JP2010126123A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire having a carcass sectional shape intensifying the hoop effect of a tread shoulder part and suppressing the diameter growth of the tread shoulder part without causing a reduction in durability or cost. <P>SOLUTION: D/W1 obtained by dividing the height D of a carcass ply in a tire equatorial plane E by the maximum width W1 of the carcass ply is set to 55-62%. The height D1 of the carcass ply at a position separated by 30% of W/2 which is half of the tire maximum width W is set to fall within a range of 100-105% of the height D of the carcass ply in the tire equatorial plane. The height D2 of the carcass ply at a position separated by 55% of W/2 which is half of the tire maximum width W is set to fall within 99-104% of the height D of the carcass ply in the tire equatorial plane. Moreover, the width of a belt ply 22 of a second layer is set to fall within 80-90% of the tire sectional width. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, each of both sides of a radial carcass made of one or more carcass plies is folded around a pair of bead cores, and a belt and a tread rubber located outside the belt are disposed radially outward of the central portion of the radial carcass. The belt is composed of at least three layers of belt plies, counted from the inner side in the radial direction, the first layer belt ply, the second layer belt ply, and the third layer belt ply. The inclination angles of the cord with respect to the equator plane are 40 to 70 degrees, 10 to 30 degrees, and 10 to 30 degrees, respectively, and the inclination of the cords of the belt plies of the second layer and the third layer are respectively The present invention relates to a pneumatic radial tire whose directions are opposite to each other with respect to the equator plane.

  In heavy-duty vehicles such as trucks, there are an increasing number of regions that limit vehicle height due to recent legal regulations. As the height of the vehicle decreases, the amount of luggage to be loaded decreases, and in order to suppress this decrease, it is desired to lower the floor of the vehicle. In order to lower the floor of the vehicle, it is effective to lower the center axis of the tire, and for that purpose, it is essential to flatten the tire.

  On the other hand, in a heavy-duty vehicle, as a belt for exerting a tagging effect, four layers called so-called mixed layers in which the directions of cords are inclined in directions opposite to each other with respect to the equator plane between adjacent layers in the radial direction. Generally, the belt ply is used.

  Since the belt has a lower tag effect at the tread shoulder portion than at the tread center portion, the tire diameter growth at the tread shoulder portion is large, thereby increasing the tension on the belt ply. This tendency becomes more prominent as the tire is flattened, that is, as the flatness ratio becomes smaller, and belt tension and groove cracking may be caused by an increase in belt tension.

  As a measure to solve such a problem, even if the number of layers of the belt ply is the same, by dividing one belt ply in the width direction and increasing the number of belt plies, the tire at the tread shoulder portion can be increased. Tires with reduced diameter growth (for example, see Patent Documents 1 and 2), and tires in which the cross-sectional shape of the carcass at no load is set so that the difference in height in the radial direction between the tread shoulder portion and the tread center portion becomes small (For example, refer to Patent Document 3).

However, the tires described in Patent Documents 1 and 2 are disadvantageous in terms of cost because the types of belt plies are increased, and the tire described in Patent Document 3 is to ensure the durability of the bead portion. It is necessary to thicken the rubber of the bead part or thicken the side wall part in order to obtain the carcass cross-sectional shape as described above, and this causes a problem that durability is lowered and cost is increased. Will be invited.
JP 2008-24104 A JP 2008-24105 A Japanese Patent Laid-Open No. 05-185806

  The present invention has been made in view of such a problem, and enhances the tread shoulder effect and reduces the diameter growth of the tread shoulder portion without causing a decrease in durability or cost. An object is to provide a tire having a cross-sectional shape.

In the present invention, each of both sides of a radial carcass made of one or more carcass plies is folded around a pair of bead cores, and a belt and a tread rubber located outside the belt are disposed radially outward of the central portion of the radial carcass. The belt is composed of at least three layers of belt plies, and counted from the inner side in the radial direction, the first layer belt ply, the second layer belt ply, and the third layer belt ply. The inclination angle of the cord with respect to the equator plane is 40 to 70 degrees, 10 to 30 degrees, and 10 to 30 degrees, respectively, and the inclination of the cords of the second and third layer belt plies In pneumatic radial tires whose directions are opposite to each other with respect to the equator plane,
When the radial distance from the radial innermost end of the radial carcass to a specific position on the radial carcass is called the carcass ply height at the specific position, the carcass ply height D at the tire equatorial plane is divided by the carcass ply maximum width W1. D / W1 is set to 55 to 62%, and the carcass ply height D1 at a position 30% away from the tire equator plane in the width direction outward by half W / 2 of the maximum tire width W is set to the tire equator plane. The carcass ply height D2 at a position separated by 55% of the half width W / 2 of the maximum tire width W is 99 to the carcass ply height D at the tire equatorial plane. The pneumatic tire is characterized in that it is in the range of -104%, and the width of the belt ply of the second layer is in the range of 80-90% of the tire cross-sectional width.

  In the present invention, it is preferable to dispose a fourth-layer belt ply in which the inclination angle of the cord with respect to the equator plane is smaller than that of the first-layer belt ply.

  According to the present invention, when the radial distance from the radial innermost end of the radial carcass to a specific position on the radial carcass is called the carcass ply height at the specific position, the carcass ply height D on the tire equatorial plane is defined as the carcass ply height. D / W1 divided by the maximum width W1 is 55 to 62%, and the carcass ply height at a position 30% away from the tire equatorial plane, half the maximum width W of the tire, W / 2. D1 is in the range of 100 to 105% of the carcass ply height D on the tire equatorial plane, and the carcass ply height D2 at a position separated by 55% of the half width W / 2 of the maximum tire width W is the carcass ply height on the tire equatorial plane. Since the ply height D is in the range of 99 to 104% and the width of the belt ply of the second layer is in the range of 80 to 90% of the tire cross-sectional width, durability and Can lead to cost reductions In addition, it is possible to provide a tire having a carcass cross-sectional shape that can enhance the hoop effect of the tread shoulder portion and suppress the diameter growth of the tread shoulder portion.

  In addition, when a fourth-layer belt ply in which the inclination angle of the cord with respect to the equator plane is smaller than that of the first-layer belt ply is provided, the cut resistance can be improved.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a tire according to an embodiment of the present invention in a cross section passing through its central axis, and FIG. 2 is a belt development view of a belt developed on a plane as seen from the outside in the radial direction of the tire. 10 folds back both sides 1a of the radial carcass 1 composed of one or more carcass plies 11 around a pair of bead cores 3, and the belt 2 on the outer side in the radial direction of the central portion 1b of the radial carcass 1 The belt 2 is composed of at least three layers of belt plies 21, 22, and 23. The belt ply 21 and the second layer of the first layer are counted from the inside in the radial direction. The inclination angles β, α1, and α2 of the cords of the eye belt ply 22 and the third layer belt ply 23 with respect to the equator plane E are 40 to 70 degrees, 10 to 30 degrees, and 10 to 30, respectively. Every time In addition, the cord plies 22 and 23 of the second layer and the third layer are configured so that the direction of the cord inclination is opposite to the equator plane E.

  A characteristic of the tire 10 is that when the radial distance from the radially innermost end P0 of the radial carcass 1 to a specific position on the radial carcass 1 is called a carcass ply height at the specific position, the carcass ply on the tire equatorial plane E D / W1 obtained by dividing height D by carcass ply maximum width W1 is 55 to 62%, and away from tire equatorial plane E in the width direction by 30% of half W / 2 of tire maximum width W The carcass ply height D1 at the position P1 is in the range of 100 to 105% of the carcass ply height D at the tire equatorial plane E, and the carcass ply height at the position P2 separated by 55% of half the tire maximum width W / 2 The height D2 is in the range of 99 to 104% of the carcass ply height D on the tire equatorial plane E, and the width W2 of the belt ply in the second layer is in the range of 80 to 90% of the tire cross-sectional width W. It is configured.

  Here, when the tire is mounted on the applied rim and the state in which the inner pressure is not filled is referred to as an unloaded state, the tire maximum width W is the tire mounted on the applied rim, The total tire width defined as the linear distance between sidewalls including all patterns and characters, etc., excluding the tire patterns and characters, etc., and the width of each layer of the belt ply and carcass ply Similarly, the width is a width measured under no load condition.

  Further, the carcass ply height refers to the height when the tire is mounted on the applied rim and measured in a no-load state in which the internal pressure is not charged.

  The applicable rim refers to a rim defined in the following standards depending on the tire size.

Also, the standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, in the United States, it is TRA's YEAR BOOK, in Europe, ETRTO's YEAR BOOK, in Japan, Japan It is JATMA YEAR BOOK of the tire association.

  The operation of the configuration having the above characteristics will be described below. D / W1 obtained by dividing the carcass ply height D on the tire equatorial plane E by the carcass ply maximum width W1, that is, the flatness of the radial carcass is 55 to 62%, but when this is less than 55%, The diameter growth of the tread shoulder increases, causing belt failure and groove cracks.If this exceeds 62%, the tension against the belt ply decreases and the diameter growth decreases. The merit of adopting the shape of the present invention is reduced.

  Further, in the present invention, the carcass ply height D1 at the position P1 separated by 30% of the half width W / 2 of the maximum tire width W from the tire equatorial plane E to the outer side in the width direction is set to the carcass ply on the tire equatorial plane E. Carcass ply height D2 at position P2 that is within a range of 100 to 105% of height D and is 55% of half W / 2 of the maximum tire width W is 99 to 104 of carcass ply height D on tire equatorial plane E. However, if D1 / D is less than 100% or D2 / D is less than 99%, the diameter growth at the center of the tread rubber will be small, but the diameter at the tread shoulder will be smaller. If the growth becomes too large and belt failure or groove cracking occurs, D1 / D exceeds 105% or D2 / D exceeds 104%, the diameter at the center of the tread Increased growth, due to belt ply buckling during vulcanization Concrete failure is increased.

  Here, when evaluating the carcass ply height D, the value at the position P2 separated by 55% of the half width W / 2 of the maximum tire width W was set as one reference value. In the belt structure made of the belt ply, from the tire equatorial plane E toward the outer side in the width direction, at a position P2 that is separated by 55% of half the maximum width W of the tire W / 2, it is due to radial growth and running due to internal pressure filling This is because the diameter growth due to belt creep is the largest.

  Further, the width W2 of the belt ply 22 of the second layer is configured to be in the range of 80 to 90% of the tire cross-sectional width W. However, when W2 / W is less than 80%, the tagging effect in the tread shoulder portion is obtained. This causes a decrease in diameter growth at the tread shoulder, which may cause belt failure and groove cracks.If this exceeds 90%, the tread rubber is used as a stitching roller when molding the tire. When used, adhesion failure when adhered to the sidewall rubber increases.

  In addition to the first to third three-layer belt plies, a fourth-layer belt ply is preferably disposed, and cut resistance can be improved.

  In the tire having the structure shown in FIG. 1, ten types of tires were created by changing the width of the belt ply of the second layer or by changing the cross-sectional shape of the radial carcass. The diameter growth rate and belt durability were evaluated.

  The specifications relating to the belt dimensions are shown in Table 1, and the evaluation results are shown in Table 2. Further, for these tires, the dependency of the diameter growth rate on the position in the width direction is shown in a graph in FIG.

The specifications common to these tires are as follows.
・ Tire size: 205 / 65R17.5
・ Rim size: 6x17.5
・ Number of belt plies driven:
1st layer: 9 / 25mm
2nd to 4th layers: 13 / 25mm
・ The width of each belt ply (mm) and the inclination angle of the cord with respect to the equator plane (°)
First layer belt ply: 150mm x 50 °
Second layer belt ply: 170mm x 16 °
3rd layer belt ply: 155mm x 16 °
4th layer belt ply: 65mm x 16 °

  In addition, the diameter growth rate in Table 2 and FIG. 3 indicates the tire outer diameter after running 5000 km by attaching the tire to the rim and running on a drum tester under a load that is 1.3 times the ETRTO standard load. Expressed as a ratio to the tire outer diameter before running. And in Table 2, this was represented by an index with the diameter growth rate of the example as 100. The larger the index, the larger the diameter growth rate.

  Further, the durability of the belt was evaluated by WSf obtained from the result of the QC drum test, that is, an index WSf represented by the product of load and speed. Here, the QC drum test is an indoor drum test in accordance with the test method defined in the standard ECE 54. The tire is run at a speed determined for each tire, and the load is gradually increased at regular intervals. The WSf is a numerical value representing the durability of the tire obtained from the test speed and the set load at the time of the failure in the QC drum test.

It is sectional drawing which shows the tire of embodiment in the cross section which passes along the center axis line. FIG. 3 is a belt development view showing the tire belt of the embodiment developed on a plane. It is a graph showing the dependence with respect to the position of a width direction of a diameter growth rate about the tire of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radial carcass 1a Radial carcass side part 1b Radial carcass center part 2 Belt 3 Bead core 4 Tread rubber 10 Tire 11 Carcass ply 21 1st layer belt ply 22 2nd layer belt ply 23 3rd layer belt ply 24 4th layer belt ply

Claims (2)

Each of the two sides of the radial carcass made of one or more carcass plies is folded around a pair of bead cores, and a belt and a tread rubber located outside the belt are arranged on the radially outer side of the central portion of the radial carcass, This belt is composed of at least three layers of belt plies, and counted from the inner side in the radial direction, the equator plane of the first layer belt ply, the second layer belt ply, and the third layer belt ply. The inclination angle of the cord relative to the belt is 40 to 70 degrees, 10 to 30 degrees, and 10 to 30 degrees, respectively, and the direction of the inclination of the cords of the second layer and the third layer belt ply is the equator plane. In pneumatic radial tires that are opposite to each other,
When the radial distance from the radial innermost end of the radial carcass to a specific position on the radial carcass is called the carcass ply height at the specific position, the carcass ply height D at the tire equatorial plane is divided by the carcass ply maximum width W1. D / W1 is set to 55 to 62%, and the carcass ply height D1 at a position 30% away from the tire equator plane in the width direction outward by half W / 2 of the maximum tire width W is set to the tire equator plane. The carcass ply height D2 at a position separated by 55% of half of the maximum width W of the tire, W / 2, is 99 to the carcass ply height D at the tire equatorial plane. A pneumatic tire characterized in that it is in the range of -104%, and the width of the belt ply of the second layer is in the range of 80-90% of the tire cross-sectional width.   The pneumatic tire according to claim 1, wherein a fourth-layer belt ply having an inclination angle of the cord with respect to the equator plane smaller than that of the first-layer belt ply is disposed.

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