JP7107104B2 - pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire in which a belt layer and a belt reinforcing layer are embedded in the tread portion, and more particularly, it effectively suppresses steering wheel drift, improves the linearity of steering stability, The present invention relates to a pneumatic tire capable of suppressing uneven shoulder wear.

A pneumatic tire generally includes a carcass layer mounted between a pair of bead portions, a plurality of belt layers disposed outside the carcass layer in the tread portion in the tire radial direction, and the belt layers outside the tire radial direction. and a belt reinforcing layer disposed on the belt. The belt layers include a plurality of belt cords that are inclined with respect to the tire circumferential direction, and are arranged so that the belt cords intersect each other between the layers. On the other hand, the belt reinforcing layer includes a plurality of band cords oriented in the tire circumferential direction.

In such a pneumatic tire, a method of designing the tire so as to increase the absolute value of the residual cornering force is employed in order to suppress steering wheel drift during vehicle running. For example, it is known that the absolute value of residual cornering of the tire increases by increasing the rigidity of the belt layer by reducing the angle of inclination of the belt cords forming the belt layer with respect to the tire circumferential direction. However, when the rigidity of the belt layer becomes excessive, there is a problem that the cornering power increases in a high-load region and the linearity of steering stability deteriorates. In other words, the linearity (linearity) of the steering stability is not good in driving conditions in which the cornering power increases from the middle stage to the latter half of the steering wheel compared to the initial stage and the movement of the vehicle becomes hypersensitive. Therefore, there is a demand for tuning that improves the linearity of steering stability (see Patent Document 1, for example).

On the other hand, it has been proposed to improve the steering stability by increasing the cornering power in the low load range (see, for example, Patent Documents 2 and 3). However, the current situation is that it is not possible to sufficiently meet the demand for improving the linearity of steering stability simply by increasing the cornering power in the low load range.

JP 2016-141268 A JP 2011-230737 A Japanese Unexamined Patent Application Publication No. 2012-17001

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire that effectively suppresses steering wheel drift, improves the linearity of steering stability, and suppresses uneven shoulder wear of the tread portion. .

The pneumatic tire of the present invention for achieving the above object includes a carcass layer mounted between a pair of bead portions, a plurality of belt layers disposed outside the carcass layer in the tire radial direction of the tread portion, a belt reinforcing layer arranged outside the belt layer in the tire radial direction, the belt layer including a plurality of belt cords inclined with respect to the tire circumferential direction, and the belt cords being arranged so as to intersect each other between the layers. and wherein the belt reinforcing layer includes a band cord oriented in the tire circumferential direction,
The plurality of belt layers has a first belt layer located inside in the tire radial direction and a second belt layer located outside in the tire radial direction, and belt cords constituting the first belt layer and the second belt layer. where X and Y are the inclination angles with respect to the tire circumferential direction at the tire center position, these inclination angles X and Y satisfy the relationship of 15°≦|Y|<|X|≦35°,
Loads corresponding to 40%, 75%, and 100% of the maximum load capacity specified by the standard are W40, W75, and W100 (kN), respectively. Let CP40, CP75, and CP100 (kN/°) be the cornering powers measured under the conditions of loading W75 and W100, respectively, let R be the aspect ratio of the pneumatic tire, let D (mm) be its outer diameter, and When the nominal cross-sectional width is A (mm), the loads W40, W75, W100 and the cornering powers CP40, CP75, CP100 are 0.05≦(R×D/2A) ² ×[(CP100−CP75)/ (W100-W75)]/[(CP75-CP40)/(W75-W40)].ltoreq.0.50.

As a result of intensive research on the relationship between the inclination angle of the belt layers with respect to the tire circumferential direction and the absolute value of the residual cornering force, the present inventors found that the first belt layer positioned radially inward of the tire and the second belt layer positioned radially outward of the tire In providing two belt layers, by lowering the angle of only the second belt layer, it is possible to increase the absolute value of the residual cornering force while suppressing excessive increases in cornering power in high load areas. This finding led to the present invention.

That is, in the present invention, when the inclination angles of the belt cords constituting the first belt layer and the second belt layer with respect to the tire circumferential direction at the tire center position are X and Y, the inclination angles X and Y are 15°. By satisfying the relationship ≤ |Y| Here, loads W40, W75, W100 and cornering powers CP40, CP75, CP100 are 0.05≦(R×D/2A) ² ×[(CP100-CP75)/(W100-W75)]/[(CP75-CP40 )/(W75−W40)]≦0.50, it is possible to suppress an excessive increase in cornering power in the high load region. As a result, steering wheel drift is effectively suppressed by increasing the absolute value of the residual cornering force, and at the same time, an appropriate cornering power is exhibited as the load increases, so that the linearity of steering stability can be improved. In particular, the easiness of outputting cornering power differs depending on the tire size, so the above relational expression is corrected by the value of (R×D/2A) ² . In other words, a tire having a lower aspect ratio and a smaller ratio of the outer diameter to the nominal section width reduces the contribution of cornering power on the high load side. Furthermore, according to the findings of the present inventors, by lowering the angle of the second belt layer positioned on the radially outer side of the tire, it is possible to obtain the effect of improving uneven shoulder wear of the tread portion.

In the present invention, n measurement points are defined to equally divide the width of the second belt layer, which is narrower than the first belt layer, and the tire circumference at each measurement point of the belt cords constituting the first belt layer is determined. Let Xi (i = 1 to n) be the inclination angle with respect to the direction, and let Yi (i = 1 to n) be the inclination angle with respect to the tire circumferential direction at each measurement point of the belt cords constituting the second belt layer. Preferably, the angles Xi and Yi satisfy the relation |Yi|<|Xi| and the inclination angles X and Y satisfy the relation |X|-|Y|≧2°. By reducing the angle of the belt cords that make up the second belt layer, it is possible to effectively improve steering wheel flow. By increasing the difference, uneven shoulder wear can be effectively suppressed. Such a relationship preferably holds across the entire width of the second belt layer.

When a tire is mounted on a vehicle used in a region such as Japan where left-hand traffic is predominant, the first belt layer is inclined in the diagonally lower right direction with respect to the tire circumferential direction, and the second belt layer is the tire. It is preferable to incline in the oblique lower left direction with respect to the circumferential direction. In the case of left-hand traffic, the road surface cant is set so that the left side is lower, but the lateral force generated by the road surface cant causes uneven wear in the shoulder area on the outside of the tread of the front left tire. becomes easier. On the other hand, by adopting a structure in which the second belt layer with a low angle is inclined in a diagonally lower left direction with respect to the tire circumferential direction, tire slippage is reduced and uneven shoulder wear of the tread is effectively prevented. can be suppressed to

When a tire is mounted on a vehicle used in regions such as the United States where right-hand traffic is predominant, the first belt layer is inclined in a diagonally lower left direction with respect to the tire circumferential direction, and the second belt layer is tilted toward the tire circumferential direction. It is preferable to incline diagonally to the lower right with respect to the direction. In the case of right-hand traffic, the road surface cant is set so that the right side is lower, but the lateral force generated by the road surface cant causes uneven wear in the shoulder area on the outer side of the tread of the front right tire. becomes easier. On the other hand, by adopting a structure in which the second belt layer with a lower angle is inclined in the lower right direction with respect to the tire circumferential direction, tire slippage is reduced and uneven shoulder wear of the tread is reduced. can be effectively suppressed.

When a plurality of lateral grooves extending in the tire width direction are formed in shoulder land portions defined by the tread portion, it is preferable that these lateral grooves are inclined in the same direction as the second belt layer with respect to the tire circumferential direction. As a result, the residual cornering force obtained by the inclination of the lateral grooves of the shoulder land portion in the same direction as the second belt layer can be increased, and steering wheel movement during running of the vehicle can be effectively suppressed.

Further, the inclination angle Z of the lateral grooves with respect to the tire width direction is preferably in the range of 5°≦|Z|≦45°. As a result, steering wheel drift can be effectively suppressed.

In the belt reinforcing layer, the inclination angle θ of the band cord with respect to the tire circumferential direction is in the range of 0°≦|θ|≦30°, and the absolute value of the inclination angle θ of the band cord with respect to the tire circumferential direction is inside the tire width direction. It is preferred that it gradually increases from . By inclining the band cords of the belt reinforcing layer within the range of the inclination angle θ and gradually increasing the absolute value of the inclination angle θ from the inside to the outside in the tire width direction, the steering wheel drift is effectively suppressed, Since the rigidity of the belt reinforcing layer is also reduced, it is possible to suppress an excessive increase in cornering power in a high-load region and improve the linearity of steering stability.

In the belt reinforcing layer, the band cords are preferably inclined in the same direction as the second belt layer with respect to the tire circumferential direction. As a result, the residual cornering force obtained by the band cords of the belt reinforcing layer being inclined in the same direction as that of the second belt layer can be increased, and steering wheel movement can be effectively suppressed when the vehicle is running.

In the present invention, the pneumatic tire is filled with air pressure of 230 kPa, and the tire circumferential direction when grounded under the conditions of loading 40%, 75%, and 100% of the maximum load capacity specified by the standard. The maximum ground contact lengths are LA1, LB1, and LC1, respectively, and the maximum ground contact widths in the tire width direction are WA1, WB1, and WC1, respectively. When LA2, LB2, and LC2 are the external contact lengths in the circumferential direction of the tire at positions , the maximum contact lengths LA1, LB1, LC1 and the external contact lengths LA2, LB2, LC2 are 1.02≦(LB2/LB1)/ It is preferable to satisfy the relationships of (LA2/LA1)≦1.25, 1.00≦(LC2/LC1)/(LB2/LB1)≦1.20, and 0.75≦LB2/LB1≦1.00. By controlling the load dependency of the ground contact shape in this manner, the linearity of steering stability can be further improved.

In the present invention, the cornering power is measured under the condition that the tire is mounted on a regular rim and filled with a predetermined air pressure and a predetermined load is applied, the camber angle is 0 °, the speed is 10 km / h, and the slip The cornering force is measured while changing the angle, and the cornering force is calculated based on the cornering force in the range where the slip angle is 0° to 1°. The contact shape of the tread portion is measured under the condition that the tire is mounted on a regular rim, filled with a predetermined air pressure, placed vertically on a flat surface, and a predetermined load is applied. The outer diameter of a pneumatic tire is measured at the center position of the tire in a state in which the tire is mounted on a regular rim and filled with a predetermined air pressure. "Regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, JATMA is a standard rim, TRA is a "Design Rim", or ETRTO. If so, it should be "Measuring Rim". Air pressure is 230 kPa. The predetermined load is 40%, 75%, or 100% of the maximum load capacity determined for each tire by each standard in the system of standards including the standards on which tires are based.

1 is a meridian sectional view showing a pneumatic tire according to an embodiment of the invention; FIG. FIG. 2 is a developed view showing a tread pattern of the pneumatic tire of FIG. 1; FIG. 2 is a developed view showing a first belt layer and a second belt layer of the pneumatic tire of FIG. 1; 4 is a graph showing the relationship between cornering power (CP) and load. FIG. 4 is a developed view showing belt cords forming a first belt layer and a second belt layer; FIG. 4 is a developed view showing an example of a belt reinforcing layer; FIG. 2 is a plan view showing the ground contact shape (40% load) of the pneumatic tire of FIG. 1; FIG. 2 is a plan view showing the ground contact shape (75% load) of the pneumatic tire of FIG. 1; FIG. 2 is a plan view showing the ground contact shape (100% load) of the pneumatic tire of FIG. 1;

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 3 show a pneumatic tire according to an embodiment of the invention. 1 to 3, CL is the tire center position, Tc is the tire circumferential direction, and Tw is the tire width direction.

As shown in FIG. 1, the pneumatic tire of this embodiment includes a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1. and a pair of bead portions 3 , 3 arranged radially inward of the sidewall portions 2 .

A carcass layer 4 is mounted between the pair of bead portions 3,3. The carcass layer 4 includes a plurality of carcass cords extending in the tire radial direction, and is folded back from the tire inner side to the outer side around the bead cores 5 arranged in the respective bead portions 3 . A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer circumference of the bead core 5 .

On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1 . These belt layers 7 include a plurality of belt cords inclined with respect to the tire circumferential direction, and are arranged so that the belt cords intersect each other between the layers. Steel cords are preferably used as the belt cords forming the belt layer 7 . At least one belt reinforcing layer 8 including a plurality of band cords oriented in the tire circumferential direction is arranged on the outer peripheral side of the belt layer 7 . It is desirable that the belt reinforcing layer 8 has a jointless structure in which a strip material formed by arranging at least one band cord and covering it with rubber is continuously wound in the tire circumferential direction. As the band cords forming the belt reinforcing layer 8, organic fiber cords such as nylon and aramid cords are preferably used.

As shown in FIG. 2, the tread portion 1 has a pair of central main grooves 11, 11 extending in the tire circumferential direction at positions on both sides of the tire center position CL, and a pair of central main grooves 11, 11 extending outward in the tire width direction from the central main grooves 11, 11. A pair of outer main grooves 12, 12 extending in the tire circumferential direction are formed at positions of . The central main groove 11 and the outer main groove 12 may have a straight shape, or may have a zigzag shape. As a result, the center land portion 20 is defined between the central main grooves 11, 11, the middle land portion 30 is defined between the center main groove 11 and the outer main groove 12, and the outside of the outer main groove 12. A shoulder land portion 40 is defined in .

A plurality of sipes 31 extending in the tire width direction are formed in each of the middle land portions 30 . The sipe 31 has a groove width of, for example, 1.0 mm or less on the tread surface. A circumferential narrow groove 32 extending in the tire circumferential direction and having a zigzag shape is formed on one side of the middle land portion 30 .

A plurality of lateral grooves 41 extending in the tire width direction are formed in each of the shoulder land portions 40 . These lateral grooves 41 do not communicate with the outer main groove 12, and the groove width on the tread surface is set within a range of 1.1 mm to 9.5 mm, for example. A plurality of sipes 42 extending in the tire width direction are formed on one side of the shoulder land portion 40 . The sipe 42 communicates with the outer main groove 12 and has a groove width of, for example, 1.0 mm or less on the tread surface.

In the pneumatic tire described above, as shown in FIG. The inclination angles of the belt cords 71C and 72C forming the first belt layer 71 and the second belt layer 72 with respect to the tire circumferential direction at the tire center position CL are X and Y, respectively. , the inclination angles X and Y satisfy the relationship of 15°≦|Y|<|X|≦35°. When the tread portion 1 is viewed from the front, the belt cords 71C and 72C forming the first belt layer 71 and the second belt layer 72 are inclined at angles X and Y with respect to the tire circumferential direction. A positive value is assumed, and a negative value is assumed when the belt cord is slanted to the left.

In the above pneumatic tire, the loads corresponding to 40%, 75%, and 100% of the maximum load capacity specified by the standard are W40, W75, and W100 (kN), respectively, and the pneumatic tire is inflated to an air pressure of 230 kPa. Let CP40, CP75, and CP100 (kN/°) be the cornering powers measured under the conditions of filling and loading W40, W75, and W100, respectively, the aspect ratio of the pneumatic tire be R, and its outer diameter be D ( mm), and the nominal cross-sectional width thereof is A (mm).

Here, loads W40, W75, W100 and cornering powers CP40, CP75, CP100 are 0.05≦(R×D/2A) ² ×[(CP100−CP75)/(W100−W75)]/[(CP75− CP40)/(W75−W40)]≦0.50.

In the pneumatic tire described above, when the inclination angles of the belt cords 71C and 72C forming the first belt layer 71 and the second belt layer 72 with respect to the tire circumferential direction at the tire center position CL are respectively X and Y, these inclination angles By satisfying the relationship of 15° ≤ |Y| < |X| can be suppressed. Here, if the absolute value of the inclination angle Y is smaller than 15°, it becomes difficult to control the linearity of the steering stability due to the increased rigidity of the belt layer 7, and if the absolute value of the inclination angle X is larger than 35°. It is not practical because tire characteristics such as cornering characteristics and steering stability are degraded.

FIG. 4 is a graph showing the relationship between cornering power (CP) and load. In FIG. 4, the tire C is a pneumatic tire having a reference structure (the inclination angles of the belt cords 71C and 72C constituting the first belt layer 71 and the second belt layer 72 with respect to the tire circumferential direction are both set to low angles). ), and the tire A is a pneumatic tire in which the belt cords 71C and 72C constituting the first belt layer 71 and the second belt layer 72 have a lower inclination angle with respect to the tire circumferential direction than the tire C, In the tire B, the inclination angle of the belt cords 72C constituting the second belt layer 72 with respect to the tire circumferential direction is set to a low angle as in the case of the tire C, while the belt cords 71C constituting the first belt layer 71 are inclined with respect to the tire circumferential direction. This is a pneumatic tire with a higher inclination angle than the tire C. As is clear from the comparison of the tires A and C, when the inclination angles of the belt cords 71C and 72C constituting the first belt layer 71 and the second belt layer 72 are both reduced, the cornering power in the high load range increases. do. On the other hand, when only the inclination angle of the belt cords 72C constituting the second belt layer 72 with respect to the tire circumferential direction is reduced (tire B), the excessive increase in cornering power in the high load region is suppressed. .

In the pneumatic tire described above, loads W40, W75, W100 and cornering powers CP40, CP75, CP100 are 0.05≦(R×D/2A) ² ×[(CP100−CP75)/(W100−W75)]. By satisfying the relationship of /[(CP75-CP40)/(W75-W40)]≤0.50, an excessive increase in cornering power in the high load range can be suppressed. As a result, appropriate cornering power is exhibited as the load increases, so the linearity of steering stability can be improved. In particular, since the above relational expression is corrected by the value of (R×D/2A) ² , tires with a lower aspect ratio and a smaller ratio of the outer diameter to the nominal cross-sectional width contribute to cornering power on the high-load side. Lower. Therefore, it is possible to exhibit moderate cornering power according to the tire size.

Here, when (R×D/2A) ² ×[(CP100-CP75)/(W100-W75)]/[(CP75-CP40)/(W75-W40)] is smaller than 0.05, the low load region On the other hand, if it is greater than 0.50, the cornering power will be excessive in the high load range, and in either case, the linearity of steering stability will be impaired. In particular, satisfying the relationship 0.10≦(R×D/2A) ² ×[(CP100-CP75)/(W100-W75)]/[(CP75-CP40)/(W75-W40)]≦0.40 It is desirable to

Further, when the angle of the belt cords 72C forming the second belt layer 72 positioned radially outward of the tire is reduced as described above, uneven shoulder wear of the tread portion 1 can be improved.

In the above pneumatic tire, as shown in FIG. 5, n measurement points _Pi (i=1 to n ), the inclination angle of the belt cord 71C constituting the first belt layer 71 with respect to the tire circumferential direction at each measurement point Pi is defined as Xi (i = 1 to n), and the belt cord 72C constituting the second belt layer 72 When the inclination angle with respect to the tire circumferential direction at each measurement point Pi is Yi (i = 1 to n), these inclination angles Xi and Yi satisfy the relationship |Yi|<|Xi| , Y satisfy the relationship |X|-|Y|≧2°.

By lowering the angle of the belt cord 72C forming the second belt layer 72, it is possible to effectively improve the handle flow, and the belt cords 71C and 72C forming the first belt layer 71 and the second belt layer 72 can be effectively improved. By increasing the angle difference at the tire center position CL, uneven shoulder wear can be effectively suppressed. Such a relationship preferably holds across the entire width of the second belt layer 72 . If the value of |X|-|Y| is smaller than 2°, the effect of simultaneously suppressing steering wheel flow and improving the linearity of steering stability is reduced, and the effect of suppressing uneven shoulder wear of the tread portion 1 is reduced. do. In particular, it is desirable that 3°≦|X|−|Y|≦7°. For the same reason, the inclination angles Xi and Yi at all the measurement points Pi should be |Xi|-|Yi|≧2°, more preferably 3°≦|Xi|-|Yi|≦7°. is desirable.

In FIG. 5, seven measurement points P ₁ to P ₇ are defined, the inclination angles at the measurement points P ₁ to P ₇ of the belt cord 71C are X ₁ to X ₇ , and the measurement points P ₁ to P 7 of the belt cord 72C are defined as X 1 to X 7 . Although the inclination angles at P ₇ are Y ₁ to Y ₇ , there should be at least five such measurement points Pi from one edge of the second belt layer 72 toward the other edge. The distance between the measurement points in the tire width direction should be in the range of 25 mm to 40 mm. As a result, it is possible to control the angle of about one out of twenty belt cords 71C and 72C, so that a desired effect can be obtained.

When the tire is mounted on a vehicle used in regions such as Japan where left-hand traffic is predominant, as shown in FIG. However, it is preferable that the second belt layer 72 is inclined in a diagonally lower left direction with respect to the tire circumferential direction. In the case of left-hand traffic, the road surface cant is set so that the left side is lower, but the lateral force generated by the road surface cant causes uneven wear in the shoulder area of the tread portion 1 on the outer side of the vehicle in the front left tire. easily occur. On the other hand, by adopting a structure in which the second belt layer 72 with a low angle is inclined in a diagonally lower left direction with respect to the tire circumferential direction, tire slippage is reduced and uneven shoulder wear of the tread portion 1 is prevented. can be effectively suppressed.

When a tire is mounted on a vehicle used in regions such as the United States where right-hand traffic is predominant, the first belt layer 71 is inclined in a diagonally lower left direction with respect to the tire circumferential direction, and the second belt layer 72 is inclined downward. It is preferable to employ a structure that is inclined in a diagonally lower right direction with respect to the tire circumferential direction, that is, a structure that is symmetrical with FIG. In the case of right-hand traffic, the road surface cant is set so that the right side is lower, but the lateral force generated by the road surface cant causes uneven wear in the shoulder area of the vehicle outer side of the tread portion 1 of the front right tire. easily occur. On the other hand, by adopting a structure in which the second belt layer 72 with a low angle is inclined in the obliquely lower right direction with respect to the tire circumferential direction, tire slippage is reduced and shoulder uneven wear of the tread portion 1 is adopted. can be effectively suppressed.

As shown in FIG. 2 , when a plurality of lateral grooves 41 extending in the tire width direction are formed in the shoulder land portion 40 partitioned by the tread portion 1 , these lateral grooves 41 extend along the second belt layer 72 in the tire circumferential direction. (See FIGS. 2 and 3). As a result, the residual cornering force obtained by the inclination of the lateral grooves 41 of the shoulder land portion 40 in the same direction as the second belt layer 72 can be increased, and steering wheel movement can be effectively suppressed when the vehicle is running.

Further, the inclination angle Z of the lateral grooves 41 with respect to the tire width direction is preferably in the range of 5°≦|Z|≦45°. As a result, steering wheel drift can be effectively suppressed. In addition, in a tire in which the linearity of steering stability is desired to be further enhanced, the effect of preventing the steering wheel drift is ensured based on the inclination angle Z of the lateral grooves 41 without making the inclination angle Y of the second belt layer 72 extremely small. It becomes possible to satisfy the target performance. Here, if the absolute value of the inclination angle Z of the lateral grooves 41 is less than 5°, the residual cornering force due to the inclination of the lateral grooves 41 becomes insufficient, and conversely, if it is greater than 45°, uneven shoulder wear tends to occur. In particular, the inclination angle Z of the lateral grooves 41 with respect to the tire width direction is preferably in the range of 7°≦|Z|≦20°.

The inclination angle Z of the lateral grooves 41 is defined by the groove width center of the lateral grooves 41 and the width of the lateral grooves 41 at the contact end position in the tire width direction when the air pressure is 230 kPa and a load of 75% of the maximum load capacity specified by the standard is applied. It is the angle formed by a straight line connecting the groove width center of the lateral groove 41 at the inner end position in the tire width direction with respect to the reference line in the tire width direction. The inclination angle Z of the lateral grooves 41 is positive when the lateral grooves 41 are inclined clockwise with respect to the reference line in the tire width direction when the tread portion 1 is viewed from the front. A negative value indicates a counterclockwise tilt with respect to the directional reference line.

FIG. 6 shows an example of the belt reinforcing layer in the pneumatic tire of the present invention. As shown in FIG. 6, in the belt reinforcing layer 8, the inclination angle θ of the band cord B with respect to the tire circumferential direction is in the range of 0°≦|θ|≦30°, and the inclination angle of the band cord B with respect to the tire circumferential direction is The absolute value of θ gradually increases from the inner side to the outer side in the tire width direction. Thus, by inclining the band cord B of the belt reinforcing layer 8 within the range of the inclination angle θ and gradually increasing the absolute value of the inclination angle θ from the inside to the outside in the tire width direction, the steering wheel flow can be effectively controlled. In addition, since the rigidity of the belt reinforcing layer 8 is also reduced, it is possible to suppress an excessive increase in cornering power in a high load region and improve the linearity of steering stability. However, if the absolute value of the inclination angle θ of the band cord B with respect to the tire circumferential direction is greater than 30°, the high-speed durability is adversely affected. The inclination angle θ of the band cords B forming the belt reinforcing layer 8 with respect to the tire circumferential direction is defined as a positive value when the band cords B are slanted to the right when the tread portion 1 is viewed from the front, and the belt cords are slanted to the left. A negative value is given when

In the belt reinforcing layer 8, the band cords B are preferably inclined in the same direction as the second belt layer 72 with respect to the tire circumferential direction. As a result, the residual cornering force obtained by the band cords B of the belt reinforcing layer 8 being inclined in the same direction as the second belt layer 72 can be increased, effectively suppressing steering wheel movement during vehicle running.

7 to 9 show the ground contact shapes (40% load, 75% load, 100% load) of the pneumatic tire in FIG. 1, respectively. In the above pneumatic tire, the pneumatic tire is filled with air pressure of 230 kPa, and the tire when grounded under the conditions of loading 40%, 75%, and 100% of the maximum load capacity specified by the standard. The maximum ground contact lengths in the circumferential direction are LA1, LB1, and LC1 (mm), and the maximum ground contact widths in the tire width direction are WA1, WB1, and WC1 (mm), respectively. Let LA2, LB2, and LC2 (mm) be the outer contact lengths in the tire circumferential direction at 40% positions of the widths WA1, WB1, and WC1, respectively.

That is, as shown in FIG. 7, the pneumatic tire is filled with air pressure of 230 kPa, and the maximum load in the tire circumferential direction when the tire is grounded under the condition of loading 40% of the maximum load capacity specified by the standard. Let LA1 be the contact length, WA1 be the maximum contact width in the tire width direction, and LA2 be the external contact length in the tire circumferential direction at a position 40% of the maximum contact width WA1 from the tire center position CL toward the outside in the tire width direction. . The outer contact length LA2 is the average value of the measured values on both sides of the tire center position CL.

Further, as shown in FIG. 8, when the pneumatic tire is filled with air pressure of 230 kPa and is grounded under the condition of loading 75% of the maximum load capacity specified by the standard, the maximum pressure in the tire circumferential direction Let LB1 be the ground contact length, WB1 be the maximum ground contact width in the tire width direction, and LB2 be the external contact length in the tire circumferential direction at a position 40% of the maximum contact width WB1 from the tire center position CL toward the outside in the tire width direction. . The outer contact length LB2 is the average value of the measured values on both sides of the tire center position CL.

Furthermore, as shown in FIG. 9, when the pneumatic tire is filled with air pressure of 230 kPa and is grounded under the condition of loading 100% of the maximum load capacity specified by the standard, the maximum load in the tire circumferential direction Let LC1 be the contact length, WC1 be the maximum contact width in the tire width direction, and LC2 be the external contact length in the tire circumferential direction at a position 40% of the maximum contact width WC1 from the tire center position CL toward the outside in the tire width direction. . The outer contact length LC2 is the average value of the measured values on both sides of the tire center position CL.

Here, the maximum ground lengths LA1, LB1, LC1 and external ground lengths LA2, LB2, LC2 preferably satisfy the following relationship.
1.02≦(LB2/LB1)/(LA2/LA1)≦1.25
1.00≦(LC2/LC1)/(LB2/LB1)≦1.20
0.75≤LB2/LB1≤1.00

By controlling the load dependency of the ground contact shape in this manner, the linearity of steering stability can be further improved. That is, LA2/LA1 means the rectangular ratio at 40% load, LB2/LB1 means the rectangular ratio at 75% load, and LC2/LC1 means the rectangular ratio at 100% load. , (LB2/LB1)/(LA2/LA1) as an index for controlling the contact shape in the low load region, and (LC2/LC1)/ as an index for controlling the contact shape in the high load region. By defining the value of (LB2/LB1), it is possible to further enhance the feeling of linearity of steering stability.

Here, if (LB2/LB1)/(LA2/LA1) or (LC2/LC1)/(LB2/LB1) deviates from the above range, the effect of improving the linearity of steering stability decreases. In particular, it is desirable to satisfy the relationships of 1.03≤(LB2/LB1)/(LA2/LA1)≤1.15 and 1.02≤(LC2/LC1)/(LB2/LB1)≤1.10.

Also, in order to improve the wear life, it is desirable to set LB2/LB1 within the above range under a load condition of 75%, which is regarded as a normal normal load. When LB2/LB1 is less than 0.75, the wear life is shortened, and when it is greater than 1.00, it becomes difficult to tune the linearity of steering stability. In particular, it is desirable to satisfy the relationship 0.80≤LB2/LB1≤0.95.

In a tire size of 205/55R16 91V, a carcass layer mounted between a pair of bead portions, two belt layers disposed outside the carcass layer in the tread portion in the tire radial direction, and the belt layer outside the tire radial direction In a pneumatic tire provided with a belt reinforcing layer arranged in the tire radial direction, the inclination angle X with respect to the tire circumferential direction of the belt cord constituting the first belt layer located on the tire radial direction inner side with respect to the tire circumferential direction at the tire center position, the tire radial direction outer side Inclination angle Y with respect to the tire circumferential direction at the tire center position of the belt cords constituting the second belt layer located at , and the belt cords of the first belt layer at five measurement points that equally divide the width of the second belt layer the inclination angles X ₁ to X ₅ of the second belt layer, the inclination angles Y ₁ to Y ₅ of the belt cords of the second belt layer at five measurement points dividing the width of the second belt layer equally, the inclination direction of the first belt layer, The direction of inclination of the second belt layer, the country of use of the tire, the direction of inclination of the lateral grooves of the shoulder land portion, the inclination angle Z of the lateral grooves of the shoulder land portion with respect to the tire width direction, and the position of the band cords forming the belt reinforcing layer at the tire center position. Inclination angle θ with respect to the tire circumferential direction, inclination angle θ with respect to the tire circumferential direction at the shoulder end position of the band cord constituting the belt reinforcing layer, inclination direction of the belt reinforcing layer, low load region CP variation coefficient P = [(CP75-CP40 )/(W75-W40)], high-load area CP variation coefficient Q = [(CP100-CP75)/(W100-W75)], Q/P, (R x D/2A) ² x (Q/P), Comparative Examples 1 to 3 and Examples in which (LB2/LB1)/(LA2/LA1), (LC2/LC1)/(LB2/LB1), and LB2/LB1 (rectangular ratio) are set as shown in Tables 1 to 4 1 to 15 tires were produced. In each tire, the width of the first belt layer on the inner side in the tire radial direction was 170 mm, the width of the second belt layer on the outer side in the tire radial direction was 160 mm, and the width of the belt reinforcing layer was 170 mm.

Regarding the inclination angles X ₁ to X ₅ of the first belt layers and the inclination angles Y ₁ to Y ₅ of the second belt layers, the inclination angle X ₃ is the same as the inclination angle X, and the inclination angle Y ₃ is the inclination angle Y , the tilt angle _X4 has the same value as the tilt angle X2, the tilt angle _Y4 has the same value as the tilt angle _Y2 , and the tilt angle _X5 has the _same value as the tilt angle _X1 . and the inclination angle _Y5 is the _same value as the inclination angle Y1, so their display is omitted. In addition, regarding the inclination direction of the first belt layer, the second belt layer, etc., "R" indicates a right-downward inclination, and "L" indicates a left-downward inclination.

These test tires were evaluated for uneven wear resistance in the shoulder region, steering wheel drift prevention performance, and linearity of steering stability by the following test methods, and the results are shown in Tables 1 to 4.

Uneven wear resistance in the shoulder area:
Each test tire was mounted on a wheel with a rim size of 16 x 6.5J, mounted on a front-wheel drive vehicle with a displacement of 2 liters, inflated to the specified air pressure for the vehicle, and after running 10,000 km at an outdoor test site, the amount of wear on the center land area. And the wear amount of the shoulder land portion was measured, and the ratio of the wear amount of the shoulder land portion to the wear amount of the center land portion was calculated. The evaluation results are shown as indices with Comparative Example 3 being 100, using the reciprocal of the above ratio. It means that the larger the index value, the better the uneven wear resistance in the shoulder region. The outdoor test site is a circuit with cant from the outer circumference to the inner circumference. Tires expected to be used in Japan are run counterclockwise, while tires expected to be used in the United States are run counterclockwise. clockwise running.

Handle flow prevention performance:
Each test tire was mounted on a wheel with a rim size of 16×6.5J and mounted on a flat belt cornering tester, and the residual cornering force of the test tire was measured under the conditions of air pressure of 230 kPa and load of 4.5 kN. The evaluation results are shown as indices with Comparative Example 3 being 100. The larger the index value, the greater the residual cornering force and the better the steering wheel drift prevention performance.

Steering stability linearity:
Each test tire was mounted on a wheel with a rim size of 16 x 6.5J, mounted on a front-wheel drive vehicle with a displacement of 2 liters, inflated to the specified air pressure for the vehicle, and run by a panelist on a paved test course. Then, a sensory evaluation was conducted on the linearity of steering stability. The evaluation results are shown as indices with Comparative Example 1 being 100. It means that the greater the index value, the better the linearity of the steering stability.

As can be seen from Tables 1 to 4, the tires of Examples 1 to 15 are superior in resistance to uneven wear in the shoulder region in comparison with Comparative Examples 1 to 3, and furthermore, handle drift prevention performance and steering performance. The stability linearity was improved in a well-balanced manner.

REFERENCE SIGNS LIST 1 tread portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt reinforcing layer 71 first belt layer 72 second belt layer

Claims (9)

A carcass layer mounted between a pair of bead portions, a plurality of belt layers arranged outside the carcass layer in the tread portion in the tire radial direction, and a belt reinforcing layer arranged outside the belt layers in the tire radial direction. and wherein the belt layer includes a plurality of belt cords inclined with respect to the tire circumferential direction, the belt cords are arranged so that the belt cords intersect each other between the layers, and the belt reinforcing layer is oriented in the tire circumferential direction. In a pneumatic tire comprising
The plurality of belt layers has a first belt layer located inside in the tire radial direction and a second belt layer located outside in the tire radial direction, and belt cords constituting the first belt layer and the second belt layer. where X and Y are the inclination angles with respect to the tire circumferential direction at the tire center position, these inclination angles X and Y satisfy the relationship of 15°≦|Y|<|X|≦35°,
Loads corresponding to 40%, 75%, and 100% of the maximum load capacity specified by the standard are W40, W75, and W100 (kN), respectively. Let CP40, CP75, and CP100 (kN/°) be the cornering powers measured under the conditions of loading W75 and W100, respectively, let R be the aspect ratio of the pneumatic tire, let D (mm) be its outer diameter, and When the nominal cross-sectional width is A (mm), the loads W40, W75, W100 and the cornering powers CP40, CP75, CP100 are 0.05≦(R×D/2A) ² ×[(CP100−CP75)/ (W100-W75)]/[(CP75-CP40)/(W75-W40)]≤0.50. Define n measurement points that equally divide the width of the second belt layer, which is narrower than the first belt layer, and the tire circumferential direction at each measurement point of the belt cords constituting the first belt layer Xi (i = 1 to n) is an inclination angle with respect to the tire circumferential direction, and Yi (i = 1 to n) is an inclination angle with respect to the tire circumferential direction at each measurement point of the belt cord constituting the second belt layer. 2. The apparatus according to claim 1, wherein the angles Xi and Yi satisfy the relation |Yi|<|Xi| and the inclination angles X and Y satisfy the relation |X|-|Y|≧2°. Pneumatic tires as described. 3. The first belt layer is inclined in a lower right direction with respect to the circumferential direction of the tire, and the second belt layer is inclined in a lower left direction with respect to the circumferential direction of the tire. The pneumatic tire described in . 3. The first belt layer is inclined in a diagonally lower left direction with respect to the tire circumferential direction, and the second belt layer is inclined in a diagonally lower right direction with respect to the tire circumferential direction. The pneumatic tire described in . A plurality of lateral grooves extending in the tire width direction are formed in the shoulder land portion defined by the tread portion, and the lateral grooves are inclined in the same direction as the second belt layer with respect to the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 4. 6. The pneumatic tire according to claim 5, wherein the inclination angle Z of the lateral grooves with respect to the tire width direction is in the range of 5[deg.]≤|Z|≤45[deg.]. In the belt reinforcing layer, the inclination angle θ of the band cord with respect to the tire circumferential direction is in the range of 0°≦|θ|≦30°, and the absolute value of the inclination angle θ of the band cord with respect to the tire circumferential direction is the tire width direction. 7. The pneumatic tire according to any one of claims 1 to 6, which gradually increases from the inner side to the outer side of the tire. The pneumatic tire according to any one of claims 1 to 7, wherein in the belt reinforcing layer, the band cords are inclined in the same direction as the second belt layer with respect to the tire circumferential direction. The maximum contact length in the tire circumferential direction when the pneumatic tire is filled with air pressure of 230 kPa and is grounded under conditions of loading 40%, 75%, and 100% of the maximum load capacity specified by the standard. are respectively LA1, LB1, and LC1, and the maximum ground contact widths in the tire width direction are WA1, WB1, and WC1, respectively. When the outer contact lengths in the tire circumferential direction are LA2, LB2, and LC2, respectively, the maximum contact lengths LA1, LB1, LC1 and the outer contact lengths LA2, LB2, LC2 are 1.02≤(LB2/LB1)/(LA2). /LA1)≤1.25, 1.00≤(LC2/LC1)/(LB2/LB1)≤1.20, 0.75≤LB2/LB1≤1.00. Item 9. The pneumatic tire according to any one of Items 1 to 8.

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