake system for a motor vehicle, which has advantages over known methods, in particular provides a clearly recognizable feedback about a state of a system of the motor vehicle to a user of the motor vehicle.This is achieved according to the invention by a method for operating a brake system for a motor vehicle having the features of claim 1. In this case, it is provided that a state variable of an exhaust gas aftertreatment device of the drive device is used as the state variable.Advantageous embodiments with expedient developments of the invention are specified in the dependent claims. It is pointed out that the exemplary embodiments explained in the description are not restrictive; rather, any variations of the features disclosed in the description, the claims and the figures can be realized.The method serves for operating the brake system. The brake system is preferably part of the motor vehicle, but can of course also be present separately therefrom, in particular up to the installation of the brake system on or in the motor vehicle. The brake system serves for decelerating the motor vehicle, in this respect therefore for providing a braking force acting on at least one wheel of the motor vehicle. The braking force is applied to the at least one wheel by means of a wheel brake. Preferably, a plurality of wheels and correspondingly a plurality of wheel brakes are present, wherein each of the wheel brakes is provided and configured for imposing the braking force on one of the wheels.The brake system may have any number of wheel brakes, each of the wheel brakes being associated with one of a plurality of wheels of the motor vehicle. Insofar as the wheel brake or the at least one wheel brake is mentioned in the context of this description, the embodiments can always be transferred to one another. Explanations concerning the at least one wheel brake can thus be transmitted to the wheel brake and embodiments concerning the wheel brake can be transmitted to the at least one wheel brake. If a plurality of wheel brakes are present, the embodiments for the wheel brake can be transferred to each of the plurality of wheel brakes. The brake system is present as a service brake of the motor vehicle or forms at least one component of such a service brake.For adjusting the braking force which can be applied to the wheel by means of the wheel brake, the brake system has the operating element. The operating element can be actuated by the user of the motor vehicle, namely preferably displaceable along the displacement path. The operating element is arranged in an interior of the motor vehicle, but at least it can be reached by the user from the interior. For example, it is in the form of a brake pedal, i.e. it is provided and configured for foot actuation by the user.Without actuation by the user, the operating element is present in an initial position. It can be displaced by the user from this into a position different from the starting position, namely by the exertion of an operating force. The brake system is provided and configured to bring about a counterforce directed counter to the operating force on the operating element, said counterforce being directed toward a displacement of the operating element in the direction of its starting position. If the counterforce is greater than the operating force, the operating element is displaced in the direction of its starting position, in particular as far as its starting position. For example, the counterforce is generated with the aid of a spring element which is connected to the operating element.The brake system has, for example, a master brake cylinder in which a master brake piston is arranged displaceably. The master brake piston, together with the master brake cylinder, limits a brake fluid volume which is variable, its size depending on the position of the master brake piston. The main brake piston is coupled to the operating element, which is present, for example, as already mentioned, as a brake pedal. The user of the motor vehicle can set a desired braking force via the operating element, which is referred to below as the predefined braking force and is preferably firmly connected to a predefined braking pressure.The brake system is preferably present as an electrohydraulic brake system. This means that, in at least one operating mode of the brake system, the brake fluid present in the brake fluid volume does not directly provide the actual brake pressure present at the wheel brake or at most provides a part thereof upon actuation of the operating element. Instead, it is provided that, when the operating element is actuated by the user of the motor vehicle, the predefined brake pressure is determined and a setpoint brake pressure is subsequently determined from the predefined brake pressure, to which an actual brake pressure present at the wheel brake is set. The determination of the predefined braking force is carried out, for example, with the aid of at least one sensor which is assigned to the operating element and / or to the master brake piston and / or to the master brake cylinder and / or to a simulator cylinder in which a simulator piston is arranged such that it can be displaced.The sensor can be designed, for example, as a displacement sensor or as a pressure sensor. In the former case, the position of the operating element or the actuation distance of the operating element is determined with the aid of the sensor, by which the operating element is displaced during its actuation. Additionally or alternatively, the pressure present in the master brake cylinder is measured by means of the sensor. From the variable measured with the aid of the sensor, i.e., for example, the position of the operating element, the actuation distance and / or the pressure, the predefined brake pressure is then determined. The setpoint brake pressure is determined from the setpoint brake pressure; for example, the setpoint brake pressure is set equal to the setpoint brake pressure. Subsequently, an actual brake pressure is applied or set at the wheel brake, which corresponds to the setpoint brake pressure.The actual brake pressure is provided, for example, by a brake pressure source, which is preferably present in the form of a pump, in particular an electrically operated pump. At least temporarily, the brake fluid volume is thus not or at least not directly connected in terms of flow to the wheel brake. In order nevertheless to give the driver of the motor vehicle haptic feedback when the operating element is actuated, a braking force simulator is preferably assigned to the master brake cylinder. This has the simulator piston, which is arranged displaceably in a simulator cylinder and is supported on a wall of the simulator cylinder via a spring element and is therefore subjected to the action of a spring force.The simulator piston together with the simulator cylinder delimits a simulator fluid volume which is variable analogously to the brake fluid volume, the size of the simulator fluid volume depending on the position of the simulator piston. The simulator fluid volume is fluidly connected to the brake fluid volume. Upon actuation of the control element, the brake fluid volume is reduced and brake fluid present in the brake fluid volume is supplied to the simulator fluid volume. The simulator fluid volume correspondingly increases, as a result of which the simulator piston is deflected counter to the spring force.Depending on the spring force, which may depend on the deflection of the simulator piston, the opposing force acts on the operating element due to the flow connection between the simulator fluid volume and the brake fluid volume, which opposing force is opposed to the operating force applied to the operating element by the user of the motor vehicle. Accordingly, the driver receives a haptic feedback via the operating element, which is substantially dependent on the deflection of the operating element from its starting position or rest position.In order to provide a level of fallback in the event of a defect in the brake system, for example in the event of a failure of the brake pressure source, there is preferably a direct flow connection between the master brake cylinder and the wheel brake. In such an embodiment of the brake system, the actual brake pressure can be built up even in the event of a defect in the brake system upon actuation of the operating element at the wheel brake. For this purpose, however, the user of the motor vehicle must apply a substantially greater operating force to the operating element than usual.Due to the ever more stringent emission gas legislation for motor vehicles, driving of the motor vehicle will be permitted in the future only when the drive device is fully operational, in particular only when the vehicle catalytic converter is fully preheated. This can be implemented, for example, by releasing a shift lever or gear selector lever of the motor vehicle to move out of a park position only when this condition is fulfilled. The user is usually informed via a display that he is not yet allowed to start. Present-day gear selector levers usually no longer have a shift gate. It is therefore only moved forward or rearward in order to select the current driving mode.If the user of the motor vehicle overlooks the display which informs him of the still missing ready-to-drive state of the motor vehicle, he tries to establish ready-to-drive state by moving the gear-wheel lever, which is not successful for him. This may have a negative effect on the mood of the user. For this reason, another procedure is selected in order to indicate to the user the lack of driving readiness, namely in that, depending on the state variable of the drive device, the noise-generating operation of the brake system is carried out at least temporarily independently of the braking force to be set. In this way, the user receives a direct and comprehensible feedback about the state of the drive device via the operating element, which he must actuate anyway for carrying out the driving operation.Since the described procedure is preferably carried out only when the motor vehicle is at a standstill, that is to say before the motor vehicle is set in motion or can set in motion, the driving mode of the motor vehicle is also not adversely affected. Rather, it is provided that noise-generating operation of the brake system is carried out only as long as the motor vehicle is held at a standstill or a movement of the motor vehicle is not permitted. The user of the motor vehicle receives direct feedback about the state of the drive device by means of the operating element via a further sensory impression.The noise-generating operation of the brake system is understood to mean an operation of the brake system in such a way that it generates a noise that is easy to recognize and that is clearly acoustically perceptible by the user in the motor vehicle. Operating the brake system on the basis of an actuation of the operating element does not fall under this, for example, but rather the noise is to be generated independently of such an actuation or the braking force to be set resulting from the actuation. Preferably, it is provided that a permanently stored noise or a permanently stored noise sequence from a plurality of noises is generated by operating the brake system, in particular a specific tone or a specific tone sequence from a plurality of tones. For example, at a specific value of the state variable, the same noise is always generated, which causes a specific impression to the user of the motor vehicle. This provides plausible feedback.The noise sequence comprises, for example, a plurality of noises, wherein each of the noises is assigned a specific noise parameter, in particular different components of the brake system are operated for different noises and / or the brake system is operated in order to achieve different loudness levels. For example, a first sound of the sound sequence is generated with a first volume and a second sound of the sound sequence is generated with a second volume different from the first volume. One of the loudnesses can also be equal to zero. For example, the noise sequence comprises a plurality of first noises with a volume different from zero, wherein a second noise with the lower second volume, in particular a volume of zero, is generated between each two of the first noises.This mode of operation of the brake system clearly and unidentifiablely indicates to the driver the operational readiness of the drive device and thus of the motor vehicle. This causes emotional binding of the user to the motor vehicle and avoids the adverse effects already described.The invention provides that a state variable of an exhaust gas aftertreatment device of the drive device is used as the state variable. The drive device serves for driving the motor vehicle, in this respect therefore for providing a drive torque directed to driving the motor vehicle. For this purpose, the drive device has a drive unit which generates the drive torque at least in part. The drive unit is present, for example, as an exhaust-gas-generating drive unit, in particular as an internal combustion engine, or as an electric traction machine.In the case of the internal combustion engine, the drive device has, in addition to the drive unit, an exhaust gas aftertreatment device to which the exhaust gas generated by the internal combustion engine is fed. The exhaust gas aftertreatment device serves for aftertreatment of the exhaust gas before it is discharged in the direction of an external environment of the motor vehicle, in particular into the external environment. At least one state variable of the exhaust gas aftertreatment device is now used to carry out the noise-generating operation of the brake system, and thus to give the driver immediate feedback about the operating state. In particular, the brake system is used for targeted generation of a noise, preferably periodically, provided that the state variable is less than a threshold value. If, on the other hand, it is greater than or equal to the threshold value, the brake system is no longer operated to generate the noise.A further development of the invention provides that a temperature of the exhaust gas aftertreatment device is used as the state variable. The exhaust gas aftertreatment device comprises, for example, a vehicle catalytic converter and / or a particle filter. The vehicle catalyst is for catalytically converting at least one pollutant to a more non-hazardous product. A conversion rate at which this conversion takes place depends in particular on a temperature of the exhaust gas aftertreatment device. If the temperature corresponds to an operating temperature of the exhaust gas aftertreatment device, a comparatively high conversion rate is achieved. If the temperature deviates from the operating temperature, if it is in particular lower, the conversion rate also decreases.For sufficient conversion of the pollutant into the more harmless products, it is necessary in this respect that the exhaust gas aftertreatment device has a temperature which corresponds at least approximately to its operating temperature. Heating of the exhaust gas aftertreatment device, in which the temperature changes in the direction of the operating temperature, is effected, for example, by the exhaust gas of the internal combustion engine itself or by means of a heating device which is operated for this purpose. The described procedure enables plausible feedback to the user that there is still no ready-to-drive state of the motor vehicle.A further development of the invention provides that during the noise-generating operation of the brake system, at least one of the following components of the brake system is actuated for generating a noise: inlet valve, outlet valve, simulator valve, isolation valve, diagnostic valve and actuator of a brake pressure source. The inlet valve serves for supplying brake fluid to one or more wheel brakes, the outlet valve serves for discharging the brake fluid from one or more wheel brakes. The isolation valve is arranged fluidically between the master brake cylinder and the at least one wheel brake. In other words, the master brake cylinder is connected to the wheel brake by the flow via the isolation valve. For example, the isolation valve is fluidically connected to the wheel brake via the inlet valve, so that when the inlet valve is open and the isolation valve is open, brake fluid can flow from the direction of the master brake cylinder in the direction of the wheel brake.The simulator valve serves for fluidic connection of the simulator cylinder to the master brake cylinder. This means that the simulator cylinder is connected fluidically to the master brake cylinder via the simulator valve. When the simulator valve is closed, the simulator cylinder is fluidically decoupled from the master brake cylinder, with the result that at least no brake fluid can flow from the master brake cylinder in the direction of the simulator cylinder or into the simulator cylinder. The diagnostic valve is, for example, fluidically arranged between a brake fluid reservoir and the master brake cylinder.The brake pressure source serves to provide brake fluid at a specific pressure to the at least one wheel brake. The brake pressure source preferably has a pump which can be driven by means of the actuator. The actuator is in particular in the form of an electric motor. It can be provided to control only one or exactly one of the mentioned components for generating the noise. Preferably, however, several or even all of the components mentioned are controlled, in particular to achieve the noise sequence. For example, the noise of the noise sequence is achieved with the aid of different components. This achieves the advantages already mentioned.A development of the invention provides that during the noise-generating operation of the brake system, a component of the brake system is used which is fastened to a resonator body. In order to generate a clearly perceptible noise with the aid of the brake system, the component which is operated for this purpose is fastened to the resonator body. The resonator body is basically any desired component of the motor vehicle which is suitable for transmitting the noise generated by means of the component into the interior of the motor vehicle or even transmitting it in an amplified manner. For example, the resonator body is in this respect a component of the motor vehicle with a low mass and sufficient vibration capability compared to its extension. This again serves to achieve the advantages already mentioned.A further development of the invention provides that a wall, in particular an end wall, of the motor vehicle is used as the resonator body. The wall is preferably designed with a comparatively small wall thickness, so that it effectively forwards the noise generated by the brake system. In particular, the wall adjoins the interior of the motor vehicle, i.e. delimits the latter or is arranged in it. The wall is preferably an end wall of the motor vehicle, which can also be referred to as a splash wall. The front wall separates the interior of the motor vehicle from an engine compartment, for example. The brake system or the component of the brake system is fastened, in particular, fastened in a sound-transmitting manner, on the side of the wall facing away from the interior. This achieves a particularly effective introduction of the noise into the interior of the motor vehicle, with the result that the driver clearly perceives the latter.A further development of the invention provides that the component of the brake system with switchable damping is fastened to the resonator body and the damping is set to a lower value during noise-generating operation of the brake system than away from the noise-generating operation. During the sound producing operation, the component is to produce a clearly audible sound. If, on the other hand, the component is operated away from the noise-generating operation, noise is usually to be avoided.For this reason, it is preferably provided to fasten the component with the switchable damping to the resonator body, for example the wall. In this respect, a fastening means is arranged between the component and the resonator body, which fastening means holds the component on the resonator body. The fastening means is adjustable with regard to its damping, for example, in the case of a first setting there is a lower damping and in the case of a second setting there is a higher damping. If the noise is to be generated with the aid of the brake system, the first setting is selected and set, otherwise the second setting. This prevents undesirable noise formation, but the desired generation of noise is carried out in a clearly perceptible manner to the user.A further development of the invention provides that during the noise-generating operation of the brake system, a plurality of components of the brake system are controlled in accordance with a stored control pattern for generating noise. The noise or the noise sequence is recorded in the activation pattern, which noise or the noise sequence is to be generated with the aid of the brake system or its components. The activation pattern thus contains, for example, a sequence of several noises, as already described for the noise sequence. With such a defined activation pattern, the user of the motor vehicle can be transmitted a clear indication of the state of the drive device.The invention further relates to a brake system for a motor vehicle, in particular for carrying out the method according to the statements within the scope of this description, having an operating element, which is displaceable in particular along a displacement path, for presetting a braking force to be set. The brake system is provided and configured to perform a noise-generating operation of the brake system at least temporarily independently of the braking force to be set, depending on a state variable of a drive device provided for driving the motor vehicle. In this case, it is furthermore provided that, depending on a state variable of a drive device provided for driving the motor vehicle, noise-generating operation of the brake system is carried out at least temporarily independently of the braking force to be set.The advantages of such an embodiment of the brake system or such a procedure have already been pointed out. Both the brake system for a motor vehicle and the method for operating it can be further developed according to the explanations within the scope of the description, so that reference is made to these in this respect.The invention naturally also relates to a motor vehicle having such a brake system. Preferably, a noise-generating component of the brake system is fastened to the resonator body of the motor vehicle. Preferably, the wall, for example the end wall, is used as resonator body.The invention also relates to a computer program product comprising instructions which cause the brake system according to the statements of this description to execute the explained method. With regard to the advantages and possible advantageous developments, reference is made in its entirety to the description.The features and combinations of features described in the description, in particular the features and combinations of features described in the following description of the figures and / or shown in the figures, can be used not only in the respectively specified combination but also in other combinations or alone without departing from the scope of the invention. Embodiments are therefore also to be considered as encompassed by the invention which are not explicitly shown or explained in the description and / or the figures, but which emerge from the explained embodiments or can be derived from them.The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without any restriction of the invention being effected. The only one is shown here FIG. 1 shows a schematic illustration of a brake system for a motor vehicle.FIG. 1 shows a schematic illustration of a brake system 1 for a motor vehicle, which has a master brake cylinder 2, a brake force simulator 3, a brake pressure source 4 and wheel brakes 5, 6, 7 and 8. The number of wheel brakes is, of course, arbitrary. In the exemplary embodiment shown, four wheel brakes 5, 6, 7 and 8 are provided, but a higher or lower number of wheel brakes may also be present. In the exemplary embodiment, the wheel brakes 5 and 7 are assigned to wheels of a first wheel axle, in particular a front wheel axle, and the wheel brakes 6 and 8 are assigned to wheels of a second wheel axle, in particular a rear wheel axle of the motor vehicle.The master brake cylinder 2 is assigned an operating element 9, which is designed here as a brake pedal. The operating element 9 is coupled to a main brake piston 10, for example via a lever connection. The master brake piston 10 is arranged displaceably in the master brake cylinder 2. In the exemplary embodiment shown, in addition to the master brake piston 10, a further brake piston 11 is arranged in the master brake cylinder 2. However, this is optional.The master brake piston 10 includes a brake fluid volume 12 together with the master brake cylinder 2. This is connected in terms of flow to a simulator fluid volume 13 of the brake force simulator 3. The simulator fluid volume 13 is delimited by a simulator piston 14 together with a simulator cylinder 15, in which the simulator piston 14 is arranged displaceably. The simulator piston 14 is preferably subjected to spring force by means of at least one spring element 16. The spring element 16 brings about a spring force on the simulator piston 14, which is directed opposite an increase in the simulator fluid volume 13.Assigned to master brake cylinder 2 and / or to operating element 9 is a sensor, not shown here, by means of which a predefined brake pressure is ascertained upon actuation of operating element 9 and a setpoint brake pressure is ascertained therefrom. Subsequently, an actual brake pressure generated by means of the brake pressure source 4 is applied to the at least one wheel brake 5, 6, 7 and 8, which corresponds to the setpoint brake pressure. The brake pressure source 4 is shown here by way of example as a pump which is driven or can be driven by means of an electric motor 17.A switching valve 18 is arranged fluidically between the brake fluid volume 12 and the simulator fluid volume 13, which switching valve can also be referred to as a simulator valve. A nonreturn valve 19 is arranged fluidically parallel to the switching valve 18. The nonreturn valve 19 is designed in such a way that it opens in the direction of the wheel brake 5, 6, 7 or 8, that is to say it allows a flow of the brake fluid from the simulator fluid volume 13, but prevents a flow in the direction of the simulator fluid volume 13.Inlet valves 20, 21, 2 20 and 23 are assigned to the wheel brakes 5, 6, 7 and 8, namely the inlet valve 20 to the wheel brake 5, the inlet valve 21 to the wheel brake 6, the inlet valve 22 to the wheel brake 7, and the inlet valve 23 to the wheel brake 8, and outlet valves 24, 25, 26 and 27 are furthermore assigned to the wheel brakes 5, 6, 7 and 8, namely the outlet valve 24 to the wheel brake 5, the outlet valve 6 to the outlet valve 25, the wheel brake 7 to the outlet valve 26 and the outlet valve 27 to the wheel brake 8.In addition, the brake system 1 has isolation valves 28, 29, 30 and 31. The inlet valves 20 and 21 are connected in parallel in terms of flow to the isolation valves 28 and 29 and via these to the master brake cylinder 2 and the brake pressure source 4, more precisely to the master brake cylinder 2 via the isolation valve 28 and to the brake pressure source 4 via the isolation valve 29. Analogously to this, the inlet valves 22 and 23 are connected in parallel in terms of flow to the isolation valves 30 and 31 and via these to the master brake cylinder 2 and the brake pressure source 4, more precisely to the brake pressure source 4 via the isolation valve 30 and to the master brake cylinder 2 via the isolation valve 31.This means that the separating valves 28 and 31 are each connected to the master brake cylinder 2, in particular the separating valve 28 to the brake fluid volume 12 and the separating valve 31 either likewise to the brake fluid volume 12 or to a further brake fluid volume 32, which is present on the side of the brake piston 11 facing away from the brake fluid volume 12. The brake fluid volume 32 is limited by the brake piston 11 together with the master brake cylinder 2.The isolation valves 29 and 30 are connected in parallel to the brake pressure source 4 in terms of flow. The outlet valve 24 is connected fluidically to the inlet valve 20 and the wheel brake 5, the outlet valve 25 is connected fluidically to the latter between the inlet valve 21 and the wheel brake, the outlet valve 26 is connected fluidically to the latter between the inlet valve 22 and the wheel brake 7, and the outlet valve 27 is connected fluidically to the inlet valve 23 and the wheel brake 8.Via the outlet valves 24, 25, 26 and 27, the respective wheel brake 5, 6, 7 and 8 is fluidically connected to a brake fluid reservoir 33. This is likewise connected fluidically via a check valve 34 to the brake pressure source 4 and via a valve arrangement 35 to the master brake cylinder 2. The valve arrangement 35 comprises, for example, a switching valve 36 and a check valve 37, which are fluidically parallel to one another. The switching valve 36 is preferably a diagnostic valve which is actuated in particular within the scope of a diagnosis of the brake system 1.The brake system 1 is set at least temporarily as a function of a state variable of a drive direction of the motor vehicle, not shown here. Preferably, it is provided to generate a noise in a targeted manner by means of the brake system 1, in particular if a state variable of the drive device 1 is less than a threshold value. On the other hand, when the state quantity is equal to or greater than the threshold value, generation of the noise is stopped.The generation of the noise takes place in particular by periodic opening and closing of at least some of the inlet valves 20 to 23, the outlet valves 24 to 27, the separating valves 28, 29, 30 and 31 and the switching valve 18. As a result, a user of the motor vehicle is provided with a direct and comprehensible acoustic feedback about the driving readiness of the motor vehicle.LIST OF REFERENCE CHARACTERS:1 Brake system 2 Master brake cylinder 3 Brake force simulator 4 Brake pressure source 5 Wheel brake 6 Wheel brake 7 Wheel brake 8 Wheel brake 9 Operating element 10 Master brake piston 11 Brake piston 12 Brake fluid volume 13 Simulator fluid volume 14 Simulator piston 15 Simulator cylinder 16 Spring element 17 Electric motor 18 Switching valve 19 Nonreturn valve 20 Inlet valve 21 Inlet valve 22 Inlet valve 23 Inlet valve 24 Outlet valve 25 Outlet valve 26 Outlet valve 27 Outlet valve 28 Separating valve 29 Separating valve 30 Separating valve 31 Separating valve 32 Brake fluid volume 33 Brake fluid reservoir 34 Nonreturn valve 35 Valve arrangement 36 Switching valve 37 Nonreturn valve

Claims

Method for operating a brake system (1) for a motor vehicle, wherein the brake system (1) has an operating element (9) for presetting a braking force to be set, wherein, as a function of a state variable of a drive device provided for driving the motor vehicle, a noise-generating operation of the brake system (1) is carried out at least temporarily independently of the braking force to be set, characterized in that a state variable of an exhaust gas aftertreatment device of the drive device is used as the state variable.Method according to Claim 1, characterized in that a temperature of the exhaust-gas aftertreatment device is used as the state variable.Method according to one of the preceding claims, characterized in that, during the noise-generating operation of the brake system (1), at least one of the following components of the brake system (1) is actuated in order to generate a noise: inlet valve (20, 21, 22, 23), outlet valve (24, 25, 26, 27), simulator valve (18), isolation valve (28, 29, 30, 31), diagnostic valve (36) and actuator of a brake pressure source (4).Method according to one of the preceding claims, characterized in that the noise-generating operation of the brake system (1) uses a component of the brake system (1) which is fastened to a resonator body.Method according to one of the preceding claims, characterized in that a wall is used as the resonator body.Method according to Claim 4 or 5, characterized in that the component of the brake system (1) with switchable damping is fastened to the resonator body and the damping is set to a lower value during the noise-generating operation of the brake system (1) than away from the noise-generating operation.Method according to one of Claims 3 to 6, characterized in that, during the noise-generating operation of the brake system (1), a plurality of components of the brake system (1) are actuated in accordance with a stored actuation pattern for generating noise.Brake system (1) for a motor vehicle, in particular for carrying out the method according to one or more of the preceding claims, having an operating element (9) for presetting a braking force to be set, wherein the brake system (1) is provided and configured to, as a function of a state variable of a drive device provided for driving the motor vehicle, carry out a noise-generating operation of the brake system (1) at least temporarily independently of the braking force to be set, characterized in that a state variable of an exhaust gas aftertreatment device of the drive device is used as the state variable.A computer program product comprising instructions for causing the braking system (1) according to claim 8 to carry out the method according to one or more of claims 1 to 7.

Images