JP2010247699A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire, especially a pneumatic tire appropriate for an automobile, capable of improving a fuel efficiency performance by reducing the weight of the tire more than before without impairing various performances of the tire, such as durability. <P>SOLUTION: The pneumatic tire includes a crossing belt 5, in which two or more rubberized layers of multiple cords aligned obliquely with respect to an equatorial plane of the tire are arranged outside in a tire radial direction of a crown area of the carcass 4 so that the cords mutually cross between the layers. In at least one layer of the crossing belt 5, a metal mono filament arranged without crossing is a reinforcement element. The carcass 4 is made of one carcass ply, and the turning height TH of the carcass is 40% or less of the entire carcass height CH. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”). Specifically, the fuel efficiency is improved by reducing the weight of the tire more than before without impairing the performance of the tire such as durability. The present invention relates to a pneumatic tire, in particular, a pneumatic tire suitable for a passenger car.

  In recent years, there has been an increasing demand for weight reduction of tires in order to improve the fuel efficiency of automobiles. When considering weight reduction in a belt portion using a conventional twisted steel cord, assuming that the tensile strength is secured above a certain level, the coating gauge of the steel belt layer has to be thinned.

  From such a viewpoint, a technique for using a metal monofilament as a cord for a belt without twisting has been developed, and various proposals have been made so far. For example, in Patent Document 1, for the purpose of improving fuel consumption and riding comfort, a rubber bundle is a unit of bundles of 3 or 4 metal wires (metal monofilaments) arranged in the width direction of the belt without being twisted. A pneumatic radial tire having an embedded belt has been proposed. Further, in Patent Document 2, in order to respond to the needs for weight reduction of tires and to solve problems such as a decrease in durability due to bending of the metal wire, the belt layer is made of a metal monofilament in the belt ply width direction. A pneumatic radial tire composed of three belt plies arranged under conditions and embedded in a covered rubber has been proposed. Furthermore, Patent Document 3 discloses a belt in which metal monofilaments are arranged in parallel in the width direction and embedded in a coated rubber for the purpose of reducing the weight of the tire and reducing rolling resistance while maintaining various tire performances. It has been reported that an inert gas such as nitrogen gas is used as a filling gas inside a tire while applying a ply.

  Further, Patent Document 4 discloses a second belt of the second layer in order to obtain a pneumatic radial tire that suppresses belt end separation and achieves both improvement in belt durability and reduction in tire weight. A technique is disclosed in which the gauge between the metal monofilaments of the first belt and the second belt at the layer end is 1.3 to 3.0 times the gauge at the tire center. Furthermore, in Patent Document 5, in addition to thickening the rubber gauge between the metal monofilaments, the filament diameter and the number of metal monofilaments are limited to a predetermined range, thereby realizing both higher weight and durability. It has been reported that

  On the other hand, there is also known a weight reduction method around the side portion and the bead portion of the tire. As a general method, a so-called LTU (LOW TURN UP) that reduces the number of carcass plies and keeps the folding height of the carcass low. Structure is mentioned. Further, in a small tire, the carcass ply generally has one layer, and weight reduction is achieved by keeping the folding height of the carcass of this one layer low. In addition, even in tires that conventionally used two carcass plies, such as ultra-high performance (UHP) tires, an attempt has been made to realize a large weight reduction by making the number of layers one layer and keeping the folding height low. ing.

JP-A-11-208210 (Claims etc.) JP 2001-334810 A (Claims etc.) JP 2002-2213 A (Claims etc.) JP 2005-349999 A (Claims etc.) JP 2007-302203 A (Claims etc.)

  As proposed so far, it is possible to reduce the weight of tires by applying metal monofilaments to the belt and by reducing the number of carcass plies. From the viewpoint of preventing global warming and the like, there is a strong demand for improving fuel efficiency by reducing the weight of tires.

Accordingly, an object of the present invention is to eliminate the problems in the above-described prior art, and without impairing the performance of the tire such as durability, and more particularly, a pneumatic tire that has improved fuel efficiency performance by reducing the weight of the tire more than ever, particularly The object is to provide a pneumatic tire suitable for use in a passenger car.

As a result of intensive studies in order to solve the above problems, the present inventor has obtained the following knowledge and has completed the present invention.

First of all, as a result of diligent studies on tires in which metal monofilaments are applied to the belt for the purpose of reducing the weight of the tire, the application of metal monofilaments to the belt not only reduces the weight of the tire, but also effectively demonstrates the circumferential rigidity of the tire It was found that weight reduction and circumferential rigidity of the tire can be achieved at a high level. With this discovery, it became possible to improve the circumferential rigidity of the tire by using a metal monofilament applied belt and bend the side portion of the tire. As a result of further intensive studies, by applying a carcass LTU structure consisting of a single carcass ply to a tire having a metal monofilament applied belt, the side portions are more easily deformed, resulting in a lighter tire, and consequently It has been found that not only the effect of reducing rolling resistance but also optimization of tire deformation can achieve further improvements in fuel efficiency without impairing tire performance such as durability. . In addition, the contribution of the case member is higher at the end of the run compared to the time when the tread rubber contributes greatly, but the effect of the tire may be more noticeable at the end of the run because the change in the side portion of the tire is larger. all right.

That is, the pneumatic tire of the present invention has a carcass extending in a toroid shape across a pair of left and right bead portions, and is inclined to the equatorial plane of the tire on the outer side in the tire radial direction of the crown region of the carcass. In a pneumatic tire having a crossing belt in which two or more rubberized layers of a plurality of arranged cords are arranged in a direction in which the cords cross each other between the layers,
At least one layer of the crossing belt is made of metal monofilaments arranged without being twisted together as a reinforcing element, and the carcass is composed of one carcass ply. % Or less.

  In the pneumatic tire of the present invention, the folded height of the carcass is preferably 30% or less of the total carcass height. The reinforcing element is preferably a bundle of metal monofilaments juxtaposed with each other as a unit, and the reinforcing element is preferably an aligned straight line. Further, the diameter of the metal monofilament is 0.18 to 0.35 mm, and the number of filaments constituting the bundle is preferably 2 to 10, more preferably the diameter of the metal monofilament is 0.20. ˜0.26 mm, and the number of filaments constituting the bundle is 5 to 7. Furthermore, the number of reinforcement elements to be driven is preferably 15 to 32 bundles / 50 mm. Furthermore, both the first belt layer of the first layer of the crossing belt and the second belt layer of the second layer are metal monofilaments arranged without being twisted together as a reinforcing element, and at the end of the second belt layer The gauge of the rubber layer between the metal monofilaments of the first belt layer and the second belt layer is preferably 1.3 to 3.0 times the gauge at the tire center.

  According to the pneumatic tire of the present invention, it is possible to achieve an improvement in fuel efficiency by reducing the weight of the tire without impairing various performances of the tire such as durability. Moreover, this effect is more remarkable at the end of traveling.

1 is a half sectional view showing a pneumatic tire according to a preferred example of the present invention. It is explanatory drawing which shows a total gauge. It is sectional drawing of the bundle | flux of a metal monofilament. It is a graph which shows the relationship between the rolling resistance (index) at the time of a new article and tire weight reduction (g) in an Example. It is a graph which shows the relationship between the rolling resistance (index) after driving | running | working in an Example, and tire weight reduction (g).

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. The illustrated tire includes a tread portion 1 that is disposed in a crown region of the carcass and forms a ground contact portion, a pair of sidewall portions 2 that extend inward in the tire radial direction continuously on both sides of the tread portion 1, and A bead portion 3 is provided on the inner peripheral side of each sidewall portion 2.

  The tread portion 1, the sidewall portion 2, and the bead portion 3 are reinforced by a carcass 4 including a single carcass ply extending in a toroidal shape from one bead portion 3 to the other bead portion 3. Further, the tread portion 1 is formed by an intersecting belt 5 including at least two layers disposed in the tire radial direction outside of the crown region of the carcass 4, and in the illustrated example, two layers of a first belt layer 5a and a second belt layer 5b. It is reinforced. The first belt layer 5a and the second belt layer 5b, which are the belt layers on the carcass 4 side, preferably have a cord driving angle of 15 to 40 ° with respect to the tire circumferential direction.

  In the present invention, a metal monofilament in which at least one layer of the crossing belt 5 is arranged without being twisted is used as a reinforcing element. In order to obtain good tire performance, untwisted metal monofilaments may be used, but by using these metal monofilaments in bundles, an appropriate reinforcing element that takes into account other performances such as strength, rigidity, and durability can be used. It becomes possible to design. For example, when the number of bundles is small, the distance to the adjacent bundle becomes short, and belt edge separation, which is a typical failure of a tire, is likely to occur. On the other hand, when the number of bundles is large, the distance along the cord surface is increased. Cracks are easily generated and belt edge separation is also likely to occur.

  In the present invention, the metal monofilaments arranged without being twisted may be straight or molded, but in order to achieve weight reduction of the tire, the vertical molding is as small as possible. Is preferable. Further, it is preferable that the reinforcing element is a straight line that is aligned, since the vertical gauge of the belt layer can be geometrically thinned.

  In order to obtain the desired effect of the present invention, preferably, the diameter of the metal monofilament is 0.18 to 0.35 mm, and the number of filaments constituting the bundle is 2 to 10, more preferably monosteel. The diameter of the filament is 0.18 to 0.35 mm, the number of filaments constituting the bundle is 3 to 8, and even more preferably, the diameter of the metal monofilament is 0.20 to 0.26 mm and the number of bundles is 5-7. If the diameter of the metal monofilament is larger than 0.35 mm, the fatigue property due to the increase in surface strain is deteriorated, and the curl is deteriorated, so that a good treat property cannot be obtained. On the other hand, if it is thinner than 0.18 mm, the workability at the time of cutting decreases with a decrease in bending rigidity, leading to an increase in manufacturing cost due to disconnection during cord manufacturing.

  In the present invention, the total gauge of the first belt layer 5a and the second belt layer 5b is preferably 0.7 to 1.1 mm from the viewpoint of weight reduction of the tire and belt durability. Here, the total gauge is represented by a distance G between the filament centers of the upper and lower belt layers, as shown in FIG. Furthermore, the gauge of the rubber layer between the metal monofilaments 10 of the first belt layer 5a and the second belt layer 5b at the end of the second belt layer 5b is 1.3 to 3.0 times the gauge at the center of the tire. It is preferable. By applying a thick gauge inter-belt rubber to the metal monofilament coated with a thin gauge at the belt end, both weight reduction of the tire and belt durability can be achieved. If this value is 1.3 times or more, belt end separation is sufficiently suppressed, and if it is 3.0 times or less, there is no problem in reducing the weight of the tire.

Furthermore, the tensile strength of the metal monofilament is preferably 2700 N / mm ² or more. As a metal monofilament having a high tensile strength, a metal monofilament containing at least 0.7 mass%, particularly at least 0.8 mass%, can be suitably used.

  Furthermore, the number of reinforcement elements to be driven is preferably 15 to 32 bundles / 50 mm. If the number of driven wires is too small, it will be difficult to ensure the tensile strength, while if it is too large, it will be difficult to secure the cord interval, which is not preferable.

  In the present invention, the number of carcass plies of the carcass 4 is one, and the turn-up height TH of the carcass ply is 40% or less, preferably 30% or less of the total carcass height CH. As a result, the side deformation is facilitated, and not only the effect of reducing the weight of the tire, and hence the low rolling resistance, but also the deformation of the tire can be optimized. A further improvement in fuel efficiency can be realized without impairing the performance. However, in order to satisfactorily lock the end portion of the carcass 4 to the bead core, it is preferably 15% or more.

  In the carcass 4, organic fiber cords extending in a direction substantially orthogonal to the tire circumferential direction, for example, an angle of 70 to 90 °, such as polyester fibers, nylon fibers, aramid fibers, polyketone fibers, and the like can be suitably used. .

The pneumatic tire of the present invention relates to improvements in the belt structure and the carcass structure, and other structures and materials are not particularly limited, and known structures and materials can be appropriately adopted. it can.

Hereinafter, the present invention will be described more specifically with reference to examples.
A pneumatic tire having a structure including the two-layer steel belt shown in FIG. 1 was manufactured under the conditions shown in Tables 1 and 2 below. The tire size was 225 / 50R17, and the driving angles of the metal monofilaments of the first belt layer 5a and the second belt layer 5b were + 26 ° and −26 °, respectively, with respect to the tire circumferential direction. In addition, as shown in FIG. 3, the “number of bundles” shown in Tables 1 and 2 below is (a) for three, (b) for four, (c) for five, When the number is six, it means a linear reinforcing element having a cross section of (d) and when it is eight (e), in which metal monofilaments are aligned. When such a bundle is used as a reinforcing element, the “number of driven-in” is the number of bundles for a width of 50 mm as one cord in the bundle.

  The obtained test tires of Examples and Comparative Examples were evaluated for the degree of weight increase (weight difference) based on Conventional Example 1. In addition, the rolling resistance when new and after running was evaluated according to the following. The results are also shown in Tables 1 and 2 below.

Rolling resistance (RR)
The drum of the new test tire was rotated by inertia until the speed decreased from 100 km / h to 20 km / h, and the time between them was measured to determine the rolling resistance, which was designated as “RR when new”. The value was displayed as an index with the “RR when new” in Conventional Example 1 being 100. The smaller the index value, the smaller the rolling resistance and the better the fuel efficiency.

  Next, the test tire was mounted on an actual vehicle, traveled in Japan for 30,000 km, and was in a state where it was almost completely worn out. Thereafter, the rolling resistance was obtained in the same manner as described above, and the result was “RR after travel”. . The value was displayed as an index with the “RR when new” in Conventional Example 1 being 100. The smaller the index value, the smaller the rolling resistance after traveling and the better the fuel efficiency.

Further, Tables 1 and 2 show “RR after travel” / “RR when new”.
The smaller this value is, the lower the rolling resistance and the lower the fuel consumption performance as the vehicle shifts from the new time to after traveling.

  As shown in Tables 1 and 2 above, metal monofilaments were applied to the two belt layers, respectively, and the carcass ply height TH of one carcass ply was set to 40% or less of the total carcass height CH. In the tires of Examples 1 to 7, as compared with the tires of the conventional example and Comparative Examples 1 to 3, all of the tires were confirmed to be lighter and improve fuel efficiency. 4 and 5, it was found that the rolling resistance becomes smaller and the improvement in fuel efficiency becomes more remarkable as the vehicle moves from the new time to the time after traveling.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass 5a 1st belt layer 5b 2nd belt layer 5 Crossing belt 10 Metal monofilament

Claims (8)

A rubberized layer of a plurality of cords having a carcass extending in a toroid-like shape across a pair of left and right bead portions and arranged at an inclination to the equatorial plane of the tire on the outer side in the tire radial direction of the crown region of the carcass In a pneumatic tire having a crossing belt in which two or more layers are arranged in a direction in which cords cross each other between layers,
At least one layer of the crossing belt is made of metal monofilaments arranged without being twisted together as a reinforcing element, and the carcass is composed of one carcass ply, and the folded height of the carcass is 40% of the total carcass height. A pneumatic tire characterized by being less than or equal to%.   The pneumatic tire according to claim 1, wherein the folded height of the carcass is 30% or less of the total carcass height.   The pneumatic tire according to claim 1 or 2, wherein the reinforcing element is a bundle of metal monofilaments juxtaposed in units.   The pneumatic tire according to any one of claims 1 to 3, wherein the reinforcing element is an aligned straight line. The pneumatic tire according to claim 3 or 4, wherein the diameter of the metal monofilament is 0.18 to 0.35 mm, and the number of filaments constituting the bundle is 2 to 10. The pneumatic tire according to claim 5, wherein the metal monofilament has a diameter of 0.20 to 0.26 mm, and the number of filaments constituting the bundle is 5 to 7. The pneumatic tire according to any one of claims 3 to 6, wherein the number of driven reinforcing elements is 15 to 32 bundles / 50 mm.   The first belt layer at the first layer and the second belt layer at the second layer of the crossing belt are both metal monofilaments arranged without being twisted together as a reinforcing element, and the first belt at the end of the second belt layer. The pneumatic tire according to any one of claims 1 to 7, wherein the gauge of the rubber layer between the metal monofilaments of the layer and the second belt layer is 1.3 to 3.0 times the gauge in the tire central portion. .

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