Patent Publication Number: US-2019176539-A1

Title: Pneumatic tire

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on Japanese Patent Application No. 2017-238866 (filed on Dec. 13, 2017) and claims priority from Japanese Patent Application No. 2017-238866. The present disclosure incorporates entire contents of Japanese Patent Application No. 2017-238866. 
     TECHNICAL FIELD 
     The present disclosure relates to a pneumatic tire. 
     BACKGROUND ART 
     As illustrated in Patent Document  1 , a pneumatic tire is known in which protrusions that span from a side wall of an outer side of a shoulder main groove to a bottom of the groove are provided in the shoulder main groove of a tread. The protrusions may prevent a land portion such as a rib of the tread from being collapsed during cornering. 
     Patent Document 1: Japanese Patent No. 4800604 
     DISCLOSURE OF THE INVENTION 
     Problem that the Invention is to Solve 
     However, when the protrusions exist in the main groove, drainage performance for water or snow by the main groove may be impaired. Further, in the related art, the influence of the protrusions in the main groove on traction property during traveling on snow has not been examined. 
     Therefore, the present disclosure is to provide a pneumatic tire having protrusions in a main groove, which is capable of preventing a land portion from being collapsed during cornering, and hardly impairs drainage performance for water or snow so that the protrusions in the main groove contributes to an improvement in traction performance during traveling on snow. 
     Means for Solving the Problem 
     In a pneumatic tire of an embodiment, in which protrusions are provided in main grooves extending in a circumferential direction of the tire, upper surfaces of the protrusions are inclined so as to be higher on a tire grounding end side and lower on a tire equator side, surfaces on stepped sides of the protrusions extend in the tire width direction, and surfaces on kick-out sides of the protrusions are inclined such that a portion closer to the tire equator side approaches to the surfaces on the stepped sides. 
     Advantage of the Invention 
     In the pneumatic tire of the embodiment, since the upper surface is inclined so as to be higher on the tire grounding end side and lower on the tire equator side, the land portion is hardly collapsed during cornering. Further, the drainage performance for water or snow is excellent as compared with a case where the upper surface is not inclined like this. Further, since the surface on the stepped side of the protrusion extends in the tire width direction, the protrusion may contribute to an improvement in the traction performance during traveling on snow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  A cross-sectional view in the width direction of a pneumatic tire of an embodiment. 
         FIG. 2  A tread pattern of the pneumatic tire of the embodiment. 
         FIG. 3  A perspective view of the vicinity of a main groove of the tread pattern of  FIG. 2 . 
         FIG. 4  (a) illustrates a cross-sectional view in the width direction of a center main groove, and (b) illustrates a cross-sectional view in the width direction of a shoulder main groove. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     As illustrated in  FIG. 1 , a bead portion  2  is provided on both sides in a tire width direction of a pneumatic tire  1 . The bead portion  2  is constituted by a bead core  2   a  made of a steel wire wound in a circular shape and a bead filler  2   b  made of rubber and provided on a radial outer side of the bead core  2   a.  A carcass ply  5  is laid across the bead portion  2  on both sides of the tire width direction. The carcass ply  5  is a sheet type member in which a plurality of ply cords arranged in a direction orthogonal to a circumferential direction of the tire are covered with rubber. The carcass ply  5  forms a frame shape of the pneumatic tire  1  between the bead portions  2  on both sides of the tire width direction, and surrounds the bead portions  2  by folding back from inside to outside in the tire width direction around the bead portions  2 . A sheet type inner liner  6  made of rubber having low air permeability is adhered to the inside of the carcass ply  5 . 
     One or a plurality of belts  7  are provided on the tire radial outer side of the carcass ply  5 . The belt  7  is a member made by covering a plurality of steel-based cords with rubber. A tread rubber  3  having a grounding surface with a road surface (hereinafter, referred to as a “grounding surface”) is provided on the tire radial outer side of the belt  7 . Further, a side wall rubber  4  is provided on both sides in the tire width direction of the carcass ply  5 . In addition to these members, according to functional requirements of the pneumatic tire  1 , members, for example, a belt lower pad or a chafer are provided. 
     A tread pattern illustrated in  FIG. 2  is formed on a surface of the tread rubber  3 . In  FIG. 2 , the vertical direction is the circumferential direction of the tire, and the lateral direction is the tire width direction. In this tread pattern, as a main groove that extends in the circumferential direction of the tire and has a wide width, a total of four main grooves, that is, two center main grooves  10  in a center region in the tire width direction that is close to a tire equator C and two shoulder main grooves  15  in an outer region in the tire width direction that is close to a tire grounding end E are formed. Then, a center land portion  30  between the two center main grooves  10 , a mediate land portion  35  between the center main groove  10  and the shoulder main groove  15 , and a shoulder land portion  40  between the shoulder main groove  15  and the tire grounding end E are provided. 
     Here, the land portion is a portion formed by being partitioned by grooves. Further, the tire grounding end E is an end portion of the grounding surface in the tire width direction in a loaded state. The loaded state is a state where the pneumatic tire is rim-assembled into a normal rim to be a normal inner pressure and loaded by a normal load. Here, the normal rim is a standard rim defined by standards such as JATMA, TRA, and ETRTO. Further, the normal load is a maximum load defined in the above standards. Further, the normal inner pressure is an inner pressure corresponding to the maximum load. 
     The center main groove  10  includes long first groove portions  11  that extend obliquely with respect to the circumferential direction of the tire, and short second groove portions  12  that are inclined with respect to the circumferential direction of the tire and extend in a direction different from that of the first groove portion  11 . Then, a first groove portion  11  and a second groove portion  12  are arranged alternately, and thus, the center main groove  10  is formed in a zigzag shape. In  FIG. 2 , a lower side is grounded first during rolling of the tire (that is, when the vehicle is traveling) As can be seen from the drawing, the first groove portion  11  is inclined such that a portion to be grounded later (in other words, a rear side in the rolling direction) heads toward the tire grounding end E side. 
     The shoulder main groove  15  includes long first groove portions  16  that extend obliquely with respect to the circumferential direction of the tire, and short second groove portions  17  that are inclined with respect to the circumferential direction of the tire and extend in a direction different from that of the first groove portion  16 . Then, a first groove portion  16  and a second groove portion  17  are arranged alternately, and thus, the shoulder main groove  15  has a zigzag shape. As can be seen from  FIG. 2 , the first groove portion  16  is inclined such that a portion to be grounded later heads toward the tire grounding end E side. 
     Further, as lateral grooves that extend in the tire width direction, first lateral grooves  20  and second lateral grooves  25  are formed. The first lateral groove  20  traverses the shoulder land portion  40  and the mediate land portion  35 , and extends to the center land portion  30  and is closed in the center land portion  30 . Further, the second lateral groove  25  traverses the shoulder land portion  40 , and extends to the mediate land portion  35  and is closed in the mediate land portion  35 . Such first lateral grooves  20  and second lateral grooves  25  are alternately arranged in the circumferential direction of the tire. The second groove portion  17  of the shoulder main groove  15  overlaps with the first lateral groove  20  and the second lateral groove  25 . 
     With the configuration of the groove as described above, the center land portion  30  between the two center main grooves  10  is configured to a rib extending in the circumferential direction of the tire without being divided by lateral grooves. Further, the mediate land portion  35  is divided by the first lateral groove  20 , and thus, is a row of a plurality of mediate blocks  36  arranged in the circumferential direction of the tire. Further, the shoulder land portion  40  is divided by the first lateral groove  20  and the second lateral groove  25 , and thus, is a row of a plurality of shoulder blocks  41  arranged in the circumferential direction of the tire. Two shoulder blocks  41  are provided for one mediate block  36 . 
     A plurality of notches  52  are formed on end portions of both sides of the width direction of the center main groove  30 , respectively. In a plan view (that is, when viewed from the tire outer radial side), the notch  52  is a triangle formed with a boundary between the center main groove  10  and the center land portion  30  as one side. As illustrated in  FIG. 3 , a side  52   a  of the triangle on the stepped side during traveling (a side that is grounded first during traveling) extends toward the tire width direction more than a side  52   b  on the kick-out side during traveling (a side that is grounded later during traveling) 
     As illustrated in  FIG. 3 , a bottom surface  53  of the notch  52  is an upper surface of a shelf portion  54  that is higher than a bottom portion of the center main groove  10 . Therefore, the notch  52  is shallower than the center main groove  10 . A depth of the notch  52  (that is, a depth from the grounding surface to the bottom surface  53 ) may be 60% or less of the depth of the center main groove  10 . 
     Further, a plurality of notches  57  are formed on an end portion of the center main groove  10  side of the mediate block  36 . In a plan view, the notch  57  is a triangle formed with a boundary between the center main groove  10  and the mediate block  36  as one side. A side  57   b  of the triangle on the kick-out side during traveling extends toward the tire width direction more than a side  57   a  on the stepped side during traveling. 
     A bottom surface  58  of the notch  57  is an upper surface of a shelf portion that is higher than a bottom portion of the center main groove  10 . Therefore, the notch  57  is shallower than the center main groove  10 . A depth of the notch  57  (that is, a depth from the grounding surface to the bottom surface  58 ) may be 60% or less of the depth of the center main groove  10 . 
     Further, a plurality of notches  62  are formed on an end portion of the shoulder main groove  15  side of the mediate block  36 . In a plan view, the notch  62  is a triangle formed with a boundary between the shoulder main groove  15  and the mediate block  36  as one side. A side  62   a  of the triangle on the stepped side during traveling extends toward the tire width direction more than a side  62   b  on the kick-out side during traveling. 
     A bottom surface  63  of the notch  62  is an upper surface of a shelf portion that is higher than a bottom portion of the shoulder main groove  10 . Therefore, the notch  62  is shallower than the shoulder main groove  15 . A depth of the notch  62  (that is, a depth from the grounding surface to the bottom surface  63 ) may be 60% or less of the depth of the shoulder main groove  15 . 
     Further, a plurality of notches  67  are formed on an end portion of the shoulder main groove  15  side of the shoulder block  41 . In a plan view, the notch  67  is a triangle formed with a boundary between the shoulder main groove  15  and the shoulder block  41  as one side. A side  67   b  of the triangle on the kick-out side during traveling extends toward the tire width direction more than a side  67   a  on the stepped side during traveling. 
     A bottom surface  68  of the notch  67  is an upper surface of a shelf portion  69  that is higher than a bottom portion of the shoulder main groove  15 . Therefore, the notch  67  is shallower than the shoulder main groove  15 . A depth of the notch  67  (that is, a depth from the grounding surface to the bottom surface  68 ) maybe 60% or less of the depth of the shoulder main groove  15 . 
     A protrusion  90  elevated from the bottom of the groove is provided in the center main groove  10 . A height of the protrusion  90  from the bottom of the groove to the highest portion thereof is not limited, but, for example, is 40% to 50% (including 40% and 50%) of the depth of the center main groove  10 . As illustrated in  FIGS. 3 and 4  ( a ), an upper surface  91  of the protrusion  90  is inclined to be higher on the tire grounding end E side (that is, mediate block  36  side) and to be lower on the tire equator C side (that is, center land portion  30  side). Further, a surface  92  on the stepped side of the protrusion  90  extends in the tire width direction, and a surface  93  on the kick-out side of the protrusion  90  is inclined such that a portion closer to the tire equator C side approaches to the surface  92  on the stepped side. Therefore, the protrusion  90  becomes thinner toward the tire equator C side. The surface  92  on the stepped side of the protrusion  90  may be slightly inclined (e.g., within ±10°) with respect to the tire width direction. 
     The protrusion  90  may be provided to be adjacent to locations on both sides of the mediate block  36  in the circumferential direction of the tire. Further, the protrusion  90  may be provided at a location adjacent to the notch  57  of the mediate block  36 . It is most desirable that the protrusion  90  is provided at a location adjacent to the notch  57  on both sides of the mediate block  36  in the circumferential direction of the tire. When the protrusion  90  is provided at the location adjacent to the notch  57  of the mediate block  36 , the protrusion  90  is located at a location (that is, on the bottom side of the groove) lower than the bottom surface  58  of the notch  57 . 
     Further, a protrusion  95  elevated from the bottom of the groove is provided in the shoulder main groove  15 . A height of the protrusion  95  from the bottom of the groove to the highest portion thereof is not limited, but, for example, is 40 to 50% (including 40% and 50%) of the depth of the shoulder main groove  15 . As illustrated in  FIGS. 3 and 4  ( b ), an upper surface  96  of the protrusion  95  is inclined to be higher on the tire grounding end E side (that is, shoulder block  41  side) and to be lower on the tire equator C side (that is, mediate block  36 ) Further, a surface  97  on the stepped side of the protrusion  95  extends in the tire width direction, and a surface  98  on the kick-out side of the protrusion  95  is inclined such that a portion closer to the tire equator C side approaches to the surface  97  on the stepped side. Therefore, the protrusion  95  becomes thinner toward the tire equator C side. The surface  97  on the stepped side of the protrusion  95  may be slightly inclined (e.g., within ±10°) with respect to the tire width direction. 
     The protrusion  95  may be provided to be adjacent to locations on both sides of the shoulder block  41  in the circumferential direction of the tire. Further, the protrusion  95  may be provided at a location adjacent to the notch  67  of the shoulder block  41 . It is most desirable that the protrusion  95  is provided at a location adjacent to the notch  67  on both sides of the shoulder block  41  in the circumferential direction of the tire. When the protrusion  95  is provided at the location adjacent to the notch  67  of the shoulder block  41 , the protrusion  95  is located at a location (that is, on the bottom side of the groove) lower than the bottom surface  68  of the notch  67 . 
     The protrusion  95  in the shoulder main groove  15  is larger in the number per unit length in the circumferential direction of the tire than the protrusion  90  in the center main groove  10 . 
     As described above, in the pneumatic tire  1  of the embodiment, since the upper surfaces  91  and  96  of the protrusions  90  and  95  are inclined to be higher on the tire grounding end E side, it is possible to prevent collapsing of the mediate block  36  or the shoulder block  41  during cornering. Further, since the upper surfaces  91  and  96  of the protrusions  90  and  95  are inclined to be lower on the tire equator C side, and further the surfaces  93  and  98  on the kick-out side of the protrusions  90  and  95  are inclined such that portions closer to the tire equator C side approach to the surfaces  92  and  97  on the stepped side, a lot of water or snow can pass through the tire equator C side in the center main groove  10  or the shoulder main groove  15 , so that the drainage performance for water or snow is secured. In addition, because the surfaces  92  and  97  on the stepped side of the protrusions  90  and  95  extend in the tire width direction, the protrusions  90  and  95  may press the snow entered into the center main groove  10  or the shoulder main groove  15  during traveling on snow. Therefore, the protrusions  90  and  95  contribute to an improvement in the traction performance during traveling on snow. 
     Further, since the protrusions  90  are provided adjacent to the locations on both sides of the mediate block  36  in the circumferential direction of the tire, it is possible to effectively prevent collapsing of the mediate block  36  during cornering. Further, since the protrusions  95  are provided adjacent to the locations on both sides of the shoulder block  41  in the circumferential direction of the tire, it is possible to effectively prevent collapsing of the shoulder block  41  during cornering. 
     Further, since the shoulder main groove  15  is provided with more protrusions  95  than the center main groove  10 , it is possible to prevent collapsing of the shoulder block  41  to which a larger force is applied during cornering, and moreover, the drainage performance for water or snow of the center main groove  10  is secured. 
     Further, because the notch  57  is formed at the location adjacent to the protrusion  90  in the mediate block  36 , the water or the snow inhibited from flowing by the protrusion  90  can bypass to the notch  57  side. Therefore, the drainage performance for water or snow of the center main groove  10  is secured. Further, because the notch  67  is formed at the location adjacent to the protrusion  95  in the shoulder block  41 , the water or the snow inhibited from flowing by the protrusion  95  can bypass to the notch  67  side. Therefore, the drainage performance for water or snow of the shoulder main groove  15  is secured. 
     Further, since the side  57   b  on the kick-out side of the triangular notch  57  on the center main groove  10  side in the mediate block  36  extends toward the tire width direction, and the side  67   b  on the kick-out side of the triangular notch  67  on the shoulder main groove  15  in the shoulder block  41  extends toward the tire width direction, the pneumatic tire  1  is excellent in traction performance. 
     The above embodiments are examples, and the scope of the present disclosure is not limited thereto. Various modifications maybe made to the above embodiments within the scope without escaping from the purpose of the present disclosure. 
     DESCRIPTION OF REFERENCE NUMERALS AND SIGNS 
     C . . . tire equator, E . . . tire grounding end,  1  . . . pneumatic tire,  2  . . . bead portion,  2   a  . . . bead core,  2   b  . . . bead filler,  3  . . . tread rubber,  4  . . . side wall rubber,  5  . . . carcass ply,  6  . . . inner liner,  7  . . . belt,  10  . . . center main groove,  11  . . . first groove portion,  12  . . . second groove portion,  15  . . . shoulder main groove,  16  . . . first groove portion,  17  . . . second groove portion,  20  . . . first lateral groove,  25  . . . second lateral groove,  30  . . . center land portion,  35  . . . mediate land portion,  36  . . . mediate block,  40  . . . shoulder land portion,  41  . . . shoulder block,  52  . . . notch,  52   a  . . . side on stepped side,  52   b  . . . side on kick-out side,  53  . . . bottom surface,  54  . . . shelf portion,  57  . . . notch,  57   a  . . . side on stepped side,  57   b  . . . side on kick-out side,  58  . . . bottom surface,  62  . . . notch,  62   a  . . . side on stepped side,  62   b  . . . side on kick-out side,  63  . . . bottom surface,  67  . . . notch,  67   a  . . . side on stepped side,  67   b  . . . side on kick-out side,  68  . . . bottom surface,  69  . . . shelf portion,  90  . . . protrusion,  91  . . . upper surface,  92  . . . surface on stepped side,  93  . . . surface on kick-out side,  95  . . . protrusion,  96  . . . upper surface,  97  . . . surface on stepped side,  98  . . . surface on kick-out side