Abstract:
Provided is a tire for winter of which on-snow performance can be improved without compromising anti-wandering performance. A tire for winter comprises a tread part The tread part is provided with: a plurality of first inclined major grooves extending at an incline from one tread end beyond a tire equator and ending without reaching another tread end; first inclined minor grooves provided between the first inclined major grooves; a plurality of second inclined major grooves extending at an incline from the other tread end, in a direction opposite the first inclined major grooves, beyond the tire equator and ending without reaching the one tread end; second inclined minor grooves provided between the second inclined major grooves; a plurality of first longitudinal grooves dividing first land parts; and a plurality of second longitudinal grooves dividing second land parts.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a tire for winter having an excellent on-snow performance. 
       BACKGROUND ART 
       [0002]    Patent Document 1 has proposed a tire for winter that includes a tread portion provided with a plurality of longitudinal grooves continuously extending in a straight manner in a circumferential direction of the tire and a plurality of lateral grooves traversing land portions between the longitudinal grooves to improve on-snow performance. 
         [0003]    Snowy road surfaces tend to have protrusions formed and extended in a driving direction by pectinate snow compactor blades in road maintenance vehicles. When a vehicle with the tires for winter drives on such snowy roads, the longitudinal grooves in the tires engage with the protrusions and a wandering phenomenon is likely to occur such that the vehicle is led along the protrusions. 
       CITATION LIST 
     Patent Literature 
       [0004]    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-298202 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    The present invention has been made in view of the foregoing problem. A major object of the present invention is to provide a tire for winter that improves on-snow performance without deteriorating wandering-proof performance. 
       Solution to Problem 
       [0006]    The present invention provides a tire for winter including a tread portion being provided with a plurality of first main inclined grooves extending obliquely from a first tread edge toward a tire equator and terminating beyond the tire equator without reaching a second tread edge, a first sub inclined groove provided between the first main inclined grooves, the first sub inclined groove extending obliquely from the first tread edge toward the tire equator in the same direction as the first main inclined grooves and terminating not beyond the tire equator, a plurality of second main inclined grooves extending obliquely from the second tread edge toward the tire equator in an opposite direction to the first main inclined grooves and terminating beyond the tire equator without reaching the first tread edge, a second sub inclined groove provided between the second main inclined grooves, the second sub inclined groove extending obliquely from the second tread edge toward the tire equator in the same direction as the second main inclined grooves and terminates not beyond the tire equator, a plurality of first longitudinal grooves dividing first land portions formed between the first main inclined grooves and inclining in the same direction as the first main inclined grooves, and a plurality of second longitudinal grooves dividing second land portions formed between the second main inclined grooves and inclining in the same direction as the second main inclined grooves. 
         [0007]    In the tire for winter according to the present invention, preferably, the first main inclined grooves have first inner ends that terminate in communication with the second main inclined grooves, the second main inclined grooves have second inner ends that terminate in communication with the first main inclined grooves, and the first main inclined grooves and the second main inclined grooves are alternately provided in a circumferential direction of the tire. 
         [0008]    In the tire for winter according to the present invention, preferably, the first main inclined grooves and the second main inclined grooves are configured as an arc shape in which an inclination angle relative to an axial direction of the tire decreases gradually toward the first tread edge and the second tread edge respectively. 
         [0009]    In the tire for winter according to the present invention, preferably, the first longitudinal grooves adjacent through the first main inclined grooves communicate with the first main inclined grooves at different positions in the axial direction of the tire. 
         [0010]    In the tire for winter according to the present invention, preferably, the first longitudinal grooves include inner first longitudinal grooves and outer first longitudinal grooves disposed axially outward of the inner first longitudinal grooves. 
         [0011]    In the tire for winter according to the present invention, preferably, the first sub inclined grooves terminate on the side of the tire equator beyond the inner first longitudinal groove. 
         [0012]    In the tire for winter according to the present invention, preferably, the second longitudinal grooves adjacent through the second main inclined grooves communicate with the second main inclined grooves at different positions in the axial direction of the tire. 
         [0013]    In the tire for winter according to the present invention, preferably, the second longitudinal grooves include inner second longitudinal grooves and outer second longitudinal grooves disposed axially outward of the inner second longitudinal grooves. 
         [0014]    In the tire for winter according to the present invention, preferably, the second sub inclined grooves terminate on the side of the tire equator beyond the inner second longitudinal grooves. 
         [0015]    In the tire for winter according to the present invention, preferably, the tread portion includes a plurality of grooves and a plurality of blocks defined by the grooves, and at least one of the blocks is provided with a stud pin or a hole for a stud pin. 
         [0016]    In the tire for winter according to the present invention, preferably, the blocks include a plurality of central blocks provided on the tire equator, and at least one of the central blocks is provided with the stud pin or the hole. 
         [0017]    In the tire for winter according to the present invention, preferably, the central blocks have approximately triangular ground contact surfaces. 
         [0018]    In the tire for winter according to the present invention, preferably, the blocks include a plurality of shoulder blocks provided on the sides nearest the tread edges, and the shoulder blocks adjacent in the circumferential direction of the tire are different width in the axial direction of the tire. 
         [0019]    In the tire for winter according to the present invention, preferably, the shoulder blocks have an axial edge extending in a zigzag manner in the axial direction of the tire. 
         [0020]    In the tire for winter according to the present invention, preferably, the first longitudinal grooves and the second longitudinal grooves have tie bars with bulging groove bottoms, and the stud pin or the hole is provided at only one of the blocks in a pair positioned on the both sides of the tie bars in the axial direction of the tire. 
       Advantageous Effects of Invention 
       [0021]    A tire for winter of the present invention includes a tread portion provided with first main inclined grooves having a length of extending beyond a tire equator from a first tread edge and second main inclined grooves having a length of extending beyond the tire equator from a second tread edge. First sub inclined grooves having a length of extending without reaching the tire equator from the first tread edge are provided between the first main inclined grooves. Second sub inclined grooves having a length of extending without reaching the tire equator from the second tread edge are provided between the second main inclined grooves. These main inclined grooves and the sub inclined grooves break protrusions on the snowy road surface along the driving direction to improve wandering-proof performance. 
         [0022]    The main inclined grooves and the sub inclined grooves generate a large snow-shearing force on snowy road and exert high traction performance on snow. In addition, the main inclined grooves and the sub inclined grooves also have tire circumferential components and provide a high lateral grip even during cornering and the like. 
         [0023]    The tire for winter of the present invention further includes a plurality of first longitudinal grooves that divides first land portions formed between the first main inclined grooves and inclines in the same direction as the first main inclined grooves, and a plurality of second longitudinal grooves that divides second land portions formed between the second main inclined grooves and inclines in the same direction as the second main inclined grooves. These longitudinal grooves complement the tire circumferential components to further enhance the lateral grip. In addition, these longitudinal grooves divide the first land portions and the second land portions to facilitate the deformation of the land portions at the time of ground contact and prevent snow clogging in the main inclined grooves and the sub inclined grooves. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0024]      FIG. 1  is a development view of a tread portion of a tire for winter of an embodiment. 
           [0025]      FIG. 2  is a cross-sectional view of  FIG. 1  taken along a line A-A. 
           [0026]      FIG. 3  is an enlarged view of a first land portion illustrated in  FIG. 1 . 
           [0027]      FIG. 4  is a development view of a tread portion of a tire for winter of another embodiment. 
           [0028]      FIG. 5  is a development view of a tread portion of a tire for winter of a comparative example. 
       
    
    
     REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               1  Tire for winter 
               2  Tread portion 
               5 A First land portion 
               5 B Second land portion 
               11  First main inclined groove 
               12  Second main inclined groove 
               21  First sub inclined groove 
               22  Second sub inclined groove 
               31  First longitudinal groove 
               32  Second longitudinal groove 
             Te 1  First tread edge 
             Te 2  Second tread edge 
           
         
       
     
       DESCRIPTION OF EMBODIMENTS 
       [0041]    An embodiment of the present invention will be described below with reference to the drawings.  FIG. 1  illustrates a tread portion  2  of a tire for winter (hereinafter, referred to as simply “tire”)  1  of the embodiment. The tire  1  of the embodiment is preferably embodied as a tire for winter for passenger cars, for example. 
         [0042]    As illustrated in  FIG. 1 , the tread portion  2  is provided with a plurality of main inclined grooves  10 , sub inclined grooves  20  and longitudinal grooves  30 . 
         [0043]    The main inclined grooves  10  extend obliquely from tread edges Te toward a tire equator C and terminate beyond the tire equator C. 
         [0044]    The tread edges Te are ground contact positions on the outermost side in a tire axial direction when the tire  1  in a normal state is placed under a normal load and brought into contact with the ground at a camber angle of 0 degrees. The normal state refers to a state in which the tire is mounted on a normal rim with a normal inner pressure but is loaded with no tire load. Unless otherwise noted herein, the dimensions of components of the tire are measured in the normal state. 
         [0045]    The term “normal rim” is a rim specified for each tire by standards in a standard system including the standards for the tire. For example, the normal rim is the “standard rim” under JATMA, the “design rim” under TRA, and the “measuring rim” under ETRTO. 
         [0046]    The term “normal inner pressure” refers to a pneumatic pressure specified for each tire by standards in a standard system including the standards for the tire. The “normal inner pressure” is the “maximum pneumatic pressure” under JATMA, the maximum value described in the table “Tire Load Limits at Various Cold Inflation Pressures” under TRA, and the “inflation pressure” under ETRTO. 
         [0047]    The term “normal load” refers to a load specified for each tire by standards in a standard system including the standards for the tire. The “normal load” is the “maximum load performance” under JATMA, the maximum value described in the table “Tire Load Limits at Various Cold Inflation Pressures” under TRA, and the “load capacity” under ETRTO. 
         [0048]    As illustrated in  FIG. 1 , the main inclined grooves  10  include first main inclined grooves  11  and second main inclined grooves  12 . 
         [0049]    The first main inclined grooves  11  extend from a first tread edge Te 1 , which is one of the tread edges, toward the tire equator C. The first main inclined grooves  11  extends beyond the tire equator C and terminate without reaching a second tread edge Te 2 , which is the other one of the tread edges. 
         [0050]    The second main inclined grooves  12  extend from the second tread edge Te 2  toward the tire equator C in an opposite direction to the first main inclined grooves  11 . The second main inclined grooves  12  extend beyond the tire equator C and terminate without reaching the first tread edge Te 1 . 
         [0051]    Since the main inclined grooves  10  traverse the tire equator C, large ground pressure acts on the main inclined grooves  10 . Therefore, during driving on snowy roads, the snow in the grooves is strongly compressed to generate a large snow-shearing force. In addition, the main inclined grooves  10  produce an excellent edge effect to enhance on-ice performance. The main inclined grooves  10  extend obliquely from the tread edges Te toward the tire equator C, and can generate a frictional force in the axial direction of the tire to suppress sideslip on snow and ice. 
         [0052]    Each of the sub inclined grooves  20  is provided between a pair of circumferentially adjacent main inclined grooves  10  and  10 . The sub inclined grooves  20  extend obliquely from the tread edges Te toward the tire equator C and terminate not beyond the tire equator C. 
         [0053]    As illustrated in  FIG. 1 , the sub inclined grooves  20  include first sub inclined grooves  21  and second sub inclined grooves  22 . 
         [0054]    Each of the first sub inclined grooves  21  is provided between a pair of circumferentially adjacent first main inclined grooves  11  and  11 . The first sub inclined grooves  21  extend obliquely in the same direction as the first main inclined grooves  11  from the first tread edge Te 1  toward the tire equator C. 
         [0055]    Each of the second sub inclined grooves  22  is provided between a pair of circumferentially adjacent second main inclined grooves  12  and  12 . The second sub inclined grooves  22  extend obliquely in the same direction as the second main inclined grooves  12  from the second tread edge Te 2  toward the tire equator C. 
         [0056]    The sub inclined grooves  20  do not traverse the tire equator C but maintain the rigidity of the blocks around the tire equator C to enhance on-snow performance and on-ice performance while maintaining driving stability on dry road surfaces. 
         [0057]    The main inclined grooves  10  and the sub inclined grooves  20  may break protrusions formed on snowy road surface along the driving direction to improve wandering-proof performance. The main inclined grooves  10  and the sub inclined grooves  20  generate a large snow-shearing force and exert high traction performance on the snowy road. In addition, the main inclined grooves  10  and the sub inclined grooves  20  also have tire circumferential components and provide a high lateral grip even during cornering and the like. 
         [0058]    In order to further enhance the foregoing effects, a groove width W 1  of the main inclined grooves  10  and a groove width W 2  of the sub inclined grooves  20  are preferably in a range of from 3.0% to 8.5% of a tread ground contact width TW, for example. The tread ground contact width TW is an axial distance between the first tread edges Te 1  and the second tread edge Te 2  in the normal state. 
         [0059]      FIG. 2  is a cross-sectional view of  FIG. 1  taken along a line A-A. As illustrated in  FIG. 2 , a groove depth d 1  of the main inclined grooves  10  and a groove depth d 2  of the sub inclined grooves  20  are preferably in a range of from 3.0 to 10.0 mm, for example. 
         [0060]    As illustrated in  FIG. 1 , preferably, the first main inclined grooves  11  according to the embodiment have first inner ends  11   i  terminating in communication with the second main inclined grooves  12 , for example. Preferably, the second main inclined grooves  12  according to the embodiment have second inner ends  12   i  terminating in communication with the first main inclined grooves  11 , for example. Accordingly, connection portions  13  between the first main inclined grooves  11  and the second main inclined grooves  12  break effectively protrusions formed on the snowy road surface to obtain a large snow-shearing force. In addition, large snow columns are likely to be formed at the connection portions  13 , thereby achieving excellent on-snow performance. 
         [0061]    The first main inclined grooves  11  and the second main inclined grooves  12  are preferably arranged alternately in the circumferential direction of the tire, for example. This suppresses effectively uneven wear of the tread portion  2 . 
         [0062]    The main inclined grooves  10  according to the embodiment are preferably formed in an arc shape in which an inclination angle θ 1  relative to the axial direction of the tire gradually decreases toward the tread edges Te. The main inclined grooves  10  maintain the rigidity around the tire equator C in the circumferential direction of the tire on which a large ground pressure acts, and moderate the rigidity of the land portions around the tread edges Te in the circumferential direction of the tire. Therefore, it is possible to maintain driving stability and enhance wandering-proof performance. In addition, the main inclined grooves  10  exert a frictional force multidirectionally to enhance on-ice driving stability in particular. 
         [0063]    The inclination angle θ 1  of the main inclined grooves  10  is preferably 35 degrees or more, more preferably 40 degrees or more, and is preferably 50 degrees or less, more preferably 45 degrees or less. The main inclined grooves  10  ensure balanced compatibility between stable driving performance and wandering-proof performance. 
         [0064]    From the same viewpoint, an inclination angle θ 2  of the sub inclined grooves  20  is preferably 20 degrees or more, more preferably 25 degrees or more, and is preferably 35 degrees or less, more preferably 30 degrees or less. 
         [0065]    The main inclined grooves  10  and the sub inclined grooves  20  are approximately parallel to the axial direction of the tire at the tread edges Te. Accordingly, during driving on a snowy road, the protrusions on the snowy road surface can be effectively broken to suppress a wandering phenomenon. 
         [0066]    The longitudinal grooves  30  divide land portions  5  formed between the main inclined grooves  10  and  10  and extend in the circumferential direction of the tire. The longitudinal grooves  30  incline in the same direction as the main inclined grooves  10  adjacent in the circumferential direction of the tire. 
         [0067]    The longitudinal grooves  30  include first longitudinal grooves  31  and second longitudinal grooves  32 . 
         [0068]    The first longitudinal grooves  31  divide first land portions  5 A formed between the first main inclined grooves  11  and  11 . The first longitudinal grooves  31  incline in the same direction as the first main inclined grooves  11 . 
         [0069]    The second longitudinal grooves  32  divide second land portions  5 B formed between the second main inclined grooves  12  and  12 . The second longitudinal grooves  32  incline in the same direction as the second main inclined grooves  12 . 
         [0070]    The longitudinal grooves  30  can complement the tire circumferential components to further enhance the lateral grip. In addition, the longitudinal grooves  30  divide the first land portions  5 A and the second land portions  5 B to facilitate the deformation of the land portions at the time of ground contact and prevent snow clogging in the main inclined grooves  10  and the sub inclined grooves  20 . 
         [0071]    In order to obtain a large snow column shearing force while suppressing snow clogging, a groove width W 3  of the longitudinal grooves  30  is desirably 2.5% to 8.0% of the tread ground contact width TW, for example. Otherwise, the groove width W 3  of the longitudinal grooves  30  is preferably 5 mm or more, more preferably 8 mm or more, and is preferably 14 mm or less, more preferably 11 mm or less. A groove depth d 3  of the longitudinal grooves  30  (illustrated in  FIG. 2 ) is desirably 3.0 to 10.0 mm, for example. 
         [0072]    As illustrated in  FIG. 1 , the tread portion  2  according to the embodiment has no main grooves continuously extending over the circumference of the tire  1  in the circumferential direction of the tire. Accordingly, the tire  1  according to the embodiment exerts excellent wandering-proof performance without being led by protrusions formed on snowy road surface in the driving direction. In addition, the tread portion  2  allows uniform arrangement of stud pins in the axial direction of the tire to exert excellent on-ice performance. 
         [0073]    In the embodiment, the longitudinal grooves  30  adjacent in the circumferential direction of the tire are provided such that at least their tire circumferential end portions are shifted in position from each other in the axial direction of the tire. 
         [0074]    Specifically, the first longitudinal grooves  31  adjacent through the first main inclined grooves  11  communicate with the first main inclined grooves  11  at different positions in the axial direction of the tire, for example. The second longitudinal grooves  32  adjacent through the second main inclined grooves  12  communicate with the second main inclined grooves  12  at different positions in the axial direction of the tire, for example. 
         [0075]    The first longitudinal grooves  31  formed in the first land portions  5 A include inner first longitudinal grooves  35  and outer first longitudinal grooves  36 . 
         [0076]    The inner first longitudinal grooves  35  are disposed on the side of the tire equator C. One ends of the inner first longitudinal grooves  35  communicate with the first main inclined grooves  11 , and the other ends of the inner first longitudinal grooves  35  communicate with the second main inclined grooves  12  adjacent in the axial direction of the tire. 
         [0077]    The outer first longitudinal grooves  36  are disposed on the outside of the inner first longitudinal grooves  35  in the axial direction of the tire. The outer first longitudinal grooves  36  communicate between the first main inclined grooves  11  and  11  adjacent in the circumferential direction of the tire. 
         [0078]    The second longitudinal grooves  32  include inner second longitudinal grooves  37  and outer second longitudinal grooves  38 . 
         [0079]    The inner second longitudinal grooves  37  are disposed on the side of the tire equator C. One ends of the inner second longitudinal grooves  37  communicate with the second main inclined grooves  12 , and the other ends of the inner second longitudinal grooves  37  communicate with the first main inclined grooves  11  adjacent in the axial direction of the tire. 
         [0080]    The outer second longitudinal grooves  38  are disposed on the outside of the inner second longitudinal grooves  37  in the axial direction of the tire. The outer second longitudinal grooves  38  communicate between the second main inclined grooves  12  and  12  adjacent in the circumferential direction of the tire. 
         [0081]    In the tire  1  with the first longitudinal grooves  31  and the second longitudinal grooves  32 , even when the longitudinal grooves  30  engage with protrusions extending in the driving direction on snowy road surface during driving on the road, the main inclined grooves  10  or the sub inclined grooves  20  break protrusions before the vehicle is led along protrusions. Therefore, it is possible to suppress effectively a wandering phenomenon. In addition, the first longitudinal grooves  31  and the second longitudinal grooves  32  further facilitate the deformation of the land portions at the time of ground contact and prevent snow clogging in the main inclined grooves  10  and the sub inclined grooves  20 . 
         [0082]      FIG. 3  is an enlarged view of the first land portion  5 A. As illustrated in  FIG. 3 , an inclination angle θ 3  of the inner first longitudinal grooves  35  in the circumferential direction of the tire and an inclination angle θ 4  of the outer first longitudinal grooves  36  in the circumferential direction of the tire are preferably 5 degrees or more, more preferably 10 degrees or more, and is preferably 20 degrees or less, more preferably 15 degrees or less. The inner first longitudinal grooves  35  and the outer first longitudinal grooves  36  provide a strong lateral grip and discharge effectively the snow from the grooves during driving on snowy roads. 
         [0083]    An intersection point P 1  between the inner first longitudinal groove  35  and the first main inclined groove  11  is desirably positioned on the outer side in the axial direction of the tire than an intersection point P 2  between the first main inclined groove  11  and the second main inclined groove  12 . A distance L 1  between the intersection point P 1  and the intersection point P 2  is preferably 15 mm or more, more preferably 18 mm or more, and is preferably 25 mm or less, more preferably 22 mm or less. Accordingly, it is possible to form large snow columns in the grooves while suppressing a wandering phenomenon, thereby achieving improvement of on-snow performance. 
         [0084]    The inner first longitudinal grooves  35  intersect the first sub inclined grooves  21 . Accordingly, the first sub inclined grooves  21  terminate beyond the inner first longitudinal grooves  35  on the tire equator C side. The inner first longitudinal grooves  35  include first portions  35 A and second portions  35 B sectioned by the first sub inclined grooves  21 . 
         [0085]    The first portions  35 A of the inner first longitudinal grooves  35  communicate between the first main inclined grooves  11  and the first sub inclined grooves  21 . The second portions  35 B of the inner first longitudinal grooves  35  communicate between the second main inclined grooves  12  and the first sub inclined grooves  21 . 
         [0086]    The inner first longitudinal grooves  35  of the embodiment have the first portions  35 A and the second portions  35 B made continuous smoothly. The inner first longitudinal grooves  35  form large snow columns in the grooves to enhance effectively on-snow performance. In addition, the inner first longitudinal grooves  35  also enhance drainage performance during driving on wet roads. 
         [0087]    The first portions  35 A and the second portions  35 B of the inner first longitudinal grooves  35  may be shifted in position from each other in the axial direction of the tire, for example. In this case, a distance L 2  (not illustrated) between an intersection point P 3  between the first portion  35 A of the first longitudinal groove  35  and the first sub inclined groove  21  and an intersection point P 4  between the second portion  35 B of the first longitudinal groove  35  and the first sub inclined groove  21  is preferably 5 mm or more, more preferably 8 mm or more, and is preferably 15 mm or less, more preferably 12 mm or less. The inner first longitudinal grooves  35  further enhance wandering-proof performance. In addition, the inner first longitudinal grooves  35  form large snow columns between the intersection point P 3  and the intersection point P 4  to further enhance on-snow performance. 
         [0088]    The intersection point P 5  between the outer first longitudinal groove  36  and the first main inclined groove  11  and the intersection point P 6  between the outer first longitudinal groove  36  and the first main inclined groove  11  adjacent in the circumferential direction of the tire are desirably shifted in position from each other in the axial direction of the tire. A distance L 3  between the intersection point P 5  and the intersection point P 6  is preferably 20 mm or more, more preferably 23 mm or more, and is preferably 30 mm or less, more preferably 27 mm or less. Accordingly, it is possible to form large snow columns between the intersection point P 5  and the intersection point P 6  while suppressing a wandering phenomenon, thereby achieving improvement of on-snow performance. 
         [0089]    The outer first longitudinal grooves  36  intersect the first sub inclined grooves  21 , for example. Accordingly, the outer first longitudinal grooves  36  include first portions  36 A and second portions  36 B sectioned by the first sub inclined grooves  21 . 
         [0090]    The first portions  36 A and the second portions  36 B of the outer first longitudinal grooves  36  are desirably shifted in position from each other in the axial direction of the tire. 
         [0091]    A distance L 4  between an intersection point P 7  between the first portion  36 A of the outer first longitudinal groove  36  and the first sub inclined groove  21  and an intersection point P 8  between the second portion  36 B of the outer first longitudinal groove  36  and the first sub inclined groove  21  is preferably 10 mm or more, more preferably 13 mm or more, and is preferably 20 mm or less, more preferably 17 mm or less. Accordingly, it is possible to form large snow columns between the portions of intersection between the outer first longitudinal grooves  36  and the first sub inclined grooves  21 , thereby exerting excellent on-snow performance 
         [0092]    As illustrated in  FIG. 1 , the inner second longitudinal grooves  37  and the outer second longitudinal grooves  38  are substantially line-symmetrical in shape to the inner first longitudinal grooves  35  and the outer first longitudinal grooves  36  with respect to the tire equator C. Therefore, the components of the inner first longitudinal grooves  35  and the outer first longitudinal grooves  36  are also included in the inner second longitudinal grooves  37  and the outer second longitudinal grooves  38 . The inner second longitudinal grooves  37  and the outer second longitudinal grooves  38 , and the inner first longitudinal grooves  35  and the outer first longitudinal grooves  36  are separated from each other with a phase difference of half pitch in the circumferential direction of the tire. 
         [0093]    The tread portion  2  has a plurality of blocks  4  formed by the plurality of grooves described above. At least one of the blocks  4  has stud pins or stud pin holes  8 . In the embodiment, the stud pins or the stud pin holes  8  are arranged at random on the respective blocks. The stud pins enhance effectively on-ice performance. The accompanying drawings do not illustrate the stud pins. 
         [0094]    A plurality of sipes  70  extending in the axial direction of the tire is arranged on the respective blocks of the embodiment. The sipes  70  exert an excellent edge effect and enhance effectively on-ice performance. The term “sipes” herein refer to grooves with a width of less than 1.0 mm. 
         [0095]      FIG. 4  is an enlarged view of the tread portion  2  of the tire for winter  1  of another embodiment of the present invention. As illustrated in  FIG. 4 , when the tread portion  2  is provided with the foregoing grooves, pluralities of central blocks  40 , middle blocks  50 , and shoulder blocks  60  are provided in the circumferential direction of the tire. 
         [0096]    The central blocks  40  are formed by the first main inclined grooves  11 , the second main inclined grooves  12 , and the inner first longitudinal grooves  35  or the inner second longitudinal grooves  37 . The central blocks  40  have approximately triangular tread surfaces, for example. 
         [0097]    At least one of the central blocks  40  has desirably stud pins or stud pin holes  8 . Since large ground pressure acts on the central blocks  41 , the central blocks  40  have the stud pins to enhance effectively on-ice performance. 
         [0098]    As illustrated in  FIG. 4 , the plurality of middle blocks  50  is provided in the circumferential direction of the tire. The middle blocks  50  are shifted in position from each other in the axial direction of the tire. When the stud pins are provided, the middle blocks  50  can be shifted in position in the axial direction of the tire to enhance effectively on-ice performance. 
         [0099]    The middle blocks  50  include first middle blocks  51  and second middle blocks  52 . The first middle blocks  51  are arranged in the first land portions  5 A and are sectioned by the first main inclined grooves  11 , the first sub inclined grooves  21 , the inner first longitudinal grooves  35 , and the outer first longitudinal grooves  36 . The second middle blocks  52  are arranged in the second land portions  5 B and are sectioned by the second main inclined grooves  12 , the second sub inclined grooves  22 , the inner second longitudinal grooves  37 , and the outer second longitudinal grooves  38 . The middle blocks  50  have approximately parallelogramic tread surfaces, for example. 
         [0100]    The shoulder blocks  60  include first shoulder blocks  61  and second shoulder blocks  62 . 
         [0101]    The first shoulder blocks  61  are arranged in the first land portions  5 A and are sectioned by the first main inclined grooves  11 , the first sub inclined grooves  21 , and the outer first longitudinal grooves  36 . The second shoulder blocks  62  are arranged in the second land portions  5 B and are sectioned by the second main inclined grooves  12 , the second sub inclined grooves  22 , and the outer second longitudinal grooves  38 . The shoulder blocks  60  have approximately rectangular tread surfaces, for example. 
         [0102]    The shoulder blocks  60  adjacent in the circumferential direction of the tire are desirably different in tire axial width. The shoulder blocks  60  are different in the amount of deformation at the time of contact with the ground, and therefore further prevent snow clogging in the main inclined grooves  10  and the sub inclined grooves  20 . 
         [0103]    The shoulder blocks  60  have desirably zigzag edges  65  extending in a zigzag manner in the axial direction of the tire, for example. The zigzag edges  65  have a plurality of small projections  66  as convex corners in the circumferential direction of the tire, for example. The zigzag edge  65  of the present embodiment has, for example, 4 to 7 small projections  66 . The zigzag edges  65  eat effectively into the road surface to exert excellent wandering-proof performance. 
         [0104]    The shoulder blocks  60  desirably have semi-open sipes  71  with first ends  71   a  that communicate with the grooves and second ends  71   b  terminating within the blocks. Accordingly, the rigidity of the shoulder blocks  60  is maintained to improve driving stability. 
         [0105]    The longitudinal grooves  30  between the shoulder blocks  60  and the middle blocks  50  have desirably tie bars  45  with bulging groove bottoms. The tie bars  45  suppress the deformation of the shoulder blocks  60  and the middle blocks  50  in the axial direction of the tire to enhance on-ice driving stability. 
         [0106]    The stud pins or the stud pin holes  8  are desirably provided in only one of the shoulder blocks  60  and the middle blocks  50  in pairs on the both ends of the tie bar  45  in the axial direction of the tire. Accordingly, the blocks without stud pins deform relatively largely to suppress snow clogging in the grooves. In addition, the blocks with the stud pins suppress effectively excessive falling of the blocks adjacent via the tie bars. Therefore, on-snow performance and on-ice performance can be enhanced in a balanced manner. 
         [0107]    In the tire for winter of the embodiment, a land ratio Lr of the tread portion  2  is preferably 55% or more, more preferably 60% or more, and is preferably 70% or less, more preferably 65% or less. This ensures compatibility between driving stability and on-snow performance. The term “land ratio” herein refers to ratio Sb/Sa of actual ground-contact area Sb to entire area Sa of a virtual ground-contact surface in which all the grooves and the sipes are filled between the tread edges Te and Te. 
         [0108]    The tread portion  2  is desirably formed from tread rubber with a JIS-A hardness of 45 to 65 degrees. The tread rubber maintains flexibility even on low temperature snowy road surfaces, and exerts excellent on-snow performance. The term JIS-A hardness herein refers to a durometer type-A hardness of rubber measured at 23 degrees C. environments in compliance with JIS-K6253. 
         [0109]    The tire for winter of the present invention has been described in detail so far. As a course of matter, however, the present invention is not limited to the illustrated embodiment but can be modified in various manners. 
       EXAMPLES 
       [0110]    The tire for winter for automobile with a size of 205/60R16 having the basic pattern illustrated in  FIG. 1  was prototyped in accordance with the specifications in Table 1. As comparative example 1, a tire including only main grooves extending continuously over the circumference of the tire and lateral grooves extending in the axial direction of the tire was prototyped. These test tires were tested for on-snow performance and wandering-proof performance. The common specifications and test method for the test tires were as follows: 
         [0111]    Mounting rim: 16×6.5 
         [0112]    Tire internal pressure: 240 kPa for front wheels and 220 kPa for rear wheels 
         [0113]    Test vehicle: Front-wheel-drive vehicle with a displacement of 2000 cc 
         [0114]    Tire mounting position: All the wheels 
         [0115]    On-Snow Performance: 
         [0116]    The test vehicle with the test tires were tested for on-snow driving performance by the driver&#39;s sensory evaluation. The larger values of test results indicate more excellence in on-snow performance with a score of 100 representing the values of the comparative example 1. 
         [0117]    Wandering-Proof Performance: 
         [0118]    The test vehicle with the test tires was driven on an icy and snowy road surface with protrusions extending in the driving direction. The test vehicle was tested for behaviors such as shaking or the like by the driver&#39;s sensory evaluation. The larger values of test results indicate more excellence in wandering-proof performance with a score of 100 representing the values of the comparative example 1. 
         [0119]    Table 1 shows the test results. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                   
                 Comp. 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Ex. 1 
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 4 
                 Example 5 
                 Example 6 
                 Example 7 
                 Example 8 
               
               
                   
               
               
                 Distance L1 between intersection point P1 
                 — 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
               
               
                 and intersection point P2 (mm) 
               
               
                 Distance L2 between intersection point P3 
                 — 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 30.0 
                 10.0 
               
               
                 and intersection point P4 (mm) 
               
               
                 Distance L3 between intersection point P5 
                 — 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 25.0 
               
               
                 and intersection point P6 (mm) 
               
               
                 Distance L4 between intersection point P7 
                 — 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 30.0 
                 15.0 
               
               
                 and intersection point P8 (mm) 
               
               
                 Inclination angle θ1 of main inclined 
                 — 
                 45.0 
                 60.0 
                 75.0 
                 40.0 
                 45.0 
                 40.0 
                 40.0 
                 40.0 
               
               
                 grooves (deg.) 
               
               
                 Inclination angle θ2 of sub inclined 
                 — 
                 30.0 
                 60.0 
                 60.0 
                 25.0 
                 30.0 
                 25.0 
                 25.0 
                 25.0 
               
               
                 grooves (deg.) 
               
               
                 Inclination angle θ3 of inner first vertical 
                 — 
                 15.0 
                 15.0 
                 15.0 
                 45.0 
                 45.0 
                 15.0 
                 10.0 
                 10.0 
               
               
                 grooves (deg.) 
               
               
                 Inclination angle θ4 of outer first vertical 
                 — 
                 15.0 
                 15.0 
                 15.0 
                 60.0 
                 45.0 
                 15.0 
                 15.0 
                 15.0 
               
               
                 grooves (deg.) 
               
               
                 On-snow performance (score) 
                 100 
                 108 
                 107 
                 104 
                 106 
                 108 
                 108 
                 104 
                 110 
               
               
                 Wandering-proof performance (score) 
                 100 
                 107 
                 108 
                 106 
                 104 
                 106 
                 109 
                 108 
                 110 
               
               
                   
               
             
          
           
               
                   
                   
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
               
               
                   
                 Example 9 
                 10 
                 11 
                 12 
                 13 
                 14 
                 15 
                 16 
                 17 
                 18 
               
               
                   
               
               
                 Distance L1 between 
                 20.0 
                 20.0 
                 15.0 
                 25.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 30.0 
                 25.0 
               
               
                 intersection point P1 and 
               
               
                 intersection point P2 (mm) 
               
               
                 Distance L2 between 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 5.0 
                 15.0 
                 10.0 
                 15.0 
               
               
                 intersection point P3 and 
               
               
                 intersection point P4 (mm) 
               
               
                 Distance L3 between 
                 20.0 
                 30.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 35.0 
                 25.0 
               
               
                 intersection point P5 and 
               
               
                 intersection point P6 (mm) 
               
               
                 Distance L4 between 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 10.0 
                 20.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
               
               
                 intersection point P7 and 
               
               
                 intersection point P8 (mm) 
               
               
                 Inclination angle θ1 of 
                 40.0 
                 40.0 
                 40.0 
                 40.0 
                 40.0 
                 40.0 
                 40.0 
                 40.0 
                 40.0 
                 45.0 
               
               
                 main inclined grooves (deg.) 
               
               
                 Inclination angle θ2 of sub 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 30.0 
               
               
                 inclined grooves (deg.) 
               
               
                 Inclination angle θ3 of inner 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 15.0 
               
               
                 first vertical grooves (deg.) 
               
               
                 Inclination angle θ4 of outer 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
               
               
                 first vertical grooves (deg.) 
               
               
                 On-snow performance (score) 
                 111 
                 109 
                 111 
                 109 
                 110 
                 109 
                 111 
                 109 
                 105 
                 107 
               
               
                 Wandering-proof performance 
                 109 
                 111 
                 109 
                 111 
                 109 
                 110 
                 109 
                 111 
                 108 
                 109 
               
               
                 (score) 
               
               
                   
               
               
                   
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
               
               
                   
                 19 
                 20 
                 21 
                 22 
                 23 
                 24 
                 25 
                 26 
                 27 
                 28 
               
               
                   
               
               
                 Distance L1 between 
                 25.0 
                 25.0 
                 5.0 
                 5.0 
                 5.0 
                 5.0 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
               
               
                 intersection point P1 and 
               
               
                 intersection point P2 (mm) 
               
               
                 Distance L2 between 
                 25.0 
                 15.0 
                 5.0 
                 5.0 
                 5.0 
                 5.0 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
               
               
                 intersection point P3 and 
               
               
                 intersection point P4 (mm) 
               
               
                 Distance L3 between 
                 25.0 
                 25.0 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
                 5.0 
                 0.0 
                 0.0 
                 0.0 
               
               
                 intersection point P5 and 
               
               
                 intersection point P6 (mm) 
               
               
                 Distance L4 between 
                 25.0 
                 15.0 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
                 5.0 
                 0.0 
                 0.0 
                 0.0 
               
               
                 intersection point P7 and 
               
               
                 intersection point P8 (mm) 
               
               
                 Inclination angle θ1 of main 
                 45.0 
                 45.0 
                 45.0 
                 30.0 
                 70.0 
                 45.0 
                 45.0 
                 45.0 
                 30.0 
                 70.0 
               
               
                 inclined grooves (deg.) 
               
               
                 Inclination angle θ2 of sub 
                 30.0 
                 30.0 
                 30.0 
                 15.0 
                 65.0 
                 30.0 
                 30.0 
                 30.0 
                 15.0 
                 65.0 
               
               
                 inclined grooves (deg.) 
               
               
                 Inclination angle θ3 of inner 
                 15.0 
                 10.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
               
               
                 first vertical grooves (deg.) 
               
               
                 Inclination angle θ4 of outer 
                 15.0 
                 10.0 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
                 15.0 
                 0.0 
                 0.0 
                 0.0 
               
               
                 first vertical grooves (deg.) 
               
               
                 On-snow performance (score) 
                 106 
                 109 
                 106 
                 107 
                 104 
                 106 
                 107 
                 107 
                 108 
                 106 
               
               
                 Wandering-proof performance 
                 110 
                 109 
                 105 
                 105 
                 105 
                 105 
                 105 
                 104 
                 104 
                 104 
               
               
                 (score) 
               
               
                   
               
             
          
         
       
     
         [0120]    As seen from Table 1, it has been revealed that the tire for winter of the example improved on-snow performance without sacrificing wandering-proof performance. 
         [0121]    The tire for winter for automobile with a size of 205/60R16 having the basic pattern illustrated in  FIG. 4  was prototyped in accordance with the specifications in Table 1. As a comparative example 2, a tire having the tread pattern illustrated in  FIG. 5  was prototyped. These test tires were tested for on-snow performance and on-ice performance. The common specifications and test method for the test tires were as follows: 
         [0122]    Mounting rim: 16×6.5 
         [0123]    Tire internal pressure: 240 kPa for front wheels and 220 kPa for rear wheels 
         [0124]    Test vehicle: Front-wheel-drive vehicle with a displacement of 2000 cc 
         [0125]    Tire mounting position: All the wheels 
         [0126]    On-Snow Performance and on-Ice Performance: 
         [0127]    The test vehicle with the test tires was tested for on-snow and on-ice driving performance by the driver&#39;s sensory evaluation. The larger values of test results indicate more excellence in on-snow performance or on-ice performance with a score of 100 representing the values of the comparative example 1. 
         [0128]    Table 2 shows the test results. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
             
             
               
                   
                 Comp. 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
               
               
                   
                 Ex. 2 
                 29 
                 30 
                 31 
                 32 
                 33 
                 34 
                 35 
                 36 
               
               
                   
               
               
                 Distance L1 between intersection point P1 
                 — 
                 20.0 
                 15.0 
                 25.0 
                 30.0 
                 35.0 
                 25.0 
                 20.0 
                 20.0 
               
               
                 and intersection point P2 (mm) 
               
               
                 Distance L2 between intersection point P3 
                 — 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 25.0 
                 10.0 
                 10.0 
               
               
                 and intersection point P4 (mm) 
               
               
                 Distance L3 between intersection point P5 
                 — 
                 25.0 
                 15.0 
                 25.0 
                 25.0 
                 35.0 
                 25.0 
                 25.0 
                 25.0 
               
               
                 and intersection point P6 (mm) 
               
               
                 Distance L4 between intersection point P7 
                 — 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 25.0 
                 15.0 
                 15.0 
               
               
                 and intersection point P8 (mm) 
               
               
                 Inclination angle θ1 of main inclined 
                 — 
                 40.0 
                 40.0 
                 40.0 
                 40.0 
                 40.0 
                 40.0 
                 30.0 
                 45.0 
               
               
                 grooves (deg.) 
               
               
                 Inclination angle θ2 of sub inclined 
                 — 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 25.0 
                 15.0 
                 30.0 
               
               
                 grooves (deg.) 
               
               
                 Inclination angle θ3 of inner first vertical 
                 — 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
               
               
                 grooves (deg.) 
               
               
                 Inclination angle θ4 of outer first vertical 
                 — 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
               
               
                 grooves (deg.) 
               
               
                 The presence or absence of tie bars 
                 — 
                 Present 
                 Present 
                 Present 
                 Present 
                 Present 
                 Present 
                 Present 
                 Present 
               
               
                 between shoulder blocks and middle 
               
               
                 blocks 
               
               
                 On-snow performance (score) 
                 100 
                 108 
                 106 
                 107 
                 107 
                 106 
                 107 
                 108 
                 107 
               
               
                 On-ice performance (score) 
                 100 
                 104 
                 105 
                 104 
                 103 
                 103 
                 103 
                 103 
                 104 
               
               
                   
               
               
                   
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
                 Example 
               
               
                   
                 37 
                 38 
                 39 
                 40 
                 41 
                 42 
                 43 
                 44 
                 45 
               
               
                   
               
               
                 Distance L1 between intersection point P1 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
               
               
                 and intersection point P2 (mm) 
               
               
                 Distance L2 between intersection point P3 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
               
               
                 and intersection point P4 (mm) 
               
               
                 Distance L3 between intersection point P5 
                 25.0 
                 15.0 
                 20.0 
                 20.0 
                 20.0 
                 20.0 
                 25.0 
                 25.0 
                 25.0 
               
               
                 and intersection point P6 (mm) 
               
               
                 Distance L4 between intersection point P7 
                 15.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
                 15.0 
                 15.0 
                 15.0 
               
               
                 and intersection point P8 (mm) 
               
               
                 Inclination angle θ1 of main inclined 
                 50.0 
                 40.0 
                 40.0 
                 45.0 
                 55.0 
                 75.0 
                 40.0 
                 40.0 
                 40.0 
               
               
                 grooves (deg.) 
               
               
                 Inclination angle θ2 of sub inclined 
                 35.0 
                 25.0 
                 25.0 
                 30.0 
                 45.0 
                 75.0 
                 25.0 
                 25.0 
                 25.0 
               
               
                 grooves (deg.) 
               
               
                 Inclination angle θ3 of inner first vertical 
                 10.0 
                 10.0 
                 15.0 
                 15.0 
                 15.0 
                 15.0 
                 25.0 
                 35.0 
                 10.0 
               
               
                 grooves (deg.) 
               
               
                 Inclination angle θ4 of outer first vertical 
                 15.0 
                 15.0 
                 20.0 
                 20.0 
                 20.0 
                 15.0 
                 25.0 
                 35.0 
                 15.0 
               
               
                 grooves (deg.) 
               
               
                 The presence or absence of tie bars 
                 Present 
                 Present 
                 Present 
                 Present 
                 Present 
                 Present 
                 Present 
                 Present 
                 Absent 
               
               
                 between shoulder blocks and middle 
               
               
                 blocks 
               
               
                 On-snow performance (score) 
                 106 
                 106 
                 108 
                 106 
                 105 
                 104 
                 107 
                 106 
                 105 
               
               
                 On-ice performance (score) 
                 103 
                 104 
                 103 
                 102 
                 102 
                 102 
                 103 
                 102 
                 103 
               
               
                   
               
             
          
         
       
     
         [0129]    As the results of the test, it has been revealed that the tire for winter of the present invention ensured on-snow performance and on-ice performance in a high degree.