JP5235034B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that can improve wet performance and wear resistance performance in a well-balanced manner.

  Conventionally, a tread surface of a pneumatic tire is provided with a lateral groove extending in the tire axial direction in order to improve traction performance. In particular, in a heavy-duty tire used for heavy-duty vehicles such as trucks and dump trucks, such lateral grooves are frequently used as lug grooves as shown in FIG.

  However, a pattern that mainly includes lateral grooves generally tends to have low wet performance. For this reason, conventionally, as shown in FIG. 9, it is formed in a zigzag shape by providing a bent portion b in the lateral groove a, and the wet performance is improved by a draining effect using the edge e of the land portion facing the bent portion b. Is planned. However, such a zigzag lateral groove a tends to easily cause chipping of a land portion starting from the edge e or uneven wear (for example, heel & toe wear) starting from the edge e as wear progresses. There is.

  The present invention has been devised in view of such a situation, and is based on the principle that the angle of the bent portion of the lateral groove is large when the tire is new and small when 50% is worn. An object of the present invention is to provide a pneumatic tire capable of improving the wear performance in a well-balanced manner.

The invention according to claim 1 of the present invention is a pneumatic tire in which a lateral groove is provided on a tread surface, and the lateral groove has a lateral groove centerline passing through the middle between the groove edges on the road surface and the tread surface that contacts the road surface. A first portion extending at an angle θ1 with respect to the tire axial direction, and a second portion extending to the first portion and extending at an angle θ2 (≠ θ1) with respect to the tire axial direction. And the transverse groove includes a third portion in which the transverse groove center line continues to the second portion and extends at an angle θ3 (≠ θ2) with respect to the tire axial direction. When the tire is new, the bending angle θa0 of the first bent portion represented by | θ2-θ1 | is 30-50 °, and when the tire is new, | θ3-θ2 The bending angle θb0 of the second bent portion represented by | The bending angle θa50 of the first bent portion at 50% wear is 0.35 to 0.65 times the angle θa0, and the second bend at 50% wear is 30 to 50 °. The bending angle θb50 of the portion is 0.35 to 0.65 times the angle θb0, the groove edge of the lateral groove is along the lateral groove center line, and the tread surface has a tire circumferential direction. A slanted narrow groove extending between adjacent lateral grooves and inclined with respect to the tire circumferential direction is provided, and the slanted narrow groove is formed at an outer angle side of the first bent portion of one of the lateral grooves, and The first bent portion and the second bent portion are connected to each other on the outer angle side of the second bent portion of the other lateral groove .

  In the invention according to claim 2, the lateral groove extends from the tread ends on both sides in the tire axial direction inner side, and the third portion is located in the tire axial direction inner side, and the tread surface includes the third portion. A zigzag narrow groove extending continuously in the tire circumferential direction while connecting the inner end side in the tire axial direction of the tire is provided, and the zigzag narrow groove is inclined to one side with respect to the tire circumferential direction and extends in a straight line. 2. The pneumatic tire according to claim 1, wherein the pneumatic tire is configured by alternately arranging the narrow width portions that are inclined in a direction opposite to the narrow width portion and linearly extend with respect to the tire circumferential direction.

  The invention according to claim 3 is the pneumatic tire according to claim 2, wherein the oblique narrow groove extends linearly in parallel with the narrow portion of the zigzag narrow groove.

  As described above, the pneumatic tire of the present invention is formed in a land portion facing the first bent portion by limiting the bending angle of the first bent portion of the lateral groove to a certain range when the tire is new. The wet performance can be improved by the edge effect.

  Further, by reducing the bending angle of the first bent portion at the time of 50% wear, the rigidity of the land portion facing the first bent portion can be increased, and the occurrence of block chipping and uneven wear can be prevented. Thus, the pneumatic tire of the present invention can improve wet performance and wear resistance performance in a well-balanced manner.

  In addition, since the second bent portion is provided in the lateral groove and the bending angle is set for the bent portion in the same manner as the first bent portion, the wet performance and the wear resistance performance can be improved in a balanced manner.

  In addition, the tread surface is provided with slanted narrow grooves extending between adjacent lateral grooves in the tire circumferential direction and connecting the first bent portion and the second bent portion of these lateral grooves. Such slanted narrow grooves do not contribute much to the improvement of drainage, but can optimize the rigidity of the land portion between the lateral grooves to mitigate the shear force generated between the road surface and other places such as when turning. In addition to contributing to improved wear, the groove width can be easily closed to ensure the rigidity of the land portion and prevent the steering stability from deteriorating.

It is an expanded view of the tread pattern which shows embodiment of this invention. It is an enlarged view of the transverse groove in the tread surface. 2 is a schematic cross-sectional view of a tread portion. It is a development view of a tread pattern showing a state at the time of 50% wear. It is an enlarged view of the transverse groove in the tread surface. It is an enlarged view of FIG. 5 which shows to a groove bottom edge. It is a fragmentary perspective view of a block. 10 is a plan view showing a tread pattern of Comparative Example 3. FIG. It is a top view which shows the conventional horizontal groove.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view (when new) of a tread pattern of a heavy-duty pneumatic tire mounted on a truck, a bus, or the like as this embodiment, and FIG. 2 is a partially enlarged view of the lateral groove 3. Moreover, the horizontal groove of FIG. 1, FIG. 2 patterns the groove edge in the tread surface which contacts a road surface. As shown in FIG. 1, a lateral groove 3 is provided on the tread surface 2. In the present example, the lateral groove 3 is formed in a lug groove shape that extends inward in the tire axial direction from the tread ends E on both sides.

  The groove width and groove depth of the lateral groove 3 are not particularly limited, but preferably the groove width is 5.0 to 12.0% of the tread width, more preferably 6.0 to 10.5%, and the groove depth is tread. It is desirable that the width is 8.0 to 10.5%, more preferably 8.5 to 10.0%. If the groove width is less than 5.0% of the tread width or the groove depth is less than 8.0%, the wet performance tends to deteriorate because the basic drainage performance is deteriorated. If the width is larger than 12.0% or the groove depth is larger than 10.5% of the tread width, the rigidity of the tread surface 2 tends to be lowered, and the driving stability and grip force on the dry pavement are impaired. Cheap. In particular, as in this embodiment, when the tire is for heavy loads, the groove width of the lateral groove 3 is preferably set to 15 mm or more.

  The tread width refers to the distance in the tire axial direction between the grounded outer ends when the tire is assembled on a regular rim, filled with a regular internal pressure, and loaded with a regular load and brought into contact with a flat surface. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO If so, use "Measuring Rim". In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. It is the maximum air pressure for JATMA and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 KPa for tires for passenger cars. Furthermore, “regular load” is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is specified for JATMA, and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”. If ETRTO, “LOAD CAPACITY”.

  In this example, the lateral groove 3 has a first portion 3a, one end of which is continuous with the tread end E and linearly extending at an angle θ1 with respect to the tire axial direction N, and the first portion 3a, which is continuous with the first portion 3a. A second portion 3b extending linearly with respect to N at an angle θ2 (≠ θ1), and a second portion 3b extending linearly with respect to the tire axial direction N at an angle θ3 (≠ θ2). 3 portion 3c. Accordingly, the lateral groove 3 has a first bent portion 5 bent at an angle | θ2-θ1 | and a second bent portion 6 bent at an angle | θ3-θ2 |. The zigzag shape extends in the tire axial direction. It is The angles θ1 to θ3 of the respective portions 3a to 3c of the lateral groove 3 can be determined by the lateral groove center line CL passing through the middle between the groove edges 7 and 7 of the lateral groove 3. In the present specification, in the angles θ1 to θ3, the counterclockwise direction is positive and the clockwise direction is negative with respect to the tire axial direction N.

  The tread surface 2 is provided with a pair of zigzag narrow grooves 4a, 4a that are zigzag-shaped and extend in the tire circumferential direction on both sides of the tire equator. The zigzag narrow groove 4a extends continuously in the tire circumferential direction while joining the inner end side in the tire axial direction of the third portion 3c of the lateral groove 3. In the present embodiment, the zigzag narrow groove 4a is slanted in one direction with respect to the tire circumferential direction and extends in a straight line, and the slanted groove 4a is slanted and straight in a direction opposite to the narrow width part 4a1 with respect to the tire circumferential direction. The wide portions 4a2 extending in a shape are arranged alternately in the tire circumferential direction. This helps to form a zigzag edge continuously in the circumferential direction of the tire to compensate for improved wet performance. The groove width of the zigzag narrow groove 4a is not particularly limited, but is smaller than the groove width of the lateral groove 3 in this example. Specifically, the narrow portion 4a1 is, for example, 2.5 to 4.5 mm, and the wide portion 4a2 is 1.0 to 3.0 times, more preferably 1.0 to 2.5 times that of the narrow portion 4a1. It is desirable to set the groove width.

  Further, the zigzag narrow groove 4a is formed on the tread surface 2 by extending between the lateral grooves 3 and 3 adjacent to each other in the tire circumferential direction and connecting the first bent portion 5 and the second bent portion 6 of these lateral grooves 3. An oblique narrow groove 4b extending linearly in parallel with the narrow width portion 4a1 is provided. The slanted narrow groove 4b is set to have a small width of, for example, a groove width of 1.0 to 4.0 mm, more preferably 1.0 to 3.0 mm. Such slanted narrow grooves 4b do not contribute much to the improvement of drainage, but optimize the rigidity of the land portion between the lateral grooves 3 and 3 to alleviate the shear force generated between the road surface and the like during turning. In addition to being able to contribute to the improvement of wear resistance, the rigidity of the land portion is secured by easily closing the groove width, so that it is possible to prevent a decrease in steering stability performance. The angle α of the narrow portion 4a1 of the zigzag narrow groove 4a and the slanted narrow groove 4b with respect to the tire circumferential direction is preferably 16 to 30 °, more preferably 22 to 27 °.

  Further, on the tread surface 2, a joint groove 4c extending between the pair of zigzag narrow grooves 4a, 4a and bent in a substantially Z shape is provided in the tire circumferential direction. As a result, the tread surface 2 of the present example has a large center block B1 having a substantially S shape in plan view aligned in the tire circumferential direction between the zigzag narrow grooves 4a, 4a, and the zigzag narrow groove 4a. A substantially hexagonal middle block B2 formed between the narrow groove 4b and a substantially hexagonal shoulder block B3 formed on the outer side in the tire axial direction of the slanted narrow groove 4b are formed.

  As shown in FIG. 2, when the tire is new, the pneumatic tire has a second bending angle θa 0 and | θ 3 −θ 2 | of the first bending portion 5 represented by | θ 2 −θ 1 |. The bending angle θb0 of the bent portion 6 is set to 30 to 50 °, and is set relatively large. As a result, sharp edges e are formed in the land portions (in this example, the middle block B2 and the shoulder block B3) located in the front and rear in the tire circumferential direction with the first and second bent portions 5 and 6 interposed therebetween. Such an edge e can cut and eliminate the water film at the time of contact with the road surface having the water film, thereby improving the wet performance.

  If the bending angle θa0 of the first bent portion 5 is less than 30 °, the effect of improving the wet performance cannot be sufficiently obtained. Conversely, if it exceeds 50 °, the edge e becomes excessively sharp and its rigidity is lowered. For this reason, not only the edge e is likely to be chipped but also uneven wear such as heel and toe wear is likely to occur, thereby reducing wear resistance. More preferably, the bending angle θa0 of the first bent portion 5 is 34.0 to 46.0 °. Further, the second bent portion 6 is not particularly limited, but in the present embodiment, similarly to the first bent portion 5, the bending angle θb0 of the second bent portion 6 is also limited to 30 to 50 °. doing. Thereby, the land part which has more edges e can be formed in the tread surface 2, and wet performance can further be improved.

  In the pneumatic tire of the present invention, the first bent portion 5 is set such that the bending angle θa50 at the time of 50% wear is 0.35 to 0.65 times the bending angle θa0 when new. In addition, in this example, the bending angle θb50 at the time of 50% wear is also set to 0.35 to 0.65 times the bending angle θb0 at the time of new article for the second bent portion 6. Here, “at the time of 50% wear” means, as shown in FIG. 3, the depth of the lateral groove 3 (maximum groove depth) by cutting the tread portion along a curved surface P parallel to the tread surface 2 at the time of a new article. (Specified by the part) is set to a state where 50% of the new item is set.

  4 is a developed view of a tread pattern of a pneumatic tire at 50% wear, FIG. 5 is an enlarged plan view of the lateral groove 3, FIG. 6 is a plan view up to the groove bottom edge, and FIG. 7 is blocks B2 and B3. Are respectively perspective views. As shown in FIGS. 5 and 6, in this embodiment, the groove edge 7 and the groove bottom edge 9 of the lateral groove 3 are set non-parallel. Thereby, each groove wall surface W1, W2,... Of the lateral groove 3 is formed by a twisted curved surface instead of a plane. The groove wall surfaces W1, W2,... Are set so that the bending angles θa, θb of the first and second bent portions 5, 6 gradually decrease as the tread surface 2 wears. ing.

  The first and second bent portions 5 and 6 have first and second bent portions as they wear because the bent angles θa50 and θb50 are smaller than the bent angles θa0 and θb0 when new at 50% wear. The rigidity in the vicinity of each edge e of the middle block B2 and the shoulder block B3 facing the portions 5 and 6 can be increased. For this reason, it is possible to suppress the occurrence of heel & toe wear starting from the edge e accompanying the progress of wear, and at the same time, it is possible to prevent the chipping of the block by making the edge e of the block non-sharp.

  If the bending angle θa50 of the first bent portion 5 at the time of 50% wear is less than 0.35 times the bending angle θa0 at the time of a new article, it is advantageous for wear resistance performance, but the edge action is reduced. The wet performance is significantly reduced. Further, when the bending angle θa50 of the first bent portion 5 at the time of 50% wear exceeds 0.65 times the bent angle θa0 at the time of a new product, it is advantageous for wet performance, but the first bent portion 5 The distortion tends to concentrate on the facing block or the edge e of the land part, and the chipping of the block and heel & toe wear are likely to be caused and the wear resistance is deteriorated. From this point of view, it is particularly desirable for the first bent portion 5 to set the bending angle θa50 at the time of 50% wear to 0.40 to 0.60 times the bending angle θa0 at the time of a new product. The same applies to the second bent portion 6.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the illustrated heavy load tires as long as the tire has a lateral groove extending in the tire axial direction, and can be applied to various categories of tires. . Further, the tread pattern can be applied to various patterns such as a lag pattern and a rib lag pattern in addition to the block-based pattern as in this example. Furthermore, although the horizontal groove 3 of the present embodiment has been shown to include the first and second bent portions 5 and 6, the present invention can be applied to a horizontal groove further including a third bent portion.

  Four types of heavy-duty radial tires with a tire size of 11R22.5 were prototyped, and wet performance (when new and 50% worn), presence or absence of land chipping, and heel & toe wear were measured. All of the prototype tires have the same internal structure and differ only in the tread pattern. The embodiment has the tread pattern shown in FIG. 1 and FIG. 3, and Comparative Example 1 is the same as FIG. 1 when it is new, but the bending angle of the bent portion substantially changes even when 50% wears. In the comparative example 2, the first and second bent portions have a large bending angle, and the comparative example 3 is generally used conventionally as shown in FIG. It has a rug pattern. The test conditions are as follows.

<Wet performance test>
The test tire is assembled on a rim (7.50 × 22.5) and filled with an internal pressure of 850 kPa, and it is mounted on two driving wheels of a 2-D truck with a constant load (10 liters). The maximum traction force at the moment when the driving wheel slips on a low μ road such as above was measured. Generally, since the maximum traction force on a low μ road of a new tire requested by a user is 15 kN, the evaluation is represented by an index with 15 kN as 100. It shows that it is so favorable that a numerical value is large. The test at the time of 50% wear was carried out after cutting a new tire into a 50% wear state and running-in for 500 km.

<Land part missing test>
The test tire is assembled on a rim (7.50 x 22.5) and filled with an internal pressure of 850 kPa, and is mounted on two wheels of a 2-D truck with a constant load (10 liters). The road test was conducted until the thickness became substantially 50%. And the number which the chip | tip has produced in the edge of the block facing the 1st, 2nd bending part was measured. The smaller the number, the better.

<Heel & toe wear test>
The road test was performed until the depth of the lateral groove was substantially 30% under the vehicle conditions. And the heel & toe wear amount was measured about the block which faced the horizontal groove. Those with a heel & toe wear of 3 mm or less are inconspicuous and pass.
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that in the tire of the example, the wet performance (when new and 50% worn) and the wear resistance are improved in a well-balanced manner. On the other hand, in Comparative Examples 1 and 2, the wet performance is good, but block chipping or heel & toe wear is severe, and there is a problem in terms of wear resistance. In Comparative Example 3, the wear resistance was relatively good, but it was confirmed that the wet performance was extremely low.

2 Tread surface 3 Horizontal groove 3a First portion 3b Second portion 3c Third portion 4b Diagonal narrow groove 5 First bent portion 6 Second bent portion θa0 Bending angle θa50 of the first bent portion when new Bending angle θb0 of the first bent part at 50% wear Bending angle θb50 of the second bent part at the time of a new article Bending angle of the second bent part at 50% wear

Claims (3)

A pneumatic tire provided with a lateral groove on the tread surface,
The transverse groove includes a first portion in which a transverse groove center line passing through the middle between the groove edges on the tread surface that contacts the road surface extends at an angle θ1 with respect to the tire axial direction, and is connected to the first portion. Including a second portion extending at an angle θ2 (≠ θ1) with respect to the direction, and
The transverse groove has a second bent portion by including a third portion in which the transverse groove center line continues to the second portion and extends at an angle θ3 (≠ θ2) with respect to the tire axial direction.
When the tire is new, the bending angle θa0 of the first bent portion represented by | θ2-θ1 | is 30 to 50 °, and when the tire is new, the second is represented by | θ3-θ2 |. The bending angle θb0 of the bent portion is 30-50 °,
The bending angle θa50 of the first bent portion at the time of 50% wear is 0.35 to 0.65 times the angle θa0, and the bending angle θb50 of the second bent portion at the time of 50% wear. Is 0.35 to 0.65 times the angle θb0,
The groove edge of the horizontal groove is along the horizontal groove center line,
Moreover the tread surface, one oblique fine grooves inclined with respect to the extending between lateral grooves and the tire circumferential direction adjacent in the tire circumferential direction is provided,
The oblique narrow groove includes the first bent portion and the second bent portion on the outer angle side of the first bent portion of one of the lateral grooves and on the outer angle side of the second bent portion of the other horizontal groove. A pneumatic tire characterized by joining a bent portion .
The lateral groove extends inward in the tire axial direction from the tread ends on both sides, and the third portion is positioned inward in the tire axial direction,
The tread surface is provided with a zigzag narrow groove extending continuously in the tire circumferential direction while joining the inner end side in the tire axial direction of the third portion,
The zigzag narrow groove has a narrow portion extending linearly and inclined to one side with respect to the tire circumferential direction, and a wide portion extending in a straight line and inclined in a direction opposite to the narrow portion with respect to the tire circumferential direction. The pneumatic tire according to claim 1, wherein the tires are arranged alternately in the tire circumferential direction.   The pneumatic tire according to claim 2, wherein the oblique narrow groove extends linearly in parallel with the narrow portion of the zigzag narrow groove.

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