JP5981893B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire with improved wear resistance and wet performance.

  Recent pneumatic tires are required to be excellent in wear resistance, that is, hard to wear and difficult to cause uneven wear.

  Patent Document 1 below proposes a pneumatic tire provided with a tie bar having a raised groove bottom in a lateral groove in order to suppress uneven wear of the tread portion. However, such a pneumatic tire has a problem in that since the groove bottom is raised, it is difficult for water to flow in the groove and wet performance is deteriorated.

JP-A-11-278016

  The present invention has been devised in view of the actual situation as described above, and improves wear resistance and wet performance on the basis of specifying the shape and the like of the groove provided in the middle block divided by sipes. The main purpose is to provide a pneumatic tire.

Among the present inventions, the invention according to claim 1 is characterized in that the tread portion has a pair of shoulder main grooves extending continuously in the tire circumferential direction on both sides of the tire equator and closest to the tread ground end, and between the pair of shoulder main grooves. Is provided with a center main groove extending continuously in the tire circumferential direction, so that a middle land portion is divided between the shoulder main groove and the center main groove on both sides of the tire equator. The middle land portion includes a middle block divided by a plurality of middle lateral grooves communicating between the shoulder main groove and the center main groove, and the middle block has an outer end in a tire axial direction. A middle lug groove that communicates with the shoulder main groove and whose inner end in the tire axial direction terminates in the middle block, and the tire circumferentially on the inner side in the tire axial direction from the inner end of the middle lug groove Provided at least one middle longitudinal groove extending in the direction that both ends of the middle longitudinal groove terminates in the middle block without connecting to the middle lateral grooves, the groove depth d1 of the middle lateral grooves, the middle longitudinal The groove depth d2 of the groove and the groove depth d3 of the middle lug groove satisfy the following expression.
d1 <d2 <d3

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the middle lateral groove includes a main body portion having a width of less than 2.0 mm.

  According to a third aspect of the present invention, the middle lateral groove includes a widened portion having a width of 2.0 mm or more, and the widened portion communicates with one of the main grooves. It is.

In the invention according to claim 4, the tread portion is provided with a pair of center main grooves disposed on both sides of the tire equator, and a center land portion divided between the pair of center main grooves. 4. The pneumatic tire according to claim 1, wherein a center lateral groove that communicates with the pair of center main grooves is provided in the center land portion. 5.

In the invention according to claim 5, the tread portion is provided with a shoulder land portion on the outer side in the tire axial direction of the shoulder main groove, and the shoulder land portion has a tire axial direction from the outer side of the tread grounding end. Extending between the plurality of shoulder lug grooves that terminate in the shoulder land portion and the shoulder lug grooves adjacent in the tire circumferential direction and extend substantially parallel to the shoulder lug groove from the outside of the tread grounding end. A shoulder sipe that terminates in the shoulder land portion, and an inner end of the shoulder lug groove and a shoulder vertical groove extending inward in the tire axial direction from the inner end of the shoulder sipe are provided. 4. The pneumatic tire according to any one of 4 above.

  The invention according to claim 6 is the pneumatic tire according to any one of claims 1 to 5, wherein the middle lateral groove is inclined at an angle of 30 to 60 degrees with respect to a tire axial direction.

  In the invention according to claim 7, each middle block is provided with two middle vertical grooves, and one middle vertical groove is provided on each side of the middle lug groove in the tire circumferential direction. A pneumatic tire according to any one of claims 1 to 6.

  The invention according to claim 8 is the pneumatic tire according to any one of claims 1 to 7, wherein at least one groove edge of the middle lug groove is curved in a direction in which the groove width increases at the outer end. It is.

  The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein at least one groove edge of the middle lateral groove is curved in a direction in which the groove width increases at the inner end in the tire axial direction. It is a pneumatic tire.

  The pneumatic tire of the present invention includes a middle block in which a middle land portion is divided by a plurality of middle lateral grooves that communicate between a shoulder main groove and a center main groove. Such a middle land portion has higher rigidity in the tire circumferential direction and exhibits excellent wear resistance as compared with a land portion divided by a wide lateral groove as in the prior art.

  Further, the middle block is provided with a middle lug groove whose outer end in the tire axial direction communicates with the shoulder main groove and whose inner end in the tire axial direction terminates in the middle block. Such a middle block has high rigidity at the inner side in the tire axial direction where a large contact pressure acts, and therefore, it is difficult for wear to occur and has excellent wet performance.

  Furthermore, the middle block is provided with at least one middle vertical groove extending in the tire circumferential direction on the inner side in the tire axial direction from the inner end of the middle lug groove. Moreover, both ends of the middle vertical groove terminate in the middle block without being connected to the middle horizontal groove. Such middle longitudinal grooves improve the drainage performance while making the rigidity of the inner and outer sides of the middle block in the tire axial direction uniform to suppress uneven wear.

  Therefore, the tire of the present invention has improved wear resistance and wet performance.

It is an expanded view of the tread part of the pneumatic tire of this embodiment. It is AA sectional drawing of FIG. It is an enlarged view of the middle land part of FIG. It is an enlarged view of the center land part of FIG. It is an enlarged view of the shoulder land part of FIG.

  As shown in FIG. 1, the pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment is suitably used as a radial tire for passenger cars, for example.

  The tread portion 2 of the tire 1 is provided with a pair of shoulder main grooves 3 and 3 and a pair of center main grooves 4 and 4. The center main groove 4 may be only one extending on the tire equator C, for example.

  The shoulder main groove 3 extends continuously in the tire circumferential direction on both sides of the tire equator C and on the tread ground contact end Te side. The shoulder main groove 3 of the present embodiment has a substantially constant groove width and extends linearly.

  The “tread grounding end Te” is a flat surface with a normal load applied to a normal tire 1 which is assembled with a normal rim (not shown) and filled with a normal internal pressure, and which is not loaded, with a camber angle of 0 °. This is the ground contact position on the outermost side in the tire axial direction when touching the ground.

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

  The “regular internal pressure” is the air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA, and “TIRE LOAD” for TRA. The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  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. “JAMATA” indicates “maximum load capacity”, and TRA indicates “TIRE” The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO.

  The center main groove 4 extends, for example, continuously between the shoulder main grooves 3 and 3 and both sides of the tire equator C in the tire circumferential direction. The center main groove 4 of the present embodiment has a substantially constant groove width and extends linearly.

  The groove width W1 of the shoulder main groove 3 and the groove width W2 of the center main groove 4 are, for example, 3.0 to 5.0% of the tread grounding width TW. Such shoulder main groove 3 and center main groove 4 effectively drain the water film between the road surface and the tread portion 2 during wet running, and improve the wet performance. The tread contact width TW is the distance in the tire axial direction between the tread contact ends Te and Te of the tire 1 in the normal state.

  FIG. 2 is a cross-sectional view taken along the line AA in FIG. As shown in FIG. 2, the groove depths d4 and d5 of the shoulder main groove 3 and the center main groove 4 are preferably 5 to 10 mm, for example.

  As shown in FIG. 1, the tread portion 2 includes a center land portion 6 between the pair of center main grooves 4, 4, a middle land portion 5, 5 between the shoulder main groove 3 and the center main groove 4, And it is divided into a pair of shoulder land parts 7 and 7 of the tire axial direction outside rather than the shoulder main grooves 3 and 3.

  FIG. 3 shows an enlarged view of the middle land portion 5. As shown in FIG. 3, the middle land portion 5 has a substantially constant width. The width W3 in the tire axial direction of the middle land portion 5 is preferably 0 of the tread ground contact width TW (shown in FIG. 1 and the same hereinafter) in order to exhibit excellent wear resistance and steering stability. .12 to 0.18 times.

  The middle land portion 5 is provided with a plurality of middle lateral grooves 11. The middle lateral groove 11 communicates between the shoulder main groove 3 and the center main groove 4. Thereby, the middle land portion 5 is divided into a plurality of middle blocks 10. Such a middle land portion 5 has higher rigidity in the tire circumferential direction and exhibits excellent wear resistance performance as compared with a land portion provided with a lateral groove having a large width.

  The middle lateral groove 11 includes a main body portion 12 extending with a width Ws of less than 2.0 mm and a widened portion 13 with a width of 2.0 mm or more.

  The widened portion 13 is provided inside the main body portion 12 in the tire axial direction. The widened portion 13 gradually increases the groove width toward the inner side in the tire axial direction. The widened portion 13 communicates with the center main groove 4. Thereby, at least one groove edge 11e of the middle lateral groove 11 is curved in a direction in which the groove width increases at the inner end 11i in the tire axial direction. For this reason, the drainage property of the middle lateral groove 11 is improved, and the chipping of the middle block 10 is suppressed. Accordingly, wear resistance and wet performance are improved.

  The middle lateral groove 11 is inclined with respect to the tire axial direction. The angle θ1 of the middle lateral groove 11 with respect to the tire axial direction is preferably 35 ° or more, more preferably 40 ° or more, and preferably 55 ° or less, more preferably 45, in order to improve wear resistance and steering stability performance. ° or less.

  As shown in FIG. 2, the groove depth d1 of the middle lateral groove 11 is preferably 0.30 times or more, more preferably 0.45 times or more, preferably 0 or more than the groove depth d5 of the center main groove 4. .50 times or less, more preferably 0.45 times or less. Such middle lateral grooves 11 improve wet performance while maintaining the rigidity of the middle land portion 5.

  As shown in FIG. 3, the tread surface 10s of the middle block 10 of the present embodiment has a substantially parallelogram shape. The middle block 10 is provided with a middle lug groove 14 and a middle vertical groove 15.

  In the middle lug groove 14, the outer end 14 o in the tire axial direction communicates with the shoulder main groove 3, and the inner end 14 i in the tire axial direction terminates in the middle block 10. Therefore, the middle block 10 has high rigidity at the inner portion in the tire axial direction where a large contact pressure acts, so that it is difficult for wear to occur and has excellent wet performance.

  The groove width W4 of the middle lug groove 14 is preferably 0.50 times or more, more preferably 0.55 times or more, preferably 0.65 times the groove width W1 of the shoulder main groove 3 (shown in FIG. 1). Hereinafter, it is more preferably 0.60 or less. Such a middle lug groove 14 maintains the rigidity of the middle land portion 5 and improves the wet performance without impairing the steering stability performance.

  From the same point of view, the length L1 of the middle lug groove 14 in the tire axial direction is preferably 0.40 times or more, more preferably 0.45 times or more, the width W3 of the middle land portion 5 in the tire axial direction. Is 0.60 times or less, more preferably 0.55 times or less.

  The middle lug groove 14 is inclined with respect to the tire axial direction in the same direction as the middle lateral groove 11. The angle θ2 of the middle lug groove 14 with respect to the tire axial direction is preferably 35 ° or more, more preferably 40 ° or more, preferably 55 ° or less, more preferably 50 ° or less. When the angle θ2 of the middle lug groove 14 with respect to the tire axial direction is smaller than 35 °, the rigidity in the tire circumferential direction of the middle land portion 5 may be lowered, and the wear resistance performance and the steering stability performance may be lowered. Conversely, if the angle θ2 is greater than 55 °, the lateral stiffness may be reduced.

  In the present embodiment, at least one groove edge 14e of the middle lug groove 14 is curved, for example, in an arc shape in a direction in which the groove width increases at the outer end 14o in the tire axial direction. Thereby, the middle lug groove 14 can exhibit high drainage.

  As shown in FIG. 2, the groove depth d3 of the middle lug groove 14 is preferably 0.50 times or more, more preferably 0.55 times or more, preferably 0 or more times the groove depth d5 of the center main groove 4. .70 times or less, more preferably 0.65 times or less. Such middle lateral grooves 11 improve wet performance while maintaining steering stability performance and wear resistance performance.

  The middle lug groove 14 has a raised portion 16 with a groove bottom portion 14d raised on the outer end 14o side in the tire axial direction. Such a middle lug groove 14 prevents an excessive decrease in rigidity on the outer side in the tire axial direction of the middle land portion 5 and suppresses uneven wear of the middle land portion 5.

  As shown in FIG. 3, the middle vertical groove 15 extends inward in the tire axial direction from the inner end 14 i of the middle lug groove 14 in the tire circumferential direction. Both ends 15 e and 15 e of the middle vertical groove 15 are terminated in the middle block 10 without being connected to the middle horizontal groove 11. Such middle vertical grooves 15 bring the rigidity of the inner and outer sides of the middle block 10 in the tire axial direction uniformly close to each other, and improve drainage while suppressing uneven wear.

  In the present embodiment, one middle vertical groove 15 is provided on each side of the middle lug groove 14 in the tire circumferential direction. Such middle vertical groove 15 further improves the above-described action, and suppresses heel and toe wear.

  The middle vertical groove 15 has a substantially constant groove width and extends linearly along the tire circumferential direction. The groove width W5 of the middle vertical groove 15 is preferably 0.8 mm or more, more preferably 1.0 mm or more, preferably 1.6 mm or less, more preferably 1.4 mm or less. Such middle vertical groove 15 exhibits excellent wet performance without impairing steering stability performance.

  From the same point of view, as shown in FIG. 2, the groove depth d2 of the middle vertical groove 15 is preferably 0.45 times or more, more preferably 0.48 times or more of the groove depth d5 of the center main groove 4. It is preferably 0.55 times or less, more preferably 0.52 times or less.

The rigidity distribution of the middle land portion 5 is affected by the groove depths of the middle lateral groove 11, middle vertical groove 15, and middle lug groove 14. Therefore, it is desirable that the groove depth d1 of the middle lateral groove 11, the groove depth d2 of the middle vertical groove 15, and the groove depth d3 of the middle lug groove 14 satisfy the following expressions (1) and (2). More preferably, it is desirable that the groove depths d1 to d3 satisfy the relationship of the following formula (3).
d1 ≦ d2 ≦ d3 (1)
d1 <d3 (2)
d1 <d2 <d3 (3)

  When the groove depth d1 of the middle lateral groove 11 is the smallest, the rigidity in the tire circumferential direction of the middle land portion 5 is relatively larger than the rigidity in the tire axial direction. In addition, when the groove depth d3 of the middle lug groove 14 disposed on the outer side in the tire axial direction of the middle vertical groove 15 is the largest, the rigidity of the middle land portion 5 gradually decreases toward the outer side in the tire axial direction. Thereby, since the middle land part 5 has the rigidity distribution according to a contact pressure, the outstanding wear resistance performance and steering stability performance are exhibited.

  FIG. 4 shows an enlarged view of the center land portion 6. The center land portion 6 is provided with a plurality of center lateral grooves 22. The center lateral groove 22 communicates with the center main grooves 4 and 4 on both sides. Thereby, the center land portion 6 is a block row in which a plurality of center blocks 20 are arranged.

  The maximum width W6 in the tire axial direction of the center land portion 6 is preferably 0.08 to 0.12 times the tread ground contact width TW.

  The center lateral groove 22 is inclined in the same direction as the middle lateral groove 11 (shown in FIG. 1). The center lateral groove 22 extends with a substantially constant groove width. The groove width W7 of the center lateral groove 22 is preferably 0.44 times or more, more preferably 0.46 times or more, preferably 0.52 times or less the groove width W2 (shown in FIG. 1) of the center main groove 4. More preferably, it is 0.50 times or less. When the groove width W7 of the center lateral groove 22 is smaller than 0.44 times the groove width W2 of the center main groove 4, the wet performance may not be improved. On the contrary, when the groove width W7 of the center lateral groove 22 is larger than 0.52 times the groove width W2 of the center main groove 4, the rigidity of the center land portion 6 is lowered, and the steering stability performance may be lowered.

  From the same point of view, as shown in FIG. 2, the groove depth d6 of the center lateral groove 22 is preferably 0.68 times or more, more preferably 0.70 times or more of the groove depth d5 of the center main groove 4. Yes, preferably 0.76 times or less, more preferably 0.74 times or less.

  The center lateral groove 22 is preferably provided with a tie bar 23 having a groove bottom portion 22d raised. Such a tie bar 23 improves the rigidity of the center land portion 6 while maintaining wet performance.

  FIG. 5 shows an enlarged view of the shoulder land portion 7. As shown in FIG. 5, the shoulder land portion 7 has a substantially constant width. The width W8 of the shoulder land portion 7 in the tire axial direction is preferably 0.20 to 0.26 times the tread contact width TW in order to achieve both turning stability performance and riding comfort performance. Such a shoulder land portion 7 exhibits excellent wear resistance performance and steering stability performance.

  The shoulder land portion 7 is provided with a shoulder lug groove 31, a shoulder sipe 32, and a shoulder longitudinal groove 33.

  The shoulder lug groove 31 extends in the tire axial direction from the outside of the tread ground contact end Te and ends in the shoulder land portion 7. Thereby, wet performance and wandering performance are improved.

  The groove width W9 of the shoulder lug groove 31 is preferably 0.62 times or more, more preferably 0.64 times or more, preferably 0.70 times or less, more preferably 0, the groove width W1 of the shoulder main groove 3. .68 times or less. Such a shoulder lug groove 31 maintains the rigidity of the shoulder land portion 7, exhibits excellent wear resistance performance, and improves wet performance and wandering performance.

  The inner end 31 i of the shoulder lug groove 31 is preferably provided with a short sipe 34 extending in the tire axial direction and communicating with the shoulder main groove 3. Such a short sipe 34 improves the drainage performance of the shoulder lug groove 31 while maintaining the rigidity of the shoulder land portion 7 on the inner side in the tire axial direction. Therefore, excellent wear resistance and wet performance are exhibited.

  The shoulder sipe 32 is provided between the shoulder lug grooves 31 that are adjacent in the tire circumferential direction. The shoulder sipe 32 extends substantially parallel to the shoulder lug groove 31 from the outside of the tread ground end Te and ends in the shoulder land portion 7. Such a shoulder sipe 32 makes the rigidity distribution of the shoulder land portion 7 uniform, suppresses uneven wear, and improves wet performance and wandering performance.

  The shoulder vertical groove 33 extends in the tire circumferential direction on the inner side in the tire axial direction from the inner end 31 i of the shoulder lug groove 31 and the inner end 32 i of the shoulder sipe 32. Both ends 33 e and 33 e of the shoulder vertical groove 33 terminate in the shoulder land portion 7 without being connected to the shoulder lug groove 31 and the shoulder sipe 32. Such a shoulder longitudinal groove 33 makes the rigidity distribution in the tire axial direction of the shoulder land portion 7 uniform, and suppresses uneven wear.

  The groove width W10 of the shoulder longitudinal groove 33 is preferably 0.8 mm or more, more preferably 1.0 mm or more, preferably 1.6 mm or less, more preferably 1.4 mm or less. Such a shoulder longitudinal groove 33 exhibits excellent wet performance without impairing steering stability performance.

  Although the pneumatic tire of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be implemented with various modifications.

A pneumatic tire of size 195 / 65R15 having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1 and tested for wet performance, turning stability performance and riding comfort performance. The common specifications and test methods for each tire are as follows.
Wearing rim: 15 × 6J
Tire internal pressure: 240 kPa
Test vehicle: Front-wheel drive vehicle, displacement 1600cc
Tire mounting position: all wheels

<Wet performance>
The test vehicle enters the following test course while gradually increasing the speed, the lateral acceleration (lateral G) of the front wheels of the test vehicle is measured, and the average lateral G of the front wheels at a speed of 55 to 80 km / h is calculated. It was done. The results are displayed as an index with the value of Comparative Example 1 being 100. It shows that it is excellent in wet performance, so that a numerical value is large.
Test course: Circulation course with a radius of 100 m Road surface: A water pool with a depth of 6 mm and a length of 6 m is installed on the asphalt road surface.

<Abrasion resistance>
The amount of wear when the test vehicle traveled 8000 km on a general road was measured. The evaluation is performed by the reciprocal of the amount of wear, and is displayed as an index with the value of Comparative Example 1 being 100. Larger values indicate better wear resistance.

  As a result of the test, it can be confirmed that the wet performance and the wear resistance performance of the tire of the example are improved as compared with the comparative example.

DESCRIPTION OF SYMBOLS 1 Tire 2 Tread part 3 Shoulder main groove 4 Center main groove 5 Middle land part 10 Middle block 11 Middle lateral groove 14 Middle lug groove 15 Middle vertical groove

Claims (9)

A pair of shoulder main grooves extending continuously in the tire circumferential direction on both sides of the tire equator and on the tread grounding end side, and a center main groove extending continuously between the pair of shoulder main grooves in the tire circumferential direction on the tread portion; A pneumatic tire in which a middle land portion is divided between the shoulder main groove and the center main groove on both sides of the tire equator,
The middle land portion includes a middle block divided by a plurality of middle lateral grooves communicating between the shoulder main groove and the center main groove,
The middle block has a middle lug groove whose outer end in the tire axial direction communicates with the shoulder main groove and whose inner end in the tire axial direction terminates in the middle block;
And at least one middle vertical groove extending in the tire circumferential direction on the inner side in the tire axial direction from the inner end of the middle lug groove,
Both ends of the middle vertical groove terminate in the middle block without being connected to the middle horizontal groove ,
The pneumatic tire according to claim 1, wherein the groove depth d1 of the middle lateral groove, the groove depth d2 of the middle vertical groove, and the groove depth d3 of the middle lug groove satisfy the following expressions.
d1 <d2 <d3   The pneumatic tire according to claim 1, wherein the middle lateral groove includes a main body portion having a width of less than 2.0 mm. The middle lateral groove includes a widened portion having a width of 2.0 mm or more,
The pneumatic tire according to claim 2, wherein the widened portion communicates with one of the main grooves. The tread portion is provided with a pair of the center main grooves disposed on both sides of the tire equator, and a center land portion divided between the pair of center main grooves,
The pneumatic tire according to any one of claims 1 to 3, wherein a center lateral groove that communicates with the pair of center main grooves is provided in the center land portion. The tread portion is provided with a shoulder land portion on the outer side in the tire axial direction of the shoulder main groove,
In the shoulder land portion,
A plurality of shoulder lug grooves extending in the tire axial direction from the outside of the tread grounding end and terminating in the shoulder land portion;
A shoulder sipe provided between the shoulder lug grooves adjacent in the tire circumferential direction and extending substantially parallel to the shoulder lug groove from the outside of the tread ground end, and terminating in the shoulder land portion;
The pneumatic tire according to any one of claims 1 to 4, wherein a shoulder longitudinal groove extending in the tire circumferential direction on the inner side in the tire axial direction from the inner end of the shoulder lug groove and the inner end of the shoulder sipe is provided.   The pneumatic tire according to any one of claims 1 to 5, wherein the middle lateral groove is inclined at an angle of 30 to 60 ° with respect to a tire axial direction. Each middle block is provided with two middle longitudinal grooves,
In addition, the middle vertical groove is a pneumatic tire according to any one of claims 1 to 6, wherein one middle longitudinal groove is provided on each side of the middle lug groove in the tire circumferential direction.   The pneumatic tire according to claim 1, wherein at least one groove edge of the middle lug groove is curved in a direction in which the groove width increases at the outer end. The pneumatic tire according to any one of claims 1 to 8, wherein at least one groove edge of the middle lateral groove is curved in a direction in which a groove width increases at an inner end in a tire axial direction.

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