JP2010247701A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-weight pneumatic tire improved in breakage durability for a projection input of a tread. <P>SOLUTION: In the tire having a carcass extending in a toroidal shape between a pair of bead cores as a framework and provided with at least two layers of belt and tread at the outside of the carcass in a radial direction, the carcass has a carcass fold back part extending to a gap between the belt and a carcass body, folded back from the carcass body extending in the toroidal shape between the pair of bead cores from the inside to the outside in a tire width direction of the tire around the bead cores. An auxiliary carcass layer is arranged between respective terminals of the carcass folded back part and between the belt and the carcass body. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, particularly a heavy-duty tire, with improved fracture durability against protrusion input in a tread portion.

In recent years, in order to consider environmental problems, various studies aimed at improving the fuel efficiency of vehicles have been conducted, and studies for reducing the weight of tires are also being conducted. As a result, a carcass is a pneumatic tire having a so-called envelope structure in which a folded end is disposed between a carcass and a belt (see Patent Document 1).
Since the carcass has an envelope structure, the number of plies constituting the carcass can be reduced, and the tire rigidity that tends to be insufficient can be reinforced by reducing the number of plies. In particular, in a flat tire, when the folded end of the carcass is present in the sidewall portion of the tire, the folded end is peeled off from the rubber (so-called separation).

In addition, the pneumatic tire must have a structure that can withstand an impact when overcoming road surface irregularities during traveling, and therefore, the tread portion needs to be strengthened. In particular, high durability, particularly high protrusion resistance (protrusion destruction durability) is required for tires compatible with REINFORCE and XL (EXTRA LOAD) that are assumed to be mounted on heavy vehicles. Specifically, in XL tires, plunger energy (which will be described later), which is an index representing protrusion resistance, is required to be twice that of a normal tire.
As a conventional technique for strengthening the tread portion and improving the fracture durability against protrusion input of the tread portion, there is an improvement in the strength of a treat member such as a carcass, a belt, or a cap. Specifically, in order to improve the strength of the treat member, methods such as increasing the cord strength of the treat member, increasing the number of cords to be driven (density), and increasing the number of treats have been taken.

Japanese Patent Laid-Open No. 10-100700

However, any of the above-described methods for improving the strength of the treat member causes an increase in the tire weight, which is disadvantageous for the environmental problems described above. Moreover, when the above method is used, there is a concern that the influence on the basic performance of the tire is increased.
SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire that achieves weight reduction of the tire and has improved fracture durability against protrusion input of the tread portion.

The gist of the present invention is as follows.
(1) In a tire including a carcass extending in a toroidal shape between a pair of bead cores and having at least two layers of belts and a tread on the outer side in the radial direction of the carcass,
The carcass is folded from the carcass main body portion extending in a toroidal shape between the pair of bead cores, from the inner side to the outer side in the tire width direction around the bead cores, and extends between the belt and the carcass main body portion. Having a carcass folded portion,
An auxiliary carcass layer is disposed between the terminals of the carcass folding portion and between the belt and the carcass main body portion.
A pneumatic tire characterized by that.

(2) The pneumatic tire according to (1), wherein the auxiliary carcass layer is provided in a region including a tire equatorial plane.

  ADVANTAGE OF THE INVENTION According to this invention, while achieving weight reduction of a tire, the pneumatic tire which improved the fracture durability with respect to the protrusion input of a tread part can be provided.

It is a width direction sectional view of the pneumatic tire of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a cross-sectional view in the width direction of the pneumatic tire of the present invention. The tire 1 of the present invention has at least two belt layers in which a single layer of carcass 3 extending in a toroidal shape between a pair of bead cores 2 is used as a skeleton, and a plurality of cords are covered with rubber on the radially outer side of the carcass 3. The belt 4 includes two layers, a first belt layer 4 a and a second belt layer 4 b in the illustrated example, and a tread 5 is disposed on the outer side in the radial direction of the belt 4.

The first belt layer 4a and the second belt layer 4b are inclined belt layers in which a large number of cords extending obliquely with respect to the tire equatorial plane CL and extending in directions intersecting with each other are covered with rubber.
In the illustrated example, the first belt reinforcement layer 6a covering the entire width direction of the belt 4 formed by covering a plurality of cords extending along the tire equatorial plane CL with rubber on the radially outer side of the belt 4, A belt reinforcing layer 6b that reinforces the belt end is further provided, but these belt reinforcing layers 6a and 6b may be omitted.

The carcass 3 is folded from the carcass main body portion 3a extending in a toroidal shape between the pair of bead cores 2 around the bead core 2 from the inner side to the outer side in the tire width direction and extends between the belt 4 and the carcass main body portion. This is a so-called envelope structure having the carcass folded portion 3b. At this time, the folding end 3E of the carcass 3 is located between the belt 4 and the carcass main body 3a, and is sandwiched between the belt 4 and the carcass main body 3a.
The carcass of the envelope structure is lighter than the carcass of the two-ply structure, and has a one-ply low turn-up structure (the carcass folding end is located at the bead portion) and a one-ply high turn-up structure (carcass folding) There is an advantageous effect that the carcass strength is high as compared with the case where the end is located in the sidewall portion. Further, since the folded end of the carcass does not exist on the sidewall portion of the tire, rubber peeling (separation) of the terminal can be avoided.

  Here, it is important to dispose the auxiliary carcass layer 7 between the belt 4 and the carcass main body portion 3a in the tread center portion. The reason for this will be described below.

Now, there is a plunger energy test as a test for measuring the fracture energy when a pneumatic tire rides over a projection on an uneven road surface, and the present inventors have determined the fracture durability against projection input of the tread portion by the plunger energy test. investigated.
The plunger energy test is based on JIS D4230, and is obtained by multiplying the plunger pressing load and the displacement when the plunger is pressed along the tire equator plane. PE) is a test for measuring. Normally, when the plunger is pressed, the carcass cord having poor strength is first broken, and then the cord of the belt is broken. As a result, the plunger breaks through the tread surface, leading to destruction of the pneumatic tire.

  The present inventors use the finite element method (FEM) to calculate the tension load of each treat member during the plunger test, and find that the tension load increases in the order of belt, carcass, and cap (belt reinforcement layer). did. Therefore, it was considered that by strengthening the carcass, the load on the belt is reduced and the plunger energy can be increased. However, if the carcass is composed of two layers in order to reinforce the carcass (two plies), the tire weight increases significantly, so it is effective to reinforce the carcass only in the tread center portion where the projection input is large. I came up with it.

As described above, in the present invention, the auxiliary carcass layer 7 is disposed only in the center region between the belt 4 and the carcass main body portion 3a and including the tire equatorial plane CL, thereby minimizing an increase in tire weight. It was possible to increase the value of the plunger energy by increasing the strength of the center region while restraining to a low level.
The cord of the auxiliary carcass layer 7 extends in a direction (including an inclination angle of 90 ° ± 10 °) orthogonal to the tire equatorial plane CL direction, similarly to the cord of the carcass 3. Further, the cord type and the number of driving of the cord of the auxiliary carcass layer 7 are also compliant with the carcass 3.

The auxiliary carcass layer 7 is a region including the tire equatorial plane CL, and is preferably provided between the folded ends 3E of the carcass folded portion 3b so as not to contact the folded ends 3E.
This is because if the ply end of the auxiliary carcass layer 7 and the folded end 3E come into contact with each other, separation may be induced.

The width W of the auxiliary carcass layer 7 is preferably 40 mm to 80 mm with the tire equatorial plane CL as the center. That is, if the width W of the auxiliary carcass layer 7 is less than 40 mm, the auxiliary carcass layer 7 may not be sufficiently effective to bear the input of the plunger, while if the width W exceeds 80 mm, the auxiliary carcass layer 7 This is because the ply end of the layer 7 and the folded end 3E are close to each other, which may induce separation.
The folded end 3E is located on the inner side in the tire width direction from the end of the belt 4, but the folded end 3E is preferably in a range that is not close to the ply end of the auxiliary carcass layer 7. This is because separation may be induced when close.

  The width W of the auxiliary carcass layer 7 needs to be set in accordance with the tire size and the tread pattern. As shown in FIG. 1, when the four circumferential grooves 8 are provided in the tread 5, these circumferential directions It is preferable that the groove 8 and the end portion of the auxiliary carcass layer 7 do not overlap in the tire radial direction.

  The pneumatic tire of the present invention and the pneumatic tire of the comparative example were prototyped under the specifications described later, and subjected to a plunger energy (PE) test.

As shown in FIG. 1, the invention example tire has a single-layer envelope structure carcass and is provided with an auxiliary carcass layer.
The comparative example tire 1 is the same as the example tire except that the auxiliary carcass layer is removed from the example tire.
The comparative example tire 2 has a two-ply structure.
The comparative example tire 3 is the same as the comparative example tire 1 except that the belt cord type is SO191.

Each of the test tires has a carcass of 2052, a belt of SO103 (only Comparative Example tire 3 is SO191, and a cap (belt reinforcing layer) is 7044.
The specifications of the auxiliary carcass layer are the same as the specifications of the carcass.
Further, 1P-E means that the carcass has a one-layer envelope structure, and 2P means that the carcass has a two-ply structure.
The tire weights in Table 1 indicate the amount of increase and the rate of increase from the comparative tire 1 with the comparative tire 1 as a reference.

Each test tire (tire size 215 / 45R17) was assembled to a rim to form a tire wheel, and after applying normal internal pressure, a plunger energy test (conforming to JIS D4230) was performed. The results are shown in Table 1.
The “regular internal pressure” refers to the air pressure corresponding to the maximum load capacity in the applicable size / ply rating, which is defined in JATMA YEAR BOOK issued in 2007 by the Japan Automobile Tire Association.

As can be seen from Table 1, in the tire of the present invention, the plunger energy is greatly increased with a slight increase in the tire weight as compared with the comparative tire 1.
When the belt cord type is changed between the comparative example tire 1 and the comparative example tire 3, the tire weight increases by 160 g, but the plunger energy hardly increases to 690J.
According to the present invention, it is possible to provide a pneumatic tire that achieves weight reduction of the tire by using a carcass having an envelope structure and that has improved fracture durability against protrusion input of the tread portion by providing an auxiliary carcass layer. It has become possible.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead core 3 Carcass 4 Belt 4a 1st belt layer 4b 2nd belt layer 5 Tread 6a 1st belt reinforcement layer 6b 2nd belt reinforcement layer 7 Auxiliary carcass layer 8 Circumferential groove 10 Plunger

Claims (2)

In a tire having a carcass extending in a toroidal shape between a pair of bead cores and having at least two layers of belts and a tread outside in the radial direction of the carcass,
The carcass is folded from the carcass main body portion extending in a toroidal shape between the pair of bead cores, from the inner side to the outer side in the tire width direction around the bead cores, and extends between the belt and the carcass main body portion. Having a carcass folded portion,
An auxiliary carcass layer is disposed between the terminals of the carcass folding portion and between the belt and the carcass main body portion.
A pneumatic tire characterized by that.   The pneumatic tire according to claim 1, wherein the auxiliary carcass layer is provided in a region including a tire equatorial plane.

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