WO2010049051A1

WO2010049051A1 - Friction ring and method for the production thereof

Info

Publication number: WO2010049051A1
Application number: PCT/EP2009/007070
Authority: WO
Inventors: Oliver Lembach; Ralph Mayer
Original assignee: Daimler Ag
Priority date: 2008-10-29
Filing date: 2009-10-02
Publication date: 2010-05-06
Also published as: DE102008053637A1; DE102008053637B4

Abstract

The invention relates to a friction ring (12) for a brake disk, which has a coating (22, 24) in at least some areas, wherein the coating (22, 24) has a thickness profile with various coating thicknesses (d1, d2, d3).

Description

Daimler AG Zimmermann Chopin

Friction ring and method for its production

The invention relates to a friction ring for a brake disc according to the preamble of claim 1 and a method for producing such a friction ring.

Coated friction rings are known in the art. Thus, DE 102 03 507 A1 discloses a brake disk for a vehicle, which comprises a base body of a metallic material which has at least one friction surface with a coating of a hard material with a high coefficient of friction. Such coatings consist for example of aluminum oxide, diamond or ceramic materials. They offer the advantage that surfaces with a high coefficient of friction can be produced, although base bodies made of relatively inexpensive and optionally also lightweight materials can be used. Coatings known from the prior art all have a constant layer thickness. Due to different thermal expansion coefficients of the base bodies and coatings, this can lead to tensions between the coating and the base body, which in the worst case can lead to a tearing of the coating. Furthermore, by uneven heat distribution in the brake disc during braking - the so-called hotspot formation - at high temperatures of the brake disc whose surface unevenly expanded, resulting in the so-called Heißrubbeln the brake disc. The location of the hotspots can be determined experimentally for a wide variety of brake disc geometries or theoretically calculated with a good approximation. Due to the uneven contact between the brake disc and brake shoes it comes in such conditions to vibration and noise, which is undesirable and reduces both the ride comfort and braking performance.

From DE 10 2005 008 569 A1 coatings are known from Einschmelzlegierungen whose Einschmelzmaterialien are preferably selected from the group, the nickel-boron-sili-zium, nickel-chromium-boron-silicon or cobalt-nickel-chromium-silicon contains. The fuser materials may additionally be applied hard particles or also solid lubricants, which are preferably selected from a group comprising molybdenum disulfide, tungsten disulfide, graphite, calcium fluoride, barium fluoride, sodium fluoride, lithium fluoride and / or boron nitride.

It is therefore an object of the present invention to further develop a friction ring according to the preamble of claim 1 and a method for producing such a friction ring, that material stresses between the coating and body of the friction ring are reduced and thermal distortions are reduced at high brake temperatures.

This object is achieved by a friction ring with the features of claim 1 and by a method having the features of claim 11.

Such a friction ring for a brake disc has a coating at least in regions. According to the invention, it is provided that the coating has a thickness profile with different coating thicknesses. In other words, the coating is applied unevenly thick on the friction surface of the friction ring. Of course, the surface of the friction ring, as used in the disc brake, is level again. By a suitable choice of the thickness profile of the coating, a load-appropriate application of the coating is possible. Criteria for the choice of the local coating thickness are on the one hand the thermal load at each point of the friction ring and on the other hand the radial course of the pressure load through the brake lining over the friction ring. By such a load-appropriate application of a coating as homogeneous a temperature field in the friction surface of the brake disc can be generated. This advantageously reduces the danger of thickness fluctuations - so-called DTVs (Disc Thickness Variation) across the brake disc. Thus, in particular the so-called hot scrubbing, so vibrations and noise, which occur during high-temperature operation of the brake disc is reduced. Likewise, the punctual wear of the brake disc at so-called hotspots, so points that heat up particularly strong, reduced.

In a preferred embodiment, the friction ring in this case has a surface profile which is designed to be complementary to the thickness profile of the coating. In other words, the combination of a profiling of the surface of the main body of the friction ring and the unevenly thick application of the coating results in a level Friction ring. This not only reduces hot scrubbing but also avoids vibrations and wear during cold operation of the brake. The type of profiling of the main body of the friction ring and the coating thickness is further dependent on the thermal expansion coefficient of the coating. As a rule, this will be higher than that of the main body of the friction ring. In combination with the non-uniform temperature profile over the friction ring, the combination of the different layer thicknesses and the different thermal expansion coefficients results in uniform thermal expansion of the entire brake disk, even in high-temperature operation. The contact of the friction ring with the brake lining of the brake shoes is uniform and plane-parallel over the entire operating range of the friction ring. Fading and lining wear are advantageously reduced.

There are various possibilities for the execution of the thickness profile in the radial direction. For example, it is possible to form the coating wedge-shaped in the radial direction, so that, for example, an increase in thickness results from the inside to the outside. Alternatively, an at least partially concave thickness profile of the coating is possible.

The execution of the thickness profile is substantially dependent on the specific design of the friction ring itself, so that, for example, a one-piece, solid friction ring, a different coating profiling is obtained as an internally ventilated friction ring. In particular, in the case of the internally ventilated friction ring, a reinforced coating outside the dimple region or the webs along the cooling channels of the internal ventilation is necessary in order to compensate for different temperature derivatives and different thermal expansions. This results in the radial and tangential direction differently extending thickness profiles.

Since the thermal expansion of the friction ring in the region of the knobs, or webs in the axial direction (perpendicular to the friction ring surface) is greater than in the areas with cooling channels, a thinner coating is preferably carried out here.

The coating is a wear-resistant friction material. Here can be widely used on known wear-resistant and friction materials, as for example, in DE 102 03 507 A1, DE 10 2005 008 569 A1. The coating preferably comprises chromium carbide and / or alumina and / or titanium dioxide and / or diamond and / or cermets. In particular, these materials are present as a component in composite materials with a metallic matrix, so-called metal matrix composites (MMC). As a metallic matrix here in particular Ni, Cr, Mo or Co alloys are suitable. Further suitable coatings are formed from intermetallic composites (IMC). A particularly preferred IMC material is formed essentially from titanium aluminides and aluminum oxide.

Other suitable coatings are W / Cr / Ni coatings or WC / Cr / Ni coatings.

All these materials are characterized by a high hardness and sometimes high toughness and temperature resistance and thus have high wear resistance. Advantageously, they also have a high temperature resistance and good coefficients of friction in the pairing with the known friction linings of disc brakes.

In addition, an intermediate layer can be provided between the coating and the main body of the friction ring. Such intermediate layers can take over several functions. On the one hand, the adhesion mediation between the coating and the base body is of great importance, so as to guarantee a secure adhesion of the coating, especially in the case of the loads of the braking operation. On the other hand, the intermediate layer can assume the function of dissipating the temperature, so that the thermal load capacity of the brake disk is increased.

Such an intermediate layer may be a layer of aluminum and / or chromium-containing nickel alloys. For particularly good temperature resistance, the use of zirconium-nickel-chromium-aluminum-yttrium alloys is also possible.

The main body of the friction ring is further preferably formed from gray cast iron or an aluminum alloy. Cast iron itself has excellent thermal conductivity, so that the thermal problems of the operation of the brake can be reduced. The use of an aluminum alloy is possible only in combination with a coating, since the coefficient of friction of aluminum is usually too low. However, in combination with a coating designed according to the invention, the use of aluminum base bodies for the friction ring can be advantageous Reduction of the unsprung masses of the motor vehicle cause. The friction ring can continue to be made in one piece with a brake disc pot or in the form of a two-piece brake disc. Inventive friction rings can be both solid and internally ventilated.

The invention further relates to a method for producing a friction ring for a brake disc which has the features mentioned. The method comprises two steps. First, a surface profile of the friction ring complementary to a thickness profile of a coating having different coating thicknesses is formed. This can already take place during the primary shaping - for example during casting - of the friction ring. Alternatively, it is possible to cast or otherwise mold a base body having a planer surface and to subsequently produce the surface profile by abrasive methods such as machining, erosion, or the like. In the following method step, a coating is finally applied to the main body of the friction ring to form the thickness profile with different coating thicknesses. As a result, preferably results in a flat friction surface. To apply the coating, thermal spraying methods such as flame spraying, plasma spraying, arc wire spraying (LDS) or the like or else physical vapor deposition (PVD) are preferably used.

Another suitable method is formed by melting the coating material, in which the carrier material is partially melted at the surface by radiation energy, the coating material is mixed with the melt and thus incorporated into the carrier material.

In the following, the invention and its embodiments will be explained in more detail with reference to the drawing. Hereby show:

1 shows a cross section through an embodiment of a brake disc with a friction ring according to the invention,

Fig. 2 is an enlarged detail of the friction ring of the brake disc shown in FIG. 1 and

Fig. 3 shows a cross section through an alternative embodiment of a brake disc with a friction ring according to the invention. Fig. 1 shows a designated as a whole with 10 brake disc for a motor vehicle. This comprises a friction ring 12 and a brake disk cup 14, wherein on the brake disk chamber 14, a receiving opening 16 is provided for fastening the brake disk 10 on an axle of the motor vehicle. In the example shown, friction ring 12 and brake disk cup 14 are made in one piece. Such brake discs are manufactured in particular as one-piece cast components, for example, cast iron. In order to improve the friction properties of the friction surfaces 18 and 20 of the friction ring 12, a coating 22, 24 is applied to the friction surfaces 18 and 20, respectively. This may be, for example, a ceramic coating of chromium carbide, aluminum oxide or titanium dioxide. Also diamond or cermet can be used.

During operation of the brake disk 10, the friction ring 12 experiences uneven heating across its friction surfaces 18 and 20. So-called hotspots form, ie zones of elevated temperature. This results in conventional brake discs to an uneven expansion of the friction ring 12, which is why the friction ring 12 is no longer plane-parallel against the brake shoes of the brake system. This creates vibrations and noises, the so-called hot scrubbing of the brake ring. In order to prevent this, the coatings 22 and 24 are not uniformly applied in the example shown of a friction ring 12 according to the invention. This is illustrated in the enlarged detail view in FIG. 2.

The coating 22 of the friction surface 20 of the friction ring 12 has a concave thickness profile, wherein the thickness of the coating 22 of a minimum thickness di at the outer edge 26 of the friction ring 12 increases radially inwardly until the coating 22 approximately in the middle of the friction ring 12 her Maximum thickness d ₂ reached, whereupon the thickness is reduced radially inward again to the value d ^. The friction ring 12 has a complementary surface profile to the coating 22, so that the overall result is a plane friction surface 20. On the second friction surface 18 of the friction ring 12, a coating 24 is applied, which takes a wedge-shaped course in its thickness radially from outside to inside. At the outer edge 26 of the friction ring 12, the coating 24 has its maximum thickness d ₃ . The thickness of the coating 24 is reduced radially inwardly to 0. Here too, the main body 28 of the friction ring 12 on its surface 18 has a complementary profile, so that in turn results in a plane friction surface 18 in the sum. The thickness profiles of the coatings 22 and 24 are chosen so that from the combination of the different coefficients of expansion of the body 28 and the coatings 22 and 24 with the different temperatures of the friction ring 12 during operation of the brake disc 10, a uniform longitudinal expansion of the entire friction ring 12 on the total friction surfaces 18 and 20 away. The friction surfaces 18 and 20 are thus both in the cold state and in active braking mode, ie in the hot state, each plan. There is no hot or cold rubbing of the brake disc, which reduces both vibration and noise and wear of the brake system.

Finally, FIG. 3 shows an alternative embodiment of a brake disk 10 'with a brake disk cup 14 and an internally ventilated friction ring 12'. The friction ring 12 'is not made massive as the friction ring 12 shown in FIGS. 1 and 2, but has air channels 30 which extend between the two friction ring halves 32 and 34. The friction ring halves 32 and 34 are supported by nubs 36 against each other. The first friction surface 18 of the friction ring half 34 is uncoated in the example shown, a coating is applied only on the friction surface 20 of the second friction ring half 32. The coating 22 of the friction ring half 32 initially has a constant thickness in a radially inner region 38. Only in a radially outer region 40 of the friction ring half 32, the coating 22 is thickened. This serves in the example shown to compensate for different temperature dissipation in the air ducts 30 and nubs 36. This is the internally ventilated brake discs 10 'particularly high risk of thickness variation of the friction ring 12' reduced by possibly occurring different thermal expansions in different areas 38, 40 of the friction ring 12 'are compensated by different extents of the coating 22 respectively.

Claims

Daimler AG Zimmermann Chopin patent claims

1. friction ring (12, 12 ') for a brake disc (10, 10'), which at least partially a coating (22, 24), characterized in that the coating (22, 24) has a thickness profile with different

Coating thicknesses (di, d ₂ , d ₃ ).

Second friction ring (12, 12 ') according to claim 1, characterized in that the friction ring (12, 12 ") has a surface profile which is complementary to the thickness profile of the coating (22, 24).

Third friction ring (12, 12 ') according to claim 1 or 2, characterized in that the thickness profile of the coating (22, 24) is wedge-shaped in the radial direction.

4. friction ring (12, 12 ') according to claim 1 or 2, characterized in that the thickness profile of the coating (22, 24) is at least partially concave.

5. friction ring (12, 12 ') according to claim 1 or 2, characterized in that the thickness profile of the coating (22, 24) follows approximately the distribution of the hotspots.

6. friction ring (12, 12 ') according to claim 1 or 2, characterized in that the thickness of the coating (22, 24) above the cooling channels is higher than above the associated knobs (36) or webs.

7. friction ring (12, 12 ') according to any one of the preceding claims, characterized in that the coating (22, 24) Cr ₃ C ₂ and / or Al ₂ O ₃ and / or TiO ₂ and / or diamond and / or MMC and / or IMC and / or cermet.

8. friction ring (12, 12 ') according to one of the preceding claims, characterized in that between the coating (22, 24) and a base body (28) of the friction ring (12, 12') an intermediate layer is provided.

9. friction ring (12, 12 ') according to claim 8, characterized in that the intermediate layer comprises aluminum and / or chromium-containing nickel alloys and / or ZrNiCrAlY alloys.

10. friction ring (12, 12 ') according to one of the preceding claims, characterized in that the base body (28) of the friction ring (12, 12') is formed from gray cast iron or an aluminum alloy.

11. A method for producing a friction ring (12, 12 ') for a brake disc (10, 10') according to one of the preceding claims, comprising the steps:

- Forming a to a thickness profile of a coating (22, 24) with different coating thicknesses (O ₁ , d ₂ , d ₃ ) complementary surface profile of the friction ring (12, 12 ');

- Applying the coating (22, 24) to form the thickness profile with different coating thicknesses (di, d ₂ , d ₃ ).

12. The method according to claim 11, characterized in that when applying the coating (22, 24) a flat friction surface (18, 20) is generated.

13. The method according to claim 11 or 12, characterized in that the coating (22, 24) is applied by a thermal spraying method or physical vapor deposition.

LIST OF REFERENCE NUMBERS

10, 10 'brake disc

12, 12 'friction ring

14 brake disk pot

16 receiving opening

18 friction surface

20 friction surface

22 coating

24 coating

26 outer edge

28 basic body

30 air duct

32 friction ring half

34 friction ring half

36 pimples

38 indoor area

40 outside area di minimum thickness d ₂ maximum thickness d ₃ maximum thickness