WO2008078352A1

WO2008078352A1 - Braking band of a disk for a disk brake

Info

Publication number: WO2008078352A1
Application number: PCT/IT2007/000884
Authority: WO
Inventors: Ralf Siegfried Goller
Original assignee: Brembo Ceramic Brake Systems S.P.A.
Priority date: 2006-12-22
Filing date: 2007-12-19
Publication date: 2008-07-03
Also published as: ATE541137T1; EP2102523A1; ITMI20062495A1; EP2102523B1

Abstract

A braking band (2) of a brake disk (1) comprises two plates (3, 3') which are connected by means of connecting elements (4) such as to internally form a ventilation duct (7) that is at least partially defined by inner surfaces (8, 81) of the plates (3, 31) and that extends from an inlet opening (10) that is radially internal relative to an axis of rotation (S) of the braking band (2) to an outlet opening (11) that is radially external relative to the axis of rotation (S). At least one of the inner surfaces (8, 81) comprises a plurality of impressions (15) that are arranged such as to define a surface structure with alternated ridges (16) and bottoms (17) in the flow direction from the inlet opening (10) to the outlet opening (11).

Description

DESCRIPTION "Braking band of a disk for a disk brake"

The object of the present invention is a braking band for a ventilated disk for a disk brake. A known type of disk for a disk brake with ventilated braking band comprises a support bell that can be connected for example to a vehicle wheel hub. A braking band co-operating with the calipers to apply the braking action on the vehicle is either connected or connectable to this bell by means of a connection. The braking band typically comprises at least two parallel plates that are separated by connecting elements ensuring the cohesion thereof . The gap between the plates forms a ventilation duct. Due to the air circulating between the plates, the disk is cooled not only on the outer sides, as in the case of a solid disk, but also on the inner sides of the braking band.

It is known that, during a braking action, the friction between the pads and the braking band turns the kinetic energy of the vehicle into heat which is absorbed by the braking system, mainly by the braking disk, from which it should be removed in order to avoid over-heating the same .

The cooling effect of the internal ventilation of the ventilated braking bands depends, besides on the area of the inner surface of the ventilation duct, also and mainly on the amount of fresh air that blows on said inner surface during a braking action.

In known braking disks, the amount of air blowing on the inner surfaces of the plates is undesirably low and an increase of the same is strongly desirable in order to obtain an improved cooling of the braking band and thus being capable of dissipating an increased amount of kinetic energy during hard breakings. The object of the present invention is thus to provide a braking band for a disk for a disk brake, which has such characteristics as to increase the amount of air that blows on the inner surfaces of the plates while braking . This object is achieved by means of a braking band for a disk for a braking disk according to claim 1.

According to the invention, the braking band comprises at least two plates being connected to each other by means of connecting elements, in which the gap between the plates forms at least one ventilation duct therein for cooling the braking band. The ventilation duct is at least partially defined by inner surfaces of the plates and extends from an inlet opening that is radially internal relative to an axis of rotation of the braking band to an outlet opening that is radially external relative to this axis of rotation. At least one of the surfaces defining the ventilation duct comprises a plurality of impressions that are arranged such as to define at least one surface structure having alternated ridges and bottoms or valleys in the flow direction from the inlet opening to the outlet opening.

In fact, by analyzing the known braking bands, it has emerged that the amount of air blowing on the inner surface of the ventilation duct is limited by two distinct phenomena. The first phenomenon is the flow resistance that is determined by the global and local shape of the ventilation duct which restrains the speed and thus the total flow rate of the air flow through the ventilation duct. The second phenomenon is the formation of an air layer adjacent to the inner surface of the ventilation duct, which remains attached thereto and prevents that the air in the center of the flow may come in direct contact with the surface to be cooled or be mixed with the layer adjacent thereto. This phenomenon reduces the amount of air blowing on the surface to be cooled with the total flow rate of the air flow being the same.

According to the invention, the formation of a plurality of impressions that are arranged such as to define a surface structure with alternated ridges and bottoms or valleys in the flow direction from the inlet opening to the outlet opening increases the local speed of the air layer adjacent to the inner surface of the ventilation duct. This speed increase entails an increase in the kinetic energy of the air, which results in small turbulences and local detachments of the air from the surface which reduce the total flow resistance by increasing the speed and cause the outer layers to be mixed with the middlemost layers of the flow. In accordance with an aspect of the invention, the amount of air blowing on the inner surface of the ventilation duct is particularly high, when the impressions have a depth exceeding 0.3 mm, preferably exceeding 0.5 mm, most preferably ranging between 0.5 mm and 1.0 mm.

In accordance with a further aspect of the invention, the diameter or, in other words, the maximum cross extension of the impressions is higher than 2 mm, preferably higher than 3 mm, most preferably this maximum cross extension ranges between 3 mm and 5 mm.

In accordance with a further aspect of the invention, the impressions have a spherical cap shape or a pyramidal shape with for example 4, 6 or 8 sides. Alternatively, the impressions can be prism-shaped. In accordance with a further aspect of the invention, the ridges being formed between the impressions have a lower width than the cross-extension of the impressions.

According to an embodiment, the impressions are arranged such that the ridges that are formed between the impressions are connected with each other to form a grid- like or honeycomb pattern.

According to an alternative embodiment, the impressions are connected with each other to form a grid- like pattern about the ridges.

According to an alternative embodiment, the impressions comprise rectilinear, curved, undulated, stepped or zigzag grooves that are arranged adjacent to each other. According to an embodiment, substantially the whole inner surface of the plates (except for the connecting elements that may remain smooth) which defines the ventilation duct is configured with alternated ridges and bottoms or valleys. Alternatively, this alternated ridges and bottoms structure is provided only in a portion, preferably the radially outer half, of the ventilation duct.

The invention can be applied with much advantage both in cast iron and braking bands made of composite or carbon-ceramic material, for example of the type C/SiC (carbon-silicon carbide) .

In order to better understand the invention and appreciate the advantages thereof, several exemplary non- limiting embodiments of the same will be described herein below, with reference to the annexed drawings, in which:

Fig. 1 illustrates a perspective view of a ventilated brake disk;

Fig. 2 illustrates a radial section of the disk in Fig. 1; Fig. 3a illustrates an embodiment of the present invention in radial section;

Fig. 3b is a partially sectioned front view of the brake disk of Fig. 3a;

Fig. 4a illustrates a second embodiment of the present invention in the radial section thereof;

Fig. 4b illustrates the brake disk in Fig. 4a in a partially sectioned front view;

Fig. 5a - 5g illustrate enlarged front views of an inner surface area of a ventilation duct of the braking band according to several embodiments of the invention;

Fig. 6a. - 6q illustrate enlarged sectional views of an inner surface area of a ventilation duct of the braking band according to several embodiments of the invention. With reference to Fig. 1, with 1 has been generally designated a brake disk of a disk brake. The disk 1 is developed about a symmetry axis S. Said symmetry axis S is also the axis of rotation of the brake disk i. The disk 1 comprises a braking band 2 with at least two plates 3 and 3' which are connected to each other by means of connecting elements 4. The braking band 2 is supported by a bell 5 by means of a connection 6 that can be configured such as to provide a linkage as one piece, or alternatively, a movable and/or removable linkage between the cap and the braking band. The bell 5 is arranged in the centre of the brake disk 1 and can be coupled by means of connection means to a vehicle wheel hub. The plates 3, 3' comprise an outer surface 9, 9' and an inner surface 8, 8' , opposite the outer surface 9, 9' . The outer surfaces 9, 9' of the plates 3, 3' are the friction surfaces of the brake disk. The inner surfaces 8, 8' of the plates 3, 3' define a ventilation duct 7 extending from an inlet opening 10 arranged at a radially inner edge of the braking band 2 and an outlet opening 11 arranged at a radially outer side of the braking band 2. The terms "radially inner" and "radially outer" relate to the symmetry axis S corresponding to the axis of rotation of the brake disk 1 and braking band thereof 2.

According to the invention, at least one of the inner surfaces 8, 8' of the plates 3, 3¹ which define the ventilation duct 7 comprises a plurality of impressions 15 that are arranged such as to define in the flow direction from the inlet opening 10 to the outlet opening 11 a surface structure with alternated ridges 16 and bottoms or valleys 17.

The operation of a brake disk 1 with the braking band according to the invention is described herein below with reference to Fig. 2.

During a braking action, the pads 14 of the brake disk are pushed against the friction surfaces 9, 9' of the braking band 2 of the brake disk 1. The friction process between the pads 14 and the braking band 2 turns the kinetic energy of the vehicle to be braked into heat which is absorbed by the plates 3 , 3 • . The rotation of the brake disk 1 generates a centrifuge force on the air contained within the ventilation duct 7, and thus a flow of cooling air 12, which is sucked from the inlet opening 10 and conveyed through the ventilation duct 7 to the outlet opening 11 from which it is released in the environment. This air flow cools the inner surfaces 8, 8¹ of the plates 3, 3¹ and prevents the braking band 2 from being over-heated.

The formation of a plurality of impressions 15 being arranged such as to define in the direction of the flow 12 a surface structure made of alternated ridges 16 and bottoms or valleys 17 increases the speed of the air flow and causes the outer layers to mix with the middlemost layers of the flow 12 thus resulting in the fact that a greater amount of air blows on the inner surfaces 8 , 8 ' of the plates during the braking action.

Fig. 2, 3a and 3b illustrate an embodiment of the invention, wherein the plates 3, 3' of the braking band 2 are connected by means of fin-like connecting elements 4.

These fins are mainly orientated in the radial direction relative to the axis of rotation S of the brake disk 1 and are preferably arranged at an even pitch from each other. The inner surfaces 8, 8' of the plates 3, 3' comprise a plurality of spherical cap-shaped impressions 15 with a depth of more than 0.3 mm, preferably more than 0.5 mm, most preferably ranging between 0.5 mm and 1.0 mm, and a diameter, or in other words, a cross-extension parallel to the middle plane of the plate 3, 3¹, of more than 2 mm, preferably more than 3 mm, most preferably ranging between 3 mm and 5 mm. In the embodiment, the ridges 16 being formed between the impressions 15 have a width that is equal or preferably lower than the cross-extension of the same and the impressions 15 are arranged such that the ridges 16 are interconnected with each other to form a grid-like pattern. Fig. 4a and 4b illustrate a further embodiment of the present invention, wherein the plates 3 and 3' of the braking band 2 are connected by means of connecting elements 4 having a substantially circular, oval, or diamond-shaped section. Said elements 4 (the so-called stakes) can be arranged along circumferences relative to the axis of rotation S and form a series of annular sequences. The inner surfaces 8, 8¹ are advantageously structured according to the modes described with reference to Fig. 2, 3a and 3b.

Fig. 5a to 5g illustrate front views of possible embodiments of the inner surfaces 8, 8¹.

In accordance with the embodiment illustrated in

Fig. 5a, the impressions 15 have a substantially spherical cap- or cylinder- or circular cone-shape and are arranged such that the ridges 16 that are formed therebetween are interconnected in a grid-like manner.

In accordance with the embodiment as illustrated in Fig. 5b, the impressions 15 have a substantially rectilinear elongated shape and are arranged parallel with each other such that the ridges 16 being formed therebetween are also rectilinear and parallel to each other .

In accordance with the embodiment as illustrated in Fig. 5c, the impressions 15 have a substantially undulated elongated shape and are arranged adjacent to each other such that the ridges 16 being formed between the impressions 15 are also undulated.

In accordance with the embodiment as illustrated in Fig. 5d, the impressions 15 have a curved shape and extend along circumferences of concentric circles such that also the ridges 16 that are formed therebetween are arc-of-circle shaped.

In accordance with the embodiment as illustrated in Fig. 5e, the impressions 15 and the ridges being formed therebetween have a zigzag shape.

In accordance with the embodiment as illustrated in

Fig. 5f, the impressions 15 have, in the front view, a rectangular shape, preferably squared, and the ridges 16 being formed therebetween are interconnected to form a wafer-shaped grid-like structure.

In accordance with the embodiment illustrated in

Fig. 5g, the front view of the impressions 15 shows a hexagonal shape and the ridges 16 being formed therebetween are connected with each other to form a substantially honeycomb shape.

Advantageously, the impressions can have a pyramidal shape with for example 4, 6 or 8 sides.

Fig. 6a to 6g illustrate sectional views of possible embodiments of the inner surfaces 8, 8'. In accordance with the embodiment as illustrated in Fig. 6a, the impressions 15 have a sectional curved shape, for example a circular shape, and the ridges 16 between the impressions 15 have a cusp-like shape. In accordance with the embodiment illustrated in Fig. 6b, the impressions 15 have a sectional trapezoid shape and also the ridges 16 between the impressions 15 have a sectional trapezoid shape.

In accordance with the embodiment as illustrated in Fig. 6c, the impressions 15 have a sectional trapezoid shape and the ridges 16 being formed between the impressions 15 have a substantially sectional triangular shape .

In accordance with the embodiment illustrated in Fig. 6d, the impressions 15 have a sectional triangular shape and also the ridges 16 between the impressions 15 have a sectional triangular shape.

In accordance with the embodiment as illustrated in

Fig. 6e, the impressions 15 have a sectional arc shape, such as arc-of-circle shape, and the ridges formed between the impressions 15 have a substantially planar plateau.

In accordance with the embodiment as illustrated in

Fig. 6f, the impressions 15 have a sectional triangular shape and the ridges 16 between the impressions 15 have a substantially planar plateau.

In accordance with the embodiment as illustrated in Fig. 6g, the impressions 15 and ridges 16 being formed between the impressions have a sectional scalene trapezium shape.

The size ranges of the impressions 15 and ridges 16, as well as the ratios between the sizes thereof which are described in relation with the embodiment in Fig. 2, 3a and 3b may also be advantageously applied to the embodiments illustrated in Fig. 5a to 5g and 6a to 6g.

The braking band as illustrated in the figures is a band made of cast iron. However, the surface structure of the inner surfaces 8, 8' described so far can be also provided with much advantage in braking bands made of composite or carbon-ceramic materials, such as of the type C/SiC (carbon-silicon carbide) .

Obviously, to the braking band 2 according to the present invention, those skilled in the art, aiming at meeting contingent and specific requirements, may carry out further modifications and variations, all being however contemplated within the scope of protection of the invention, such as defined in the annexed claims.

Claims

1. A braking band (2) of a disk (1) for a disk brake, comprising two plates (3, 3') being connected with each other by connecting elements (4) , wherein the gap between said plates internally forms a ventilation duct (7) for cooling said braking band (2) , wherein said ventilation duct (7) is at least partially defined by inner surfaces

(8, 8') of the plates (3, 3¹), and extends from an inlet opening (10) that is radially internal relative to an axis of rotation (S) of the braking band (2) to an outlet opening (11) that is radially external relative to said axis of rotation (S) , characterized in that at least one of the surfaces (8, 8¹) of the plates (3, 3¹) which define the ventilation duct (7) comprises a plurality of impressions (15) that are arranged such as to define a surface structure with alternated ridges (16) and bottoms or valleys (17) in the flow direction from the inlet opening (10) to the outlet opening (11) .

2. The braking band (2) according to claim 1, wherein said impressions (15) have a depth of more than 0.3 mm, preferably more than 0.5 mm, most preferably ranging between 0.5 mm and 1.0 mm.

3. The braking band (2) according to claim 1 or 2, wherein the impressions (15) have a diameter or maximum cross-extension of more than 2 mm, preferably more than 3 mm, most preferably ranging between 3 mm and 5 mm.

4. The braking band (2) according to any preceding claim, wherein the impressions (15) have a spherical cap-shape.

5. The braking band (2) according to any claim 1 to 3, wherein the impressions (15) have a pyramidal shape.

6. The braking band (2) according to any preceding claim, wherein the ridges (16) that are formed between the impressions (15) have a width lower than the cross- extension of the impressions (16) .

7. The braking band (2) according to any preceding claim, wherein the impressions (15) are arranged such that the ridges (16) being formed between the impressions (15) are interconnected to form a grid-like or honeycomb pattern.

8. The braking band (2) according to any claim 1 to 6, wherein the impressions (15) are connected with each other such as to form a grid-like groove pattern about the ridges (16) .

9. The braking band (2) according to any claim 1 to 6, wherein the impressions (15) comprise grooves that are arranged adjacent to each other and have a shape being selected from the group comprising:

- rectilinear shape,

- curved shape, - undulated shape, - stepped shape,

- zigzag shape.

10. The braking band (2) according to any preceding claim, wherein substantially the entire inner surface (8, 8¹) of the plates (3, 3') in that part thereof which defines the ventilation duct (7) is configured with alternated ridges (16) and bottoms (17) .

11. The braking band (2) according to any claim 1 to 10, wherein said surface structure with alternated ridges (16) and bottoms (17) is provided only in a portion of the ventilation duct (7) .

12. The braking band (2) according to the preceding claim, wherein said surface structure with alternated ridges (16) and bottoms (17) is provided only in a radially outer half of the ventilation duct (7) .

13. The braking band (2) according to any preceding claim, wherein said braking band (2) is made of cast iron.

14. The braking band (2) according to any preceding claim, wherein said braking band (2) is made of composite or carbon-ceramic material of the C/SiC type.

15. A disk (1) for a disk brake, comprising a braking band (2) according to one of the preceding claims.

16. A disk brake, comprising a disk (1) for a disk brake according to claim 15.