JP7077619B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

Conventionally, pneumatic tires for the purpose of suppressing noise of a block pattern and improving uneven wear resistance have been known. For example, there is known a pneumatic tire in which a circumferential main groove is arranged in a zigzag manner and the zigzag is arranged so as to be displaced in the circumferential direction (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-76658

By the way, as a method for improving rolling resistance Coefficient (RRC), a wide block row may be arranged in the center. When the block row is moved closer to the center portion to increase the rigidity of the center region in this way, the amount of deformation of the shoulder portion becomes relatively large. As a result, the strain of the main groove bottoms at both ends of the wide block row increases, and there is a concern that groove cracks may occur. The conventional pneumatic tire described above has room for improvement in suppressing the occurrence of groove cracks while improving the rolling resistance.

The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of suppressing the occurrence of groove cracks while improving rolling resistance.

In order to solve the above-mentioned problems and achieve the object, the pneumatic tire according to an embodiment of the present invention is provided between two circumferential main grooves extending in the tire circumferential direction and the two circumferential main grooves. It is provided with at least one circumferential narrow groove arranged and a circumferential reinforcing layer provided inside the tire radial direction of the two circumferential main grooves, and the two circumferential main grooves are provided in the tire meridional cross section. The ratio Ws / Wm of the width Ws in the tire width direction at both ends of the circumferential reinforcement layer to the distance Wm in the tire width direction between the outer ends of the groove in the tire width direction is 1 or more and 1.2 or less, and the tread. The ratio of the groove width of the circumferential narrow groove to the developed width TDW is 0.007 or more and 0.024 or less, and one of the circumferential fine grooves is provided on the equatorial plane of the tire, and the two are provided. The circumferential main groove is the outermost circumferential main groove in the tire width direction, and no other circumferential main groove is provided between the two circumferential main grooves in the tire meridional cross section. The relationship between the tread radius RC from the tire equatorial plane to the outer end of the circumferential main groove in the tire width direction and the tread radius RA from the tire equatorial plane to the ground contact end is RC <RA .

A land portion defined by the at least one circumferential narrow groove and the two circumferential main grooves is provided, and the tire width direction of the arrangement range of the land portion between the two circumferential main grooves is provided. The ratio of the width to the tread expansion width TDW is 0.55 or more and 0.70 or less, and the ratio of the groove widths of the two circumferential main grooves to the tread expansion width TDW is 0.025 or more and 0.055 or less. The ratio of the groove width of the circumferential fine groove to the groove width of the two circumferential main grooves is preferably 0.15 or more and 0.45 or less.

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

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.

In the tire meridional cross section, the ratio RS / RA of the tread radius RS from the outer end of the circumferential main groove in the tire width direction to the ground contact end with respect to the tread radius RA is 0.50 or more and 1.20 or less. preferable.

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

In the tire meridional cross section, the total gauge of the center portion measured along the normal line drawn from the tread surface to the center of the thickness of the carcass layer along the tire equatorial plane is Tc, and the total gauge of the center portion is defined as Tc. The width to the outer end in the tire width direction is We, and along the normal line drawn from the tread surface to the center of the thickness of the carcass layer at a position of 0.33 We from the center portion to the outer side in the tire width direction. The measured total gauge is T1, and the total gauge measured along the normal line drawn from the tread surface to the center of the thickness of the carcass layer at a position of 0.66 We from the center to the outside in the tire width direction is T2. Assuming that the total gauge measured along the normal line drawn from the tread surface to the center of the thickness of the carcass layer at the position of the outer end of the circumferential main groove in the tire width direction is T3, Tc ≧ T1 ≧ T2 ≧ It is preferable that T3 and T3 / Tc ≦ 0.98.

When the total gauge of the shoulder portion measured along the normal line drawn from the ground contact end to the center of the thickness of the carcass layer is Tsh, the total gauge of the shoulder portion is 1.10 ≤ Tsh / Tc ≤ 1.50. preferable.

When the belt width on the side of the cross belt arranged in the tread portion where the width in the tire width direction is small is WB0 and the total tire width is _Wt , 0.72 ≤ _WB0 / Wt ≤ 0.82. preferable.

In the tire meridional cross section, the diameter _DBC of the circumferential reinforcing layer along the equatorial plane of the tire to the outer side of the tire radial direction and the tire of the circumferential reinforcing layer at the position of the outer end portion of the circumferential reinforcing layer in the tire width direction. When the diameter difference from the diameter _DBS to the outside in the radial direction | _DBC - _DBS | is _DBD , it is preferable that DBD / Ws ≦ _0.022 .

In the pair of crossed belts, when the belt arranged on the outer side in the tire radial direction is the belt on the side where the width in the tire width direction is small, the width of the belt is set to _WBO and the carcass cross-sectional width is set to _WC . When, it is preferable that W _BO / _WC ≧ 0.74.

For pneumatic tires, when the outer diameter at the position along the equatorial plane of the tire is DC and the outer diameter at the ground contact end is _DS , and the diameter difference | _{DC - DS} | is _DD . , _DD / TDW ≦ 0.085.

The flatness, which is a percentage of the ratio of the cross-sectional height of the tire to the cross-sectional width of the tire, is preferably 70% or less.

The pneumatic tire according to the present invention can suppress the occurrence of groove cracks while improving the 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 developed view showing a tread pattern of a pneumatic tire. FIG. 3 is a cross-sectional view of a pneumatic tire in the tire meridian direction. FIG. 4 is an enlarged view showing a part of FIG. 3. FIG. 5 is a cross-sectional view of a pneumatic tire in the tire meridian direction. FIG. 6 is an enlarged view showing a part of FIG. 5. FIG. 7 is a cross-sectional view of a pneumatic tire in the tire meridian direction. FIG. 8 is an enlarged view showing a part of FIG. 7. FIG. 9 is a diagram for explaining the relationship between the tread radius of the center portion on the equator surface of the tire and the tread radius of the shoulder portion. FIG. 10 is a diagram for explaining the relationship between the tread radius of the center portion on the equatorial plane of the tire and the tread radius of the shoulder portion. FIG. 11 is a diagram for explaining the relationship between the tread radius of the center portion on the equator surface of the tire and the tread radius of the shoulder portion. FIG. 12 is a developed view showing another example of the tread pattern of a pneumatic tire. FIG. 13 is a developed view showing another example of the tread pattern of the pneumatic tire. FIG. 14 is a developed view showing another example of the tread pattern of a pneumatic tire.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of each embodiment, the same or equivalent components as those of the other embodiments are designated by the same reference numerals, and the description thereof will be simplified or omitted. The present invention is not limited to each embodiment. In addition, the components of each embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. It should be noted that the plurality of modifications described in this embodiment can be arbitrarily combined within the range of those skilled in the art.

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

In FIG. 1, the cross section in the tire meridian direction means a cross section when a tire is cut on a plane including a tire rotation axis (not shown). Further, the reference numeral CL is a tire equatorial plane, and refers to a plane that passes through the center point of the tire in the direction of the tire rotation axis and is perpendicular to the tire rotation axis. 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 the left and right sidewall portions. 16 and 16 and rim cushion rubbers 17 and 17 constituting the left and right bead portions are provided. The belt layer 14 has a structure in which a plurality of belt plies are laminated. In FIG. 1, the belt layer 14 has a configuration in which a high-angle belt 141, a pair of crossed belt plies 142, 143, and a belt cover 144 are laminated. A bead filler may be provided on the outer side of the bead core 11 in the tire radial direction. The above-mentioned tire internal structure shows a typical example of a pneumatic tire, but is not limited thereto.

[Tread part]
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 surface CL and a first circumferential main groove 21 on both sides of the tire equatorial surface CL. A pair of second circumferential main grooves 22 extending in the tire circumferential direction at a position outside the tire width direction, and a pair of third grooves extending in the tire circumferential direction at a position outside the tire width direction with respect to the second circumferential main groove 22. It is provided with 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 are arranged symmetrically with respect to the tire equatorial plane CL. The groove depth 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 duty to display a wear indicator specified in JATTA at the bottom of the groove.

Here, the groove width of the first circumferential direction main groove 21 is W1, the groove width of the second circumferential direction main groove 22 is W2, and the groove width of the third circumferential direction 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 facing wall surfaces of the grooves.

In this example, the tread portion 20 includes a total of three circumferential main grooves 21 and a second circumferential main groove 22, which are circumferential narrow grooves. However, the tread portion 20 may include a total of one, that is, at least one, a first circumferential main groove 21 and a 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, preferably 0.010 or more, with respect to the tread development width TDW. It is more preferably 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 direction main groove 21 and the second circumferential direction main groove 22 becomes the first land portion 31 extending in the tire circumferential direction. The first land portion 31 is divided into a plurality of blocks 31B by the lug groove 24 extending in the tire width direction. That is, the first land portion 31 is composed of a plurality of blocks 31B which are divided by the lug groove 24 and arranged in the tire circumferential direction.

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

Here, as shown in FIG. 2, in the tread portion 20, all the lug grooves 24 have the inner end in the tire width direction facing one side in the tire rotation direction than the outer end in the tire width direction. Has a directional pattern. For example, when the upper side of FIG. 2 is the kicking side in the tire rotation direction and the lower side of FIG. 2 is the stepping side in the tire rotation direction, all the lug grooves 24 are in the tire width direction rather than the outer end in the tire width direction. The inner end faces the stepping side in the tire rotation direction. That is, in the land portions 31 and 32 on both sides of the tire equatorial plane CL, the lug groove 24 is inclined with respect to the tire width direction so that the inclination direction becomes a V-shaped tone. Traction performance is improved because the inclination of the lug groove 24 is V-shaped in the land portions 31 and 32 on both sides of the tire equatorial surface CL.

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 expansion width TDW is preferably in the range of 0.55 or more and 0.70 or less, preferably 0.60 or more and 0. It is more preferably .65 or less. By arranging a wide block in this range, the rigidity of the tread portion 20 can be increased and the rolling resistance can be reduced. Here, in the tread portion 20, the lengths of the blocks 31B and 32B in the tire width direction are set to Wa1 and Wa2. The length WH is the width including all the block rows except the shoulder portion, that is, WH = W1 + 2 × Wa1 + 2 × W2 + 2 × Wa2. It is preferable that the ratios of the lengths Wa1 and Wa2 to the tread development width TDW, Wa1 / TDW and Wa2 / TDW, are both 0.15 or more and 0.20 or less. The smaller the ratio Wa1 / TDW and Wa2 / TDW, the smaller the rigidity of the block. When the ratios Wa1 / TDW and Wa2 / TDW are within the above ranges, the drainage performance can be improved while suppressing the rolling resistance. The tread deployment width TDW is the distance in the tire width direction at both ends of the third land portion 33, which is the two shoulder land portions, on the outer side in the tire width direction. The tread development width TDW refers to the linear distance between both ends in the development view of the tread portion 20 of the tire 1 when the tire 1 is assembled on the specified rim and the specified internal pressure is applied and no load is applied.

Further, in the tread portion 20, the first circumferential main groove 21 and the second circumferential main groove other than the outermost third circumferential main groove 23 adjacent to the outermost land portion in the tire width direction among the plurality of land portions. 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 groove 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 and the ratio W2 / W3 of the groove 23 with respect to the groove width 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 is divided into 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, so that the tread portion 20 is in contact with the ground. The first circumferential main groove 21 and the second circumferential main groove 22 are closed, and the blocks 31B and 32B act as wide blocks. The wide blocks of blocks 31B and 32B can reduce rolling resistance. The positions of the blocks 31B in the tire circumferential direction are deviated from each other on the left and right land portions 31 and 31 sandwiching the tire equatorial plane CL. Since the position in the tire circumferential direction is deviated, the noise when the pneumatic tire 1 touches the ground can be reduced.

Further, in the tread portion 20, the ratio of the groove width W3 of the outermost third circumferential main groove 23 in the tire width direction to the tread development width TDW is preferably 0.025 or more and 0.055 or less, preferably 0.030. It is more preferably 0.050 or less. In the tread portion 20, the ratio of the groove width of the lug groove 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 1.20 or more and 1.50 or less. Is more preferable. The same applies to the block 32B of the other land portion 32. If the aspect ratio is within this range, the drainage effect and the rolling resistance suppressing effect due to the support between the blocks are large. The aspect ratio is the ratio of the maximum value LB of the length L of the block 31B in the tire circumferential direction to the maximum value of the length E of the block 31B in the tire width direction.

It is preferable that the ratio of the maximum value LB of the length L in the tire circumferential direction of the block 31B to the tire outer peripheral length 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 pi. The diameter of the pneumatic tire 1 is measured as a no-load state while the pneumatic tire 1 is mounted on a specified rim to apply a specified internal pressure (for example, 900 kPa).

Here, the specified rim means an "applicable rim" specified in JATMA, a "Design Rim" specified in TRA, or a "Measuring Rim" specified in ETRTO. The specified internal pressure means the "maximum air pressure" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or "INFLATION PRESSURES" specified in ETRTO. The specified load means the "maximum load capacity" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "LOAD CAPACITY" specified in ETRTO. However, in JATTA, in the case of a passenger car tire, the specified internal pressure is an air pressure of 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

[Shoulder part]
Returning to FIG. 2, in the tread portion 20, the land portion outside the tire width direction of the third circumferential main groove 23, which is the outermost peripheral circumferential main groove, becomes the third land portion 33. The third land portion 33 is a shoulder land portion located on the shoulder portion of the tread portion 20. The third land portion 33 may have a shoulder lug groove extending in the tire width direction (not shown), 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 the ratio of the length in the tire width direction of the third land portion 33, which is the shoulder land portion, to the tire width direction length of the land portion other than the third land portion 33 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 of the tire width direction lengths of the land portions other than the third land portion 33 to the tire width direction length Wb of the third land portion 33, Wa1 / Wb and Wa2 / Wb, are both 0.70 or more and 1.00 or less. Is preferable.

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

Returning to FIG. 1, the belt layer 14 includes a circumferential reinforcing layer 140 between the crossed belt plies 142 and 143. The circumferential reinforcement layer 140 is a 0-degree belt layer formed by winding a belt cord at an angle of substantially 0 degrees along the tire circumferential direction, for example, an angle of 0 to 5 degrees. The circumferential reinforcement layer 140 may have a separate structure. That is, it does not have to be arranged below the third circumferential main groove 23 and not below the first circumferential main groove 21 and the second circumferential main groove 22.

In FIG. 1, the distance in the tire width direction between the outer ends of the two third circumferential main grooves 23, which are the circumferential main grooves, in the tire width direction is defined as Wm. Further, the width of both ends of the circumferential reinforcing layer 140 in the tire width direction is defined as Ws. At this time,
1 ≦ Ws / Wm ≦ 1.2
Is preferable. That is, the ratio Ws / Wm of the width Ws to the distance Wm is preferably 1 or more and 1.2 or less. The closer the land portion is between the two main grooves 23 in the third circumferential direction, the higher the rigidity and the lower the rolling resistance. On the other hand, since the amount of deformation of the shoulder portion becomes relatively large and the strain of the groove bottom of the third circumferential main groove 23 increases, the occurrence of groove cracks can be prevented by providing the circumferential reinforcing layer 140. Can be done. At this time, if the value of the ratio Ws / Wm is 1 or more and 1.2 or less, the circumferential reinforcing layer 140 has a width equal to or wider than the outer end of the third circumferential main groove 23 in the tire width direction. , Deformation of the groove bottom can be effectively suppressed. If the value of the ratio Ws / Wm is less than 1, it is difficult to suppress the deformation of the groove bottom. Further, when the value of the ratio Ws / Wm exceeds 1.2, the same effect as in the case of 1.2 or less can be obtained. However, on the other hand, when the value of the ratio Ws / Wm exceeds 1.2, the mass of the tire 1 as a whole increases and the rolling resistance increases, which is not preferable.

FIG. 3 is a cross-sectional view of the pneumatic tire 1 in the tire meridian direction. FIG. 4 is an enlarged view showing a part of FIG. 3. In FIGS. 3 and 4, the diameter of the circumferential reinforcing layer 140 along the tire equatorial plane CL to the outer side in the tire radial direction is defined as _DBC , and the circumferential reinforcing layer 140 is reinforced in the circumferential direction at the position of the outer end portion in the tire width direction. The diameter of the layer 140 to the outside in the tire radial direction is defined as _DBS . In FIGS. 3 and 4, when the difference between the diameter _DBC and the diameter _DBS , that is, the diameter difference | _DBC - _DBS | is _DBD ,
D _BD / Ws ≤ 0.022
Is preferable. That is, the ratio _DBD / _Ws of the diameter difference DBD to the width Ws in the tire width direction at both ends of the circumferential reinforcing layer 140 is preferably 0.022 or less. When the value of the ratio D _BD / Ws is larger than 0.022, the deformation at the time of touchdown becomes large, and it is difficult to suppress the distortion of the groove bottom of the main groove 23 in the third circumferential direction. When the value of the ratio D _BD / Ws is 0.022 or less, the deformation at the time of touchdown becomes small, and the distortion of the groove bottom of the main groove 23 in the third circumferential direction can be reduced. The diameter D _BC and the diameter D _BS are measured for a single tire in a no-inflated state.

Further, in FIG. 4, among the pair of crossed belt plies 142 and 143, when the width of the belt ply 143 arranged on the outer side in the tire radial direction is _WBO and the cross-sectional width of the carcass layer 13 is _WC , the carcass is used. The ratio _WBO / _WC of the width WBO of the belt ply 143 to the cross _- sectional width _WC of the layer 13 is preferably 0.74 or more. If the ratio W _BO / _WC is less than 0.74, the effective belt width is not sufficient and it is difficult to suppress the distortion of the main groove bottom. The larger the value of the ratio W _BO / _WC , the more the effective belt width can be secured and the distortion of the bottom of the main groove can be suppressed.

FIG. 5 is a cross-sectional view of the pneumatic tire 1 in the tire meridian direction. FIG. 6 is an enlarged view showing a part of FIG. 5. In FIGS. 5 and 6, for the pneumatic tire 1, the diameter difference when the outer diameter at the position along the tire _equatorial plane _CL is DC and the outer diameter at the position of the ground contact end _T is DS. When _-DS | is _DD
DD / TDW ≤ 0.085
Is preferable. That is, the ratio _DD / TDW of the diameter difference _DD with respect to the tread development width TDW is preferably 0.085 or less. When the value of the ratio _DD / TDW is larger than 0.085, the deformation at the time of touchdown becomes large, and it is difficult to suppress the distortion of the bottom of the main groove. When the value of the ratio _DD / TDW is 0.085 or less, the deformation at the time of touchdown becomes small, and the strain at the bottom of the main groove can be reduced. The outer diameter _DC and the outer diameter DS are measured for a single tire in a no _- inflated state.

FIG. 7 is a cross-sectional view of the pneumatic tire 1 in the tire meridian direction. In FIG. 7, the tread radius from the tire equatorial surface CL to the outer end portion 23T of the third circumferential main groove 23 in the tire width direction is RC, and the tread radius from the tire equatorial surface CL to the ground contact end T is RA. In addition, it is preferable that RC <RA. The tire profile is measured using a radius ruler for a single tire in a no-inflated state.

Further, 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 ground contact length near the tire equatorial surface CL and the ground contact end T becomes long, and the ground contact length near the outermost third circumferential groove 23 becomes short. Become. In the case of such a ground contact shape, there is a concern that uneven wear (rail wear) may occur at the groove end portion of the third circumferential groove 23 having a short ground contact length. In order to suppress such uneven wear, specifically, the tread radius RA and the tread radius RA so as to satisfy RC <RA in the range where 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. It is preferable to set the value of RC.

In FIG. 7, assuming that the tread radius of the shoulder portion from the end 23T on the outer side in the tire width direction of the main groove 23 in the third circumferential direction to the ground contact end T is RS, the ratio RS / RA of the tread radius RS to the tread radius RA is It is preferably 0.50 or more and 1.20 or less, and more preferably 0.70 or more and 1.00 or less. When the ratio RS / RA is in such a range, uneven shoulder wear can be effectively suppressed. The tread radius of the shoulder portion has a smaller effect on the uneven wear resistance of the shoulder than the tread radius of the center portion near the tire equatorial surface CL. Specifically, it is preferable that 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, and the ratio RS / RA is set to satisfy the above range.

Further, in FIG. 7, the relationship between the tread radius RS, the tread radius RC, and the tread radius RA is preferably RS <RC <RA. It is preferable that the center portion on the equatorial surface CL of the tire is flatter than the shoulder portion in order to reduce the amount of deformation of the bottom of the main groove at the time of touchdown and to suppress groove cracks. Further, when the 3-point tread radius RA passing through the tire equatorial surface CL and the ground 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 reduced, and the groove can be reduced. It is preferable to suppress cracks.

In FIG. 7, the distance along the tire width direction from the tire equatorial surface CL to the outer end portion 23T of the third circumferential main groove 23 in the tire width direction is defined as D1, and the distance from the tire equatorial surface CL to the ground contact end T is defined as D1. When the distance along the tire width direction is D2, the value of the ratio D1 / D2 of the distance D1 to the distance D2 is preferably 0.60 or more and 0.75 or less.

FIG. 8 is an enlarged view showing a part of FIG. 7. In FIG. 8, the total gauge of the center portion along the tire equatorial plane CL is Tc, and the width from the center portion on the tire equatorial plane CL to the outer end portion 23T of the third circumferential main groove 23 in the tire width direction is We. And. Further, in FIG. 8, the total gauge at the position of 0.33 We from the center portion on the tire equatorial plane CL toward the outside in the tire width direction is set to T1, and the main groove 23 in the third circumferential direction from the center portion on the tire equatorial plane CL. The total gauge at the position of 0.66 We toward the outside in the tire width direction is T2, and the total gauge at the position of the outer end portion 23T in the tire width direction of the main groove 23 in the third circumferential direction from the center portion on the tire equatorial plane CL. Is T3, the ratio of the total gauge T3 to the total gauge Tc in the center portion at the position of the end portion 23T on the outer side in the tire width direction of the main groove 23 in the third circumferential direction is 0.98 or less, and
Tc ≧ T1 ≧ T2 ≧ T3
Is preferable. If the tread gauges are distributed in this way, it is possible to obtain a ground contact shape having a high effect of suppressing uneven wear when this profile is adopted. When the tread gauge is the same or increases from the center portion to the end of the outer main groove, the contact length of the center portion tends to be short, and a drum-shaped ground contact shape tends to be formed. As described above, by gradually reducing the tread gauge, it is possible to prevent the ground contact shape from becoming a drum shape. The total gauges Tc and T1 to T3 are measured along a normal line drawn from the tread surface toward the carcass layer 13.

In FIG. 8, when the total gauge of the shoulder portion measured along the normal line drawn from the ground contact end T to the center of the thickness of the carcass layer 13 is Tsh, the total gauge Tsh of the shoulder portion is relative to the total gauge Tc of the center portion. The ratio Tsh / Tc 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.

Returning to FIG. 7, when the belt width on the side of the cross belt arranged in the tread portion where the width in the tire width direction is small is WB0 and the total tire width is _Wt , the ratio of the belt width _WB0 to the total tire width Wt. _WB0 / 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 total tire width Wt and the belt width _WB0 have such a relationship, it is possible to obtain a ground contact shape having a high effect of suppressing uneven wear. The total tire width Wt is a measured value when inflated at a specified internal pressure (for example, 900 kPa).

9, 10 and 11 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. 9, 10 and 11 show the tread radius exaggerated over the actual tread radius.

In FIG. 9, the tread radius RC of the center portion passes through the intersection of the tire equatorial plane CL and the tread plane, and the tire equatorial plane CL side of the third circumferential groove 23, that is, the end portion 23I and the inner end portion 23I in the tire width direction. It passes through the end portion 23T of the groove 23 in the three-circumferential direction on the outer side in the tire width direction. Further, in FIG. 9, the position of the center point of the tread radius RS ₁ of the shoulder portion is located on the CL side of the tire equatorial plane, that is, inside in the tire width direction with respect to the end portion 23T. Therefore, the position of the ground contact end T in the tire radial direction is a position inside the tire radial direction with respect to the position of the end portion 23T. The distance between the ground contact end T and the end portion 23T along the tire radial direction is G1.

In FIG. 10, the tread radius RC of the center portion passes through the intersection of the tire equatorial plane CL and the tread plane, and the tire equatorial plane CL side of the third circumferential groove 23, that is, the tire width, as in the case of FIG. It passes through the end portion 23I on the inner side in the direction and the end portion 23T on the outer side in the tire width direction of the groove 23 in the third circumferential direction. Further, in FIG. 10, the position of the center point of the tread radius RS ₂ of the shoulder portion passes through the midpoint of the straight line connecting the end portion 23T and the ground contact end T, and extends inward in the tire radial direction along the tire radial direction. It is a position on a straight line (not shown). Therefore, the position of the ground contact end T in the tire radial direction is the same as the position of the end portion 23T.

In FIG. 11, the tread radius RC of the center portion passes through the intersection of the tire equatorial plane CL and the tread plane, and is on the tire equatorial plane CL side of the third circumferential groove 23, as in the case of FIGS. 9 and 10. That is, it passes through the inner end 23I in the tire width direction and the outer end 23T in the tire width direction of the third circumferential groove 23. Further, in FIG. 11, the position of the center point of the tread radius RS ₃ of the shoulder portion is located outside the ground contact end T in the tire width direction. Therefore, the position of the ground contact end T in the tire radial direction is a position outside the tire radial direction with respect to the position of the end portion 23T. The distance between the ground contact end T and the end portion 23T along the tire radial direction is G2.

In the pneumatic tire 1 of this example, the tread radius RC in the center portion and the tread radius RS in the shoulder portion may have any of the relationships shown in FIGS. 9, 10 and 11. As shown in FIG. 9, when the position of the ground contact end T in the tire radial direction is the position inside the tire radial direction from the position of the end portion 23T, there is an advantage that the ground contact length of the center portion is extended and the traction performance is improved. .. Further, as shown in FIG. 10, when the position of the ground contact end T in the tire radial direction is the same as the position of the end portion 23T, there is an advantage that the rolling resistance is improved. Further, as shown in FIG. 11, when the position of the ground contact end T in the tire radial direction is a position outside the tire radial direction from the position of the end portion 23T, the ground contact pressure of the shoulder portion increases and the steering stability (improvement of cornering power). There is an advantage that (depending on) is improved.

By the way, the flatness of the pneumatic tire 1 described above is, for example, 70% or less. In the case of a tire 1 having a relatively low flatness of 70% or less (that is, 70%, 65%, 60% ...), the ground contact shape tends to be a square shape or a drum shape. Therefore, for the low flat size tire 1, the effect of optimizing the ground contact shape according to the present embodiment is great. The flatness ratio is a percentage of the ratio of the cross-sectional height of the tire 1 to the cross-sectional width of the tire 1. The cross-sectional width of the tire 1 is the width obtained by removing the pattern, characters, etc. on the side surface of the tire from the total tire width Wt. The cross-sectional height of the tire 1 is ½ of the difference between the outer diameter of the tire 1 and the diameter of the rim on which the tire 1 is mounted.

[Other configuration examples of the tread portion]
The tread portion 20 shown in FIG. 2 has a V-shaped inclination direction of the lug groove 24 at the land portions 31 and 32 on both sides of the tire equatorial plane CL, so that the traction performance is improved. As another configuration example of the tread portion, the pneumatic tire 1 may have the tread portions 20A to 20C shown in FIGS. 12 to 14. 12 to 14 are development views showing another example of the tread pattern of the pneumatic tire 1. In any of the tread portions of FIGS. 2, 12, 13, and 14, the groove is closed at the time of touchdown to form a wide rib block, so that the rolling resistance performance can be improved.

In the tread portion 20A shown in FIG. 12, the arrangement of the lug grooves 24 with respect to the tire peripheral direction is the same. When the lug groove 24 is arranged in this way, the groove is closed at the time of touchdown to form a wide rib block, so that the rolling resistance performance can be improved. Further, according to the pneumatic tire 1 having the tread portion 20A shown in FIG. 12, the positions of the lug grooves 24 (adjacent in the tire width direction) that divide the block of the tread portion 20A in the tire circumferential direction are substantially the same. This improves the stone biting resistance. Further, according to the pneumatic tire 1 having the tread portion 20A shown in FIG. 12, the tire so that the inclination direction of the lug groove 24 becomes a V-shaped tone at the land portions 31 and 32 on both sides of the tire equatorial plane CL. By being inclined with respect to the width direction, water on the road surface can be pushed out to the outside 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. 13 is arranged so that the lug groove 24 communicates with the tire equatorial plane CL toward the outside in the tire width direction. When the lug groove 24 is arranged in this way, the groove is closed at the time of touchdown to form a wide rib block, so that the rolling resistance performance can be improved. Further, according to the pneumatic tire 1 having the tread portion 20B shown in FIG. 13, the drainage performance is improved by communicating with each lug groove 24 that divides the block of the tread portion 20B. Further, according to the pneumatic tire 1 having the tread portion 20B shown in FIG. 13, in the land portions on both sides of the tire equatorial plane CL, the inclination direction of the lug groove 24 is in the V-shaped basic tone in the tire width direction. On the other hand, by inclining, the water on the road surface can be pushed out 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. 14, the tread portion 20C without the lug groove 24 may be used. In FIG. 14, the tread portion 20C has a first land portion 31, a second land portion 32, and a third land portion 33. Since the first land portion 31, the second land portion 32, and the third land portion 33 do not have the lug groove 24, the blocks are not partitioned and 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 in the tire width direction of the rib arrangement range to the tread deployment width TDW is preferably in the range of 0.55 or more and 0.70 or less. It is more preferably 0.60 or more and 0.65 or less. When the rib-shaped first land portion 31 and second land portion 32 are adopted, the same effect as when the first land portion 31 and the second land portion 32 having the blocks 31B and 32B are adopted has the same effect. can get.

In FIGS. 2, 12, and 13, the case where the lug groove 24 extends linearly has been described, but the lug groove 24 may be bent in the middle of the extension. Further, the lug groove 24 may be bent at two points in the middle of the extension, and the lug groove 24 as a whole may have a Z-shape. Even if the lug groove 24 is bent in the middle of extension, the traction performance is improved because the inclination direction of the lug groove 24 is V-shaped at the land portions 31 and 32 on both sides of the tire equatorial surface CL. do.

Further, by bending the lug groove 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 groove 24 does not have to be V-shaped in the tread portion 20.

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

[summary]
According to the pneumatic tire 1 of this example, the rolling resistance performance can be improved by closing the groove and forming a wide rib block at the time of touchdown. Further, according to the pneumatic tire 1 of this example, the traction property can be improved by forming a directional pattern and providing a V-shaped lug groove. Further, according to the pneumatic tire 1 of this example, the heel-and-toe uneven wear can be improved by arranging the blocks at the same position and equalizing the load applied at the time of touchdown. Further, according to the pneumatic tire 1 of this example, the passing noise can be reduced because the lug grooves do not communicate with each other.

[Example]
Tables 1 to 5 are tables showing the results of performance tests of pneumatic tires according to the embodiment of the present invention. In this performance test, rolling resistance performance and groove crack resistance were evaluated for multiple types of test tires. The size of the pneumatic tire 1 used for the evaluation is 315 / 70R22.5. The pneumatic tire 1 was mounted on the specified rim and tested.

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

An indoor drum tester was used to evaluate the groove crack resistance. In the evaluation of groove crack resistance performance, the test tire was filled with the specified internal pressure, and the circumference after running a drum for 20000 km at a specified load and speed of 50 km / h in an atmosphere with an ambient temperature of 30 ° C. and an ozone concentration of 150 pphm. The reciprocal of the total length of cracks generated in the directional main groove was evaluated by an index based on the conventional example (100). The larger this value is, the better the groove crack resistance is.

Further, as a comparison target, a tire of a comparative example was prepared, and the rolling resistance performance and the groove crack resistance were evaluated in the same manner as described above. The tire of the comparative example is a tire having a circumferential fine groove and a circumferential main groove and not having a circumferential reinforcing layer. In the tire of the comparative example, the ratio of the groove width of the circumferential groove to the tread expansion width TDW is 0.025, and the ratio of the width in the tire width direction of the land arrangement range to the tread expansion width TDW is 0. The ratio of the groove width of the circumferential main groove to the tread expansion width TDW is 0.02, and the ratio of the groove width of the circumferential fine groove to the groove width of the two circumferential main grooves is 0. It is 05, and the ratio of the groove width of the lug groove to the tread development width TDW is 0.020. In the tire of the comparative example, the relationship between the tread radius RC and the tread radius RA is RC> RA, the ratio RC / RA of the tread radius RC to the tread radius RA is 0.50, and the ratio RC / RA to the tread radius RA is 0.50. The ratio RS / RA of the tread radius RS is 0.50, the relationship of each tread radius is not RS <RC <RA, the relationship of each total gauge is not Tc ≧ T1 ≧ T2 ≧ T3, and the ratio T3 / Tc is. It is 1.00. In the tire of the comparative example, the ratio Tsh / Tc of the total gauge Tsh of the shoulder portion to the total gauge Tc of the center portion is 1.00, and the ratio _WB0 / _Wt of the belt width WB0 to the total tire width Wt is 1.00. It is 0.70, the ratio _DBD / _Ws of the diameter difference DBD to the width Ws of the circumferential reinforcing layer is 0.03, and the ratio _WBO / W of the width _WBO of the belt to the carcass cross-sectional width _WC . _C is 0.70, the ratio _DD / TDW of the diameter difference _DD to the tread expansion width TDW is 0.09, and the flatness ratio is 80%.

As shown in Tables 1 to 5, the tires 1 of Examples 1 to 56 are reinforced in the circumferential direction with respect to the distance Wm in the tire width direction between the outer ends of the two circumferential main grooves in the tire width direction. The ratio Ws / Wm of the width Ws of the layer is 1 or more and 1.2 or less. In the tires of Examples 3 to 56, the ratio of the groove width of the circumferential narrow groove to the tread expansion width TDW is 0.007 or more and 0.024 or less. In the tires of Examples 7 to 56, the ratio of the width in the tire width direction of the land portion arrangement range to the tread deployment width TDW is 0.55 or more and 0.70 or less. In the tires of Examples 13 to 56, 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 Examples 7 to 56, 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 of Examples 21 to 56, the land portion is divided into blocks by lug grooves, and the ratio of the groove width of the lug groove to the tread development width TDW is 0.003 or more and 0.016 or less. In the tires of Examples 25 to 56, the relationship between the tread radius RC and the tread radius RA is RC <RA. In the tires of Examples 26 to 56, the ratio RC / RA of the tread radius RC to the tread radius RA is 0.60 or more and 0.90 or less. The tires of Examples 26 to 56 have a ratio RS / RA of tread radius RS to tread radius RA of 0.50 or more and 1.20 or less. In the tires of Examples 32 and 35 to 56, the relationship of each tread radius is RS <RC <RA. In the tires of Examples 36 to 56, 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 Examples 38 to 56, 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 Examples 45 to 56, the ratio _WB0 / _Wt of the belt width WB0 to the total tire width Wt is 0.72 or more and 0.82 or less. In the tires of Examples 50 to 56, the ratio _DBD / _Ws of the diameter difference DBD to the width Ws of the circumferential reinforcing layer is 0.022 or less. In the tires of Examples 51 to 56, the ratio _WBO / _WC of the belt width _WBO to the carcass cross-sectional width _WC is 0.74 or more. The tires of Examples 53 to 56 have a ratio _DD / TDW of the diameter difference _DD with respect to the tread expansion width TDW of 0.085 or less. The tires of Examples 54 to 56 have a flatness of 70% or less.

As shown in Tables 1 to 5, according to Examples 1 to 56, the circumferential reinforcing layer with respect to the distance Wm in the tire width direction between the outer ends of the two circumferential main grooves in the tire width direction. When the ratio Ws / Wm of the width Ws is 1 or more and 1.2 or less, and when the ratio of the groove width of the circumferential groove to the tread expansion width TDW is 0.007 or more and 0.024 or less, the arrangement of the land portion. When the ratio of the width in the tire width direction of the range to the tread expansion width TDW is 0.55 or more and 0.70 or less, the ratio of the groove width of the circumferential main groove to the tread expansion width TDW is 0.025 or more and 0. When it is 055 or less, when the ratio of the groove width of the circumferential fine groove to the groove width of the two circumferential main grooves is 0.15 or more and 0.45 or less, the land portion is divided into blocks by the lug groove. When the ratio of the groove width of the lug groove to the tread expansion width TDW is 0.003 or more and 0.016 or less, the relationship between the tread radius RC and the tread radius RA is RC <RA, the tread. When the ratio RC / RA of the tread radius RC to the radius RA is 0.60 or more and 0.90 or less, and when the ratio RS / RA of the tread radius RS to the tread radius RA is 0.50 or more and 1.20 or less. , When the relationship of each tread radius is RS <RC <RA, when the relationship of each total gauge is Tc ≧ T1 ≧ T2 ≧ T3 and the ratio T3 / Tc is 0.98 or less, the total gauge of the center part. When the ratio Tsh / Tc of the total gauge Tsh of the shoulder portion to Tc is 1.10 or more and 1.50 or less, the ratio of the belt width _WB0 to the total tire width Wt is 0.72 ≦ _WB0 / Wt ≦. When it is 0.82, the ratio of the diameter difference DBD to the width Ws of the circumferential reinforcing layer _DBD / Ws is _0.022 or less, the ratio W of the belt width _WBO to the carcass cross-sectional width _WC . Good when _BO / _WC is 0.74 or more, when the ratio _DD / TDW of the diameter difference _DD to the tread expansion width TDW is 0.085 or less, and when the flatness ratio is 70% or less. It can be seen that various results can be obtained.

1 Pneumatic tire 11 Bead core 13 Carcass layer 14 Belt layer 15 Tread rubber 16 Side wall rubber 17 Rim cushion rubber 20, 20A, 20B, 20C Tread part 21 First circumference main groove 22 Second circumference direction main groove 23 Third circumference Direction Main groove 24 Rug groove 31 First land part 31B, 32B Block 32 Second land part 33 Third land part 140 Circumferential reinforcement layer 141 High angle belt 142, 143 Cross belt ply 144 Belt cover CL Tire equatorial surface TDW tread deployment width

Claims (13)

Two circumferential main grooves extending in the tire circumferential direction, at least one circumferential narrow groove arranged between the two circumferential main grooves, and the tire radial direction of the two circumferential main grooves. It is provided with a circumferential reinforcing layer provided inside, and in the tire meridional cross section, the circumferential reinforcing layer with respect to the distance Wm in the tire width direction between the outer ends of the two circumferential main grooves in the tire width direction. The ratio Ws / Wm of the width Ws in the tire width direction at both ends is 1 or more and 1.2 or less, and 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 law of nature,
One of the circumferential grooves is provided on the equatorial plane of the tire.
The two circumferential main grooves are the outermost circumferential main grooves in the tire width direction.
No other circumferential main groove is provided between the two circumferential main grooves.
In the tire meridional cross section, the relationship between the tread radius RC from the tire equatorial plane to the outer end of the circumferential main groove in the tire width direction and the tread radius RA from the tire equatorial plane to the ground contact end is RC <RA. Pneumatic tires . A land portion defined by the at least one circumferential narrow groove and the two circumferential main grooves is provided, and the tire width direction of the arrangement range of the land portion between the two circumferential main grooves is provided. The ratio of the width to the tread expansion width TDW is 0.55 or more and 0.70 or less.
The ratio of the groove widths of the two circumferential main grooves to the tread expansion width TDW is 0.025 or more and 0.055 or less.
The pneumatic tire according to claim 1, wherein the ratio of the groove width of the circumferential fine groove to the groove width of the two circumferential main grooves is 0.15 or more and 0.45 or less. The land portion is divided into blocks by a lug groove extending in the tire width direction, and the ratio of the groove width of the lug groove to the tread expansion width TDW is 0.003 or more and 0.016 or less. Pneumatic tires listed in. The pneumatic tire according to any one of claims 1 to 3, wherein the ratio RC / RA of the tread radius RC to the tread radius RA is 0.60 or more and 0.90 or less. A claim that the ratio RS / RA of the tread radius RS from the outer end of the circumferential main groove in the tire width direction to the ground contact end with respect to the tread radius RA is 0.50 or more and 1.20 or less in the tire meridional cross section . 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 . In the tire meridional cross section, the total gauge of the center portion measured along the normal line drawn from the tread surface to the center of the thickness of the carcass layer along the tire equatorial plane is defined as Tc, and the total gauge of the center portion is defined as Tc. The width to the outer end in the tire width direction is We, and along the normal line drawn from the tread surface to the center of the thickness of the carcass layer at a position of 0.33 We from the center to the outer side in the tire width direction. The measured total gauge is T1, and the total gauge measured along the normal line drawn from the tread surface to the center of the thickness of the carcass layer at a position of 0.66 We from the center to the outside in the tire width direction is T2. Let T3 be the total gauge measured along the normal line drawn from the tread surface to the center of the thickness of the carcass layer at the position of the outer end of the main groove in the circumferential direction in the tire width direction.
Tc ≧ T1 ≧ T2 ≧ T3 and T3 / Tc ≦ 0.98
The pneumatic tire according to any one of claims 1 to 6 . When the shoulder total gauge measured along the normal line provided with the carcass layer and drawn from the ground contact 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 . When the belt width on the side of the cross belt arranged in the tread where the width in the tire width direction is small is _WB0 and the total tire width is Wt.
0.72 ≤ W _B0 / Wt ≤ 0.82
The pneumatic tire according to any one of claims 1 to 8 . In the tire meridional cross section, the diameter _DBC of the circumferential reinforcing layer along the equatorial plane of the tire to the outer side of the tire radial direction and the tire of the circumferential reinforcing layer at the position of the outer end portion of the circumferential reinforcing layer in the tire width direction. When the diameter difference from the diameter _DBS to the outside in the radial direction | _DBC - _DBS | is _DBD ,
D _BD / Ws ≤ 0.022
The pneumatic tire according to any one of claims 1 to 9 . In the pair of crossed belts, when the belt arranged on the outer side in the tire radial direction is the belt on the side where the width in the tire width direction is small, the width of the belt is set to _WBO and the carcass cross-sectional width is set to _WC . When
W _BO / _WC ≧ 0.74
The pneumatic tire according to any one of claims 1 to 10 . For pneumatic tires, when the outer diameter at the position along the equator surface of the tire is DC and the outer diameter at the ground contact end is _DS , and the diameter difference | _{DC - DS} | is _DD . ,
_DD / TDW ≤ 0.085
The pneumatic tire according to any one of claims 1 to 11 . The pneumatic tire according to any one of claims 1 to 12 , wherein the flatness, which is a percentage of the ratio of the cross-sectional height of the tire to the cross-sectional width of the tire, is 70% or less.

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