JP6317942B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that can suppress the occurrence of a hydroplaning phenomenon.

  The following Patent Document 1 proposes a pneumatic tire in which a land portion is divided between circumferential grooves extending in a tire circumferential direction of a tread portion. The land portion includes a projecting portion having a profile that has a smooth convex shape toward the outer side in the tire radial direction in a tire meridian section including the tire rotation axis. Both ends of the profile of the protrusion are connected to the groove wall of each circumferential groove. Such a land portion is described as suppressing the occurrence of a hydroplaning phenomenon on a wet road surface.

JP 2005-31890 A

  The profile of the protrusion is formed by a smooth single arc. However, since the radius of curvature of the arc of the projecting portion is formed to be relatively large in order to obtain a sufficient ground contact area of the land portion, there is room for further improvement in the suppression effect of the hydroplaning phenomenon.

  This invention is made | formed in view of the above actual conditions, and makes it the main objective to provide the pneumatic tire which can further raise the inhibitory effect of a hydroplaning phenomenon.

  The present invention is a pneumatic tire in which a land portion is divided between the circumferential grooves by providing at least two circumferential grooves extending continuously in the tire circumferential direction in the tread portion, The tread portion has a virtual tread profile that smoothly connects the tread ends along the tire lumen surface in the tire meridian cross section including the tire rotation axis, and the land portion is outside of the virtual tread profile in the tire radial direction. The projecting portion has a projecting profile that protrudes outward in the tire radial direction in the tire meridian cross section, and the projecting profile is formed of a plurality of arcs having different radii of curvature. It is characterized by.

  In the pneumatic tire according to the present invention, the land portion is preferably a rib that is continuous in the tire circumferential direction.

  In the pneumatic tire according to the present invention, the circumferential groove includes a first circumferential groove and a second circumferential groove having a larger groove volume than the first circumferential groove. It is desirable that a top portion located on the outermost side in the tire radial direction is located closer to the first circumferential groove than the center in the width direction of the land portion.

  In the pneumatic tire according to the present invention, the projecting profile includes a first arc extending from the top toward the first circumferential groove, and a second arc extending from the top toward the second circumferential groove. Preferably, the radius of curvature of the first arc is smaller than the radius of curvature of the second arc.

  In the pneumatic tire according to the present invention, it is preferable that the second circumferential groove is provided on a tread end side with respect to the first circumferential groove.

  The land portion of the pneumatic tire of the present invention includes a protruding portion that protrudes outward in the tire radial direction from the virtual tread profile. The projecting portion has a projecting profile that is convex outward in the tire radial direction in the tire meridian cross section. The protruding profile is formed from a plurality of arcs having different radii of curvature. For this reason, the protrusion profile of this invention can form the protrusion part which protruded more sharply to the tire radial direction outer side, maintaining smoothness compared with the case where it forms with a single circular arc. Such a protrusion effectively guides the water on the road surface to the circumferential groove by dividing the water on the road surface into left and right. Thereby, the pneumatic tire of the present invention can suppress the occurrence of the hydroplaning phenomenon to a higher speed region.

It is an expanded view of the tread part of one Embodiment of this invention. It is AA sectional drawing of FIG. It is the elements on larger scale near the crown land part of FIG. It is an expanded sectional view near the crown land part of other embodiments of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of the tread portion 2 of the pneumatic tire of the present embodiment (hereinafter sometimes simply referred to as “tire”). The pneumatic tire of this embodiment can be suitably used for passenger cars.

  As shown in FIG. 1, the tread portion 2 is provided with at least two circumferential grooves 3 in the present embodiment.

  The circumferential groove 3 includes, for example, a first circumferential groove 3C extending on the tire equator C and a pair of second circumferential grooves 3S extending on both outer sides of the first circumferential groove 3C. Each circumferential groove 3 extends linearly continuously in the tire circumferential direction. In a preferred embodiment, the second circumferential groove disposed on the tread end Te side has a larger groove volume than the first circumferential groove 3C. Such a tread pattern can enhance drainage performance while maintaining a large land ratio in the center region of the tread and improving straight running stability.

  The “tread end” Te is a position on the outermost side in the tire axial direction of the contact surface when a normal load is applied to a normal tire and contacted with a flat surface with a camber angle of 0 °. The tire axial distance between the tread ends Te and Te in the normal state is defined as the tread width TW.

  The “normal state” is a no-load state in which a tire is assembled on a normal rim (not shown) and filled with a normal internal pressure. In this specification, unless otherwise specified, the dimensions of each part of the tire are values in a normal state.

  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, “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. For example, “maximum air pressure” for JATMA, “TIRE” for TRA The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of 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. For example, “maximum load capacity” for JATMA and “ The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO.

  FIG. 2 is a cross-sectional view taken along the line AA in FIG. As shown in FIG. 2, the groove width GW1 of the first circumferential groove 3C is, for example, 2% to 9%, more preferably 6% of the tread width TW in order to ensure rigidity and drainage of the tread portion 2. It is preferably in the range of ˜9%. Similarly, the groove depth D1 of the first circumferential groove 3C is preferably 6.0 mm or more, more preferably 8.0 mm or more, and preferably 12.0 mm or less.

  The groove width GW2 of the second circumferential groove 3S is preferably in the range of 3% to 13% of the tread width TW, for example, in order to ensure a larger groove volume than the first circumferential groove 3C. The groove depth D2 of the second circumferential groove 3S is preferably determined within the same range as the first circumferential groove 3C.

  As shown in FIG. 1, the tread portion 2 is divided into a plurality of land portions 4 by the circumferential grooves 3 described above. The land portion 4 includes, for example, a pair of crown land portions 4C and 4C and a pair of shoulder land portions 4S and 4S.

  Each crown land portion 4C is divided between the first circumferential groove 3C and the second circumferential groove 3S. In this embodiment, the crown land portion 4C is formed as a rib extending continuously in the tire circumferential direction. A rib means the land part which continues in the tire circumferential direction in which the transverse groove which crosses over the full width is not provided.

  On the other hand, the crown land portion 4C may be provided with a lug groove 5 having one end terminating in the land portion, a sipe 6 having a cut of 1 mm or less, and the like. These grooves and the like are useful for relaxing the rigidity of the crown land portion 4 and improving the wear resistance performance, as well as improving the traction performance and drainage performance.

  Each shoulder land portion 4S is divided between the second circumferential groove 3S and the tread end Te. In this embodiment, the shoulder land portion 4S is provided with a plurality of shoulder lateral grooves 10. Each shoulder lateral groove 10 communicates between the second circumferential groove 3S and the tread end Te. Thereby, a plurality of shoulder blocks are sectioned in the shoulder land portion 4S of the present embodiment. Such a shoulder land portion 4S can be effectively drained outward in the tire axial direction on a wet road surface, and is useful for enhancing the drainage of the tread portion 2. For example, it is desirable that a sipe 11 extending along the shoulder lateral groove 10 is provided in the shoulder land portion 4S located inside the vehicle when the vehicle is mounted. This improves ride comfort and wear resistance.

  As shown in FIG. 2, the axial width CW of the crown land portion 4C and the axial width SW of the shoulder land portion 4S are not particularly limited, but the rigidity of the tread portion 2 and the ground contact area at the time of ground contact are determined. In order to ensure, for example, a range of 15% to 25% of the tread width TW is preferable.

  FIG. 3 shows a partially enlarged view near the crown land portion 4C of FIG. As shown in FIG. 2 or FIG. 3, the tread portion 2 has a virtual tread profile 2P that smoothly connects the tread ends Te and Te along the tire lumen surface S in the tire meridian cross section including the tire rotation axis. doing. The virtual tread profile 2P is separated from the tire lumen surface S by a distance h in the normal direction. This distance h is equal to the distance in the normal direction from the tread end Te to the tire cavity surface S.

  As shown in FIG. 3, the crown land portion 4 </ b> C between the first circumferential groove 3 </ b> C and the second circumferential groove 3 </ b> S includes a protruding portion 7. The protruding portion 7 is a portion that protrudes outward in the tire radial direction from the virtual tread profile 2P.

  The protruding portion 7 has a protruding profile 7P that is convex outward in the tire radial direction in the tire meridian cross section. The protruding profile 7P is formed by smoothly connecting a plurality of arcs having different radii of curvature, in the present embodiment, the first arc 8a and the second arc 8b.

  The projecting profile 7P of the present embodiment can form the projecting portion 7 that projects more sharply on the outer side in the tire radial direction while maintaining a smooth contour as compared with the case of being formed by a single arc. Such a protrusion 7 guides the water on the road surface to the first circumferential groove 3C and the second circumferential groove 3S by effectively dividing the water on the wet road surface into left and right. Thereby, the tire of the present invention can suppress the occurrence of the hydroplaning phenomenon by shifting to a higher speed region.

  An end 7a on the inner side in the tire axial direction of the protruding profile 7P of the present embodiment is connected to the outer end of the groove wall 12 of the first circumferential groove 3C, for example. Similarly, the end 7b on the outer side in the tire axial direction of the protruding profile 7P of the present embodiment is connected to the outer end of the groove wall 13 of the second circumferential groove 3S, for example. Each of the groove walls 12 and 13 extends outward from the groove bottom in the tire radial direction.

  The protruding profile 7P has a top portion 7T located on the outermost side in the tire radial direction. In the present embodiment, the top portion 7T is located closer to the first circumferential groove 3C than the center in the width direction of the crown land portion 4C. Thus, by determining the position of the top portion 7T of the projecting profile 7P, when the projecting portion 7 comes into contact with the road surface, much of the water on the road surface divided left and right by the top portion 7T enters the second circumferential groove 3S. Be guided.

  As described above, since the second circumferential groove 3S of the present embodiment has a larger groove volume than the first circumferential groove 3C, the water on the guided road surface is effectively in the second circumferential direction. It is discharged to the outside of the tire via the groove 3S. In addition, since the second circumferential groove 3S is located on the tread end Te side, even when road surface water overflows from the second circumferential groove 3S, the tread end Te side outwards the tread portion 2. And easily discharged. Therefore, the protrusion 7 can guide the water on the road surface that has been cut off on the wet road surface while effectively dispersing the water in the first circumferential groove 3C and the second circumferential groove 3S. Thereby, the crown land portion 4 </ b> C is more easily grounded by scraping the water on the road surface. Thus, the tire of the present embodiment can shift the occurrence of the hydroplaning phenomenon to a higher speed range.

  FIG. 3 shows a distance L in the tire axial direction between the top 7T of the protruding profile 7P and the end 7a on the first circumferential groove 3C side. This distance L can be set according to the ratio of the groove volume of the first circumferential groove 3C and the groove volume of the second circumferential groove 3S, for example. The distance L is preferably in the range of 5% to 45% of the axial width CW (shown in FIG. 2) of the crown land portion 4C, for example. When the distance L is less than 5% of the axial width CW, the wear resistance performance of the crown land portion 4C may be deteriorated. Conversely, if the distance L is greater than 45% of the axial width CW, there is a possibility that the water on the road surface cannot be effectively guided.

  The protruding profile 7P of the present embodiment is composed of a first arc 8a extending from the top 7T toward the first circumferential groove 3C and a second arc 8b extending from the top 7T toward the second circumferential groove 3S. The curvature radius R1 of the first arc 8a is smaller than the curvature radius R2 of the second arc 8b. Such a projecting profile 7P can exert the above-described action more effectively.

  The protrusion height H that is the distance in the tire radial direction between the top portion 7T of the protrusion profile 7P and the virtual tread profile 2P is not particularly limited, but is preferably 0.1 to 2.0 mm, for example. When the protrusion height H is less than 0.1 mm, the effect of scraping off water on the road surface may be reduced. On the contrary, when the protrusion height H is larger than 2.0 mm, the wear resistance performance of the crown land portion 4C may be deteriorated.

  FIG. 4 shows an enlarged cross-sectional view of the vicinity of a crown land portion 4C of a tire according to another embodiment of the present invention. In the embodiment of FIG. 4, the second circumferential groove 3S having a large groove volume is provided on the tire equator C, and the first circumferential groove 3C having a small groove volume is provided on the tread end Te side. . On the other hand, in the protrusion 7 of the crown land portion 4C, the top portion 7T of the protrusion profile 7P is located on the first circumferential groove 3C side from the center in the width direction of the crown land portion 4C. In this embodiment, as in the above embodiment, the occurrence of the hydroplaning phenomenon can be shifted to a higher speed region, and the occurrence of the hydroplaning phenomenon can be further suppressed.

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

Tires (size: 225 / 45R17) having the basic pattern shown in FIG. 1 and based on the specifications of Table 1 were prototyped and their performance was tested. As Comparative Example 1, a tire in which the crown land portion did not have a protruding portion was prototyped and similarly tested.
The test method is as follows.

<Hydroplaning resistance>
Each test tire is mounted on all wheels of the test vehicle under the following conditions, and a wet road surface having a 10 mm water film on which the tire on one side of the test vehicle runs, and a dry road on which the tire on the other side of the test vehicle runs. I drove on a test road consisting of a road surface. Thereafter, the speed was measured when the difference in slip ratio between the tire on one side and the tire on the other side exceeded 10%. A result is shown by the index | exponent which sets the comparative example 1 to 100, and it is excellent in hydroplaning performance, so that a numerical value is large.
Rims: 17 × 7.5J
Internal pressure: 230 kPa

<Abrasion resistance>
After the test, the groove depths of the first circumferential groove and the second circumferential groove were measured. A result is shown by the index | exponent which sets Comparative Example 1 to 100, and it is excellent in abrasion resistance performance, so that a numerical value is large.

  As shown in Table 1, it was confirmed that the tires of each example were further improved in anti-hydroplaning performance, that is, the effect of suppressing the hydroplaning phenomenon.

2 Tread part 2P Virtual tread profile 3 Circumferential main groove 4 Land part 7 Protrusion part 7P Protrusion profile S Tire lumen surface Te Tread end

Claims (5)

By providing at least two circumferential grooves extending continuously in the tire circumferential direction in the tread portion, a pneumatic tire in which a land portion is divided between the circumferential grooves,
The tread portion has a virtual tread profile that smoothly connects between tread ends along the tire lumen surface in a tire meridian section including a tire rotation axis,
The land portion includes a protruding portion that protrudes outward in the tire radial direction from the virtual tread profile,
The projecting portion has a projecting profile that is convex outward in the tire radial direction in the tire meridian cross section,
The protruding profile is formed from a plurality of arcs having different radii of curvature ,
The circumferential groove includes a first circumferential groove and a second circumferential groove having a larger groove volume than the first circumferential groove,
The projecting profile is such that the outermost apex located in the tire radial direction is located closer to the first circumferential groove than the center in the width direction of the land portion,
Wherein said top portion axially of the distance between the end portion of the first circumferential groove, pneumatic tire, wherein 25% to 45% range der Rukoto axial width of the land portion.   The pneumatic tire according to claim 1, wherein the land portion is a rib continuous in a tire circumferential direction. The pneumatic tire according to claim 1, wherein a shoulder lateral groove that communicates between the second circumferential groove and a tread end is provided . The projecting profile includes a first arc extending from the top toward the first circumferential groove, and a second arc extending from the top toward the second circumferential groove,
The pneumatic tire according to any one of claims 1 to 3 , wherein a radius of curvature of the first arc is smaller than a radius of curvature of the second arc. The pneumatic tire according to any one of claims 1 to 4, wherein the second circumferential groove is provided closer to a tread end than the first circumferential groove.

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