WO2008010379A1

WO2008010379A1 - Pneumatic tire for heavy load

Info

Publication number: WO2008010379A1
Application number: PCT/JP2007/062437
Authority: WO
Inventors: Kazutaka Matsuzawa
Original assignee: Bridgestone Corporation
Priority date: 2006-07-19
Filing date: 2007-06-20
Publication date: 2008-01-24
Also published as: JP2008024104A

Abstract

A tire which can be used without losing durability and partial abrasion resistance until the tread abrades thoroughly by making radial growth of a pneumatic tire for heavy load uniform in the tire width direction. Second and third adjoining belt layers (12, 13) out of first through fourth belt layers (11-14) arranged sequentially from radial inside toward outside of the tire are layers having relatively small belt angles with respect to the equatorial plane of the tire (CL) and crossing in the reverse directions with respect to the equatorial plane of the tire (CL). The third crossing belt layer (13) is divided in the tire width direction and constituted of a center portion side inner belt layer piece (13A) and a shoulder portion side outer belt layer piece (13B). The dividing position is located on the inside of a main groove (9) on the outermost side in the tire width direction, and radial growth of the shoulder portion is suppressed by enhancing radial growth suppression effect of the outer belt layer piece (13B), thus making radial growth uniform in the tire width direction.

Description

Specification

Heavy duty pneumatic tire

Technical field

TECHNICAL FIELD [0001] The present invention relates to a pneumatic tire used in a heavy load region such as a truck or a bus, for example, and more particularly makes the tire diameter growth more uniform in the tire width direction during internal pressure filling or running. The present invention relates to a heavy duty pneumatic tire.

Background art

[0002] Pneumatic tires for heavy loads are generally subjected to a large load when the vehicle is running, etc., and therefore, three or more belt layers are arranged on the outer peripheral side of the carcass layer of the tread portion to provide a sufficient tread portion. In addition to ensuring rigidity, a high tagging effect is exhibited.

FIG. 3 is a half sectional view in the tire width direction schematically showing a belt layer of such a conventional heavy duty pneumatic tire, although it is not described in the patent literature.

[0003] As shown in the figure, the pneumatic tire 60 includes a first belt layer 11, a second belt layer 12, a third belt layer 13, and a tread portion 8 in order from the inner side to the outer side in the tire radial direction. And a fourth belt layer 14. Each of these belt layers: :! To 14 are sequentially arranged adjacent to each other between the carcass layer of the tread portion 8 and the tread rubber, and a plurality of cords such as metal cords such as steel and organic fiber cords are disposed in the inside thereof. Of parallel reinforcing elements. The reinforcing elements of each of the belt layers 11 to 14 are arranged so as to be inclined at a predetermined angle with respect to the tire equatorial plane CL (tire circumferential direction). The inclination angle of the reinforcing element is called the belt angle of the belt layer.

[0004] In this tire 60, the belt angle of the second and third belt layers 12, 13 with respect to the tire equatorial plane CL is relatively small (for example, 25 degrees or less), and in opposite directions to the tire equatorial plane CL. Forming. That is, the second and third belt layers 12 and 13 are crossing layers in which the reinforcing elements cross in opposite directions, and the tension in the same direction increases the rigidity against deformation in the tire circumferential direction (hereinafter referred to as circumferential rigidity). The main function is to suppress the growth of the tire outer diameter. In the tire 60, the belt angle of the first belt layer 11 is set in the same direction as the belt angle of the second belt layer 12 adjacent to the outer peripheral side with respect to the tire equatorial plane CL, and a larger angle. The belt angle of the fourth belt layer 14 is set in the same direction as the belt angle of the third belt layer 13 adjacent to the inner circumferential side with respect to the tire equatorial plane CL and substantially the same. It is formed at a certain angle.

[0005] Here, in general, in a pneumatic tire, if the growth of the outer diameter of the tire at the time of internal pressure filling or running is not uniform in the tire width direction, the contact shape at the time of rolling on the road surface may deteriorate. The contact pressure becomes uneven in the tire width direction, and uneven wear tends to occur in the tread portion. At the same time, there is a risk that durability at the location where the diameter growth is large will increase and the durability may decrease. Therefore, the diameter growth will start from the center portion (center side in the tire width direction) to the shoulder portion (on both ends in the tire width direction). It is desirable that it is uniform.

[0006] However, in the conventional heavy-duty pneumatic tire 60 provided with such a crossing layer, the diameter growth amount of the shoulder portion tends to be larger than that of the center portion. That is, in the tire 60, during vulcanization, which is a part of the manufacturing process, the tension in the circumferential direction of the tire acts on the belt layer, whereby the belt layer in the center portion is stretched in the circumferential direction of the tire, and the tire width direction The belt angle with respect to the tire equatorial plane CL becomes smaller. On the other hand, in the shoulder portion, the tension in the tire circumferential direction is smaller than the center portion, and as the center portion shrinks in the tire width direction, it is pulled inward in the tire width direction. The belt angle becomes larger compared to the center part with less.

[0007] Further, during vulcanization, a mold (die) bone is pushed into the tread portion 8 to form a main groove or the like extending in the tire circumferential direction, but the outermost tire width side (shoulder portion side) is formed. In the vicinity of the outer main groove 9, the tread rubber is pushed by the bone of the mold and moves greatly in the tire width direction and the tire radial direction. Due to the rubber flow during vulcanization, the belt layer in the vicinity of the outermost main groove 9 is pulled in the tire width direction and pushed toward the center in the tire radial direction. The change in the belt angle is the smallest, and in some cases, the belt angle relative to the tire equatorial plane CL may be larger than before partial vulcanization.

[0008] As described above, the belt angle of the shoulder portion with respect to the tire equatorial plane CL tends to be larger than the benolet angle of the center portion, and accordingly, the shoulder portion (especially near the outermost main groove 9). ), The circumferential rigidity of the above-mentioned crossing layer, that is, the effect of suppressing the radial growth is also lowered. As a result, in this tire 60, the diameter growth amount of the shoulder portion tends to be larger than that of the center portion. Since there is a tendency for the diameter growth to become non-uniform in the tire width direction, there is a risk that uneven wear resistance and durability will be reduced.

[0009] In order to cope with such problems, conventionally, a pneumatic tire has been proposed in which a part of a plurality of belt layers is divided in the tire width direction to achieve uniform diameter growth. (See Patent Document 1).

FIG. 4 is a developed plan view schematically showing a part of the structure of the tread portion of the conventional pneumatic tire.

As shown, the pneumatic tire 100 includes a first belt between a carcass layer (not shown) of the tread portion 101 and a tread rubber (not shown) in order from the inner side to the outer side in the tire radial direction. Layer 102, second belt layer 103, full band layer 104, and split band layer 105

[0011] The first and second belt layers 102 and 103 are crossing layers in which the belt angle crosses in the opposite direction to the tire equatorial plane CL and at the same angle. Here, the first belt layer 102 Is divided in the tire width direction around the tire equatorial plane CL, and is formed by two split belt layer pieces 102A. In contrast, the full band layer 104 has a reinforcing element 104A inclined at a smaller angle with respect to the tire equatorial plane CL, and covers the first and second belt layers 102 and 103 from the outer side in the tire radial direction. Are arranged as follows. Further, the split band layer 105 has the reinforcing element 105A inclined in the opposite direction to the reinforcing element 104A of the full band layer 104 and at the same angle with respect to the tire equatorial plane CL, and on the tire equatorial plane CL. The center band layer 105B is divided into two shoulder band layers 105C arranged near both ends in the tire width direction.

[0012] According to this pneumatic tire 100, since the first belt layer 102 is divided on the tire equatorial plane CL, the circumferential rigidity of the center portion of the belt layer can be lowered, and the radial growth suppression effect in the vicinity thereof can be further improved. The power to make it smaller is S. Further, the shoulder band layer 105C improves the circumferential rigidity of the shoulder portion, so that the diameter growth in the vicinity thereof can also be suppressed. As a result, in the tire 100, as compared with the pneumatic tire 60 described above, the diameter growth is made more uniform in the tire width direction, and uneven wear resistance and durability can be improved.

[0013] However, in this conventional pneumatic tire 100, the rigidity between the split belt layer pieces 102A is Since the center band layer 105B is disposed in the center portion in order to alleviate the step, the circumferential rigidity in the vicinity thereof is also increased. As for the distance between the split belt layer pieces 102A, etc., there are no provisions for optimizing the effect of suppressing the radial growth of the center part. There is a risk that the circumferential rigidity and diameter growth in the vicinity will become excessive and insufficient, resulting in unevenness.

[0014] In addition, in the tire 100, the effect of suppressing the belt angle of the belt portion of the shoulder portion from becoming large during vulcanization is low, and the circumferential rigidity of the shoulder portion of the crossing layer (radiation growth suppressing effect) is reduced. ) Is also low. Furthermore, although the shoulder band layer 105C increases the circumferential rigidity of the shoulder portion, the arrangement position thereof is not considered in relation to the crossing layer, the main groove, etc. There is also a possibility that the diameter growth near the groove 9 cannot be suppressed. As described above, in the conventional pneumatic tire 100, the effect of uniformizing the belt angle, the circumferential rigidity, and the diameter growth in the tire width direction is still not sufficient.

[0015] In particular, in recent years, the flattening force is increasing even in heavy-duty pneumatic tires. With this flattening, the width of the tire is widened, and the belt angle of the crossing layer in the shoulder portion with respect to the tire equatorial plane CL is also large. Tend to be. As a result, the tendency to reduce the effect of suppressing the diameter growth near the shoulder portion also appears more conspicuously.Therefore, the degree to which the diameter growth becomes uneven in the tire width direction is increased, causing the occurrence of uneven wear and the decrease in durability. Is also likely to occur. Therefore, in such a flat tire, it is necessary to surely suppress the effect of suppressing the radial growth from becoming nonuniform in the tire width direction and to make the radial growth more uniform.

Patent Document 1: Japanese Patent Laid-Open No. 4 154403

Disclosure of the invention

Problems to be solved by the invention

[0017] The present invention has been made in view of the above-described conventional problems, and the object thereof is to make the diameter growth of a heavy duty pneumatic tire more uniform in the tire width direction, and the tread is completely worn from the beginning. In other words, tires can be used without impairing durability and uneven wear resistance.

Means for solving the problem [0018] The invention of claim 1 includes at least three belt layers disposed on the outer circumferential side of the carcass layer of the tread portion, and a main groove disposed on the outer circumferential side of the belt layer and extending in the tire circumferential direction. A heavy-duty pneumatic tire provided with a tread rubber, wherein the belt layer is adjacent to the tire layer in the radial direction of the tire and the belt angle intersects with the tire equatorial plane in opposite directions. And at least one belt layer of the crossing layer is divided in the tire width direction on both sides of the tire equatorial plane, and all the dividing positions of the divided belt layer in the tire width direction are Of the main grooves, located on the inner side in the tire width direction of the outermost main grooves formed on the outermost side in the tire width direction, and the belt angle of the divided belt layer with respect to the tire equatorial plane is 25 degrees or less, the same of Within the divided belt layer, the belt angle of the belt layer piece located on the outer side in the tire width direction is smaller than the belt angle of the belt layer piece located on the inner side in the tire width direction with respect to the tire equatorial plane. It is characterized by that.

The invention according to claim 2 is the heavy duty pneumatic tire according to claim 1, wherein the belt angle of each belt layer piece located on each of the outer side and the inner side in the tire width direction in the same separated belt layer. The directions are opposite to each other with respect to the tire equatorial plane.

The invention according to claim 3 is the heavy duty pneumatic tire according to claim 1 or 2, wherein the distance in the tire width direction between the divided position of the divided belt layer and the tire equatorial plane is Of these, the width is the widest and the width of the widest belt layer is between 1/4 and 2/3 of the distance in the tire width direction between the outer edge in the tire width direction and the tire equatorial plane. The invention of claim 4 is the heavy-duty pneumatic tire according to any one of claims 1 to 3, wherein the narrowest belt layer having the narrowest width among the belt layer pieces of the divided belt layer. The width of the piece is 1/10 or more and 2Z3 or less of the distance in the tire width direction between the outer end in the tire width direction of the widest belt layer of the widest belt layer of the belt layers and the tire equatorial plane. To do.

The invention's effect

[0019] According to the present invention, the diameter growth of a heavy-duty pneumatic tire can be made more uniform in the tire width direction, and the durability and uneven wear resistance are deteriorated from when it is new to when the tread is completely worn out. Na Tires can be used without tingling.

Brief Description of Drawings

FIG. 1 is a half sectional view in the tire width direction schematically showing a belt layer of a heavy duty pneumatic tire of the present embodiment.

FIG. 2 is a half sectional view in the tire width direction schematically showing a belt layer of a heavy duty pneumatic tire of another embodiment.

FIG. 3 is a half sectional view in the tire width direction schematically showing a belt layer of a conventional heavy duty pneumatic tire.

FIG. 4 is a developed plan view schematically showing a part of the structure of a tread portion of a conventional pneumatic tire.

Explanation of symbols

[0021] 1 ... Pneumatic tire for heavy load, 4 ... Pneumatic tire for heavy load, 8 ... Tread part, 9 ... Outermost main groove, 11 '' '1st belt layer, 12 ··· 2nd belt layer, 13 ··· 3rd belt layer, 13Α · 'Inner belt layer piece, 13Β · · · Outer belt layer piece, 14 · · · 4th belt layer, 14Α · · · Noret layer piece, 14Β ·· 'Outer belt layer piece, CL- ·' Tire equatorial plane.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

The heavy-duty pneumatic tire of the present embodiment is a tire used in a heavy-load region such as a bus or a truck, for example, and has a radial structure carcass layer extending between a pair of bead cores in a toroidal shape, and a carcass in a tread portion. It has a known structure, for example, comprising at least three belt layers (such as three layers or four layers) disposed on the outer peripheral side of the layer and a tread rubber disposed on the outer peripheral side of the belt layer. A main groove extending in the tire circumferential direction is formed on the surface of the tread rubber.

FIG. 1 is a half cross-sectional view in the tire width direction schematically showing the belt layer of the heavy duty pneumatic tire of the present embodiment.

As shown in the figure, the pneumatic tire 1 includes a first belt layer 11, a second belt layer 12, a third belt layer 13, and a fourth belt layer in order from the inner side to the outer side in the tire radial direction. A belt layer with a four-layer structure consisting of a belt layer 14 is provided. Each of these belt layers: :! ~ 14 tread Between the carcass layer of part 8 and the tread rubber, they are sequentially arranged adjacent to each other, and there are a plurality of parallel reinforcing elements such as metal cords such as steel and organic fiber cords inside. .

[0024] In this tire 1, the second and third belt layers 12 and 13 adjacent in the tire radial direction are relatively small angles (here, 16 degrees) with a belt angle of 25 degrees or less with respect to the tire equatorial plane CL. In addition, the crossing layers cross in opposite directions with respect to the tire equatorial plane CL. Further, the first belt layer 11 is formed at a belt angle that is the same as the belt angle of the second belt layer 12 adjacent to the outer peripheral side and a larger angle (here, 50 degrees) with respect to the tire equatorial plane CL. The belt angle of the fourth belt layer 14 is the same as the belt angle of the third belt layer 13 adjacent to the inner circumferential side and the belt angle in the same direction with respect to the tire equatorial plane CL (16 degrees in this case). It is formed. Within each of these belt layers 11 to 14, the second belt layer 12 is the widest belt layer having the widest width (the width between the outer end portions in the tire width direction), and the fourth belt layer 14 on the outermost circumferential side. The first belt layer 11 and the third belt layer 13 having the narrowest width are formed to have a width that is approximately between the second belt layer 12 and the fourth belt layer 14.

[0025] In addition to the above, in this heavy-duty pneumatic tire 1, at least one belt layer (here, the third belt layer 13) constituting the crossing layer is divided in at least one place in the tire width direction. Yes. In the present embodiment, the third belt layer 13 is located at one location on each side of the tire equatorial plane CL (two locations in total), and the dividing position in the tire width direction is the outermost portion in the tire width direction (the shoulder portion). It is divided so that it is on the inner side in the tire width direction than the outermost main groove 9 formed on the side). Therefore, the third belt layer 13 includes an inner belt layer piece 13A located on the inner center side in the tire width direction and a pair located on both shoulder sides on the outer side in the tire width direction (in the figure, only one side is shown. E) outer belt layer piece 13B. These belt layer pieces 13A and 13B have the same belt angle direction with respect to the tire equatorial plane CL, and are divided so that the width of the outer belt layer piece 13B is narrower than that of the inner belt layer piece 13A. It is arranged at a predetermined interval in the direction.

[0026] Here, as described above, the crossing layer including the third belt layer 13 has high circumferential rigidity, and mainly exerts the tension in the same direction to exert the effect of suppressing the radial growth of the tire outer diameter. However, at the time of vulcanization, the belt angle relative to the tire equatorial plane CL of the shoulder is larger than that of the center There is a tendency that the diameter growth suppression effect becomes low. However, in the heavy-duty pneumatic tire 1 of the present embodiment, the third belt layer 13 constituting the crossing layer is divided at the inner side in the tire width direction from the outermost main groove 9 positioned on the shoulder side. The belt angle of the shoulder portion (outer belt layer piece 13B) can be suppressed from becoming larger than that of the center portion (inner belt layer piece 13A).

[0027] That is, in the tire 1, even if the inner belt layer piece 13A is deformed by the tension in the tire circumferential direction (the direction in which the belt angle is reduced) during vulcanization, the inner side in the tire width direction ( Tension force in the direction of increasing the beret angle) Since it does not act on the outer belt layer piece 13B, the difference in the change in belt angle between the belt layer pieces 13A and 13B during vulcanization can be further reduced. As a result, in this tire 1, the circumferential rigidity and the radial growth suppressing effect of the shoulder portion and the center portion of the crossing layer can be made more uniform than before, and the diameter growth of the shoulder portion at the time of internal pressure filling or the like is suppressed, and the center portion is suppressed. And the difference in the diameter growth amount can be further reduced. In addition, since the dividing position in the tire width direction is on the inner side in the tire width direction than the outermost main groove 9, it is possible to reliably suppress the radial growth particularly in the vicinity of the outermost main groove 9, which tends to increase the radial growth. be able to. As a result, the contact shape of the tire when rolling on the road surface can be improved, and the contact pressure can also be made more uniform in the tire width direction, thereby suppressing uneven wear in the tread portion 8. At the same time, since the distortion generated in the tread portion 8 can be reduced, the durability of the tire 1 can also be improved.

[0028] Therefore, in this heavy-duty pneumatic tire 1, the diameter growth of the tire 1 can be made more uniform in the tire width direction, and the durability and uneven wear resistance can be improved from when it is new to when the tread is completely worn out. Tire 1 can be used without loss.

[0029] Here, the distance in the tire width direction between the divided position of the divided third belt layer 13 and the tire equatorial plane CL is the widest belt layer (here, the widest belt layer) having the widest width among all belt layers. 2) The belt width in the tire width direction between the outer edge of the belt layer 12) and the tire equatorial plane CL, that is, the belt width from the tire equatorial plane CL (BW in the figure) is 1Z4 or more and 2Z3 or less. Is preferred. This is because the inner belt layer piece 13A becomes less rigid in the circumferential direction if the belt width BW is less than 1Z4 in the tire width direction at the dividing position. On the contrary, if it is larger than 2Z3, the dividing position will be the most In addition to increasing the possibility of exerting force near the outermost main groove 9 where the diameter growth amount increases, the width of the outer belt layer 13B becomes narrower, and sufficient circumferential rigidity is required to suppress the diameter growth of the shoulder portion. This is because there is a risk that sex cannot be obtained. Therefore, it is preferable that the belt layer 13 is divided outside the outermost main groove 9 as described above. As described above, the dividing position is preferably inside the outermost main groove 9.

[0030] The width of the narrowest belt layer piece (herein, the outer belt layer piece 13B) having the narrowest width among the belt layer pieces 13A and 13B in the divided third belt layer 13 (F in the figure) Force If the belt width from the tire equatorial plane CL of the widest belt layer (second belt layer 12) is smaller than lZlO of the belt width BW, the belt width of the outer belt layer piece 13B becomes narrower, and sufficient radial growth suppression effect is obtained. There is a fear that it cannot be used. On the other hand, if it is larger than 2/3, the belt width of the other belt layer piece (in this case, the inner beret layer piece 13A) becomes relatively narrow, and the effect of suppressing the diameter growth may not be sufficient. There is. Therefore, the width F of the narrowest belt layer piece is preferably within 1/10 to 2/3 of the belt width BW from the tire equatorial plane CL of the widest belt layer within this range. All of the divided belt layer pieces can exhibit sufficient rigidity as a belt layer constituting the crossing layer.

[0031] In the third belt layer 13, the belt angles of the belt layer pieces 13A and 13B may be different angles. In this case, the belt angle with respect to the tire equatorial plane CL of the outer belt layer piece 13B located on the outer side in the tire width direction in the same third belt layer 13 divided is set to the inner belt located on the inner side in the tire width direction. It is preferable to make it smaller than the belt angle of the layer piece 13A with respect to the tire equatorial plane CL. In this case, the effect of suppressing the radial growth of the shoulder portion of the crossing layer, which tends to decrease, can be maintained high, and the radial growth of the shoulder portion can be more reliably suppressed. At this time, it is effective and more preferable to make the belt angle of the outer belt layer piece 13B with respect to the tire equatorial plane CL 2 to 4 degrees smaller than that of the inner belt layer piece 13A.

[0032] Similarly, the belt angle direction of each of the belt layer pieces 13A and 13B located on the outer side and the inner side in the tire width direction in the same third belt layer 13 is divided into the tire equatorial plane CL. Here, for example, the inner belt layer piece 13A may be in the same direction with respect to the belt angle of the other second belt layer 12 constituting the crossing layer and the tire equatorial plane CL. The belt angle of the outer belt layer piece 13B may be crossed in the opposite direction to the belt angle of the second belt layer 12. In this case, the diameter growth restraining effect of the center portion that increases the diameter growth restraining effect of the shoulder portion can be lowered, and the diameter growth in the tire width direction can be achieved by optimizing the magnitude of the effect of each part. It becomes possible to achieve further uniformization. Since the inner belt layer piece 13A can be preset to the second belt layer 12 and the outer belt layer 13B can be preset to the fourth belt layer 14, respectively, before the green tire is molded, four times are required in the past. This process can improve the productivity of manufacturing tires because the belt can be attached only three times. If the belt angle of each of the belt layer pieces 13A and 13B is reversed from that described above, the diameter growth of the center portion can be suppressed.

[0033] In the present embodiment, one third belt layer 13 constituting the crossing layer is divided, but the other belt layer 12 may be divided in the tire width direction. , 13 can be divided together. As described above, the above-described effects can be more efficiently obtained when the crossing layer that mainly bears the circumferential tension and has a high diameter growth suppression effect is divided. However, since a belt layer having a belt angle of 25 degrees or less with respect to the tire equatorial plane CL can exert a radial growth suppressing effect while bearing a certain amount of circumferential tension, such other belt layer (here, the first belt layer) is used. The four belt layers 14) may be divided together with the division of the crossing layers (belt layers 12, 13). Therefore, in order to obtain the above effects, it is necessary to divide at least one of the belt layers (here, the crossing layers) whose belt angle with respect to the tire equatorial plane CL is 25 degrees or less.

[0034] Further, here, the third belt layer 13 is divided at one place on each side of the tire equatorial plane CL (two places in total). For example, the third belt layer 13 is divided into a total of three places and the belt layer is divided into four belt layer pieces. As long as all the dividing positions in the tire width direction are on the inner side in the tire width direction with respect to the outermost main groove 9, for example, it may be divided at two or more locations.

[0035] In the above embodiment, an example in which the third belt layer 13 is divided is shown. Next, another belt in which the fourth belt layer 14 is divided to make the diameter growth uniform in the tire width direction is shown. Embodiments will be described.

FIG. 2 is a half cross-sectional view in the tire width direction schematically showing the belt layer of this heavy duty pneumatic tire. As shown in the figure, the heavy-duty pneumatic tire 4 of the present embodiment is similar to the tire 1 described above in that the tread portion 8 and the first belt layer 11 and the crossing layer are sequentially formed from the inner side to the outer side in the tire radial direction. The second belt layer 12 and the third belt layer 13, the fourth belt layer 14, and a belt layer having a powerful four-layer structure. However, in this tire 4, in addition to not dividing the third belt layer 13, instead, the fourth belt layer 14 is formed wider and arranged to the shoulder side, and The tire 1 is different from the tire 1 in that it is divided on both sides of the tire equatorial plane CL so that the dividing position in the tire width direction is inside the outermost main groove 9 in the tire width direction.

In the present embodiment, in this way, the fourth belt layer 14 is divided, and the inner belt layer piece 14A positioned on the inner side in the tire width direction and the pair of outer belt layer pieces positioned on the outer side in the tire width direction. Consists of 14B. In addition, in this tire 4, the belt angles of the inner belt layer piece 14A and the outer belt layer piece 14B are formed in opposite directions and different angles with respect to the tire equatorial plane CL (here, the outer side of the inner belt layer piece 14A). The belt angle of the belt layer piece 14B with respect to the tire equatorial plane CL is reduced) and the belt angle of the outer belt layer piece 14B is set to the belt angle of the third belt layer 13 in the adjacent crossing layer and the tire equatorial plane. The outer side belt layer pieces 14B and the third belt layer 13 are crossed in the opposite direction to CL. The outer belt layer piece 14B is disposed on the inner side in the tire radial direction of the outermost main groove 9 formed on the shoulder portion side, and is formed wider than the groove width of the outermost main groove 9, and is It is arranged so as to cover the inner radial force of the tire over the entire width of the main groove 9.

Therefore, in the heavy-duty pneumatic tire 4 of the present embodiment, the effect of suppressing the radial growth of the shoulder portion can be enhanced, and the radial growth is effectively suppressed to change the radial growth in the tire width direction. Each effect similar to that of the tire 1 described above can be obtained, for example, the amount can be made uniform.

[0039] (Tire test)

In order to confirm the effect of the present invention, the tires of the two types of examples described above (hereinafter referred to as “exemplary products 1 and 2”) and the tires of the conventional examples (hereinafter referred to as “conventional products”) were produced, and A tire growth test was performed when the internal pressure was filled. These tires are all heavy-duty pneumatic radial tires with a tire size of 385 / 55R22.5 as defined by ETRTO (The European Time and Rim Technical Organization, 2006). [0040] First, the configuration of the belt layer of each tire will be described.

The conventional product is a tire including the belt layers 11 to 14 having the configuration described in FIG. 3 and is formed in a conventional belt layer structure in which the belt layer is not divided. In the conventional product, the second belt layer 12 and the third belt layer 13 are cross layers, and the respective belt angles are formed in the opposite direction and the same angle (16 degrees) with respect to the tire equatorial plane CL. Further, the first belt layer 11 is formed at a belt angle of 50 degrees in the same direction with respect to the belt angle of the second belt layer 12 adjacent to the outer peripheral side and the tire equatorial plane CL, and the fourth belt layer 14 is The belt angle was formed at the same angle (16 degrees) in the same direction with respect to the belt angle of the third benolet layer 13 adjacent to the inner peripheral side and the tire equatorial plane CL. The belt layers 11 to 14 of the products 1 and 2 are configured in substantially the same manner as the conventional product, and only different configurations will be described below.

[0041] The implemented product 1 is a tire including the belt layers 11 to 14 configured as described in FIG. 1, and the third belt layer 13 is divided in the tire width direction, and the divided third belt layer 13 is divided. The belt angle of each belt layer piece 13A, 13B was changed. The inner belt layer piece 13A has a belt angle of 16 degrees with respect to the tire equatorial plane CL, and the outer belt layer piece 13B has a belt angle with respect to the tire equatorial plane CL of 14 degrees, which is smaller.

[0042] The implemented product 2 is a tire including the belt layers 11 to 14 configured as described in FIG. 2, and the belt angles and directions of the belt layer pieces 14A and 14B of the divided fourth belt layer 14 are determined. Changed. The inner belt layer piece 14A forms a belt angle with respect to the tire equatorial plane CL at 16 degrees, and the outer belt layer piece 14B forms a belt angle with respect to the tire equatorial plane CL at a smaller 14 degrees. The equatorial plane CL was formed in directions opposite to each other. Further, the belt angle of the outer belt layer piece 14B was reversed with respect to the belt angle of the third belt layer 13 and the tire equatorial plane CL, and they were crossed with each other.

[0043] In the tire growth test, each of the above tires is mounted on a rim having a rim width of 11.75 inches, and the internal pressure is set to lOOkPa and 900 kPa. , Called perimeter). After the measurement, the difference in circumference between the internal pressure of 900 kPa and the internal pressure of lOOkPa is divided by the circumference of the internal pressure of lOOkPa, and the ratio is determined as the growth rate at the internal pressure in each part of the center and shoulder parts. By comparing these differences, the uniformity of tire growth in the tire width direction was evaluated. [0044] Table 1 shows the structural specifications and test results of the belt layer of each tire.

The direction of each belt layer in the table is indicated by R when the belt angle (reinforcing element) is rising to the right, and L when it is rising to the left, as seen from the outside in the tire radial direction. Belt angle with respect to plane CL. Each internal pressure growth rate and growth rate difference are expressed as percentages, and the smaller the growth rate difference, the higher the uniformity of diameter growth in the tire width direction.

[0045] [Table 1]

[0046] As shown in Table 1, with the conventional product, the growth rate difference between the center and shoulder is as large as 0.5%. The uniformity in the tire width direction of the diameter growth was becoming low. On the other hand, the growth rate differences between the implemented products 1 and 2 are all low, 0.1% and 0.2%, respectively. It can be seen that the uniformity in the tire width direction is improved. The diameter growth after running has a proportional relationship with the diameter growth at the time of internal pressure filling, and the results are the same as the above evaluation. It can be seen that uniformity can be maintained.

From the above results, according to the present invention, the diameter growth of the heavy-duty pneumatic tire can be made more uniform in the tire width direction, and the durability and uneven wear resistance are impaired from the time of new article to the complete wear of the tread. It has been proved that tires can be used without any problems.

Claims

The scope of the claims

[1] At least three belt layers disposed on the outer circumferential side of the carcass layer of the tread portion, and a tread rubber disposed on the outer circumferential side of the belt layer and having a main groove extending in the tire circumferential direction. A heavy duty pneumatic tire,

The belt layer includes an intersection layer composed of belt layers adjacent to each other in the tire radial direction and intersecting in opposite directions with respect to the tire equatorial plane.

At least one of the belt layers of the crossing layer is divided in the tire width direction on both sides of the tire equatorial plane, and all the dividing positions in the tire width direction of the divided belt layers are all of the main grooves. A belt angle with respect to the tire equatorial plane of the divided belt layer that is located on the inner side in the tire width direction with respect to the outermost main groove formed on the outermost side in the tire width direction is 25 degrees or less;

Within the same divided belt layer, the belt angle of the belt layer piece located on the outer side in the tire width direction with respect to the tire equatorial plane is set to be larger than the belt angle of the belt layer piece located on the inner side in the tire width direction with respect to the tire equatorial plane. A heavy duty pneumatic tire characterized by a small size.

[2] A heavy duty pneumatic tire as set forth in claim 1,

In the same divided belt layer, the belt angle direction of each belt layer piece located on the outer side and the inner side in the tire width direction is opposite to each other with respect to the tire equatorial plane. Heavy duty pneumatic tire.

[3] The heavy duty pneumatic tire according to claim 1 or 2,

The tire width direction distance between the divided position of the divided belt layer and the tire equatorial plane is the widest of the belt layers, the outer end in the tire width direction of the widest belt layer and the tire equatorial plane. A heavy-duty pneumatic tire characterized in that it is not less than 1/4 and not more than 2/3 of the distance in the width direction of the tire.

[4] The heavy duty pneumatic tire according to any one of claims 1 to 3, wherein the width force of the narrowest narrow belt layer piece among the belt layer pieces of the divided belt layer is the belt. It is characterized in that it is 1/10 or more and 2/3 or less of the distance in the tire width direction between the outer end in the tire width direction of the widest belt layer of the widest layer and the tire equatorial plane. Heavy duty pneumatic tire.