Method for adjusting the clearance of a disc brake, brake pad and service brake for a motor vehicle

Abstract

A method is proposed for adjusting the clearance of a disc brake (10) for a motor vehicle, comprising a brake caliper (12), a brake piston, a brake disc (16), brake pads, at least one drive unit (30) assigned to a brake pad and capable of applying a restoring force to the assigned brake pad, and at least one sensor assigned to the brake pad coupled to the drive unit (30), whereby a physical value of the brake pad is determined, the physical value is compared with an assigned predetermined limit value or a predetermined limit value range, and the brake pad is adjusted by an assigned drive unit (30) if necessary. Furthermore, a brake pad and a service brake for a motor vehicle are proposed.

Description

[0001] The invention relates to a method for adjusting a clearance of a disc brake, a brake pad and a service brake for a motor vehicle.

[0002] Brake pads on disc brakes are typically reset after braking. This occurs, for example, when an elastic brake piston seal is deformed during braking and then returns to its original shape after the brake is released. This causes the brake piston to be driven along, which also resets the brake pad associated with the brake piston. This separates the brake pad from the brake disc, creating a clearance between the brake pad and brake disc, ensuring that unnecessary fuel consumption and brake wear are avoided due to brake pad drag. Reset using elastic reset elements, e.g., reset arms integrated into bearing clips, is also common.

[0003] The clearance of the outer brake pad of floating-caliper brakes is usually adjusted using springs. The restoring forces must be higher on the outer side than on the inner side, as the outer brake pad must overcome the frictional forces in the housing guide and also move the entire brake caliper.

[0004] A disadvantage of these systems is that conventional pad return springs achieve comparatively low return forces. As a result, these return mechanisms are unable to reliably return the brake caliper over the entire service life of a disc brake. The return force may no longer be sufficient, particularly when contaminated, resulting in increased friction between the pads and the pad guide. As the level of contamination increases, the spring force may no longer be sufficient to fully return the pads.

[0005] Furthermore, if the disc deflects while cornering, the brake caliper is displaced relative to the brake carrier. This usually cannot be compensated for by pad return springs.

[0006] Another disadvantage is that the clearance changes over time due to wear on the brake pad and brake disc. For example, the clearance is subject to constant changes even during vehicle operation, due, among other things, to the changing temperature of the brakes.

[0007] Furthermore, the individual brakes of a motor vehicle can have different clearances. As a result, the individual brakes can have different response times and, in some cases, braking forces.

[0008] Based on this, the object of the invention is to provide a method by which the air gap of a disc brake can be adjusted reliably and precisely. Furthermore, a corresponding brake pad is to be provided that allows for reliable and precise adjustment.

[0009] The stated object is achieved according to the invention by a method for adjusting a clearance of a disc brake for a motor vehicle, comprising a brake calliper, a brake piston, a brake disc, brake pads, at least one drive unit which is associated with a brake pad and by means of which a restoring force can be applied to the associated brake pad, and at least one sensor which is associated with the at least one brake pad coupled to the drive unit, characterized by the following method steps: a) determining at least one physical value of the brake pad by means of the at least one sensor associated with the brake pad; b) comparing the determined physical value with an associated predetermined limit value or a predetermined range of limits; and c) if the at least one assigned limit value of the at least one specific physical value of the brake pad is reached or undershot or lies outside the limit value range, adjusting the brake pad by the drive unit assigned to the brake pad depending on the specific physical value and adjusting the clearance to another value not equal to zero.

[0010] The disc brake is the vehicle’s service brake.

[0011] The basic idea of ​​the invention is to use the physical value to determine whether the brake pad is still in contact with the brake disc and / or how large the clearance is, i.e. how large the distance is between the brake pad and the brake disc.

[0012] “Determining” at least one physical value by means of the sensor means estimating or detecting the physical value.

[0013] Based on this, by comparing the at least one physical value with the specified limit value or the specified limit value range, it can be determined whether further adjustment of the brake pad is necessary or whether the brake pad is already in a position in which a desired clearance is present.

[0014] Consequently, the positioning of the brake pad and thus also the clearance can be determined based on the physical value and, if necessary, an active adjustment of the brake pad can be carried out.

[0015] The specified limit value or the specified limit value range is set so that there is no contact between the brake pad and the brake disc, or so that the clearance is as large as necessary to prevent unwanted contact between the brake pad and the brake disc in every driving situation and yet sufficiently small to ensure rapid brake response when applied.

[0016] The terms limit value and limit value range are synonymous with setpoint value and setpoint range.

[0017] One aspect provides that steps a) to c) are carried out continuously by an electronic control unit as long as the determined physical value of the brake pad reaches or falls below the predetermined limit value or is outside the limit value range or has reached a target position at which a predetermined clearance exists.

[0018] This allows a particularly precise and accurate adjustment of the brake pad to a desired position.

[0019] Furthermore, the adjustment of the brake pad can be carried out by the drive unit assigned to the brake pad in step c) by activating the drive unit depending on the determined physical value for a period of time derived therefrom.

[0020] This allows for particularly quick and easy adjustment of the brake pad. Furthermore, it also allows for relatively precise adjustment of the brake pad, since the adjustment via the drive unit is dependent on a specific physical value.

[0021] In addition, the physical value of the brake pad can be the pressure with which the brake pad is applied to the brake disc and / or the clearance.

[0022] If the physical value of the brake pad is the pressure with which the brake pad is applied to the brake disc, this is a particularly simple way of determining whether the brake pad is still in contact with the brake disc and accordingly at least a residual friction torque acts on the brake disc through the brake pad, or whether the brake disc can run freely and there is no contact between the brake pad and the brake disc.

[0023] If the physical value of the brake pad is the air gap, this not only allows you to determine whether or not there is contact between the brake pad and the brake disc, but also how large the air gap, if any, already exists.

[0024] If the physical value is the travel distance of the brake pad, this not only makes it possible to determine whether there is contact between the brake pad and the brake disc or not, but also how large the air gap that may already exist is or whether the brake pad has reached a desired target position or how far the axial distance of the brake pad is from a desired target position.

[0025] This makes it possible to determine whether the air gap is too small, so that the brake pad would rub against the brake disc despite the air gap, for example during dynamic driving, or whether the air gap is too large, which would impair the response of the brakes.

[0026] If the physical value of the brake pad affects both the pressure with which the brake pad is applied to the brake disc and the air gap or the axial brake pad position, a particularly precise adjustment of the air gap can be made on this basis.

[0027] Multiple sensors can also be provided on the brake pad, and multiple drive units can be coupled to the brake pad. Furthermore, each of the drive units can be assigned to a sensor, whereby in step c), the brake pad can be adjusted individually by each drive unit based on the respective assigned sensor.

[0028] This would allow, for example, the leading edge of the brake pad to be adjusted independently of the trailing edge. This is particularly advantageous when there is uneven brake pad wear, for example, where one area of ​​the brake pad is still in contact with the brake disc, while a clearance has already formed between the brake disc and another area of ​​the brake pad.

[0029] Steps a) to c) can be carried out automatically after the service brake is applied.

[0030] This has the advantage that the respective brake pad is realigned relative to the brake disc each time, so that the desired clearance is always present and any wear on the brake pad and brake disc is permanently taken into account.

[0031] The object mentioned at the outset is also achieved by a brake pad having a pad carrier plate, a friction material layer provided on the pad carrier plate and at least one sensor associated with the brake pad, wherein the at least one sensor is a pressure sensor and / or a contactless distance sensor and wherein the sensor is arranged at least partially between the pad carrier plate and the friction material layer.

[0032] The sensor is integrated into the brake pad itself. This has the advantage that no additional space is required for the sensor.

[0033] In addition, integrating the sensor into the brake pad makes it particularly easy to determine whether the brake pad is still subjected to pressure on the brake disc and / or whether the brake pad has a clearance to the brake disc and how large this clearance is.

[0034] The brake pad may comprise at least two sensors, one of the sensors being provided in the region of an incoming side of the brake pad and the other sensor being provided in the region of an outgoing side of the brake pad.

[0035] This allows the sensors located at different areas of the brake pad to individually determine whether there is contact between the respective brake pad area and the brake disc, or how large the clearance is between a particular brake pad area and the brake disc. This also allows the determination of whether the brake pad is evenly worn.

[0036] In addition, even if one sensor fails, data can still be collected by the second, still functioning sensor.

[0037] Additionally or alternatively, the brake pad may comprise at least two sensors, wherein one of the sensors is arranged in the radially inner region relative to the brake disc and the other sensor is arranged in the radially outer region.

[0038] The resulting advantages can be seen from the above explanations, whereby the advantages are further increased if sensors are provided on the incoming side, on the outgoing side, in the radially inner area and in the radially outer area of ​​the brake pad.

[0039] In addition, the brake pad can have at least one coupling point at which the brake pad can be coupled to at least one drive unit, wherein in the region of the at least one coupling point a restoring force can be applied to the brake pad by the at least one drive unit.

[0040] This allows for particularly easy adjustment of the brake pad.

[0041] Furthermore, the at least one coupling point can be arranged in the region of the at least one sensor.

[0042] This makes it possible to first record the corresponding physical values ​​using the sensor and, in the next step, to directly influence this physical value by adjusting the brake pad via the drive unit arranged at the respective coupling point.

[0043] This allows each area of ​​the brake pad where a coupling point is located in the area of ​​a sensor to be precisely adjusted.

[0044] The at least one drive unit can be an electromagnetic drive unit having at least one coil core, via which a magnetic force can be applied to the brake pad by means of a coil. The coil core can form the coupling point or be attached to the coupling point.

[0045] An electromagnetic drive unit requires little space. Despite its compact design, it also allows for high forces to be applied to the brake pad if necessary.

[0046] The at least one sensor may be a piezoelectric sensor.

[0047] Piezoelectric sensors are versatile and particularly robust. They are particularly suitable as pressure sensors, but can also be used as contactless distance sensors, particularly in the form of ultrasonic sensors.

[0048] The position detection of the brake pad and thus the determination of the travel distance or the determination of the clearance can also be carried out via one or more sensors that are not integrated in the brake pad, but which can feed a physical value as an input signal into the electronic control system.

[0049] The object mentioned at the outset is also achieved by a service brake for a motor vehicle with a brake pad according to the invention and with an electronic control unit for carrying out the method according to the invention.

[0050] The resulting advantages can be seen in the above paragraphs.

[0051] The invention is described below with reference to an embodiment illustrated in the accompanying drawings, in which: - Fig. 1 a perspective view of a disc brake according to a first alternative for carrying out the method according to the invention; - Fig. 2 the disc brake Fig. 1 in a front view; - Fig. 3 the disc brake Fig. 1 in a sectional view along the plane III-III; - Fig. 4 a schematic representation of the disc brake according to the first alternative in a plan view; - Fig. 5 a schematic representation of a brake pad according to the invention according to a first option in a front view; - Fig. 6 the brake pad Fig. 4 in a rear view; - Fig. 7 a perspective view of a disc brake according to a second alternative for carrying out the method according to the invention; - Fig. 8 the disc brake Fig. 7 in a front view; - Fig. 9 the disc brake Fig. 7 in a sectional view along the plane IX-IX in Fig. 8; - Fig. 10 is a schematic representation of the disc brake according to the second alternative in a plan view; - Fig. 11 is a schematic representation of a brake pad according to the invention according to a second option in a front view; and - Fig. 12 a schematic representation of a brake pad according to the invention according to a third option in a front view.

[0052] In the Fig. 1 to 4, a disc brake 10 of a service brake for a motor vehicle according to a first alternative is shown.

[0053] The disc brake 10 comprises a brake calliper 12 (here, for example, designed as a floating calliper) with a space 14 in which a brake disc 16 and brake pads 18 arranged on both sides of the brake disc 16 are provided (the brake disc 16 is only in the Fig. 3 and Fig. 4).

[0054] The brake pads 18 can be pressed against the brake disc 16 by a brake piston 20 that is linearly displaceable along an axial direction A, so that a braking force can be provided.

[0055] In addition, a brake carrier 22 is provided, on which the brake caliper 12 is movably mounted. Furthermore, the brake carrier 22 serves to connect the disc brake 10 to the vehicle.

[0056] The brake carrier 22 comprises webs 24 extending in the axial direction A, which run laterally along the brake calliper 12, and an outer structure 26 which runs along the front side of the brake calliper 12 and couples the ends of the webs 24 to one another (see Fig. 2).

[0057] Guide grooves 28 are provided on the webs 24 on the side facing the brake calliper 12, along which the brake pads 18 are guided in the axial direction A.

[0058] Furthermore, each of the brake pads 18 is assigned a drive unit 30, which is coupled to the respective brake pad 18. The Fig. The drive unit 30 shown in Figures 1 to 4 is designed as an electromagnetic drive unit and can apply a magnetic force to the associated brake pad 18.

[0059] The drive units 30 serve to adjust the brake pads 18 along the axial direction A, whereby, among other things, a restoring force can be applied to the associated brake pad 18 by the respective drive unit 30. The drive units 30 are not intended to activate the service brake to decelerate the vehicle.

[0060] Alternatively, it is also conceivable that only one of the brake pads 18 is assigned a drive unit 30.

[0061] The drive unit 30 comprises a coil core 32 coupled to the associated brake pad 18 and a coil 34 which extends from the outer structure 26 of the brake carrier 22 and is arranged in a recess 38 of the brake caliper 12, wherein the recess 38 is formed by two fingers 40 of the brake caliper 12.

[0062] The following will be based on the Fig. 4 to 6 the structure of the brake pads 18 will be discussed in more detail.

[0063] Each of the brake pads 18 has a pad carrier plate 42 on which a friction material layer 44 is provided.

[0064] In addition, at least one sensor 46 is assigned to each of the brake pads 18, wherein the at least one sensor 46 is a pressure sensor 48 and / or a contactless distance sensor 50. In the following, all variants of the sensor 46 are indicated by the use of the reference numerals 46, 48, 50.

[0065] Furthermore, the sensor 46 can be designed as a piezoelectric sensor.

[0066] The sensor 46 allows to detect a clearance L (see in particular Fig. 4). If the sensor 46 is a contactless distance sensor 50, the clearance L can be measured.

[0067] The at least one sensor 46 is arranged between the lining carrier plate 42 and the friction material layer 44 of the brake pads 18 (see in particular Fig. 5).

[0068] As is particularly evident from Fig. 5 and Fig. As can be seen from Figure 6, the brake pad 18 can also have several sensors 46, 48, 50.

[0069] Accordingly, on both brake pads 18, a sensor 46, 48, 50 is arranged in the area of ​​an incoming side 52 and a further sensor 46, 48, 50 is arranged in the area of ​​an outgoing side 54.

[0070] Furthermore, a sensor 46, 48, 50 is arranged in a radially inner region 56 relative to the brake disc 16 and an additional sensor 46, 48, 50 is arranged in a radially outer region 58.

[0071] Alternatively, more or fewer than four sensors can be provided in the brake pad.

[0072] In addition, a coupling point 60 is provided on the brake pads 18, at which the drive unit 30 can be coupled to the brake pad 18 in order to be able to apply a restoring force to the brake pad 18 (see in particular Fig. 4).

[0073] In addition, an electronic control unit 62 is provided which is electrically coupled to the sensors 46, 48, 50 and the drive units 30.

[0074] In the Fig. 7 to 11, a disc brake 10 according to a second alternative is shown.

[0075] In contrast to the Fig. 1 to 6, the disc brake 10 according to the second alternative has two drive units 30 per brake pad, which are provided in the region of the webs 24 of the brake carrier 22.

[0076] The coils 34 are each provided on the brake carrier 22, while the coil cores 32 are provided in the area of ​​the incoming side 52 and the outgoing side 54 of the brake pads 18.

[0077] Accordingly, the Fig. According to a second option, the brake pad 18 shown in Fig. 11 also has two coupling points 60, wherein the coil cores 32 are connected to the coupling points 60.

[0078] In addition, the coupling points 60 are arranged in the area of ​​the sensors 46, 48, 50, so that a drive unit 30 is each assigned to the sensors 46, 48, 50 in the area of ​​the incoming side 52 and the outgoing side 54.

[0079] In Fig.Figure 12 shows a brake pad 18 according to a third option. In this case, the brake pad 18 has four coupling points 60, so that each sensor 46, 48, 50 is assigned a drive unit.

[0080] The following explains a method for adjusting the air gap L of the disc brake 10. This method can be performed for both brake pads 18 or just for a single brake pad 18.

[0081] The first step of the method involves determining a physical value of the respective brake pad 18. This is done via the sensors 46, 48, 50 assigned to the brake pad 18.

[0082] The physical value is, for example, the pressure exerted by the brake pad 18 on the brake disc 16. Accordingly, the sensor 46 is a pressure sensor 48 (for example, a piezoelectric sensor).

[0083] Additionally or alternatively, the physical value can also be the clearance L between the brake pad 18 and the brake disc 16, so that the sensor 46 is additionally or alternatively designed as a contactless distance sensor 50.

[0084] In the next step, the determined physical value is compared with an assigned predefined limit value or a predefined limit value range.

[0085] If the physical value is the pressure with which the brake pad 18 is applied against the brake disc 16, it is advisable for the specified limit value or limit value range to select it in such a way that no residual torque (for example due to a dragging brake pad 18) acts on the brake disc 16 or this braking torque is negligibly small.

[0086] If the physical value additionally or alternatively corresponds to the clearance L between the brake pad 18 and the brake disc 16, the specified limit value or the specified limit value range could be selected such that, despite the clearance, an optimal response behavior of the brakes can be achieved and that there is no contact between the brake disc 16 and the brake pads 18 even during dynamic driving.

[0087] If several sensors 46, 48, 50 are provided, each of the physical values ​​determined by the sensors 46, 48, 50 is compared with a predetermined limit value or a predetermined limit value range.

[0088] If the assigned limit value of the specific physical value of the brake pad 18 is reached or exceeded or if this value lies outside the specified limit value range, the respective brake pad 18 is adjusted by the at least one drive unit 30.

[0089] The adjustment by the drive unit 30 takes place depending on the determined physical value, wherein the air gap L is set at least to a different value not equal to zero.

[0090] The determination of the physical value and the comparison of the determined physical value with an assigned limit value or a limit value range are carried out continuously by the electronic control unit 62 as long as the determined physical value of the brake pad 18 reaches or falls below the predetermined limit value or is outside the predetermined limit value range or until the brake pad 18 has reached a predetermined target position at which a predetermined air gap L is present.

[0091] Alternatively, the adjustment of the brake pad 18 by the associated drive unit 30 can also be carried out by activating the drive unit 30 as a function of the determined physical value for a period of time derived therefrom.

[0092] If the deviation is particularly large when comparing the physical value with the associated predefined limit value or the predefined limit value range, the drive unit 30 is activated for a longer period of time than if only a small deviation exists.

[0093] In the disc brake 10 according to the second alternative, in step c) the adjustment of the brake pad 18 can be carried out individually by each drive unit 30 on the basis of the physical value determined by the respective associated sensor 46, 48, 50.

[0094] If, for example, the specified limit value is reached or exceeded only by one of the specific physical values ​​of the brake pad 18 or is outside the limit value range, the brake pad 18 is also only adjusted using the drive unit 30 assigned to the respective sensor 46, 48, 50.

[0095] The procedure can be carried out automatically after the service brake is applied.

[0096] Alternatively, it is also possible for the procedure to be carried out only after a service brake application in which a certain threshold value has been exceeded, which is suitable for characterising the intensity of a service brake.

Claims

[1] Method for adjusting a clearance of a disc brake (10) for a motor vehicle, comprising a brake calliper (12), a brake piston (20), a brake disc (16), brake pads (18), at least one drive unit (30) associated with a brake pad (18) and by means of which a restoring force can be applied to the associated brake pad (18), and at least one sensor (46, 48, 50) associated with the at least one brake pad (18) coupled to the drive unit (30), characterized by the following procedural steps: a) determining at least one physical value of the brake pad (18) by means of the at least one sensor (46, 48, 50) associated with the brake pad (18); b) comparing the determined physical value with an associated predetermined limit value or a predetermined range of limits; and c) if the at least one assigned limit value of the at least one specific physical value of the brake pad (18) is reached or undershot or lies outside the limit value range, adjusting the brake pad (18) by the drive unit (30) assigned to the brake pad (18) depending on the specific physical value and adjusting the air gap to another value not equal to zero. [2] Method according to claim 1, characterized by that steps a) to c) are carried out continuously by an electronic control unit (62) as long as the determined physical value of the brake pad (18) reaches or falls below the predetermined limit value or lies outside the limit value range or until a predetermined target position at which a predetermined air gap exists has been reached. [3] Method according to claim 1, characterized bythat the adjustment of the brake pad (18) is carried out by the drive unit (30) assigned to the brake pad (18) in step c) by activating the drive unit (30) as a function of the determined physical value for a period of time derived therefrom. [4] Method according to one of the preceding claims, characterized by that the physical value of the brake pad (18) is the pressure with which the brake pad (18) is applied to the brake disc (16), and / or the clearance and / or the travel distance of the brake pad (18). [5] Method according to one of the preceding claims, characterized bythat a plurality of sensors (46, 48, 50) are provided on the brake pad (18) and a plurality of drive units (30) are coupled to the brake pad (18) and that each of the drive units (30) is assigned to a sensor (46, 48, 50), wherein in step c) an adjustment of the brake pad (18) is carried out individually by each drive unit (30) on the basis of the respective assigned sensor (46, 48, 50). [6] Method according to one of the preceding claims, characterized by that steps a) to c) are carried out automatically after the service brake is applied. [7] Brake pad with a pad carrier plate, a friction material layer (44) provided on the pad carrier plate and at least one sensor (46, 48, 50) assigned to the brake pad (18), wherein the at least one sensor (46, 48, 50) is a pressure sensor (48) and / or a contactless distance sensor (50) and wherein the sensor (46, 48, 50) is arranged at least partially between the pad carrier plate and the friction material layer (44). [8] Brake pad according to claim 7, characterized by that the brake pad (18) comprises at least two sensors (46, 48, 50), wherein one of the sensors (46, 48, 50) is provided in the region of an incoming side (52) of the brake pad (18) and the other sensor (46, 48, 50) is provided in the region of an outgoing side (54) of the brake pad (18). [9] Brake pad according to claim 7 or 8, characterized bythat the brake pad (18) comprises at least two sensors (46, 48, 50), wherein one of the sensors (46, 48, 50) is arranged in the radially inner region (56) relative to the brake disc (16) and the other sensor (46, 48, 50) is arranged in the radially outer region (58). [10] Brake pad according to one of claims 7 to 9, characterized by that the brake pad (18) has at least one coupling point (60) at which the brake pad (18) can be coupled to at least one drive unit (30), and that in the region of the at least one coupling point (60) a restoring force can be applied to the brake pad (18) by the at least one drive unit (30). [11] Brake pad according to claim 10, characterized by that the at least one coupling point (60) is arranged in the region of the at least one sensor (46, 48, 50). [12] Brake pad according to claim 10 or 11, characterized bythat the at least one drive unit (30) is an electromagnetic drive unit which has at least one coil core (32) via which a magnetic force can be applied to the brake pad (18) by means of a coil (34). [13] Brake pad according to one of claims 7 to 12, characterized by that the at least one sensor (46, 48, 50) is a piezoelectric sensor. [14] Service brake for a motor vehicle with a brake pad (18) according to one of claims 7 to 13 and with an electronic control unit (62) for carrying out the method according to one of claims 1 to 6.

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