WO2020073086A1

WO2020073086A1 - Disc brakes rotor and method of manufacture

Info

Publication number: WO2020073086A1
Application number: PCT/AU2019/051089
Authority: WO
Inventors: Stephen Patrick Gavin
Original assignee: Disc Brakes Australia Pty. Limited
Priority date: 2018-10-09
Filing date: 2019-10-09
Publication date: 2020-04-16
Also published as: AU2019356796A1; CN112771283A; TW202043642A

Abstract

A disc brake rotor; the rotor comprising opposing brake bands separated by arrays of pillars; the pillars integral with, and extending between, opposing internal surfaces of the opposing brake bands; the rotor further comprising a connector ring structure forming an integral casting with the opposing brake bands; the connector ring structure projecting radially outwardly and inwardly from an inner ring of pillars of the arrays of pillars.

Description

DISC BRAKE ROTOR AND METHOD OF MANUFACTURE

TECHNICAL FIELD

[0001] The present invention relates to disc brakes for vehicles and, more particularly, to disc brake rotors.

BACKGROUND

[0002] The increasing popularity of the larger and therefore heavier passenger vehicles, such as the range of so-called“sport utility vehicles” or SUVs, has demanded an increase in size of the disc brakes fitted to these vehicles. Similarly, the greater comparative weight of electric vehicles due to their heavy batteries has also demanded large disc brake systems, even though at least some of the braking effort can be supplied by regenerative braking.

[0003] Apart from increased thermal expansion and the impost of increased“unsprung weight” of these larger systems, they also have health and safety issues for personnel having to lift and fit serviced or replacement disc rotors. These concerns have seen a shift away from integral disc rotors, in which the brake bands and mounting bell are comprised of a single integral casting, towards floating“hat” designs in which the mounting bell is a separate component of a lighter material and connected to the brake bands in a manner to allow for differential thermal expansion.

[0004] Examples of such hybrid systems are disclosed in the patents to Brembo, US5810123, US8733517 and US2014/0158486. Each of these disclose brake bands of cast iron connected by connector elements to a mounting bell of cast alloy. In the case of US5810123, short fins project inwardly from the cast brake bands to engage with forked projections from the mounting bell with pins passing through apertures in both fins and the forked projections. US8733517 discloses an arrangement in which, in one embodiment, projecting“drive elements” engage with niches provided in the inner periphery of the brake band casting. In US2014/0158486, integrally cast fingers project radially inward from the cast brake bands to engage with an annular groove around the periphery of the mounting bell.

[0005] A disadvantage of each of these systems is that the two opposing brake bands are effectively thermally isolated. In each of US5810123 and US2014/0158486 there is minimal cast material projecting from the brake bands which may allow heat dissipation, while in US8733517 there is none at all. These existing designs incorporate a circular pattern of attachment mechanisms which create a variation in the cross sectional mass and therefore a greater thermal gradient in these regions. These attachment mechanisms also interrupt balanced flow of cooling air passing through the ventilation gallery. [0006] The typical one-piece rotor in which the mounting bell is integrally cast with either the outer or inner brake band is disadvantaged by means of the brake band connected with the mounting bell generates a different thermal gradient to the opposing brake band. This causes thermal deformation in the form of coning which reduces the effective contact surface and increasing tensile stresses leading to metal fatigue.

[0007] It is an object of the present invention to address or at least ameliorate some of the above disadvantages.

Notes

[0008] The term“comprising” (and grammatical variations thereof) is used in this specification in the inclusive sense of“having” or“including”, and not in the exclusive sense of“consisting only of’.

[0009] The above discussion of the prior art in the Background of the invention, is not an admission that any information discussed therein is citable prior art or part of the common general knowledge of persons skilled in the art in any countiy.

SUMMARY OF INVENTION

[00010] Accordingly, in a first broad form of the invention, there is provided a disc brake rotor; the rotor comprising opposing brake bands separated by arrays of pillars; the pillars integral with, and extending between, opposing internal surfaces of the opposing brake bands; the rotor further comprising a connector ring structure forming an integral casting with the opposing brake bands; the connector ring structure projecting radially outwardly and inwardly from an inner ring of pillars of the arrays of pillars.

[00011] Preferably, the arrays of pillars comprise the inner ring of pillars and an outer ring of pillars.

[00012] Preferably, a radial line of the rotor passing through the centre of any pillar of the inner ring of pillars is a bisector of radial lines of the rotor passing through centres of adjacent pillars of the outer ring of pillars; the adjacent pillars disposed to opposite sides of the radial line through the centre of the pillar of the inner ring of pillars.

[00013] Preferably, connection between the opposing brake bands and the connector ring structure is through the inner ring of pillars; castings of the inner ring of pillars being integral with the casting of the connector ring structure.

[00014] Preferably, opposing sides of the connector ring structure are spaced apart from the opposing internal surfaces of the opposing brake bands. [00015] Preferably, annular spacing between the opposing sides of the connector ring structure and opposing internal surfaces of the opposing brake bands define ventilation entries for air flow through the arrays of pillars.

[00016] Preferably, an outer periphery of the connector ring structure lies approximately midway between the inner ring of pillars and the outer ring of pillars.

[00017] Preferably, the outer periphery of the connector ring structure is shaped so that flows of ventilating air pass through venturi-like constrictions between formations on the opposing internal surfaces of the brake bands and external surfaces of the connecting ring structure thereby increasing volume of cooling air passing between the pillars.

[00018] Preferably, the disc brake rotor is a component of a disc brake rotor assembly; the disc brake rotor assembly comprising the disc brake rotor and a mounting bell for mounting the assembly to a wheel hub of a vehicle.

[00019] Preferably, an inner periphery of the connector ring structure is provided with a number of equally-spaced inwardly directed projections; the projections provided with apertures adapted to receive therethrough headed securing bolts securing the mounting bell to the connector ring structure.

[00020] Preferably, the apertures are elongated slots; elongation of the slots providing for radially sliding movement of the securing bolts in the slots.

[00021] Preferably, an outer periphery of the central mounting bell is provided with apertures for receiving the securing bolts for assembly of the central mounting bell to the connector ring structure.

[00022] Preferably, the opposing brake bands, the arrays of pillars and the connector ring structure form an integral casting with a mounting bell; the mounting bell projecting outwardly from an inner periphery of the connector ring structure.

[00023] In another broad form of the invention, there is provided a method of producing a disc brake rotor of a disc brake; the rotor comprising opposing brake bands separated by arrays of pillars integral with and extending between internal surfaces of the opposing brake bands; the rotor further comprising a connector ring structure integrally connected with an inner ring of pillars of the arrays of pillars; the method including the steps of:

forming two sand cores,

placing the two sand cores back to back in a sand-casting box; the sand-casting box defining outer surfaces of the disc brake rotor,

casting the rotor,

removing the casting from the sand-casting box,

removing sand of the sand cores from the casting. [00024] Preferably, each sand core conforms to a three-dimensional CAD solid model; the solid model defining space between a median plane of the rotor and an internal surface of a brake band of the opposing brake bands and between the arrays of pillars; a portion of an underside of each sand core defining an external surface of the connector ring structure.

[00025] Preferably, a first of the two sand cores conforms to a three-dimensional CAD solid model; the solid model defining space between a median plane of the rotor and an internal surface of an outer one of the opposing brake bands and between the arrays of pillars; the solid model farther defining outward facing surfaces of a mounting bell integral with the connector ring structure.

[00026] Preferably, a second of the two sand cores conforms to a three-dimensional CAD solid model defining space between a median plane of the rotor and an internal surface of an inner one of the opposing brake bands and between the arrays of pillars; the solid model further defining inward facing surfaces of a mounting bell integral with the connector ring structure.

[00027] Preferably, three-dimensional data of the three-dimensional CAD model is used to 3D print the sand core conforming to the three-dimensional solid CAD model.

[00028] Preferably, the rotor is part of a disc brake rotor assembly; the assembly including a mounting bell releasably attached to the connector ring structure.

[00029] In a further broad form of the invention, there is provided a disc brake rotor assembly; the assembly comprising a casting of a rotor and a casting of a mounting bell; the rotor including opposing brake bands separated by arrays of pillars; the pillars integral with, and extending between, opposing internal surfaces of the opposing brake bands; the rotor further comprising a connector ring structure forming an integral casting with the opposing brake bands; the connector ring structure projecting radially outwardly and inwardly from an inner ring of pillars of the arrays of pillars.

[00030] Preferably, casting material of the mounting bell is of lesser density than casting material of the rotor.

[00031] Preferably, the mounting bell is secured to inwardly projecting elements at an inner peripheiy of the connector ring structure; the inwardly projecting elements provided with radially elongated slots.

[00032] Preferably, the mounting bell is provided at its outer periphery with corresponding apertures; headed mounting bolts through the corresponding apertures securing the mounting bell through the radially elongated slots.

[00033] Preferably, the elongated slots provide for differential expansion between the casting of the rotor and the casting of the mounting bell. BRIEF DESCRIPTION OF DRAWINGS

[00034] Embodiments of the present invention will now be described with reference to the accompanying drawings wherein:

[00035] Figure 1 is a perspective view of a disc brake rotor assembly according to a first preferred embodiment of the invention,

[00036] Figure 2 is a front view of a rotor casting of the disc brake rotor assembly of figure 1 showing hidden detail of a pillar array interconnecting opposing brake bands,

[00037] Figure 2A is a perspective view of the rotor casting of figure 2,

[00038] Figure 3 is a sectioned end view of the rotor casting of figures 2 and 2A,

[00039] Figure 4 is an enlargement of a portion of the cross section of figure 3 taken on a radial line through an opposing pair of pillars of the outer ring of pillars,

[00040] Figure 4A is a similar enlarged portion taken on a radial line through an opposing pair of pillars of the inner ring of pillars,

[00041] Figure 5 is a sectioned view of the rotor casting and a central mounting bell fastened to a connector ring structure of the rotor casting,

[00042] Figure 6 is an enlargement of a portion of the sectioned view of figure 5,

[00043] Figure 7 is a perspective view of an outer face of one of a pair of identical sand cores for producing the casting of the rotor of figures 2 through 7,

[00044] Figure 8 is a perspective view of the opposite face of one of the pair of identical sand cores of figure 7,

[00045] Figure 9 is a cross section view of two of the identical and cores of figure 7 placed back to back for casting the rotor of figures 2 through 6,

[00046] Figure 10 is a perspective view of a further preferred embodiment of a disc brake rotor according to the invention,

[00047] Figure 11 is a cross section view of the disc brake rotor of figure 10.

DESCRIPTION OF EMBODIMENTS

First Preferred Embodiment

[00048] With reference to Figures 1 to 6, a disc brake rotor assembly 10 according to this first preferred embodiment of the invention, includes a rotor 12 and mounting bell 13 for mounting to the wheel hub (not shown) of a vehicle. The rotor 12 is comprised of opposing brake bands 14,16 separated by arrays of pillars 18. The pillars 18 are integral with, and extend between, opposing internal surfaces 20,22 of the opposing brake bands as well known in the art.

[00049] The rotor 12 further comprises a connector ring stracture 24 which forms an integral casting with the opposing brake bands 14,16 and with the pillars 18. The connector ring structure 24 projects radially outwardly and inwardly from an inner ring of pillars 26 of the arrays of pillars 18.

It can be seen from figure 2 (and also from figure 4A) that the outer periphery 28 of the connector ring structure 24 lies approximately midway between the inner ring of pillars 26 and the outer ring of pillars 30.

[00050] It is also clear from figure 4A that the connection between the opposing braked bands 14,16 and the connector ring structure 24 is by means of the pillars of the inner ring of pillars 26, so that, in a sense, pillars 26 of the inner ring can be considered as“passing through” the connector ring structure 24, even though the inner pillars and the connector ring form an integral casting.

[00051] With particular reference to figure 2, it can be seen that the inner and outer rings of pillars 26,30 are arranged such that a radial line 32 of the rotor 12 passing through the centre of any pillar of the inner ring of pillars 26 is a bisector of radial lines 34,36 of the rotor passing through centres of adjacent pillars of the outer ring of pillars 30; the adjacent pillars being disposed at opposite sides of the radial line 32.

[00052] As best seen in figure 4, the connector ring structure 24 is sized in thickness so that opposing surfaces 36,38 of the connector ring structure 24 are spaced apart from the opposing internal surfaces 20,22 of the opposing brake bands 14,16 thus providing annular spacing defining ventilation entries for air flow through the arrays of pillars. The design enables even flow of cooling air from both inner and outer directions while maintaining a consistent cross-sectional area throughout the entire diameter of the brake bands.

[00053] It can be seen also from figures 3 and 4 that the periphery 28 of the connector ring structure is shaped so that the flow of ventilating air passes through venturi-like constrictions between formations 40,42 on the internal surfaces of the brake bands 14,16, thereby increasing the velocity and thus volume of cooling air passing between the pillars 18.

[00054] As shown in figures 2 and 4, an inner periphery 44 of the connector ring structure 24, which extends inwardly to project from between the opposing brake bands 14,16, is provided with a number of equally-spaced, inwardly directed projections 46, each provided with an aperture 47 adapted to receive therethrough a headed securing bolt 48 (as shown in figures 1, 5 and 6) for securing the mounting bell 13 to the connector ring structure as shown in figures 5 and 6. The apertures 47 are in the form of elongated slots with the long axes of the slots radially aligned with the centre of the rotor. The width of the apertures 47 is such as to provide sliding fit clearance for the shoulder diameter of the bolts 48 so that the elongation of the slots provides for radially sliding movement of the securing bolts in the apertures to allow for differential thermal expansion of the rotor 12 relative the mounting bell 11. Preferably, the headed securing bolts 48 are threaded and retained by lock nuts 50. [00055] The rotor 12 is produced by casting. Initially, a CAD solid model is prepared which defines the internal space between a median plane 51 of the rotor and the internal surface of a brake band, the pillars of the pillar array, as well as the outer surface of the connector ring structure. The CAD data may be used to produce a mould (not shown) by CNC machining for example or by 3D printing. This mould can then be used to form two identical sand cores, one of which 52 is shown in figure 7. More preferably, two sand cores 52 and 54, two sides of one of which are shown in figures 7 and 8, may be 3D printed directly from the CAD data.

[00056] As shown in figure 9 two such sand cores 52 and 54 are placed back to back, outward facing sides 56,58 to define the internal surfaces 40,42 of the opposing brake bands 14,16 with the apertures 55 (see figures 7 and 8) defining the arrays of pillars 18. Cavities 64 (see figure 8) formed on the respective rear sides 60,62 of the sand cores 52 and 54 combine to define the connector ring structure 24, when the sand cores are placed back to back as shown in figure 9.

[00057] The casting of the mounting bell is in material which is of a lesser density than the casting of the rotor, thereby allowing a significant reduction in the weight of the rotor assembly with the concomitant benefits of health and safety as well as a reduction in the unsprung weight of the vehicle to which the assemblies are fitted.

Second Preferred Embodiment

[00058] In this preferred embodiment with reference now to figures 10 and 11, a disc brake rotor 112 according to the invention, is in the form of a one-piece casting. As in the first preferred embodiment described above, the rotor 100 includes opposing brake bands 114,116 interconnected by arrays of pillars 118, arranged, as above, in an inner ring 126 and outer ring 130.

[00059] In this embodiment also, the rotor 112 also includes a connector ring structure 124 as described for the first embodiment above, projecting inwardly from between the brake bands 114,116, which is integral with the inner ring of pillars 126. The connector ring structure 124 of this embodiment is configured at its outer periphery 128 in the same manner as described above, as can be seen from the cross section view of figure 11.

[00060] In this embodiment however, the connector ring structure 124 forms an integral casting with a mounting bell 113 projecting from the inner periphery 144 of the connector ring structure.

[00061] The method of casting the rotor 100 and its integral mounting bell 113 of this embodiment is similar in principle to that described for the first embodiment above, but with sand cores which now incorporate the form of the mounting bell 113. As before, each of two sand cores are formed from models of the spaces forming the inside regions between the brake bands 114,116, the arrays of pillars 118 and the connector ring, as well as, in this embodiment, the external surfaces of the mounting bell 113, can be derived from the solid CAD modelling of the rotor and the sand cores generated, preferably by 3D printing.

[00062] A first of the two sand cores conforms to a three-dimensional CAD solid model defining the space between a median plane of the rotor and an internal surface of an outer one of the opposing brake bands and between the arrays of pillars. The solid model further defines the outward facing surfaces of the mounting bell 113. The second of the two sand cores conforms to a three- dimensional CAD solid model which defines the space between the median plane of the rotor and an internal surface of the inner brake band, between the arrays of pillars as well as defining the inward facing surfaces of a mounting bell.

Claims

1. A disc brake rotor; the rotor comprising opposing brake bands separated by arrays of pillars; the pillars integral with, and extending between, opposing internal surfaces of the opposing brake bands; the rotor further comprising a connector ring structure forming an integral casting with the opposing brake bands; the connector ring structure projecting radially outwardly and inwardly from an inner ring of pillars of the arrays of pillars.

2. The disc brake rotor of claim 1 wherein the arrays of pillars comprise the inner ring of pillars and an outer ring of pillars.

3. The disc brake rotor of claim 2 wherein a radial line of the rotor passing through the centre of any pillar of the inner ring of pillars is a bisector of radial lines of the rotor passing through centres of adjacent pillars of the outer ring of pillars; the adjacent pillars disposed to opposite sides of the radial line through the centre of the pillar of the inner ring of pillars.

4. The disc brake rotor of claim 2 or 3 wherein connection between the opposing brake bands and the connector ring structure is through the inner ring of pillars; castings of the inner ring of pillars being integral with the casting of the connector ring structure.

5. The disc brake rotor of claim 1 wherein opposing sides of the connector ring structure are spaced apart from the opposing internal surfaces of the opposing brake bands.

6. The disc brake rotor of claim 5 wherein annular spacing between the opposing sides of the connector ring structure and opposing internal surfaces of the opposing brake bands define ventilation entries for air flow through the arrays of pillars.

7. The disc brake rotor of any one of claims 2 to 6 wherein an outer periphery of the connector ring structure lies approximately midway between the inner ring of pillars and the outer ring of pillars.

8. The disc brake rotor of claim 7 wherein the outer periphery of the connector ring structure is shaped so that flows of ventilating air pass through venturi-like constrictions between formations on the opposing internal surfaces of the brake bands and external surfaces of the connecting ring structure thereby increasing volume of cooling air passing between the pillars.

9. The disc brake rotor of any one of claims 1 to 8 wherein the disc brake rotor is a component of a disc brake rotor assembly; the disc brake rotor assembly comprising the disc brake rotor and a mounting bell for mounting the assembly to a wheel hub of a vehicle.

10. The disc brake rotor of claim 9 wherein an inner periphery of the connector ring structure is provided with a number of equally-spaced inwardly directed projections; the projections provided with apertures adapted to receive therethrough headed securing bolts securing the mounting bell to the connector ring structure.

11. The disc brake rotor of claim 10 wherein the apertures are elongated slots; elongation of the slots providing for radially sliding movement of the securing bolts in the slots.

12. The disc brake rotor of claim 10 or 11 wherein an outer periphery of the central mounting bell is provided with apertures for receiving the securing bolts for assembly of the central mounting bell to the connector ring structure.

13. The disc brake rotor of any one of claims 1 to 8 wherein the opposing brake bands, the arrays of pillars and the connector ring structure form an integral casting with a mounting bell; the mounting bell projecting outwardly from an inner periphery of the connector ring structure.

14. A method of producing a disc brake rotor of a disc brake; the rotor comprising opposing brake bands separated by arrays of pillars integral with and extending between internal surfaces of the opposing brake bands; the rotor further comprising a connector ring structure integrally connected with an inner ring of pillars of the arrays of pillars; the method including the steps of:

forming two sand cores,

- placing the two sand cores back to back in a sand-casting box; the sand-casting box defining outer surfaces of the disc brake rotor,

casting the rotor,

removing the casting from the sand-casting box,

removing sand of the sand cores from the casting.

15. The method of claim 14 wherein each sand core conforms to a three-dimensional CAD solid model; the solid model defining space between a median plane of the rotor and an internal surface of a brake band of the opposing brake bands and between the arrays of pillars; a portion of an underside of each sand core defining an external surface of the connector ring structure.

16. The method of claim 14 wherein a first of the two sand cores conforms to a three-dimensional CAD solid model; the solid model defining space between a median plane of the rotor and an internal surface of an outer one of the opposing brake bands and between the arrays of pillars; the solid model further defining outward facing surfaces of a mounting bell integral with the connector ring structure.

17. The method of claim 14 wherein a second of the two sand cores conforms to a three- dimensional CAD solid model defining space between a median plane of the rotor and an internal surface of an inner one of the opposing brake bands and between the arrays of pillars; the solid model further defining inward facing surfaces of a mounting bell integral with the connector ring structure.

18. The method of any one of claims 14 to 17 wherein three-dimensional data of the three- dimensional CAD model is used to 3D print the sand core conforming to the three-dimensional solid CAD model.

19. The method of any one of claims 17 or 18 wherein the rotor is part of a disc brake rotor assembly; the assembly including a mounting bell releasably attached to the connector ring structure.

20. A disc brake rotor assembly; the assembly comprising a casting of a rotor and a casting of a mounting bell; the rotor including opposing brake bands separated by arrays of pillars; the pillars integral with, and extending between, opposing internal surfaces of the opposing brake bands; the rotor further comprising a connector ring structure forming an integral casting with the opposing brake bands; the connector ring structure projecting radially outwardly and inwardly from an inner ring of pillars of the arrays of pillars.

21. The disc brake rotor assembly of claim 20 wherein casting material of the mounting bell is of lesser density than casting material of the rotor.

22. The assembly of claim 20 or 21 wherein the mounting bell is secured to inwardly projecting elements at an inner periphery of the connector ring structure; the inwardly projecting elements provided with radially elongated slots.

23. The assembly of claim 22 wherein the mounting bell is provided at its outer periphery with corresponding apertures; headed mounting bolts through the corresponding apertures securing the mounting bell through the radially elongated slots.

24. The assembly of claim 22 or 23 wherein the elongated slots provide for differential expansion between the casting of the rotor and the casting of the mounting bell.