JP2017030639A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that is improved in uneven abrasion resistance performance while maintaining cornering performance.SOLUTION: A plurality of recessed parts 10 are provided on a step face of a tread part 2. Each recessed part 10 has a closed contour shape 11 formed of smooth curved lines on the surface of the tread part 2, and has an inclined surface 12 which gradually decreases in depth from an outer tread end Te2 toward an inner tread end Te1, in a cross section thereof along a tire shaft direction. A length in the tire shaft direction of the inclined surface 12 occupies 60% or more of a length in the tire shaft direction of the recessed part 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire that has improved uneven wear resistance while maintaining cornering performance.

  For example, Patent Document 1 below proposes a pneumatic tire in which a recess is provided in a tread portion. Such a recess is useful for improving wet performance, increasing the outer surface area of the tread portion, and improving heat dissipation.

  Generally, when a vehicle turns, a large contact pressure acts on a tire on the outer side in the turning direction (hereinafter referred to as “outside tire”), so that the tread portion of the outside tire is easily worn. The tread portion of the out-side tire is subjected to a resultant force of gravity and a centrifugal force directed outward in the turning direction when the vehicle turns. For this reason, when the vehicle is turning, the recess provided in the tread portion of the out-side tire has a tendency that a large contact pressure acts on the edge on the inner tread end side, and the edge is likely to be unevenly worn. Therefore, the pneumatic tire of Patent Document 1 has room for further improvement with respect to improvement in uneven wear resistance.

Japanese Patent Laying-Open No. 2015-58912

  The present invention has been devised in view of the above-mentioned problems, and based on improving the shape of the recess provided in the tread portion, the uneven wear resistance performance is improved while maintaining the cornering performance. The main purpose is to provide a pneumatic tire.

  The present invention is a pneumatic tire having a tread portion in which an outer tread end and an inner tread end are defined by specifying a mounting direction to a vehicle, and a plurality of tread portions on the tread portion include a tread portion. Each of the recesses has a closed contour shape consisting of a smooth curve on the surface of the tread portion, and the inner side from the outer tread end side in the cross section along the tire axial direction. It has an inclined surface whose depth gradually decreases toward the tread end side, and the length of the inclined surface in the tire axial direction constitutes 60% or more of the length of the concave portion in the tire axial direction. It is said.

  In the pneumatic tire of the present invention, it is desirable that the inclined surface constitutes 70% or more of the length of the concave portion.

  In the pneumatic tire of the present invention, it is desirable that the concave portion has an oval shape having a length in the tire axial direction larger than a length in the tire circumferential direction in a plan view of the tread portion.

  In the pneumatic tire according to the aspect of the invention, in the planar view of the tread portion, the centroid of the contour shape is positioned closer to the outer tread end side than the center position of the length of the concave portion in the tire axial direction. Is desirable.

  In the pneumatic tire according to the present invention, in the plan view of the tread portion, the length of the concave portion in the tire circumferential direction is 0.2 to 0.8% of the tire outer peripheral length on the tire equator. The length in the tire axial direction is preferably 4.0 to 7.5% of the tread contact width.

  In the pneumatic tire according to the aspect of the invention, it is preferable that the concave portions are arranged so that the concave projection regions obtained by projecting the concave portions in the tire axial direction do not overlap each other.

  In the pneumatic tire of the present invention, the tread portion includes an inner tread portion between the tire equator and the inner tread end, and an outer tread portion between the tire equator and the outer tread end, The inner tread portion is provided with at least one main groove extending continuously in the tire circumferential direction, the recess is provided only in the outer tread portion, and the outer tread portion includes It is desirable that no main groove extending continuously in the tire circumferential direction is provided.

  A plurality of recesses are provided on the tread surface of the tread portion of the pneumatic tire of the present invention. Each concave portion has a closed contour shape formed of a smooth curve on the surface of the tread portion. Such a recess having a closed contour shape can prevent stress concentration on a specific part even when a contact pressure is applied to the tread portion. Therefore, such a recessed part improves the heat dissipation of a tread part, maintaining the rigidity of a tread part. This is useful for exhibiting excellent cornering performance.

  The recess has an inclined surface whose depth gradually decreases from the outer tread end side toward the inner tread end side in the cross section along the tire axial direction. The length of the inclined surface in the tire axial direction constitutes 60% or more of the length of the concave portion in the tire axial direction. Thereby, in the inner tread end side, the angle between the tread surface and the inclined surface is increased. For this reason, even when a large contact pressure acts on the inner tread edge side edge in the recess of the out-side tire when turning the vehicle, a part of the inclined surface is deformed to sufficiently increase the contact area in the vicinity of the edge. . Therefore, uneven wear of the edge on the inner tread end side is suppressed.

It is an expanded view of the tread part of the pneumatic tire of one embodiment of the present invention. It is an enlarged view of the outer tread part of FIG. It is the sectional view on the AA line of the recessed part of FIG. FIG. 3 is a cross-sectional view of the recess of FIG. 2 along the line BB. It is an enlarged plan view of the recessed part of FIG. It is an enlarged view of the inner tread part of FIG. It is an expanded view of the tread part of the pneumatic tire of a comparative example. It is CC sectional view taken on the line of the recessed part of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment. The pneumatic tire 1 of the present embodiment is used, for example, for passenger cars, and is particularly preferably used as a high-performance tire premised on use on both public road traveling and circuit traveling.

  The tread portion 2 has a tread pattern in which the direction of mounting on the vehicle is specified. The direction of mounting on the vehicle is displayed by, for example, characters or marks on a sidewall (not shown) or the like. In FIG. 1, when the tire 1 is mounted on a vehicle, the right side of FIG. 1 corresponds to the vehicle inner side, and the left side of FIG. 1 corresponds to the vehicle outer side.

  By specifying the direction of mounting on the vehicle, the tread portion 2 has an inner tread end Te1 positioned on the inner side of the vehicle when the vehicle is mounted and an outer tread end Te2 positioned on the outer side of the vehicle when mounted on the vehicle. .

  Each of the tread ends Te1 and Te2 is a flat surface with a normal load applied to a normal tire 1 which is assembled with a normal rim (not shown) and filled with a normal internal pressure and is not loaded, and a camber angle of 0 °. This is the contact position on the outermost side in the tire axial direction when the contact is made on the ground.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JAMATA” is the “highest air pressure”, TRA is the table “TIRE LOAD LIMITS AT” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  “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. “JATMA” is “Maximum load capacity”, TRA is “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO.

  The tread portion 2 includes an inner tread portion 5 between the tire equator C and the inner tread end Te1, and an outer tread portion 6 between the tire equator C and the outer tread end Te2.

  FIG. 2 shows an enlarged view of the outer tread portion 6 of FIG. As shown in FIG. 2, the outer tread portion 6 is provided with a plurality of recesses 10. Each concave portion 10 has a closed contour shape 11 formed of a smooth curve on the surface of the tread portion 2. The concave portion 10 having such a closed contour shape 11 can prevent stress concentration on a specific portion even when a contact pressure is applied to the tread portion 2. Therefore, such a recessed part 10 improves the heat dissipation of the tread part 2 while maintaining the rigidity of the tread part 2. This is useful for exhibiting excellent cornering performance.

  FIG. 3 shows a cross-sectional view of the recess 10 in FIG. As shown in FIG. 3, the recess 10 has a cross section along the tire axial direction from the outer tread end Te2 side (left side in FIG. 3, the same applies hereinafter) to the inner tread end Te1 side (FIG. 3). The right side, and the same applies hereinafter). The length L2 of the inclined surface 12 in the tire axial direction constitutes 60% or more of the length L1 of the concave portion 10 in the tire axial direction.

  In the concave portion 10 configured as described above, the angle between the tread surface 2s and the inclined surface 12 is increased on the inner tread end Te1 side. For this reason, even when a large contact pressure acts on the edge 14 on the inner tread end Te side in the concave portion 10 of the out-side tire when the vehicle turns, a part of the inclined surface 12 is deformed and the contact area near the edge 14 Increase. Therefore, uneven wear of the edge 14 on the inner tread end Te1 side is suppressed.

  In order to further exhibit the above-described effects, the length L2 of the inclined surface 12 is preferably 70% or more, more preferably 75% or more of the length L1 of the recess 10. On the other hand, when the inclined surface 12 is excessively large, the volume of the recess 10 is reduced, and as a result, the wet performance may be reduced. For this reason, the length L2 of the inclined surface 12 is preferably 90% or less of the length L1 of the recess 10.

  As a preferred aspect, the inclined surface 12 of the present embodiment is gradually reduced in depth at a constant rate. That is, the inclined surface 12 is linear in the cross section along the tire axial direction. Such an inclined surface 12 can increase the contact area in the vicinity of the edge 14 more smoothly when a large contact pressure acts on the edge 14.

  At the edge 14 of the recess 10, the angle θ1 between the tread surface 2s and the inclined surface 12 is preferably 150 ° or more, more preferably 155 ° or more. Thereby, the uneven wear of the edge 14 is suppressed more effectively. The angle θ1 is preferably 170 ° or less, more preferably 165 ° or less. Thereby, the volume of the recessed part 10 is ensured and the improvement of wet performance can be anticipated.

  The concave portion 10 of the present embodiment has a vertical surface 16 extending along the tire radial direction on the outer tread end Te2 side. Thereby, during wet running, the edge 21 on the outer tread end Te1 side can cut the water film, and the hydroplaning phenomenon is suppressed.

  FIG. 4 shows a cross-sectional view of the recess 10 in FIG. As shown in FIG. 4, the concave portion 10 of the present embodiment has wall surfaces 22 and 22 that are symmetrical to each other at the center position of the concave portion 10 in the tire circumferential direction, for example, in a cross section along the tire circumferential direction. Such a recess 10 is useful for suppressing uneven wear of the edges 23, 23 on both sides in the tire circumferential direction.

  FIG. 5 shows an enlarged plan view of the recess 10 of FIG. As shown in FIG. 5, the concave portion 10 of the present embodiment has an oval shape in which the length L1 in the tire axial direction is larger than the length L3 in the tire circumferential direction, for example, in a plan view of the tread portion 2. Is desirable. Such a recess 10 is difficult to be deformed in the tire axial direction, suppresses excessive deformation of the tread portion 2 in the tire axial direction, and thus helps to improve cornering performance. However, the concave portion 10 is not limited to such a contour shape, and may be, for example, an elliptical shape.

  In order to exhibit the above-mentioned effect while maintaining the wet performance, the length L3 of the recess 10 in the tire circumferential direction is preferably 0.50 times or more than the length L1 of the recess 10 in the tire axial direction, more preferably. It is 0.55 times or more, preferably 0.65 times or less, more preferably 0.60 times or less.

  The length L3 of the concave portion 10 in the tire circumferential direction is, for example, 0.20 to 0.80% of the tire outer circumferential length Lc (not shown) on the tire equator C, and more preferably 0.40 to 0.0. 50%. The length L1 of the recess 10 in the tire axial direction is, for example, 4.0 to 7.5% of the tread contact width TW (shown in FIG. 1), and more preferably 6.0 to 7.0%. Such a recess 10 can improve wet performance and heat dissipation of the tread portion 2 while maintaining the rigidity of the tread portion 2. As shown in FIG. 1, the tread contact width TW is a distance in the tire axial direction between the inner tread end Te1 and the outer tread end Te2 of the tire 1 in the normal state.

  As shown in FIG. 5, when the concave portion 10 has an oval shape or an elliptical shape, the long axis 17 may be inclined at an angle θ2 (not shown) of 20 ° or less with respect to the tire axial direction.

  Since the recess 10 has the inclined surface 12 (shown in FIG. 3), the volume on the inner tread end Te1 side is small, and the wet performance may be reduced. In order to suppress this problem, the concave portion 10 of the present embodiment is arranged such that the maximum width position in the tire circumferential direction is closer to the outer tread end Te2 side than the center position of the length of the concave portion 10 in the tire axial direction. Thereby, the volume of a recessed part is ensured by the outer side tread end Te2 side, and wet performance is maintained by extension. Therefore, the centroid 18 of the contour shape 11 of the recess 10 of the present embodiment is located on the outer tread end Te1 side with respect to the center position of the length of the recess 10 in the tire axial direction.

  As shown in FIG. 2, it is desirable that the recesses 10 are arranged so that, for example, the recess projection areas a obtained by projecting the recesses 10 in the tire axial direction do not overlap each other. Such an arrangement of the recesses 10 can exhibit high heat dissipation while maintaining the rigidity of the outer tread portion 6.

  As shown in FIG. 1, it is desirable that the outer tread portion 6 is not provided with a main groove extending continuously in the tire circumferential direction. Thereby, the rigidity of the outer tread portion 6 is increased, and excellent cornering performance is obtained.

  FIG. 6 shows an enlarged view of the inner tread portion 5 of FIG. As shown in FIG. 6, the inner tread portion 5 is provided with at least one main groove 25 extending continuously in the tire circumferential direction. The main groove 25 of the present embodiment extends, for example, linearly along the tire circumferential direction. Moreover, the main groove 25 of this embodiment extends, for example, with a constant groove width. However, the main groove 25 is not limited to such an aspect, and may be an aspect extending in a zigzag shape or a wave shape, or an aspect extending while increasing or decreasing the groove width.

  The main groove 25 includes, for example, a first main groove 26 provided on the tire equator C side. As a preferred embodiment, the distance L5 in the tire axial direction from the tire equator C to the groove center line 26c of the first main groove 26 is 0.10 to 0.25 times the width W1 of the inner tread portion 5. The first main groove 26 effectively discharges the water film near the tire equator C to the outside of the tire during wet running. The width W1 of the inner tread portion 5 means the length in the tire axial direction from the tire equator C to the inner tread end Te1.

  The main groove 25 preferably further includes a second main groove 27 disposed between the first main groove 26 and the inner tread end Te1. As a preferred embodiment, the distance L6 in the tire axial direction from the tire equator C to the groove center line 27c of the second main groove 27 is 0.35 to 0.75 times the width W1 of the inner tread portion 5. Thereby, the position of the second main groove 27 is optimized, and the pattern rigidity near the tire equator C and the pattern rigidity near the inner tread end Te1 are secured in a well-balanced manner.

  For example, the inner tread portion 5 preferably includes a plain rib 28 in which neither a groove nor a sipe is provided between the first main groove 26 and the second main groove 27. The width W2 of the plain rib 28 in the tire axial direction is preferably 0.15 to 0.25 times the width W1 of the inner tread portion 5, for example. Such a plain rib 28 has high rigidity, and is useful for, for example, enhancing the steering stability during circuit driving.

  As a desirable mode, the inner tread portion 5 is provided with a lateral groove 30 extending in the tire axial direction in addition to the main groove 25 described above. The lateral groove 30 includes, for example, a first lateral groove 31 provided on the inner tread end Te1 side.

  For example, the first lateral groove 31 terminates from the inner tread end Te <b> 1 inward in the tire axial direction and does not reach the second main groove 27. Such first lateral grooves 31 can improve wet performance while maintaining the rigidity of the land portion between the inner tread end Te1 and the second main groove 27.

  The lateral groove 30 may include a second lateral groove 32 provided on the tire equator C side in addition to the first lateral groove 31. For example, one end of the second lateral groove 32 communicates with the first main groove 26 and extends to the outer tread end Te2 side. For example, the second lateral groove 32 of the present embodiment straddles the tire equator C and terminates in the outer tread portion 6. Such a second lateral groove 32 enhances wet performance, enhances heat dissipation of the land near the tire equator C, and consequently decreases grip performance due to excessive heat generation of the tread rubber (hereinafter simply referred to as “thermal sag”). Can be suppressed.

  The length L8 of the second lateral groove 32 in the tire axial direction is preferably smaller than the length L7 of the first lateral groove 31 in the tire axial direction, for example. As a preferred embodiment, the length L8 of the second lateral groove 32 is 0.70 to 0.85 times the length L7 of the first lateral groove 31, for example. Such second lateral grooves 32 are useful for improving wet performance and steering stability in a well-balanced manner.

  The pitch P2 in the tire circumferential direction of the second lateral grooves 32 is preferably larger than the pitch P1 in the tire circumferential direction of the first lateral grooves 31. As a preferred embodiment, the pitch P2 of the second lateral grooves 32 is, for example, 1.85 to 2.15 times the pitch P1 of the first lateral grooves 31. Such second lateral grooves 32 are useful for improving wet performance while maintaining the rigidity of the land portion near the tire equator C and maintaining steering stability during circuit driving.

  As shown in FIG. 1, the inner tread portion 5 is provided with the main grooves 26 and 27 and the lateral grooves 31 and 32 described above, thereby ensuring wet performance and heat dissipation. For this reason, the recessed part 10 is not provided in the inner tread part 5, but is provided only in the outer tread part 6. Such an arrangement of the recesses 10 improves the wet performance and the cornering performance in a well-balanced manner.

  As mentioned above, although the pneumatic tire of one embodiment of the present invention was explained in detail, the present invention is not limited to the above-mentioned specific embodiment, and can be carried out by changing to various modes.

A pneumatic tire of size 205 / 55R16 having the basic tread pattern of FIG. 1 was manufactured based on the specifications in Table 1. As Comparative Example 1, as shown in FIG. 7, the contour of the concave portion is circular, and as shown in FIG. 8, the depth of the concave portion is constant in the cross section along the tire axial direction. A prototype tire was built. The cornering performance and uneven wear resistance performance of each test tire were tested. The common specifications and test methods for each test tire are as follows.
Rim: 16 × 7.0JJ
Tire internal pressure: 200kPa

<Cornering performance>
The cornering performance when driving on the asphalt circuit course with the following test vehicle equipped with the test tire was evaluated based on the driver's sensuality. A result is a score which sets the comparative example 1 to 100, and shows that steering stability is excellent, so that a numerical value is large.
Test vehicle: 2000cc displacement, rear-wheel drive vehicle Test tire mounting position: all wheels

<Uneven wear resistance>
After running a certain distance with the test vehicle, the wear amount of the edge on the inner tread end side of the recess was measured. The result is an index with Comparative Example 1 being 100, and the smaller the value, the smaller the wear amount of the edge and the better the uneven wear resistance.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the cornering performance and the uneven wear resistance performance of the pneumatic tire of the example were improved in a well-balanced manner.

2 Tread part 5 Inner tread part 6 Outer tread part 10 Recessed part 11 Contour shape 12 Inclined surface Te1 Inner tread edge Te2 Outer tread edge

Claims (7)

A pneumatic tire having a tread portion in which an outer tread end and an inner tread end are defined by specifying a mounting direction to the vehicle,
A plurality of recesses are provided on the tread surface of the tread portion,
Each of the recesses has a closed contour shape consisting of a smooth curve on the surface of the tread portion,
In the cross section along the tire axial direction, having an inclined surface whose depth gradually decreases from the outer tread end side toward the inner tread end side,
The pneumatic tire is characterized in that a length of the inclined surface in the tire axial direction constitutes 60% or more of a length of the concave portion in the tire axial direction.   The pneumatic tire according to claim 1, wherein the inclined surface constitutes 70% or more of the length of the concave portion.   3. The pneumatic tire according to claim 1, wherein the concave portion has an oval shape having a length in a tire axial direction larger than a length in a tire circumferential direction in a plan view of the tread portion.   4. The pneumatic tire according to claim 3, wherein, in the plan view of the tread portion, the centroid of the contour shape is located closer to the outer tread end side than the center position of the length of the recess in the tire axial direction. .   In a plan view of the tread portion, the length of the concave portion in the tire circumferential direction is 0.2 to 0.8% of the tire outer circumferential length on the tire equator, and the length of the concave portion in the tire axial direction is The pneumatic tire according to any one of claims 1 to 4, which is 4.0 to 7.5% of a tread contact width.   The pneumatic tire according to any one of claims 1 to 5, wherein each of the recesses is disposed without overlapping a recess projection region obtained by projecting the recess in the tire axial direction. The tread portion includes an inner tread portion between the tire equator and the inner tread end, and an outer tread portion between the tire equator and the outer tread end,
The inner tread portion is provided with at least one main groove extending continuously in the tire circumferential direction,
The concave portion is provided only in the outer tread portion,
Moreover, the pneumatic tire according to any one of claims 1 to 6, wherein the outer tread portion is not provided with a main groove extending continuously in the tire circumferential direction.

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