JP5133635B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that has improved uneven wear resistance performance of a land portion on the innermost side in the vehicle width direction when the vehicle is mounted.

  A tire with a so-called asymmetric pattern in which the tread pattern is asymmetric with respect to the tire equatorial plane is a portion that is on the outside of the vehicle when mounted on the vehicle, while the portion that is on the inside of the vehicle when mounted on the vehicle, in order to improve steering stability It is general that the functions are separated from each other in order to improve drainage.

  In load rolling during actual use of a tire, a camber angle is often given to the tire, and this camber angle has a great influence on tire wear, steering stability, drainage, and the like.

  Since the load movement (front turning) during braking of the vehicle works to increase the negative camber angle of the tire mounted on the vehicle (the direction of the letter C when looking at the left and right tires from the front of the vehicle), There is a problem in that the load in the rotational direction increases on the inner side when the vehicle is mounted, and uneven wear tends to occur on the inner land portion when the vehicle is mounted.

  This uneven wear is caused by the difference between the tire diameter at the contact point and the tire diameter at the center of the tread, and the contact point side is dragged with respect to the road surface during running, and the contact point side wears more than the tire equator side. (Shoulder wear). In particular, when the rigidity of the land portion on the inner side when the vehicle is mounted is too high, such uneven wear tends to occur.

In order to aim at such uneven wear resistance of the land portion, a technique is known in which a plurality of independent depressions (concave portions) are arranged in the circumferential direction on the shoulder side land portion (see, for example, Patent Document 1).
JP 2006-76338 A

  By arranging the depression in the land portion, the rigidity of the land portion can be partially reduced and the progress of shoulder drop wear can be suppressed. However, as shown in Patent Document 1, the width of the tire is arranged in the land portion where the depression is arranged. If there are other groove elements, there is a problem in that they affect each other and cause another new uneven wear such as heel and toe wear.

  The present invention has been made to solve the above problems, and aims to provide a pneumatic tire with higher uneven wear resistance than conventional ones that can suppress not only shoulder wear but also other uneven wear. To do.

The invention according to claim 1 is a pneumatic tire provided with a plurality of land portions defined on a tread by a plurality of circumferential main grooves, and is an innermost land portion disposed on the vehicle inner side when the vehicle is mounted. A plurality of independent first dents arranged along the tire circumferential direction on the ground contact end side, and a plurality of independent second dents longer on the tire equatorial plane side in the tire circumferential direction than the first depression. Are arranged along the tire circumferential direction, and the first depression has a dimension in the tire circumferential direction within twice the dimension in the tire width direction, and the innermost land portion includes the first depression. It is characterized in that the depressions are provided in at least two rows in the tire width direction .

Next, the operation of the pneumatic tire according to claim 1 will be described.
In the pneumatic tire according to claim 1, a plurality of independent first depressions are arranged along the tire circumferential direction on the ground contact end side of the innermost land portion arranged on the vehicle inner side when the vehicle is mounted. The land portion rigidity on the ground contact end side is reduced, the contact pressure is lowered, wear on the ground contact end side is suppressed, and shoulder drop wear generated on the ground contact end side of the innermost land portion is suppressed.

Further, in the innermost land portion, a plurality of independent second depressions that are longer in the tire circumferential direction than the first depression are arranged along the tire circumferential direction on the tire equatorial plane side. Land contact characteristics can be optimized, and since there is no lug groove component connected to the circumferential main groove, occurrence of new uneven wear such as heel and toe wear can be suppressed. A 2nd hollow is a shape long in the circumferential direction, and drainage property is also ensured by arrange | positioning two or more along the circumferential direction.
The term “independent” as used herein means not connected to the circumferential main groove and the lug groove for draining water in the grounding surface at the time of grounding.

Further, in the first depression, the tire circumferential direction dimension is within twice the tire width direction dimension, and the tire circumferential direction dimension and the tire width direction dimension are made as equal as possible, so that the periphery of the first depression It is possible to make the rigidity uniform, and it is possible to suppress the occurrence of new uneven wear due to the uneven rigidity around the recess.

Furthermore, it becomes easy to adjust the rigidity of the innermost land portion by providing at least two rows of first recesses in the tire width direction. In particular, when the width of the innermost land portion is wide, the effect of suppressing uneven wear may be insufficient if the number of the first recesses is one, so the number of rows of the first recesses is set according to the width of the innermost land portion. It is preferable to use two or more rows so as to obtain a sufficient uneven wear suppression effect.

The invention of claim 2 is the pneumatic tire according to claim 1, wherein the first recess is farther from the tire equatorial plane, is larger in volume, it is characterized in that.

Next, the operation of the pneumatic tire according to claim 2 will be described .
When the innermost land portion is viewed in a cross section in the tread width direction, the shoulder drop wear has the largest amount of wear on the ground contact end side, and the amount of wear decreases toward the tire equatorial plane side.
Therefore, in order to suppress the shoulder wear, it is effective to increase the volume of the first recess farther from the tire equatorial plane and reduce the compression rigidity particularly near the ground contact edge.

The invention according to claim 3 is the pneumatic tire according to claim 1 or claim 2 , wherein the second recess has a tire circumferential direction dimension that is at least three times the tire width direction dimension. It is characterized by that.

Next, the operation of the pneumatic tire according to claim 3 will be described .
By setting the dimension in the tire circumferential direction of the second depression disposed on the tire equatorial plane side to be three times or more the dimension in the tire width direction, high drainage can be obtained in the innermost land portion.
Note that if the second dent is made longer than the contact length at the position where the second dent is formed, air column resonance noise may be generated in the second dent at the time of contact, so the length of the second dent. Is preferably shorter than the contact length at the formation position of the second depression.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the second recess is connected by a sipe in the tire circumferential direction. It is said.

Next, the operation of the pneumatic tire according to claim 4 will be described .
The depression that is not connected to the main groove and is independent in the land portion may cause a pumping sound (pattern noise) during traveling.
In the pneumatic tire according to claim 4, by connecting the second depressions to each other with a sipe in the tire circumferential direction, the internal air is grounded via the sipe when the second depression comes into contact with the road surface. It is possible to escape to the other second indentation side. Therefore, the air in the second depression is suppressed from being compressed at the time of grounding, and the generation of pumping noise is suppressed.

  The sipe that connects the second depressions has a groove width that is not completely closed when grounded, and the groove width is preferably in the range of 0.3 to 2.0 mm. If the sipe is completely closed at the time of grounding, the generation of the pumping sound cannot be suppressed. On the other hand, if the groove width of the sipe is too wide, the second groove and the sipe form a circumferential groove continuously in the circumferential direction, and the land portion rigidity of the innermost land portion is excessively lowered. Will be affected.

  As described above, according to the pneumatic tire of the present invention, there is an effect that the uneven wear resistance performance higher than the conventional one can be obtained.

Hereinafter, a pneumatic tire 10 according to an embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the tread 12 of the pneumatic tire 10 of the present embodiment has a first circumferential main groove 14 on the outer side of the tire equator plane CL when the vehicle is mounted (the arrow direction OUT direction is the outer side when the vehicle is mounted). And the second circumferential main groove 16 is formed on the inner side of the tire equatorial plane CL when the vehicle is mounted (the arrow IN direction is the inner side when the vehicle is mounted), and the second circumferential main groove 16 is inner when the vehicle is mounted. In addition, a third circumferential main groove 18 is formed, and the first land portion 20, the first circumferential main groove 14 and the second circumferential main groove 18 are disposed outside the first circumferential main groove 14 when the vehicle is mounted. Between the circumferential main groove 16, the second land portion 22, between the second circumferential main groove 16 and the third circumferential main groove 18, the third land portion 24, the third circumference A fourth land portion 26 is defined inside each of the direction main grooves 18 when the vehicle is mounted.

  The first land portion 20 includes a first lug groove 28 that traverses the first land portion, and a second lug groove 30 that extends from the ground contact end 12E side to the tire equatorial plane CL side and terminates in the land portion. Are alternately formed in the circumferential direction. Further, the first land portion 20 is formed with a first sipe 32 extending in the circumferential direction and a second sipe 34 that connects the second lug groove 30 and the first circumferential main groove 14. Yes.

  Here, the ground contact edge 12E means that the pneumatic tire 10 is mounted on a standard rim defined in JATMA YEAR BOOK (2007, Japan Automobile Tire Association Standard), and applied size and ply rating in JATMA YEAR BOOK. This is when the maximum load capacity is loaded with 100% internal pressure of the air pressure (maximum air pressure) corresponding to the maximum load capacity (bold load in the internal pressure-load capacity correspondence table). When the TRA standard or ETRTO standard is applied at the place of use or manufacturing, the respective standards are followed.

  The second land portion 22 includes a first inclined groove portion 36A that extends from the circumferential main groove 14 inwardly with respect to the tire circumferential direction toward the inner side when the vehicle is mounted, and terminates in the land portion. The slope groove portion 36A slopes rightward with respect to the tire circumferential direction from the end portion in the land portion of the inclined groove portion 36A and ends in the land portion, and the angle with respect to the tire circumferential direction is set smaller than that of the first slope groove portion 36A. A plurality of V-shaped grooves 36 including the second inclined groove portions 36B are formed at intervals in the tire circumferential direction.

In the second land portion 22, a short third lug groove 40 is formed on an extension line of the first lug groove 28 formed in the first land portion 20.
Further, the second land portion 22 includes a third sipe 42 that connects the intermediate portion of the first inclined groove portion 36A and the first circumferential main groove 14, and an intermediate portion between one end of the second inclined groove portion 36B. A fourth sipe 44 that connects the portion and the second circumferential main groove 16 is formed.

  The third land portion 24 is formed with a fifth sipe 46 having one end connected to the third circumferential main groove 18 and the other end terminating in the land portion. A round hole 47 is formed in the end portion.

In the fourth land portion 26, two first dent rows 50 in which a plurality of independent first dents 48 are arranged along the tire circumferential direction are arranged on the ground contact end 12E side. The first dent row 50 is disposed closer to the ground contact end 12E than the center of the fourth land portion 26 in the width direction.
The first recess 48 of the present embodiment has a trapezoidal shape in which the side on the ground contact end 12E side is shorter than the side on the tire equatorial plane CL side, but may have other shapes. The first depression 48 preferably has a tire circumferential dimension L that is within twice the tire width dimension W, and the tire circumferential dimension and the tire width dimension are as equal as possible. The depth of the first recess 48 is set within a range of 40 to 100% of the height dimension of the fourth land portion 26 (= the groove depth dimension of the third circumferential main groove 18). It is preferable.

Further, the fourth land portion 26 has a second dent row 54 in which a plurality of independent second dents 52 are arranged along the tire circumferential direction on the tire equatorial plane CL side with respect to the first dent row 50. Has been placed.
The second recess 52 is set to have a longer tire circumferential dimension than the first recess 48. The second recess 52 is preferably set to have a tire circumferential direction dimension that is at least three times the tire width direction dimension and shorter than the contact length at the position where the second recess 52 is formed.

The depth of the second recess 52 is set within a range of 40 to 100% of the height dimension of the fourth land portion 26 (= the groove depth dimension of the third circumferential main groove 18). It is preferable.
In the present embodiment, the second recesses 52 are connected to each other by a sipe 56 in the tire circumferential direction.
The groove width of the sipe 56 is set so as not to be completely closed when grounding, and the groove width is preferably within a range of 0.3 to 2.0 mm.

In addition, the 2nd land part 22, the 3rd land part 24, and the 4th land part 26 are not completely divided | segmented by the lug groove which crosses a land part, but are what is called a rib shape. .
Incidentally, in the pneumatic tire 10 of the present embodiment, there is no designation of the rotation direction.

(Function)
In the pneumatic tire 10 of the present embodiment, a plurality of first depressions 48 are arranged along the tire circumferential direction on the outer portion in the tire width direction of the fourth land portion 26 arranged on the vehicle inner side when the vehicle is mounted. Thus, the rigidity of the land portion on the ground contact end side of the fourth land portion 26 is lowered, and the shoulder fall wear on the ground contact end side can be suppressed. In the first recess 48, the tire circumferential dimension is set to be within twice the tire width dimension, and the tire circumferential dimension and the tire width dimension are made as equal as possible. The rigidity around the recess 48 is made uniform, and the occurrence of new uneven wear due to the non-uniform rigidity around the first recess 48 is suppressed.

Here, when the dimension L in the tire circumferential direction of the first depression 48 exceeds twice the dimension W in the tire width direction, the first depression 48 becomes a groove shape long in the tire circumferential direction, and the first depression 48 There is a possibility that the peripheral rigidity becomes non-uniform and new uneven wear occurs, or the lateral rigidity of the fourth land portion 26 is lowered to affect the steering stability.
Further, when the depth of the first recess 48 is less than 40% of the height dimension of the fourth land portion 26, the first recess 48 becomes shallow, so the recess disappears early, and uneven wear (shoulder fall). The effect of suppressing wear) cannot be maintained over a long period of time.

  In the fourth land portion 26 arranged on the vehicle inner side when the vehicle is mounted, the third circumferential main groove 18 is longer on the tire equatorial plane CL side and longer in the tire circumferential direction than the first recess 48. Since the plurality of independent second depressions 52 that are not connected to each other are arranged along the tire circumferential direction, the rigidity of the fourth land portion 26 on the tire equatorial plane CL side is appropriately reduced, and the fourth land portion 26 is optimized, and since there is no lug groove component extending in the tread width direction, occurrence of new uneven wear such as heel and toe wear in the fourth land portion 26 is also suppressed.

  The second depression 52 is long in the circumferential direction, and the dimension in the tire circumferential direction is set to be three times or more the dimension in the tire width direction, and such second depression 52 is arranged in the circumferential direction in the fourth land portion 26. Therefore, high drainage is ensured in the fourth land portion 26.

  Furthermore, in this embodiment, since the 2nd hollow 52 is connected to the circumferential direction with the sipe 56, when the 2nd hollow 52 contacts a road surface, internal air is grounded via the sipe 56. It is possible to escape to the other second recess 52 side that is not present, and the generation of pumping noise is suppressed.

Here, when the depth of the second depression 52 is less than 40% of the height dimension of the fourth land portion 26, the second depression 52 becomes shallow, so the depression disappears early, and the second depression 52 The effect of suppressing uneven wear due to 52 cannot be maintained for a long time.
Further, if the groove width of the sipe 56 is less than 0.3 mm, the sipe 56 may be completely closed when grounding, and if the sipe 56 is completely closed, generation of a pumping sound cannot be suppressed. On the other hand, if the groove width of the sipe 56 exceeds 2.0 mm, the groove width of the sipe 56 is too wide, and the second recess 52 and the sipe 56 form a circumferential groove continuously in the circumferential direction. Other land performances are affected, for example, the land portion rigidity of the land portion 26 of 4 is too low.

[Other Embodiments]
In the present embodiment, the first land row 26 is provided with two first indentation rows 50, but the number of the first indentation rows 50 depends on the required shoulder fall wear suppression effect. You can increase or decrease. For example, if the width of the fourth land portion 26 is increased, three or more first depression rows 50 may be provided accordingly, and if one row is sufficient, one row may be provided.

  In the present embodiment, the first recesses 48 have the same size, but the first recesses 48 may not all have the same size. For example, in the fourth land portion 26, it is preferable to set the volume of the first depression 48 on the ground contact end side larger than the volume of the first depression 48 on the tire equatorial plane CL side. Thereby, in the 4th land part 26, the compression rigidity of the vicinity of a contact end can be reduced rather than the tire equator surface CL, and shoulder fall wear can be suppressed more effectively. Methods for increasing the volume include changing the depth, changing the maximum size of the tread in plan view, and the like.

  In the fourth land portion 26, as described above, the volume of the first depression 48 may be changed as a method for reducing the compression rigidity in the vicinity of the ground contact edge than the tire equatorial plane CL. A method in which the circumferential interval (pitch) of the first depressions 48 in the first depression row 50 is made smaller than the circumferential interval (pitch) of the first depressions 48 in the first depression row 50 on the tire equatorial plane side. There is.

(Test example)
In order to confirm the effect of the present invention, a pneumatic tire of a conventional example and a pneumatic tire of an example to which the present invention was applied were prepared and subjected to uneven wear resistance tests.

  Example: A pneumatic tire having the tread pattern of the above-described embodiment. The width of the second recess is 3 mm, the length is 21 mm, the depth is 7.5 mm, the width of the sipe connecting the second recesses is 0.7 mm, and the depth is 7.5 mm.

  Conventional example: A pneumatic tire having the tread pattern shown in FIG. In the tread 100 shown in FIG. 2, reference numerals 102, 104, 106, and 108 are circumferential main grooves, reference numerals 110, 112, 114, 116, and 118 are land portions, reference numerals 120, 122, and 123 are lug grooves, and reference numeral 124. , 126, 127 are sipes, 128 is a bent groove having a substantially L shape made up of a lug groove portion 128A and a circumferential groove portion 128B, 130, 132 are depressions whose tread plan view shape is triangular, and 134 Is a sipe extending from the depression 130 toward the tread end, and reference numeral 100E is a ground end. The groove depths of the lug groove portion 128A and the circumferential groove portion 128B are each 7.5 mm, the lug groove portion 128A has a width of 3 mm and a length of 12 mm, and the circumferential groove portion 128B has a width of 4 mm and a length of 12 mm.

  Uneven wear test method: Pneumatic tires are mounted on a real vehicle (load: equivalent to two real vehicles) and mode driving is performed assuming highways, city roads, and mountain slopes. Evaluation was made after measuring 5000 km from the bottom of the innermost circumferential main groove in the region on the tire equatorial plane side of the innermost land, where the land was recessed (the lowest part). did. The evaluation is as described in Table 1 below, and the index is displayed with the height of the conventional example as 100, and the larger the value, the better the uneven wear resistance.

試験の結果、本発明の適用された実施例の空気入りタイヤは、車両装着時最内側の陸部において、従来例の空気入りタイヤよりもタイヤ赤道面側の偏摩耗が大幅に抑制されており、耐偏摩耗性能に優れていることが分かった。

As a result of the test, in the pneumatic tire of the example to which the present invention was applied, the uneven wear on the tire equatorial plane side was significantly suppressed in the innermost land portion when the vehicle was mounted, compared to the pneumatic tire of the conventional example. It was found that it was excellent in uneven wear resistance.

It is a top view of the tread of the pneumatic tire concerning one embodiment of the present invention. It is a top view of the tread of the pneumatic tire concerning a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 1st circumferential main groove 16 2nd circumferential main groove 18 3rd circumferential main groove 20 1st land part 22 2nd land part 24 3rd land part 26 2nd 4 land parts 48 first dent 52 second dent 56 sipe

Claims (4)

A pneumatic tire having a plurality of land portions partitioned by a plurality of circumferential main grooves on a tread,
A plurality of independent first depressions are arranged along the tire circumferential direction on the ground contact end side in the innermost land portion arranged on the inner side of the vehicle when the vehicle is mounted, and from the first depression on the tire equatorial plane side. A plurality of independent second depressions that are long in the tire circumferential direction are arranged along the tire circumferential direction ,
The first recess has a tire circumferential direction dimension that is within twice the tire width direction dimension,
The pneumatic tire according to claim 1, wherein the innermost land portion is provided with at least two rows of the first depressions in the tire width direction . 2. The pneumatic tire according to claim 1 , wherein the volume of the first depression increases as the distance from the tire equatorial plane increases. 3. The pneumatic tire according to claim 1, wherein the second depression has a tire circumferential direction dimension that is three times or more of a tire width direction dimension. 4. The pneumatic tire according to any one of claims 1 to 3, wherein the second depression is connected by a sipe in a tire circumferential direction.

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