Patent Publication Number: US-2021188003-A1

Title: Non-pneumatic tire and wheel assembly with integrated spoke structure

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to vehicle tires and non-pneumatic tires, and more particularly, to a non-pneumatic tire. 
     BACKGROUND OF THE INVENTION 
     The pneumatic tire has been the solution of choice for vehicular mobility for over a century. The pneumatic tire is a tensile structure. The pneumatic tire has at least four characteristics that make the pneumatic tire so dominate today. Pneumatic tires are efficient at carrying loads, because all of the tire structure is involved in carrying the load. Pneumatic tires are also desirable because they have low contact pressure, resulting in lower wear on roads due to the distribution of the load of the vehicle. Pneumatic tires also have low stiffness, which ensures a comfortable ride in a vehicle. The primary drawback to a pneumatic tire is that it requires compressed fluid. A conventional pneumatic tire is rendered useless after a complete loss of inflation pressure. 
     A tire designed to operate without inflation pressure may eliminate many of the problems and compromises associated with a pneumatic tire. Neither pressure maintenance nor pressure monitoring is required. Structurally supported tires such as solid tires or other elastomeric structures to date have not provided the levels of performance required from a conventional pneumatic tire. A structurally supported tire solution that delivers pneumatic tire-like performance would be a desirous improvement. 
     Non pneumatic tires are typically defined by their load carrying efficiency. “Bottom loaders” are essentially rigid structures that carry a majority of the load in the portion of the structure below the hub. “Top loaders” are designed so that all of the structure is involved in carrying the load. Top loaders thus have a higher load carrying efficiency than bottom loaders, allowing a design that has less mass. 
     Thus, an improved non pneumatic tire is desired that has all the features of the pneumatic tires without the drawback of the need for air inflation is desired. 
     SUMMARY OF THE INVENTION 
     The invention provides in a first aspect a non-pneumatic tire and wheel assembly comprising an outer annular ring having a ground contacting tread portion and a shear band, one or more spoke disks, wherein each spoke disk has an outer ring mounted to the shear band, and an inner ring mounted to the wheel, wherein each spoke disk has at least two spokes, wherein each of said spoke disks has one or more anchors for mounting in aligned mating slots of the wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood through reference to the following description and the appended drawings, in which: 
         FIG. 1  is a perspective view of a first embodiment of a non-pneumatic tire and wheel assembly of the present invention; 
         FIG. 2  is a cross-sectional perspective view of the non-pneumatic tire and wheel assembly of  FIG. 1 ; 
         FIG. 3  is an exploded view of non-pneumatic tire and wheel assembly of  FIG. 1 ; 
         FIG. 4  is a perspective view of the wheel of the present invention; 
         FIG. 5  is a cross-sectional view of the wheel of the present invention; 
         FIG. 6  is a close up front view of the spokes of the nonpneumatic tire and wheel of the present invention; 
         FIG. 7  is a front view of the wheel of the present invention; 
         FIG. 8  is a close-up view of the wheel slot and anchor of the present invention; 
         FIG. 9  is a front view of the wheel and spoke structure of the present invention; 
         FIG. 10  is a cross-sectional view of the wheel and spoke structure of  FIG. 9 ; 
         FIG. 11  is a front view of a sector of the wheel and spoke structure of  FIG. 9 ; 
         FIG. 12  is a close up view of a portion of the wheel and spoke structure prior to pretensioning, while  FIG. 13  illustrates the spokes of  FIG. 12  after pretensioning; and 
         FIG. 14  illustrates a cross-sectional view of the tread band and shear band. 
     
    
    
     DEFINITIONS 
     The following terms are defined as follows for this description. 
     “Equatorial Plane” means a plane perpendicular to the axis of rotation of the tire passing through the centerline of the tire. 
     “Meridian Plane” means a plane parallel to the axis of rotation of the tire and extending radially outward from said axis. 
     “Hysteresis” means the dynamic loss tangent measured at 10 percent dynamic shear strain and at 25° C. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The non-pneumatic tire and wheel assembly  100  of the present invention is shown in  FIGS. 1-3 . The nonpneumatic tire of the present invention includes an outer annular band  200  surrounding one or more spoke disks  400  which are integrally mounted to a wheel  500 . The outer annular band  200  includes a radially outer surface having a ground engaging tread  210 . The tread  210  may be conventional in design, and include the various elements known to those skilled in the art of tread design such as ribs, blocks, lugs, grooves, and sipes as desired to improve the performance of the tire in various conditions. As shown in  FIG. 14 , a shear band  300  is located radially inward of the tread, and allows the non-pneumatic tire of the present invention to be a top loaded structure, so that the shear band  300  and the spoke disks efficiently carry the load. The shear band  300  together with the spoke disks  400  are designed so that the stiffness of the spoke disks  400  is directly related to the spring rate of the tire. The spoke disks  400  are designed to be structures that buckle or deform in the tire footprint yet are unable to carry a compressive load. This allows the rest of the spokes not in the footprint area the ability to carry the load. It is desired to minimize this compressive load on the spokes for the reasons set forth above and to allow the shear band to bend to overcome road obstacles. The approximate load distribution is such that approximately 90-100% of the load is carried by the shear band and the upper spokes, so that the lower spokes carry virtually zero of the load, and preferably less than 10%. 
     The shear band  300  is preferably annular, and is shown in cross-section in  FIG. 14 , and is preferably located radially inward of the tire tread  210 . The shear band  300  includes a first and second reinforced elastomer layer  310 , 320  separated by a shear matrix  330  of elastomer. Each inextensible layer  310 , 320  may be formed of parallel inextensible reinforcement cords  311 , 321  embedded in an elastomeric coating. The reinforcement cords  311 , 321  may be steel, aramid, or other inextensible structure. In the first reinforced elastomer layer  310 , the reinforcement cords  311  are oriented at an angle Φ in the range of 0 to about +/−10 degrees relative to the tire equatorial plane. In the second reinforced elastomer layer  320 , the reinforcement cords  321  are oriented at an angle φ in the range of 0 to about +/−10 degrees relative to the tire equatorial plane. Preferably, the angle Φ of the first layer is in the opposite direction of the angle φ of the reinforcement cords in the second layer. That is, an angle +Φ in the first reinforced elastomeric layer and an angle −φ in the second reinforced elastomeric layer. 
     The shear matrix  330  has a thickness in the range of about 0.10 inches to about 0.2 inches, more preferably about 0.15 inches. The shear matrix is preferably formed of an elastomer material having a shear modulus G in the range of 2.5 to 40 MPa, and more preferably in the range of 20 to 40 MPA. The shear band has a shear stiffness GA and a bending stiffness EI. It is desirable to maximize the bending stiffness of the shearband EI and minimize the shear band stiffness GA. The acceptable ratio of GA/EI would be between 0.01 and 20, with an ideal range between 0.01 and 5. EA is the extensible stiffness of the shear band, and it is determined experimentally by applying a tensile force and measuring the change in length. The ratio of the EA to EI of the shear band is acceptable in the range of 0.02 to 100 with an ideal range of 1 to 50. 
     In an alternative embodiment, the shear band may comprise any structure which has the above described ratios of GA/EI and EA/EI. The tire tread is preferably wrapped about the shear band and is preferably integrally molded to the shear band. 
     Spoke Disk &amp; Wheel 
     The non-pneumatic tire of the present invention further includes at least one spoke disk  400 , and preferably at least two disks which may be spaced apart at opposed ends of the non-pneumatic tire. In the tire and wheel assembly shown in  FIGS. 1-3 , there are four spoke disks mounted upon wheel  500 . The spoke disk functions to carry the load transmitted from the shear layer. The disks are primarily loaded in tension and shear, and carry no load in compression. A first exemplary spoke disk  400  is shown in  FIG. 3  and  FIG. 6 . The disk  400  is annular, and has an outer annular ring  406  and a radially inner annular ring  403 . Each spoke disk  400  may be optionally divided into two or more sectors for ease of assembly. 
     As shown in  FIG. 11 , the spoke disk  400  is formed of a plurality of spoke members  410 , 420 , 440 , 450  that are joined together at a junction  430  to form upper and lower triangles  470 , 480 . The upper triangle  470  has sides formed by spoke members  410 ,  420  and outer annular ring  406 . The lower triangle  480  has sides formed by spoke members  440 , 450  and inner annular ring  460 . As shown in  FIGS. 8, 11, 12 and 13 , each spoke disk  400  has a plurality of anchors  600  which extend radially inward of the inner annular ring  403 . Each anchor  600  is preferably round or elliptical in shape, although any desired shape will work. Each anchor is received in a complementary shaped slot  700  located on an outer annular ring  710  of wheel  500 . Each anchor snugly fits into each slot  700  for mating reception. Each anchor is stretched to be received within slots  700  as shown in  FIG. 13 , which results in pretensioning of the spokes. The inner annular ring  403  of the spoke disk preferably includes an optional gap  408  located between the anchors. 
     One or more of the anchors  600  may further include an interior recess  610  that extends across the anchor in the tire&#39;s axial direction. The interior recess  605  preferably includes a pin  610  that is secured within the interior recess  605  after the anchors are received in the complementary shaped slot  700 . The pins  610  prevent pullout of the anchors from the complementary shaped mating slots. The pins  610  may be annular. 
     The wheel  500  is shown in  FIGS. 4-6 . The wheel  500  is preferably split into two halves  510 , 520  as shown in  FIG. 6 . Each wheel rim half may be injection molded and then assembled together with fasteners, as shown in  FIG. 6 . The wheel  500  further includes a stamped metal center plate  550  which may be bolted to a vehicle hub motor. The wheel  500  further includes the slots  700  as described above. The anchors  600  of each of the spoke disks are slid into the aligned slots  700  in order to mount the spoke disks to the wheel  500 . The wheel may optionally further include retaining rings located on each end of the wheel in order to keep the spoke disks from sliding off the wheel. 
     Each spoke disk  400  as described herein has an axial thickness A that is substantially less than the axial thickness AW of the non-pneumatic tire. The axial thickness A is in the range of 5-40% of AW, more preferably 15-30% AW. If more than one disk is utilized, than the axial thickness of each disk may vary or be the same. 
     Each spoke disk has a spring rate SR which may be determined experimentally by measuring the deflection under a known load. One method for determining the spoke disk spring rate k is to mount the spoke disk to a hub, and attaching the outer ring of the spoke disk to a rigid test fixture. A downward force is applied to the hub, and the displacement of the hub is recorded. The spring rate k is determined from the slope of the force deflection curve. It is preferred that the spoke disk spring rate be greater than the spring rate of the shear band. It is preferred that the spoke disk spring rate be in the range of 4 to 12 times greater than the spring rate of the shear band, and more preferably in the range of 6 to 10 times greater than the spring rate of the shear band. 
     Preferably, if more than one spoke disk is used, all of the spoke disks have the same spring rate. The spring rate of the non-pneumatic tire may be adjusted by increasing the number of spoke disks. Alternatively, the spring rate of each spoke disk may be different by varying the geometry of the spoke disk or changing the material. It is additionally preferred that if more than one spoke disk is used, that all of the spoke disks have the same outer diameter. 
     The spoke disks are preferably formed of an elastic material, more preferably, a thermoplastic elastomer. The material of the spoke disks is selected based upon one or more of the following material properties. The tensile (Young&#39;s) modulus of the disk material is preferably in the range of 45 MPa to 650 MPa, and more preferably in the range of 85 MPa to 300 MPa, using the ISO 527-1/-2 standard test method. The glass transition temperature is less than −25 degree Celsius, and more preferably less than −35 degree Celsius. The yield strain at break is more than 30%, and more preferably more than 40%. The elongation at break is more than or equal to the yield strain, and more preferably, more than 200%. The heat deflection temperature is more than 40 degree C. under 0.45 MPa, and more preferably more than 50 degree C. under 0.45 MPa. No break result for the Izod and Charpy notched test at 23 degree C. using the ISO 179/ISO180 test method. Two suitable materials for the disk are commercially available by DSM Products and sold under the trade name ARNITEL PM581 and ARNITEL PL461. 
     Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.