WO2007001246A1

WO2007001246A1 - Variable radial and/or lateral compliance wheel

Info

Publication number: WO2007001246A1
Application number: PCT/US2005/015478
Authority: WO
Inventors: Eric Anderfaas; Dean Banks; David Clemens; Peter Lenoach; Brian Miller
Original assignee: Millenworks, Inc.
Priority date: 2005-06-13
Filing date: 2005-06-13
Publication date: 2007-01-04

Abstract

A type of wheel that operates on a variety of surfaces. Various embodiments have a means for changing stresses in wheel segments while the wheel is being operated that causes the stiffness of the wheel to change. Related methods are provided.

Description

VARIABLE RADIAL AND/OR LATERAL COMPLIANCE WHEEL

TECHNICAL FIELD The present invention generally relates to a wheel for ground vehicles. More particularly, the present invention relates to a wheel for a ground vehicle, which includes a hub having a center axis of rotation and a plurality of wheel segments engaged with the hub and connecting to a radial wheel band with tread elements appropriate for the intended usage of the vehicle, where the hub and plurality of wheel segments are adapted to rotate about the center axis, and where the attachment points to the hub of the plurality of wheel segments can be moved in the direction of the axis of rotation.

BACKGROUND ART Various mechanisms currently exist for varying the ground contact pressure of a tire while a vehicle is being driven. This capability allows a vehicle to traverse soft soils by lowering the pressure within the tire, without compromising on-road performance. This is commonly achieved by varying the pressure within the carcass of a tire through the control of an air valve mounted on the wheel that can vent the tire's internal air to atmospheric pressure or to the pressure produced by an onboard air compressor plumbed through an airtight rotary seal. The commercial term for such a system is Central Tire Inflation System (CTIS). One such system is U.S. Patent No. 5,553,647, "Central tire inflation system," (Miroslav), that describes a pressure air source, plumbing, valve, pressure sensor, and control system for varying the internal air pressure of a tire while driving. The shortcomings of this design are complexity, sensitivity to the elements, cost, and inability of the system to maintain adequate tire pressure when the tire is badly damaged.

Several patents have addressed this latter concern of pneumatic tire vulnerability with runflat inserts (U.S. Patent No. 6,263,935, "Radial ply pneumatic runflat tire," (Oare, et. al.)) or tires that do not rely on fluidic pressure for load carrying, a.k.a. non-pneumatic tires, (U.S. Patent No. 6,431 ,235, "Non-pneumatic tire and rim combination," (Steinke, et. al.)). The shortcomings of this system are weight and fixed tire stiffness.

The present invention describes a novel way of combining the benefits of variable tire stiffness with a damage tolerant tire design.

DISCLOSURE OF INVENTION The present invention provides a variable stiffness wheel for support of ground vehicle traverse over a variety of terrain under various loading conditions. In one preferred embodiment, the variable stiffness wheel includes a plurality of wheel segments whose attachments to the center rotating hub (inner and outer) can be moved in the direction of the axis of rotation, thereby changing the tension of these elements, which is convenient for tuning the ground contact pressure of the tire for the terrain being traversed. The inner attachment being accommodated via a sliding flange located towards the vehicle and the outer being accommodated via another sliding flange located away from the vehicle. Additionally, this method can be used to vary other wheel stiffness parameters such as vertical stiffness, lateral stiffness, torsional stiffness (about the axis of rotation or about an axis perpendicular to the axis of rotation) which can affect overall vehicle behavior.

With the inner and outer wheel segment attachment points close together tensioning the spokes, the vertical stiffness of the wheel is increased to provide excellent on-road performance (cornering, steering feel, low rolling resistance, etc.). This configuration also provides increased payload carrying capacity.

With the inner and outer wheel segment attachment points spread apart from one another, the vertical stiffness of the wheel is reduced, enlarging the contact patch of the wheel with the ground and improving tire/terrain enveloping performance. The lower ground pressure gives the vehicle better off-road mobility on soft soils like mud, sand, and snow. With the inner and outer wheel segment attachment points spread far apart from one another, the vehicle can be lowered to facilitate transportation in low clearance vehicles like aircraft. The lower ground pressure of this configuration is also beneficial to ramps and cargo floors that have strict limits on floor loading pressure due to floor structure limitations imposed by weight constraints, as is the case with many aircraft.

The inner and outer wheel segment attachment points can be varied from the maximum and minimum spacing while driving to suit the immediate needs of the vehicle.

Multiple inner and outer wheel segments can be stacked to produce a wheel with varying radial stiffness across the width of the wheel. This is beneficial for improving the lateral performance of the wheel by controlling the dynamic camber of the tire during a cornering maneuver. This can also be beneficial for changing the heading of the vehicle while driving with little or no steering of the tire. By making the stiffness of the innermost pair of inner and outer wheel segments stiff er than the outermost pair, resulting forces at the wheel/road contact patch will serve to pull the vehicle in the direction of the outermost pair of wheel segments. By reversing the relative stiffness between the two sections, the wheel can force the vehicle in the opposite direction. This has the potential of simplifying the steering system, reducing cost and weight, improving the durability of the suspension/steering system by eliminating vulnerable steering links, and reclaiming the swept volume lost to the tire as it steers for other vehicle components or cargo.

BRIEF DESCRIPTION OF DRAWINGS The present invention will be further explained with reference to the appended Figures, wherein like structure is referred to by like numerals throughout the several views, and wherein: Figure 1 is an isometric view of a preferred embodiment of a wheel of variable stiffness of the present invention; Figure 2 is a side view of the variable stiffness wheel of Figure 1 ; Figure 3 is a detail isometric view of a cutaway of the variable stiffness wheel of Figure 1 , showing the movable elements of the wheel with a portion of the wheel removed.

Figure 1 illustrates one preferred embodiment of the variable stiffness wheel 10. The variable stiffness wheel 10 includes a hub 1 1 , fixed 12a 13b and movable flanges 12b 13a, and a plurality of wheel segments 17, 18 engaged with the flanges 12 13 and an outer traction element 16. The hub 11 includes an internal flange which can be used to locate an adaptor plate allowing the wheel to be mounted on a spindle (not shown) which allows the variable stiffness wheel to rotate about the center axis. The wheel segments 17, 18 are distributed evenly around the hub 11. In the illustrated embodiment, the wheel 10 includes 120 wheel segments on four different wheel segment planes. It should be obvious to anyone skilled in the art that the variable stiffness wheel 10 may include fewer or more wheel segments 17, 18 and fewer or more wheel segment planes. The variable stiffness wheel 10 also includes sliding guides 15 engaged with the hub 11 and flanges 12a, 12b, 13a, 13b (the 'a' flanges defining the 'inner' wheel segments and the 'b' flanges defining the 'outer' wheel segments) which affix the base of the plurality of wheel segments 17, 18 to the hub 11. Flanges 13b and 12b are positively affixed to the wheel to restrict linear movement along the axis of rotation. Flanges 12a, 13a slide along the guides 15 and are loaded with preload adjusters 14 that are in contact with the flanges 12a, 13a and the hub 11. Alternatively, all rings may be fixed or sliding, or some combination thereof. Each of the wheel segments 17, 18 are shaped to generally nest between adjacent wheel segments 17, 18, but may also be stacked in sideview perspective (see Figure 2).

Figure 3 illustrates a detail isometric view of the variable stiffness wheel 10 with the traction element 16 sectioned away to illustrate the hub 11 , sliding rings 2a, 2b, 3a, 3b, and the plurality of wheel segments 7, 8. Figure 3 illustrates the variable stiffness wheel 10 in one particular preload position, where the spacing between the rings 2a, 2b, 3a, 3b is at a nominal position. Where the ring pairs (2a, 2b and 3a, 3b) are closest together, the radial preload on the wheel segments 7, 8 will be at its greatest. This results in the highest radial stiffness of the wheel. Where the ring pairs (2a, 2b and 3a, 3b) are furthest apart, the radial preload on the wheel segments 7,8 will be at its lowest and the angle of the wheels segments 7, 8 will be at their greatest angle with respect to the vertical applied load. With the lowest preload and weakest wheel segment angle, this provides the lowest radial stiffness of the wheel.

Each of the wheel segments 7, 8 is engaged with the hub 11 via the rings 2a, 2b, 3a, 3b, so that the segments 7, 8 may move laterally relative to the hub 11 at the point where the segments 7, 8 attach to the movable rings 2a, 3a. Rings 2b, 3b may also be made to move in such a manner as to control the lateral spacing between the ring pairs 2a, 2b and 3a, 3b. Control of this spacing is preferably accomplished through linear actuators (not shown) acting on preload adjusters 4. Alternatively, the preload adjusters 4 may be actuated through other linear or rotary electromechanical, fluidic, magnetic, or other means of exerting a force at the base of the movable rings 3a, 3b. Alternatively, the wheel segments 7, 8 may be directly actuated radially or semi-radially, as in the case of a camera shutter.

Other means of adjusting preload tension/compression on the plurality of wheel segments may also include hollow wheel segment structures filled with a pressurized medium, utilization of smart materials like artificial muscles and other shape memory alloys (SMAs), biomaterials, or the replacement of wheel segments with linear or rotary actuators.

Claims

1. A wheel system comprising: a hub having a center axis of rotation; a plurality of wheel segments; a radial wheel band with tread elements appropriate for the intended usage of the wheel; said wheel segments are engaged with the hub and connecting to the radial wheel band; said hub and wheel segments are adapted to rotate about the center axis; a control system; said control system including a routine for also adjusting stiffness of said wheel in response to at least on sensed condition so as to change effective stiffness of said wheel system;

2. A wheel system according to claim 1 , where said wheel segments form a pair of wheel segment plates.

3. A wheel system according to claim 1, where said wheel segments form multiple pairs of wheel segment plates.

4. A wheel system according to claim 1, wherein said control system is an open loop system.

5. A wheel system according to claim 1 , wherein said control system is a closed loop system.

6. A wheel system according to claim 1 wherein the applied stress to the said wheel segments is accomplished by moving attachment points of said wheel segments to said hub closer together or away from one another with respect to the axis of rotation of the hub.

7. A wheel system according to claim 1 wherein the applied stress to the said wheel segments is accomplished by direct actuation of the wheel segments.

8. A wheel system according to claim 1 wherein the applied stress to the said wheel segments is accomplished by filling the wheel segments with a pressurized medium.

9. A wheel system according to claim 1 wherein the applied stress to the said wheel segments is accomplished by adjusting the actuation means of the smart materials (e.g. artificial muscles, shape memory alloys, biomaterials) used in the wheel segments.

10_. A wheel system according to claim 1 wherein the applied stress to the said wheel segments is accomplished by utilizing linear or rotary actuators as said wheel segments.