JP2012020702A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving stone-biting resistant performance, even if a bottom width of a groove is narrow.SOLUTION: This pneumatic tire 1 has a pattern of a land part 5 divided by main grooves 3A and 3B in the tire circumferential direction and a peripheral groove 4 in the tire width direction. A projection part 6 is arranged for projecting toward the tread side from the groove bottom of the main groove 3A in an intersection part between the main groove 3A and the peripheral groove 4 and projecting toward the peripheral groove 4 side from a sidewall 5a of the land part 5 opposed by sandwiching the main groove 3A to an opening part to the main groove 3A of the peripheral groove 4 in its intersection part. Its projection part 6 is formed in a shape and a position for discharging a stone of its intersection part and communicating the main groove 3A in the tire circumferential direction even in the last stage of abrasion of a tread 2a.

Description

  The present invention relates to a pneumatic tire having a land pattern such as a block constituted by a main groove in the tire circumferential direction and a lateral groove in the tire width direction.

  In this type of pneumatic tire, there is a possibility that stones that have entered the intersection of the main groove and the lateral groove may not be removed, and this is particularly likely to occur at the end of wear on the tread. And when such a stone biting occurs, the groove bottom of the main groove is cut by so-called stone drilling, which may cause a decrease in durability and a correction rate due to rust of the belt. Conventionally, in order to improve such an inconvenience, for example, as in Patent Documents 1 and 2 below, there is a technique in which a protrusion (so-called stone ejector) is provided at the groove bottom at the intersection to prevent the stone from being caught. Are known.

JP 2003-54220 A International Publication No. 2006/043373

  However, in the case of a pneumatic tire having a narrow groove bottom of the main groove, for example, a heavy duty pneumatic tire having a large groove depth and a narrow groove width, a stone ejector is placed on the groove bottom of the narrow main groove. It is difficult to secure the installation space, and even if it can be installed in analogy, there is a possibility that sufficient size and strength of the stone ejector cannot be secured. For this reason, in such a pneumatic tire with a narrow groove bottom of the main groove, there is a possibility that it is not possible to avoid the stone biting at the intersection of the main groove and the lateral groove.

  Accordingly, the object of the present invention is to provide a pneumatic tire capable of improving the inconvenience of such a conventional example and improving the stone biting performance even if the width of the bottom of the main groove is narrow. To do.

  In order to achieve the above object, the present invention provides a pneumatic tire having a land portion pattern divided by a main groove in the tire circumferential direction and a lateral groove in the tire width direction, at the intersection of the main groove and the lateral groove. From the side wall of the land portion that protrudes from the groove bottom of the main groove toward the tread side and that faces the opening of the transverse groove to the main groove at the intersection portion with the main groove interposed therebetween. It is characterized by providing a protruding portion that protrudes toward the lateral groove.

  Here, it is preferable that the protruding portion is formed in a shape and a position where the stone at the intersection is discharged and the main groove communicates in the tire circumferential direction even at the end of wear of the tread.

  Further, the protruding portion gradually increases from the side wall to the side groove side as it goes from the tread surface side to the groove bottom side of the main groove, and as the side groove side goes to the side wall side. It is desirable to have an inclined surface that gradually increases the amount of protrusion from the groove bottom to the tread surface side of the main groove.

  Moreover, it is desirable that the inclined surface has an inclination angle of 30 degrees or more with respect to the normal line of the tread surface.

  Further, when the groove depth of the horizontal groove is shallower than the groove depth of the main groove and there is a step between the main groove and the horizontal groove, the groove width on the tread surface side of the main groove at the end of wear of the tread surface is increased. If the groove width on the tread surface side of the groove formed by the protrusion and the step at the end of wear of the tread is “W2”, the protrusion is formed in a shape such that the groove width W2 is W2 ≦ W1. It is desirable to do.

  Further, the width of the groove on the tread surface side of the main groove when new is “W”, and the maximum width of the protruding portion from the end of the tread surface when new on the side wall provided with the protrusion to the lateral groove side is the starting point. When the protruding amount is “T”, the protruding portion is preferably formed in a shape such that the maximum protruding amount T is T ≧ 0.5 * W.

  Further, it is desirable that the protruding portion is formed such that a cross section cut in the tire circumferential direction has a mountain shape or a trapezoidal shape whose width increases from the tread surface side toward the groove bottom side of the main groove.

  Further, it is desirable that the side wall on the main groove side in the land portion has an inclined surface that approaches the side wall of the land portion that faces the main groove while facing the main groove.

  Moreover, it is desirable to change the inclination angle of the inclined surface of the side wall in the tire circumferential direction.

  The main groove preferably has a narrow groove width and a deep groove depth.

  In the case where a plurality of the main grooves are provided, it is preferable that the protrusions are provided at least near the tire center among the main grooves.

  The land pattern is preferably for heavy duty tires and studless tires.

  In the pneumatic tire according to the present invention, the stone rolling in the main groove can be discharged by the protruding portion of the intersection portion, and the stone biting performance at the intersection portion is improved. In particular, since the projecting portion is integrated with the land portion, the projecting portion can be provided even for a main groove having a narrow groove bottom. Therefore, this protrusion can improve the stone biting performance even in a pneumatic tire having such a narrow main groove.

FIG. 1 is a development view showing a part of a tread surface of a tread portion in a pneumatic tire according to the present invention. FIG. 2 is a developed view showing a part of the tread surface of the tread portion in the pneumatic tire according to the present invention, and is a diagram showing a specific example thereof. 3 is a cross-sectional view taken along line AA in FIG. 4 is a cross-sectional view taken along line BB in FIG. FIG. 5 is a cross-sectional view taken along the line CC of FIG. FIG. 6 is a perspective view schematically showing a protruding portion, a land portion, and the like. 7 is a cross-sectional view taken along line BB in FIG. FIG. 8 is a diagram showing the results of a tire performance test. FIG. 9 is a development view showing a part of the tread surface of the tread portion in the pneumatic tire according to the present invention, and is a diagram showing another specific example. 10 is a cross-sectional view taken along line DD of FIG. FIG. 11 is a developed view showing a part of the tread surface of the tread portion in the pneumatic tire according to the present invention, and is a diagram showing another specific example.

  Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments.

  The pneumatic tire according to the present invention has a land pattern divided by a main groove extending in the tire circumferential direction and a lateral groove extending in the tire width direction in the tread portion, and the main groove and the lateral groove Protrusions for improving stone biting performance are provided at the intersections. The protruding portion protrudes from the groove bottom of the main groove toward the tread side at the intersection, and faces the opening to the main groove of the lateral groove at the intersection with the main groove interposed therebetween. It projects from the side wall of the land portion toward the lateral groove. The lateral grooves in the tire width direction referred to here include not only those parallel to the axial direction of the tire rotation axis but also those inclined at an inclination angle smaller than 45 degrees with respect to the axial direction.

  Here, the protruding portion may protrude from the entire wall surface of the side wall of the land portion, but the width (the width in the tire circumferential direction) equivalent to the width of the opening portion (the width in the tire circumferential direction), the opening You may make it protrude from the predetermined area | region (a part of wall surface etc.) of the wall surface of the side wall like the width | variety narrower than the width | variety of a part, the width | variety wider than the width | variety of the opening part. By projecting from the entire wall surface, the groove width of the main groove is narrowed and the drainage performance may be reduced.In this case, the projecting portion is projected from a predetermined area of the wall surface to improve the drainage performance of the main groove. What is necessary is just to improve.

[Embodiment 1]
A pneumatic tire according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a development view showing a part of a tread surface (a surface in contact with a road surface, a so-called tread surface) 2a of a tread portion 2 in the pneumatic tire 1 of the present embodiment.

  The tread portion 2 includes a plurality of main grooves 3A and 3B extending in the tire circumferential direction and a plurality of lateral grooves 4 extending in the tire width direction. The main groove 3A is formed closer to the tire center CL than the main groove 3B. Two of these main grooves 3A and 3B are prepared in this example. The tread portion 2 is formed with land portions 5 such as a plurality of blocks and ribs divided by the main grooves 3 </ b> A and 3 </ b> B and the lateral grooves 4.

  During vehicle travel, stones on the travel path may enter the main grooves 3A and 3B. Most of the stone slips out of the main grooves 3A and 3B as the tire rotates, but a part of the stone is caught in the intersection of the main grooves 3A and 3B and the lateral grooves 4 (opening portions of the lateral grooves 4 to the main grooves 3A and 3B). May become impossible. Here, the side wall 5a on the main groove 3A, 3B side in the land portion 5 is inclined so as to face the tread surface 2a side (that is, toward the other bottom of the land portion 5 facing the groove bottom of the main grooves 3A, 3B). In the case of an approaching inclined surface), the elastic force can be applied to the stone against the tread surface 2a against the pressing force from the stone. Stones are easily discharged. In particular, stones are more easily discharged as the inclination angle of the inclined surface increases. However, when the groove widths of the main grooves 3A and 3B are narrow and the groove depth is deep, there is a limit to the expansion of the inclination angle, and it is difficult to obtain an inclined surface having an inclination angle suitable for discharging stones.

  Therefore, the tread portion 2 is provided with a protruding portion 6 as a stone biting suppression groove that suppresses the occurrence of stone biting at each intersection of the main grooves 3A, 3B and the lateral groove 4. The projecting portion 6 discharges the stone that has rolled to the intersection portion in the main grooves 3A and 3B during traveling of the vehicle or the stone that has entered the intersection portion. Here, in particular, at the intersection of the main groove 3A and the lateral groove 4 near the tire center CL, such a stone biting is more likely to occur than the main groove 3B near the tire shoulder. For this reason, it is preferable to provide the protruding portion 6 at least at the intersection of the main groove 3A and the lateral groove 4 near the tire center CL. Moreover, although this protrusion part 6 can suppress the biting of a stone by providing in at least 1 row | line | column of each row | line | column of the land part 5 located in a line with the tire circumferential direction, for example, it is provided in all the intersection parts. Most preferred. In the present embodiment, projecting portions 6 are provided on the respective land portions 5 that form all the intersections in the two main grooves 3A near the tire center CL. The protrusion 6 protrudes from the groove bottom of the main groove 3A toward the tread surface 2a side at the intersection to discharge the stone, and at the opening to the main groove 3A of the lateral groove 4 at the intersection. On the other hand, it is formed in a shape projecting from the side wall 5a of the land portion 5 facing the main groove 3A toward the lateral groove 4 side. Below, this protrusion part 6 is explained in full detail.

  In this embodiment, the groove width of the main grooves 3A, 3B is specifically narrow and the groove depth is deep, for example, a deep groove pneumatic tire 1, for example, a pattern of land portions 5 for heavy load tires and studless tires. The pneumatic tire 1 will be described as an example (FIG. 2). This type of deep groove pneumatic tire 1 is such that the main grooves 3A and 3B have a relationship of the following formula 1. In Formula 1, “W” indicates the groove width on the tread surface 2a side of the main grooves 3A and 3B when new, and “GDm” indicates the groove depth of the main grooves 3A and 3B when new (FIG. 3). ). FIG. 3 is a cross-sectional view taken along line AA in FIG. Although FIG. 3 shows the main groove 3A side, the main groove 3B closer to the tire shoulder has the same shape as the main groove 3A.

    0.2 ≦ W / GDm ≦ 0.6 (1)

  In the tread portion 2 of the pneumatic tire 1, as shown in FIG. 3, the groove widths of the main grooves 3A, 3B maximize the groove width W on the tread surface 2a side when new, and gradually increase toward the groove bottom. It is narrower. Here, the side surfaces of the main grooves 3A and 3B (that is, the side walls 5a on the main grooves 3A and 3B side of the land portion 5) are illustrated as inclined surfaces having the same inclination angle α. The inclination angle α is an angle formed between the normal to the tread surface 2a and the side wall 5a on the main grooves 3A and 3B side of the land portion 5. For example, the inclination angle α is preferably set to 5 degrees or more in order to reduce rolling resistance and improve steering stability due to the high rigidity of the land portion 5.

  Further, in the tread portion 2, as shown in FIG. 4, the groove depth GDs of the lateral groove 4 is shallower than the groove depth GDm of the main grooves 3A, 3B, and the main grooves 3A, 3B and A step 7 is formed between the lateral grooves 4. Therefore, it can be said that the protruding portion 6 exemplified here has a shape protruding from the side wall 5a of the land portion 5 toward the wall surface on the main groove 3A, 3B side in the step 7. FIG. 4 is a cross-sectional view taken along line BB in FIG. Although FIG. 4 shows the main groove 3A side, the main groove 3B side has the same shape as the main groove 3A side.

  The protrusion 6 is formed in a shape and a position where the stone at the intersection is discharged. Further, the protruding portion 6 is formed in a shape and a position where the main groove 3A communicates in the tire circumferential direction from the new article to the end of wear of the tread 2a, so that drainage performance is ensured even at the end of wear. To. The last stage of wear refers to the time when wear has progressed to or near the wear limit. The wear limit is when the wear progresses to such an extent that the basic tire performance such as grip performance reaches the end of its life. For example, when wear progresses until a so-called slip sign is exposed on the tread 2a. Say that. Further, in the pneumatic tire 1 having the step 7, the end of wear is also determined when the wear progresses until the step 7 is exposed as the tread surface 2 a, that is, until the lateral groove 4 is eliminated.

  Specifically, as shown in FIGS. 4 to 6, the protruding portion 6 gradually increases in the protruding amount from the side wall 5 a to the lateral groove 4 side from the tread surface 2 a side toward the groove bottom side of the main groove 3 </ b> A. And it has the inclined surface from which the protrusion amount to the tread surface 2a side gradually increases from the groove bottom of the main groove 3A toward the side wall 5a side from the lateral groove 4 side. Here, the inclined surface has an inclination angle β larger than the inclination angle α of the side wall 5a on the main groove 3A, 3B side in the land portion 5 (β> α). The inclination angle β is an angle formed between a normal line to the tread surface 2a and the wall surface of the protruding portion 6, and is preferably set to, for example, 30 degrees or more in order to improve the stone discharging performance. FIG. 5 is a cross-sectional view taken along the line CC of FIG. 2, and FIG. 6 is a perspective view simply showing the protruding portion 6, the land portion 5 and the like.

  Further, as shown in FIGS. 5 and 6, the protruding portion 6 gradually extends from the groove bottom of the main groove 3 </ b> A toward the tread surface 2 a side from the maximum protruding portion (here, the central portion of the inclined surface) toward the tire circumferential direction. The amount of protrusion to the surface decreases and is formed in a shape that leads to the groove bottom. Thereby, the stone that has rolled in the main groove 3 </ b> A is discharged outside while rolling on the mountain-shaped slope of the protrusion 6. In other words, the protrusion 6 has an inclined surface that connects the valley to the mountain and the mountain to the valley in such a tire circumferential direction, so that the rolling stone does not stop as a wall by itself, Can improve the stone discharging performance.

  Moreover, it is preferable to arrange | position this protrusion part 6 in the range of the width Wp equivalent to the groove width of the horizontal groove 4 projected on the side wall 5a toward the tire width direction (FIG. 2). Thereby, this protrusion part 6 becomes easy to discharge | emit without stopping the stone which entered the intersection part or the stone which rolled in the main groove | channel 3A to the intersection part there. At this time, the protruding portion 6 may be formed in a shape that is entirely within the range of the width Wp, or may be formed in a size that exceeds the range of the width Wp. In particular, the protrusion 6 can enhance the stone discharging effect by arranging the maximum protrusion within the range of the width Wp. Here, some of the lateral grooves 4 have a constant groove width, and other than the main groove width in the central portion or the like, the opening to the main groove 3A is wider in the tire circumferential direction as shown in FIG. There is also. Accordingly, the width Wp is the projected width of the lateral groove 4 having a constant groove width, and the maximum groove width at the opening end is projected if the lateral groove 4 is wide at the opening. The width may be set.

  Further, the protruding portion 6 may extend from the groove bottom of the main groove 3A to the tread surface 2a. However, since the cross-sectional area of the main groove 3A around the protruding portion 6 becomes narrower as the tread surface 2a wears out, in this case, the main groove 3A becomes a wall in the tire circumferential direction, and drains when the vehicle travels. There is a possibility of reducing the performance. Therefore, it is preferable that the protrusion 6 keeps the amount of protrusion from the groove bottom of the main groove 3A within a predetermined range.

  For example, if the radius of the circle (for example, the maximum inscribed circle of the triangle) in FIG. 2 formed by the side walls 5a of the three land portions 5 at the intersection of the new article is “r” and the diameter is “d (= 2r)” If the outer shape is replaced with a sphere, there is a high possibility that a stone corresponding to a sphere having a radius r or more is bitten at the intersection. For this reason, in order to prevent the stone from being bitten at the intersection, for example, within a range shallower than the groove depth of the diameter d starting from the tread surface 2a side when new, more preferably from the groove depth of the radius r Alternatively, the shape of the protrusion 6 may be formed so that a part thereof exists within a shallow range. Thereby, the protrusion 6 can discharge the stone that has rolled into the intersection part in the main groove 3A or the stone that has entered the intersection part from a new article, and suppresses a decrease in drainage performance. it can.

  On the other hand, since the land portion 5 is distorted in the tire circumferential direction or the like by the driving force or the braking force during traveling from the time of the new article until the predetermined wear progresses, the width of the lateral groove 4 widens and the intersection portion viewed from the tread 2a The area of will expand. For this reason, since the stone at the intersection is easy to be discharged within the range from this new time until the predetermined wear progresses, the protrusion 6 may not be present. On the other hand, from the predetermined wear state to the end of wear, the groove depth of the main groove 3A and the transverse groove 4 becomes shallow and the rigidity of the land portion 5 becomes high, so that the groove width of the transverse groove 4 is difficult to expand. The area of the intersection seen from the tread 2a is difficult to expand. In particular, at the end of wear, since the lateral grooves 4 are eliminated, the intersection portion cannot be expected to expand. For this reason, it is desirable to provide the protrusion 6 in a shape and a position where the stone discharging effect is exhibited from the predetermined wear state to the end of wear.

  Therefore, in the present embodiment, until the tread 2a is worn by a predetermined amount (predetermined ratio) from when it is new, in other words, the remaining groove depth GDm1 of the main groove 3A is not more than a predetermined ratio of the groove depth GDm when new. The protrusion 6 is not exposed as the tread surface 2a until That is, the protrusion 6 is disposed within a predetermined ratio or less from the groove bottom at the groove depth GDm at the time of a new article. Here, the predetermined ratio of wear (predetermined ratio of the remaining groove depth GDm1) is the wear ratio relative to the new article (groove depth at the new article) when the intersection portion is insufficiently expanded by the braking / driving force and the stone is difficult to be discharged. The ratio of the remaining groove depth GDm1 to GDm may be set, for example, 30%, 40%, 50% (70%, 60%, 50%) or the like. Thereby, even if the abrasion of the predetermined ratio or more occurs, the protruding portion 6 can discharge the stone that has rolled into the intersection portion in the main groove 3A or the stone that has entered the intersection portion. In addition, the protruding portion 6 can ensure drainage performance until the predetermined ratio of wear occurs, and the protrusion shape can suppress a decrease in drainage performance when wear of the predetermined ratio or more occurs. Further, the predetermined ratio of wear (predetermined ratio of the remaining groove depth GDm1) is not only such stone discharge performance, but also changes in tire performance (grip performance, drainage performance, etc.) due to wear required as a design concept. Change) may be taken into consideration.

  Furthermore, here, the main groove when the wear of the tread 2a at a predetermined rate has progressed since the new article (that is, when the remaining groove depth GDm1 of the main groove 3A is a predetermined ratio of the groove depth GDm at the new article). The cross-sectional area in the tire width direction in 3A and in the tire radial direction is defined as a main groove cross-sectional area S (FIG. 3), and when viewed in the tire circumferential direction, in the tire width direction in the protruding portion 6 in a range overlapping with the main groove cross-sectional area S. In addition, the maximum cross-sectional area in the tire radial direction is defined as the cross-sectional area D of the protrusion (FIG. 4). The protrusion cross-sectional area D is for ensuring the stone biting performance while ensuring the drainage performance when worn over a predetermined ratio from the time of a new article, and is set to a value that satisfies these. Here, the protrusion 6 may be formed in such a shape that the cross-sectional area S of the main groove and the cross-sectional area D of the protrusion are used, and the cross-sectional area D of the protrusion satisfies the relationship of the following formula 2.

    0.3 * S ≦ D ≦ 0.8 * S (2)

  The reason why the cross-sectional area D of the projecting portion is 80% or less of the cross-sectional area S of the main groove is that the main groove 3A around the projecting portion 6 is left at 20% or more with respect to the location where the projecting portion 6 does not exist. This is because the main groove 3A can be communicated in the tire circumferential direction even after wear, and drainage performance after wear can be ensured. On the other hand, the reason why the cross-sectional area D of the projecting portion is set to 30% or more of the cross-sectional area S of the main groove is that if it is narrower than this, stones are not easily discharged from the main groove 3A.

  Here, the predetermined ratio of wear at this time (predetermined ratio of the remaining groove depth GDm1) is the same as described above. For example, if there is a request that the drainage performance may be lowered within a range that does not hinder driving when worn to some extent, the predetermined ratio of wear (predetermined ratio of the remaining groove depth GDm1) is set to 30. % (70%) or the like. On the other hand, if there is a demand that the drainage performance does not need to be changed greatly until it approaches the end of wear, a predetermined ratio of wear (remaining groove depth GDm1) The predetermined ratio may be determined as 70% (30%) or the like. Here, the protruding portion 6 is disposed within a predetermined ratio or less from the groove bottom at the groove depth GDm at the time of a new article, but a part of the protruding portion 6 exists in a range larger than the predetermined ratio. Even if it has, the protrusion part cross-sectional area D is set to the relationship of the formula 2.

  In this pneumatic tire 1, by setting the position and shape of the protrusion 6 as shown above, even if wear progresses, stone discharge is suppressed while suppressing the deterioration of drainage performance by the protrusion 6. Performance can be ensured.

  Further, the protrusion 6 has a groove width W1 on the tread surface 2a side and a protrusion 6 in a portion where the protrusion 6 does not exist in the main groove 3A at the last stage of wear of the tread 2a (for example, the remaining groove depth GDm1 is 3 mm). Using the groove width W2 on the tread surface 2a side of the part (FIG. 7), it is formed into a shape that satisfies the relationship of Equation 3 below. Here, the groove width W2 refers to the groove width on the tread surface 2a side of the groove formed by the maximum projecting portion of the projecting portion 6 toward the lateral groove 4 and the side wall of the step 7 at the end of wear of the tread surface 2a. This groove width W2 is for ensuring resistance to stone biting while suppressing the occurrence of cracks at the groove bottom, and is set to a value that satisfies these.

    0.5 * W1 ≦ W2 ≦ W1 (3)

  The reason why the groove width W2 is made equal to or less than the groove width W1 is that when the groove width W2 becomes wider than the groove width W1, the stone that has rolled the main groove 3A to the intersection or the stone that has entered the intersection is a step difference from the protrusion 6 This is because there is a possibility that it stops during 7 and cannot be removed. Therefore, here, by forming the protruding portion 6 so that the groove width W2 is equal to or less than the groove width W1, the stone that has rolled to the intersection portion or the stone that has entered the intersection portion of the main groove 3A of the groove width W1 is obtained. Without stopping between the protrusion 6 and the step 7, the protrusion 6 discharges outside. On the other hand, if the groove width W2 is narrower than 50% of the groove width W1, there is a possibility that a crack (crack) may be formed in the groove bottom of the groove formed between the protruding portion 6 and the step 7. Therefore, here, in order to avoid the crack, the protruding portion 6 is formed so that the groove width W2 is 50% or more of the groove width W1.

  Here, the shape of the protruding portion 6 is defined by the relationship of the groove widths W1 and W2, but the protruding portion 6 is further provided at both ends of the tire circumferential direction at the end of wear and the side walls of the step 7 or the adjacent land portion. It is desirable that the shortest distance I between the side wall 5a and the side wall 5a is similarly defined (0.5 * W1 ≦ I ≦ W1) to determine the shape. Thus, by forming the protruding portion 6 so that the interval I is equal to or less than the groove width W1, the protruding portion 6 is formed between the both end portions and the side wall of the step 7 or the side wall 5a of the adjacent land portion 5. However, it is difficult for stones to stop, and the discharge effect of the stones can be enhanced. Further, by forming the protruding portion 6 so that the interval I is 50% or more of the groove width W1, it can be formed between both end portions of the protruding portion 6 and the side wall of the step 7 or the side wall 5a of the adjacent land portion 5. Generation of cracks at the groove bottom of the groove can be suppressed.

  In the pneumatic tire 1 according to this embodiment, by providing the protruding portion 6 having the above-described shape at the intersection of the main groove 3A and the lateral groove 4, the stone that has been rolled to the intersection in the main groove 3A. Or the stone which entered the intersection part is discharged | emitted by the protrusion part 6 without stopping at the intersection part. At this time, in the pneumatic tire 1, for example, the protruding portion 6 is formed in a shape in which the protruding portion cross-sectional area D is 80% or less of the main groove cross-sectional area S, and the protruding portion 6 has a groove depth when new. By disposing within a range of a predetermined ratio (for example, 70%) or less starting from the groove bottom at the height GDm, it is possible to ensure good stone biting performance without deteriorating drainage performance during vehicle travel. . Further, in the pneumatic tire 1, for example, by forming the protruding portion 6 so as to ensure a groove width W2 of 50% or more of the groove width W1, occurrence of cracks in the groove bottom can be avoided, so durability is improved. Good stone biting performance can be ensured without damage.

  Here, in the pneumatic tire 1 having a narrow groove width and a deep groove depth in the main grooves 3A and 3B given as an example, the groove bottoms of the main grooves 3A and 3B are narrowed, and the conventional stone The ejector cannot be installed. However, since the protrusion part 6 of this embodiment can also be arrange | positioned also in such a pneumatic tire 1, it can obtain favorable stone biting performance compared with the past. In addition, the pneumatic tire 1 has an inclination angle α on the side wall 5a of the land portion 5 in order to reduce rolling resistance and improve steering stability by increasing the rigidity of the land portion 5. Accordingly, the groove bottoms of the main grooves 3A and 3B become narrower. Since the protrusion part 6 of this embodiment can also be arrange | positioned also in such a pneumatic tire 1, favorable stone biting performance can be obtained, aiming at the fall of rolling resistance, and the improvement of steering stability.

  Further, the pneumatic tire 1 can integrally form the protruding portion 6 with the land portion 5, so that the productivity is higher than the conventional stone ejector provided alone at the groove bottom, and the cost can be kept low. For example, since a conventional stone ejector is provided as a single protrusion on a narrow groove bottom, an air vent hole cannot be provided in the mold, and there is a possibility that a bear may be generated by an air trap during vulcanization. On the other hand, since the protrusion part 6 of this embodiment is united with the land part 5, the utilization of the air vent hole of the land part 5 is possible, and generation | occurrence | production of a bear can be suppressed. Therefore, when these are compared, the pneumatic tire 1 of this embodiment has higher productivity than the conventional one and can reduce the cost.

[Embodiment 2]
Next, Embodiment 2 of the pneumatic tire according to the present invention will be described with reference to FIG. The second embodiment is obtained by further restricting the shape of the protruding portion 6 with respect to the pneumatic tire 1 of the first embodiment described above.

  The protrusion 6 of the second embodiment defines a range of the maximum protrusion amount T of the protrusion 6 toward the lateral groove 4 in addition to the conditions of the shape shown in the first embodiment. As shown in FIG. 7, the maximum projecting amount T is such that the end of wear (for example, the remaining groove depth GDm1 is 3 mm) from the end of the side wall 5a provided with the projecting portion 6 on the tread surface 2a side when new is used. It is the shortest distance in the tire width direction to the end. This maximum protrusion amount T is for ensuring resistance to stone biting while suppressing an increase in tire weight, and is set to a value that satisfies these requirements. Here, using the maximum protrusion amount T and the groove width W of the new main groove 3A, the protrusion 6 is formed in a shape in which the maximum protrusion amount T falls within the range of the following expression 4.

    0.5 * W ≦ T ≦ 1.5 * W (4)

  The reason why the maximum protrusion amount T is set to 150% or less of the groove width W of the main groove 3A at the time of a new article is that the tire weight may be increased more than before by increasing the maximum protrusion amount T beyond that. . On the other hand, the reason why the maximum protrusion amount T is set to 50% or more of the groove width W of the main groove 3A in the new article is that if the maximum protrusion amount T is less than 50% of the groove width W, the function as the protruding portion 6 can be achieved. This is because there is a possibility that stones cannot be discharged.

  In the pneumatic tire 1 of this embodiment, by providing the protruding portion 6 having the above-described shape at the intersection of the main groove 3A and the lateral groove 4, good stone-resisting performance can be achieved while suppressing an increase in tire weight. Can be secured.

[Example]
Below, the performance test result of the pneumatic tire which concerns on this invention is shown based on FIG.

  In this performance test, a pneumatic tire having a tire size of 275 / 80R22.5 was assembled to a normal rim, filled with 95% of the normal internal pressure, 97% of the normal load was added, and the total weight of the 2-D.4 vehicle was 25 t. The test vehicle was mounted on the front steering shaft of the test vehicle. The regular rim referred to herein is a “standard rim” defined in JATMA, a “Design Rim” defined in TRA, or a “Measuring Rim” defined in ETRTO. The normal internal pressure means “maximum air pressure” defined by JATMA, a maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

  Here, together with the pneumatic tires of Examples 1 and 2 according to the present invention, a pneumatic tire of a conventional example and a pneumatic tire of a comparative example, which are comparison targets of performance test results, are also shown. The pneumatic tire of Example 1 is the pneumatic tire 1 having the protruding portion 6 of Embodiment 1 described above. The pneumatic tire of Example 2 is the pneumatic tire 1 having the protrusion 6 of Embodiment 2 described above. In other words, the conventional pneumatic tire is obtained by removing the protrusions 6 from the pneumatic tires of Examples 1 and 2. The pneumatic tire of the comparative example is one having a projecting portion obtained by slightly changing the setting conditions of the projecting portion 6 of the first and second embodiments.

  Here, the evaluation test of the stone biting performance and the evaluation test of the drainage performance were performed. Further, comparison of tire weight and confirmation of the presence or absence of cracks at the groove bottom of the main groove 3A were also performed.

  The stone biting performance is evaluated by running a gravel road (off-road course) or a paved road (asphalt road) at a predetermined speed of 30,000 km with a test vehicle equipped with pneumatic tires. The number of stones biting at the intersection with the lateral groove 4 is measured. As a result of the evaluation, the number of stone bites in the conventional pneumatic tire is represented by an index value 100, and other pneumatic tires are indexed based on the difference in the number of stone bites. The index value indicates that the larger the value, the better the stone biting performance.

  The drainage performance is evaluated by braking a wet paved road (wet asphalt road) from a speed of 60 km / h (WET braking) with a test vehicle equipped with pneumatic tires, and measuring the difference in braking distance three times or more. The average value was indexed. The evaluation results show that the conventional pneumatic tire has an index value of 100, and the larger the index value, the better the drainage performance. This drainage performance evaluation test was conducted both when new and when worn at 50%.

  In the tire weight comparison test, the tire weight of each pneumatic tire was measured. Here, the tire weight of the pneumatic tire of Example 1 is represented by an index value of 100, and other pneumatic tires are also indexed based on the weight difference. The index value indicates that the larger the value, the lighter the weight.

  The evaluation method of the presence or absence of a crack (crack) at the groove bottom of the main groove 3A is that a crack is generated at the intersection of the main groove 3A and the lateral groove 4 in the pneumatic tire subjected to the evaluation test of the stone biting performance. If there is a crack, index it according to the degree of the crack. The evaluation result shows that a pneumatic tire without cracks has an index value of 100, and the smaller the index value, the higher the degree of crack occurrence.

  Each type of pneumatic tire to be tested has a common land portion 5 pattern, main grooves 3A and 3B, lateral grooves 4, and a step 7. In the pneumatic tire of Example 1, the setting conditions for the groove width W2, the projecting section sectional area D, and the inclination angle β of the projecting section 6 are within the above range. Out of the above range. On the other hand, in the pneumatic tire of Example 2, the setting conditions for the groove width W2, the projecting section sectional area D, the inclination angle β of the projecting section 6 and the maximum projecting amount T are all within the above range. In the pneumatic tire of the comparative example, the setting conditions for the projecting section sectional area D and the inclination angle β of the projecting section 6 are within the above range, and the setting conditions for the groove width W2 and the maximum projecting amount T are excluded from the above range. Yes.

  According to the test results of FIG. 8, the pneumatic tires of Examples 1 and 2 and the comparative example in which the protrusions 6 are provided at the intersections of the main grooves 3A and the lateral grooves 4 are compared to the conventional pneumatic tires. It can be seen that the stone biting performance is excellent while ensuring the same drainage performance when new and 50% worn. Further, when the pneumatic tires of Example 1 and Example 2 are compared, the pneumatic tire of Example 2 has the maximum projecting amount T of the projecting portion 6 within the range of the above-described formula 4, so that As compared with the pneumatic tire, it is possible to secure the drainage performance equivalent to the conventional one and improve the stone biting performance more than the conventional one while reducing the weight of the tire due to the miniaturization of the protruding portion 6. Further, the pneumatic tires of Example 1 and Example 2 do not generate cracks in the groove bottom of the main groove 3A, but the pneumatic tire of the comparative example in which the groove width W2 is narrower than the above lower limit range is It can be seen that a crack is generated at the bottom of the groove.

  By the way, in the description so far, since the tread portion 2 having the step 7 between the main grooves 3A, 3B and the lateral groove 4 is illustrated, a groove is created between the protruding portion 6 and the step 7, and the groove of the groove Using the width W2, the shape of the protrusion 6 can be defined from Equation 3 above. However, since there is also a tread portion without such a step 7, in this case, if the protruding amount of the protruding portion 6 toward the horizontal groove 4 is small, stones stop between the protruding portion 6 and the horizontal groove 4. There is a possibility that. For this reason, for example, the protrusion 6 in this case has an interval I between the side wall 5a of the adjacent land portion 5 within the above-described range (0.5 * W1 ≦ I ≦ W1) at the end of wear. The shape is set so that the largest projecting end portion toward the lateral groove 4 reaches the opening end portion of the lateral groove 4 to the main groove 3A or enters the lateral groove 4 beyond the opening end portion. Thereby, this protrusion part 6 can suppress the stop of the stone between the horizontal grooves 4, and can discharge | emit outside, suppressing generation | occurrence | production of the crack in the groove bottom of the groove | channel which comprises the space | interval I.

  Further, in the description so far, the projection portion 6 whose cross-sectional shape cut in the tire circumferential direction is a mountain shape as shown in FIG. 5 is illustrated, but the intersection of the main groove 3A and the lateral groove 4 is shown in FIG. 9 and FIG. 10 may be provided with a protrusion 16 having a trapezoidal cross-sectional shape cut in the tire circumferential direction. The cross-sectional shape is a trapezoid whose width increases from the tread surface 2a side toward the groove bottom side of the main groove 3A. FIG. 10 is a sectional view taken along the line DD of FIG. In the protruding portion 16, the length of the upper bottom of the cross-sectional view (the upper side in FIG. 10) is constant from the side wall 5a to the groove bottom of the main groove 3A.

  As with the previous protrusion 6, the protrusion 16 gradually increases in the amount of protrusion from the side wall 5a to the lateral groove 4 as it goes from the tread surface 2a side to the groove bottom side of the main groove 3A. It has an inclined surface where the amount of protrusion from the groove bottom of the main groove 3A toward the tread surface 2a side gradually increases from the 4 side toward the side wall 5a, and the inclination angle β of the inclined surface is set to 30 degrees or more. Is done. Further, like the protruding portion 6, the protruding portion 16 is disposed within a predetermined ratio (for example, 70%) or less from the groove bottom at the groove depth GDm at the time of a new product in order to ensure drainage performance at the end of wear. Then, the protrusion cross-sectional area D is formed into a shape that falls within the range of the above formula 2. Further, similarly to the protruding portion 6, the protruding portion 16 is formed in a shape in which the groove width W <b> 2 is within the range of the above formula 3. Thereby, in this pneumatic tire 1, the same effect as what provided the above-mentioned projection part 6 can be acquired. Further, since the protrusion 16 has a higher rigidity than the mountain-shaped protrusion 6, particularly on the protruding end side, the stone discharging effect can be enhanced.

  Further, the protruding portion 16 may be formed in a shape in which the maximum protruding amount T falls within the range of the above expression 4, similarly to the protruding portion 6 shown in the second embodiment. Thereby, in this pneumatic tire 1, the same effect as what provided the projection part 6 can be acquired.

  Furthermore, the protrusions 6 and 16 described so far are configured such that the side surfaces of the main grooves 3A and 3B (side walls 5a on the main grooves 3A and 3B side of the land portion 5) are formed with the same inclination angle α. However, the present invention may be applied to a case where the inclination angle of the side surface is changed in the tire circumferential direction. In other words, the inclination angle of the side wall 5a may be changed in order to increase the rigidity of the land portion 5. However, since the protrusions 6 and 16 can be applied to this case, the rolling due to the rigidity of the land portion 5 is increased. Good stone-resisting performance can be obtained while reducing resistance and improving steering stability. For example, in FIG. 11, one side wall 15a (side surface of the main groove 13A) of each land portion 15 is configured with different inclination angles, and the side wall 15a and the main groove 13A are formed at the intersection of the main groove 13A and the lateral groove 14. A pneumatic tire 11 including a protruding portion 6 protruding from the groove bottom is shown as an example. The side wall 15a of the pneumatic tire 11 (side surface of the main groove 13A) gradually decreases the inclination angle α2 on both sides in the tire circumferential direction with respect to the inclination angle α1 of the place where the protrusion 6 is disposed ( α1> α2). Also in this pneumatic tire 11, the protrusions 6 and 16 can achieve the same effects as those described above.

  As described above, the pneumatic tire according to the present invention is useful for improving the stone biting performance at the intersection of the main groove and the lateral groove.

DESCRIPTION OF SYMBOLS 1,11 Pneumatic tire 2 Tread part 2a Tread surface 3A, 3B, 13A Main groove 4,14 Horizontal groove 5,15 Land part 5a, 15a Side wall 6,16 Protrusion part 7 Level difference CL Tire center

Claims (12)

In a pneumatic tire having a land pattern divided by a main groove in the tire circumferential direction and a lateral groove in the tire width direction,
Projecting from the bottom of the main groove toward the tread surface at the intersection of the main groove and the lateral groove, and sandwiching the main groove with respect to the opening of the lateral groove to the main groove at the intersection A pneumatic tire characterized in that a protruding portion is provided that protrudes from the side wall of the land portion facing toward the lateral groove side.   2. The pneumatic tire according to claim 1, wherein the protruding portion is formed in a shape and a position for discharging the stone at the intersection and communicating the main groove in the tire circumferential direction even at the end of wear of the tread.   The protruding portion gradually increases from the side wall toward the lateral groove side from the tread surface side toward the groove bottom side of the main groove, and gradually increases from the lateral groove side toward the side wall side. The pneumatic tire according to claim 1, wherein the pneumatic tire has an inclined surface in which a protruding amount from a groove bottom to a tread surface side of the main groove increases.   The pneumatic tire according to claim 3, wherein the inclined surface has an inclination angle of 30 degrees or more with respect to a normal line of the tread surface.   When the groove depth of the horizontal groove is shallower than the groove depth of the main groove and there is a step between the main groove and the horizontal groove, the groove width on the tread surface side of the main groove at the end of wear of the tread surface is expressed as “W1. “When the groove width on the tread surface side of the groove formed by the protrusion and the step at the end of wear of the tread is“ W2 ”, the protrusion is formed in a shape such that the groove width W2 is W2 ≦ W1. The pneumatic tire according to any one of claims 1 to 4, characterized in that:   The width of the groove on the tread surface side of the main groove when new is "W", and the maximum protrusion amount of the protrusion from the end of the tread surface when new on the side wall provided with the protrusion to the lateral groove side The protrusion is formed in a shape in which the maximum protrusion amount T satisfies T ≧ 0.5 * W, where “T” is “T”. The described pneumatic tire.   The projecting portion is formed such that a cross section cut in a tire circumferential direction has a mountain shape or a trapezoidal shape in which a width increases from a tread surface side toward a groove bottom side of the main groove. The pneumatic tire according to any one of 6.   The side wall on the main groove side in the land portion has an inclined surface that approaches the side wall of the land portion that faces the main groove while facing the main groove toward the groove bottom of the main groove. A pneumatic tire according to any one of the above.   The pneumatic tire according to claim 8, wherein an inclination angle of the inclined surface of the side wall is changed in a tire circumferential direction.   The pneumatic tire according to any one of claims 1 to 9, wherein the main groove has a narrow groove width and a deep groove depth.   The pneumatic unit according to any one of claims 1 to 10, wherein when there are a plurality of the main grooves, the protrusions are provided at least near the tire center in each of the main grooves. tire.   The pneumatic tire according to any one of claims 1 to 11, wherein the land portion pattern is for heavy-duty tires and studless tires.

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