JP5964009B2 - Pneumatic tire - Google Patents

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 a tire circumferential direction and a lateral groove in a tire width direction, the main groove and the lateral groove in the land portion. A groove portion is provided in the vicinity of the intersection portion and at a position isolated from the main groove and the lateral groove, and the groove portion that pushes and widens the sidewall by the pressing force input to the side wall of the land portion at the intersection portion. Yes.

  Here, it is desirable that the groove portion is provided at least in a land portion that faces the opening portion of the lateral groove in each of the land portions forming the intersection portion.

  Further, the groove portion provided in the land portion facing the opening portion of the lateral groove is at least within a projected width region on the land portion where the groove width of the opening portion is projected toward the pressing direction of the pressing force. It is desirable to place one part.

  In addition, it is desirable that the groove is disposed in a range equal to or greater than a predetermined ratio of the projection width region where a desired amount of side wall deformation due to the pressing force can be obtained.

  In addition, the groove is formed to have a length in the longitudinal direction at which a desired amount of deformation of the side wall due to the pressing force is obtained at the intersection, and the longitudinal direction is the same as the direction orthogonal to the pressing direction of the pressing force. It is desirable to arrange so as to be inclined at an angle smaller than 45 degrees with respect to the orthogonal direction.

  In addition, the groove portion is formed so as to have a groove width at which a desired amount of side wall deformation due to the pressing force is obtained at the intersection, and the groove width is parallel to the pressing direction of the pressing force or It is desirable to arrange so as to be inclined at an angle smaller than 45 degrees with respect to the pressing direction.

  Moreover, it is desirable to form the groove portion so as to have a groove width that can ensure a desired rigidity of the land portion.

  Moreover, it is desirable that the groove width of the groove portion becomes narrower toward the groove bottom.

  Further, the groove portion is provided within a range corresponding to the groove width of the main groove from an end portion on the tread surface side of the side wall on the intersection portion side of the land portion in the pressing direction of the pressing force on the land portion. Is desirable.

  Further, when the width of the pressing force in the land portion in the pressing direction is “Wb”, the groove portion is on the side wall on the intersection portion side of the land portion in the pressing direction of the pressing force on the land portion. It is desirable to provide at a position 5% or more of the width Wb and 0.5 mm or more from the end on the tread side.

  Moreover, when the side wall on the intersection portion side in the land portion has an inclined surface that approaches the other land portion that forms the intersection portion toward the groove bottom of the main groove, the groove portion may be provided on the side wall. desirable.

  Further, it is desirable to provide a plurality of the groove portions.

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

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

  When a stone enters the intersection of the main groove and the lateral groove, the pressing force from the stone acts on the side wall of the land portion forming the intersection. In the pneumatic tire according to the present invention, the side wall is pushed and widened by the groove portion on the land portion at that time, and the intersection portion is enlarged, so that the stone at the intersection portion is discharged outside. In addition, a part of the side wall at that time is pushed and widened while being tilted toward the groove portion, and becomes an inclined surface facing the tread surface side. For this reason, in this pneumatic tire, an extruding action of the stone at the intersection portion due to the inclined surface and an extruding action of the stone at the intersection portion due to the elastic force accompanying the deformation of the side wall occur, so that the discharging effect is enhanced. In particular, since the groove portion is formed on the land portion, it can be provided even if the main groove has a narrow groove width at the groove bottom. Therefore, this groove portion 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 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 specific examples of the first, second and fourth embodiments. 3 is a cross-sectional view taken along line AA in FIG. FIG. 4 is a cross-sectional view taken along the line AA in FIG. 2, and shows the movement of the side wall when stones enter. FIG. 5 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 of the third embodiment. FIG. 6 is a cross-sectional view taken along the line AA in FIG. FIG. 7 is a cross-sectional view taken along the line AA in FIG. 2, and is a view showing the movement of the side wall when the stone by the groove portion of the fourth embodiment enters. FIG. 8 is a development view showing a part of the tread surface of the pneumatic tire according to the present invention, and is a diagram showing a specific example of the fifth embodiment. FIG. 9 is a cross-sectional view taken along line BB in FIG. FIG. 10 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 view showing another example of the fifth embodiment. 11 is a cross-sectional view taken along line CC in FIG. FIG. 12 is a diagram showing a tire performance test result.

  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 portion pattern divided into 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 in the land portion A groove portion having a groove width that tilts the side wall by a pressing force input to the side wall of the land portion at the intersection portion is provided in the vicinity of the intersection portion with the horizontal groove and at a position isolated from the main groove and the horizontal groove. It is a thing. 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.

[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.

  Accordingly, the tread portion 2 is provided with a groove portion 6 as a stone biting suppression groove that suppresses the occurrence of stone biting in the land portion 5 at the intersection of the main grooves 3A, 3B and the lateral groove 4. The groove 6 discharges the stones that have rolled into the intersections in the main grooves 3A and 3B during traveling of the vehicle or the stones that have entered the intersections. 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, the groove 6 is preferably provided at least in the land 5 at the intersection of the main groove 3A and the lateral groove 4 near the tire center CL. Further, for example, the groove 6 can be suppressed in at least one of the rows of the land portions 5 arranged in the tire circumferential direction. preferable. In the present embodiment, the groove portions 6 are provided in the land portions 5 that form all the intersections in the two main grooves 3A near the tire center CL. Below, this groove 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 Equation 1, “Wm” indicates the groove width of the main grooves 3A and 3B, and “GDm” indicates the groove depth of the main grooves 3A and 3B when new (FIG. 3). In the tread portion 2 of the pneumatic tire 1, as shown in FIG. 3, the groove width Wm of the main grooves 3A, 3B is substantially constant from the tread surface 2a side to the groove bottom when new. 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. Note that the width of the lateral groove 4 is also substantially constant.

    0.2 ≦ Wm / GDm ≦ 0.6 (1)

  In the main grooves 3A and 3B having a constant groove width Wm, stones are easily bitten at the intersections with the lateral grooves 4 as described above. Here, when the stone is biting into the intersection, a pressing force is applied from the stone to the side walls 5a of the three land portions 5 that form the intersection. When a pressing force from a stone is applied to the side wall of each conventional land portion, the side wall is pushed out in a direction to expand the intersection, but the side wall is not deformed so that the stone can be discharged to the outside. Therefore, the groove portion 6 of the present embodiment deforms the side wall 5a to such an extent that the pressing force from the stone can be absorbed, and expands the side wall 5a until the stone is discharged to the outside along with the deformation. Is formed in a shape and a position that can be enlarged.

  The groove 6 may be provided in at least one of the three land portions 5 forming one intersection portion. When the land portion 5 facing the main groove 3A with respect to the opening portion of the transverse groove 4 at the intersection is sandwiched between the main grooves 3A, the groove portion 6 has the tire width direction as the groove width. The circumferential direction is the longitudinal direction. On the other hand, when the other two land portions 5 are to be set, the groove portion 6 has a pressing direction of the pressing force applied from the stone as the groove width, and a direction orthogonal to the pressing direction of the pressing force is the longitudinal direction. In addition, although the pressing direction by a stone changes according to the shape of a stone, etc., it is set as one direction which took the average for convenience, for example. The groove 6 is better provided in the land 5 facing the opening of the lateral groove 4 than the other two land 5 in productivity. Therefore, the groove 6 is preferably provided at least in the land portion 5 facing the opening of the lateral groove 4. Here, it illustrates as what is provided only in the land part 5 facing the opening part of the horizontal groove 4.

  When a pressing force is input to the side wall 5a of the land portion 5 at the intersection portion, the groove portion 6 expands the side wall 5a to enlarge the intersection portion, thereby discharging the stone at the intersection portion to the outside. Is. Therefore, as shown in FIGS. 2 and 3, the groove 6 is located near the intersection of the main groove 3 </ b> A and the lateral groove 4 in the land portion 5 and at a position isolated from the main groove 3 </ b> A and the lateral groove 4. Provide. When such a groove portion 6 is formed at a position that is too far from the intersection portion, and the shape is too small, the side wall 5a cannot be expanded to such an extent that the stone is encouraged to be discharged. For this reason, the groove 6 needs to have an appropriate position and shape on the land portion 5.

  First, the position in the pressing direction by the stone on the land portion 5 (in this example, the tire width direction) is determined starting from the end of the side wall 5a on the intersection portion side on the tread surface 2a side when new. Here, since the main groove 3A and the lateral groove 4 having a constant groove width are illustrated, the wall surface of the side wall 5a on the intersection portion side may be used as a starting point.

  The position in the pressing direction is within a range of a predetermined distance A shown in FIG. 2 from the wall surface of the side wall 5a. When the groove portion 6 has the same shape, the side wall 5a is more likely to be deformed by the pressing force as the groove portion 6 is closer to the wall surface, but is less likely to be deformed as the groove portion 6 is separated from the wall surface. For this reason, the predetermined distance A is a distance at which the side wall 5a can be expanded to the extent that the stone at the intersection is discharged when a pressing force is applied. This predetermined distance A is the shape of the groove portion 6 (groove width, length, groove depth, etc.), the position in the direction orthogonal to the pressing direction of the groove portion 6 (in this example, the tire circumferential direction), the rigidity, elasticity, etc. of the land portion 5. Therefore, it is preferable to decide after taking these into consideration. Further, the size of the stone that would have been bitten by the intersection portion in the past is largely determined by the width of the intersection portion and the groove width Wm of the main groove 3A. Therefore, the predetermined distance A is set to, for example, the groove width Wm of the main groove 3A in consideration of this point. Thus, by forming the groove 6 within a predetermined distance A from the wall surface of the side wall 5a, when a pressing force is applied to the side wall 5a, a part of the side wall 5a tilts toward the groove 6 side. It can be expanded and the intersection can be enlarged.

  On the other hand, when the groove part 6 is too close to the wall surface of the side wall 5a, the productivity of the groove part 6 and the durability of the land part 5 may be reduced. For this reason, the groove 6 is formed at a position separated from the wall surface by a predetermined distance B or more shown in FIG. The predetermined distance B is, for example, a distance at which the groove portion 6 can be easily produced and a decrease in durability of the land portion 5 due to the presence of the groove portion 6 can be suppressed. This predetermined distance B is the shape of the groove portion 6 (groove width, length, groove depth, etc.), the position in the direction orthogonal to the pressing direction of the groove portion 6 (the tire circumferential direction in this example), the rigidity and elasticity of the land portion 5, and the like. Therefore, it is preferable to decide after taking these into consideration. For example, here, 5% of the width Wb (mm) in the pressing direction (in this example, the tire width direction) of the pressing force in the land portion 5 is compared with 0.5 mm, and the larger value is set as the predetermined distance B. To do. That is, the groove portion 6 is provided at a position that is 5% or more of the width Wb of the land portion 5 and 0.5 mm or more from the end portion. Thereby, the productivity of the groove part 6 is improved, and a decrease in durability of the land part 5 can be suppressed.

  Subsequently, with respect to the position in the direction orthogonal to the pressing direction by the stone on the land portion 5 (in this example, the tire circumferential direction), the lateral groove 4 shown in FIG. 2 that faces the land portion 5 with the main groove 3A interposed therebetween. It is determined based on the groove width of the opening portion. The groove part 6 projects the groove width of the opening part toward the land part 5 in the pressing direction of the pressing force (in this example, the tire width direction), and within the projected width region Wp of the groove width of the projected opening part. At least a part is formed. This exemplary projected width region Wp is the groove width itself in the opening portion of the lateral groove 4. Thereby, when the stone rolls to the intersection part or enters the intersection part, the side wall 5a can be expanded by the pressing force of the stone. Here, the groove 6 is preferably present at least on an extension line in the pressing direction. This is because the pressing force from the stone acts near the groove 6 in the side wall 5a, so that the side wall 5a can be easily deformed.

  Next, the groove 6 is set to a shape that can obtain a desired amount of deformation of the side wall 5a suitable for discharging the stone at the intersection when a pressing force is applied. In order to expand the side wall 5a when the pressing force is applied, it is necessary to set an appropriate groove width Ws. This is because if the groove width Ws is too narrow, it may not be possible to obtain a deformation amount of the side wall 5a suitable for stone discharge. For this reason, the groove width Ws is set such that a desired amount of deformation of the side wall 5a suitable for discharging the stone at the intersection can be obtained. Here, the groove width Ws varies depending on other shapes (length, groove depth, etc.) of the groove 6, the position of the groove 6, the rigidity and elasticity of the land portion 5, and so on. It is preferable to decide by Further, the groove width Ws may be determined with reference to the size of a stone that would have been bitten by the intersection portion in the past. Here, the groove width Ws is set to 10% or more of the groove width Wm of the main groove 3A. This is because if the groove width Ws is narrower than 10% of the groove width Wm of the main groove 3A, it is difficult to spread the side wall 5a until the stone is discharged.

  On the other hand, if the groove width Ws is too wide, the rigidity of the land portion 5 is reduced, which may cause an increase in rolling resistance and a decrease in steering stability during vehicle travel. Moreover, in the land part 5, the tread surface 2a around the groove part 6 may be partly worn. For this reason, an upper limit is provided for the groove width Ws. The upper limit is a width that can ensure the desired rigidity of the land portion 5 that does not cause an increase in rolling resistance, a decrease in running stability, or uneven wear, and other shapes (length, groove depth, etc.) of the groove portion 6. Since it varies depending on the position of the groove portion 6 and the rigidity and elasticity of the land portion 5, it is preferable to determine these in consideration. For example, here, the groove width Ws is set to 20% or less of the width Wb in the pressing direction of the pressing force in the land portion 5 (in this example, the tire width direction).

  In this way, the groove 6 may be set to a groove width Ws that is a deformation amount of the desired side wall 5a that can discharge the stone at the intersection while securing the rigidity of the land portion 5, for example, the groove width Ws. Is formed in a narrow groove satisfying 0.1 * Wm ≦ Ws ≦ 0.2 * Wb. Thereby, since the rigidity of the land portion 5 is maintained, it is possible to discharge the stone at the intersection while suppressing the increase in rolling resistance, the decrease in steering stability, and uneven wear.

  Subsequently, if the groove depth of the groove portion 6 is too shallow, the side wall 5a is difficult to be deformed from the time of a new article, and there is a possibility that the stone at the intersection point cannot be discharged. Furthermore, the groove portion 6 having a shallow groove depth cannot deform the side wall 5a at the end of wear, and the groove portion 6 disappears depending on the groove depth, so that the stone at the intersection cannot be discharged. Here, the groove depth of the groove 6 is made substantially equal to the groove depth of the main groove 3A in order to ensure the stone discharging performance at the end of wear. Thereby, the stone biting performance can be secured from the new article to the end of wear.

  Here, the end 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, it is preferable that the groove portion 6 is optimized with respect to the length L in the longitudinal direction so as to obtain a deformation amount of the side wall 5a suitable for discharging stones. If the length L is too short, the side wall 5a is difficult to be spread.

  Here, the groove 6 is arranged such that the longitudinal direction is the same as the direction orthogonal to the pressing direction of the pressing force (the tire circumferential direction in this example), but the longitudinal direction is 45 with respect to the orthogonal direction. You may arrange | position so that it may incline at an angle smaller than a degree. In other words, the groove 6 is arranged so that the groove width Ws is parallel to the pressing direction of the pressing force, but the groove width Ws is inclined at an angle smaller than 45 degrees with respect to the pressing direction. You may arrange so. In other words, if the longitudinal direction of the groove 6 and the pressing direction of the pressing force are the same, the side wall 5a cannot be expanded with a pressing force that is large enough for the stone to enter the intersection. Even if it can be spread, an unreasonable force acts on the land portion 5, which may reduce the durability of the land portion 5. On the other hand, the side wall 5a is preferably land portion by inclining the longitudinal direction at an angle smaller than 45 degrees with respect to the orthogonal direction, preferably by making the longitudinal direction coincide with the orthogonal direction. Without exerting an unreasonable force on 5, a part of the portion 5 is tilted and widened at the maximum by the groove width Ws.

  In the pneumatic tire 1 of this embodiment, the stone S is formed in the main groove 3A by providing the groove portion 6 having the above shape at the position in the land portion 5 that forms the intersection of the main groove 3A and the lateral groove 4. 4, when the side wall 5a is pushed by the stone S and deforms to the groove 6 side when it rolls to the intersection part, the intersection part is enlarged and the stone S Can be discharged outside. Furthermore, a part of the side wall 5a at that time is pushed and widened while tilting toward the groove 6 side, and becomes an inclined surface facing the tread surface 2a side. For this reason, in this pneumatic tire 1, the stone is pushed out at the intersection by the inclined surface and the stone is pushed out by the elastic force caused by the deformation of the side wall 5 a, so that the discharge effect is enhanced. . Further, in this pneumatic tire 1, since the groove width Ws of the groove portion 6 is optimized as described above, the stone-resistant without increasing the rolling resistance, lowering the steering stability, and causing uneven wear of the tread surface 2a. The biting performance can be improved.

  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, since the groove bottoms of the main grooves 3A and 3B are narrow, the conventional stone The ejector cannot be installed. However, since the groove part 6 of this embodiment can also be arrange | positioned also in such a pneumatic tire 1, the favorable stone biting performance can be obtained compared with the past.

  By the way, it is preferable to set the above-mentioned predetermined distance B, that is, the wall thickness between the wall surface of the side wall 5 a and the wall surface of the groove portion 6 on the intersection portion side to a length equivalent to the groove width Ws of the groove portion 6. Although depending on the groove width Ws of the groove 6, if the wall thickness is too small with respect to the groove width Ws of the groove 6, the elongation when the side wall 5 a is expanded increases, and the durability of the part may be reduced. Because there is.

  Furthermore, when providing the groove part 6 in the land part 5 other than the illustration above, it is preferable to pay attention to the following points.

  First, when the position in the pressing direction on the land portion 5 is determined, 5% of the pressing direction width Wb of the land portion 5 is compared with 0.5 mm, and the larger value is set to the predetermined distance B. Although set, it is desirable to use the width Wb in the tire width direction. This is because the width Wb may be extremely shorter than the tire width direction depending on the pressing direction. Even if the width Wb in the pressing direction is used, since the comparison with 0.5 mm is performed, the rigidity of the land portion 5 can be maintained.

  Further, when setting the groove width Ws of the groove portion 6, the width in the tire width direction in the land portion 5 is larger than the width Wb in the pressing direction of the pressing force in the land portion 5, as in determining the position in the pressing direction. It is preferable to use Wb.

[Embodiment 2]
Next, a pneumatic tire according to a second embodiment of the present invention will be described.

  About how much the groove portion 6 described above exists within the projected width region Wp, the shape of the groove portion 6 (groove width, length, groove depth, etc.) and the pressing direction of the groove portion 6 (in this example, the tire width direction). Since it varies depending on the position, the rigidity and elasticity of the land portion 5, etc., it is preferable to determine these in consideration. For this reason, the groove 6 is also present in a range of a predetermined ratio or more of the projection width region Wp in consideration of these. The predetermined ratio may be set to a value at which a desired amount of deformation of the side wall 5a that enables the stone to be discharged by the pressing force is obtained, for example, 60%.

  Here, even when the ratio of the groove portion 6 in the projected width region Wp (the cover ratio of the groove portion 6) is less than 60%, the side wall 5a can be expanded by the pressing force, and the stone is discharged by expanding the intersection portion. Can be planned. However, when the proportion of the groove portion 6 in the projected width region Wp is 60% or more, the deformation amount of the side wall 5a can be increased as compared with the case where the groove portion 6 is less than that, so that the intersection portion can be further expanded and more effective. The stone at the intersection can be discharged.

  Further, in combination with the coverage of the groove 6, the groove 6 is formed so that the length L in the longitudinal direction is at least a predetermined ratio of the projected width region Wp, and the side wall 5 a suitable for stone discharge is formed. It is desirable to obtain a deformation amount. The length L varies depending on the other shape of the groove 6 (groove width, groove depth, etc.), the position of the groove 6 and the rigidity and elasticity of the land portion 5, and should be taken into account. Is preferred. For example, the length L in the longitudinal direction of the groove 6 is 60% or more of the projection width region Wp. In the illustrated pneumatic tire 1, if the length L in the longitudinal direction of the groove 6 is shorter than 60% of the projected width region Wp, it is difficult to obtain a deformation amount of the side wall 5a suitable for stone discharge.

  On the other hand, if the length L in the longitudinal direction is too long, the side wall 5a is likely to be deformed even before and after the intersection in the main groove 3A, and there is a possibility that stones may be caught therein. For this reason, an upper limit is set on the length L in the longitudinal direction of the groove 6 in order to prevent the stone from being bitten at other than the intersection. Here, the length L in the longitudinal direction is formed to be equal to or less than a predetermined ratio of the projection width region Wp. The predetermined ratio may be set to a value that does not cause the deformation of the side wall 5a due to the pressing force so as not to cause the stone to be caught in other than the intersection portion in the main groove 3A, for example, 150%.

  In this way, the groove 6 may be set to a length L in the longitudinal direction that allows a desired amount of deformation of the side wall 5a that enables the stone to be discharged by the pressing force at the intersection. For example, the projection width region Wp is used. And 0.6 * Wp ≦ L ≦ 1.5 * Wp. Thereby, this groove part 6 can discharge | emit the stone of the intersection part, preventing the biting of stones other than an intersection part. Here, when providing the groove part 6 in the land part 5 other than this illustration, the length L of the longitudinal direction of the groove part 6 should just be decided on the basis of the projection width area | region Wp same as the illustration, for example, 0.6 * Wp ≦ L ≦ 1.5 * Wp.

[Embodiment 3]
Next, Embodiment 3 of the pneumatic tire according to the present invention will be described with reference to FIG.

  In the pneumatic tire 1 of Embodiments 1 and 2 described above, only one groove portion 6 is provided. However, in Embodiment 3, a plurality of groove portions are provided. About the position of the pressing direction on the land part 5 in each groove part, a groove width, and a groove depth, it is set as the same as the groove part 6 of Embodiment 1 and 2. FIG. Further, each groove portion may be arranged such that its longitudinal direction is the same as the orthogonal direction to the pressing direction, and the longitudinal direction has an angle smaller than 45 degrees with respect to the orthogonal direction. You may arrange. In the arrangement, all the groove portions may have the same longitudinal direction, and at least one longitudinal direction of each groove portion may be different from the other longitudinal direction. Furthermore, each of the groove portions may be arranged at the same position as viewed from the side wall 5a on the intersection portion side with respect to the position in the pressing direction on the land portion 5, and at least one of them may be arranged at another position. May be. On the other hand, the position and length in the direction orthogonal to the pressing direction on the land portion 5 are set slightly different from those of the groove portion 6, and will be described using the following examples.

  The code | symbol 16 of FIG. 5 shows the groove part of this Embodiment. The groove portion 16 includes first to third groove portions 16a, 16b, and 16c.

  The position in the direction orthogonal to the pressing direction on the land portion 5 will be described. In the illustrated groove portion 16, any one of the first to third groove portions 16a, 16b, and 16c is arranged on the extension line in the pressing direction by the stone, and at least one of them is the projection width region Wp. To exist within. Thereby, when the stone rolls to the intersection part or enters the intersection part, the side wall 5a can be expanded by the pressing force of the stone. The groove portion 16 is also present in a range of a predetermined ratio (for example, 60%) or more of the projected width region Wp. In this case, all or a part of the groove portion 16, that is, the first to third groove portions 16a, 16b, The predetermined ratio is ensured by all of 16c or any one of them.

  Next, the length will be described. The groove 16 has a total value of the lengths La, Lb, and Lc of the first to third grooves 16a, 16b, and 16c that is at least a predetermined ratio (for example, 60%) of the projection width region Wp. Is set so that the deformation amount of the side wall 5a suitable for stone discharge is obtained, and the total value thereof is set to be equal to or less than a predetermined ratio (for example, 150%) of the projection width region Wp. Prevent stone biting outside of the area.

  As described above, by providing the groove portion 16 composed of the first to third groove portions 16a, 16b, and 16c on the land portion 5 that forms the intersection portion of the main groove 3A and the lateral groove 4, the stone is also formed in the main groove 3A. When the inside rolls to the intersection part or enters the intersection part, the side wall 5a is pushed by the stone and deforms to the groove part 16 side, so that the intersection part is enlarged and the stone is discharged outside. it can. Further, since the groove portion 16 can be said to be obtained by dividing the groove portion 6 of the first and second embodiments into a plurality of portions, the first to third groove portions 16a, 16b, 16c are smaller than the groove portion 6, and the land portion 5 It is easy to increase the rigidity. Therefore, the pneumatic tire 1 of this embodiment can improve rolling resistance and steering stability as compared with those of the first and second embodiments. Furthermore, since the groove 16 can reduce the opening on the tread surface 2a side of the first to third grooves 16a, 16b, and 16c, it can also suppress the biting of stones into these, and its effect is higher than that of the groove 6. .

  Here, the groove 16 may be mixed with the groove 6 of the first and second embodiments as illustrated in FIG.

[Embodiment 4]
Next, Embodiment 4 of the pneumatic tire according to the present invention will be described with reference to FIGS. 6 and 7.

  In each of the first to third embodiments described above, the groove portion 6 and the groove portion 16 (first to third groove portions 16a, 16b, and 16c) having a constant groove width are illustrated, but the groove portions 6 and 16 are represented by the groove portions 26 described below. May be replaced.

  As shown in FIGS. 6 and 7, the groove portion 26 of this embodiment has a groove width Ws narrowed toward the groove bottom. The groove width Ws is set to the groove width in the groove portion 6 of the first and second embodiments from the groove width on the tread surface 2a at the time of a new article having the maximum width to the groove width on the groove bottom side having the minimum width. Is preferably applied. As a result, the pneumatic tire 1 can obtain a desired amount of deformation of the side wall 5a at the intersection portion while ensuring the rigidity of the land portion 5, while suppressing an increase in rolling resistance and a decrease in driving stability. The stone can be discharged by the pressing force at the intersection.

  Further, even if the groove 26 is set to the maximum allowable width on the tread surface 2a side when new, the groove width gradually decreases toward the groove bottom. Therefore, the groove portion 26 can increase the rigidity of the land portion 5 as compared with the groove portions 6 and 16 of the first to third embodiments in which the maximum allowable width extends to the groove bottom. In order to obtain the same rigidity of the land portion 5 as that of the groove portion 26 by the groove portions 6 and 16, it is necessary to make the groove width narrower than the allowable maximum width. On the other hand, the fact that the groove width is wide means that the deformation amount of the side wall 5a can be increased with respect to the narrow groove width, so that the intersection portion can be further enlarged and the elastic force accompanying the deformation of the side wall 5a is also increased. , It will be easier to discharge the stone at the intersection. Therefore, if the groove 26 is required to have equivalent rolling resistance and steering stability with the same rigidity of the land portion 5 as compared with the grooves 6 and 16 of the first to third embodiments, the stone at the intersection will be discharged. If the equivalent stone discharging performance is required, the rolling resistance and the handling stability can be improved by the highly rigid land portion 5.

  Here, in this groove part 26, the side wall on the opposite side is inclined instead of the side wall on the main groove 3A side. Considering the ease of deformation by the pressing force of the side wall 5a and the strength that can withstand the deformation, such a shape that the wall thickness between the wall surface of the side wall 5a and the wall surface of the side wall on the main groove 3A side in the groove portion 26 becomes constant. However, the groove 26 may be inclined on the side wall on the main groove 3A side, or both side walls may be inclined.

  Further, in the case of a plurality of groove portions such as the groove portion 16, all of the plurality of groove portions may be shaped like the groove portion 26, and at least one of them may be shaped like the groove portion 26 and remain. The shape of the groove may be constant.

[Embodiment 5]
Next, a fifth embodiment of the pneumatic tire according to the present invention will be described with reference to FIGS.

  In the pneumatic tire 1 according to the present embodiment, in order to reduce rolling resistance and improve steering stability by increasing the rigidity of the land portion 15, an inclination angle is provided on the side wall 15a of the land portion 15 on the main groove 13A side. It is a thing. It is assumed that the inclined surface of the side wall 15a approaches the other land 15 side facing the main groove 13A as it goes toward the groove bottom. This one inclined surface may be constituted by one same inclination angle, or may be one in which the inclination angle is changed in the tire circumferential direction. In this example, since the latter is the side wall 15a made of an inclined surface having a change, the side wall of the main groove 13A changes in the tire circumferential direction. For this reason, since the rigidity of the land portion 15 can be increased more than that having the same inclination angle, it is possible to further reduce rolling resistance and improve steering stability.

  Also in such a pneumatic tire 1, at least one of the groove portions 6, 16, and 26 described above is formed in at least one land portion 15 that forms an intersection portion of the main groove 13 </ b> A and the lateral groove 4. In this case, the shape of the grooves 6, 16, and 26 and the position in the land portion 15 are set similarly to the above-described example. Thereby, the pneumatic tire 1 can obtain the same effects as those obtained by the respective groove portions 6, 16, and 26. 8 and 9 exemplify those provided with the groove 6 of the first and second embodiments.

  Here, as described above, when the side wall 15a on the intersection portion side has an inclined surface, the stone at the intersection portion is easily discharged, and the effect is particularly high when it is new. In the pneumatic tire 1, since the groove portion 6 (groove portions 16 and 26) is further provided, a high stone discharging performance can be obtained until the wear progresses to some extent from the new article. However, since the side wall 15a is an inclined surface, the thickness between the inclined surface of the side wall 15a and the groove portion 6 becomes thicker as it approaches the groove bottom, as shown in FIG. Therefore, when the wear progresses, particularly at the end of wear, the thick wall and the shallow groove portion 6 increase the rigidity between the inclined surface and the groove portion 6, and the side wall 15a is deformed to the groove portion side. Since it becomes difficult to do so, there is a possibility that the stone discharging performance is lowered.

  Therefore, when forming a groove portion in this type of land portion 15, for example, it is preferable to replace the groove portion 6 (groove portions 16 and 26) with an inclined groove portion on the main groove 13A side. The groove portion has the inclination angle of the wall surface on the main groove 13A side as close as possible to the inclination angle of the inclined surface of the side wall 15a, and preferably has the same inclination angle. Thereby, since the rigidity between the inclined surface of the side wall 15a and the groove portion from the time when the wear progresses to the end of wear can be lowered, it is possible to promote the deformation of the side wall 15a to the groove portion side. Therefore, the stone discharge performance can be improved.

  Further, the groove portion formed in this type of land portion 15 may be as follows. In the case where the side wall 15a on the intersection portion side has an inclined surface, the stone discharging effect can be obtained even if there is no groove in the land portion 15 as long as the wear progresses to some extent from the time of the new article. Therefore, the groove portion may be any groove portion that can exhibit the stone discharging effect during the period from the progress of wear to the end of wear. Therefore, in this type of land portion 15, as shown in FIGS. 10 and 11, for example, a groove portion 36 may be provided on the side wall 15a. In that case, the space which forms the groove part 36 is needed for the side wall 15a. For this reason, the groove part 36 on the side wall 15a is provided when the inclination angle of the side wall 15a is, for example, 10 degrees or more and a space for forming the groove part 36 can be secured. In the pneumatic tire 1 in this case, at least one of the groove portions 6, 16 and 26 may be applied as the groove portion 36.

  The shape of the groove portion 36 is basically set to be the same as the shape of each groove portion 6, 16, 26. However, the groove depth may be set so that the groove bottom has the same height as the groove bottom of the main groove 13A. In the groove portion 36, the position in the direction orthogonal to the pressing direction on the land portion 15 is set to be the same as that of the groove portions 6, 16, and 26.

  On the other hand, in the groove portion 36, the position in the pressing direction on the land portion 15 may be determined as follows. As described above, the stone discharging effect can be obtained even if the groove portion 36 does not exist in the land portion 15 until the wear progresses to some extent from the time of the new article. From this, the position in the pressing direction on the side wall 15a of the land portion 15 is determined, for example, by determining the wear amount Qw of the tread surface 2a from the new time when the stone at the intersection can be discharged without the groove portion 36. Is set so that the end portion on the tread surface 2a side becomes a part of the wall surface on the intersection portion side in the groove portion 36. Thereby, in this pneumatic tire 1, the stone at the intersection can be discharged without depending on the groove portion 36 until the wear progresses to some extent from the new tire. In this pneumatic tire 1, when wear further progresses, the side wall 15 a is pushed and widened by the groove portion 36, and stones are discharged by expanding the intersection portion.

[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, the pneumatic tires of Conventional Examples 1 and 2 and the pneumatic tires of Comparative Examples 1 and 2 that are the comparison targets of the performance test results are also shown. . The pneumatic tire of Example 1 is the pneumatic tire 1 of Embodiment 1 described above. The pneumatic tire of Example 2 is the pneumatic tire 1 of Embodiment 2 described above. The pneumatic tire of the conventional example is, in other words, the one in which the groove portion 6 is not provided in the pneumatic tire of Examples 1 and 2. The pneumatic tire of Conventional Example 2 has a notch in the land portion. The notch means a shape as in the case where the groove portion 6 of the first and second embodiments communicates with the main groove 3A. The pneumatic tires of Comparative Examples 1 and 2 have a groove portion in which the setting conditions of the groove portion 6 of Embodiment 2 are slightly changed.

  Here, the evaluation test of the stone biting performance and the evaluation test of the steering stability were 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 pneumatic tire of Conventional Example 1 is represented by an index value 100, and the other pneumatic tires are indexed based on the difference in the number of stones. The index value indicates that the larger the value, the better the stone biting performance.

  In addition, the stone biting performance based on the belt arrival rate of the stone at the intersection of the pneumatic tire was also evaluated. The belt arrival rate is the arrival rate of stones when the groove bottom of the main groove is cut by stone drilling, and the number of stones reaching the belt with the number of stones biting into the intersection part It is the percentage of what was divided. The evaluation method is to use a test vehicle equipped with pneumatic tires on a gravel road (off-road course) or paved road (asphalt road) at a predetermined speed, and at the intersection when the tread wears 80% from the beginning. Measure the number of stones biting and the number of stones reaching the belt. The evaluation result indicates a belt arrival rate based on the number of stones bitten at the intersection and the number of stones reaching the belt. This belt reachability indicates that the smaller the numerical value, the less the stone reaches the belt, and the better the stone biting performance.

  As a method for evaluating the steering stability, a feeling evaluation was performed when the test vehicle on which a pneumatic tire was mounted traveled on a dry road at a predetermined speed. The evaluation result expresses the feeling in the pneumatic tire of Conventional Example 1 with an index value of 100, and also indexes other pneumatic tires based on the difference in feeling based on this. The index value indicates that the larger the value, the better the steering stability.

  Each type of pneumatic tire to be tested has a common land portion 5 pattern, main grooves 3A, 3B, and lateral grooves 4. In the pneumatic tire of Example 1, the groove width Ws of the groove portion 6 and the position of the pressing force on the land portion 5 in the pressing direction (tire width direction) are within the above range. Setting conditions for the length L and the proportion of the groove 6 in the projected width region Wp (coverage ratio of the groove 6) are excluded from the above range. On the other hand, the pneumatic tire of Example 2 has all these setting conditions within the above range. The pneumatic tire of Comparative Example 1 has a groove width Ws narrower than the above range among these setting conditions. On the other hand, the pneumatic tire of Comparative Example 2 has a groove width Ws wider than the above range among the set conditions.

  According to the test results of FIG. 12, the pneumatic tires of Examples 1 and 2 in which the groove portion 6 is provided in the land portion 5 in the vicinity of the intersection of the main groove 3A and the lateral groove 4 are the air of the conventional examples 1 and 2. It can be seen that the resistance to stone biting is improved with respect to the entering tire while suppressing a decrease in steering stability. Further, when the pneumatic tires of Example 1 and Example 2 are compared, the pneumatic tire of Example 2 is obtained by optimizing the length L of the groove portion 6 and the coverage ratio of the groove portion 6, so It can be seen that the number of stone bites is smaller than that of the entering tire and the stones do not reach the belt, so that the stone biting performance is excellent. Note that the pneumatic tire of Conventional Example 2 can reduce the number of stone bites compared to Conventional Example 1 by providing a notch in the land portion, but the belt arrival rate increases and the steering stability decreases. Resulting in.

  Here, the pneumatic tire of Comparative Example 1 in which the groove width Ws is narrowed has the same stone resistance performance and steering stability as the pneumatic tire of Conventional Example 1. Therefore, it can be seen that the groove 6 should not have the groove width Ws too narrow. In addition, the pneumatic tire of Comparative Example 2 with a wider groove width Ws has the effect of reducing the number of stone bites equivalent to that of the pneumatic tire of Example 1, and reaches the belt more than the pneumatic tire of Example 1. The rate can be lowered. However, the pneumatic tire of Comparative Example 2 has lower steering stability than the conventional one. For this reason, it can be seen that the groove portion 6 causes a decrease in steering stability due to a decrease in rigidity of the land portion 5 by making the groove width Ws too wide.

  By the way, in one pneumatic tire, you may comprise only one kind of groove part (any one of the groove parts 6, 16, 26, 36), and each groove part 6, 16, 26, 36 of You may comprise combining at least 2 or more types of these.

  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 Pneumatic tire 2 Tread part 2a Tread surface 3A, 3B, 13A Main groove 4 Horizontal groove 5,15 Land part 5a, 15a Side wall 6, 16, 26, 36 Groove part 16a 1st groove part 16b 2nd groove part 16c 3rd groove part CL Tire center

Claims (11)

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,
In the vicinity of the intersection of the main groove and the horizontal groove in the land portion and at a position isolated from the main groove and the horizontal groove, the opening is formed long in the longitudinal direction while opening toward the tread. one in the land portion provided with a groove portion that is isolated from the intersections end within the land portion are arranged in a straight line via the side walls of the land portion with provided terminated without Oremagara,
The groove portion is provided in a land portion facing the opening portion of the lateral groove in the intersection portion of each land portion forming the intersection portion,
The land portion is configured so that the groove width of the opening portion of the lateral groove is directed in the pressing direction of the pressing force so that the side wall is expanded by the pressing force input to the side wall of the land portion at the intersection portion. And the groove width Ws of the main groove in the pressing direction of the pressing force and the groove width Wm of the main groove have a relationship of 0.1 * Wm ≦ Ws. Meets
The groove is formed to have a length in the longitudinal direction where a desired amount of deformation of the side wall due to the pressing force can be obtained at the intersection, and the longitudinal direction is the same as a direction orthogonal to the pressing direction of the pressing force. Or arranged to incline at an angle smaller than 45 degrees with respect to the orthogonal direction ,
The land portion has an inclined surface that approaches the other land portion that forms the intersection portion as the side wall on the intersection portion side approaches the groove bottom of the main groove, and the groove portion is provided on the side wall. And pneumatic tires.   The groove portion provided in the land portion facing the opening portion of the lateral groove has at least one portion in a projected width region on the land portion in which the groove width of the opening portion is projected toward the pressing direction of the pressing force. The pneumatic tire according to claim 1, wherein:   The pneumatic tire according to claim 2, wherein the groove portion is arranged in a range equal to or greater than a predetermined ratio of the projected width region where a desired amount of deformation of the side wall due to the pressing force can be obtained.   The groove portion is formed so as to have a groove width at which a desired amount of side wall deformation due to the pressing force is obtained at the intersection, and the groove width is the same direction as the pressing direction of the pressing force or the pressing force. The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is disposed so as to be inclined at an angle smaller than 45 degrees with respect to the direction.   The pneumatic tire according to any one of claims 1 to 4, wherein the groove portion is formed to have a groove width that can ensure a desired rigidity of the land portion.   The pneumatic tire according to any one of claims 1 to 5, wherein a groove width of the groove portion becomes narrower toward a groove bottom.   The groove portion is provided within a range corresponding to a groove width of the main groove from an end portion on a tread surface side of a side wall on the intersection portion side of the land portion in a pressing direction of the pressing force on the land portion. The pneumatic tire according to any one of claims 1 to 6.   When the width in the pressing direction of the pressing force in the land portion is “Wb”, the groove portion is the tread side on the side wall on the intersection portion side of the land portion in the pressing direction of the pressing force on the land portion. The pneumatic tire according to any one of claims 1 to 7, wherein the pneumatic tire is provided at a position that is at least 5% of the width Wb and at least 0.5 mm apart from an end of the pneumatic tire. The pneumatic tire according to any one of claims 1 to 8, wherein an inclination angle of the inclined surface of the side wall on the main groove side in the land portion is changed in a tire circumferential direction. The pneumatic tire according to any one of claims 1 to 9 , wherein a plurality of the groove portions are provided. The pneumatic tire according to any one of claims 1 to 10 , wherein the pattern of the land portion is for a heavy load tire and for a studless tire.

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