JP2012218496A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving heating resistant performance of a tire.SOLUTION: This pneumatic tire 1 includes: a pair of bead cores 2 and 2; a pair of bead fillers 3 and 3 respectively arranged outside in the tire radial direction of the pair of bead cores 2 and 2; a carcass layer 4 extended between the pair of bead cores 2 and 2; tread rubber 6 arranged outside in the tire radial direction of the carcass layer 4 and constituting a tread part; and a pair of sidewall rubbers 7 and 7 respectively arranged outside in the tire width direction of the carcass layer 4 and constituting right-left sidewall parts. In a cross-sectional view in the tire meridian direction, an average loss tangent tanδ_in and the cross-sectional area S_in of one side tread area and an average loss tangent tanδ_out and the cross-sectional area S_out of the other side tread area, have the relationship of 0.10≤(tanδ_in×S_in)/(tanδ_out×S_out)≤0.90.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve the heat resistance of the tire.

  In recent years, with pneumatic tires applied to heavy trucks and buses, in order to reduce fuel consumption and reduce weight (improve transportation efficiency), tire mounting methods used for vehicle drive shafts and trailer shafts have been used in the past. The dual mounting method is shifting to the single mounting method.

  In such a single mounting type pneumatic tire, (a) since the load load per one is larger than that of the dual mounting type pneumatic tire, the amount of heat generated by the tire tends to increase. In addition, (b) the vehicle inner side region of the tire mounted on the vehicle is more susceptible to the influence of brake heat, engine heat, and the like than the vehicle outer side region. Furthermore, in recent years, the demand for low-floor low-flat single tires with a flatness ratio of 55 or less is increasing. In such low-flat pneumatic tires, the above trends (a) and (b) appear. easy. For this reason, in the conventional pneumatic tire, there exists a subject which should suppress the raise of internal temperature and to improve the heat-resistant performance of a tire.

  In addition, the technique described in patent document 1 is known as a pneumatic tire relevant to this invention.

JP 2007-83913 A

  An object of the present invention is to provide a pneumatic tire capable of improving the heat resistance of the tire.

  In order to achieve the above object, a pneumatic tire according to the present invention is bridged between a pair of bead cores, a pair of bead fillers disposed on the outer side in the tire radial direction of the pair of bead cores, and the pair of bead cores. A carcass layer, a tread rubber disposed on the outer side in the tire radial direction of the carcass layer and constituting a tread portion, and a pair of sidewalls disposed on the outer side in the tire width direction of the carcass layer and constituting left and right sidewall portions A pneumatic tire comprising rubber, and ± 30 of the tire cross-section height SH in the tire radial direction centered on the tire maximum width position outside the bead filler, the carcass layer and the tread rubber in the tire width direction. An area within the range of [%] is called a side tread area, and the side tread area When the average value of the loss tangent is called the average loss tangent, the average loss tangent tanδ_in and the cross-sectional area S_in of one of the side tread regions and the average loss tangent of the other side tread region in a cross-sectional view in the tire meridian direction. The tan δ_out and the cross-sectional area S_out have a relationship of 0.10 ≦ (tan δ_in × S_in) / (tan δ_out × S_out) ≦ 0.90.

  In the pneumatic tire according to the present invention, the average loss tangent tanδ_in_up and the cross-sectional area S_in_up of the outer portion in the tire radial direction when the one side tread region is divided into two in the tire radial direction with the tire maximum width position as a boundary, It is preferable that the average loss tangent tanδ_in_low and the cross-sectional area S_in_out of the inner portion in the tire radial direction have a relationship of 0.10 ≦ (tanδ_in_up × S_in_up) / (tanδ_in_low × S_in_low) ≦ 0.90.

  Further, in the pneumatic tire according to the present invention, the average loss tangent tanδ_in_out and the cross-sectional area S_in_out of the outer portion in the tire width direction when the one side tread region is equally divided in the tire width direction, and the inner portion in the tire width direction The average loss tangent tanδ_in_in and the cross-sectional area S_in_in preferably have a relationship of 0.10 ≦ (tanδ_in_out × S_in_out) / (tanδ_in_in × S_in_in) ≦ 0.90.

  In the pneumatic tire according to the present invention, it is preferable that the sidewall rubber in one of the side tread regions is made of a plurality of rubber materials having different loss tangents.

  In the pneumatic tire according to the present invention, one side tread region is positioned on the inner side in the vehicle width direction, and the other side tread region is positioned on the outer side in the vehicle width direction to specify the mounting direction to be mounted on the vehicle. It is preferable to have.

  In the pneumatic tire according to the present invention, the nominal tire width is 355 [mm] or more, the tire flatness is 55 [%] or less, the rim diameter of the specified rim is 17.5 [inch] or more, and a single tire It is preferably applied to a heavy duty tire that employs a mounting method.

  In the pneumatic tire according to the present invention, the reference heat generation amount tanδ_in × S_in of one side tread region is set smaller than the reference heat generation amount tanδ_out × S_out of the other side tread region. When the vehicle is mounted on the inside in the vehicle width direction, heat generation in the sidewall portion on the inner side in the vehicle width direction is suppressed. Thereby, there exists an advantage which the heat-proof performance of a tire improves.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a sidewall portion of the pneumatic tire depicted in FIG. FIG. 3 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 4 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 5 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. The figure shows a heavy duty radial tire. FIG. 2 is a cross-sectional view showing a sidewall portion of the pneumatic tire depicted in FIG. 3 and 4 are explanatory views showing a modified example of the pneumatic tire shown in FIG.

  In this embodiment, the inner side in the vehicle width direction and the outer side in the vehicle width direction of the tire are defined on the basis of the vehicle mounting state of the tire.

  The pneumatic tire 1 includes a pair of bead cores 2 and 2, a pair of bead fillers 3 and 3, a carcass layer 4, a belt layer 5, a tread rubber 6, and a pair of sidewall rubbers 7 and 7. (See FIG. 1). The pair of bead cores 2 and 2 has an annular structure and constitutes the core of the left and right bead portions. The pair of bead fillers 3 and 3 are disposed on the outer circumference in the tire radial direction of the pair of bead cores 2 and 2 to reinforce the bead portion. The carcass layer 4 is bridged in a toroidal shape between the left and right bead cores 2 and 2 to constitute a tire skeleton. Further, both end portions of the carcass layer 4 are wound and locked outward in the tire width direction so as to wrap the bead core 2 and the bead filler 3. The belt layer 5 includes a plurality of stacked belt members 51 to 53 and is disposed on the outer periphery in the tire radial direction of the carcass layer 4. The tread rubber 6 is disposed on the outer circumference in the tire radial direction of the carcass layer 4 and the belt layer 5 to constitute a tread portion of the tire. The pair of side wall rubbers 7 and 7 are arranged on the outer side in the tire width direction of the carcass layer 4 to constitute left and right side wall portions.

  In this embodiment, the rim cushion rubber 82 is disposed so as to cover the winding end of the carcass layer 4 from the outer side in the tire width direction (see FIG. 2). Further, a bead rubber 81 is arranged so as to cover a part of the turn-up portion of the carcass layer 4 and the rim cushion rubber 82 from the inner side in the tire radial direction. A belt cushion rubber 83 is sandwiched between the end portion of the belt layer 5 (the innermost belt material 51) and the carcass layer 4 and extends along the carcass layer 4 inward in the tire radial direction. Further, the sidewall rubber 7 has a shape elongated in the tire radial direction, and extends from the bead portion to the shoulder portion to constitute the wall surface of the sidewall portion. At this time, the end of the side wall rubber 7 in the tire radial direction is the outer end in the tire width direction of the reversing end of the carcass layer 4, a part of the bead filler 3, the end of the bead rubber 81, and a part of the rim cushion rubber 82. Covering from. Further, the end portion of the sidewall rubber 7 on the outer side in the tire radial direction covers the side portion of the tread rubber 6 and part of the belt cushion rubber 83 from the outer side in the tire width direction.

[Side tread area, average loss tangent, and standard heating value]
Here, outside the bead filler 3, the carcass layer 4 and the tread rubber 6 in the tire width direction and within the range of ± 30 [%] of the tire cross-section height SH in the tire radial direction with the tire maximum width position A as the center. A certain region is called a side tread region (see FIG. 1). This side tread region is defined for each of the left and right sidewall portions. The rubber material constituting the side tread region is mainly the sidewall rubber 7, but other rubber materials such as a part of the rim cushion rubber 82, an end of the bead rubber 81, and a part of the belt cushion rubber 83, for example. May also be included (see FIG. 2).

  The average value of loss tangent is called average loss tangent. In this embodiment, the average loss tangent tan δ_in of the side tread region on the inner side in the vehicle width direction and the average loss tangent tan δ_out of the side tread region on the outer side in the vehicle width direction are calculated based on the following formula (1). Note that k is the number of rubber materials arranged in the side tread region. tan δk is a loss tangent of each rubber material, and is a ratio E ′ / E ″ of the storage elastic modulus E ′ and the loss elastic modulus E ″ at 60 [° C.]. In this embodiment, tan δk is a value when measured using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho) under the conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ± 2%, and a temperature of 60 [° C.]. It is used. Sk is a cross-sectional area of each rubber material in a cross-sectional view in the tire meridian direction.

  The product of the average loss tangent and the cross-sectional area is referred to as a reference heat generation amount. The smaller the reference calorific value, the smaller the actual calorific value H [kcal] during rolling of the tire, which is preferable. In this embodiment, the reference heat generation amount in the side tread region on the inner side in the vehicle width direction is tanδ_in × S_in, and the reference heat generation amount in the side tread region on the outer side in the vehicle width direction is tanδ_out × S_out.

  The tire maximum width position A and the tire cross-section height SH are measured values when the tire is mounted on a specified rim, applied with a specified internal pressure, and in a no-load state.

  Here, the prescribed rim refers to “applied rim” prescribed in JATMA, “Design Rim” prescribed in TRA, or “Measuring Rim” prescribed in ETRTO. The specified internal pressure means “maximum air pressure” specified by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. The specified load means the “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO. However, in JATMA, in the case of tires for passenger cars, the specified internal pressure is air pressure 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

[Reference calorific value of side tread area]
In recent years, with pneumatic tires applied to heavy trucks and buses, in order to reduce fuel consumption and reduce weight (improve transportation efficiency), tire mounting methods used for vehicle drive shafts and trailer shafts have been used in the past. The dual mounting method is shifting to the single mounting method.

  In such a single mounting type pneumatic tire, (a) since the load load per one is larger than that of the dual mounting type pneumatic tire, the amount of heat generated by the tire tends to increase. In addition, (b) the vehicle inner side region of the tire mounted on the vehicle is more susceptible to the influence of brake heat, engine heat, and the like than the vehicle outer side region. Furthermore, in recent years, the demand for low-floor low-flat single tires with a flatness ratio of 55 or less is increasing. In such low-flat pneumatic tires, the above trends (a) and (b) appear. easy. For this reason, in the conventional pneumatic tire, there exists a subject which should raise the heat-resistant performance of a tire by suppressing the raise of internal temperature.

  Therefore, the pneumatic tire 1 has the following configuration in order to improve heat resistance (see FIGS. 1 and 2).

  That is, the ratio (tanδ_in × S_in) / (tanδ_out × S_out) between the reference heat generation amount tanδ_in × S_in of the side tread region on the inner side in the vehicle width direction and the reference heat generation amount tanδ_out × S_out of the side tread region on the outer side in the vehicle width direction is It is preferable to have a relationship of 0.10 ≦ (tanδ_in × S_in) / (tanδ_out × S_out) ≦ 0.90, and a relationship of 0.10 ≦ (tanδ_in × S_in) / (tanδ_out × S_out) ≦ 0.80 It is more preferable. Accordingly, the reference heat generation amount tanδ_out × S_out in the side tread region on the inner side in the vehicle width direction is set to be relatively small. At this time, it is preferable that tanδ_in <tanδ_out.

  Here, the reference heat generation amounts tanδ_in × S_in and tanδ_out × S_out of each side tread region can be arbitrarily set by adjusting the average loss tangents tanδ_in and tanδ_out and the cross-sectional areas S_in and S_out of each side tread region. For example, (a) each cross-sectional area S_in, S_out is constant (S_in = S_out), and the average loss tangent tanδ_in of the side tread region on the inner side in the vehicle width direction is relatively small (tanδ_in <tanδ_out), (b) each The average loss tangent tanδ_in and tanδ_out are constant (tanδ_in = tanδ_out), and the cross-sectional area S_in of the side tread region on the inner side in the vehicle width direction is relatively small (S_in <S_out), or (c) the inner side in the vehicle width direction There is a configuration in which the average loss tangent tanδ_in and the cross-sectional area S_in of the side tread region are reduced (tanδ_in <tanδ_out and S_in <S_out), respectively.

  In general, from the viewpoint of ensuring tire uniformity, the cross-sectional areas S_in and S_out of the left and right side tread regions are preferably set equal (S_in = S_out). In such a case, the average loss tangent tanδ_in of the side tread region on the inner side in the vehicle width direction is set to be small according to the above pattern (a), and the ratio of the left and right reference calorific values (tanδ_in × S_in) / (tanδ_out × S_out) ) Is adjusted.

  The average loss tangents tanδ_in and tanδ_out of the side tread region greatly depend on the loss tangent of the side wall rubber 7 because the side wall rubber 7 occupies most of the cross-sectional area of the side tread region. Therefore, by setting the loss tangent of the sidewall rubber 7 on the inner side in the vehicle width direction to be smaller than the loss tangent of the sidewall rubber 7 on the outer side in the vehicle width direction, the ratio of the reference heat generation amount (tanδ_in × S_in) / (tanδ_out × S_out ) Can be adjusted easily.

  Further, when providing a difference in the cross-sectional areas S_in and S_out of the left and right side tread regions, for example, the thicknesses of the rubber materials (particularly, the sidewall rubber 7) constituting the left and right side tread regions are different from each other. Thus, the ratio of the reference heat generation amount (tan δ_in × S_in) / (tan δ_out × S_out) can be easily adjusted.

  Further, when the loss tangent of the rubber material is reduced, the modulus of the rubber material is also reduced. For this reason, the loss tangent of the rubber material (particularly, the sidewall rubber 7) constituting the side tread region can be appropriately set within a range in which the structural strength of the sidewall portion can be secured. Therefore, the lower limit values of the average loss tangents tan δ_in and tan δ_out depend on the loss tangent of the rubber material constituting the side tread region.

  Further, in this embodiment, the sidewall rubber 7 having a single structure and a uniform loss tangent is disposed on each of the left and right sidewall portions (see FIGS. 1 and 2). Further, the loss tangent of the sidewall rubber 7 on the inner side in the vehicle width direction is set smaller than the loss tangent of the sidewall rubber 7 on the outer side in the vehicle width direction. Thereby, the ratio of the reference heat generation amount (tan δ_in × S_in) / (tan δ_out × S_out) is adjusted to be within a predetermined range.

  However, the present invention is not limited to this, and the sidewall rubber 7 having a two-color structure or a multicolor structure may be disposed on the sidewall portion (see FIGS. 3 and 4). For example, a side wall rubber 7 having a two-color structure is disposed on one or both of the side wall portions, and the ratio of the reference calorific value (tan δ_in × S_in) / (tan δ_out × S_out) of the left and right side tread regions can be adjusted. . At this time, only the sidewall rubber 7 on the inner side in the vehicle width direction may have a two-color structure (see FIGS. 3 and 4), or only the sidewall rubber 7 on the outer side in the vehicle width direction has a two-color structure. (Not shown). Even in such a configuration, the average loss tangent tan δ_in and tan δ_out of each side tread region are defined by the above equation (1).

  For example, in the modification shown in FIG. 3, the sidewall rubber 7 on the inner side in the vehicle width direction has a two-color structure including an upper portion 71 on the outer side in the tire radial direction and a lower portion 72 on the inner side in the tire radial direction. The upper portion 71 and the lower portion 72 are made of a sheet-like rubber material having a single structure and a uniform loss tangent, and are disposed adjacent to each other in the tire radial direction with the vicinity of the tire maximum width position A as a boundary. Further, the loss tangent of the upper portion 71 is set smaller than the loss tangent of the lower portion 72. Specifically, the average loss tangent tanδ_in_up and the cross-sectional area S_in_up of the outer portion in the tire radial direction when the side tread region on the inner side in the vehicle width is divided into two in the tire radial direction with the tire maximum width position A as a boundary, and the tire radial direction The average loss tangent tanδ_in_low and the cross-sectional area S_in_low of the inner portion have a relationship of 0.10 ≦ (tanδ_in_up × S_in_up) / (tanδ_in_low × S_in_low) ≦ 0.90. Thereby, the average loss tangent tanδ_in of the sidewall rubber 7 on the inner side in the vehicle width direction is adjusted and set to be smaller than the average loss tangent tanδ_out of the sidewall rubber 7 on the outer side in the vehicle width direction. The sidewall rubber 7 on the outer side in the vehicle width direction has a single structure and a uniform loss tangent (see FIG. 1). In FIG. 3, the upper portion 71 of the sidewall rubber 7 is hatched.

  In the modification shown in FIG. 3, only the sidewall rubber 7 on the inner side in the vehicle width direction has a two-color structure. Similarly, the sidewall rubber 7 on the outer side in the vehicle width direction may have a two-color structure. (Not shown). At this time, similarly, the average loss tangent tanδ_out_up and the cross-sectional area S_out_up of the tire radial direction outer portion of the side tread region and the average loss tangent tanδ_out_low and the cross-sectional area S_out_low of the tire radial direction inner portion are 0.10 ≦ (tanδ_out_up × S_out_up) / (tan δ_out_low × S_out_low) ≦ 0.90 is preferably set.

  Further, in the modification shown in FIG. 3, the sidewall rubber 7 has a two-color structure, but the sidewall rubber 7 further has a multicolor structure including three or more rubber members having different loss tangents. (Not shown). Also in such a configuration, it is preferable that the loss tangent of the outermost rubber portion in the tire radial direction is set to be smaller than the loss tangent of the other rubber portions.

  For example, in the modification shown in FIG. 4, the sidewall rubber 7 on the inner side in the vehicle width direction has a two-color structure including an outer portion 73 on the outer side in the tire width direction and an inner portion 74 on the inner side in the tire width direction. Have. The outer portion 73 and the inner portion 74 are made of a sheet-like rubber material having a single structure and a uniform loss tangent, and are bonded together to constitute the front and back of the sidewall rubber 7. Further, the loss tangent of the outer portion 73 is set smaller than the loss tangent of the inner portion 74. Specifically, the average loss tangent tanδ_in_out and the cross-sectional area S_in_out of the outer portion in the tire width direction when the side tread region on the inner side in the vehicle width direction is divided into two in the tire width direction, and the average loss tangent tanδ_in_in of the inner portion in the tire width direction and The cross-sectional area S_in_in has a relationship of 0.10 ≦ (tanδ_in_out × S_in_out) / (tanδ_in_in × S_in_in) ≦ 0.90. Thereby, the average loss tangent tanδ_in of the sidewall rubber 7 on the inner side in the vehicle width direction is adjusted and set to be smaller than the average loss tangent tanδ_out of the sidewall rubber 7 on the outer side in the vehicle width direction. The sidewall rubber 7 on the outer side in the vehicle width direction has a single structure and a uniform loss tangent (see FIG. 1). In FIG. 4, the outer portion 73 of the sidewall rubber 7 is hatched.

  In the modification shown in FIG. 4, only the sidewall rubber 7 on the inner side in the vehicle width direction has a two-color structure. Similarly, the sidewall rubber 7 on the outer side in the vehicle width direction may have a two-color structure. (Not shown). At this time, similarly, the average loss tangent tanδ_out_out and the cross-sectional area S_out_out of the outer portion in the tire width direction of the side tread region and the average loss tangent tanδ_out_in and the cross-sectional area S_out_in of the inner portion in the tire width direction are 0.10 ≦ (tanδ_out_out × S_out_out) / (tan δ_out_in × S_out_in) ≦ 0.90 is preferably set.

  In the modification shown in FIG. 4, the sidewall rubber 7 has a two-color structure, but the sidewall rubber 7 further has a multicolor structure including three or more rubber members having different loss tangents. (Not shown). Even in such a configuration, it is preferable that the loss tangent of the outermost rubber portion in the tire width direction is set to be smaller than the loss tangent of the other rubber portions.

  The average loss tangents tanδ_in and tanδ_out of the side tread region are known loss tangents of rubber materials (for example, sidewall rubber 7, bead rubber 81, rim cushion rubber 82, belt cushion rubber 83, etc.) included in the side tread region. It can be set arbitrarily by adjusting the method. As a method for reducing the loss tangent of the rubber material, for example, a method of reducing the amount of carbon, using a carbon having a large particle diameter, or compounding silica can be employed.

[effect]
As described above, the pneumatic tire 1 includes the pair of bead cores 2 and 2, the pair of bead cores 2 and 2, the pair of bead fillers 3 and 3 disposed on the outer side in the tire radial direction, and the pair of bead cores 2. The carcass layer 4 spanned between the two, the tread rubber 6 disposed on the outer side in the tire radial direction of the carcass layer 4 and constituting the tread portion, and the left and right sides respectively disposed on the outer side in the tire width direction of the carcass layer 4 A pair of side wall rubbers 7 and 7 constituting the wall portion is provided (see FIGS. 1 and 2). Further, in a cross-sectional view in the tire meridian direction, the average loss tangent tanδ_in and the cross-sectional area S_in of one side tread region and the average loss tangent tanδ_out and the cross-sectional area S_out of the other side tread region are 0.10 ≦ (tanδ_in × S_in) / (tan δ_out × S_out) ≦ 0.90.

  In such a configuration, the reference heat generation amount tanδ_in × S_in of one side tread region is set smaller than the reference heat generation amount tanδ_out × S_out of the other side tread region, so that the tire moves the one side tread region inward in the vehicle width direction. When mounted on the vehicle toward the vehicle, heat generation in the sidewall portion on the inner side in the vehicle width direction is suppressed. Thereby, there exists an advantage which the heat-proof performance of a tire improves.

  Further, the ratio of the reference calorific value in the side tread region (tan δ_in × S_in) / (tan δ_out × S_out) is optimized, so that there is an advantage that the heat resistance performance of the tire is appropriately improved. For example, if (tan δ_in × S_in) / (tan δ_out × S_out) <0.10, the occurrence of ozone cracks in the side tread region outside the vehicle is promoted, which is not preferable. Further, when 0.90 <(tan δ_in × S_in) / (tan δ_out × S_out), the thermal degradation of the sidewall portion on the inner side in the vehicle width increases due to the influence of the brake heat of the vehicle and the engine heat, which is not preferable. .

  Further, in the pneumatic tire 1, the average loss tangent tanδ_in_up and the cross-sectional area S_in_up of the outer portion in the tire radial direction when one side tread region is divided into two in the tire radial direction with the tire maximum width position A as a boundary, and the tire diameter The average loss tangent tanδ_in_low and the cross-sectional area S_in_out of the inner portion in the direction have a relationship of 0.10 ≦ (tanδ_in_up × S_in_up) / (tanδ_in_low × S_in_low) ≦ 0.90 (see FIG. 3). When the tire is mounted on the vehicle, the outer portion in the tire radial direction is more easily affected by the brake heat and engine heat of the vehicle than the inner portion in the tire radial direction. Therefore, in the above configuration, the reference calorific value tanδ_in_up × S_in_up in the tire radial outer region is set to be smaller than the reference calorific value tanδ_in_low × S_in_low in the tire radial inner region, whereby the sidewall portion in the tire radial outer portion is set. Heat generation is suppressed. Thereby, there exists an advantage which the heat-proof performance of a tire improves.

  Further, in this pneumatic tire 1, the average loss tangent tanδ_in_out and the cross-sectional area S_in_out of the outer portion in the tire width direction when one side tread region is divided into two equal parts in the tire width direction, and the average loss tangent of the inner portion in the tire width direction tanδ_in_in and cross-sectional area S_in_in have a relationship of 0.10 ≦ (tanδ_in_out × S_in_out) / (tanδ_in_in × S_in_in) ≦ 0.90 (see FIG. 4). When the tire is mounted on the vehicle, the outer portion in the tire width direction is more easily affected by the brake heat of the vehicle and the engine heat than the inner portion in the tire width direction. Accordingly, in the above configuration, the reference calorific value tanδ_in_out × S_in_out in the outer region in the tire width direction is set to be smaller than the reference calorific value tanδ_in_in × S_in_in in the inner region in the tire width direction. Heat generation is suppressed. Thereby, there exists an advantage which the heat-proof performance of a tire improves.

  Further, in the pneumatic tire 1, the sidewall rubber 7 in one side tread region has a plurality of rubber materials having different loss tangents (for example, the upper portion 71 and the lower portion 72, the outer portion 73 and the inner portion). 74) (see FIGS. 3 and 4). Such a configuration has an advantage that the average loss tangents tanδ_in and tanδ_out in the side tread region can be easily adjusted because the sidewall rubber 7 has a multicolor structure made of a plurality of rubber materials.

  Further, as described above, the pneumatic tire 1 is mounted so that one of the side tread regions is positioned on the inner side in the vehicle width direction and the other side tread region is positioned on the outer side in the vehicle width direction. Preferably it has a direction designation. With such a configuration, there is an advantage that the tire performance is appropriately ensured by designating the tire mounting direction. It should be noted that the tire mounting direction is usually written on the side wall portion of the tire, for example, with an inside-outside designation.

[Applicable to]
In general, in a heavy duty tire in which a nominal tire width is 355 [mm] or more, a tire flatness is 55 [%] or less, a rim diameter of a specified rim is 17.5 [inch] or more, and a single mounting method is adopted. Since the load load per tire is larger than that of a dual-mounting type pneumatic tire, there is a problem that the amount of heat generated by the tire tends to increase. Therefore, by applying the configuration of the pneumatic tire 1 (see FIGS. 1 to 4) to such a heavy load tire, there is an advantage that the effect of improving the heat resistance of the tire can be remarkably obtained.

[performance test]
In this embodiment, a performance test related to heat generation resistance was performed on a plurality of pneumatic tires having different conditions. In these performance tests, a pneumatic tire having a tire size of 435 / 45R22.5 is assembled to a specified rim of JATMA, and a specified pneumatic pressure and a specified load of JATMA are applied to the pneumatic tire.

  In the performance test related to heat resistance, the temperature in the side tread region after traveling for 60 minutes under the condition of a traveling speed of 60 km / h is measured with an indoor drum tester. Further, the temperature is measured at each of four locations in the side tread region on the inner side in the vehicle width direction and the side tread region on the outer side in the vehicle width direction. Then, based on the average value of the measured temperatures, index evaluation using the conventional example as a reference (100) is performed. In this evaluation, the higher the index, the more preferable the temperature rise in the side tread region on the inner side in the vehicle width direction is suppressed. If the index is 105 or more, it is recognized that there is an advantage.

  In the pneumatic tires 1 of Examples 1 to 9, the average loss tangent tan δ_in and the cross-sectional area S_in of one side tread region and the average loss tangent tan δ_out and the cross-sectional area of the other side tread region in a cross-sectional view in the tire meridian direction S_out has a relationship of 0.10 ≦ (tan δ_in × S_in) / (tan δ_out × S_out) ≦ 0.90. The ratio of the cross-sectional areas S_in and S_out of the side tread region is in the range of 0.50 ≦ S_in / S_out ≦ 1.00.

  Moreover, in the pneumatic tire 1 of Examples 1-4, the sidewall rubber 7 has a single structure (refer FIG. 1 and FIG. 2).

  In the pneumatic tires 1 of Examples 5 and 6, the sidewall rubber 7 has a two-color structure that is divided into two in the tire radial direction (see FIG. 3). Further, the average loss tangent tanδ_in_up and the cross-sectional area S_in_up of the tire radial direction outer portion and the average loss tangent tanδ_in_low and the cross-sectional area S_in_out of the tire radial inner portion are 0.10 ≦ (tanδ_in_up × S_in_up) / (tanδ_in_low × S_in_low) ≦ 0.90.

  In the pneumatic tires 1 of Examples 7 and 8, the sidewall rubber 7 has a two-color structure that is divided into two in the tire width direction (see FIG. 4). Further, the average loss tangent tanδ_in_out and the cross-sectional area S_in_out of the outer portion in the tire width direction and the average loss tangent tanδ_in_in and the cross-sectional area S_in_in of the inner portion in the tire width direction are 0.10 ≦ (tanδ_in_out × S_in_out) / (tanδ_in_in × S_in_in) ≦ 0.90 (see FIG. 4).

  The pneumatic tire 1 of Example 9 has a tire size of 275 / 70R22.5. For this reason, the cross-sectional areas S_in and S_out of each side tread region are smaller than those of the pneumatic tires 1 of Examples 1 to 8.

  In the conventional pneumatic tire, the sidewall portions have a symmetrical structure, and the average loss tangent and the cross-sectional area of the left and right side tread regions are equal. Further, the sidewall rubber 7 has a single structure. Therefore, (tan δ_in × S_in) / (tan δ_out × S_out) = 1.00.

  As shown in the test results, it can be seen that in the pneumatic tires 1 of Examples 1 to 9, the heat resistance of the tire is improved (see FIG. 5). Further, when Example 2 is compared with Examples 5, 6 and Examples 7 and 8, the sidewall rubber 7 has a two-color structure, and loss tangents tanδ_in_up, tanδ_in_out of the predetermined portion (upper portion 71 or outer portion 73) thereof. It can be seen that the heat resistance performance of the tire is efficiently improved by setting a small value.

  1 Pneumatic tire, 2 bead core, 3 bead filler, 4 carcass layer, 5 belt layer, 6 tread rubber, 7 side wall rubber, 51 to 53 belt material, 71 upper part, 72 lower part, 73 outer part, 74 inner part , 81 Bead rubber, 82 Rim cushion rubber, 83 Belt cushion rubber

Claims (6)

A pair of bead cores, a pair of bead fillers arranged on the outer side in the tire radial direction of the pair of bead cores, a carcass layer spanned between the pair of bead cores, and an outer side of the carcass layer in the tire radial direction. A pneumatic tire comprising a tread rubber constituting a tread portion and a pair of sidewall rubbers arranged on the outer side in the tire width direction of the carcass layer and constituting left and right sidewall portions,
A region located outside the bead filler, the carcass layer, and the tread rubber in the tire width direction and within the range of ± 30 [%] of the tire cross-section height SH in the tire radial direction with the tire maximum width position as a center. When calling the average value of the loss tangent of the side tread region and the average loss tangent together with the tread region
In a cross-sectional view in the tire meridian direction, an average loss tangent tanδ_in and a cross-sectional area S_in of one side tread region and an average loss tangent tanδ_out and a cross-sectional area S_out of the other side tread region are 0.10 ≦ (tanδ_in A pneumatic tire having a relationship of × S_in) / (tanδ_out × S_out) ≦ 0.90.   When the one side tread region is divided into two in the tire radial direction with the tire maximum width position as a boundary, an average loss tangent tanδ_in_up and a cross-sectional area S_in_up of a tire radial direction outer portion, and an average loss tangent tanδ_in_low of a tire radial inner portion and The pneumatic tire according to claim 1, wherein the cross-sectional area S_in_out has a relationship of 0.10 ≦ (tan δ_in_up × S_in_up) / (tan δ_in_low × S_in_low) ≦ 0.90.   The average loss tangent tanδ_in_out and the cross-sectional area S_in_out of the outer portion in the tire width direction and the average loss tangent tanδ_in_in and the cross-sectional area S_in_in of the inner portion in the tire width direction when the one side tread region is bisected in the tire width direction, The pneumatic tire according to claim 1, wherein the pneumatic tire has a relationship of 0.10 ≦ (tan δ_in_out × S_in_out) / (tan δ_in_in × S_in_in) ≦ 0.90.   The pneumatic tire according to claim 2 or 3, wherein the sidewall rubber in one of the side tread regions is made of a plurality of rubber materials having different loss tangents.   5. One of the side tread regions is positioned on the inner side in the vehicle width direction, and the other side tread region is positioned on the outer side in the vehicle width direction to specify a mounting direction to be mounted on the vehicle. Pneumatic tire described in one.   Applicable to heavy duty tires with a nominal tire width of 355 [mm] or more, a tire flatness of 55 [%] or less, a rim diameter of a specified rim of 17.5 [inch] or more, and a single mounting method. The pneumatic tire according to any one of claims 1 to 5.

Images