JP4957786B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that is particularly suitable as a tire for a light truck in which uneven wear resistance is improved without reducing snow handling stability.

  In general, in the tread pattern provided in the pneumatic tire, the lug groove inclined with respect to the tire circumferential direction has an extension component in the tire circumferential direction and an extension component in the tire width direction. Both a longitudinal braking / driving effect and a lateral slip prevention effect can be achieved. Therefore, many block patterns having such inclined lug grooves are used for winter tires that require excellent performance on snow (see, for example, Patent Document 1).

  On the other hand, since tires have different wear characteristics depending on the front and rear wheels of the vehicle and their mounting positions, rotation of the mounting positions is regularly performed so that the wear of all tires is made uniform and lasts longer. Yes. However, in a tire having a directional pattern in which the rotation direction of the tire is specified, the rotation direction of the tire is fixed, and therefore rotation is limited only to the replacement of the tire between the front and rear wheels mounted on the same side on both sides of the vehicle. End up. Therefore, in tires with a heavy load on the shoulder when turning, such as light truck tires, if the directional block pattern as described above is used, rotation can only be performed between front and rear wheel tires on the same side. Depending on the rotation of the tire, uneven wear of the shoulder portion cannot be suppressed.

  As a measure for suppressing such uneven wear of the shoulder portion, it is conceivable to place a rib having no heel and toe wear in place of the block in the shoulder portion. However, when ribs are arranged on the shoulder portion, there is a problem in that the performance on snow is deteriorated because the traction on snow due to the lug grooves is lowered.

JP 2002-274126 A

  An object of the present invention is to solve the above-described problems, and to provide a pneumatic tire in which uneven wear resistance is improved without reducing snow handling in a tire having a directional pattern. It is in.

  In order to achieve the above object, the pneumatic tire of the present invention is provided with a plurality of main grooves extending in the tire circumferential direction on the tread surface, and obliquely between adjacent main grooves inside the outermost main groove. Air in which lag grooves communicating with each other are intermittently arranged in the tire circumferential direction to form a block row composed of a plurality of blocks, and a plurality of sipes in the tire width direction are provided on these blocks to form a directional pattern. In the tire, an end lug groove extending from the shoulder edge toward the outermost main groove so as not to be connected to the main groove is intermittently provided in the tire circumferential direction. The chamfering amount is periodically changed in the tire circumferential direction at the edge portion on the inner side in the tire width direction of the rib. Characterized in that intermittently or continuously forming a plurality of chamfer with Jo.

  Moreover, in the structure mentioned above, it is preferable to comprise as described in (1)-(6) below.

(1) The depth of the maximum chamfered portion of the chamfered portion is set to 30 to 60% of the maximum depth of the main groove. (2) The maximum chamfered portion of the chamfered portion is arranged so as to wrap on the extended line of the end lug groove.
(3) One chamfered portion is formed per 0.5 to 2 pitches of the end lug groove.
(4) A chamfered portion is formed in the block adjacent to the outermost main groove along the edge portion on the outermost main groove side, and the chamfered amount of the chamfered portion is set to the maximum chamfered portion of the chamfered portion on the rib side. The corresponding portion is changed to the minimum, and the portion corresponding to the minimum chamfered portion is changed to the maximum.
(5) A large number of fine grooves that are inclined with respect to the tire circumferential direction are arranged in parallel on the tread surface of the block.
(6) The number of the main grooves is three, and at the center portion inside the outermost main groove, a bottom raised portion is formed on the tire center side of the lug groove in the block row, and the groove of the lug groove The width is changed so that the portion of the bottom raised portion is narrower than the portion other than the raised portion.

  The pneumatic tire having the above-described configuration is particularly suitable as a light truck tire used under conditions of an air pressure of 350 kPa or more.

  According to the present invention, a plurality of main grooves extending in the tire circumferential direction are provided on the tread surface, and the lug grooves that communicate obliquely between the adjacent main grooves on the inner side of the outermost main groove are provided in the tire circumferential direction. An outermost main groove in a pneumatic tire in which a block row composed of a plurality of blocks is formed intermittently, and a directional pattern is formed by providing a number of sipes in the tire width direction to these blocks. Endless lug grooves that extend from the shoulder edge toward the outermost main groove so as not to be connected to the main groove are intermittently arranged in the tire circumferential direction, and many extend in the tire width direction. A plurality of chamfers having a shape in which the chamfering amount periodically changes in the tire circumferential direction are intermittently or alternately formed on the inner edge of the rib in the tire width direction. Because it is formed continuously, uneven wear resistance can be improved by making the rigidity of the shoulder portion continuous in the circumferential direction, and the rotation of the tire is limited only between the front and rear wheels on the same side of the vehicle Even if it exists, the uneven wear of a shoulder part can be suppressed. Further, the edge length of the rib is increased by continuously or intermittently forming a plurality of chamfered portions having a shape in which the chamfering amount periodically changes in the tire circumferential direction at the edge portions of the ribs. In addition to the performance on snow based on the above, it is possible to improve the edge effect of the ribs and improve the snow maneuverability.

FIG. 1 is a front view of a tread surface of a pneumatic tire according to an embodiment of the present invention. 2 is an enlarged front view and side view of a chamfered portion on the rib side of the pneumatic tire of FIG. FIG. 3 is an enlarged cross-sectional view showing a narrow groove formed on a tread surface of a block adjacent to the center main groove of the pneumatic tire of FIG. 4 is an enlarged plan view showing a block adjacent to a center main groove of the pneumatic tire of FIG. 5 is a view taken along the line XX of the block adjacent to the center main groove of the pneumatic tire of FIG.

  In the pneumatic tire of the present invention shown in FIG. 1, the tread T has one center main groove 1 located on the tire equator E and extending in the tire circumferential direction, and tires located on both sides of the center main groove 1. Two outer main grooves 2 extending in the circumferential direction are provided, and a plurality of lug grooves 3 are intermittently arranged in the tire circumferential direction so as to communicate obliquely between the main grooves 1 and 2. Further, the shoulder portion S outside the outer main groove 2 is provided with an endless lug groove 4 extending intermittently in the tire circumferential direction from the shoulder edge toward the outer main groove 2 so as not to be connected to the outer main groove 2. Has been placed. In this way, two rows of block rows composed of a plurality of blocks 5 are defined in the center portion C inside the outer main groove 2, and a plurality of end ends are formed in the shoulder portion S outside the outer main groove 2. Ribs 6 having lug grooves 4 are formed. On the surfaces of the blocks 5 and the ribs 6, a plurality of sipes 7 each having a zigzag shape in plan view and extending in the tire width direction are provided.

  The number of main grooves extending in the circumferential direction provided in the tread T is not limited to three, that is, the center main groove 1 and the outer main groove 2 as shown in FIG. Moreover, the shape of the sipe 7 is not particularly limited as long as it is formed so as to extend in the tire width direction.

  The lug grooves 3 provided in the center portion C are arranged such that the inclination angle θ (see FIG. 4) with respect to the tire circumferential direction is in the range of 40 ° to 60 °, and are inclined opposite to the tire equator E. is doing. Here, the inclination angle θ is an angle formed by the groove width center line of the lug groove 3 with respect to the tire circumferential direction. Further, the lug groove 3 is symmetrical with respect to the center main groove 1 and is shifted by a half cycle in the circumferential direction on both sides of the center main groove 1. In addition, the endless lug groove 4 provided in the shoulder portion S has an inclination angle of 35 ° to 90 ° with respect to the tire circumferential direction and is inclined in opposite directions with respect to the tire equator E. The tread pattern thus formed is a directional pattern in which the tire rotation direction is designated in the arrow R direction.

  The directional pattern having the lug grooves 3 and the end lug grooves 4 inclined with respect to the tire circumferential direction has an extension component in the tire circumferential direction and an extension component in the tire width direction, so that the vehicle when biting snow is used. Both the front / rear braking / driving effect and the lateral slip prevention effect can be achieved. However, in such a directional pattern, tire rotation can only be performed between the front and rear wheels on the same side of the vehicle, so when the shoulder portion is a block row, heel and toe wear is promoted and uneven wear can be suppressed. difficult. However, as shown in FIG. 1, by forming the rib 6 having the land portion continuous in the circumferential direction on the shoulder portion S, the rigidity of the shoulder portion S is made continuous, so that uneven wear of the shoulder portion can be suppressed.

  A plurality of chamfered portions 8 having a shape in which the chamfering amount periodically changes in the tire circumferential direction are formed intermittently or continuously at the edge portion on the inner side in the tire width direction of the rib 6. Here, the change in the chamfering amount means that the sizes in the width direction and the depth direction change along the circumferential direction of the rib 6. As shown in the front view of FIG. 2A and the side view of FIG. 2B, the maximum chamfered portion 8a having the largest chamfering amount is a portion that is chamfered most in the depth direction and the width direction. The minimum chamfered portion 8b is a portion where chamfering in the depth direction and the width direction is minimum or zero.

  The shape of the chamfered portion 8 is such that the amount of chamfering periodically changes in the tire circumferential direction, so that the edge length can be increased and an edge component acting in the braking / driving direction can be added, so excellent on-snow performance Can be maintained. If the chamfered portion 8 has a uniform shape with the chamfering amount not changing over the entire circumference, the edge length cannot be increased, so the performance on snow cannot be improved.

  The depth and / or width of the maximum chamfered portion 8a of the chamfered portion 8 may be 30 to 60% of the maximum depth D of the main grooves 1 and 2. By setting this range, the edge length can be sufficiently increased, and the traction on snow can be improved. Preferably, the maximum depth D of the main grooves 1 and 2 is 40 to 50%. If the depth and / or width of the maximum chamfered portion 8a is smaller than 30% of the main groove depth D, the force applied between the lug groove 4 and the outer main groove 2 cannot be released, so uneven wear resistance is improved. descend. On the other hand, if it is larger than 60% of the main groove depth D, the snow handling performance deteriorates because the block rigidity is too low.

  The maximum chamfered portion 8a of the chamfered portion 8 may be arranged so as to wrap on the extended line of the end lug groove 4. In the region on the extended line of the end lug groove 4, stress is more concentrated than in the other regions of the rib 6. Therefore, the maximum chamfered portion 8 a is disposed in this region to reduce the rigidity, thereby concentrating. The distributed stress can be easily dispersed and uneven wear can be suppressed. If the maximum chamfered portion 8a does not wrap on the extension line of the lug groove 4, stress concentrates on a region on the extension line of the lug groove 4 and induces uneven wear.

  One chamfered portion 8 may be formed per 0.5 to 2 pitches of the end lug grooves 4. Here, the pitch of the end lug grooves 4 is an interval in the tire circumferential direction between the adjacent end lug grooves 4. If the chamfered portions 8 are formed at a rate of one at intervals smaller than 0.5 pitch, the number of the chamfered portions 8 is excessively increased, so that the block rigidity is excessively lowered and the uneven wear resistance is lowered. On the other hand, if the chamfered portion 8 is formed at a rate of 1 at intervals larger than 2 pitches, a portion having high rigidity and a portion having low rigidity are formed on the edge portion of the rib 6, and the difference in rigidity between these becomes large. Wear cannot be suppressed.

  In addition to providing the chamfered portion 8 at the edge portion of the rib 6, the chamfered portion 9 is formed along the edge portion on the outer main groove 2 side in the block 5 facing the outer main groove 2. In addition, the amount of chamfering of the chamfered portion 9 is changed so that the portion corresponding to the maximum chamfered portion 8a of the chamfered portion 8 on the rib 6 side is minimized and the portion corresponding to the minimum chamfered portion 8b is maximized. Good.

  By forming the chamfered portion 9 in this way, the edge component with respect to the front-rear direction of the block 5 is increased, so that the performance on snow can be further improved. Also, uneven wear is further suppressed by minimizing the chamfering amount of the portion corresponding to the maximum chamfered portion 8a of the chamfered portion 8 on the rib 6 side and maximizing the chamfering amount of the portion corresponding to the minimum chamfered portion 8b. Can do. The chamfering amount of the chamfered portion 9 is the maximum in the portion corresponding to the maximum chamfered portion 8a of the chamfered portion 8, and the minimum in the portion corresponding to the minimum chamfered portion 8b, that is, the chamfered portion 8 and the chamfered portion 9 have the largest chamfered portion. When the same and the minimum chamfered portion match, the high rigidity portion and the low rigidity portion can be alternated along the outer main groove 2 between the matching maximum chamfer portion and the minimum chamfer portion. Uneven wear resistance is reduced.

  In this pneumatic tire, a large number of fine grooves 10 that are inclined with respect to the tire circumferential direction are arranged in parallel on each tread surface of the block 5. These fine grooves 10 are fine grooves shallower than the sipe 7. New tires have a thin rubber film formed on the block surface during vulcanization molding, which impedes running performance on icy and snowy road surfaces. However, by providing such a fine groove 10, the water film generated between the icy and snowy road surface and the tread surface is effectively removed by the fine groove 10, thereby improving the performance on ice and the performance on snow in the initial use. be able to. Further, when the fine grooves 10 are provided on the tread surface of the block 5, the presence of these fine grooves 10 promotes the peeling of the tread surface, so that the time until the original characteristics of the tread rubber are exhibited is shortened. It is done.

  As shown in FIG. 3, the fine groove 10 may have a groove width w of 0.1 to 0.8 mm and a groove depth d of 0.1 to 0.8 mm. If the groove width w is smaller than 0.1 mm, the fine groove 10 has insufficient water film removal effect and snow removal performance. Stability is reduced.

  The pitch p of the fine grooves 10 is preferably in the range of 2.5 to 5.0 mm. By setting the pitch p of the fine grooves 10 within this range, the fine groove 10 can be reliably prevented from being crushed when a high load is applied to the tire, and even on high load conditions, It is possible to improve the performance on snow. If the pitch p of the fine grooves 10 is smaller than 2.5 mm, the effect of improving the performance on ice and the performance on snow under a high load condition is lowered, and conversely if it is larger than 5.0 mm, the effect of removing the water film becomes insufficient.

  As shown in FIG. 4, the inclination angle α of the fine groove 10 with respect to the tire circumferential direction is preferably set in the range of 40 ° to 60 °. If the inclination angle α of the fine groove 10 is smaller than 40 °, the edge of the fine groove 10 hardly contributes to the braking performance, and conversely if larger than 60 °, the edge of the fine groove 10 hardly contributes to prevention of skidding.

  As shown in FIGS. 4 and 5, a bottom raised portion 3 a may be formed on the tire center side at the groove bottom of the lug groove 3. At this time, the groove width of the lug groove 3 may be changed so that the bottom raised portion 3a is narrower than the portion other than the bottom raised portion 3a. Thus, by forming the bottom raised portion 3a on the tire center side of the lug groove 3 and changing the groove width of the lug groove 3 in proportion to the groove depth, the block rigidity near the bottom raised portion 3a is increased. In addition, the handling stability on the dry road surface can be improved. Moreover, since the bottom raising and the narrowing of the lug groove 3 are combined, when the block rigidity is increased, the drainage performance can be favorably maintained by the cooperation of the center main groove 1 and the lug groove 3.

  The groove depth D3a of the lug groove 3 in the bottom raised portion 3a is preferably in the range of 40 to 60% of the groove depth D1 of the center main groove 1, and the groove depth of the lug groove 3 with respect to the groove depth D1 of the center main groove 1 When the ratio of the length D3a is less than 40%, the drainage performance and the snow drainage performance are deteriorated. Conversely, when the ratio exceeds 60%, the effect of improving the driving stability on the dry road surface becomes insufficient. Further, the groove width W3a of the portion of the raised portion 3a is preferably in the range of 30 to 50% of the groove width W3 of the portion other than the raised portion 3a, and the ratio of the minimum groove width W3a to the maximum groove width W3 of the lug groove 3 If the ratio is less than 30%, the drainage performance and snow drainage performance are degraded. Conversely, if the ratio exceeds 50%, the block rigidity does not change so much and the effect of improving the steering stability on the dry road surface becomes insufficient.

  13 types of pneumatics with the tire sizes common to 195 / 75R16C 107 / 105R, and Examples 1 to 11 in which the specifications are different as shown in Table 1 as shown in Table 1 with the conventional examples 1 and 2 as shown in FIG. Tires were manufactured (see Table 1).

  Conventional Example 1 is an example in which a block row is also provided in the shoulder portion and a chamfered portion is formed on the inner side in the tire width direction of the block. Conventional Example 2 is an example in which a rib having no chamfered portion is provided on the shoulder portion.

  Examples 1 to 11 are examples in which ribs having chamfered portions are provided on the shoulder portions of the tread pattern as shown in FIG.

  Examples 1 to 7 are examples in which the number of pitches per chamfered portion is 3 and the maximum chamfered portion is arranged in the middle of the lug groove. In Example 1, the depth of the maximum chamfered portion is 20% of the maximum main groove depth. In Example 2, the depth of the maximum chamfered portion is 30% of the maximum main groove depth. In Example 3, the depth of the maximum chamfered portion is 40% of the maximum main groove depth. In Example 4, the depth of the maximum chamfered portion is 50% of the maximum main groove depth. In Example 5, the depth of the maximum chamfered portion is 60% of the maximum main groove depth. In Example 6, the depth of the maximum chamfered portion is 70% of the maximum main groove depth. In Example 7, the depth of the maximum chamfered portion is 45% of the maximum main groove depth.

  In Examples 8 to 11, the depth of the maximum chamfered portion is 45% of the maximum main groove depth, and the maximum chamfered portion is disposed at the end of the extended lug groove. In Example 8, the number of pitches per chamfer is 3 pitches. In Example 9, the number of pitches per chamfered portion is one pitch. In Example 10, the number of pitches per chamfered portion is 0.5 pitch. In Example 11, the number of pitches per chamfer is set to 2 pitches.

  These 13 types of tires were assembled on a 16x51 / 2J rim, filled with air pressure of 280 kPa at the front and 450 kPa at the rear. Uneven wear resistance and snow handling performance were measured.

  Uneven wear resistance was indicated by an index in which the appearance of a tire after traveling 4000 km on a public road was visually evaluated with the above vehicle, and the evaluation value of a conventional tire was 100. The smaller the index value, the better the uneven wear resistance.

  For snow handling performance, the vehicle was run at 0-100 km / h on the above-mentioned vehicle, and the feeling evaluation was shown by a 100-point method. The larger the index value, the better the snow maneuverability.

  As described above, the pneumatic tire according to the present invention is suitable for improving uneven wear resistance in a tire having a directional pattern without reducing snow handling.

DESCRIPTION OF SYMBOLS 1 Center main groove 2 Outer main groove 3 Lug groove 3a Bottom raising part 4 Ended lug groove 5 Block 6 Rib 7 Sipe 8, 9 Chamfer part 8a Maximum chamfer part 8b Minimum chamfer part 10 Fine groove

Claims (8)

A plurality of main grooves extending in the tire circumferential direction are provided on the tread surface, and lug grooves that obliquely communicate with each other between the main grooves adjacent to each other inside the outermost main groove are intermittently arranged in the tire circumferential direction. In a pneumatic tire in which a block row composed of a plurality of blocks is formed, and a directional pattern is formed by providing a large number of sipes in the tire width direction in these blocks.
The shoulder portion outside the outermost main groove is intermittently arranged in the tire circumferential direction with end lug grooves extending so as not to be connected to the main groove from the shoulder edge toward the outermost main groove. A plurality of chamfers having a shape in which the chamfering amount is periodically changed in the tire circumferential direction, formed on a rib having a large number of sipes extending in the tire width direction. A pneumatic tire formed intermittently or continuously.   The pneumatic tire according to claim 1, wherein the depth of the maximum chamfered portion of the chamfered portion is 30 to 60% of the maximum depth of the main groove.   The pneumatic tire according to claim 1 or 2, wherein a maximum chamfered portion of the chamfered portion is disposed so as to wrap on an extension line of the end lug groove.   The pneumatic tire according to claim 1, 2, or 3, wherein one chamfered portion is formed per 0.5 to 2 pitches of the end lug groove.   A chamfered portion is formed in the block adjacent to the outermost main groove along the edge portion on the outermost main groove side, and the chamfered amount of the chamfered portion corresponds to the maximum chamfered portion of the chamfered portion on the rib side. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is changed so that the portion corresponding to the minimum chamfered portion is maximized.   The pneumatic tire according to any one of claims 1 to 5, wherein a plurality of fine grooves inclined in the tire circumferential direction are arranged in parallel on the tread surface of the block.   The number of the main grooves is three, and at the center portion inside the outermost main groove, a bottom raised portion is formed on the tire center side of the lug groove in the block row, and the groove width of the lug groove is The pneumatic tire according to any one of claims 1 to 6, wherein a portion of the bottom raised portion is changed so as to be narrower than a portion other than the bottom raised portion.   The pneumatic tire according to any one of claims 1 to 7, which is a light truck tire used under conditions of an air pressure of 350 kPa or more.

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