METHOD FOR DETERMINING THE CURRENT AIR CLEARANCE OF A BRAKE DEVICE AND BRAKE SYSTEM

Description

[0001] The present invention relates to a method and a braking system for determining the air 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, brake clearance refers specifically to the distance between the brake pad and brake disc of a braking system when the brakes are not engaged. This clearance can vary over the service life of a braking system. Due to component wear, the clearance typically increases continuously over the operating life of a braking system, although this is usually compensated for by mechanical solutions to maintain a constant clearance. Conversely, dirt and deposits on the brake components reduce the clearance. Both excessive and insufficient clearance can be detrimental if they exceed a certain tolerance range.

[0003] If the brake pedal clearance is too large, the pedal travel increases, leading to a delayed build-up of braking force and ultimately longer braking distances. Conversely, if the clearance is too small, there is a risk that the two friction surfaces 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 accelerated wear on the brake components. Furthermore, the residual braking torque generates high temperatures, which not only negatively impact braking performance but can also lead to permanent damage to the brake components due to localized overheating.

[0004] For safety reasons, it would be advisable to determine the current brake clearance of a motor vehicle's brake system at least at certain intervals. Methods and systems for determining the brake clearance of a motor vehicle's brake system are known, for example, from DE 10 2017 131 252 A1 or WO 2014 / 041160 A1.

[0005] Unfortunately, the known systems and methods are either not designed to accurately detect the current air gap of a brake device, so that a sufficiently reliable prediction regarding the need to replace brake components is not possible, or the systems and methods are so complex and expensive that high costs are incurred for the manufacture and maintenance of the systems.

[0006] It is therefore the object of the present invention to at least partially eliminate the disadvantages described above; in particular, it is the object of the present invention to provide a method for determining the clearance of a brake device of a motor vehicle that enables the most accurate and reliable prediction possible regarding the need for maintenance or repair of a brake device and is itself as cost-effective to manufacture and maintain as possible.

[0007] The foregoing problem is solved by a method with 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 will become apparent from the dependent claims, the description, and the drawings. The technical features disclosed with respect to the method according to the invention also apply in connection with the braking system and the motor vehicle according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always makes, or can make, reciprocal references. Advantageous embodiments of the invention are set forth in the dependent claims.

[0008] The inventive method for operating a motor vehicle's braking system 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 inventive method can be used in motor vehicles with a hydraulic braking system. However, use of the inventive method in motor vehicles with an electronic braking system or electronic assistance is also conceivable.

[0009] The inventive method for operating a braking system of a motor vehicle comprises the steps of acquiring parameters to determine the start point and end point of a braking process build-up using a sensor unit, determining the start point and end point of the build-up process based on the acquired parameters using a processing unit, and determining the current air gap of the brake device based on the determined start point and end point of the build-up process using the processing unit.

[0010] In carrying out the method according to the invention, the current brake clearance can be determined, in particular, by defining a start and end point of a braking process. Within the scope of the invention, it has been recognized that by determining the start and end points of a braking process, a particularly precise determination of the current brake clearance is possible, thereby guaranteeing a particularly reliable prediction regarding the necessity of replacing brake components. Furthermore, the method according to the invention can be carried out in a straightforward manner using simple means, so that no high manufacturing and maintenance costs are incurred.

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

[0012] When applying the brakes of a braking device, three states or phases can generally be distinguished. In the first state or phase, there is preferably no brake pressure and the brake is in the open position. In this first state or phase, there is therefore preferably no contact or only an irregular and very infrequent contact (e.g., less than one contact per second) that is audible or perceptible. In the second state or phase, the build-up process, the brake pressure is preferably built up and the initial clearance is finally overcome (endpoint of the second state or phase). At the point when the initial clearance is overcome, the brake pressure is generally less than 5 bar. The brake pressure build-up is preferably achieved by filling the wheel brake with hydraulic or brake fluid.The starting point of the build-up process can advantageously be understood as the 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. The end point of the build-up process can advantageously be understood as the 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 clearance is completely overcome, continuous contact between the brake pad and brake disc occurs.In the third state, the brake pressure can be increased to a maximum of approximately 200 bar after overcoming the initial clearance, with the wheels advantageously locking up from around 100 bar. Additional brake fluid volume can be pumped into the wheel brakes to compensate for elastic deformations of the brake system resulting from 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. For example, in the second state or phase, the build-up process, initial sporadic impact noises from the brake disc and brake pad can be detected, representing the audible initial contact between the brake pads and the brake disc when the brake system is filled with hydraulic or brake fluid. As the filling process and the brake pressure build-up progresses, an intensification of the impact noises can be perceived until finally no impact noises can be detected when the brake disc is in permanent contact with the brake pads in the third phase.The cause of the perceptible impact noises in the second phase is primarily a wobbling motion of the brake disc, which is intended to move the friction lining to both sides and ensure contact-free operation when the brakes are not applied. If the perceived noises can be attributed to the filling of the brake system with hydraulic or brake fluid, the amount of clearance at that time can be advantageously determined. In the third phase, impact noises are no longer perceptible, but grinding noises or brake squeal may occur. The firm contact of the brake pads with 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, by a frequency shift in perceptible acoustic signals.

[0014] With a view to achieving the most precise, yet simple and cost-effective, determination of the air clearance of a motor vehicle's brake system, the invention advantageously provides that the detection of parameters for determining the start and end points of a braking process is carried out by means of acoustic sensors, preferably by means of moisture sensors or ultrasonic sensors, wherein the moisture sensors are in particular designed as piezoelectric sensors and / or the ultrasonic sensors are used or designed in a dual function as parking distance sensors of the motor vehicle. The ultrasonic sensors can be arranged on the outside of the vehicle body, particularly when used in the dual function as parking distance sensors.The moisture sensors, preferably designed as piezoelectric sensors, can be arranged, in particular, in a wheel arch of the vehicle and are suitable for capturing acoustic signals in the wheel arch. The moisture sensors can preferably be arranged approximately at the level of the wheel center or slightly below, behind the wheel, in the wheel center plane, especially where spray water picked up by the tire tread on a wet road surface is primarily flung there by centrifugal force. Alternatively or cumulatively, other sensors, such as microphones, temperature sensors, or sensors from noise reduction systems, can also be provided, by means of which parameters for determining the start and end points of a braking process can be recorded. For example, temperature sensors can be used to...In conjunction with a heating model, the residual braking torques can be roughly determined indirectly via the offset temperature above the ambient temperature. At a constant driving speed without brake application, the offset temperature is proportional to the residual braking torque.

[0015] For the simple and reliable detection of the start and end points of a braking process, it is advantageously possible to determine the start point of the braking process by detecting the initial contact between a brake pad and a brake disc, and to determine the end point of the braking process by detecting continuous contact between the brake pad and the brake disc. Continuous contact can be defined, for example, as a contact duration exceeding 0.3 seconds.

[0016] In the context of a particularly precise and informative determination of the current clearance of a brake system, the invention advantageously provides that, in addition to a start and end point of the brake system's build-up phase, a rest state of the brake system is determined in which the brake system is not actuated. The start point is preferably defined by the transition from the rest state to the build-up phase. Determining the rest state, or rest phase, makes it possible to determine the start point for the build-up phase more precisely, particularly due to the possibility of comparison. The rest state, or rest phase, can preferably be detected using acoustic sensors, for example, by detecting normal driving noises.Ideally, a level surface and / or a quiet driving environment should be created to eliminate sporadic contact between the brake pads and brake disc due to an uneven road surface. Conversely, if, in the first state without road vibrations or brake application, contact noise from the wheel brakes is more frequent, this can already indicate low brake pad clearance and increased braking torque.

[0017] Similarly, according to the invention, it can advantageously be provided that, in addition to a start point and an end point of the braking process's build-up phase, a braking state of the braking device is defined in which the braking device is fully actuated, wherein the end point of the build-up phase is preferably defined by the transition of the build-up phase into the braking state. By determining the state or phase of full actuation, it is possible, particularly due to the possibility of comparison, to determine the end point for the build-up phase more precisely.

[0018] According to the invention, a simple and particularly precise method for determining the current brake clearance of a brake device can advantageously be provided by determining the brake clearance based on the time difference between the start and end points of the build-up process. This determination is preferably carried out by comparing a calculated 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 preferably also the filling rate, the filled volume, or the displacement of the brake pad, since these quantities are directly related.

[0019] To utilize the knowledge of the current brake clearance for monitoring residual braking torques or controlling the brakes, it can further be provided that countermeasures are initiated based on the determined brake clearance of the braking device, whereby the countermeasures preferably include a repair and / or maintenance procedure. During a repair or maintenance visit, for example, checking the wheel brakes can be recommended. A technically skilled customer can also detect increased residual braking torques at a wheel, particularly by comparing the temperatures between the sides of the vehicle. For this purpose, for example, a longer distance could be driven at a constant speed without applying the brakes, in order to avoid active braking torques as much as possible.

[0020] As part of increasing driving safety, it may also be advantageously provided that, based on the specific air gap of the brake device, a warning message is sent to the driver of the motor vehicle, wherein the warning message is preferably sent when a threshold value of a parameter for determining the air gap is exceeded or fallen below.

[0021] In order to ensure a particularly precise and meaningful determination of the clearance of a brake device, the invention provides that measures are introduced before and / or during the acquisition of parameters for determining the start point and the end point of a build-up process of a braking process in order 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 brake pressure, especially under distance control, targeted slow reduction of brake pressure, especially under distance control.

[0022] Advantageously, the wheel brake control can be selected in specific situations so that the second phase is carried out under particularly favorable conditions. For example, a brake disc wiper or similar device can be used to remove a layer of water from a brake disc and / or brake pad. To remove this water layer, a moderate brake pressure could be briefly applied, causing the brake disc to engage and the water film to be wiped away. Alternatively or additionally, the brake pressure build-up during this process can be very gradual, allowing for a simple and reliable determination of the start and end points of the build-up process based on the recorded parameters. Furthermore, distance monitoring can be performed while driving.To traverse the second phase very slowly, brake pressure can be built up very gradually shortly before the necessary deceleration via the wheel brakes occurs. It is understood that the starting and ending points 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 detecting the transition from the third back to the first phase (brake pressure release). With regard to a deliberately slow build-up and release of brake pressure, it would also be advantageous in normal braking to implement a slow build-up and release of brake pressure at individual wheels or axles, which is applicable to almost any comfort braking system and particularly easy to implement in an electromechanical braking system.

[0023] It is 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 sequence, but also in a different sequence. In particular, individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out repeatedly, e.g., 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 also relates to a braking system designed to carry out a method described above. This braking system 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 to determine the start and end points of a braking build-up process; and a processing unit for determining the start and end points of a braking build-up process and for determining the brake clearance based on the determined start and end points of the build-up process. The braking system according to the invention thus offers the same advantages as those already described in detail with regard to the method according to the invention.

[0025] The invention also relates to a motor vehicle comprising a braking system as described above. The braking system according to the invention thus has the same advantages as those already described in detail with regard to the method 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 can each 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 air clearance of a brake device of a motor vehicle, Fig. 2 a schematic representation of a brake system according to the invention arranged within a motor vehicle, Fig. 3 an enlarged view of a brake device of a brake system according to the invention.

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

[0029] The inventive method comprises the steps of acquiring 100 parameters to determine the start 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 start point T1 and the end point T2 of the build-up process based on the acquired parameters by means of a processing unit 6, and determining 300 the air gap of the brake device 10 based on the determined start point T1 and end point T2 of the build-up process by means of the processing unit 6.

[0030] The acquisition of 100 parameters for determining the start 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 acoustic sensors, preferably by means of moisture sensors or ultrasonic sensors, wherein the moisture sensors are in particular designed as piezo sensors and / or the ultrasonic sensors can be used in a dual function as parking distance sensors of the motor vehicle 80.

[0031] Determining the starting point T1 of the braking process build-up can also be done by detecting a starting point of contact between a brake pad 16 and a brake disc 12, and determining the end point T2 of the braking process build-up can be done 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] Furthermore, it is 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 into the braking state.

[0034] The determination of the air clearance of the brake 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 assembly process.

[0035] Furthermore, it is conceivable that, based on the specific air gap of the brake device 10, countermeasures such as a repair and / or maintenance procedure are initiated.

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

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

[0038] Fig. 2 Figure 1 shows a schematic representation of a braking system 2 according to the invention arranged within a motor vehicle 80.

[0039] As in Fig. 2 As can be seen, the braking system 2 according to the invention comprises a Fig. 3a brake device 10 described in more detail, a sensor unit 4 for recording 100 parameters for determining the start 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 start point T1 and the end point T2 of a build-up process of a braking process and for determining 300 the clearance of the brake device 10 based on the determined start point T1 and end point T2 of the build-up process.

[0040] Fig. 3 Figure 1 shows an enlarged view of the brake device 10 of the brake 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] Using the inventive method and the inventive brake system 2, it is particularly possible to determine the current free play of a brake device with exceptional precision by defining a start and end point of a braking process and thereby guaranteeing a particularly reliable prediction regarding the necessity of replacing brake components. Furthermore, the inventive method can be implemented easily and simply, so that no high manufacturing and maintenance costs are incurred. Reference symbol list

[0042] 2Brake system 4Sensor unit 4'Sensors 6Processing unit 10Brake device 12Brake disc 14Brake caliper 16Brake pad 80Motor vehicle 100 Recording parameters to determine the start and end points of a build-up process or a braking process 200 Determining the start and end points of the build-up process or the braking process 300 Determining the brake clearance of the brake device based on the determined start and end points of the build-up process or the braking process T1Start point of the braking process build-up process T2End point of the braking process build-up process ΔTTime difference

Claims

1. Method for determining an actual air clearance of a braking device (10) of a motor vehicle (80), comprising the steps of: - recording (100) parameters for determining a start point (T1) and an end point (T2) of a build-up process of a braking process by means of a sensor unit (4), the build-up process of a braking process being the phase of a braking process between a rest state of the braking device (10), in which the braking device (10) is not actuated, and a braking state of the braking device (10), in which the braking device (10) is fully actuated, - determining (200) the start point (T1) and the end point (T2) of the build-up process on the basis of the recorded parameters by means of a processing unit (6), - determining (300) the air clearance of the braking device (10) on the basis of the determined start point (T1) and end point (T2) of the build-up process by means of the processing unit (6), characterized in that before and / or during the recording (100) of parameters for determining the start point (T1) and the end point (T2) of the build-up process of a braking process, measures are introduced to increase the accuracy of the determination, the measures comprising one of the following steps: - cleaning the surface of a brake disk (12) and / or of a brake pad (16), - building up a brake pressure in a targeted, slow manner, especially under distance control, - reducing a brake pressure in a targeted, slow manner, especially under distance control.

2. Method according to claim 1, characterized in that recording (100) parameters for determining the start point (T1) and the end point (T2) of the build-up process of a braking process is carried out by means of acoustic sensors, preferably by means of wetness sensors or ultrasonic sensors, the wetness sensors being in particular designed as piezo sensors and / or the ultrasonic sensors being used in a dual function as parking distance sensors of the motor vehicle (80).

3. Method according to claim 1 or 2, characterized in that determining (200) the start point (T1) of the build-up process of the braking process is carried out by detecting a start point of contact between a brake pad (16) and a brake disk (12) and determining (200) the end point (T2) of the build-up process of the braking process is carried out by detecting permanent contact between the brake pad (16) and the brake disk (12), permanent contact being ascertained by the exceeding of a permanent contact duration of preferably 0.3 seconds.

4. Method according to any of the preceding claims, characterized in that in addition to the start point (T1) and the end point (T2) of the build-up process of the braking process, the rest state of the braking device (10) is determined, in which the braking device (10) is not actuated, the start point (T1) being preferably defined by the transition from the rest state to the build-up process.

5. Method according to any of the preceding claims, characterized in that in addition to the start point (T1) and the end point (T2) of the build-up process of the braking process, the braking state of the braking device (10) is determined, in which the braking device (10) is fully actuated, the end point (T2) of the build-up process being preferably defined by the transition of the build-up process into the braking state.

6. Method according to any of the preceding claims, characterized in that determining (300) the air clearance of the braking device (10) is based on the time difference (ΔT) between the start point (T1) and the end point (T2) of the build-up process, the air clearance preferably being determined (300) by comparing an established time difference (ΔT) with reference values.

7. Method according to any of the preceding claims, characterized in that, on the basis of the determined air clearance of the braking device (10), an introduction of countermeasures is provided, the countermeasures preferably comprising a repair and / or maintenance process.

8. Method according to any of the preceding claims, characterized in that a warning message is sent to the driver of the motor vehicle (80) on the basis of the determined air clearance of the braking device (10), the warning message being preferably sent when a threshold value of a parameter for determining the air clearance is exceeded or fallen below.

9. Brake system (2) for arrangement within a motor vehicle (80), configured to perform a method according to any of the preceding claims, comprising: - a braking device (10), comprising a brake disk (12), a brake caliper (14) and a brake pad (16) which is arranged on the brake caliper (14), at least partially between the brake caliper (14) and the brake disk (12), - a sensor unit (4) for recording (100) parameters for determining the start point (T1) and the end point (T2) of the build-up process of a braking process, wherein the build-up process of a braking process is the phase of a braking process between a rest state of the braking device (10), in which the braking device (10) is not actuated, and a braking state of the braking device (10), in which the braking device (10) is fully actuated, - a processing unit (6) for determining (200) the start point (T1) and the end point (T2) of the build-up process of a braking process and for determining (300) the air clearance of the braking device (10) on the basis of the determined start point (T1) and end point (T2) of the build-up process, wherein the brake system (2) is designed, before and / or during the recording (100) of parameters for determining the start point (T1) and the end point (T2) of the build-up process of a braking process, to introduce measures to increase the accuracy of the determination, wherein the measures comprise one of the following steps: - cleaning the surface of the brake disk (12) and / or of the brake pad (16), - building up a brake pressure in a targeted, slow manner, especially under distance control, - reducing a brake pressure in a targeted, slow manner, especially under distance control.

10. Motor vehicle (80), comprising a brake system (2) according to claim 9.