Patent Publication Number: US-2021178831-A1

Title: Pneumatic tire

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a pneumatic tire. 
     Description of the Background Art 
     Generally, each sidewall portion of a pneumatic tire is covered with a rubber having a small thickness. Therefore, projections and recesses called bulges and dents tend to appear locally on the sidewall portion, due to, for example, residual air or joint portions of a carcass that is an internal structure member of the tire. These projections and recesses do not affect the performance of the tire but may cause deterioration of the appearance of the tire. 
     In order to make the projections and recesses inconspicuous, various pneumatic tires in which decorative patterns are formed on the surfaces of sidewall portions thereof have been proposed (see, for example, Japanese Laid-Open Patent Publication No. 2014-136487). 
     In recent years, there has been an increasing demand for further improving the appearance of sidewall portions. 
     The present invention has been made in view of the above-described problem, and a main object of the present invention is to provide a pneumatic tire that can effectively prevent projections and recesses on a sidewall portion thereof from becoming conspicuous. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a pneumatic tire having a pair of sidewall portions, wherein: an outer surface of at least one of the pair of sidewall portions includes a decorative region extending in a tire circumferential direction; in the decorative region, a plurality of pattern elements are arranged at intervals in the tire circumferential direction and a tire radial direction, whereby the decorative region includes a plurality of circumferential pattern lines in each of which the pattern elements are aligned in the tire circumferential direction, and a plurality of radial pattern lines in each of which the pattern elements are aligned in the tire radial direction; in each of the circumferential pattern lines, lengths in the tire circumferential direction of the pattern elements are changed in the tire circumferential direction; and in each of the radial pattern lines, lengths in the tire radial direction of the pattern elements are changed in the tire radial direction. 
     In the tire according to the present invention, preferably, in at least one of the circumferential pattern lines, the lengths in the tire circumferential direction of the pattern elements adjacent to each other in the tire circumferential direction are different from each other. 
     In the tire according to the present invention, preferably, in at least one of the circumferential pattern lines, the lengths in the tire circumferential direction of the pattern elements are gradually decreased toward one side in the tire circumferential direction. 
     In the tire according to the present invention, preferably, in at least one of the circumferential pattern lines, the intervals between the pattern elements are gradually increased toward the one side in the tire circumferential direction. 
     In the tire according to the present invention, preferably, in at least one of the radial pattern lines, the lengths in the tire radial direction of the pattern elements adjacent to each other in the tire radial direction are different from each other. 
     In the tire according to the present invention, preferably, in at least one of the radial pattern lines, the lengths in the tire radial direction of the pattern elements are gradually decreased toward one side in the tire radial direction. 
     In the tire according to the present invention, preferably, in at least one of the radial pattern lines, the intervals between the pattern elements are gradually increased toward the one side in the tire radial direction. 
     In the tire according to the present invention, preferably, a plurality of linear patterns is formed on surfaces of the pattern elements. 
     In the tire according to the present invention, preferably, the linear patterns are inclined in the same direction relative to the tire circumferential direction. 
     In the tire according to the present invention, preferably, in the decorative region, a non-patterned portion having no linear pattern on a surface thereof is formed between the pattern elements adjacent to each other. 
     In the tire according to the present invention, preferably, the number of the circumferential pattern lines provided is three or more. 
     In the tire according to the present invention, preferably, each of the radial pattern lines is inclined relative to the tire radial direction. 
     In the tire according to the present invention, preferably, the pattern elements each have a parallelogram shape in a plan view. 
     The outer surface of the sidewall portion of the pneumatic tire according to the present invention includes a decorative region extending in the tire circumferential direction. In the decorative region, a plurality of pattern elements is arranged at intervals in the tire circumferential direction and a tire radial direction, whereby the decorative region includes a plurality of circumferential pattern lines in each of which the pattern elements are aligned in the tire circumferential direction, and a plurality of radial pattern lines in each of which the pattern elements are aligned in the tire radial direction. In each of the circumferential pattern lines, the lengths in the tire circumferential direction of the pattern elements are changed in the tire circumferential direction, and in each of the radial pattern lines, the lengths in the tire radial direction of the pattern elements are changed in the tire radial direction. 
     Each circumferential pattern line changes the degrees of light reflection of the pattern elements in the tire circumferential direction. In addition, each radial pattern line changes the degrees of light reflection of the pattern elements in the tire radial direction. Therefore, the outer surface of the sidewall portion on which the circumferential pattern lines and the radial pattern lines are disposed can reflect light in a complicated manner to effectively prevent projections and recesses from becoming conspicuous. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an enlarged view of a sidewall portion of a tire according to an embodiment; 
         FIG. 2  is an enlarged view of a circumferential pattern line in  FIG. 1 ; 
         FIG. 3  is an enlarged view of a radial pattern line in  FIG. 1 ; 
         FIG. 4  is an enlarged perspective view of a pattern element in  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of a linear pattern in  FIG. 4 ; 
         FIG. 6  is a cross-sectional view of a linear pattern according to another embodiment of the present invention; and 
         FIG. 7  is an enlarged view of a sidewall portion of a tire of a comparative example. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
       FIG. 1  is an enlarged view of a sidewall portion  3  of a pneumatic tire (hereinafter, sometimes referred to simply as “tire”)  1  according to the present embodiment. The tire  1  according to the present embodiment has a pair of sidewall portions  3  on both sides of a tread portion  2 . The tire  1  according to the present embodiment is for a passenger car. However, the present invention is not limited to such a mode, and may be applied to, for example, tires for a motorcycle and tires for a heavy-duty vehicle. 
     In the present description, unless otherwise specified, dimensions and the like of components of the tire  1  are measured in a normal state. The normal state is a state where: the tire  1  is mounted on a normal rim and inflated to a normal internal pressure; and no load is applied to the tire  1 . 
     The “normal rim” is a rim that is defined, in a standard system including a standard on which the tire is based, by the standard for each tire, and is, for example, the “standard rim” in the JATMA standard, the “Design Rim” in the TRA standard, or the “Measuring Rim” in the ETRTO standard. 
     The “normal internal pressure” is an air pressure that is defined, in a standard system including a standard on which the tire is based, by the standard for each tire, and is the “maximum air pressure” in the JATMA standard, the maximum value indicated in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, or the “INFLATION PRESSURE” in the ETRTO standard. 
     In the tire  1  according to the present embodiment, the outer surface of at least one of the pair of sidewall portions  3  has a decorative region  5  extending in the tire circumferential direction. In the present embodiment, each of the pair of sidewall portions  3  has a decorative region  5 . 
     The decorative region  5  includes a circumferential pattern line  6  and a radial pattern line  7  formed by a plurality of pattern elements  8 . In the circumferential pattern line  6 , the plurality of pattern elements  8  are aligned in the tire circumferential direction by being arranged at intervals in the tire circumferential direction. In the radial pattern line  7 , the plurality of pattern elements  8  are aligned in the tire radial direction by being arranged at intervals in the tire radial direction. In the decorative region  5 , a plurality of circumferential pattern lines  6  are aligned in the tire radial direction, and, in the present embodiment, three or more circumferential pattern lines  6  are aligned. In addition, in the decorative region  5 , a plurality of radial pattern lines  7  are aligned in the tire circumferential direction. One pattern element  8  is a component of both the circumferential pattern line  6  and the radial pattern line  7 . 
     In each circumferential pattern line  6 , the lengths in the tire circumferential direction of the pattern elements  8  are changed in the tire circumferential direction. In addition, in each radial pattern line  7 , the lengths in the tire radial direction of the pattern elements  8  are changed in the tire radial direction. 
     Each circumferential pattern line  6  changes the degrees of light reflection of the pattern elements  8  in the tire circumferential direction. In addition, each radial pattern line  7  changes the degrees of light reflection of the pattern elements  8  in the tire radial direction. Therefore, the outer surface of the sidewall portion  3  on which the circumferential pattern lines  6  and the radial pattern lines  7  are disposed can reflect light in a complicated manner to effectively prevent projections and recesses from becoming conspicuous (hereinafter, such an effect is sometimes referred to as “camouflaging performance”). 
       FIG. 2  shows an enlarged view of one circumferential pattern line  6 . As shown in  FIG. 2 , in at least one of the circumferential pattern lines  6 , the lengths in the tire circumferential direction of the pattern elements  8  adjacent to each other in the tire circumferential direction are different from each other. As a preferable mode, in the present embodiment, in at least one of the circumferential pattern lines  6 , the lengths L 1  in the tire circumferential direction of the pattern elements  8  are gradually decreased toward one side a in the tire circumferential direction. Such a circumferential pattern line  6  exhibits excellent camouflaging performance. 
     In order to further enhance the camouflaging performance, in at least one of the circumferential pattern lines  6 , the intervals L 2  between the pattern elements  8  are preferably gradually increased toward the one side a in the tire circumferential direction. 
     Each pattern element  8  includes two first edges  8   a  extending in the tire circumferential direction. In at least one of the circumferential pattern lines  6 , each of the first edges  8   a  of two pattern elements  8  adjacent to each other is located in a virtual belt having a width smaller than that of the circumferential pattern line  6  and extending along the circumferential pattern line  6 . The width of the virtual belt is, for example, not greater than 50% and preferably not greater than 20% of the width of the circumferential pattern line  6 . 
     In the present embodiment, in at least one of the circumferential pattern lines  6 , each of the first edges  8   a  of two pattern elements  8  adjacent to each other is located on substantially the same straight line or on substantially the same curved line extending with a constant curvature. In a more preferable mode, all of the plurality of pattern elements  8  included in the circumferential pattern line  6  are arranged in the above-described relationship. Such arrangement of the pattern elements  8  can suppress problems such as deterioration of the processability and maintainability of a vulcanization mold for molding the outer surface of the sidewall portion  3  and increase of vulcanization molding defects. The “substantially” means that a dimensional error normally included in a rubber molded product and a dimensional error that occurs when the tire is filled with the internal pressure is tolerated, and two first edges  8   a  that are located on the straight line or the curved line when being displaced by about 1.0 mm are included in the present embodiment. 
     As shown in  FIG. 1 , in the present embodiment, each of the plurality of circumferential pattern lines  6  is formed in the above-described mode. Accordingly, further excellent camouflaging performance is achieved. 
     Each radial pattern line  7  is inclined relative to the tire radial direction. In a preferable mode, of the plurality of radial pattern lines  7  aligned in the tire circumferential direction, the radial pattern lines  7  disposed closer to the one side in the tire circumferential direction have larger angles relative to the tire radial direction. Accordingly, the camouflaging performance is further improved. 
       FIG. 3  shows an enlarged view of one radial pattern line  7 . As shown in  FIG. 3 , in at least one of the radial pattern lines  7 , the lengths L 3  in the tire radial direction of the pattern elements  8  adjacent to each other in the tire radial direction are different from each other. As a preferable mode, in the present embodiment, in at least one of the radial pattern lines  7 , the lengths in the tire radial direction of the pattern elements  8  are gradually decreased toward one side b in the tire radial direction. 
     In order to further enhance the camouflaging performance, in at least one of the radial pattern lines  7 , the intervals L 4  between the pattern elements  8  are gradually increased toward the one side b in the tire radial direction. 
     Each pattern element  8  includes two second edges  8   b  extending in the tire radial direction. Each of the second edges  8   b  of two pattern elements  8  adjacent to each other is located in a virtual belt having a width smaller than that of the radial pattern line  7  and extending along the radial pattern line  7 . The width of the virtual belt is, for example, not greater than 50% and preferably not greater than 20% of the width of the radial pattern line  7 . In the present embodiment, in at least one of the radial pattern lines  7 , each of the second edges  8   b  of two pattern elements  8  adjacent to each other is located on substantially the same straight line or on substantially the same curved line extending with a constant curvature. In a more preferable mode, all of the plurality of pattern elements  8  included in the radial pattern line  7  are arranged in the above-described relationship. Such arrangement of the pattern elements  8  serves to suppress deterioration of the processability and maintainability of the vulcanization mold and vulcanization molding defects. 
     As shown in  FIG. 1 , in the present embodiment, each of the plurality of radial pattern lines  7  is formed in the above-described mode. Accordingly, further excellent camouflaging performance is achieved. 
     At least one pattern element  8  has a parallelogram shape in a plan view. In the present embodiment, each of the plurality of pattern elements  8  has a parallelogram shape. The parallelogram shape of the present embodiment includes not only a shape with linear two sides parallel to each other but also a shape with curved two sides parallel to each other. 
     The pattern elements  8  have, for example, linear patterns  10  formed on the surfaces thereof. The linear patterns  10  of the present embodiment are inclined in the same direction relative to the tire circumferential direction. In the present embodiment, a non-patterned portion  12  having no linear pattern on the surface thereof is formed between the adjacent pattern elements  8  to make a contrast with the pattern elements  8 . The non-patterned portion  12  of the present embodiment is composed of, for example, a smooth surface. 
       FIG. 4  shows an enlarged perspective view of one pattern element  8 . As shown in  FIG. 4 , in each pattern element  8  of the present embodiment, the linear pattern  10  is formed by ridges  15  projecting from the bottom surface of a recess portion  13 . A vulcanization mold for forming such pattern elements  8  has excellent air dischargeability during vulcanization molding. Therefore, the pattern elements  8  of the present embodiment serve to suppress vulcanization molding defects such as bareness. 
       FIG. 5  shows a cross-sectional view, of the linear pattern  10 , orthogonal to the longitudinal direction of the linear pattern  10 . As shown in  FIG. 5 , the cross-sectional shape of each ridge  15  included in the linear pattern  10  is, for example, a trapezoidal shape. In order to suppress vulcanization molding defects, the height h 1  of each ridge  15  is preferably smaller than the depth dl of the recess portion  13  of the pattern element  8 . The height h 1  of each ridge  15  is, for example, 40% to 80% of the depth dl of the recess portion  13 . 
     Each ridge  15  includes two inclined surfaces  16  extending from the bottom surface of the recess portion  13 . The angle θ 1  between the two inclined surfaces  16  is, for example, 20 to 90°. In addition, the width W 1  of each ridge  15  is, for example, 0.2 to 0.6 mm. 
       FIG. 6  shows a cross-sectional view of a linear pattern  10  according to another embodiment. As shown in  FIG. 6 , the cross-sectional shape of each ridge  15  included in the linear pattern  10  may be, for example, a semicircular shape. In this case, the radius r 1  thereof is, for example, 0.4 to 1.2 mm A vulcanization mold for forming such a linear pattern  10  is less likely to be clogged with dirt in the grooves forming the ridges and thus exhibits excellent maintainability. 
     Although the particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made to practice the present invention. 
     EXAMPLES 
     Tires having a size of 205/55R16 and including the decorative region shown in  FIG. 1  on a sidewall portion thereof were produced. As a comparative example, a tire including a decorative region a shown in  FIG. 7  on a sidewall portion thereof was produced as a test tire. The decorative region a of the comparative example includes a plurality of projections c projecting from a base surface b on which linear patterns d are disposed. The tire of the comparative example is substantially the same as the tires of examples, except for the configuration of the outer surface of the sidewall portion. Each test tire was tested for camouflaging performance and a rate of occurrence of bareness. The common specifications and the test methods for the test tires are as follows. 
     Mount rim: 16×6.5 J 
     Tire internal pressure: 200 kPa 
     &lt;Camouflaging Performance&gt; 
     The outer surface of the sidewall portion was visually observed from various directions outdoors in fine weather, and the observer made sensory evaluation for a state of occurrence of projections and recesses on the sidewall portion. The results are indicated as scores with the result of the comparative example being regarded as 100. A higher value indicates that the camouflaging performance is better. 
     &lt;Rate of Occurrence of Bareness&gt; 
     Each test tire was produced in a fixed quantity, and the rate of occurrence of bareness on the outer surface of the sidewall portion was measured. The results are indicated as indexes with the rate of occurrence of bareness of the comparative example being regarded as 100. A lower value indicates that the rate of occurrence of bareness is lower and that the result is better. 
     The results of the tests are shown in Table 1. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Compar- 
                   
                   
               
               
                   
                 ative 
                 Exam- 
                 Exam- 
               
               
                   
                 Example 
                 ple 1 
                 ple 2 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Drawing showing sidewall portion 
                 FIG. 7 
                 FIG. 1 
                 FIG. 1 
               
               
                 Drawing showing cross-section of linear 
                 — 
                 FIG. 4 
                 FIG. 5 
               
               
                 pattern 
               
               
                 Camouflaging performance (score) 
                 100 
                 120 
                 115 
               
               
                 Rate of occurrence of bareness (index) 
                 100 
                 85 
                 89 
               
               
                   
               
            
           
         
       
     
     As a result of the tests, it was confirmed that the tire of each Example effectively made the projections and recesses on the sidewall portion inconspicuous. In addition, it was confirmed that the tire of each Example suppressed occurrence of bareness.