Drum brake, in particular for a utility vehicle

Abstract

The invention relates to a drum brake, in particular for a utility vehicle, having the following features: a brake drum (1) which can be rotated about an axis of rotation; a brake lining arrangement having a plurality of brake linings (2), wherein: each brake lining (2) has a friction lining carrier and a friction lining arranged thereon; the brake lining arrangement is mounted in a receiving space of the brake drum (11); the brake linings (2) can be pressed against the lateral inner surface of the brake drum (1) radially with respect to an axis of rotation of the brake drum (1); the lateral inner surface is designed as a friction surface; a brake cylinder arrangement for actuating the brake linings (2) is arranged in the receiving space of the brake drum (1); in each case a displaceable wedge mechanism (11) on a parallel to the axis of rotation of the brake drum (1), said wedge mechanism (11) resting against the brake lining arrangement; the wedge mechanism (11) can be displaced from a non-braking position into a braking position by displacing a piston (10) of the brake cylinder arrangement; an adjuster (3) which is operatively connected to the brake lining arrangement, the brake drum being designed in such a way that the adjuster (3) is fastened to a wedge ring (9) which is arranged in the receiving space of the brake drum (1), wherein the adjuster (3) has an axle (8) which can be rotated by means of a linear drive (6) and which is held on a stationary support bearing (17) and wherein a freewheel (4), an overload coupling (5) and an output unit (7) are connected to the axle (8).

Description

[0001] 2024PF00109 23.08.2024

[0002] DESCRIPTION

[0003] Drum brake, especially for a commercial vehicle

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

[0005] Such a drum brake has a brake drum with friction surfaces arranged on the inner surface, against which, during braking, several brake linings of a brake lining arrangement bear their friction linings under pressure.

[0006] The brake linings are actuated by means of a brake cylinder arrangement located in the receiving space of the brake drum, wherein pressure wedges are provided on each side of the friction lining carrier facing away from the friction lining, which rest on a wedge mechanism that is movable parallel to the axis of rotation of the brake drum.

[0007] This wedge mechanism can be moved from an engaged position to a braking position by shifting a piston of the brake cylinder assembly parallel to the axis of rotation of the brake drum. An adjuster is operatively connected to the brake pad assembly, allowing the so-called brake clearance to be adapted to different operating conditions.

[0008] An electrically activated adjuster is known from the prior art, but it requires a large number of functional components, the use of which can only be realized with considerable, costly effort.

[0009] For example, a separate power supply is required, as is complex safety logic to prevent malfunctions. Furthermore, care must be taken to ensure that the electrical and electronic components are not subjected to thermal overload, which in turn requires appropriate measures.

[0010] Other factors influencing the function of this adjuster are vibration and shock loads on the electrical and electronic components, which can occur particularly in the area of ​​unsprung axles, 2024PF00109

[0011] - 2 - this is especially true when vehicles with such drum brakes are used off-road under correspondingly high loads.

[0012] The invention is based on the objective of further developing a drum brake of the generic type in such a way that it is easier and more cost-effective to manufacture, its service life is increased and its operational reliability is improved.

[0013] The new adjuster is characterized first and foremost by the fact that it does not use any electrical or electronic components, but rather functions purely mechanically.

[0014] Furthermore, the compact design of the new adjuster is particularly noteworthy, as it allows it to be integrated into the drum brake without any special structural modifications. The existing relevant components and interfaces for the electric adjuster can be used without modification, which naturally also contributes to cost reduction.

[0015] This results equally from the fact that no control unit is now required, nor is a complex safeguard logic against malfunctions.

[0016] The system uses exclusively mechanical components, some with functionality already familiar from pneumatically actuated disc brakes. No separate power supply is required, as the adjuster is activated via the brake mechanism.

[0017] By eliminating the need for separate control components such as cables, connectors, or the like, the adjuster is fully integrated into the interior of the drum brake. This results in a high level of protection against external influences and requires no additional installation space outside the drum brake. Due to its low complexity and purely mechanical design, only minimal development effort is required.

[0018] When the drum brake is activated, the adjuster, which is rigidly connected to a wedge ring, is simultaneously actuated. The wedge ring is moved by an integrated actuator and its piston by means of compressed air. 2024PF00109

[0019] - 3 - Subsequently, the brake linings are pressed against the inner wall of the brake drum by the wedge mechanism, whereby in the first phase of movement the play between the brake linings and the brake drum, the so-called clearance, is overcome. Within this range, the adjuster does not perform any adjusting movement, but is merely moved axially.

[0020] According to the invention, the adjuster is attached to the aforementioned wedge ring located inside the brake drum and comprises functional components in the form of a freewheel, an overload clutch, and an axle carrying an output unit, which is held on a stationary support bearing and is rotatable by means of a linear drive. According to one aspect of the invention, this linear drive is designed as a reversible groove bushing with guide rollers guided therein.

[0021] Alternatively, the linear drive can also be formed from a tapered recirculating thread or ball screw thread, a steep thread unit, e.g. a plastic threaded bushing with threaded bolts, a ramp mechanism with or without rolling elements, a bevel gear with rack and pinion drive, a cable pull mechanism with deflection pulleys or a hydrostatic drive with master and slave cylinders.

[0022] In its function as an adjuster, the linear drive, for example the reversible groove bushing with the guide rollers guided in the grooves, first converts the linear movement initiated by the brake mechanism into a rotary movement.

[0023] The ratio of the linear movement of the reversing groove bushing to the rotary movement can be controlled by the helix angle of the reversing grooves, and thus also the speed of the adjusting effect.

[0024] The rotary motion of the linear actuator is transmitted via the freewheel to the overload clutch, preferably a ball ramp clutch, the freewheel preferably being designed as an axial freewheel. In one embodiment, the clamping effect in the locking direction is achieved by the interaction of a ball ramp mechanism and a cone clutch. 2024PF00109

[0025] - 4 -

[0026] The friction clutch, which is designed, for example, as a conical clutch, is compressed by the axial force generated by the ball ramp mechanism. It is important that the frictional torque induced by the conical clutch is greater than the torque generated by the ball ramp mechanism. This ensures the self-locking effect crucial for a freewheel.

[0027] The overload coupling, which, as mentioned, is designed as a ball ramp coupling, transmits the rotary motion in case of excessive clearance via an output unit, e.g. in the form of a gear, to brake-side adjusting components to reduce the clearance.

[0028] However, if the clearance is within a specified range, no adjustment can occur due to the brake-side adjusting components being subjected to high loads. Therefore, the rotational movement within the ball ramp coupling is absorbed by the balls running up the ramps. The switching torque of the ball ramp coupling results from the force exerted by a preload spring (designed as a compression spring) and the geometry of the ramp coupling.

[0029] Further advantageous embodiments of the invention are characterized in the dependent claims.

[0030] An exemplary embodiment is described below with reference to the attached drawings.

[0031] They show:

[0032] Figure 1 shows a drum brake in a front view in the direction of arrow X in Figure 2.

[0033] Figure 2 shows a cross-section through a part of the drum brake corresponding to the section line AA in Figure 1.

[0034] Figure 3 shows a part of the drum brake in a longitudinal section, corresponding to section line BB in Figure 1 2024PF00109

[0035] - 5 -

[0036] Figure 4 shows a follower according to the invention as a detail in a perspective view.

[0037] Figure 5 shows a half-section of the follower in a side view.

[0038] Figure 1 shows a front view of a known drum brake for a commercial vehicle, with a brake drum 1 rotatably mounted about an axis of rotation. A brake lining assembly (not shown) with several brake linings 2 is mounted therein, each having a friction lining carrier and a friction lining arranged on the carrier.

[0039] In the event of braking, the brake linings 2 are pressed radially to the axis of rotation of the brake drum 1 against an inner surface of the brake drum 1, which is designed as a friction surface. A brake cylinder assembly is provided inside the brake drum 1 to actuate the brake linings 2.

[0040] By means of a wedge mechanism 11 recognizable in figure 3, which can be displaced parallel to the axis of rotation of the brake drum 1 by a piston 10, the respective brake lining 2 is moved from a non-braking position to a braking position.

[0041] According to the invention, an adjuster 3, which is in operative connection with the brake pad assembly, is attached on one side to a wedge ring 9 (Figure 2) and on the other side to a stationary support bearing 17.

[0042] Furthermore, the adjuster 3 has an axis rotatable by means of a linear drive 6, to which a freewheel 4, an overload clutch 5 and an output unit 7 are connected. This is particularly evident in Figure 5.

[0043] Figure 4 shows the adjuster 3 in detail in a perspective view. It can also be seen that the linear drive 6 consists of a reversible groove bushing 14 with reversible grooves 15, each containing a 2024PF00109

[0044] - 6 -

[0045] Guide roller 16 is guided, which is part of a bearing bushing 13 that is axially displaced by rotation of the axis 8 during braking.

[0046] The freewheel 4 is coupled to the reversing groove bushing 14 and has a freewheel ramp contour on one side and an outer cone contour on the other.

[0047] The overload clutch 5, designed as a conventional ball ramp clutch, is operatively connected to the freewheel 4 by a ramp disc 5.2 arranged on the side facing the freewheel 4. This ramp disc is formed by the closed end face of a sleeve 5.1 of the output unit 7, in which a compression spring 5.3, surrounding the shaft 8, is positioned. The spring is supported on one side by the ramp disc 5.2 and on the other side by a spring support disc 5.4. An output unit 7 in the form of a gear 7.1 is mounted on the sleeve 5.1 and engages with the brake mechanism.

[0048] Functionally, the following situation arises in an operating condition in which the air clearance is within the target range.

[0049] Here, after overcoming the initial clearance, the brake linings 2 are pressed against the friction surfaces of the brake drum 1. Once the initial clearance is overcome, the axial movement of the adjuster 3 is stopped, causing the axle 8 to strike the support bearing 17. Furthermore, the clearance is adjusted by the positioning of the support bearing 17.

[0050] After overcoming the response path, the adjuster 3 is activated, according to the aforementioned movement sequence. The axial movement is performed exclusively by the bearing bushing 13.

[0051] As mentioned, once the clearance is overcome, a contact force is generated between the brake linings 2 and the brake drum 1. Rotation of the brake-side adjusting components, for example, a threaded spindle 12 as shown in Figure 3, is no longer possible. The rotational movement of the shaft 8 is compensated within the adjuster, thus preventing unintended adjustment and / or damage to the adjuster 3 due to overload. 2024PF00109

[0052] - 7 -

[0053] When the brake is released, all components in the force flow are returned to their initial position. This applies equally to the adjuster 3; that is, the balls of the ball ramp coupling in the overload coupling 5 move to a zero position in which no torque from the overload coupling 5 is effective.

[0054] If the brake clearance is greater than the specified dimension, the brake linings 2 do not yet make contact with the brake drum 1 after overcoming the travel distance of the adjuster 3. Since the adjuster 3 now performs a rotary movement due to the previously described operating principle, an adjustment process occurs, i.e., a reduction of the brake clearance. As soon as the brake linings 2 make contact with the brake drum 1, the adjustment process ends. When the brake is released, the overload clutch 5 is returned to its initial position.

[0055] During brake maintenance, for example to replace the brake pads 2, it is necessary to manually actuate the adjuster 3 using a tool. To enable this, the support bearing 17 is designed so that manual actuation of the adjuster 3 is also possible.

[0056] To replace the brake pads 2, the adjusting mechanism must be turned back in the opposite direction of adjustment. For this purpose, the support bearing 17 is connected to the adjuster 3 by means of a positive-locking coupling on its end face.

[0057] Since the adjuster 3 must be rotated in the locking direction of the freewheel 4 when turning it back, the rotational movement takes place in the overload clutch 5.

[0058] For this purpose, a switching torque of the overrun clutch 5 must be overcome, for which a reset head 18 is connected to the shaft 8 and is freely accessible from the outside. 2024PF00109

[0059] - 8 -

[0060] Reference symbol list

[0061] 1 brake drum

[0062] 2 brake pads

[0063] 3 adjusters

[0064] 4 Free run

[0065] 5 overload clutch

[0066] 5.1 Sleeve

[0067] 5.2 Ramp disc

[0068] 5.3 Compression spring

[0069] 5.4 Spring support disc

[0070] 6 Linear actuator

[0071] 7 Output unit

[0072] 7.1 Gear

[0073] 8-axis

[0074] 9 wedge ring

[0075] 10 pistons

[0076] 11 Wedge mechanism

[0077] 12 threaded spindle

[0078] 13 storage box

[0079] 14 Reversible socket

[0080] 15 helical groove

[0081] 16 Leadership role

[0082] 17 support bearings

[0083] 18 Reset head

Claims

2024PF00109 - 9 - Claims 1. Drum brake, in particular for a commercial vehicle, with the following features: a brake drum (1) rotatable about an axis of rotation, a brake lining assembly with several brake linings (2), wherein each brake lining (2) has a friction lining carrier and a friction lining arranged thereon, the brake lining assembly is mounted in a receiving space of the brake drum (1), the brake linings (2) can be pressed radially to an axis of rotation of the brake drum (1) against an inner surface of the brake drum (1), the inner surface of the drum is designed as a friction surface, a brake cylinder assembly for actuating the brake linings (2) is arranged in the receiving space of the brake drum (1), a wedge mechanism (11) which is displaceable on a wedge mechanism (11) parallel to the axis of rotation of the brake drum (1) and which bears against the brake lining assembly, the wedge mechanism (11) can be displaced from a non-braking position to a braking position by moving a piston (10) of the brake cylinder assembly, an adjuster (3),which is in operative connection with the brake lining assembly, characterized in that the adjuster (3) is attached to a wedge ring (9) which is arranged in the receiving space of the brake drum (1), wherein the adjuster (3) has an axis (8) rotatable by means of a linear drive (6) which is held on a stationary support bearing (17), and wherein a freewheel (4), an overload clutch (5) and an output unit (7) are connected to the axis (8).

2. Drum brake according to claim 1, characterized in that the linear drive (6) consists of a helical groove bushing (14) connected to the axis (8) with helical grooves (15) in which guide rollers (16) of a bearing bushing (13) are guided. 2024PF00109 - 10 - 3. Drum brake according to claim 1 or 2, characterized in that the linear drive (6) consists of a ball screw, a steep screw unit, a ramp mechanism, a bevel gear with rack drive, a cable pull mechanism or a hydrostatic drive.

4. Drum brake according to one of the preceding claims, characterized in that the freewheel (4) consists of a clamping roller freewheel, a clamping body freewheel, a coiling spring freewheel or a ratchet mechanism.

5. Drum brake according to one of the preceding claims, characterized in that the overload coupling (5) is designed as a ball ramp coupling or as a friction coupling in the form of a cone or tapered coupling, a lamellar coupling, a friction lining coupling or a helical spring coupling, or a torsion spring or torsion spring coupling or a ball recirculation mechanism.

6. Drum brake according to one of the preceding claims, characterized in that the output unit (7) consists of a gear (7.1) mounted on a sleeve (5.1 ) is held.

7. Drum brake according to one of the preceding claims, characterized in that the sleeve (5.1 ) at its end facing the freewheel (4) serves as a ball ramp (5.2) is trained.

8. Drum brake according to one of the preceding claims, characterized in that a compression spring (5.3) is arranged in the sleeve (5.1) which surrounds the axle (8) and forms the ball ramp (5.2) on the end face facing the freewheel (4). 2024PF00109 - 11 - 9. Drum brake according to one of the preceding claims, characterized in that the compression spring (5.3) is supported on one side on the ball ramp (5.2) and on the other side on a spring support disc (5.4).

10. Drum brake according to one of the preceding claims, characterized in that a return head for receiving a tool is arranged at the end of the axis (8) facing away from the linear drive (6).

11. Drum brake according to one of the preceding claims, characterized in that the linear drive (6) is connected to the bearing bushing (13).

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