WO2019171553A1

WO2019171553A1 - Pneumatic tire

Info

Publication number: WO2019171553A1
Application number: PCT/JP2018/009070
Authority: WO
Inventors: 孝志芝井
Original assignee: 横浜ゴム株式会社
Priority date: 2018-03-08
Filing date: 2018-03-08
Publication date: 2019-09-12
Also published as: JP6729808B2; JPWO2019171553A1

Abstract

Provided is a pneumatic tire that can suppress uneven center wear in a tread and improve the linearity of steering stability. Cornering powers CP40, CP75, and CP100 (kN/°), which are respectively obtained by measurements under the condition that loads W40, W75, W100 (kN) respectively corresponding to 40%, 75%, and 100% of a stipulated standard maximum load carrying capacity are applied to a pneumatic tire filled with 230 kPa of air, an aspect ratio R, an outside diameter D (mm), and a nominal section width A (mm) satisfy the following relationship: 0.05 ≤ (R × D/2A)²× [(CP100 - CP75)/(W100 - W75)]/[(CP75 - CP40)/(W75 - W40)] ≤ 0.50. When a tread (1) is divided into a central region having a width corresponding to 53% of the maximum ground contact width WB1 with the load W75 applied and outside regions that are outside the central region, the groove area Sc of the central region and the groove areas Ss of the outside regions satisfy the following relationship: 0.80 ≤ Sc/Ss ≤ 0.98.

Description

Pneumatic tire

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can suppress the center uneven wear of the tread portion and improve the linearity of steering stability.

A pneumatic tire is generally disposed in a tire tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and on the inner side in the tire radial direction of the sidewall portions. A pair of bead portions, a carcass layer mounted between the pair of bead portions, and a structure including a plurality of belt layers disposed on the outer side in the tire radial direction of the carcass layer in the tread portion. doing.

In such a pneumatic tire, particularly in the case of a passenger car tire for a new car, it is required to improve the linearity of steering stability as a permanent problem (for example, see Patent Document 1). For example, in a driving state in which the vehicle movement (the effectiveness of the rudder) is delayed in the initial stage of steering, while the cornering power increases from the middle of the steering to the second half and the vehicle moves more sensitively, the driving stability becomes linear. (Linear feeling) is not good. Therefore, there is a need for tuning that improves the linearity of steering stability.

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 present condition is that it cannot fully respond to the request | requirement of the linearity of steering stability only by raising the cornering power of a low load area.

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

An object of the present invention is to provide a pneumatic tire capable of suppressing the center uneven wear of the tread portion and improving the linearity of steering stability.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. In a pneumatic tire provided with a pair of bead portions arranged on the inner side in the tire radial direction of
Loads corresponding to 40%, 75%, and 100% of the maximum load capacity defined in the standard are W40, W75, and W100 (kN), respectively, and the pneumatic tire is filled with an air pressure of 230 kPa, and the load W40, The cornering powers measured under the conditions of loading W75 and W100 are CP40, CP75 and CP100 (kN / °), respectively, the flatness ratio of the pneumatic tire is R, and the outer diameter is D (mm). When the nominal sectional width is A (mm), the loads W40, W75, W100 and the cornering power CP40, CP75, CP100 are 0.05 ≦ (R × D / 2A) ² × [(CP100−CP75) / (W100−W75)] / [(CP75−CP40) / (W75−W40)] ≦ 0.50 is satisfied,
The pneumatic tire is filled with air pressure of 230 kPa, and the maximum contact width in the tire width direction when grounded under the condition of applying the load W75 is WB1, and the tread portion is the maximum contact width WB1 centering on the tire equator. When the area is divided into a central area having a width corresponding to 53% of the above and an outer area outside the central area within the maximum ground contact width WB1, the groove area Sc of the central area and the grooves of the outer area The area Ss satisfies the relationship of 0.80 ≦ Sc / Ss ≦ 0.98.

In the present invention, the groove area Sc of the central region and the groove area Ss of the outer region satisfy the relationship of 0.80 ≦ Sc / Ss ≦ 0.98, and the groove area Sc in the central region is reduced, thereby reducing the tread. It is possible to secure the rigidity in the central region of the portion and suppress the center uneven wear. Further, by reducing the groove area Sc in the central region and increasing the rigidity in the central region of the tread portion, it is possible to ensure high cornering power from the low load region. Moreover, 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 is satisfied, it is possible to suppress an excessive increase in cornering power in the high load region. As a result, the tire moves without delay from the initial steering of the steering wheel, and an appropriate cornering power is exhibited as the load increases, so that the linearity of steering stability can be improved. In particular, since the cornering power easily varies depending on the tire size, the above relational expression is corrected by the value of (R × D / 2A) ² . In other words, the tire with a lower aspect ratio and a smaller outer diameter reduces the contribution of cornering power on the high load side.

In the present invention, in the tread portion, a central main groove extending in the tire circumferential direction, an outer main groove extending in the tire circumferential direction at a position outside the central main groove in the tire width direction, and a tire width direction from the outer main groove A tread pattern in which a plurality of central lateral grooves extending in the tire width direction at the inner position is formed can be employed.

In this case, in order to secure rigidity in the center region of the tread portion, to suppress uneven wear in the center of the tread portion, and to secure high cornering power from a low load region, the following structure may be employed. That is, it is preferable that the inclination angle θcl formed by the side wall of the central lateral groove with respect to the normal line of the tread surface satisfies the relationship of 0 ° ≦ θcl ≦ 10 °. The groove depth Dcl of the central lateral groove preferably satisfies the relationship of 0.20 ≦ Dcl / GDc ≦ 0.90 with respect to the groove depth GDc of the central main groove. The central lateral groove has a bottom raised portion in a part of the longitudinal direction, and the groove depth Da at the bottom raised portion has a relationship of 0.20 ≦ Da / Dcl ≦ 0.90 with respect to the groove depth Dcl of the central lateral groove. It is preferable to satisfy. It is preferable that the groove depth GDc of the central main groove satisfies the relationship 0.85 ≦ GDc / GDs ≦ 1.00 with respect to the groove depth GDs of the outer main groove. Further, when a plurality of outer lateral grooves extending in the tire width direction are formed in the tread portion at positions outside the outer main groove in the tire width direction, the groove depth Dcl of the central lateral groove is equal to the groove depth Dsl of the outer lateral groove. It is preferable that the relationship of 0.50 ≦ Dcl / Dsl ≦ 1.00 is satisfied. Furthermore, it is preferable that all of the central lateral grooves formed on the inner side in the tire width direction than the outer main groove have a groove width of 1.0 mm or less. Alternatively, it is preferable that all the grooves except the central main groove and the outer main groove formed in the tread portion have a groove width of 1.0 mm or less.

In the present invention, a pneumatic tire is filled with an air pressure of 230 kPa, and the tires in the circumferential direction when grounded under the conditions of loading 40%, 75%, and 100% of the maximum load capacity defined by the standard, respectively. The maximum contact lengths are LA1, LB1, and LC1, respectively, the maximum contact widths in the tire width direction are WA1, WB1, and WC1, respectively, and 40% of the maximum contact widths WA1, WB1, and WC1 from the tire center position toward the outside in the tire width direction. When the external contact lengths in the tire circumferential direction at the position of LA are LB2, 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 / It is preferable to satisfy the relation B1 ≦ 1.00. By controlling the load dependence of the ground contact shape in this way, the linearity of steering stability can be further improved.

In the present invention, when the tread portion includes a plurality of belt cords that are inclined with respect to the tire circumferential direction, and a plurality of belt layers in which the belt cords intersect with each other are embedded, It is preferable that the inclination angle α with respect to the tire circumferential direction satisfies the relationship of 21 ° ≦ α ≦ 30 °. By not reducing the inclination angle α of the belt cord at the center of the tire to an extremely low angle, the load dependency of the cornering power is controlled by suppressing the increase in the rigidity of the belt layer, and the linearity of steering stability is further improved. Can do.

The inclination angle α of the belt cord with respect to the tire circumferential direction at the tire center position and the inclination angle β of the belt cord with respect to the tire circumferential direction at the belt end position satisfy the relationship of 18 ° ≦ β <α ≦ 30 °. Is preferred. By setting the inclination angle β at the belt end position of the belt cord to a small value, shoulder uneven wear can be suppressed, and the increase in rigidity of the belt layer in the central region of the tread is suppressed, and the cornering power depends on the load. The controllability can be controlled and the linearity of steering stability can be further improved.

The pneumatic tire of the present invention is preferably a passenger car tire having an aspect ratio of 0.65 or less. ADVANTAGE OF THE INVENTION According to this invention, in the tire for passenger cars in which the linearity of steering stability is requested | required strictly, it becomes possible to make compatible both partial wear resistance and steering stability.

In the present invention, the cornering power is set such that the camber angle is set to 0 °, the speed is set to 10 km / h under the condition that a predetermined load is applied in a state where a 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 the range where the slip angle is 0 ° to 1 °. The ground contact shape of the tread portion is measured under a condition in which a tire is assembled on a regular rim and filled with a predetermined air pressure, placed vertically on a plane and loaded with a predetermined load. The outer diameter of the pneumatic tire is measured at the tire center position 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 determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “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 defined by each standard for each tire in a standard system including the standard on which the tire is based.

FIG. 1 is a meridian cross-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. FIG. 3 is a plan view showing a ground contact shape (40% load) of the pneumatic tire of FIG. FIG. 4 is a plan view showing a ground contact shape (75% load) of the pneumatic tire of FIG. FIG. 5 is a plan view showing a ground contact shape (100% load) of the pneumatic tire of FIG. 6 is a cross-sectional view showing a central main groove, an outer main groove, and an outer lateral groove (lug groove) formed in the tread portion of the pneumatic tire of FIG. FIG. 7 is a cross-sectional view showing a central lateral groove (lag groove) formed in the tread portion of the pneumatic tire of FIG. FIG. 8 is a cross-sectional view showing an outer lateral groove (lag groove) formed in the tread portion of the pneumatic tire of FIG. FIG. 9 is a development view showing a tread pattern of a pneumatic tire according to another embodiment of the present invention. FIG. 10 is a development view showing a tread pattern of a pneumatic tire according to still another embodiment of the present invention. FIG. 11 is a cross-sectional view showing a central lateral groove (sipe) formed in the tread portion of the pneumatic tire of FIGS. 9 and 10. FIG. 12 is a cross-sectional view showing a modification of the central lateral groove (sipe). FIG. 13 is a development view showing a belt layer constituting the pneumatic tire of the present invention.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 show a pneumatic tire according to an embodiment of the present invention. In FIG. 2, CL is a tire center position, Tc is a tire circumferential direction, and Tw is a tire width direction.

As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of

sidewall portions

2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

The carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of carcass cords extending in the tire radial direction, and is folded back from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery 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 cross each other between the layers. A steel cord is preferably used as the belt cord constituting the belt layer 7. On the outer peripheral side of the belt layer 7, at least one belt reinforcing layer 8 including a plurality of band cords oriented in the tire circumferential direction is disposed. It is desirable that the belt reinforcing layer 8 has a jointless structure in which at least one band cord is aligned and rubber-coated strip material is continuously wound in the tire circumferential direction. As the 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 includes 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 the tire

main body

11, 11 outside the central

main grooves

11, 11. A pair of outer

main grooves

12 and 12 extending in the tire circumferential direction at the position are formed. 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 and 11, and a middle land portion 30 is defined between the central main groove 11 and the outer main groove 12. A shoulder land portion 40 is defined in the area.

A plurality of central lateral grooves 31 extending in the tire width direction are formed in each of the middle land portions 30. The central lateral groove 31 includes a central lug groove 31A having a groove width on the tread surface in the range of 1.1 mm to 9.0 mm and a central sipe 31B having a groove width on the tread surface of 1.0 mm or less. . The central lug grooves 31A and the central sipes 31B are alternately arranged along the tire circumferential direction. Further, 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.

Each of the shoulder land portions 40 is formed with a plurality of outer lateral grooves 41 extending in the tire width direction. The outer lateral groove 41 includes at least one of an outer lug groove 41A having a groove width of 1.1 mm to 9.5 mm on the tread surface and an outer sipe 41B having a groove width of 1.0 mm or less on the tread surface. Yes. In the form in which both are present, the outer lug grooves 41A and the outer sipes 41B are alternately arranged along the tire circumferential direction.

In the above 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 pneumatic tire is filled with an air pressure of 230 kPa. The cornering powers measured under the conditions of loads W40, W75, and W100 are CP40, CP75, and CP100 (kN / °), respectively, 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 is satisfied.

FIGS. 3 to 5 show the ground contact shapes (40% load, 75% load, 100% load) of the pneumatic tire of FIG. 1, respectively. In the pneumatic tire described above, a tire when the pneumatic tire is filled with 230 kPa of air pressure and is grounded under a condition in which a load of 40%, 75%, and 100% of the maximum load capacity specified by the standard is applied, respectively. The maximum contact length in the circumferential direction is LA1, LB1, LC1 (mm), and the maximum contact width in the tire width direction is WA1, WB1, WC1 (mm), respectively. External contact lengths in the tire circumferential direction at positions 40% of the widths WA1, WB1, and WC1 are LA2, LB2, and LC2 (mm), respectively.

That is, as shown in FIG. 3, the maximum in the tire circumferential direction when the pneumatic tire is filled with 230 kPa of air pressure and contacted with a load of 40% of the maximum load capacity defined in the standard is applied. 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 toward the outer side in the tire width direction is LA2. . The external ground contact length LA2 is an average value of measured values on both sides of the tire center position CL.

Moreover, as shown in FIG. 4, the maximum in the tire circumferential direction when the pneumatic tire is filled with 230 kPa of air pressure and grounded under a condition where a load of 75% of the maximum load capacity defined by the standard is applied. 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 toward the outer side in the tire width direction is LB2. . The external contact length LB2 is an average value of measured values on both sides of the tire center position CL.

Further, as shown in FIG. 5, the maximum in the tire circumferential direction when the pneumatic tire is filled with 230 kPa of air pressure and grounded under the condition of applying a load of 100% of the maximum load capacity defined by the standard. 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 the position of 40% of the maximum contact width WC1 from the tire center position CL toward the outer side 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, the tread portion 1 includes a tire having a width corresponding to 53% of the maximum ground contact width WB1 around the tire equator (that is, the tire center position CL) and the tire within the maximum ground contact width WB1 than the center region Xc. When divided into the outer region Xs which is the outer side in the width direction, the groove area Sc (mm ² ) of the central region Xc and the groove area Ss (mm ² ) of the outer region Xs satisfy the following relationship.
0.80 ≦ Sc / Ss ≦ 0.98

The groove area Sc of the central region Xc means the total area of the groove components formed in the central region Xc on the tire circumference, and the groove area Ss of the outer region Xs is the groove component formed in the outer region Xs on the tire circumference. It means the total area. When the groove component has a chamfered portion, the area of the chamfered portion is also included in the total area of the groove component.

In the pneumatic tire described above, the groove area Sc of the central region Xc and the groove area Ss of the outer region Xs satisfy the relationship of 0.80 ≦ Sc / Ss ≦ 0.98, and the groove area Sc in the central region Xc is By reducing it, the rigidity in the center area | region Xc of the tread part 1 can be ensured, and center uneven wear can be suppressed. Further, by increasing the rigidity in the central region Xc of the tread portion 1 by reducing the groove area Sc in the central region Xc, high cornering power can be ensured from the low load region.

Here, if Sc / Ss is smaller than 0.80, the groove area Sc in the central region Xc is insufficient, so that the wet performance is deteriorated. Conversely, if Sc / Ss is larger than 0.98, center uneven wear occurs. It becomes easy and the improvement effect of the linearity of steering stability becomes insufficient. In particular, it is desirable to satisfy the relationship 0.85 ≦ Sc / Ss ≦ 0.96.

Moreover, 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 is satisfied, it is possible to suppress an excessive increase in cornering power in the high load region. As a result, the tire moves without delay from the initial steering of the steering wheel, and an appropriate cornering power is exhibited as the load increases, so that the linearity of steering stability can be improved. That is, it is possible to provide a tire in which yaw does not suddenly rise after a few seconds after inputting a constant turning steering. In particular, since the above relational expression is corrected by the value of (R × D / 2A) ² , the tire with a lower flatness ratio and a smaller ratio of the outer diameter to the nominal section width contributes to the cornering power on the higher load side. Reduce. 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 In contrast, if the cornering power is excessively larger than 0.50, the cornering power in the high load region becomes excessive, and in any case, the linearity of steering stability is impaired. In particular, the relationship of 0.10 ≦ (R × D / 2A) ² × [(CP100−CP75) / (W100−W75)] / [(CP75−CP40) / (W75−W40)] ≦ 0.40 is satisfied. It is desirable to do.

In the pneumatic tire, the maximum contact lengths LA1, LB1, and LC1 and the external contact lengths LA2, LB2, and LC2 may 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 at 40% load, LB2 / LB1 means the rectangular ratio at 75% load, and LC2 / LC1 means the rectangular ratio at 100% load. The value of (LB2 / LB1) / (LA2 / LA1) is specified as an index for controlling the ground contact shape in the low load area, and (LC2 / LC1) / By defining the value of (LB2 / LB1), the linearity of steering stability can be improved more precisely.

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

Also, in order to extend the wear life, it is desirable to set LB2 / LB1 within the above range under a load condition of 75% that is regarded as a general service load. When LB2 / LB1 is smaller than 0.75, the wear life is shortened. Conversely, when LB2 / LB1 is larger than 1.00, it is difficult to tune the linearity of steering stability. In particular, it is desirable to satisfy the relationship of 0.80 ≦ LB2 / LB1 ≦ 0.95.

As described above, in the tread portion 1, the central main groove 11 extending in the tire circumferential direction, the outer main groove 12 extending in the tire circumferential direction at a position outside the central main groove 11 in the tire width direction, and the outer main groove 12. In a pneumatic tire having a tread pattern in which a plurality of central lateral grooves 31 extending in the tire width direction are formed at positions on the inner side in the tire width direction than the tread portion, the rigidity in the central region Xc of the tread portion 1 is secured. The structure shown in FIGS. 6 to 8 can be employed in order to suppress the center uneven wear of 1 and to ensure high cornering power from a low load range.

That is, as shown in FIG. 7, the inclination angle θcl formed by the side wall of the central lateral groove 31 (particularly, the central lug groove 31A) with respect to the normal line of the tread surface should satisfy the relationship of 0 ° ≦ θcl ≦ 10 °. By setting the inclination angle θcl of the central lateral groove 31 in the above range, the rigidity in the central region Xc of the tread portion 1 can be ensured. Here, if θcl is smaller than 0 ° and the side wall has an overhang shape, the rigidity in the central region Xc is lowered. Conversely, if it is larger than 10 °, the drainage is adversely affected. In particular, it is desirable to satisfy the relationship of 1 ° ≦ θcl ≦ 8 °.

As shown in FIG. 6, the groove depth Dcl of the central transverse groove 31 should satisfy the relationship of 0.20 ≦ Dcl / GDc ≦ 0.90 with respect to the groove depth GDc of the central main groove 11. Thereby, the rigidity in the center area | region Xc of the tread part 1 is securable. Here, when Dcl / GDc is smaller than 0.20, the drainage performance is adversely affected. Conversely, when Dcl / GDc is larger than 0.90, the rigidity in the central region Xc is lowered.

The central lateral groove 31 (particularly, the central lug groove 31A) has a bottom raised portion 33 in a part of its longitudinal direction, and the groove depth Da at the bottom raised portion 33 is 0. 0 relative to the groove depth Dcl of the central lateral groove 31. It is preferable that the relationship of 20 ≦ Da / Dcl ≦ 0.90 is satisfied. Here, the bottom raised portion 33 is disposed at a position opening adjacent to the outer main groove 12. By providing such a raised portion 33, the rigidity in the central region Xc of the tread portion 1 can be ensured. Here, if Da / Dcl is greater than 0.90, the effect on rigidity is reduced, and conversely if it is less than 0.20, drainage is adversely affected.

The groove depth GDc of the central main groove 11 should satisfy the relationship of 0.80 ≦ GDc / GDs ≦ 1.00 with respect to the groove depth GDs of the outer main groove 12. Thereby, the rigidity in the center area | region Xc of the tread part 1 is securable. Here, when GDc / GDs is smaller than 0.80, the drainage is adversely affected. Conversely, when GDc / GDs is larger than 1.00, it is difficult to ensure rigidity in the central region Xc of the tread portion 1. .

When a plurality of outer lateral grooves 41 extending in the tire width direction are formed in the tread portion 1 at positions outside the outer main grooves 12 in the tire width direction, the groove depth Dcl of the central lateral groove 31 is the groove depth of the outer lateral grooves 41. It is preferable to satisfy a relationship of 0.50 ≦ Dcl / Dsl ≦ 1.00 with respect to Dsl (see FIGS. 7 and 8). Thereby, the rigidity in the center area | region Xc of the tread part 1 is securable. Here, if Dcl / Dsl is smaller than 0.50, the drainage is adversely affected. Conversely, if Dcl / Dsl is larger than 1.00, it is difficult to ensure rigidity in the central region Xc of the tread portion 1. .

9 and 10 each show a tread pattern of a pneumatic tire according to another embodiment of the present invention. 9 and 10, the same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 9, all of the central lateral grooves 31 formed on the inner side in the tire width direction from the outer main groove 12 are constituted by a central sipe 31B having a groove width of 1.0 mm or less. Thus, by making all the central lateral grooves 31 into the central sipe 31B having a groove width of 1.0 mm or less, the rigidity in the central region Xc of the tread portion 1 is ensured, the center uneven wear is suppressed, and from the low load region. High cornering power can be secured. In FIG. 9, the circumferential narrow groove 32 formed on the inner side in the tire width direction from the outer main groove 12 is also configured to have a groove width of 1.0 mm or less.

In FIG. 10, all the grooves excluding the central main groove 11 and the outer main groove 12 formed in the tread portion 1 have a groove width of 1.0 mm or less. In this case, rigidity can be ensured over the entire area of the tread portion 1.

The central sipe 31B may have a constant groove width from the tread surface to the groove bottom as shown in FIG. 11, or, as shown in FIG. 12, the chamfered portion 34 is formed at the opening to the tread surface. You may have. A similar structure can be adopted for the outer sipe 41B.

In the pneumatic tire described above, when the tread portion 1 includes a plurality of belt cords C that are inclined with respect to the tire circumferential direction, and a plurality of belt layers 7 in which the belt cords C cross each other are embedded, As shown in FIG. 13, the inclination angle α of the belt cord C with respect to the tire circumferential direction at the tire center position CL preferably satisfies the relationship of 21 ° ≦ α ≦ 30 °. By not reducing the inclination angle α of the belt cord C at the tire center position CL extremely, the increase in rigidity of the tread portion 1 caused by the belt layer 7 is suppressed, and the load dependency of the cornering power is controlled and controlled. The stability linearity can be further improved. Here, if the inclination angle α is smaller than 21 °, it becomes difficult to control the linearity of the steering stability due to the increase in rigidity of the belt layer 7, and conversely if it is larger than 30 °, the cornering characteristics and the like are deteriorated. Not right.

The inclination angle α of the belt cord C with respect to the tire circumferential direction at the tire center position CL and the inclination angle β of the belt cord C with respect to the tire circumferential direction at the belt end position BE have a relationship of 18 ° ≦ β <α ≦ 30 °. It is good to be satisfied. By reducing the inclination angle β of the belt cord C at the belt end position BE, shoulder uneven wear can be suppressed, and the inclination angle α of the belt cord C at the tire center position CL can be extremely reduced. By not making the angle, the increase in rigidity of the belt layer 7 in the central region Xc of the tread portion 1 can be suppressed to control the load dependency of the cornering power, and the linearity of the steering stability can be further improved. In particular, the difference between the inclination angle α and the inclination angle β is preferably 3 ° or more. A structure in which the inclination angle β of the belt cord C with respect to the tire circumferential direction at the belt end position BE is smaller than the inclination angle α of the belt cord C with respect to the tire circumferential direction at the tire center position CL is preferable. The belt cord C may be inclined at a constant angle with respect to the tire circumferential direction over the entire width, and the inclination angles α and β may be set to the same value, or α <β.

As shown in FIG. 13, the belt layer 7 has a high angle region Ac on the center side in which the inclination angle of the belt cord C is in the range of α ± 1 ° and a shoulder in which the inclination angle of the belt cord C is in the range of β ± 1 °. The low-angle region As on the side, the width Lc of the high-angle region Ac is ½ or more of the total width L of the belt layer 7, and the width Ls of each low-angle region As is 1 of the total width L of the belt layer 7. It is good that it is / 8 or more. Thus, by setting the high-angle area Ac on the center side and the low-angle area As on the shoulder side of the belt layer 7 as described above, the rigidity distribution of the tread portion 1 can be optimized. Here, when the width Lc of the high angle region Ac is smaller than ½ of the entire width L of the belt layer 7, the function as the belt layer 7 is deteriorated, and the width Ls of the low angle region As is the entire width of the belt layer 7. If it is smaller than 1/8 of L, the rigidity in the tire circumferential direction in the outer region Xs of the tread portion 1 cannot be sufficiently increased. The width Lc of the high angle area Ac and the width Ls of the low angle area As are set based on the total width L of each belt layer 7.

The pneumatic tire described above is suitable as a tire for passenger cars having a flatness ratio of 0.65 or less. In a tire for a passenger car in which linearity of steering stability is strictly required, it is possible to achieve both uneven wear resistance and steering stability.

In the embodiment described above, a tread pattern including four main grooves in the tread portion has been described. However, the present invention includes a tread pattern including three main grooves in the tread portion, and a V-shaped main groove in the tread portion. It is applicable also to the tread pattern which contains.

With a tire size of 205 / 55R16 91V, a carcass layer is mounted between a pair of bead portions, two belt layers are embedded outside the carcass layer in the tire radial direction of the tread portion, and the tread portion extends in the tire circumferential direction. A pair of central main grooves, a pair of outer main grooves extending in the tire circumferential direction at a position on the outer side in the tire width direction from the central main grooves, and extending in the tire width direction at a position on the inner side in the tire width direction from the outer main grooves. In a pneumatic tire in which a plurality of central lateral grooves and a plurality of outer lateral grooves extending in the tire width direction at positions outside the outer main grooves in the tire width direction are formed, the tire circumference at the tire cord center position of the belt cord The inclination angle α with respect to the direction, the inclination angle β with respect to the tire circumferential direction at the belt end position of the belt cord, the groove depth GDs of the outer main groove, the groove depth Dsl of the outer lateral groove, and the ratio GDc / G s, inclination angle θcl of the side wall of the central lateral groove, groove depth GDc of the central main groove, groove depth Dcl of the central lateral groove, ratio Dcl / GDc, groove depth Da at the raised portion of the central lateral groove, ratio Da / Dcl, Ratio Dcl / Dsl, groove width of the central lateral groove, groove width of the outer lateral groove, ratio Sc / Ss of the groove area Sc of the central region and the groove region Ss of the outer region, CP variation coefficient X = [(CP75−CP40) / (W75-W40)], high load range CP variation coefficient Y = [(CP100-CP75) / (W100-W75)], (R × D / 2A) ² × (Y / X), (LB2 / LB1) Tires of Comparative Examples 1 to 3 and Examples 1 to 10 in which / (LA2 / LA1), (LC2 / LC1) / (LB2 / LB1), and LB2 / LB1 (rectangular ratio) were set as shown in Table 1 were manufactured. .

偏 These test tires were evaluated for uneven wear resistance (shoulder region, center region), steering stability linearity, and wet performance by the following test methods, and the results are also shown in Table 1.

Uneven wear resistance (shoulder region, center region):
Each test tire is mounted on a wheel with a rim size of 16 × 6.5J and mounted on a friction energy measurement tester. Under the conditions of air pressure of 230 kPa and load load of 4.5 kN, average friction in the shoulder region and center region of the tread portion Energy was measured. The measured values are obtained by measuring the frictional energy at a total of four points of 2 locations in the tire width direction × 2 locations in the tire circumferential direction, which are 10 mm intervals in each region, and averaging them. The evaluation result uses the reciprocal of the measured value, and the uneven wear resistance in the shoulder region is indicated by an index with Comparative Example 1 as 100, and the uneven wear resistance in the center region is an index with Comparative Example 2 as 100. Showed. The larger the index value, the better the uneven wear resistance.

Steering stability linearity:
Each test tire is mounted on a wheel with a rim size of 16 x 6.5 J and mounted on a front-wheel drive vehicle with a displacement of 2 liters. The vehicle is filled with the specified air pressure, and a running test is conducted by a paneler on a test course consisting of a paved road. Then, sensory evaluation was performed on the linearity of steering stability. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the linearity of steering stability.

Wet performance:
Each test tire is mounted on a wheel with a rim size of 16 x 6.5J and mounted on a front-wheel drive vehicle with a displacement of 2 liters. The specified air pressure of the vehicle is filled, and a running test is conducted by a panel on a watered test course. The sensory evaluation on the handling stability on the wet road surface was conducted. The evaluation results are shown as an index with Comparative Example 1 as 100. A larger index value means better wet performance.

As can be seen from Table 1, the tires of Examples 1 to 10 were excellent in uneven wear resistance, linearity of steering stability, and wet performance in comparison with Comparative Example 1. On the other hand, the tires of Comparative Examples 2 and 3 were not always sufficient in improving these performances.

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 11 Central main groove 12 Outer main groove 31 Central lateral groove 31A Central lug groove 31B Central sipe 41 Outer lateral groove 41A Outer lug groove 41B outer sipe

Claims

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In the provided pneumatic tire,
Loads corresponding to 40%, 75%, and 100% of the maximum load capacity defined in the standard are W40, W75, and W100 (kN), respectively, and the pneumatic tire is filled with an air pressure of 230 kPa, and the load W40, The cornering powers measured under the conditions of loading W75 and W100 are CP40, CP75 and CP100 (kN / °), respectively, the flatness ratio of the pneumatic tire is R, and the outer diameter is D (mm). When the nominal sectional width is A (mm), the loads W40, W75, W100 and the cornering power CP40, CP75, CP100 are 0.05 ≦ (R × D / 2A) 2 × [(CP100−CP75) / (W100−W75)] / [(CP75−CP40) / (W75−W40)] ≦ 0.50 is satisfied,
The pneumatic tire is filled with air pressure of 230 kPa, and the maximum contact width in the tire width direction when grounded under the condition of applying the load W75 is WB1, and the tread portion is the maximum contact width WB1 centering on the tire equator. When the area is divided into a central area having a width corresponding to 53% of the above and an outer area outside the central area within the maximum ground contact width WB1, the groove area Sc of the central area and the grooves of the outer area A pneumatic tire characterized in that the area Ss satisfies a relationship of 0.80 ≦ Sc / Ss ≦ 0.98.
A central main groove extending in the tire circumferential direction in the tread portion, an outer main groove extending in the tire circumferential direction at a position on the outer side in the tire width direction from the central main groove, and a position on the inner side in the tire width direction from the outer main groove The pneumatic tire according to claim 1, wherein a plurality of central lateral grooves extending in the tire width direction are formed.
3. The pneumatic tire according to claim 2, wherein an inclination angle θcl formed by a side wall of the central lateral groove with respect to a normal line of the tread surface satisfies a relationship of 0 ° ≦ θcl ≦ 10 °.
The groove depth Dcl of the central transverse groove satisfies a relationship of 0.20 ≦ Dcl / GDc ≦ 0.90 with respect to the groove depth GDc of the central main groove. Pneumatic tire.
The central transverse groove has a bottom raised portion in a part of its longitudinal direction, and the groove depth Da at the bottom raised portion is 0.20 ≦ Da / Dcl ≦ 0.90 with respect to the groove depth Dcl of the central transverse groove. The pneumatic tire according to any one of claims 2 to 4, wherein the relationship is satisfied.
The groove depth GDc of the central main groove satisfies a relationship of 0.85 ≦ GDc / GDs ≦ 1.00 with respect to the groove depth GDs of the outer main groove. The pneumatic tire according to Crab.
A plurality of outer lateral grooves extending in the tire width direction are formed in the tread portion at positions outside the outer main groove in the tire width direction, and the groove depth Dcl of the central lateral groove is set to the groove depth Dsl of the outer lateral groove. 7. The pneumatic tire according to claim 2, wherein a relationship of 0.50 ≦ Dcl / Dsl ≦ 1.00 is satisfied.
The pneumatic tire according to any one of claims 2 to 7, wherein all of the central lateral grooves formed on the inner side in the tire width direction from the outer main groove have a groove width of 1.0 mm or less.
The pneumatic tire according to any one of claims 2 to 7, wherein all grooves except the central main groove and the outer main groove formed in the tread portion have a groove width of 1.0 mm or less.
Maximum contact length in the tire circumferential direction when the pneumatic tire is filled with air pressure of 230 kPa and contacted with a load of 40%, 75%, and 100% of the maximum load capacity determined by the standard, respectively. Are LA1, LB1, and LC1, respectively, and the maximum ground contact widths in the tire width direction are WA1, WB1, and WC1, respectively, at positions 40% of the maximum ground contact widths WA1, WB1, and WC1 from the tire center position toward the outside in the tire width direction. When 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 ≦ The pneumatic tire according to any one of claims 1 to 9, characterized by satisfying the .00 relationship.
The tread portion includes a plurality of belt cords that are inclined with respect to the tire circumferential direction, and a plurality of belt layers in which the belt cords intersect with each other are embedded, and the tire circumferential direction at the tire center position of the belt cord The pneumatic tire according to any one of claims 1 to 10, wherein an inclination angle α with respect to the angle satisfies a relationship of 21 ° ≦ α ≦ 30 °.
The inclination angle α of the belt cord with respect to the tire circumferential direction at the tire center position and the inclination angle β of the belt cord with respect to the tire circumferential direction at the belt end position satisfy a relationship of 18 ° ≦ β <α ≦ 30 °. The pneumatic tire according to claim 11.
The pneumatic tire according to any one of claims 1 to 12, wherein the pneumatic tire is a passenger tire having a flatness ratio of 0.65 or less.