GB2583457A

GB2583457A - A brake disc cover

Info

Publication number: GB2583457A
Application number: GB1904751.3A
Authority: GB
Inventors: Hadley Ian
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2019-04-04
Filing date: 2019-04-04
Publication date: 2020-11-04
Anticipated expiration: 2039-04-04
Also published as: GB201904751D0; GB2583457B

Abstract

A brake disc cover 20 comprises an outboard portion 30 which receives a filter (34, fig 5), and an inboard portion 60 which fits together with the outboard portion 30 to form the brake disc cover 20. The inboard portion 60 defines an inboard air volume 64, and the outboard portion 30 defines an outboard air volume (40). A dust funnel 67 is in fluidic communication with a first opening (84) of a passage 80 which passes over an outside edge 12 of a brake disc. The passage 80 fluidically connects the inboard air volume 64 to the outboard air volume (40). In use, airflow from the outboard air volume (40) exits the brake disc cover 20 via the filter (34), and part of the airflow from the inboard air volume 64 passes along the passage 80 and exits the brake disc cover 20 via the outboard air volume (40) and the filter (34). The outboard portion 30 comprises at least one vane (56) which directs outboard airflow towards the filter (34). Reference is also made to a vehicle having the brake disc cover.

Description

A BRAKE DISC COVER

TECHNICAL FIELD

The present disclosure relates to a brake disc cover. Aspects of the invention relate to a brake disc cover and to a vehicle comprising a brake disc cover.

BACKGROUND

Motor vehicle braking systems commonly comprise iron, or to a lesser extent, steel, aluminium or composite brake discs which are attached to the wheels of the vehicle such that they rotate with the wheels. Brake calipers comprising opposing brake pads are arranged around the brake discs. In braking, the brake pads are brought into frictional engagement with the brake disc by hydraulic actuators within the calipers, thus resisting the continued rotation of the brake disc, and hence the wheel. The majority of the dissipated kinetic energy is transformed to heat.

The action of braking causes wear to the brake pads and discs generating particulate matter commonly referred to as brake dust. Brake dust comprises particles of coarse, fine and ultra-fine material which can build-up on alloy wheels leading to discolouration and customer dissatisfaction. The particles may also enter the environment outside of the vehicle potentially adding to environmental pollution.

It is known to fit vehicles with devices designed to filter brake dust out of the airflows surrounding the brake disc in use before it can reach the environment. Existing solutions which involve arranging filters or vacuum equipment around the brake disc are thought to be very limited in how effective they are in capturing brake dust (some having undergone computational fluid dynamics (CFD) study carried out by the applicant). Some are also known to significantly degrade brake disc cooling by shrouding the disc, also indicated by the applicant's CFD analysis.

It is an aim of the present invention to address one or more of the disadvantages associated

with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a brake disc cover and to a vehicle comprising a brake disc cover.

According to an aspect of the present invention there is provided a brake disc cover comprising an outboard portion and an inboard portion, wherein the outboard portion is configured to receive a filter, the brake disc cover being configured so that, in use, the outboard portion is located substantially on an outboard side of a brake disc, and the inboard portion is located substantially on an inboard side of the brake disc, wherein the inboard portion defines an inboard air volume located between an inboard side of the brake disc and the inboard portion, and the outboard portion defines an outboard air volume located between an outboard side of the brake disc and the outboard portion, wherein the brake disc cover comprises a passage which defines a first fluidic communication path between a first passage opening and a second passage opening, the first passage opening being configured, in use, for fluidic communication with the inboard air volume, and the second passage opening being configured, in use, for fluidic communication with the outboard air volume, wherein the passage extends from the first passage opening to the second passage opening over an outer edge of the brake disc, wherein the brake disc cover is configured so that, in use, at least part of an outboard airflow from the outboard air volume exits the brake disc cover via the filter, and at least a first part of an inboard airflow from the inboard air volume passes along the passage from the first passage opening to the second passage opening and exits the brake disc cover via the outboard air volume and the filter. In an example, the outboard portion comprises a filter.

Optionally the outboard portion of the cover may comprise at least one vane configured so that, in use, the at least part of the outboard airflow is directed towards the filter by the at least one vane.

The filter optionally comprises a first part and a second part, wherein the brake disc cover is configured so that, in use, the at least a part of the outboard airflow exits the brake disc cover via the first part of the filter, and the at least first part of the inboard airflow exits the brake disc cover via the second part of the filter. The first part of the filter may comprise one or more discrete filter elements, and the second part of the filter may comprise one or more discrete filter elements. Optionally the filter is arcuate in form and wherein the first part of the filter is located radially inward of the second part of the filter.

The outboard portion may optionally comprise a first wall which divides the outboard air volume into a first zone and a second zone, wherein the first part of the filter is located substantially within the first zone, and the second part of the filter is located substantially within the second zone.

The outboard portion may also comprise at least one second wall which divides the second zone into a plurality of sub-zones, wherein the passage comprises a manifold configured so that the second passage opening communicates only with a first number of sub-zones such that, in use, the at least first part of the inboard airflow flows along the passage and out of the brake disc cover via the first number of sub-zones.

Optionally the brake disc cover is configured so that, in use, at least a second part of the inboard airflow passes over the outer edge of the brake disc via a second fluidic communication path and exits the brake disc cover via the filter.

The brake disc cover is optionally configured so that, in use, the at least a second part of the inboard airflow exits the brake disc cover via the second part of the filter.

The at least a second part of the inboard airflow may exit the brake disc cover via a second number of the sub-zones.

Optionally the inboard portion comprises an inboard peripheral wall configured, in use, to prevent at least a part of the brake dust produced during vehicle braking from exiting the brake disc cover towards an inboard side of a vehicle.

The inboard portion may optionally comprise an inlet configured, in use, to receive air flow from a brake cooling system.

The outboard and inboard portions optionally fit together so that, in use, the brake disc cover encloses a substantial portion of the brake disc. The brake disc cover may substantially enclose the brake caliper.

Optionally the brake disc cover is configured so that, in use, the filter is located rotationally downstream of the brake caliper with respect to the rotational direction of the brake disc when the vehicle is travelling forwards.

Optionally the brake disc cover may be configured so that the at least first part of the inboard airflow exits the second passage opening into the outboard airflow.

In another aspect there is provided a vehicle comprising a brake disc cover as described above.

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 shows a vehicle in accordance with an embodiment of the invention; Figure 2 shows a side view of a brake disc cover, in accordance with an embodiment of the invention, mounted on a vehicle brake assembly; Figure 3 shows a perspective view of the inboard side of the brake disc cover of Figure 2, when mounted on a vehicle brake assembly; Figure 4 shows a perspective view of part of the inboard side of the brake disc cover of Figure 2 when not mounted on a vehicle brake assembly; Figure 5 shows a perspective view of the interior of an outboard portion of the brake disc cover of Figure 2 when not mounted on a vehicle brake assembly; Figure 6 shows a sectional perspective view of the brake disc cover of Figure 2, with a section removed along the line X-X as shown in Figure 2; Figure 7 shows a perspective view of the interior of an inboard portion of the brake disc cover of Figure 2 when not mounted on a vehicle brake assembly; and Figure 8 shows a perspective view of the brake disc cover corresponding to the view of Figure 3 with fluidic communication paths and air flows depicted.

DETAILED DESCRIPTION

Figure 1 shows a vehicle 1 having a front end 3 and a rear end 5 and comprising a brake assembly 2 located at each wheel 4 of the vehicle 1 for slowing or stopping the vehicle 1 (only two of four wheels are shown in Figure 1). Each brake assembly 2 comprises a brake disc 6 attached to a wheel 4, and a brake caliper 8 arranged around a portion of the brake disc 6.

The brake calipers 8 are attached to the suspension knuckle (not shown) of the vehicle 1 to provide a reaction force during braking. The brake discs 6 are rigidly fixed to the hubs of the wheels 4 such that the wheels 4 and the brake discs 6 rotate together. The brake calipers 8 house hydraulically actuated brake pads (not shown) which are typically made of a high friction material. The brake pads are positioned on either side of the brake discs 6 by the brake calipers 8 such that actuation of the brake pads by the hydraulic actuators causes the brake pads to clamp against the brake discs 6 to slow or stop the rotation of the wheels 4.

Referring now to Figures 1, 2 and 3, a brake disc cover 20 is shown mounted on brake assembly 2 located on a wheel 4 at the front end 3 of the vehicle. For the sake of clarity, only one brake assembly 2 is described below. However, it will be understood that the same arrangement of brake assembly 2 and brake disc cover 20 is provided at the other front wheel 4 of the vehicle 1.

The brake disc cover 20 comprises an outboard portion 30 and an inboard portion 60 which may be formed as two or more separate parts which fit together during assembly of the vehicle 1 to form the complete brake disc cover 20. Alternatively, the brake disc cover 20 may be retrofitted to an existing brake assembly 2. In use, the brake disc cover 20 surrounds at least part of both the inboard 7a and outboard 7b sides of the brake disc 6 and the brake caliper 8, where the inboard side 7a of the brake disc 6 is that facing into the vehicle 1, and the outboard side 7b of the brake disc 6 is that facing away from the vehicle 1.

The outboard portion 30 of the brake disc cover 20 is formed as a single moulded or pressed part comprising two main regions. The first region comprises a caliper shell 58 and the second region comprises an outboard shell 31. The caliper shell 58 is shaped to fit over the brake caliper 8 in close conformity, in use, when the brake disc cover 20 is mounted on the brake assembly 2. As shown in the Figures, the caliper shell 58 substantially encloses the brake caliper 8. In the example shown, the caliper shell 58 encloses the brake caliper 8. However, in certain embodiments, the fraction of the brake caliper 8 enclosed by the caliper shell 58 may be as little as 50%.

The outboard shell 31 is curvilinear in form and extends from the caliper shell 58 across the top of the brake disc 6 to a position below a horizontal centreline H-H of the brake disc 6 such that a substantial portion of the outboard side 7b of the brake disc 6 is covered by the outboard portion 30 of the brake disc cover 20. In the example shown, approximately 70% of the outboard side 7b of the brake disc 6 is covered by the outboard portion 30 of the brake disc cover 20. However, in certain embodiments of the invention, the outboard portion 30 may not cover a substantial portion of the outboard side 7b and in some embodiments as little as 20% of the outboard side 7b may be covered by the outboard portion 30 of the brake disc cover 20. In other examples, up to 100% of the outboard side 7b may be covered.

The outboard shell 31 comprises a filter section 29 and a cooling section 28. The filter section 29 extends from the caliper shell 58 across the top of the brake disc 6 to a position past a vertical centreline V-V of the brake disc 6, and the cooling section 28 extends from the end of the filter section to the furthest circumferential extremity 26 of the outboard shell 31 with respect to the caliper shell 58.

The filter section 29 of the outboard shell 31 comprises an outboard peripheral wall 32 which has a substantially planar region 37, a curvilinear outer edge region 35, and a curvilinear inner edge region 27 (Figure 5). The planar region 37 is crescent shaped and orientated such that it is substantially parallel to the outboard side 7b of the brake disc 6. The curvilinear outer edge region 35 extends from an outer radial edge 39 of the planar region 37 towards the inboard side 7a of the brake disk 6 in use, and the curvilinear inner edge region 27 (Figure 5) extends from an inner radial edge 25 of the planar region 37 towards the inboard side 7a of the brake disk 6 in use. A plurality of vents 33 extend substantially across the width of the planar region 37 of the outboard peripheral wall 32 in a radial direction with respect to the brake disc 6.

Figure 4 shows a perspective view of part of the brake disc cover 20 when not mounted on a vehicle brake assembly 2 with the outboard portion 30 and inboard portion 60 fitted together.

Figure 5 shows a similar perspective view to that of Figure 4 with part of the inboard portion removed for clarity. As shown most clearly in Figure 5, a first interior wall 44 extends from the caliper shell 58 to the cooling section 28. The first interior wall 44 is substantially curvilinear in from and substantially parallel to the outer edge region 35 and inner edge region 27 of the outboard peripheral wall 32 (Figure 2). Two second interior walls 50 extend in a radial direction with respect to the brake disc 6 in use from the first interior wall 44 to the outer edge region of the outboard peripheral wall 32. Three vanes 56 project from an inner surface of the planar region 37 (Figure 2) of the outboard peripheral wall 32 in a curved path towards the caliper shell 58. The distal ends 24 of the vanes 56 are substantially in line with the innermost edges of the first interior wall 44 and the inner edge region 27 of the outboard peripheral wall 32.

A filter 34 is located adjacent to the inner surface of the planar region 37 of the outboard peripheral wall 32. The filter 34 comprises a first part 36 located radially inward of the first interior wall 44 and a second part 38 located radially outward of the first interior wall 44. The filter 34 comprises two layers (not shown), a coarse layer for filtration of coarser brake dust particles and a fine layer for filtration of finer brake dust particles. The filter 34 is removable and replaceable. If desired only the first part 36 or second part 38 of the filter 34 may be removed and replaced at any one time. However, both parts would normally be removed and replaced at the same time during routine servicing of the vehicle 1. The filter 34 may comprise a single filter which comprises cut-outs for the vanes 56 and which fits behind a gap between the first 44 and second 50 interior walls and the inner surface of the planar region 37 of the outboard peripheral wall 32. Alternatively, the vanes 56 may be flush with the inboard face of the filter so that one simple single filter block or pad without cut-outs for the vanes 56 could be accommodated. However, it is envisaged that the filter 34 comprises two discrete filter elements for ease of fitting.

The outboard peripheral wall 32 provides an outboard boundary which defines an outboard air volume 40 (Figure 4). The outboard air volume 40 is also bounded, in use, by the outboard side 7b of the brake disc 6. It will be understood that the outboard air volume 40 is not a sealed air volume, but rather is a volume of air located between the outboard side 7b of the brake disc 6 and outboard portion 30 of the brake disc cover 20 in use.

The outboard air volume 40 is separated into a first zone 46 and a second zone 48 by the first interior wall 44, wherein the first zone 46 is located radially inward of the first interior wall 44 and the second zone 48 is located radially outward of the first interior wall 44. Consequently, the first part 36 of the filter 34 located substantially within the first zone 46 and the second part 38 of the filter 34 located substantially within the second zone 48. It will be understood that some of the filter 34 may be located outside of the first 46 and second 48 zones. For example, the filter 34 may overlap the first interior wall 44 or the outer edges of the first 46 and second 48 zones. The second zone 48 is further subdivided into three sub-zones 51 by the radially extending second interior walls 50.

The cooling section 28 of the outboard portion 30 comprises an outboard air duct 59 for receiving air from a brake cooling system in use as will be described further below.

Referring back to Figures 3 and 4, the inboard portion 60 of the brake disc cover 20 attaches to the suspension knuckle (not shown) by means of fasteners 61. The inboard portion 60 is substantially C-shaped and, in use, substantially surrounds the portion of the inboard side 7a of the brake disc 6 that is not covered by the brake caliper 8. The inboard portion 60 is formed of a single moulded or pressed part which, in use, extends from an upper portion 57 of the caliper shell 58 to a lower portion 55 of the caliper shell 58, following the curve of the brake disc 6.

A lower region 63 of the inboard portion 60 comprises an inboard peripheral wall 62 which extends from the lower portion 55 of the caliper shell 58 to a position near the horizontal axis H-H (Figure 2) of the brake disc 6. An upper region 65 of the outboard portion 60 comprises an inlet opening 70 for receiving an airflow in use, in this case cooling air from a brake cooling system. An inlet wing 72 is provided at the mouth of the inlet opening 70 to assist in funnelling the cooling air into the brake disc cover 20 in use. An edge wing 73 is configured to direct some of the cooling air flow across an outer edge 12 of the brake disc 6 towards the outboard air duct 59.

The upper region 65 of the inboard portion 60 also comprises a dust funnel 67 located adjacent to the upper portion 57 of the caliper shell 58. The dust funnel 67 defines an inboard air volume 64 which is bounded by an inboard peripheral funnel wall 69 of the dust funnel 67, and by the inboard side 7a of the brake disc 6 in use. It will be understood that the inboard air volume 64 is not a sealed air volume, but rather is a volume of air located between the brake disc 6 and outboard peripheral funnel wall 69 of the brake disc cover 20 in use.

The dust funnel 67 is in fluidic communication with a first opening 84 of a passage 80 which extends from the dust funnel 67 to a second opening 86 of the passage 80. The passage 80 expands in cross-sectional area from the first opening 84 to the second opening 86 such that a second end of the passage 80 forms a manifold 88.

Referring to Figures 4 and 5, the outboard portion 30 and the inboard portion 60 of the brake disc cover 20 fit together in use, when fitted to the brake assembly, such that the second end 86 of the passage 80 engages with a first sub-zone 52 of the three sub-zones 51. The first sub zone 52 is thus in exclusive fluidic communication with a first fluidic communication path 82 (Figure 8) defined by the passage 80. The remaining two sub-zones 51 form a second number of sub zones 54 which are not in fluidic communication with the first fluidic communication path 82. When the vehicle 1 is travelling forwards, the brake disc 6 rotates with the wheel 4 in an anti-clockwise direction with respect to the view of Figure 2 with the brake caliper 8 located at the rear of the brake disc. Were the brake caliper 8 to be located at the front of the brake disc 6 in the view of Figure 2, the rotation of the brake disc 6, and hence the wheel 4, would be clockwise. In either case, the outboard shell 31 comprising the filter section 29 and the cooling section 28 is located adjacent to the upper portion 57 of the caliper shell 58 rotationally downstream of the brake caliper 8 with respect to the rotational direction of the wheel 4 when travelling forwards.

Referring to Figure 3, air from a brake cooling system (not shown) is received into the inlet 70 directed by inlet wing 72 in use. Some of the cooling air is directed by edge wing 73 into the outboard duct 59 of the cooling section 28 of the outboard portion 30 of the brake disc cover 20 to be passed over and cool the outboard side 7b (Figure 2) of the brake disc 6.

Cooling air which is not directed to the outboard duct 59 is directed by the inlet wing 72, and carried by the rotation of the brake disc 6, in the rotational direction of the brake disc 6.

Atmospheric air surrounding the brake assembly 2 is also carried by the rotation of the brake disc 6, in the rotational direction of the brake disc 6.

Air moves with the brake disc 6 through the brake caliper 8 as the brake disc 6 rotates. During braking, brake dust from the brake pads (not shown) and disc 6 becomes entrained within the airflow and so is carried out of the brake caliper 8 by the airflow.

Brake dust which exits the brake caliper 8 on the outboard side 7b of the brake disc 6 enters the first zone 46 of the outboard air volume 40. The rotation of the brake disc 6 and the momentum of the airflow on the outboard side of the brake disc 6 causes air in the in first zone 46 of the outboard air volume 40 to flow from the brake caliper 8 in the direction of the cooling section 28 to define an outboard airflow 90 (Figure 5). A part of the outboard airflow 90 is directed by the vanes 56 towards the first part 36 of the filter 34. The brake dust is filtered from this part of the outboard airflow 90 by the first part 36 of the filter as it passes through the filter and out of the vents 33 to the outside environment.

Brake dust which exits the brake caliper 8 on the inboard side 7a of the brake disc 6 enters the inboard air volume 64 bounded by the dust funnel 67. The rotation of the brake disc 6 and the momentum of the airflow on the inboard side 7a of the brake disc 6 causes air in the inboard air volume 64 to flow from the brake caliper 8 in the direction of the first opening 84 of the passage 80 to define an inboard airflow 95 (Figure 7). A first part 96 (Figure 8) of the inboard airflow 95 enters the first opening 84 of the passage 80 and passes along the first fluidic communication path 82 to the second opening 86 of the passage 80 where it enters the first sub-zone 52 of the outboard air volume 40 and exits the brake disc cover 20 through the second part 38 of the filter 34. Brake dust carried by this first part of the inboard airflow is filtered from the airflow by the filter.

A second part 97 (Figure 8) of the inboard airflow 95 flows over the outer edge 12 of the brake disc and into the second number of sub-zones 54 thus defining a second fluidic communication path 98 (Figure 8) between the inboard air volume 46 and the outboard air volume 40. The second part 97 of the inboard airflow 95 then exits the brake disc cover 20 through the second part 38 of the filter 34. Brake dust carried by this second part 97 of the inboard airflow is filtered from the airflow by the filter.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. In particular, it is not essential that the outboard air volume 40 be separated into different zones 46, 48 and sub-zones 51, 52 as described above. In one example, the outboard air volume 40 is not separated into zones 46, 48 and both the first 96 and second 97 parts of the inboard airflow 95, which pass along the first 82 and second 98 fluidic communication paths respectively, enter into the outboard air volume 40 and exit the brake disc cover 20 via the filter 34.

It will be understood that any number of sub-zones 51 may be provided and that the first sub zone 52 may be further divided by additional second interior walls 50 into more than one sub-zone 51 such that the second end 86 of the passage 80 communicates with a first number of subzones 52.

As can be seen most clearly from Figures 2 and 3, when the brake disc cover 20 is fitted to the brake assembly 2 of the vehicle 1, the brake disc cover 20 covers a substantial portion of the brake disc 6. It will be understood that a substantial portion in this context means any amount of the brake disc 6 exceeding 50% of the entire external surface of the brake disc including the inboard side 7a, outboard side 7b, and edge 12.

As mentioned above, the brake disc cover 20 described above with reference to Figures 2 to 6 is configured for use with a brake cooling system (not shown). In particular, the opening 70, the inlet wing 72 and edge wing 73 of the inboard portion 60 are configured to receive cooling air from a brake cooling system in use. It will be understood that it is not essential that the brake disc cover 20 comprise an opening 70 or wings 72, 73, and it is not essential that the brake disc cover 20 be used in conjunction with a brake cooling system. For example, where a brake disc cover 20 is used on a rear brake assembly 2 of a vehicle 1, which would not typically have a brake cooling system associated with it, the opening 70 may be replaced by a continuation of the inboard peripheral wall 62 and the wings 72, 73 may be omitted. In this case, airflow within the brake disc cover 20 is generated by the rotation of the brake disc 6 in use, and airflow from a brake cooling system is not required to drive the airflow through the brake disc cover 20.

In the example brake disc cover 20 described above, the caliper shell 58 is formed together with the outboard shell 31 as a single moulded part forming the outboard portion 30. It will be understood that the caliper shell 58 may be formed together with the inboard portion 60, or may be formed partially together with the outboard portion 30 and inboard portion 60, to be fitted together to form the complete caliper shell 58 on assembly of the brake disc cover 20.

Similarly, in the example brake disc cover 20 described above, the filter section 29 of the outboard shell 31 extends from the caliper shell 58 across the top of the brake disc 6 to a position past a vertical centreline V-V of the brake disc 6, and the cooling section 28 extends from the end of the filter section 29 to a position past a horizontal centreline H-H of the brake disc 6. It will be understood that the configuration described above is merely one embodiment of the invention and that any arrangement of filter section 29 and cooling section 28 may be selected according to design preference. In addition, in certain embodiments of the invention, the outboard portion 30 may not comprise a cooling section 28. For example, in the situation where no brake cooling system is present as is typical for the rear brake assembly 2 of a vehicle 1.

Claims

CLAIMS1. A brake disc cover comprising an outboard portion and an inboard portion, wherein the outboard portion is configured to receive a filter, the brake disc cover being configured so that, in use, the outboard portion is located substantially on an outboard side of a brake disc, and the inboard portion is located substantially on an inboard side of the brake disc, wherein the inboard portion defines an inboard air volume located between an inboard side of the brake disc and the inboard portion, and the outboard portion defines an outboard air volume located between an outboard side of the brake disc and the outboard portion, wherein the brake disc cover comprises a passage which defines a first fluidic communication path between a first passage opening and a second passage opening, the first passage opening being configured, in use, for fluidic communication with the inboard air volume, and the second passage opening being configured, in use, for fluidic communication with the outboard air volume, wherein the passage extends from the first passage opening to the second passage opening over an outer edge of the brake disc, wherein the brake disc cover is configured so that, in use, at least part of an outboard airflow from the outboard air volume exits the brake disc cover via the filter, and at least a first part of an inboard airflow from the inboard air volume passes along the passage from the first passage opening to the second passage opening and exits the brake disc cover via the outboard air volume and the filter.
2. A brake disc cover according to claim 1, wherein the outboard portion comprises at least one vane configured so that, in use, the at least part of the outboard airflow is directed towards the filter by the at least one vane.
3. A brake disc cover according to claim 1 or 2, wherein the outboard portion comprises a filter.
4. A brake disc cover according to claim 3, wherein the filter comprises a first part and a second part, wherein the brake disc cover is configured so that, in use, the at least a part of the outboard airflow exits the brake disc cover via the first part of the filter, and the at least first part of the inboard airflow exits the brake disc cover via the second part of the filter.
5. A brake disc cover according to claim 4, wherein the first part of the filter comprises one or more discrete filter elements, and wherein the second part of the filter comprises one or more discrete filter elements.
6. A brake disc cover according to claim 4 or 5, wherein the filter is arcuate in form and wherein the first part of the filter is located radially inward of the second part of the filter.
7. A brake disc cover according to any one of claims 4 to 6, wherein the outboard portion comprises a first wall which divides the outboard air volume into a first zone and a second zone, wherein the first part of the filter is located substantially within the first zone, and the second part of the filter is located substantially within the second zone.
8. A brake disc cover according to any one of claims 1 to 7, configured so that, in use, at least a second part of the inboard airflow passes over the outer edge of the brake disc via a second fluidic communication path and exits the brake disc cover via the filter.
9. A brake disc cover according to claim 8 where dependent directly or indirectly on claim 4, configured so that, in use, the at least a second part of the inboard airflow exits the brake disc cover via the second part of the filter.
10. A brake disc cover according to any preceding claim, wherein the inboard portion comprises an inboard peripheral wall configured, in use, to prevent at least a part of the brake dust produced during vehicle braking from exiting the brake disc cover towards an inboard side of a vehicle.
11. A brake disc cover according to any preceding claim, wherein the inboard portion comprises an inlet configured, in use, to receive air flow from a brake cooling system.
12. A brake disc cover according to any preceding claim, wherein the outboard and inboard portions fit together so that, in use, the brake disc cover encloses a substantial portion of the brake disc.
13. A brake disc cover according to claim 12, wherein the brake disc cover substantially encloses the brake caliper.
14. A brake disc cover according to any preceding claim, configured so that, in use, the filter is located rotationally downstream of the brake caliper with respect to the rotational direction of the brake disc when the vehicle is travelling forwards.
15. A brake disc cover according to claim 1, configured so that the at least first part of the inboard airflow exits the second passage opening into the outboard airflow.
16. A vehicle comprising a brake disc cover according to any one of the preceding claims.