JP2005186703A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for off-road use improving riding comfort also at the time of traveling on-road. <P>SOLUTION: In this pneumatic tire, lug patterns cut in a tire width direction are provided from a tread center over a shoulder part in a tread. A main lug groove maximum width for forming the lug patterns is more than ä(tire outer peripheral length in tire equatorial plane/number of main lug grooves in relation to a tire peripheral direction)×2/5}. The width of a center region of the tread is within the width of the tread×55% with the tread center as a center. In the center region, at least a land part row continuously or intermittently arranged in the tire peripheral direction is provided. When a tread outer surface diameter except the land part row in the tire equatorial plane is taken as ϕ1 and a tread outer surface diameter including the land part row is taken as ϕ2, ϕ2>ϕ1 is established. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an off-road pneumatic tire, and more particularly to an off-road pneumatic tire that may travel in a muddy area.

  Conventionally, tread patterns for off-road pneumatic tires, especially those that may run in muddy areas, are rug patterns with a wide main groove width to improve traction and self-cleaning characteristics in muddy areas. Is the mainstream.

In addition to the lug pattern, there are also rib and lug patterns for adding a rib pattern formed in the tire circumferential direction for the purpose of improving riding comfort. The rib and lug pattern is designed to exhibit maneuverability and stability with the rib at the center and drive with the lug in the shoulder, and can be used for both on-road and off-road.
JP 63-215405 A Japanese Patent Laid-Open No. 3-86602 JP-A-4-2311201 JP-A-7-205614

  However, the off-road tire having a lag pattern with a wide main groove width has a problem that vibration occurs when traveling on-road. Also, in the rib / lag pattern, vibration occurred when the load applied to the tire increased during on-road traveling. Such vibration was generated by hitting the lug pattern portion against the ground contact surface.

  Therefore, in view of the above problems, the present invention arranges the land portion row continuously or intermittently in the tire circumferential direction, and concentrates the ground pressure at the time of installation on the land portion row, thereby traveling on road. Another object of the present invention is to provide a pneumatic tire for off-road with improved ride comfort.

  In order to solve the above-described problem, a first feature of the present invention is a pneumatic tire having a lug pattern carved in a tire width direction from the tread center to a shoulder portion on the tread, and the lug pattern is formed. The maximum width of the main lug groove is {(the tire outer circumference length at the tire equatorial plane / the number of the main lug grooves with respect to the tire circumferential direction) × 2/5} or more, and the width of the center region of the tread is centered on the tread center. The tread has a width of 55% or less, and has at least one land portion row arranged continuously or intermittently in the tire circumferential direction in the center region, and the tread outer surface diameter excluding the land portion row in the tire equator plane. Is a pneumatic tire in which φ2> φ1 where φ1 is φ1 and tread outer surface diameter including the land portion row is φ2. Here, the “equator plane” refers to a plane that is perpendicular to the tire rotation axis and passes through the center of the tire tread.

  The maximum width of the main lug groove is {(the tire outer circumference length at the tire equator / the number of the main lug grooves with respect to the tire circumferential direction) × 2/5} or more, and the width of the center region of the tread is centered on the tread center. In a pneumatic tire suitable for traveling in a muddy area that is less than 55% of the tread width, by placing the land part row in the center region, the ground pressure is concentrated on the land part row, The contact pressure can be lowered to reduce vibration caused by hitting the lug pattern. For this reason, the off-road pneumatic tire according to the first feature of the present invention can improve the ride comfort even when traveling on road.

  In the pneumatic tire according to the first feature of the present invention, it is desirable that φ1 and φ2 satisfy a relationship of 0.1 <{(φ2-φ1) / φ1} × 100 <0.7. According to the land portion row having such a step amount, the ground pressure is moderately concentrated on the land portion row, and vibration can be reduced.

  The second feature of the present invention is a pneumatic tire having a lug pattern carved in the tire width direction from the tread center to the shoulder portion on the tread, wherein the main lug groove maximum width forming the lug pattern is , {(Tire outer circumference length on tire equatorial plane / number of main lug grooves in tire circumferential direction) × 2/5} or more, and the width of the center area of the tread is centered on the tread center × 55% of the tread. And at least one land portion row arranged continuously or intermittently in the tire circumferential direction in the center region, and at the time of 50-60% load rolling of the maximum load capacity, the land portion row and the land portion row The gist of the invention is that the tire is a pneumatic tire that contacts the surface of the lug pattern disposed on the shoulder side in the tire width direction at the same time. Here, the “maximum load capacity” refers to the maximum load of a single wheel in the applicable size described in the TRA (The Tire and Rim Assosiation, INC.) Standard.

  By increasing the contact pressure in the center region in this way, the contact pressure in the shoulder portion is reduced, and vibration caused by hitting the lug pattern portion can be reduced. For this reason, the off-road pneumatic tire according to the second feature of the present invention can improve the ride comfort even when traveling on road.

  According to the present invention, it is possible to provide an off-road pneumatic tire that has improved riding comfort even when traveling on road.

  Next, first to third embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(First embodiment)
As shown in FIG. 1A, the pneumatic tire 10a according to the first embodiment includes a lug pattern 25a carved in the tire width direction (arrow B direction) on the tread 12a from the tread center to the shoulder portion. Have. The maximum width RW of the main lug groove 26a forming the lug pattern 25a is equal to or greater than {(tire outer circumference length on the tire equatorial plane / number of main lug grooves in the tire circumferential direction) × 2/5}. Here, “the tire outer circumference length on the equator plane” is the outer circumference of the outer surface of the tread that does not include a land portion row to be described later. A lag pattern having a maximum width RW of less than this is not suitable for tires that have poor self-cleaning performance in muddy areas and may travel in muddy areas. Further, the width CW of the center area of the tread is within the width TW × 55% of the tread centering on the center of the tread. A lag pattern of more than this is not suitable for tires that have reduced traction in a muddy area and may travel in a muddy area.

  The pneumatic tire 10a according to the first embodiment includes at least one land portion row disposed continuously or intermittently in the tire circumferential direction (arrow A direction) in the center region 30a. As shown in FIG. 1B, the land portion row 20a has a tread outer surface diameter excluding the land portion row 20a on the tire equator plane, φ1, and a tread outer surface diameter including the land portion row 20a is φ2. > Φ1, more specifically, 0.1 <{(φ2−φ1) / φ1} × 100 <0.7.

(Second Embodiment)
As shown in FIG. 2A, the pneumatic tire 10b according to the second embodiment includes a lug pattern 25b carved in the tire width direction (arrow B direction) from the tread center to the shoulder portion, and the tire circumferential direction. And a rib pattern 27b installed continuously in the direction of arrow A. The rib pattern 27b may have a zigzag outline shown in FIG. 2A, or may have a linear outline shown in FIG.

  The maximum width RW of the main lug groove 26b forming the lug pattern 25b is equal to or greater than {(tire outer circumference length on the tire equatorial plane / number of main lug grooves in the tire circumferential direction) × 2/5}. The width CW of the center region 30b of the tread is within the tread width TW × 55% with the tread center as the center.

  The pneumatic tire 10b according to the second embodiment includes at least one land portion row arranged continuously or intermittently in the tire circumferential direction (arrow A direction) on the rib pattern 27b in the center region 30b. . As shown in FIG. 2 (b), the land portion row 20b has a tread outer surface (rib pattern 27b surface) diameter excluding the land portion row 20b on the tire equator surface, and a tread outer surface including the land portion row 20a ( Rib pattern 27b surface) When the diameter is φ2, φ2> φ1, more specifically, 0.1 <{(φ2−φ1) / φ1} × 100 <0.7.

(Third embodiment)
As shown in FIG. 3, the pneumatic tire 10c according to the third embodiment includes a lug pattern 25c carved in the tire width direction (arrow B direction) from the tread center to the shoulder portion, and the tire circumferential direction (arrow A). And a rib pattern 27c arranged continuously in the direction). On the rib pattern 27c, a narrow groove 28c is formed in the tire width direction so as to close at the time of ground contact. The rib pattern 27c may have the linear outline shown in FIG. 3 or the zigzag outline shown in FIG.

  The maximum width RW of the main lug groove 26c forming the lug pattern 25c is equal to or greater than {(tire outer circumference length on the tire equatorial plane / number of main lug grooves in the tire circumferential direction) × 2/5}. Further, the width CW of the center region 30c of the tread is within the tread width TW × 55% with the tread center as the center.

  The pneumatic tire 10c according to the third embodiment includes at least one land portion row arranged continuously or intermittently in the tire circumferential direction (arrow A direction) on the rib pattern 27c in the center region 30c. . A cross-sectional view of the land portion row is the same as FIG. If the diameter of the tread outer surface (the surface of the rib pattern 27c) excluding the land portion row on the tire equator plane is φ1, and the outer surface of the tread (the surface of the rib pattern 27c) including the land portion row is φ2, φ2> φ1. Is designed to be in the range of 0.1 <{(φ2-φ1) / φ1} × 100 <0.7.

(Operation and effect of the pneumatic tire according to the present embodiment)
The pneumatic tire according to the first to third embodiments includes a lug pattern 25 engraved in the tire width direction from the tread center to the shoulder portion on the tread, and the main lug groove 26 forming the lug pattern 25 is the largest. The width RW is equal to or greater than {(the tire outer circumferential length at the tire equator plane / the number of main lug grooves in the tire circumferential direction) × 2/5}, and the width CW of the center region of the tread is centered on the tread center. Since it is within TW x 55%, it is suitable for traveling in a muddy area. Further, by arranging the land portion row 20 in the center region 30, the ground pressure is concentrated on the land portion row 20, the contact pressure of the lug portions on both sides can be lowered, and the vibration caused by hitting the lug pattern portion can be reduced. For this reason, the off-road pneumatic tire according to the first to third embodiments can improve the ride comfort even when traveling on road.

  Moreover, when the land part row | line | column 20 of the above designs is provided, the lug arrange | positioned to the shoulder side of the tire width direction of the land part row | line | column 20 and the land part row | line | column 20 at the time of 50-60% load rolling of the maximum load capacity. The pattern surface is grounded at the same time. For this reason, by increasing the ground contact pressure in the center region, the ground contact pressure in the shoulder portion is reduced, and vibration caused by hitting the lug pattern portion can be reduced.

  Examples of the pneumatic tire according to the embodiment of the present invention will be described in detail below. In order to confirm the effect of the present invention, five types of tires of Examples 1 to 7 to which the present invention was applied and one type of tire of a comparative example were actually mounted, and vibration performance was evaluated by a feeling test. The tire sizes of Examples 1 to 5 and the comparative example are 23.5R25.

  The tread patterns of Examples 1 to 5 were set in the shape shown in FIG. 1 described in the first embodiment. The tread pattern of Example 6 was set to the shape shown in FIG. 2 described in the second embodiment. The tread pattern of Example 7 was set to the shape shown in FIG. 3 described in the third embodiment. The tread outer surface diameter φ1 excluding the land row was 1600 mm. The tread outer surface diameter φ2 including the land portion row was 1602 mm, 1604 mm, 1606 mm, 1608 mm, and 1610 mm in Examples 1 to 5, and 1604 mm in Examples 6 and 7.

  On the other hand, the tread pattern of the tire of the comparative example has a shape having a block 140 in the center region 130 in addition to the lug pattern 126 as shown in FIG. Since the tire of the comparative example did not have a land portion row, both φ1 and φ2 were 1600 mm.

  In the test, the tire described above was assembled to a 19.50 / 2.5 × 25 rim at an internal pressure of 525 kPa, mounted on a construction vehicle (ADT), and a feeling evaluation was performed by a test driver. The tire rim and internal pressure are based on the applicable rim and air pressure-load capacity correspondence table defined in the TRA (The Tire and Rim Assosiation, INC.) Standard.

(result)
The results of the above test are shown in Table 1. The result is expressed by a feeling score of a maximum of 10 points, with 10 points indicating the least vibration and good ride comfort.

  When Examples 1-7 are compared with Comparative Examples, it can be seen that Examples 1-7 have higher feeling evaluation. For this reason, if the center region is provided with a land portion row, the tread outer surface diameter excluding the land portion row on the tire equator plane is φ1, and the tread outer surface diameter including the land portion row 20a is φ2, then φ2> φ1 It can be seen that the tire according to the embodiment has less vibration and good ride comfort. Furthermore, when φ1 and φ2 are in the range of 0.1 <{(φ2-φ1) / φ1} × 100 <0.7, it can be seen that there is less vibration and the ride comfort is good.

  Moreover, in Example 2-Example 4, it turns out that feeling evaluation is especially high. Therefore, it can be seen that the tire according to the present embodiment in the range of 0.2 <{(φ2−φ1) / φ1} × 100 <0.5 has particularly low vibration and good ride comfort.

  As described above, it can be seen that the tire according to the present embodiment includes the land portion row and improves the vibration performance by adjusting the height thereof.

(A) is a top view of the tread of the pneumatic tire which concerns on embodiment of this invention, (b) is AA sectional drawing of (a). (A) is a top view of the tread of the pneumatic tire which concerns on embodiment of this invention, (b) is BB sectional drawing of (a). It is a top view of the tread of the pneumatic tire concerning the embodiment of the present invention. It is a top view of the tread of the conventional pneumatic tire.

Explanation of symbols

10a, 10b, 10c ... pneumatic tires 12a, 12b, 12c ... treads 20a, 20b, 20c ... land row 25a, 25b, 25c ... lugs 26a, 26b, 26c ... lug grooves 27b, 27c ... ribs 28c ... narrow grooves 30a 30b, 30c ... center area 140 ... block

Claims (3)

A pneumatic tire having a lug pattern carved in the tire width direction from the tread center to the shoulder portion on the tread,
The maximum width of the main lug groove forming the lug pattern is {(the tire outer circumference length at the tire equatorial plane / the number of the main lug grooves in the tire circumferential direction) × 2/5} or more,
The width of the center region of the tread is within the width of the tread × 55% around the center of the tread,
In the center region, comprising at least one land portion row arranged continuously or intermittently in the tire circumferential direction,
A pneumatic tire characterized in that φ2> φ1 when the tread outer surface diameter excluding the land portion row on the tire equator plane is φ1 and the tread outer surface diameter including the land portion row is φ2.   The pneumatic tire according to claim 1, wherein the φ1 and the φ2 satisfy a relationship of 0.1 <{(φ2−φ1) / φ1} × 100 <0.7. A pneumatic tire having a lug pattern carved in the tire width direction from the tread center to the shoulder portion on the tread,
The maximum width of the main lug groove forming the lug pattern is {(the tire outer circumference length at the tire equatorial plane / the number of the main lug grooves in the tire circumferential direction) × 2/5} or more,
The width of the center region of the tread is within the width of the tread × 55% around the center of the tread,
In the center region, comprising at least one land portion row arranged continuously or intermittently in the tire circumferential direction,
A pneumatic tire characterized in that the land portion row and the lug pattern surface arranged on the shoulder side in the tire width direction of the land portion row are simultaneously grounded at the time of 50 to 60% load rolling of the maximum load capacity.

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