JP2017081286A - Heavy duty tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heavy duty tire capable of improving a cooling efficiency and preventing tire breakage.SOLUTION: In a heavy duty tire, plural lug grooves 33 whose ends open at a tread end and which cross with a tire circumferential direction, and plural land part blocks 41 partitioned by the lug grooves are formed on a tread 101. The land part side of an area in which the land part side formed outside a land part block in a tread width direction crosses with one land part inside formed at the lug groove side of the land part block is made to be an arc-shaped part having an arc shape in a plane view. The arc-shaped part comprises a first arc-shaped part 45 in contact with the land part inside, and a second arc-shaped part 46 outside the first arc-shaped part. The curvature radius of the second arc-shaped part is formed larger than the curvature radius of the first arc-shaped part. Thus, the temperature increase of the tread 101 can be restrained.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heavy duty tire, and more particularly to a technique for improving tire cooling efficiency.

  Heavy duty tires such as ultra-large ORR (off-the-road radial) have a plurality of lug grooves formed in the tread portion for the purpose of reducing the temperature rise in the tread portion (see, for example, Patent Document 1). That is, when the tire rotates in contact with the road surface, an air flow is generated in the opposite direction to the tire rotation direction, so that the air flows into the lug groove to cool the tread portion of the tire. To do.

  In addition, a plurality of land blocks are partitioned in the tread portion by the plurality of lug grooves. In the conventional land portion block, a portion where the land portion side surface which is the side of the landless block and the land portion inner surface forming the lug groove intersects is a corner portion. Therefore, the air flowing into the lug groove flows in contact with the corner portion, so that the air resistance is large and the air cannot efficiently flow into the lug groove. For this reason, the problem that cooling efficiency falls arises.

  Furthermore, since the portion where the land side surface and the land inner surface of the land block intersect is a corner, the stress due to wear when the tire contacts the road surface is concentrated on the corner, and the corner is cracked. May occur. Further, the cracks may expand and eventually a part of the tire may be damaged.

JP 2014-12259 A

  As described above, the conventional heavy-duty tire has a problem in that the air does not easily flow into the lug groove and the cooling efficiency of the tread portion is poor. Furthermore, there has been a problem that stress may concentrate on the corner of the land block and part of the tire may be damaged.

  The present invention has been made in order to solve such a conventional problem, and an object of the present invention is to provide a heavy duty tire capable of improving cooling efficiency and preventing tire damage. It is to provide.

  In order to achieve the above object, a heavy load tire according to the first feature of the present invention is a heavy load tire having a tread portion, and at least one end portion of the tread portion is open to a tread end, Further, a plurality of lug grooves intersecting in the tire circumferential direction and a plurality of land portion blocks defined by the lug grooves are formed, and a land portion side surface formed on the outer side in the tread width direction of the land portion block; The land portion side surface in a region intersecting with one land portion inner surface formed on the lug groove side of the land block is an arc-shaped portion having an arc shape in plan view.

  Further, the heavy load tire according to the second feature is the heavy load tire according to the first feature, wherein the arc-shaped portion includes a first arc-shaped portion in contact with the inner surface of the land portion, and the first arc-shaped portion. The second arc-shaped portion is also an outer second arc-shaped portion, and the radius of curvature of the second arc-shaped portion is larger than the radius of curvature of the first arc-shaped portion.

  In the heavy-duty tire according to the present invention, air can smoothly flow into the lug groove, so that the cooling efficiency can be improved, and the temperature rise of the tread portion can be suppressed. Furthermore, since the corner portion of the land block has an arc-shaped surface, it is possible to avoid stress due to wear during traveling from being concentrated on one point and to prevent damage to the tire.

FIG. 1 is a development view showing a configuration of a heavy duty tire according to an embodiment of the present invention. FIG. 2 is a partially broken perspective view showing the configuration of the heavy duty tire according to the embodiment of the present invention. FIG. 3 is an explanatory view showing details of lug grooves in the heavy duty tire according to the embodiment of the present invention. FIG. 4 is a perspective view showing details of lug grooves of the heavy duty tire according to the embodiment of the present invention. FIG. 5 is a development view showing a configuration of a heavy duty tire according to a comparative example. FIG. 6 is a characteristic diagram showing the relationship between the negative ratio and the heat transfer coefficient of the heavy duty tire according to one embodiment of the present invention and the heavy duty tire according to the comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a development view of a heavy load tire 100 (hereinafter simply referred to as “tire 100”) according to an embodiment of the present invention, FIG. 2 is a partially broken perspective view of the tire 100, and FIG. 4 is an enlarged view of the tread end of the lug groove 33 shown in FIG. In FIG. 2, only one direction (that is, half) of the equator line CL in the tread width direction of the tire 100 is shown.

  A reference numeral 101 illustrated in FIG. 1 indicates a tread portion of the tire 100, and reference numerals 102 and 103 indicate a buttress portion of the tire 100. That is, the tread portion 101 is a surface that mainly contacts the road surface, and the buttress portions 102 and 103 are shown as development views. 1 indicates the tread width direction of the tire 100, the arrow tcd indicates the circumferential direction (tire circumferential direction) of the tire 100, and the arrow Y1 indicates the rotational direction of the tire 100.

  As shown in FIGS. 1 and 2, the tread portion 101 includes a narrow central groove portion 11 along the equator line CL, and a narrow outer groove portion 12 a formed in parallel to the central groove portion 11. 12b is formed. The outer groove portions 12 a and 12 b are formed at equal intervals with respect to the central groove portion 11.

  Further, the tread portion 101 is formed with a plurality of inclined groove portions 13 having a certain inclination with respect to the circumferential direction tcd. A plurality of the inclined groove portions 13 are formed in parallel to each other so as to reach the outer groove portion 12a from the central groove portion 11 and the outer groove portion 12b from the central groove portion 11. Moreover, the inclined groove part 13 reaching from the central groove part 11 to the outer groove part 12a and the inclined groove part 13 reaching from the central groove part 11 to the outer groove part 12b are arranged in a staggered manner.

  On the tread end side of the tread portion 101, a lug groove 33 having a relatively wider groove width than the above-described groove portions 11, 12a, 12b, 13 is formed for each of the two inclined groove portions 13. The lug groove 33 is formed at a right angle (90 °) with respect to the circumferential direction tcd of the tire 100, and further extends from the tread end of the tread portion 101 to the buttress portion 102. That is, the lug groove 33 is open at the tread end.

  Further, the end of the lug groove 33 on the equator line CL side is inclined at a constant angle (see reference numeral r <b> 1 in FIG. 1) and communicates with the inclined groove part 13. Therefore, the air that has flowed into the lug groove 33 flows into the outer groove portions 12a and 12b, the inclined groove portions 13, and the central groove portion 11, so that the entire tread portion 101 can be cooled by this air flow. In this embodiment, an example in which the lug groove 33 is formed at a right angle (90 °) with respect to the circumferential direction tcd is shown, but the range may be 45 ° to 90 ° with respect to the circumferential direction tcd. it can.

  A region of the tread portion 101 defined by each lug groove 33 is a land portion block 41. That is, as typically shown in FIG. 2, on the tread end side of the tread portion 101, a plurality of land portion blocks 41 partitioned by two adjacent lug grooves 33 and the outer groove portion 12a (or 12b) are formed. ing. As shown in FIG. 2, the tire 100 includes a bead core 51, a carcass layer 52, and a plurality of belt layers 53.

The tread end surface of the land block 41 is a land side surface 42, and the two inner surfaces of the land block 41 are a first land portion inner surface 43a and a second land portion inner surface 43b, respectively. As shown in FIGS. 1 and 2, the first land portion inner surface 43a is an inner surface on the near side in the rotational direction Y1 of the tire 100, and the second land portion inner surface 43b is an inner surface on the far side in the rotational direction Y1. .
The tread end of the land block 41 is a chamfered portion 44 whose corners are chamfered in a tapered shape or an arc shape.

  As shown in FIGS. 3 and 4, a first arc-shaped portion 45 and a second arc-shaped portion 46 are formed in a region “R1” where the land portion side surface 42 and the first land portion inner surface 43a intersect. Yes. The first arc-shaped portion 45 is, for example, an arc having a radius of curvature of 30 [mm] (planar arc shape) in plan view. The second arc-shaped portion 46 is, for example, an arc having a radius of curvature of 190 [mm] (plan view arc shape) in plan view. That is, the radius of curvature of the second arc-shaped portion 46 is larger than the radius of curvature of the first arc-shaped portion 45. In this embodiment, the radius of curvature of the second arc-shaped portion 46 is 190 [mm]. However, the radius of curvature of the second arc-shaped portion 46 is larger than 30 [mm] and 1000 [mm] or less. Is desirable. More preferably, it is set to 800 [mm] or less.

  As described above, the tire 100 is formed on the road surface by forming the first arc-shaped portion 45 and the second arc-shaped portion 46 in the intersection region “R1” where the first land portion inner surface 43a and the land portion side surface 42 intersect. When rotating in contact with the air, the air easily flows into the lug groove 33. That is, when the tire 100 rotates in the direction of the arrow Y1 shown in FIG. 2, air flows into the lug groove 33 from the relatively opposite direction, that is, the direction of the arrow Y2. At this time, since the first arc-shaped portion 45 and the second arc-shaped portion 46 are formed, air smoothly flows into the lug groove without stagnation. Furthermore, since the inflowing air flows into the outer groove portions 12a and 12b, the inclined groove portion 13, and the central groove portion 11, the tread portion 101 can be efficiently cooled to suppress heat generation.

  Next, as a comparative example of the tire 100 according to this embodiment, a tire 200 that does not include the first arc-shaped portion 45 and the second arc-shaped portion 46 will be described.

  FIG. 5 shows a development view of the tire 200 according to the comparative example. The tire 200 does not include the first arc-shaped portion 45 and the second arc-shaped portion 46 unlike the tire 100 shown in the present embodiment, and the land portion side surface 42 and the first land portion inner surface 43a are not provided. It has a corner and touches it. That is, as indicated by reference numeral “R2” in FIG. 5, the land portion side surface 42 of the lug groove 33 and the first land portion inner surface 43a are in contact with each other with corner portions, and the intersection portions are corner portions. Yes. More specifically, it is a corner as shown by a two-dot chain line denoted by reference numeral P1 in FIG.

Then, the inventor made a negative ratio [%] and a heat transfer coefficient [W / (m ²⁾ for the tire 100 according to this embodiment shown in FIGS. 1 to 4 and the tire 200 according to the comparative example shown in FIG. -Correlation with K)] was measured, and experimental data as shown in FIG. 6 was obtained. Here, the “negative ratio” indicates the ratio of the area of the region that does not contact the road surface due to the presence of grooves or the like to the entire area of the tread portion 101 of the tire 100.

As understood from the characteristic diagram of FIG. 6, the tire 200 (Q1) shown in the comparative example has a negative ratio of 19.7 [%] and a heat transfer coefficient of 13.8 [W / (m ^2]. K)], and the tire 100 (Q2) shown in this embodiment has a negative ratio of 18.7 [%] and a heat transfer coefficient of 14.6 [W / (m ² · K)]. It was. Therefore, it has been found that by adopting this embodiment, a high heat transfer coefficient can be obtained while maintaining a negative ratio.

  Thus, in the tire 100 according to the present embodiment, the arc-shaped portion is formed in the intersecting region R1 where the first land portion inner surface 43a and the land portion side surface 42 are in contact with each other. Specifically, the first arc-shaped portion 45 and the second arc-shaped portion 46 are formed. Therefore, when the tread portion 101 of the tire 100 rotates in contact with the road surface, an air flow in the direction opposite to the tire rotation direction easily flows into the lug groove 33. As a result, the cooling efficiency of the tread portion 101 can be improved, and an excessive temperature rise of the tread portion 101 can be suppressed.

  Further, the radius of curvature of the second arc-shaped portion 46 is set larger than the radius of curvature of the first arc-shaped portion 45. For example, the radius of curvature of the first arc-shaped portion 45 is set to 30 [mm], and the radius of curvature of the second arc-shaped portion 46 is set to 190 [mm]. For this reason, it becomes possible to flow an air flow into a lug groove more smoothly, and it can prevent that the stress by abrasion concentrates on one point. For this reason, generation | occurrence | production of problems, such as a crack generating in the corner | angular part of a land block, can be avoided like the past, and the trouble that the tire 100 is damaged can be prevented.

  In the present embodiment, the first arc-shaped portion 45 and the second arc-shaped portion 45 are formed on the land portion side surface 42 in the region (R1) where the first land portion inner surface 43a (one land portion inner surface) and the land portion side surface 42 intersect. Although the example which forms the two circular arc shape parts of the circular arc shape part 46 was demonstrated, this invention is not limited to this, You may make it form only the 1st circular arc shape part 45. FIG.

  Even in such a configuration, it is possible to smoothly allow air to flow into the lug groove 33 and to avoid generation of cracks due to concentration of stress.

  As mentioned above, although the heavy load tire 100 of this invention was demonstrated based on embodiment of illustration, this invention is not limited to this, The structure of each part is replaced with the thing of the arbitrary structures which have the same function. be able to.

  For example, in the present embodiment, an example is shown in which the lug groove 33 is formed in a direction perpendicular to the circumferential direction of the tread portion 101 (90 °), but the present invention is not limited to this. However, it can be in the range of 45 ° to 90 °.

11 Central groove portion 12a, 12b Outer groove portion 13 Inclined groove portion 33 Lug groove 41 Land block 42 Land portion side surface 43a First land portion inner surface 43b Second land portion inner surface 44 Chamfered portion 45 First arc shape portion 46 Second arc shape portion 51 Bead core 52 Carcass layer 53 Belt layer 100 Tire (heavy duty tire)
101 Tread 102, 103 Buttress 200 Tire (Comparative Example)
CL Equatorial Line R1, R2 Intersection area

Claims (2)

A heavy duty tire having a tread portion,
The tread portion is formed with a plurality of lug grooves having at least one end opening at the tread end and intersecting in the tire circumferential direction, and a plurality of land portion blocks partitioned by the lug grooves,
The land portion side surface in a region where the land portion side surface formed on the outer side in the tread width direction of the land block and the one land portion inner surface formed on the lug groove side of the land block intersects in plan view. A heavy-duty tire characterized by being an arc-shaped portion having an arc shape. The arc-shaped portion is a first arc-shaped portion in contact with the land portion inner surface, and a second arc-shaped portion outside the first arc-shaped portion, and the radius of curvature of the second arc-shaped portion is the first The heavy duty tire according to claim 1, wherein the tire is larger than a radius of curvature of the arc-shaped portion.

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