Patent Publication Number: US-2021170800-A1

Title: Tire

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     The present application claims priority to Japanese patent application JP 2019-223073, filed on Dec. 10, 2019 and Japanese patent application JP 2020-180791, filed on Oct. 28, 2020, the entire contents of each of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a tire. 
     Description of the Background Art 
     Japanese Laid-Open Patent Publication No. 2015-139194 suggests a tire (hereinafter, may be referred to as “4-rib tire”) having a tread portion sectioned into four land portions. In the tire disclosed in Japanese Laid-Open Patent Publication No. 2015-139194, the arrangement of grooves is described as being for steering stability. 
     In recent years, enhanced performance of vehicles requires a tire to exhibit more excellent steering stability. Meanwhile, enhancement of steering stability may cause degradation of ride comfort depending on arrangement of grooves. 
     The present disclosure has been made in view of the aforementioned and other problems, and an aspect of the present disclosure is to provide a 4-rib tire exhibiting excellent steering stability while maintaining ride comfort. 
     SUMMARY 
     The present disclosure is directed to a tire including a tread portion. The tread portion can include three circumferential grooves extending between two tread ends continuously in a tire circumferential direction, and four land portions demarcated by the circumferential grooves. The circumferential grooves can include two shoulder circumferential grooves and one crown circumferential groove disposed between the two shoulder circumferential grooves. The land portions can include two shoulder land portions including the tread ends, and two middle land portions demarcated between the shoulder circumferential grooves and the crown circumferential groove. Each of the two middle land portions can include: a circumferential sipe extending continuously in the tire circumferential direction; a plurality of first middle lateral grooves extending from the crown circumferential groove and terminating in a corresponding one of the middle land portions without connecting with the circumferential sipe; and a plurality of second middle lateral grooves extending from a corresponding one of the shoulder circumferential grooves and terminating in the corresponding one of the middle land portions without connecting with the circumferential sipe. Each of the two shoulder land portions can include a plurality of shoulder lateral grooves extending from a corresponding one of the tread ends and terminating in a corresponding one of the shoulder land portions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a development of a tread portion of a tire according to one embodiment of the present disclosure; 
         FIG. 2  is an enlarged view of a portion of  FIG. 1 ; 
         FIG. 3  is an enlarged view of a portion of  FIG. 1 ; 
         FIG. 4  is a development of a tread portion of a tire according to another embodiment of the present disclosure; 
         FIG. 5  is an enlarged view of a portion of  FIG. 4 ; 
         FIG. 6  is an enlarged cross-sectional view taken along a line A-A in  FIG. 5 ; 
         FIG. 7  is an enlarged cross-sectional view of a first middle sipe and a first chamfered portion according to an embodiment of the present disclosure; and 
         FIG. 8  is an enlarged view showing an outer middle land portion and an inner middle land portion of a tire according to comparative example. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present disclosure will be described below with reference to the drawings. 
       FIG. 1  is a development of a tread portion  2  of a tire  1  according to an embodiment of the present disclosure. The tire  1  of the present embodiment is, for example, a pneumatic tire for a passenger car. However, the tire  1  of the present disclosure is not limited to such a tire. As shown in  FIG. 1 , the tire  1  of the present embodiment has the tread portion  2  having, for example, a designated mounting direction to a vehicle. The mounting direction to the vehicle is indicated on, for example, the sidewall portion or the like by characters or a mark. 
     The tread portion  2  has three circumferential grooves  3  extending between two tread ends To and Ti continuously in the tire circumferential direction (vertically with reference to  FIG. 1 ), and four land portions  4  demarcated by the circumferential grooves  3 . 
     The two tread ends To and Ti include the outer tread end To located on the outer side of the vehicle when the tire  1  is mounted to the vehicle and the inner tread end Ti located on the inner side of the vehicle when the tire  1  is mounted to the vehicle. 
     The outer tread end To and the inner tread end Ti are outermost ground contact positions in the tire axial direction (horizontally with reference to  FIG. 1 ) in a case where, when the tire  1  as a pneumatic tire is in a normal state where the tire  1  is mounted on a normal rim, is inflated with normal internal pressure, and is under no load, a normal load is applied to the tire  1  and the tire  1  is brought in contact with a plane at a camber angle of 0°. Unless otherwise specified, dimensions and the like of components of the tire  1  are indicated as values measured in the normal state. 
     The term “normal rim” represents a rim that is defined by a standard, in a standard system including the standard with which the tire complies, 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 term “normal internal pressure” represents an air pressure that is defined by a standard, in a standard system including the standard with which the tire complies, for each tire, and is the “maximum air pressure” in the JATMA standard, the maximum value recited in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, or the “INFLATION PRESSURE” in the ETRTO standard. 
     The term “normal load” represents a load that is defined by a standard, in a standard system including the standard with which the tire complies, for each tire, and is the “maximum load capacity” in the JATMA standard, the maximum value recited in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, or the “LOAD CAPACITY” in the ETRTO standard. 
     According to one or more embodiments, the circumferential groove  3  extends linearly parallel to the tire circumferential direction with a constant groove width. However, the circumferential groove  3  may extend in a wavy manner or extend so as to regularly change the groove width. 
     The circumferential grooves  3  include two shoulder circumferential grooves  5  and one crown circumferential groove  6 . One of the shoulder circumferential grooves  5  is disposed on one side lateral to the tire equator and the other of the shoulder circumferential grooves  5  is disposed on the other side lateral thereto. The crown circumferential groove  6  is disposed between the two shoulder circumferential grooves  5 . In the present embodiment, a circumferential edge of the crown circumferential groove  6  on the outer tread end To side is disposed on the tire equator. 
     The two shoulder circumferential grooves  5  include an outer shoulder circumferential groove  5 A and an inner shoulder circumferential groove  5 B. The outer shoulder circumferential groove  5 A is disposed between the outer tread end To and the tire equator. The inner shoulder circumferential groove  5 B is disposed between the inner tread end Ti and the tire equator. 
     For example, a distance in the tire axial direction from the tire equator to the groove center line of the shoulder circumferential groove  5  is preferably 15% to 25% of a tread width TW. For example, a distance in the tire axial direction from the tire equator to the groove center line of the crown circumferential groove  6  is preferably not greater than 5% of the tread width TW. The tread width TW is a distance in the tire axial direction from the outer tread end To to the inner tread end Ti in the normal state. 
     Each circumferential groove  3  has a groove width that is greater than at least 1.5 mm, preferably not less than 3.0 mm, and more preferably not less than 4.0 mm. For example, each circumferential groove  3  preferably has a groove width that is 5.0% to 8.0% of the tread width TW. For example, the groove depth of each circumferential groove  3  is preferably 5 to 12 mm. 
     In the present embodiment, a groove width W of the shoulder circumferential groove  5  is less than a groove width W 2  of the crown circumferential groove  6 . Specifically, the groove width W 1  of the shoulder circumferential groove  5  is 91% to 99% of the groove width W 2  of the crown circumferential groove  6 , and is preferably 94% to 98% thereof. 
     In one or more embodiments, the total of the groove widths W 1 , W 2  of the circumferential grooves  3  is 15% to 27% of the tread width TW. Thus, steering stability and ride comfort can be enhanced in a well-balanced manner. 
     The land portions  4  include two shoulder land portions  7  that may include the outer tread end To and the inner tread end Ti, respectively, and two middle land portions  8  demarcated between the shoulder circumferential grooves  5  and the crown circumferential groove  6 . In the present embodiment, the two shoulder land portions  7  include an outer shoulder land portion  7 A that may include the outer tread end To and an inner shoulder land portion  7 B that may include the inner tread end Ti. The two middle land portions  8  include an outer middle land portion  8 A and an inner middle land portion  8 B. The outer middle land portion  8 A can be on a side associated with (e.g., adjacent to) the outer shoulder land portion  7 A and is demarcated between the outer shoulder circumferential groove  5 A and the crown circumferential groove  6 . The inner middle land portion  8 B can be on a side associated with (e.g., adjacent to) the inner shoulder land portion  7 B and is demarcated between the inner shoulder circumferential groove  5 B and the crown circumferential groove  6 . 
       FIG. 2  is an enlarged view of  FIG. 1  showing the outer middle land portion  8 A and the inner middle land portion  8 B. As shown in  FIG. 2 , the outer middle land portion  8 A and the inner middle land portion  8 B each include a circumferential sipe  10  extending continuously in the tire circumferential direction, a plurality of first middle lateral grooves  11  extending from the crown circumferential groove  6  and terminating in the middle land portion  8  without connecting with the circumferential sipe  10 , and a plurality of second middle lateral grooves  12  extending from the shoulder circumferential groove  5  and terminating in the middle land portion  8  without connecting with the circumferential sipe  10 . In the description herein. “sipe” refers to a cut having a width of not greater than 1.5 mm. 
     The circumferential sipe  10  can allow appropriate reduction of stiffness in the tire axial direction and enhancement of ride comfort while maintaining stiffness of the middle land portion  8  in the tire circumferential direction. The first middle lateral grooves  11  and the second middle lateral grooves  12  terminate in the middle land portion  8  without connecting with the circumferential sipe  10 , and thus can allow ride comfort to be enhanced while maintaining stiffness of the middle land portion  8  in the tire circumferential direction. 
     The two middle land portions  8  in which stiffness in the tire circumferential direction is maintained can also contribute to enhancement of steering stability. Furthermore, the tire  1  having the two middle land portions  8  can be expected to exert relatively high cornering force also in a case where ground contact pressure is low and a slip angle is small. Therefore, for example, in a case where the tires  1  of the present disclosure are mounted to all wheels of a front-wheel-drive vehicle, cornering force can be sufficiently exerted by rear wheel tires, convergence of yawing of the vehicle can be facilitated at the start of cornering, and excellent steering stability can be exhibited. 
     In the present embodiment, in each of the outer middle land portion  8 A and the inner middle land portion  8 B, an angle of the first middle lateral groove  11  relative to the tire axial direction is different from an angle of the second middle lateral groove  12  relative to the tire axial direction. Thus, frictional force can be exerted in multiple directions by edges of the lateral grooves  11 ,  12  during running on a wet road surface, to enhance wet performance. 
       FIG. 3  is an enlarged view of  FIG. 1  showing the outer shoulder land portion  7 A and the inner shoulder land portion  7 B. As shown in  FIG. 3 , in the present disclosure, the two shoulder land portions  7  each include a plurality of shoulder lateral grooves  15  extending from the outer tread end To or the inner tread end Ti and terminating in the shoulder land portion  7 . Therefore, excellent steering stability can be exhibited while ride comfort is maintained. 
     A more specific structure of the present embodiment will be described below. In the present embodiment, in a case where the tire  1  is mounted to a front-wheel-drive vehicle, the width of each land portion  7 ,  8  in the tire axial direction can be specified as follows in order to exhibit more excellent steering stability. 
     As shown in  FIG. 1  and  FIG. 3 , a width W 3  of the outer shoulder land portion  7 A in the tire axial direction is greater than a width W 6  of the inner shoulder land portion  7 B in the tire axial direction. The width W 6  of the inner shoulder land portion  7 B in the tire axial direction is greater than a width W 4  of the outer middle land portion  8 A in the tire axial direction. The width W 4  of the outer middle land portion  8 A in the tire axial direction is greater than a width W 5  of the inner middle land portion  8 B in the tire axial direction. 
     In other words, the width of each of the shoulder land portions  7  in the tire axial direction is set to be greater than the width of the middle land portion  8  in the tire axial direction. In comparison between the two shoulder land portions  7  or comparison between the two middle land portions  8 , the width of the land portion on the outer tread end To side is set to be greater than the width of the land portion on the inner tread end Ti side. 
     In a case where the tires  1  having such a structure according to the present embodiment are mounted to all wheels of a front-wheel-drive vehicle, the front wheel tires can exert high cornering force to enhance responsiveness to steering, whereas the rear wheel tires can also sufficiently exert cornering force to facilitate convergence of yawing of the vehicle at the start of the cornering. Therefore, in the present embodiment, in a case where the tires  1  are mounted to all wheels of a front-wheel-drive vehicle, more excellent steering stability can be exhibited. 
     The width W 3  of the outer shoulder land portion  7 A is preferably not less than 23% of the tread width TW. The width W 3  of the outer shoulder land portion  7 A is preferably 140% to 146% of the width W 5  of the inner middle land portion  8 B. The width W 6  of the inner shoulder land portion  7 B is preferably 120% to 126% of the width W 5  of the inner middle land portion  8 B. The width W 4  of the outer middle land portion  8 A is preferably 101% to 105% of the width W 5  of the inner middle land portion  8 B. Whichever of front and rear wheels of a vehicle the tire  1  having such a structure according to the present embodiment is used for, high cornering force can be exerted and steering stability can be enhanced. 
     As shown in  FIG. 2 , the circumferential sipe  10  in the middle land portion  8  can be disposed at the center portion of the middle land portion  8  in the tire axial direction. The circumferential sipe  10  having such a structure can exhibit the above-described effects, and can allow striking sound to be reduced when the middle land portion  8  comes into contact with the ground, thereby enhancing noise performance. A distance in the tire axial direction from the circumferential edge of the middle land portion  8  on the tire equator side to the circumferential sipe  10  is preferably 20% to 80% of the width of the middle land portion  8  in the tire axial direction, and more preferably 40% to 60% thereof. In the present embodiment, the circumferential sipe  10  can be disposed at the center position of the middle land portion  8  in the tire axial direction. 
     A width of the circumferential sipe  10  is not greater than 1.5 mm and preferably 0.6 to 1.2 mm. A depth of the circumferential sipe  10  is, for example, 1.5 to 4.0 mm. The circumferential sipe  10  is, for example, disposed over 80% to 100% of the entire circumference of the tire. 
     The first middle lateral groove  11  is, for example, inclined relative to the tire axial direction. In the present embodiment, the first middle lateral grooves  11 A in the outer middle land portion  8 A and the first middle lateral grooves  11 B in the inner middle land portion  8 B are inclined in the same direction (right-downward direction in  FIG. 2 ). An angle θ 1  of the first middle lateral groove  11  relative to the tire axial direction is, for example, 10 to 30°, and preferably 19 to 25°. The first middle lateral grooves  11  having such a structure can contribute to well-balanced enhancement of ride comfort and steering stability. 
     The second middle lateral groove  12 A in the outer middle land portion  8 A is, for example, inclined relative to the tire axial direction in the same direction as the first middle lateral groove  11 . An angle θ 2  of the second middle lateral groove  12 A relative to the tire axial direction is less than the angle θ 1  of the first middle lateral groove  11 . The angle θ 2  is, for example, 8 to 20°. 
     An angle of the second middle lateral groove  12 B in the inner middle land portion  8 B relative to the tire axial direction is, for example, less than the angle θ 2  of the second middle lateral groove  12 A in the outer middle land portion  8 A. The angle of the second middle lateral groove  12 B in the inner middle land portion  8 B relative to the tire axial direction is not greater than 10° and preferably not greater than 5°. For instance, in the present embodiment, the second middle lateral groove  12  can extend parallel to the tire axial direction. 
     One pitch length between the first middle lateral grooves  11  and one pitch length between the second middle lateral grooves  12  in the tire circumferential direction are the same one pitch length P 1 . A distance L 1  in the tire circumferential direction between the inner end of the first middle lateral groove  11  on the circumferential sipe  10  side and the inner end of the second middle lateral groove  12  on the circumferential sipe  10  side is preferably not greater than 10% of the one pitch length P 1 . Thus, the first middle lateral grooves  11  and the second middle lateral grooves  12  can allow effective reduction of stiffness of the middle land portion  8 , enhancement of ride comfort, and reduction of striking sound in the case of the middle land portion  8  coming into contact with the ground. 
     A length L 2  of the first middle lateral groove  11  in the tire axial direction and a length L 3  of the second middle lateral groove  12  in the tire axial direction are, for example, 25% to 45% of the width (that is, the width W 4  of the outer middle land portion  8 A or the width W 5  of the inner middle land portion  8 B), in the tire axial direction, of the land portion in which the grooves are disposed. 
     Each of the length L 2  of the first middle lateral groove  11  and the length L 3  of the second middle lateral groove  12  is preferably 7.0 to 12.0 mm and more preferably 8.0 to 10.0 mm. A distance L 4  in the tire axial direction from the inner end of the first middle lateral groove  11  or the second middle lateral groove  12  on the circumferential sipe  10  side to the circumferential sipe  10  is, for example, 3.0 to 5.0 mm. The first middle lateral grooves  11  and the second middle lateral grooves  12  having such a structure can contribute to well-balanced enhancement of steering stability and ride comfort. 
     From the same standpoint, each of a groove width W 8  of the first middle lateral groove  11  and a groove width W 9  of the second middle lateral groove  12  is, for example, not greater than 3.5 mm, and preferably 1.8 to 2.2 mm. 
     In the present embodiment, a region obtained by extending the first middle lateral groove  11 A in the outer middle land portion  8 A along the length direction toward the inner tread end Ti preferably overlaps the end portion of the first middle lateral groove  11 B in the inner middle land portion  8 B on the crown circumferential groove  6  side. Thus, the land portions can integrally exert cornering force to enhance steering linearity. 
     From the same standpoint, a distance L 7  in the tire circumferential direction between the end of the first middle lateral groove  11 A in the outer middle land portion  8 A and the end of the first middle lateral groove  11 B in the inner middle land portion  8 B is preferably not greater than 20% of the one pitch length P 1 . 
     The inner middle land portion  8 B includes a plurality of inner middle sipes  18 . The inner middle sipe  18  extends from the inner shoulder circumferential groove  5 B and terminates in the inner middle land portion  8 B without connecting with the circumferential sipe  10 . The inner middle sipes  18  can allow reduction of stiffness of the inner middle land portion  8 B and enhancement of ride comfort and noise performance. 
     A length L 5  of the inner middle sipe  18  in the tire axial direction is, for example, ¥ 25% to 45% of the width W 5  of the inner middle land portion  8 B in the tire axial direction. The length L 5  of the inner middle sipe  18  is, for example, 7.0 to 12.0 mm and preferably 8.0 to 10.0 mm. 
     A width of the inner middle sipe  18  is, for example, 0.5 to 1.5 mm and preferably 0.5 to 0.7 mm. An angle of the inner middle sipe  18  relative to the tire axial direction is, for example, 0.9 to 1.5°. 
     In the present embodiment, the inner middle sipe  18  and the second middle lateral groove  12  alternate in the tire circumferential direction. A distance L 6  in the tire circumferential direction between the inner middle sipe  18  and the second middle lateral groove  12  is, for example, 35% to 50% of one pitch length P 2  between the second middle lateral grooves  12  in the tire circumferential direction. The inner middle sipes  18  arranged in such a manner can allow the above-described effects to be exhibited while reducing uneven wear in the inner middle land portion  8 B. 
     In the present embodiment, the outer middle land portion  8 A does not include grooves and sipes other than the circumferential sipe  10 , the first middle lateral grooves  11 , and the second middle lateral grooves  12  described above. In the present embodiment, the inner middle land portion  8 B does not include grooves and sipes other than the circumferential sipe  10 , the first middle lateral grooves  11 , the second middle lateral grooves  12 , and the inner middle sipes  18  described above. 
     As shown in  FIG. 3 , the shoulder lateral groove  15  is, for example, inclined relative to the tire axial direction. In the present embodiment, the shoulder lateral groove  15  is inclined relative to the tire axial direction in the direction opposite to that of the first middle lateral groove  11  (shown in  FIG. 2 ). An angle θ 3  of the shoulder lateral groove  15  relative to the tire axial direction is, for example, 5 to 40°. The shoulder lateral groove  15  having such a structure can have an edge that allows frictional force to be exerted in a direction different from that of the first middle lateral groove  11 , and can contribute to enhancement of steering stability. 
     A groove width W 12  of the shoulder lateral groove  15  is, for example, 2.0 to 8.0 mm. A length L 8  of the shoulder lateral groove  15  in the tire axial direction is, for example, 50% to 80% of the width (that is, the width W 3  of the outer shoulder land portion  7 A or the width W 6  of the inner shoulder land portion  7 B), in the tire axial direction, of the land portion in which the shoulder lateral groove  15  is disposed. 
     A distance L 9  in the tire axial direction from the inner end of the shoulder lateral groove  15  to the shoulder circumferential groove  5  is, for example, 5 to 25 mm and preferably 12 to 20 mm. The distance L 9  is preferably greater than the distance in the tire axial direction between the first middle lateral groove  11  and the second middle lateral groove  12  (shown  FIG. 2 ). Thus, stiffness of the shoulder land portion  7  can be sufficiently assured. 
     The length of the shoulder lateral groove  15 B in the inner shoulder land portion  7 B in the tire axial direction can be preferably less than the length of the shoulder lateral groove  15 A in the outer shoulder land portion  7 A in the tire axial direction. Thus, stiffness can be assured near the inner tread end Ti and steering stability can be further enhanced. 
     The shoulder land portion  7  includes, for example, a plurality of shoulder sipes  25 . The shoulder sipes  25  are inclined relative to the tire axial direction. The shoulder sipe  25  is, for example, inclined in the same direction as the shoulder lateral groove  15  adjacent thereto. An angle of the shoulder sipe  25  relative to the tire axial direction is, for example, 5 to 40°. The shoulder sipe  25  extends across the shoulder land portion  7 . In the present embodiment, the shoulder sipe  25  and the shoulder lateral groove  15  alternate in the tire circumferential direction. A width of the shoulder sipe  25  is, for example, 0.6 to 1.2 mm. 
     As shown in  FIG. 1 , a distance in the tire circumferential direction between the end of the shoulder sipe  25 A in the outer shoulder land portion  7 A on the shoulder circumferential groove  5  side and the end of the second middle lateral groove  12 A on the shoulder circumferential groove  5  side is preferably not greater than 10% of one pitch length between the second middle lateral grooves  12  in the tire circumferential direction. Thus, the land portions can integrally exert cornering force to enhance steering linearity. 
     From the same standpoint, a distance in the tire circumferential direction between the end of the shoulder sipe  25 B in the inner shoulder land portion  7 B on the shoulder circumferential groove  5  side and the end of the inner middle sipe  18  on the shoulder circumferential groove  5  side is preferably not greater than 10% of one pitch length between the inner middle sipes  18  in the tire circumferential direction. 
     The shoulder land portion  7  does not include grooves and sipes other than the shoulder lateral grooves  15  and the shoulder sipes  25  described above. 
     In the present embodiment, the land portions include the above-described grooves and sipes. Therefore, stiffness of the outer shoulder land portion  7 A in the tire circumferential direction can be higher than stiffness of the inner shoulder land portion  7 B in the tire circumferential direction. Stiffness of the inner shoulder land portion  7 B in the tire circumferential direction can be higher than stiffness of the outer middle land portion  8 A in the tire circumferential direction. Stiffness of the outer middle land portion  8 A in the tire circumferential direction can be higher than stiffness of the inner middle land portion  8 B in the tire circumferential direction. The tire  1  having such a stiffness distribution can exert high cornering force, and can allow steering linearity to be enhanced. 
       FIG. 4  is a development of a tread portion  2  of a tire  1  according to another embodiment of the present disclosure.  FIG. 5  is an enlarged view of the outer middle land portion  8 A and the inner middle land portion  8 B shown in  FIG. 4 . The structure in the embodiment shown in  FIG. 1  to  FIG. 3  can be applied to the structure which is not described in the present embodiment. 
     As shown in  FIG. 4  and  FIG. 5 , in the present embodiment, the two middle land portions  8  (the outer middle land portion  8 A and the inner middle land portion  8 B) each include a plurality of first middle sipes  31  extending from the crown circumferential groove  6  and terminating in the middle land portion  8  without connecting with the circumferential sipe  10 , and a plurality of second middle sipes  32  extending from the shoulder circumferential groove  5  and terminating in the middle land portion  8  without connecting with the circumferential sipe  10 . The first middle sipes  31  and the second middle sipes  32  having such structures can allow stiffness of the middle land portion  8  to be maintained and allow steering stability to be further enhanced. The above-described structure of the first middle lateral groove  11  can be applied to the structure (for example, the length, the angle, and the pitch) of the first middle sipe  31  in a planar view of the tread. Similarly, the above-described structure of the second middle lateral groove  12  can be applied to the structure of the second middle sipe  32  in a planar view of the tread. 
       FIG. 6  is an enlarged cross-sectional view taken along a line A-A in  FIG. 5 . As shown in  FIG. 6 , a first chamfered portion  33  is disposed, on the outer side of the first middle sipe  31  in the tire radial direction, so as to be opened at the ground contact surface of the middle land portion  8 . The first chamfered portion  33  is opened with the width greater than the width of the first middle sipe  31 . The first chamfered portions  33  can be disposed on sipe edges on both sides of the first middle sipe  31  in the tire circumferential direction. The first chamfered portion  33  having such a structure can allow reduction of strain of the ground contact surface of the middle land portion  8  and reduction of uneven wear. However, the present disclosure is not limited thereto, and, for example, the first middle sipe  31  may extend with a constant width from the bottom portion of the first middle sipe  31  to the ground contact surface of the middle land portion  8 . 
     An opening width W 14  of the first chamfered portion  33  is, for example, 3.0 to 4.5 times a width W 13  of the first middle sipe  31 . A depth d 4  of the first chamfered portion  33  is, for example, not greater than 30% of the entire depth d 3  from the ground contact surface of the middle land portion  8  to the bottom of the first middle sipe  31 , and is preferably 15% to 25% thereof. 
     The first chamfered portion  33  includes, for example, an inclined surface  35  connecting with the ground contact surface of the middle land portion  8 . For example, the inclined surface  35  is inclined, at an angle of 10 to 45°, relative to the normal line that passes through the opening edge of the first chamfered portion  33  and is orthogonal to the ground contact surface of the middle land portion  8 . 
     Similarly, as shown in  FIG. 5 , a second chamfered portion  34  is disposed, on the outer side of the second middle sipe  32  in the tire radial direction, so as to be opened at the ground contact surface of the middle land portion  8 . The second chamfered portions  34  can be disposed on sipe edges on both sides of the second middle sipe  32  in the tire circumferential direction. The above-described structure of the first chamfered portion  33  shown in  FIG. 6  can be applied to the second chamfered portion  34 . 
       FIG. 7  shows a first chamfered portion  33  according to another embodiment. As shown in  FIG. 7 , the first chamfered portion  33  may be, for example, disposed on a sipe edge on one side of the first middle sipe  31  in the tire circumferential direction. The first chamfered portion  33  having such a structure allows reduction of strain of the ground contact surface while maintaining stiffness of the middle land portion  8 . The embodiment shown in  FIG. 7  can be also applied to the second middle sipe  32  and the second chamfered portion  34 . 
     Although the tires according to the embodiments of the present disclosure have been described above in detail, the present disclosure is not limited to the above-described specific embodiments, and various modifications can be made to implement the present disclosure. 
     EXAMPLES 
     Sample tires each having a basic tread pattern shown in  FIG. 1  and the size of 205/55R16 were produced according the specifications indicated in Tables 1 and 2. A sample tire having an outer middle land portion a and an inner middle land portion b shown in  FIG. 8  was produced as a comparative example. Each of the outer middle land portion a and the inner middle land portion b in the comparative example had a plurality of lateral grooves c extending across the land portion, and had no circumferential sipe extending continuously in the tire circumferential direction. The tire of the comparative example had substantially the same pattern as shown in  FIG. 1  except for the above-described structures. Each test tire was tested for steering stability, ride comfort, and noise performance. Specifications common to the test tires and a test method are as follows. 
     Rim: 16×6.5JJ 
     Tire internal pressure: 220 kPa 
     Test vehicle: front-wheel-drive car having an engine displacement of 1500 cc 
     Positions at which the tires were mounted: All wheels 
     &lt;Steering Stability&gt; 
     Sensory evaluation was made by a driver for steering stability when the driver drove the above-described test vehicle on a dry road surface. The results are indicated as scores with the score of the comparative example being 100. The greater the value is, the better steering stability is. 
     &lt;Ride Comfort&gt; 
     Sensoryevaluationwasmadebyadriverforridecomfortwhenthedriverdrove the above-described test vehicle on a dry road surface. The results are indicated as scores with the score of the comparative example being 1. The greater the value is, the better ride comfort is. 
     &lt;Noise Performance&gt; 
     The above-described test vehicle was driven to run on a dry road surface at 40 to 100 km/h, and the highest sound pressure of noise in the vehicle was measured in this case. The results are indicated as indexes with the sound pressure of the comparative example being 100. The less the value is, the less the noise is in the running and the better the noise performance is. 
     The test results are indicated in Tables 1 and 2. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Comp. Ex. 
                 Ex. 1 
                 Ex. 2 
                 Ex. 3 
                 Ex. 4 
                 Ex. 5 
                 Ex. 6 
                 Ex. 7 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Figure showing middle 
                 FIG. 8 
                 FIG. 2 
                 FIG. 2 
                 FIG. 2 
                 FIG. 2 
                 FIG. 2. 
                 FIG. 2 
                 FIG. 2 
               
               
                 land portion 
               
               
                 Width W3 of outer 
                 143 
                 143 
                 140 
                 142 
                 144 
                 146 
                 143 
                 143 
               
               
                 shoulder land portion/ 
               
               
                 width W5 of inner 
               
               
                 middle land portion (%) 
               
               
                 Width W6 of inner 
                 123 
                 123 
                 123 
                 123 
                 123 
                 123 
                 120 
                 122 
               
               
                 shoulder land portion/ 
               
               
                 width W5 of inner 
               
               
                 middle land portion (%) 
               
               
                 Width W4 of outer 
                 102 
                 102 
                 102 
                 102 
                 102 
                 102 
                 102 
                 102 
               
               
                 middle land portion/ 
               
               
                 width W5 of inner 
               
               
                 middle land portion (%) 
               
               
                 Steering stability 
                 100 
                 107 
                 105 
                 107 
                 107 
                 108 
                 104 
                 106 
               
               
                 (score) 
               
               
                 Ride comfort 
                 100 
                 100 
                 101 
                 100 
                 100 
                 98 
                 101 
                 101 
               
               
                 (score) 
               
               
                 Noise performance 
                 100 
                 99 
                 99 
                 99 
                 99 
                 100 
                 98 
                 99 
               
               
                 (index) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Ex. 8 
                 Ex. 9 
                 Ex. 10 
                 Ex. 11 
                 Ex. 12 
                 Ex. 13 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Figure showing 
                 FIG. 2 
                 FIG. 2 
                 FIG. 2 
                 FIG. 2 
                 FIG. 2 
                 FIG. 2 
               
               
                 middle land 
               
               
                 portion 
               
               
                 Width W3 of 
                 143 
                 143 
                 143 
                 143 
                 143 
                 143 
               
               
                 outer shoulder 
               
               
                 land portion/ 
               
               
                 width W5 
               
               
                 of inner middle 
               
               
                 land portion 
               
               
                 (%) 
               
               
                 Width W6 of 
                 124 
                 126 
                 123 
                 123 
                 123 
                 123 
               
               
                 inner shoulder 
               
               
                 land portion/ 
               
               
                 width W5 
               
               
                 of inner middle 
               
               
                 land portion 
               
               
                 (%) 
               
               
                 Width W4 of 
                 102 
                 102 
                 100 
                 101 
                 103 
                 105 
               
               
                 outer middle 
               
               
                 land portion/ 
               
               
                 width W5 
               
               
                 of inner middle 
               
               
                 land portion 
               
               
                 (%) 
               
               
                 Steering 
                 107 
                 107 
                 104 
                 106 
                 107 
                 107 
               
               
                 stability 
               
               
                 (score) 
               
               
                 Ride comfort 
                 100 
                 99 
                 101 
                 100 
                 100 
                 100 
               
               
                 (score) 
               
               
                 Noise 
                 99 
                 100 
                 99 
                 99 
                 99 
                 100 
               
               
                 performance 
               
               
                 (index) 
               
               
                   
               
            
           
         
       
     
     According to the test results, it was confirmed that the tires of the examples exhibited excellent steering stability while maintaining ride comfort. It was also confirmed that the tires of the examples exhibited excellent noise performance. 
     Sample tires having the middle land portions shown in  FIG. 5  were produced according to the specifications in Table 3, and the same tests as described above were made. 
     The test results are indicated in Table 3. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Ex. 14 
                 Ex. 15 
                 Ex. 16 
                 Ex. 17 
                 Ex. 18 
                 Ex. 19 
                 Ex. 20 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Figure showing 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
               
               
                 middle land 
               
               
                 portion 
               
               
                 Width W3 of outer 
                 143 
                 140 
                 142 
                 144 
                 146 
                 143 
                 143 
               
               
                 shoulder land portion/ 
               
               
                 width W5 of inner 
               
               
                 middle land portion (%) 
               
               
                 Width W6 of inner 
                 123 
                 123 
                 123 
                 123 
                 123 
                 120 
                 122 
               
               
                 shoulder land portion/ 
               
               
                 width W5 of inner 
               
               
                 middle land portion (%) 
               
               
                 Width W4 of outer 
                 102 
                 102 
                 102 
                 102 
                 102 
                 102 
                 102 
               
               
                 middle land portion/ 
               
               
                 width W5 of inner 
               
               
                 middle land portion (%) 
               
               
                 Steering stability 
                 108 
                 106 
                 107 
                 108 
                 108 
                 105 
                 107 
               
               
                 (score) 
               
               
                 Ride comfort 
                 100 
                 100 
                 100 
                 100 
                 97 
                 100 
                 100 
               
               
                 (score) 
               
               
                 Noise performance 
                 98 
                 98 
                 99 
                 98 
                 99 
                 98 
                 98 
               
               
                 (index) 
               
               
                   
               
            
           
         
       
     
     According to the test results, it was confirmed that the tires of the examples indicated in Table 3 also exhibited excellent steering stability while maintaining ride comfort. It was also confirmed that the tires of the examples exhibited excellent noise performance. 
     In view of the above, aspects of the embodiments include a variety of features, such as those described below. 
     In the tire according to the present disclosure, the tread portion preferably has a designated mounting direction to a vehicle. The two tread ends preferably include an outer tread end located on an outer side of a vehicle when the tire is mounted to the vehicle, and an inner tread end located on an inner side of the vehicle when the tire is mounted to the vehicle. The two shoulder land portions preferably include an outer shoulder land portion including the outer tread end and an inner shoulder land portion including the inner tread end. The two middle land portions preferably include an outer middle land portion adjacent to the outer shoulder land portion and an inner middle land portion adjacent to the inner shoulder land portion. 
     In the tire according to the present disclosure, a width of the outer shoulder land portion in a tire axial direction is preferably greater than a width of the inner shoulder land portion in the tire axial direction. 
     In the tire according to the present disclosure, a width of the inner shoulder land portion in a tire axial direction is preferably greater than a width of the outer middle land portion in the tire axial direction. 
     In the tire according to the present disclosure, a width of the outer middle land portion in a tire axial direction is preferably greater than a width of the inner middle land portion in the tire axial direction. 
     In the tire according to the present disclosure, a stiffness of the outer shoulder land portion in the tire circumferential direction is preferably higher than a stiffness of the inner shoulder land portion in the tire circumferential direction. 
     In the tire according to the present disclosure, the outer shoulder land portion preferably includes a plurality of shoulder sipes extending across the outer shoulder land portion. A distance in the tire circumferential direction between an end of each of the shoulder sipes on the shoulder circumferential groove side and an end of a corresponding one of the second middle lateral grooves in the outer middle land portion on the shoulder circumferential groove side is preferably not greater than 10% of one pitch length between the second middle lateral grooves in the tire circumferential direction. 
     In the tire according to the present disclosure, the inner middle land portion preferably includes a plurality of inner middle sipes extending from a corresponding one of the shoulder circumferential grooves and terminating in the inner middle land portion. 
     In the tire according to the present disclosure, the inner shoulder land portion preferably includes a plurality of shoulder sipes extending across the inner shoulder land portion. A distance in the tire circumferential direction between an end of each of the shoulder sipes in the inner shoulder land portion on the shoulder circumferential groove side and an end of a corresponding one of the inner middle sipes on the shoulder circumferential groove side is preferably not greater than 10% of one pitch length between the inner middle sipes in the tire circumferential direction. 
     In the tire according to the present disclosure, a groove width of each of the shoulder circumferential grooves is preferably less than a groove width of the crown circumferential groove. 
     In the tire according to the present disclosure, an angle of each of the first middle lateral grooves relative to a tire axial direction and an angle of each of the second middle lateral grooves relative to the tire axial direction are preferably different from each other in each of the two middle land portions. 
     In the tire according to the present disclosure, each of the two shoulder land portions preferably includes a plurality of shoulder sipes extending across a corresponding one of the shoulder land portions. The shoulder lateral grooves and the shoulder sipes are preferably inclined relative to a tire axial direction. 
     A tire according to a second aspect of the present disclosure is directed to a tire including a tread portion. The tread portion includes three circumferential grooves extending between two tread ends continuously in a tire circumferential direction, and four land portions demarcated by the circumferential grooves. The circumferential grooves include two shoulder circumferential grooves and one crown circumferential groove disposed between the two shoulder circumferential grooves. The land portions include two shoulder land portions including the tread ends, and two middle land portions demarcated between the shoulder circumferential grooves and the crown circumferential groove. Each of the two middle land portions includes: a circumferential sipe extending continuously in the tire circumferential direction: a plurality of first middle sipes extending from the crown circumferential groove and terminating in a corresponding one of the middle land portions without connecting with the circumferential sipe; and a plurality of second middle sipes extending from a corresponding one of the shoulder circumferential grooves and terminating in a corresponding one of the middle land portions without connecting with the circumferential sipe. Each of the two shoulder land portions includes a plurality of shoulder lateral grooves extending from a corresponding one of the tread ends and terminating in a corresponding one of the shoulder land portions. 
     In the tire according to the present disclosure, a first chamfered portion is preferably disposed on an outer side of each of the first middle sipes in a tire radial direction so as to be opened at a ground contact surface of a corresponding one of the middle land portions. 
     In the tire according to the present disclosure, the first chamfered portion is preferably disposed on each of sipe edges on both sides of each of the first middle sipes in the tire circumferential direction. 
     In the tire according to the present disclosure, a second chamfered portion is preferably disposed on an outer side of each of the second middle sipes in a tire radial direction so as to be opened at a ground contact surface of a corresponding one of the middle land portions. 
     In the tire according to the present disclosure, the second chamfered portion is preferably disposed on each of sipe edges on both sides of each of the second middle sipes in the tire circumferential direction. 
     In the tire according to the present disclosure, the tread portion preferably has a designated mounting direction to a vehicle. The two tread ends preferably include an outer tread end located on an outer side of a vehicle when the tire is mounted to the vehicle, and an inner tread end located on an inner side of the vehicle when the tire is mounted to the vehicle. The two shoulder land portions preferably include an outer shoulder land portion including the outer tread end and an inner shoulder land portion including the inner tread end. The two middle land portions preferably include an outer middle land portion adjacent to the outer shoulder land portion and an inner middle land portion adjacent to the inner shoulder land portion. A width of the outer shoulder land portion in a tire axial direction is preferably greater than a width of the inner shoulder land portion in the tire axial direction. A width of the inner shoulder land portion in the tire axial direction is preferably greater than a width of the outer middle land portion in the tire axial direction. A width of the outer middle land portion in the tire axial direction is preferably greater than a width of the inner middle land portion in the tire axial direction. 
     In the tire according to the present disclosure, the tread portion preferably has a designated mounting direction to a vehicle. The two tread ends preferably include an outer tread end located on an outer side of a vehicle when the tire is mounted to the vehicle, and an inner tread end located on an inner side of the vehicle when the tire is mounted to the vehicle. The two shoulder land portions preferably include an outer shoulder land portion including the outer tread end and an inner shoulder land portion including the inner tread end. The two middle land portions preferably include an outer middle land portion adjacent to the outer shoulder land portion and an inner middle land portion adjacent to the inner shoulder land portion. A width of the outer shoulder land portion in a tire axial direction is preferably greater than a width of the inner shoulder land portion in the tire axial direction. The outer shoulder land portion preferably includes a plurality of shoulder sipes extending across the outer shoulder land portion. A distance in the tire circumferential direction between an end of each of the shoulder sipes on the shoulder circumferential groove side and an end of a corresponding one of the second middle sipes in the outer middle land portion on the shoulder circumferential groove side is preferably not greater than 10% of one pitch length between the second middle sipes in the tire circumferential direction. 
     In the tire according to the present disclosure, the inner middle land portion preferably includes a plurality of inner middle sipes extending from a corresponding one of the shoulder circumferential grooves and terminating in the inner middle land portion. The inner shoulder land portion preferably includes a plurality of shoulder sipes extending across the inner shoulder land portion. A distance in the tire circumferential direction between an end of each of the shoulder sipes in the inner shoulder land portion on the shoulder circumferential groove side and an end of a corresponding one of the inner middle sipes on the shoulder circumferential groove side is preferably not greater than 10% of one pitch length between the inner middle sipes in the tire circumferential direction. 
     In the tire according to the present disclosure, the tread portion includes the three circumferential grooves and the four land portions demarcated by the circumferential grooves. The land portions include the two shoulder land portions including the tread ends, and the two middle land portions demarcated between the shoulder circumferential grooves and the crown circumferential groove. 
     Each of the two middle land portions includes the circumferential sipe extending continuously in the tire circumferential direction, a plurality of first middle lateral grooves extending from the crown circumferential groove and terminating in the middle land portion without connecting with the circumferential sipe, and a plurality of second middle lateral grooves extending from the shoulder circumferential groove and terminating in the middle land portion without connecting with the circumferential sipe. 
     The circumferential sipe allows appropriate reduction of stiffness in the tire axial direction and enhancement of ride comfort while maintaining stiffness of the middle land portion in the tire circumferential direction. Furthermore, the first middle lateral grooves and the second middle lateral grooves terminate in the middle land portion without connecting with the circumferential sipe, and, therefore, ride comfort is enhanced while stiffness of the middle land portion in the tire circumferential direction is maintained. 
     Meanwhile, the two middle land portions in which stiffness in the tire circumferential direction is maintained also contribute to enhancement of steering stability. 
     Furthermore, each of the two shoulder land portions of the present disclosure includes a plurality of shoulder lateral grooves extending from the tread end and terminating in the shoulder land portion. Therefore, excellent steering stability can be exhibited while ride comfort is maintained.