JP2011102073A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve on-ice performance and rut travel performance in a well-balanced state. <P>SOLUTION: This pneumatic tire is 0.75-0.95 in the ratio TW/SW of a tread width TW to a tire maximum width SW between the tread end Te in a normal state of being no-load of being installed in the normal rim and being filled with normal internal pressure. A thin groove 15 continuously extending in the tire peripheral direction is arranged on a buttress surface 14, and an angle α formed by the center line 15G of this thin groove 15 and a normal 6n of a carcass of passing through an intersection e1 of crossing between an extension line 15e of the center line 15G and the carcass 6, is within 10 degrees. A tread part 2 is also provided with a pair of shoulder main grooves 8c continuously extending in the tire peripheral direction on the most tread end Te side, and the groove depth D3 of the thin groove 15 falls within a range of 20-50% of the groove depth D2 of the shoulder main grooves 8c. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that improves on-ice performance and saddle running performance in a well-balanced manner.

  Conventionally, a pneumatic tire has been proposed in which a tread width and a land ratio are increased to ensure a large contact area. Since such a pneumatic tire can obtain a large frictional force with respect to the road surface, traveling performance is improved on an icy road surface.

  By the way, in the above-mentioned pneumatic tire, as shown in FIG. 10 (a), when a normal load n1 determined by the standard is applied, an appropriate grounding width w1 is ensured, so that it is optimal and large. Although a ground contact area can be obtained, in the case of a relatively small load n2 less than the normal load, as shown in FIG. 10B, the ground contact width w2 is smaller than the ground contact width w1, so that a desired ground contact area is obtained. Can not get.

  Also, a pneumatic tire having a wide tread width is likely to cause wandering in which a part of the tread or a buttress surface easily comes into contact with a slope of a kite or the like, and the tire fluctuates due to an external force from the road surface. For this reason, increasing the ground contact area increases the performance on ice while deteriorating the wandering resistance. Related technologies include the following.

JP 2008-222158 A

  The present invention has been devised in view of the above-described problems. The tread width with respect to the maximum tire width is increased, and a specific-shaped narrow groove extending continuously in the tire circumferential direction is provided on the buttress surface. The main objective is to provide a pneumatic tire that secures an optimum ground contact area regardless of the load state, improves the performance on ice, and also improves the anti-wandering performance.

  The invention according to claim 1 of the present invention includes a carcass extending from the tread portion to the bead core of the bead portion through the sidewall portion, and a belt layer disposed outside the carcass in the tire radial direction and inside the tread portion. In a normal state in which the pneumatic tire is equipped with a normal rim and is not loaded with a normal internal pressure, the ratio TW / SW between the tread width TW between the tread ends and the tire maximum width SW is 0. The buttress surface which is 75 to 0.95 and is an outer region in the tire radial direction of the sidewall portion is provided with a narrow groove extending continuously in the tire circumferential direction, and the tire rotation shaft in the normal state is In the tire meridian cross section, the angle formed by the center line of the narrow groove and the normal line of the carcass passing through the intersection where the extension line of the center line intersects the carcass is The tread portion is provided with a pair of shoulder main grooves extending continuously in the tire circumferential direction at the tread end side, and the groove depth of the narrow groove is equal to that of the shoulder main groove. It is characterized by being 20 to 50% of the groove depth.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the narrow groove is provided in an area of 80% or more and 90% or less of the tire cross-sectional height from the bead base line.

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the shortest distance between the groove bottom of the narrow groove and the intersection is 3 to 8 mm.

  According to a fourth aspect of the present invention, in the tread portion, a shoulder lateral groove extending between the shoulder main groove and the tread end is spaced apart in the tire circumferential direction, so that a plurality of shoulder blocks are arranged in the tire circumferential direction. A shoulder block row is provided, and the shoulder block row is a notch in which a crossing portion where the outer wall surface of the shoulder block in the tire axial direction and the tread surface of the shoulder block intersect is chamfered over its entire length. The pneumatic tire according to claim 1, wherein every other block is provided in the tire circumferential direction.

  According to a fifth aspect of the present invention, in the tread portion, a shoulder lateral groove extending between the shoulder main groove and the tread end is provided in the tire circumferential direction, whereby a plurality of shoulder blocks are arranged in the tire circumferential direction. A shoulder block row is provided, and the shoulder block row is a notched block chamfered with a triangular slope at the top where the outer wall surface, the tread surface, and the block wall surface facing the shoulder lateral groove intersect. The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is provided continuously in a tire circumferential direction.

  In the normal state, the pneumatic tire of the present invention is formed to have a wide tread width of 0.75 to 0.95 times the tire maximum width. The buttress surface is provided with a narrow groove extending continuously in the tire circumferential direction, and the narrow groove is limited to a specific shape. Specifically, in the tire meridian cross section including the tire rotation axis in the normal state, the narrow groove is formed by a center line thereof and a normal line of the carcass passing through an intersection where the extension line of the center line intersects the carcass. The angle is within 10 degrees. The depth of the narrow groove is set to 20 to 50% of the depth of the shoulder main groove.

  As a result of various experiments, the narrow groove defined as described above reduces the rigidity of the buttress part and flexibly deforms the buttress part even when a load smaller than the normal load is applied. Can be secured greatly. Even when the tread edge or buttress surface comes into contact with the slope of the ridge, the narrow groove of the buttress surface is deformed from the narrow groove as a starting point to absorb the reaction force from the road surface, thereby preventing the occurrence of wandering. As described above, the pneumatic tire of the present invention can improve the wandering resistance performance while ensuring a large contact area and improving the performance on ice.

  Further, in the pneumatic tire according to claim 4 or 5, the reaction force from the road surface can be further reduced by cutting out the outer surface of the shoulder block even when it collides with a saddle. For this reason, wandering resistance is further improved.

It is a right half sectional view (XX section of Drawing 2) of a pneumatic tire showing an embodiment of the present invention. FIG. It is an expanded sectional view of the buttress part of FIG. It is sectional drawing showing the effect of this invention. (A), (b) is an expanded sectional view showing the shape of a narrow groove. It is a perspective view of the shoulder block of this embodiment. It is a perspective view of the shoulder block which shows other embodiment. (A), (b) is an expanded view showing the tread pattern of an Example. (A) is an Example and (b) is a development view showing a tread pattern of a comparative example. (A), (b) is sectional drawing of the tire which shows the aspect of contact width.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a right half sectional view of the pneumatic tire 1 of the present embodiment, and FIG. 2 is a development view thereof. The cross-sectional view of FIG. 1 represents a meridian cross section including a tire rotation axis in a normal state in which the rim is assembled on a normal rim (not shown) and is filled with a normal internal pressure. When there is no notice in particular, the dimension of each part of a tire, etc. are values measured in this normal state.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. “Standard Rim” for JATMA, “Design Rim” for TRA For ETRTO, "Measuring Rim". In addition, the “regular internal pressure” is an air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "Maximum value", ETRTO, "INFLATION PRESSURE".

  As shown in FIG. 1, the pneumatic tire (hereinafter, simply referred to as “tire”) 1 of the present embodiment reaches the bead core 5 of the bead portion 4 from the tread portion 2 through the sidewall portion 3. A carcass 6 and a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2 are provided. In the present embodiment, a studless tire for a passenger car is shown.

  The carcass 6 includes a main body portion 6a straddling a pair of bead cores 5 and 5 in a toroidal manner, and a folded portion 6b which is continuous from both sides of the main body portion 6a and is folded from the inner side to the outer side in the tire axial direction around the bead core 5. And at least one carcass ply 6A. In the carcass ply 6A, carcass cords made of, for example, organic fibers are arranged at an angle of, for example, 75 to 90 ° with respect to the tire equator C direction.

  The belt layer 7 includes, for example, two outer belt plies 7A and 7B in the tire radial direction, and the inner belt ply 7A is formed wider than the outer belt ply 7B. Each of the belt plies 7A and 7B has a highly elastic belt cord such as a steel cord inclined at an angle of 15 to 40 ° with respect to the tire equator C. The belt plies 7A and 7B are inclined so that the belt cords cross each other. As a result, the belt layer 7 tightens the carcass 6 over substantially the entire width of the tread portion 2 to increase the rigidity of the tread portion 2.

  The tread portion 2 is provided with a plurality of main grooves 8 extending continuously in the tire circumferential direction and a plurality of lateral grooves 9 extending in a direction intersecting with the main grooves 8. These main grooves 8 and lateral grooves 9 can exhibit drainage and snow column shearing functions.

  The main groove 8 is, for example, a pair of center main grooves 8a disposed closest to the tire equator C and extending in the tire circumferential direction on both sides thereof, a pair of middle main grooves 8b disposed on the outside thereof, and the tire. It includes a pair of shoulder main grooves 8c that are arranged on the outer side in the axial direction and extend most on the tread end Te side. Since all of the main grooves 8 of the present embodiment are formed in a straight line, it is possible to exhibit excellent drainage performance and to suppress unstable behavior such as vehicle wobbling and single flow during braking. This is desirable in terms of ensuring stable performance. The shape of the main groove 8 can be appropriately changed without being limited to the illustrated form.

  The tread portion 2 includes one center land portion 10 extending between the center main grooves 8a and 8a, and a pair of first middle land portions extending between the center main groove 8a and the middle main groove 8b. 11, a pair of second middle land portions 12 extending between the middle main groove 8b and the shoulder main groove 8c, and a pair of shoulder land portions 13 extending outward in the tire axial direction of the shoulder main groove 8c. Each is formed.

  The center land portion 10, the pair of first middle land portions 11, the pair of second middle land portions 12, and the pair of shoulder land portions 13 have a center lateral groove 9 a and a first middle lateral groove, respectively. 9b, a second middle lateral groove 9c and a shoulder lateral groove 9d are formed. As a result, each of the land portions 10 to 13 includes a center block row 10R and a first middle block row in which the center block 10b, the first middle block 11b, the second middle block 12b, and the shoulder block 13b are arranged in the tire circumferential direction. 11R, a second middle block row 12R, and a shoulder block row 13R. Each block 10b to 13b is preferably formed with a plurality of sipings s extending in a zigzag shape in the tire axial direction, for example.

  As shown in FIGS. 1 and 2, the groove widths of the center main groove 8a and the middle main groove 8b (the groove width perpendicular to the longitudinal direction of the groove, the same shall apply to other grooves hereinafter) W1 and the groove depth. D1 (represented as representative of the center main groove 8a in FIG. 1) is not particularly limited, but in order to ensure a well-balanced drainage performance and performance on ice, the groove width W1 is 5 to 9 mm. Desirably, the groove depth D1 is preferably 8 to 10 mm.

  Further, as shown in FIGS. 2 and 3, if the groove width W2 and the groove depth D2 of the shoulder main groove 8c are too large, the contact area may be reduced or the block rigidity may be excessively reduced. If it is too small, drainage or the like from the vicinity of the tire equator C to the tread end Te side may not be performed smoothly. From such a viewpoint, the groove width W2 is preferably 3 to 4% of the tread width TW, which is the tire axial distance between the tread ends Te and Te, and the groove depth D2 is 8 to 10 mm. desirable.

  Further, as shown in FIG. 2, the position of the shoulder main groove 8c is not particularly limited. For example, the tire axial direction distance L1 between the center line 8G and the tread end Te is the tread width. Preferably 16 to 20% of TW is desirable. Thereby, the rigidity of the shoulder block 13b is sufficiently ensured, and the turning performance is enhanced.

  As shown in FIG. 2, each of the lateral grooves 9a to 9c of the present embodiment is formed to include an enlarged portion in which the groove width expands toward the tread end Te side. This is desirable in that the length of the groove edges of the lateral grooves 9a to 9c is increased and the grip on the ice road surface is enhanced. The shoulder lateral groove 9d has a groove width larger than that of the other lateral grooves 9a to 9c and substantially constant. This is desirable in that the lateral rigidity of the shoulder block 13b can be secured. In addition, the shape of the said horizontal groove 9 can be suitably changed, without being restrict | limited to the illustrated form.

  Although not particularly limited, the tire axial length BW (represented by the width of the shoulder block 13b in FIG. 2) of each of the blocks 10b to 13b is too small. There is a risk that the ground contact area will decrease, and conversely if it is too large, the groove volume of the main groove 8 will decrease, and the drainage / snow drainage performance may decrease. From such a viewpoint, the tire axial length BW of each of the blocks 10b to 13b is preferably 22 mm to 33 mm.

  In the pneumatic tire 1 of the present invention, the ratio TW / SW between the tread width TW, which is the distance in the tire axial direction between the tread ends Te, Te, and the maximum tire width SW is 0.75 to 0.95. . As a result, the tread width TW is larger than the tire maximum width SW and a large contact area is ensured, so that a large frictional force is obtained against the ice road surface. Therefore, the performance on ice of the pneumatic tire 1 of the present invention is improved.

  The tread end Te is defined as the outermost contact end in the tire axial direction when a normal load is applied to the pneumatic tire 1 in a normal state and is grounded on a flat surface with a camber angle of 0 degrees. The “regular load” is a load determined by each standard for each tire in a standard system including the standard on which the tire is based. “JATMA” is “maximum load capacity”, and TRA is a table. The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” if it is ETRTO, but if the tire is for a passenger car, the load is equivalent to 88% of each of the above loads. .

  Further, the “maximum tire width” refers to the tire axial distance between the tire maximum width positions M and M that protrude most outward in the tire axial direction, excluding protrusions such as letters and rim protectors in the sidewall portion. .

  As shown in FIG. 1, when the pneumatic tire 1 of the present invention is defined using a ratio TW / CW of the tread width TW and the maximum carcass width CW, the ratio TW / CW is 0.77 to It is desirable that it is 0.98. The “maximum carcass width” refers to the distance in the tire axial direction between the maximum carcass width points m and m where the center line of the thickness of the main body portion 6a of the carcass ply 6A protrudes to the outermost side in the tire axial direction.

  Further, the tire 1 has a buttress surface 14 that is an outer region of the sidewall portion 3 in the tire radial direction. The buttress surface 14 is an inclined surface 14a including an outer wall surface on the outer side in the tire axial direction of the shoulder block 13b extending from the tread end Te inward in the tire radial direction toward the outer side in the tire axial direction.

As shown in FIG. 3, the buttress surface 14 is provided with a narrow groove 15 extending linearly continuously in the tire circumferential direction. Such a narrow groove 15 moderately reduces the rigidity of the buttress portion including the buttress surface 14. Thereby, as shown in FIG. 4, the pneumatic tire 1 of the present embodiment secures a ground contact area equivalent to that when a normal load is applied even when a load n2 smaller than the normal load is applied. it can. For example, in the tire 1 of the present embodiment, when a load of 90% or more of the normal load is applied, it is possible to ensure a contact area equal to the contact area when the normal load is applied.

  Also, the buttress surface 14 provided with the narrow groove 15 can be flexibly deformed by opening and closing the narrow groove 15 when receiving an external force from the side, for example. For this reason, even when the pneumatic tire 1 of this embodiment contacts with the slope of the heel, the narrow groove 15 is deformed flexibly so as to be caught on the slope, riding on the slope, and reaction force from the slope. Can absorb. Thereby, the tire 1 of this embodiment can exhibit the outstanding wandering performance.

  In order to effectively exhibit the above-described action, the groove depth D3 of the narrow groove 15 needs to be regulated to 20 to 50% of the groove depth D2 of the shoulder main groove. If the groove depth D3 of the narrow groove 15 is less than 20% of the groove depth D2, the rigidity of the buttress portion cannot be sufficiently lowered, and consequently a large ground contact area cannot be secured. On the other hand, if the groove depth D3 exceeds 50%, the rigidity of the buttress portion is excessively reduced, and uneven wear is likely to occur in the vicinity of the tread end Te. Sexually deteriorates. From such a viewpoint, the groove depth D3 of the narrow groove 15 is preferably 25% or more, and preferably 45% or less of the groove depth D2 of the shoulder main groove.

  As shown in FIG. 3, the groove depth D3 of the narrow groove 15 is measured in a direction perpendicular to the plane HP connecting the outer edge 15x of the narrow groove 15 in the tire radial direction and the inner edge 15y in the tire radial direction. The maximum length.

  In the pneumatic tire 1 of the present invention, the center line 15G of the narrow groove 15, the extension line 15e of the center line 15G, and the carcass 6 intersect in the tire meridian section including the tire rotation axis in the normal state. The angle α formed with the normal 6n of the carcass 6 passing through the intersection point e1 is set within 10 degrees, more preferably within 8 degrees. That is, the narrow groove 15 is provided so that the center line 15G approximates the normal direction of the carcass 6. Thereby, in the pneumatic tire 1 of the present embodiment, the stress that compresses the groove bottom of the narrow groove 15 is transmitted in a substantially perpendicular direction to the carcass ply 6A at the time of collision with the slope of the heel, etc. It is possible to prevent a large shearing force from acting on the carcass cord at the portion, and to prevent damage such as carcass cord loose at this portion. On the other hand, when the angle α is larger than 10 degrees, such an effect cannot be sufficiently expected.

  The center line 15G of the narrow groove 15 is a straight line connecting the midpoint P1 of the plane HP and the deepest portion 15p of the groove bottom 15s where the narrow groove 15 is closest to the outer surface of the carcass 6 in the tire meridian cross section. Shall be defined as

  Further, as shown in FIG. 3, the shortest distance Ha between the deepest portion 15p of the narrow groove 15 and the intersection point e1 can be variously determined, but if it is too small, the rigidity of the buttress portion is significantly reduced. Cracks and chips starting from the groove bottom are likely to occur, and steering stability may be deteriorated. On the other hand, if the shortest distance Ha is too large, the rigidity of the buttress portion cannot be lowered appropriately, and the effect of securing the ground contact area and improving the wandering property at the time of low load tends to be reduced. From such a viewpoint, in order to more effectively exhibit the above-described effects, the shortest distance Ha is preferably 3 mm or more, more preferably 4 mm or more, and preferably 6 mm or less, more preferably 8 mm or less. .

  Further, as shown in an enlarged view in FIG. 5 (a), the shape of the narrow groove 15 of the present embodiment is such that the cross section of the tire meridian is from an arc portion 16 formed of an arc having a curvature radius r1 of, for example, 2.0 mm or more. The groove bottom 15 s and a pair of groove wall surfaces 15 h extending linearly from the groove bottom 15 s to the buttress surface 14, and the groove width gradually increases toward the buttress surface 14.

  In this embodiment, the arc portion 16 is formed with a central angle θ1 smaller than 180 degrees. The narrow groove 15 having such a circular arc part 16 can flexibly deform and disperse the external force acting on the groove bottom 15s, and can effectively prevent cracks occurring in the groove bottom 15s. However, when the radius of curvature r1 of the arc portion 16 increases, stress tends to concentrate at the intersection e2 between the groove bottom 15s of the narrow groove 15 and the groove wall surface 15h, and cracks tend to occur. From such a viewpoint, the radius of curvature r1 is preferably 2 mm or less, more preferably 3 mm or less.

  The shape of the narrow groove 15 is not limited to the shape as described above. For example, as shown in FIG. 5B, the central angle θ1 of the arc portion 16 having an arc shape is 180 degrees or more. And the groove cross section can be made into a flask shape. In this embodiment, the external force applied to the groove bottom 15s can be more effectively dispersed, and the occurrence of cracks and the like can be suppressed for a longer period.

  Further, the groove width W3 of the narrow groove 15 is not particularly limited. However, if it is too large, the rigidity of the buttress portion tends to be remarkably lowered. Conversely, if it is too small, the buttress portion may be sufficiently deformed. Tend to be difficult. From such a viewpoint, the groove width W3 is preferably 60% or more, more preferably 65% or more, and preferably 80% or less, more preferably 75% or less of the groove width W2 of the shoulder main groove 8c. Is desirable.

  Moreover, the arrangement position of the narrow groove 15 is not particularly limited, but if it is too close to the tread end Te, the narrow groove 15 may disappear early due to wear, and conversely, the tread end Te. Even if it is too far from the distance, there is a possibility that improvement in wandering performance cannot be expected sufficiently. From such a viewpoint, it is desirable that the narrow groove 15 is provided in an area A1 of 80 to 90% of the tire cross-section height H. Here, “provided in the region A1” means that at least one of the outer edge 15x and the inner edge 15y of the narrow groove 15 is provided in the region A1, as shown in FIG. 5A. means. The tire cross-sectional height H is a distance in the tire radial direction from the bead base line BL to the outermost position in the tire radial direction of the tread portion 2 in the unloaded normal state.

  Further, as a more preferable aspect, as shown in FIG. 6, the shoulder block 13b includes an outer wall surface 13bs on the outer side in the tire axial direction of the shoulder block 13b, a tread surface 13bn of the shoulder block 13b, and the shoulder lateral groove 9d. The top portion 13c1 intersecting with the block wall surface 13bh facing the surface includes a notched block 13B1 having a chamfered portion 17 chamfered by a triangular slope 17a. As a result, as shown in FIG. 2, the shoulder lateral groove 9d is formed with an enlarged portion 16 in which the groove width W2 is enlarged on the outer end side in the tire axial direction. For example, it is desirable that the notch block 13B1 is provided continuously in the tire circumferential direction. The pneumatic tire 1 having such a notched block 13B1 can more effectively disperse the stress at the time of contact with the heel by removing the edge of the top portion 13c1 that easily contacts the heel by chamfering. Further, the wandering resistance can be further improved.

  In order to exhibit the above-described effects more effectively, the tire circumferential direction width W5 and the tire axial direction width W6 of the chamfered portion 17 are preferably 15% of the tire axial direction length BW of the shoulder block 13b. Above, more preferably 20% or more, and more preferably 30% or less, more preferably 25% or less.

  Further, as shown in FIG. 6, the notch block 13B1 is provided with the narrow groove 15 and the chamfered portion 17 side by side. The surface distance L2 is desirably 5 mm or more, more preferably 6 to 7 mm. As a result, a synergistic effect between the narrow groove 15 and the chamfered portion 17 is obtained, and the wandering performance can be further improved.

FIG. 7 further shows another embodiment of the present invention.
In this embodiment, the shoulder block 13b is a rectangular surface in which an intersecting portion 13c2 (illustrated by a two-dot chain line) extending in the circumferential direction where the outer wall surface 13bs and the tread surface 13bn intersect is chamfered over its entire length. It is formed as a notch block 13B2 having a chamfered portion 17 made of 17b. Such a notch block 13B2 has a small tire axial length BW of the tread surface 13bn, so that it does not easily collide with the heel and helps to reduce the chance of wandering. On the other hand, such notch blocks 13B2 are likely to cause a reduction in the contact width, so as shown in FIG. 8A, every other notch block 13B2 is provided in the tire circumferential direction in the shoulder block row 13R. Is desirable. Thereby, an excessive decrease in the contact area can be suppressed.

  In order to effectively exhibit the above-described effects, the chamfering width W7 between the intersecting portion 13c2 and the tread surface 13bn is preferably 15% or more of the length BW in the tire axial direction of the shoulder block 13b. Is desirably 20% or more, preferably 30% or less, more preferably 25% or less.

  Further, as shown in FIG. 8B, in the shoulder block row 13R, all the shoulder blocks 13b may be the notched blocks 13B2. In this case, the chamfer width W7 is preferably 8% or more, more preferably 12% or more, and preferably 20% or less, more preferably 16% or less of the length BW of the shoulder block 13b in the tire axial direction. It is desirable that the chamfer width W7 be smaller than that in the case of FIG. Thereby, the block rigidity of each shoulder block 13b (namely, shoulder block row | line | column 13R) is equalized, and generation | occurrence | production of uneven wear can be suppressed.

  Further, the rectangular inclined surface 17b provided in the notch block 13B2 is a concave curved surface that protrudes inward in the tire radial direction and has a curvature radius r2 of 8 mm or more in order to further exhibit the wandering resistance performance. It is desirable. Such a concave curved surface can further improve the wandering resistance performance by locally sharpening the tread end Te to facilitate deformation.

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

  In order to confirm the effect of the present invention, a studless tire for a passenger car having a tire size of 195 / 65R15 91Q having the internal structure of FIG. 1 and the pattern of FIG. These were tested for ice braking performance, wandering resistance, crack resistance and uneven wear resistance. All parameters except those shown in Table 1 were the same. In this test, W5 and W6 have the same length, and Table 1 shows W5 as a representative. The main common specifications are as follows.

Tread width TW: 185mm
Shoulder main groove groove width W2 / TW: 3.4%
Shoulder main groove depth D2: 8.9 mm
Shoulder main groove placement position L1 / TW: 18%
Slot width W3 / W2 of narrow groove: 65%
Groove depth D3 / D2: 45%
Fine groove area H1: H x 85%
Land ratio: 67% (Comparative Example 1)
The test method is as follows.

<Ice braking performance>
A sample tire is assembled to a rim (15 x 6.5 J) with internal pressure (200 kPa) and mounted on all wheels of a domestic FF vehicle with a displacement of 1998 cm ³ and run on the icy road under a single driver. The braking distance required from the braking at 30 km / h until the vehicle completely stopped after braking in an all-wheel locked state was measured. The results were expressed as an index with Comparative Example 1 as 100. The larger the value, the better. Each test tire was tested after running on a dry road for 100 km.

<Wandering resistance>
The vehicle with the test tires mounted on all the wheels was run on an icy and snowy road test course with a saddle. The wandering resistance was evaluated with a score of Comparative Example 1 as 100 based on the sensory evaluation of the driver, with emphasis on the way the handle is taken on the road surface. The larger the value, the better.

<Crack resistance>
The test tire was mounted on a 15 × 6.5 J rim, and was run on a drum having a diameter of 3 m at an internal pressure of 200 kPa, a longitudinal load of 4.62 kN, and a speed of 100 km / h for about 30,000 km. The number of cracks generated at the bottom of the narrow groove was measured. The result was an index with Example 1 as 100. The smaller the value, the better.

<Uneven wear resistance>
The rotation limit distance was measured when each sample tire was run on the two front wheels of the vehicle. The result was an index with Comparative Example 1 as 100. The larger the value, the better. The test results are shown in Table 1.

  According to the test results, both the braking performance on ice and the anti-wandering performance have been improved by the present invention, which proved to be a significant invention.

2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6n Carcass normal line 7 Belt layer 8c Shoulder main groove 14 Buttress surface 15 Fine groove 15G Fine groove center line 15e Fine groove center line extension line e1 Intersection Te Tread edge

Claims (5)

A pneumatic tire comprising a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion, and a belt layer disposed outside the carcass in the tire radial direction and inside the tread portion,
In the normal state in which the normal rim is mounted and the normal internal pressure is filled, the ratio TW / SW between the tread width TW between the tread ends and the tire maximum width SW is 0.75 to 0.95.
The buttress surface, which is an outer region in the tire radial direction of the sidewall portion, is provided with a narrow groove extending continuously in the tire circumferential direction,
In the tire meridian cross section including the tire rotation axis in the normal state, the angle formed by the center line of the narrow groove and the normal line of the carcass passing through the intersection of the extension of the center line and the carcass is within 10 degrees. And
In addition, the tread portion is provided with a pair of shoulder main grooves extending continuously in the tire circumferential direction at the tread end side, and the groove depth of the narrow groove is 20 to 20 times the groove depth of the shoulder main groove. A pneumatic tire characterized by being 50%.   2. The pneumatic tire according to claim 1, wherein the narrow groove is provided in an area of 80% or more and 90% or less of a tire cross-sectional height from a bead base line.   The pneumatic tire according to claim 1 or 2, wherein the shortest distance between the groove bottom of the narrow groove and the intersection is 3 to 8 mm. The tread portion is provided with a shoulder block row in which a plurality of shoulder blocks are arranged in the tire circumferential direction by separating the shoulder lateral grooves extending between the shoulder main groove and the tread end in the tire circumferential direction.
The shoulder block row has a notch block in which a crossing portion where an outer wall surface on the outer side in the tire axial direction of the shoulder block intersects with a tread surface of the shoulder block is chamfered over the entire length thereof in the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 3, provided every third. The tread portion is provided with a shoulder block row in which a plurality of shoulder blocks are arranged in the tire circumferential direction by separating the shoulder lateral grooves extending between the shoulder main groove and the tread end in the tire circumferential direction.
In the shoulder block row, a notch block having a chamfered crest with a triangular slope at the top where the outer wall surface, the tread surface, and the block wall surface facing the shoulder lateral groove intersect is provided continuously in the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 3.

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