JP2017043120A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve drainage performance, snow-road performance, and ice-road performance with good balance.SOLUTION: The pneumatic tire comprises a pair of middle block rows 6R in which middle blocks 6A partitioned by center main grooves 3A, shoulder main grooves 3B, and middle lateral grooves 4A are disposed at intervals in a tire circumference direction, and a pair of shoulder land parts 7 partitioned by the shoulder main grooves 3B and a grounding end Te, whose rotation direction R is specified. The middle blocks 6A are provided with a middle siping 13 and middle thin grooves 14 which are inclined from the middle lateral grooves 4A to a tire equator C, toward a first arrival side in the rotation direction R, and terminated in the middle blocks 6A. The middle thin grooves 14 are 2.0-5.0 mm in groove widths and comprise sharrow groove parts 15 which are small in groove depths at a last arrival side in the rotation direction R.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire in which snow / ice road performance, particularly traction performance on snow road and ABS brake performance (brake performance of an antilock brake system) are improved in a well-balanced manner.

  There is known a winter pneumatic tire having a block pattern in which snow removal performance is enhanced by providing a tread portion with a main groove extending in the tire circumferential direction and a lateral groove connecting between the main grooves.

  FIG. 7 shows a graph showing the relationship between the friction coefficient and the slip ratio, where the vertical axis represents the friction coefficient and the horizontal axis represents the slip ratio. In the graph of FIG. 7, a tire having a high rigidity in the center land portion of the tread portion is indicated by a solid line, and a tire having a low rigidity is indicated by a broken line. A tire with a low rigidity at the center land portion has a lower coefficient of friction at a slip rate of 20% to 30%, which is a practical range of ABS brake operation, than a tire with a high rigidity. For this reason, a tire with low rigidity in the center land portion has a wheel speed that is less likely to follow the vehicle body speed than a tire with high rigidity. As a result, a tire having a low rigidity at the center land portion has a slower recovery of the wheel speed (that is, a reduction in the slip ratio) and a longer time for releasing the ABS than a tire having a high rigidity. It stretches. Therefore, a tire having a low rigidity in the center land portion has a problem that a brake performance during ABS operation (hereinafter, referred to as “ABS brake performance”) is deteriorated as compared with a tire having a high rigidity. Related technologies include the following.

JP 2009-269500 A

  The present invention has been devised in view of the actual situation as described above. The middle block is provided with middle siping and middle narrow grooves, and the groove width, groove depth and shape of the middle narrow grooves are defined. The main purpose of the present invention is to provide a pneumatic tire in which snow road performance, in particular, traction performance on snow road and braking performance during ABS operation are improved in a well-balanced manner.

  The present invention provides one or two center main grooves extending continuously in the tire circumferential direction on the tire equator or on both sides in the tire axial direction of the tire equator in the tread portion, and the tire axially outer side of the center main groove on the tire. The center main groove and the shoulder main groove are provided by providing a pair of shoulder main grooves extending continuously in the circumferential direction and a plurality of middle lateral grooves that connect between the center main groove and the shoulder main groove. A pair of middle block rows in which middle blocks divided by the middle lateral grooves are separated in the tire circumferential direction, and a pair of shoulder land portions divided by the shoulder main groove and the ground contact end, and rotate. A pneumatic tire having a designated direction, wherein the middle block is inclined toward the tire equator side toward middle arrival and a first arrival side in a rotational direction from the middle lateral groove, And a middle narrow groove that terminates in the middle block, the middle narrow groove has a groove width of 2.0 to 5.0 mm, and a groove depth is small on the rear arrival side in the rotational direction. It comprises a shallow groove part.

  In the pneumatic tire according to the present invention, the middle siping includes a middle inner sipe extending inward in the tire axial direction from the middle narrow groove, and a middle outer sipe extending in the tire axial direction outward from the middle narrow groove, It is preferable that the middle inner sipe and the middle outer sipe extend from the middle narrow groove toward the rear arrival side in the rotation direction.

  The pneumatic tire according to the present invention has a ground contact surface in which a normal load is loaded on a normal rim and filled with a normal internal pressure, and a normal load is applied to the flat rim at a camber angle of 0 °. When ½ of the maximum width in the tire axial direction is the ground contact half width, the maximum width in the tire axial direction of the middle block on the ground contact surface is preferably 35% to 45% of the ground contact half width.

  In the pneumatic tire according to the present invention, it is preferable that the groove width of the middle narrow groove is 0.3 to 0.8 times the groove width of the middle lateral groove.

  In the pneumatic tire according to the present invention, the middle narrow groove includes a deep groove portion having a groove depth larger than the shallow groove portion, and the groove depth of the deep groove portion is 70% of the groove depth of the center main groove. It is desirable that it is ˜100%.

  The present invention provides one or two center main grooves extending continuously in the tire circumferential direction on the tire equator or on both sides in the tire axial direction of the tire equator in the tread portion, and the tire axially outer side of the center main groove on the tire. The center main groove and the shoulder main groove are provided by providing a pair of shoulder main grooves extending continuously in the circumferential direction and a plurality of middle lateral grooves that connect between the center main groove and the shoulder main groove. A pair of middle block rows in which middle blocks divided by the middle lateral grooves are separated in the tire circumferential direction, and a pair of shoulder land portions divided by the shoulder main groove and the ground contact end, and rotate. A pneumatic tire having a designated direction, wherein the middle block has middle siping and ends at both ends in the middle block, and is directed toward the first arrival side in the rotational direction. With inclined to the tire equator side, width is characterized in that it is provided with a middle slot is 2.0 to 5.0 mm.

  In the pneumatic tire of the present invention, one or two center main grooves extending continuously in the tire circumferential direction on the tire equator or on both sides in the tire axial direction of the tire equator in the tread portion, and the tire shaft of the center main groove A center main groove and a shoulder main groove are provided by providing a pair of shoulder main grooves extending continuously in the tire circumferential direction and a plurality of middle lateral grooves connecting between the center main groove and the shoulder main grooves. A pair of middle block rows in which middle blocks separated by middle lateral grooves are spaced apart in the tire circumferential direction; and a pair of shoulder land portions separated by shoulder main grooves and ground contact ends; and the rotational direction is It is specified.

  The middle block is provided with middle siping and a middle narrow groove that is inclined toward the tire equator side from the middle lateral groove toward the first arrival side in the rotation direction and ends in the middle block. Since middle siping has an edge component in the tire axial direction or the tire circumferential direction, it improves ice road performance. Since the middle narrow groove has a tire axial component, it improves the traction performance on snowy roads. Further, since the stress in the tire axial direction acts on the middle narrow groove from the middle block due to grounding, snow in the groove is pushed out. Thereby, snow removal performance improves. Furthermore, the middle narrow groove is inclined outward in the tire axial direction toward the rear arrival side in the rotational direction. For this reason, the snow in the middle narrow groove is smoothly discharged to the shoulder main groove using the rotation of the tire. Therefore, the snow removal performance is further improved.

  The middle narrow groove has a groove width of 2.0 to 5.0 mm. Such middle narrow grooves enhance the middle block block rigidity and snow removal performance in a well-balanced manner. Moreover, since the middle narrow groove includes a shallow groove portion having a small groove depth on the rear arrival side in the rotation direction, the rigidity of the middle block is further enhanced. Therefore, since the recovery of the wheel speed is accelerated at the time of braking when the ABS is operated, the ABS brake performance is improved. Further, when the middle block in the vicinity of the shallow groove portion is grounded, stress on the first arrival side acts on the shallow groove portion. Thereby, snow removal performance improves further.

It is an expanded view of the tread part which shows one Embodiment of this invention. It is AA sectional drawing of FIG. It is an enlarged view of the middle block of FIG. It is a perspective view of a middle block. It is an enlarged view of the center block of FIG. It is an expanded view of the tread part which shows other embodiment of this invention. It is a figure which shows the relationship between the friction coefficient at the time of ABS brake, and a slip ratio.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the pneumatic tire of this embodiment (hereinafter, simply referred to as “tire”) can be suitably used as, for example, a winter tire and has an asymmetric configuration in which the rotation direction R of the tire is specified. With a tread pattern. The rotation direction R of the tire is displayed by characters or the like on a sidewall portion (not shown), for example.

  The tread portion 2 of the tire according to the present embodiment includes a pair of center main grooves 3A extending continuously in the tire circumferential direction on both sides in the tire axial direction of the tire equator C, and the tire axial direction outside of the center main groove 3A on the tire circumferential side. A pair of shoulder main grooves 3B extending continuously in the direction is provided. Thereby, in the tread portion 2 of the present embodiment, one center land portion 5, a pair of middle land portions 6, 6, and a pair of shoulder land portions 7, 7 are formed. The center land portion 5 is divided by a pair of center main grooves 3A and 3A. The middle land portion 6 is divided into a center main groove 3A and a shoulder main groove 3B. The shoulder land portion 7 is divided by the shoulder main groove 3B and the ground contact end Te. The center main groove 3A may be, for example, one groove extending continuously on the tire equator C in the tire circumferential direction.

  The “grounding end” Te is applied to a flat tire with a camber angle of 0 ° by applying a normal load to an unloaded normal tire that is assembled to a normal rim (not shown) and filled with a normal internal pressure. It is determined as a contact position on the outermost side in the tire axial direction of the contact surface. A distance in the tire axial direction between the ground contact Te and Te is determined as a ground contact width TW, and a distance ½ of the ground contact width TW is defined as a ground half width BW. When there is no notice in particular, the dimension of each part of a tire, etc. are values measured in this normal state.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. “Standard Rim” for JATMA, “Design Rim” for TRA For ETRTO, "Measuring Rim". In addition, the “regular internal pressure” is an air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum value described in TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" for ETRTO, but 180 kPa for tires for passenger cars.

  The “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. “Maximum load capacity” for JATMA, “Table for TRA” The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is for a passenger car, the load is equivalent to 88% of the load.

  The center main groove 3A of the present embodiment includes a long side portion 8 inclined toward the tire equator C side toward the rotational direction first arrival side, and a short side portion 9 inclined toward the ground contact end Te toward the rotational direction first arrival side. It becomes a zigzag shape. The short side portion 9 connects between the long side portions 8 and 8 and has a smaller length in the tire circumferential direction than the long side portion 8. Since the center main groove 3A increases the edge component in the tire axial direction, the snow column shearing force, driving force, and braking force are increased. Therefore, snow road performance and ice road performance are improved.

  When the angle α1a with respect to the tire circumferential direction of the long side portion 8 becomes small, the edge component in the tire axial direction may be reduced. When the angle α1a of the long side portion 8 is increased, the snow drainage resistance of the center main groove 3A is increased, and the snow drainage performance may be deteriorated. For this reason, the angle α1a of the long side portion 8 is preferably 7 ° or more, and preferably 18 ° or less. From the same viewpoint, the angle α1b of the short side portion 9 with respect to the tire circumferential direction is preferably 40 ° or more, and preferably 60 ° or less. The angle α1a of the long side portion 8 is obtained as the angle of the groove center line 10a. Further, the angle α1b of the short side portion 9 is obtained as the angle of the groove center line 10b. Moreover, the groove center line 10 of the center main groove 3A including the groove center lines 10a and 10b is obtained as a straight line that alternately connects the intermediate points s1 and the intermediate points s2. The intermediate point s1 is the innermost point a1 in the tire axial direction of the inner groove edge 10x on the inner side in the tire axial direction of the center main groove 3A, and the tire axial direction of the outer groove edge 10y on the outer side in the tire axial direction of the center main groove 3A. It is provided at an intermediate position with the innermost point a2. The intermediate point s2 is provided at an intermediate position between the outermost point a3 in the tire axial direction of the inner groove edge 10x and the outermost point a4 in the tire axial direction of the outer groove edge 10y.

  The shoulder main groove 3B of the present embodiment has a linear shape along the tire circumferential direction. Such a shoulder main groove 3B can improve snow discharge performance by smoothly discharging the snow in the groove toward the rear arrival side in the rotation direction.

  About the groove width of each main groove 3A, 3B (the groove width perpendicular to the groove center line, hereinafter the same applies to other grooves) W1a, W1b and groove depths D1a, D1b (shown in FIG. 2) Various definitions can be made in accordance with common practice. However, if these groove widths or groove depths are reduced, snow road performance may be deteriorated. Conversely, when these groove widths or groove depths are increased, the rigidity of the land portions 5 to 7 may be reduced. For this reason, the groove widths W1a and W1b of the main grooves 3A and 3B are preferably 2% to 8% of the grounding width TW, for example. As for groove depth D1a, D1b of each main groove 3A, 3B, 8.0-14.0 mm is desirable, for example.

  In this embodiment, the tire axial distance L1 between the center main groove 3A and the tire equator C is preferably equal to the contact width TW in order to secure the rigidity in the tire axial direction of the land portions 5 to 7 in a balanced manner. 5% to 15%. Further, the tire axial direction distance L2 between the shoulder main groove 3B and the tire equator C is preferably 30% to 40% of the ground contact width TW. The positions of the main grooves 3A and 3B are specified by the groove center lines 10 and 11, but the groove center line 10 is a zigzag non-linear shape like the center main groove 3A of the present embodiment. In this case, the center line G1 having the amplitude of the groove center line 10 is used.

  In the middle land portion 6, middle lateral grooves 4 </ b> A that connect between the center main groove 3 </ b> A and the shoulder main grooves 3 </ b> B are provided in the tire circumferential direction. Accordingly, the middle land portion 6 is formed as a middle block row 6R in which middle blocks 6A divided between the middle lateral grooves 4A and 4A are spaced in the tire circumferential direction.

  The middle lateral groove 4A extends from the center main groove 3A toward the shoulder main groove 3B while being inclined toward the rear arrival side in the rotation direction R. Such a middle lateral groove 4A can obtain a snow column shear force by pressing and solidifying snow in the groove, and can improve snow road performance. Note that when the groove width W2 and the groove depth D2 of the middle lateral groove 4A are increased, the rigidity of the middle block 6A may be decreased. For this reason, the groove width W2 of the middle lateral groove 4A is preferably 8% to 16% of one pitch length P of the middle block 6A. The groove depth D2 (shown in FIG. 2) is preferably 80% to 120% of the groove depth D1a of the center main groove 3A.

  FIG. 3 shows a middle land portion 6 on the right side of the tread portion 2 of FIG. As shown in FIG. 3, the middle lateral groove 4A preferably includes a steeply inclined portion 12a and a gently inclined portion 12b. The steeply inclined portion 12a extends at an angle α2a of 60 to 80 degrees with respect to the tire circumferential direction from the center main groove 3A. The gently inclined portion 12b extends from the steeply inclined portion 12a with an angle α2b (> α2a) of 70 to 90 degrees with respect to the tire circumferential direction.

  Such a steeply inclined portion 12a can efficiently discharge the snow in the groove to the shoulder main groove 3B side, and can greatly improve the snow discharging performance. Moreover, since the gentle inclination part 12b has a large tire axial direction component, it can improve a snow column shear force. The middle lateral groove 4A is not limited to such an aspect, and may be an aspect (α2a = α2b) extending linearly.

  The middle block 6A includes a middle siping 13 and a middle narrow groove that is inclined toward the tire equator C side from the middle lateral groove 4A toward the first arrival side (lower side in FIG. 3) in the rotational direction R and ends in the middle block 6A. 14 are provided. Accordingly, the middle block 6A is divided into a first arrival side piece 17A, an inner piece 17B, and an outer piece 17C. The first arrival side small piece 17A extends from the center main groove 3A to the shoulder main groove 3B on the first end side in the rotational direction R of the middle narrow groove 14 without interruption. The inner small piece 17B is sandwiched between the middle narrow groove 14 and the center main groove 3A on the rear arrival side in the rotation direction R of the first arrival side small piece 17A. The outer small piece 17C is sandwiched between the middle narrow groove 14 and the shoulder main groove 3B on the rear arrival side in the rotation direction R of the first arrival side small piece 17A.

  Since the middle siping 13 has an edge component in the tire axial direction or the tire circumferential direction, the ice road performance is improved. Since the middle narrow groove 14 has a tire axial component, it improves the traction performance on snowy roads. Further, since the stress in the tire axial direction acts on the middle narrow groove 14 from the middle block 6A (the inner small piece 17B and the outer small piece 17C) due to grounding, snow in the groove is pushed out. Thereby, snow removal performance improves. Further, the middle narrow groove 14 is inclined outward in the tire axial direction toward the rear arrival side in the rotation direction R. For this reason, the snow in a groove | channel is discharged | emitted smoothly using the rotation of a tire to the shoulder main groove | channel 3B. Therefore, the snow removal performance is further improved.

  The first arrival side small piece 17A increases the rigidity of the first arrival side of the middle block 6A. Therefore, the fall of the middle block 6A during ABS braking is suppressed and the recovery of the wheel speed is accelerated, so that the ABS brake performance is improved. In order to effectively exhibit such an action, the shortest distance L3 between the middle narrow groove 14 and the middle lateral groove 4A is preferably 5% or more of the maximum length L4 in the tire circumferential direction of the middle block 6A. When the shortest distance L3 is large, the tire axial direction component of the middle narrow groove 14 may be small. For this reason, the shortest distance L3 is preferably 13% or less of the maximum length L4 of the middle block 6A.

  The maximum width W3 in the tire axial direction of the middle block 6A is preferably 35% to 45% of the ground contact half width BW. When the maximum width W3 of the middle block 6A is small, the length of the middle lateral groove 4A in the tire axial direction is not secured, and the snow column shear force may be reduced. Further, the rigidity of the middle block 6A in the tire axial direction may be reduced. Conversely, when the maximum width W3 of the middle block 6A is large, the rigidity in the tire axial direction of the center land portion 5 and the shoulder land portion 7 may be reduced.

  Further, the maximum width W4 of the inner small piece 17B in the tire axial direction is preferably 15% to 25% of the ground contact half width BW. Similarly, the maximum width W5 of the outer small piece 17C in the tire axial direction is preferably 15 to 30% of the ground contact half width BW. Thereby, the rigidity in the tire axial direction of the inner small piece 17B and the outer small piece 17C is ensured in a well-balanced manner, and uneven wear resistance is improved.

  The inner small piece 17B has an inner rear edge 18a extending in the tire axial direction on the rear arrival side in the rotation direction R. The angle θ1 of the inner rear edge 18a with respect to the tire axial direction is preferably 10 to 30 °. When the angle θ1 is small, the edge component in the tire circumferential direction becomes small, and the turning performance may be deteriorated. When the angle θ1 is large, the rigidity in the tire circumferential direction of the inner small piece 17B is reduced, and the traction performance may be deteriorated.

  The outer small piece 17C has an outer rear edge 18b extending in the tire axial direction on the rear arrival side in the rotation direction R. An angle θ2 between the outer rear edge 18b and the outer groove edge 14a in the tire axial direction of the middle narrow groove 14 is preferably 100 to 140 °. Thereby, the rigidity of the outer small piece 17C can be largely maintained.

  When the groove width W6 of the middle narrow groove 14 exceeds 5.0 mm, the rigidity of the middle block 6A is lowered and the ABS brake performance is deteriorated. Conversely, when the groove width W6 is less than 2.5 mm, the snow removal performance deteriorates. From such a viewpoint, the groove width W6 is more preferably 4.5 mm or less, and more preferably 3.0 mm or more.

  When the angle α3 of the middle narrow groove 14 with respect to the tire circumferential direction is small, the tire axial direction component is small, and the traction performance on a snowy road may be small. On the other hand, when the angle α3 of the middle narrow groove 14 is large, the rigidity of the inner small piece 17B and the outer small piece 17C is reduced, and the uneven wear resistance performance may be deteriorated. For this reason, the angle α3 of the middle narrow groove 14 is preferably 5 ° or more, more preferably 7 ° or more, preferably 30 ° or less, more preferably 25 ° or less.

  The middle narrow groove 14 includes a shallow groove portion 15 having a small groove depth extending toward the rear arrival side in the rotation direction R, and a deep groove portion disposed on the first arrival side with respect to the shallow groove portion 15 and having a groove depth larger than the shallow groove portion 15. 16 and. Such a shallow groove portion 15 further increases the rigidity of the middle block 6A. Therefore, the recovery of the wheel speed is accelerated during braking with the ABS operated, and the ABS brake performance is improved. Further, when the inner rear edge 18a and the outer rear edge 18b are grounded, stress on the first arrival side acts on the shallow groove portion 15. Thereby, snow removal starts from the shallow groove portion 15, and the snow of the entire middle narrow groove 14 can be smoothly discharged. For this reason, the snow removal performance is further improved.

  In order to perform snow removal from the shallow groove portion 15 more smoothly, the groove width W6 of the middle narrow groove 14 is 0.5 to 0.9 times the groove width W2 (shown in FIG. 1) of the middle lateral groove 4A. It is desirable.

  When the length L5 in the tire circumferential direction of the shallow groove portion 15 is small, there is a possibility that the above-described action cannot be effectively exhibited. Conversely, if the length L5 of the shallow groove portion 15 in the tire circumferential direction is large, the snow column shear force may be reduced. For this reason, the length L5 of the shallow groove portion 15 is preferably 15% to 45% of the maximum length L4 of the middle block 6A. Further, it is desirable that the shallow groove portion 15 extends from the middle lateral groove 4A.

  FIG. 4 shows a perspective view of the middle block 6A. As shown in FIG. 4, the groove depth D3a of the shallow groove portion 15 is preferably 30% or more, more preferably 35% or more of the groove depth D3b of the deep groove portion 16, and preferably 60% or less. More preferably, it is 55% or less. Thereby, the ABS brake performance and the snow removal performance are improved in a more balanced manner.

  The groove depth D3b of the deep groove portion 16 of the middle narrow groove 14 is preferably 70% or more of the groove depth D1a (shown in FIG. 2) of the center main groove 3A in order to exert a large snow column shearing force, more preferably 75% or more. When the groove depth of the deep groove portion 16 is large, the rigidity of the middle block 6A may be reduced. For this reason, the groove depth D3b of the deep groove portion 16 is preferably 100% or less, more preferably 95% or less of the groove depth D1a of the center main groove 3A.

  As shown in FIG. 3, the middle siping 13 includes a middle inner sipe 13A, an outer sipe 13B, and an inner small sipe 13C. The middle inner sipe 13A extends inward in the tire axial direction from the middle narrow groove 14. The middle outer sipe 13B extends from the middle narrow groove 14 to the outer side in the tire axial direction. The inner small sipe 13C is a semi-open type in which one end is opened by the center main groove 3A and the other end is terminated in the middle block 6A.

  The middle inner sipe 13A and the middle outer sipe 13B extend from the middle narrow groove 14 to the rear arrival side in the rotation direction R. Such sipes 13A and 13B reduce the inner narrow piece 17B and the outer small piece 17C in the direction of narrowing the groove width of the middle narrow groove 14 during braking that receives external force from the road surface from the first arrival side to the rear arrival side in the rotation direction R. Can be transformed into Therefore, the snow in the middle narrow groove 14 is more smoothly discharged.

  The middle inner sipe 13A is an open-type siping that connects between the middle narrow groove 14 and the center main groove 3A or the middle lateral groove 4A. Similarly, the middle outer sipe 13B is an open-type siping that connects between the middle narrow groove 14 and the shoulder main groove 3B. By such middle inner sipe 13A and middle outer sipe 13B, the inner small piece 17B and the outer small piece 17C are easily deformed, and the draining effect using the middle narrow groove 14 is enhanced.

  The middle inner sipe 13A and the middle outer sipe 13B preferably have an angle α4 with respect to the tire axial direction of 5 to 30 °. When the angle α4 is small, the inner small piece 17B and the outer small piece 17C may not be sufficiently deformed toward the middle narrow groove 14 side. On the other hand, when the angle α4 is large, the edge component in the tire axial direction is excessively decreased, and the traction performance may be decreased. From such a viewpoint, the angle α4 is more preferably 15 ° or more, and more preferably 25 ° or less.

  Further, it is desirable that the angle α4 of the middle inner sipe 13A and the middle outer sipe 13B is the same. Thereby, since the inner small piece 17B and the outer small piece 17C can be uniformly deformed, uneven wear on the inner small piece 17B and the outer small piece 17C is suppressed.

  The inner small sipe 13C can increase the edge component while suppressing the decrease in rigidity of the first arrival side piece 17A, and can improve the performance on ice. In order to effectively exhibit such an action, it is desirable that the inner small sipe 13C extends in parallel with the middle inner sipe 13A.

  As shown in FIG. 1, the center land portion 5 has a center sub-groove 20 extending continuously along the tire equator C, and a center lateral groove 4B extending between the center sub-groove 20 and the center main groove 3A. Provided. Thus, the center land portion 5 is formed as a center block row 5R in which center blocks 5A divided by the center sub-groove 20, the center main groove 3A, and the center lateral groove 4B are spaced in the tire circumferential direction.

  FIG. 5 shows an enlarged view of the center land portion 5. As shown in FIG. 5, the center sub-groove 20 includes a first inclined portion 20a and a second inclined portion 20b. The first inclined portion 20a is inclined toward the rotation direction R on one side in the tire axial direction (in FIG. 5, it is inclined on the right side toward the arrival side in the rotation direction). The second inclined portion 20b connects the first inclined portions 20a and 20a and is inclined to the other side in the tire axial direction. Such a center sub-groove 20 improves the steering stability performance on a snowy road in a well-balanced manner while suppressing a decrease in rigidity of the center land portion 5. For this reason, the groove width W8 of the center sub-groove 20 is preferably 0.5% to 1.5% of the ground contact width TW and is smaller than the main groove. The groove depth D4 (shown in FIG. 2) is preferably 20% to 50% of the groove depth D1a of the center main groove 3A.

  In addition, in the first inclined portion 20a and the second inclined portion 20b of the present embodiment, angles α5a and α5b with respect to the tire circumferential direction and lengths L6a and L6b in the tire circumferential direction are set to be the same. Thereby, the center subgroove 20 can exhibit the edge component of each 1st inclination part 20a and the 2nd inclination part 20b with sufficient balance, and can improve on-ice performance.

  In order to effectively exhibit the above-described action, the angles α5a and α5b are preferably 3 to 10 °. The lengths L6a and L6b are preferably 5% to 11% of the ground contact width TW (shown in FIG. 1). The angles α5a and α5b and the lengths L6a and L6b are specified on the groove center line 20c of the center sub-groove 20.

  The center lateral groove 4B extends from the zigzag apex 21 of the center sub-groove 20 to the rear side of the rotational direction R from the one side or the other side in the tire axial direction. Such center lateral groove 4B can effectively increase the edge component in the tire axial direction and the snow column shear force. The groove width W9 of the center lateral groove 4B is preferably 0.5% to 1.5% of the ground contact width TW. The groove depth D5 (shown in FIG. 2) is preferably 50% to 80% of the groove depth D1a of the center main groove 3A. Furthermore, the angle α6 of the center lateral groove 4B with respect to the tire axial direction is preferably 10 to 30 °.

  The center block 5A is provided with a slot 22 extending in a reverse direction from the zigzag apex 21 of the center sub-groove 20 to the center lateral groove 4B and terminating in the center block 5A. Such a slot 22 effectively increases the snow column shearing force of the center lateral groove 4B. Further, the slot 22 ensures the rigidity of the center block 5A and maintains the ABS brake performance. In order to effectively exhibit the above-described action, the groove width W10 of the slot 22 is preferably 0.5% to 1.5% of the ground contact width TW (shown in FIG. 1). The groove depth D6 (shown in FIG. 2) is preferably 60% to 100% of the groove depth D1a of the center main groove 3A. Further, the angle α7 of the slot 22 with respect to the tire axial direction is preferably the same as the angle α6 of the center lateral groove 4B.

  In the center block 5A, an open type center siping 23 that connects between the center sub-groove 20 and the center main groove 3A is provided in the tire circumferential direction. Such a center siping 23 further improves the performance on ice.

  The center siping 23 is preferably inclined at the same angle as the center lateral groove 4B and the slot 22 arranged in the tire circumferential direction. Thereby, the rigidity of the center block 5A is ensured greatly, and the ABS brake performance is further improved.

  As shown in FIG. 1, the shoulder land portion 7 has shoulder lateral grooves 4 </ b> C communicating between the shoulder main grooves 3 </ b> B and the ground contact Te in the tire circumferential direction. Thereby, the shoulder land portion 7 is formed as a shoulder block row 7R in which a shoulder block 7A sandwiched between the shoulder lateral grooves 4C and 4C is provided.

  In this embodiment, the shoulder lateral groove 4C extends in a zigzag shape. Such a shoulder lateral groove 4C has a tire circumferential direction component, and can improve turning performance on an icy road. The groove width W11 of the shoulder lateral groove 28 is preferably 2% to 4% of the ground contact width TW in order to ensure a good balance between the snow column shearing force and the rigidity of the shoulder block 7A. The groove depth D8 (shown in FIG. 2) is preferably 70% to 100% of the groove depth D1b of the shoulder main groove 3B.

  Further, the shoulder block 7A is provided with a semi-open type shoulder siping 26 extending outward from the shoulder main groove 3B in the tire axial direction and terminating in the shoulder block 7A. Such shoulder siping 26 improves the ice road performance and the snow road performance in order to secure a large edge component while suppressing a decrease in the rigidity of the shoulder block 7A. The angle α8 of the shoulder siping 26 with respect to the tire axial direction is preferably 1 to 10 °.

  FIG. 6 shows a tread portion 2 according to another embodiment of the present invention. As shown in FIG. 6, the middle block 6A is provided with a middle slot 30 that is inclined toward the tire equator C side toward the rotational direction R first arrival side and ends at both ends in the middle block 6A. That is, the middle block 6A of this embodiment is different from the middle block 6A of the previous embodiment in that the groove depth of the shallow groove portion 15 is set to 0 mm. Since such a middle slot 30 further increases the block rigidity of the middle block 6A on the rear arrival side in the rotational direction, the ABS brake performance is further improved. In order to improve the ABS braking performance and the traction performance due to the edge component of the middle slot 30 in the tire axial direction in a well-balanced manner, the shortest distance L7 between the middle slot 30 and the middle lateral groove 4A is preferably the maximum length L4 of the middle block 6A. 5% to 13%.

  The groove width W12 of the middle slot 30 is preferably 2.0 to 5.0 mm. The groove depth (not shown) is preferably 70% to 100% of the groove depth D1a of the center main groove 3A. Further, the angle α9 of the middle slot 30 with respect to the tire circumferential direction is 5 to 40 °.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, this invention is changed and implemented in various aspects, without being limited to said specific embodiment.

A pneumatic tire of size 225 / 65R17 having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1, and the traction performance and ABS brake performance of each sample tire were tested. The common specifications are as follows.
Grounding width TW: 180mm
Center main groove:
Groove width W1a: 8.0 mm
Groove depth D1a: 11.2mm
Shoulder main groove:
Groove width W1b: 8.0 mm
Groove depth D1b: 11.2mm
Middle lateral groove:
Groove width W2: 4.0 mm
Groove depth D2: 10.2 mm
Middle narrow groove:
Angle α3: 6 °
Center minor groove Groove width W8: 3.0mm
Groove depth D4: 6.5 mm
Center lateral groove Groove width W9: 2.5mm
Groove depth D5: 6.0 mm
Shoulder lateral groove Groove width W11: 6.0 mm
Groove depth D8: 10.0mm
Middle slot Groove depth: 9.0mm
Angle α9: 7 °
The test method is as follows.

<Traction performance on snowy roads>
Each sample tire was mounted on all wheels of a 3500cc four-wheel drive vehicle under the following conditions, and a test course on a snowy road (excluding a snowy snowy road) was run by one driver. The driving characteristics related to gripping force at the time of starting, accelerating and turning were evaluated by the driver's sensuality. The results are displayed with a score of Example 1 being 100. The larger the value, the better.
Rim: 17 × 6.5J
Internal pressure: 220kPa (4 wheels)

<ABS brake performance>
Using the test vehicle, the braking distance from the speed of 30 km / h until the vehicle was stopped was measured on the mirror burn-like icy road under the temperature of 0 ° C., and the brake was applied. The result is an index with the braking distance of Example 1 as 100, and the larger the value, the better.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples had significantly improved traction performance and ABS brake performance on snowy roads as compared with the comparative examples.

3A Center main groove 3B Shoulder main groove 4A Middle lateral groove 6A Middle block 6R Middle block row 7 Shoulder land 13 Middle siping 14 Middle narrow groove 15 Shallow groove C Tire equator R Rotating direction Te Grounding end

Claims (6)

One or two center main grooves extending continuously in the tire circumferential direction on the tire equator or on both sides in the tire axial direction of the tire equator in the tread portion, and continuously on the tire axial direction outside of the center main groove in the tire circumferential direction By providing a pair of shoulder main grooves extending and a plurality of middle lateral grooves that connect between the center main groove and the shoulder main groove,
A pair of middle block rows in which middle blocks divided by the center main groove, the shoulder main groove, and the middle lateral groove are separated in the tire circumferential direction;
Comprising a pair of shoulder land sections separated by the shoulder main groove and the ground contact end, and
A pneumatic tire with a specified direction of rotation,
The middle block is provided with middle siping and a middle narrow groove that is inclined toward the tire equator side toward the first arrival side in the rotational direction from the middle lateral groove and ends in the middle block,
The pneumatic tire according to claim 1, wherein the middle narrow groove has a groove width of 2.0 to 5.0 mm and a shallow groove portion having a small groove depth on a rear arrival side in the rotation direction. The middle siping includes a middle inner sipe extending inward in the tire axial direction from the middle narrow groove, and a middle outer sipe extending in the tire axial direction outward from the middle narrow groove,
2. The pneumatic tire according to claim 1, wherein the middle inner sipe and the middle outer sipe extend from the middle narrow groove toward a rear arrival side in the rotation direction. 1 / of the maximum width in the tire axial direction of the ground contact surface that is loaded with a normal load and grounded to a flat surface with a camber angle of 0 ° on a normal tire with a normal rim assembled and filled with a normal internal pressure. If 2 is the ground half width,
The pneumatic tire according to claim 1 or 2, wherein a maximum width of the middle block in the tire axial direction on the contact surface is 35% to 45% of the contact half width.   The pneumatic tire according to any one of claims 1 to 3, wherein a groove width of the middle narrow groove is 0.3 to 0.8 times a groove width of the middle lateral groove. The middle narrow groove includes a deep groove portion having a groove depth larger than that of the shallow groove portion,
The pneumatic tire according to any one of claims 1 to 4, wherein a groove depth of the deep groove portion is 70% to 100% of a groove depth of the center main groove. One or two center main grooves extending continuously in the tire circumferential direction on the tire equator or on both sides in the tire axial direction of the tire equator in the tread portion, and continuously on the tire axial direction outside of the center main groove in the tire circumferential direction By providing a pair of shoulder main grooves extending and a plurality of middle lateral grooves that connect between the center main groove and the shoulder main groove,
A pair of middle block rows in which middle blocks divided by the center main groove, the shoulder main groove, and the middle lateral groove are separated in the tire circumferential direction;
Comprising a pair of shoulder land sections separated by the shoulder main groove and the ground contact end, and
A pneumatic tire with a specified direction of rotation,
The middle block has a middle siping, a middle end that ends in the middle block, is inclined toward the tire equator side toward the first arrival side in the rotational direction, and has a width of 2.0 to 5.0 mm. A pneumatic tire provided with a slot.

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