GB2566710A - Brake disc - Google Patents

Abstract

A vented brake disc (Figure 3, 34) for use in a vehicle (Figure 1, 10), the brake disc comprising two cheeks or plates (Figure 3, 54/56) spaced to form an air gap (Figure 3, 58) there between. The centers of the plates are aligned along a central axis (Figure 3, C), and a plurality of rows of pillars are disposed in the air gap (Figure 5, R), extending orthogonally between opposing faces of the cheeks. The pillars in each row are aligned along a radius (Figure 5, r), the plurality of rows of pillars comprising a first (R1) and second (R2) row of pillars. Within a first row of pillars a first (61) and second pillar (62) are arranged to from a radial gap (80) there between, providing a flow path on to third pillar (63) in an adjacent second row of pillars. The lengths of the pillars are greater that their widths. Further, the brake disc may have a repeating pattern of first and second rows spaced at equal distances around the plates. Also included is a claim to a vented brake disc for use with a caliper, and on a vehicle.

Description

The present disclosure relates to a vented brake disc. Aspects of the invention relate to a brake disc, a brake assembly incorporating the brake disc and to a vehicle incorporating the brake disc or brake assembly.

BACKGROUND

To improve the performance of disc brakes, it is known to provide vented brake discs that incorporate an air gap between two plates or ‘cheeks’ of the brake disc. The air gap creates a greater surface area of vented brake discs which generates a greater cooling effect. The cooling of the brake disc is further enhanced by air flowing through the brake disc air gap and across the ‘internal’ faces of the brake disc. The cheeks of the brake disc are connected by pillars and the design and arrangement of these influence the air flow through the brake disc and the cooling efficiency of the brake disc. The pillars increase the surface area of the brake disc and direct the air flow through the body of the brake disc.

However, pillar arrangements that provide increased surface area can decrease the air flow velocity, as the increased density of the pillars can lead to a higher degree of blockage and therefore reduced air flow velocities within the air gap. Conversely pillars that are arranged to produce improved, directed air flow, such as those with a more elongated cross section, results in a reduced surface area due to the larger pillar sizes.

The present invention has been devised to mitigate or overcome at least some of the above-mentioned problems.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to a brake disc, a brake assembly and a vehicle comprising the brake disc or brake assembly.

According to an aspect of the present invention there is provided a vented brake disc for use in a vehicle, the brake disc comprising: two cheeks spaced to form an air gap therebetween, wherein the centres of the cheeks are aligned along a central axis; and a plurality of rows of pillars disposed in the air gap and extending orthogonally between opposing faces of the cheeks; wherein the pillars in each row are aligned along a radius; the plurality of rows of pillars comprising: a first row of pillars comprising: a first pillar, situated on a radially innermost position on the first row, and a second pillar, situated radially adjacent to the first pillar, a second row of pillars comprising: a third pillar, situated on a radially innermost position on the second row, wherein the first pillar and the second pillar form a radial gap therebetween, and the third pillar is positioned at a radial distance greater than a radial distance of the first pillar and less than or equal to a radial distance of the second pillar, such that the radial gap formed between the first pillar and the second pillar form an air passage facilitating air flow on to the third pillar, and wherein the lengths of the first, second and third pillars are greater than their respective widths;

Advantageously, this arrangement of pillars within a brake disc enhances the cooling effect of the brake disc by increasing the surface area across which cooling air is able to flow. In addition, the air passage formed by the radial gap provides for increased air velocities and therefore increased heat transfer and more efficient cooling of the brake disc.. Furthermore, the brake disc is non-handed, ensuring that the brake disc can be mounted on either side of the vehicle without the requirement of specific tailoring. This reduces manufacturing costs as well as the likelihood of mounting the disc incorrectly.

The remaining rows may form a repeating pattern of the first and second rows.

The rows may be uniformly distributed within the airgap.

The angular separation between adjacent radii may be equal for all adjacent radii.

The first row may contain at least one more pillar than the second row.

The first row may comprise four pillars and the second row may comprise 3 pillars

The third pillar may be radially offset from the second pillar such that an innermost end of the third pillar extends radially inwardly of the radial gap.

The first and second pillars may comprise a single pillar with the radial gap formed in its centre.

The pillars may be arranged as a radially innermost group and a radially outermost group, wherein the dimensional characteristics of the radially innermost pillars differs to those of the radially outermost pillars.

The width of the radially innermost pillars may be less than the width of the radially outermost pillars.

The radially innermost pillars may be stadium-like in cross section.

The radially outermost pillars may be elliptical in cross section.

The radially outer most pillar of the first row may have a radially outermost point at an equal radial distance from the central axis as a radially outermost point of a radially outermost pillar of the second row.

According to another aspect of the present invention, there is provided a brake assembly for a vehicle, the brake assembly comprising a vented brake disc according to the preceding aspect of the invention.

According to another aspect of the present invention, there is provided a vehicle comprising at least one brake disc or one brake assembly according to the preceding aspects of the invention.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective of a vehicle incorporating a vented brake disc according to an embodiment of the invention;

Figure 2 is a cross-sectional diagram of a wheel assembly of the vehicle of Figure 1 according to an embodiment of the invention;

Figure 3 is a perspective view of a brake disc according to an embodiment of the invention forming part of the corner assembly of Figure 2;

Figure 4 is a cross-sectional view of a pillar forming part of the brake disc of Figure 3;

Figure 5 is a plan view of a cheek of the brake disc forming part of the brake disc of Figure 3, with radii overlaid indicating rows of pillars;

Figure 6 is an enlarged view of Figure 5 with only two radii shown indicating rows of pillars;

Figure 7 is a plot of the air velocity magnitude temperature within the brake disc of Figure 3.

Figure 8 is a plot of the characteristic temperature within the brake disc of Figure 3.

DETAILED DESCRIPTION

Figure 1 shows a perspective view of a vehicle 10 that incorporates a brake disc (not shown in Figure 1) according to an embodiment of the invention. The vehicle 10 includes a pair of front suspension corner assemblies 12 (left and right) and a pair of rear suspension corner assemblies 14 (left and right), only the right hand ones of which are shown here.

Each suspension corner assembly 12, 14 includes a wheel assembly comprising a wheel 16 onto which a tyre 18 is mounted, the wheel 16 being connected to a rotatable axle (not shown in Figure 1) and housed within a respective wheel arch 20 in a conventional manner.

Figure 2, which is not to scale and has been slightly simplified to improve the clarity of the figure, shows a cross sectional representation of a wheel assembly of the vehicle 10, referred to generally as 22. Considering both Figures 1 and 2, the wheel assembly 22, which is housed within an associated wheel arch 20 of the vehicle 10, includes a wheel 16, a tyre 18 and a brake assembly 24, where the wheel assembly 22 is rotatable about a front axle 26 of the vehicle 10. Although not shown here, the wheel assembly 22 forms part of the front or rear suspension corner assembly 12, 14 and so is mounted to and interacts with other components related to the suspension of the vehicle 10.

The wheel 16 includes a circular, central portion 28 that is connected to the wheel hub 30 via a mount 32 of a brake disc 34 by a plurality of fixings 36 extending through both the central portion 28 of the wheel 16 and the wheel hub 30. The wheel hub 30 is fixed to the front rotatable axle 26.

The axis of rotation C of the wheel assembly 22 is arranged so that it lies along the axis of rotation of the axle 26.

The wheel 16 further comprises a plurality of spokes 38, extending radially outwardly from the central portion 28 of the wheel 16, and an annular rim 40 that encircles the spokes 38 and central portion 28. The spokes 38 connect to the central portion 28 of the wheel 16 at one end 42 and extend radially outwardly from the central portion 38 to connect to an inner face 44 of the rim 40 at their opposite, distal ends 46.

The rim 40 incorporates an outwardly facing recess 48 for receiving a portion of a tyre 18 to be mounted on the wheel 16. The rim 40 also surrounds a cavity 52 in which other components of the wheel assembly 22 are housed, such as the hub 30 and the brake assembly 24.

The brake disc 34 comprises a pair of annular cheeks 54, 56 spaced apart from one another to form an air gap 58 between the cheeks 54, 56 so that, in use, air flows over a greater surface area of the disc 34 as would ordinarily flow over a solid brake disc that did not have two cheeks. The cheeks 54, 56 are spaced apart, and the air gap 58 maintained, using an internal structure having a plurality of pillars 60. The internal structure defines an air flow path for allowing air flow radially outwardly through the brake disc 34, as will be discussed later.

The brake disc mount 32 is connected to one of the cheeks 56. The mount 32 incorporates a plurality of fixing holes (not shown) through which the wheel fixings 36 may be passed. The wheel hub 30 is configured to sandwich the mount 32 between it and the central portion 28 of the wheel 16. The wheel fixings 36 fix the hub 30 and brake disc 34 to the wheel 16, so that when the hub 30 rotates, both the wheel 16 and the brake disc 34 rotate too.

Other configurations of the wheel hub and axle relative to the brake disc, as well as configurations of other known components, are equally compatible with the present invention.

Each brake assembly 24 additionally comprises a calliper 62. The brake assembly is required to enable slowing or stopping of the vehicle 10, and this is implemented by using the calliper 62 to apply a force to the brake disc, creating friction to reduce the rotational speed of each wheel 16 and tyre 18. However, applying friction to the brake disc converts the rotational kinetic energy to heat energy that must be efficiently dissipated from the brake disc to reduce the likelihood of adverse effects due to overheating. The brake disc of the invention, improves the cooling efficiency of the system, thereby allowing for a higher level of performance by the brake system. To implement a braking action on the rotating brake disc 34 and wheel 16, the calliper 62 exerts an inward force on the outer faces of the cheeks 54, 56.

As illustrated by Figure 3, each cheek 54, 56 of the brake disc 34 is annular in shape, and both cheeks 54, 56 are arranged to surround a main, or central, axis C of the wheel assembly 22, such that the centres of the cheeks 54, 56 are aligned with the main axis C, the plane of each cheek 54, 56 being perpendicular to the main axis. The main axis passes directly through the central point, and point of rotational symmetry, of the annular cheeks 54, 56. The axis C is the axis about which the axle 26 and the wheel hub 30 rotate, as shown in Figure 2.

Both cheeks 54, 56 are of identical diameter and are aligned so that the air gap 58 between the cheeks 54, 56 is constant across the full radial extent.

The pillars 60 disposed within the air gap 58 will now be described. The shape of the individual pillars 60 will be considered with reference to Figure 4, while the arrangement of pillars 60 on the brake disc 34 will be discussed with reference to Figures 5 and 6.

In characterising the pillars 60: width refers to the dimension of the pillar parallel to the tangent of the circumference of the cheeks 54, 56; length refers to the dimension extending radially from the central axis C; and depth refers to the dimension of the pillars orthogonal to the inner surfaces 55, 57 of the cheeks. Each of these refer to the dimension where it intersects the centre point of all three axes of the pillar 60.

As illustrated in Figure 4, each individual pillar 60 flares at either end to provide a draft angle with the inner surface 55, 57 of each cheek 54, 56 between which the pillars 60 extend orthogonally. The width of each pillar 60 is thus smallest at the centre point along its depth. Each pillar 60 extends orthogonally between the cheeks 54, 56 of the brake disc 34 and across the air gap 58 between the cheeks 54, 56. As the air gap 58 formed between the cheeks 54, 56 of the brake disc 34 is constant, and each pillar 60 extends from the inner surface 55 of one cheek 54 to the inner surface 57 of the opposite cheek 56, the depth of each pillar 60 is identical.

Manufacturing the brake disc 34 comprises a casting or moulding process. Incorporating a draft angle on the pillars 60 ensures that a disc core, which is used to form the air gap 58 and pillars 60 when manufacturing the brake disc 34, can be removed safely from the brake disc 34 without damage.

Turning now to Figures 5 and 6, which both illustrate the same arrangement of pillars 60 relative to one cheek 54 of the brake disc 34, it can be seen that the pillars 60 are arranged in to a plurality of rows R corresponding to radii r which lie on the plane of the inner cheek surface 55. The radii r are uniformly distributed about the inner cheek surface 55 and the rows R repeat in pairs. This arrangement advantageously improves air flow and the cooling efficiency of the brake disc 34 once fully assembled.

Additionally, the arrangement is devised so that each brake disc 34 is non-handed, and can therefore be fitted to either side of a vehicle 10. This significantly reduces manufacturing costs and time, and reduces the risk of errors in fitting.

The pillars 60 within the rows R can be broadly split into groups of radially innermost pillars 91 and radially outermost pillars 92. The pillars 60 have varying cross sections, but are all rounded in some form and have a length greater than their width. The innermost pillars 91 are narrower and have a stadium-like cross section, whereas the outermost pillars 92 are wider and have a more elliptical cross section. The width of the pillars 60 increases within each row R, starting from the pillar 60 at a radially innermost position to a pillar 60 at a radially outermost pillar.

In more detail, a first row R1 of pillars 60 is arranged on a first radius r1, In this example there are four pillars 61, 62, 64, 65 within the row R1, however this may be varied in dependence on the sizing of the disc and the pillars.

A second row R2 of pillars 60 is arranged on a second radius r2 adjacent to the first radius r1. In this and other examples there is one less pillar in R2 than in R1, in this example there are therefore three pillars 63, 66, 67 in the second row R2.

A first pillar 61 is situated as the radially innermost pillar in the first row R1. A second pillar 62 is situated adjacent to the first pillar 61, at a more outwardly radial position, within the first row R1. The spacing of the second pillar 62 with respect to the first pillar 61 forms a radial gap therebetween. The radial gap 80 extends radially between the first pillar 61 and the second pillar 62. The radial gap 80 may be an uninterrupted empty region between the first and second pillars 61, 62, with no other pillars 60 obstructing the gap.

A third pillar 63 is situated as the radially innermost pillar in the second row R2. This position places it in a more radially outward position than the first pillar 61 and a more radially inward position than the second pillar 62. The third pillar therefore radially overlaps with the radial gap 80. The radial gap 80 has a length that is smaller than the length of the first, second and third pillars 61, 62, 63, which are substantially equal in length. The radial gap 80 therefore forms an air passage allowing air flow on to the third pillar 63, whilst the first and second pillar are arranged with a close enough proximity to simulate the effect of a single pillar having a greater length, directing more air flow in a radially outward direction through the air gap 58.

In some examples the third pillar 63 may be at the same radial distance as the second pillar 62.

The first, second and third pillars 61, 62, 63 all have a stadium-like cross section as with the rest of the radially innermost pillars 91. The remaining pillars 64, 65, 66, 67 in the first and second rows R1, R2 are more elliptical in cross-section as with the rest of the radially outermost pillars 92. The radially outermost 92 pillars are substantially similar in cross section with the exception of the radially outermost pillar 65 of the first row R1. This pillar 65 has a shorter length than the others, such that its most radially outer point is at a substantially equal radial position as the most radially outer point of the radially outermost pillar 67 of the second row R2.

The pillars of the first row R1 are radially offset from their corresponding pillars in the second row R2. These pillar pairs can be seen to be formed as 62 & 63, 64 & 66 and 65 & 67. The radially innermost point of the pillars 63, 66, 67 of the second row R2 are at more radially inwards position than their corresponding pillars 62, 64, 65 in the first row R1. The first pillar has no corresponding pillar within the second row R2.

In some examples, the pillars 60 have widths of less than 10mm. In some examples the radially innermost pillars may have widths greater than 3mm and less than 5mm. The radially outermost pillars 92 may have widths greater than 4.5mm and less than 6.5mm. In one example, the first and second pillars 61, 62 have widths of 3.5mm, the third pillar 63 has a width of 4mm, the pillars at the next radial position 64, 66 have widths of 5mm and the final pillars 65, 67 have widths of 6mm.

In some examples, the pillars are expected to have lengths of less than 20mm with the radially outermost pillar 65 of the first row R1 having a length less than 15mm. In some examples the radially outermost pillar 65 of the first row R1 may have a length greater than 8mm and less than 11 mm. The remaining pillars 61,62, 63, 64, 66, 67 may have a length greater than 10 mm and less than 15 mm. In one example, the radially outermost pillar 65 of the first row R1 has a length of 10mm, the first and second pillars have a length or 11.2 mm, the third pillar has a length of 10.5mm, the pillars at the next radial position 64, 66 have lengths of 12.5mm and the radially outermost pillar 67 of the second row R2 has a length of 14mm.

In some examples, the radial gap 80 is expected to be less than 12mm. In some examples, the radial gap 80 is expected to be greater than 4mm and less than 8mm. In one example, the radial gap is 6 mm.

In some examples the gaps between other radially adjacent pillars 60 may be substantially equal to the radial gap 80. In other examples they may be longer or shorter in dependence on the number of pillars 60 in a row R, the length of the pillars 60 and the diameter of the brake disc 34.

These dimensions provide for a pillar density and pillar shapes that provide improved air flow and a surface area to volume ratio. The dimensions of the pillars 60 and the radial gap 80 will be dependent on the size of the brake disc 34 and its cooling requirements. The greater the surface area to volume ratio the better the heat transfer, which however must be balanced with manufacturing constraints, such as minimum pillar and gap sizes.

In some examples, the outer pillar is positioned at least 5mm from the edge of the outer edge of the brake disc.

The first and second rows R1, R2 are repeated in a uniform pattern, ie: R1, R2, R1, R2, R1 etc, such that each first row R1 has a second row R2 adjacent to it on either side, and each second row R2 has a first row R1 adjacent to it on either side.

An even number of radii r are distributed uniformly about the inner cheek surfaces 55, 57, such that all the radii r are spaced at equal angles from those that are adjacent. In some examples there are greater than 50 rows and less than 90 rows. In some examples the angular separation between adjacent radii r is greater than 0.07 radians and less than 0.12 radians. For example, in one example there are 74 rows R (37 corresponding to the arrangement of the first row R1 and 37 corresponding to the arrangement of the second row R2) arranged on respective radii, and therefore have an angular separation of approximately 0.085 radians between adjacent radii r.

The brake disc 34 may comprise any number of rows R of pillars 60, and thus any number of radii r on the inner cheek surfaces 55, 57 of which the rows R pillars 60 are arranged. The number of rows R and the number of pillars 60 within a row R are parameters defined by the available surface area of the brake disc 34, the pillar widths and lengths, and the minimum spacing required between pillars.

The use of pillars in this manner means that one design of brake disc can be produced and used on both sides of a vehicle. The pattern of pillars reduces the amount of stagnant air within the air gap between the cheeks, while improving the transfer of heat from the disc to the air flowing through the air gap.

The effect of the arrangement of the pillars 60 when the brake disc 34 is in use will now be described with respect to figures 7 and 8. Both of these figures show models of the brake disc rotating in an anti-clockwise direction and the air flow within the air gap 58 will therefore be in a predominantly clockwise direction. The air flow will also be in a radially outward direction as the air intake is directed at the centre of the disc 34.

According to the principle of mass continuity; the rate at which a mass of a fluid enters and leaves a system, i.e. the air flow rate, must remain constant. This therefore results in an increase in fluid velocity and a decrease in pressure when the fluid flow enters a constriction or choke point, in what is known as the Venturi effect. Therefore as the air flow within the air gap 58 traverses the radial gap 80 its local velocity increases within the region relative to the surrounding air flow. This provides a higher velocity air flow in the anti-clockwise facing face of the third pillar 63, highlighted as region A in figures 7 and 8.

An increased velocity at a point will result in improved heat transfer in a form of forced convection. Figure 8 provides a characteristic temperature profile, highlighting the cooling benefits of the pillars 60 in general, and more specifically the radial gap 80 and its benefits to the cooling in the region adjacent to the third pillar 63, also shown as region A in figure 8.

It will be appreciated that any size of pillars, any number of rows, and any number of pillars per row are possible providing an adequate air flow passage is made available to achieve the desired cooling flow between the cheeks. The numbers here depend upon the size of the disc and the manufacturing tolerances available.

It is also envisaged that the air gap 58 may have a width of greater than 7mm. It is possible for an air gap to have a width in the range from 7mm to 25mm, and the air gap may have a width greater than these measurements depending upon the diameter of the cheeks. The thickness of the cheeks may be designed to be greater than 7mm, and may fall in the range of 8mm to 13mm. The designed thickness will be dependent upon the forces and stresses expected to be exerted upon and exerted by the disc.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.

Claims (15)

1. A vented brake disc for use in a vehicle, the brake disc comprising:

two cheeks spaced to form an air gap therebetween, wherein the centres of the cheeks are aligned along a central axis; and a plurality of rows of pillars disposed in the air gap and extending orthogonally between opposing faces of the cheeks;

wherein the pillars in each row are aligned along a radius; the plurality of rows of pillars comprising:

a first row of pillars comprising:

a first pillar, situated on a radially innermost position on the first row, and a second pillar, situated radially adjacent to the first pillar, a second row of pillars comprising:

a third pillar, situated on a radially innermost position on the second row, wherein the first pillar and the second pillar form a radial gap therebetween, and the third pillar is positioned at a radial distance greater than a radial distance of the first pillar and less than or equal to a radial distance of the second pillar, such that the radial gap formed between the first pillar and the second pillar form an air passage facilitating air flow on to the third pillar, and wherein the lengths of the first, second and third pillars are greater than their respective widths.

2. A brake disc according to claim 1 wherein the remaining rows form a repeating pattern of the first and second rows.

3. A brake disc according to claims 1 or 2 wherein the rows are uniformly distributed within the airgap.

4. A brake disc according to any preceding claim wherein the angular separation between adjacent radii is equal for all adjacent radii.

5. A brake disc according to any preceding claim wherein the first row contains at least one more pillar than the second row.

6. A brake disc according to any preceding claim wherein the first row comprises four pillars and the second row comprises 3 pillars.

7. A brake disc according to any preceding claim wherein the third pillar is radially offset from the second pillar such that an innermost end of the third pillar extends radially inwardly of the radial gap.

8. A brake disc according to any preceding claim wherein the first and second pillars comprise a single pillar with the radial gap formed in its centre.

9. A brake disc according to any preceding claim wherein the pillars are arranged as a radially innermost group and a radially outermost group, wherein the dimensional characteristics of the radially innermost pillars differs to those of the radially outermost pillars.

10. A brake disc according to claim 9 wherein the width of the radially innermost pillars is less than the width of the radially outermost pillars.

11. A brake disc according to claims 9 or 10 wherein the radially innermost pillars are stadium-like in cross section.

12. A brake disc according to any of claims 9 to 11 wherein the radially outermost pillars are elliptical in cross section.

13. A brake disc according to any preceding claim wherein a radially outer most pillar of the first row has a radially outermost point at an equal radial distance from the central axis as a radially outermost point of a radially outermost pillar of the second row.

14. A brake assembly for a vehicle, the brake assembly comprising the vented brake disc of any preceding claim and a brake calliper.

15. A vehicle comprising at least one brake disc according to any of claims 1 to 13 or at least one brake assembly according to claim 14.