JP2013071555A - Pneumatic tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire capable of achieving both reduction of rolling resistance and maintenance of wet performance and used for a heavy load vehicle.SOLUTION: This pneumatic tire for a heavy load is formed by arranging circumferential main grooves 3, 4 on a tread of a tread part by interposing a tire equator E, and partitioning the tread of the tread part into a center region Z1 and both side regions Z2, Z3. The tire is structured such that, in the center region Z1, a circumferential thin groove 6 being at least one circumferential thin groove 6 extending along the tire circumferential direction, and having an opening of the circumferential thin groove 6 closed at tire grounding is arranged, and two or more center rib-like land parts 8, 9 are partitioned and formed; shoulder circumferential grooves 11, 12 extending along the tire circumferential direction are arranged on the outer sides in the tire width direction of the circumferential main grooves 3, 4; and when it is assumed that the groove width of each of the circumferential main grooves 3, 4, that of each of the shoulder circumferential grooves 11, 12, and that of the circumferential thin groove 6 are W1, W2 and W3, respectively, the relationship of W1>W2>W3 is satisfied.

Description

  The present invention relates to a tire used for heavy-duty vehicles such as trucks and buses, which can realize both reduction of rolling resistance and maintenance of wet performance.

  In general, a heavy-duty pneumatic tire used in a heavy-duty vehicle such as a truck or a bus has, for example, a plurality of circumferential mains extending along a tire circumferential direction D1 on a tread surface as shown in FIG. A tire having a so-called rib pattern in which grooves 50 to 54 are provided to define a plurality of rib-like land portions, and a plurality of circumferential main grooves and tires extending along the tire circumferential direction on a tread portion tread surface There is a tire having a so-called block pattern in which a plurality of block land portions are defined by disposing a width direction main groove extending along the width direction.

  A tire having a rib pattern has a short total length when the opening ends of grooves and sipes to be arranged are short, so there are few edge components present in the tire contact surface, and improvement in wet performance due to the edge effect cannot be expected, It is possible to ensure wet performance by increasing the width of the circumferential main groove. In addition, regarding the reduction of rolling resistance, the rib-like land portion is integrally connected in the tire circumferential direction, so the land portion rigidity is high with respect to the input in the circumferential direction acting during driving and braking, and the deformation amount of the land portion is Although it can be suppressed, with respect to the input in the tire width direction that acts during turning, etc., the rib-shaped land portions are partitioned by the wide circumferential main grooves, so the amount of deformation of the land portions increases to some extent. There was a tendency, and when viewed comprehensively, there was a problem that the rolling resistance could not be reduced sufficiently.

  As a tire having a rib pattern that achieves both maintenance of wet performance and reduction of rolling resistance, for example, in Patent Document 1, the rib-shaped land portion extends 0.5 to 1.5 mm across the tire width direction. A plurality of widthwise narrow grooves having a groove width of about a degree are further provided to form a rib-like land portion as a block-like land portion, and further to the block-like land portion in the width direction with respect to the tire axial direction. A pneumatic tire having a tread pattern in which a closed sipe inclined in a direction opposite to the narrow groove is provided is described.

  The pneumatic tire described in Patent Document 1 has an edge that exists in the tire ground contact surface by disposing a widthwise narrow groove or a closed sipe in the rib-like land portion instead of widening the groove width of the circumferential main groove. Although the component is effectively increased and the wet performance is improved, since the rib-like land portion is partitioned into the block-like land portions by arranging the width direction narrow grooves, each block-like land portion Is substantially divided by the narrow grooves in the width direction, the rigidity to the input in the tire width direction is lowered, and accordingly, the deformation amount of the block-shaped land portion in the tire width direction is increased. The effect of reducing rolling resistance is not sufficient. In order to suppress a decrease in the rigidity of the block-shaped land portion, it is conceivable to make the grooves that define the block-shaped land portion shallow, or to make each block-shaped land portion large. There is a problem that the distance that can be traveled is reduced when the dividing groove is shallow, and when each block-like land portion is formed large, the edge component in the ground contact surface is reduced, and there is a concern that the wet performance may be reduced. Will be.

  On the other hand, a tire having a block pattern is advantageous in terms of wet performance because each block land portion is partitioned by a circumferential main groove and a width direction main groove, so there are many edge components in the tire ground contact surface. However, the block land portions adjacent to each other across the circumferential main groove and the width direction main groove only show the rigidity of the individual block land portions without contacting each other at the time of tire contact, and the rigidity of the block land portion itself is Since it is small and the deformation amount is large, there is a problem that the rolling resistance increases.

JP 2000-177333 A

  Therefore, an object of the present invention is to provide a tire used for heavy-duty vehicles such as trucks and buses, which can realize both reduction of rolling resistance and maintenance of wet performance.

  The present invention has been made to solve the above-described problems, and the heavy-duty pneumatic tire of the present invention has a pair of circumferential main grooves extending along the tire circumferential direction on the tread portion tread surface, and the tire equator. In a heavy-duty pneumatic tire in which a tread portion tread is divided into a central area and both lateral areas, at least one circumferentially narrow line extending along the tire circumferential direction is provided in the central area. A circumferential narrow groove that is a groove and closes the opening of the circumferential narrow groove at the time of tire contact is formed to define at least two central rib-shaped land portions, and the circumferential main groove has a tire width direction. At least one shoulder circumferential groove extending along the tire circumferential direction is provided on the outer side, the groove width of the circumferential main groove is W1, the groove width of the shoulder circumferential groove is W2, and the circumferential direction When the groove width of the narrow groove is W3 And it is characterized in satisfying a relation W1> W2> W3.

  In the heavy duty pneumatic tire of the present invention, the central rib-shaped land portion is further provided with a plurality of widthwise narrow grooves extending transversely in the tire width direction in the central rib-shaped land portion. It is preferable that the section is formed as a central block-shaped land portion, and the openings in the circumferential narrow groove and the width narrow groove are both closed when the tire contacts the ground.

  In the heavy duty pneumatic tire of the present invention, the groove width of the circumferential narrow groove is preferably 0.5 mm or more and 3 mm or less.

  Furthermore, in the heavy duty pneumatic tire of the present invention, it is preferable that the groove width of the narrow groove in the width direction is 0.3 mm or more and 3.0 mm or less.

  Furthermore, in the heavy duty pneumatic tire of the present invention, the groove width of the circumferential main groove is preferably 5 mm or more and 30 mm or less.

  Moreover, in the heavy duty pneumatic tire of the present invention, the groove width of the shoulder circumferential groove is preferably 3 mm or more and 10 mm or less.

  According to the present invention, it is possible to provide a tire used for a heavy-duty vehicle such as a truck or a bus, which can realize both reduction of rolling resistance and maintenance of wet performance.

1 is a development view of a part of a tread portion of a heavy-duty pneumatic radial tire according to an embodiment of the present invention. FIG. 6 is a partial development view of a tread portion of a heavy-duty pneumatic radial tire according to another embodiment of the present invention. FIG. 6 is a development view of a part of a tread portion of a conventional heavy-duty pneumatic radial tire. FIG. 7 is a development view of a part of a tread portion of another conventional heavy-duty pneumatic radial tire.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawing, the direction indicated by arrow D1 is the tire circumferential direction, and the direction indicated by arrow D2 is the tire width direction.

  The heavy-duty pneumatic tire having the tread portion 1 shown in FIG. 1 has a pair of circumferential main grooves 3 and 4 extending along the tire circumferential direction D1 on the tread surface of the tread portion 1 with the tire equator E interposed therebetween. It is set. The pair of circumferential main grooves 3 and 4 are arranged at positions where the tread surface of the tread portion 1 is divided into a central region Z1 and both side regions Z2 and Z3.

  The “central area” here refers to the area of the tread portion tread having a width corresponding to 50% or less of the tread width TW centering on the tire equator E, and the “lateral area” The tread portion tread area is located on the outer side in the tire width direction of the central zone Z1 across the circumferential main grooves 3 and 4, and is divided by the circumferential main groove 3 or 4 and the tread end E1 or E2.

  The main feature of the present invention is that the land portion located in the central area Z1 of the tread portion tread and the land portions located in the side areas Z2, Z3 of the tread portion tread are appropriately partitioned by various grooves, respectively. More specifically, at least one circumferential narrow groove extending along the tire circumferential direction D1, in FIG. 1, one circumferential narrow groove 6 is disposed in the central region Z1, and at least Two or more central rib-shaped land portions, in FIG. 1, two central rib-shaped land portions 8 and 9 are partitioned and the circumferential narrow groove 6 is closed when the tire is in contact with the ground. 6, the opposite side walls of the central rib-shaped land portions 8 and 9 located adjacent to each other in the tire width direction are in contact with each other, and in addition, tires are provided in the side regions Z2 and Z3. At least one shoulder extending in the circumferential direction D1, here a shoulder Circumferential grooves 11 and 12 are arranged, respectively, and two lateral rib-like land portions 13, 14, 16, and 17 are defined, and the groove widths of the circumferential main grooves 3 and 4 are set to W1, respectively. When the groove width of the shoulder circumferential grooves 11 and 12 is W2, and the groove width of the circumferential narrow groove is W3, the relationship between the groove widths of the grooves is W1> W2> W3, thereby rolling resistance. Reduction and maintenance of wet performance can be realized in both.

  That is, the present invention provides a pair of relatively wide circumferential main grooves 3 and 4 that divide the tread portion tread into a central area Z1 and side areas Z2 and Z3 and shoulder circumferences located in the side areas Z2 and Z3. By disposing the directional grooves 11 and 12, drainage is ensured and at least one circumferential narrow groove 6 having a relatively narrow width extending along the tire circumferential direction D1 is disposed in the central zone Z1. Then, by forming at least two or more central rib-shaped land portions 8 and 9, the circumferential narrow grooves 6 are respectively sandwiched when the openings of the circumferential narrow grooves 6 are closed at the time of tire contact. The central rib-shaped land portions 8 and 9 located adjacent to each other are in contact with each other to support each other, so that the central rib-shaped land portions 8 and 9 positioned in the central zone Z1 Not only for input in direction D1, As a result of the fact that adjacent central rib-shaped land portions 8, 9 can be opposed to each other in the width direction D2, the central zone Z1 Since the deformation amount of the land portions 8 and 9 located in the region can be effectively suppressed, the rolling resistance can be remarkably suppressed. The term “when the tire is in contact with the ground” as used herein specifically refers to the time when the tire is mounted on a regular rim, set to a regular internal pressure, placed in a stationary state perpendicular to the flat plate, and loaded with a regular load. means. Here, the regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  The groove width W1 of the circumferential main grooves 3 and 4 is preferably 5 mm or more from the viewpoint of ensuring drainage. On the other hand, if the groove width W1 of the circumferential main grooves 3 and 4 is wider than 30 mm, the area ratio of the tread land portion located in the tire contact area becomes too low (negative ratio is too high), and the wear performance is reduced. It tends to occur. For this reason, the upper limit of the groove width W1 of the circumferential main grooves 3 and 4 is preferably 30 mm.

  In addition, as shown in FIG. 1, the extending shape of the circumferential main grooves 3 and 4 is made to be a zigzag shape or a corrugated shape, which increases the edge component in the width direction and improves driving / braking performance and drainage performance. However, the circumferential main grooves 3 and 4 do not have to have the same zigzag shape, and are shifted by a half pitch in the circumferential direction or have different amplitudes. It is also possible to arrange them at different wavelengths.

  Further, the groove width W3 of the circumferential narrow groove 6 is set to be 3 mm or less in order to prevent the rolling resistance from increasing by setting the width to such an extent that the opening is closed when the tire is in contact with the ground (when rolling the tire load). preferable. On the other hand, if the groove width of the circumferential narrow groove 6 is narrower than 0.5 mm, the drainage improvement effect is not recognized as compared with the rib-like land portion in which the circumferential narrow groove is not provided. The lower limit value of the groove width of 6 is preferably 0.5 mm.

  In addition, as shown in FIG. 1, the extending shape of the circumferential narrow groove 6 may be a zigzag shape or a corrugated shape to increase the edge component in the width direction and improve driving / braking performance and drainage performance. Although it is preferable in terms of being able to be performed, it may be linear, the zigzag shape of each circumferential narrow groove 6 does not need to be the same, and is shifted by a half pitch in the circumferential direction or arranged with a different amplitude or wavelength. You can also.

  When the extending shape of the circumferential narrow groove 6 is a zigzag shape, it is constituted by two narrow groove portions 6a and 6b extending alternately in different directions at an angle θ1 within a range of ± 50 ° with respect to the tire circumferential direction. It is preferable. This is because when the angle θ1 exceeds ± 50 °, the corners of the land portions are angular, the rigidity of the corner portions of the land portions is reduced, and problems such as rubber chipping may occur.

  Further, since the shoulder circumferential grooves 11 and 12 have the largest deformation (opening and closing) at the time of running, if the groove width is too narrow, distortion is concentrated and groove cracks are likely to occur, and conversely if the groove width W2 is too wide. Since the rigidity and volume of the adjacent land portions 13, 14, 16, 17 cannot be secured, the rolling resistance increases or the travelable distance decreases, the groove width W2 of the shoulder circumferential grooves 11, 12 is 3 mm. It is preferable to set it to 10 mm or less.

  In addition, as shown in FIG. 1, the extending shape of the shoulder circumferential grooves 11 and 12 is a zigzag shape or a corrugated shape, which increases the edge component in the width direction and improves driving / braking performance and drainage performance. However, the shoulder circumferential grooves 11 and 12 do not need to have the same zigzag shape, and are shifted by a half pitch in the circumferential direction or arranged with different amplitudes or wavelengths. You can also.

  In addition, the width of the side rib-shaped land portions 13, 14, 16, 17 divided by the shoulder circumferential grooves 11, 12 in the side regions Z2, Z3 is 10% or more and 20% or less with respect to the tread width TW. It is preferable to do. When the width of the side rib-shaped land portions 13, 14, 16, 17 is less than 10% of the tread width TW, the rigidity of the side rib-shaped land portions 13, 14, 16, 17 is insufficient and the rolling resistance is reduced. This is because the reduction cannot be sufficiently achieved, and if it exceeds 20%, it becomes difficult to make the groove width W2 of the shoulder circumferential grooves 11 and 12 into a sufficient groove width and the drainage performance is lowered. .

  Further, in the present invention, as shown in FIG. 2, a plurality of width direction narrow grooves 19 extending across the tire width direction D2 are further disposed in the central rib-shaped land portions 8 and 9, as shown in FIG. The center rib-shaped land portions 8 and 9 shown in the figure are partitioned and formed as center block-shaped land portions 21 and 22, and the openings of the circumferential narrow grooves 6 and the width-direction narrow grooves 19 are closed at the time of ground contact. The rigidity of the land portion located in the central zone Z1 is such that the central block-shaped land portions 21 and 22 located adjacent to each other with the narrow groove 6 and the width-direction narrow groove 19 in contact with each other are supported. This is preferable in that the drainage performance is further improved by effectively increasing the edge component while suppressing the deformation of the central block land portions 21 and 22. In FIG. 2, for convenience of explanation, each one central block land portion 21, 22 is shown as a hatched portion.

  The groove width of the width direction narrow groove 19 is set to a width that closes the opening when the tire is in contact with the tire (when the tire is loaded and rolled) so that the rolling resistance does not increase. Preferably, it is 1.5 mm or less. The extending direction of the width direction narrow groove 19 is 55 on the obtuse angle side with respect to the tire circumferential direction in order to ensure the rigidity of the corner portions of the land portions 21 and 22 defined by the width direction narrow groove 19 and to avoid rubber chipping. A range of ˜90 ° is preferable.

  Further, in the present invention, in order to further increase the edge component, as shown in FIG. 2, a width direction auxiliary narrow groove 23 extending in a crank shape in the tire width direction is disposed in each central block-shaped land portion 21, 22. Then, while dividing into two small block land portions 21a, 21b, 22a, 22b, each small block land portion 21a, 21b, 22a, 22b extends in the tire width direction and terminates in the land portion. Although the case where the width direction sub-thin groove 25 is provided is shown, such a configuration can be appropriately provided as necessary.

  Further, in the present invention, as shown in FIG. 2, a plurality of lateral width direction grooves 27 extending transversely in the tire width direction D2 are formed in the side rib-shaped land portions 13 and 17 located on the outermost side in the tire width direction. , 28 may be provided to partition the plurality of side block land portions 30, 31, thereby improving the drainage performance toward the tire side. In addition, it is preferable that the groove width of the lateral width direction groove | channels 27 and 28 exists in the range of 4-12 mm. If the groove width of the lateral width direction grooves 27 and 28 is less than 4 mm, the effect of improving the drainage to the side of the tire is not sufficient, and if the groove width is wider than 12 mm, the ground contact area is reduced, thereby stabilizing the steering. In addition to the deterioration of the property, the side block land portions 30 and 31 become smaller and the side block land portions 30 and 31 tend to be deformed and the rolling resistance tends to increase as the land portion rigidity decreases. Because.

  In addition, in the present invention, the side block land portion 30 and the side block land portion 30 positioned adjacent to the side width direction grooves 27 and 28 with the side width direction grooves 27 and 28 interposed therebetween, and It is preferable to dispose raised shallow bottom portions 33 and 34 that connect the side block land portion 31 and the side block land portion 31 respectively. With this configuration, the side block land portion 30 does not deteriorate the drainage performance. , 31 can be effectively suppressed.

  The raised shallow bottom portions 33 and 34 have an extension length L of 0.3 to 0.8 times the width of the side block land portions 30 and 31, and the lateral width direction grooves 27 of the raised shallow bottom portions 33 and 34. , 28 from the groove bottom position is preferably in the range of 0.5 to 0.8 times the groove depth of the lateral width direction groove. If the extending length L of the raised shallow bottom portions 33 and 34 is less than 0.3 times the width of the side block land portions 30 and 31, the land block rigidity of the side block land portions 30 and 31 is insufficient, and uneven wear occurs. In addition, when the extending length L of the raised shallow bottom portions 33 and 34 exceeds 0.8 times the width of the side block land portions 30 and 31, the edge component at the end of use of the tire is This is because there is a risk that the drainage performance to the side of the tire will be remarkably reduced. This is because if the height of the raised shallow bottom portions 33, 34 is less than 0.5 times the groove depth of the lateral width direction grooves 27, 28, the block rigidity is reduced, and uneven wear tends to occur. When the height of the raised shallow bottom portions 33, 34 exceeds 0.8 times the groove depth of the lateral width direction grooves 27, 28, the lateral width direction grooves 27, 28 are disposed to the side of the tire. This is because the effect of improving the drainage performance tends to be insufficient.

  As another embodiment, although not shown in the figure, a tire in which two circumferential narrow grooves are arranged in the central region of the tread portion tread to partition three rib-like land portions or block-like land portion rows, Alternatively, the tire may be one in which three zigzag circumferential narrow grooves are provided in the central region of the tread surface, and four rib-like land portions or block-like land portion rows are partitioned. In the above embodiment, it has been described that one shoulder circumferential groove is provided in each of the side regions Z2 and Z3. However, two or more shoulder circumferential grooves are provided in each of the side regions Z2 and Z3. In addition, the land portion defined by the shoulder circumferential groove may be further divided into blocks by a plurality of sipes as in the central block land portion. Can be mentioned.

  Next, a heavy-duty pneumatic tire according to the present invention was prototyped and its performance was evaluated, which will be described below.

  The tires of Examples 1 to 6 have a tire size of 315 / 70R22.5, and the configuration of the tread portion was produced as shown in Table 1. In the present invention, the tread pattern has structural features, and the other tire structures are the same as the conventional heavy-duty pneumatic tire. For comparison, the tire size is 315 / 70R22.5 and the tire of Conventional Example 1 having a tread pattern as shown in FIG. 4, the groove width of the circumferential main groove, the groove width of the shoulder circumferential groove, and the circumferentially narrow width. A tire of Comparative Example 1 in which the relationship between the groove width and the groove width is out of the scope of the present invention was also manufactured.

(Test method)
About each said test tire, the tire was mounted | worn on the applicable rim | limb (rim size: 9.00), and rolling resistance, wet performance, and a groove crack were evaluated.
The rolling resistance is measured by measuring the rolling resistance force of the axle using a drum tester (speed: 80 km / h) having a steel plate surface with a diameter of 1.7 m under conditions of tire internal pressure: 900 kPa and load load: 3350 kgf. evaluated. This rolling resistance measurement was performed in accordance with ISO18164 using a smooth drum and a force type.
Wet performance is evaluated by the feeling of a professional driver when turning a test course with a wet road surface with a depth of 2 mm at a speed of 30 km / h and a radius of 20 m under the conditions of tire internal pressure: 900 kPa and load load: 3350 kgf. did.
Groove cracks were analyzed for the distortion of the groove in the shoulder circumferential groove using the finite element method, and the ease of occurrence was examined from the analysis results.
Table 2 shows the evaluation results. The values of rolling resistance, wet performance, and groove crack in Table 2 are all shown as index ratios when the conventional tire is set to 100, and the larger the rolling resistance and wet performance values, the better the performance. As for the groove crack, the larger the numerical value, the greater the distortion at the groove bottom and the higher the probability of occurrence of the groove crack.

  From the results shown in Table 2, according to the tires of Examples 1 to 6, it is possible to achieve both rolling resistance and wet performance.

  Thus, according to the present invention, it is possible to provide a tire used for heavy-duty vehicles such as trucks and buses, which can realize both reduction of rolling resistance and maintenance of wet performance.

DESCRIPTION OF SYMBOLS 1 Tread part 3,4 Circumferential main groove 6 Circumferential narrow groove 8,9 Central rib-shaped land part 11,12 Shoulder circumferential groove 13,14,16,17 Lateral rib-shaped land part 19 Width-direction narrow groove 21, 22 Central block land portion 23 Width direction auxiliary narrow groove 25 Width direction auxiliary narrow groove 27, 28 Side width direction groove 30, 31 Side block land portion 33, 34 Raised shallow groove portion E Tire equator W1 Groove of circumferential main groove Width W2 Shoulder circumferential groove width W3 Circumferential groove width Z1 Central area Z2, Z3 Side area

Claims (6)

A pair of circumferential main grooves extending along the tire circumferential direction are arranged on the tread portion tread with the tire equator interposed therebetween, and the tread portion tread is divided into a central region and both side regions. In entering tires,
In the central region, at least one circumferential narrow groove extending along the tire circumferential direction, the circumferential narrow groove closing the opening of the circumferential narrow groove when contacting the tire is disposed, and at least two or more central ribs A section of land,
At least one shoulder circumferential groove extending along the tire circumferential direction on the outer side in the tire width direction of the circumferential main groove,
When the groove width of the circumferential main groove is W1, the groove width of the shoulder circumferential groove is W2, and the groove width of the circumferential narrow groove is W3, the relationship of W1>W2> W3 is satisfied. A heavy duty pneumatic tire.   The central rib-shaped land portion is further provided with a plurality of widthwise narrow grooves extending transversely in the tire width direction, and the central rib-shaped land portion is defined as a central block-shaped land portion. The heavy duty pneumatic tire according to claim 1, wherein both the circumferential narrow grooves and the width narrow grooves are closed.   The heavy duty pneumatic tire according to claim 1 or 2, wherein a groove width of the circumferential narrow groove is 0.5 mm or more and 3 mm or less.   The pneumatic tire for heavy loads according to any one of claims 1 to 3, wherein a groove width of the narrow groove in the width direction is 0.3 mm or more and 3.0 mm or less.   The heavy duty pneumatic tire according to any one of claims 1 to 4, wherein a groove width of the circumferential main groove is 5 mm or more and 30 mm or less. The heavy tire for heavy loads according to any one of claims 1 to 5, wherein a groove width of the shoulder circumferential groove is 3 mm or more and 10 mm or less.

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