Patent Publication Number: US-2021178827-A1

Title: Non-pneumatic tire

Description:
TECHNICAL FIELD 
     The present disclosure relates to a non-pneumatic tire. 
     BACKGROUND ART 
     Generally, a plurality of grooves are formed on a tread of a tire. In such a tire, so-called stone holding in which stones are caught in the grooves during running sometimes occurs. The stone holding can cause cracks on bottoms of the grooves and sidewalls of the grooves, and can cause vibration and noise. In order to suppress the stone holding, for example, there are measures such as providing protrusions on the bottoms of the grooves as in the following Patent Document 1. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: JP-A-2016-199073   
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     It is an object of the present disclosure to provide a non-pneumatic tire capable of suppressing the stone holding. 
     Means for Solving the Problems 
     A non-pneumatic tire of the present disclosure includes: an inner annular portion; an outer annular portion provided concentrically on an outer side of the inner annular portion; a plurality of coupling portions coupling the inner annular portion and the outer annular portion to each other; a tread provided on an outer side of the outer annular portion; and a groove formed on the tread. 
     The groove includes a protrusion protruding inward of the groove from a groove sidewall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view showing a non-pneumatic tire according to the present embodiment. 
         FIG. 2  is a cross-sectional view taken along a line A-A of the non-pneumatic tire of  FIG. 1 .   
         FIG. 3  is an enlarged view of a main part of the non-pneumatic tire of  FIG. 2 . 
         FIG. 4  is a view of a tread when viewed from an outer circumference thereof. 
         FIG. 5  is views for explaining a function to discharge a stone. 
         FIG. 6  is an enlarged view of a main part of a non-pneumatic tire according to another embodiment. 
         FIG. 7  is an enlarged view of a main part of a non-pneumatic tire according to still another embodiment. 
         FIG. 8  is an enlarged view of a main part of a non-pneumatic tire according to yet another embodiment. 
         FIG. 9  is an enlarged view of a main part of a non-pneumatic tire according to a further embodiment. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of a non-pneumatic tire will be described with reference to the drawings. 
     The non-pneumatic tire T includes a support structure SS for supporting a load from a vehicle. The non-pneumatic tire T of the present disclosure just needs to include such a support structure SS as described above. A member corresponding to a tread, a reinforcing layer, members for   accommodation to an axle and a rim, or the like may be provided on an outer side (outer circumference side) and an inner side (inner circumference side) of the support structure SS. 
     In the present embodiment, as shown in  FIG. 1 , a tread  4  is provided outside the support structure SS. The tread  4  is made of, for example, rubber as in the conventional pneumatic tire, and includes a pattern (groove) on an outer circumferential surface thereof as in the conventional pneumatic tire. The support structure SS and the tread A are adhered to each other by an adhesive. 
     As shown in a front view of  FIG. 1 , in the non-pneumatic tire T of the present embodiment, the support structure SS includes: an inner annular portion  1 ; an outer annular portion  2  provided concentrically on an outer side of the inner annular portion  1 ; and a plurality of coupling portions  3  which couple the inner annular portion  1  and the outer annular portion  2  to each other. 
     The support structure SS in the present disclosure is formed of an elastic material. From a viewpoint of enabling integral molding at the time of manufacturing the support structure SS, it is preferable that the inner   annular portion  1 , the outer annular portion  2 , and the coupling portion  3  be basically made of the same material except a reinforcing structure. Moreover, for example, as a base material of the support structure SS, there may be adopted a thermoplastic elastomer such as polyester elastomer, a crosslinked rubber such as natural rubber, or other resins (for example, a thermoplastic resin such as polyethylene resin, and a thermosetting resin such as polyurethane resin). Furthermore, for example, a reinforcing material such as a fiber or a metal cord may be embedded inside the base material. 
     From a viewpoint of improving uniformity, it is preferable that the inner annular portion  1  have a cylindrical shape with a constant thickness. Moreover, on an inner circumferential surface of the inner annular portion  1 , it is preferable to provide irregularities and the like for maintaining fitting property in order to mount the non-pneumatic tire T to the axle and the rim. Note that, though the thickness of the inner annular portion  1  is not particularly limited, the thickness is appropriately set from viewpoints of reducing a weight and improving a durability while sufficiently transmitting force to the coupling portion  3 .   
     Although an inner diameter of the inner annular portion  1  is not particularly limited, the inner diameter is appropriately determined according to dimensions of the rim and the axle on which the non-pneumatic tire T is to tee mounted, and the like. Although a width of the inner annular portion  1  in a tire width direction WD is not particularly limited, the width is appropriately determined depending on a purpose, a length of the axle, and the like. 
     From the viewpoint of improving the uniformity, it is preferable that the outer annular portion  2  have a cylindrical shape with a constant thickness. Note that, though the thickness of the outer annular portion  2  is not particularly limited, the thickness is appropriately set from the viewpoints of reducing the weight and improving the durability while sufficiently transmitting force from the coupling portion  3 . 
     Although an inner diameter of the outer annular portion  2  is not particularly limited, the inner: diameter is appropriately determined depending on the purpose and the like. Moreover, though a width of the outer annular portion  2  in the tire width direction WD is not particularly limited, the width is appropriately determined depending on the purpose and the like. Note that,   preferably, the width of the outer annular portion  2  is the same as the width of the inner annular portion  1 . 
     The coupling portions  3  couple the inner annular portion  1  and the outer annular portion  2  to each other. A plurality of the coupling portions  3  are provided so as to be independent of one another in the tire circumferential direction CD by placing appropriate intervals between the coupling portions  3 . Although the number of coupling portions  3  is not particularly limited, the number is appropriately set from viewpoints of reducing the weight, improving power transmission, and improving the durability while sufficiently supporting the load from the vehicle. 
     The plurality of coupling portions  3  are configured such that first coupling portions  31  and second coupling portions  32  are arrayed along the tire circumferential direction CD. In this case, it is preferable that the first coupling portions  31  and the second coupling portions  32  be arrayed alternately with each other along the tire circumferential direction CD. This makes it possible to further reduce dispersion of the ground contact pressure during tire rolling. 
     From the viewpoint of improving the uniformity, it is   preferable that a pitch in the tire circumferential direction CD between the first coupling portions  31  and the second coupling portions  32  be set constant. 
     Each of the first coupling portions  31  is extended from one side WD 1  in the tire width direction of the inner annular portion  1  toward other side WD 2  in the tire width direction of the outer annular portion  2 . Meanwhile, each of the second coupling portions  32  is extended from the other side WD 2  in the tire width direction of the inner annular portion  1  toward the one side WD 1  in the tire width direction of the outer annular portion  2 . That is, the first coupling portion  31  and the second coupling portion  32 , which are adjacent to each other, are disposed in a substantially X shape when viewed from the tire circumferential direction CD. 
     The first coupling portion  31  and the second coupling portion  32  when viewed from the tire circumferential direction CD are preferably symmetric to each other with respect to a tire equatorial plane as shown in  FIG. 2 . Therefore, hereinafter, the first coupling portion  31  will mainly be described. 
     The first coupling portion  31  has an elongated plate-like  shape extending from the inner annular portion  1  to the outer annular portion  2 . In the first coupling portion  31 , a plate thickness t is smaller than a plate width w, and a plate thickness direction is oriented to the tire circumferential direction CD. That is, the first coupling portion  31  has a plate shape extending in the tire radial direction RD and in the tire width direction WD. The first coupling portion  31  and the second coupling portion  32  are formed into such an elongated plate shape. In this way, even if the plate thickness t is reduced, the first coupling portion  31  and the second coupling portion  32  can obtain desired rigidity by setting the plate width w to be wide. Therefore, the durability can be improved. Moreover, the number of first coupling portions  31  and the number of second coupling portions  32  are increased while thinning the plate thickness t. In this way, gaps between the coupling portions adjacent to one another in the tire circumferential direction CD can be reduced while maintaining the rigidity of the entire tire. Therefore, the dispersion of the ground contact pressure during the tire rolling can be reduced. 
     Although the thickness t is not particularly limited, the thickness t is appropriately set from the viewpoints of reducing the weight and improving the durability while   sufficiently transmitting force from the inner annular portions  1  and the cuter annular portions  2 . Although the plate width W is not particularly limited, the plate width w is appropriately set from the viewpoints of reducing the weight and improving the durability while sufficiently transmitting force from the inner annular portions  1  and the outer annular portions  2 . 
     The first coupling portion  31  includes an inner connecting portion  31   a  connected to the inner annular portion  1  and an outer connecting portion  31   b  connected to the outer annular portion  2 . 
     Although a shape of the inner connecting portion  31   a  is not particularly limited, the inner connecting portion  31   a  is formed into a rectangular shape in the present embodiment. A longitudinal direction of the inner connecting portion  31   a  is parallel to the tire width direction WD. Note that the longitudinal direction of the inner connecting portion  31   a  does not have to be parallel to the tire width direction WD, and for example, may intersect the tire width direction WD. 
     Although a shape of the outer connecting portion  31   b  is not particularly limited, the outer connecting portion    31   b  is formed into a rectangular shape in the present embodiment. A longitudinal direction of the outer connecting portion  31   b  is parallel to the tire width direction WD. Note that the longitudinal direction of the outer connecting portion  31   b  does not have to be parallel to the tire width direction WD, and for example, may intersect the tire width direction WD. 
     A tread surface  4   a  of the tread  4  of the present embodiment is parallel to the tire width direction WD and is flat from one end to the other end in the tire width direction WD. The tread surface  4   a  of the tread  4  does not necessarily have to be flat and may have a curvature. However, the curvature of the tread surface  4   a  is preferably small, and for example, a radius of curvature of the tread surface  4   a  is preferably 490 mm or more, more preferably 810 mm or more. The radius of curvature here is a radius of curvature when the tread surface  4   a  has one curvature, or is a radius of curvature of a curvature closest to the tire equatorial plane when the tread surface  4   a  has a plurality of curvatures along the tire width direction WD. Moreover, a difference between a maximum outer diameter and minimum outer diameter of the tread surface  4   a  is preferably 10 mn or less, more preferably 6 mm or less. Usually, the maximum outer diameter of the   tread surface  4   a  is an outer diameter of the tread surface  4   a  on the tire equatorial plane, and the minimum outer diameter of the tread surface  4   a  is an outer diameter of the tread surface  4   a  on both ends in the tire width direction WD. 
       FIG. 4  is a view of the tread  4  when viewed from an outer circumference thereof. Portions shown by broken lines in  FIG. 4  are outer connecting portions  31   b  and  32   b . The tread  4  includes annular connecting portion regions  40  and  40  located outward of the outer connecting portions  31   b  and  32   b  in the tire radial direction. The connecting portion regions  40  and  40  overlap the outer connecting portions  31   b  and  32   b  in the tire radial direction RD when viewed from the tire circumferential direction CD. 
     A plurality of grooves are formed on the outer circumferential surface of the tread  4 . In the present embodiment, three main grooves  5  extending in the tire circumferential direction CD are formed. The main groove  5  is formed on a center of the tread  4  in the tire width direction WD and on the connecting portion regions  40  and  40 . The main grooves  5  may be aligned with the tire circumferential direction CD, may be inclined with respect thereto, or may be zigzag as long as extending in the tire   circumferential direction CD. Lateral grooves extending in the tire width direction WD may be formed on the outer circumferential surface of the tread  4 . The lateral grooves may be aligned with the tire width direction WD or may be inclined with respect thereto as long as extending in the tire width direction WD. 
     Cross section of the main grooves  5  have a rectangular shape. However, the cross sections of the main grooves  5  are not limited to such a rectangular shape, and may have a trapezoidal shape in which groove bottoms are narrower than groove openings. Each of the main grooves  5  includes groove sidewalls  5   a  and  5   a  extending along the tire radial direction RD, and a groove bottom  5   b  coupling inner ends of both of the groove sidewalls  5   a  in the tire radial direction to each other. The groove sidewalls  5   a  and  5   a  are flat surfaces passing through an end of the groove opening and an end of the groove bottom  5   b.    
     The main groove  5  includes protrusions  50  protruding inward of the groove from the groove sidewalls  5   a . The main groove  5  includes the protrusions  50  individually protruding from both of the groove sidewalls  5   a . In the present embodiment, among the three main grooves  5 , only the main grooves  5  located on the connecting portion   regions  40  and  40  include the protrusions  50 . 
     The main grooves  5  include the protrusions  50 , whereby stones can be suppressed from entering the main groove from the groove openings, and the stone holding can be suppressed. Moreover, the main grooves  5  include the protrusions  50 , whereby, even if stones enter the same, a direct contact between the groove sidewalls  5   a  and the stones can be prevented, and a crack in the groove sidewalls  5   a  can be prevented. 
     Further, the protrusions  50  also have a function to discharge a stone that has entered each of the main grooves  5 . When the tread surface  4   a  of the tread  4  has a curvature like a general pneumatic tire, stones are caught in the main groove  5  due to narrowing of a groove width of the main groove  5  when the tire touches the ground, but as the tire rolls, a groove width of the main groove  5  returns to an original value thereof, and the stones are discharged by centrifugal force. On the other hand, when the tread surface  4   a  of the tread  4  is flat or substantially flat, the groove width of the main groove  5  is almost the same no matter whether or not the tire touches the ground, and accordingly, force to discharge the held stones is weak, but the discharge of the stones can be urged by the   protrusions  50 . 
     A specific function to discharge a stone by the protrusions  50  will be described with reference to  FIG. 5 . When the tread surface  4   a  of the tread  4  is flat or substantially flat, the groove width of the main groove  5  is almost unchanged when the tire touches the ground, and as shown in  FIG. 5( a ) , lands  41  on both sides of the main groove  5  are compressed in the tire radial direction RD. Along with this, the protrusions  50  are moved inward (toward the groove bottom) in the tire radial direction and enter an inside of a stone  9  in the tire radial direction. Thereafter, when a compression load on the lands  41  is released as the tire rolls, the protrusions  50  are moved outward (toward the opening) in the tire radial direction as shown in  FIG. 5( b ) , and exert the function to discharge the stone  9 . 
     As shown in  FIG. 3 , a cross section of each of the protrusions  50  is triangular, and the protrusion  50  includes a protrusion outer surface  50   a  facing outward in the tire radial direction and a protrusion inner surface  50   b  facing inward in the tire radial direction. The protrusion outer surface  50   a  is substantially parallel to the tire width direction WD. On the other hand, the   protrusion inner surface  50   b  is inclined so as to approach the groove sidewall  5   a  toward the groove bottom  5   b  with respect to the tire radial direction RD corresponding to a depth direction of the main groove  5 . That is, the protrusion  50  is provided so that the groove width becomes wider toward the groove bottom  5   b  by the protrusion inner surface  50   b.    
     The protrusion  50  protrudes toward the opening of the main groove  5 . In other words, a protrusion direction of the protrusion  50  (indicated by an arrow in  FIG. 3 ) is inclined with respect to the tire width direction WD so as to approach the groove opening toward a tip  50   c  of the protrusion  50 . The protrusion direction of the protrusion  50  is a direction from a center of a proximal end  50   d  toward a center of the tip  50   c . The protrusion  50  protrudes toward the opening of the main groove  5 , whereby the protrusion  50  becomes a “guard” and can effectively suppress the entrance of a stone, while a stone that has entered the main groove  5  is easily discharged. 
     The main groove  5  may include a plurality of the protrusions  50  along the depth direction of the main groove  5 . In the present embodiment, cross sections of the plurality of protrusions  50  have a sawtooth shape. The   plurality of protrusions  50  may have the same shape or may have different shapes from one another. For example, the protrusion  50  closer to the opening of the main groove  5  may be smaller than the protrusion  50  closer to the groove bottom. 
     Further, when only one protrusion  50  is provided along the depth direction of the main groove  5 , the entrance of a stone can be effectively suppressed if the protrusion  50  is located closer to the opening than the center of the groove sidewall  5   a  in the depth direction, and meanwhile, a stone can be effectively discharged if the protrusion  50  is located closer to the groove bottom than the center of the groove sidewall  5   a  in the depth direction. 
     The protrusions  50  may be continuously provided along the direction in which the main groove  5  extends. In the present embodiment, the protrusions  50  are continuously provided along the tire circumferential direction CD. However, the protrusions  50  do not have to be continuously provided along the tire circumferential direction CD, and may be provided intermittently. For example, one protrusion  50  may be provided for each repeating pitch of a tread pattern.   
     A length (protrusion amount) p from the groove sidewall  5   a  to the tip  50   c  is preferably 20% or more, more preferably 30% or more of the groove width gw. Further, the protrusion amount p is preferably 45% or less, more preferably 40% or less of the groove width gw. 
     As described above, the non-pneumatic tire T according to the present embodiment includes: the inner annular portion  1 ; the outer annular portion  2  provided concentrically on the outer side of the inner annular portion  1 ; the plurality of coupling portions  3  coupling the inner annular portion  1  and the outer annular portion  2  to each other; the tread  4  provided on the outer side of the outer annular portion  2 ; and the main groove  5  formed on the tread  4 , 
     wherein the main groove  5  includes the protrusions  50  protruding inward of the groove from the groove sidewall  5   a.    
     According to this non-pneumatic tire T, the main grooves  5  include the protrusions  50 , whereby a stone can be suppressed from entering the main groove from each of the groove openings, and the stone holding can be suppressed. 
     Further, in the non-pneumatic tire T according to the   present embodiment, the protrusions  50  may be configured to protrude toward the opening of each of the main grooves  5 . With this configuration, the protrusion  50  becomes a “guard” and can effectively suppress the entrance of a stone, while a stone that has entered the main groove  5  is easily discharged. 
     Further, in the non-pneumatic tire T according to the present embodiment, the main groove  5  may include a plurality of the protrusions  50  along the groove depth direction. With this configuration, a stone can be effectively suppressed from entering the main groove from the groove opening. 
     Further, in the non-pneumatic tire T according to the present, embodiment, the main groove  5  may include protrusions  50  protruding from both of the groove sidewalls  5   a . With this configuration, a stone can be effectively suppressed from entering the main groove from the groove opening. 
     Further, in the non-pneumatic tire T according to the present embodiment, the main grooves  5  including the protrusions  50  may be formed in the connecting portion regions  40  located on the outer side in the tire radial   direction of the outer connecting portions  31   b  and  32   b  of the coupling portions  3  and the outer annular portion  2 . Since the ground contact pressure is high in the connecting portion regions  40  located on the outer side of the outer connecting portions  31   b  and  32   b  in the tire radial direction, damage due to the stone holding is likely to increase. Therefore, the main grooves  5  formed on the connecting portion regions  40  include the protrusion  50 , whereby it is possible to focus on measures against the stone holding in the connecting portion regions  40 . 
     Further, in the non-pneumatic tire T according to the present embodiment, the protrusions  50  may be continuously provided along the extending direction of the main grooves  5 . With this configuration, the stone holding can be effectively suppressed in the entire tire. 
     Although the embodiments of the present disclosure have been described above with reference to the drawings, it should be considered that the specific configurations are not limited to these embodiments. The scope of the present disclosure is shown not only by the above description of the embodiments but also by the claims, and further includes all modifications within the meanings and the scope, which are equivalent to those in the claims.   
     It is possible to adopt the structure adopted in each of the above embodiments in any other embodiment. The specific configuration of each of the portions is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure. 
     The non-pneumatic tire is not limited to the configuration of the above-described embodiments, and is not limited to the above-described functions and effects. Moreover, as a matter of course, the non-pneumatic tire can be modified in various ways within the scope without departing from the spirit of the present invention. For example, as a matter of course, the respective configurations, the respective methods and the like of the above-described plurality of embodiments may be arbitrarily adopted and combined (the respective configurations, the respective methods and the like according to one embodiment may be applied to a configuration, a method and the like according to another embodiment). Moreover, as a matter of course, one or a plurality of configurations, methods and the like according to the following various modification examples may be arbitrarily selected and adopted for the configurations, the methods and the like according to the   above-described embodiments. 
     (1) In the non-pneumatic tire T according to the above embodiment, the protrusions  50  and  50  protruding from both of the groove sidewalls  5   a  and  5   a  are provided at the same positions in the depth direction of each of the main grooves  5 , but the present disclosure is not limited to this. For example, as shown in  FIG. 6 , the protrusions  50  and  50  protruding from both of the groove sidewalls  5   a  and  5   a  may be provided at different positions in the depth direction of the main groove  5 . 
     (2) Further, in the non-pneumatic tire T according to the above embodiment, the protrusion outer surface  50   a  of the protrusion  50  is substantially parallel to the tire width direction WD, but the present disclosure is not limited to this. For example, as shown in  FIG. 7 , similarly to the protrusion inner surface  50   b , the protrusion outer surfaces  50   a  may be inclined with respect to the tire radial direction RD so as to approach the groove sidewalls  5   a  toward the groove bottom  5   b . With this configuration, a stone can be effectively suppressed from entering the main groove from the groove opening. 
     (3) Further, in the non-pneumatic tire T according to   the above embodiment, the main groove  5  includes a plurality of the protrusions  50  along the groove depth direction of the main groove  5 , but the present disclosure is not limited to this. For example, as shown in  FIG. 8 , the main groove  5  may include only one protrusion  50  in the depth direction of the main groove  5 . When a plurality of the protrusions  50  are provided, the protrusion  50  on the outer side in the tire radial direction may hinder the function to discharge a stone by the protrusions  50  formed on the inner side in the tire radial direction, but the one protrusion  50  does not hinder such a discharge function. 
     (4) Further, in the non-pneumatic tire T according to the above embodiment, the cross section of the protrusion  50  is triangular, but the present disclosure is not limited to this. For example, as shown in  FIG. 9 , the cross section of the protrusion  50  may be rectangular. 
     (5) Further, in the non-pneumatic tire T according to the above embodiment, the protrusions  50  are continuously provided along the extending direction of the main groove  5 , but the present disclosure is not limited to this. Drainage can be ensured by intermittently providing the protrusions  50  along the extending direction of the main groove  5 . Further, the protrusions  50  may be provided   mainly near an intersection of the main groove  5  and an auxiliary groove. 
     (6) Further, in the non-pneumatic tire T according to the above embodiment, the main groove  5  formed on the center of the tread  4  in the tire width direction does not have the protrusion  50 , but may have the protrusion  50 . At this time, the main groove  5  on the center of the tread  4  in the tire width direction may include only one protrusion  50  in the depth direction of the main groove  5 , and the main groove  5  of each of the connecting portion regions  40  may include a plurality of the protrusions  50  in the depth direction of the main groove  5 . Further, the auxiliary groove may include the protrusion  50 . 
     (7) Further, in the non-pneumatic tire T according to the above embodiment, the plurality of coupling portions  3  are configured such that the first coupling portions  31  and the second coupling portions  32  are arrayed along the tire circumferential direction CD, but the shape of the coupling portions  3  is not particularly limited. For example, the coupling portions  3  may have a rectangular plate shape or the like which couples the inner annular portion  1  and the outer annular portion  2  to each other.   
     DESCRIPTION OF REFERENCE SIGNS 
     T Non-pneumatic tire 
     SS Support structure 
       1  Inner annular portion 
       2  Outer annular portion 
       3  Coupling portion 
       4  Tread 
       4   a  Tread surface 
       5  Main groove 
       5   a  Groove sidewall 
       5   b  Groove bottom 
       31  First coupling portion 
       31   a  Inner connecting portion 
       31   b  Outer connecting portion 
       32  Second coupling portion 
       32   b  Outer connecting portion 
       40  Connecting portion region 
       41  Land 
       50  Protrusion 
       50   a  Protrusion outer surface 
       50   b  Protrusion inner surface 
       50   c  Tip 
       50   d  Proximal end p CD Tire circumferential direction   
     RD Tire radial direction 
     WD Tire width direction