Note: Descriptions are shown in the official language in which they were submitted.
1
Title: Variable compliance metallic wheel comprising torque measuring device
1. Field of Invention
The present invention relates to a non-pneumatic tire that can be used without
filling it with
pressurized air, with the capacity to alter its flexibility during operation
as well as to measure the
torque generated by or submitted to the wheel axis during operation.
2. Description of Related Art
US 6170544 B1 Hottebart Jan.9,2001 refers to a Non-Pneumatic Deformable Wheel
US 2017/0120671 Al Miles et al. May 4, 2017 refers to Non-Pneumatic Tire with
Partially Compliant
Hub
US 2018/0072095 Al Anderfaas et al. Mar.15, 2018 refers to Variable Compliance
Wheel
US 8950451 B2 Akihiko Abe Feb.10, 2015 refers to Non-Pneumatic Tire
US 20020096237 Al Buhroe et al. Jul. 25, 2002 refers to Compliant rim wheel
and assembly
US 2009/0211675 Al Louden B. Aug. 27, 2009 refers to Non-Pneumatic Tyre
Assembly
US 2014/0110024 Al Anderfaas et al. Apr. 24, 2014 refers to Variable
Compliance Wheel
US 2016/0193876 Al Kyo et al. Jul. 7, 2016 refers to Non-Pneumatic Tire
US 2011/0240193 Al Matsuda et al. Oct. 6, 2011 refers to Non-Pneumatic Tire
and Method of
Manufacturing Same
US 2009/0033051 Al Ahnert 5. Feb. 5, 2009 refers to Stroller Wheel with
Modular Suspension
US 2009/0294000 Al Cron S.M. Dec. 3, 2009 refers to Variable Stiffness Spoke
for a Non-Pneumatic
Assembly
US 2016/0016426 Al Endicott J.M. Jan. 21, 2016 refers to Non-Pneumatic Wheel
Assembly with
Removable Hub
US 2004/0069385 Al Timoney et al. Apr. 15, 2004 refers to Wheel
US 2016/0214435 Al Schaedler et al. Jul. 8, 2016 refers to Wheel Assemblies
with Non-Pneumatic
Tires
An important number of patents has been deposited in the field of non-
pneumatic wheels. Non
pneumatic wheels have the advantages of pneumatic tires regarding shock
absorption from road
irregularities, while avoiding the disadvantages, such as tire failure due to
puncturing. In recent years
Date Recue/Date Received 2021-02-08
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patent applications, as is shown on the list above, a non-pneumatic tire
including an attachment body
attached to an axle, a ring-shaped body configured to surround the attachment
body from the outside in a
tire radial direction, and a plurality of connecting members disposed between
the attachment body and the
ring-shaped body in a tire circumferential direction have been proposed.
Additionally in recent years,
research has been addressing the use of metallic wheels for planetary
exploration, since on planets without
or with very thin atmosphere the use of pneumatic tires is impossible, due to
the presence of radiation that
quickly deteriorates rubber and could render inflated tires useless.
Additionally, the measuring of the torque developed on the wheel axis by an
electric motor used for driving
the wheel, when a high ratio reduction gearbox is used, represents a technical
problem that requires the
use of a torque sensor combined with a continuous rotation electrical
connection (slip ring), in order to
measure the developed torque. This assembly has substantial volume and
increased price and mass. The
measurement of the torque on the other hand, is important for the safety of
the vehicle, especially when
the wheel is mounted on unmanned rovers operating in remote areas or on other
planets.
3. Brief Description of the Invention
According to an aspect of the present invention, there is provided a variable
compliance non-pneumatic
wheel, comprising: a stationary tubular body attached to a vehicle chassis and
being an axle of rotation of
the wheel; a tubular member forming a hub, mounted on the stationary tubular
body and freely rotating
relative to the stationary tubular body, the tubular member comprising a
series of mounting rods on a
periphery of the tubular member and on both sides facing two different width-
wise sides of the wheel; a
number of interconnected caterpillar-like tiles forming an outer periphery of
the wheel, which are free to
rotate relative to one another and configured to be in contact with the ground
during wheel operation; a
plurality of connecting spring members each connecting a specific mounting rod
of a specific side of the hub
and a periphery tile on the same wheel width-wise side, mounted between the
said tubular hub and a body
of the tile in a circular circumferential direction and configured to connect
the hub and the tile body to each
other, wherein said tubular member forming the hub is split in two parts, each
part being free to rotate
relative to the other part, with each part carrying approximately a half
number of mounting rods and
connecting the spring members on a respective width-wise side of the wheel.
Some embodiments of the invention provide a non-pneumatic wheel design that
has the possibility to
behave like a pneumatic tire, but also modify its radial stiffness by means of
a mechanism carried inside the
wheel, that is able to operate even when the wheel is in motion, as well as a
simple torque sensor solution
Date Recue/Date Received 2023-03-03
87962012
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that can be incorporated in the drive train of the wheel and monitor the
torque developed by, or exerted to
the wheel during its operation.
4. Advancement over the State of Art
The invention proposes a solution to stiffness adjustment of non-pneumatic
wheels as well as a solution to
durability issues related to elastic materials (metallic, resin etc), used as
deformable spokes for non-
pneumatic wheels. The invention proposes a specially designed leaf spring
element that is tailored for the
specific function of stiffness adjustment and presents the desired durability
requirements during operation,
combined with its specially designed shape that enables the variation of the
radial flexibility of the wheel by
the counter-rotation of the hub disks holding these springs. In that way, the
proposed invention solves both
durability issues related to non-pneumatic wheels as well as the issue of
regulating wheel stiffness, as a
function of road condition and wheel axis load. The invention provides a
technically viable simple solution
for the regulation of wheel radial stiffness, even when the wheel is in
operation, through the motorized
counter- rotation of the said hub disks. Finally, the invention proposes a
simple and robust solution for
measuring the torque developed or
Date Recue/Date Received 2023-03-03
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exerted on the wheel axis during operation, which is a feature needed for the
safety of the operation
70 of unmanned electric vehicles moving on rough terrain, especially if
they operate in remote
environments or other planets. In such cases, if for example, a wheel becomes
blocked, the torque
sensor can inform the controller of the vehicle and prevent damage on the
motor of the wheel.
5. Brief Description of the Drawings
75 Other objects, features and advantages will occur to those skilled in
the art from the following
description of a preferred embodiment and the accompanying figures, without
departing from the
spirit of the invention.
Figure 1 presents the two split hubs of the wheel with two spring elements
mounted on them,
connected to a single tile.
80 Figure 2 presents the side view of the two split hubs assembly with 3
pairs of springs mounted on
them, with the relative angle between the two hubs in relaxed position.
Figure 3 presents the side view of the two split hubs assembly with 3 pairs of
springs mounted on
them, with the relative angle between the two hubs in preload position.
Figure 4 presents a detail of the spring.
85 Figure 5 presents the two split hubs of the wheel with the rigid lever
that links the first hub and
transmits forces to the second hub in disassembled view.
Figure 5.1 presents the assembled hubs with springs as well as the rigid lever
linking the hubs.
Figure 5.2 presents the assembled hubs with springs and tiles as well as the
rigid lever linking the two
hubs.
90 Figure 6 presents the slip ring used to provide power to the preload
mechanism of the springs and
the details of the preload mechanism prior to assembly.
Figure 7 presents the fully assembled preload mechanism connected to the rigid
lever linking the
hubs.
Figure 8 presents the fixed hollow axis of the wheel with the drive motor and
internal gear.
95 Figure 9 presents the isolated drive motor and gearbox assembly as well
as the torque measuring
system.
Figure 10 presents a rear view of the motor mechanism and torque measuring
system
Figure 11 presents the complete wheel assembly.
100
6. Disclosure of the Preferred Embodiment
Date Recue/Date Received 2021-02-08
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Hereinafter, an embodiment of a non-pneumatic tire according to the present
invention will be
described with reference to FIGS. 1 to 11.
Figure 1 presents the two split hubs of the wheel, split hub 1 and split hub
2, on each one of which a
105 leaf spring 3 and 4 respectively is mounted on one of a plurality of
holes of their periphery, by means
of a mounting rod. The springs are free to rotate around their mounting rods.
Both springs are shown
connected to a single tile 5, via also a freely rotating joint that also
serves as free rotating joint
connecting the tile with its adjacent tiles, thus forming a circular multi-
tile caterpillar chain,
representing the part of the wheel that enters in contact with the ground. The
relative angle
110 between the two split hubs can be modified, in a way to bring closer
the mounting points of each
spring on their respective hub and also decrease the distance of the concave
sections of each of the
two springs 3 and 4. To better appreciate the effects of such angle variation,
figures 2 and 3 need to
be presented.
Figure 2 presents the side view of the same said assembly of the two split
hubs, only this time 3
115 springs numbered 6, 7 and 8 are mounted on 3 adjacent mounting rods of
the hub 2 and another 3
springs numbered 9, 10, 11 are mounted on 3 adjacent rods of hub 1, with each
pair of said springs
connected to 3 adjacent tiles of the wheel periphery ( Hubs 1 and 2 are seen
from the side). In this
figure, the relative angle between hub 1 and hub 2 is in fully relaxed
position, with the mounting
points 12 and 13 of springs 8 and 9 on their respective hubs being at maximum
distance. Also, it can
120 be seen that the curved tails of each spring (for example tail 14 of
spring 7) are not in contact with
the bodies of their respective adjacent springs (tail 14 is not in contact
with the body of spring 6, etc).
In this case, a zero pre-load condition exists in all springs. A radial force
exerted on a tile, for example
the tile supported by springs 8 and 9, generates easily the deformation of the
said springs. It must be
noted that the wheel assembly in this case is unable to transmit torques to
the periphery of the
125 wheel, since the springs rotate freely around their respective joints
and in that way the torque is not
transmitted. The case is therefore illustrated here as an example of spring
condition. This condition
can be encountered during the manufacturing of the wheel, but it is avoided
during the use of the
wheel in operation. During operation, the springs must be at least preloaded
at a minimum value, in
order to be able to transmit torques to the wheel periphery. This situation is
depicted in an
130 exaggerated manner in Figure 3. In Figure 3, the relative angle of the
two hubs has been modified by
a few degrees. This rotation has brought much closer the mounting points 12
and 13 of springs 8 and
9 respectively. These new positions have forced the tails of each said spring
to come in contact with
the respective body of the adjacent spring, therefore forcing each said spring
element to preload
against the corresponding spring of the opposite hub that is connected on the
same tile (for example,
135 spring 8 and 9). The generated resulting force from each pair of
springs pushes each tile along the
Date Recue/Date Received 2021-02-08
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radial dimension, in a way to increase the periphery of the wheel. Since the
tiles are all
interconnected, the periphery of the wheel does not change, but the resulting
forces generated by all
springs increase the apparent radial stiffness of the wheel, since the
deformation of the pre-loaded
springs for a given radial load requires now a much higher force. However, in
this exaggerated
140 condition where the mounting rods 12 and 13 have come so close to each
other, again the wheel
hubs cannot transmit important torques to the wheel periphery. A very
important torque would
again cause the spring pair to rotate instead to cause the wheel to rotate.
The ideal preload range
condition for each wheel assembly is therefore in middle locations between the
location shown in
Figure 2 and the location shown in Figure 3 and depends on the individual
spring stiffness and the
145 torque we desire to transmit to the wheel. Based on tests performed on
a 0.34m diameter wheel,
built according to the principles exposed in the present invention, an
increase of 4 times of the
apparent stiffness can be achieved for a given such wheel for axis loads of
the order of 250N. This
means that the difference in the hub vertical displacement (overall
deformation of the elastic wheel)
for a given load placed on the wheel axis, (in the order of 250N), between the
"fully preloaded"
150 spring condition and the "minimally preloaded" spring condition, is
400%. In other words, the
achieved flexibility variation based on the principle exposed in the present
invention can be in the
order of 400 % (a minimally preloaded wheel presents a deflection 4 times
higher than the deflection
of the fully preloaded wheel). The degree of deflection of a wheel is
generally important, since it
affects the section of the wheel periphery that is in contact with the ground,
therefore affecting the
155 ground pressure of the wheel and increasing the traction capacity of
the wheel on loose soils etc.
In Fig 4 the preferred embodiment of the spring element is presented. The
spring is mounted on the
rod of each said hub of the wheel from the adequately shaped curved section
12, which is large
enough to permit the free rotation of the spring around the mounting rod but
yet the spring cannot
disengage from the rod. In a similar manner, the other end of the spring 15 is
mounted on the tile
160 articulation, permitting the free rotation of the spring around the
fixing rod, yet not allowing the
spring to disengage from the rod. The spring also comprises a curved section
16, presenting a
concave part and a convex part. The spring further comprises a free curved
tail 14, placed at the
proximity of the mounting section 12 and in the opposite direction of the
concave section of the
spring. The role of the tail is depicted in Figure 3 above, showing that in
case the two split hubs
165 counter-rotate, the tail is pressed on the next adjacent spring body,
preventing the rotation of the
springs and contributing to the preload of the springs, generating the
increase of stiffness of the
wheel.
The forces generated by this counter-rotation of the hubs depend on the
stiffness of the springs
used. For the presented embodiment, the overall wheel stiffness had values
varying from 2.5kN/m to
Date Recue/Date Received 2021-02-08
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170 10kN/m, requiring the generation of an important torque for the counter-
rotation of the hubs, in the
order of 300Nm for the specific embodiment. This torque is a residual
constraint between the two
hubs and has to be conserved, otherwise the wheel will lose its pre-set
stiffness and become more
flexible. A strong rigid lever is used in order to transmit this important
torque between the two hubs
and is shown on Figure 5. In this Figure the two hubs are shown dismantled,
for better understanding
175 of the different parts. The rigid lever linking the hubs is part 17,
which is permanently fixed on hub 2
through the fixing pad 18, and extents to hub 1 traversing the opening 19
where it engages with the
flexibility variation mechanism. Figure 5.1 presents the assembled hubs with
all the assembled
springs without tiles and the linking lever 17 extending from hub 1. Figure
5.2 presents the
assembled hubs with springs and tiles. Figure 6 presents the flexibility
variation mechanism, which is
180 mounted on a plate 28 that is fixed on hub 1 and rotates together with
the wheel rotation. The plate
comprises an electric motor 21, that uses power provided by a continuously
rotating electrical
connection (slip ring) 20, which is mounted on the central, fixed axis of the
wheel 32. The motor 21
engages through spur gears to a supplementary reduction gear-train 22, finally
engaging a heavy
duty ball-screw drive 23 that pulls a double bicycle-type chain 24, on which
lever 17 is attached. By
185 the rotation of the said motor, powered through the slip ring 20, it is
possible to develop very
important forces on the lever 17, producing the counter rotation of the two
hubs and resulting to the
increase of the stiffness of the wheel. Figure 7 presents the flexibility
variation mechanism
assembled and fixed on the side of hub 1, with the double chain 24 mounted on
the rigid linking lever
17 and causing its motion relative to the hub 1. Figure 7 also presents a
linear potentiometer 25,
190 used to track the position of the tensioning chariot of the ball-screw
drive on the screw, in order to
enable the exact regulation of the desired stiffness of the wheel during
stiffness variation operation.
The potentiometer signal is also transmitted through the said slip ring 20
towards a micro-processor
based controller that can be used to operate the wheel.
Figure 8 presents a cut along the width-wise part of the wheel assembly, where
the split hubs 1 and 2
195 are visible, the flexibility variation motor 21 is shown on the rear
part of the figure, while the slip ring
20 is also shown providing power to the flexibility variation motor. The fixed
hollow axis of the wheel
32 is also shown, comprising the drive motor of the wheel 27, which engages
through spur gears 31,
30 and 29 the internal gear 26 which is fixed inside hub 2, transmitting
driving power for the wheel to
rotate. A hollow, circular- shaped part 33 is supporting the drive motor while
on the same time it
200 permits to the motor to rotate freely inside it and it is fixed inside
the hollow axis 32. The Figure 9
presents in more detail the assembly of the drive-train, with the motor 27
supported longitudinally
but free to rotate inside the hollow part 33, with the semi-circular part 39
and 34 supporting the
gears and being fixed inside the hollow axis 32 and with the cross-shaped
lever 35 being fixed on the
Date Recue/Date Received 2021-02-08
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front side of the motor 27 and being also able to rotate together with it.
Figure 10 presents the
205 assembly view from the other side, with two sliding bearings 43
supporting the free rotation of the
motor inside part 33 (not shown in figure 10) and the cross shaped part 35
held in position with the
help of two helicoidal springs36 and 37, which have their other extremities
fixed on parts 38 and 39
supporting the gear-train and being fixed inside the hollow axis 32. When the
motor generates a
torque in order to set the wheel in motion, the spur gear 31 engages on the
gear train and tends to
210 transmit this torque. By reaction, this same torque is transmitted on
the body of the motor 27, which
then rotates in the opposite direction, until the forces generated inside the
springs 36 and 37 stop
the rotation of the body of the motor. The motion of the motor, is transmitted
via the cross-shaped
lever part 35 and the linkage 40 towards the lever 41, which is fixed on the
rotating axle of a rotating
potentiometer 42, which is also fixed on part 34 and connected to the inside
of the hollow axis 32. In
215 that way, any torque developed by the motor 27 or even generated
externally on the wheel and
finally transmitted to the motor (even when the motor is un-powered), is
measured by the
potentiometer. Therefore, the effort generated inside the gear-train 31, 30,
29 and finally
transmitted to the internal gear 26, operating the rotation of the wheel, can
be monitored with the
said potentiometer 42. It must be noted that the accuracy of the torque
measurement depends on
220 the non linear Coulomb friction present in the gear train 29 30 31 and
26. The presence of high
friction in this gear- train, may alter the precision with which the torque is
measured. For best
results, the transmission ratio used in the said gear-train should not exceed
30:1, depending on the
quality of the gears, type of lubricant used, environmental conditions,
contamination etc. The
present embodiment has a gear ratio of 20:1, with a capacity to generate and
measure torques on
225 the wheel periphery in the order of 30Nm. Figure 11 presents the
assembled wheel with springs, tiles
and tensioning mechanism.
Date Recue/Date Received 2021-02-08
