JP2019093860A - Pneumatic tire - Google Patents

Abstract

To improve an uneven wear resistance of a shoulder part while improving a rolling resistance.SOLUTION: A pneumatic tire 1 comprises: two circumferential direction main grooves which extend in a tire circumferential direction; at least one circumferential direction narrow groove which is located between two circumferential direction main grooves; and a land part which is partitioned by at least one circumferential direction narrow groove and two circumferential direction main grooves. A ratio of a width in a tire width direction of an arrangement range of the land part to a tread development width is 0.55 to 0.70, and a ratio of a groove width of the circumferential direction narrow groove to two circumferential direction main grooves is 0.15 to 0.45. In a tire meridian cross section, a tread radius RA from a tire equator plane CL to a ground contact end is larger than a tread radius RC from the tire equator plane CL to a tire width direction outer side end of the circumferential direction main groove.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  DESCRIPTION OF RELATED ART Conventionally, the pneumatic tire aiming at the noise suppression of a block pattern and a bearing-resistant improvement is known. For example, there is known a pneumatic tire in which circumferential main grooves are disposed in a zigzag manner and the zigzags are disposed so as to be displaced in the circumferential direction (for example, Patent Document 1).

JP 2012-76658 A

  By the way, as a method of improving rolling resistance (RRC; Rolling Resistance Coefficient), a wide block row may be arranged at the center. As described above, when the block row is brought close to the center portion to increase the rigidity of the center region, there is a concern that the contact shape changes and uneven wear may occur in the shoulder portion. The conventional pneumatic tire described above has room for improvement in suppressing uneven wear while improving rolling resistance.

  The present invention has been made in view of the above, and an object thereof is to provide a pneumatic tire capable of suppressing uneven wear of a shoulder portion while improving rolling resistance.

  In order to solve the problems described above and to achieve the object, a pneumatic tire according to an aspect of the present invention includes two circumferential main grooves extending in the tire circumferential direction and a space between the two circumferential main grooves. The tire having a land portion defined by at least one circumferential narrow groove and the land portion defined by the at least one circumferential thin groove and the two circumferential main grooves The ratio of the width in the width direction to the tread development width TDW is 0.55 or more and 0.70 or less, and the ratio of the groove width of the circumferential narrow groove to the groove width of the two circumferential main grooves is 0. The tread radius RC from the tire equatorial plane to the tire width direction outer end of the circumferential main groove in the tire meridional section and the tread radius RA from the tire equatorial plane to the ground end in the tire meridional section The relationship with is RC <RA.

  The ratio of the groove width of the circumferential narrow groove to the tread spread width TDW is 0.007 or more and 0.024 or less, and the ratio of the groove width of the two circumferential main grooves to the tread spread width TDW is 0 It is preferable that it is .025 or more and 0.055 or less.

  The land portion is divided into blocks by lug grooves extending in the tire width direction, and the ratio of the groove width of the lug grooves to the tread development width TDW is preferably 0.003 to 0.016. .

  It is preferable that ratio RC / RA of the said tread radius RC with respect to the said tread radius RA is 0.60 or more and 0.90 or less.

  In the tire meridional section, the ratio RS / RA of the tread radius RS from the tire width direction outer end of the circumferential main groove to the tread edge relative to the tread radius RA is 0.50 or more and 1.20 or less preferable.

  It is preferable that the relationship of the said tread radius RS, the said tread radius RC, and the said tread radius RA is RS <RC <RA.

  In the tire meridional section, the total gauge of the center along the tire equatorial plane is Tc, the width from the center to the end of the circumferential main groove on the outer side in the tire width direction is We, and the width from the center to the tire The total gauge at the position of 0.33 We toward the outside in the direction T1, the total gauge at the position of 0.66 We toward the outside in the tire width direction from the center portion T2, the outer end of the circumferential main groove in the tire width direction Assuming that the total gauge at the position of the part is T3, it is preferable that Tc ≧ T1 ≧ T2 ≧ T3 and T3 / Tc ≦ 0.98.

  It is 1.10 ≦ Tsh / Tc ≦ 1.50 when a shoulder portion total gauge including a carcass layer and measured along a normal drawn from the ground end to the center of the thickness of the carcass layer is Tsh. preferable.

Assuming that the belt width on the side where the width in the tire width direction is smaller is W _B0 and the total tire width is Wt of the cross belt disposed in the tread portion, 0.72 ≦ W _B0 /Wt≦0.82 preferable.

When the width of the belt disposed on the outer side in the tire radial direction is W _BO and the carcass cross-sectional width is W _C among the pair of cross belts, it is preferable that W _BO / W _C 0.70.74.

Assuming that the outer diameter of the position along the tire equatorial plane is D _C and the outer diameter of the position of the ground contact end is D _S , the diameter difference | D _C −D _S | of the pneumatic tire is D _D It is preferable that D _D /TDW≦0.085.

  The aspect ratio, which is a percentage of the ratio of the height of the section of the tire to the width of the section of the tire, is preferably 70% or less.

  ADVANTAGE OF THE INVENTION The pneumatic tire concerning this invention can suppress generation | occurrence | production of the partial abrasion of a shoulder part, improving rolling resistance.

FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire. FIG. 3 is a cross-sectional view in the tire meridian direction showing the pneumatic tire. FIG. 4 is a diagram showing a part of FIG. 3 in an enlarged manner. FIG. 5 is a cross-sectional view in the tire meridian direction showing the pneumatic tire. FIG. 6 is a diagram showing a part of FIG. 5 in an enlarged manner. FIG. 7 is a view for explaining the relationship between the tread radius at the center portion on the tire equatorial plane and the tread radius at the shoulder portion. FIG. 8 is a view for explaining the relationship between the tread radius at the center portion on the tire equatorial plane and the tread radius at the shoulder portion. FIG. 9 is a view for explaining the relationship between the tread radius at the center portion on the tire equatorial plane and the tread radius at the shoulder portion. FIG. 10 is a developed view showing another example of the tread pattern of the pneumatic tire. FIG. 11 is a developed view showing another example of the tread pattern of the pneumatic tire. FIG. 12 is a developed view showing another example of the tread pattern of the pneumatic tire.

  Hereinafter, embodiments of the present invention will be described in detail based on the drawings. In the following description of each embodiment, the same or equivalent components as or to those of the other embodiments are denoted by the same reference numerals, and the description thereof will be simplified or omitted. The present invention is not limited by the embodiments. Further, constituent elements of each embodiment include those that can be easily replaced by persons skilled in the art or those that are substantially the same. A plurality of modifications described in this embodiment can be arbitrarily combined within the scope of one skilled in the art.

  FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire 1 according to an embodiment of the present invention. FIG. 1 shows a cross-sectional view of one side region in the tire radial direction of the pneumatic tire 1 (hereinafter, may be simply referred to as the tire 1). FIG. 2 is a development view showing a tread pattern of the pneumatic tire 1.

  In FIG. 1, the cross section in the tire meridian direction refers to a cross section when the tire is cut along a plane including a tire rotation axis (not shown). Further, a reference symbol CL is a tire equatorial plane, which means a plane perpendicular to the tire rotation axis passing through the center point of the tire in the tire rotation axis direction. Further, the tire width direction means a direction parallel to the tire rotation axis, and the tire radial direction means a direction perpendicular to the tire rotation axis.

  In FIG. 1, the pneumatic tire 1 includes a pair of bead cores 11 and 11, a carcass layer 13, a belt layer 14, a tread rubber 15 constituting a tread portion 20, and sidewall rubbers constituting left and right sidewall portions. 16 and 16 and rim cushion rubbers 17 and 17 that constitute left and right bead portions. The belt layer 14 is configured by laminating a plurality of belt plies. In FIG. 1, the belt layer 14 has a configuration in which a high angle belt 141, a pair of cross belt plies 142 and 143, and a belt cover 144 are stacked. A bead filler may be provided on the outer side of the bead core 11 in the tire radial direction. In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

[Tread section]
As shown in FIG. 2, the tread portion 20 has a first circumferential main groove 21 extending in the tire circumferential direction at the position of the tire equatorial plane CL, and a first circumferential main groove 21 on both sides of the tire equatorial plane CL. A pair of second circumferential main grooves 22 extending in the tire circumferential direction at a position further outward in the tire width direction than the second circumferential main groove 22 and a pair of third circumferential grooves extending in the tire circumferential direction at a position in the tire width direction And a circumferential main groove 23.

  The first circumferential main groove 21, the second circumferential main groove 22, and the third circumferential main groove 23 are five circumferential main grooves extending in the tire circumferential direction. It is preferable that the second circumferential main groove 22 and the third circumferential main groove 23 be disposed in symmetrical positions with respect to the tire equatorial plane CL. The groove depth of each of the first circumferential main groove 21, the second circumferential main groove 22, and the third circumferential main groove 23 is, for example, 13 mm or more and 23 mm or less. The first circumferential main groove 21, the second circumferential main groove 22, and the third circumferential main groove 23 are grooves having a display duty of a wear indicator defined in JATMA at the groove bottom.

  Here, the groove width of the first circumferential main groove 21 is W1, the groove width of the second circumferential main groove 22 is W2, and the groove width of the third circumferential main groove 23 is W3. The groove width W3 of the third circumferential main groove 23 is larger than the groove width W1 of the first circumferential main groove 21 and the groove width W2 of the second circumferential main groove 22. The groove width is the distance between the opposing wall surfaces of the groove.

  The tread portion 20 has a total of three first circumferential main grooves 21 and second circumferential main grooves 22 which are circumferential narrow grooves in this example. However, the tread portion 20 may be provided with a total of one, ie, at least one, of the first circumferential main groove 21 and the second circumferential main groove 22 which are circumferential narrow grooves. The groove widths of the first circumferential main groove 21 and the second circumferential main groove 22 which are circumferential narrow grooves are preferably 0.007 or more and 0.024 or less with respect to the tread development width TDW, and 0.010 or more It is more preferable that it is 0.020 or less. The groove width W1 and the groove width W2 are, for example, 1 [mm] or more and 5 [mm] or less. The groove width W3 is, for example, 5 [mm] or more and 15 [mm] or less. The groove width W1 of the first circumferential main groove 21, the groove width W2 of the second circumferential main groove 22, and the groove width W3 of the third circumferential main groove 23 are not limited to the above ranges.

  The tread portion 20 is divided into a plurality of land portions by forming the first circumferential main groove 21, the second circumferential main groove 22, and the third circumferential main groove 23. Specifically, in the tread portion 20, the land portion between the first circumferential main groove 21 and the second circumferential main groove 22 becomes a first land portion 31 extending in the tire circumferential direction. The first land portion 31 is divided into a plurality of blocks 31B by lug grooves 24 extending in the tire width direction. That is, the first land portion 31 is constituted by a plurality of blocks 31 B divided by the lug grooves 24 and arranged in the tire circumferential direction.

  In the tread portion 20, a land portion between the second circumferential main groove 22 and the third circumferential main groove 23 becomes a second land portion 32 extending in the tire circumferential direction. The second land portion 32 is divided into a plurality of blocks 32B by lug grooves 24 extending in the tire width direction. That is, the second land portion 32 is constituted by a plurality of blocks 32B divided by the lug grooves 24 and arranged in the tire circumferential direction.

  Here, as shown in FIG. 2, in the tread portion 20, all the lug grooves 24 face the end in the tire width direction more than the end in the tire width direction toward one side in the tire rotation direction. Have a directional pattern. For example, when the upper side in FIG. 2 is the kicking side in the tire rotation direction and the lower side in FIG. 2 is the treading-in side in the tire rotation direction, all the lug grooves 24 are in the tire width direction than the end portions in the tire width direction The inner end is directed to the tread-in side of the tire rotation direction. That is, in the land portions 31 and 32 on both sides of the tire equatorial plane CL, the lug grooves 24 are inclined with respect to the tire width direction such that the inclination direction of the lug grooves 24 is V-shaped. In the land portions 31 and 32 on both sides of the tire equatorial plane CL, the inclination of the lug grooves 24 is V-shaped, thereby improving the traction performance.

  In the tread portion 20, the ratio of the length WH in the tire width direction of the arrangement range of the blocks 31B and 32B to the tread development width TDW is preferably in the range of 0.55 or more and 0.70 or less, preferably 0.60 or more and 0 More preferably, it is not more than .65. By arranging the wide block in this range, the rigidity of the tread portion 20 can be enhanced and the rolling resistance can be reduced. Here, in the tread portion 20, the lengths in the tire width direction of the blocks 31B and 32B are set to Wa1 and Wa2. The length WH is a width including all block rows except the shoulder portion, that is, WH = W1 + 2 × Wa1 + 2 × W2 + 2 × Wa2. It is preferable that the ratios Wa1 / TDW and Wa2 / TDW of the lengths Wa1 and Wa2 to the tread development width TDW are both 0.15 or more and 0.20 or less. The smaller the ratio Wa1 / TDW or Wa2 / TDW, the smaller the rigidity of the block. If the ratios Wa1 / TDW and Wa2 / TDW are in the above ranges, drainage performance can be improved while suppressing rolling resistance. The tread development width TDW is a distance in the tire width direction of both ends in the tire width direction of the third land portion 33 which is two shoulder land portions. The tread spread width TDW refers to a linear distance between both ends in the developed view of the tread portion 20 of the tire 1 when no load is applied in a state where the tire 1 is rim-assembled to a prescribed rim and filled with a prescribed internal pressure.

  Further, in the tread portion 20, the first circumferential main groove 21 other than the outermost third circumferential main groove 23 adjacent to the land portion on the outermost side in the tire width direction among the plurality of land portions, the second circumferential main groove The ratio of the groove width of 22 to the tread development width TDW is preferably 0.007 or more and 0.024 or less, and more preferably 0.010 or more and 0.020 or less. In the tread portion 20, the outermost third circumferential main of the groove width W1 of the first circumferential main groove 21 other than the outermost third circumferential main groove 23 and the groove width W2 of the second circumferential main groove 22 The ratio W1 / W3 to the groove width W3 of the groove 23 and the ratio W2 / W3 are both preferably 0.15 or more and 0.45 or less, and more preferably 0.30 or more and 0.40 or less.

  As described above, the tread portion 20 divides the first land portion 31 and the second land portion 32 by the first circumferential main groove 21 and the second circumferential main groove 22 having a narrow groove width, whereby the tread portion 20 is grounded. The first circumferential main groove 21 and the second circumferential main groove 22 are closed, and the blocks 31B and 32B function as wide blocks. The wide blocks of blocks 31B and 32B reduce rolling resistance. The positions of the block 31B in the tire circumferential direction are shifted with respect to the left and right land portions 31, 31 sandwiching the tire equatorial plane CL. By shifting the position in the tire circumferential direction, noise when the pneumatic tire 1 is in contact with the ground can be reduced.

  Furthermore, in the tread portion 20, the ratio of the groove width W3 of the third circumferential main groove 23 on the outermost side in the tire width direction to the tread development width TDW is preferably 0.025 or more and 0.055 or less, and 0.030 More preferably, it is at least 0.050. In the tread portion 20, the ratio of the groove width of the lug grooves 24 to the tread development width TDW is preferably 0.003 or more and 0.016 or less, and more preferably 0.007 or more and 0.012 or less. The lug groove 24 preferably has a groove depth DL of 5.0 mm or more and 20.0 mm or less.

  The ratio of the vertical length to the horizontal length of the block 31B constituting the land portion 31, that is, the aspect ratio is preferably 1.10 or more and 1.70 or less, and is 1.20 or more and 1.50 or less. Is more preferred. The same applies to the blocks 32B of the other land portions 32. If an aspect ratio is a value of this range, the drainage effect and the rolling resistance inhibitory effect by supporting of blocks will be large. The aspect ratio is a ratio of the maximum value LB of the length L in the tire circumferential direction of the block 31B to the maximum value of the length E in the tire width direction of the block 31B.

  Preferably, the ratio of the maximum value LB of the length L of the block 31B in the tire circumferential direction to the outer circumferential length of the tire along the tire circumferential direction is 0.010 or more and 0.030 or less. The tire outer peripheral length can be calculated by multiplying the diameter of the pneumatic tire 1 by the circumference ratio π. The diameter of the pneumatic tire 1 is measured as an unloaded state while attaching the pneumatic tire 1 to a prescribed rim and applying a prescribed internal pressure (for example, 900 kPa).

  Here, the defined rim refers to the “application rim” defined in JATMA, the “design rim” defined in TRA, or the “measuring rim” defined in ETRTO. Further, the specified internal pressure means the "maximum air pressure" defined in JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES" defined in TRA, or "INFLATION PRESSURES" defined in ETRTO. The specified load means the "maximum load capacity" defined in JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined in TRA, or "LOAD CAPACITY" defined in ETRTO. However, in the case of a passenger car tire in JATMA, the prescribed internal pressure is the air pressure of 180 [kPa], and the prescribed load is 88 [%] of the maximum load capacity.

[Shoulder]
Returning to FIG. 2, in the tread portion 20, the land portion on the outer side in the tire width direction of the third circumferential main groove 23 which is the outermost circumferential main groove is the third land portion 33. The third land portion 33 is a shoulder land portion located in the shoulder portion of the tread portion 20. The third land portion 33 may have a shoulder lug groove (not shown) extending in the tire width direction, and may be divided into a plurality of blocks by the shoulder lug groove. In that case, the groove width of the shoulder lug groove is preferably 0.5 mm or more and 5.0 mm or less.

  It is preferable that ratio of the tire width direction length of land parts other than the 3rd land part 33 to the tire width direction length of the 3rd land part 33 which is a shoulder land part is 0.70 or more and 1.00 or less. The tire width direction length of the first land portion 31 which is a land portion other than the third land portion 33 is Wa1, and the tire width direction length of the second land portion 32 which is a land portion other than the third land portion 33 is Wa2. Then, the ratios Wa1 / Wb and Wa2 / Wb of the tire width direction length of the land portion other than the third land portion 33 to the tire width direction length Wb of the third land portion 33 are both 0.70 or more and 1.00 or less Is preferred.

  Here, the tire circumferential direction length of the tread surface of the tread portion 20 is taken as TL (not shown). It is preferable that ratio Wb / TL of tire width direction length Wb of the 3rd land part 33 which is a shoulder land part to tire peripheral direction length TL of the contact surface of tread part 20 is 0.20 or less. The tire circumferential direction length TL of the contact surface of the tread portion is measured as a no-load state while mounting the pneumatic tire 1 on a prescribed rim to apply a prescribed internal pressure.

FIG. 3 is a cross-sectional view in the tire meridian direction showing the pneumatic tire 1. FIG. 4 is a diagram showing a part of FIG. 3 in an enlarged manner. 3 and 4, the pneumatic tire 1, the outer diameter of the position along the tire equatorial plane CL and D _C, diameter difference when the outer diameter of the position of the ground terminal T D _S, and | D _C When −D _S | is D _D ,
D _D /TDW≦0.085
Is preferred. That is, for the tread width TDW, it preferably has a specific _D D / TDW diameter difference _{D D} is 0.085 or less. When the value of the ratio D _D / TDW is larger than 0.085, deformation at the time of grounding becomes large, and it is difficult to suppress the distortion of the main groove bottom. If the value of the ratio D _D / TDW is 0.085 or less, the deformation at the time of grounding becomes small, and the distortion of the main groove bottom can be reduced. Note that the outer diameter D _C and the outer diameter D _S, is measured for the tire 1 single no-inflated. The position of the ground contact end T is a ground contact end when the tire 1 is mounted on a rim and a prescribed internal pressure and a prescribed load are applied.

  FIG. 5 is a cross-sectional view in the tire meridian direction showing the pneumatic tire 1. In FIG. 5, when the tread radius from the tire equatorial plane CL to the end of the third circumferential main groove 23 on the outer side in the tire width direction is RC, and the tread radius from the tire equatorial plane CL to the ground contact end T is RA. It is preferable that RC <RA. By RC <RA, it is possible to enhance the uneven wear resistance performance of the shoulder portion. In addition, a tire profile is measured using a radius ruler about the tire 1 single-piece | unit of a no inflation state.

  The ratio RC / RA of the tread radius RC to the tread radius RA is preferably 0.60 or more and 0.90 or less, and more preferably 0.70 or more and 0.80 or less. If the tread radius RC is too small, the contact length of the tire equatorial plane CL and the ground contact end T becomes long, and the contact length of the outermost third circumferential main groove 23 becomes short and the contact length becomes short. It becomes. In the case of such a ground contact shape, there is a concern that uneven wear (rail wear) may occur at the groove end of the third circumferential main groove 23 having a short ground contact length. In order to suppress such uneven wear, specifically, in a no-inflate state, for example, when the tread radius RA is 1200 or more and 1500 or less, and the tread radius RC is 900 or more and 1200 or less, RC <RA It is preferable to set the values of the tread radiuses RA and RC to satisfy the conditions. In the inflated state, for example, the values of the tread radiuses RA and RC are set so as to satisfy RC <RA in the range of the tread radius RA of 700 to 900 and the tread radius RC of 600 to 800. Is preferred.

  In FIG. 5, assuming that the tread radius of the shoulder in the tire width direction outer end of the third circumferential main groove 23 to the tread end T is RS, the ratio RS / RA of the tread radius RS to the tread radius RA is 0 It is preferable that it is .50 or more and 1.20 or less, and it is more preferable that it is 0.70 or more and 1.00 or less. If the ratio RS / RA is in such a range, uneven wear of the shoulder can be effectively suppressed. The tread radius of the shoulder portion has less influence on the uneven wear of the shoulder portion as compared to the tread radius of the center portion near the tire equatorial plane CL. Specifically, in a no-inflate state, for example, a radius setting in which the ratio RS / RA satisfies the above range when the tread radius RA is 1200 or more and 1500 or less, and the tread radius RS is 800 or more and 1500 or less. It is preferable to do. In the inflated state, for example, it is preferable to set a radius setting in which the ratio RS / RA satisfies the above range in a range where the tread radius RA is 700 or more and 900 or less and the tread radius RS is 600 or more and 1000 or less.

  Furthermore, in FIG. 5, it is preferable that the relationship of tread radius RS, tread radius RC, and tread radius RA is RS <RC <RA. It is preferable that the center portion on the tire equatorial plane CL be flat than the shoulder portion in order to reduce the amount of deformation of the bottom of the main groove at the time of contact with the ground and to suppress uneven wear of the shoulder portion. In addition, if the 3-point tread radius RA passing through the tire equatorial plane CL and the contact ends T on both sides is larger than the tread radius RS and RC of the center portion and the shoulder portion, the amount of deformation of the main groove bottom can be made smaller. It is preferable in order to suppress uneven wear of the part.

  In FIG. 5, the distance from the tire equatorial plane CL to the end of the third circumferential main groove 23 on the outer side in the tire width direction is D1, and the tire from the tire equatorial plane CL to the contact end T is D1. When the distance along the width direction is D2, the value of the ratio D1 / D2 of the distance D1 to the distance D2 is preferably 0.64 or more and 0.74 or less.

  FIG. 6 is a diagram showing a part of FIG. 5 in an enlarged manner. In FIG. 6, the total gauge of the center along the tire equatorial plane CL is Tc, and the width from the center on the tire equatorial plane CL to the end 23T of the third circumferential main groove 23 on the outer side in the tire width direction is We I assume. Further, in FIG. 6, a total gauge at a position of 0.33 We from the center on the tire equatorial plane CL toward the outer side in the tire width direction is T1, and the third circumferential main groove 23 from the center on the tire equatorial plane CL. The total gauge at the position of 0.66 We toward the tire width direction outer side of the tire is T2, and the total gauge at the tire width direction outer end 23T of the third circumferential main groove 23 from the center on the tire equatorial plane CL Assuming that T3 is, the ratio of the total gauge T3 at the position of the end 23T of the third circumferential main groove 23 on the outer side in the tire width direction to the total gauge Tc in the center is 0.98 or less, and Tc ≧ T1 ≧ It is preferable that T2 ≧ T3. If the tread gauges are distributed in this manner, it is possible to obtain a ground contact shape having a high effect of suppressing uneven wear of the shoulder portion when adopting this profile. When the tread gauges are the same or increase from the center portion toward the outermost main groove end, the contact length of the center portion tends to be short and in contact with the hourglass. As described above, by gradually reducing the tread gauge, it is possible to suppress the contact shape from becoming a drum shape. The total gauges Tc and T1 to T3 are measured along the normal drawn from the tread surface toward the center of the thickness of the carcass layer 13.

  In FIG. 6, assuming that the total gauge of the shoulder portion measured along the normal drawn from the ground end T to the center of the thickness of the carcass layer 13 is Tsh, the total gauge Tsh of the shoulder portion with respect to the total gauge Tc of the center portion. The ratio Tsh / Tc of is preferably 1.10 or more and 1.50 or less, and more preferably 1.20 or more and 1.40 or less. If the total gauge Tc in the center portion and the total gauge Tsh in the shoulder portion have such a relationship, it is possible to obtain a ground contact shape having a high effect of suppressing uneven wear in the shoulder portion.

Referring back to FIG. 5, when the width of the cross belt disposed in the tread portion is W _B0 and the total width of the tire is Wt, the ratio of the belt width W _{B0 to} the total width Wt of the tire is shown. W _B0 / Wt is preferably 0.72 or more and 0.82 or less, and more preferably 0.74 or more and 0.76 or less. If the tire total width Wt and the belt width W _B0 have such a relationship, it is possible to obtain a ground contact shape having a high uneven wear suppressing effect on the shoulder portion. The tire total width Wt is a measured value when inflated at a prescribed internal pressure (for example, 900 kPa).

  FIGS. 7, 8 and 9 are diagrams for explaining the relationship between the tread radius RC of the center portion on the tire equatorial plane CL and the tread radius of the shoulder portion. Figures 7, 8 and 9 show the tread radius in exaggeration over the actual tread radius.

In FIG. 7, the tread radius RC at the center portion passes through the intersection of the tire equatorial plane CL and the tread surface, and the end e at the tire equatorial plane CL side of the third circumferential main groove 23, that is, the inner side in the tire width direction The end 23T of the third circumferential main groove 23 on the outer side in the tire width direction passes through. Further, in FIG. 7, the tread radius RS ₁ of the shoulder portion, the position of its center point is located on the equatorial plane CL side, namely the tire width direction inside the tire than the end 23T. Therefore, the position in the tire radial direction of the ground contact end T is a position on the inner side in the tire radial direction than the position of the end 23T. The distance along the tire radial direction between the ground contact end T and the end 23T is G1. Here, the ratio G1 / (D _D / 2) of the distance G1 to one side (that is, D _D / 2) of the diameter difference D _D described with reference to FIG. 4 is 0.2 or more and 0.5 or less Is preferred. When the ratio G1 / (D _D / 2) is in such a range, the effect of suppressing uneven wear of the shoulder portion is high.

In FIG. 8, the tread radius RC of the center portion passes through the intersection of the tire equatorial plane CL and the tread surface as in the case of FIG. 7, and the tire equatorial plane CL side of the third circumferential main groove 23, ie, the tire It passes through the end 23I on the inner side in the width direction and the end 23T on the outer side in the tire width direction of the third circumferential main groove 23. Further, in FIG. 8, the position of the center point of the tread radius RS ₂ of the shoulder portion is extended inward in the tire radial direction along the tire radial direction through the middle point of the straight line connecting the end 23T and the ground contact end T. It is a position on a straight line (not shown). For this reason, the position in the tire radial direction of the ground contact end T is the same position as the position of the end 23T.

In FIG. 9, the tread radius RC of the center portion passes through the intersection of the tire equatorial plane CL and the tread surface, as in the case of FIGS. 7 and 8, and the tire equatorial plane CL of the third circumferential main groove 23 It passes through the end 23I on the side, that is, the inner side in the tire width direction, and the end 23T on the outer side in the tire width direction of the third circumferential main groove 23. Further, in FIG. 9, the position of the center point of the tread radius RS ₃ of the shoulder portion is positioned outside the tread end T in the tire width direction. Therefore, the position in the tire radial direction of the ground contact end T is a position outside the position of the end 23T in the tire radial direction. The distance along the tire radial direction between the ground contact end T and the end 23T is G2. Here, the ratio G2 / (D _D / 2) of the distance G2 to one side (that is, D _D / 2) of the diameter difference D _D described with reference to FIG. 4 is 0.3 or more and 1.4 or less Is preferred. If the ratio G2 / (D D / ₂₎ falls within such range, a high effect of suppressing the uneven wear of the shoulder portion.

  In the pneumatic tire 1 of this example, the tread radius RC at the center portion and the tread radius RS at the shoulder portion may have any relationship of FIG. 7, FIG. 8 and FIG. As shown in FIG. 7, in the case where the position in the tire radial direction of the ground contact end T is a position on the inner side in the tire radial direction with respect to the position of the end 23T, the traction length is improved by extending the contact length of the center portion. is there. Also, as shown in FIG. 8, when the position of the ground contact end T in the tire radial direction is equivalent to the position of the end 23 T, there is an advantage that shoulder partial wear can be suppressed, and an advantage that rolling resistance is improved. There is. Furthermore, as shown in FIG. 9, when the position of the ground contact end T in the tire radial direction is a position outside the position of the end 23T in the tire radial direction, steering stability is improved by extending the contact length of the shoulder portion. It has the advantage of

  The flatness of the pneumatic tire 1 described above is, for example, 70% or less. In the case of a relatively low flatness tire 1 having a flatness of 70% or less (that is, 70%, 65%, 60%, etc.), the ground contact shape tends to be a square shape or an hourglass shape. For this reason, for the low flat size tire 1, the effect of making the ground contact shape according to the present embodiment appropriate is large. The flatness is a percentage of the ratio of the height of the cross section of the tire 1 to the width of the cross section of the tire 1. The cross-sectional width of the tire 1 is the width of the total tire width Wt excluding patterns, characters and the like on the side surface of the tire. The sectional height of the tire 1 is half of the difference between the outer diameter of the tire 1 and the diameter of the rim on which it is mounted.

[Another configuration example of the tread portion]
In the tread portion 20 shown in FIG. 2, the traction performance is improved because the inclination direction of the lug grooves 24 is V-shaped in the land portions 31, 32 on both sides of the tire equatorial plane CL. As another configuration example of the tread portion, the pneumatic tire 1 may have tread portions 20A to 20C shown in FIGS. 10 to 12. 10 to 12 are developed views showing another example of the tread pattern of the pneumatic tire 1. The rolling resistance of the tread portion shown in FIGS. 2, 10, 11, and 12 can be improved by closing the groove at the time of grounding to form a wide rib block.

  The tread portion 20A shown in FIG. 10 has the same arrangement of lug grooves 24 in the tire circumferential direction. When the lug grooves 24 are arranged as described above, the grooves are closed at the time of grounding to form a wide rib block, whereby the anti-rolling resistance performance can be improved. Further, according to the pneumatic tire 1 having the tread portion 20A shown in FIG. 10, the positions in the tire circumferential direction of the respective lug grooves 24 (adjacent to the tire width direction) for dividing the block of the tread portion 20A are substantially the same. Thus, the resistance to stone biting is improved. Furthermore, according to the pneumatic tire 1 having the tread portion 20A shown in FIG. 10, in the land portions 31 and 32 on both sides of the tire equatorial plane CL, the inclination direction of the lug grooves 24 is V-shaped. By inclining with respect to the width direction, water on the road surface can be pushed outward in the tire width direction, the drainage performance of the pneumatic tire 1 is improved, and the wet braking performance is improved.

  The tread portion 20B shown in FIG. 11 is disposed such that the lug grooves 24 communicate with each other from the tire equatorial plane CL outward in the tire width direction. When the lug grooves 24 are arranged as described above, the grooves are closed at the time of grounding to form a wide rib block, whereby the anti-rolling resistance performance can be improved. Further, according to the pneumatic tire 1 having the tread portion 20B shown in FIG. 11, the drainage performance is improved because the lug grooves 24 for dividing the block of the tread portion 20B communicate with each other. Furthermore, according to the pneumatic tire 1 having the tread portion 20B shown in FIG. 11, in the land width portions on both sides across the tire equatorial plane CL, the direction of inclination of the lug grooves 24 is V-shaped. By being inclined to the side, water on the road surface can be pushed outward in the tire width direction, the drainage performance of the pneumatic tire 1 is improved, and the wet braking performance is improved.

  As shown in FIG. 12, the tread portion 20 </ b> C may have no lug groove 24. In FIG. 12, the tread portion 20 </ b> C includes a first land portion 31, a second land portion 32 and a third land portion 33. The first land portion 31, the second land portion 32, and the third land portion 33 do not have the lug grooves 24 and no block is divided, and they have a rib shape continuous in the tire circumferential direction. . In the first land portion 31 and the second land portion 32, the ratio of the length WH of the tire arrangement direction of the rib to the tread development width TDW is preferably in the range of 0.55 or more and 0.70 or less, It is more preferable that it is 0.60 or more and 0.65 or less. Also in the case where the first land portion 31 and the second land portion 32 in the rib shape are adopted, the same effect as in the case where the first land portion 31 and the second land portion 32 having the blocks 31B and 32B are adopted can get.

  In FIG.2, FIG.10 and FIG.11, although the case where the lug groove 24 was extended linearly was demonstrated, you may bend in the middle of extension. Further, the lug grooves 24 may be bent at two places in the middle of the extension, and the lug grooves 24 may be formed in a Z shape as a whole. Even when the lug grooves 24 are bent in the middle of extension, the traction performance is improved by the slope direction of the lug grooves 24 being V-shaped in the land portions 31, 32 on both sides across the tire equatorial plane CL. Do.

  In addition, by bending the lug grooves 24, the rigidity of the tread portion is increased, and the rolling resistance can be reduced. In order to increase the rigidity of the tread portion and reduce the rolling resistance, the inclination direction of the lug grooves 24 in the tread portion 20 may not be V-shaped.

  By the way, in order to reduce rolling resistance, the first land portion 31 and the second land portion 32 are divided by the first circumferential main groove 21 and the second circumferential main groove 22 having a narrow groove width, and The one circumferential main groove 21 and the second circumferential main groove 22 may be closed, and the blocks 31B and 32B may function as wide blocks. In order to realize this function, the inclination direction of the lug grooves 24 may not be V-shaped.

[Summary]
According to the pneumatic tire 1 of the present example, the groove is closed at the time of grounding to form a wide rib block, whereby the anti-rolling resistance performance can be improved. Further, according to the pneumatic tire 1 of the present embodiment, the tread radius RC from the tire equatorial plane CL to the tire width direction outer end of the circumferential main groove in the tire meridional section is from the tire equatorial plane CL to the ground contact end Because it is smaller than the tread radius RA (RC <RA), the uneven wear resistance performance of the shoulder portion can be enhanced.

[Example]
Tables 1 to 5 are tables showing the results of performance tests of the pneumatic tire according to the embodiment of the present invention. In this performance test, evaluation regarding rolling resistance resistance performance and uneven wear resistance performance was performed on a plurality of test tires. The size of the pneumatic tire 1 used for evaluation is 315 / 70R22.5. The vehicle used for the evaluation is a vehicle in which a trailer is connected to a 6 × 4 tractor.

  An indoor drum tester was used to evaluate the rolling resistance resistance performance. In the evaluation of anti-rolling resistance performance, the test tire was filled with normal internal pressure, and the resistance at a load of 4 kN and a speed of 50 km / h was measured. Based on the measurement results, index evaluation was performed with the conventional tire as a standard (100). This evaluation shows that the larger the index, the smaller the rolling resistance and the better the rolling resistance performance.

  The evaluation regarding the uneven wear resistance performance is an uneven wear of the shoulder portion after traveling 40,000 km by mounting on the rim of 22.5 × 9.00 of the tire 1 and setting the air pressure to 900 kPa, mounting on the drive shaft of the tractor head and traveling 40,000 km The amount was measured. The measurement results were indexed using the tire of the conventional example as the standard (100). This evaluation shows that the larger the index is, the better the uneven wear resistance performance is. The tire according to the conventional example does not have a circumferential narrow groove and a circumferential main groove, and has a tread portion which does not form a wide rib block at the time of grounding.

Further, as comparative objects, the tires of Comparative Example 1 and Comparative Example 2 were prepared, and evaluations on rolling resistance resistance performance and uneven wear resistance performance were performed in the same manner as described above. The tire of Comparative Example 1 has a circumferential narrow groove and a circumferential main groove, and the width of the arrangement range of the land portion between the two circumferential main grooves with respect to the tread development width TDW. The ratio of the groove width of the circumferential narrow groove to the groove width of the circumferential groove is 0.36, and the relationship between the tread radius RC and the tread radius RA is RC> RA . In the tire of Comparative Example 1, the ratio of the groove width of the circumferential narrow groove to the tread spread width TDW is 0.015, and the ratio of the groove width of the circumferential main groove to the tread spread width TDW is 0.040. The land portion of the tire of Comparative Example 1 is divided into blocks by lug grooves, the ratio of the groove width of the lug grooves to the tread spread width TDW is 0.007, and the ratio of the tread radius RC to the tread radius RA: RC / The ratio of the tread radius RS to the tread radius RA is 1.05, the ratio RS / RA of the tread radius RS is 0.45, and the relationship between each tread radius is not RS <RC <RA. In the tire of Comparative Example 1, the relationship of each total gauge is Tc ≧ T1 ≧ T2 ト ー タ ル T3, and the ratio T3 / Tc is 0.98 or less, and the ratio Tsh of the total gauge Tsh of the shoulder portion to the total gauge Tc of the center portion / Tc is 1.55, the tire total width Wt, the ratio _W B0 / Wt 0.70 belt width _{W B0,} for the carcass section width _{W C,} the ratio _W BO / _{W C} of the width _{W BO} of the belt is zero. 73, the ratio D _D / TDW of the radial difference D _D to the tread development width TDW is 0.09. The tire of Comparative Example 1 has an aspect ratio of 80%.

The tire of Comparative Example 2 has a circumferential narrow groove and a circumferential main groove, and the width of the arrangement range of the land portion between the two circumferential main grooves with respect to the tread spread width TDW. The ratio of the groove width of the circumferential narrow groove to the groove width of the circumferential groove is 0.24, the relationship between the tread radius RC and the tread radius RA is RC> RA . In the tire of Comparative Example 2, the ratio of the groove width of the circumferential narrow groove to the tread development width TDW is 0.010, and the ratio of the groove width of the circumferential main groove to the tread development width TDW is 0.040. The land portion of the tire of Comparative Example 2 is divided into blocks by lug grooves, the ratio of the groove width of the lug grooves to the tread spread width TDW is 0.010, and the ratio RC of the tread radius RC to the tread radius RA is RC / The ratio of the tread radius RS to the tread radius RA is 0.55, the ratio RS / RA of the tread radius RS is 1.25, and the relationship between each tread radius is not RS <RC <RA. In the tire of Comparative Example 2, the relationship of each total gauge is Tc 2 T1 に 対 す る T2 、 T3, and the ratio T3 / Tc is 0.98 or less, and the ratio Tsh of the total gauge Tsh of the shoulder portion to the total gauge Tc of the center portion / Tc 1.45, the tire total width Wt, the ratio _W B0 / Wt 0.74 belt width _{W B0,} for the carcass section width _{W C,} the ratio _W BO / _{W C} of the width _{W BO} of the belt is zero. 76, the ratio D _D / TDW of the radial difference D _D to the tread development width TDW is 0.09. The tire of Comparative Example 2 has an aspect ratio of 80%.

  As shown in Tables 1 to 5, in the tires 1 of Examples 1 to 52, the width in the tire width direction of the arrangement range of the land portion between the two circumferential main grooves with respect to the tread development width TDW The ratio is 0.55 or more and 0.70 or less. In the tire 1 of the example 1 to the example 52, the ratio of the groove width of the circumferential narrow groove to the groove width of the two circumferential main grooves is 0.15 or more and 0.45 or less. In the tires 1 of the example 1 to the example 52, the relationship between the tread radius RC and the tread radius RA is RC <RA. In the tires 1 of Examples 11 to 52, the ratio of the groove width of the circumferential narrow groove to the tread development width TDW is 0.007 or more and 0.024 or less. In the tire 1 of Example 16 to Example 52, the ratio of the groove width of the circumferential main groove to the tread development width TDW is 0.025 or more and 0.055 or less.

In the tires of Example 21 to Example 52, land portions are divided into blocks by lug grooves, and the ratio of the groove width of the lug grooves to the tread development width TDW is 0.003 or more and 0.016 or less. In the tires of Example 26 to Example 52, the ratio RC / RA of the tread radius RC to the tread radius RA is 0.60 or more and 0.90 or less. In the tires of Example 31 to Example 52, the ratio RS / RA of the tread radius RS to the tread radius RA is 0.50 or more and 1.20 or less. In the tires of Example 36 to Example 52, the relationship of each tread radius is RS <RC <RA. In the tires of Example 37 to Example 52, the relationship of each total gauge is Tc ≧ T1 ≧ T2 ≧ T3 and the ratio T3 / Tc is 0.98 or less. In the tires of Example 38 to Example 52, the ratio Tsh / Tc of the total gauge Tsh of the shoulder portion to the total gauge Tc of the center portion is 1.10 or more and 1.50 or less. In the tires of Example 43 to Example 52, the ratio W _B0 / Wt of the belt width W _B0 to the total tire width Wt is 0.72 or more and 0.82 or less. Tires of Examples 52 Examples 48, against the carcass section width _{W C,} the ratio _W BO / _{W C} of the width _{W BO} of the belt is 0.74 or more. Tires of Examples 52 Examples 49, for tread width TDW, the ratio _D D / TDW diameter difference _{D D} is 0.085 or less. The tires of Example 50 to Example 52 have a flatness of 70% or less.

As shown in Tables 1 to 5, according to Examples 1 to 52, the ratio of the width of the land arrangement range to the tread development width TDW is 0.55 or more and 0.70 or less. In the case where the ratio of the groove width of the circumferential narrow groove to the tread development width TDW is 0.007 or more and 0.024 or less, the ratio of the groove width of the circumferential main groove to the tread development width TDW is 0.025 or more When the ratio of the groove width of the circumferential narrow groove to the groove width of the two circumferential main grooves is not less than 0.15 and not more than 0.055, the tread radius RC and the tread radius RA When the relationship with is RC <RA, the land portion is divided into blocks by the lug grooves, and the ratio of the groove width of the lug grooves to the tread development width TDW is 0.003 or more and 0.016 or less , Tread radius R When the ratio RC / RA of the tread radius RC to that of 0.60 to 0.90, when the ratio RS / RA of the tread radius RS to the tread radius RA is 0.50 to 1.20, When the relationship of tread radius is RS <RC <RA, the relationship of each total gauge is Tc ≧ T1 ≧ T2 ≧ T3 and when the ratio T3 / Tc is 0.98 or less, relative to the total gauge Tc of the center portion the ratio Tsh / Tc total gauge Tsh shoulder portion, when it is 1.10 to 1.50, with respect to the tire total width Wt, the ratio of the belt width _{W B0} is _{0.72 ≦ W B0 / Wt ≦ 0} . If it is 82, with respect to the carcass section width _{W C,} when the ratio _W BO / _{W C} of the width _{W BO} of the belt is 0.74 or more, against the tread width TDW It can be seen that when the ratio D _D / TDW of the diameter difference D _D is 0.085 or less, good results are obtained when the flatness is 70% or less.

DESCRIPTION OF SYMBOLS 1 pneumatic tire 11 bead core 13 carcass layer 14 belt layer 15 tread rubber 16 sidewall rubber 17 rim cushion rubber 20, 20A, 20B, 20C tread portion 21 first circumferential main groove 22 second circumferential main groove 23 third circumferential Direction main groove 24 Lug groove 31 first land portion 31B, 32B block 32 second land portion 33 third land portion 141 high angle belt 142, 143 cross belt ply 144 belt cover CL tire equatorial plane TDW tread development width

Claims (12)

Two circumferential main grooves extending in the tire circumferential direction, at least one circumferential narrow groove disposed between the two circumferential main grooves, and the at least one circumferential narrow groove A land section separated by a circumferential main groove of the book,
The ratio of the width in the tire width direction of the arrangement range of the land portion to the tread development width TDW is 0.55 or more and 0.70 or less,
The ratio of the groove width of the circumferential narrow groove to the groove width of the two circumferential main grooves is 0.15 or more and 0.45 or less,
In the tire meridional section, the relationship between the tread radius RC from the tire equatorial plane to the outer edge of the circumferential main groove in the tire width direction and the tread radius RA from the tire equatorial plane to the ground end is RC <RA There is a pneumatic tire. The ratio of the groove width of the circumferential narrow groove to the tread development width TDW is 0.007 or more and 0.024 or less,
The pneumatic tire according to claim 1, wherein a ratio of groove widths of the two circumferential main grooves to the tread development width TDW is 0.025 or more and 0.055 or less.   The land portion is divided into blocks by lug grooves extending in the tire width direction, and the ratio of the groove width of the lug grooves to the tread development width TDW is 0.003 or more and 0.016 or less. Or the pneumatic tire as described in 2.   The pneumatic tire according to any one of claims 1 to 3, wherein a ratio RC / RA of the tread radius RC to the tread radius RA is 0.60 or more and 0.90 or less.   In the tire meridional cross section, the ratio RS / RA of the tread radius RS from the tire width direction outer end of the circumferential main groove to the tread radius RA with respect to the tread radius RA is 0.50 or more and 1.20 or less. The pneumatic tire according to any one of claims 1 to 4. The relationship between the tread radius RS, the tread radius RC, and the tread radius RA is RS <RC <RA
The pneumatic tire according to claim 5, which is In the tire meridional section, the total gauge of the center along the tire equatorial plane is Tc, the width from the center to the end of the circumferential main groove on the outer side in the tire width direction is We, and the width from the center to the tire The total gauge at the position of 0.33 We toward the outside in the direction T1, the total gauge at the position of 0.66 We toward the outside in the tire width direction from the center portion T2, the outer end of the circumferential main groove in the tire width direction Assuming that the total gauge at the position of the part is T3,
Tc T T1 T T2 、 T3 and T3 / Tc 0.9 0.98
The pneumatic tire according to any one of claims 1 to 6, which is When a shoulder portion total gauge including a carcass layer and measured along a normal drawn from the ground end to the center of the thickness of the carcass layer is Tsh,
1.10 ≦ Tsh / Tc ≦ 1.50
The pneumatic tire according to claim 7. Assuming that the belt width on the side with the smaller width in the tire width direction is W _B0 and the total tire width is Wt, of the cross belts arranged in the tread portion,
0.72 ≦ W _B0 /Wt≦0.82
The pneumatic tire according to any one of claims 1 to 8, which is When the width of the belt disposed on the outer side in the tire radial direction is W _BO and the carcass cross-sectional width is W _C among the pair of cross belts,
W _BO / W _C 0.7 0.74
The pneumatic tire according to any one of claims 1 to 9, which is Pneumatic tire, the outside diameter of the position along the tire equatorial plane and D _C, diameter difference when the outer diameter of the position of the ground terminal D _S, and | when was the _D D _| D C _-D S ,
D _D /TDW≦0.085
The pneumatic tire according to any one of claims 1 to 10, wherein   The pneumatic tire according to any one of claims 1 to 11, wherein an aspect ratio, which is a percentage of a ratio of a section height of the tire to a section width of the tire, is 70% or less.

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