ZA201001114B - Disc brake assembly for a two wheel vehicle - Google Patents

Description

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FIELD OF THE INVENTION pe

This invention relates to a disc cover for a disc brake assembly, especially suitable for two wheel vehicles such as motorcycles and scooters.

BACKGROUND TO THE INVENTION

Disc brakes are commonly employed in two wheel vehicles such as : motorcycles and scooters. In a disc brake, a braking disc — typically of stainless steel, cast iron, ceramic or other composite — is connected to a wheel and/or axle of the wheel of the vehicle. During braking, actuation of the brake by the rider causes brake pads to be forced against one or both faces of the braking disc. This creates a frictional force and a resultant temperature increase of the braking disc and thus a braking action is created which can be used to slow the vehicle or bring it to a complete stop. Typically, a disc brake is mounted to a front wheel of the two wheel vehicle. The ability of the disc bake to release heat rapidly is an important factor in :

B the proper operation of the braking system and thus good airflow to remove heat from the disc brake is desirable.

It is desirable to keep disc brakes substantially free of water or mud which may typically be thrown up into them particularly in wet weather. If mud or water do impinge upon the disc brake, braking effectiveness and efficiency are reduced; the : vehicle may become unstable jeopardizing vehicle rider safety. In addition, wear of the brake pads and/or disc may become problematic leading to ineffective braking, frequent replacement of brake pads and compromised rider safety.

To this end, the manufacture of dis brakes has involved the manufacture of covers for braking discs. Prior art disc brake covers completely or substantially completely enclose the entire braking disc and are provided with holes to allow dust and water to drain from the disc brake cover. In addition, such holes or vents may assist in the prevention of overheating.

Disc brakes are described in a number of patents. For example, US 4,226,308 describes a disc brake having a series of fan elements attached to a wheel attaching axis and adapted to be nested in a stored configuration or overlapping and covering the disc when deployed. Other prior art discloses brake :

© disc covers which are disposed to prevent water, mud and other detritus thrown up from road level accessing the braking disc. To this end, disc covers may often completely enclose or enclose a predominant portion of the disc cover.

The entry of water and mud into disc brakes may be a particularly severe problem in rural areas in India. During monsoon season, especially, the risk of entry : of water and mud into disc brakes substantially increases. The problem is : exacerbated in that mud and other deleterious materials can be thrown up under the mudguard of a wheel where it can become particularly concentrated and can subsequently fall bake down into the brake disc area. Brake pad wear increases.

Braking effectiveness and wear problems are therefore a particular concern in India and it would be highly desirable to provide a disc cover, disc brake assembly, and two wheel vehicle less prone to these hazards. | B

SUMMARY OF THE INVENTION

With this object in view, the present invention provides — in a first aspect — a : disc cover attachable to a ‘vehicle structural support member to be mounted proximate to a disc brake assembly comprising a braking disc and an associated ] braking caliper wherein said disc cover shields a portion of the braking disc from impingement of deleterious material emanating from above the disc brake assembly.

The vehicle structural support member is part of a two wheel vehicle, such as a motorcycle as described further herein, and may take the form of a frame, the front portion of that frame comprising front fork tubes or members. In such case, at least that portion of the disc brake assembly located between a fork tube and said associated brake caliper is covered and protected. Such provision is advantageously made irrespective of any angle of inclination of the front fork tubes.

In this regard it may be appreciated that the front fork tubes of a motorcycle frame are typically inclined relative to a vertical axis of the motorcycle. Advantageously the disc brake assembly and disc cover are attached to the same structural support member such that there is no relative motion between the non-rotating parts of the disc brake assembly and the disc cover. It should also be appreciated that the invention is equally applicable to both sides of a vehicle in the case that the vehicle is equipped with a dual disc braking system.

+2010/04114

Preferably, the cover for the braking disc is located only in an uppermost : region of the disc brake thus allowing for effective cooling of the disc by leaving the : lower region of the disc uncovered.

In operation the effective braking area of the brake disc comprises an annular area defined by the radial extent of the brake pads, this annular area extending from an inner radius to an outer radius (the outer radius usually approximating the physical outer radius of the brake disc itself. | oo

Preferably, the radial extent of the cover for the braking disc extends only outwardly from the inner radius of the effective braking area of the disc.

Preferably, the radial extent of the cover for the braking disc extends over only a portion of the effective braking area of the disc.

The disc cover may be located to shield and protect a determined portion, . such as a segment, of the braking disc when deployed. To this end, the disc cover may surround the determined portion of the braking disc. Although the term oo “segment” may be used here in its geometric sense, the term is to be understood as used more broadly in this specification where the context requires. The disc cover may provide protection selective to the region of the brake caliper, the ‘most susceptible region, from the point of view of entry of damaging dirt to the disc brake assembly, being further discussed below.

Essentially, the disc cover provides an obstacle to deleterious material such as water, dirt, mud or other detritus entering the interface between the braking © medium, typically in the form of a brake pad, and the braking disc. It is sticking of ~~ mud and dirt particles at an interface between the braking disc and brake pad that causes potentially serious wear especially during a monsoon season. The protected portion or region of the braking disc is that most prone to impingement of deleterious material such as water, mud or other detritus particularly flowing downward, such as may arise under gravity — but may also be induced from relative wind velocity effects and momentum and deflection, from the mudguard and vehicle structural support, toward the brake caliper, during driving or riding conditions. Contrary to prior disc cover constructions which have focused on deleterious material thrown up from road level, the present disc cover is, counter-intuitively, located to obstruct, and desirably prevent potential damaging effects from, a flow of deleterious material flowing downward from the mudguard and vehicle structural support, during driving, in a direction of the brake caliper. The problem is particularly acute if the vehicle structural support includes member(s) where mud and so on accumulate or which “form restrictions forcing mud and dirt flows toward susceptible regions of the disc brake assembly. Such a member may include a brace fender located in the region of the front fork tubes of a motorcycle structural frame which resists upward flow of mud and so on and tends to cause a downward flow of dirt back toward the disc brake. _ If the braking disc, being circular, has its uppermost point designated 0°/360°, and the brake caliper is located in the region extending over a segment of the braking disc, for example defined by radii extending to endpoints between 300° and 360° (-60° and 0°), around the circumference of the braking disc, the disc cover will extend over at least a predominant portion of this region, especially protecting at : least the most susceptible uppermost portion of the brake caliper, where apertures may be located and a downward flow of deleterious material is most likely to impinge ~ and access the brake/pad interface causing undesirable wear of brake pads.

The most susceptible segment of the braking disc over which the disc cover is required to extend is determined by observation and experimentation in the testing facility. for disc brakes to be used in particular motorcycles. Parameters that may be tested in the experimentation include mud exit angle, the angle at which mud typically exits the mud guard (and how this may change at typical vehicle speeds expected in such driving conditions), as well as radial and axial clearances of the disc. cover portion from the braking disc. For one motorcycle model, the necessary segment of the braking disc to be covered and protected by the disc cover is a region including the segment defined at least in part by plural radii extending to endpoints in the range of angles 300 to 360° (-60 to about 0°). The above defined segments or regions are located close to the front fork tubes and correspond with a gap through which the above-mentioned downward flow of deleterious material may enter the disc brake assembly to cause poor or dangerous performance and wear.

However, it is convenient for the protected segment to range over a larger segment of the braking disc, than here defined by way of example, though less than the entirety of the braking disc. :

To that end, the disc cover may also advantageously extend over a greater segment of the braking disc, this segment extending in the forward vehicle direction, for example to an angle of less than about +90° from the uppermost point of the braking disc. It has been found that there is some advantage in having this angular extent slightly greater than the angular extent of the mudguard. A portion of the disc cover, where a surface of increasing downward slope is present, may be configured to form a beaded surface or a gutter to promote downward flow of deleterious material such as mud, water and so on back toward road level by guiding any mud, water and so on downwardly and to the sides of the cover so as to reduce such material simply sliding off the cover and back on to the brake disc. This beaded surface or gutter adds to the rigidity of the disc cover. This portion of the disc cover may extend in the forward vehicle direction.

For sound engineering reasons (including the transference and reaction of braking loads to the front tubes and suspension) the brake caliper may be located, relative to the braking disc, rearward of the front fork tubes or member(s). It is desirable for the brake caliper to have apertures provided in its surface, such apertures being used to access the brake pads for maintenance purposes. In accordance with the present invention, such apertures may still be provided, the disc cover being disposed to minimize the potential for mud and other detritus entering . the brake caliper through those apertures. } oo

The disc cover may have respective faces opposed to respective opposing faces of the braking disc with a controlled clearance between disc cover and braking disc. The respective faces of the disc cover are joined by a web such that the portion of the disc cover surrounding or enclosing the portion of the braking disc has an approximate U shape in cross section. However, it will be understood that a perfect U shape is not required. Other sections may also be employed in accordance with the invention. For example, the base of the U may be widened and the arms of the U contracted so that there is only a small portion overlap of the arms of the U with respective opposing faces of the braking disc.

The disc cover has a generally rounded channel shape viewed from the side.

The portion of the disc cover disposed towards the front of a wheel is open with the web surface having a downwardly oriented angle to assist mud escape and water drainage. However, the disc cover may include flange(s) to aid connection of the disc cover to the vehicle structural support.

As the disc cover surrounds or encloses only a portion of the braking disc, there is less necessity for the provision of holes or vents to facilitate drainage or to reduce risk of overheating. Such holes or vents may even be dispensed with altogether. ‘Avoidance of the holes may increase the durability of the cover as stress cracking, which may originate at such holes under severe conditions, is less likely. :

The disc cover is fixedly connected to the vehicle structural support by any desired coupling means. However, in a particularly advantageous arrangement, additional bosses may be formed or welded on to the front tube(s) of a motorcycle frame to enable ‘flanges or similar connection means on the disc cover to be connected to it by fastening means such as by bolting. :

The disc cover is advantageously made of a material resistant to warpage. oo : In a further aspect, the present invention provides a disc brake assembly comprising: a) a braking disc; Co : b) a brake caliper mounted relative to the braking disc; and .C) a cover for the braking disc wherein the cover, as above described, is located to shield a portion of the braking disc, providing protection for the brake assembly at least in the region of the brake caliper.

In a still further aspect, the present invention provides a two wheel vehicle : comprising: oo | oo (a) a vehicle structural support member; (b) a disc brake assembly connected to the vehicle structural support member and including a braking disc, a brake caliper mounted relative to the braking disc and a braking medium; and ~~ (c) a cover for the braking disc } wherein the cover, as above described, is located proximate the disc brake assembly : to shield a portion of the braking disc, providing protection for the disc brake assembly at least in the region of the brake caliper. ‘The disc cover of the invention is applied most conveniently at the front wheel of a motorcycle though it may be used at a rear wheel if a disc brake is fitted to the ~ rear wheel. More commonly, however, the rear wheel will be fitted with a drum brake and issues’ of protection from entry of dirt to the brake are different in that circumstance.

The vehicle is advantageously one in which a mudguard is placed in the region above the disc brake.

The disc cover and other aspects of the present invention may be more fully understood from the following description of a preferred embodiment of the invention made with reference to the accompanying drawings in which:

Fig. 1 is a perspective front view of a front wheel of a motorcycle including the _ brake disc cover of an embodiment of the invention;

Fig. 2a is a side view of the front wheel of the motorcycle shown in Fig. 1 and showing the direction of mud/detritus flow relative to the front wheel and disc; points marked M, illustrate the mud path along the wheel and arrows marked W illustrate . mud falling towards interface during running due to wind

Fig. 2b is a side view of the front wheel of the motorcycle shown in Figs 1 and 2a without the mud/detritus flow directions for ease of illustration of the brake disc : cover of this embodiment of the invention; - oo Fig. 3 is a front view of the front wheel of the motorcycle shown in Figs. 1 and 2; oo

Fig. 4 is a perspective partial rear view of the front wheel of the motorcycle shown in Figs. 1 to 3; and oo | oo

Fig. 5 is a side cross sectional view of the disc cover shown in Figs. 1 to 4. i Fig. 6 shows perspective views of the disc cover.

Referring now to Figs. 1 to 3, there is shown the front wheel 10 of a motorcycle including a mudguard 11 and disc brake assembly 20. The front wheel is mounted to the front portion or member of the motorcycle structural support or frame. The front portion of the motorcycle may be, or may form an extension of, the front fork tubes 15 of the motorcycle frame. The disc brake assembly 20 is mounted on the front wheel 10 and comprises a braking disc 30, an associated brake caliper 24 and brake pads 27 (shown in Fig. 5). The braking disc 30 is shown with cross- drilled holes in the effective braking area of the disc to aid in brake cooling. Brake caliper 24 is located rearward of front fork tubes 15. A structural member or brace fender 50 is connected between the respective front fork tubes 15 to impart greater rigidity to the front portion of the motorcycle frame. ’

It may be observed that, if the uppermost point of braking disc 30 is designated 0°/360°, the brake caliper 24 extends over a sector of the braking disc 30 defined between radii of braking disc 30 respectively extending to endpoints at about 270° and about 0° (about -90° and about 0°) around the circumference of the braking “disc 30. It is noted that the front fork tubes 15, are inclined at about -25°. While the brake caliper 24 could be of fixed type, floating type is preferred in the illustrated embodiment for the purpose of reducing cost. The brake pads 27 have a clearance from braking disc 30 under normal riding conditions. When braking is initiated by a mechanical or hydraulic means, such as when the rider of the motorcycle engages the brake, the brake pad 27 is brought into closer contact with the braking disc 30. . This slows the rotation of the braking disc 30, the rotation of the wheel and may be employed to control speed of the motorcycle: and bring it to a complete stop if © required. EE

There is a gap or clearance at the interface between the braking disc 30 and brake pads 27 in the region of the brake caliper 24. If not protected, deleterious material such as water, mud and dirt may enter this interface causing lodgment of dirt and sticking of the braking disc 27 and brake pads 30. Such sticking would lead to wear and earlier failure or ineffective performance of the brake with compromised safety. Water or mud/dirt particles may also cause braking instability and this also compromises safety. ‘During operation of the motorcycle, flows of mud and dirt around the front : ‘wheel 10 of the motorcycle and below mudguard 11 have been observed by the

Applicant as conveniently shown in Fig. 2a. Mud and dirt are thrown upward from a road or other driving surface and flow in a direction generally clockwise about the front wheel 10. A significant stream of mud and dirt will impinge on the brace fender 50, of the motorcycle frame, which forms a restriction which causes mud and dirt to flow downward, under gravity, toward the uppermost portion of the brake caliper 24.

Another significant stream of mud and dirt will continue to be thrown around the mudguard 11 to flow downward toward the braking disc 30 away from the brake caliper 24. This stream will be directed at an angle, when running into the wind, dictated by motorcycle speed.

The most significant potential problem that occurs due to downward flow of mud and dirt accumulating on the brace fender restriction 50 is illustrated by Figs. 3 8 LL and 4 which show a gap 29 between the front fork tube 15 and brake caliper 24.

This gap 29 is located above braking disc 30 and corresponds with a region where a significant downward flow of deleterious material in the form of water, mud and dirt . from brace fender 50 occurs. It also corresponds with an uppermost portion of the brake caliper 24 which is most susceptible to damaging entry of mud and dirt to the disc brake assembly 20. oo

Accordingly, disc cover 40 is selectively located below mudguard 11 in a oo segment defined by respective radii extending to endpoints between about 300 and 360° (-60 and 0°) around the circumference of the braking disc 30 as shown in Fig. 2b providing protection for this region. Cover is therefore provided for that portion of a the disc brake assembly 20 located between the front fork tube 15 and the brake caliper 24. This location of disc cover 40 obstructs and prevents flow of mud/dirt through gap 29 and into the disc brake assembly 20. The restricted mud falls into the disc pad interface due to gravity marked as Xin fig 2a. The Applicant has found that this is sufficient to achieve significant reductions in wear of the brake pads 27 and more effective disc brake performance in wet conditions.

The disc cover 40 also extends in the forward motorcycle direction, forward of :

Co front fork tubes 15, to also deflect mud and dirt away from this portion of braking disc being a segment broadly defined by radii extending to endpoints between about 0° and +90° around the circumference of braking disc 30 (there being some © advantage in having this angular extent slightly greater than the angular extent of the . mudguard 11). However, this portion of the disc brake assembly 20 is much less susceptible to wear and other damage than the region of the uppermost portion of brake caliper 24 as described above. This forward portion of the disc cover 40 only partially covers the radial extent of the disc brake 30, in this case extending radially inwardly to cover slightly less than the effective braking area of the disc brake 30 (the inner radius of the effective braking area being defined by the inner most crossed drilled holes as best seen Figs 2a and 2b).

The disc cover 40 is desirably made of a material which resists warpage. A polymer-ceramic composite, such as talc filled polypropylene or plain polypropylene is selected for the disc cover portion 40 of the illustrated embodiment.

The disc cover 40 is of rounded or circular channel shape formed in a single piece and having faces 41 and 42 opposing respective opposite faces 31 and 32 of the braking disc 30. Faces 41 and 42 are joined by web 43 so as to form a U shaped enclosure over the previously discussed regions of the braking disc 30 intended to be protected by the disc cover 40. However, disc cover 40 also has a portion 45 extending in the forward vehicle direction forward of front fork tubes 15 and the role of portion 45 is discussed below. The clearance of the faces 41 and 42 ~ of the disc cover 40 from the faces 31 and 32 of the braking disc 30 is controlled so that the disc cover 40 does not interfere with the operation of the disc brake 20. To this end, there is provided a radial clearance of about 7.5 mm, the radial clearance being that distance from the circumferential extent of the braking disc 30 to the web surface 43; and an axial clearance of about 5 mm between each of faces 41 and faces 31 and 32 of braking disc 30. These clearances referred as radial clearance oo (marked R) and axial clearance (marked A) are also conveniently shown in Fig. 5 + which also shows brake pads 27.

It may be observed that the disc cover 40 has increasing downward slope in . ~ the portion 45 of disc cover 40 extending in the forward vehicle direction forward of front fork tubes 15. This portion 45 of the disc cover 40 having downward slope forms a bead or a gutter which promotes downward flow of mud/detritus along a safe path back towards road level. This also adds to rigidity of the disc cover 40.

The disc cover 40 is provided with flange 54 to enable the disc cover 40 to be bolted to bosses 52 formed on at least one front fork tube 15 of the motorcycle as indicated in Figs. 1 and 3. Connection is made at two locations, alongside front fork tube 15 and at the front of the front fork tube 15. It will be further noted that bottom : 50 of the front fork tube 15 of the motorcycle is connected to the hub of the front : wheel 10. It will further be noted that the brake caliper 24 is bolted to the front fork tube 15 of the motorcycle.

The disc cover 40 is not provided with holes, for de-gassing or drainage, as in : prior constructions. This may achieve a greater durability for the disc cover 40 as . the risk of stress cracking, which is a common cause of failure in disc covers provided with holes, is much reduced.

The disc cover 40 is useful for prevention of entry of mud and dirt particles to a clearance between braking disc 30 and brake pads 27 to an extent that would cause an unacceptable degree of wear on the braking disc 30 and breakdown of the disc brake assembly. Further, as the disc cover 40 surrounds only a portion of the

2010/0 1114 braking disc 30, it is of lesser cost than prior art constructions and also ensures that good airflow over the disc brake is maintained. :

Modifications and variations to the disc cover of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are intended to be within the scope of the present invention. . . N | | 11 | .

Claims (27)

' Ne CL I CLAIM: | TT

1. A disc cover attachable to a vehicle structural support member to be mounted proximate to a disc brake assembly comprising a braking disc and an associated braking caliper wherein said disc cover shields a portion of the braking disc from impingement of deleterious material emanating from above the disc " brake assembly.

2. A disc cover of claim 1 wherein the vehicle structural support member is part of a two wheel vehicle and takes the form of a frame, the front portion of that frame comprising front fork tubes.

3. - A disc cover of claim 2 wherein at least that portion of the disc brake assembly located between said fork tubes and said associated brake caliper is covered and protected.

4. A disc cover of any one of the preceding claims being located only in an uppermost region of the disc brake allowing for effective cooling of the disc by leaving the lower region of the disc uncovered.

5. A disc cover of any one of the preceding claims being located to-shield and protect a determined portion of the braking disc when deployed.

6. A disc cover of any one of the preceding claims wherein the radial extent of the disc cover that covers the disc brake is equal to or less then the radial extent of the effective braking area of the disc brake. :

7. A disc cover of claim 6 wherein the radial extent of the disc cover that covers the disc brake is less than the radial extent of the effective braking area of } the disc brake.

8. A disc cover of claim 6 wherein there is minimal or no radial extent of the disc cover is overlapping with the effective braking area of disc brake.

. _ oo 22010701114

9. A disc cover of any one of the preceding claims wherein said determined portion of said braking disc is a segment of said braking disc.

10. A disc cover of any one of the preceding claims wherein said disc cover surrounds the determined portion of the braking disc.

11. A disc cover of any one of the preceding claims providing protection selective to the region of said brake caliper. 5

12. A disc cover of any one of the preceding claims being located to obstructa flow of deleterious material flowing downward from the mudguard and vehicle . structural support during driving and entering the brake caliper. | :

13. A disc cover of any one of the preceding claims being circular and having uppermost point designated 0°/360°, with the brake caliper being located in the region extending over a segment of the disc brake defined by radii extending to endpoints between 300° and 360° (-60° and 0°), around the circumference of the braking disc, the disc cover extending over at least a predominant portion of this region. Co

14. A disc cover of claim 13 wherein said region is located close to the front fork tubes and corresponds with a gap through which a downward flow of deleterious material may enter the disc brake assembly to cause poor or dangerous performance and wear.

15. A disc cover of claim 13 or 14 extending over a larger segment of the braking disc, than between 300° and 360°.

16. A disc cover of claim 13 wherein the disc cover extends over a segment less than the entirety of the braking disc.

C =2010/701114

17. A disc cover of any one of claims 13 to 16 wherein said segment also extends in the forward vehicle direction. oo

18. A disc cover of claim 17 wherein said segment extends in the forward vehicle direction to an angle of less than about +90° from the uppermost point of So the braking disc.

19. A disc cover of claim 18 wherein said segment has an angular extent : slightly greater than the angular extent of the mudguard. ~

20. A disc cover of any one of the preceding claims wherein a portion of the said disc cover having a surface of increasing downward slope is configured to : form a beaded surface or a gutter. ~

21. Adisc cover of claim 20 wherein said portion of said disc cover extends in the forward vehicle direction.

22. A disc cover of any one of claims 3 to 21 as dependent from claim 2 wherein said brake caliper is located, relative to the braking disc, rearward of the front tube member(s). - :

23. Adisc cover of any one of the preceding claims comprising flange(s) to aid connection of the disc cover to the vehicle structural support. i

24. A disc cover of claim 23 wherein said flange(s) connect to bosses formed on the vehicle structural member.

25. A disc brake assembly comprising: (a) abraking disc; (b) a brake caliper mounted relative to the braking disc; and (c) a cover for the braking disc

: wherein the cover, as defined in any one of claims 1 to 24, is located to shield a portion of the braking disc, providing protection for the brake assembly at least in the region of the brake caliper.

26. A two wheel vehicle comprising: (a) a vehicle structural support member; : (b) a disc brake assembly connected to the vehicle structural support member and including a braking disc, a brake caliper : mounted relative to the braking disc and a braking medium; and : : (c) a cover for the braking disc; wherein the cover, as defined in any one of claims 1 to 24, is located proximate the disc brake assembly to shield a portion of the braking disc, providing protection for the disc brake assembly at least in the region of the brake caliper. =~

27. A vehicle as claimed in claim 26 wherein said disc cover is applied at the front wheel of a motorcycle. DATED THIS THE 16™ DAY OF FEBRUARY 2010 I & FISHER + APPLICANT'S PATENT ATTORNEYS : | -