DRUM BRAKE WITH ROTATABLE BRAKE SHOE ASSEMBLY

Abstract

The invention relates to a drum brake assembly for braking a wheel a motor vehicle that rotates about a rotation axis, with: a brake drum having a back wall section extending at an angle to the rotation axis and a circumferential wall section, at least one brake shoe assembly,
wherein each of the brake shoe assembly and brake drum has a contact portion for contacting the respective other of the brake shoe assembly and brake drum to generate a braking force; and
wherein the brake shoe assembly is configured to be coupled to a rotatable axle component of the motor vehicle to rotate relative to the brake drum about the rotation axis.

Claims

1. A drum brake assembly for braking a wheel a motor vehicle that rotates about a rotation axis, with: a brake drum having a back wall section extending at an angle to the rotation axis and a circumferential wall section, at least one brake shoe assembly, wherein each of the brake shoe assembly and brake drum has a contact portion for contacting the respective other of the brake shoe assembly and brake drum to generate a braking force; and wherein the brake shoe assembly is configured to be coupled to a rotatable axle component of the motor vehicle to rotate relative to the brake drum about the rotation axis.

2. The drum brake assembly according to claim 1, wherein the brake drum is not rotatable about the rotation axis.

3. The drum brake assembly according to claim 1, wherein the brake drum is configured to be coupled to a non-rotatable axle knuckle.

4. The drum brake assembly according to claim 1, wherein at least one of the brake shoe assembly and the brake drum is radially displaceable so as to contact the respective other of the brake shoe assembly and brake drum.

5. The drum brake assembly according to claim 4, wherein the contact portion of the radially displaceable one of the brake shoe assembly and brake drum comprises at least one ring segment.

6. The drum brake assembly according to claim 5, wherein the contact portion of the respective other of the brake shoe assembly and brake drum is formed as a continuous ring.

7. The drum brake assembly according to claim 4, further comprising an actuator for displacing the respective radially displaceable one of the brake shoe assembly and brake drum.

8. The drum brake assembly according to claim 1, further comprising a brake dust cover that is arranged adjacent to at least one of the contact portions.

9. The drum brake assembly according to claim 1, wherein the back wall section is intersected by the rotation axis.

10. An axle assembly for a motor vehicle, the axle assembly comprising a drum brake assembly according to to claim 1 and a rotatable axle component, the brake shoe assembly of the drum brake assembly being coupled to the rotatable axle component.

11. A motor vehicle, comprising an axle assembly according to claim 10.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0037] Embodiments of the invention are discussed below with respect to the attached schematic figures. Throughout the figures, same features may be marked with same reference signs.

[0038] FIG. 1 shows a sectional view of a drum brake assembly according to a first embodiment of the invention.

[0039] FIG. 2 shows a sectional view of a brake drum assembly according to the prior art.

[0040] FIG. 3 is a front view of the drum brake assembly according to the first embodiment.

[0041] FIG. 4 shows a drum brake assembly according to a second embodiment of the invention.

[0042] FIG. 5 shows a sectional view of the brake drum of drum brake assembly according to a third embodiment of the invention.

[0043] FIG. 6 shows a front view of the drum brake assembly according to the fourth embodiment of the invention.

[0044] FIG. 7 shows a sectional view of a drum brake assembly according to a fifth embodiment of the invention.

[0045] FIG. 8 shows a sectional view of a drum brake assembly according to a sixth embodiment of the invention.

[0046] FIG. 9 shows a sectional view of a drum brake assembly according to a seventh embodiment of the invention.

[0047] FIG. 10 shows a sectional view of a drum brake assembly according to an eighth embodiment of the invention.

[0048] FIG. 11 shows a sectional view of a drum brake assembly according to an ninth embodiment of the invention.

DETAILED DESCRIPTION

[0049] First referring to FIG. 2, a sectional view of a drum brake assembly 1 according to the prior art is shown. The drum brake assembly 1 comprises a brake drum 2 that is fixed to an axle shaft 3. The axle shaft 3 and the brake drum 2 jointly rotate about a rotation axis R. The sectional plane of FIG. 2 contains the rotation axis R.

[0050] The brake drum 3 comprises a circular and plate-shape back wall section 4. The back wall section 4 extends orthogonally to the rotation axis R. The brake drum 3 also comprises a circumferential wall section 5 forming a cylinder mantle surface and being connected to or integrally formed with the back wall section 4. The brake drum is a massive metallic part that is typically produced by casting.

[0051] Within the brake drum 3 and facing an inner circumferential face of the circumferential wall section 5, a brake shoe assembly 6 is arranged. The brake shoe assembly 6 comprises two brake shoes 9. These are coupled to a non-rotatable backing plate (not illustrated). Each brake shoe 9 comprises a friction lining 7 forming a ring section of a limited angular dimension of less than 120°. Also, each brake shoe 9 and is radially displaceable to contact the inner circumferential face of the circumferential wall section 5.

[0052] In this existing configuration, the massive and comparatively heavy brake drum 2 is rotated. This requires a lot of energy during each acceleration.

[0053] FIG. 1 shows an alternative concept according to a first embodiment of the invention. A drum brake assembly 10 again comprises a brake drum 12. The brake drum 12 comprises at least two segments 24, each segment containing a segment of a back wall section 14 and of a circumferential wall section 15. More precisely, both of its a back wall section 14 and circumferential wall section 15 are segmented, each segment being smaller than a full circle. The circumferential wall section 15 and in particular its inner circumferential face which provides a contact portion 26 thus forms a ring segment (see also FIGS. 2-4 discussed below).

[0054] Also, a brake shoe assembly 16 is again arranged within the brake drum 12, comprising two support portions 19 carrying a friction lining 20. The friction lining 20 is formed as a continuous ring and provides a circular contact portion 26 of the brake shoe assembly 16. The brake shoe assembly 16 is fixed to a rotatable axle shaft 22 (i.e. to a rotatable axle component). The circumferential wall section 15 axially spans across and covers the contact portion 26 of the brake shoe assembly 16.

[0055] The brake drum 12 is not rotatably fixed to said axle shaft 22. Instead, the brake drum 12 is generally non-rotatable about the rotation axis R. Yet, its segments 24 are radially displaceable, e.g. by each being slidingly connected to a non-rotating vehicle component 25. In FIG. 1, arrows indicate a radial displacement of the segments 24 radially inward towards and against the friction lining 20. Each segment 24 is connected to a non-illustrated actuator (e.g. a hydraulic or electric cylinder) for providing said displacement.

[0056] The drum brake assembly 10 and axle component 22 form an axle assembly 11 according to an embodiment of this invention.

[0057] FIG. 3 is a front view of the drum brake assembly 10 of FIG. 1. It can be seen that actually four support portions 19 are provided that carry the ring-shaped friction lining 20. Also, the segments 24 of the drum brake 12 are shown, with the circumferential wall section 15 forming a ring segment. The segments of the back wall section 14 that are each connected to one of said ring segments are indicated by dotted lines.

[0058] FIG. 4 shows an alternative embodiment with only one segment 24 of the brake drum 12. This increases weight savings but can be accompanied with a reduced braking effect compared to the embodiment of FIG. 3.

[0059] FIG. 5 shows another alternative embodiment with three segments 24 of the brake drum 12. The segments 24 are spaced apart from one another by a uniform angular distance to provide a uniform braking effect.

[0060] Each of the segments 24 in FIGS. 4 and 5 is configured similarly to the segments 24 of FIGS. 1 and 3. The number of segments 24 can be larger than three.

[0061] FIGS. 6-9 show further embodiments in which the contact portion 26 of the brake shoe assembly 16 is not shaped as a continuous ring but is segmented into ring segments. Each contact area segment is comprised by a respective friction lining segment and each friction lining segment is supported by a support portion 19. In each of these embodiments, the brake drum 12 is again not rotatable, whereas the brake shoe assembly 16 is rotatable and connected to a rotating axle component 22.

[0062] Referring to the embodiments of FIGS. 6 and 7, the drum brake 12 and specifically its circumferential wall section 15 is not segmented into ring segments. Instead, it is formed as a continuous ring having a respectively continuous contact area 26.

[0063] FIG. 6 is a sectional view of the brake drum 12 with the sectional plane including a rotation axis R of the axle component 22. From FIG. 6, it is evident that the back wall section 14 is plate-shaped and circular and extends orthogonally to and being intersected by the rotation axis R. At both of its radial outer ends, it merges with the circumferential wall section 15. At its central portion 17, the back wall section 14 is preferably closed. If provided with an e.g. weight reducing through-hole, the axle component 22 does not extend therethrough or is at least not mechanically connected to the central portion 17.

[0064] FIG. 8 is a sectional view of another embodiment of a drum brake assembly 10. The brake shoe assembly 16 of this drum brake assembly 10 is configured similarly to FIG. 7. As further optional components, a resetting spring 28 according to known configurations and an electric actuator 30 are shown. The electric actuator 30 is supplied with electric power via a non-illustrated slip ring that is coupled to the axle component 22.

[0065] The electric actuator 30 comprises radially displaceable cylinders 31 configured to radially displace (e.g. by way of tilting movement according to known configurations and/or with the friction lining (segments) 20 being tiltably connected to the support portions 19 the friction lining segments 20 to contact the adjacent contact area 26 of the brake drum 12. Alternatively, the support portions 19 may be radially displaced by the actuator 30 or, in other words, may form radially displaceable cylinders.

[0066] The brake drum 12 is fixed to a non-rotatable component 25, in particular formed by an axle knuckle 27. For doing so, through holes 32 are provided in the back wall section 14 for receiving non-illustrated fixing bolts.

[0067] As a further optional feature, a brake dust cover 34 is shown. The brake dust cover 34 is a planar ring-shaped member. Its inner diameter D1 is large enough to receive the axle component 22, whereas its outer diameter D2 is large enough to be connected an open end face 35 of the circumferential wall section 15. The brake dust cover 34 is thus adjacent to both contact portions 26 and radially overlaps with both contact portions 26 (i.e. of the brake drum 12 as well as the brake shoe assembly 16). It thus shields said contact portions 26 from the surroundings to limit the emission of brake dust.

[0068] The embodiment of FIG. 9 is largely similar to the embodiment of FIG. 8 apart from the non-rotatable fixation of the brake drum 12 in the motor vehicle. Specifically, in FIG. 9, the circumferential wall section 15 is connected to a non-rotatable axle component 25 (e.g. an axle knuckle 27), the latter being only schematically indicated by dotted lines and e.g. being outside of a sectional second plane.

[0069] FIG. 10 shows an embodiment similar to that of FIG. 8 and FIG. 11 shows an embodiment similar to that of FIG. 9. In both cases, the only difference to the embodiments of FIG. 8 and FIG. 9, respectively, is a reduced sized of the brake drum 12. More precisely, the brake drum 12 is not formed as a cylindrical member with the back wall section 14 forming a circular base surface, but only as a half cylinder. Accordingly, the back wall section 14 is shaped as a half circle and the circumferential wall section 16 as a half ring segment (or half cylindrical mantel surface). This may increase weight savings while possibly reducing an achievable braking effect compared to FIGS. 8 and 9. Optionally, the back wall section 14 is still intersected by the rotation axis R e.g. to increase the size and stiffness brake drum 12.