JP4616072B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that can improve braking performance without impairing wear performance or rolling resistance performance.

  Conventionally, in a pneumatic tire, as a technique for improving braking performance, it is common to form a tread cap with a rubber compound having high frictional resistance. However, with this method, although the braking performance is improved, it is predicted that the wear performance and the rolling resistance performance are deteriorated.

  By the way, in Japanese Patent Laying-Open No. 2005-35405 (Patent Document 1), in order to reduce road noise and rolling resistance, an adjacent rim is disposed between a carcass and a rim flange wound around a bead core and a bead filler. It is disclosed that a damping rubber layer having a larger tan δ than the cushion is provided.

This Patent Document 1 discloses that a rubber sheet having a high loss tangent is interposed between the carcass and the rim cushion rubber in the bead portion, but does not mention the topping rubber of the carcass layer. Patent Document 1 is a technique for achieving both road noise and rolling resistance, and does not disclose the braking performance targeted by the present invention.
JP 2005-35405 A

  The present invention provides a pneumatic tire capable of improving the braking performance without deteriorating the reverse performance by disposing a rubber having a high loss tangent in a predetermined region in the width direction of the topping rubber of the carcass layer. For the purpose.

  The present inventor considered that the energy required for braking, that is, the energy consumed during braking, contributed greatly to the loss energy due to rubber hysteresis. For this reason, a tire with a large difference between the loss energy during braking and the loss energy during steady load loading consumes a large amount of energy and is considered to improve braking performance. And when this loss energy was analyzed, the site | part with a large loss energy discovered that it was a topping rubber in the bead core part of a carcass layer. For this reason, if a topping rubber with a high loss tangent is arranged in the part so that the loss energy of this part becomes high, the braking performance can be improved without impairing the reverse performance such as wear performance and rolling resistance performance. As a result, the present invention was reached.

  That is, the pneumatic tire according to the present invention is arranged on the outer side in the radial direction of the carcass in the tread portion and the carcass formed of at least one carcass layer that is locked by the bead core of the bead portion from the tread portion through the buttress portion. A pneumatic tire including a plurality of belt layers, wherein the carcass layer is formed by covering a carcass cord with a topping rubber, and the topping rubber of the carcass layer is topped at a bead core portion that wraps the bead core. The rubber is made of a rubber having a higher loss tangent than the topping rubber at the tread center portion.

  Here, the topping rubber of the carcass layer is not only the bead core part, but also the topping rubber in the bead part including the bead core part is made of a rubber having a higher loss tangent than the topping rubber in the tread center part. Also good. The bead core portion or the topping rubber of the bead portion preferably has a loss tangent at a temperature of 25 ° C. of 0.15 to 0.50.

  According to the present invention, the rubber constituting the carcass layer is braked by increasing the loss energy of the bead core portion by using the rubber having a higher loss tangent than the tread center portion for the bead core portion having a large contribution of the energy loss rate. Therefore, it is possible to effectively obtain the energy required for this purpose, and thus it is possible to improve the braking performance without impairing other performance. The contribution of the bead core part in this way is considered to be due to an increase in distortion around the bead part, particularly the bead core during braking, because the bead part is in contact with the wheel.

  Further, according to the present invention, it is not necessary to change the blending of the tread cap rubber in order to improve the braking performance, so that it is possible to suppress the deterioration of the contradiction performance such as the wear performance and the rolling resistance performance.

  Hereinafter, a pneumatic tire according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view in the tread width direction of a pneumatic tire 10 according to a first embodiment of the present invention. The tire 10 includes a pair of left and right bead portions BD and a buttress portion BAT, and a tread portion TR that extends between the buttress portions BAT.

  The bead portion BD is provided with an annular bead core 18 formed by winding a bead wire in the tire circumferential direction, and a rubber bead filler 20 is disposed on the outer periphery in the radial direction of the bead core 18.

  A carcass 22 is provided between the pair of left and right bead cores 18. The carcass 22 passes from the tread part TR through the padless part BAT, and is locked by being folded back from the inside to the outside by the bead core 18 in the bead part BD. The carcass 22 includes at least one carcass layer in which carcass cords (not shown) made of organic fiber cords are arranged at right angles to the tire circumferential direction. In this embodiment, the carcass layer 24 includes one carcass layer 24. . The carcass layer 24 is constituted by covering the front and back of a cord array composed of a plurality of carcass cords arranged in parallel as described above with topping rubber.

  A belt 26 is disposed on the outer side in the radial direction of the carcass 22 in the tread portion TR. The belt 26 is provided so as to overlap the radial outer peripheral surface of the crown portion of the carcass 22, and at least a belt layer formed by inclining and arranging a non-extensible belt cord such as a steel cord at a shallow angle with respect to the tire circumferential direction. Two layers are overlapped so that the belt cords intersect each other, and in this embodiment, the belt cord is composed of two layers of an inner first belt layer 28 and an outer second belt layer 30. Among them, the inner first belt layer 28 adjacent to the carcass 22 is wider, that is, the first belt layer 28 is the maximum width belt layer. These belt layers 28 and 30 are configured by covering the front and back of a cord array composed of a plurality of belt cords arranged in parallel as described above with topping rubber.

  In this embodiment, in the present embodiment, the topping rubber of the carcass layer 24 is configured as follows. That is, as shown in FIG. 2, the topping rubber 38a of the bead portion BD is made of a rubber having a higher tan δ than the topping rubber 38b of the tread center portion CE.

  More specifically, the topping rubber 38a of the bead portion BD is made of a rubber having a higher tan δ than the other regions, that is, the tread center portion CE, the tread shoulder portion SH, and the topping rubber 38b of the dressless portion BAT. Further, rubber having a tan δ of 0.1 to 0.3 is used as the topping rubber 38b in the region other than the bead portion BD including the tread center portion CE, whereas the tan δ of the topping rubber 38a of the bead portion BD is 0.00. A rubber of 15 to 0.50 is used. Further, the difference between tan δ of the topping rubber 38a of the bead portion BD and tan δ of the topping rubber 38b of the tread center portion CE is preferably 0.05 or more.

  Here, the loss tangent tan δ is a viscoelastic spectrometer (manufactured by UBM). For a sample having a width of 5 mm, a thickness of 1 mm, and a length of 20 mm, the initial strain is 10%, the dynamic strain is 3%, the frequency is 15 Hz, and the temperature is 25 ° C. It is the value measured under the conditions.

  Further, the bead portion BD is an area radially inward from the maximum tire cross-sectional width position 32 (a position where the width is maximum in a cross section obtained by cutting the tire in the tread width direction) in the tire 10 after vulcanization molding. It is.

  Further, the tread shoulder portion SH is a side portion in the range of 15 to 35% of the width W from each width direction end 28A of the first belt layer (maximum width belt layer) 28 in the tire 10 after vulcanization molding. It is an area portion, more preferably a side area portion within a range of 20 to 30% of the width W. In this embodiment, 25% of the width W, that is, the width W is set in the tread width direction. It is the outer side section when divided into four equal parts.

  The tread center portion CE is a remaining central area portion of the tread shoulder portion SH in the width W of the first belt layer 28. In this embodiment, the center when the width W is equally divided into four in the tread width direction. It is a central area part consisting of two sections.

  Furthermore, the tread portion TR is an area where the tread center portion CE and the tread shoulder portion SH are combined.

  The padless portion BAT is a section from each width direction end 28A of the first belt layer 28 to the maximum tire cross-sectional width position 32 along the tire outer periphery.

  In order to make the topping rubber of the carcass layer 24 different in a predetermined region in the width direction in this way, for example, a rubber sheet in which a rubber having a high tan δ is disposed in a predetermined region in the width direction is aligned. The front and back sides of the code array may be sandwiched between the rubber sheets. Alternatively, when the cords are covered one by one with the topping rubber and are arranged to form the carcass layer 24, the cords covered with the topping rubber having a high tan δ may be arranged in a predetermined region in the width direction. Good.

  In the pneumatic tire 10 of the present embodiment configured as described above, the rubber 38a having a higher tan δ than the other portions is used for the bead portion BD for the topping rubber of the carcass layer 24. It is possible to increase the energy and effectively obtain the energy necessary for braking, and thus it is possible to improve the braking performance without impairing other performance. In particular, since a rubber having a high tan δ is used for the topping rubber 38 itself that is in direct contact with the cord of the carcass 22 in this way, compared with a case where a rubber sheet having a high tan δ is disposed outside the carcass 22, Loss energy can be increased more effectively and the braking performance can be improved.

  FIG. 3 is a schematic cross-sectional view of the carcass 22 according to the second embodiment. In this embodiment, as for the topping rubber of the carcass layer 24, only the bead core portion BC is formed of the rubber 38a having a higher tan δ than other portions.

  That is, the topping rubber of the carcass layer 24 is such that the topping rubber 38a of the bead core portion BC is more than the topping rubber 38b in a region other than the bead core portion BC in the tread center portion CE, tread shoulder portion SH, padless portion BAT, and bead portion BD. Made of rubber with high tan δ.

  Here, the bead core portion BC is a portion that wraps the bead core 18, and more specifically, a carcass portion that is in contact with the bead core 18 so as to wrap the bead core 18 from the lower side. Further, the tan δ of each of the topping rubbers is in the range of 0.15 to 0.50 for the bead core portion BC and in the range of 0.1 to 0.3 for the other portions, as in the first embodiment. The difference between the two is preferably 0.05 or more. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  As described above, the portion where the contribution of the energy loss rate to the braking performance is large is the bead core portion BC among the bead portions BD. Therefore, by using the topping rubber 38a having a high tan δ only in this portion, the rolling resistance is deteriorated. While suppressing more reliably, the braking performance can be improved.

  Note that when the topping rubber of the bead portion BD is made of a rubber having a high tan δ as in the first embodiment, it is not always necessary to use a rubber having a high tan δ throughout the bead portion, and the vicinity including the bead core portion BC. By using rubber having a high tan δ at the portion, it is possible to suppress the deterioration of rolling resistance as much as possible.

  Further, in the present invention, for example, in the second embodiment, a tread shoulder portion may be used as long as a rubber having a tan δ higher than that of the tread center portion CE is used as the topping rubber of the bead core portion BC or the bead portion BD. A rubber having a high tan δ similar to that of the bead core part BC can be used for the SH and the padless part BAT.

(Examples 1 and 2 and Comparative Examples 1 and 2)
As the tires of Examples 1 and 2 and Comparative Examples 1 and 2, pneumatic radial tires having a cross-sectional structure shown in FIG. 1 were prepared as tire sizes: 215 / 65R16 and configured as shown in Table 1 below. Here, Comparative Example 1 is a control tire, and Comparative Example 2 is a tire whose braking performance is improved by the conventional method. Compared with Comparative Example 1, the rubber composition of the tread cap improves the braking performance. The tire has the same configuration as that of Comparative Example 1 except that the composition of resistance is changed. Further, in Examples 1 and 2, the topping rubber configuration of the carcass layer is changed as shown in Table 1 with respect to Comparative Example 1 (Example 1 is an example shown in FIG. 2, Example 2 is shown in FIG. 3). The other tires have the same configuration as that of Comparative Example 1. Further, the composition of each topping rubber is as shown in Table 2 below. In Table 1, the friction coefficient of the tread cap of each tire is displayed as an index with Comparative Example 1 as 100.

  The tires of Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated and measured for braking performance, wear performance, and rolling resistance. Evaluation and measurement methods are as follows.

-Braking performance: Rim used: 17 x 7.5 JJ, air pressure: 220 kPa, and each tire is mounted on a 2500 cc passenger car. After accelerating the passenger car to 100 km / h in the run-up section and maintaining the test speed of 100 km / h in the initial speed adjustment section, at the same time as passing through the braking start point, the brake pedal is quickly stepped on and maintained until it stops. Read the stop distance. The result is an inverse exponential display with the stopping distance of Comparative Example 1 being 100, and the larger the value, the better the braking performance.

Wear performance: Rim used: 17 x 7.5 JJ, air pressure: 220 kPa, each tire is mounted on a 2500 cc passenger car and travels 10,000 km on a test course (mixed urban area and highway). The amount of wear of the tread center portion CE and the tread shoulder portion SH is measured, and the average of both is calculated. The results are index evaluated with the wear amount of Comparative Example 1 being 100, and the larger the value, the better the wear performance.

Rolling resistance: Measured according to the test method of ISO / WD 18164, indexed with the rolling resistance of Comparative Example 1 as 100, and the smaller the value, the better the rolling resistance performance.

  As shown in Table 1, in Comparative Example 2 according to the conventional method, although the braking performance was improved as compared with Comparative Example 1, the wear performance and the rolling resistance were deteriorated. On the other hand, in Example 1, although the rolling resistance was slightly deteriorated, the braking performance was greatly improved while suppressing the deterioration as compared with Comparative Example 2 and without impairing the wear performance at all. Further, in Example 2, the braking performance was improved without impairing the wear performance and the rolling resistance at all.

It is a tread width direction sectional view of a pneumatic tire concerning an embodiment of the present invention. It is a cross-sectional schematic diagram of the carcass in 1st Embodiment. It is a cross-sectional schematic diagram of the carcass in 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Pneumatic tire, 18 ... Bead core, 22 ... Carcass, 24 ... Carcass layer, 26 ... Belt, 28 ... 1st belt layer (maximum width belt layer), 30 ... 2nd belt layer, 38a ... tan-delta of a carcass layer High topping rubber, 38b ... Topping rubber with low tan δ of the carcass layer, TR ... Tread part, CE ... Tread center part, SH ... Tread center part, BAT ... Buttress part, BD ... Bead part, BC ... Bead core part

Claims (3)

A carcass composed of at least one carcass layer locked from a tread portion through a buttress portion with a bead core of a bead portion, and a belt composed of a plurality of belt layers arranged radially outward of the carcass in the tread portion. A pneumatic tire,
The carcass layer is formed by covering a carcass cord with a topping rubber, and the topping rubber of the carcass layer is made of a rubber having a higher loss tangent than the topping rubber at the bead core portion wrapping the bead core than the topping rubber at the tread center portion. A pneumatic tire characterized by that.   2. The pneumatic tire according to claim 1, wherein the topping rubber of the carcass layer is made of a rubber having a higher loss tangent than a topping rubber in a bead portion including the bead core portion than a topping rubber in a tread center portion.   The pneumatic tire according to claim 1 or 2, wherein the topping rubber of the bead core portion has a loss tangent at a temperature of 25 ° C of 0.15 to 0.50.

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