JP6535571B2 - Heavy duty tire - Google Patents

Description

  The present invention relates to a heavy load tire, and more particularly to a technology for improving the cooling efficiency of the tire.

  In heavy duty tires such as super-large ORR (off-the-road radial), a plurality of lug grooves are formed in the tread portion in order to reduce the temperature rise of 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 rotational direction of the tire, and this air flow causes air to flow into the lug groove to cool the tread portion of the tire. Do.

  Further, the land portions are divided into the tread portion by the plurality of lug grooves. In the land block in the related art, a corner where the land side surface on the side of the landless block on the landless side of the land block intersects with the land inner surface forming the lug groove is a corner. Therefore, the air flowing into the lug groove comes into contact with the corner, and the air resistance is large, and the air can not efficiently flow into the lug groove. For this reason, the problem that a cooling efficiency falls arises.

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

JP, 2014-12459, A

  As described above, the conventional heavy load tire has a problem that the air does not easily flow into the lug grooves and the cooling efficiency of the tread portion is poor. Furthermore, there has been a problem that stress is concentrated at the corner of the land block and a part of the tire may be broken.

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

In order to achieve the above object, the heavy load tire according to the first aspect 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 at the tread end. Further, a plurality of lug grooves intersecting in the tire circumferential direction, a plurality of land portion blocks partitioned by the lug grooves, a central groove along the tire circumferential direction, and an inclined groove inclined with respect to the central groove Is formed, and 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 portion block and one land portion inner surface formed on the lug groove side of the land portion block intersect The inner end of the lug groove is formed to be inclined in the same direction as the inclined groove with respect to the circumferential direction of the tire, and the lug groove is further formed. The inner end of the Communicates with one end of the groove, the other end of the inclined groove, characterized in that communicates with the central groove.

  The heavy load tire according to the second aspect is the heavy load tire according to the first aspect, wherein the arc-shaped portion is a first arc-shaped portion contacting the inner surface of the land portion and the first arc-shaped portion The second arc-shaped portion is also an outer side, 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 load tire according to the present invention, since the air can be smoothly introduced into the lug grooves, the cooling efficiency can be improved, and as a result, the temperature rise of the tread portion can be suppressed. Furthermore, since the corner portions of the land block are arc-shaped, stress concentration due to wear during traveling can be avoided from being concentrated at one point, and damage to the tire can be prevented.

FIG. 1 is a developed view showing the configuration of a heavy load tire according to an embodiment of the present invention. FIG. 2 is a partially broken perspective view showing the configuration of the heavy load tire according to the embodiment of the present invention. FIG. 3 is an explanatory view showing the details of lug grooves of the heavy load tire according to the embodiment of the present invention. FIG. 4 is a perspective view showing the details of lug grooves of the heavy load tire according to the embodiment of the present invention. FIG. 5 is a developed view showing a configuration of a heavy load 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 load tire according to the embodiment of the present invention and the heavy load tire according to the comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a developed 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 cutaway perspective view of the tire 100, and FIG. FIG. 4 is an enlarged view of the tread end of the lug groove 33 shown in FIG. 2. In FIG. 2, only one direction (that is, half) is shown with respect to the equator line CL in the tread width direction of the tire 100.

  Reference numeral 101 shown in FIG. 1 denotes a tread portion of the tire 100, and reference numerals 102 and 103 denote buttress portions of the tire 100. That is, the tread portion 101 is a surface mainly in contact with the road surface, and the buttress portions 102 and 103 are shown as developed views. Further, the arrow twd shown in FIG. 1 indicates the tread width direction of the tire 100, the arrow tcd indicates the circumferential direction of the tire 100 (tire circumferential direction), and the arrow Y1 indicates the rotation direction of the tire 100.

  As shown in FIGS. 1 and 2, in the tread portion 101, a narrow central groove 11 along the equatorial line CL, and a narrow outer groove 12a formed parallel to the central groove 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, in the tread portion 101, a plurality of inclined groove portions 13 having a constant inclination with respect to the circumferential direction tcd are formed. A plurality of inclined grooves 13 are formed in parallel with each other so as to reach the outer groove 12 a from the central groove 11 and the outer groove 12 b from the central groove 11. Further, the inclined groove portions 13 reaching the outer groove portion 12a from the central groove portion 11 and the inclined groove portions 13 reaching the outer groove portion 12b from the central groove portion 11 are arranged in a zigzag manner.

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

  Further, the end on the equatorial line CL side of the lug groove 33 is inclined at a constant angle (see reference numeral r1 in FIG. 1) and is in communication with the inclined groove portion 13. Accordingly, the air flowing into the lug grooves 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 the present embodiment, an example in which the lug grooves 33 are formed at a right angle (90 °) with respect to the circumferential direction tcd is shown, but a range of 45 ° to 90 ° with respect to the circumferential direction tcd it can.

  The area of the tread portion 101 divided by each lug groove 33 is a land 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 an outer groove portion 12a (or 12b) are formed. ing. Further, 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 surface of the tread end 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 inner surface 43a and a second land inner surface 43b, respectively. As shown in FIGS. 1 and 2, the first land inner surface 43a is the inner surface on the front side of the rotational direction Y1 of the tire 100, and the second land inner surface 43b is the inner surface on the back side of the rotational direction Y1. .
The tread end of the land block 41 is a chamfered portion 44 whose corner portion is chamfered in a tapered or arc shape.

  As shown in FIGS. 3 and 4, the first arc-shaped portion 45 and the second arc-shaped portion 46 are formed in a region “R1” where the land side surface 42 and the first land inner surface 43 a intersect. There is. The first arc-shaped portion 45 is, for example, an arc with a radius of curvature of 30 mm in a plan view (an arc shape in a plan view). The second arc-shaped portion 46 is, for example, an arc with a radius of curvature of 190 mm in a plan view (an arc shape in a 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 the present embodiment, the radius of curvature of the second arc-shaped portion 46 is 190 [mm], but the radius of curvature of the second arc-shaped portion 46 is greater than 30 [mm] and not greater than 1000 [mm]. It is desirable to More preferably, it is desirable to set it as 800 [mm] or less.

  Thus, 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, the tire 100 is a road surface. When rotating in contact with the air, air can easily flow 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, the air smoothly flows into the lug groove without stagnation. Furthermore, since the air that has flowed in 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 the present embodiment, a tire 200 not provided with the first arc-shaped portion 45 and the second arc-shaped portion 46 will be described.

  FIG. 5 shows a developed view of a tire 200 according to a comparative example. The tire 200 does not include the first arc-shaped portion 45 and the second arc-shaped portion 46 as in the tire 100 shown in the present embodiment, and the land portion side surface 42 and the first land portion inner surface 43 a It has contact with the corner. That is, as shown by the code "R2" in FIG. 5, the land side surface 42 of the lug groove 33 and the first land inner surface 43a are in contact with each other with a corner, and the intersection is a corner. There is. More specifically, as shown by the two-dot chain line of the code P1 in FIG.

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

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

  Thus, in the tire 100 according to the present embodiment, an arc-shaped portion is formed in the intersection region R1 where the first land portion inner surface 43a and the land portion side surface 42 are in contact with each other. In detail, 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 opposite to the rotation direction of the tire is likely to flow 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.

  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 is possible to allow the air flow to more smoothly flow into the lug groove, and further, it is possible to prevent stress due to wear from being concentrated at one point. For this reason, generation | occurrence | production of the problem of a crack arising in the corner | angular part of a land part block conventionally can be avoided, and the trouble that the tire 100 is damaged can be prevented.

  Further, in the present embodiment, the first arc-shaped portion 45 and the second arc-shaped portion 45 are formed on the land side surface 42 in a region (R1) where the first land inner surface 43a (one land inner surface) and the land side surface 42 intersect. Although the example in which the two arc-shaped portions of the arc-shaped portion 46 are formed has been described, the present invention is not limited to this, and only the first arc-shaped portion 45 may be formed.

  Even in such a configuration, air can be smoothly introduced into the lug grooves 33, and generation of cracks due to stress concentration can be avoided.

  The heavy load tire 100 of the present invention has been described above based on the illustrated embodiment, but the present invention is not limited to this, and the configuration of each part is replaced with an arbitrary configuration having the same function. be able to.

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

11 central groove portion 12a, 12b outer groove portion 13 inclined groove portion 33 lug groove 41 land portion block 42 land portion side surface 43a first land portion inner surface 43b second land portion inner surface 44 chamfered portion 45 first arc shaped portion 46 second arc shaped portion 51 Bead core 52 Carcass layer 53 Belt layer 100 Tire (heavy load tire)
101 tread portion 102, 103 buttress portion 200 tire (comparative example)
CL equatorial line R1, R2 intersection area

Claims (2)

A heavy duty tire having a tread portion,
In the tread portion, a plurality of lug grooves having at least one end opened at the tread end and intersecting in the tire circumferential direction, a plurality of land portion blocks partitioned by the lug grooves, and the tire circumferential direction A central groove along the groove and an inclined groove inclined with respect to the central groove ;
The land portion side surface of a region where a land portion side surface formed on the outer side in the tread width direction of the land portion block and one land portion inner surface formed on the lug groove side of the land portion block intersect in plan view It is considered as an arc-shaped portion having an arc shape ,
The inner end of the lug groove is formed to be inclined in the same direction as the inclined groove with respect to the circumferential direction of the tire, and the inner end of the lug groove communicates with one end of the inclined groove, A heavy load tire, wherein the other end of the inclined groove communicates with the central groove . The arc-shaped portion is a first arc-shaped portion in contact with the inner surface of the land portion, and a second arc-shaped portion outside the first arc-shaped portion, and the curvature radius of the second arc-shaped portion is the first The tire for heavy load according to claim 1, characterized in that the radius of curvature of the arc-shaped portion is larger.

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