JP2017088174A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to exhibit good snow road performance and stable operation performance.SOLUTION: A pneumatic tire 1 includes a shoulder land part 5 on a tire axial direction outer side of a shoulder major groove 3 in a tread part 2. The shoulder land part 5 includes: a first shoulder siping 8 which extends from the shoulder major groove 3 to a tread end Te side, and of which an outer end 8e in a tire axial direction terminates in the shoulder land 5; and a second shoulder siping 9 which extends from an inner end 9i, which is positioned on the tread end Te side with respect to the outer end 8e of the first shoulder siping 8, to the tread end Te side. The inner end 9i of the second shoulder siping 9 is provided at a position where the first shoulder siping 8 is virtually extended to the tire axial direction outer side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire capable of exhibiting good icy and snowy road performance and steering stability performance.

  In recent years, in pneumatic tires for winter, there are increasing opportunities to travel on dry roads in addition to icy and snowy roads. Such a pneumatic tire is required to have not only good icy and snowy road performance but also excellent steering stability performance on a dry road.

  In order to improve icy and snowy road performance, for example, a pneumatic tire in which a large number of sipes are provided in a tread portion has been proposed.

  However, the pneumatic tire as described above cannot exhibit excellent steering stability performance on a dry road because the rigidity of the tread portion is small.

JP 2010-285035 A

  The present invention has been devised in view of the above-described problems, and is based on improving the sipe provided in the shoulder land, and can improve the snow and snow road performance and the steering stability performance in a well-balanced manner. The main purpose is to provide tires.

  The present invention is a pneumatic tire including a shoulder main groove extending continuously in a tire circumferential direction on a tread end side in a tread portion, and a shoulder land portion outside the shoulder main groove in the tire axial direction. The land portion includes a first shoulder sipe extending from the shoulder main groove toward the tread end side and having an outer end in the tire axial direction terminating in the shoulder land portion, and the tread end side from the outer end of the first shoulder sipe. A second shoulder sipe extending from the inner end located on the tread end side to the tread end side, and the inner end of the second shoulder sipe is provided at a position virtually extending the first shoulder sipe outward in the tire axial direction. It is characterized by that.

  In the pneumatic tire according to the present invention, it is preferable that the second shoulder sipe extends on an extension line obtained by virtually extending the first shoulder sipe outward in the tire axial direction.

  In the pneumatic tire according to the present invention, the tread portion includes at least one center main groove extending continuously in the tire circumferential direction on the inner side in the tire axial direction of the shoulder main groove, the shoulder main groove, and the center main groove. A middle land portion that is divided between the groove and the middle land portion, the first end being located in the center main groove or the shoulder main groove and the second end terminating in the middle land portion. It is desirable that a plurality of middle lug grooves are provided, and the width of the middle lug groove is changed in a stepwise manner from the first end toward the second end.

  In the pneumatic tire according to the present invention, the middle land portion is provided with a plurality of first middle sipes that connect between the center main groove and the shoulder main groove, and the middle lug groove and the first adjacent to the middle lug groove. It is preferable that a chamfered portion that is inclined inward in the tire radial direction toward the first end side is provided in the land portion piece divided between one middle sipe.

  In the pneumatic tire according to the present invention, the middle land portion extends from the second end of the middle lug groove to the side opposite to the first end and communicates with the center main groove or the shoulder main groove. It is desirable to have 2 middle rib sipes.

  In the pneumatic tire according to the present invention, the shoulder land portion includes a shoulder lug groove extending inward in the tire axial direction from the tread end and an inner end terminating at the shoulder land portion, the inner end of the shoulder lug groove, It is desirable that a third shoulder sipe that connects between the shoulder main grooves is provided.

  In the pneumatic tire according to the present invention, the tread portion is divided between the center main groove and a pair of center main grooves extending continuously in the tire circumferential direction on the inner side in the tire axial direction of the shoulder main groove. A center land portion, and the center land portion is provided with a plurality of center lug grooves having a first end located in the center main groove and a second end terminating in the center land portion. It is desirable that the groove width of the groove changes so as to decrease stepwise from the first end toward the second end.

  In the pneumatic tire of the present invention, the shoulder land portion includes a first shoulder sipe extending from the shoulder main groove to the tread end side and having an outer end in the tire axial direction terminating in the shoulder land portion, and an outer end of the first shoulder sipe. And a second shoulder sipe extending from the inner end located on the tread end side to the tread end side. The inner end of the second shoulder sipe is provided at a position where the first shoulder sipe is virtually extended outward in the tire axial direction. Each such sipe exhibits a frictional force against the icy and snowy road surface, so that the icy and snowy road performance is improved. In addition, since the first shoulder sipe and the second shoulder sipe are separated from each other in the tire axial direction, the shoulder land portion ensures high rigidity of the shoulder land portion and exhibits excellent steering stability performance on a dry road. . Furthermore, the first shoulder sipe and the second shoulder sipe cooperate to exert a large frictional force equivalent to one virtual sipe that is virtually extended from the first shoulder sipe and joined to the second shoulder sipe. Therefore, the performance on ice and snow roads is further improved.

  Therefore, the pneumatic tire of the present invention improves the snow / snow road performance and the steering stability performance in a well-balanced manner.

It is an expanded view of the tread part of the pneumatic tire of one embodiment of the present invention. It is an enlarged view of the shoulder land part of FIG. It is an enlarged view of the middle land part of FIG. It is an enlarged view of the center land part of FIG. It is a perspective view near a middle chamfer.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a pneumatic tire 1 showing an embodiment of the present invention. A pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment is suitably used as a pneumatic tire for a passenger car, for example.

  As shown in FIG. 1, the tread portion 2 has a shoulder main groove 3 extending continuously in the tire circumferential direction on the tread end Te side, and a tire axial direction inner side of the shoulder main groove 3 continuously in the tire circumferential direction. At least one center main groove 4 extending is provided. One center main groove 4 of this embodiment is provided on each side of the tire equator C (two in total).

  The “tread end” Te is obtained when a normal load is applied to a normal tire 1 that is assembled with a normal rim and filled with a normal internal pressure, and a normal load is applied to the flat tire with a camber angle of 0 degrees. It is determined as the ground contact position on the outermost side in the tire axial direction. In the normal state, the distance in the tire axial direction between the tread ends Te and Te is determined as the tread contact width TW. Unless otherwise noted, the dimensions and the like of each part of the tire are values measured in a normal state.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, ETRTO Then "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JAMATA” is the “maximum air pressure”, TRA is the table “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO. When the tire is for a passenger car, the normal internal pressure is 180 kPa.

  “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” is “maximum load capacity”, TRA is “TIRE LOAD” The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO. When the tire is for a passenger car, the normal load is a load corresponding to 88% of the load.

  Each main groove 3 and 4 is linear along the tire circumferential direction. Such main grooves 3 and 4 increase the rigidity of land portions in the vicinity of the main grooves 3 and 4, suppress unstable behavior such as vehicle wobbling and single flow during braking, and improve steering stability performance. Moreover, since the main grooves 3 and 4 discharge | emit the snow in a groove | channel smoothly to the last arrival side of a rotation direction, snow removal performance is improved.

  The groove width W1 of each of the main grooves 3 and 4 is not particularly limited, but is preferably a tread ground contact width from the viewpoint of improving the snow drainage performance when traveling on a snowy road and the steering stability performance on a dry road with a good balance. 2% to 9% of TW. Further, the groove depth (not shown) of the shoulder main groove 3 and the groove depth Dc (shown in FIG. 5) of the center main groove 4 are preferably 6.5 to 8.5 mm.

  The tread portion 2 is divided into a pair of shoulder land portions 5, a pair of middle land portions 6, and a center land portion 7 disposed on the tire equator C by the main grooves 3 and 4. The shoulder land portion 5 is formed between the shoulder main groove 3 and the tread end Te. The middle land portion 6 is formed between the center main groove 4 and the shoulder main groove 3. The center land portion 7 is formed between the center main grooves 4 and 4.

  FIG. 2 is an enlarged view of the shoulder land portion 5 on the right side of FIG. As shown in FIG. 2, the shoulder land portion 5 is provided with a plurality of first shoulder sipes 8, second shoulder sipes 9, third shoulder sipes 12, and shoulder lug grooves 14 in the tire circumferential direction. . In this specification, a sipe is defined as a narrow groove having a width of less than 2.0 mm. A groove extending in the tire axial direction such as a lug groove is defined as a wide groove-like body having a groove width of 2.0 mm or more.

  The first shoulder sipe 8 extends from the shoulder main groove 3 to the tread end Te side, and the outer end 8e in the tire axial direction terminates in the shoulder land portion 5.

  The second shoulder sipe 9 extends from the inner end 9 i located on the tread end Te side to the tread end Te side with respect to the outer end 8 e of the first shoulder sipe 8. The inner end 9i of the second shoulder sipe 9 is provided at a position where the first shoulder sipe 8 is virtually extended outward in the tire axial direction.

  Since each of these sipes 8 and 9 exhibits a frictional force against the icy and snowy road surface, the icy and snowy road performance is improved. Further, since the first shoulder sipe 8 and the second shoulder sipe 9 are separated from each other in the tire axial direction, the shoulder land portion 5 has high rigidity, and excellent steering stability performance on a dry road is exhibited. Further, the first shoulder sipe 8 and the second shoulder sipe 9 cooperate with each other, so that the first shoulder sipe 8 is virtually extended and the large frictional force equivalent to one virtual sipe joined to the second shoulder sipe 9 is obtained. As a result, icy and snowy road performance is further improved. The “virtually extended position” refers to an aspect in which the inner end 9i of the second shoulder sipe 9 is provided on the extension line 8c obtained by extending the center line of the first shoulder sipe 8, and of course, the extension line 8c and the inner end 9i. And the shortest distance (not shown) includes 3 mm or less.

  In the present embodiment, the second shoulder sipe 9 extends on the extension line 8 c of the first shoulder sipe 8. As a result, the first shoulder sipe 8 and the second shoulder sipe 9 provide a single virtual sipe that extends smoothly, so that even greater frictional force is exerted on the icy snow road, further improving the icy snow road performance. improves. In a more preferred embodiment, the extension line 8 c extends in the second shoulder sipe 9 by at least 50% of the length of the second shoulder sipe 9. In the present embodiment, the extension line 8 c extends in the second shoulder sipe 9.

  In this embodiment, the extension line 8c of the first shoulder sipe 8 forms a smooth arc. Thereby, both the shoulder sipes 8 and 9 exhibit a large frictional force in many directions, and improve the snowy and snowy road performance.

  Between the outer end 8e of the first shoulder sipe 8 and the inner end 9i of the second shoulder sipe 9, there is an interrupted portion 10 where no sipe is formed. When the distance L1 in the tire axial direction of the interrupted portion 10 is large, the first shoulder sipe 8 and the second shoulder sipe 9 cannot cooperate, and the effect of improving the frictional force is greatly reduced. When the distance L1 of the interrupted portion 10 is small, there is a possibility that the rigidity of the shoulder land portion 5 cannot be effectively increased. For this reason, the distance L1 of the discontinuous portion 10 is preferably 5% to 14% of the maximum width Ws of the shoulder land portion 5 in the tire axial direction.

  When the length L2 of the first shoulder sipe 8 in the tire axial direction is small, the interrupted portion 10 is disposed on the shoulder main groove 4 side, and therefore, the rigidity on the tread end Te side on which a greater lateral force acts during turning is greater. There is a risk of significant reduction. For this reason, the length L2 of the first shoulder sipe 8 is preferably 50% or more of the maximum width Ws of the shoulder land portion 5. If the length L2 of the first shoulder sipe 8 in the tire axial direction is excessively large, the rigidity balance of the shoulder main groove 3 side region 5A and the tread end Te side region 5B of the shoulder land portion 5 may be deteriorated. For this reason, the length L2 of the first shoulder sipe 8 is preferably 65% or less of the maximum width Ws of the shoulder land portion 5.

  In this embodiment, the second shoulder sipe 9 extends to the tread end Te. Thereby, the outstanding frictional force with respect to an icy and snowy road is exhibited.

  The depth (not shown) of the first shoulder sipe 8 and the second shoulder sipe 9 is preferably 40 to 80% of the depth of the shoulder main groove 3.

  The shoulder lug groove 14 extends inward in the tire axial direction from the tread end Te, and an inner end 14 i thereof terminates at the shoulder land portion 5. Such a shoulder lug groove 14 can discharge the snow in the lug groove to the outside of the tread end Te, and thus improves the performance on ice and snow roads.

  The groove width W2 of the shoulder lug groove 14 is preferably 30% to 50% of the groove width W1 of the shoulder main groove 3. When the groove width W2 of the shoulder lug groove 14 is large, the rigidity of the shoulder land portion 5 may be greatly reduced. When the groove width W2 of the shoulder lug groove 14 is small, the snow column shearing force becomes small, and the traction on the snow road may be reduced. In the shoulder lug groove 14 of the present embodiment, the groove width W2 gradually increases toward the outer side in the tire axial direction. Thereby, snow is discharged more smoothly.

  In order to increase the snow column shear force while ensuring a large rigidity of the shoulder land portion 5, the length L3 of the shoulder lug groove 14 in the tire axial direction is preferably 70% to 90% of the maximum width Ws of the shoulder land portion 5. %.

  The third shoulder sipe 12 connects between the inner end 14 i of the shoulder lug groove 14 and the shoulder main groove 3. Such a third shoulder sipe 12 can grip more snow by opening and closing the shoulder lug groove 14 at the time of grounding.

  The third shoulder sipe 12 is smoothly connected to the shoulder lug groove 14. Thereby, the rigidity of the shoulder land portion 5 is secured high. In the present embodiment, the sipe edge 12a on one side of the third shoulder sipe 12 and the groove edge 14a on one side of the shoulder lug groove 14 are smoothly connected.

  The depth of the third shoulder sipe 12 is preferably 25 to 80% of the groove depth of the shoulder main groove 3. The groove depth (not shown) of the shoulder lug groove 14 is preferably 50 to 80% of the groove depth of the shoulder main groove 3.

  The shoulder sipes 8, 9, 12 and the shoulder lug groove 14 are inclined in the same direction. Thereby, the rigidity of the shoulder land portion 5 is ensured to be high. In the present embodiment, the angles α1 of the shoulder sipes 8, 9, 12 and the shoulder lug grooves 14 with respect to the tire axial direction are gradually reduced toward the tread end Te side. As a result, the pattern rigidity on the outer side in the tire axial direction of the shoulder land portion 5 to which a relatively large lateral force acts during turning can be improved, so that favorable snowy and snowy road performance can be obtained. From such a viewpoint, the angle α1 of the shoulder sipes 8, 9, 12 and the shoulder lug groove 14 is preferably 30 degrees or less.

  FIG. 3 is an enlarged view of the middle land portion 6 on the right side of FIG. As shown in FIG. 3, the middle land portion 6 includes a plurality of middle lug grooves 18, first middle sipes 21, and second middle sipes 22 in the tire circumferential direction.

  The middle lug groove 18 includes a first middle lug groove 18A and a second middle lug groove 18B. The first middle lug groove 18 </ b> A has a first end 19 a located in the shoulder main groove 3 and a second end 20 a terminating in the middle land portion 6. The second middle lug groove 18B has a first end 19b located in the center main groove 4 and a second end 20b terminating in the middle land portion 6. The first middle lug grooves 18A and the second middle lug grooves 18B are alternately provided in the tire circumferential direction. As a result, a large snow column shear force is exhibited, and the rigidity of the middle land portion 6 can be ensured in a well-balanced manner in the tire axial direction to maintain steering stability performance.

  The middle lug groove 18 changes such that the groove width decreases stepwise from the first end 19 toward the second end 20. Thereby, the snow in the middle lug groove 18 is smoothly discharged into the shoulder main groove 3 or the center main groove 4.

  The middle lug groove 18 of the present embodiment includes a wide portion 23 and a narrow portion 24 having a groove width smaller than that of the wide portion 23. The wide portion 23 has the first end 19 of the middle lug groove 18 and extends inward of the middle land portion 6. The narrow portion 24 is connected to the wide portion 23 via the step portion 25 and has the second end 20 of the middle lug groove 18. The wide portion 23 and the narrow portion 24 of the present embodiment have equal width portions having the same groove width. Since such a middle lug groove 18 has a large edge component, it increases the frictional force with the ice road surface.

  In the present embodiment, the groove edge 23a on one side of the wide portion 23 and the groove edge 24a on one side of the narrow portion 24 form one smooth groove edge. Thereby, the rigidity of the middle land part 6 is ensured higher.

  The length L5 of the wide portion 23 in the tire axial direction is preferably 35% to 50% of the length L6 of the middle lug groove 18 in the tire axial direction. When the length L5 of the wide portion 23 is less than 35% of the length L6 of the middle lug groove 18, the groove volume of the wide portion 23 becomes small, and the snow column shear force may be reduced. When the length L5 of the wide portion 23 exceeds 50% of the length L6 of the middle lug groove 18, the rigidity of the middle land portion 6 may be greatly reduced.

  The groove width W3 of the wide portion 23 is preferably larger than the groove width W4 of the narrow portion 24. Thereby, the snow in the middle lug groove 18 can be smoothly removed to the main grooves 3 and 4 without excessively reducing the rigidity of the middle land portion 6. The groove width W3 of the wide portion 23 is preferably 35% to 55% of the groove width W1 of the shoulder main groove 3.

  The length L6 of the middle lug groove 18 is preferably 50% to 90% of the maximum width Wm of the middle land portion 6 in order to increase the snow column shear force while ensuring the rigidity of the middle land portion 6.

  The first middle sipes 21 are connected between the center main groove 4 and the shoulder main groove 3. A plurality of first middle sipes 21 are provided between the first middle lug groove 18A and the second middle lug groove 18B, and two in the present embodiment.

  The second middle sipe 22 includes a shoulder sipe 22A and a center sipe 22B. The shoulder sipe 22A joins the second end 20b of the second middle lug groove 18B and the shoulder main groove 3. The center sipe 22B joins the second end 20a of the first middle lug groove 18A and the center main groove 4. Thereby, the middle lug groove 18 can be opened and closed greatly, and in order to effectively secure snow, the snow column shear force is increased.

  The second middle sipe 22 is smoothly connected to the middle lug groove 18. Thereby, the rigidity of the middle land portion 6 is ensured to be high. In the present embodiment, the sipe edge 22a on one side of the second middle sipe 22 and the groove edge 18a on one side of the middle lug groove 18 are smoothly connected.

  The middle lug groove 18, the first middle sipe 21, and the second middle sipe 22 are inclined in the same direction. Thereby, the rigidity of the middle land portion 6 is ensured to be high. In the present embodiment, the angles α2 of the middle sipes 21 and 22 and the middle lug groove 18 with respect to the tire axial direction are gradually reduced toward the tread end Te side. As a result, it is possible to increase the pattern rigidity on the outer side in the tire axial direction of the middle land portion 6 to which a relatively large lateral force acts during turning, so that favorable icy and snowy road performance can be obtained.

  Compared with the shoulder land portion 5, the middle land portion 6 is subjected to a larger ground pressure when traveling straight ahead. For this reason, it is desirable that the angle α2 of the middle sipes 21 and 22 and the middle lug groove 18 is larger than the angle α1 of the first shoulder sipe 8. The angle α2 of the middle sipes 21 and 22 and the middle lug groove 18 is preferably 30 to 45 degrees.

  The depth D1 (shown in FIG. 5) of the first middle sipe 21 and the depth (not shown) of the second middle sipe 22 are preferably 25 to 80% of the depth of the shoulder main groove 3. The groove depth (not shown) of the middle lug groove 18 is preferably 50 to 80% of the groove depth of the shoulder main groove 3.

  The middle land portion 6 has a middle land portion piece 26 that is divided between the middle lug groove 18 and a first middle sipe 21 adjacent to the middle lug groove 18.

  The middle land portion piece 26 is provided with a middle chamfered portion 27 inclined inward in the tire radial direction toward the first end 19 side. Such a middle chamfer 27 maintains a high rigidity of the middle land piece 26 in the vicinity of the first end 19 where the rigidity tends to be small, and ensures excellent steering stability performance.

  The middle chamfer 27 includes a first middle chamfer 27A adjacent to the first middle lug groove 18A and a second middle chamfer 27B adjacent to the second middle lug groove 18B. Thereby, since the rigidity of the middle land portion 6 is balanced on both sides in the tire axial direction, the ice / snow road performance and the steering stability performance are further maintained. The middle chamfered portion 27 is formed over the tire circumferential direction of the middle land portion piece 26. Thereby, the above-mentioned operation is effectively exhibited.

  The middle chamfered portion 27 of the present embodiment communicates only with the wide portion 23 of the middle lug groove 18. When the middle chamfered portion 27 extends to the narrow portion 24, the ground contact area of the middle land portion 6 is greatly reduced, and the steering stability performance may be deteriorated. From such a viewpoint, the length L7 of the middle chamfered portion 27 in the tire axial direction is preferably 1 to 4 mm. The maximum depth (not shown) of the middle chamfered portion 27 is preferably 15 to 80% of the groove depth Dc of the center main groove 4.

  FIG. 4 is an enlarged view of the center land portion 7 of FIG. As shown in FIG. 4, the center land portion 7 is provided with a plurality of center lug grooves 30, first center sipes 31, and second center sipes 32 in the tire circumferential direction.

  The center lug groove 30 includes a first center lug groove 30A and a second center lug groove 30B. The first center lug groove 30A has a first end 33a located in one center main groove 4a (right center main groove in FIG. 4) and a second end 34a terminating in the center land portion 7. . The second center lug groove 30B has a first end 33b located in the other side center main groove 4b (left side main main groove in FIG. 4) and a second end 34b terminating in the middle land portion 6. . The first center lug grooves 30A and the second center lug grooves 30B are alternately provided in the tire circumferential direction. As a result, a large snow column shear force is exhibited, and the rigidity of the center land portion 7 is ensured in a well-balanced manner in the tire axial direction, so that the steering stability performance can be maintained.

  The center lug groove 30 changes such that the groove width decreases stepwise from the first end 33 toward the second end 34. Thereby, the snow in the center lug groove 30 is smoothly discharged to the center main groove 4.

  The center lug groove 30 of the present embodiment includes a wide portion 35 and a narrow portion 36 having a groove width smaller than that of the wide portion 35. The wide portion 35 has a first end 33 of the center lug groove 30 and extends from the center main groove 4 toward the inside of the center land portion 7. The narrow portion 36 is connected to the wide portion 35 via the step portion 39 and has the second end 34 of the center lug groove 30. The wide portion 35 and the narrow portion 36 of the present embodiment have equal width portions having the same groove width. Since the center lug groove 30 has a large edge component, the frictional force with the ice road surface is increased.

  In the present embodiment, the groove edge 35a on one side of the wide portion 35 and the groove edge 36a on one side of the narrow portion 36 form one smooth groove edge. Thereby, the rigidity of the center land part 7 is ensured higher.

  The first center sipes 31 are connected between the center main grooves 4 and 4. A plurality of first center sipes 31 are provided between the first center lug groove 30A and the second center lug groove 30B, and two in the present embodiment.

  The second center sipe 32 includes a second center sipe 32a on one side that connects the second center lug groove 30B and the center main groove 4a on one side, a first center lug groove 30A, and the center main groove 4b on the other side. And the second center sipe 32b on the other side. Thereby, the center lug groove 30 can be greatly opened and closed, and in order to ensure snow effectively, the snow column shear force is increased.

  The center lug groove 30, the first center sipe 31, and the second center sipe 32 are inclined in the same direction. In the present embodiment, the angle α3 with respect to the tire axial direction of the center lug groove 30, the first center sipe 31, and the second center sipe 32 is the same. Thereby, the rigidity of the center land part 7 is ensured highly.

  The center lug groove 30 and the middle lug groove 18 are inclined in opposite directions. As a result, the lateral force acting on the center lug groove 30 and the middle lug groove 18 is canceled out, so that the straight running stability performance on ice and snow roads and dry roads is improved. From the viewpoint of effectively exhibiting the above action, the angle α3 of the center sipes 31, 32 and the center lug groove 30 is preferably 35 to 50 degrees.

  The depth (not shown) of the first center sipe 31 and the second center sipe 32 is preferably 25 to 80% of the depth of the shoulder main groove 3. The groove depth D2 (shown in FIG. 5) of the center lug groove 30 is preferably 50 to 80% of the groove depth of the shoulder main groove 3.

  The center land portion 7 has a center land portion piece 37 divided between the center lug groove 30 and a first center sipe 31 adjacent to the center lug groove 30.

  The center land portion piece 37 is provided with a center chamfered portion 38 that is inclined inward in the tire radial direction toward the first end 33 side. Such a center chamfered portion 38 maintains a high rigidity of the center land portion piece 37 in the vicinity of the first end 33, the rigidity of which tends to be small, and ensures excellent steering stability performance.

  The center chamfered portion 38 includes a first center chamfered portion 38A adjacent to the first center lug groove 30A and a second center chamfered portion 38B adjacent to the second center lug groove 30B. As a result, the rigidity of the center land portion 7 is balanced on both sides in the tire axial direction, so that the ice / snow road performance and the steering stability performance are maintained high.

  The center chamfered portion 38 is formed over the tire circumferential direction of the center land portion piece 37. Thereby, the above-mentioned operation is effectively exhibited.

  In the present embodiment, the center chamfered portion 38 communicates only with the wide portion 35 of the center lug groove 30. When the center chamfered portion 38 extends to the narrow portion 36, the ground contact area of the center land portion 7 is greatly reduced, and the steering stability performance may be deteriorated. From such a viewpoint, the length L8 of the center chamfered portion 38 in the tire axial direction is preferably 1 to 4 mm. The maximum depth D3 (shown in FIG. 5) of the center chamfered portion 38 is preferably 15 to 80% of the groove depth Dc of the center main groove 4.

  FIG. 5 is a cross-sectional view of the vicinity of the center chamfered portion 38. As shown in FIGS. 1 and 5, in the present embodiment, an overlapping portion 40 is formed in which the center chamfered portion 38 and the wide portion 23 of the middle lug groove 18 overlap in the tire circumferential direction. Such an overlapping portion 40 forms a groove-like body extending in the tire axial direction with the wide portion 23, the center main groove 4, and the center chamfered portion 38, and exerts a large snow column shearing force to improve the performance of icy and snowy roads. Improve. The wide portion 35 of the center lug groove 30 adjacent to the center chamfered portion 38 and the wide portion 23 of the middle lug groove 18 are displaced in the tire circumferential direction. Thereby, since the snow in the center lug groove 30 and the middle lug groove 18 is discharged | emitted smoothly to the center main groove 4, snow removal performance improves and ice snow road performance improves.

  As mentioned above, although embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention is not limited to illustrated embodiment, and can be deform | transformed and implemented in a various aspect.

A pneumatic tire of size 215 / 60R16 having the basic pattern shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the icy / snow road performance and steering stability performance of each sample tire were tested. The common specifications and test methods for each sample tire are as follows.
Tread contact width TW: 166mm
Middle chamfer length: 2mm
Middle chamfer depth: 2mm
Center chamfer length: 2mm
Center chamfer depth: 2mm
Middle lug groove depth: 6mm
Center lug groove depth: 6mm
In Comparative Example 1, the second shoulder sipe is not provided.

<Ice / snow road performance / operation stability performance>
Each test tire is mounted on all wheels of a 1800cc front-wheel drive passenger car under the following conditions, and the test driver runs the vehicle on a test course on an ice and snow road surface and a test course on a dry asphalt road surface. The driving characteristics related to steering response, traction, grip, etc. were evaluated by the test driver's sensuality. The results are displayed with a score of Comparative Example 1 as 100. The larger the value, the better.
Rim (all wheels): 16 × 6J
Internal pressure (all wheels): 210kPa
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that the icy and snowy road performance and the steering stability performance are improved in a well-balanced manner as compared with the tire of the comparative example. In addition, the same test was carried out by changing the tire size, but showed the same tendency as the test result.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Shoulder main groove 5 Shoulder land part 8 First shoulder sipe 8e Outer end 9 Second shoulder sipe 9i Inner end Te tread end

Claims (6)

A pneumatic tire including a shoulder main groove extending continuously in the tire circumferential direction on the tread end side in the tread portion, and a shoulder land portion on the outer side in the tire axial direction of the shoulder main groove,
In the shoulder land portion, a first shoulder sipe extending from the shoulder main groove to the tread end side and having an outer end in the tire axial direction terminating in the shoulder land portion,
A second shoulder sipe extending from the inner end located on the tread end side to the tread end side from the outer end of the first shoulder sipe,
The inner end of the second shoulder sipe is provided at a position where the first shoulder sipe is virtually extended outward in the tire axial direction,
In the shoulder land portion, a shoulder lug groove extending inward in the tire axial direction from the tread end and the inner end terminating in the shoulder land portion,
A third shoulder sipe that connects between the inner end of the shoulder lug groove and the shoulder main groove is provided;
The pneumatic tire according to claim 1, wherein the first shoulder sipe, the second shoulder sipe, and the third shoulder sipe have a width of less than 2.0 mm.   The pneumatic tire according to claim 1, wherein the second shoulder sipe extends on an extension line obtained by virtually extending the first shoulder sipe outward in the tire axial direction. The tread portion includes at least one center main groove extending continuously in the tire circumferential direction on the inner side in the tire axial direction of the shoulder main groove, and a middle section divided between the shoulder main groove and the center main groove. Including the land,
The middle land portion is provided with a plurality of middle lug grooves having a first end located in the center main groove or the shoulder main groove and a second end terminating in the middle land portion,
3. The pneumatic tire according to claim 1, wherein a groove width of the middle lug groove is changed in a stepwise manner from the first end toward the second end. The middle land portion is provided with a plurality of first middle sipes that connect between the center main groove and the shoulder main groove,
The land piece segmented between the middle lug groove and the first middle sipe adjacent to the middle lug groove is provided with a chamfered portion inclined inward in the tire radial direction toward the first end side. 3. The pneumatic tire according to 3.   The middle land portion is provided with a second middle sipe extending from the second end of the middle lug groove to the opposite side to the first end and communicating with the center main groove or the shoulder main groove. The pneumatic tire according to 3 or 4. The tread portion includes a pair of center main grooves extending continuously in the tire circumferential direction inside the tire main groove in the tire axial direction, and a center land portion divided between the center main grooves,
The center land portion is provided with a plurality of center lug grooves having a first end located in the center main groove and a second end terminating in the center land portion,
The pneumatic tire according to any one of claims 1 to 5, wherein a groove width of the center lug groove is changed in a stepwise manner from the first end toward the second end.

Images