WO2002038979A1

WO2002038979A1 - Disc brake rotor

Info

Publication number: WO2002038979A1
Application number: PCT/IT2000/000470
Authority: WO
Inventors: Giovanni Mario Tironi
Original assignee: Freni Brembo S.P.A.
Priority date: 2000-11-13
Filing date: 2000-11-13
Publication date: 2002-05-16
Also published as: AU2001218859A1

Abstract

The disk is formed by a bell (2), by an annular braking band (3), and by coupling means (30) between the bell and the braking band. The bell (2) had, around its periphery, a plurality of radial recesses (6) with parallel sides and the coupling means comprise a corresponding plurality of drive elements (30) each of which is inserted, so as to be movable only radially, in a corresponding radial recess (6) of the bell (2). To permit quick and easy assembly and a firm and quiet coupling between the bell (2) and the braking band (3), each drive element (30) is formed by a single shaped block fixed to the braking band (3) by fixing means with resilient axial play (31, 37) having two opposed parallel faces (30-1) which engage in abutment with the sides of the corresponding radial recess (6) of the bell (2), and which have axial retention tabs (30-2) that engage the edges of the corresponding recess (6) on opposed surfaces of the bell (2).

Description

DISC BRAKE ROTOR

The present invention relates to disk brakes and, more particularly, to a composite disk-brake disk as defined in the preamble to Claim 1.

A disk brake of the type used as a braking device in motor vehicles comprises an annular cast-iron disk, commonly known as the braking band, which is usually integral with a hub, commonly known as the bell that is connected to a wheel of the vehicle, and a caliper which is fixed to the hub-carrier, is disposed around the braking band, and is provided with brake linings or pads. The caliper acts on the pads by means of an hydraulic operation, so as to bring the pads into contact with the two opposed braking surfaces of the braking band. If the wheel with the respective bell and braking-band assembly is rotating, the action of the caliper brings about a braking effect due to the friction between the pads the braking surfaces of the braking band with consequent heating of the disk, that is, of the assembly composed of the bell and the braking band. As is known, this heating leads to undesired deformation due to the temperature difference between the band and the bell. To prevent this problem and to provide high-performance braking devices, composite disks in which the braking band and the bell are constituted by two distinct parts made of different materials, connected to one another by suitable coupling means, have been proposed. The materials used are usually cast iron for the braking band and aluminium alloys for the bell. The different thermal expansion coefficients of the two materials require that the coupling means between the bell and the braking band should not lead to excessively rigid radial or axial restraints. To take account of these requirements, the coupling means used up to now are somewhat complex.

The main object of the present invention is to provide a composite disk-brake disk with a simple and reliable coupling between the braking band and the bell. This object is achieved by the provision of the composite disk-brake disk defined and characterized in general in Claim 1.

The invention will be understood better from the following detailed description of two non-limiting embodiments thereof, given with reference to the appended drawings, in which:

Figure 1 is an axonometric view of a bell and of a braking band of a known disk brake, Figure 2 is an axonometric view of a known coupling unit usable for the coupling between a bell and a braking band such as those shown in Figure 1, with parts separated,

Figure 3 shows, in section, the known coupling unit of Figure 2, installed,

Figure 4 is an axonometric view of the composite disk-brake disc according to the invention, with parts separated,

Figures 5 and 6 are axonometric views showing two faces of the disk according to the invention, assembled, and

Figure 7 is an axonometric view showing a face of an assembled disk according to a variant of the invention.

In Figure 1, a bell 2 and a braking band 3 of a known disk-brake disk are shown as two axially aligned, separate parts. The bell 2 is formed by a single part made of aluminium alloy and has a drilled flange 4 for the fixing of the disk to the hub of a wheel, and a peripheral ring 5 with a plurality (ten in this embodiment) of radial recesses 6 with parallel sides distributed uniformly around its periphery. The braking band 3 is composed of two substantially annular, parallel, cast-iron plates 7 joined together by spacer elements 8. The annular plate 7 facing towards the bell 2 has a plurality of through-holes 9 distributed uniformly in the vicinity of its inner edge with the same spacing as the radial recesses 6 of the bell.

The bell 2 and the braking band 3 are joined together by coupling units 10 such as those shown in Figures 2 and 3. In particular, a coupling unit 10 comprises a screw 11, a first washer 12, a second washer 13, a lock nut 14, a first spacer 15 formed by a shaped bush with four sides comprising two pairs of parallel sides, a leaf-spring-like flat spring 16, and a second spacer 17 formed by a tubular element with an intermediate collar 18 having two opposed lateral chamfers .

Assembly takes place by inserting the second spacer 17 in each hole 9 of the annular plate 7 until the collar 18 is brought into abutment with the surface of the plate, fitting the first spacer 15 onto the second spacer 17 until it is in abutment with the collar 18, moving the bell 2 up to the plate 7 in a manner such that the first spacers 15 of the coupling units 10 enter the recesses 6 of the peripheral ring 5 of the bell, inserting the screws 11 in the respective first washers 12 and in the respective second spacers 17, fitting the flat springs 16 in a manner such that their ends are in contact with the surface of the bell 2, fitting the second washers 13, and screwing the nuts 14 onto the ends of the screws 11 until they are fully tightened. During assembly, each of the second spacers 17 is positioned in a manner such that one of the chamfers of the collar 18 is disposed adjacent a corresponding projection 33 (Figure 3) of the plate 7. Upon completion of the assembly, each coupling unit 10 is connected to the plate 7, and the bell 2 is spaced from the plate 7 by the collars 18 and is urged against the collars by the flat springs 16.

The spacers 15 are of a size such that the distance between the two parallel sides adjacent the sides of the recesses 6 is only slightly less than the width of the radial recesses 6, that is, the tangential play in the coupling is very small. The depth of the radial recesses 6, on the other hand, is quite large to allow for free relative radial movement to take account of the dimensional variations of the bell 2 and of the band 3 due both to the different expansion coefficients of the materials and to their different, temperatures when the disk is heated during a braking operation. With regard to axial expansion, the coupling units 10 allow for sufficient axial play by virtue ^• of the fact that the height of the first spacers 15 is greater than the thickness of the peripheral ring _.5 of the bell. The springs 16 serve to prevent vibrations and axial movements which would cause undesired noise. The projections 33 serve to prevent any possible rotation of the second spacers 17 about their axes.

As can easily be seen, the known coupling units described above are constituted by many separate parts some of which have to be oriented appropriately during assembly, so that assembly is rather laborious.

This disadvantage is overcome by the provision of the disk according to the invention. As can be seen in Figure 4, in which components identical or corresponding to those of Figures 1 to 3 are indicated by the same reference numerals, each of the coupling means between the bell 2 and the braking band 3 comprises only three parts, more precisely, a drive element 30, a screw 31, and a washer 32. The bell 2 differs from that according to the prior art shown in Figure 1 in that it has a continuous peripheral groove 36 which extends radially throughout the width of the peripheral ring 5, that is, at least throughout the radial extent of the recesses 6. The axial position in which the groove 36 is formed is such as to create a flexible peripheral tongue 37 on the side of the bell farthest from the braking band 3. The outer surface of the peripheral ring 5 of the bell 2 is preferably shaped in a manner such that the thickness of the tongue 37 decreases from the periphery of the bell towards its interior.

The drive element 30 is constituted by a single block, preferably made of steel, shaped to fit in a corresponding radial recess 6 of the bell 2 so as to be movable substantially only radially. In particular, each block 30 has two opposed parallel faces 30-1 spaced apart by a distance only slightly less than the width of the recess so that, when the block 30 is in position, it can move freely between the sides of the recess. Each block 30 also has four projections 30-2 which define ^' the two opposed faces 30-1 so as to form four tabs. The distance between the tabs 30-2 is slightly less than the thickness of the peripheral ring 5 of the bell^' so that, when each block 30 is in position, it engages the opposed surfaces of the bell 2 at the edges of the corresponding recess 6 by interference, by virtue of the resilience of the tongue 37. The drive elements or blocks 30 are fixed to the braking band 3 by the screws 31 which are screwed into corresponding threaded holes 30-3 in the drive blocks 30. Each block 30 preferably has a cylindrical appendage 30-4 through which the hole 30-3 extends and which engages in a corresponding hole 35 provided in the plate 7 of the braking band 3. The axial extent of the cylindrical appendage 30-4 is slightly less than the thickness of the plate 7. To assemble the disk, the drive elements 30 are inserted in the recesses 6 of the bell 2 and remain in place by interference, the braking band 3 is brought up to the bell 2 in a manner such that the cylindrical appendages 30-4 of the drive blocks 30 enter the corresponding holes 35, and the fixing screws 31 are tightened, after the interposition of the washers 32. The assembled unit is as shown in Figures 5 and 6.

As explained above, the dimensions of the drive blocks 30 and of the radial recesses 6 of the bell are such as to allow the blocks 30 to slide radially in the recesses so that the band 3 and the bell 2 are free to expand independently of one another. Moreover, it will be noted that the tabs 30-2 of the drive blocks 30 are spaced apart in a manner such that, in combination with the flexible tongue 37, they allow for the resilient axial play which is necessary to compensate for the different axial expansions of the bell 2 and of the band 3 and to prevent relative movements which could cause vibrations and noise during the rotation of the wheel to . which the disk brake is connected.

According to the variant shown in Figure 7, instead of a continuous peripheral groove, the bell 2 has a number of peripheral cavities 38 equal to the number of recesses 6. The cavities 38 extend radially, for example, as semicircular millings each centred on a recess 6 and form, around the respective recesses, flexible diaphragms 39 which perform exactly the same function as the tongue 37 of the disk shown in Figure 4. It is clear from the foregoing that the composite disk according to the invention can be assembled quickly and easily by virtue of the small number of parts of which the coupling units are composed. For the same reason, the coupling between the bell and the braking band is firm and quiet.

Although only two embodiments of the invention have been described and illustrated, clearly many variants and modifications are possible within the scope of the same inventive concept. For example, the invention may be implemented with the same advantages with the use of materials other than those indicated in the embodiments described for the bell and for the band, such as steel, cast iron or titanium for the bell and carbon/silicon carbide, or other light composite material for the band.

Claims

1. A composite disk-brake disk comprising a bell (2), an annular braking band (3), and coupling means (30) between the bell and the braking band, the bell (2) having, around its periphery, a plurality of radial recesses (6) with parallel sides, and the coupling means

(30) comprising a corresponding plurality of drive elements (30) each of which is inserted, so as to be movable substantially only radially, in a corresponding radial recess (6) of the bell (2) , characterized in that each drive element (30) is formed by a single shaped block fixed to the braking band (3) by fixing means with resilient axial play (31, 37, 39) having two opposed parallel faces (30-1) which engage in abutment with the sides of the corresponding radial recess (6) of the bell (2), and having axial retention tabs (30-2) that engage the edges of the corresponding recess (6) on opposed surfaces of the bell (2).

2. A disk according to Claim 1 in which each drive element (30) has a threaded hole (30-3) with an axis parallel to the two opposed faces (30-1) of the shaped block (30) , and in which the fixing means comprise a screw (31) which extends through a hole (35) in the braking band (3) and engages the threaded hole (30-3) of a respective shaped block (30) .

3. A disk according to Claim 2 in which each drive element (30) has a cylindrical appendage (30-4) which is coaxial with the threaded hole (30-3), and which engages the corresponding hole (35) of the braking band (3) .

4. A disk according to any one of Claims 1, 2 and 3, in which the bell (2) has a continuous peripheral groove

(36) which extends radially^' at least throughout the radial extent of the recesses (6) to form a flexible peripheral tongue (37) , and in which the resilient fixing means (31, 37) comprise the flexible peripheral tongue

(37) .

5. A disk according to Claim 4 in which the bell (2) is shaped in a manner such that the thickness of the flexible peripheral tongue (37) decreases from the periphery of the bell (2) towards its interior.

6. A disk according to any one of Claims 1, 2 and 3 in which the bell (2) has a plurality of peripheral cavities (38) which extend radially in the region of the recesses of the bell (6) to form respective flexible diaphragms (39) , and in which the resilient fixing means (31, 39) comprise the flexible diaphragms (39) .

7. A disk according to Claim 6 in which the bell (2) is shaped in a manner such that the thickness of the flexible diaphragms (39) decreases from the periphery of the bell (2) towards its interior.