Drum brake and method for adjusting multiple brake shoes of a drum brake mounted in a receiving space of a brake drum

Abstract

A drum brake (1), in particular for a utility vehicle, has a brake drum (2) which is rotatably mounted about an axis of rotation (D) and multiple brake shoes (3) which are mounted in a receiving space of the brake drum (2) and each have a friction lining carrier (32) and a friction lining (31) arranged thereon, wherein the brake shoes (3) can be pressed, radially with respect to an axis of rotation (D) of the brake drum (2), against a casing inner surface, in the form of a friction surface, of the brake drum (2), a brake cylinder arrangement (4) rotationally fixedly arranged on an anchor plate (8) in the receiving space of the brake drum (2) for actuating the brake shoes (3), a pressure wedge (33) which is arranged on a side of the friction lining carrier (32) facing away from the friction lining (31) and rests on a wedge mechanism that can be shifted parallel to the axis of rotation (D) of the brake drum (2), wherein the wedge mechanism can be shifted from a non-braking position into a braking position by shifting a service brake piston (42) of the brake cylinder arrangement (4) parallel to the axis of rotation (D) of the brake drum (2), wherein the brake shoes (3) can be adjusted by means of an adjusting device (270) which has a threaded sleeve (71, 171) or a toothed ring (271), wherein the adjusting device (270) has an electromotive drive (18) which is coupled to the threaded sleeve (71, 171) or the toothed ring (271), at least one sensor detecting a clearance between at least one of the brake shoes (3) and the casing inner surface of the brake drum (2), as well as an adjustment control unit (ECU), with which a target clearance that is variable according to the operating state of the drum brake (1) can be adjusted. The invention also relates to a method for adjusting multiple brake shoes (3) of a drum brake (1), which brake shoes are mounted in a receiving space of a brake drum (2).

Description

[0001] 2024PF00068 12.09.2024

[0002] Drum brake and method for adjusting several brake shoes of a drum brake mounted in a receiving space of a brake drum

[0003] DESCRIPTION

[0004] The present invention relates to a drum brake, in particular for a commercial vehicle, according to the preamble of claim 1.

[0005] The invention further relates to a method for adjusting several brake shoes of such a drum brake which are mounted in a receiving space of a brake drum.

[0006] A drum brake of this type is, for example, made from the

[0007] WO 2022 / 263324A1 known.

[0008] In the drum brake described there, several brake linings are pressed radially outwards against the inner surface of a brake drum via a wedge mechanism. Furthermore, in this drum brake, a brake cylinder assembly for actuating the brake shoes is located within the drum's mounting area.

[0009] The brake shoes can be adjusted via an adjusting device, either with a threaded sleeve or a toothed ring directly or via the wedge mechanism, in order to always maintain sufficient clearance between the brake shoes and the inner surface of the brake drum.

[0010] Modern brake shoe adjustment devices, commonly used to compensate for lining wear, are mechanical components. These devices are typically designed so that if a predefined minimum clearance is exceeded, the distance between the brake shoes and the inner surface of the brake drum is automatically readjusted to the minimum clearance. However, falling below the minimum clearance does not result in any change to the adjustment mechanism.

[0011] Due to the limited possibility of only ever reducing the brake clearance, the design of the drum brake components must take into account that the energy released during braking is largely converted into heat. Most of this heat is transferred into the brake drum, causing it to heat up considerably and expand significantly during operation.

[0012] This leads to an increase in the air clearance, and in this case the adjusting device reduces the air clearance again.

[0013] As the brake drum cools down and contracts, the clearance is reduced without this being actively sought by the adjusting device.

[0014] In the case of an unfavorable design, this can lead to the brake drum shrinking onto the brake shoes, thus unintentionally blocking the drum brake.

[0015] The object of the present invention is to provide a drum brake and a method for adjusting several brake shoes of a drum brake mounted in a receiving space of a brake drum, with which the problem described above can be prevented.

[0016] The problem is solved by a drum brake with the features of claim 1 and by a method for adjusting several brake shoes of a drum brake mounted in a receiving space of a brake drum with the features of claim 7.

[0017] The drum brake according to the invention has a brake drum rotatably mounted about an axis of rotation.

[0018] The drum brake further comprises several brake shoes mounted in a receiving space of the brake drum, each with a friction lining carrier and a friction lining arranged on it.

[0019] The brake shoes can be pressed radially towards a rotational axis of the brake drum against an inner surface of the brake drum designed as a friction surface.

[0020] The drum brake further comprises a brake cylinder assembly arranged in the receiving space of the brake drum on an anchor housing in a rotationally fixed manner for actuating the brake shoes, as well as a pressure wedge arranged on a side of the friction lining carrier facing away from the friction lining, which rests on a wedge mechanism that is movable parallel to the axis of rotation of the brake drum.

[0021] The wedge mechanism can be moved from a non-braking position to a braking position by shifting a service brake piston of the brake cylinder assembly parallel to the axis of rotation of the brake drum.

[0022] The brake shoes are adjustable via an adjusting device which has a threaded sleeve or a toothed ring.

[0023] The adjusting device has an electric motor drive coupled to the threaded sleeve or the toothed ring, as well as at least one sensor that detects a clearance between at least one of the brake shoes and the inner surface of the brake drum, and an adjusting control unit with which a target clearance variable depending on the operating state of the drum brake can be set.

[0024] With such an adjusting device of a drum brake according to the invention, it is now possible to vary the clearance depending on the condition of the drum brake and thus to both reduce and increase the clearance.

[0025] Advantageous embodiments of the invention are the subject of the dependent claims.

[0026] According to an advantageous embodiment of the drum brake according to the invention, the adjusting device for detecting the clearance can be controlled by the adjusting control unit in such a way that the brake shoes can be moved by the adjusting device from a non-braking position of the brake shoes to a braking position of the brake shoes in which the friction lining of at least one of the brake shoes rests against the inner surface of the brake drum designed as a friction surface, wherein the sensor is designed to detect an adjustment movement of a moving component of the adjusting device.

[0027] By recording the adjustment movement of a moving component of the adjusting device, it is thus possible in a simple way to deduce the clearance from the adjustment movement and thus to easily determine the clearance.

[0028] According to one advantageous embodiment, the sensor is designed as an angle sensor.

[0029] According to an advantageous further development, the sensor designed as an angle sensor is configured to detect the rotary movement of a drive shaft of the electric motor drive or the threaded sleeve or the gear ring.

[0030] According to an alternative preferred embodiment, the sensor is designed as a stroke sensor with which a brake stroke of at least one of the brake shoes can be detected from the non-braking position of the brake shoes to the braking position.

[0031] For condition-based change of the brake clearance, it is also conceivable, according to another advantageous embodiment, to measure the brake drum temperature via an additional sensor, for example in the form of a temperature sensor, and accordingly to adjust the brake clearance adapted to the drum temperature by means of algorithms stored in the adjuster control unit.

[0032] The inventive method for adjusting several brake shoes of a drum brake as described above, which are mounted in a receiving space of a brake drum, is characterized by the following process steps: a. Moving the brake shoes by the electric motor drive of the adjusting device from a non-braking position of the brake shoes to a braking position of the brake shoes, in which the friction lining of at least one of the brake shoes rests against the inner surface of the brake drum, designed as a friction surface, to determine a current clearance; b. Outputting the determined current clearance to the adjusting control unit; c. Determining a target clearance by the adjusting control unit; d. Moving the brake shoes back by the electric motor drive of the adjusting device from the braking position of the brake shoes to a position of the brake shoes corresponding to the target clearance.

[0033] By allowing a clearance that adapts to the current state of the drum brake, shrinkage of the brake drum onto the brake shoes can be prevented. Furthermore, the energy consumption of the drum brake 1 can be reduced by maintaining a constant clearance.

[0034] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. The drawings show:

[0035] Fig. 1 is an isometric representation of a variant embodiment of a drum brake of the generic type,

[0036] Fig. 2 is an isometric sectional view of the drum brake according to Figure 1 ,

[0037] Fig. 3 shows an isometric sectional view of a variant embodiment of a drum brake of the generic type with an alternatively designed adjusting device,

[0038] Fig. 4 shows another sectional view of an embodiment of a drum brake of the generic type with a further alternative design of an adjusting device,

[0039] Fig. 5 shows a sectional view of a drum brake according to the invention with an adjusting device according to the invention coupled to it.

[0040] Fig. 6 shows a sectional view of an alternative embodiment of a drum brake with stroke sensor according to the invention.

[0041] Fig. 7 shows a flowchart for adjusting the drum brake during ferry operation and

[0042] Fig. 8 shows a flowchart for adjusting the drum brake during servicing. In the following figure descriptions, terms such as top, bottom, left, right, front, rear, etc., refer exclusively to the exemplary representation and position of the drum brake, brake drum, adjusting device, adjusting shaft, and the like as chosen in the respective figures. These terms are not to be understood as restrictive; that is, these references may change due to different working positions, mirror-symmetrical design, or similar factors.

[0043] In Figure 1, reference numeral 1 designates a drum brake of the generic type as described in detail in WO 2022 / 263324 A1, the contents of which are hereby incorporated into this application.

[0044] In principle, the drum brake 1 has a brake drum 2 rotatably mounted about a pivot axis D, which, as shown in Figure 2, is connected in a rotationally fixed manner to a hub 13 and a rim 14 radially enclosing the brake drum 2.

[0045] As shown by way of example in Figure 4, several brake shoes 3 with a respective friction lining carrier 32 and a friction lining 31 arranged on it are arranged radially inside a space in the brake drum 2.

[0046] The brake shoes 3 can be pressed radially to the axis of rotation D of the brake drum 2 against an inner surface of the brake drum 2 designed as a friction surface in order to carry out a braking process.

[0047] To carry out this radial pressing movement of the brake shoes 3 against the inner surface of the brake drum 2, a brake cylinder arrangement 4 is arranged in the receiving space of the brake drum 2 on an anchor housing 8 in a rotationally fixed manner.

[0048] The brake cylinder assembly 4 has a housing 41 in which a service brake piston 42 is slidably arranged parallel to the axis of rotation D of the brake drum 2. Furthermore, a parking brake piston 43 is slidably arranged relative to the housing 41 parallel to the axis of rotation D of the brake drum 2 and can be acted upon by the spring force of a spring element 5.

[0049] Furthermore, compressed air inlets are provided, which lead firstly into a service brake pressure chamber between the housing 41 and the service brake piston 42 and secondly into a parking brake pressure chamber 46 between the housing 41 and the parking brake piston 43.

[0050] Figure 1 shows a first pressure fluid inlet 81 and a second pressure fluid inlet 82 for the supply / exhaustion of compressed air into the service brake pressure chamber and the parking brake pressure chamber 46, respectively.

[0051] The movement of the service brake piston 42 is always important for the actuation of the brake shoes 3; this movement is effected by supplying compressed air to the service brake pressure chamber in the event of an intended reduction in the speed of the commercial vehicle, a so-called service braking process.

[0052] In the event of the intended locking of the brake, which serves to prevent the commercial vehicle from unintentionally rolling away in a parked situation, compressed air present in the parking brake pressure chamber 46 during ferry operation is released from the parking brake pressure chamber 46, resulting in a displacement of the parking brake piston 43 towards the service brake piston 42. This displacement is caused by the force exerted by the spring element 5 on the rear side of the parking brake piston 43 facing away from the service brake piston 42.

[0053] To transmit the movement of the service brake piston 42 to the brake shoes 3, a respective pressure wedge 33 is arranged on a side of the friction lining carrier 32 facing away from the friction lining 31 as part of a respective brake shoe 3.

[0054] This pressure wedge 33 rests on a wedge ring 260 which is movable parallel to the axis of rotation D of the brake drum 2, as shown by way of example in Figure 4.

[0055] The wedge ring 260 can be moved from a non-braking position to a braking position by moving the service brake piston 42 of the brake cylinder assembly 4 parallel to the axis of rotation D of the brake drum 2. In this embodiment shown in Figure 4, a return spring 20, designed here as a leaf spring, serves to return the wedge ring 260 from the braking position to the non-braking position. This return spring is supported on the armature housing 8 and presses the brake shoe 3 against the pressure wedge 33 from the inside of the brake drum. An adjusting device with an adjusting drive 75 serves to maintain a clearance between the friction linings 31 of the brake shoes 3 and the inner surface of the brake drum 2 as constant as possible.

[0056] The adjusting drive 75 in the generic drum brake 1 is designed as a mechanical drive.

[0057] In the drum brake according to the invention, the adjusting device 270 has an electromechanical drive 18 coupled to the threaded sleeve 71, 171 or the toothed ring 271, at least one sensor detecting a clearance between at least one of the brake shoes 3 and the inner surface of the brake drum 2, and an adjusting control unit ECU with which a target clearance variable depending on the operating state of the drum brake 1 can be set.

[0058] The adjusting device 270 can be controlled by the adjusting control unit ECU to detect the air gap in such a way that the brake shoes 3 can be moved by the adjusting device 270 from a non-braking position of the brake shoes 3 to a braking position of the brake shoes 3 in which the friction lining 31 of at least one of the brake shoes 3 rests against the inner surface of the brake drum 2 designed as a friction surface.

[0059] The sensor is designed to detect an adjustment movement of a moving component of the adjusting device 270.

[0060] This sensor can be configured as an angle sensor. This angle sensor is preferably designed to detect the rotational movement of a drive shaft of the electric motor drive 18 or the rotational movement of the threaded sleeve 71, 171 or the toothed ring 271. The clearance can be calculated from the signal output by such an angle sensor, and the data can be forwarded directly to a vehicle CAN bus if required.

[0061] It is also conceivable to design the sensor as a stroke sensor S, as shown by way of example in Figure 6, with which a brake stroke of at least one of the brake shoes 3 can be detected from the non-braking position of the brake shoes 3 to the braking position. Furthermore, it is also conceivable to provide at least one additional sensor coupled to the adjustment control unit ECU.

[0062] In particular, a temperature sensor that detects the current brake drum temperature can be provided, taking into account the problem described above of the brake drum expanding as a result of a temperature increase of the brake drum when adjusting the brake shoes.

[0063] This allows the air clearance to be adjusted to the expansion state of the brake drum.

[0064] Instead of an additional temperature sensor, it is also conceivable to estimate the temperature of the brake drum using algorithms and, depending on this, to adjust the current air clearance via a function logic integrated into a software.

[0065] The gear wheel 77 shown in Figure 5 is driven by the electric motor drive 18 and preferably by an intermediate gearbox 19. The direction of drive can result in either an increase or a decrease in the clearance. In the embodiment shown in Figure 5, the gear wheel 77 meshes with a toothed ring 173 of the adjusting device.

[0066] In the variant shown in Fig. 2, in which the mechanical adjusting drive 75 is replaced by an electric motor drive 18 shown in Fig. 5, the adjusting shaft 76 driven by the electric motor drive 18 meshes via a gear wheel 77 with a toothing of a toothed ring 73 of the threaded sleeve 71 of the adjusting device 7.

[0067] The same applies to the embodiment of the drum brake 1 shown in Fig. 3. Here too, the gear ring 173 of the threaded sleeve 171 is driven via the gear wheel 177.

[0068] On this threaded sleeve 171, two axially spaced threads 172a, 172b are formed, which are shaped in opposite directions and thus allow adjusting rings 162, 163 to move a pressure wedge 133, for example shown in Figure 6, radially by axially approaching or axially moving them away from each other, in order to adjust the clearance accordingly, as is also explained in the above-mentioned WO 2022 / 263324 A1.

[0069] In the variant of the brake drum shown in Fig. 4, the clearance adjustment is carried out directly by radially adjusting the brake shoes 230 themselves.

[0070] In the exemplary embodiment shown in Fig. 6, such radial adjustment of the brake shoes 230 is also shown, in which the (not shown in this section) gear wheel 77 drives the toothed ring 73, which in turn meshes with a gear 36 of the brake shoe 3 and thus adjusts the clearance.

[0071] Fig. 7 shows an exemplary flowchart for adjusting the air clearance in ferry operation of a vehicle equipped with such a drum brake 1.

[0072] In order to perform an adjustment of the air play during ferry operations, certain conditions must be met so that the adjustment can be carried out during ferry operations.

[0073] First, the system checks whether the electronic control unit (ECU) is ready for adjustment. If so, it checks whether the parking brake unit (FBA) and the service brake unit are released.

[0074] Provided the above-mentioned conditions are met, the adjustment control unit ECU controls the electromechanical drive 18 of the adjustment device 270 in such a way that the brake shoes 3 move from a current non-braking position of the brake shoes 3 to a braking position of the brake shoes 3 in which the friction lining 31 of at least one of the brake shoes 3 rests against the inner surface of the brake drum 2 designed as a friction lining.

[0075] When the friction lining 31 is in contact with the inner surface of the brake drum 2, the clearance is 0 mm.

[0076] Subsequently, the radial distance traveled by the brake shoes 3, as detected by the sensor, is output to the electronic control unit (ECU). This distance corresponds to the current brake clearance. The ECU then determines a condition-based target brake clearance. This condition-based target brake clearance represents the currently optimal brake clearance.

[0077] Based on this condition-based, currently optimized air clearance, the adjustment control unit ECU controls the electric motor drive 18 to move the brake shoes 3 from the current position in contact with the inner surface of the brake drum 2 back to a position corresponding to the determined target air clearance.

[0078] This sets the currently optimal airflow.

[0079] It is also conceivable, after determining the optimized target clearance, to ascertain whether the wear limit of the friction linings of the brake shoes 3 has been reached.

[0080] If this is the case, the driver of the vehicle will be notified.

[0081] Furthermore, it is possible to use the currently optimized ventilation system for so-called condition-based maintenance or prognostic health management.

[0082] By adjusting the currently optimal, condition-based clearance, it is possible to prevent the brake drum 2 from shrinking onto the brake shoes 3. Furthermore, the energy consumption of the drum brake 1 can be reduced by maintaining a constant clearance.

[0083] Figure 8 shows another flowchart that represents a simulation of the airflow during service operation.

[0084] Here, after the adjustment process starts, a diagnostic mode is activated and then it is checked whether it is possible to activate the diagnostic mode.

[0085] The system then checks whether the vehicle is secured, the adjustment mechanism is ready, and the parking brake and service brake are released. A further check is then performed to ensure the vehicle is secured. If any of these checks fail, either an error message is displayed or the program returns to its initial state.

[0086] Provided all conditions are met, the desired airflow pattern is set according to the steps described above.

[0087] During the inspection at the service center, particular attention is paid to ensuring that the vehicle is stationary and that there is no brake demand.

[0088] Provided these conditions are met, the operator will be asked to secure the vehicle against rolling away, which must be confirmed by the operator.

[0089] Provided all prerequisites for adjustment are met, the operator can enter a desired brake pad clearance. Such a clearance might be, for example, the maximum possible clearance to facilitate changing the brake shoe linings.

[0090] Reference symbol list

[0091] 1 drum brake

[0092] 2 brake drums

[0093] 3 brake shoes

[0094] 31 friction lining

[0095] 32 friction lining carriers

[0096] 33 Pressure wedge

[0097] 34 pistons

[0098] 35 threaded dies

[0099] 36 gear

[0100] 37 gear teeth

[0101] 4 brake cylinder arrangement

[0102] 41 cases

[0103] 42 service brake pistons

[0104] 43 Parking brake pistons

[0105] 46 Parking brake pressure chamber

[0106] 5 spring element

[0107] 6 wedge ring

[0108] 71, 171 Threaded sleeve

[0109] 72, 172a, 172b thread

[0110] 73, 173 Sprocket

[0111] 74 gear teeth

[0112] 75 Adjuster drive

[0113] 76 Adjuster shaft

[0114] 77, 177 Gear wheel

[0115] 270 Adjustment device

[0116] 8 anchor housings

[0117] 81 First pressure fluid inlet 82 Second pressure fluid inlet

[0118] 9 sleds

[0119] 10 Return spring

[0120] 11 Dust outlet

[0121] 13 Hub

[0122] 14 rim

[0123] 15 screw bolts

[0124] 17 rolling bearings

[0125] 18 electric motor drive

[0126] 19 gearboxes

[0127] 20 Return spring

[0128] ECU adjustment control unit

[0129] D axis of rotation x direction y direction z direction

Claims

Claims 1. Drum brake (1), in particular for a commercial vehicle, comprising - a brake drum (2) rotatably mounted about an axis of rotation (D), - several brake shoes (3) mounted in a receiving space of the brake drum (2) with a respective friction lining carrier (32) and a friction lining (31) arranged on it , - wherein the brake shoes (3) can be pressed radially towards an axis of rotation (D) of the brake drum (2) against an inner surface of the brake drum (2) designed as a friction surface, - a brake cylinder assembly (4) arranged in the receiving space of the brake drum (2) on an anchor housing (8) in a rotationally fixed manner for actuating the brake shoes (3), - a pressure wedge (33) arranged on a side of the friction lining carrier (32) facing away from the friction lining (31), which rests on a wedge mechanism that is movable parallel to the axis of rotation (D) of the brake drum (2), - wherein the wedge mechanism can be moved from a non-braking position to a braking position by moving a service brake piston (42) of the brake cylinder assembly (4) parallel to the axis of rotation (D) of the brake drum (2), - wherein the brake shoes (3) are adjustable via an adjusting device (270) which has a threaded sleeve (71, 171) or a toothed ring (271), characterized in that - the adjusting device (270) has an electromechanical drive (18) coupled to the threaded sleeve (71 , 171 ) or the toothed ring (271 ), at least one sensor detecting a clearance between at least one of the brake shoes (3) and the inner surface of the brake drum (2), and an adjusting control unit (ECU) with which a target clearance variable depending on the operating state of the drum brake (1 ) can be set.

2. Drum brake (1) according to claim 1, characterized in that the adjusting device (270) for detecting the air gap can be controlled by the adjusting control unit (ECU) such that the brake shoes (3) can be moved by the adjusting device (270) from a non-braking position of the brake shoes (3) to a braking position of the brake shoes (3), when the friction lining (31) of at least one of the brake shoes rests against the inner surface of the brake drum (2) designed as a friction surface, are movable, wherein the sensor is designed to detect an adjustment movement of a moving component of the adjusting device (270).

3. Drum brake (1 ) according to claim 2, characterized in that the sensor is designed as an angle sensor.

4. Drum brake (1 ) according to claim 3, characterized in that the sensor is configured to detect the rotary movement of a drive shaft of the electric motor drive (18) or of the threaded sleeve (71 , 171 ) or of the toothed ring (271 ).

5. Drum brake (1 ) according to claim 2, characterized in that the sensor is designed as a stroke sensor (S) with which a brake stroke of at least one of the brake shoes (3) can be detected from the non-braking position of the brake shoes (3) to the braking position.

6. Drum brake (1 ) according to one of the preceding claims, characterized by at least one further sensor coupled to the adjustment control unit (ECU), in particular a temperature sensor detecting a current brake drum temperature.

7. A method for adjusting several brake shoes (3) of a drum brake (1) mounted in a receiving space of a brake drum (2) according to one of the preceding claims, comprising the following method steps: a. Moving the brake shoes (3) by the electric motor drive (18) of the adjusting device (270) from a non-braking position of the brake shoes (3) to a braking position of the brake shoes (3) in which the friction lining (31) of at least one of the brake shoes bears against the inner surface of the brake drum (2), designed as a friction surface, to determine a current clearance; b. Outputting the determined current clearance to the adjusting control unit (ECU); c. Determining a target clearance by the adjusting control unit (ECU); d. Retraction of the brake shoes (3) by the electromotor drive () of the adjusting device (270) from the braking position of the brake shoes (3) to a position of the brake shoes (3) corresponding to the nominal clearance.

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