JP2007001350A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for improving projection resistance while restraining increase of the weight and cost of a tire. <P>SOLUTION: This pneumatic radial tire comprises a belt layer 14 arranged outside in a tire radial direction of a carcass between a pair of bead parts, a belt protection layer 15 arranged outside in a tire radial direction of the belt layer 14, and a tread part 16 installed outside in a tire radial direction of the belt protection layer 15. A plurality of main peripheral grooves 18 are formed on the tread part 16, and a land lane 22 is formed on a tire equatorial part 20. The belt protection layer 15 is constituted of a spiral layer 24 wound in a tire peripheral direction, and has the same widths on both sides of the tire equator. An overlap area 28 across a tire equator CL is formed on the belt protection layer 15 along the tire peripheral direction. The width BP of the overlap area 28 is 50% larger than the width BR of the land lane 22, and within 25% of a tire ground width. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire with improved protrusion resistance, and more particularly to a pneumatic radial tire that is optimal for use as a tire for passenger cars or a tire for high load loads.

  Pneumatic radial tires that are subject to high loads, especially tires that support REINFORCE and XL (EXTRA LOAD), require higher durability than standard tires and general size tires with an LI (road index) of 100 or less. In particular, high resistance to protrusions (protrusion destruction) is required. In order to achieve these, (1) adoption of a high-strength belt, (2) installation of a belt reinforcement layer (installation of multiple sheets in some cases) (3) application of a belt reinforcement layer material having high breaking strength, (4) Reinforcing means such as increasing the tread gauge from the tread surface to the belt reinforcing layer is taken.

  However, none of these strengthening means are suitable for tires that require low rolling resistance because they significantly increase the weight and cost of the tire, and environmental problems such as recent energy and resource savings. It goes against the flow of product development considering

  As a countermeasure, Patent Document 1 discloses a technique for improving the tire strength while increasing the strength of the second belt ply rather than the strength of the first belt ply and reducing the weight and cost. However, making the belt treat (belt ply) type different between the first belt and the second belt increases the types of materials to be prepared in the manufacturing process, increases the number of materials preparation switching work, and secures a material storage space. Is required. For this reason, a manufacturing cost will rise and even if the cost increase of a raw material can be suppressed, a total cost will rise. There is also a concern that manufacturing mistakes may be caused by an increase in the types of belts handled.

  Patent Documents 2 and 3 disclose a technique for disposing an auxiliary layer having excellent penetration resistance at the tire crown portion and combating the penetration of protrusions such as nails and stones. There is a concern about the adverse effect of increasing the weight and cost due to the addition of the auxiliary layer.

  By the way, in the test for measuring the breaking strength of a tire, a protrusion is pressed against the tire equator until the belt cord or carcass cord is broken, so that the tire is greatly deformed. For this reason, it is considered that a measure for improving the breaking strength of the tire constituent member to be broken and a measure for suppressing the deformation of the indented portion are effective.

  It has been mentioned above that the former measure has drawbacks. As a countermeasure against the latter, a tread pattern having a rib row or a block row at the tire equator portion may be used to form a circular rubber ring in the tread portion, thereby suppressing the bending deformation of the tread portion. However, this alone does not provide sufficient breaking strength, and it is also necessary to suppress tire deformation by a skeleton member.

As measures for suppressing tire deformation by the skeletal member, increasing the partial overlapping part of the belt reinforcement layer increases the shear rigidity between the members, increases the resistance when the tire deforms, and suppresses the deformation of the tire. It is effective to improve the fracture strength. However, if the overlapping part of the belt reinforcing layer is increased, the belt reinforcing material is disposed at a position close to the groove bottom, and the clearance between the groove carved in the tread portion of the tire is not sufficiently ensured. For this reason, the cord is easily exposed as soon as a slight cut occurs in the groove bottom. When the cord is exposed, there is a concern about a serious situation such as tire separation or rust due to water entering during rainy weather, so a new measure is required to avoid exposing the cord.
JP 2001-1717 A Japanese Patent Laid-Open No. 2003-1917112 JP-A-6-286417

  In view of the above facts, an object of the present invention is to provide a pneumatic radial tire with improved protrusion resistance while suppressing an increase in tire weight and cost.

  The invention according to claim 1 is a bead portion including a pair of bead cores, a carcass straddling between the bead portions, a belt layer disposed on the outer side in the tire radial direction of the carcass, and an outer side in the tire radial direction of the belt layer. And a tread portion provided on the outer side in the tire radial direction of the belt protective layer, wherein the tread portion has a plurality of circumferential main grooves, and at least a tire equator portion or A pneumatic radial tire in which a land row is formed by blocks or ribs in the vicinity thereof, wherein the belt protection layer is composed of a spiral layer wound in the tire circumferential direction and is the same on both sides of the tire equator. The belt protective layer is formed with an overlap region across the tire equator along the tire circumferential direction, and the width of the overlap region is In parts column of more than 50% of the width, and is characterized in that within 25% of the tire contact width.

  The cords constituting the spiral layer (spiral belt layer) are often nylon cords, aramid fibers, mixed cords of nylon cords and aramid fibers, and the like that are frequently used as belt reinforcing materials.

  When the width of the overlap region is less than 50% of the width of the land portion row, it is difficult to sufficiently support the land portion when the projection comes into contact with the land portion, and is wider than 25% of the tire ground contact width. And the weight becomes too heavy like the conventional tire which piled up the belt.

  The circumferential main grooves may extend in a zigzag shape in the tire circumferential direction, or may extend in a zigzag shape in the tire circumferential direction. The term “zigzag extending in the tire circumferential direction” means that the groove portions extending in the same direction as the tire circumferential direction and the groove portions extending obliquely with respect to the tire circumferential direction are alternately extended in the tire circumferential direction. It is said that the groove portions extending in the same direction are arranged in a staggered manner. The phrase “zigzag extending in the tire circumferential direction” means that the groove portions that are inclined with respect to the tire circumferential direction extend in the tire circumferential direction while turning back so that the inclination directions are alternate.

  According to the first aspect of the present invention, in order to improve the protrusion resistance (protrusion breaking property) in the belt protective layer (belt reinforcing layer), the land portion row is provided to suppress the tire deformation, thereby providing a tire tag. Rigidity is increased to make the tire difficult to deform. A rib row is particularly effective as the land portion row. By providing the overlap region in this way, the interlaminar shear rigidity between the tire radial treats (between the plies) increases, the resistance against tire deformation caused by external force increases, and a tire that is difficult to deform is obtained. Can do. Therefore, it is possible to provide a pneumatic radial tire with improved protrusion resistance (protrusion destruction property) in the tire equator and its vicinity without adding a new member, that is, while suppressing the weight and cost of the tire.

  This pneumatic radial tire is most suitable for use as a tire for passenger cars, and is also suitable for use as a tire for high load loads such as large-size tires, reinforced tires and XL-compliant tires.

  The invention described in claim 2 is characterized in that the belt protective layer covers the belt layer over its entire width.

  Thereby, it can be set as the pneumatic radial tire which improved the projection resistance in a tire equator part or its neighborhood over the belt layer full width.

  By the way, in order to set the overlap amount of the belt protection layer beyond the land row width of the tire equator and to eliminate the concern about the ease of exposure of the belt protection layer, the groove of the land row of the tire equator It is effective to preliminarily set the side wall portion of the land portion of the mold so that the portion close to the bottom is raised and the cross section is stepped.

  Accordingly, the invention according to claim 3 is characterized in that the land portion row has a stepped portion that expands stepwise toward the bottom of the circumferential main groove.

  As a result, the cord of the belt protective layer can be formed into a shape that can be easily embedded in the rubber layer, that is, the cord of the belt protective layer can be hardly exposed from the tire surface.

  Here, it is preferable from the viewpoint of maneuverability to provide a land row such as a rib row or a block row at the tire equator, but if the width of this land row is excessively widened, the hydrobraking property of the rainy road is impaired. It will be. In other words, the width of this land portion row is naturally limited, and it is about 15 mm at most, and even a tire having a wide section width can be said to be a practical limit of 20 mm. As described above, although there is a limit to the width of the land portion row, the overlap width of the belt protective layer is preferably more than 15 mm or 20 mm from the demand for improvement of the protrusion breakability. In particular, in a large tire having an LI exceeding 100, or a tire displaying XL or a reinforcement, it is difficult to sufficiently improve the protrusion breakage unless the overlap amount is at least 10 mm.

  Therefore, in the invention according to claim 4, the land portion row straddles the tire equator, the width of the overlap region is 10 mm or more, and the end in the tire width direction of the overlap region is the land portion row. It is located within 2 mm from the tire width direction end to the tire equator side.

  The invention according to claim 5 is characterized in that the depth position of the stepped portion is shallower within a range of 0.5 to 2 mm than the depth position of the deepest portion of the circumferential main groove.

  As a result, a gauge of about 1.5 mm can be secured between the belt protective layer and the tire surface, and the risk of cord exposure is further reduced. In addition, since the rubber gauge is not increased excessively and there is no need to add an additional rubber sheet, an increase in tire weight and cost can be further suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, it can be set as the pneumatic radial tire which improved protrusion resistance, suppressing the increase in the weight and cost of a tire.

  Hereinafter, embodiments will be described and embodiments of the present invention will be described. In the second and subsequent embodiments, the same components as those already described are denoted by the same reference numerals and description thereof is omitted.

[First Embodiment]
First, the first embodiment will be described. As shown in FIG. 1, the pneumatic radial tire 10 according to the present embodiment is a tire for buses and trucks to which a high load is applied.

  The pneumatic radial tire 10 includes a bead portion 13 including a pair of bead cores 11, a carcass 12 straddling the bead portions 13, and a belt layer including a plurality of layers (for example, two layers) disposed on the outer side in the tire radial direction of the carcass 12. 14, a belt protective layer 15 (see FIG. 2) disposed on the outer side of the belt layer 14 in the tire radial direction, and a tread portion 16 provided on the outer side of the belt protective layer 15 in the tire radial direction.

  In the bead portion 13, a bead filler (not shown) is disposed outside the bead core 11 in the tire radial direction. Further, a sidewall portion 17 is formed on the tire side of the carcass 12.

  As shown in FIG. 2, a plurality of circumferential main grooves 18 are formed in the tread portion 16, and a land portion row (rib row) 22 composed of ribs is provided on the tire equator portion 20. ) It is formed so as to straddle CL.

  The belt protective layer 15 covers the belt layer 14 over the entire width. Further, as shown in FIG. 3, the belt protective layer 15 is composed of a spiral layer 24 wound in the tire circumferential direction and has the same width on both sides of the tire equator CL.

  Further, an overlap region 28 straddling the tire equator CL is formed in the belt protective layer 15 along the tire circumferential direction. The width BP of the overlap region 28 is 50% or more of the width BR of the land portion row 22 and within 25% of the tire ground contact width W.

  The cord 26 constituting the spiral layer 24 is composed of nylon cord, aramid fiber, a mixed cord of nylon cord and aramid fiber, etc. that are frequently used as a belt reinforcing material.

  In the present embodiment, in order to improve the protrusion resistance (protrusion breaking property) in the belt protective layer 15, the pneumatic radial tire 10 is provided by providing the land portion row 22 composed of ribs in order to suppress tire deformation. Is sufficiently increased to make the pneumatic radial tire 10 difficult to deform.

  In addition, since the width BP of the overlap region 28 is 50% or more of the width of the land portion row 22, the land portion row 22 can be sufficiently supported when the protrusion comes into contact with the land portion row 22. Furthermore, since the width BP of the overlap region 28 is within 25% of the tire ground contact width W, the tire does not become too heavy even if the overlap region 28 is formed.

  By providing the overlap region 28 in this manner, the interlayer shear rigidity between the tires in the tire radial direction is increased, the resistance against tire deformation caused by an external force is increased, and the tire can be hardly deformed.

  Therefore, the pneumatic radial tire 10 with improved protrusion resistance (protrusion breaking property) at the tire equator 20 without adding a new member, that is, while suppressing the weight and cost of the tire can be obtained.

  The belt protective layer 15 covers the belt layer 14 over the entire width. As a result, the pneumatic radial tire 10 with improved protrusion resistance in the tire equator portion 20 and in the vicinity thereof over the entire width of the belt layer 14 can be obtained.

[Second Embodiment]
Next, a second embodiment will be described. As shown in FIG. 4, in the present embodiment, a stepped portion 40 that expands stepwise toward the groove bottom portion 39 of the circumferential main groove 38 is formed in place of the land portion row 22 as compared with the first embodiment. A land portion row (rib row) 42 is provided, and a belt protective layer 45 having a width corresponding to the land portion row 42 is provided in place of the belt protective layer 15.

  The land portion row 42 straddles the tire equator CL as in the first embodiment.

  As in the first embodiment, the belt protective layer 45 is formed of a spiral layer wound in the tire circumferential direction and has the same width on both sides of the tire equator CL. In the belt protective layer 45, an overlap region 48 that straddles the tire equator CL is formed along the tire circumferential direction.

  The width BP of the overlap region 48 is 50% or more of the width BR of the land portion row 42 and within 25% of the tire ground contact width.

  In this embodiment, the width BP of the overlap region 48 is set to 10 mm or more, so that the cord 46 constituting the belt protective layer 45 can be easily embedded in the rubber layer, that is, the belt protective layer 45. The cord can be made difficult to be exposed from the tire surface.

  The tire width direction end 48E of the overlap region 48 is located within L = 2 mm on the tire equator side from the tire width direction end 42E of the land portion row 42.

  Further, the depth position of the stepped portion 40 is shallower by ΔD than the depth position of the deepest portion 39M of the circumferential main groove 38. Here, ΔD is in the range of 0.5 to 2 mm. As a result, a gauge of about 1.5 mm can be secured between the belt protective layer 45 and the deepest portion 39M, and the risk of cord exposure is further reduced. In addition, since the rubber gauge is not increased excessively and there is no need to add an additional rubber sheet, an increase in tire weight and cost can be further suppressed.

[Third Embodiment]
Next, a third embodiment will be described. As shown in FIG. 5, in the present embodiment, the circumferential main groove 58 is located on the tire equator CL.

  Further, a belt protective layer 55 is provided in place of the belt protective layer 15 described in the first embodiment. As in the first embodiment, the belt protective layer 55 is formed of a spiral layer wound in the tire circumferential direction and has the same width on both sides of the tire equator CL.

  Further, an overlap region 68 that straddles the tire equator CL is formed in the belt protective layer 55 along the tire circumferential direction. The width BP of the overlap region 68 is set within 25% of the tire ground contact width.

  The belt protective layer 55 is an overlap region in an area of 50% or more of the land portion row width with respect to any of the land portion rows 52R and 52L in the vicinity of the tire equator CL forming the circumferential main groove 58. 68 is formed. That is, it overlaps in a region of 50% or more of the width BR1 of the land portion row 52R, and overlaps in a region of 50% or more of the width BR2 of the land portion row 52L.

  Thereby, even if the plunger (protrusion) abuts on either the left or right land portion row 52R, 52L in the vicinity of the tire equator CL, sufficient protrusion resistance (protrusion breaking property) can be obtained.

[Fourth Embodiment]
Next, a fourth embodiment will be described. As shown in FIG. 6, in the present embodiment, the circumferential main groove 78 is disposed at an asymmetrical position on both sides of the tire equator CL, and the tire equator CL does not pass through the center of the land portion row 72.

  Further, a belt protective layer 75 is provided in place of the belt protective layer 15 described in the first embodiment. As in the first embodiment, the belt protective layer 75 is formed of a spiral layer wound in the tire circumferential direction and has the same width on both sides of the tire equator CL.

  Further, the belt protective layer 75 is formed with an overlap region 88 straddling the tire equator CL along the tire circumferential direction. The width BP of the overlap region 88 is set to be within 25% of the tire ground contact width.

  The belt protective layer 75 is an area that is 50% or more of the width of the land portion row portion for each of the land portion row portions 72R and 72L that constitute one side of the land portion row 72 with respect to the tire equator CL. Are overlapping. That is, it overlaps in a region of 50% or more of the width BR1 of the land portion row portion 72R and overlaps in a region of 50% or more of the width BR2 of the land portion row portion 72L.

  As a result, sufficient protrusion resistance (protrusion destruction) can be obtained even if the plunger comes into contact with either the left or right land portion row portion 72R, 72L of the tire equator CL.

<Test example>
In order to confirm the effect of the present invention, the present inventor made an example of the pneumatic radial tire 10 of the first embodiment (hereinafter referred to as an example tire) and three examples of a conventional pneumatic radial tire (hereinafter referred to as an example of a pneumatic radial tire). The tire of Conventional Example 1, the tire of Conventional Example 2, and the tire of Conventional Example 3 were prepared, and performance evaluation was performed.

  Table 1 shows the conditions of each tire in this test example.

また、本試験例では、全てのタイヤについて、標準リムに組み込み後、正規内圧にして試験を行った。

Further, in this test example, all tires were tested with normal internal pressure after being incorporated into a standard rim.

  In this test example, in performing the performance evaluation, the index in the tire of the conventional example 1 was set as the index 100, and the index used as the relative evaluation was calculated for the other tires.

  The evaluation results are also shown in Table 1. In the evaluation results of Table 1, the larger the index for the plunger level and the hydroplaning level, the higher the performance, and the lower the index, the higher the performance for the weight. The plunger level is a measurement result obtained in a tire breaking strength measurement test, and is a test in which a protrusion is pressed against the tire equator until the belt cord or carcass cord is broken.

  In the tire of Conventional Example 1, the plunger level was not ensured.

  In the tire of Conventional Example 2, the plunger level was secured, but the groove bottom gauge was not secured. The groove bottom gauge is the rubber thickness from the deepest portion of the circumferential main groove to the cord of the belt protective layer.

  In the tire of Conventional Example 3, both the plunger level and the groove bottom gauge were secured. However, the increase in weight and the deterioration of hydroplaning due to the groove change were significant.

  On the other hand, in the tire of the example, both the plunger level and the groove bottom gauge were secured. And the increase in weight and the deterioration of the hydroplaning property were remarkably small and hardly deteriorated.

  The embodiments of the present invention have been described above with reference to the embodiments. However, these embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. Needless to say, the scope of rights of the present invention is not limited to the above embodiment.

1 is a tire radial direction cross-sectional view of a pneumatic radial tire according to a first embodiment. It is a conceptual diagram which shows arrangement | positioning of a belt protective layer with the pneumatic radial tire which concerns on 1st Embodiment. It is a conceptual diagram which shows arrangement | positioning of a belt protective layer with the pneumatic radial tire which concerns on 1st Embodiment. It is a conceptual diagram which shows arrangement | positioning of a belt protective layer in the pneumatic radial tire which concerns on 2nd Embodiment. It is a conceptual diagram which shows arrangement | positioning of a belt protective layer in the pneumatic radial tire which concerns on 3rd Embodiment. It is a conceptual diagram which shows arrangement | positioning of a belt protective layer with the pneumatic radial tire which concerns on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic radial tire 11 Bead core 12 Carcass 13 Bead part 14 Belt layer 15 Belt protective layer 16 Tread part 18 Circumferential main groove 20 Tire equatorial part 22 Land part row 24 Spiral layer 28 Overlapping area 39 Groove bottom part 39M Deepest part 40 Step Part 42 land part row 45 belt protective layer 48 overlap region 52R land part row 52L land part row 55 belt protective layer 58 circumferential main groove 68 overlap region 72 land part row 72R land part row part 72L land part row part 75 belt Protective layer 78 Circumferential main groove 88 Overlap region CL Tire equator

Claims (5)

A bead portion including a pair of bead cores, a carcass straddling between the bead portions, a belt layer disposed on the outer side in the tire radial direction of the carcass, and a belt protective layer disposed on the outer side in the tire radial direction of the belt layer; A tread portion provided on the outer side in the tire radial direction of the belt protective layer,
The tread portion is a pneumatic radial tire in which a plurality of circumferential main grooves are formed, and at least a tire equator portion or a land portion row is formed by blocks or ribs in the vicinity thereof,
The belt protective layer is composed of a spiral layer wound in the tire circumferential direction and has the same width on both sides of the tire equator,
In the belt protective layer, an overlap region straddling the tire equator is formed along the tire circumferential direction,
A pneumatic radial tire characterized in that the width of the overlap region is 50% or more of the width of the land portion row and within 25% of the tire ground contact width.   The pneumatic radial tire according to claim 1, wherein the belt protective layer covers the belt layer over the entire width.   3. The pneumatic radial tire according to claim 1, wherein the land portion row has a stepped portion that expands stepwise toward a groove bottom portion of the circumferential main groove. The land part row straddles the tire equator,
The width of the overlap region is 10 mm or more,
4. The pneumatic radial tire according to claim 3, wherein a tire width direction end of the overlap region is located within 2 mm on a tire equator side from a tire width direction end of the land portion row.   5. The pneumatic radial tire according to claim 4, wherein a depth position of the stepped portion is shallower within a range of 0.5 to 2 mm than a depth position of the deepest portion of the circumferential main groove.

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