JP2017035900A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a drainage performance, a snow road performance and an ice road performance in a well balanced manner.SOLUTION: A pneumatic tire comprises: shoulder lateral grooves 4A, each of which extends between a shoulder main groove 3A and a ground-contact end Te; and middle lateral grooves 4B, each of which extends between the shoulder main groove 3A and a center main groove 3B. An average groove width of the middle lateral groove 4B is 7 to 11% of the maximum length La of a middle block 6 in the tire circumferential direction. The middle lateral groove 4B comprises: a middle inner part 11 inclined toward one side from the center main groove 3B; a middle center part 12 curved toward one side from an end part 11e of the middle inner part 11; and a middle outer part 13 inclined toward one side from an end part 12e of the middle center part 12. The shoulder lateral groove 4A is formed in a tire circumferential direction area R1 between an inner end 11i of the middle inner part 11 in one of the middle lateral groove 4B and an outer end 13s of the middle outer part 13 in the other middle lateral groove 4B adjacent to the one of the middle lateral grooves 4B in the tire circumferential direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire in which drainage performance, snow road performance, and ice road performance are improved in a balanced manner.

  Winter pneumatic tires travel not only on snowy and icy roads but also on wet roads. Therefore, such a pneumatic tire for winter is required to have high drainage performance as well as snow road performance and ice road performance.

  For example, in order to improve ice road performance, it has been proposed to increase the ground contact area of the tread portion for the purpose of increasing pattern rigidity and frictional force. However, this method has a problem that the drainage performance and snow road performance are deteriorated because the groove width of the main groove and the lateral groove is reduced. Thus, the ice road performance, the drainage performance, and the snow road performance have a reciprocal relationship, and it has been difficult to improve all these performances in a well-balanced manner. Related technologies include the following.

JP 2008-308010 A

  The present invention has been devised in view of the actual situation as described above, and defines the average groove width and shape of the middle lateral groove, and also specifies drainage performance and snow road performance based on specifying the location of the shoulder lateral groove. The main object of the present invention is to provide a pneumatic tire with improved icy road performance in a well-balanced manner.

  The present invention provides a pair of shoulder main grooves extending continuously in the tire circumferential direction on the tread portion, 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 grooves. A plurality of shoulder lateral grooves extending between the shoulder main groove and the grounding end, and a plurality of middle lateral grooves extending between the shoulder main groove and the center main groove, thereby providing the grounding end. And a shoulder block divided by the shoulder main groove and the shoulder lateral groove are separated by a pair of shoulder block rows spaced in the tire circumferential direction, and the shoulder main groove, the center main groove, and the middle lateral groove. A pneumatic tire comprising a pair of middle block rows in which the middle blocks are spaced apart in the tire circumferential direction, wherein the middle lateral groove has an average The width is 7 to 11% of the maximum length of the middle block in the tire circumferential direction, and is inclined from the center main groove to one side in the tire circumferential direction at an angle of 3 to 15 ° with respect to the tire axial direction. A middle inner portion extending from the end of the middle inner portion to the one side in the tire circumferential direction and having a length in the tire circumferential direction of 75 to 200% of the average groove width of the middle lateral groove A middle outer portion extending from the end of the middle middle portion to the one side in the tire circumferential direction at an angle of 3 to 15 ° with respect to the tire axial direction and continuing to the shoulder main groove, The shoulder lateral groove is a tire circumferential region between an inner end of the middle inner portion of one middle lateral groove and an outer end of the middle outer portion of another middle lateral groove adjacent to the one middle lateral groove in the tire circumferential direction. Be formed into And features.

  In the pneumatic tire according to the present invention, the length in the tire axial direction of the middle inner portion is preferably 30 to 50% of the maximum length in the tire axial direction of the middle block.

  In the pneumatic tire according to the present invention, it is desirable that the shoulder lateral groove is inclined to the side opposite to the middle lateral groove from the shoulder main groove toward the ground contact end.

  In the pneumatic tire according to the present invention, the tread portion includes a plurality of center lateral grooves extending between the center main grooves, and the center lateral grooves are the outer ends of the middle outer portions of the middle lateral grooves, and the shoulder lateral grooves. Preferably, it is formed in a tire circumferential region between the intersections of the contact point and the ground contact end.

  In the pneumatic tire of the present invention, a pair of shoulder main grooves extending continuously in the tire circumferential direction on the tread portion, and a pair extending continuously in the tire axial direction on the inner side in the tire axial direction of the shoulder main grooves. Provided with a center main groove, a plurality of shoulder lateral grooves extending between the shoulder main groove and the grounding end, and a plurality of middle lateral grooves extending between the shoulder main groove and the center main groove. A pair of shoulder block rows in which shoulder blocks divided by a shoulder main groove and a shoulder horizontal groove are separated in the tire circumferential direction, and a middle block divided by the shoulder main groove, the center main groove, and the middle horizontal groove are tire circumferences. It comprises a pair of middle block rows spaced in the direction.

  The average width of the middle lateral groove is defined as 7 to 11% of the maximum length of the middle block in the tire circumferential direction. Thereby, the rigidity in the tire circumferential direction of the middle block, the drainage resistance of the middle lateral groove, and the groove volume are enhanced in a well-balanced manner. Therefore, braking force and snow column shearing force on the icy road are exhibited, and the icy road performance, drainage performance and snowy road performance are improved.

  Further, the middle lateral groove extends from the center main groove at an angle of 3 to 15 ° with respect to the tire axial direction toward the one side in the tire circumferential direction and extends from the end of the middle inner portion in the tire circumferential direction. Middle middle portion bent to one side and having a length in the tire circumferential direction of 75 to 200% of the average groove width of the middle lateral groove, and 3 to 15 ° with respect to the tire axial direction from the end of the middle middle portion And an outer middle portion extending at one angle in the tire circumferential direction and extending to the shoulder main groove. Such a middle inner part and a middle outer part exhibit a large edge effect in the tire axial direction to further increase the braking force and snow column shear force. Further, since the middle middle portion is inclined in the same direction as the middle inner portion and the middle outer portion, the drain resistance of the middle lateral groove is ensured to be small and the edge component in the tire circumferential direction is increased. Therefore, ice road performance, drainage performance and snow road performance are further improved in a balanced manner.

  Further, the shoulder lateral groove is a tire circumference between an inner end of the middle inner portion of one middle lateral groove and an outer end of the middle outer portion of the other middle lateral groove adjacent to the one middle lateral groove in the tire circumferential direction. It is formed in the direction area. That is, a land portion of the middle block is formed inside the shoulder lateral groove in the tire axial direction via the shoulder main groove. Thereby, since the rigidity in the tire axial direction of the tread portion is equalized over the tire circumferential direction, the ice road performance is stably exhibited.

It is an expanded view of the tread part which shows one Embodiment of this invention. It is an expanded sectional view of the XX part of FIG. It is an enlarged view of the middle block of FIG. It is an enlarged view of the left half of the tread part of FIG. It is an expanded view of the tread part of the pneumatic tire of a comparative example.

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 the tread portion 2 has the most ground contact end. A pair of shoulder main grooves 3A extending continuously in the tire circumferential direction on the Te side and a pair of center main grooves 3B extending continuously in the tire axial direction on the inner side in the tire axial direction of the shoulder main grooves 3A are provided. Further, the tread portion 2 of the present embodiment includes a plurality of shoulder lateral grooves 4A extending between the shoulder main groove 3A and the ground contact Te, and a plurality of middle extending between the shoulder main groove 3A and the center main groove 3B. A plurality of center lateral grooves 4C extending between the lateral grooves 4B and the center main grooves 3B, 3B are provided.

  Thereby, the tread portion 2 of the present embodiment includes a pair of shoulder block rows 5R, a pair of middle block rows 6R, and a center block row 7R. The shoulder block row 5R includes shoulder blocks 5 spaced in the tire circumferential direction. The shoulder block 5 is divided into a ground contact Te, a shoulder main groove 3A, and a shoulder lateral groove 4A. The middle block row 6R has middle blocks 6 spaced in the tire circumferential direction. The middle block 6 is divided into a shoulder main groove 3A, a center main groove 3B, and a middle lateral groove 4B. The center block row 7R has center blocks 7 spaced in the tire circumferential direction. The center block 7 is divided into a pair of center main grooves 3B and center lateral grooves 4C.

  The tread pattern of the present embodiment is formed in a substantially point-symmetric pattern except for a variable pitch with an arbitrary point on the tire equator C as the center.

  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. Is defined as the contact position on the outermost side in the tire axial direction. The distance in the tire axial direction between the ground contact Te and Te is determined as the tread ground contact width TW. 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.

  Each main groove 3A, 3B of this embodiment extends in a zigzag shape in the tire circumferential direction. Such main grooves 3A and 3B increase the edge component in the tire axial direction, and thus increase the snow column shear force, driving force, braking force, and the like. Therefore, snow road performance and ice road performance are improved.

  FIG. 2 is a sectional view taken along line XX in FIG. As shown in FIGS. 1 and 2, the groove widths of the main grooves 3A and 3B (the groove width perpendicular to the longitudinal direction of the grooves, the same applies to other grooves hereinafter) W1 and the groove depth D1 Can be variously determined in accordance with common practice. However, when these groove widths or groove depths are reduced, drainage performance and snowy road performance may be deteriorated. Conversely, when these groove widths or groove depths are increased, the ground contact area and rigidity of each of the blocks 5 to 7 may be reduced, and ice road performance may be deteriorated. For this reason, the groove width W1 of the main grooves 3A and 3B is desirably 3 to 9% of the tread ground contact width TW, for example. The groove depth D1 of the main grooves 3A and 3B is preferably 6 to 15 mm, for example.

  In order to ensure a good balance between the rigidity in the tire axial direction and the drainage performance of each block 5 to 7, the tire axial distance L1 between the shoulder main groove 3A and the tire equator C is 25 to 35% of the tread ground contact width TW. Is desirable. From the same viewpoint, the tire axial direction distance L2 between the center main groove 3B and the tire equator C is desirably 5 to 15% of the tread contact width TW. Each position of the main grooves 3A and 3B is specified by the groove center line. However, when the main groove 3 is a zigzag non-linear line as in this embodiment, the center of the amplitude of the groove center line is used. Lines G1 and G2 are used.

  FIG. 3 is a partially enlarged view of the vicinity of the middle block 6 provided in the left half of the tread portion 2 of FIG. As shown in FIG. 3, the average groove width W2g (shown in FIG. 1) of the middle lateral groove 4B is defined as 7 to 11% of the maximum length La (shown in FIG. 1) of the middle block 6 in the tire circumferential direction. The When the average groove width W2g of the middle horizontal groove 4B is less than 7% of the maximum length La of the middle block 6, the groove volume of the middle horizontal groove 4B becomes small, and the snow column shear force and drainage performance deteriorate. On the contrary, when the average groove width W2g exceeds 11% of the maximum length La of the middle block 6, the land area of the middle block 6 becomes small, and the ice road performance deteriorates. For this reason, the average groove width W2g of the middle lateral groove 4B is preferably 8% or more, preferably 10% or less of the maximum length La of the middle block 6. The “average groove width” refers to the area of the lateral groove on the ground contact surface along the inclination of the groove center line 8c when a normal load is applied to the tire in the normal state and grounded on a flat surface with a camber angle of 0 °. The groove width divided by the length (hereinafter, the length along such an inclination is referred to as “actual length” in this specification).

  The middle lateral groove 4 </ b> B of the present embodiment includes a middle inner part 11, a middle central part 12, and a middle outer part 13. The middle inner portion 11 extends from the center main groove 3B. The middle middle portion 12 extends from the end portion 11e of the middle inner portion 11 on the outer side in the tire axial direction. The middle outer portion 13 extends from the outer end 12e of the middle middle portion 12 in the tire axial direction and continues to the shoulder main groove 3A. The middle inner portion 11 is inclined to one side in the tire circumferential direction (upward to the left in FIG. 3) at an angle α1 of 3 to 15 ° with respect to the tire axial direction. The middle outer portion 13 is inclined to the one side in the tire circumferential direction at an angle α2 of 3 to 15 ° with respect to the tire axial direction. The middle inner portion 11 and the middle outer portion 13 exhibit a large edge effect in the tire axial direction and increase the braking force and snow column shear force. The middle middle portion 12 is bent toward the one side in the tire circumferential direction. Since such middle center part 12 inclines in the same direction of a tire axial direction with middle inner part 11 and middle outer part 13, it maintains the drainage resistance of middle lateral groove 4B small. The middle middle portion 12 has a length L3 in the tire circumferential direction that is 75 to 200% of the average groove width W2g of the middle lateral groove 4B. For this reason, the edge component in the tire circumferential direction increases. Therefore, ice road performance, drainage performance and snow road performance are further improved in a balanced manner.

  In the present embodiment, the middle central portion 12 extends linearly and with a constant width. Accordingly, the edge component in the tire circumferential direction of the middle block 6 is increased while the drainage resistance is kept small.

  When the length L3 in the tire circumferential direction of the middle middle portion 12 exceeds 200% of the average groove width W2g of the middle lateral groove 4B, the drainage resistance of the middle lateral groove 4B increases and the drainage performance deteriorates. Further, when the length L3 is increased, the rigidity of the middle block 6 in the tire axial direction is decreased, and the turning performance on an icy road is deteriorated. Conversely, when the length L3 of the middle central portion 12 is less than 75% of the average groove width W2g, the edge component in the tire circumferential direction cannot be increased. For this reason, the length L3 of the middle central portion 12 is preferably 80% or more, and preferably 160% or less of the average groove width W2g of the middle lateral groove 4B.

  In order to effectively exhibit the above-described action, the angle α3 of the middle middle portion 12 with respect to the tire axial direction is preferably 45 ° or more, more preferably 50 ° or more, preferably 75 ° or less, more preferably 70 °. It is as follows.

  The middle inner part 11 and the middle outer part 13 extend linearly with a certain width. Thereby, the edge component of the middle block 6 in the tire axial direction and the drainage resistance are enhanced in a well-balanced manner.

  The middle lateral groove 4 </ b> B of the present embodiment projects the end of the middle block 6 outward on both sides in the tire circumferential direction of the middle block 6 by the middle inner portion 11, the middle central portion 12 and the middle outer portion 13. Vertical protrusions 14 and 14 to be formed are formed. Such vertical protrusions 14 increase the rigidity in the tire axial direction and improve the turning performance.

  If the angles α1 and α2 of the middle inner portion 11 and the middle outer portion 13 with respect to the tire axial direction are less than 3 °, the edge component in the tire circumferential direction cannot be increased, and the turning performance cannot be improved. Conversely, when the angles α1 and α2 of the middle inner portion 11 and the middle outer portion 13 exceed 15 °, the edge component in the tire axial direction becomes smaller, and the braking force and snow column shear force are reduced. For this reason, the angles α1 and α2 of the middle inner portion 11 and the middle outer portion 13 are preferably 5 ° or more, and preferably 13 ° or less.

  It is desirable that the angle α2 of the middle outer portion 13 and the angle α1 of the middle inner portion 11 are different. Thereby, the braking force and driving force at the time of turning can be made high according to the turning angle. If the difference | α2−α1 | between the angle α2 of the middle outer portion 13 and the angle α1 of the middle inner portion 11 becomes excessively large, the rigidity step in the tire axial direction of the middle block 6 may increase and the turning performance may deteriorate. There is. Therefore, the difference | α2−α1 | between the angle α2 of the middle outer portion 13 and the angle α1 of the middle inner portion 11 is preferably 1.0 to 5.0 °.

  When the length L4 of the middle inner portion 11 in the tire axial direction becomes excessively large or excessively small, the rigidity in the tire axial direction of one of the vertical convex portions 14 in the tire circumferential direction of the middle block 6 decreases. The turning performance may not be improved. Therefore, the length L4 of the middle inner portion 11 is preferably 25% or more, more preferably 30% or more, and further preferably 35% or more of the maximum length Lb of the middle block 6 in the tire axial direction. The length L4 is preferably 50% or less, more preferably 45% or less, and still more preferably 40% or less of the maximum length Lb.

  Further, the length L5 of the middle outer portion 13 in the tire axial direction is preferably larger than the length L4 of the middle inner portion 11. As a result, the rigidity in the tire axial direction of the vertical convex portion 14b arranged on the outer side in the tire axial direction is ensured to be large, and the large lateral force at the time of turning can be counteracted, thereby improving the turning performance. If the length L5 of the middle outer portion 13 is excessively larger than the length L4 of the middle inner portion 11, the rigidity in the tire axial direction of the vertical convex portion 14a disposed on the inner side in the tire axial direction becomes small, and the turning Performance may not improve. Therefore, the length L5 of the middle outer portion 13 is preferably 40% or more, more preferably 45% or more, preferably 70% or less, more preferably, the maximum length Lb of the middle block 6 in the tire axial direction. 65% or less, more preferably 60% or less.

  FIG. 4 shows the land portion of the substantially left half of the tread portion 2 of FIG. As shown in FIG. 4, the shoulder lateral groove 4A of the present embodiment is formed as a zigzag groove extending in a zigzag shape.

  The shoulder lateral groove 4A includes an inner end 11i of the middle inner portion 11 of one middle lateral groove 4Ba and an outer end 13s of the middle outer portion 13 of another middle lateral groove 4Bb adjacent to the one middle lateral groove 4Ba in the tire circumferential direction. It is formed in the tire circumferential direction region R1 between. That is, a land portion of the middle block 6 is formed on the inner side in the tire axial direction of the shoulder lateral groove 4A via the shoulder main groove 3A. Thereby, since the rigidity of the tread portion 2 in the tire axial direction is equalized in the tire circumferential direction, the ice road performance is stably exhibited. From such a viewpoint, one end 16e in the tire circumferential direction of the shoulder lateral groove 4A (formed on the ground contact end Te in FIG. 4) and the other end 16i in the tire circumferential direction (in FIG. 4, the inner side in the tire axial direction). Is preferably formed in the region R1 in the tire circumferential direction. The inner end 11 i of the middle inner portion 11 refers to the inner end in the tire axial direction of the groove center line 11 c of the middle inner portion 11. Further, the outer end 13s of the middle outer portion 13 refers to the outer end of the groove center line 13c of the middle outer portion 13 in the tire axial direction.

  In order to effectively exhibit the above-described action, the tire axial length L6 from the intersection T of the shoulder lateral groove 4A and the tire circumferential region R1 to the ground contact Te is the maximum length of the shoulder block 5 in the tire axial direction. It is desirable to be provided in the range of 35 to 65% of Lc. More specifically, the intersection T is a point where the groove center line of the shoulder lateral groove 4A and the intermediate position R1a in the tire circumferential direction of the tire circumferential region R1 intersect. In the case where the shoulder lateral groove 4A is a zigzag non-linear line as in the present embodiment, the intersection point T is specified by the center line 15 of the amplitude of the groove center line.

  In this embodiment, the shoulder lateral groove 4A is inclined to the opposite side of the middle lateral groove 4B from the shoulder main groove 3A toward the grounding end Te (lower left in FIG. 4). As a result, during straight traveling, the inclination of the shoulder lateral grooves 4A and the middle lateral grooves 4B cancels out, so that the edge component in the tire axial direction is exerted high, and traveling stability performance is improved. Further, during cornering, the edge component in the tire circumferential direction of the shoulder lateral groove 4A is exhibited, so that cornering performance is improved. In order to exhibit such an action more effectively, the angle α4 of the center line 15 of the amplitude of the shoulder lateral groove 4A with respect to the tire axial direction is preferably 5 ° or more, more preferably 7 ° or more, and preferably It is 17 ° or less, more preferably 15 ° or less.

  Further, the shoulder block 5 of the present embodiment is provided with a straight shoulder narrow groove 17 that divides the shoulder block 5 in the tire axial direction by extending in the tire circumferential direction. Thereby, the water film on the tread surface of the shoulder block 5 is discharged from the shoulder lateral groove 4A to the grounding end Te through the shoulder narrow groove 17, so that the drainage performance is improved.

  In this embodiment, the shoulder lateral groove 4A includes an inner groove portion 18 that is disposed on the inner side in the tire axial direction than the shoulder thin groove 17 and an outer groove portion 19 that is disposed on the ground contact end Te side with respect to the shoulder thin groove 17. Composed. The groove width W3a of the inner groove portion 18 is preferably 50% or more, more preferably 60% or more, preferably 90% or less, more preferably 80% or less, of the groove width W3b of the outer groove portion 19. Thereby, ensuring of the rigidity of the shoulder block 5 and improvement of drainage performance are exhibited with a good balance.

  The groove width W3a of the inner groove portion 18 is preferably 0.5% or more, more preferably 1.0% or more of the tread ground contact width TW (shown in FIG. 1), preferably 3.0% or less. More preferably, it is 2.5% or less. The groove width W3b of the outer groove portion 19 is preferably 1.5% or more of the tread ground contact width TW, more preferably 2.0% or more, preferably 4.0% or less, more preferably 3.5% or less. is there.

  In the present embodiment, the zigzag pitch of the inner groove portion 18 is smaller than the zigzag pitch of the outer groove portion 19. Thereby, the rigidity on the ground contact end Te side of the shoulder block 5 on which a large lateral force acts during turning is ensured. Moreover, the inner side groove part 18 exhibits the edge effect of a tire axial direction, and improves turning performance.

  In the present embodiment, the center lateral groove 4C is formed in the tire circumferential direction region R2 between the outer end 13s of the middle outer portion 13 of the middle lateral groove 4B and the intersection K between the shoulder lateral groove 4A and the ground contact end Te. Thereby, since the rigidity of the tread portion 2 in the tire axial direction is equalized over the tire circumferential direction, stable turning performance is exhibited. In order to effectively exhibit such an action, if all of the grooves on the intersection K side from the position of the tire equator C of the center lateral groove 4C are formed in the tire circumferential region R2 having the intersection K. Good. The “intersection K” is an intermediate position in the tire circumferential direction of the opening width at the ground contact end Te of the shoulder lateral groove 4A.

  In the center lateral groove 4C of the present embodiment, the groove width W4 of the center lateral groove 4C gradually increases from the center portion 4Ca in the tire axial direction toward both end portions 4Ce. Such a center lateral groove 4C can smoothly discharge the snow in the center lateral groove 4C to the center main groove 3B. Further, since the center lateral groove 4C has a large groove volume at both end portions 4Ce, the snow column shear force is improved.

  The groove width W4 of the center lateral groove 4C is preferably 0.5% or more, more preferably 1.0% or more, preferably 3.5% or less, more preferably 2.0% or less of the tread ground contact width TW. is there.

  As shown in FIG. 2, the groove depth D3 of the shoulder lateral groove 4A, the groove depth D2 of the middle lateral groove 4B, and the groove depth D4 of the center lateral groove 4C are preferably 4 mm or more, more preferably 6 mm or more. The thickness is preferably 12 mm or less, more preferably 10 mm or less. Thereby, the rigidity and groove volume of each of the blocks 5 to 7 are ensured with a good balance.

  In the present embodiment, it is represented by a ratio (Sb / Sa) of the total area Sb of the treads of all the blocks 5 to 7 and the total surface area Sa of the tread obtained by filling all the grooves 3 and 4 of the tread portion 2. The land ratio is set to 68-72%. Thereby, ice road performance, snow road performance, and drainage performance are improved with good balance.

  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 195 / 80R15 having the basic pattern of FIG. 1 or FIG. 5 was prototyped based on the specifications in Table 1, and the drainage performance, ice performance (braking force) and snow performance of each sample tire were tested. It was. In Example 9, the shoulder lateral groove is inclined in the same direction as the middle lateral groove. The common specifications are as follows.
Tread contact width TW: 162mm
La: Maximum length of the middle block in the tire circumferential direction Lb: Maximum length of the middle block in the tire axial direction <main groove>
Groove width W1: 6.0 to 8.0 mm
Groove depth D1: 12.5mm
Ratio of tire axial direction distance L1 of shoulder main groove to tread contact width TW (L1 / TW): 0.28
Ratio (L2 / TW) between the tire axial direction distance L2 of the center main groove and the tread contact width TW (0.10): 0.10
<Horizontal groove>
Center lateral groove width W4: 3.0 to 6.0 mm
Inner groove width W3a: 4.0 to 6.0 mm
Groove width W3b of outer groove: 6.0 to 8.0 mm
Groove depth D2 to D4 of each lateral groove: 7.0 to 10.5 mm
The test method is as follows.

<Snow road performance>
Each sample tire was mounted on all wheels of a 2700cc four-wheel drive vehicle under the following conditions, and was run on a snowy road test course by one driver. The driving characteristics at this time, such as steering response, rigidity, and grip, were evaluated by the driver's sensuality. The results are displayed with a score of Comparative Example 1 being 100. The larger the value, the better.
Rim 15 × 6J
Internal pressure: 350 kPa (front wheel)
Internal pressure: 425 kPa (rear wheel)
Load: 4.9kN

<Ice performance (braking force)>
The test vehicle traveled on an icy road test course, suddenly braked from a speed of 30 km / h, and the braking distance until stopping was measured. The result is displayed as an index with the reciprocal of the braking distance of Comparative Example 1 as 100. The larger the value, the better.

<Drainage performance>
The test vehicle was run on a wet asphalt road test course having a total length of 2000 m, and the running time at that time was measured. In order to make the wet conditions the same, the water depth on the road surface was unified to 5 mm immediately before traveling. The result is displayed as an index with the reciprocal of the traveling time of Comparative Example 1 as 100. 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 drainage performance, snowy road performance, and icy road performance of the tires of the examples were significantly improved as compared with the comparative example.

3A Shoulder main groove 3B Center main groove 4A Shoulder horizontal groove 4B Middle horizontal groove 6 Middle block 11 Middle inner part 12 Middle central part 13 Middle outer part La Maximum length of the middle block in the tire circumferential direction R1 Tire circumferential area Te Grounding end

Claims (4)

A pair of shoulder main grooves extending continuously in the tire circumferential direction on the tread portion, the pair of center main grooves extending continuously in the tire axial direction on the inner side in the tire axial direction of the shoulder main grooves, By providing a plurality of shoulder lateral grooves extending between the groove and the grounding end, and a plurality of middle lateral grooves extending between the shoulder main groove and the center main groove,
A pair of shoulder block rows in which shoulder blocks divided by the ground contact end, the shoulder main groove, and the shoulder lateral groove are spaced in the tire circumferential direction, and the shoulder main groove, the center main groove, and the middle lateral groove, A pneumatic tire comprising a pair of middle block rows in which the middle blocks divided by
The middle lateral groove has an average groove width of 7 to 11% of the maximum length of the middle block in the tire circumferential direction, and
Middle inner portion extending from the center main groove to the tire circumferential direction at an angle of 3 to 15 ° with respect to the tire axial direction, bent from the end of the middle inner portion to the one side in the tire circumferential direction And a middle middle portion having a length in the tire circumferential direction of 75 to 200% of an average groove width of the middle lateral groove, and an angle of 3 to 15 ° with respect to the tire axial direction from the end of the middle middle portion. It consists of a middle outer part that inclines to the one side in the tire circumferential direction and continues to the shoulder main groove,
The shoulder lateral groove is a tire between an inner end of the middle inner portion of one middle lateral groove and an outer end of the middle outer portion of another middle lateral groove adjacent to the one middle lateral groove in the tire circumferential direction. A pneumatic tire formed in a circumferential region.   2. The pneumatic tire according to claim 1, wherein a length of the middle inner portion in the tire axial direction is 30 to 50% of a maximum length of the middle block in the tire axial direction.   3. The pneumatic tire according to claim 1, wherein the shoulder lateral groove is inclined toward the side opposite to the middle lateral groove from the shoulder main groove toward the ground contact end. The tread portion includes a plurality of center lateral grooves extending between the center main grooves,
The center lateral groove is formed in a tire circumferential region between an outer end of the middle outer portion of the middle lateral groove and an intersection between the shoulder lateral groove and the ground contact end. The described pneumatic tire.

Images