U.S. patent application number 11/766650 was filed with the patent office on 2008-07-03 for endless belt drive for a vehicle.
This patent application is currently assigned to BOMBARDIER RECREATIONAL PRODUCTS INC.. Invention is credited to Jeannot Belanger, Robert Bessette, Bertrand Mallette.
Application Number | 20080156548 11/766650 |
Document ID | / |
Family ID | 36601324 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080156548 |
Kind Code |
A1 |
Mallette; Bertrand ; et
al. |
July 3, 2008 |
Endless Belt Drive for a Vehicle
Abstract
An endless belt system for a vehicle having a negative trail
steering geometry is provided. The endless belt system replaces the
wheels that steer a vehicle, particularly an all-terrain vehicle,
to provide increased steerability and floatation over soft
terrain.
Inventors: |
Mallette; Bertrand;
(Rock-Forest, CA) ; Belanger; Jeannot; (Granby,
CA) ; Bessette; Robert; (Mont-St-Gregoire,
CA) |
Correspondence
Address: |
OSLER, HOSKIN & HARCOURT LLP (BRP)
2100 - 1000 DE LA GAUCHETIERE ST. WEST
MONTREAL
QC
H3B4W5
omitted
|
Assignee: |
BOMBARDIER RECREATIONAL PRODUCTS
INC.
Valcourt
QC
SOUCY INTERNATIONAL INC.
Drummondville
QC
|
Family ID: |
36601324 |
Appl. No.: |
11/766650 |
Filed: |
June 21, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/CA05/01949 |
Dec 21, 2005 |
|
|
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11766650 |
|
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60637450 |
Dec 21, 2004 |
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Current U.S.
Class: |
180/9.1 ;
305/127 |
Current CPC
Class: |
B62D 55/14 20130101;
B62D 55/244 20130101; B62K 13/00 20130101; B62D 55/26 20130101;
B62D 55/10 20130101; B62D 55/084 20130101; B62D 55/04 20130101;
B62D 55/24 20130101; B62D 15/00 20130101; B62M 27/02 20130101; B62D
55/112 20130101; B62K 5/01 20130101; B62D 55/108 20130101; B62D
55/065 20130101; B62D 17/00 20130101; B62M 2027/027 20130101; B62D
55/12 20130101; B62M 2027/022 20130101; B62K 2005/001 20130101 |
Class at
Publication: |
180/9.1 ;
305/127 |
International
Class: |
B62D 55/065 20060101
B62D055/065 |
Claims
1.-12. (canceled)
13. A drive system suitable for use on a vehicle having: a frame
having a front portion, a rear portion and a longitudinal axis; an
engine supported by the frame; a seat supported by the frame to
accommodate a rider; and a manually-operable steering device
connected to the frame to accept steering input from the rider; the
drive system comprising: a drive-system frame operatively
connectable to the frame of the vehicle so as to be capable of
pivotal movement with respect to the frame of the vehicle relative
to the longitudinal axis of the vehicle such that the drive system
may be pivoted to steer the vehicle, and so as to be incapable of
pivotal movement with respect to the frame of the vehicle in a
plane parallel to the longitudinal axis and normal to the ground
when the vehicle is on flat level terrain and steered straight; a
rail pivotally mounted to the drive-system frame; a ground-engaging
endless belt in sliding engagement with the rail such that a ground
contact area of the belt is below the rail when the vehicle is on
flat level terrain, the belt being operatively connectable to the
engine to propel the vehicle; and the drive system being
operatively connectable to the steering device of the vehicle.
14. The drive system of claim 13, further comprising a plurality of
wheels about which the belt is disposed, the wheels being
associated with the rail so as to pivotally move in unison
therewith with respect to the drive-system frame.
15. The drive system of claim 14, further comprising a stopper for
limiting pivotal movement of the rail.
16. The drive system of claim 13, further comprising a belt
tensioner associated with the endless belt for maintaining a
tension of the belt constant notwithstanding pivotal movement of
the rail.
17. The drive system of claim 14, wherein the rail is pivotally
mounted to the drive system frame about a pivot axis, and wherein a
load axis, being defined by the resultant load statically
equivalent to the distribution of loads across the ground contact
area of the belt with the ground, intersects the pivot axis.
18. An all-terrain vehicle, comprising: a frame having a front
portion, a rear portion and a longitudinal axis; an engine
supported by the frame; a straddle seat supported by the frame to
accommodate a rider; a handlebar connected to the frame to accept
steering input from the rider; a first drive system as recited in
claim 14 at a front left side of the vehicle; and a second drive
system as recited in claim 14 at a front right side of the
vehicle.
19. The all-terrain vehicle of claim 18, further comprising a
steering angle stopper limiting a steering angle of at least one of
the drive systems, the steering angle stopper disposed on the
vehicle such that a steering linkage of the vehicle does not bear a
force created when the stopper is engaged.
20. A vehicle comprising: a frame having a front portion, a rear
portion and a longitudinal axis; an engine supported by the frame;
a seat supported by the frame to accommodate a rider; a
manually-operable steering device connected to the frame to accept
steering input from the rider; a suspension system movably
connected to the frame, the suspension system including a shock
absorbing element; a drive system connected to the suspension
system and capable of pivotal movement with respect to the
longitudinal axis of the frame to steer the vehicle, the drive
system operatively connected to the steering device, the drive
system having: a plurality of wheels; ground-engaging endless belt
rotatable about the plurality of wheels; a steering angle stopper
limiting a steering angle of the drive system, the steering angle
stopper disposed on the vehicle such that a steering linkage of the
vehicle does not bear a force created when the stopper is
engaged.
21. The vehicle of claim 20, wherein the drive system further
comprises a rail with which the belt is in sliding engagement.
22. The vehicle of claim 20, wherein the stopper is mounted on the
frame.
23. The vehicle of claim 20, wherein the stopper is mounted on the
drive system.
24. The vehicle of claim 20, wherein the stopper is mounted on the
suspension system.
25. The vehicle of claim 20, wherein the vehicle is an all-terrain
vehicle, the seat is a straddle seat, and the steering device is a
handlebar.
26. The vehicle of claim 21, wherein the stopper is mounted on the
frame.
27. The vehicle of claim 21, wherein the stopper is mounted on the
drive system.
28. The vehicle of claim 21, wherein the stopper is mounted on the
suspension system.
29. The vehicle of claim 21, wherein the vehicle is an all-terrain
vehicle, the seat is a straddle seat, and the steering device is a
handlebar.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a division of International
Application PCT/CA2005/001949, entitled ENDLESS BELT DRIVE FOR
VEHICLE, with an International filing date of Dec. 21, 2005.
Through that International Application, the present application
claims the priority of U.S. Provisional Patent Application Ser. No.
60/637,450, entitled ALL-TERRAIN VEHICLE WITH TRACK, filed on Dec.
21, 2004. These applications are incorporated herein by reference
in their entirety.
FIELD OF THE INVENTION
[0002] This invention relates to endless belt drive systems for
vehicles, and specifically to those endless belt drive systems
which pivot in order to steer the vehicle to which they are
attached.
BACKGROUND OF THE INVENTION
[0003] All-terrain vehicles are one kind of straddle type vehicle,
so called because they have a straddle seat that supports at least
one rider sitting in a straddle fashion. These vehicles have
generally, although not necessarily, four wheels contacting the
ground and supporting the vehicle via a suspension. An engine,
supported by the frame, is operatively connected to at least one of
the wheels to propel the vehicle. Handlebars are typically
pivotally connected to the frame in front of the straddle seat and
are operatively connected to the front wheels to steer the vehicle.
Fenders and fairings offer protection for the rider against
projectiles from the wheels when the vehicle is in motion.
[0004] As their name would suggest, all-terrain vehicles are
designed to travel over various types of terrain. To that end, they
are generally equipped with low pressure tires (i.e. "balloon
tires" generally having a pressure less than 138 kilopascal (or 20
psi) which have a large contact patch with the ground. This large
contract patch reduces the pressure exerted on the ground by the
tire. This low pressure applied on the ground is advantageous for
these vehicles as it allows them to go over soft terrain like mud,
sand or snow.
[0005] Particularly with reference to snow-covered terrain, these
balloon tires are not an always optimal as on snow it becomes
increasingly difficult for the vehicle to move when the thickness
of snow on the ground becomes significant. This is so because,
depending on the snow conditions, it may happen that pressure
applied on the snow surface by even the balloon tires becomes too
great to support the vehicle. The tires thus begin to sink in the
snow. The further the tires sink into the snow the more likely that
the lower portion of the frame of the vehicle will come into
contact with the snow surface. This situation is not at all
desirable as when the frame touches the snow on the ground it
begins to direct transfers the load of the vehicle onto the snow
surface. Friction between the frame and the snow on the ground
creates drag when the vehicle moves. The pressure provided on the
ground by the tires progressively diminishes and traction may be
subsequently lost in favor of greater contact between the lower
portion of the frame and the ground.
[0006] Moreover, the wheels have less traction when the drag
increases and their friction with the snow surface diminishes. The
tires begin to slip over the ground surface while the vehicle
becomes more and more supported by the frame contacting directly
the snow on the ground, until the tires completely loose traction
on the snow--the vehicle is then struck.
[0007] An alternative known in the art provides an replacing the
wheels with an endless belt system (or track systems) when the
vehicle is to be used in snowy conditions. Many types of such
systems exist. For example, some endless belt systems have been
designed to be added over the wheels of an all-terrain vehicle.
Sometimes the addition of either a number of additional wheels or a
track supporting structure is required to be added to the existing
vehicle. Other endless belt systems have been designed to
completely replace the wheels.
[0008] Replacement of the wheels by endless belt systems provides a
larger contact area (patch) on the ground compared to size of the
contact area (patch) of a wheel on the ground--even with a low
pressure balloon tire. Floatation over the snow is increased and
the lower portion of the frame is maintained at a greater distance
from the snow surface. The vehicle can be used in deeper snow
because floatation and traction are preserved.
[0009] These systems, while good, are not without their drawbacks.
For one, the size of the contact patch also affects the ease of
steering the vehicle. On a wheeled or tracked vehicles, the wheels
that steer the vehicle are turned about a pivot point on the ground
(more precisely over the steering axis) based on the steering
geometry of the vehicle. The contact area of the wheel or track
that surrounds the pivot point on the ground of the steering wheels
opposes, via friction, the rotational movement of the wheel or
track about this pivot point. Thus, the larger the contact area on
the ground the more area there is to generate friction which
opposed the movement about the pivot point, and the tougher it is
to rotate the patch around the pivot point. Therefore, the larger
contact area on the ground generated by an endless belt system
inherently increases the force needed to steer the vehicle.
[0010] Another difficulty is that some endless belt systems are
fixedly connected to the frame of the vehicles. This prevents the
systems from tracking the shape of the uneven terrain over which
the vehicle is traveling. In prior art systems that are pivotally
attached the to frame, in the past, they have always been pivotally
attached about what would have been the hub of the wheel if a wheel
had been attached. This means that the system must have rather
large movements in order to track the shape of the terrain, which
is still not optimal. In other type of system, the traction
provided is thus somewhat limited because the contact area of the
endless belt is not capable of adapting to the ground's
imperfections.
[0011] Finally, normally these endless belt systems are used on
vehicles that were designed to accommodate wheels. These belt
systems are sold typically in the aftermarket by those other than
the original equipment manufacturers. Thus, the suspension, drive
train, steering linkages, etc. have all been designed to sustain
the loads generated by wheels, and not necessarily by belt systems.
Belt systems typically generate higher mechanical loads as they are
heavier than wheels and require more force in order to steer. In
some circumstances, on some vehicles, improvement is required in
order to sustain such loads.
[0012] Accordingly, there remains a need for an improved endless
belt system for vehicles, and particularly all-terrain vehicles,
which ameliorates some of the deficiencies associated with prior
art systems.
SUMMARY OF THE INVENTION
[0013] The present invention attempts to ameliorate some of such
aforementioned deficiencies. It should be noted that various
features of the present invention are herein described. It should
be understood that while each feature contributes to an aspect of
the present invention, the present invention has many aspects.
Thus, it is not necessary for all features to be present in every
embodiment. In this respect, it is not necessary that every
embodiment make ameliorations to or alleviate every drawback herein
noted with respect to the prior art.
[0014] Accordingly, in one aspect, one or more embodiments of the
present invention provide a drive system suitable for use on a
vehicle having: [0015] a frame having a front portion, a rear
portion and a longitudinal axis; [0016] an engine supported by the
frame; [0017] a seat supported by the frame to accommodate a rider;
[0018] a manually-operable steering device pivotally connected to
the frame to accept steering input from the rider; [0019] the drive
system comprising: [0020] a drive-system frame operatively
connectable to the frame of the vehicle so as to be capable of
pivotal movement with respect the frame of the vehicle relative to
the longitudinal axis of the vehicle such that the drive system may
be pivoted to steer the vehicle, the drive system being operatively
connectable to the steering device of the vehicle; [0021] a
ground-engaging endless belt movably disposed on the drive-system
frame and operatively connectable to the engine to propel the
vehicle; and [0022] when the drive system is connected to the
vehicle, and when the vehicle is on flat level terrain, the drive
system has a steering axis, about which the drive system pivots to
steer the vehicle, a load axis, being defined by the resultant load
statically equivalent to the distribution of loads across a contact
area of the endless belt with the ground, and a point of
intersection of the mean load axis and the ground is longitudinally
forward of a point of intersection of the projection of the
steering axis onto the ground and the ground, whereby the drive
system has a negative trail.
[0023] It should be noted that although the invention was described
as have a particular utility with respect to all-terrain vehicles,
it is contemplated that it could be applied to other types of
vehicles experiencing similar drawbacks, such as tractors.
[0024] Preferably, a longitudinal distance between the point of
intersection of the load axis and the ground and the point of
intersection of the projection of the steering axis onto the ground
and the ground is not greater than 250 mm. More preferably, this
distance is not greater than 150 mm. Still more preferably, this
distance is not less than 10 mm and not greater than 100 mm. Most
preferably, it is not less than 40 cm and not greater than 45
cm.
[0025] It is also preferred the present drive systems further
comprise a rail pivotally mounted to the drive-system frame about
which the endless belt is disposed, and that the rail be pivotally
mounted to the drive system frame about a pivot axis, and that the
load axis intersects the pivot axis. It is also preferred that the
pivotal movement of the rail about the pivot axis be limited by a
stopper.
[0026] Additionally, it is preferred that the a belt tensioner be
associated with the endless belt for maintaining a tension of the
belt constant notwithstanding pivotal movement of the rail.
[0027] It is also preferred that a caster of the steering axis is
positive.
[0028] As was previously stated, the present invention has
particularly utility on all-terrain vehicles that comprise: [0029]
a frame having a front portion, a rear portion and a longitudinal
axis; [0030] an engine supported by the frame; [0031] a straddle
seat supported by the frame to accommodate a rider; [0032] a
handlebar pivotally connected to the frame to accept steering input
from the rider; and [0033] a drive systems described hereinabove on
both the front left side and front right side of the vehicle.
[0034] On such vehicles, it is preferred that a steering angle
stopper limits a steering angle of at least one of the drive
systems, the steering angle stopper being disposed on the vehicle
such that a steering linkage of the vehicle does not bear a force
created when the stopper is engaged.
[0035] In another aspect, one or more embodiments of the present
invention provides a drive system suitable for use on a vehicle
having: [0036] a frame having a front portion, a rear portion and a
longitudinal axis; [0037] an engine supported by the frame; [0038]
a seat supported by the frame to accommodate a rider; and [0039] a
manually-operable steering device pivotally connected to the frame
to accept steering input from the rider; [0040] the drive system
comprising: [0041] a drive-system frame operatively connectable to
the frame of the vehicle [0042] so as to be capable of pivotal
movement with respect to the frame of the vehicle relative to the
longitudinal axis of the vehicle such that the drive system may be
pivoted to steer the vehicle, and [0043] so as to be incapable of
pivotal movement with respect to the frame of the vehicle in a
plane parallel to the longitudinal axis and normal to the ground
when the vehicle is on flat level terrain and steered straight;
[0044] a rail pivotally mounted to the drive-system frame; [0045] a
ground-engaging endless belt in sliding engagement with the rail
such that a ground contact area of the belt is below the rail when
the vehicle is on flat level terrain, the belt being operatively
connectable to the engine to propel the vehicle; and [0046] the
drive system being operatively connectable to the steering device
of the vehicle.
[0047] In such aspects, it is preferred that the drive system
further comprises a plurality of wheels about which the belt is
disposed, and that the wheels are associated with the rail so as to
pivotally move in unison therewith with respect to the drive-system
frame. A stopper may limiting pivotal movement of the rail. It is
also preferred that a belt tensioner be associated with the endless
belt for maintaining a tension of the belt constant notwithstanding
pivotal movement of the rail.
[0048] It is preferred that the rail be pivotally mounted to the
drive system frame about a pivot axis, and that a mean load axis,
being the normal projection onto the ground of a mean load point of
loads across the ground contact area of the belt with the ground,
intersects the pivot axis.
[0049] As was previously stated, the present invention has
particularly utility on all-terrain vehicles that comprise a frame
having a front portion, a rear portion and a longitudinal axis;
[0050] an engine supported by the frame; [0051] a straddle seat
supported by the frame to accommodate a rider; [0052] a handlebar
pivotally connected to the frame to accept steering input from the
rider; [0053] a first drive system as recited in any one of claims
12 to 16 at a front left side of the vehicle; and [0054] a second
drive system as recited in any one of claims 12 to 16 at a front
right side of the vehicle.
[0055] It is preferred that such vehicles have a steering angle
stopper limiting a steering angle of at least one of the drive
systems, and that the steering angle stopper is disposed on the
vehicle such that a steering linkage of the vehicle does not bear a
force created when the stopper is engaged.
[0056] In yet another aspect, one or more embodiments of the
present invention provide a vehicle comprising: [0057] a frame
having a front portion, a rear portion and a longitudinal axis;
[0058] an engine supported by the frame; [0059] a seat supported by
the frame to accommodate a rider; [0060] a manually-operable
steering device pivotally connected to the frame to accept steering
input from the rider; [0061] a suspension system movably connected
to the frame, the suspension system including a shock absorbing
element; [0062] a drive system connected to the suspension system
and capable of pivotal movement with respect to the longitudinal
axis of the frame to steer the vehicle, the drive system
operatively connected to the steering device, the drive system
having: [0063] a plurality of wheels; [0064] ground-engaging
endless belt rotatable about the plurality of wheels; [0065] a
steering angle stopper limiting a steering angle of the drive
system, the steering angle stopper disposed on the vehicle such
that a steering linkage of the vehicle does not bear a force
created when the stopper is engaged.
[0066] It is preferred that the drive system further comprises a
rail with which the belt is in sliding engagement.
[0067] Preferred mounting positions for the stopper are on the
frame, the drive system, and the suspension.
[0068] As was previously stated, the present invention has
particularly utility on all-terrain vehicles wherein the seat is a
straddle seat and the steering device is a handlebar.
[0069] Additional and/or alternative advantages and salient
features of the invention will become apparent from the following
detailed description, which, taken in conjunction with the annexed
drawings, disclose preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0070] For a better understanding of the present invention as well
as other objects and further features thereof, reference is made to
the following description which is to be used in conjunction with
the accompanying drawings, where:
[0071] FIGS. 1a and 1b depict front-left side elevation views of an
all-terrain vehicle according to one embodiment of the present
invention. FIG. 1 depicts an all-terrain vehicle with wheels on it
and FIG. 2 depicts an all-terrain vehicle with an endless belt
system replacing the wheels;
[0072] FIG. 2 depicts a left side elevation view of an endless belt
system on a front-left portion of an all-terrain vehicle with a cut
section allowing to see the steering linkage behind the track;
[0073] FIG. 3a depicts a front elevation view of a left side of an
all-terrain vehicle with an endless belt system aligned to be
installed on a the front left hub of the all-terrain vehicle in
replacement of the wheel;
[0074] FIG. 3b depicts a front elevation view of a left side of an
all-terrain vehicle having a MacPherson suspension with an endless
belt system installed on the front left spindle;
[0075] FIG. 4a depicts a front elevation view of a left side of an
all-terrain vehicle having a double A-arms suspension with an
endless belt system installed on the front left spindle;
[0076] FIG. 4b depicts a front elevation view of a left side of an
all-terrain vehicle having a MacPherson suspension with a wheel
installed on the front left spindle;
[0077] FIGS. 5a to 5c depict left elevation side views of front
endless belt system depicting different angles for the endless belt
system and its contact area;
[0078] FIG. 6 depicts a bottom-right-front perspective view of an
endless belt system installed on an all-terrain vehicle;
[0079] FIG. 6a depicts a top view of the left front side of an
all-terrain vehicle with a wheel;
[0080] FIG. 6b depicts a top view of the left front side of an
all-terrain vehicle with a steered wheel;
[0081] FIG. 6c depicts a top view of the left front side of an
all-terrain vehicle with an endless belt;
[0082] FIG. 6d depicts a top view of the left front side of an
all-terrain vehicle with a steered endless belt;
[0083] FIG. 7 depicts an exploded view of a front track kit;
[0084] FIG. 8 depicts an exploded view of a rear track kit;
[0085] FIG. 9a depicts a left side elevation view of an all-terrain
vehicle with wheel and tire installed and depicting different
steering and suspension geometries;
[0086] FIG. 9b depicts a left elevation view of an endless belt
system installed on an all-terrain vehicle with the endless belt
removed and depicting the different steering and suspension
geometries;
[0087] FIG. 10a depicts a front elevation view of the left side of
an all-terrain vehicle with wheel and tire installed and depicting
different steering and suspension geometries;
[0088] FIG. 10b depicts a front elevation view of an endless belt
system installed on an all-terrain vehicle with the endless belt
removed and depicting different steering and suspension
geometries;
[0089] FIG. 11a depicts the profile of the endless belt used to
steer the vehicle; and
[0090] FIG. 11b depicts the profile of the endless belt not used to
steer the vehicle.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0091] FIG. 1 a depicts an all terrain vehicle 10 having a straddle
seat 20 to accommodate one or more riders. A rider (not shown)
sitting in a straddle fashion may hold the handlebars 22 to steer
the vehicle. The frame 60 is supported by four wheels (three of
them are visible on FIG. 1a) 26, 28 and 30 spaced apart from a
longitudinal axis 45 of the vehicle. The front wheels are
associated with a front axle 40 and hub axis 69 and are operatively
connected to the engine via a front drive system affixed to the
front portion of the frame. The rear wheels are associated with a
rear axle 42 and are operatively connected to the engine via a rear
drive system affixed to a rear portion of the frame. In use, the
rider puts his feet on footrests 24 disposed on each lateral side
of the vehicle. The rider is protected against projections from the
wheels by front fenders 34 and rear fenders 32. A front and a rear
rack 38, 36 are convenient for carrying cargo on the vehicle.
[0092] FIG. 1b illustrates an all-terrain vehicle with an endless
belt system replacing each of the four wheels. Each endless belt
system may be (but all are not required to be) operatively
connected to the engine to propel the vehicle, provide traction to
the vehicle and ensure maximum floatation and optimal traction on
soft terrain. Endless belt system 50 has replaced the front left
wheel while endless belt systems 52, 54 and 56 have replaced the
front right wheel, the left rear wheel and the right rear wheel,
respectively.
[0093] A more precise view of belt system 50 is presented in FIG.
2. Belt system 50 is removeably connected to hub 68 by fasteners
80. The hub 68 is rotatively held by knuckle 66. The hub 68
previously connected the front left wheel 28 to the vehicle and
provided the rotational motion to the wheel. With the belt system
50, the rotational motion of hub 68 is transferred to sprocket
wheel 112 that turns the endless belt 100 (or track) about hub axis
69 and sprocket axis 122 by knobs 120 which interface with
corresponding structures on belt 100, similar to the rear drive
system of a snowmobile. Endless belt 100 is maintained in place by
sprocket 112 at the belt's then upper portion and by corner wheels
102, 104 at the then forward and rearward portions of the endless
belt. Corner wheels preferably have a diameter of 25 cm however,
different wheel diameters are considered within the scope of the
present application. Support wheels 106 maintain the then bottom
portion of belt 100 in place and limit the friction between the
belt and rail 108 when supporting the vehicle on the ground.
[0094] The corner wheels 102, 104 and the support wheels 106 are
maintained in their position by rail 108 and link 110 (which in
this embodiment should be considered to be a frame). Support wheels
of the present embodiment have a diameter of approximately 10 cm to
15 cm. Different wheel diameters could be used and be within the
scope of the present application. The rail is pivotally mounted to
link 110 thus allowing angular variations in the contact area 101
to allow the endless belt to follow imperfections or unevenness in
the terrain over which the vehicle may be passing.
[0095] Link 110 is made by aluminum casting to achieve low cost,
lightweight and rust resistance. Fiber-charged plastics (to yield
improved stiffness) or other materials and/or processes could be
used without departing from the scope of the present application.
In the present embodiment rail 108 is made of UHMW via compression
molding process.
[0096] Contact area 101 is to the endless belt what the contact
patch is to a tire. The contact area is the portion of the endless
belt that, is most of the time, in contact with the ground and
through which (in most instances) the load is transmitted. (The
pivotal movement of the rail will be discussed further in the
description.) Link 110 is maintained by roller bearings (not shown
on FIG. 2 but can be seen on FIG. 7) over hub axis 69 meaning the
hub can turn sprocket 112 without turning link 110. Link 110 can
therefore transmit the load applied to the track system by the
vehicle from hub 68 and knuckle 66 and is prevented from turning by
a separate anti-rotation connector 111 attached to the vehicle via
spacer 140 (not shown on FIG. 2, can be seen on FIG. 6).
[0097] Still referring to FIG. 2, it should be noted that in most
cases belt systems installed on the front portion of the vehicle
need to be steerable. A steering column 62 connected on one end to
handlebars 22 and on the other end to steering link 64 moves
knuckle 66, as was the case when wheels were present on the
vehicle. Also referring to FIG. 2, frame 60 is shown with top
Macpherson suspension connector 72.
[0098] FIG. 3a depicts an unassembled endless belt system 50
replacing wheel 28. It is possible to see fasteners 80 on hub 68.
The hub is rotated by half shaft 74 that transmits power from the
engine via a front drive shaft and a front differential. It can be
appreciated that the suspension system presented in the embodiment
of FIG. 3a is a Macpherson type suspension. This suspension type
has a shock absorber 70 (a strut) connected between the frame 60
(via connector 72) and the lower A-arm 76 (via knuckle 66). At the
bottom of the rail is affixed slider 124, made of low friction
material to reduce the friction between link 110 and endless belt
100 when the belt cannot be entirely supported by support wheels
106. Additionally, an adjustment mechanism 78 is provided to set
the tension of endless belt 100 by moving the front and rear corner
wheels apart. In this embodiment a bolt on adjustment mechanism 78
can be turned to adjust the position of the front corner wheels
axle. This changes the peripheral distance over all corner wheels,
support wheels and the sprocket. The endless belt can therefore be
removed from the mechanical structure of the track system for
maintenance and put back in place with the adequate tension.
[0099] FIG. 3b depicts the track system of FIG. 3a installed on the
left front hub of the all-terrain vehicle. The anti-rotation
connector 111 connects the link 110 to the lower A-arm 76 to
prevent relative movements between the link and the A-arm. The
connection of anti-rotation connector 111 under lower A-arm 76 is
preferably positioned in line with steering axis 230 (described
later in this description) to avoid other movements of the endless
belt system when the vehicle is steered. Should the connection of
anti-rotation connector 111 not be in line with steering axis 230
the endless belt system would not move only accordingly to the
steering movement.
[0100] The connection of the anti-rotation connector 111 to
suspension arm 76 could be connected not in line with steering axis
230 and provide desirable effects. For instance, self centering of
the steering can be augmented if the connection of the
anti-rotation connector 111 to the vehicle is located next to the
steering axis. This would slightly rotate link 110 over hub axis 69
when the vehicle is steered. Depending on the disposition of the
anti-rotation link 111 on the vehicle, the rear angular limiter 116
contacts rail 108 thus moving down the rear end of the endless belt
that is on the exterior side when riding the vehicle in a
curve.
[0101] FIG. 4a shows the same arrangement as presented on FIG. 3b
but instead uses a double A-arm suspension configuration. Knuckle
66 is connected on its upper portion to top A-arm 77. The shock
absorber 70 is connected at its upper extremity to connector 72 and
connects the top A-arm 77 at its lower extremity. FIG. 4b depicts
the same view as FIG. 3b with a wheel installed.
[0102] FIGS. 5a, 5b and 5c depict the pivotal movement of rail 108
in respect to link 110. The rail can pivot over pivot axis 114 and
has two angular limiters defined as front link portion limiter 118
and rear link portion limiter 116. The pivotal movement is limited
when either the front or the rear angular limiters 118, 116 enters
in contact with rail 108. FIG. 5a shows the limit on one side of
the pivotal motion; rear link portion 116 is in contact with rail
108 thus providing angle .alpha..sub.0=0.degree.. FIG. 5b presents
an intermediate angle .alpha. in the pivotal motion; neither the
front nor the rear link portions 118, 116 contact rail 108. This is
the range where the endless belt system is used most of the time to
align the angle of contact area 101 to the ground condition. FIG.
5c is the limit of the pivotal motion on the other side; front link
portion 118 is in contact with rail 108 and .alpha..sub.max=maximum
angular displacement. In the present situation .alpha..sub.max is
between 22.degree. and 25.degree.. At rest, on flat horizontal
surface with contact area 101 substantially parallel with the
ground, at .alpha..sub.0=020 , the rear link portion 116 is in
contact with rail 108. This means the angular displacement is
mostly done forward to improve stability. The angular displacement
a disclosed in this embodiment is an example of an applicable
displacement. The scope of the present invention encompasses other
angular variations .alpha.' as well as other means for limiting the
travel of the rail. Also, rail 108 in this embodiment maintains the
endless track in position on the track system while allowing
angular variation of the contact area's 101 of the endless belt.
Further, the peripheral distance between sprocket 112, corner
wheels 104, 104 and support wheels 106 remains substantially the
same as the angle .alpha. varies. This prevent change in the
endless belt tension. Also, the angle .alpha. is restricted to
avoid the endless belt contacts the fenders of the vehicle.
[0103] The mass 85 of the vehicle is not transferred vertically in
line with hub axis 69. Pivot 114 pivotally connecting rail 108 to
link 110 is where the load of the vehicle 85 is vertically
transferred to the ground when angle .alpha. is between
.alpha..sub.0 and .alpha..sub.max. Therefore the load axis 85 falls
in vertical line with pivot 114. When rail 108 reaches maximum
angles .alpha..sub.0 and .alpha..sub.max axis 85 moves from axis
114 because a portion of the load transfer between link 110 and
rail 108 passes through front or rear angular limiters 118, 116.
During normal operation, angle .alpha. does not, most of the time,
reach its maximum value. FIG. 6 shows the under surface of the
track system. Anti-rotation connector 111 ensures the track system
will not turn over the hub axis 69 when sprocket 112 turns.
Connector 111 is fastened on one end to the lower A-arm 76 and to
link 110 via bracket 130. The anti-rotation connector is adjustable
in length to allow modification of the link 110 angular position in
respect to the lower A-arm 76. In this embodiment, a rod end is
used to connect the anti-rotation connector to the A-arm for
permitting rotation of the endless belt system when the vehicle is
steered. A spacer 140 is also added to distance the connecting
point of connector 111 on A-arm 76. This allows one to modify the
movements of the endless belt system when the vehicle is
steered.
[0104] Still referring to FIG. 6 a steering angle limiter 134 is
provided to substantially reduce steering angle .theta.. There are
greater forces and stresses on the mechanical parts when the
vehicle is steered because of the increased friction provided by
the endless belt system (in comparison to a wheel). The endless
belt system installed on the vehicle is wider than a wheel. The
enlarged distance between the outermost portion of the endless belt
system and the steering axis changes the force ratio between the
handlebars and the endless belt system. For at least these reasons,
the steering linkages 64 and the half shafts 74 are substantially
more stressed.
[0105] Now referring to FIGS. 6a, 6b, 6c and 6d, the steering angle
limiter 134 in the present embodiment reduces of about 7.degree.
the steering angle .theta. on each side (from neutral to fully
right hand turned for instance). The steering angle limiter 134 is
disposed next to the track system to prevent high mechanical loads
from reaching the steering linkage 64 and the steering column 62 by
abutting against the bracket 130 which is fixed to the rail 108. It
is possible to clearly see on FIG. 6d the angular stopper 134
contacting a portion of rail 108 thus limiting the steering
movement of the endless belt system. Another way to limit the
steering angle would be to use an augmented angular stopper on
steering column 64. In the latter case all the efforts applied to
the endless belt system would be supported by the steering linkage,
which is undesirable. Moreover, steering angle limiter 134 of the
present embodiment is fastened to lower A-arm 76, thus any
undesirable forces coming from a sudden impact on the track system
would be transferred to the A-arm 76 rather than to the steering
components 64, 66, etc. It is therefore possible to remove steering
angle limiter 134 to get back to the original steering geometry.
This is useful when the vehicle alternates between the wheels and
the endless belt systems depending on the ground conditions.
[0106] FIG. 7 is an exploded view of the endless belt system
designed to be installed in replacement of steering wheels. FIG. 8
is an exploded view of the endless belt system designed to be
installed in replacement of non-steering wheels; in the present
situation on the rear axle. The main difference between the endless
belt system replacing steering wheels and the endless belt system
replacing non-steering wheels is that the rail 108 of the endless
belt system for non-steering wheels is not pivotally connected to
the link 110. Either, or both, the front or rear link portions 116,
118 are fastened to rail 108 on endless belt systems to be
installed on non-steering wheels. The pivotal movement is therefore
only possible, in this embodiment, for endless belt systems
installed in replacement of steering wheels to achieve the results
that will be described further in this text.
[0107] There are three main parameters on wheeled vehicle
suspension and steering geometry: toe, camber and caster. Endless
belt systems have different geometrical parameters than do wheels.
This has an effect on the vehicles to which they are attached's
behaviors. The larger contact area with the ground makes track
systems harder to turn over the steering axis 230 (or caster axis).
Caster is the angle to which the steering pivot axis is tilted
forward or rearward from vertical, as viewed from the side. If the
pivot axis is tilted backward (that is, the top pivot is positioned
farther rearward than the bottom pivot), then the caster is
positive; if he pivot axis is tilted forward, then the caster is
negative. Positive caster tends to straighten the wheel when the
vehicle is traveling forward, and thus is used to enhance
straight-line stability. The forces that causes the wheel to follow
the steering axis is proportional to the distance between the
steering axis and the wheel's load axis (which in the context of
the present application should be understood to be the mean load
axis, being the normal projection onto the ground of a mean load
point of loads across the ground contact area of the endless belt
with the ground), the greater the distance, the greater the force.
This distance is referred as "trail". When the steering axis
intersects the ground in front of the load axis the trail is
referred as a positive trail as opposed to negative trail which
when the steering axis intersects the ground behind the load
axis.
[0108] Most wheeled vehicles use a positive trail for the reasons
stated above. A negative trail on a wheeled vehicle would likely
provide instability because the steering wheels would tend to
completely turn 180.degree. over the steering axis. Nonetheless,
the present inventors have realized that this force pushing the
wheel to turn (with a negative trail) is helpful when applied with
track systems. An endless belt system is quite different mainly
because of its size (height, width) and its larger contact area
with the ground. The much larger contact area 101 (patch) of an
endless belt system provides resistance against rotational movement
over the steering axis. This resistance is undesirable because it
makes the endless belt system harder to steer, but it adds
stability. A negative trail applied on an endless belt system uses
this resistance caused by the contact patch friction with the
ground and opposes the tendency to completely turn the track kit
180.degree. over the steering axis to bring the steering effort to
an acceptable level. In sum, the tendency to completely turn the
track system 180.degree. over the steering axis provided by the
negative trail is damped by the higher friction generated by the
large contact patch. An adequate negative trail provides a lighter
steering effect without causing instability.
[0109] FIGS. 9a and 9b depict left side elevation views of a front
steering wheel and a front steering endless belt system on an
all-terrain vehicle. On the wheeled vehicle of FIG. 9a the steering
axis 230 is angled E in respect to vertical 210 from hub axis 69.
Steering axis 230 passes along the top pivot point 180 and the
lower pivot point (not shown) of the Macpherson suspension strut of
this embodiment. The positive trail, distance in front of the true
vertical projection 210 of the mass application on the ground, is
indicated by identifier F. F being the distance between the
vertical projection 200 of steering axis 230 intersecting ground
level 220. The distance between the hub axis 69 and the ground 220
is indicated by identifier A.
[0110] On the vehicle with a track system of FIG. 9b the steering
axis 230 is angled E in respect to vertical 210 from hub axis 69.
This angle is no different from the wheeled vehicle because the
suspension connections are not altered by the endless belt system.
Steering axis 230 passes along the top pivot point 180 and the
lower pivot point (not shown) of the Macpherson suspension strut of
this embodiment. As opposed to the wheeled vehicle of FIG. 9b, the
load 85 is applied on the ground with vertical load projection 240
originating from pivot 114. The vertical load projection 240 is
considered instead of vertical projection 210 because the non
rotatable link 110 pushes forward over pivot 114 the vertical
application of the vehicle's load to the ground. The negative trail
D is the distance between vertical projection 200 of steering axis
230 intersecting ground 220 (or contact area 101) and load
projection 240. Negative trail D at ground level is preferably
about 40-45 mm between steering axis 230 and the load axis 85. The
distance between the hub axis 69 and the ground 220 is expressed by
A'.
[0111] The anti-rotation connector 111 geometry in conjunction with
the negative trail provides a more balanced steering. The negative
trail helps the endless belt systems to rotate over steering axis
230 from its straight position and the anti-rotation connector 111
geometry conversely helps bring back straight the steering once
turned.
[0112] Still referring to FIG. 9b, it is possible to notice the
vertical elevation of both front and rear corner wheels 102, 106.
The elevation of front corner wheels 102 from the ground helps
maintain the endless belt system over the snow on the ground when
the vehicle moves forward. The elevation of rear corner wheels 104
from the ground helps maintain the endless belt system over the
snow on the ground when the vehicle moves rearward. Should rear
corner wheels 104 be substantially at the same level as ground 220
the endless belt system would tend to dig in soft snow instead of
floating over snow when moving rearward. The large diameter of
corner wheels 102, 104 also help push more snow under the contact
area of the endless belt system.
[0113] FIGS. 10a and 10b are respectively the side elevation views
of FIGS. 9a and 9b. On these figures it is possible to appreciate
the Macpherson type suspension with suspension strut 70 connected
at its top portion to suspension connector 72 via top strut pivot
180 and pivotally connected at its lower portion, through knuckle
66, to ball joint 290. The axis defined by top pivot 180 and lower
ball joint 290 is steering axis 230 over which the wheel or the
endless belt system rotates to steer the vehicle. Angle B is the
angle between the steering axis and vertical 280.
[0114] Distance D on FIG. 10a is the distance of the steering axis
230 to the center line of wheel 28 at ground level 220. Distance C
is from the vehicle's center line 300 to the wheel center line H.
Applied to the endless belt system depicted on FIG. 10b, distance
D' is larger and on the opposite side (proximal side) of the
endless belt system's contact area center line H' due to larger
distance C' between the center of the vehicle 300 and contact
area's center line H'. Distance A' between the hub axis 69 and
ground 220 is also larger than distance A because the endless belt
system is higher than a wheel. The resulting higher ground
clearance may help circulating in deep snow while limiting the
friction between the frame of the vehicle and the snow.
[0115] Endless belt systems installed in replacement of steering
wheels on an all-terrain vehicle need to pivot over the steering
axis to steer the vehicle. Usually, on most snow vehicles, like
snowmobiles, endless belt propulsion mechanisms do not turn over a
steering axis to steer vehicles. Skis in front of the vehicle
provide steering or, on a multi laterally disposed endless belt
propulsion systems, steering of the vehicle may be accomplished by
speed differentiation between the different endless belt
systems.
[0116] The tread profile on the steering endless belts are
different in order to improve steerability of the vehicle. Because
the steering endless belt has to pivot over the steering axis, the
sides of the steering endless belt treads are disposed at an angle
.omega. from the surface dictated by the surface of the belt. As
shown on FIG. 11a, the angle .omega. diminishes the force needed to
turn the endless belt over the steering axis. The tread protrusions
are smaller the further they are from the steering axis. Using a
tread profile with the angle .omega. on the sides may help improve
steerability but has also the effect to reduce traction on the
snow. Using a different profile on the steering endless belt
systems as opposed to non-steering belt systems (as seen on FIG.
11b) allows to one get a lighter steering on the front end and a
optimal traction on the rear end.
[0117] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention is not to be
limited to the disclosed embodiments and elements, but, to the
contrary, is intended to cover various modifications, combinations
of features, equivalent arrangements, and equivalent elements
included within the spirit and scope of the appended claims.
Furthermore, the dimensions of features of various components that
may appear on the drawings are not meant to be limiting, and the
size of the components therein can vary from the size that may be
portrayed in the figures herein. Thus, it is intended that the
present invention covers the modifications and variations of the
invention, provided they come within the scope of the appended
claims and their equivalents.
* * * * *