Method for operating a braking system

Abstract

Method for determining a current clearance of a braking device (10) of a motor vehicle (80), comprising the steps: - detecting (100) parameters for determining the starting point (T1) and the end point (T2) of a build-up process of a braking process by means of a sensor unit (4), - determining (200) the starting point (T1) and the end point (T2) of the assembly process on the basis of the recorded parameters by means of a processing unit (6), - determining (300) the clearance of the braking device (10) on the basis of the determined starting point (T1) and end point (T2) of the build-up process by means of the processing unit (6), - wherein the determination (300) of the clearance of the braking device (10) is determined on the basis of the time difference (ΔT) between the starting point (T1) and the end point (T2) of the build-up process.

Description

[0001] The present invention relates to a method and a braking system for determining a clearance of a braking device of a motor vehicle. Furthermore, the invention relates to a motor vehicle comprising a braking system according to the invention.

[0002] In automotive engineering, a clearance is understood to mean the distance between the brake pad and the brake disc of a braking device when the brake is not actuated. Over the service life of a braking device, the clearance can vary within certain ranges. For example, the clearance generally increases continuously over the operating life of a braking device due to wear and tear on the components. However, this is usually compensated for by mechanical solutions in order to keep the clearance constant. On the other hand, dirt and deposits on the braking components lead to a reduction in the clearance. Both an excessively large or too small clearance can be disadvantageous if a tolerance range is exceeded.

[0003] If the clearance is too large, the pedal travel increases, which leads to a delayed build-up of braking force and ultimately longer braking distances. If the clearance is too small, however, there is a risk that the two friction partners will touch even when the brake pedal is not depressed, resulting in undesirable residual braking torque. This not only increases fuel consumption but also causes increased wear on the brake components. Furthermore, the residual braking torque generates high temperatures, which not only negatively impact the braking force itself but can also lead to permanent damage to the brake components through localized overheating.

[0004] For safety reasons, it would be advisable to determine the current clearance of a motor vehicle's brake systems at least at specific intervals. Generic methods and systems for determining the clearance of a motor vehicle's brake systems are known, for example, from DE 10 2017 131 252 A1, WO 2014 / 041160 A1, DE 10 2019 100 183 A1, DE 10 2017 103 763 A1, or DE 102 11 813 A1.

[0005] The disadvantage is that the known systems and methods are either not designed to detect the current clearance of a brake device accurately enough, so that a sufficiently reliable forecast regarding the need to replace brake components is not possible, or the systems and methods are designed to be so complex and expensive that high costs are incurred for the production and maintenance of the systems.

[0006] It is therefore the object of the present invention to at least partially remedy the disadvantages described above, in particular it is the object of the present invention to provide a method for determining a clearance of a brake device of a motor vehicle, which method enables the most accurate and reliable prognosis possible with regard to the need for maintenance or repair of a brake device and at the same time can be manufactured and maintained as cost-effectively as possible.

[0007] The above object is achieved by a method having the features of claim 1, a braking system according to claim 10, and a motor vehicle according to claim 11. Further features and details of the invention emerge from the subclaims, the description, and the drawings. The technical features disclosed for the method according to the invention also apply in connection with the braking system according to the invention or the motor vehicle according to the invention, and vice versa, so that with regard to the disclosure, reference is or can always be made to the individual aspects of the invention. Expedient embodiments of the invention are set forth in the dependent claims.

[0008] The method according to the invention for operating a braking system of a motor vehicle can preferably be used in a passenger car or a truck, but also in a motorcycle, a scooter, an excavator, a forklift, or the like. In particular, the method according to the invention can be used in motor vehicles with a hydraulic braking system. However, use of the method according to the invention in motor vehicles with an electronic braking system or electronic assistance is also conceivable.

[0009] The method according to the invention for operating a braking system of a motor vehicle comprises the steps of detecting parameters for determining the starting point and the end point of a build-up process of a braking process by means of a sensor unit, determining the starting point and the end point of the build-up process on the basis of the detected parameters by means of a processing unit, and determining the current clearance of the braking device on the basis of the determined starting point and end point of the build-up process by means of the processing unit.

[0010] When implementing the method according to the invention, the current clearance of the braking device can be determined, in particular, by determining a starting point and an end point of a build-up process of a braking operation. Within the scope of the invention, it has been recognized that by determining the starting point and the end point of a build-up process of a braking operation, a particularly precise determination of the current clearance is possible, which guarantees a particularly reliable forecast regarding the need to replace brake components. Furthermore, the method according to the invention can be carried out in a straightforward manner using simple means, thus avoiding high costs for production and maintenance.

[0011] According to the invention, a build-up process of a braking process can preferably be understood as the phase of a braking process that lies between a resting state and full actuation of the braking device, i.e., the phase between a starting point and an end point in which a braking pressure is built up. Parameters for determining the starting point and the end point of a build-up process of a braking process can also be understood as measured values ​​that can preferably be detected by sensors.

[0012] When applying a brake on a braking device, a distinction can generally be made between three states or phases. In the first state or phase, there is preferably no brake pressure and the brake is in an open state. In this first state or phase, there is preferably no contact or only irregular and very infrequent contact (e.g., less than one contact per second) is audible or acoustically perceptible. In the second state or phase, the build-up process, the brake pressure is preferably built up and the clearance is finally overcome (end point of the second state or phase). At the time the clearance is overcome, the brake pressure is generally less than 5 bar. The brake pressure is preferably built up by filling the wheel brake with hydraulic or brake fluid.A starting point of the build-up process can advantageously be understood as a first point in time at which regular contact between the brake disc and brake pad is perceptible or audible when the pressure increases, or the last point in time at which regular contact is still perceptible or audible when the pressure decreases. An end point of the build-up process can advantageously be understood as a last point in time at which regular contact between the brake disc and brake pad is perceptible or audible when the pressure increases, or the first point in time at which regular contact is perceptible or audible when the pressure decreases. In the third state or phase, which advantageously begins when the air gap is completely overcome, there is, in particular, continuous contact between the brake pad and brake disc.In the third state, the brake pressure can be increased to a maximum of approximately 200 bar after overcoming the clearance up to the locking limit, whereby the wheels can advantageously lock at approximately 100 bar. Volume can continue to be pumped into the wheel brake to compensate for elastic deformations of the brake system due to the high forces and the compressibility of the brake fluid.

[0013] According to the invention, the various states or phases can advantageously be acoustically detected and assigned. Thus, in the second state or phase, the build-up process, for example, the first sporadic impact noises from the brake disc and brake pad can be detected, which represent the audible initial contact between the brake pads and the brake disc when the brake device is filled with hydraulic or brake fluid. During the course of the filling process and the progressive build-up of brake pressure, an intensification of the impact noises can then be perceived, until finally, impact noises can no longer be perceived when the brake disc is permanently in contact with the brake pads in the third phase.The cause of the perceptible impact noises in the second phase is in particular a wobbling movement of the brake disc, which is intended to move the friction lining to both sides and ensure that there is no contact when the brake device is not actuated. If the perceived noises can be attributed to the filling of the brake device with hydraulic or brake fluid, this can advantageously be used to determine how large the clearance was at that time. Although impact noises are no longer perceptible in the third phase, perceptible grinding noises or brake squeal can occur in the third phase. The firm contact of the brake pads against the brake disc in the third phase can lead to a change in the natural frequency of the entire system. A transition to the third phase can therefore be detected, for example, via a frequency shift of perceptible acoustic signals.

[0014] With a view to determining the clearance of a braking device of a motor vehicle as precisely as possible, while also being simple and cost-effective, the invention can advantageously provide for the detection of parameters for determining the starting point and the end point of a build-up of a braking operation to be carried out by means of ultrasonic sensors, wherein the ultrasonic sensors are preferably used or designed to have a dual function as parking distance sensors of the motor vehicle. The ultrasonic sensors can be arranged on the body of the vehicle - in particular in the dual function as parking distance sensors. Likewise, other sensors, such as microphones or temperature sensors, can be provided alternatively or cumulatively, by means of which parameters for determining the starting point and the end point of a build-up of a braking operation can be detected.By using temperature sensors, for example, in conjunction with a heating model, the residual braking torque can be roughly determined indirectly via the offset temperature above the ambient temperature. The offset temperature is proportional to the residual braking torque at a constant driving speed without brake application.

[0015] Within the scope of simple and reliable detection of a starting point and an end point of a braking device's build-up process, it can advantageously be provided that the starting point of the braking process's build-up process is determined by detecting a starting point of contact between a brake pad and a brake disc, and the end point of the braking process's build-up process is determined by detecting permanent contact between the brake pad and the brake disc. Permanent contact can be defined, for example, as a permanent contact duration of more than 0.3 seconds.

[0016] Within the scope of a particularly precise and meaningful determination of the current clearance of a braking device, it can advantageously be provided according to the invention that, in addition to a starting point and an end point of the build-up process of the braking process, a rest state of the braking device is determined in which the braking device is not actuated, wherein the starting point is preferably defined by the transition from the rest state to the build-up process. By determining the rest state or the rest phase, it is possible to determine the starting point for the build-up process more precisely, particularly due to the comparison option. The rest state or the rest phase can preferably be detected by means of ultrasonic sensors via a detection of normal driving noises.Ideally, a level surface and / or a quiet driving environment can be created to eliminate sporadic contact between the brake pads and the brake disc due to an uneven road surface. On the other hand, if contact noise from the wheel brake increases in the initial condition without road surface excitation and brake application, this can already indicate a low clearance and increased braking torque.

[0017] Likewise, the invention can advantageously provide that, in addition to a starting point and an end point of the build-up process of the braking process, a braking state of the braking device is determined in which the braking device is fully actuated, wherein the end point of the build-up process is preferably defined by the transition of the build-up process to the braking state. By determining the state or phase of complete actuation, it is possible, particularly due to the comparison option, to determine the end point for the build-up process more precisely.

[0018] As part of a simple and particularly precise method for determining the current clearance of a braking device, the invention provides that the clearance of the braking device is determined based on the time difference between the starting point and the end point of the build-up process, with the clearance preferably being determined by comparing a determined time difference with reference values. It is understood that, advantageously, not only the time of brake pressure build-up or filling with brake fluid should be defined, but also the filling speed or the filled volume or the displacement of the brake pad should preferably be taken into account, since these variables are directly related to one another.

[0019] In order to use the knowledge of the current air gap to monitor the residual braking torques or to control the brake, it can further be provided that countermeasures are initiated based on the determined air gap of the braking device, wherein the countermeasures preferably comprise a repair and / or maintenance process. During a repair or maintenance visit to the workshop, for example, a check of the wheel brakes can be recommended. A technically experienced customer can also detect increased residual braking torques on a wheel, in particular additionally, by comparing the temperatures between the sides of the vehicle. To this end, one could, for example, drive a longer distance at a constant speed and without applying the brakes in order to avoid active braking torques as much as possible.

[0020] In order to increase driving safety, it can also advantageously be provided for the purpose of anticipatory driving that a warning message is sent to the driver of the motor vehicle on the basis of the determined air gap of the braking device, wherein the warning message is preferably sent when a threshold value of a parameter for determining the air gap is exceeded or undershot.

[0021] In order to ensure a particularly precise and meaningful determination of a clearance of a braking device, it may also be advantageous if, before and / or during the recording of parameters for determining the starting point and the end point of a build-up process of a braking process, measures are introduced to increase the accuracy of the determination, wherein the measures preferably comprise one of the following steps: - Cleaning the surface of a brake disc and / or brake pad, - Targeted, slow build-up of braking pressure, especially while controlling the distance, - Targeted slow reduction of brake pressure, especially while controlling the distance.

[0022] Advantageously, the control of the wheel brake can be selected in selected situations so that the second phase is completed under particularly favorable conditions. For example, a brake disk wiper or the like can be provided, by means of which a layer of water on a brake disk and / or brake pad can be removed. To remove a layer of water, a moderate brake pressure could be built up briefly, for example, so that the brake disk is applied and a water film can be removed. Alternatively or cumulatively, brake pressure can be built up very slowly when carrying out the method in question, so that the start point and end point of the build-up process can be determined easily and reliably on the basis of the recorded parameters. Furthermore, a distance check can be carried out while driving.In order to drive through the second phase very slowly, brake pressure can be built up very slowly shortly before the necessary deceleration via the wheel brakes. It goes without saying that, in practice, the starting point and end point of the build-up process can be determined both by detecting the transition from the first to the third phase (brake pressure build-up), and by transitioning from the third phase back to the first phase (brake pressure reduction). With regard to a targeted, slow build-up and release of brake pressure, a slow build-up and release of brake pressure on individual wheels or axles could also be advantageously provided during normal braking. This is applicable to almost any comfort braking and is particularly easy to implement with an electromechanical braking system.

[0023] It is also understood that individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out in the proposed order, but also deviating from the proposed order. Individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out repeatedly, for example, cyclically. It is further understood that individual, several, or all of the mandatory and optional steps of the method according to the invention can also be implemented by a computer.

[0024] The invention furthermore relates to a braking system, in particular for carrying out a method described above. The braking system in question comprises a braking device with a brake disc, a brake caliper, and a brake pad arranged on the brake caliper, at least partially between the brake caliper and the brake disc; a sensor unit for detecting parameters for determining the starting point and end point of a build-up of a braking operation; a processing unit for determining the starting point and end point of a build-up of a braking operation; and for determining the clearance of the braking device based on the determined starting point and end point of the build-up. Thus, the braking system according to the invention offers the same advantages as those already described in detail with regard to the method according to the invention.

[0025] The invention also further relates to a motor vehicle comprising a braking system as described above. Thus, the braking system according to the invention has the same advantages as those already described in detail with regard to the method according to the invention and the braking system according to the invention.

[0026] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0027] They show: Fig. 1 a schematic representation of the individual steps of a method according to the invention for determining a current clearance of a braking device of a motor vehicle, Fig. 2 a schematic representation of a braking system according to the invention arranged within a motor vehicle, Fig. 3 an enlarged view of a braking device of a braking system according to the invention.

[0028] Fig. 1 shows a schematic representation of the individual steps of a method according to the invention for determining a current clearance of a braking device 10 of a motor vehicle 80.

[0029] The method according to the invention comprises the steps of detecting 100 parameters for determining the starting point T1 and the end point T2 of a build-up process of a braking process by means of a sensor unit 4, determining 200 the starting point T1 and the end point T2 of the build-up process on the basis of the detected parameters by means of a processing unit 6, and determining 300 the clearance of the braking device 10 on the basis of the determined starting point T1 and end point T2 of the build-up process by means of the processing unit 6.

[0030] The detection 100 of parameters for determining the starting point T1 and the end point T2 of a build-up process of a braking process can be carried out, for example, by means of ultrasonic sensors, wherein the ultrasonic sensors can preferably be used in a dual function as parking distance sensors of the motor vehicle 80.

[0031] The determination 200 of the starting point T1 of the build-up process of the braking process can further be carried out by detecting a starting point of contact between a brake pad 16 and a brake disc 12, and the determination 200 of the end point T2 of the build-up process of the braking process can be carried out by detecting a permanent contact between the brake pad 16 and the brake disc 12.

[0032] In addition to a starting point T1 and an end point T2 of the build-up process of the braking process, a rest state of the braking device 10 can also be determined in which the braking device 10 is not actuated, wherein the starting point T1 can preferably be defined by the transition from the rest state to the build-up process.

[0033] In addition, it is also conceivable that, in addition to a starting point T1 and an end point T2 of the build-up process of the braking process, a braking state of the braking device 10 is determined in which the braking device 10 is fully actuated, wherein the end point T2 of the build-up process can preferably be defined by the transition of the build-up process to the braking state.

[0034] The determination 300 of the clearance of the braking device 10 can also be determined in particular on the basis of the time difference ΔT between the starting point T1 and the end point T2 of the build-up process.

[0035] In addition, it is also conceivable that countermeasures, such as a repair and / or maintenance process, are initiated on the basis of the determined air gap of the braking device 10.

[0036] A warning message can also be sent to the driver of the motor vehicle 80 based on the determined clearance of the braking device 10.

[0037] Finally, it is also conceivable that before and / or during the recording of 100 parameters for determining the starting point T1 and the end point T2 of a build-up process of a braking process, measures are introduced to increase the accuracy of the determination.

[0038] Fig. 2 shows a schematic representation of a braking system 2 according to the invention arranged within a motor vehicle 80.

[0039] As in Fig. 2, the braking system 2 according to the invention comprises a Fig. 3 braking device 10, which is described in more detail in FIG. 3, a sensor unit 4 for detecting 100 parameters for determining the starting point T1 and the end point T2 of a build-up process of a braking process, and a processing unit 6 for determining 200 the starting point T1 and the end point T2 of a build-up process of a braking process and for determining 300 the clearance of the braking device 10 on the basis of the determined starting point T1 and end point T2 of the build-up process.

[0040] Fig. 3 shows an enlarged view of the braking device 10 of the braking system 2 according to the invention, with a brake disc 12, a brake caliper 14 and a brake pad 16 arranged on the brake caliper 14, at least partially between the brake caliper 14 and the brake disc 12.

[0041] By means of the method according to the invention and the braking system 2 according to the invention, it is possible, in particular, to determine the current clearance of a braking device in a particularly precise manner by determining a starting point and an end point of a build-up process of a braking process, thereby guaranteeing a particularly reliable forecast regarding the need to replace brake components. Furthermore, the method according to the invention can be implemented in a straightforward manner using simple means, thus avoiding high manufacturing and maintenance costs. List of reference symbols 2 braking system 4 Sensor unit 4' sensors 6 Processing unit 10 Braking device 12 brake disc 14 brake caliper 16 brake pad 80 motor vehicles 100 Recording of parameters for determining the start point and end point of a build-up process of a braking process 200 Determining the start point and end point of the braking build-up process 300 Determining the clearance of the braking device based on the determined start point and end point of the build-up process of the braking process T1 Starting point of the build-up process of the braking process T2 End point of the build-up process of the braking process ΔT time difference

Claims

[1] Method for determining a current clearance of a braking device (10) of a motor vehicle (80), comprising the steps: - detecting (100) parameters for determining the starting point (T1) and the end point (T2) of a build-up process of a braking process by means of a sensor unit (4), - determining (200) the starting point (T1) and the end point (T2) of the assembly process on the basis of the recorded parameters by means of a processing unit (6), - determining (300) the clearance of the braking device (10) on the basis of the determined starting point (T1) and end point (T2) of the build-up process by means of the processing unit (6), - wherein the determination (300) of the clearance of the braking device (10) is determined on the basis of the time difference (ΔT) between the starting point (T1) and the end point (T2) of the build-up process. [2] Method according to claim 1, characterized bythat the detection (100) of parameters for determining the starting point (T1) and the end point (T2) of a build-up process of a braking process is carried out by means of ultrasonic sensors, wherein the ultrasonic sensors are preferably used in a dual function as parking distance sensors of the motor vehicle (80). [3] Method according to claim 1 or 2, characterized by that the determination (200) of the starting point (T1) of the build-up process of the braking process takes place via the detection of a starting point of contact between a brake pad (16) and a brake disc (12) and the determination (200) of the end point (T2) of the build-up process of the braking process takes place via the detection of a permanent contact between the brake pad (16) and the brake disc (12). [4] Method according to one of the preceding claims, characterized bythat in addition to a starting point (T1) and an end point (T2) of the build-up process of the braking process, a rest state of the braking device (10) is determined in which the braking device (10) is not actuated, wherein the starting point (T1) is preferably defined by the transition from the rest state to the build-up process. [5] Method according to one of the preceding claims, characterized by that in addition to a starting point (T1) and an end point (T2) of the build-up process of the braking process, a braking state of the braking device (10) is determined in which the braking device (10) is fully actuated, wherein the end point (T2) of the build-up process is preferably defined by the transition of the build-up process into the braking state. [6] Method according to one of the preceding claims, characterized by that the determination (300) of the air gap is carried out by comparing a determined time difference (ΔT) with reference values. [7] Method according to one of the preceding claims, characterized by that on the basis of the determined air gap of the braking device (10) an initiation of countermeasures is provided, wherein the countermeasures preferably comprise a repair and / or maintenance process. [8] Method according to one of the preceding claims, characterized by that on the basis of the determined air gap of the braking device (10) a warning message is sent to the driver of the motor vehicle (80), wherein the warning message is preferably sent when a threshold value of a parameter for determining the air gap is exceeded or undershot. [9] Method according to one of the preceding claims, characterized bythat before and / or during the detection (100) of parameters for determining the starting point (T1) and the end point (T2) of a build-up process of a braking process, measures are introduced to increase the accuracy of the determination, wherein the measures preferably comprise one of the following steps: - cleaning the surface of a brake disc (12) and / or a brake pad (16), - Targeted, slow build-up of braking pressure, especially while controlling the distance, - Targeted, slow reduction of brake pressure, particularly while controlling the distance. [10] Braking system (2) for arrangement within a motor vehicle (80), for carrying out a method according to one of the preceding claims, comprising: - a braking device (10) comprising a brake disc (12), a brake calliper (14) and a brake pad (16) arranged on the brake calliper (14), at least partially between the brake calliper (14) and the brake disc (12), - a sensor unit (4) for detecting (100) parameters for determining the starting point (T1) and the end point (T2) of a build-up process of a braking process, - a processing unit (6) for determining (200) the starting point (T1) and the end point (T2) of a build-up process of a braking process and for determining (300) the clearance of the braking device (10) on the basis of the determined starting point (T1) and end point (T2) of the build-up process. [11] Motor vehicle (80) comprising a braking system (2) according to claim 10.

Images