JP2012179965A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heel and toe wear performance while maintaining the one-sided flow performance or wet performance of a vehicle.SOLUTION: A pneumatic tire 1 has a plurality of main grooves 3 including a pair of shoulder main grooves 4 on a tread 2. Width Ls of shoulder lands 6 are 10 to 15% of a tread ground contact width TW. The shoulder lands 6 have: first shoulder lateral grooves 15 which extend from the shoulder main grooves 4 to a vicinity of a tread ground contact end Te and are inclined in tire axial direction at 10 to 35 degrees; second shoulder lateral grooves 16 which are inclined to the tire axial direction at 10 to 35 degrees and terminate at an inner side in the tire axial direction from the first shoulder lateral grooves 15 between the first shoulder lateral grooves 15, 15 adjacent circumferentially in the tire; and third shoulder lateral grooves 17 which extend inward in the tire axial direction from the outside of the tire axial direction of the tread ground contact end Te and terminate at a vicinity of the tread ground contact end Te.

Description

  The present invention relates to a pneumatic tire having improved heel-and-toe wear resistance while maintaining vehicle single flow performance, wet performance, and the like.

  Although a plurality of blocks are formed in the tread portion, in recent years, it has been desired to improve the heel and toe wear resistance performance of the blocks. In order to improve the heel and toe wear resistance, the depth and groove width and / or the number of lateral grooves separating the blocks, especially the shoulder lateral grooves provided on the tread grounding end side, are reduced to increase the block pattern rigidity. It is known to do.

  However, the above-described method has a problem that the wet performance deteriorates due to a decrease in the volume of the groove and the edge component. Further, in order to prevent a single flow on a road surface on which the vehicle mainly travels (for example, a road surface inclined for drainage), a large residual cornering force (hereinafter sometimes simply referred to as “residual CF”) is secured. Although necessary, the above-described method has a problem that the residual CF tends to be small. Thus, there is a tradeoff between improving the heel and toe wear resistance and ensuring the wet performance and the single flow performance, and it has been difficult to achieve both. Related technologies include the following.

Japanese Patent Laid-Open No. 2-182505 JP-A-6-32117

  The present invention has been devised in view of the above problems, and limits the land width of the shoulder land portion, and includes the first shoulder lateral groove, the second shoulder lateral groove and the third shoulder groove provided in the shoulder land portion. The main object is to provide a pneumatic tire capable of improving the heel and toe wear resistance while maintaining the wet performance and the one-flow performance, etc., based on the limitation of the shape and end position of the shoulder lateral groove.

  The invention according to claim 1 of the present invention is a pneumatic tire in which a plurality of land portions are divided into a tread portion by a plurality of main grooves extending continuously in a tire circumferential direction. The land portion includes a shoulder land portion on the outer side in the tire axial direction of the shoulder main groove and a land on the center side on the inner side in the tire axial direction from the shoulder main groove. The shoulder land portion has a land width which is a distance in the tire axial direction from the outer edge of the shoulder main groove in the tire axial direction to the tread ground contact end, and is 10 to 15% of the tread ground contact width. The shoulder land portion has a first shoulder lateral groove having an outer end extending from the shoulder main groove in the vicinity of the tread grounding end and inclined at an angle of 10 to 35 degrees with respect to the tire axial direction. The first shoulder lateral grooves adjacent to each other in the tire circumferential direction are inclined in the same direction as the shoulder main grooves and at an angle of 10 to 35 degrees with respect to the tire axial direction, and on the inner side in the tire axial direction from the first shoulder lateral grooves. A second shoulder lateral groove having an outer end that terminates, and a third shoulder lateral groove having an inner end that extends from the outer side in the tire axial direction of the tread ground end to the inner side in the tire axial direction and terminates in the vicinity of the tread ground end. It is characterized by that.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein a land sea ratio of the shoulder land portion is 4.0 to 6.5%.

  According to a third aspect of the present invention, the tire axial distance between the inner end of the third shoulder lateral groove and the outer end of the first shoulder lateral groove is −2 to 5 mm. This is a tire.

  The invention according to claim 4 is the shortest distance between the inner end of the third shoulder lateral groove and the outer end of the first shoulder lateral groove, the inner end of the third shoulder lateral groove, and the second shoulder lateral groove. And the shortest distance between the outer end of the first shoulder lateral groove and the outer end of the second shoulder lateral groove is 40 to 80% of the land width of the shoulder land portion. A pneumatic tire according to any one of claims 1 to 3.

  According to a fifth aspect of the present invention, the groove width of the third shoulder lateral groove is larger than the groove width of the first shoulder lateral groove, and the groove width of the first shoulder lateral groove is the groove of the second shoulder lateral groove. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is larger than a width.

  Further, in the invention according to claim 6, the land portion on the center side has a land portion width of 110 to 160% of the land portion width of the shoulder land portion, and at least one row of the land portions on the center side includes: 6. The center side lateral groove extending over the entire width thereof is spaced apart in the tire circumferential direction, and the angle of the center side lateral groove with respect to the tire axial direction is larger than the angle of the first shoulder lateral groove. A pneumatic tire according to claim 1.

  According to a seventh aspect of the present invention, the outer end of the first shoulder lateral groove and the inner end of the third shoulder lateral groove are alternately and staggered in the tire circumferential direction. The pneumatic tire according to any one of the above.

  The pneumatic tire of the present invention includes a shoulder land portion on the outer side in the tire axial direction of the shoulder main groove by including a pair of shoulder main grooves extending most on the tread grounding end side in the tread portion. In the shoulder land portion, the land portion width, which is the distance in the tire axial direction from the outer edge of the shoulder main groove in the tire axial direction to the tread contact end, is defined as 10 to 15% of the tread contact width. Further, the shoulder land portion has a first shoulder lateral groove having an outer end extending from the shoulder main groove in the vicinity of the tread grounding end and inclined at an angle of 10 to 35 degrees with respect to the tire axial direction, and the tire circumferential direction. The outer end which inclines between the said 1st shoulder horizontal groove in the same direction as the said shoulder main groove and an angle of 10-35 degree | times with respect to a tire axial direction, and terminates inside a tire axial direction from the said 1st shoulder horizontal groove And a third shoulder lateral groove having an inner end extending from the outer side in the tire axial direction of the tread grounding end to the inner side in the tire axial direction and terminating in the vicinity of the tread grounding end.

  In such a pneumatic tire, since the shoulder main groove is provided at a position where the camber amount is large (tread grounding end side), the first to third shoulder lateral grooves provided in the shoulder land portion serve as residual CF of the tire. Helps to increase the impact. In particular, the first shoulder lateral groove is limited to an angle of 10 to 35 degrees with respect to the tire axial direction, and the second shoulder lateral groove is limited to an angle of 10 to 35 degrees with respect to the tire axial direction. 6 is ensured and uniformed, and the edge component is effectively exhibited. Moreover, the contribution with respect to the drainage property of the shoulder lateral groove provided in a shoulder land part can be made small by the land part width | variety of a shoulder land part being prescribed | regulated in the range smaller than before. Furthermore, coupled with limiting the angles of the first and second shoulder lateral grooves, the difference in slip amount between the heel side and the toe side in the tire circumferential direction can be reduced in and out of the tire axial direction of the shoulder land portion. Sensitivity to generate heel and toe wear due to a rigid step can be reduced. Further, since the third shoulder lateral groove extends from the outer side in the tire axial direction of the tread ground end to the inner side in the tire axial direction and terminates in the vicinity of the tread ground end, the edge effect is further combined with the first and second shoulder lateral grooves 15 and 16. Demonstrated. Therefore, in the pneumatic tire 1 of the present invention, the heel and toe wear resistance performance, the single flow performance and the wet performance are improved in a well-balanced manner.

It is an expanded view of the tread part which shows the pneumatic tire of one Embodiment of this invention. It is the elements on larger scale of FIG. It is sectional drawing of the XX part of FIG. It is an expanded view of the tread part which shows a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a pneumatic tire (hereinafter, simply referred to as “tire”) 1 of the present embodiment is suitably used as a tire for passenger cars, for example, and the tread portion 2 includes a tire circumference. A plurality of main grooves 3 extending continuously in the direction are provided.

  In the present embodiment, the main groove 3 includes a pair of shoulder main grooves 4 extending most on the tread grounding end Te side and a pair of center main grooves 5 arranged inside the shoulder main grooves 4. Since the main grooves 3 of this embodiment are all formed in a straight line, they are desirable in that they exhibit excellent drainage performance and suppress unstable behavior such as vehicle wobbling and single flow during driving and braking.

  The tread portion 2 is formed with a pair of shoulder land portions 6 extending outward in the tire axial direction of the shoulder main groove 4 and a land portion 7 on the center side in the tire axial direction from the shoulder main groove 4. . The land portion 7 on the center side of the present embodiment includes a pair of middle land portions 8 extending between the center main groove 5 and the shoulder main groove 4, and a crown land portion 9 extending between the center main grooves 5, 5. It is out.

  The widths of the shoulder main groove 4 and the center main groove 5 (the groove width perpendicular to the longitudinal direction of the groove, the same applies to other grooves hereinafter) W1, W2 and groove depths D1, D2 (shown in FIG. 3) Can be variously determined according to common practice. However, if the groove widths W1 and W2 and / or the groove depths D1 and D2 are too large, the rigidity of the tread portion 2 may be reduced. Conversely, if the groove widths are too small, the drainage property may be reduced. Therefore, for example, the groove width W1 is desirably 1.5 to 6.0% of the tread grounding width TW, and the groove width W2 is desirably 1.5 to 6.0% of the tread grounding width TW, for example. . The groove depths D1 and D2 are preferably 6.0 to 9.0 mm.

  The shoulder main groove 4 is provided at a position where the tire axial distance L1 between the center line 4G of the shoulder main groove 4 and the tread ground contact Te is 11 to 18% of the tread ground width TW. As a result, the land width Ls of the shoulder land portion 6 can be reduced, and the drainage performance can be improved because the drainage can be smoothly performed to the tread grounding end Te side. The center main groove 5 has a tire axial distance L2 between the center line 5G of the center main groove 5 and the tire equator C, preferably at a position of 7.0 to 12.0% of the tread contact width TW. Provided. Thereby, the rigidity of the shoulder land portion 6, the crown land portion 9, and the middle land portion 8 is ensured with a good balance.

  Here, the “tread grounding end Te” is a flat tire with a normal load applied to a normal tire 1 in a normal state in which a normal rim is assembled with a normal rim and filled with a normal internal pressure. It is determined as the ground contact position on the outermost side in the tire axial direction when grounded. The distance in the tire axial direction between the tread ground contact Te and Te is the tread ground contact width TW. Further, the dimensions and the like of each part of the tire are values in the normal state unless otherwise specified.

  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, “Standard Rim” for JATMA and “Design Rim” for TRA. For ETRTO, use "Measuring Rim".

  The “regular internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA and table for TRA. The maximum value described in TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" for ETRTO, but 180 kPa for tires for passenger cars.

  Furthermore, “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “Maximum load capacity” for JATMA, “TIRE” for TRA The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is “LOAD CAPACITY” in the case of ETRTO.

  The shoulder land portion 6 includes a first shoulder lateral groove 15 extending from the shoulder main groove 4 in the vicinity of the tread ground contact end Te, and the shoulder main groove 4 between the first shoulder lateral groove 15 adjacent in the tire circumferential direction. A second shoulder lateral groove 16 that extends in the same direction and has an outer end 16e that terminates on the inner side in the tire axial direction from the first shoulder lateral groove 15, and an inner side in the tire axial direction from the outer side in the tire axial direction of the tread grounding end Te. A third shoulder lateral groove 17 having an inner end 17i that extends in the vicinity of the tread grounding end Te is provided.

  The term “near the tread ground contact Te” means not only on the tread ground contact Te but within 20% of the land width Ls of the shoulder land portion 6 within and outside the tread ground contact Te in the tire axial direction. 15e and the inner end 17i are included.

  1 and 2, the first shoulder lateral groove 15 extends linearly from the shoulder main groove 4 to the vicinity of the tread ground contact Te. The first shoulder lateral grooves 15 are inclined at an angle θ1 of 10 to 35 degrees with respect to the tire axial direction. When the angle θ1 is larger than 35 degrees, the rigidity step in the tire circumferential direction of the shoulder land portion 6 becomes large, and the heel and toe wear resistance performance deteriorates. Conversely, when the angle θ1 is less than 10 degrees, the residual CF becomes excessively small and the one-flow performance is deteriorated. From such a viewpoint, the angle θ1 is more preferably 15 degrees or more, and more preferably 30 degrees or less.

  Since the second shoulder lateral groove 16 of the present embodiment extends linearly and terminates in the tire axial direction inner side than the first shoulder lateral groove 15, the rigidity of the shoulder land portion 6 is secured to ensure high heel and toe wear resistance. Help maintain.

  If the length L7 of the second shoulder lateral groove 16 in the tire axial direction increases, the rigidity of the shoulder block-shaped portion 6A tends to deteriorate. On the other hand, when the length L7 is small, the edge effect is hardly exhibited and the residual CF may be too small. From this point of view, the length L7 is preferably 25% or more, more preferably 30% or more, and preferably 55% or less, more preferably 50% or less of the land portion width Ls of the shoulder land portion 6. Is desirable.

  The second shoulder lateral groove 16 is inclined at an angle θ2 of 10 to 35 degrees with respect to the tire axial direction. When the angle θ2 is larger than 35 degrees, the rigidity step in the tire circumferential direction of the shoulder land portion 6 is increased, and the heel and toe wear resistance is deteriorated. On the other hand, when the angle θ2 is less than 10 degrees, the residual CF becomes excessively small and the one-flow performance is deteriorated. From such a viewpoint, the angle θ2 is more preferably 15 degrees or more, and more preferably 30 degrees or less.

  The second shoulder lateral groove 16 is preferably provided approximately in the middle of the tire circumferential direction length Lt of the shoulder block-shaped portion 6A. When the second shoulder lateral groove 16 is provided closer to the length of 35% of the tire circumferential direction length Lt than the first shoulder lateral groove 15, the rigidity of the shoulder block-shaped portion 6A in the tire circumferential direction is reduced, and heel and Toe wear performance may be deteriorated. From such a viewpoint, it is desirable that the second shoulder lateral groove 16 is provided far from the first shoulder lateral groove 15 by 35% or more, more preferably 45% or more of the tire circumferential direction length Lt.

  Further, the third shoulder lateral groove 17 of the present embodiment includes a linear portion 17a extending linearly from the tire axial direction outer side of the tread ground end Te to the tire axial direction inner side, and the second shoulder connected to the linear portion 17a. It consists of an arcuate portion 17b extending in an arc shape in the direction of the outer end 16e of the lateral groove 16. Such a third shoulder lateral groove 17 can improve drainage performance while ensuring noise performance because the arcuate portion 17b is provided on the tread grounding end Te side.

  Moreover, as for angle (theta) 4 with respect to the tire axial direction in the tire axial direction inner end part of the arc-shaped part 17b, 20-50 degrees are desirable. If the angle θ4 increases, the rigidity of the shoulder land portion 6 may be excessively reduced. From such a viewpoint, the angle θ4 is preferably 40 degrees or less.

  Further, it is desirable that the first to third shoulder lateral grooves 15, 16 and 17 have the same tire circumferential pitch P. Thereby, the rigidity of each shoulder block-shaped part 6A can be ensured uniformly and largely.

  As shown in FIGS. 1 and 2, in such a pneumatic tire 1, the shoulder main groove 4 is provided at a position where the camber amount is large (that is, the tread grounding end Te side), and the first to third shoulders are provided. The lateral grooves 15, 16, and 17 are useful for increasing the influence on the residual CF of the tire. Further, since the angle θ1 of the first shoulder lateral groove 15 and the angle θ2 of the second shoulder lateral groove 16 are set to predetermined values, the rigidity of the shoulder land portion 6 is ensured and uniform, and the edge component is effective. To be demonstrated. Furthermore, the land portion width Ls of the shoulder land portion 6 is a distance in the tire axial direction from the outer edge 4e of the shoulder main groove 4 in the tire axial direction to the tread contact end Te, and the land portion width Ls is 10 to 10 of the tread contact width TW. Since the range is defined as 15%, which is smaller than the conventional range, the contribution to the drainage of the shoulder lateral grooves 15, 16 and 17 provided in the shoulder land portion 6 can be reduced. Furthermore, coupled with limiting the angles of the first and second shoulder lateral grooves, the difference in slip amount between the heel side and the toe side in the tire circumferential direction can be reduced both inside and outside in the tire axial direction. Sensitivity to generate heel and toe wear can be reduced. Further, since the third shoulder lateral groove 17 terminates in the vicinity of the tread grounding end Te, the edge effect is further exhibited in combination with the first and second shoulder lateral grooves 15 and 16. Therefore, in the pneumatic tire 1 of the present invention, the heel and toe wear resistance performance, the single flow performance and the wet performance are improved in a well-balanced manner.

  Further, the land sea ratio of the shoulder land portion 6 is preferably 4.0% or more, and more preferably 6.5% or less. When the land sea ratio increases, the rigidity of the shoulder land portion 6 decreases, and the heel and toe wear resistance tends to deteriorate. On the contrary, when the land sea ratio is small, the drainage tends to be deteriorated.

  The land sea ratio is the shoulder land portion assuming that the entire area L of the outer surface of the shoulder land portion 6 on the inner side in the tire axial direction from the tread contact edge Te (the first to third shoulder lateral grooves 15, 16 and 17 are all filled). 6) and the total area S on the outer surface of the first to third shoulder lateral grooves 15, 16 and 17 arranged on the inner side in the tire axial direction from the tread contact end Te (S / L).

  Further, when the tire axial distance La between the inner end 17i of the third shoulder lateral groove 17 and the outer end 15e of the first shoulder lateral groove 15 increases, the third shoulder lateral groove 17 and / or the first shoulder lateral groove 15 There is a tendency for the drainage performance to decrease and the wet performance to deteriorate. On the other hand, when the distance La is decreased, the rigidity of the shoulder land portion 6 is decreased and the heel and toe wear resistance may be deteriorated. From such a viewpoint, the distance La is preferably −2 mm or more, more preferably 0 mm or more, and preferably 5 mm or less, more preferably 4 mm or less. In addition, the minus (-) display of the distance La indicates an aspect in which the first shoulder lateral groove 15 and the third shoulder lateral groove 17 overlap in the tire axial direction.

  Further, the shortest distance L3 between the inner end 17i of the third shoulder lateral groove 17 and the outer end 15e of the first shoulder lateral groove 15, the inner end 17i of the third shoulder lateral groove 17 and the outer end 16e of the second shoulder lateral groove 16 The shortest distance L4 and the shortest distance L5 between the outer end 15e of the first shoulder lateral groove 15 and the outer end 16e of the second shoulder lateral groove 16 are preferably 40% or more of the land portion width Ls of the shoulder land portion 6, more preferably. Is 45% or more, preferably 80% or less, more preferably 75% or less. That is, when the shortest distances L3, L4, and L5 are out of the specified numerical range, the rigidity of the shoulder land portion 6, particularly the rigidity of the shoulder land portion 6 in the tire circumferential direction is reduced, and the heel and toe wear resistance is deteriorated. Tend.

  The groove width W5 of the third shoulder lateral groove 17 is larger than the groove width W3 of the first shoulder lateral groove 15, and the groove width W3 of the first shoulder lateral groove 15 is the groove width of the second shoulder lateral groove 16. It is desirable to be larger than W4. That is, when the groove width W3 of the first shoulder lateral groove 15 is larger than the groove width W5 of the third shoulder lateral groove 17, the rigidity of the shoulder land portion 6 is likely to be reduced, and the heel and toe wear resistance may be easily deteriorated. . Further, if the groove width W3 of the first shoulder lateral groove 15 is smaller than the groove width W4 of the second shoulder lateral groove 16, the drainage performance of the first shoulder lateral groove 15 becomes difficult to be exhibited, and the wet performance tends to deteriorate. However, if the groove width W5 of the third shoulder lateral groove 17 is too larger than the groove width W3 of the first shoulder lateral groove 15, the rigidity of the buttress portion (not shown) may be excessively reduced. Similarly, if the groove width W3 of the first shoulder lateral groove 15 is too larger than the groove width W4 of the second shoulder lateral groove 16, the rigidity of the shoulder land portion 6 may be reduced. From such a viewpoint, the ratio (W5 / W3) of the groove width between the first shoulder lateral groove 15 and the third shoulder lateral groove 17 is more preferably 120% or more, and preferably 400% or less, more preferably 300. % Or less is desirable. Similarly, the groove width ratio (W3 / W4) between the first shoulder lateral groove 15 and the second shoulder lateral groove 16 is more preferably 105% or more, and preferably 200% or less, more preferably 150% or less. desirable.

  Further, from the viewpoint of improving the heel and toe wear resistance and the wet performance in a well-balanced manner, the groove depth D3 (not shown) of the first shoulder lateral groove 15 is preferably 3.0 mm or more, more preferably 4.0 mm or more. Preferably, it is 8.0 mm or less, more preferably 7.0 mm or less. Further, the groove depth D4 (not shown) of the second shoulder lateral groove 16 is preferably 3.0 mm or more, more preferably 4.0 mm or more, and preferably 8.0 mm or less, more preferably 7.0 mm or less. Is desirable. Further, the groove depth D5 of the third shoulder lateral groove 17 is preferably 4.0 mm or more, more preferably 5.0 mm or more, and preferably 9.0 mm or less, more preferably 8.0 mm or less. The groove depth D5 (not shown) of the third shoulder lateral groove 17 is a depth at a position of 20% of the land portion width Ls of the shoulder land portion 6 on the outer side in the tire axial direction from the tread ground contact Te.

  The outer end 15e of the first shoulder lateral groove 15 and the inner end 17i of the third shoulder lateral groove 17 are preferably alternately and staggered in the tire circumferential direction. That is, the outer end 15e of the first shoulder lateral groove 15 and the inner end 17i of the third shoulder lateral groove 17 are separated from each other in the tire circumferential direction, so that the rigidity in the vicinity of the shoulder land portion 6, particularly in the vicinity of the tread ground contact end Te. Since the heel and toe wear resistance is greatly improved, the edge components of the first and third shoulder lateral grooves 15 and 17 are effectively exhibited to suppress the residual CF from becoming excessively large. To help.

  The land widths Lm and Lc of the middle land portion 8 and the crown land portion 9 are preferably 110 to 160% of the land width Ls of the shoulder land portion 6. That is, if the land portion widths Lm and Lc are too large compared with the land portion width Ls, the rigidity balance between the land portions 6 and 7 is deteriorated, and the steering stability performance is deteriorated. On the contrary, when the land widths Lm and Lc are smaller than the land width Ls, the rigidity of the middle land portion 8 and the crown land portion 9 is reduced, so that the stability during straight traveling deteriorates and The effect of the invention is not exhibited.

  Further, at least one row of the land portions 7 on the center side, in the present embodiment, the middle land portion 8 has middle main lateral grooves 18 extending across the entire width of the middle land portion 8 (land portion width Lm). Established. That is, in the middle land portion 8, a middle block 8 </ b> A having a substantially parallelogram shape is formed by the middle main lateral groove 18, the center main groove 5, and the shoulder main groove 4.

  The middle main horizontal groove 18 of the present embodiment includes a first small inclined portion 18a that is inclined at an angle θ3a with respect to the tire axial direction from the shoulder main groove 4 toward the tire equator C side and extends in a small length, and the first small inclined portion. A large inclined portion 18b that is connected to an inner end of the portion 18a in the tire axial direction and has a larger angle θ3b with respect to the tire axial direction than the first small inclined portion; and an inner end of the large inclined portion 18b in the tire axial direction. The center main groove 5 includes a second small inclined portion 18c extending at an angle θ3c smaller than that of the large inclined portion 18b. The angle θ3 of the middle main lateral groove 18 with respect to the tire axial direction is preferably larger than the angle θ1 of the first shoulder lateral groove from the viewpoint of improving the one-flow performance and the heel and toe wear resistance in a well-balanced manner.

  Such middle main lateral groove 18 is useful for discharging the water film on the road surface near the tire equator C to the shoulder main groove 4 side through the center main groove 5. In addition, since the first small inclined portion 18a and the second small inclined portion 18c having a small angle with respect to the tire axial direction are connected to the middle land portion 8, a large rigidity in the tire axial direction is ensured. For this reason, the pneumatic tire 1 of this embodiment improves with good balance between wet performance and steering stability performance.

  Further, it is desirable that an intermediate tie bar 19 for raising the groove bottom 18s of the middle main transverse groove 18 with a small length in the longitudinal direction is provided at a substantially midpoint position of the middle main transverse groove 18 in the tire axial direction. Such an intermediate tie bar 19 improves the rigidity in the tire circumferential direction of the middle blocks 8A and 8A arranged on both sides in the tire circumferential direction, and suppresses the crushing of the middle main lateral groove 18 to improve the wet performance. Help secure.

  Further, the middle land portion 8 includes a middle outer lateral groove 20 that inclines toward the tire equator C side from the shoulder main groove 4 and terminates without reaching the center main groove 5, and from the center main groove 5 to the tire. An in-middle lateral groove 21 that is inclined toward the outer side in the axial direction and ends without reaching the center main groove 5 is provided.

  Further, the crown land portion 9 includes a narrow crown groove 22 having a small groove width that inclines toward the tire equator C side from the center main groove 5 and terminates without reaching the tire equator C, and in the tire circumferential direction. A short crown groove 23 having a small groove length disposed between the spaced apart narrow crown grooves 22 and 22 and extending from the center main groove 5 toward the tire equator C side and ending without reaching the tire equator C. And are provided.

  The middle outer lateral groove 20, the middle inner lateral groove 21, the crown narrow groove 22 and the crown short groove 23 are useful for improving the drainage performance while ensuring the rigidity of the middle land portion 8 and the crown land portion 9 respectively. .

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.

Pneumatic tires (size: 215 / 55R17) having the pattern of FIG. 1 and based on the specifications in Table 1 were manufactured and tested for their respective performance. The common specifications are as follows.
Rim size: 7J
Tread contact width: 170mm
<Center main groove>
Groove width W1 / Tread contact width TW: 4.5%
Groove depth D1: 8.2 mm
Angle with respect to tire equator C: 0 degree Installation position: L2 / TW from tire equator C
<Shoulder main groove>
Groove width W2 / tread contact width TW: 4.9%
Groove depth D2: 8.2 mm
Angle relative to tire equator C: 0 degree <first shoulder lateral groove>
Groove width W3: 0.8mm
Groove depth D3: 6.0 mm
<Second shoulder lateral groove>
Groove width W4: 0.6mm
Groove depth D4: 6.0 mm
Tire axial length L7 / Ls: 40%
<Third shoulder cross groove>
Groove width W5: 2.0mm
Groove depth D5: 6.6 mm
<Center main transverse groove>
Groove width W6: 2.0mm
Groove depth D6: 6.0 mm
The test method is as follows.

<Operation stability and wet performance>
Four tyres of each test tire are mounted on a domestic FF vehicle with a displacement of 2400cm ³ and filled with an internal pressure of 230 kPa, driving on a dry asphalt road surface and a wet asphalt road surface (water depth 5mm) with one driver on the steering wheel. The handling stability when dry and wet related to responsiveness, rigidity, grip, etc. was evaluated by sensory evaluation of the driver. The results are displayed as an index with Comparative Example 1 as 100. The larger the value, the better.

<Heel and toe wear resistance>
Each test tire travels 20000km on the asphalt road surface, measures the unevenness between the shoulder land, the so-called heel and toe wear amount at 10 locations, and compares the average reciprocal of the difference (absolute value) between them. It is indicated by an index where 1 is 100. The larger the value, the more uniform the wear and the better the wear resistance.

<Residual CF>
Each sample tire was run on a flat belt machine at a speed of 10 km / H and a load of 4900 N in accordance with JASO C607 for testing. The result is an average value of measured values of 20 sample tires. The closer the numerical value is to 100N, the larger the residual CF, indicating that a vehicle equipped with this tire is good because it can travel on a sloping road surface for drainage, for example, without flowing alone.
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that the tires of the examples have improved various performances as compared with the comparative examples.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Main groove 4 Shoulder main groove 4e The outer edge of the shoulder main groove of the tire axial direction
5 Center main groove 6 Shoulder land portion 7 Center-side land portion 15 First shoulder transverse groove 16 Second shoulder transverse groove 17 Third shoulder transverse groove C Tire equator Ls Shoulder land portion Land width Te Tread grounding end TW Tread grounding width θ1 First Angle θ2 with respect to the tire axial direction of the first shoulder lateral groove Angle with respect to the tire axial direction of the second shoulder lateral groove

Claims (7)

A pneumatic tire in which a plurality of land portions are divided by a plurality of main grooves extending continuously in the tire circumferential direction on the tread portion,
The main groove includes a pair of shoulder main grooves extending most on the tread grounding end side,
The land portion includes a shoulder land portion on the outer side in the tire axial direction of the shoulder main groove, and a land portion on the center side on the inner side in the tire axial direction from the shoulder main groove,
In the shoulder land portion, a land portion width that is a distance in the tire axial direction from the outer edge of the shoulder main groove in the tire axial direction to the tread ground contact end is 10 to 15% of the tread ground contact width,
Moreover, in the shoulder land,
A first shoulder lateral groove having an outer end extending in the vicinity of the tread grounding end from the shoulder main groove and inclined at an angle of 10 to 35 degrees with respect to the tire axial direction;
Between the first shoulder lateral grooves adjacent in the tire circumferential direction is inclined at an angle of 10 to 35 degrees in the same direction as the shoulder main grooves and with respect to the tire axial direction, and is terminated at the inner side in the tire axial direction from the first shoulder lateral grooves. A second shoulder transverse groove having an outer end to
A pneumatic tire comprising a third shoulder lateral groove having an inner end extending from the outer side in the tire axial direction of the tread grounding end to the inner side in the tire axial direction and terminating in the vicinity of the tread grounding end.   The pneumatic tire according to claim 1, wherein a land sea ratio of the shoulder land portion is 4.0 to 6.5%.   The pneumatic tire according to claim 1 or 2, wherein a distance in a tire axial direction between the inner end of the third shoulder lateral groove and the outer end of the first shoulder lateral groove is -2 to 5 mm. The shortest distance between the inner end of the third shoulder lateral groove and the outer end of the first shoulder lateral groove;
The shortest distance between the inner end of the third shoulder lateral groove and the outer end of the second shoulder lateral groove;
4. The shortest distance between the outer end of the first shoulder lateral groove and the outer end of the second shoulder lateral groove is 40 to 80% of a land portion width of the shoulder land portion. 5. Pneumatic tire described in 2.   The groove width of the third shoulder lateral groove is larger than the groove width of the first shoulder lateral groove, and the groove width of the first shoulder lateral groove is larger than the groove width of the second shoulder lateral groove. The pneumatic tire in any one of 4 thru | or 4. The land part on the center side has a land part width of 110 to 160% of the land part width of the shoulder land part,
At least one row of land portions on the center side has transverse grooves on the center side extending across the entire width thereof, and is arranged in the tire circumferential direction.
The pneumatic tire according to any one of claims 1 to 5, wherein an angle of the center side lateral groove with respect to a tire axial direction is larger than the angle of the first shoulder lateral groove.   The pneumatic tire according to any one of claims 1 to 6, wherein the outer end of the first shoulder lateral groove and the inner end of the third shoulder lateral groove are alternately and staggered in the tire circumferential direction.

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