Patent Publication Number: US-2021188013-A1

Title: Pneumatic Tire

Description:
TECHNICAL FIELD 
     The present technology relates to a pneumatic tire. 
     BACKGROUND ART 
     In the technical field related to pneumatic tires, a pneumatic tire as disclosed in Japan Patent Publication No. 2013-537134 has been known that includes a sipe provided with a chamfered portion. 
     SUMMARY 
     Dry performance and wet performance of a pneumatic tire are expected to improve depending on formation conditions of a chamfered portion in a sipe. 
     An aspect of the present technology is to provide a pneumatic tire that can provide good dry performance and wet performance in a compatible manner. 
     According to an aspect of the present technology, a pneumatic tire as follows is provided. The pneumatic tire includes a sipe that is formed in a tread rubber and has an opening extending in a first direction in a surface of the tread rubber. The opening is provided between a first edge of the tread rubber extending in the first direction and a second edge of the tread rubber adjacent to the first edge in a second direction orthogonal to the first direction. The first edge and the second edge are divided into a first range defined in the first direction and a second range different from the first range. In the first range, the first edge is provided with a first chamfered portion. In the second range, the second edge is provided with a second chamfered portion. In the first range, the second edge is not provided with a chamfered portion. In the second range, the first edge is not provided with a chamfered portion. 
     According to an aspect of the present technology, in the first range, the first edge is provided with a first chamfered portion. In the second range, the second edge is provided with a second chamfered portion. In the first range, the second edge is not provided with a chamfered portion. In the second range, the first edge is not provided with a chamfered portion. In driving of a pneumatic tire, high traveling stability is obtained on both of dry road surfaces and wet road surfaces by the edge effect of the first edge and the second edge. Additionally, when the sipe contacts the ground, the opening of the sipe is closed. When the opening is closed, the first edge provided with the first chamfered portion and the second edge without a chamfered portion support each other in the first range, and the second edge provided with the second chamfered portion and the first edge without a chamfered portion support each other in the second range. The edge provided with a chamfered portion and the edge without a chamfered portion support each other, so that rigidity of the tread rubber when ground contact is maintained. For example, rigidity of the tread rubber is increased further in a structure in which an edge provided with a chamfered portion and an edge without a chamfered portion support each other than in a structure in which edges each provided with a chamfered portion support each other. Thus, traveling stability is improved. Additionally, during ground contact, a space is created between the first chamfered portion and a road surface, and a space is created between the second chamfered portion and the road surface. The created spaces ensure drainage properties during driving on wet road surfaces. Therefore, high traveling stability is obtained on wet road surfaces. In this way, according to an aspect of the present technology, the first range in which the first edge is provided with the first chamfered portion and the second edge is not provided with a chamfered portion and the second range in which the second edge is provided with the second chamfered portion and the first edge is not provided with a chamfered portion are defined. Thus, good dry performance and wet performance can be provided in a compatible manner. 
     In the aspect of the present technology, the first range preferably includes a first end portion of the opening in the first direction, and the second range preferably includes a second end portion of the opening in the first direction. 
     In this way, at the time of driving on a wet road surface, water collected in the space between the first chamfered portion and the road surface is smoothly discharged from the first end portion of the opening, and water collected in the space between the second chamfered portion and the road surface is smoothly discharged from the second end portion of the opening. Therefore, high traveling stability is obtained on wet road surfaces, and wet performance is improved. 
     In the aspect of the present technology, the first range is preferably defined between the first end portion and a central portion of the opening in the first direction, and the second range is preferably defined between the second end portion and the central portion of the opening in the first direction. 
     In this way, rigidity of the tread rubber is equalized in the first direction, and excellent traveling stability can be obtained. Additionally, the size of the space between the first chamfered portion and the road surface is substantially equal to the size of the space between the second chamfered portion and the road surface. Thus, discharge performance of water collected in the space between the first chamfered portion and the road surface and discharge performance of water collected in the space between the second chamfered portion and the road surface are made uniform. Therefore, high traveling stability is obtained on wet road surfaces, and wet performance is improved. 
     In the aspect of the present technology, the first edge and the second edge are preferably further divided into a third range different from the first range and the second range, and both of the first edge and the second edge are not preferably provided with a chamfered portion in the third range. 
     In this way, high traveling stability is obtained on both of dry road surfaces and wet road surfaces by the edge effect of the first edge and the second edge in the third range without a chamfered portion. Additionally, when the sipe is in contact with the ground and the opening of the sipe is closed, the first edge without a chamfered portion and the second edge without a chamfered portion support each other in the third range. Thus, rigidity of the tread rubber when ground contact is maintained. 
     In the aspect of the present technology, the first range preferably includes a first end portion of the opening in the first direction, the second range preferably includes a second end portion of the opening in the first direction, and the third range is preferably defined between the first range and the second range. 
     In this way, at the time of driving on a wet road surface, while rigidity of the tread rubber is maintained by the third range defined between the first range and the second range, water collected in the space between the first chamfered portion and the road surface is smoothly discharged from the first end portion of the opening, and water collected in the space between the second chamfered portion and the road surface is smoothly discharged from the second end portion of the opening. 
     In the aspect of the present technology, a dimension of the third range in the first direction is preferably less than or equal to 30% of a dimension of the opening in the first direction. 
     In this way, wet performance is maintained. With the dimension of the third range being great, greater than 30% of the dimension of the opening, when in contact with the ground, the space between the first chamfered portion and the road surface and the space between the second chamfered portion and the road surface are not sufficiently secured, and drainage properties during driving on wet road surfaces may decrease. The dimension of the third range is less than or equal to 30% of the dimension of the opening, so that a decrease in wet performance can be suppressed while ensuring rigidity of the tread rubber. 
     In the aspect of the present technology, a plurality of the first ranges and the second ranges are preferably defined at intervals in the first direction. 
     In this way, rigidity of the tread rubber can be equalized in both of the first direction and the second direction, and excellent traveling stability can be obtained. Additionally, a plurality of spaces between the first chamfered portion and a road surface and between the second chamfered portion and the road surface are provided, so that high traveling stability is obtained on wet road surfaces, and wet performance is improved. 
     According to the aspect of the present technology, a pneumatic tire is provided that can provide good dry performance and wet performance in a compatible manner. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view schematically illustrating an outline of a sipe according to the present technology. 
         FIG. 2  is a plan view schematically illustrating an outline of the sipe according to the present technology. 
         FIG. 3  is a plan view schematically illustrating an outline of the sipe according to the present technology. 
         FIG. 4  is a plan view schematically illustrating an outline of the sipe according to the present technology. 
         FIG. 5  is a plan view schematically illustrating an outline of the sipe according to the present technology. 
         FIG. 6  is a plan view schematically illustrating an outline of the sipe according to the present technology. 
         FIG. 7  is a plan view schematically illustrating an outline of the sipe according to the present technology. 
         FIG. 8  is a cross-sectional view schematically illustrating an outline of the sipe according to the present technology. 
         FIG. 9  is a cross-sectional view schematically illustrating an outline of the sipe according to the present technology. 
         FIG. 10  is a meridian cross-sectional view schematically illustrating a part of a pneumatic tire according to the present embodiment. 
         FIG. 11  is a diagram illustrating one example of a tread portion of the pneumatic tire according to the present embodiment. 
         FIG. 12  is a plan view illustrating one example of a sipe according to the present embodiment. 
         FIG. 13  is a perspective view illustrating one example of the sipe according to the present embodiment. 
         FIG. 14  is a plan view illustrating one example of the sipe according to the present embodiment. 
         FIG. 15  is a perspective view illustrating one example of the sipe according to the present embodiment. 
         FIG. 16  is a plan view illustrating one example of the sipe according to the present embodiment. 
         FIG. 17  is a perspective view illustrating one example of the sipe according to the present embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An outline of a pneumatic tire  1  according to the present technology will be described. In the following description, the pneumatic tire  1  is also referred to as a tire  1  when appropriate. The tire  1  according to the present technology includes a tread rubber  8  in which a sipe  100  is formed. 
     The sipe  100  is a narrow groove including an opening  103  formed in a surface of the tread rubber  8 . When the sipe  100  is in a ground contact state, the opening  103  of the sipe  100  is closed by elastic deformation of the tread rubber  8 . When the sipe  100  is in a non-ground contact state, the opening  103  of the sipe  100  is opened by the elastic deformation of the tread rubber  8 . The sipe  100  generally has a groove width of less than or equal to 1.5 mm. The opening  103  of the sipe  100  may extend in a tire lateral direction or a tire circumferential direction. 
     The sipe  100  according to the present technology is a so-called chamfered sipe, and an edge that defines the opening  103  of the sipe  100  is provided with a chamfered portion. The inventor has found that good dry performance and wet performance of the tire  1  can be provided in a compatible manner by appropriately setting formation conditions of the chamfered portion in the sipe  100 . Note that, in the present specification, the dry performance represents the capability of traveling stability like gripping force in at least one of driving, braking, and turning on dry road surfaces. The wet performance represents the capability of traveling stability like gripping force in at least one of driving, braking, and turning on wet road surfaces. 
     Hereinafter, an outline of the sipe  100  according to the present technology will be described with reference to  FIGS. 1 to 7 .  FIGS. 1 to 7  are plan views each schematically illustrating an outline of the sipe  100  according to the present technology and each illustrate a part of the surface of the tread rubber  8  provided with the sipe  100 . Note that, the surface of the tread rubber  8  is a surface in contact with a road surface in driving of the tire  1 , and is also referred to as a tread surface, a contact patch, or a road contact surface. 
     An example illustrated in  FIG. 1  will be described. In  FIG. 1 , the sipe  100  includes the opening  103  extending in a first direction in the surface of the tread rubber  8 . The first direction and a second direction orthogonal to the first direction are defined in the surface of the tread rubber  8 . The opening  103  is provided between a first edge  101  of the tread rubber  8  extending in the first direction and a second edge  102  of the tread rubber  8  adjacent to the first edge  101  in the second direction. 
     The first edge  101  and the second edge  102  are divided into a first range A and a second range B. The first range A and the second range B are defined to be side by side in the first direction. The first range A and the second range B are different ranges. The first range A and the second range B do not overlap each other. 
     The first range A has a certain width in the first direction and is a band region extending in the second direction. The second range B has a certain width in the first direction and is a band region extending in the second direction. A part of the first edge  101  is disposed in the first range A, and another part of the first edge  101  is disposed in the second range B. A part of the second edge  102  is disposed in the first range A, and another part of the second edge  102  is disposed in the second range B. The part of the first edge  101  faces the part of the second edge  102  in the first range A. The other part of the first edge  101  faces the other part of the second edge  102  in the second range B. 
     The first edge  101  in the first range A is provided with a first chamfered portion  105 . The second edge  102  in the second range B is provided with a second chamfered portion  106 . The second edge  102  in the first range A is not provided with a chamfered portion. The first edge  101  in the second range B is not provided with a chamfered portion. 
     In the present specification, the first range A is defined as a range in which the first chamfered portion  105  is provided in the entire region of the first edge  101  disposed in the first range A and a chamfered portion is not provided in the entire region of the second edge  102  disposed in the first range A. The second range B is defined as a range in which the second chamfered portion  106  is provided in the entire region of the second edge  102  disposed in the second range B and a chamfered portion is not provided in the entire region of the first edge  101  disposed in the second range B. 
     In other words, as illustrated in  FIG. 1 , the first chamfered portion  105  and the second chamfered portion  106  are provided so as not to overlap each other in both of the first direction and the second direction. 
     As illustrated in  FIG. 1 , the opening  103  has a first end portion E 1 , a second end portion E 2 , and a central portion M in the first direction. In the example illustrated in  FIG. 1 , the first range A includes the first end portion E 1  of the opening  103 , and the second range B includes the second end portion E 2  of the opening  103 . In other words, the first chamfered portion  105  is formed so as to include at least the first end portion E 1 , and the second chamfered portion  106  is formed so as to include at least the second end portion E 2 . 
     Additionally, in the example illustrated in  FIG. 1 , the first range A is defined between the first end portion E 1  and the central portion M of the opening  103 , and the second range B is defined between the second end portion E 2  and the central portion M of the opening  103 . In other words, the first chamfered portion  105  is formed between the first end portion E 1  and the central portion M, and the second chamfered portion  106  is formed between the second end portion E 2  and the central portion M. A position of an end portion on the central portion M side of the first chamfered portion  105  is substantially equal to a position of an end portion on the central portion M side of the second chamfered portion  106  in the first direction. 
     Additionally, in the example illustrated in  FIG. 1 , a dimension Wa of the first range A is equal to a dimension Wb of the second range B in the first direction. In other words, a dimension of the first chamfered portion  105  is equal to a dimension of the second chamfered portion  106  in the first direction. 
     Additionally, in the example illustrated in  FIG. 1 , a dimension of the first chamfered portion  105  is equal to a dimension of the second chamfered portion  106  in the second direction. 
     Note that, as illustrated in  FIG. 2 , the dimension Wa of the first range A (the dimension of the first chamfered portion  105 ) may be different from the dimension Wb of the second range B (the dimension of the second chamfered portion  106 ) in the first direction. Additionally, the dimension of the first chamfered portion  105  may be different from the dimension of the second chamfered portion  106  in the second direction. 
     According to the present technology, the first edge  101  in the first range A is provided with the first chamfered portion  105 . The second edge  102  in the second range B is provided with the second chamfered portion  106 . The second edge  102  in the first range A is not provided with a chamfered portion. The first edge  101  in the second range B is not provided with a chamfered portion. In driving of the tire  1 , high traveling stability is obtained on both of dry road surfaces and wet road surfaces by the edge effect of the first edge  101  and the second edge  102 . Additionally, when the sipe  100  is in contact with the ground, the opening  103  is closed. Thus, the first edge  101  provided with the first chamfered portion  105  and the second edge  102  without a chamfered portion support each other in the first range A, and the second edge  102  provided with the second chamfered portion  106  and the first edge  101  without a chamfered portion support each other in the second range B. The edge provided with a chamfered portion and the edge without a chamfered portion support each other, so that rigidity (namely, block rigidity) of the tread rubber  8  when ground contact is maintained. For example, block rigidity is increased further in a structure in which an edge provided with a chamfered portion and an edge without a chamfered portion support each other than in a structure in which edges each provided with a chamfered portion support each other. As a result, traveling stability is improved. Additionally, when in ground contact, a space is created between the first chamfered portion  105  and a road surface, and a space is created between the second chamfered portion  106  and the road surface. The created spaces ensure drainage properties during driving on wet road surfaces. Therefore, high traveling stability is obtained on wet road surfaces. In this way, according to the present technology, the first range A in which the first edge  101  is provided with the first chamfered portion  105  and the second edge  102  is not provided with a chamfered portion and the second range B in which the second edge  102  is provided with the second chamfered portion  106  and the first edge  101  is not provided with a chamfered portion are defined. Thus, good dry performance and wet performance can be provided in a compatible manner. 
     Additionally, according to the present technology, the first range A includes the first end portion E 1  of the opening  103 , and the second range B includes the second end portion E 2  of the opening  103 . In other words, the first chamfered portion  105  is formed to the end of the first edge  101 , and the second chamfered portion  106  is formed to the end of the second edge  102 . Thus, at the time of driving on a wet road surface, water collected in the space between the first chamfered portion  105  and the road surface is smoothly discharged from the first end portion E 1  side, and water collected in the space between the second chamfered portion  106  and the road surface is smoothly discharged from the second end portion E 2  side. Therefore, high traveling stability is obtained on wet road surfaces, and wet performance is improved. 
     Additionally, in the example illustrated in  FIG. 1 , the first range A is defined between the first end portion E 1  and the central portion M of the opening  103 , and the second range B is defined between the second end portion E 2  and the central portion M of the opening  103 . In this way, rigidity of the tread rubber  8  is equalized in the first direction, and excellent traveling stability can be obtained. Additionally, the size of the space between the first chamfered portion  105  and the road surface is substantially equal to the size of the space between the second chamfered portion  106  and the road surface. Thus, discharge performance of water collected in the space between the first chamfered portion  105  and the road surface and discharge performance of water collected in the space between the second chamfered portion  106  and the road surface are made uniform. Therefore, high traveling stability is obtained on wet road surfaces, and wet performance is improved. 
     Additionally, as in the example illustrated in  FIG. 2 , the dimension Wa of the first range A (the dimension of the first chamfered portion  105 ) is different from the dimension Wb of the second range B (the dimension of the second chamfered portion  106 ) in the first direction, so that traveling stability during turning of the tire  1  can be improved. For example, when the tire  1  is mounted on a vehicle, the tire  1  is mounted such that the first chamfered portion  105  having the dimension Wa shorter than the dimension Wb of the second chamfered portion  106  is disposed outward from the vehicle. Thus, traveling stability during turning can be maintained. 
     Next, an example illustrated in  FIG. 3  will be described. In  FIG. 3 , the first edge  101  and the second edge  102  are further divided into the first range A, the second range B, and a third range C different from the first range A and the second range B. 
     The third range C has a certain width in the first direction and is a band region extending in the second direction. A part of the first edge  101  is disposed in the first range A, another part of the first edge  101  is disposed in the second range B, and another part of the first edge  101  is disposed in the third range C. A part of the second edge  102  is disposed in the first range A, another part of the second edge  102  is disposed in the second range B, and another part of the second edge  102  is disposed in the third range C. The part of the first edge  101  faces the part of the second edge  102  in the first range A, the other part of the first edge  101  faces the other part of the second edge  102  in the second range B, and the other part of the first edge  101  faces the other part of the second edge  102  in the third range C. 
     The first edge  101  in the third range C is not provided with a chamfered portion, and the second edge  102  in the third range C is also not provided with a chamfered portion. 
     In the present specification, the third range C is defined as a range in which a chamfered portion is not provided in the entire region of the first edge  101  disposed in the third range C and a chamfered portion is also not provided in the entire region of the second edge  102  disposed in the third range C. 
     In the example illustrated in  FIG. 3 , the first range A includes the first end portion E 1  of the opening  103 , the second range B includes the second end portion E 2  of the opening  103 , and the third range C is defined between the first range A and the second range B in the first direction. 
     A dimension Wc of the third range C in the first direction is defined to be less than or equal to 30% of a dimension Wh of the opening  103  in the first direction, preferably less than or equal to 20%. 
     The dimension Wh is preferably greater than or equal to 15 mm and less than or equal to 35 mm. The dimension Wc is preferably greater than or equal to 1 mm and less than or equal to 7 mm. 
     According to the present technology, high traveling stability is obtained on both of dry road surfaces and wet road surfaces by the edge effect of the first edge  101  and the second edge  102  in the third range C without a chamfered portion. Additionally, when the sipe  100  is in ground contact and the opening  103  is closed, the first edge  101  and the second edge  102  that are not provided with a chamfered portion support each other in the third range C. Thus, rigidity of the tread rubber  8  when ground contact is maintained. 
     On the other hand, with the dimension Wc of the third range C being too great, when in ground contact, a space between the first chamfered portion  105  and a road surface and a space between the second chamfered portion  106  and the road surface are not sufficiently secured, and drainage properties during driving on wet road surfaces may decrease. Thus, the dimension Wc of the third range C is less than or equal to 30% of the dimension Wh of the opening  103 , preferably less than or equal to 20%. 
     Additionally, the first range A includes the first end portion E 1  of the opening  103 , the second range B includes the second end portion E 2  of the opening  103 , and the third range C is defined between the first range A and the second range B. Thus, at the time of driving on a wet road surface, while block rigidity is maintained by the third range C defined between the first range A and the second range B, water collected in the space between the first chamfered portion  105  and the road surface is smoothly discharged from the first end portion E 1  of the opening  103 , and water collected in the space between the second chamfered portion  106  and the road surface is smoothly discharged from the second end portion E 2  of the opening  103 . 
     Note that, as illustrated in  FIG. 4 , the first range A may not include the first end portion E 1  of the opening  103  in the first direction, and the second range B may not include the second end portion E 2  of the opening  103  in the first direction. In the example illustrated in  FIG. 4 , the third range C without a chamfered portion is defined to include the first end portion E 1  and the second end portion E 2 . 
     Additionally, as illustrated in  FIG. 5 , the third range C may be defined to include the first end portion E 1  and the second end portion E 2  and defined between the first range A and the second range B in the first direction. 
     Next, an example illustrated in  FIG. 6  will be described. In  FIG. 6 , a plurality of first ranges A and second ranges B are defined at intervals in the first direction. The first range A and the second range B are alternately disposed in the first direction. 
     According to the present technology, the plurality of first ranges A and second ranges B are defined at intervals in the first direction, so that rigidity of the tread rubber  8  can be equalized in both of the first direction and the second direction, and excellent traveling stability can be obtained. Additionally, a plurality of spaces between the first chamfered portion  105  and a road surface and between the second chamfered portion  106  and the road surface are provided, so that high traveling stability is obtained on wet road surfaces, and wet performance is improved. 
     Note that, as illustrated in  FIG. 7 , when the plurality of first ranges A and second ranges B are defined at intervals in the first direction, the third range C may be disposed between the first range A and the second range B. 
     In the examples illustrated in  FIGS. 1 to 7 , the first direction is a tire lateral direction, and the second direction is a tire circumferential direction. Note that, the first direction may be a tire circumferential direction, and the second direction may be a tire lateral direction. 
       FIG. 8  is a cross-sectional view schematically illustrating an outline of the sipe  100  according to the present technology and corresponds to a view taken along line I-I in the direction of the arrows in  FIG. 1 . Note that, the structure of the sipe  100  illustrated in  FIGS. 2 to 7  is also the same as the structure illustrated in the cross-sectional view of  FIG. 8 . Additionally,  FIG. 8  is the cross-sectional view of the sipe  100  including the first chamfered portion  105 , and the structure of the sipe  100  including the second chamfered portion  106  is also the same as the structure illustrated in the cross-sectional view of  FIG. 8 . 
     As illustrated in  FIG. 8 , the first chamfered portion  105  has a flat inclined surface. In other words, the first edge  101  is plane chamfered (corner chamfered), and thus the first chamfered portion  105  is formed. On the other hand, the second edge  102  is not chamfered, an inner surface of the sipe  100  is orthogonal to the surface of the tread rubber  8 , and an angle that the inner surface of the sipe  100  forms with the surface of the tread rubber  8  is substantially 270°. 
     A dimension Hm of the first chamfered portion  105  in a tire radial direction is greater than or equal to 1 mm and less than or equal to 4 mm, and a dimension Dc of the first chamfered portion  105  in the second direction is greater than or equal to 1 mm and less than or equal to 5 mm. A groove width Dm being a dimension in the second direction of a narrow portion including a groove bottom of the sipe  100  is greater than or equal to 0.4 mm and less than or equal to 1.5 mm. Additionally, a groove depth Hh being a dimension in the tire radial direction from the groove bottom of the sipe  100  to the surface of the tread rubber  8  is greater than or equal to 4 mm and less than or equal to 8 mm. A ratio of the dimension Hm to the groove depth Hh is preferably 25%≤Hm/Hh≤50%. A ratio of the dimension Dc to the groove width Dm is preferably 300%≤Dc/Dm≤1500%. An inclination angle θ of the first chamfered portion  105  with respect to the tire radial direction is preferably 14°≤θ≤78°, and is preferably 45°. 
     Note that, as illustrated in  FIG. 9 , the first chamfered portion  105  may have a curved surface. In other words, the first edge  101  is rounded chamfered (R chamfered), and thus the first chamfered portion  105  may be formed. Note that, in the example illustrated in  FIG. 9 , the first chamfered portion  105  is a rounded chamfer formed so as to project (bulge) toward the opening  103 , but may be formed so as to be recessed with respect to the opening  103 . 
     The outline of the tire  1  according to the present technology is described above. The present technology provides the tire  1  that can provide good dry performance and wet performance in a compatible manner. Additionally, noise performance and uneven wear resistance performance can also be improved by appropriately disposing the chamfered portion of the sipe  100 . Hereinafter, embodiments being specific examples according to the present technology will be described. 
     Embodiments 
     Embodiments according to the present technology will be described with reference to the drawings. However, the present technology is not limited to those embodiments. The constituents of the embodiments described below can be combined with one another as appropriate. In addition, some of the constituents may not be used in some embodiments. 
       FIG. 10  is a cross-sectional view illustrating a part of the tire  1  according to the present embodiment. The tire  1  is rotatable about a rotation axis AX while being mounted on a rim.  FIG. 10  illustrates a meridian cross-section passing through the rotation axis AX of the tire  1 . The rotation axis AX of the tire  1  is orthogonal to a tire equatorial plane CH. The tire equatorial plane CH indicates the center of the tire  1  in the tire lateral direction. 
     In the present specification, a direction parallel with the rotation axis AX is referred to as the tire lateral direction. A radiation direction with respect to the rotation axis AX is referred to as the tire radial direction. A rotation direction of the tire  1  about the rotation axis AX is referred to as the tire circumferential direction. Additionally, the tire equatorial plane CH is referred to as a tire center CH as appropriate. 
     In the present embodiment, the outer side in the tire lateral direction represents a position at a distance from or a direction away from the tire center CH in the tire lateral direction. The inner side in the tire lateral direction represents a position in the vicinity of or a direction closer to the tire center CH in the tire lateral direction. The outer side in the tire radial direction represents a position at a distance from or a direction away from the rotation axis AX in the tire radial direction. The inner side in the tire radial direction represents a position in the vicinity of or a direction closer to the rotation axis AX in the tire radial direction. A first side in the tire circumferential direction represents a direction designated in the tire circumferential direction. A second side in the tire circumferential direction represents a direction opposite to the direction designated in the tire circumferential direction. 
     The tire  1  includes a carcass  2 , a belt layer  3 , a belt cover  4 , bead portions  5 , a tread portion  6 , and sidewall portions  7 . The tread portion  6  includes the tread rubber  8 . The sidewall portions  7  each include a side rubber  9 . 
     The carcass  2  is a reinforcing member that forms the framework of the tire  1 . The carcass  2  includes carcass cords and functions as a pressure vessel when the tire  1  is filled with air. The carcass  2  includes carcass cords made of organic fibers and rubber that covers the carcass cords. Note that, the carcass  2  may include carcass cords made of polyester, carcass cords made of nylon, carcass cords made of aramid, and carcass cords made of rayon. 
     The bead portions  5  are reinforcing members that support the carcass  2 . The bead portions  5  are disposed on both sides of the carcass  2  in the tire lateral direction and support both end portions of the carcass  2 . The carcass  2  is folded back at bead cores  51  of the bead portions  5 . The bead portions  5  fix the tire  1  to a rim. The bead portions  5  each include the bead core  51  and a bead filler  52 . 
     The carcass  2  includes carcass body portions  21  and carcass folded back portions  22  formed by being folded back at the bead cores  51 . The carcass folded back portion  22  is a portion disposed outward in the tire lateral direction with respect to the carcass body portion  21  by folding the carcass  2  back at the bead core  51 . The bead core  51  is a member in which bead wires are wound into a ring shape. The bead wires are steel wires. The bead filler  52  is a rubber material that is disposed in a space formed by the carcass  2  between the carcass body portion  21  and the carcass folded back portion  22  of the carcass  2  folded back at the bead core  51 . 
     The belt layer  3  is a reinforcing member that holds the form of the tire  1 . The belt layer  3  includes belt cords and is disposed between the carcass  2  and the tread rubber  8 . The belt layer  3  includes belt cords made of metal fibers and rubber that covers the belt cords. Note that the belt layer  3  may include belt cords made of organic fibers. The belt layer  3  includes a first belt ply  31  and a second belt ply  32 . The first belt ply  31  and the second belt ply  32  are layered such that the belt cords of the first belt ply  31  and the belt cords of the second belt ply  32  intersect. 
     The belt cover  4  is a reinforcing member that protects and reinforces the belt layer  3 . The belt cover  4  includes cover cords and is disposed outward from the belt layer  3  with respect to the rotation axis AX of the tire  1 . The belt cover  4  includes cover cords made of metal fibers and rubber that covers the cover cords. Note that the belt cover  4  may include cover cords made of organic fibers. 
       FIG. 11  is a plan view illustrating a part of the tread portion  6 . As illustrated in  FIGS. 10 and 11 , the tread portion  6  includes the tread rubber  8  and has grooves provided in a predetermined pattern design. The grooves are provided in the tread rubber  8 . The tread rubber  8  protects the carcass  2 . The tread portion  6  includes a land portion disposed between the grooves. The land portion has the surface (tread surface, contact patch, road contact surface) of the tread rubber  8  in contact with a road surface. The grooves include a plurality of main grooves  10  disposed in the tire circumferential direction, lug grooves  12  including at least a part of the lug grooves  12  disposed in the tire lateral direction, and the sipe  100 . Additionally, the tread portion  6  includes a center portion  13  including a tire center CH and shoulder portions  14  provided on both sides of the center portion  13  in the tire lateral direction. 
     In the present embodiment, four main grooves  10  are provided in the tire lateral direction. Three ribs  11  being land portions are provided between those main grooves  10 . The ribs  11  include a center rib  11 B disposed at the center in the tire lateral direction, a second rib  11 A disposed on one of sides of the center rib  11 B in the tire lateral direction, and a second rib  11 C disposed on the other side of the center rib  11 B in the tire lateral direction. The tire center CH passes through the center rib  11 B. The three ribs  11  ( 11 A,  11 B, and  11 C) are provided on the center portion  13 . 
     The center rib  11 B and the second rib  11 A are each provided with the sipe  100 . The opening  103  of the sipe  100  extends in the tire lateral direction. In the example illustrated in  FIG. 11 , the opening  103  of the sipe  100  is slightly inclined to the tire circumferential direction. 
     In the present embodiment, a sipe  100 A provided in the second rib  11 A has an opening structure in which the sipe  100 A penetrates the second rib  11 A in the tire lateral direction. One of end portions and the other end portion of the sipe  100 A in the tire lateral direction are connected to the main grooves  10  located on both sides of the second rib  11 A. 
     In the present embodiment, a sipe  100 B provided in the center rib  11 B has a semi-closed structure in which one of end portions of the sipe  100 B is connected to the main groove  10  on one of sides of the center rib  11 B, and the other end portion is terminated in the center rib  11 B. 
     First Embodiment 
       FIG. 12  is a plan view illustrating one example of the sipe  100 A according to the present embodiment.  FIG. 13  is a perspective view illustrating one example of the sipe  100 A according to the present embodiment.  FIG. 12  is a plan view schematically illustrating a part of the second rib  11 A provided with the sipe  100 A.  FIG. 13  is a perspective view schematically illustrating a part of the second rib  11 A provided with the sipe  100 A. 
     As illustrated in  FIGS. 12 and 13 , sipes  100 A are disposed at regular intervals in the tire circumferential direction. The opening  103  of the sipe  100 A extends in the tire lateral direction and is slightly inclined to the tire circumferential direction. In the example illustrated in  FIGS. 12 and 13 , the first range A and the second range B are defined, and the third range C is not defined. In a surface parallel with the surface of the tread rubber  8 , an external form and a dimension of the first chamfered portion  105  are substantially equal to an external form and a dimension of the second chamfered portion  106 . In the present embodiment, the external form of the first chamfered portion  105  and the external form of the second chamfered portion  106  are substantially quadrangular and are formed to have a uniform width in the tire circumferential direction. Additionally, a corner of the first chamfered portion  105  and a corner of the second chamfered portion  106  at the central portion M of the opening  103  are formed with a curved line and are rounded. 
     Note that, in the example illustrated in  FIGS. 12 and 13 , the third range C without a chamfered portion may be provided between the first chamfered portion  105  and the second chamfered portion  106 , as described with reference to  FIG. 3 . 
     Second Embodiment 
       FIG. 14  is a plan view illustrating one example of a sipe  100 C according to the present embodiment.  FIG. 15  is a perspective view illustrating one example of the sipe  100 C according to the present embodiment. 
     As illustrated in  FIGS. 14 and 15 , sipes  100 C are disposed at regular intervals in the tire circumferential direction. The opening  103  of the sipe  100 C extends in the tire lateral direction and is slightly inclined to the tire circumferential direction. In the example illustrated in  FIGS. 14 and 15 , the first range A and the second range B are defined, and the third range C is not defined. In a surface parallel with the surface of the tread rubber  8 , an external form and a dimension of the first chamfered portion  105  are substantially equal to an external form and a dimension of the second chamfered portion  106 . In the present embodiment, the external form of the first chamfered portion  105  and the external form of the second chamfered portion  106  are substantially triangular and are provided such that a corner having the most acute angle faces the central portion M of the opening  103 . 
     Note that, in the example illustrated in  FIGS. 14 and 15 , the third range C without a chamfered portion may be provided between the first chamfered portion  105  and the second chamfered portion  106 , as described with reference to  FIG. 3 . 
     Third Embodiment 
       FIG. 16  is a plan view illustrating one example of a sipe  100 D according to the present embodiment.  FIG. 17  is a perspective view illustrating one example of the sipe  100 D according to the present embodiment. 
     As illustrated in  FIGS. 16 and 17 , sipes  100 D are disposed at regular intervals in the tire circumferential direction. The opening  103  of the sipe  100 D extends in the tire lateral direction and is slightly inclined to the tire circumferential direction. In the example illustrated in  FIGS. 16 and 17 , the first range A and the second range B are defined, and the third range C is not defined. A plurality of first ranges A and second ranges B are defined at intervals in a longitudinal direction of the opening  103  (substantially the tire lateral direction), and the first range A and the second range B are alternately disposed. In a surface parallel with the surface of the tread rubber  8 , an external form and a dimension of the first chamfered portion  105  are substantially equal to an external form and a dimension of the second chamfered portion  106 . In the present embodiment, the external form of the first chamfered portion  105  and the external form of the second chamfered portion  106  are substantially triangular and are provided such that one side of the triangle is adjacent to the opening  103  and one corner protrudes away from the opening  103 . 
     Note that, in the example illustrated in  FIGS. 16 and 17 , the third range C without a chamfered portion may be provided between the first chamfered portion  105  and the second chamfered portion  106 , as described with reference to  FIG. 7 . 
     Examples 
     Next, a result of an evaluation test performed on the tire  1  according to the present technology will be described. In the evaluation test, tires having a tire size of 245/40R18 were used. 
     As tires being evaluation subjects, tires according to Conventional Example 1, Conventional Example 2, and Conventional Example 3 and tires  1  according to Example 1, Example 2, Example 3, and Example 4 according to the present technology were prepared. Note that, structures of main grooves and lug grooves of the tires according to Conventional Examples 1, 2, and 3 and the tires according to Examples 1, 2, 3, and 4 are the same as the structures described with reference to  FIGS. 10 and 11 . 
     The tire according to Conventional Example 1 is a tire without a sipe. In other words, the tire according to Conventional Example 1 is a tire excluding the sipe  100  from the tire  1  described with reference to  FIGS. 10 and 11 . 
     The tires according to Conventional Examples 2 and 3 are tires each provided with a sipe. The tires according to Conventional Examples 2 and 3 are tires each provided with a sipe in the position of the sipe  100  of the tire  1  described with reference to  FIGS. 10 and 11 . 
     The tire according to Conventional Example 2 is a tire provided with the sipe without a chamfered portion. 
     The tire according to Conventional Example 3 is a tire in which a chamfered portion is provided in the entire region of a first edge and a second edge of an opening of the sipe. 
     The tire  1  according to Example 1 is the tire  1  having the sipe  100 A and the sipe  100 B described with reference to  FIGS. 10, 11, 12, and 13 . 
     The tires according to Examples 2, 3, and 4 are tires each provided with a sipe in the position of the sipe  100  of the tire  1  described with reference to  FIGS. 10 and 11 . 
     The tire  1  according to Example 2 is the tire  1  having the sipe  100 C described with reference to  FIGS. 14 and 15 . 
     The tire  1  according to Example 3 is the tire  1  having a sipe defined in the third range C described with reference to  FIG. 3  between the first range A and the second range B of the sipe  100 C described with reference to  FIGS. 14 and 15 . 
     The tire  1  according to Example 4 is the tire  1  having the sipe  100 D described with reference to  FIGS. 16 and 17 . 
     Evaluation items of the evaluation test were (1) dry performance, (2) wet braking performance, (3) wet turning performance, (4) noise performance, and (5) uneven wear resistance performance. 
     In the evaluations of dry performance, the test vehicle was driven at a speed of from 60 km/h to 100 km/h on a test course of a dry road surface having a flat circuit. Then, the test driver performed a sensory evaluation regarding steering while lane changing and cornering and stability while traveling forward. Results of the evaluations are expressed as index values and evaluated with Conventional Example 1 being assigned as the reference ( 100 ), and higher values are preferable. 
     In the evaluations of wet braking performance, the test vehicle was driven at a speed of 40 km/h on an asphalt road surface covered with 1 mm of water. Then, the test driver performed a sensory evaluation regarding stability while braking. Results of the evaluations are expressed as index values and evaluated with Conventional Example 1 being assigned as the reference ( 100 ), and higher values are preferable. 
     In the evaluations of wet turning performance, the test vehicle was driven at a speed of 40 km/h on an asphalt road surface covered with 1 mm of water. Then, the test driver performed a sensory evaluation regarding stability of steering characteristics while lane changing and cornering. Results of the evaluations are expressed as index values and evaluated with Conventional Example 1 being assigned as the reference ( 100 ), and higher values are preferable. 
     In the evaluations of noise performance, the test vehicle was driven at a speed of 80 km/h on an international organization for standardization (ISO) test road, and a sound pressure level of the pass-by noise (vehicle external noise) was measured and evaluated. Results of the evaluations are expressed as index values and evaluated with Conventional Example 1 being assigned as the reference ( 100 ). It is preferable that a sound pressure level is lower with higher values. 
     In the evaluations of uneven wear resistance performance, the test vehicle was driven for 50000 km on a paved road, and then the amount of wear of a second rib and uneven wear occurring in the second rib were observed and evaluated. Results of the evaluations are expressed as index values and evaluated with Conventional Example 1 being assigned as the reference ( 100 ), and higher values are preferable. 
     The results of the evaluation test on the five evaluation items described above are shown in Table 1. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Conventional 
                 Conventional 
                 Conventional 
                 Example 
                 Example 
                 Example 
                 Example 
               
               
                   
                 Example 1 
                 Example 2 
                 Example 3 
                 1 
                 2 
                 3 
                 4 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Dry 
                 100 
                 105 
                 100 
                 105 
                 110 
                 110 
                 115 
               
               
                 performance 
               
               
                 Wet braking 
                 100 
                 95 
                 100 
                 110 
                 105 
                 105 
                 105 
               
               
                 performance 
               
               
                 Wet turning 
                 100 
                 95 
                 100 
                 105 
                 105 
                 105 
                 105 
               
               
                 performance 
               
               
                 Noise 
                 100 
                 105 
                 105 
                 110 
                 110 
                 110 
                 110 
               
               
                 performance 
               
               
                 Uneven wear 
                 100 
                 105 
                 105 
                 110 
                 110 
                 110 
                 110 
               
               
                 resistance 
               
               
                 performance 
               
               
                   
               
            
           
         
       
     
     As shown in Table 1, it is clear that the evaluations of all the items of (1) dry performance, (2) wet braking performance, (3) wet turning performance, (4) noise performance, and (5) uneven wear resistance performance are higher in Examples than in Conventional Examples. As described above, it is clear that the tire  1  according to the present technology has high quality.