JP5753375B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that can improve uneven wear resistance.

  Conventionally, a pneumatic tire is known in which a plurality of land portions extending in the tire circumferential direction are divided into a tread portion by a plurality of vertical grooves extending in the tire circumferential direction. In such a pneumatic tire, the vertical groove can smoothly guide the water film interposed between the tread surface and the road surface in the tire circumferential direction, and drainage performance can be improved.

  Further, in recent years, in order to improve uneven wear resistance, for example, as shown in FIG. 4, in the meridional section including the tire shaft, the ground contact surface of the land portion a is protruded outward in the tire radial direction. A pneumatic tire formed by an arc having a radius of curvature r is known. Such a pneumatic tire can suppress a large contact pressure from being generated at both ends b and b of the land portion a, and can suppress uneven wear at that portion. Related documents include the following (see Patent Document 1 below).

JP 2009-23601 A

  However, the pneumatic tire as described above could suppress uneven wear on both ends b and b side of the land portion a, but conversely, the ground pressure on the center c side of the land portion a increases, There was a problem that uneven wear was likely to occur.

  The present invention has been devised in view of the actual situation as described above, and the ground contact surface of the land portion includes a central arc surface and an outer arc surface having a smaller radius of curvature than the central arc surface, Basically, the ratio of the radius of curvature between the central arc surface and the outer arc surface, and the camber amount, which is the distance in the tire radial direction between the outer end of the outer arc surface and the virtual line of the central arc surface, is limited to a predetermined range. The main purpose is to provide a pneumatic tire capable of improving uneven wear resistance.

The invention described in claim 1 of the present invention is a pneumatic tire in which a plurality of land portions extending in the tire circumferential direction are divided into a tread portion by a plurality of longitudinal grooves extending in the tire circumferential direction, and the tire shaft is In the meridional section, the ground contact surface of each land portion includes a central arc surface formed of a single arc that passes through the center in the tire axial direction and is convex outward in the tire radial direction, and the tire arc direction of the central arc surface in the tire axial direction. It includes an outer arcuate surface formed of arc of 30-50% of the radius of curvature of the radius of curvature of the contiguous and the central arcuate surface on at least one tire axial direction width of the central arcuate surface 30 of the width of the land portion The camber amount that is a distance in the tire radial direction between the outer end of the outer arc surface in the tire axial direction and the virtual line obtained by extending the central arc surface toward the outer end of the outer arc surface is 70%. , In the tire axial direction of the land portion 0.5 to 1.5%, and the longitudinal grooves include a pair of center longitudinal grooves extending in the tire circumferential direction on both sides of the tire equator, and a pair of shoulder longitudinal grooves arranged on the outside thereof, The land portion includes a shoulder land portion outside the shoulder flutes and a middle land portion between the adjacent center flutes and the shoulder flutes, and the ratio of the camber amount to the width of the middle land portions Is larger than the ratio of the camber amount to the width of the shoulder land portion.

Further, an invention according to claim 2, wherein said central arcuate surface is a pneumatic tire according to claim 1 which is disposed on an arc connecting the tread ground end of a single radius of curvature.

The invention of claim 3, wherein, the front Kiriku portion includes a center land portion extending between a pair of the center circumferential groove in the tire circumferential direction, the center land portion is communicated with one end one of the center circumferential groove And a center narrow groove that terminates without the other end reaching the other center longitudinal groove is provided in the tire circumferential direction, and the center narrow groove has a tie bar having a groove bottom raised at the other end. Item 3. The pneumatic tire according to Item 1 or 2.

  The tie bar may have a maximum length in the tire axial direction of 80 to 95% of a maximum width in the tire axial direction of the center land portion, and the center narrow groove of the tie bar. The pneumatic tire according to claim 3, wherein a height from the deepest portion is 20 to 50% of a groove depth of the vertical groove.

  In the invention according to claim 5, the maximum width in the tire axial direction of the center land portion is 38 to 46% of the tread half width that is the length in the tire axial direction from the tire equator C to the tread contact end. A pneumatic tire according to claim 3 or 4.

  In the present specification, unless otherwise specified, the dimensions of each part of the tire are values specified in a normal state in which a rim is assembled on a normal rim and a normal internal pressure is filled.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JATMA is a standard rim, TRA is “Design Rim”, and ETRTO is a standard rim. If present, it means "Measuring Rim".

  The “regular internal pressure” is the air pressure determined by the standard for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, ETRTO Then, “INFLATION PRESSURE” is set, but when the tire is for a passenger car, the pressure is uniformly set to 180 kPa.

  In the pneumatic tire of the present invention, a plurality of land portions extending in the tire circumferential direction are divided into tread portions by a plurality of longitudinal grooves extending in the tire circumferential direction. In the meridional section including the tire axis, the ground contact surface of each land portion passes through the center in the tire axial direction and has a central arc surface formed of a single arc protruding outward in the tire radial direction, and the tire axial direction of the central arc surface And an outer arc surface formed of an arc having a curvature radius of 30 to 50% of the curvature radius of the central arc surface.

  The camber amount, which is the distance in the tire radial direction between the outer end of the outer arc surface in the tire axial direction and the virtual line obtained by extending the central arc surface toward the outer end of the outer arc surface, is the width of the land portion in the tire axial direction. It is set to 0.5 to 1.5%.

  Such a pneumatic tire can reduce the difference in contact pressure between the central arc surface and the outer arc surface while reducing the contact pressure on the outer arc surface, and uneven wear occurs over the entire contact surface of the land. Can be suppressed.

It is an expanded view of the tread part of the pneumatic tire of this embodiment. It is AA sectional drawing of FIG. It is sectional drawing which expands and shows the center land part of FIG. It is sectional drawing of the conventional land part.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the pneumatic tire 1 of the present embodiment is configured as a summer tire for passenger cars. Also, the tread portion 2 of the present embodiment is divided into a plurality of land portions 4 extending in the tire circumferential direction by a plurality of vertical grooves 3 extending in the tire circumferential direction, and the left-right asymmetric in which the mounting direction to the vehicle is designated The tread pattern is formed. The direction of mounting on the vehicle is clearly indicated by letters (for example, “INSIDE” and / or “OUTSIDE”) on the sidewall portion of the tire 1 (not shown).

  The longitudinal groove 3 is composed of at least two and four in this embodiment, and is formed as a straight groove extending linearly along the tire circumferential direction. Such a straight groove can smoothly discharge the water film interposed between the road surface and the ground contact surface 2t to the outside during straight traveling and turning, and can improve drainage performance. Preferably, the groove width W1 of the longitudinal groove 3 is set to, for example, about 5 to 20% of the tread half width 0.5 TW, and the groove depth D1 is set to about 8 to 15% of the tread half width 0.5 TW. The tread half width 0.5 TW is a half of the tread width (the length in the tire axial direction from the tread ground contact end 2 i on the vehicle inner side to the tread ground contact end 2 o on the vehicle outer side).

  The longitudinal groove 3 includes an outer shoulder longitudinal groove 3A disposed on the outermost side of the vehicle, an inner shoulder longitudinal groove 3B disposed on the innermost side of the vehicle, and a pair of center longitudinal grooves extending on both sides of the tire equator C in the tire circumferential direction. It is configured to include 3C and 3D. The center vertical grooves 3C and 3D are divided into an outer center vertical groove 3C disposed on the vehicle outer side and an inner center vertical groove 3D disposed on the vehicle inner side.

By these vertical grooves 3A, 3B, 3C and 3D , the land portion 4 is divided into an outer shoulder land groove 4A, an inner shoulder vertical groove 3B and a vehicle, which are divided by an outer shoulder vertical groove 3A and a tread grounding end 2o on the vehicle outer side. The inner shoulder land portion 4B divided by the inner tread grounding end 2i, the outer middle land portion 4C divided by the outer shoulder vertical groove 3A and the outer center vertical groove 3C, the inner shoulder vertical groove 3B and the inner center vertical groove 3D. Are formed by an inner middle land portion 4D and a pair of center longitudinal grooves 3C and 3D.

  Each land portion 4A to 4E is provided with a lateral groove 5 extending in a direction intersecting with the longitudinal groove 3. Such a lateral groove 5 can guide the water film interposed between the road surface and the ground contact surface 2t of the land portion 4 and the water in the longitudinal groove 3 in the tire axial direction, thereby improving the drainage performance. Further, the groove width W2 of the lateral groove 5 is set to, for example, about 2 to 6% of the tread half width 0.5TW, and the groove depth (not shown) is set to about 3 to 12.0% of the tread half width 0.5TW. desirable.

  The outer shoulder land portion 4A is provided with an outer shoulder lateral groove 11 extending gently from the outer shoulder vertical groove 3A to the vehicle outer side. The outer shoulder lateral groove 11 has an inner end that opens at the outer shoulder longitudinal groove 3A, and an outer end that terminates beyond the tread grounding end 2o outside the vehicle. Thus, the outer shoulder land portion 4A is formed in the outer shoulder block 16 having a substantially horizontally long rectangular shape in plan view. Such an outer shoulder block 16 can increase the rigidity in the tire axial direction to improve the steering stability performance, and can suppress the occurrence of uneven wear.

  The inner shoulder land portion 4B is provided with an inner shoulder lateral groove 12 that is gently inclined from the outer side of the tread grounding end 2i on the inner side of the vehicle to the inner side in the tire axial direction and terminates without reaching the inner shoulder vertical groove 5B. Further, the inner shoulder land portion 4B is connected with an inner shoulder narrow groove 17 extending from the inner end 12i of the inner shoulder lateral groove 12 with a small inclination with respect to the tire circumferential direction and connecting the inner shoulder lateral grooves 12 adjacent in the tire circumferential direction. The Such an inner shoulder land portion 4B is formed with ribs 18 extending in the tire circumferential direction, and can increase the tire circumferential rigidity to suppress uneven wear.

  The outer middle land portion 4C is provided with an outer middle horizontal groove 13 whose outer end in the tire axial direction is continuous with the outer shoulder vertical groove 3A and whose inner end in the tire axial direction is opened by the outer center vertical groove 3C. The outer middle lateral groove 13 extends more greatly than the outer shoulder lateral groove 11. Thereby, the outer middle land portion 4C is divided into outer middle blocks 19 having a substantially parallelogram shape. Such an outer middle block 19 can improve the rigidity in the tire axial direction and the tire circumferential direction in a well-balanced manner, and is useful for improving the straight running stability performance and the steering stability performance on the dry road surface.

  The inner middle land portion 4D is provided with an inner middle lateral groove 14 extending between the inner shoulder vertical groove 3B and the inner center vertical groove 3D. The inner middle lateral groove 14 has a steeper slope than the inner shoulder lateral groove 12, and a water film interposed between the ground contact surface 2t of the inner middle land portion 4D and the road surface is effective outward in the tire axial direction by the rotation of the tire 1. Can be guided.

  Further, the inner middle horizontal groove 14 of the present embodiment includes a first inner middle horizontal groove 14A whose outer end in the tire axial direction is continuous with the inner shoulder vertical groove 3B and whose inner end in the tire axial direction is opened by the inner center vertical groove 3D. Further, the outer end in the tire axial direction is connected to the inner shoulder vertical groove 3B, and the inner end in the tire axial direction includes the second inner middle lateral groove 14B that terminates without reaching the inner center vertical groove 3D. The first and second inner middle lateral grooves 14A and 14B are alternately arranged in the tire circumferential direction, and can improve drainage performance while suppressing an excessive decrease in rigidity of the inner middle land portion 4D.

  The center land portion 4E is provided with a center lateral groove 15 extending between the outer center longitudinal groove 3C and the inner center longitudinal groove 3D. The center lateral groove 15 has one end communicating with the outer center longitudinal groove 3C and the other end extending beyond the tire equator C without reaching the inner center longitudinal groove 3D, and one end with the outer center longitudinal groove 15C. A center thick groove 15B is provided which communicates with 3C and terminates without the other end passing over the tire equator C and reaching the inner center longitudinal groove 3D.

  The center narrow grooves 15A and the center thick grooves 15B are alternately spaced in the tire circumferential direction, and the center thick grooves 15B are formed wider than the center narrow grooves 15A. Thereby, the said center land part 4E is formed in the rib shape extended in a tire circumferential direction, can raise the rigidity of a tire circumferential direction, and can improve the uneven wear-proof performance.

As shown in FIGS. 2 and 3, the ground contact surface 2 t of each land portion 4 </ b> A to 4 </ b> E of the present embodiment passes through the center in the tire axial direction and protrudes outward in the tire radial direction in the meridional section including the tire shaft. A central arc surface 21 composed of a single arc of the center, and an outer end 21t in the tire axial direction of the central arc surface 21 extending to at least one of the tire axial directions and 30 to 50% of the curvature radius R1 of the central arc surface 21 And an outer circular arc surface 22 made of an arc having a radius of curvature R2.

  Further, a camber amount L1 that is a tire radial direction distance between an outer end 22t of the outer arc surface 22 in the tire axial direction and a virtual line 21V obtained by extending the central arc surface 21 toward the outer end 22t of the outer arc surface 22 is The width W3 (W3a, W3b, W3c, W3d, W3e) in the tire axial direction of each land portion 4 is set to 0.5 to 1.5%.

  Since the curvature radius R2 of the outer arc surface 22 is smaller than the curvature radius R1 than the central arc surface 21, the ground contact surface 2t of each of the land portions 4A to 4E can reduce the contact pressure of the outer arc surface 22; Uneven wear at that portion can be suppressed. Moreover, as a result of various experiments, by defining the curvature radii of the central arc surface 21 and the outer arc surface 22 with the ratio as described above, the arc surfaces 21 and 22 can be grounded uniformly. It was found that the difference in the ground pressure can be reduced. Therefore, the tire 1 of the present embodiment can suppress uneven wear at the central arc surface 21 (shown in FIG. 3) like the conventional tire shown in FIG. 4, and uneven wear over the entire contact surface 2t. It can be suppressed.

  If the radius of curvature R2 of the outer arc surface 22 is less than 30% of the radius of curvature R1 of the central arc surface 21, the arc of the outer arc surface 22 becomes excessively small and the contact pressure of the central arc surface 21 increases. There is a risk that uneven wear may occur at that portion. On the contrary, when the radius of curvature R2 exceeds 50% of the radius of curvature R1, the contact pressure of the outer arc surface 22 becomes excessively large, and uneven wear may occur at that portion. From such a viewpoint, the curvature radius R2 is preferably 33% or more, more preferably 35% or more, and preferably 48% or less, more preferably 45% or less, of the curvature radius R1.

  Further, if the camber amount L1 is less than 0.5% of the width W3 of the land portion 4, the contact pressure of the outer arc surface 22 may be excessively increased. Conversely, if the camber amount L1 exceeds 1.5% of the width W3, the contact pressure of the central arc surface 21 may become excessively large. From this point of view, the camber amount L1 is preferably 0.7% or more, more preferably 0.8% or more, and preferably 1.3% or less, more preferably 1 of the width W3. .2% or less is desirable.

  The central arc surface 21 is preferably disposed on an arc V1 connecting the tread grounding ends 2i and 2o with a single curvature radius R3. Thereby, each land part 4 can make the difference of the contact pressure with the central circular arc surface 21 of the land part 4 adjacent in the tire axial direction small, and can suppress uneven wear effectively. The transition to turning can be made smooth and the transient characteristics can be improved.

  In order to effectively exhibit the above-described action, the curvature radius R1 of the central arc surface 21 and the curvature radius R3 of the arc V1 are preferably 1000% or more, more preferably 2000% of the width W3 of the land portion 4. The above is desirable, preferably 7000% or less, and more preferably 6000% or less.

  In addition, if the width W4 of the central arc surface 21 in the tire axial direction is small, uneven wear may occur on the central arc surface 21. On the contrary, even if the width W4 is large, there is a possibility that uneven wear occurs on the outer arc surface 22. From such a viewpoint, the width W4 is preferably 30% or more, more preferably 35% or more, and preferably 70% or less, more preferably 65% or less of the width W3 of the land portion 4.

  The curvature radius R2 of the outer arc surface 22 may be either single or multiradius, but it is preferable that the outer arc surface 22 is composed of a single arc like the central arc surface 21. Moreover, when the curvature radius R2 consists of multiradius, it should just satisfy 30 to 50% of the curvature radius R1 of the central circular arc surface 21.

  As shown in FIG. 2, the outer arc surface 22 is formed on the inner side in the tire axial direction of the outer shoulder land portion 4A and the inner shoulder land portion 4B, and the outer middle land portion 4C, the inner middle land portion 4D, and It is preferably formed on both sides in the tire axial direction of the center land portion 4E. As a result, the ground contact surfaces 2t of the land portions 4A to 4E can ground the central arc surface 21 and the outer arc surface 22 evenly during straight traveling and turning, and can effectively suppress uneven wear. .

  Further, the maximum width W3e in the tire axial direction of the center land portion 4E is 38% or more, more preferably 40% or more of the tread half width 0.5TW (shown in FIG. 1). When the maximum width W3e is reduced, the rigidity of the center land portion 4E is reduced, and improvement in uneven wear resistance performance cannot be expected as compared with other land portions 4. On the other hand, even if the maximum width W3e is too large, the difference in rigidity from the other land portions 4 becomes large, which may cause uneven wear. From such a viewpoint, the maximum width W3e is preferably 46% or less, more preferably 44% or less, with a tread half width of 0.5 TW.

  As shown in FIG. 3, the center narrow groove 15A preferably has a tie bar 23 with a groove bottom raised at the other end 15Ai. Such a tie bar 23 can increase the rigidity in the tire circumferential direction of the center land portion 4E where the ground contact pressure becomes the largest during straight traveling, and can effectively suppress uneven wear.

  In order to effectively exhibit such an action, the maximum length L2 of the tie bar 23 in the tire axial direction is preferably 80% or more, more preferably the maximum width W3e of the center land portion 4E in the tire axial direction. 87% or more is desirable. If the maximum length L2 is small, the rigidity of the center land portion 4E may not be sufficiently increased. On the contrary, even if the maximum length L2 is too large, the rigidity of the center land portion 4E is excessively increased, and uneven wear occurs between the other land portions 4 and the drainage performance may be deteriorated. From such a viewpoint, the maximum length L2 is preferably 95% or less, more preferably 92% or less of the maximum width W3e.

  From the same viewpoint, the height H1 from the deepest portion 15Ab of the center narrow groove 15A of the tie bar 23 is preferably 20% or more, more preferably 23% or more of the groove depth D1 of the vertical groove 3. Further, it is preferably 50% or less, more preferably 47% or less.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Tires having the basic structure shown in FIG. 1 and having land portions shown in Table 1 were manufactured, and their performance was evaluated. The common specifications are as follows.
Tire size: 175/65 R15
Rim size: 15 × 5J
Tread half width 0.5TW: 60mm
Vertical groove:
Groove width W1: 6.5 mm
Groove depth D1: 7.6 mm
Ratio (W1 / 0.5TW): 10.8%
Ratio (D1 / 0.5TW): 12.7%
Horizontal groove:
Groove width W2: 3.0 mm
Groove depth: 5.3mm
Ratio (W2 / 0.5TW): 5%
Ratio (groove depth / 0.5 TW): 8.8%
Arc connecting between the tread ground ends:
Curvature radius R3: 400mm
The test method is as follows.

<Uneven wear resistance>
Each test tire is assembled to the above rim, filled with 230 kPa of internal pressure, mounted on all wheels of a 1000cc FF car, traveled on a dry asphalt road surface for 8000 km, and the groove depth of the inner and outer center vertical grooves And the average of the groove depths of the inner and outer shoulder longitudinal grooves were measured at three locations on the tire circumference, and all average values were measured. The smaller the value, the better.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples could improve uneven wear resistance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Longitudinal groove 4 Land part 21 Central circular arc surface 22 Outer circular arc surface

Claims (5)

A pneumatic tire in which a plurality of land portions extending in the tire circumferential direction are divided by a plurality of vertical grooves extending in the tire circumferential direction on the tread portion,
In the meridional section including the tire axis, the ground contact surface of each land portion passes through the center in the tire axial direction and is a central arc surface formed of a single arc protruding outward in the tire radial direction,
An outer circular arc surface that is continuous with at least one of the central arc surface in the tire axial direction and includes an arc having a curvature radius of 30 to 50% of the curvature radius of the central arc surface;
The width of the central arc surface in the tire axial direction is 30 to 70% of the width of the land portion,
The amount of camber, which is the distance in the tire radial direction between the outer end of the outer arc surface in the tire axial direction and the virtual line obtained by extending the central arc surface toward the outer end of the outer arc surface, 0.5 to 1.5% of the axial width,
The longitudinal grooves include a pair of center longitudinal grooves extending in the tire circumferential direction on both sides of the tire equator, and a pair of shoulder longitudinal grooves disposed on the outside thereof.
The land portion includes a shoulder land portion outside the shoulder flutes, and a middle land portion between the adjacent center flutes and the shoulder flutes,
The ratio of the said camber amount with respect to the width | variety of the said middle land part is larger than the ratio of the said camber amount with respect to the width | variety of the said shoulder land part, The pneumatic tire characterized by the above-mentioned.

The central arcuate surfaces, the pneumatic tire according to claim 1 which is disposed on an arc connecting the tread ground end of a single radius of curvature.
Before Kiriku portion includes a center land portion extending between a pair of the center circumferential groove in the tire circumferential direction,
The center land portion has one end communicating with one center longitudinal groove and a center narrow groove that terminates without the other end reaching the other center longitudinal groove.
The pneumatic tire according to claim 1, wherein the center narrow groove has a tie bar having a groove bottom raised at the other end.
The tie bar has a maximum length in the tire axial direction of 80 to 95% of a maximum width in the tire axial direction of the center land portion,
The pneumatic tire according to claim 3, wherein a height of the tie bar from the deepest portion of the center narrow groove is 20 to 50% of a groove depth of the vertical groove.   5. The pneumatic tire according to claim 3, wherein a maximum width in the tire axial direction of the center land portion is 38 to 46% of a tread half width that is a length in the tire axial direction from the tire equator C to the tread ground contact end. tire.

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