JP6013979B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that improves snow road performance while maintaining steering stability performance.

  Winter pneumatic tires travel not only on snowy roads but also on dry roads. Therefore, such a pneumatic tire for winter is required to improve not only snow road performance but also steering stability performance.

  For example, in order to improve snow road performance, it has been proposed to increase the volume of the lateral groove of the tread portion in order to increase the snow column shear force. However, this method has a problem that the rigidity of the tread portion is reduced and the steering stability performance is deteriorated. Thus, the steering stability performance and the snowy road performance have a contradictory relationship, and it has been difficult to improve both of these performances in a balanced manner. Related technologies include the following.

JP 2012-176282 A

  The present invention has been devised in view of the actual situation as described above, and is based on the improvement of the arrangement position and the groove depth of the middle lateral groove, and the air with improved snow road performance while maintaining the steering stability performance. The main purpose is to provide tires.

  In the tread portion, one or a pair of center main grooves extending continuously on the tire equator or both sides of the tire equator in the tire circumferential direction, and the tire axial direction outer side of the center main groove in the tire circumferential direction. A pneumatic tire provided with a pair of shoulder main grooves extending continuously, and a plurality of middle lateral grooves connecting between the center main groove and the shoulder main groove, wherein the center main groove A zigzag shape in which a long side portion inclined to one side with respect to a direction and a short side portion inclined in the opposite direction to the long side portion and having a length smaller than the long side portion are alternately arranged The middle lateral groove has an inner end in the tire axial direction communicating with the long side portion of the center main groove, and the middle lateral groove has an inner portion in the tire axial direction from an intermediate position of the tire axial length. And an outer portion outside the tire axial direction The average groove depth of the outer section is characterized less than the average groove depth of the inner portion.

  In the pneumatic tire according to the present invention, the angle of the short side portion with respect to the tire axial direction is greater than 0 degree and not more than 70 degrees, and the angle of the long side portion with respect to the tire axial direction is not less than 70 degrees and 90 degrees. Desirably less than a degree.

  In the pneumatic tire according to the present invention, it is preferable that the groove width of the middle lateral groove is constant.

  In the pneumatic tire according to the present invention, the middle lateral groove has a first portion having a smallest groove depth on the outer side, and the groove depth at a position where the middle lateral groove communicates with the shoulder main groove. However, it is desirable that it is larger than the groove depth of the first portion.

  In the present invention, one or a pair of center main grooves extending continuously in the tire circumferential direction on the tire equator or on both sides of the tire equator in the tread portion, and the tire axial direction outer side of the center main groove being continuous in the tire circumferential direction. A pneumatic tire provided with a pair of extending shoulder main grooves and a plurality of middle lateral grooves that connect between the center main groove and the shoulder main grooves. Thereby, a plurality of middle blocks divided by the center main groove, the middle main groove, and the middle lateral groove are provided in the tread portion in the tire circumferential direction.

  The center main groove is alternately arranged with a long side portion inclined to one side with respect to the tire circumferential direction and a short side portion inclined in a direction opposite to the long side portion and having a length smaller than the long side portion. It is zigzag. Since such a center main groove includes a tire axial component, it exerts a snow column shear force and improves snow road performance.

  In the middle lateral groove, the inner end in the tire axial direction communicates with the long side portion of the center main groove. That is, the short side portion of the center main groove is not provided at both ends in the tire circumferential direction, which is a region where the rigidity of the middle block is small. For this reason, a snow column with a large component in the tire axial direction is formed in an area where the rigidity of the middle block is large. Therefore, a large snow column shear force is exhibited, and the snow road performance is further improved.

  The middle lateral groove has an inner portion on the inner side in the tire axial direction and an outer portion on the outer side in the tire axial direction from an intermediate position of the length in the tire axial direction. The average groove depth of the outer part is smaller than the average groove depth of the inner part. Thereby, since the rigidity of the outer side of the middle block in the tire axial direction is ensured, the steering stability performance is improved.

It is an expanded view of the tread part which shows one Embodiment of this invention. It is an enlarged view of the center main groove of FIG. It is sectional drawing of the XX part of FIG. It is an enlarged view of the middle block vicinity of the right side of FIG. It is sectional drawing of a middle lateral groove. It is an expanded view of the tread part of other embodiment of this invention. It is an expanded view of the tread part of embodiment 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 the present embodiment (hereinafter sometimes simply referred to as “tire”) is suitably used as, for example, a studless tire. The tread portion 2 of the tire has a pair of center main grooves 3, 3 extending continuously in the tire circumferential direction on both sides of the tire equator C, and the tire axially outer side of the center main groove 3 is continuous in the tire circumferential direction. A pair of extending shoulder main grooves 4 and 4 are provided. In the present embodiment, the tread portion 2 has a plurality of middle lateral grooves 5 that connect between the center main groove 3 and the shoulder main groove 4, and a plurality of shoulders that connect between the shoulder main groove 4 and the ground contact Te. A lateral groove 6 is provided.

  The tread portion 2 of the present embodiment includes a center land portion 7 divided by a pair of center main grooves 3 and 3, a plurality of middle portions divided by the center main groove 3, the shoulder main groove 4 and the middle lateral groove 5. A pair of middle block rows 8R in which the blocks 8 are arranged in the tire circumferential direction, and a pair of shoulder blocks 9 in which a plurality of shoulder blocks 9 divided by the shoulder main groove 4, the ground contact Te and the shoulder lateral grooves 6 are arranged in the tire circumferential direction. A block row 9R is provided.

  The “ground contact end” is a normal load loaded state in which a normal load is loaded on a normal rim that is assembled with a normal rim and filled with a normal internal pressure, and a normal load is applied to a flat surface with a camber angle of 0 °. 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 ground contact ends Te and Te is determined as the tread 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.

  “Regular rim” is a rim that is 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, it is “Measuring Rim”. “Normal 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. “JATMA” is the “highest 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.

  FIG. 2 shows an enlarged view of the center main groove 3 on the right side of FIG. As shown in FIG. 2, the center main groove 3 has a long side portion 10 inclined to one side with respect to the tire circumferential direction (inclined to the left in FIG. 2) and a length smaller than the long side portion 10. The short side part 11 is included. The short side portion 11 is inclined in the opposite direction to the long side portion 10 (inclined upward in FIG. 2). The center main groove 3 has a zigzag shape in which the long side portions 10 and the short side portions 11 are alternately arranged. Since such a center main groove 3 includes a tire axial direction component, it exerts a snow column shear force and improves snow road performance.

  The angle of the center main groove 3 is obtained as the angle of the groove center line 12. In this specification, the groove center line 12 of the center main groove 3 is defined as the center line of the groove bottom that forms the innermost portion of the groove in the radial direction of the tire, and the groove center line 12a extending over the long side portion 10 and the short side And a groove center line 12 b extending through the portion 11. FIG. 2 shows a virtual line 3e that assists in distinguishing between the long side portion 10 and the short side portion 11.

  The angle α1 of the long side portion 10 with respect to the tire axial direction is preferably 70 degrees or more and less than 90 degrees. That is, when the angle α1 of the long side portion 10 is less than 70 degrees, the rigidity in the tire circumferential direction of the center land portion 7 and the middle block 8 may be reduced. When the angle α1 of the long side portion 10 exceeds 90 degrees, the rigidity of the center land portion 7 sandwiched between the long side portion 10 and the short side portion 11 becomes small, and the steering stability performance may be deteriorated. For this reason, the angle α1 of the long side portion 10 is more preferably 75 degrees or more, and more preferably 85 degrees or less.

  The angle α2 of the short side portion 11 with respect to the tire axial direction is desirably larger than 0 degree and not larger than 70 degrees. That is, when the angle α2 of the short side portion 11 is 0 degrees or less, the rigidity of the center land portion 7 sandwiched between the long side portion 10 and the short side portion 11 becomes small, and the steering stability performance may be deteriorated. . When the angle α2 of the short side portion 11 exceeds 70 degrees, the tire axial direction component of the center main groove 3 may be small. For this reason, the angle α2 of the short side portion 11 is more preferably 5 degrees or more, and more preferably 65 degrees or less.

  In order to exert a large snow column shear force while ensuring high rigidity of the center land portion 7 and the middle block 8, the length L1 in the tire circumferential direction of the long side portion 10 and the length in the tire axial direction of the short side portion 11 The ratio L2 / L1 with L2 is preferably 10% to 40%.

  As shown in FIG. 1, the shoulder main groove 4 of the present embodiment has a linear shape along the tire circumferential direction. Such a shoulder main groove 4 ensures high rigidity of the middle block 8 and the shoulder block 9 and improves steering stability performance.

  Groove width of each main groove 3, 4 (groove width measured in a direction perpendicular to the groove center line, hereinafter the same applies to other grooves) W1, W2 and groove depths D1, D2 (in FIG. 3) (Shown) can be variously determined in accordance with common practice. The groove widths W1 and W2 of the main grooves 3 and 4 are preferably 2% to 6% of the tread ground contact width TW, for example. As for groove depth D1, D2 of each main groove 3 and 4, 10-20 mm is desirable, for example.

  In order to ensure the balance of the rigidity in the tire axial direction of the center land portion 7 and each of the blocks 8 and 9, the tire axial distance La between the center main groove 3 and the tire equator C is 5% to the tread ground contact width TW. 13% is desirable. The tire axial distance Lb between the shoulder main groove 4 and the tire equator C is preferably 24% to 32% of the tread contact width TW. Note that, as in the present embodiment, the position of the zigzag non-linear center main groove 3 is specified by the center line G3 of the amplitude of the groove center line 12. The position of the shoulder main groove 4 is specified by the groove center line 13.

  FIG. 4 shows an enlarged view of the vicinity of the middle block 8 on the right side of FIG. As shown in FIG. 4, the middle lateral groove 5 has an inner end 5 i in the tire axial direction communicating with the long side portion 10 of the center main groove 3. Thereby, the short side part 11 of the center main groove 3 is located between the middle lateral grooves 5 and 5 adjacent in the tire circumferential direction. In other words, the short side portion 11 is not provided at both ends 8e, 8e in the tire circumferential direction, which is a region where the rigidity of the middle block 8 is small. For this reason, a snow column having a large tire axial direction component due to the short side portion 11 is formed in a region where the rigidity of the middle block 8 is large. Therefore, a large snow column shearing force is exhibited and snow road performance is improved.

  From the viewpoint of effectively exhibiting the above-described action, the groove center line G5 of the middle lateral groove 5 is at a position of 40% to 60% of the tire circumferential direction length of the groove edge 10e on the outer side in the tire axial direction of the long side portion 10. It is desirable to cross.

  FIG. 5 shows a cross-sectional view of the middle lateral groove 5. As shown in FIG. 5, the middle lateral groove 5 has an inner portion 14 on the inner side in the tire axial direction from an intermediate position 5c (indicated by a phantom line) in the tire axial direction length, and on the outer side in the tire axial direction from the intermediate position 5c. And an outer portion 15. In the present embodiment, the average groove depth (indicated by imaginary line) Db of the outer side portion 15 is smaller than the average groove depth (indicated by imaginary line) Da of the inner side portion 14. Thereby, since the rigidity of the outer side of the middle block 8 in the tire axial direction is ensured, the steering stability performance is improved. When the average groove depth Db of the outer side portion 15 is excessively smaller than the average groove depth Da of the inner side portion 14, the snow pillar formed by the middle lateral groove 5 becomes small, and there is a possibility that snow road performance is deteriorated. From such a viewpoint, the average groove depth Da of the inner portion 14 is preferably 110% to 130% of the average groove depth Db of the outer portion 15.

  The middle lateral groove 5 includes a first portion 16 having a minimum groove depth in the outer portion 15, a second portion 17 having a groove depth larger than that of the first portion 16 on the outer side of the first portion 16 in the tire axial direction, A third portion 18 having a groove depth larger than that of the first portion 16 is provided inside the first portion 16 in the tire axial direction. Such a first portion 16 ensures a higher rigidity of the middle block 8 on the outer side in the tire axial direction.

  The first portion 16 includes an inner portion 14 in the present embodiment. Thereby, the rigidity of the middle block 8 is further enhanced. The length L4 of the first portion 16 in the tire axial direction is preferably 35% to 65% of the length L3 of the middle lateral groove 5 in the tire axial direction. The groove depth D3a of the first portion 16 is preferably 50, which is the groove depth D2 of the shoulder main groove 4, from the viewpoint of exerting a high snow column shear force by the middle lateral groove 5 while ensuring the rigidity of the middle block 8. % To 70%.

  The second portion 17 has an outer end in the tire axial direction communicating with the shoulder main groove 4. That is, the groove depth D3b at the position where the middle lateral groove 5 communicates with the shoulder main groove 4 is larger than the groove depth D3a of the first portion 16. Such a second portion 17 exerts a large snow column shear force while ensuring the rigidity of the middle block 8 on the outer side in the tire axial direction. If the groove depth D3b of the middle lateral groove 5 at the communication position is excessively larger than the groove depth D3a of the first portion 16, the rigidity of the middle block 8 on the outer side in the tire axial direction cannot be ensured, and steering stability is improved. Performance may deteriorate. For this reason, the groove depth D3b of the second portion 17 is preferably 110% to 140% of the groove depth D3a of the first portion 16. From the same viewpoint, the groove depth D3b of the second portion 17 is preferably 60% to 80% of the groove depth D2 of the shoulder main groove 4.

  From the viewpoint of effectively exhibiting the above-described action, the length L5 of the second portion 17 in the tire axial direction is preferably 1% to 10% of the length L3 of the middle lateral groove 5 in the tire axial direction.

  The third portion 18 has an inner end in the tire axial direction communicating with the center main groove 3. That is, the groove depth D3c at the position where the middle lateral groove 5 communicates with the center main groove 3 is larger than the groove depth D3a of the first portion 16. Thereby, a big snow column is formed. The groove depth D3c of the third portion 18 is preferably 110% to 140% of the groove depth D3a of the first portion 16 in order to ensure the rigidity of the middle block 8 on the outer side in the tire axial direction. The groove depth D3c of the third portion 18 is preferably 60% to 80% of the groove depth D1 of the center main groove 3.

  As shown in FIG. 4, it is desirable that the groove width W3 of the middle lateral groove 5 is constant. Such a middle lateral groove 5 is provided with a first portion 16, a second portion 17, and a third portion 18 (shown in FIG. 5), and the above-described operation due to the change of the groove depth is effective. Can be demonstrated. That is, by making the groove width W3 of the middle lateral groove 5 constant, the rigidity of the middle block 8 on the outer side in the tire axial direction is ensured, and the steering stability performance is improved, and a large snow column is formed and the snow road performance. Will improve. When the middle horizontal groove 5 has a minimum portion where the groove width of the middle horizontal groove 5 is minimum and a maximum portion where the groove width is maximum (not shown), The ratio of the groove width of the part to the groove width of the minimum part is preferably 1.2 or less.

  In order to form a large snow column while ensuring the rigidity of the middle block 8, the groove width W3 of the middle lateral groove 5 is preferably 5% to 15% of the maximum length Lc of the middle block 8 in the tire axial direction.

  The angle α3 of the middle lateral groove 5 with respect to the tire axial direction is preferably 5 to 15 degrees. That is, when the angle α3 of the middle lateral groove 5 is less than 5 degrees, the tire circumferential direction component of the middle block 8 becomes small, and the steering stability performance may be deteriorated. When the angle α3 of the middle lateral groove 5 exceeds 15 degrees, the snow column shear force by the middle lateral groove 5 becomes small, and the traction and braking force on the snow road may be reduced.

  The middle block 8 includes an inner notch 20 that terminates in the middle block 8 extending outward from the short side 11 of the center main groove 3 in the tire axial direction, and a middle block 8 extending from the shoulder main groove 4 inward in the tire axial direction. An outer notch 21 that terminates inside is provided. Such notches 20 and 21 can exert a snow column shearing force by compacting and shearing snow therein. The depths D4 and D5 (shown in FIG. 3) of the inner notch 20 and the outer notch 21 are smaller than the groove depths D1 and D2 of the main grooves 3 and 4 with which the notches 20 and 21 are in contact. For this reason, the rigidity of the middle block 8 is ensured high.

  The center land portion 7 is provided with a center notch portion 22 that terminates in the center land portion 7 without extending to the tire equator C from the long side portion 10 of the center main groove 3 inward in the tire axial direction. Such center notch 22 further improves snowy road performance. The depth D6 (shown in FIG. 3) of the center notch portion 22 is smaller than the groove depth D1 of the center main groove 3.

  As shown in FIG. 1, in the present embodiment, the shoulder lateral groove 6 is a tire between the inclined portion 6 a inclined at a small angle with respect to the tire axial direction from the shoulder main groove 4, and between the inclined portion 6 a and the ground contact Te. And an axial portion 6b extending along the axial direction. The inclined portion 6a and the axial direction portion 6b of the present embodiment extend linearly. Such a shoulder lateral groove 6 can exert a large snow column shearing force and can improve snow road performance.

  In the present embodiment, the center land portion 7, the middle block 8, and the shoulder block 9 are respectively provided with sipings 24a to 24c that are inclined with respect to the tire axial direction or the tire axial direction and extend linearly. Thereby, the running performance on an icy road is improved. The siping 24a of the center land portion 7 extends along the tire axial direction in order to ensure straight running stability performance on an icy road. The sipings 24b and 24c of the middle block 8 and the shoulder block 9 extend in parallel with the lateral grooves 5 and 6, respectively, in order to ensure high rigidity of the blocks 8 and 9. Note that the sipings 24a to 24c are not limited to linear ones, and may be, for example, zigzag or wave.

  The shoulder block 9 of the present embodiment is provided with a circumferential siping 25 extending along the tire circumferential direction. Such a circumferential siping 25 exhibits an edge effect in the tire circumferential direction, and thus greatly improves the turning performance. The circumferential siping 25 is desirably provided at a position of 40 to 60% of the length in the tire axial direction of the shoulder block 9 in order to ensure high rigidity of the shoulder block 9.

  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. For example, the center main groove 3 may be one that extends continuously on the tire equator C in the tire circumferential direction (not shown).

A pneumatic tire of size 205 / 80R16 having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1, and the traction performance of each sample tire on snowy roads, steering stability performance on dry asphalt roads, wear resistance performance, Abrasion appearance and drainage performance on wet roads were tested. The common specifications and test methods are as follows.
Tread contact width TW: 164mm
Shoulder main groove depth: 13.0mm
Groove depth of inner notch: 9.5mm
Groove depth of outer notch: 7.5mm
Center notch groove depth: 9.5mm
Groove depth of inclined part: 6.0 mm
Groove depth in the axial direction: 12.0mm

<Traction performance on snowy roads>
Each sample tire was mounted on all wheels of a four-wheel drive vehicle with a maximum output of 477 KW under the following conditions. One test driver drove the test vehicle on a snowy road (excluding a snowy snowy road), and the running characteristics related to traction at this time were evaluated by the test driver's sensuality. The results are displayed with a score of Comparative Example 1 being 100. The larger the value, the better.
Rim: 16 × 6.0J
Internal pressure: 600kPa (all wheels)
Load capacity: 14.7kN

<Steering stability>
In the test vehicle, a test driver drove a test course on a dry asphalt road, and characteristics relating to handle response, rigidity, grip, and the like were evaluated by sensory evaluation of the driver. The results are displayed with a score of Comparative Example 1 being 100. The larger the value, the better.

<Drainage performance>
In the test vehicle, a test driver drove a test course on a wet asphalt road, and the braking distance until the vehicle stopped was measured by operating a full brake from a speed of 30 km / h. The result is evaluated by the reciprocal of the braking distance, and is displayed as an index with the value of Comparative Example 1 being 100. The larger the value, the better.

<Abrasion resistance>
In the above test vehicle, a test driver traveled 3000 km on a dry asphalt road test course. Thereafter, the remaining amount of the groove in the middle position of the middle lateral groove in the tire axial direction was measured at six locations in the tire circumferential direction, and the average value of the remaining amount of the groove was obtained. The results were displayed as an index with the value of Comparative Example 1 as 100. The larger the value, the better.

<Wear appearance>
The wear appearance of the middle lateral groove of the tire used for the above-mentioned wear resistance performance was confirmed. The results are displayed as a score with the value of Comparative Example 1 being 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 tire of the example was significantly improved as compared with the comparative example. In addition, the test was performed using one tire having a center main groove extending on the tire equator and a tire having a changed tire size. For all tires, the tires of the examples are the same as the tires of the comparative example. It was better than the test result.

3 Center main groove 4 Shoulder main groove 5 Middle lateral groove 10 Long side
11 Short side part 14 Inner part 15 Outer part

Claims (4)

One or a pair of center main grooves extending continuously in the tire circumferential direction on the tire equator or on both sides of the tire equator on the tread portion, and continuously extending in the tire circumferential direction on the outer side in the tire axial direction of the center main groove. A pneumatic tire provided with a pair of shoulder main grooves, and a plurality of middle lateral grooves that connect between the center main groove and the shoulder main groove,
The center main groove has a long side portion inclined to one side with respect to the tire circumferential direction and a short side portion inclined in the opposite direction to the long side portion and having a length smaller than the long side portion. Zigzag arranged in the
The middle lateral groove has an inner end in the tire axial direction communicating with the long side portion of the center main groove, and the middle lateral groove has an inner portion in the tire axial direction from an intermediate position of the tire axial direction length, An outer portion on the outer side in the tire axial direction,
The pneumatic tire according to claim 1, wherein an average groove depth of the outer portion is smaller than an average groove depth of the inner portion. The angle of the short side with respect to the tire axial direction is greater than 0 degree and less than or equal to 70 degrees,
The pneumatic tire according to claim 1, wherein an angle of the long side portion with respect to a tire axial direction is 70 degrees or more and less than 90 degrees.   The pneumatic tire according to claim 1 or 2, wherein a groove width of the middle lateral groove is constant.   The middle lateral groove has a first portion having a minimum groove depth on the outer side, and the groove depth at the position where the middle lateral groove communicates with the shoulder main groove is greater than the groove depth of the first portion. The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is larger.

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