JPH10278513A - Pneumatic tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the bite of a foreign material by providing each lateral groove with a groove bottom upheaval part, and providing each circumferential main groove with a groove bottom upheaval part, and forming a surface of these upheaval parts so as to be projected and curved toward a tread, and forming both wall surfaces and both the groove bottom upheaval parts of both the lateral groove and the circumferential main groove so as to be smoothly continued to each other. SOLUTION: A groove bottom of each circumferential main groove 2 and each lateral groove 3 is formed with a groove bottom upheaval part 2R and a groove bottom upheaval part 3R, which have a vertex and of which both side parts from the vertex are formed with a gradual down-slope surface toward a groove bottom thereof so as to form a projecting curved surface, and projections, in which a degree of projection is increased toward these upheaval parts 2R, 3R, is formed in the groove wall surface. With this structure, contact area of a foreign material and both the wall surfaces and the groove bottom upheaval part 3R of the lateral groove 3 is reduced, and a surface area of the foreign material inside of the lateral groove at an open side is increased, and the angle of inclination of both the wall surfaces of the lateral groove 3 is increased in relation to other wall surface, and as a result, a foreign material holding force of the lateral groove 3 is lowered, and the foreign material is easily discharged out of a tire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic radial tire for heavy loads, and more particularly, to a block pattern for use in heavy vehicles such as construction vehicles and general dump trucks traveling on rough terrain and other irregular terrain. For pneumatic radial tires for off-road use, in particular, it effectively prevents foreign substances such as stones scattered on a rough road surface from biting into the grooves that define the block, and effectively prevents the bottom of the groove from being generated by the foreign substances that have been bitten. The present invention relates to a pneumatic radial tire for heavy loads which can be prevented.

[0002]

2. Description of the Related Art Heavy-duty pneumatic radial tires with a block pattern that exerts power on traction performance and skid resistance when traveling on rough terrain are provided to define blocks to improve the wear life of tread rubber. It is the present situation that deeper grooves and narrower widths are being implemented for such grooves. However, these wear life improving means simultaneously increase the chance of foreign matter such as pebbles and crushed stones scattered in the wasteland to bite into the groove.

[0003] The foreign matter biting into the groove is not limited to this, and as a result of the direct action of force applied to the foreign matter with the rolling load of the tire, the foreign matter damages the groove bottom or the periphery thereof, and this damage further develops. Or a big crack,
Alternatively, the foreign substance itself is buried in the rubber, and cracks are generated around the buried foreign substance. In any case, the crack reaches the cord layer of the belt, and eventually causes a separation failure. .

The means for avoiding this kind of failure caused by foreign matter being caught is mainly applied to the circumferential groove of the rib pattern. The simplest means is to provide a flat surface called a platform at the bottom of the groove. 12 (a) and 12 (b), a part of the platform is provided in the groove width direction (the former), and a groove is provided as an improved type of the platform. A device having a projection called a stone ejector at the center in the width direction (the latter) is known.

[0005]

However, when a simple platform is applied to the groove of the block pattern, the rigidity of the block is increased. On the other hand, the wear resistance and the groove bottom crack resistance are improved. Decreases (increase in the calorific value of the tread portion) and does not appear to have a deep groove in appearance, which not only impairs the meaning of the deep groove,
During the middle to late wear of the tread rubber, the platform part appears on the tread at a time and becomes a pattern that is significantly different from the tread pattern of the new tire, so the function of the block pattern intended to improve the traction performance at the corner angle and the anti-skid resistance is significantly impaired. As a result, these performances are greatly deteriorated.

Therefore, as a means for improving these inconveniences, an improved platform and a stone ejector shown in FIGS. 12A and 12B have been proposed. Unlike conventional simple platforms, these means do not significantly increase the block rigidity from new tires to the end of wear, so they do not greatly impair traction performance or skid resistance, but on the ground surface Since the narrow groove is formed at the bottom of the block having a large movement, the concentration of stress is increased. As a result, the effect of preventing foreign matter from being caught at the corner becomes meaningless due to cracks generated at the bottom of the narrow groove.

Therefore, the invention described in claims 1 to 9 of the present invention is based on the premise that the groove for defining the block is further deepened and further narrowed, so that the tread portion of the block pattern has After securing the point that it can exhibit excellent traction and skid resistance under sufficient flexibility, it prevents foreign substances such as pebbles and crushed stones from getting into the groove, causing foreign matter to get in It is an object of the present invention to provide a pneumatic radial tire for heavy loads having a long life and capable of preventing occurrence of groove bottom cracks.

[0008]

In order to achieve the above object, the invention described in claim 1 of the present invention is directed to a plurality of tread portions extending along the circumference of the tread surface in a central region excluding both side regions of the tread surface. A circumferential main groove and a plurality of lateral grooves extending between adjacent circumferential main grooves and opening to each main groove, and the tread surface circumference is formed by the plurality of circumferential main grooves and the number of lateral grooves. In a heavy-duty pneumatic radial tire having a block pattern formed by defining a large number of block rows along, each lateral groove has a groove width portion in which the distance between the lateral edges of adjacent blocks in the block row is uniform. Each lateral groove has a groove bottom ridge extending across the groove bottom at an intermediate position of the block lateral edge length in the uniform groove width portion, and each circumferential main groove is a vertical edge of each block in the block row. And the vertical facing each other under uniform groove width Each circumferential main groove has a groove bottom ridge extending across the groove bottom at an intermediate position of the longitudinal edge length of the land portion, and these ridges have grooves facing the tread surface. It has a curved surface that protrudes in the extending direction, and both wall surfaces of the lateral groove and the circumferential main groove toward the groove bottom protrusion increase in the degree of convex protrusion from the tread surface to the protrusion, and the groove bottom protrusion is smooth. It is characterized by being connected to.

Here, the heavy-duty pneumatic radial tire (hereinafter simply referred to as a tire) comprises a tread portion, a pair of side wall portions and a pair of bead portions connected to both sides thereof, and a bead core having these portions embedded in the bead portion. It is customary to provide a radial carcass that reinforces each other and a belt that strengthens the tread portion at the outer periphery thereof, and the circumferential main groove formed on the tread surface includes a zigzag groove in addition to a straight groove. The lateral groove includes a groove that is inclined with respect to the width direction in addition to a groove that extends in the width direction.

The surface of the raised portion provided at the bottom of each of the lateral groove and the circumferential main groove has a convex curved surface facing the tread surface, and therefore the groove bottom raised portion is gently sloped from the top to the bottom hem and tapered. And the end surface of the inclined surface is connected to the groove bottoms on both sides. Further, the groove bottom protruding portions as viewed in the cross section in the groove width direction of the lateral groove and the circumferential main groove are connected to both wall surfaces of the lateral groove and the circumferential main groove via small arcs.

Foreign matter is easily trapped in a groove portion having a uniform groove width. The smaller the groove width with respect to the groove depth and the smaller the inclination angle of the groove wall surface with respect to the tread surface, the more easily foreign matter is trapped. As in the invention described in claim 2, 50% or more of the entire horizontal edge length and the entire vertical edge length of each block is the horizontal edge and the vertical edge of the block related to the formation of the groove bottom ridge, and According to the third aspect of the present invention, the ratio of the width of the lateral groove and the circumferential main groove located on both sides of the groove bottom raised portion to the groove depth is within the range of 0.9 to 0.2. It is effective to achieve the object of the present invention that the inclination angle of both wall surfaces of these grooves is in the range of 12 to 0 °.

In a preferred embodiment relating to the actual shape of the groove bottom ridge, the length of the groove bottom ridge measured in the direction in which the groove extends, as in the invention as set forth in claim 4, is determined by the lateral direction involved in the formation of the ridge. 6. The maximum height of the ridge measured from the groove bottom on both sides of the groove bottom ridge, as in the invention according to claim 5, being within the range of 20 to 50% of each of the edge length and the vertical edge length. Is in the range of 10 to 40% of the groove depth on both sides of the groove bottom ridge. Here, the groove bottom ridge length is the length between both end edges of the inclined surface at the top of the groove bottom ridge described above, and the maximum height of the ridge is at the above-mentioned top.

[0013] The wall surfaces of the lateral groove facing the groove bottom ridge may take various suitable embodiments, one of which is the lateral groove in which the groove bottom ridge is located, and The convex overhang surface of both wall surfaces of each circumferential main groove is
It has a smooth curved surface that gradually increases the degree of convex protrusion from the tread surface to the groove bottom. As a modified example, as in the invention described in claim 7, the lateral groove and the periphery where the groove bottom protrusion is located are provided. The convex overhang of both wall surfaces of the direction main groove has a plurality of slits cut in the direction in which the groove extends from the curved surface while having a smooth curved surface,
These slits have bottom portions on the same wall surfaces as both wall surfaces of the groove located on both sides of the groove bottom protrusion. This modification has the effect of alleviating a slight increase in block rigidity at the groove bottom protrusion.

In another preferred embodiment, as in the invention as set forth in claim 8, the protruding projections of both wall surfaces of the lateral groove and the circumferential main groove where the groove bottom protrusion is located are formed from the tread surface to the groove bottom. In a further preferred embodiment, each of the lateral groove and the circumferential main groove in which the groove bottom protruding portion is located is formed in a stepwise manner to increase the degree of protruding protrusion. The convex overhang of both wall surfaces increases the degree of convex overhang while alternately repeating a convex shape and a concave shape from the tread surface toward the groove bottom. These two cases also help to alleviate a slight increase in block rigidity, as in the case of the slit described above.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a development view of a part of the tread of the tire. In FIG.
In the central region CR excluding both side regions, a plurality of circumferential main grooves 2 extending along the circumference of the tread surface 1, in the illustrated example, two circumferential main grooves 2 at point symmetrical positions on both sides of the tire equatorial plane E, and adjacent circumferential main grooves 2. A plurality of lateral grooves 3 extending between the grooves 2 and 2 are provided, and these lateral grooves 3 open to each of the main grooves 2 and 2. Note that the tread surface center region CR here is surrounded by (6/8) × TW width that equally divides the tire equatorial plane E out of (1/8) × TW obtained by dividing the development width TW of the tread surface 1 into eight equal parts. Refers to the area.

A row of a large number of blocks 4 is defined along the circumference of the tread 1 by the two circumferential main grooves 2 and a large number of the lateral grooves 3. The illustrated tread pattern has a large number of side grooves 5 extending to the center area CR in both side areas SR of the tread 1, that is, an area surrounded by the (1/8) × TW width. Also, since it communicates with the circumferential main grooves 2, 2, many rows of blocks 6 are also formed in both side regions SR. Therefore, in the example shown in FIG. 1, the entire tread surface 1 is made up of blocks.

Here, the lateral groove 3 has a groove width w ₃ portion in which the distance between the lateral edges e _{3 of the} blocks 4 adjacent to each other in the row of the blocks 4 is uniform, and each lateral groove 3 has a uniform groove width. It comprises a groove bottom ridges 3R extending across the groove bottom at the intermediate position of the length L ₃ of the lateral edge e ₃ blocks 4 in w ₃ portions. The groove bottom raised portion 3R has a convex curved surface whose surface faces the tread surface 1.

Furthermore circumferential main groove 2, land zone with a vertical edge e facing each other under the longitudinal edge e ₂ a uniform groove width w ₂ of each block 4 in rows of blocks 4, in the illustrated example Block 6
To form Circumferential main grooves 2 are longitudinal edges e, extending across the groove bottom at the intermediate position of the length L ₂ of the e ₂ groove bottom ridges 2R
Is provided. Hereinafter, the groove bottom raised portion 2R and the groove bottom raised portion 3R will be described in detail with the groove bottom raised portion 3R as a representative for convenience, and the groove bottom raised portion 2R will read the transverse groove 3 as the circumferential main groove 2. , And the same as the groove bottom raised portion 3R only by replacing the reference numeral 3 or the subscript 3 with the reference numeral 2 or the subscript 2.

The width of the groove 3 is determined by the width w of the lateral groove 3.
₃ is shown in FIG. 2 as a cross-sectional view along the line II-II passing through the center.
In FIG. 2, the length bisection CL ₃ of the groove bottom ridge 3R in the direction in which the horizontal groove 3 extends passes through the ridge apex P and is approximately at the middle of the length L ₃ of the block lateral edge e ₃ along the horizontal groove 3. To position. The groove bottom protruding portion 3R forms a gentle downward slope on both sides from the vertex P toward the groove bottom 3B, and the remaining groove bottom 3B excluding the groove bottom protruding portion 3R at the end edges 3Re of both the slopes. Connect smoothly. In FIG. 1, the terminal 3Re is indicated by a two-dot chain line.

Both wall surfaces of the lateral groove 3 toward the groove bottom ridge 3R will be described in detail with reference to FIGS.
Here, FIG. 3 is an enlarged view of a circle A portion of a two-dot chain line shown in FIG. 1, FIG. 4 is a cross-sectional view taken along a line IV-IV shown in FIG. 3, and FIG. FIG. 3 is an end view showing a cross section of a groove wall surface 3W of a lateral groove 3 along a line aa to gg and a cross section of groove bottoms 3R and 3B shown in FIG.

Referring to FIG. 3 to FIG. 5, both wall surfaces 3W of the lateral groove 3 toward the groove bottom ridge 3R extend from the tread surface 1 to the groove bottom as shown in FIGS. Is increased and the groove bottom ridge 3R is smoothly connected. In FIG. 3, the state of the protruding overhang 3WR is indicated by a two-dot chain line adjusted to positions corresponding to the bb line to the ff line. In FIG. 3, a straight line CL ′ ₃ shown by a dashed line passes through the vertex P of FIG. 2, and a straight line 3Re ′ shown by a two-dot chain line is a line segment passing through the end edges 3Re of both inclined surfaces of the groove bottom ridge 3R. Two line segments 3R
A two-dot chain line drawn at a position corresponding to the bb line to the ff line (see FIG. 4) in the area sandwiched by e 'projects toward the center of the groove width of the lateral groove 3 and has two lines. Is connected to the wall surface 3W of the lateral groove 3 having no raised portion 3R at the position of the line segment 3Re '. A small chamfered arc may be provided at this connection position.

By examining the number of tires actually used in the market, the position of a tire having a block pattern rolling on a road surface on which foreign substances such as pebbles and crushed stones are scattered and biting these foreign substances into grooves was examined. Most of the grooves that bite foreign matter have relatively small groove width changes at the contact surface of the rolling tire tread, and have a substantially uniform groove width. Although it depends on the shape of the sheath groove, it has been found that the foreign matter biting frequency is generally higher in the circumferential main groove, and sometimes the lateral groove is higher.

Therefore, as a result of performing statistical processing on the biting positions of the circumferential main groove 2 and the lateral groove 3, the foreign matter biting frequency shows a substantially normal distribution, and the peak of this normal distribution curve indicates the circumferential main groove 2 and the lateral groove. Vertical edge e of block 4 along 3
₂ conforms substantially 1/2 point and transverse edges e ₃ respective lengths L ₂ and the length L ₃ (longitudinal edges e of the block 6), and facilities the majority (hatched area normal distribution curve surrounded The portion of the circumferential main groove 2 and the horizontal groove within a range of 0.2 to 0.5 times the length L (L ₂ , L ₃ ) of each of the vertical edge e ₂ and the horizontal edge e ₃ of the block 4 I found out that there are three parts. The result of the statistical processing is shown in FIG. 9 as a diagram.

As shown in FIG. 10 which shows an example of the lateral groove 3 ', the foreign matter has a large contact area with the groove wall surface, as shown in FIG. Therefore, even if the lateral groove 3 'is opened at the kick-out portion in the ground contact surface of the rolling of the tire and the groove width is widened, there is little chance that foreign matter is discharged to the outside of the tire. This is exactly the same for the conventional circumferential main groove.

On the other hand, each of the circumferential main groove 2 and the lateral groove _{3 at} the intermediate position between the lengths L ₂ and L ₃ of the vertical edge e ₂ and the horizontal edge e _{3 of} the block 4 having the peak value of the foreign substance biting frequency, respectively. The bottom of the groove has a vertex P, and both side portions from the vertex P are formed of a convex curved surface which forms a groove bottom 2B (not shown) and a gentle downward slope toward the groove bottom 3B and projects toward the tread surface 1. Forming a groove bottom ridge 2R and a groove bottom ridge 3R;
By forming a convex overhang 3WR (2WR, not shown) that increases the degree of convexity toward the groove bottom raised portion 2R and the groove bottom raised portion 3R on the groove wall surface 3W (2W, not shown), the following operation is achieved. It works.

That is, as shown in FIG. 11, (1) First, foreign matter and both wall surfaces 3W (2) of the lateral groove 3 (the circumferential main groove 2)
W) and the contact area between the groove bottom ridge 3R (groove bottom ridge 2) can be reduced, and (2) the lateral groove 3 (the circumferential main groove 2) in the foreign matter in connection with the above. (3) Finally, the inclination angle of both wall surfaces 3W (2W) of the lateral groove 3 (circumferential main groove 2) becomes larger than that of the other wall portions, so that the lateral groove 3 The foreign matter gripping force of the (circumferential main groove 2) is much smaller than that of the conventional lateral groove 3 '(conventional circumferential main groove). As a result, foreign substances can be released to the outside of the tire more easily.

(4) Naturally, since the rubber gauge from the surface of each of the groove bottom raised portions 2R and the groove bottom raised portions 3R to the cord layer of the belt is thicker than the conventional lateral groove 3 '(conventional circumferential main groove), the presence of foreign matter This also has the effect of making it difficult for the wound to reach the cord layer of the belt.

Referring again to FIG. 2, based on FIG. 9 of the statistical curve mentioned above, the end 3
The length of the groove bottom ridges 3R between Re L _3R, it is seen that the in the range of 20-50% of the block edge length L ₃ is compatible. Even if it is less than 20% or more than 50%, the practical effect is not so much obtained, and especially when it exceeds 50%, the pattern image after the middle stage of wear of the tread rubber changes greatly, and the traction performance and the side slip resistance deteriorate. It is not possible. This is because the groove bottom ridge 2 provided in the circumferential main groove
The same applies to R.

The vertex P of the groove bottom protrusion 3R has a length L_3Rof
Groove depth D measured from groove bottom 3B on both sides _Three10-40% of
Having a maximum height t that is in the range,
When the maximum height of 3R is less than 10%, the above-mentioned effect (1)
~ (4) cannot be obtained sufficiently, but exceeds 40%
Block, the block rigidity becomes too high, and the tread rubber
The ridge 3R appears on the surface relatively early in wear,
Pattern effect cannot be exhibited.
It is compatible. This is the same for the groove bottom protrusion 2R.
It is.

With respect to the shape of the convex protrusion 3WR of both wall surfaces 3W toward the groove bottom protrusion 3R, in the range described with reference to FIGS. 3 to 5, a smooth curved surface whose degree of protrusion gradually increases from the tread surface 1 toward the groove bottom. 6 to 8 are sectional views similar to FIG. 4. This FIG.
The modification shown in FIG.
It can be applied to R as it is.

A projecting overhang 3WR of both wall surfaces 3W shown in FIG.
Is an example having a plurality of slits S thinly cut in each overhang, and an example in which the depth of cut is up to the same surface as the groove wall surface excluding the convex overhang 3WR of the lateral groove 3. Can be adjusted as appropriate.

A convex overhang 3WR on both wall surfaces 3W shown in FIG.
Is an example having a shape in which the degree of uplift is increased in a step-like manner from the tread surface 1 toward the groove bottom, and the both wall surfaces 3W shown in FIG.
The convex overhang 3WR is an example having a shape that increases the degree of protuberance while alternately repeating a convex shape and a concave shape from the tread surface 1 toward the groove bottom.

The convex overhang 3WR shown in FIGS. 6 to 8 contributes to making the contact area with the foreign matter once caught smaller than the smooth curved surface shown in FIG. Also, the provision of the protruding overhang 3WR also helps to moderately reduce the slight improvement in rigidity of the block 4.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A radial ply tire for construction vehicles having a size of 24.00R49, a tread pattern as shown in FIG. 1, a carcass comprising one ply of rubber coating of a radially arranged steel cord, and a belt comprising six layers of steel. Consists of a code cross layer. Circumferential main groove width w ₂ in the groove 2 is 50 mm, the groove width w ₃ of the lateral grooves 3 and 48 mm, length of the edge e ₂ of block 4 along the circumferential direction main groove 2 L ₂
Is 96 mm, the length L of the edge e ₃ of the block 4 along the lateral groove 3
₃ is 100 mm, these lengths L ₂ and the maximum height t the groove bottom located substantially in the middle of the L ₃ is, the main groove 2 of a depth D ₂
30%, the groove bottom ridge having an apex P corresponding to 30% of the groove depth D ₃ 2R, provided 3R, the length of the groove bottom ridges 2R block 4 edge e ₂ of the length L ₂ of The length L _3R of the groove bottom protrusion _3R was set to about 40% of the length L ₃ of the edge e ₃ of the block 4.

Both wall surfaces of the lateral groove toward the groove bottom raised portion 3R are formed by convex protrusions having smooth curved surfaces which gradually increase the degree of protrusion from the tread surface 1 toward the groove bottom as shown in FIGS. Although not shown, the groove bottom ridge 2R is also shown in FIGS.
In the same manner as shown in FIG. 6, the protrusion was formed by a convex protrusion having a smooth curved surface whose degree of protrusion gradually increased from the tread surface 1 toward the groove bottom. To confirm the effect of this embodiment, a comparative example the height t of the vertex P is matched to all of the other embodiments is 5% of the respective groove depth D ₂ and the groove depth D _3, also the groove bottom ridges Circumferential main groove and lateral groove 3 'having no convex overhang on both wall surfaces of the groove
An actual vehicle test was performed on these test tires by preparing a conventional example provided with the above.

The test vehicle actually operates in the same quarry 3
77 ton dump trucks, all of which have the same model type so that the evaluation result is not biased, and after each test tire is mounted on these test vehicles and operated for one week, the degree of stone biting is checked. Was. The stone biting degree is calculated by dividing the number of pitches (the number of lateral grooves 3) into which the stone is bit by the total pitch number (the number of all lateral grooves 3) 32 by 1
It was expressed as a percentage (%) multiplied by 00. The bite of a foreign substance (stone) is a phenomenon that occurs remarkably in the case of a new tire in which the wear of the tread rubber does not progress.

The degree of biting of the obtained stones was 0% in the example, about 8% in the comparative example and 12% in the conventional example. From the results of the field tests including this comparative example, it can be seen that the foreign matter biting resistance of the example is much better than the conventional tire. In addition, the excellent traction performance, braking performance and skid resistance of the block pattern were evaluated by the truck operator throughout the test period, but the comparative example as well as the examples showed performance comparable to the conventional example. I was able to confirm. In addition, tires with convex overhangs on both wall surfaces of the lateral groove having slits, tires with convex overhangs having a stepped shape, and tires with convex and concave alternately arranged in convex overhangs were also subjected to the same test evaluation as above, It has also been confirmed that the results show good results.

[0038]

According to the first to seventh aspects of the present invention, while the original performance of the block pattern is sufficiently maintained, the resistance to foreign matter biting can be significantly improved. Accordingly, it is possible to provide a long-life heavy-load pneumatic radial tire capable of preventing the occurrence of cracks at the groove bottom caused by foreign matter being caught.

[Brief description of the drawings]

FIG. 1 is a developed view of a tread showing an example of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a groove bottom ridge taken along line II-II of the lateral groove shown in FIG.

FIG. 3 is an enlarged view of a lateral groove portion surrounded by a circle A shown in FIG.

FIG. 4 is a cross-sectional view taken along a line IV-IV shown in FIG. 3;

FIG. 5 is an end view along aa to gg shown in FIG. 4;

FIG. 6 is a cross-sectional view showing a modified example of the convex overhang of both wall surfaces of the lateral groove shown in FIG.

FIG. 7 is a cross-sectional view of another modified example of the convex protrusion of both wall surfaces of the lateral groove shown in FIG.

FIG. 8 is a cross-sectional view of another modified example of the projecting protrusion on both wall surfaces of the lateral groove shown in FIG. 4;

FIG. 9 is an explanatory diagram of a relationship between a horizontal edge length and a vertical edge length of a block and a frequency of foreign matter biting.

FIG. 10 is an explanatory view of a state in which a foreign substance is caught in a conventional lateral groove.

FIG. 11 is an explanatory diagram of a state in which a protrusion of a lateral groove shown in FIG. 1 is caught by a foreign substance.

FIG. 12 is a cross-sectional view in the width direction of a groove showing a conventional example of preventing foreign matter from being caught.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Tread surface 2 Circumferential main groove 2R Groove bottom raised portion 3 Transverse groove 3R Groove bottom raised portion 3WR Horizontal groove both wall convex protrusion 3Re Groove bottom raised portion end edge 3B Bottom of lateral groove excluding groove bottom raised portion 4 Block 5 Side region lateral groove 6 lateral directions of the side portions block E tire equatorial plane w ₂ uniform circumferential main groove width w ₃ of uniform transverse grooves width e ₂ groove width w ₂ parts of the block 4 longitudinal edges e ₃ groove width w ₃ portion of the block 4 L ₂ groove width w ₂ parts vertical edge length L ₃ of the block 4 groove width w ₃ portion of the block 4 of the lateral length L _3R groove bottom ridge end rim length between D ₃ lateral groove depth P groove bottom ridge Part vertex t Groove bottom ridge top height TW Tread development width CR Tread center area SR Tread both sides area

Claims (9)

[Claims] 1. A plurality of circumferential main grooves extending along the circumference of the tread in a central area excluding both sides of the tread tread;
A plurality of lateral grooves extending between adjacent circumferential main grooves and having a plurality of lateral grooves opening to each main groove, and a plurality of blocks along the circumference of the tread surface by the plurality of circumferential main grooves and the number of lateral grooves. In a heavy-duty pneumatic radial tire having a block pattern defining a row, each lateral groove has a groove width portion in which a distance between lateral edges of adjacent blocks in a block row is uniform, and each lateral groove has a width. A groove bottom ridge extending across the groove bottom at an intermediate position of the block lateral edge length in the uniform groove width portion, and each circumferential main groove has a uniform groove width with the vertical edge of each block in the block row. Forming a land portion having longitudinal edges opposed to each other below the base portion, wherein each circumferential main groove has a groove bottom ridge extending across the groove bottom at an intermediate position of the longitudinal edge length of the land portion, The raised portion has a curved surface that is convex in the direction in which the groove extends toward the tread surface. For both heavy and heavy loads, both wall surfaces of the lateral groove and the circumferential main groove toward the groove bottom protruding portion increase the degree of convex protrusion from the tread surface to the protruding portion and smoothly connect to the groove bottom protruding portion. Pneumatic radial tire. 2. The tire according to claim 1, wherein 50% or more of the entire horizontal edge length and the entire vertical edge length of each block are the horizontal edge and the vertical edge of the block related to the formation of the groove bottom protrusion. 3. The value of the ratio of the groove width to the groove depth of the lateral groove and the circumferential main groove located on both sides of the groove bottom protrusion is 0.9 to 0.9.
The tire according to claim 1 or 2, wherein the angle is within a range of 0.2 and the inclination angle of both wall surfaces of the grooves is within a range of 12 to 0 °. 4. The length of the groove bottom ridge measured in the direction in which the groove extends is within a range of 20 to 50% of each of the lateral edge length and the vertical edge length involved in the formation of the ridge. Tire described in. 5. The maximum height of the ridge measured from the groove bottom on both sides of the groove bottom ridge is 10 to 40 of the groove depth on both sides of the groove bottom ridge.
The tire according to any one of claims 1 to 4, which is in the range of%. 6. The projecting surfaces of both wall surfaces of the lateral groove and the circumferential main groove in which the groove bottom protrusion is located have a smooth curved surface that gradually increases the degree of projecting from the tread surface toward the groove bottom. Tires described in 1 to 5. 7. The projecting protrusions on both wall surfaces of the lateral groove and the circumferential main groove where the groove bottom ridge is located have a smooth curved surface and a plurality of cuts in the direction in which the groove extends from the curved surface. The tire according to any one of claims 1 to 5, further comprising slits, wherein the slits have bottom portions on the same wall surfaces as both side walls of the groove located on both sides of the groove bottom protrusion. 8. The protruding protrusion of both wall surfaces of the lateral groove and the circumferential main groove in which the groove bottom protruding portion is located increases stepwise from the tread surface toward the groove bottom to increase the degree of protruding protrusion.
5. The tire described in 5. 9. The convex protrusion of both wall surfaces of the lateral groove and the circumferential main groove in which the groove bottom protrusion is located increases the degree of convex protrusion while alternately repeating the convex shape and the concave shape from the tread surface toward the groove bottom. The tire according to claim 1.