JP2018122723A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire, which can achieve reduction in rolling resistance while securing abrasion resistance of a tread part.SOLUTION: A pneumatic tire 1 has a laminate structure of a belt layer 14, a base rubber layer 152 provided outside in a tire radial direction of the belt layer and a cap rubber layer 151 provided outside in the tire radial direction of the base rubber layer. A ratio of a grounding area outside attachment with respect to a vehicle in a tread surface of a tread part 3 is larger than a ratio of a grounding area inside attachment with respect to the vehicle in the tread surface. A tangent loss of the cap rubber layer 151 is larger than a tangent loss of the base rubber layer 152. A thickness of the base rubber layer 152 along a normal line leading from an end part outside in a tire radial direction outside attachment with respect to the vehicle to the tread surface in the belt layer 14 is larger than a thickness of the base rubber layer 152 along a normal line leading from an end part outside in the tire radial direction inside attachment with respect to the vehicle to the tread surface in the belt layer 14.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  In recent years, there has been an increasing demand for compatibility between steering stability and low rolling performance. In order to realize a reduction in rolling resistance, it is generally effective to reduce the hysteresis loss of the tread portion. One method is to reduce the rubber layer of the tread portion and reduce the hysteresis loss of the entire tread portion. For example, in Patent Document 1, the rubber gauge of the tread portion undertread (base rubber layer) is made thicker at the shoulder portion than at the center portion, thereby improving the steering stability and the rolling resistance coefficient (RRC). To reduce.

Japanese Patent No. 5779703

  When the cap rubber layer is reduced in order to reduce rolling resistance, there is a concern that the wear resistance is lowered, and there is room for improvement.

  This invention is made | formed in view of the above, Comprising: The objective is to provide the pneumatic tire which can implement | achieve reduction of rolling resistance, ensuring the abrasion resistance of a tread part.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to an aspect of the present invention is a pneumatic tire including a mounting direction display unit that indicates a mounting direction with respect to a vehicle, and a tread portion. The tread portion has a laminated structure of a belt layer, a base rubber layer provided on the outer side in the tire radial direction of the belt layer, and a cap rubber layer provided on the outer side in the tire radial direction of the base rubber layer, and the tire equator The ground contact area ratio of the tread surface of the tread portion with respect to the vehicle mounting outside the vehicle is larger than the ground contact area ratio of the tread surface with respect to the vehicle mounting inner side, and the tangent loss of the cap rubber layer is the base rubber. Larger than the tangent loss of the layer, with the tire equatorial plane as a reference, and the belt layer on the outer side in the tire radial direction of the vehicle on the outside The thickness of the base rubber layer along the normal line from the portion toward the tread surface is equal to the base rubber along the normal line from the end portion on the outer side in the tire radial direction on the inner side of the vehicle in the belt layer toward the tread surface. Greater than layer thickness.

  Further, the belt layer with respect to the thickness Gin of the base rubber layer along the normal line from the tire radial inner end on the vehicle inner side to the tread surface with respect to the tire equator surface as a reference. In this case, the ratio Gout / Gin of the thickness Gout of the base rubber layer along the normal line from the outer end in the tire radial direction outside the vehicle to the tread surface is Gout / Gin ≧ 2.0. preferable.

  With reference to the tire equator plane, the cap rubber layer thickness Lout along the normal line from the tire radial outer end of the belt layer on the outer side of the tire to the tread surface is attached to the tread portion. It is preferable that Lout ≧ H−2.0 mm with respect to the depth H of the provided main groove.

  Based on the tire equator plane, the thickness of the base rubber layer along the normal line from the outer end in the radial direction of the tire on the outer side of the tire in the belt layer to the tread surface is determined in the belt layer. The region GW, which is at least twice the thickness of the base rubber layer along the normal line from the outer end in the tire radial direction on the inner side to the tread surface with respect to the mounting, is based on the tire equatorial surface, and the belt The ratio GW / with respect to the area W from the intersection of the normal to the tread surface and the tread surface from the outer end in the tire radial direction on the outer side of the vehicle mounted on the vehicle to the outermost main groove end of the tread portion W is preferably 0.7 or more and 0.9 or less.

  It is preferable that the tread portion has a lug groove, and the thickness of the cap rubber layer along the normal line from the belt layer toward the tread surface at the groove bottom of the lug groove is 1.0 mm or more.

  The base rubber layer along the normal line from the arbitrary point of the belt layer on the outer side to the vehicle to the tread surface from the position of the main groove located on the outermost side of the vehicle with respect to the tire equatorial plane. The thickness of the tread surface is 0.5 mm or more, and the tread surface from an arbitrary point of the belt layer on the inner side of mounting on the vehicle from the position of the main groove positioned on the innermost side of mounting on the vehicle with respect to the tire equator surface The base rubber layer preferably has a thickness of 0.5 mm or more along a normal line directed to.

  From the tire equator plane as a reference, between the position of the main groove located on the outermost mounting position on the vehicle and the position of the main groove positioned on the innermost mounting position on the vehicle, from an arbitrary point of the belt layer to the tread surface The thickness of the base rubber layer along the normal line is preferably 0.5 mm or more.

  Based on the tire equator plane, the thickness of the base rubber layer along the normal line from the tire width direction end of the belt layer on the outer side of the mounting to the vehicle toward the tread surface is the inner side of the mounting on the vehicle. It is preferable that the thickness of the base rubber layer is three times or more along the normal line from the end of the belt layer in the tire width direction toward the tread surface.

  It is preferable that tan δ at 60 ° C. of the cap rubber layer is 0.15 or more and 0.40 or less, and tan δ of the base rubber layer is 0.05 or more and 0.15 or less.

  The rubber hardness indicated by JIS-A hardness in accordance with JIS-K6253 under the condition of 20 ° C. of the cap rubber layer is 60 or more and 80 or less, and in accordance with JIS-K6253 under the condition of 20 ° C. of the base rubber layer. The rubber hardness indicated by the JIS-A hardness is preferably from 50 to 60.

  The pneumatic tire according to the present invention reduces the rolling resistance while ensuring the wear resistance of the tread portion by changing the ratio of the base rubber layer outside the vehicle and the base rubber layer inside the vehicle in an asymmetric pattern. Can be realized.

FIG. 1 is a meridional sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a mounting inner portion of the pneumatic tire 1 with respect to the vehicle with respect to an example of a tread portion having a cross section in the tire meridian direction. FIG. 3 is an enlarged view showing a mounting outer portion of the pneumatic tire 1 with respect to the vehicle with respect to an example of a tread portion of a cross section in the tire meridian direction. FIG. 4 is an enlarged view showing a mounting outer portion of the pneumatic tire 1 with respect to the vehicle with respect to an example of a tread portion in a cross section in the tire meridian direction. FIG. 5 is an enlarged view showing a mounting outer portion of the pneumatic tire 1 with respect to the vehicle with respect to an example of a tread portion of a cross section in the tire meridian direction. FIG. 6 is an enlarged view showing a mounting outer portion of the pneumatic tire 1 with respect to the vehicle with respect to an example of a tread portion in a cross section in the tire meridian direction.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description of each embodiment, the same or equivalent components as those in the other embodiments are denoted by the same reference numerals, and the description thereof is simplified or omitted. In addition, this invention is not limited by each embodiment. The constituent elements of each embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. Further, a plurality of modifications described in this embodiment can be arbitrarily combined within the scope 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. FIG. 2 is an enlarged view showing a mounting inner portion of the pneumatic tire 1 with respect to the vehicle with respect to an example of a tread portion having a cross section in the tire meridian direction. FIGS. 3 to 6 are enlarged views of an outer portion of the pneumatic tire 1 attached to the vehicle with respect to an example of a tread portion having a cross section in the tire meridian direction. Moreover, these figures have shown the radial tire for passenger cars as an example of a pneumatic tire. The cross section in the tire meridian direction means a cross section when the tire is cut along a plane including a tire rotation axis (not shown). Reference sign CL denotes a tire equator plane, which is a plane that passes through the center point of the tire in the tire rotation axis direction and is perpendicular to the tire rotation axis. The tire width direction means a direction parallel to a tire rotation axis (not shown), and the tire radial direction means a direction perpendicular to the tire rotation axis.

  As shown in FIG. 1, a pneumatic tire 1 has an annular structure centered on a tire rotation axis, a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, and a belt layer. 14, a tread rubber 15, a pair of sidewall rubbers 16 and 16, and a pair of rim cushion rubbers 17 and 17.

  The pair of bead cores 11 and 11 has an annular structure and constitutes the core of the left and right bead portions. The pair of bead fillers 12 and 12 are disposed on the outer periphery in the tire radial direction of the pair of bead cores 11 and 11 to reinforce the bead portion.

  The carcass layer 13 is bridged in a toroidal shape between the left and right bead cores 11 and 11 to form a tire skeleton. Further, both end portions of the carcass layer 13 are wound and locked outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass layer 13 is formed by rolling a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with a coat rubber, and has an absolute value of 80 [deg]. A carcass angle of 95 [deg] or less (inclination angle in the fiber direction of the carcass cord with respect to the tire circumferential direction). In the configuration of FIG. 1, the carcass layer 13 has a single-layer structure composed of a single carcass ply. However, the present invention is not limited to this, and the carcass layer 13 has a multilayer structure formed by laminating a plurality of carcass plies. Also good.

  The belt layer 14 is formed by laminating a pair of cross belts 141 and 142 and a belt cover 143, and is arranged around the outer periphery of the carcass layer 13. The pair of cross belts 141 and 142 is formed by rolling a plurality of belt cords made of steel or organic fiber material with a coating rubber, and has an absolute value of a belt angle of 20 [deg] or more and 40 [deg] or less. Have. Further, the pair of cross belts 141 and 142 have belt angles with different signs from each other (inclination angle of the fiber direction of the belt cord with respect to the tire circumferential direction), and are laminated so that the fiber directions of the belt cords cross each other. (Cross ply structure). The belt cover 143 is formed by rolling a plurality of belt cords made of steel or organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) covered with a coat rubber, and has an absolute value of −10 [deg] or more. The belt angle is 10 [deg] or less. Further, the belt cover 143 is disposed so as to be laminated on the outer side in the tire radial direction of the cross belts 141 and 142.

  The tread rubber 15 is disposed on the outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute the tread portion 3 of the tire. The tread rubber 15 includes a cap rubber layer 151, a base rubber layer 152, and left and right wing tips 153 and 153. The cap rubber layer 151 has a tread pattern and constitutes an exposed portion (such as a tread surface) of the tread rubber 15. The base rubber layer 152 is disposed between the cap rubber layer 151 and the belt layer 14 and constitutes a base portion of the tread rubber 15. The wing tips 153 are respectively arranged at the left and right end portions of the cap rubber layer 151 in the tire width direction and constitute a part of the buttress portion.

  For example, in the configuration of FIG. 1, the base rubber layer 152 provided on the outer side in the tire radial direction of the belt layer 14 and the cap rubber layer 151 provided on the outer side in the tire radial direction of the base rubber layer 152 are stacked. It has become. The cap rubber layer 151 has a structure that covers the entire base rubber layer 152 while sandwiching the base rubber layer 152 between the belt layer 14 and the cap rubber layer 151. In addition, wing tips 153 and 153 are arranged at the boundary portions between the left and right end portions of the cap rubber layer 151 and the left and right sidewall rubbers 16 and 16, respectively, and are exposed on the surface of the buttress portion.

  The pair of sidewall rubbers 16, 16 are arranged on the outer side in the tire width direction of the carcass layer 13 to constitute the left and right sidewall portions 6. For example, in the configuration of FIG. 1, the end portion of the sidewall rubber 16 on the outer side in the tire radial direction is inserted into the lower layer of the tread rubber 15 and is sandwiched between the tread rubber 15 and the carcass layer 13. .

  The pair of rim cushion rubbers 17 and 17 are arranged on the outer sides in the tire width direction of the left and right bead cores 11 and 11 and the bead fillers 12 and 12, respectively, and constitute left and right bead portions. For example, in the configuration of FIG. 1, the end portion of the rim cushion rubber 17 on the outer side in the tire radial direction is inserted into the lower layer of the sidewall rubber 16 and sandwiched between the sidewall rubber 16 and the carcass layer 13. ing. The pair of rim cushion rubbers 17, 17 are respectively disposed on the inner side in the tire radial direction of the wound portions of the left and right bead cores 11, 11 and the carcass layer 13, and serve as contact surfaces of the left and right bead portions with respect to the rim flange (not shown). Configure.

  The tread portion 3 includes main grooves 21 and 22. The main grooves 21 and 22 may be circumferential main grooves extending in the tire circumferential direction, inclined main grooves extending in the tire circumferential direction and extending in the tire width direction, or protruding in the tire circumferential direction. And a plurality of V-shaped inclined main grooves extending in the tire width direction and opening at the left and right tread ends. In the tread portion 3, the main grooves 21, 22 define land portions 30, 31, 32. The tread portion 3 may have lug grooves that cross the land portions 30, 31, and 32.

  The main groove is a groove having a wear indicator indicating the end of wear, and generally has a groove width of 5.0 [mm] or more and a groove depth of 7.5 [mm] or more. The lug groove means a lateral groove having a groove width of 2.0 [mm] or more and a groove depth of 3.0 [mm] or more.

[Indication of vehicle mounting direction]
The pneumatic tire 1 has a mounting direction display unit (not shown) that indicates a mounting direction with respect to the vehicle. The mounting direction display part is configured by, for example, marks or irregularities attached to the sidewall part of the tire. For example, ECER30 (European Economic Commission Regulation Article 30) obligates the installation of a mounting direction display section on the side wall that is on the outer side in the vehicle width direction when the vehicle is mounted.

[Tread surface contact area ratio]
The pneumatic tire 1 is based on the tire equatorial plane CL, and the ground contact area ratio of the tread portion 3 on the tread surface with respect to the vehicle is greater than the ground contact area ratio of the tread surface with respect to the vehicle on the inner side. That is, the pneumatic tire 1 has a tread portion 3 having a tread pattern that is asymmetrical in the tire width direction with respect to the tire equatorial plane CL. By increasing the base rubber layer on the outside, which has a larger ground contact area ratio than the inner side and the shoulder block has a higher block rigidity, it is possible to suppress a decrease in the rigidity of the tread and reduce the effect on steering stability. be able to.

  Here, the contact area ratio is a value obtained by dividing the value obtained by subtracting the groove area from the contact area by the contact area. The outer shape of the contact surface of the tread portion 3 when the tread portion 3 of the pneumatic tire 1 comes into contact with the road surface is generally elliptical. The ground contact area is an area of a region surrounded by the outline of the ground contact surface of the tread portion 3. In other words, the ground contact area is an area of the ground contact surface of the tread portion 3 when it is assumed that the tread portion 3 has no groove. The groove area is the total sum of the groove openings of the grooves in the grounded tread portion 3. Here, the groove refers to a groove whose groove opening does not close even when grounded.

[Base rubber]
In FIG. 2, with reference to the tire equatorial plane CL, the thickness of the base rubber layer 152 along the normal 181 from the end of the belt 142 on the outer side in the tire radial direction outside the vehicle to the vehicle in the belt layer 14 toward the tread surface is shown. Gin, and the thickness of the cap rubber layer 151 is Lin. Further, in FIG. 3, the thickness of the base rubber layer 152 along the normal 182 from the end of the belt 142 on the inner side in the tire radial direction on the inner side of the vehicle to the vehicle to the tread surface with respect to the tire equatorial plane CL. The thickness is Gout, and the thickness of the cap rubber layer 151 is Lout. At this time, as shown in FIGS. 2 and 3, the pneumatic tire 1 has a thickness Gout larger than the thickness Gin.

  As shown in FIGS. 2 and 3, the tire equatorial plane CL is used as a reference, and the belt layer 14 is along a normal line 181 from the end of the belt 142 on the inner side in the tire radial direction on the vehicle to the tread surface. The ratio Gout / Gin of the thickness Gout of the base rubber layer 152 along the normal line 182 from the end of the belt 142 on the outer side in the tire radial direction outside the vehicle to the vehicle to the tread surface with respect to the thickness Gin of the base rubber layer 152 is Gout / Gin ≧ 2.0 is preferable. When the thickness ratio Gout / Gin is less than 2.0, the effect of reducing RRC is low, which is not preferable. That is, the thickness of the base rubber layer 152 is different between the inner side and the outer side of the vehicle, and the thickness of the base rubber layer 152 is asymmetric in the tire width direction in the meridional section. In FIG. 2, the vicinity of the intersection T where the normals 181 and 182 intersect with the tread surface is the tire ground contact end.

  Here, in FIG. 2, the thickness of the base rubber layer 152 along the normal line 191 from the end of the wide belt 141 toward the tread surface is defined as Fin. In FIG. 3, the thickness of the base rubber layer 152 along the normal 192 from the end of the wide belt 141 toward the tread surface is defined as Fout. At this time, the ratio Fout / Fin of the thickness Fout to the thickness Fin is more preferably Fout / Fin ≧ 3.0. That is, with reference to the tire equatorial plane CL, the thickness of the base rubber layer 152 along the normal line 192 from the end in the tire width direction of the belt 141 on the outer side to the vehicle to the tread surface is the belt 141 on the inner side to the vehicle. This is at least three times the thickness of the base rubber layer 152 along the normal 191 from the end in the tire width direction toward the tread surface. If the thickness Fin and the thickness Fout have such a relationship, RRC can be further reduced.

[Cap rubber]
As shown in FIG. 4, the thickness of the cap rubber layer 151 along the normal 182 from the end of the outermost layer (outer in the tire radial direction) of the belt 142 toward the tread surface from the tread surface is defined as Lout. . Further, the depth of the main groove 22 provided in the tread portion 3 is H. At this time, the relationship between the thickness Lout and the depth H is preferably Lout ≧ H−2.0 mm. By setting to such a relationship, exposure of the base rubber layer to near the wear limit can be suppressed. The depth H of the groove 22 is measured as the maximum value of the distance from the tread surface to the groove bottom in an unloaded state in which the pneumatic tire 1 is mounted on the specified rim and filled with the specified internal pressure. Moreover, in the structure which a groove | channel has a partial uneven | corrugated | grooved part and a sipe in a groove bottom, groove depth is measured except these.

  Here, the specified rim refers to an “applied rim” defined in JATMA, a “Design Rim” defined in TRA, or a “Measuring Rim” defined in ETRTO. The specified internal pressure means “maximum air pressure” specified by JATMA, the maximum value of “TIRE LOAD LIMITATIONS VARIOUS COLOR INFRATION PRESURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. In JATMA, in the case of a tire for a passenger car, the specified internal pressure is an air pressure of 180 [kPa].

[Area with thick base rubber layer]
2 and 3, with reference to the tire equatorial plane CL, the thickness Gout of the base rubber layer 152 along the normal line 182 from the outer end in the radial direction of the tire on the outside of the vehicle to the tread surface of the belt 142. Is a region from the end portion on the outer side in the tire radial direction on the inner side to the vehicle to the end 222 of the region that is more than twice the thickness Gin of the base rubber layer 152 along the normal 181 toward the tread surface. Region GW shown in FIG. Further, in FIG. 5, the tread portion 3 is determined from the intersection T of the tread surface with the normal line 182 from the end portion on the outer side in the tire radial direction on the outer side of the vehicle mounted on the vehicle to the tread surface with reference to the tire equatorial plane CL. A region up to the end 221 of the outermost main groove 22 is defined as a region W. At this time, the ratio W / GW of the region GW to the region W is preferably in the range of 0.7 to 0.9. That is, the region GW is preferably in the range of 70% to 90% of the region W. When the relationship between the region GW and the region W is outside the above range, the effect of reducing RRC is low.

[Thickness of cap rubber layer in lug groove]
As shown in FIG. 6, the pneumatic tire 1 may have lug grooves 23 in the tread portion 3. In that case, the thickness Gc of the cap rubber layer 151 at the groove bottom of the lug groove 23 is preferably 1.0 mm or more.

[Base rubber layer thickness]
By the way, with reference to the tire equator CL, the thickness of the base rubber layer 152 along the normal from the position of the main groove 22 positioned on the outermost mounting side to the vehicle to the tread surface from an arbitrary point of the outer belt 142 mounted to the vehicle. The length is 0.5 mm or more, and the method is directed from the position of the main groove 22 positioned on the innermost mounting side to the vehicle to the tread surface from an arbitrary point on the inner side of the belt layer 14 mounted on the vehicle with respect to the tire equatorial plane CL. The thickness of the base rubber layer 152 along the line is preferably 0.5 mm or more. That is, in the shoulder portions located at both ends of the tread portion 3, the thickness of the base rubber layer 152 along the normal from the arbitrary point of the belt 142 toward the tread surface is 0.5 mm or more even at the thinnest portion. Is preferred.

  Further, the tread surface from an arbitrary point of the belt 142 between the position of the main groove 22 positioned on the outermost mounting side with respect to the vehicle and the position of the main groove 22 positioned on the innermost mounting side with respect to the vehicle with respect to the tire equatorial plane CL. It is preferable that the thickness of the base rubber layer 152 along the normal line toward the surface is 0.5 mm or more. That is, in the center portion excluding both ends of the tread portion 3, the thickness of the base rubber layer 152 along the normal line from the belt 142 toward the tread surface is preferably 0.5 mm or more even at the thinnest portion.

[Physical properties of base rubber layer and cap rubber layer]
In the pneumatic tire 1, the tangent loss (tan δ) of the cap rubber layer 151 is larger than the tangent loss of the base rubber layer 152. For example, tan δ at 60 ° C. of the cap rubber layer 151 is preferably 0.15 or more and 0.40 or less, and tan δ of the base rubber layer 152 is preferably 0.05 or more and 0.15 or less. Rolling resistance can be reduced by increasing the proportion of the amount of base rubber with a small tangent loss. Further, since the rolling resistance can be reduced without reducing the total amount of rubber of the cap rubber layer and the base rubber layer, the wear resistance can be maintained.

  In the pneumatic tire 1, the rubber hardness of the cap rubber layer 151 and the rubber hardness of the base rubber layer 152 are preferably in the following ranges, for example. That is, the rubber hardness indicated by the JIS-A hardness in accordance with JIS-K6253 under the condition of 20 ° C. of the cap rubber layer 151 is 60 or more and 80 or less, and under the condition of 20 ° C. of the base rubber layer 152 JIS-K6253. It is preferable that the rubber hardness shown by the JIS-A hardness based on JIS-A is 50 or more and 60 or less.

[First embodiment]
Actual tires were evaluated using tires created under the following conditions. The tire size is 195 / 65R15, the tire air pressure is 230 [kPa], and the vehicle used for actual vehicle evaluation is an FR vehicle with a displacement of 2000 [cc]. Tires having the same size and the structures shown in Table 1 and Table 2 were prepared as comparative examples and examples, and the following (1-1), (1-2) and (1-3) were carried out.

  As a conventional tire, the pattern of the tread portion 3 is asymmetrical with respect to the equatorial plane CL, and the contact area ratio is 70% on the inner side with respect to the vehicle, 70% on the outer side, and the thickness of the base rubber on the inner side. And the thickness of the base rubber on the outer side of the mounting were symmetrical (that is, the thicknesses were equal), and the above-mentioned ratio Gout / Gin was 1.0. Since the tire of this conventional example has a depth H−2.0 mm = 4.8 mm of the main groove 22 and a thickness Lout of 9.3 mm, the relationship between the thickness Lout and the depth H is Lout ≧ H−. 2.0 mm, the thickness Gout of the base rubber outside the mounting is 1.0 mm, and the ratio Fout / Fin is 1.0.

(1-1) Rolling resistance The rolling resistance of a tire was measured and the difference was indexed. The result of the conventional example is set to 100, and the larger the index, the smaller the resistance.

(1-2) Abrasion A test tire was mounted on a vehicle, pattern running was performed on a test course, and the amount of wear was measured. The difference was indexed. The result of the conventional example is set to 100, and the larger the index, the better the performance.

(1-3) Steering stability A test tire was mounted on a vehicle, a test driver traveled on a test course, evaluated, and the difference was indexed. The result of the conventional example is set to 100, and the larger the index, the better the performance.

  In the first embodiment, as a comparative example 1, the tread portion 3 has an asymmetric pattern with reference to the equator plane CL, and the ground contact area ratio is 70% on the inner side of the vehicle, 70% on the outer side of the vehicle, and the base on the inner side of the vehicle. A tire was prepared in which the thickness of the rubber and the thickness of the base rubber on the outside of the mounting were symmetrical (that is, the thicknesses were equal), and the ratio Gout / Gin was 1.0. In the tire of Comparative Example 1, since the depth H-2.0 of the main groove 22 is 4.8 mm and the thickness Lout is 9.3 mm, the relationship between the thickness Lout and the depth H is Lout ≧ H. -2.0 mm, the thickness Gout of the base rubber outside the mounting is 0.9 mm, and the ratio Fout / Fin is 1.0.

  In the first example, as a comparative example 2, the tread portion 3 has an asymmetric pattern with the equator plane CL as a reference, and the ground contact area ratio is 65% on the inner side with respect to the vehicle, 75% on the outer side, and on the inner side. A tire was prepared in which the thickness of the base rubber and the thickness of the base rubber on the outside of the mounting were asymmetric (that is, the thicknesses were different), and the ratio Gout / Gin was 2.0. In the tire of Comparative Example 2, since the depth H−2.0 of the main groove 22 is 5.3 mm and the thickness Lout is 4.8 mm, the relationship between the thickness Lout and the depth H is Lout <H. -2.0 mm, the thickness Gout of the base rubber outside the mounting is 5.5 mm, the above ratio GW / W is 0.7, and the above ratio Fout / Fin is 2.0.

  Further, in the first embodiment, as a comparative example 3, the tread portion 3 has an asymmetric pattern with the equatorial plane CL as a reference, and the contact area ratio is 65% on the inner side with respect to the vehicle, 75% on the outer side, and on the inner side. A tire was prepared in which the thickness of the base rubber and the thickness of the outer base rubber were asymmetric (that is, the thicknesses were different) and the ratio Gout / Gin was 4.5. In the tire of Comparative Example 3, since the depth H−2.0 of the main groove 22 is 4.8 mm and the thickness Lout is 4.8 mm, the relationship between the thickness Lout and the depth H is Lout = H−. 2.0 mm, the thickness Gout of the base rubber outside the mounting is 5.5 mm, the above ratio GW / W is 0.6, and the above ratio Fout / Fin is 2.0.

  As can be seen from the first to tenth embodiments, the ground contact area ratio of the tread portion 3 on the tread surface with respect to the vehicle on the basis of the tire equatorial plane CL is larger than the ground contact area ratio on the tread surface with respect to the vehicle on the inner side of the mounting. The tangent loss of the cap rubber layer 151 is larger than the tangent loss of the base rubber layer 152, and the normal to the tread surface from the tire radial outer end of the belt layer 14 on the vehicle outer side in the belt layer 14 with reference to the tire equatorial plane CL. When the thickness of the base rubber layer 152 along the line 182 is larger than the thickness of the base rubber layer 152 along the normal line 181 from the end portion on the outer side in the tire radial direction on the inner side of the vehicle in the belt layer 14 toward the tread surface. Good results were obtained.

  Further, the belt layer 14 with respect to the thickness Gin of the base rubber layer 152 along the normal line 181 from the tire radial inner end on the vehicle inner side to the tread surface with respect to the tire equatorial plane CL as a reference. In the case where the ratio Gout / Gin of the thickness Gout of the base rubber layer along the normal line 182 from the end portion on the outer side in the tire radial direction outside the vehicle to the tread surface is Gout / Gin ≧ 2.0, Good results were obtained.

  With reference to the tire equatorial plane CL, the thickness Lout of the cap rubber layer along the normal line from the tire radial outer end of the belt layer 14 to the tread surface on the outer side of the vehicle is attached to the tread portion. Good results were obtained when Lout ≧ H−2.0 mm with respect to the depth H of the provided main groove.

  With reference to the tire equatorial plane CL, the thickness of the base rubber layer along the normal line 182 from the outer end of the outer side in the tire radial direction toward the tread surface on the belt layer 14 to the vehicle is determined by the belt layer 14 to be mounted on the vehicle. A region GW that is at least twice the thickness of the base rubber layer 152 along the normal line 181 from the inner end in the tire radial direction toward the tread surface is based on the tire equatorial plane CL, and the belt layer 14 , The ratio GW / with respect to the region W from the intersection T between the normal to the tread surface and the tread surface from the outer end of the outer side in the tire radial direction mounted to the vehicle to the end of the outermost main groove 22 of the tread 3 Good results were obtained when W was 0.7 or more and 0.9 or less.

  Further, when the tread portion 3 has the lug groove 23 and the thickness of the cap rubber layer 151 along the normal line from the belt layer 14 toward the tread surface at the groove bottom of the lug groove 23 is 1.0 mm or more. Good results were obtained.

  The thickness of the base rubber layer 152 along the normal line from the arbitrary point of the belt layer 14 on the outer side of the vehicle to the vehicle to the tread surface from the position of the main groove 22 positioned on the outermost side of the vehicle on the basis of the tire equatorial plane CL. Normal to the tread surface from an arbitrary point of the belt layer 14 on the inner side of the vehicle mounted from the position of the main groove 22 positioned on the innermost side of the vehicle with respect to the tire equatorial plane CL. Good results were obtained when the thickness of the base rubber layer 152 along the line was 0.5 mm or more.

  With reference to the tire equatorial plane CL, the belt layer 14 is located at an arbitrary point on the tread surface between the position of the main groove 22 positioned on the outermost mounting position on the vehicle and the position of the main groove 22 positioned on the innermost mounting position on the vehicle. Good results were obtained when the thickness of the base rubber layer 152 along the normal to which it goes was 0.5 mm or more.

  With reference to the tire equatorial plane CL, the thickness of the base rubber layer 152 along the normal 192 from the end in the tire width direction of the belt layer 14 on the outer side of the vehicle to the tread surface to the tread surface is equal to the belt layer 14 on the inner side of the vehicle. Good results were obtained when the thickness of the base rubber layer 152 was 3 times or more along the normal line 191 from the end in the tire width direction toward the tread surface. According to the tires of Examples 1 to 10, both the RCC reduction effect and the steering stability performance can be improved.

[Second Embodiment]
In the second embodiment, the tires of the first to tenth embodiments are mounted on the rim so that the relationship between the vehicle outer side and the vehicle inner side is opposite to that of the first embodiment, and the following (2-1), ( 2-2) and (2-3) are performed.

(2-1) Rolling resistance The rolling resistance of the tire was measured and the difference was indexed. The result of the conventional example is set to 100, and the larger the index, the smaller the resistance.

(2-2) Abrasion A test tire was mounted on a vehicle, pattern running was performed on a test course, and the amount of wear was measured. The difference was indexed. The result of the conventional example is set to 100, and the larger the index, the better the performance.

(2-3) Braking performance On a dry road surface, the distance from the initial speed of 100 km / h to braking and stopping was measured. Using the reciprocal of the measured value, comparison was made with an index. The result of the conventional example is set to 100, and the larger the index, the better the performance.

  The tires of the conventional example and the tires of Comparative Examples 1 to 3 were also mounted on the rim so that the relationship between the vehicle outer side and the vehicle inner side was opposite to that of the first example. As can be understood from Tables 3 and 4, as can be seen from Example 1 to Example 10, if the relationship between the vehicle outer side and the vehicle inner side is reversed from that of the first example, the braking performance can be improved. It has been found suitable. According to the tires of Examples 1 to 10, both the RCC reduction effect and the braking performance can be improved.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 3 Tread part 11 Bead core 12 Bead filler 13 Carcass layer 14 Belt layer 15 Tread rubber 16 Side wall rubber 17 Rim cushion rubber 21, 22 Main groove 23 Lug groove 30, 31, 32 Land part 141, 142 Belt 143 Belt Cover 151 Cap rubber layer 152 Base rubber layer 153 Wing tip CL Tire equatorial plane

Claims (10)

A pneumatic tire comprising a mounting direction display unit indicating a mounting direction with respect to a vehicle, and a tread portion,
The tread portion has a laminated structure of a belt layer, a base rubber layer provided on the outer side in the tire radial direction of the belt layer, and a cap rubber layer provided on the outer side in the tire radial direction of the base rubber layer,
Based on the tire equator plane, the contact area ratio of the tread surface of the tread portion on the outside of the vehicle mounted on the tread surface is larger than the contact area ratio of the tread surface on the inside of the vehicle mounted on the tread surface,
The tangent loss of the cap rubber layer is larger than the tangent loss of the base rubber layer,
With reference to the tire equator plane, the thickness of the base rubber layer along the normal line from the outer end in the radial direction of the tire outside the mounting to the vehicle in the belt layer toward the tread surface is the belt layer. A pneumatic tire having a thickness greater than the thickness of the base rubber layer along a normal line from the end portion on the inner side in the tire radial direction toward the tread surface to the inner side.   In the belt layer, with respect to the thickness Gin of the base rubber layer along a normal line from the tire radial outer end of the mounting inner side with respect to the vehicle to the tread surface with respect to the tire equator surface as a reference. The ratio Gout / Gin of the thickness Gout of the base rubber layer along the normal line from the outer end in the tire radial direction outside the mounting to the vehicle toward the tread surface is Gout / Gin ≧ 2.0. The described pneumatic tire.   With reference to the tire equator plane, the cap rubber layer thickness Lout along the normal line from the tire radial outer end of the belt layer on the outer side of the tire to the tread surface is attached to the tread portion. The pneumatic tire according to claim 1, wherein Lout ≧ H−2.0 mm with respect to the depth H of the provided main groove. Based on the tire equator plane, the thickness of the base rubber layer along the normal line from the outer end in the radial direction of the tire on the outer side of the tire in the belt layer to the tread surface is determined in the belt layer. The region GW which is more than twice the thickness of the base rubber layer along the normal line from the end on the tire radial outside on the inner side to the tread surface,
Outermost main groove end of the tread portion from the intersection of the normal line from the tire radial outer end portion of the belt outer layer mounted on the vehicle to the tread surface and the tread surface with respect to the tire equator plane as a reference The pneumatic tire according to any one of claims 1 to 3, wherein the ratio GW / W is 0.7 or more and 0.9 or less with respect to the region W.   The tread portion has a lug groove, and the thickness of the cap rubber layer along the normal line from the belt layer toward the tread surface at the groove bottom of the lug groove is 1.0 mm or more. Item 5. The pneumatic tire according to any one of Items 4.   The base rubber layer along the normal line from the arbitrary point of the belt layer on the outer side to the vehicle to the tread surface from the position of the main groove located on the outermost side of the vehicle with respect to the tire equatorial plane. The thickness of the tread surface is 0.5 mm or more, and the tread surface from an arbitrary point of the belt layer on the inner side of mounting on the vehicle from the position of the main groove positioned on the innermost side of mounting on the vehicle with respect to the tire equator surface The pneumatic tire according to any one of claims 1 to 5, wherein a thickness of the base rubber layer along a normal line toward the center is 0.5 mm or more.   From the tire equator plane as a reference, between the position of the main groove located on the outermost mounting position on the vehicle and the position of the main groove positioned on the innermost mounting position on the vehicle, from an arbitrary point of the belt layer to the tread surface The pneumatic tire according to any one of claims 1 to 6, wherein the thickness of the base rubber layer along the normal line is 0.5 mm or more.   Based on the tire equator plane, the thickness of the base rubber layer along the normal line from the tire width direction end of the belt layer on the outer side of the mounting to the vehicle toward the tread surface is the inner side of the mounting on the vehicle. The pneumatic tire according to any one of claims 1 to 7, wherein the pneumatic tire is at least three times the thickness of the base rubber layer along a normal line from the end of the belt layer in the tire width direction toward the tread surface. .   The tan δ at 60 ° C of the cap rubber layer is 0.15 or more and 0.40 or less, and the tan δ of the base rubber layer is 0.05 or more and 0.15 or less. The pneumatic tire according to one.   The rubber hardness indicated by JIS-A hardness in accordance with JIS-K6253 under the condition of 20 ° C. of the cap rubber layer is 60 or more and 80 or less, and in accordance with JIS-K6253 under the condition of 20 ° C. of the base rubber layer. The pneumatic tire according to any one of claims 1 to 9, wherein the rubber hardness indicated by the JIS-A hardness is 50 or more and 60 or less.

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