JP2020032888A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire which suppresses steering wheel flow, improves linearity of steering stability, and restricts uneven shoulder wear.SOLUTION: In a pneumatic tire, belt cords 71C, 72C constituting a first belt layer 71 on the inside in a radial direction and a second layer 72 on the outside in the radial direction have inclined angles X, Y relative to a tire circumferential direction at a tire center position, that satisfy a relationship of 15°≤|Y|<|X|≤35°. Further, in the pneumatic tire, with regard to cornering power CP40, CP75, CP100 (kN/°), a flat ratio R, an outer diameter D(mm), and a nominal sectional width A(mm), that are measured under a pneumatic pressure of 230 kPa and under the condition of loading the weights W40, W75, W100 (kN) corresponding to 40%, 75%, 100% of the maximum load capacity specified in the standards, the following relationship is satisfied: 0.05≤(R*D/2A)*[(CP100-CP75)/(W100-W75)]/[(CP75-CP40)/(W75-W40)]≤0.50.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pneumatic tire in which a belt layer and a belt reinforcing layer are embedded in a tread portion. More specifically, the present invention relates to a pneumatic tire, which more effectively suppresses steering wheel flow, improves the linearity of steering stability, and further improves the tread portion. The present invention relates to a pneumatic tire capable of suppressing uneven shoulder wear.

  A pneumatic tire generally has a carcass layer mounted between a pair of bead portions, a plurality of belt layers disposed radially outward of the carcass layer in the tread portion, and a tire radial outer portion of the belt layer. And a belt reinforcing layer disposed on the belt. The belt layer includes a plurality of belt cords inclined with respect to the tire circumferential direction, and the belt cords are arranged so as to cross 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, in order to suppress the steering wheel flow during running of the vehicle, a method of designing the tire such that the absolute value of the residual cornering force is increased is adopted. For example, it is known that the absolute value of the residual cornering of the tire increases by decreasing the inclination angle of the belt cord constituting the belt layer with respect to the tire circumferential direction to increase the rigidity of the belt layer. However, when the rigidity of the belt layer becomes excessive, there is a problem that the cornering power in a high load region increases, and the linearity of steering stability deteriorates. In other words, in a running state in which the cornering power increases from the middle to the second half of the steering compared to the initial stage of steering and the movement of the vehicle becomes excessive, the linearity of steering stability is not good. Therefore, tuning is required to improve the linearity of the steering stability (for example, see Patent Document 1).

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

JP-A-2006-141268 JP 2011-230737 A JP 2012-17001 A

  An object of the present invention is to provide a pneumatic tire capable of effectively suppressing steering wheel flow, improving the linearity of steering stability, and further suppressing uneven shoulder wear of a tread portion. .

To achieve the above object, the pneumatic tire of the present invention has a carcass layer mounted between a pair of bead portions, and a plurality of belt layers disposed radially outward of the carcass layer in the tread portion, A belt reinforcing layer disposed outside the belt layer in the tire radial direction, wherein the belt layer includes a plurality of belt cords inclined with respect to the tire circumferential direction, and the belt cords are arranged so as to cross each other between the layers. Is, in the pneumatic tire wherein the belt reinforcing layer includes a band cord oriented in the tire circumferential direction,
The plurality of belt layers include a first belt layer located on the radially inner side of the tire and a second belt layer located on the radially outer side of the tire, and a belt cord forming the first belt layer and the second belt layer. When the inclination angles with respect to the tire circumferential direction at the tire center position are X and Y, 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 defined by the standard are W40, W75, and W100 (kN), respectively. The pneumatic tire is filled with an air pressure of 230 kPa, and The cornering power measured under the condition of loading W75 and W100 is CP40, CP75 and CP100 (kN / °), the flatness ratio of the pneumatic tire is R, and the outer diameter is D (mm). When the nominal width of the cross section 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. It is.

  The inventor of the present invention has conducted intensive studies on the relationship between the inclination angle of the belt layer with respect to the tire circumferential direction and the absolute value of the residual cornering force. As a result, the first belt layer located inside the tire radial direction and the second belt layer located outside the tire radial direction are located. In providing the two belt layers, by reducing the angle of only the second belt layer, it is possible to increase the absolute value of the residual cornering force while suppressing an excessive increase in the cornering power in a high load range. Having found this, the present invention has been achieved.

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, respectively, these inclination angles X and Y are 15 °. By satisfying the relationship of ≦ | Y | <| X | ≦ 35 °, it is possible to increase the absolute value of the residual cornering force, while suppressing an excessive increase in the cornering power in a high load range. Here, 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, it is possible to suppress an excessive increase in cornering power in a high load range. As a result, the steering wheel flow 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 the steering stability can be improved. Particularly, since the easiness of the cornering power varies depending on the tire size, 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 sectional width reduces the contribution of the cornering power on the high load side. Further, according to the knowledge of the present inventor, by reducing the angle of the second belt layer located on the outer side in the tire radial direction, an effect of improving shoulder uneven wear of the tread portion can be obtained.

  In the present invention, n measurement points for equally dividing the width of the second belt layer, which is narrower than the first belt layer, are defined, and the tire circumference at each measurement point of the belt cord constituting the first belt layer is defined. When the inclination angle with respect to the tire direction is Xi (i = 1 to n) and the inclination angle with respect to the tire circumferential direction at each measurement point of the belt cord constituting the second belt layer is Yi (i = 1 to n), It is preferable that the angles Xi and Yi satisfy the relationship of | Yi | <| Xi | and that the inclination angles X and Y satisfy the relationship of | X | − | Y | ≧ 2 °. By reducing the angle of the belt cords constituting the second belt layer, the steering wheel flow can be effectively improved, and the angles of the belt cords constituting the first belt layer and the second belt layer at the tire center position are reduced. By increasing the difference, uneven shoulder wear can be effectively suppressed. Preferably, such a relationship holds over 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 mainly used, the first belt layer is inclined obliquely to the lower right with respect to the tire circumferential direction, and the second belt layer is mounted on the tire. It is preferable to be inclined diagonally lower left with respect to the circumferential direction. In the case of left-hand traffic, a road surface cant is set so that the left side becomes lower, but due to the lateral force generated by the road surface cant, uneven wear occurs in the shoulder area on the tread part outside the vehicle in the tire on the front left wheel. It will be easier. On the other hand, by adopting a structure in which the second belt layer having a reduced angle is inclined obliquely downward and leftward with respect to the tire circumferential direction, the slip of the tire is reduced, and the shoulder uneven wear of the tread portion is effectively prevented. Can be suppressed.

  When a tire is mounted on a vehicle used in an area such as the United States where right-hand traffic is mainly used, the first belt layer is inclined obliquely to the lower left with respect to the tire circumferential direction, and the second belt layer is tilted toward the tire circumferential direction. It is preferable to be inclined diagonally downward and to the right with respect to the direction. In the case of right-hand traffic, a road surface cant is set so that the right side is lowered.However, due to the lateral force generated by the road surface cant, uneven wear occurs in the shoulder region on the tread portion outside the vehicle in the tire on the front right wheel. It will be easier. On the other hand, by adopting a structure in which the lower angled second belt layer is inclined obliquely downward and rightward with respect to the tire circumferential direction, the slip of the tire is reduced, and the uneven wear of the shoulder of the tread portion is reduced. Can be suppressed.

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

  The inclination angle Z of the lateral groove with respect to the tire width direction is preferably in the range of 5 ° ≦ | Z | ≦ 45 °. Thereby, the steering wheel flow can be effectively suppressed.

  In the belt reinforcing layer, the tilt 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 tilt angle θ of the band cord with respect to the tire circumferential direction is the inner side in the tire width direction. It is preferred that it gradually increases from the outside. By inclining the band cord of the belt reinforcing layer in 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 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 range and improve the linearity of steering stability.

  In the belt reinforcing layer, it is preferable that the band cord is inclined in the same direction as the second belt layer with respect to the tire circumferential direction. Thereby, the residual cornering force obtained by inclining the band cord of the belt reinforcing layer in the same direction as the second belt layer can be increased, and the flow of the steering wheel during running of the vehicle can be effectively suppressed.

  In the present invention, the pneumatic tire is filled with an air pressure of 230 kPa, and the tire circumferential direction when the tire is grounded under the conditions of 40%, 75%, and 100% of the maximum load capacity specified by the standard, respectively. The maximum contact lengths are set to LA1, LB1, and LC1, respectively, and the maximum contact widths in the tire width direction are set to WA1, WB1, and WC1, respectively. Assuming that the external contact lengths in the tire circumferential direction at the position of are respectively LA2, LB2 and LC2, the maximum contact lengths LA1, LB1 and LC1 and the external contact lengths LA2, LB2 and LC2 are 1.02 ≦ (LB2 / LB1) / (LA2 / LA1) ≦ 1.25, 1.00 ≦ (LC2 / LC1) / (LB2 / LB1) ≦ 1.20, 0.75 ≦ LB2 / L Preferably satisfies the relationship of 1 ≦ 1.00. By controlling the load dependency of the ground contact shape in this way, the linearity of steering stability can be further improved.

  In the present invention, the cornering power is set to a camber angle of 0 °, a speed of 10 km / h, a slip speed of 10 km / h under a condition that a predetermined load is applied in a state where the tire is assembled on a regular rim and a predetermined air pressure is filled. The cornering force is measured while changing the angle, and is calculated based on the cornering force in a range where the slip angle is 0 ° to 1 °. The ground contact shape of the tread portion is measured under the condition that the tire is rim-assembled on a regular rim, and the tire is placed vertically on a plane with a predetermined air pressure charged and a predetermined load is applied. The outer diameter of the pneumatic tire is measured at the center of the tire in a state where the tire is assembled on a regular rim and filled with a predetermined air pressure. The “regular rim” is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, a standard rim for JATMA, a “Design Rim” for TRA, or an ETRTO In this case, “Measuring Rim” is set. The air pressure is 230 kPa. Further, the predetermined load is a load of 40%, 75% or 100% of the maximum load capacity specified for each tire in the standard system including the standard on which the tire is based.

1 is a meridian sectional view showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. 1. FIG. 2 is a development view showing a first belt layer and a second belt layer of the pneumatic tire of FIG. 1. 4 is a graph showing a relationship between a cornering power (CP) and a load. FIG. 4 is a development view showing a belt cord constituting a first belt layer and a second belt layer. It is a development view showing an example of a belt reinforcement layer. FIG. 2 is a plan view showing a ground contact shape (40% load) of the pneumatic tire of FIG. 1. FIG. 2 is a plan view illustrating a ground contact shape (75% load) of the pneumatic tire of FIG. 1. FIG. 2 is a plan view illustrating a 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 present 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 according to the present embodiment includes a tread portion 1 extending in the tire circumferential direction and having an annular shape, and a pair of sidewall portions 2 and 2 disposed on both sides of the tread portion 1. And a pair of beads 3, 3 arranged radially inward of the sidewalls 2 in the tire radial direction.

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

  On the other hand, a plurality of belt layers 7 are buried 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. As the belt cord constituting the belt layer 7, a steel cord is preferably used. 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 at least one band cord is aligned and a rubber-coated strip material is continuously wound in the tire circumferential direction. As a band cord constituting the belt reinforcing layer 8, an organic fiber cord such as nylon or aramid is 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 tire width direction outer side than the central main grooves 11, 11. And a pair of outer main grooves 12, 12 extending in the tire circumferential direction are formed at the position. 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, a center land portion 20 is defined between the central main grooves 11, 11, a middle land portion 30 is defined between the central main groove 11 and the outer main groove 12, and an outer side of the outer main groove 12. , A shoulder land portion 40 is sectioned.

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

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

  In the pneumatic tire, as shown in FIG. 3, the plurality of belt layers 7 are located on the inner side in the tire radial direction and the outer side in the tire radial direction and are wider than the first belt layer 71. Have a narrow second belt layer 72, and the belt cords 71C, 72C constituting the first belt layer 71 and the second belt layer 72 have inclination angles X, Y with respect to the tire circumferential direction at the tire center position CL. , The inclination angles X and Y satisfy the relationship of 15 ° ≦ | Y | <| X | ≦ 35 °. The inclination angles X and Y 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 such that when the tread portion 1 is viewed from the front, the belt cords fall rightward. The value is a plus value, and the value when the belt cord falls to the left is a minus value.

  In the pneumatic tire, the loads corresponding to 40%, 75%, and 100% of the maximum load capacity defined by the standards are W40, W75, and W100 (kN), respectively, and the air pressure of 230 kPa is applied to the pneumatic tire. The cornering power measured under the conditions of loading and applying loads W40, W75, and W100 is CP40, CP75, and CP100 (kN / °), the flatness ratio of the pneumatic tire is R, and the outer diameter is D ( mm), and the nominal cross-sectional width is A (mm).

Here, 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.

  In the pneumatic tire described above, when 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 at the tire center position CL are X and Y, respectively, When the angles X and Y satisfy the relationship of 15 ° ≦ | Y | <| X | ≦ 35 °, the absolute value of the residual cornering force is increased, while the cornering power in a high load region is excessively increased. 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 an increase in the 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 deteriorate.

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

In the pneumatic tire described above, the loads W40, W75, W100 and the 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, it is possible to suppress an excessive increase in cornering power in a high load range. As a result, an appropriate cornering power is exhibited as the load increases, so that the linearity of the steering stability can be improved. In particular, since the above relational expression is corrected by the value of (R × D / 2A) ² , the tire having a lower aspect ratio and a smaller ratio of the outer diameter to the nominal sectional width contributes to the contribution of the cornering power on the higher load side. Lower. Therefore, an appropriate cornering power can be exhibited 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 range is obtained. If the cornering power is too large, on the other hand, if it is larger than 0.50, the cornering power in the high load range becomes excessive, and in any case, the linearity of the steering stability is impaired. In particular, the relationship 0.10 ≦ (R × D / 2A) ² × [(CP100-CP75) / (W100-W75)] / [(CP75-CP40) / (W75-W40)] ≦ 0.40 is satisfied. It is desirable to do.

  Further, as described above, when the angle of the belt cord 72C constituting the second belt layer 72 located on the outer side in the tire radial direction is reduced, an effect of improving uneven shoulder wear of the tread portion 1 is obtained.

In the pneumatic tire, as shown in FIG. 5, n measurement points Pi (i = 1 to n) that equally divide the width W ₇₂ of the second belt layer 72 that is narrower than the first belt layer 71. ), 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 Xi (i = 1 to n), and the belt cord 72C constituting the second belt layer 72 The inclination angles Xi and Yi satisfy the relationship of | Yi | <| Xi |, and Yi (i = 1 to n) with respect to the tire circumferential direction at each measurement point Pi. , Y satisfy the relationship of | X | − | Y | ≧ 2 °.

  By lowering the angle of the belt cord 72C constituting the second belt layer 72, the handle flow can be effectively improved, and the belt cords 71C, 72C constituting the first belt layer 71 and the second belt layer 72 can be improved. By increasing the angle difference at the tire center position CL, shoulder uneven wear can be effectively suppressed. Preferably, such a relationship is established over the entire width of the second belt layer 72. When the value of | X |-| Y | is less than 2 °, the effect of suppressing the steering wheel flow and improving the linearity of the steering stability is reduced, and the effect of suppressing the uneven wear of the tread portion 1 on the shoulder is reduced. I do. In particular, it is desirable that 3 ° ≦ | X | − | Y | ≦ 7 °. For the same reason, | Xi | − | Yi | ≧ 2 °, more preferably 3 ° ≦ | Xi | − | Yi | ≦ 7 °, for the inclination angles Xi and Yi at all the measurement points Pi. Is desirable.

Figure in 5 defines the seven measuring points P ₁ to P _7, the inclination angle at the measurement point P ₁ to P ₇ of belt cords 71C and X ₁ to X _7, measurement points P ₁ ~ of belt cords 72C The inclination angles at P ₇ are Y ₁ to Y ₇ , but it is sufficient that there are at least five such measurement points Pi from one edge of the second belt layer 72 to the other edge. The interval between the measurement points in the tire width direction is preferably in the range of 25 mm to 40 mm. This makes it possible to control the angle of about one out of every twenty belt cords 71C and 72C, so that a desired effect can be obtained.

  When a tire is mounted on a vehicle used in a region such as Japan where left-hand traffic is mainly used, the first belt layer 71 is inclined downward and obliquely to the tire circumferential direction as shown in FIG. Then, it is preferable that the second belt layer 72 is inclined obliquely to the lower left with respect to the tire circumferential direction. In the case of left-hand traffic, a road surface cant is set so that the left side is lowered. However, uneven wear is caused in the shoulder region on the outer side of the tread portion 1 in the tire on the front left wheel due to the lateral force generated by the road surface cant. It is easy to occur. On the other hand, by adopting a structure in which the second belt layer 72 having a reduced angle is inclined obliquely to the lower left with respect to the tire circumferential direction, slip of the tire is reduced, and uneven wear of the shoulder of the tread portion 1 is reduced. It can be suppressed effectively.

  When a tire is mounted on a vehicle used in a region such as the United States where right-hand traffic is mainly performed, the first belt layer 71 is inclined obliquely to the lower left with respect to the tire circumferential direction, and the second belt layer 72 is inclined. It is preferable to adopt a structure inclined obliquely downward and rightward with respect to the tire circumferential direction, that is, a structure symmetrical to FIG. In the case of right-hand traffic, a road surface cant is set so that the right side becomes lower. However, uneven wear is caused in the shoulder region on the outer side of the tread portion 1 in the tire on the right front wheel due to the lateral force generated by the road surface cant. It is easy to occur. On the other hand, by adopting a structure in which the lower angled second belt layer 72 is inclined obliquely downward and rightward with respect to the tire circumferential direction, the slip of the tire is reduced, and the uneven wear of the shoulder of the tread portion 1 is caused. 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 are formed in the second belt layer 72 in the tire circumferential direction. It is preferable to incline in the same direction as (see FIGS. 2 and 3). Thereby, the residual cornering force obtained by inclining the lateral groove 41 of the shoulder land portion 40 in the same direction as the second belt layer 72 can be increased, and the flow of the steering wheel during running of the vehicle can be effectively suppressed.

  The inclination angle Z of the lateral groove 41 with respect to the tire width direction is preferably in the range of 5 ° ≦ | Z | ≦ 45 °. Thereby, the steering wheel flow can be effectively suppressed. Further, in a tire for which the linearity of the steering stability is to be further increased, the effect of preventing the steering wheel from flowing can be secured based on the inclination angle Z of the lateral groove 41 without making the inclination angle Y of the second belt layer 72 extremely small. It is possible to satisfy the target performance. Here, if the absolute value of the inclination angle Z of the lateral groove 41 is smaller than 5 °, the residual cornering force due to the inclination of the lateral groove 41 becomes insufficient, and if it is larger than 45 °, uneven shoulder wear tends to occur. In particular, it is desirable that the inclination angle Z of the lateral groove 41 with respect to the tire width direction is in the range of 7 ° ≦ | Z | ≦ 20 °.

  The inclination angle Z of the lateral groove 41 is such that the air pressure is 230 kPa, the center of the lateral groove 41 and the lateral groove 41 at the contact end position in the tire width direction when a load of 75% of the maximum load capacity specified in the standard is applied. The straight line connecting the center of the width of the lateral groove 41 at the end position on the inner side in the tire width direction is the angle formed by the reference line in the tire width direction. When the tread portion 1 is viewed from the front, the inclination angle Z of the lateral groove 41 is a plus value when the lateral groove 41 is inclined clockwise with respect to the reference line in the tire width direction, and the lateral groove 41 is the tire width. A value that is inclined in a counterclockwise direction with respect to the direction reference line is a negative value.

  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. The absolute value of θ gradually increases from the inside to the outside in the tire width direction. As described above, the band cord B of the belt reinforcing layer 8 is inclined in the range of the inclination angle θ, and the absolute value of the inclination angle θ is gradually increased from the inside to the outside in the tire width direction, so that the steering wheel flow is effectively performed. And the rigidity of the belt reinforcing layer 8 is also reduced, so that an excessive increase in cornering power in a high load range can be suppressed, and the linearity of steering stability can be improved. However, when the absolute value of the inclination angle θ of the band cord B with respect to the tire circumferential direction is larger than 30 °, the high-speed durability is adversely affected. The inclination angle θ of the band cord B constituting the belt reinforcing layer 8 with respect to the tire circumferential direction is a positive value when the tread portion 1 is viewed from the front when the band cord B falls rightward, and the belt cord falls leftward. Is a negative value.

  In the belt reinforcing layer 8, the band cord B is preferably inclined in the same direction as the second belt layer 72 with respect to the tire circumferential direction. Thereby, the residual cornering force obtained by inclining the band cord B of the belt reinforcing layer 8 in the same direction as the second belt layer 72 can be increased, and the flow of the steering wheel during running of the vehicle can be effectively suppressed.

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

  That is, as shown in FIG. 7, when the pneumatic tire is filled with pneumatic pressure of 230 kPa and grounded under the condition that a load of 40% of the maximum load capacity specified in the standard is applied, the maximum in the tire circumferential direction is obtained. The contact length is LA1, the maximum contact width in the tire width direction is WA1, and 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 to the outside in the tire width direction is LA2. . The external contact length LA2 is an average value of measured values on both sides of the tire center position CL.

  As shown in FIG. 8, the pneumatic tire is filled with an air pressure of 230 kPa, and when the tire is grounded under the condition that a load of 75% of the maximum load capacity specified in the standard is applied, the maximum in the tire circumferential direction is obtained. The contact length is LB1, the maximum contact width in the tire width direction is WB1, and 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 to the outside in the tire width direction is LB2. . The external contact length LB2 is an average value of the measured values on both sides of the tire center position CL.

  Further, as shown in FIG. 9, when the pneumatic tire is filled with an air pressure of 230 kPa and the tire is grounded under the condition that a load of 100% of the maximum load capacity specified in the standard is applied, the maximum in the tire circumferential direction is obtained. The contact length is LC1, the maximum contact width in the tire width direction is WC1, and 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 to the outside in the tire width direction is LC2. . The external contact length LC2 is an average value of measured values on both sides of the tire center position CL.

Here, it is preferable that the maximum ground lengths LA1, LB1, and LC1 and the external ground lengths LA2, LB2, and LC2 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 way, the linearity of steering stability can be further improved. That is, LA2 / LA1 means the rectangular ratio under a 40% load, LB2 / LB1 means the rectangular ratio under a 75% load, and LC2 / LC1 means the rectangular ratio under a 100% load. The value of (LB2 / LB1) / (LA2 / LA1) is defined as an index for controlling the contact shape in the low load region, and (LC2 / LC1) / is used as an index for controlling the contact shape in the high load region. By defining the value of (LB2 / LB1), the feeling of the linearity of the steering stability can be further enhanced.

  Here, if (LB2 / LB1) / (LA2 / LA1) or (LC2 / LC1) / (LB2 / LB1) is out of the above range, the effect of improving the linearity of the steering stability decreases. In particular, it is desirable to satisfy the following relations: 1.03 ≦ (LB2 / LB1) / (LA2 / LA1) ≦ 1.15, 1.02 ≦ (LC2 / LC1) / (LB2 / LB1) ≦ 1.10.

  In order to improve the wear life, it is desirable to set LB2 / LB1 in the above range under a load condition of 75% which is regarded as a general normal load. If LB2 / LB1 is smaller than 0.75, the wear life is shortened, and if it is larger than 1.00, tuning of steering stability linearity becomes difficult. In particular, it is desirable to satisfy the relationship of 0.80 ≦ LB2 / LB1 ≦ 0.95.

Tire size 205 / 55R16 91V, a carcass layer mounted between a pair of bead portions, two belt layers disposed radially outside of the carcass layer in the tread portion, and tire radial direction outside of the belt layer In the pneumatic tire provided with the belt reinforcing layer disposed in the tire, the inclination angle X with respect to the tire circumferential direction at the tire center position of the belt cord constituting the first belt layer located inside the tire radial direction, the tire radial direction outside The belt cords of the first belt layer at five measurement points at which the inclination angle Y with respect to the tire circumferential direction at the tire center position of the belt cords constituting the second belt layer positioned at the tire center position and the width of the second belt layer are equally set the inclination angle X ₁ to X _5, the inclination angle Y ₁ to Y ₅ in the belt cord of the second belt layer at five measurement points for the width of the second belt layer equally, first bell G, the inclination direction of the second belt layer, the country of use of the tire, the inclination direction of the lateral groove in the shoulder land portion, the inclination angle Z of the lateral groove in the shoulder land portion with respect to the tire width direction, the band cord constituting the belt reinforcement layer At the center of the tire with respect to the tire circumferential direction, the tilt angle of the band cords constituting the belt reinforcing layer with respect to the tire circumferential direction at the shoulder terminal position, the tilt direction of the belt reinforcing layer, and the low load area CP variation coefficient P = [(CP75-CP40) / (W75-W40)], high load range CP variation coefficient Q = [(CP100-CP75) / (W100-W75)], Q / P, (R × D / 2A) ² × Comparative examples in which (Q / P), (LB2 / LB1) / (LA2 / LA1), (LC2 / LC1) / (LB2 / LB1), and LB2 / LB1 (rectangular ratio) are set as shown in Tables 1 to 4. It was manufactured tires to 3 and Examples 1 to 15. In each of the tires, 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.

For inclination angles Y ₁ to Y ₅ in the tilt angle X ₁ to X ₅ and the second belt layer of the first belt layer, the inclination angle X ₃ is consistent with the inclination angle X, the inclination angle Y ₃ is the inclination angle Y is intended to match the inclination angle X ₄ is inclined angle X ₂ identical values, the inclination angle Y ₄ is the same value as the inclination angle Y _2, the inclination angle X ₅ is a tilt angle X ₁ the same value There, since the inclination angle Y ₅ are the same value as the inclination angle Y _1, omitted their display. Regarding the inclination direction of the first belt layer, the second belt layer, and the like, "R" indicates a downward slope, and "L" indicates a downward slope.

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

Partial wear resistance in the shoulder area:
Each test tire is mounted on a rim size 16 × 6.5J wheel, mounted on a front-wheel drive vehicle with a displacement of 2 liters, filled with the specified air pressure of 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 were indicated by an index with Comparative Example 3 being 100 using the reciprocal of the ratio. The larger the index value, the better the uneven wear resistance in the shoulder region. The outdoor test site is a circuit that has a cant from the outer side to the inner side, and runs counterclockwise for tires that are expected to be used in Japan, and tires that are expected to be used in the United States. About clockwise traveling.

Handle flow prevention performance:
Each test tire was mounted on a wheel having a rim size of 16 × 6.5 J and mounted on a flat belt type cornering tester, and the residual cornering force of the test tire was measured under the conditions of an air pressure of 230 kPa and a load of 4.5 kN. The evaluation results were indicated by an index with Comparative Example 3 being 100. The larger the index value, the larger the residual cornering force and the better the handle flow prevention performance.

Linearity of steering stability:
Each test tire is mounted on a rim size 16 x 6.5 J wheel, mounted on a front-wheel drive vehicle with a displacement of 2 liters, filled with the specified air pressure of the vehicle, and run by a panelist on a test course consisting of paved roads Then, the sensory evaluation was performed on the linearity of the steering stability. The evaluation results were indicated by an index with Comparative Example 1 being 100. The larger 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 uneven wear resistance in the shoulder region in comparison with Comparative Examples 1 to 3, and are further improved in steering wheel flow prevention performance and steering. The linearity of stability was improved in a well-balanced manner.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement 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 disposed radially outward of the carcass layer in the tread portion, and a belt reinforcing layer disposed radially outward of the belt layer. A belt cord including a plurality of belt cords in which the belt layer is inclined with respect to the tire circumferential direction, wherein the belt cords are arranged so as to intersect with each other between the layers, and the belt reinforcing layer is oriented in the tire circumferential direction. In pneumatic tires containing
The plurality of belt layers include a first belt layer located on the radially inner side of the tire and a second belt layer located on the radially outer side of the tire, and a belt cord forming the first belt layer and the second belt layer. When the inclination angles with respect to the tire circumferential direction at the tire center position are X and Y, respectively, 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 defined by the standard are W40, W75, and W100 (kN), respectively. The pneumatic tire is filled with an air pressure of 230 kPa, and The cornering power measured under the condition of loading W75 and W100 is CP40, CP75 and CP100 (kN / °), the flatness ratio of the pneumatic tire is R, and the outer diameter is D (mm). When the nominal width of the cross section 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 Tire enters.   The tire circumferential direction at each of the measurement points of the belt cord constituting the first belt layer is defined by defining n measurement points for equally dividing the width of the second belt layer that is narrower than the first belt layer. Xi (i = 1 to n), and Yi (i = 1 to n) with respect to the tire circumferential direction at each measurement point of the belt cord constituting the second belt layer. The angle Xi, Yi satisfies the relationship | Yi | <| Xi |, and the inclination angles X, Y satisfy the relationship | X | − | Y | ≧ 2 °. The pneumatic tire as described.   The first belt layer is inclined obliquely downward and rightward with respect to the tire circumferential direction, and the second belt layer is inclined obliquely downward and leftward with respect to the tire circumferential direction. A pneumatic tire according to claim 1.   The first belt layer is inclined obliquely downward and leftward with respect to the tire circumferential direction, and the second belt layer is inclined obliquely downward and rightward with respect to the tire circumferential direction. A pneumatic tire according to claim 1.   A plurality of lateral grooves extending in the tire width direction are formed in the shoulder land portion partitioned by the tread portion, and these 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, wherein:   The pneumatic tire according to claim 5, wherein an inclination angle Z of the lateral groove with respect to the tire width direction is in a range of 5 ° ≦ | Z | ≦ 45 °.   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 determined in the tire width direction. The pneumatic tire according to any one of claims 1 to 6, wherein the pressure gradually increases from inside to outside.   The pneumatic tire according to any one of claims 1 to 7, wherein in the belt reinforcing layer, the band cord is inclined in the same direction as the second belt layer with respect to a tire circumferential direction.   The maximum contact length in the tire circumferential direction when the pneumatic tire is filled with a pneumatic pressure of 230 kPa and contacted with a load of 40%, 75%, and 100% of the maximum load capacity specified by the standard. Are defined as LA1, LB1, and LC1, respectively, and the maximum contact widths in the tire width direction are defined as WA1, WB1, and WC1, respectively. Assuming that the external contact lengths in the tire circumferential direction are LA2, LB2 and LC2, respectively, the maximum contact lengths LA1, LB1 and LC1 and the external contact lengths LA2, LB2 and LC2 are 1.02 ≦ (LB2 / LB1) / (LA2 /LA1)≦1.25, 1.00 ≦ (LC2 / LC1) / (LB2 / LB1) ≦ 1.20, 0.75 ≦ LB2 / LB1 ≦ 1 The pneumatic tire according to claim 1, characterized by satisfying the 00 relationships.

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