Patent Publication Number: US-2019193482-A1

Title: Pneumatic tire

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of Japanese Patent Application No. 2017-246902 filed on Dec. 22, 2017, the content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Technical Field 
     The present invention relates to a pneumatic tire. 
     Related Art 
     A pneumatic tire disclosed in Japanese Patent No. 4449203 includes a recessed mark, and a protruded portion adjacent to the recessed mark, both formed in a surface of a sidewall portion, and specifies a volume ratio of the recessed mark to the protruded portion. According to this pneumatic tire, rubber of the recessed portion is shifted to the protruded portion during tire vulcanization molding to avoid a thickness change of the sidewall portion at a mark position and thereby prevent bending of a carcass layer at the mark position. 
     However, the pneumatic tire disclosed in Japanese Patent No. 4449203 still has room for improvement concerning local bending of the carcass layer and air resistance of the sidewall portion. 
     SUMMARY 
     An object of the present invention is to provide a pneumatic tire which includes a sidewall portion provided with marks, the tire capable of reducing air resistance in the sidewall portion while reducing local bending of a carcass layer. 
     An aspect of the present invention provides a pneumatic tire including: a carcass layer that has a toroidal shape and extends between a pair of bead portions; a sidewall portion, one of the pair of bead portions being provided at an inner end of the sidewall portion in a tire radial direction; and a mark formed in an outer surface of the sidewall portion. The mark includes a recessed portion provided in the outer surface of the sidewall portion and recessed inward in a tire width direction, and a mark body defined by the recessed portion. A top surface of the mark body coincides with a reference surface corresponding to the outer surface of the sidewall portion, or is located inside the reference surface in a normal direction of the reference surface. 
     According to this configuration, the mark is constituted by the recessed portion recessed from the outer surface of the sidewall portion, and the mark body defined by the recessed portion. Accordingly, local bending of the carcass layer can be more reduced compared with the configuration in which the mark body is constituted by a recessed portion. Moreover, the whole of the mark including the mark body is located inside the reference surface of the sidewall portion in the normal direction of the reference surface. Accordingly, air resistance at the sidewall portion can be reduced. 
     An offset amount in the normal direction between the top surface of the mark body and the reference surface of the side wall portion may be 15% or smaller of a dimension of the sidewall portion in the normal direction. 
     According to this configuration, the offset amount in the normal direction of the reference surface between the top surface of the mark body and the reference surface of the sidewall portion is set within the appropriate range. Accordingly, effective reduction of local bending of the carcass layer located inside the mark body in the normal direction is achievable. When the offset amount in the normal direction of the reference surface between the top surface of the mark body and the reference surface of the sidewall portion is larger than 15% of the dimension of the sidewall portion in the normal direction of the reference surface, local bending of the carcass layer located inside the mark body in the normal direction increases. 
     The recessed portion may include a first surface continuous with the top surface of the mark body, and a second surface continuous with the outer surface of the sidewall portion. 
     The recessed portion may include a third surface that connects the first surface and the second surface. 
     The first surface may be linear in a cross section orthogonal to a direction in which the recessed portion extends. An angle formed by the first surface and the normal direction in the cross section orthogonal to the direction in which the recessed portion may extend lies in a range from 5° inclusive to 30° inclusive. 
     According to this configuration, the angle formed by the first surface of the recessed portion and the normal direction of the reference surface in the cross section orthogonal to the direction in which the recessed portion extends is specified within the appropriate range. Accordingly, local bending of the carcass layer can be reduced while securing visibility of the mark. When the angle formed by the first surface of the recessed portion and the normal direction of the reference surface is larger than the above range, the boundary between the mark body and the recessed portion becomes unclear. In this case, sufficient visibility of the mark cannot be secured. When the angle formed by the first surface of the recessed portion and the normal direction of the reference surface is smaller than the above range, the dimension of the recessed portion in the direction orthogonal to the normal direction becomes excessively larger. In this case, an area of the recessed portion affecting the shape of the carcass layer increases. 
     A maximum dimension of the recessed portion in a direction orthogonal to the normal direction in a cross section orthogonal to a direction in which the recessed portion extends may lie in a range from 2.5 times inclusive to 5 times inclusive a maximum dimension of the recessed portion in the normal direction. 
     According to this configuration, the maximum dimension of the recessed portion in the direction orthogonal to the normal direction of the reference surface is specified in the appropriate range described above (2.5 times inclusive to 5 times inclusive maximum dimension of recessed portion in normal direction) in the cross section orthogonal to the direction in which the recessed portion extends. In this case, local bending of the carcass layer can be reduced while securing visibility of the mark. When the maximum dimension of the recessed portion in the direction orthogonal to the normal direction of the reference surface is larger than the above range, the dimension of the recessed portion in the direction orthogonal to the normal direction of the reference surface becomes excessively larger. In this case, an area of the recessed portion affecting the shape of the carcass layer increases. When the maximum dimension of the recessed portion in the direction orthogonal to the normal direction of the reference surface is smaller than the above range, a visible area of the recessed portion decreases. In this case, sufficient visibility cannot be secured. 
     According to the present invention, the mark is constituted by the recessed portion recessed from the outer surface of the sidewall portion, and the mark body defined by the recessed portion. Accordingly, local bending of the carcass layer can be more reduced compared with the configuration in which the mark body is constituted by a recessed portion. Moreover, the whole of the mark including the mark body is located inside the reference surface of the sidewall portion in the normal direction of the reference surface. Accordingly, air resistance at the sidewall portion can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and the other features of the present invention will become apparent from the following description and drawings of an illustrative embodiment of the invention in which: 
         FIG. 1  is a cross-sectional view of a pneumatic tire in a meridian direction according to a first embodiment of the present invention; 
         FIG. 2  is a perspective view of a mark according to the first embodiment as viewed from an outside in a tire width direction; 
         FIG. 3  is a cross-sectional view of a main part taken along a line III-Ill of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of a sidewall portion according to a second embodiment of the present invention, as a view corresponding to  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of a sidewall portion according to a third embodiment of the present invention, as a view corresponding to  FIG. 3 ; and 
         FIG. 6  is a cross-sectional view of a sidewall portion according to a fourth embodiment of the present invention, as a view corresponding to  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be hereinafter described with reference to the accompanying drawings. In the accompanying drawings referred to below, a tire radial direction and a tire width direction are given reference signs TR and TW, respectively. 
     First Embodiment 
     Referring to  FIG. 1 , a pneumatic tire  1  includes a tread portion  10 , a sidewall portion  20 , and a pair of bead portions  30 . The sidewall portions  20  extend from both end portions of the tread portions  10  in the tire width direction TW while curving toward the inside in the tire radial direction TR. Each of the bead portions  30  is provided at an inner end of the corresponding sidewall portion  20  in the tire radial direction TR. A carcass layer  40  having a toroidal shape is extended between the pair of bead portions  30  inside the pneumatic tire  1 . The accompanying drawing does not show internal structures except for the carcass layer  40 . 
     The sidewall portion  20  of the present embodiment has an outer surface  20   a  having an arcuate shape in a tire meridian cross section. Referring to  FIG. 2  in conjunction with the foregoing figure, a mark  50  is formed in the outer surface  20   a  of the sidewall portion  20 . According to the present embodiment, the mark  50  has a shape similar to an alphabetic capital letter “T” as shown in  FIG. 2 . The mark  50  includes a recessed portion  51  recessed inward in the tire width direction TW from the outer surface  20   a  of the sidewall portion  20 , and a mark body  52  defined by the recessed portion  51 . 
     The recessed portion  51  of the present embodiment is so formed as to line an edge of the letter “T”. The mark body  52  is therefore so defined as to represent the letter “T”. For example, in the cross section shown in  FIG. 3 , the recessed portion  51  includes recesses  51 A and  51 B formed at two different positions of the sidewall portion  20  in the tire radial direction TR. This cross section is a cross section orthogonal to directions in which the recesses  51 A and  51 B extend, and is a tire meridian cross section according to the present embodiment. Each of the recesses  51 A and  51 B of the present embodiment includes a first surface  51   a  continuous with a top surface  52   a  of the mark body  52 , and a second surface  51   b  continuous with the outer surface  20   a  of the sidewall portion  20 . The first surface  51   a  of the present embodiment is formed continuously with the second surface  51   b . Each of the first surfaces  51   a  of the recesses  51 A and  51 B of the present embodiment has a linear shape extending in the tire width direction TW in the tire meridian cross section. An angle θ formed by each of the first surfaces  51   a  of the recessed portions  51 A and  51 B and a normal direction N of a reference surface  21  passing through a reference point P in the tire meridian cross section is set within a range from 5° inclusive to 30° inclusive. The reference point P of the present embodiment is a boundary point between the mark body  52  and each of the recesses  51 A and  51 B. The second surface  51   b  of each of the recesses  51 A and  51 B of the present embodiment is arcuate in the tire meridian cross section. 
     A maximum dimension L of each of the recesses  51 A and  51 B in a direction orthogonal to the normal direction N is set within a range from 2.5 times inclusive to 5 times inclusive a maximum dimension W of each of the recesses  51 A and  51 B in the normal direction N. 
     The top surface  52   a  of the mark body  52  of the present embodiment is a curved surface that coincides with the reference surface  21  corresponding to the outer surface  20   a  of the sidewall portion  20 . 
     The reference surface  21  is a virtual curved surface which represents an outer surface of the sidewall portion  20  in a configuration not including the mark  50 , and smoothly connects the outer surface  20   a  of the sidewall portion  20 . 
     According to the foregoing configuration, the mark  50  is constituted by the recessed portion  51  recessed from the outer surface  20   a  of the sidewall portion  20 , and the mark body  52  defined by the recessed portion  51 . Accordingly, local bending of the carcass layer  40  can be more reduced compared with the configuration in which the mark body  52  is constituted by a recessed portion. Moreover, the whole of the mark  50  including the mark body  52  is located inside the reference surface  21  of the sidewall portion  20  in the normal direction N of the reference surface  21 . Accordingly, air resistance at the sidewall portion  20  can be reduced. 
     The angle θ formed by each of the first surfaces  51   a  of the recesses  51 A and  51 B and the normal direction N of the reference surface  21  in the cross section orthogonal to the directions in which the recesses  51 A and  51 B extend is specified within the appropriate range described above (from 5° inclusive to 30° inclusive). Accordingly, local bending of the carcass layer  40  can be reduced while securing visibility of the mark  50 . When the angle θ formed by each of the first surfaces  51   a  of the recessed portions  51 A and  51 B and the normal direction N of the reference surface  21  is larger than the above range, the boundary between the mark body  52  and the recesses  51 A and  51 B becomes unclear. In this case, sufficient visibility of the mark  50  cannot be secured. When the angle θ formed by each of the first surfaces  51   a  of the recesses  51 A and  51 B and the normal direction N of the reference surface  21  is smaller than the above range, the dimension of each of the recess  51 A and the recess  51 B in the direction orthogonal to the normal direction N becomes excessively larger. In this case, areas of the recesses  51 A and  51 B affecting the shape of the carcass layer  40  increase. 
     Moreover, the maximum dimension L of each of the recesses  51 A and  51 B in the direction orthogonal to the normal direction N is specified in the appropriate range described above (2.5 times inclusive to 5 times inclusive maximum dimension W of recesses  51 A and  51 B in normal direction N). In this case, local bending of the carcass layer  40  can be reduced while securing visibility of the mark  50 . When the maximum dimension L of each of the recesses  51 A and  51 B in the direction orthogonal to the normal direction N is larger than the above range, the dimension of each of the recess  51 A and the recess  51 B in the direction orthogonal to the normal direction N becomes excessively larger. In this case, areas of the recesses  51 A and  51 B affecting the shape of the carcass layer  40  increase. When the maximum dimension L of each of the recesses  51 A and  51 B in the direction orthogonal to the normal direction N is smaller than the above range, visible areas of the recesses  51 A and  51 B decrease. In this case, sufficient visibility cannot be secured. 
     While the recesses  51 A and  51 B appearing in the tire meridian cross section have been described in the present embodiment, but the embodiment is not limited thereto, and other parts in the recessed portion  51  may have a configuration similar to the recesses  51 A and  51 B in a cross section orthogonal to the direction in which the recessed portion  51  extends. For example, the recessed portion  51  has a configuration similar to the recesses  51 A and  51 B in a cross section along a line C in  FIG. 2 . 
     In second to fourth embodiments described below, elements identical or similar to the corresponding elements of the first embodiment are given identical reference numbers, and detailed description of these elements are not repeated. In addition, advantageous effects similar to those of the first embodiment are produced in the following respective embodiments unless particularly noted otherwise. 
     Second Embodiment 
     Referring to  FIG. 4 , the top surface  52   a  of the mark body  52  of the present embodiment is disposed inside the reference surface  21  of the sidewall portion  20  in the normal direction of the reference surface  21 . The top surface  52   a  of the mark body  52  is substantially parallel to the reference surface  21  of the sidewall portion  20  in the tire meridian cross section. An offset amount d in the normal direction of the reference surface  21  between the top surface  52   a  of the mark body  52  and the reference surface  21  of the sidewall portion  20  is set in a range of 15% or smaller of a dimension WS of the sidewall portion  20  in the normal direction. The dimension WS of the sidewall portion  20  in the normal direction is a dimension of the sidewall portion  20  in the normal direction at an outermost point PS of the sidewall portion  20  in the tire width direction TW. 
     According to this configuration, the offset amount d in the normal direction between the top surface  52   a  of the mark body  52  and the reference surface  21  of the sidewall portion  20  is specified within the appropriate range (15% or smaller of dimension WS of sidewall portion  20  in normal direction). Accordingly, effective reduction of local bending of the carcass layer  40  located inside the mark body  52  in the normal direction is achievable. When the offset amount d in the normal direction between the top surface  52   a  of the mark body  52  and the reference surface  21  of the sidewall portion  20  is larger than 15% of the dimension WS of the sidewall portion  20  in the normal direction, local bending of the carcass layer  40  located inside the mark body  52  in the normal direction increases. 
     Third Embodiment 
     Referring to  FIG. 5 , the second surface  51   b  of each of the recesses  51 A and  51 B of the present embodiment is linear in the tire meridian cross section. 
     Fourth Embodiment 
     Referring to  FIG. 6 , each of the recesses  51 A and  51 B of the present embodiment includes a third surface  51   c  that connects the first surface  51   a  and the second surface  51   b . The third surface  51   c  is linear in the tire meridian cross section. 
     Although the specific embodiments of the present invention have been described, the present invention is not limited to the above embodiments. Various modifications may be made without departing from the scope of the present invention. 
     For example, the sidewall portion  20  may include serrations. 
     The mark  50  may be constituted by any mark selected from a letter, a figure, and a symbol, or a combination of these. For example, the character represented by the mark  50  is not limited to the alphabetic capital letter “T” as shown in the above embodiment.