Note: Descriptions are shown in the official language in which they were submitted.
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DISC BRAKE SYSTEM
BACKGROUND OF T~E INVENTION
The field of the present invention is braking
systems and more specifically disc brake systems generally
employed with motorcycles.
In conventional disc brake systems for motorcycles,
the brake disc is installed on one or both sides of the wheel
hub. These discs are generally exposed to open air so that the
heat of friction generated during braking is dissipated at a
sufficient rate by the movement of the disc or discs through
the air.
Either by design choice or responsive to certain
intended applications of the brake, the brake disc may be
enclosed between the hub and a side panel. The brake is then
shielded from dirt, water and the like which generally will
reduce wear. In such enclosed systems, ~he enclosure also
acts to shield the brake disc from the open air. Consequently,
heat dissipation is reduced. Conventionally, such shielded
disc brakes have been made larger than the braking require-
ments would suggest to reduce the concentration of heat and to
increase heat dissipation. Additionally, ventilating of ~he
disc itself has been employed to increase dissipation.
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As it is always advantageous to avoid excessive
unsprung weight on a vehicle and as it is also advantageous
to use small, light components on motorcycles, reduction in
the overall size of a disc braking system is considered
beneficial. In the event that shielding of a brake disc is
also desired, the requirement for larger discs to accommodate
the reduced heat dissipation accompanying shielding comes into
conflict with the overall goal of reducing component weight.
Thus, increased weight has generally been accepted as an
unavoidable liability associated with shielded disc brake
designs.
The incorporation of intricate features on the disc
such as employed with ventilated discs to increase cooling
efficiency also have drawbacks. The disc must necessarily be
made of thick metal rather than thin metal in view of head mass
considerations. Consequently, the use of even more material
in the disc for cooling features is not advantageous for
weight considerations. Greater design intricacy also can
create problems regarding fabrication and assembly.
Another difficulty associated with brake disks is the
mounting of these disks to the hub. When additional cooling
features or increased disk diameter are required, it is
advantageous to mount the disk at its periphery so that the
calipher member may be placed inside to interfere as little
as possible with any cooling mechanism or air flow. Further-
more, placement of the caliphers on the inside is advantageous
on a motorcycle where compact design is important. The earlier
mounting design of such externally supported disks requires
that the bolts mounting the disk to the hub be placed under
substantial stress during braking. Such designs generally
require more component parts and have a tendency to prevent
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the free thermal expansion of the disk in the radially outward
direction.
SUMMARY OF T~l~ INVENTION
The pres.ent invention relates to an improved disc brake
system for motorcycles of the shielded type which reduces the
requirement for the aforementioned substantial increase in
weight. To accomplish.this result, improved cooling performance
is achieved by the present invention without detracting from
the shielding so that the brake discs may be smaller in size,
approaching the size of brake discs of comparable unshielded
systems.
To accomplish.the foregoing result, the present
invention provides a disk brake system for a motorcycle having
a wheel hub, said disc brake system including a brake disc
fixed on one side thereof to rotate with said hub, a caliper
member fixed to the motorcycle for braking engagement with
said brake disc, and a side panel covering said brake disc on
the other side thereof and having a cooling air introduction
port, wherein the improvement comprises means for inducing
radial, outward air flow, said air flow inducing means being
radially adjacent to the periphery of said brake disc and
fixed to rotate with the hub. The air flow inducing means
may include a radial flow fan composed of a plurality of
vanes annularly spaced outwardly of the disc or simply an
annular passage through which air may pass under the
influence of the
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rotational motion of the disc and the hub. Such additions
may be made in light alloy separate from the disc itself.
In association with the employment of a radial flow fan, a
ventilated disc may be employed where the radial passage-
ways through the disc are aligned with the passageways
between vanes. In another aspect of the present invention
it is also contemplated that the fan may be employed as a
means for locking the disc itself into position on the hub,
reducing components and the stresses on same.
Accordingly, it is an object of the present inven-
tion to provide an improved disc brake system for motorcycles.
It is a further object to provide a shielded disc brake system
which is relatively light in weight and exhibits efficient
disc cooling. Other objects and advantages will appear
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a detailed cross-sectional view of a brake
disc and mounting boss of the prior art.
Figure 2 is a side view of a first embodiment of the
present invention illustrating a motorcycle hub and disc
brake system.
Figure 3 is a cross-sectional view taken along line
3-3 of Figure 2.
Figure 4 is a side view of a second embodiment of the
present invention.
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Figure 5 is a cross-sectional view taken along line
5-5 of Figure 4.
Figure 6 is a side view of a third embodiment of
the present invention.
Figure 7 is a cross-sectional view taken along line
7-7 of Figure 6.
Figure 8 is an embodiment similar to that of
Figures 6 and 7 but for the front rather than rear wheel of
a motorcycle and incorporating dual discs.
Figure 9 is a side view of a fourth embodiment of
the present invention.
Figure 10 is a cross-sectional view taken along line
10-10 of Figure 9.
DETAILED DESCRIPTION OF T~E PREFERRED EMBODI~ENT
An earlier mounting design for externally supported
disks is illustrated in Figure 1 of the drawings. In Figure
1, a brake disk a is fixed to a mounting boss b on the hub
by means of a rod or bolt c extending through a mounting hole
d in the brake disk a. An enlarged mounting boss e on the
brake disk a was employed to meet with the mounting boss b
through which the bolt c passed. The prior art device
illustrated in Figure 1 requires that the bolt c be placed
under substantial stress during braking.
Turning in detail to the drawings, Figures 2 and 3
illustrate the rear wheel assembly of a motorcycle including
a rear fork assembly 10, a rear wheel axle 12 and a rear
wheel hub 14. The hub 14 is supported by the rear fork
assembly 10 and rotatably mounted about the rear wheel axle
12 and a bearing 16. As can best be seen in Figure 3, a
final drive flange 18 is fixed to the hub 14 and includes a
driven sprocket 20 bolted to the final driven flange 18 by
bolts 22.
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On the side of the hub 14 opposite the driven
sprocket 20 is a disc brake system including a brake disc
24. The brake disc 24 is mounted at its outer periphery to
the hub 14. Three sets of mounting projections ~6 and 28
define cutout portions between the pro3ections of each set.
The wheel hub 14 includes three bosses 30 which extend
laterally toward the brake disc 24 to engage the sets of
mounting projections. The fit between the disc 24 and the
bosses 30 is loose to accommodate thermal expansion.
Mounted to the rear fork assembly 10 is a caliper
member 32. The caliper member is fixed against rotating
with the hub 14 and brake disc 24; and includes pads 34 and
36 positioned on either side of the brake disc 24. These pads
may be forced into braking engagement with the brake disc 24
upon operation of a caliper piston 38 in a conventional
manner. The caliper member spans the disc from the inside for
compactness and to avoid interference with disc cooling.
The disc brake system includes a side panel 40
which covers the side of the brake disc 24 away from the hub
14. The side panel 40 extends radially outwardly to
adjacent the periphery of the brake disc 24. The hub 14
also extends by means of a flange 42 to adjacent the outer
periphery of the brake disc 24. Thus, an annular slearance
or passageway is defined between the flange 42 of the hub 14
and the outermost extension of the side panel 40. The surround-
ing of the brake disc 24 by the hub 14 and its flange 42 and
by the side panel 40 prevents the deposit of water, dust and
the like on the brake disc.
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1 1 ~320~
To promote cooling of the braking system which is
subject to frictional heating during use of the brakes, cool-
ing air introduction ports 44 are provided through the side
panel 40 inwardly of the brake disc 24. These cooling air
introduction ports are positioned such that incoming air
will flow radially outwardly past the brake disc 24 as can
be seen by the arrows in Figure 3.
A centrifugal or radial flow cooling fan 46 is
positioned radially adjacent to the periphery of the brake
disc 24. In the embodiment of Figures 2 and 3, the cooling
fan is integral with the hub 14 and includes a plurality of
vanes 48 which may be arranged for maximum induced radial flow
through the annular passageway. In the embodiment of Figures
2 and 3, the vanes 48 are integrally formed with the flange
42 of the hub 14. Rotation of the hub 14 by the driving of
the motorcycle will cause the vanes 48 to act as a means for
inducing radial, outward air flow in a manner consistent with
a centrigugal fan. To a certain extent, the mere existence
of the annular passageway adjacent the periphery of the brake
disc 24 in combination with both the rotation of the brake
disc 24 and of the hub 14 and ~associated flange 42 will
create or induce air flow from the cooling air introduction
ports, past the brake disc 24 and between the extremities of
the side panel 40 and the wheel hub flange 42.
A shroud or ring 50 is positioned about the fan 46
to close the distal ends of the vanes 4~. This shroud or ring
50 is fixed by fasteners 52 to the mounting bosses 30 of the
hub 14. The placement of the ring 50 retains the brake disc
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24 in its axial position. The sets of mounting projections
26 and 28 retain the brake disc 2~ from rotational movement.
Thus, the brake disc is securely positioned in place. The
mounting of the brake disc including the mounting projections
26 and 28 about the bosses 30 and the retaining ring or vane
shroud 50 is unlike the prior art illustrated in Figure 1.
In the preferred embodiment of the present invention, the
mounting projections 26 and 28 provide integral loading on the
brake disc 24 rather than through a bolt shaft as in the prior
art.
Looking next to the embodiment of Figures 4 and 5,
similar reference numeral-s are employed to designate identi-
cal or substantially identical components to those of the
embodiment of Figures 2 and 3. The additional feature presented
in the embodiment of Figures 4 and 5 is the employment of a
ventilated brake disc 24. The ventilated brake disc includes
radial passages 54 extending centrally through the brake disc
24. Webs 56 separate the passages 54 and help to strengthen
the disc. The embodiment~of Figures 4 and 5 further illustrate
the iongitudinal alignment of the vanes 48 with the webs 56
to create relatively continuous flow paths through the brake
disc 24 and through the fan 46.
The embodiments of Figures 6, 7 and 8 also employ
corresponding numbers to the earlier embodiments. In Figures
6 and 7j a rear wheel for a motorcycle is disclosed as in the
prior embodiments. In Figure 8, the same air flow scheme is
employed on a front wheel device employing dual brake disc 24.
Front forks 58 are thus employed in the embodiment of Figure 8.
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The means for inducing radial air flow in the
embodiment of Figures 6 through 8 is simply the presence of
a space between the flange 42 of the hub 14 and the side
panel 40. Furthermore, the rotation of the disc 24 and
of the hub 14 induce flow from the cooling air introduction
ports 44 in a radially outward direction through the passage-
way between the hub and the side panel. A ring 50 is again
bolted to the mounting bosses 30 but does not form a shroud
for any vanes of an annular fan.
Looking then to the embodiment of Figures 9 and 10,
corresponding numbers are again employed. In this embodiment,
the vanes 48 are integrally associated with the shroud and__~
mounting ring 50. The flange 42 extending from the hub 14 to
adjacent the periphery of the disc 24 includes an additional
segment extending adjacent the side of the vanes 48 as can best
be seen in Figure 10. By separately forming the fan, the fan
may be of any appropriate material rather than the specific
light alloy of the hub.
Thus, through the embodiments of the present inven-
tion disclosed above, both weight and size reduction can be
achieved with shielded disc brake systems without compromising
cooling requirements. While embodiments and applications of
this invention have been shown and described, it would be
apparent to those skilled in the art that many more modifica-
tions are possible without departing from the inventive concepts
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herein described. The invention, therefore, is not to be
restricted except by the spirit of the appended claims.
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