DRUM BRAKE CONSISTING OF TWO OR MORE PARTS CONNECTED BY ISOLATING MATERIAL

Abstract

A brake drum includes an outer drum, at least one layer of heat resistant adhesive, provided at least on the inner radial surface of the outer drum, and an inner drum provided inside the outer drum connected with the outer drum via the at least one adhesive layer.

Claims

1. A brake drum, comprising an outer drum, at least one layer of heat resistant adhesive, provided at least on an inner radial surface of the outer drum, an inner drum provided inside the outer drum connected to the outer drum via the at least one adhesive layer.

2. The brake drum according to claim 1, wherein the inner drum is formed with one closed base side.

3. The brake drum according to claim 1, wherein the inner drum is formed with two open base sides.

4. The brake drum according to claim 1, wherein the at least one layer of heat resistant adhesive is thermally insulating.

5. The brake drum according to claim 1, wherein at least one additional layer of heat resistant adhesive is pro-vided at least on an inner radial surface of the inner drum, an additional inner drum provided inside the inner drum connected to the inner drum via the at least one additional layer of heat resistant adhesive.

6. The brake drum according to claim 5, wherein further additional layers of heat resistant adhesive and further additional inner drums are nested within the inner drum.

7. The brake drum according to claim 1, wherein the inner drum is additionally secured inside the outer drum via mechanical means.

8. The brake drum according to claim 1, wherein the outer drum and the inner drum are formed of different materials.

9. The brake drum according to claim 5, wherein the at least one additional inner drum is made of a material different from the mate-rial of the outer drum and the material of the inner drum.

10. The brake drum according to claim 9, wherein the materials have different thermal expansion coefficients.

11. The brake drum according to claim 1, wherein a wall of the outer drum comprises at least one cavity.

12. The brake drum according to claim 1, wherein a wall of the inner drum comprises at least one cavity.

13. The brake drum according to claim 11, wherein the at least one cavity is filled with thermally insulating material.

14. A method of producing a brake drum according to claim 1, wherein at least one of the outer drum and the inner drum is provided by casting or sheet bending, at least the layer of heat resistant adhesive is provided by additive manufacturing methods.

15. A drum brake assembly for a motor vehicle, comprising a brake drum according to claim 1, at least one brake shoe arranged within the brake drum, at least one brake cylinder connected to the at least one brake shoe, wherein the at least one brake shoe is displaceable by the brake cylinder relative to the brake drum, such that during braking the brake shoe contacts the brake drum.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0033] Embodiments of the invention are described in further detail below with respect to the attached schematic figures. Same features may be marked with the same reference signs throughout the figures.

[0034] FIG. 1 is a schematic cross section of a brake drum known in the prior art.

[0035] FIG. 2 is a schematic representation of the thermal expansion of brake drum known in the prior art during and after braking operation.

[0036] FIG. 3 is a schematic cross section of a brake drum according to a first embodiment.

[0037] FIG. 4 is a schematic cross section of a brake drum according to a second embodiment.

[0038] FIG. 5 is a schematic cross section of a brake drum according to a third embodiment.

[0039] FIG. 6 is a schematic cross section of a brake drum according to a fourth embodiment.

[0040] FIG. 7 is a schematic cross section of a brake drum according to a fifth embodiment.

[0041] FIG. 8 is a schematic cross section of a brake drum according to a sixth embodiment.

[0042] FIG. 9 is a schematic plan view of a drum brake assembly comprising a described brake drum.

DETAILED DESCRIPTION

[0043] FIG. 1 shows a simplified cross section of an abstracted brake drum as it is known from the prior art. The plane of the cross section is a plane through the rotational axis of the brake drum. The depicted brake drum is axially symmetrical. The base sides of the drum are assumed to be substantially circular. The brake drum is depicted as a truncated cone or a cylinder with slightly oblique side surfaces. One base side of the drum is closed, the other base side is open.

[0044] The brake drum depicted in FIG. 1 is formed of a single piece. In practice, it may be formed of cast iron. In a drum brake, the inner surface of the rotating brake drum provides the friction surface against which the brake shoes are pushed during braking operation. The resulting friction slows down the rotation of the brake drum and the coupled elements. However, this friction also results in the production of considerable heat. This leads the brake drum to expand during and after braking. This thermal expansion is depicted in FIG. 2 with the dotted lines. Due to the geometry of the brake drum, the material expands outwards, both radially and along the rotational axis. This leads to an increased distance between the inner surface of the brake drum and the brake shoes. The result is a decreased braking efficiency, known as brake fade.

[0045] FIG. 3 shows a first embodiment of the brake drum 1 according to the invention. To overcome the described problem, the brake drum 1 consists of two drums nested inside each other. The outer drum 2 and the inner drum 4 have substantially the same form, with the inner drum 4 being scaled down so as to fit inside the outer drum 2. The outer drum 2 and the inner drum 4 are connected to each other with a layer of a heat resistant adhesive 3.

[0046] The layer of heat resistant adhesive 3 provides a fixed connection between the drum parts and additionally provides a barrier for heat dissipation inside the brake drum 1. During breaking operation, the outer drum 2 therefore heats up to a lesser degree than the inner drum 4. As a result, the outer drum 2 also expands to a lesser degree. Since the inner drum 4 is confined by the outer drum 2, it is forced to expand inwards, towards the brake shoes. This increases brake efficiency in comparison with a standard brake drum.

[0047] To improve this effect, the layer of heat resistant adhesive 3 can be formed of an adhesive that has thermally insulating properties, to confine heat dissipation largely to the inner drum 4. The outer drum 2 and the inner drum 4 can also be formed of different materials with different thermal expansion coefficients. To provide for a reliable confinement of the inner drum 4, the outer drum may be formed of a material that has a very low thermal expansion coefficient. If the adhesive layer 3 provides good insulation, the outer drum 2 may also be formed of a lightweight material such as aluminum, which otherwise exhibits high thermal expansion. To provide the friction surface of the inner drum 4, cast iron may be advantageous due to its wear-resistance. By choosing materials with different physical properties, such as weight, wear-resistance, thermal conductance and thermal expansion and designing the thickness of the drum parts accordingly, expansion behavior of the brake drum can effectively be controlled.

[0048] The adhesive layer 3 may provide the additional advantage of providing a vibrational damping element between the outer drum 2 and inner drum 4, resulting in less noise emission.

[0049] FIG. 4 shows a second embodiment of the brake drum according to the invention. In this embodiment, the inner drum 4 is secured inside the outer drum 2 not just by the adhesive layer 3, but also by mechanical means 5, which may constitute bolts or rivets. These mechanical means 5 reinforce the connection between the outer drum 2 and the inner drum 4 and can so further restrict the expansion of the drums against each other. Additionally, these mechanical means 5 may serve as controlled paths for heat dissipation.

[0050] FIGS. 5 and 6 show two embodiments in which the inner drum 4 has a different form than the outer drum 4. While the outer drum 2 is closed on its (left) base side, the inner drum 4 is open on both of its base sides. Accordingly, inner drum 4 only abuts against the inner circumference of the outer drum 2 and only the inner circumference of the outer drum 2 is provided with a layer of heat resistant adhesive 3. FIGS. 5 and 6 also show possible paths of heat transfer within the brake drum 1 as dotted arrows. While is hindered in its dissipation through the side walls of the drum by the adhesive layer 3, heat transfer through the base side of the outer drum 2 is unimpeded. As a result, these embodiments allow the transport of heat out of the brake drum 1 while controlling the heating, and therefore expansion, of the side surfaces of the brake drum 1. In the third embodiment of FIG. 5, the outer drum 2 and the inner drum 4 are only connected via the adhesive layer 3. FIG. 6 shows a fourth embodiment in which the additional physical means 5 are used to connect outer drum 2 and inner drum 4.

[0051] FIG. 7 shows a fifth embodiment that uses multiple layers of inner drums. As in previous embodiments, a first inner drum 4 is connected with the outer drum 2 via a heat resistant adhesive layer 3. An additional layer of a heat resistant adhesive 6 is provided on the inner surface of the first inner drum 4 and a second inner drum 7 is provided within it. Using multiple adhesive layers 3, 6 like this and choosing the material of the first inner drum 4 with advantageous thermal properties can lead to a better thermal insulation and allows for improved control over the behavior of the brake drum 1 under braking operation.

[0052] FIG. 8 shows a sixth embodiment of a brake drum according to the invention. In this embodiment, the outer drum 2 and the inner drum 4 are formed with hollow cavities 8 therein. These cavities 8 reduce the weight of the brake drum 1 and can provide additional thermal insulation, as well as support to dissipate structural noise. The cavities 8 may be air-filled or filled with an insulating material. While FIG. 8 shows cavities 8 in both the outer and the inner drum, they may also be limited to one drum parts.

[0053] The described embodiments are not exclusive to one another, but can of course be combined to achieve a combination of the described effects.

[0054] To produce a brake drum 1 according to the invention, at least one of the outer drum 2 or the inner drum 4 can be formed by casting or sheet bending. As a result, these drum parts can be easily produced with the same tools used to produce conventional brake drums. The adhesive layer 3 may be applied to the inner surface of the outer drum 2 by additive manufacturing. The method of producing a brake drum 1 therefore only involves relatively few, simple steps.

[0055] The brake drum 1 can then be placed in a regular drum brake assembly, as is shown in FIG. 9. A drum brake assembly 9 comprises a brake drum 1, brake shoes 10 and brake cylinders 11. The brake drum 1 may comprise any of the features of the embodiments described above. During braking operation, the brake shoes 10 are pressed by the brake cylinders 11 against the inner radial surface of the brake drum 1, which is formed by the inner drum 4. The resulting friction heats up the inner drum 4. However, since heat dissipation and thermal expansion are controlled due to the combination of outer drum 2, adhesive layer 3 and inner drum 4, the surface of the inner drum 4 does not expand away from the brake shoes 11 and brake fade is prevented.