JP5150077B2 - Pneumatic radial tire for light truck - Google Patents

Description

  The present invention relates to a pneumatic radial tire for a small truck mounted on a small truck.

  Pneumatic radial tires for small trucks are strongly desired to ensure both the wear resistance and fuel efficiency required for pneumatic tires for trucks and buses and the high speed durability required for pneumatic tires for passenger cars. ing. Various research and development have been conducted on pneumatic radial tires for small trucks to ensure wear resistance and the like, and as a prior art of pneumatic radial tires for small trucks that ensure abrasion resistance, etc., patent literature There is one shown in 1.

  That is, the pneumatic radial tire for a small truck according to the prior art includes a pair of bead portions, and each bead portion has a bead core. Further, a single carcass layer is provided between the pair of bead cores so as to extend in a toroidal shape, and this carcass layer is formed by coating a plurality of steel cords with rubber.

  A belt layer is provided on the outer side in the tire radial direction of the crown region of the carcass layer, and the belt layer is formed by rubber coating a plurality of steel cords. Further, a belt reinforcing layer is provided on the outer side in the tire radial direction of the belt layer, and this belt reinforcing layer is formed by spirally winding a ribbon-shaped strip material coated with an organic fiber cord in the tire circumferential direction. It is. A tread portion is provided outside the belt reinforcing layer in the tire radial direction, and a plurality of main grooves extending in the tire circumferential direction are formed on the surface of the tread portion.

  Therefore, according to the pneumatic radial tire for small trucks according to the prior art, since the carcass layer is formed by coating a plurality of steel cords with rubber, the number of carcass layers and belt layers can be increased, The change in the diameter growth of the pneumatic radial tire for small trucks can be suppressed without increasing the cord diameter. Therefore, an increase in rolling resistance due to the weight increase of the pneumatic radial tire for a small truck can be suppressed, and wear resistance can be ensured while ensuring low fuel consumption.

In addition, since a belt reinforcing layer is formed by spirally winding a ribbon-shaped strip material in the tire circumferential direction on the outer side of the belt layer in the tire radial direction, the belt layer can be prevented from being lifted by centrifugal force during high-speed running. High speed durability can be ensured.
JP 2001-26204 A

  By the way, in the pneumatic radial tire for small trucks according to the prior art, in order to further improve the wear resistance and extend the life of the tire, the tread gauge (thickness of the tread part) is increased and the rigidity of the tread part is sufficiently increased. Need to be increased. On the other hand, if the tread gauge is thick, the heat inside the tire cannot be efficiently dissipated during high-speed driving, impairing high-speed durability, and increasing the weight of pneumatic radial tires for small trucks, thus inhibiting fuel efficiency. Is done. That is, the pneumatic radial tire for small trucks according to the prior art has a problem that it is extremely difficult to maintain high-speed durability and low fuel consumption while further improving wear resistance.

  In the case of pneumatic radial tires for small trucks, correction (retreading) is usually performed in order to further extend the life of the tires. However, pneumatic radial tires for small trucks according to the prior art are corrected. I do not consider that.

  Therefore, in order to solve the above-mentioned problems, the present invention can sufficiently increase the rigidity of the tread portion, suppress an increase in rolling resistance due to weight, and efficiently dissipate heat inside the tire during high-speed running. Another object of the present invention is to provide a pneumatic radial tire for a small truck having a novel configuration that does not damage the belt reinforcing layer by buffing during correction.

  A first feature of the present invention (a feature of the invention described in claim 1) is a pair of bead portions each having a bead core, and a plurality of bead cores provided so as to extend in a toroid shape between the pair of bead cores. At least one carcass layer formed by rubber-coating a steel cord; and at least two belt layers provided on the outer side in the tire radial direction of the crown region of the carcass layer and formed by rubber-coating a plurality of steel cords; A belt reinforcing layer provided on the outer side in the tire radial direction of the belt layer and spirally wound in the tire circumferential direction with a ribbon-like strip material coated with an organic fiber cord, and provided on the outer side in the tire radial direction of the belt reinforcing layer A pneumatic radial tire for a small truck having a tread portion having a plurality of main grooves formed on a surface thereof and extending in a tire circumferential direction. The distance between the imaginary curve passing through the bottom of the main groove near the edge of the belt portion and parallel to the surface of the tread portion and the belt reinforcing layer is within the same region in the tire width direction as the outer belt layer. 3 to 6 mm.

  The first feature described above is based on two new findings obtained as a result of repeating various tests on a pneumatic radial tire for a small truck. Here, the first novel finding is that when the distance between the virtual curve and the belt reinforcing layer exceeds 6 mm in the same tire width direction region as the outer belt layer, the groove bottom of the main groove. The gauge (thickness of the groove bottom) becomes too thick, which increases the rolling resistance due to the weight of the pneumatic radial tire for small trucks and makes it difficult to efficiently dissipate the heat inside the tire during high speed running. Is. The second new finding is that if the distance between the virtual curve and the belt reinforcing layer is less than 3 mm in the same tire width direction region as the outer belt layer, the rigidity of the tread portion is reduced. It is difficult to raise the belt sufficiently, and the belt reinforcing layer may be damaged by the buff during correction.

  According to the first feature, since the carcass layer is formed by rubber coating a plurality of the steel cords, the number of the carcass layer and the belt layer is increased, or the cord diameter of the steel cord is increased. The change of the diameter growth of the pneumatic radial tire for small trucks can be suppressed without doing so. Further, since the belt reinforcing layer formed by spirally winding a ribbon-shaped strip material in the tire circumferential direction is provided on the outer side in the tire radial direction of the belt layer, the belt layer is lifted by centrifugal force during high-speed running. Can be suppressed.

  And since the distance between the virtual curve and the belt reinforcing layer is 3 to 6 mm within the same tire width direction region as the outer belt layer, the rigidity of the tread portion is sufficiently increased and the small truck is used. While suppressing the increase in rolling resistance due to the weight of the pneumatic radial tire, it is possible to efficiently dissipate the heat inside the tire during high speed running. For the same reason, the belt reinforcing layer is not damaged by the buffing at the time of correction.

  A second feature of the present invention (a feature of the invention described in claim 2) is that, in addition to the first feature, a tire circumferential direction is formed by an edge of the tread portion and the main groove near the edge of the tread portion The gist is that the ribs extending to the right are partitioned.

  According to the invention described in claim 1 or claim 2, while sufficiently increasing the rigidity of the tread portion, it is possible to suppress an increase in rolling resistance due to the weight of the pneumatic radial tire for a small truck, and at the time of high-speed running Since the internal heat can be efficiently radiated, the pneumatic radial tire for small trucks can maintain high-speed durability and low fuel consumption while further improving wear resistance. .

  Further, since the belt reinforcing layer is not damaged by buffing at the time of correction, the pneumatic radial tire for a small truck with the worn tread portion can be reliably reused as the correction tire, and the tire life is further extended. Can do.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  Here, FIG. 1 is a view showing a main part of a pneumatic radial tire for a small truck according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the pneumatic radial tire for a small truck according to an embodiment of the present invention. FIG. 3 is a partial perspective view showing one carcass layer and two belt layers.

  As shown in FIGS. 2 and 3, the pneumatic radial tire 1 for a small truck according to the embodiment of the present invention is assembled to a rim (not shown) and includes a pair of bead portions 3. Yes. Each bead portion 3 includes a bead core 5 and a bead filler 7 disposed outside the bead core 5 in the tire radial direction R.

  Between the pair of bead cores 5, a single carcass layer 9 is provided so as to extend in a toroidal shape, and both ends of the carcass layer 9 are tires around the corresponding bead cores 5 from the inner side in the tire width direction W. They are moored so as to be folded outward in the width direction W. The carcass layer 9 is formed by rubber coating a plurality of steel cords 11, and the plurality of steel cords 11 extend in the radial direction. Note that the cord tension per steel cord 11 is 140 kgf or more.

  Two belt layers 13 and 15 are provided on the outer side in the tire radial direction R of the crown region of the carcass layer 9, and the belt layers 13 and 15 are formed by rubber coating a plurality of steel cords 17. Therefore, the belt width of the inner belt layer 13 is larger than the belt width of the outer belt layer 15. Note that the cord tension per one steel cord 17 is 200 kgf or more.

  Here, the plurality of steel cords 17 in the inner belt layer 13 and the plurality of steel cords 17 in the outer belt layer 15 extend in a direction crossing each other, and a plurality of steel cords 17 in the two belt layers 13 and 15 are formed. A network structure is formed by the steel cords 17 and the plurality of steel cords 11 in the carcass layer 9.

  A first belt reinforcing layer 19 is provided on the outer side in the tire radial direction R of the belt layers 13 and 15, and second belt reinforcing layers 21 are provided on both ends of the first belt reinforcing layer 19, respectively. Yes. The first belt reinforcing layer 19 and the second belt reinforcing layer 21 are formed by spirally winding a ribbon-like strip material in which a nylon cord (an example of an organic fiber cord) 23 is covered with rubber in the tire circumferential direction C. is there. The ribbon-shaped strip material may be spirally wound at intervals in the tire circumferential direction C.

  Here, the end portions of the first belt reinforcing layer 19 and the second belt reinforcing layer 21 are located between the end portion of the inner belt layer 13 and the end portion of the outer belt layer 15. The width of the first belt reinforcement layer 19 is equal to or less than the width of the outer belt layer + 5 mm, and the width of the second belt reinforcement layer 21 is equal to or greater than 25 mm.

  A tread portion 25 is provided on the outer side in the tire radial direction R of the first belt reinforcing layer 19 and the second belt reinforcing layer 21, and the tread gauge (thickness of the tread portion 25) is 14 to 18 mm at a predetermined position. ing. The predetermined position refers to a position separated from the edge of the outer belt layer 13 inward in the tire width direction W by only 5% of the belt width of the outer belt layer 13.

  A rib 29 extending in the tire circumferential direction C is defined by an end edge (tread end edge) of the tread portion 25 and a main groove 27 close to the end edge of the tread portion 25, in other words, a shoulder region of the tread portion 25. A rib 29 extending in the tire circumferential direction C is formed. Thereby, the rigidity of the shoulder area | region of the tread part 25 can fully be raised, and the deterioration of uneven wear resistance can be prevented.

  As shown in FIGS. 1 and 2, an imaginary curve VC passing through the bottom of the main groove 27 near the edge of the tread portion 25 and parallel to the surface of the tread portion 25, and a belt reinforcing layer (first belt reinforcing layer 19 The distance from the second belt reinforcing layer 21) is 3 to 6 mm in the same region in the tire width direction W as the outer belt layer 13.

  The above-described configuration is based on two new findings obtained by repeating various tests (abrasion test, high-speed drum endurance test, and correctability determination test) on the pneumatic radial tire 1 for light trucks. It is. Here, the first new finding is that the distance between the virtual curve VC and the belt reinforcement layer (the first belt reinforcement layer 19 and the second belt reinforcement layer 21) is the same as the outer belt layer 15 in the tire width direction W. If it exceeds 6 mm in the region, the groove bottom gauge (groove bottom thickness) of the main groove 27 becomes too thick, which causes an increase in rolling resistance due to the weight of the pneumatic radial tire 1 for small trucks and high speed running. Sometimes it becomes difficult to efficiently dissipate the heat inside the tire. The second new finding is that if the distance between the virtual curve VC and the belt reinforcing layers 19 and 21 is less than 3 mm in the same region in the tire width direction W as the outer belt layer 15, the tread portion 25. It is difficult to sufficiently increase the rigidity of the belt, and the belt reinforcing layers 19 and 21 may be damaged by the buff during correction.

  A pair of side regions on the outer side surface of the carcass layer 9 is provided with side wall portions 31, and an inner liner 33 is provided on the inner side surface of the carcass layer 9.

  Next, the operation and effect of the embodiment of the present invention will be described.

  Since the carcass layer 9 is formed by coating a plurality of steel cords 11 with rubber, the number of the carcass layer 9 and the belt layers 13 and 15 is increased, or the diameters of the steel cords 11 and 17 are increased. Without changing, the change in the diameter growth of the pneumatic radial tire 1 for a small truck can be suppressed. Further, since the first belt reinforcing layer 19 and the second belt reinforcing layer 21 formed by spirally winding a ribbon-shaped strip material in the tire circumferential direction C are provided outside the tire radial direction R of the belt layers 13 and 15, It is possible to suppress the belt layers 13 and 15 from being lifted by centrifugal force during high-speed traveling.

  Since the distance between the virtual curve VC and the belt reinforcing layers 19 and 21 is 3 to 6 mm within the same region in the tire width direction W as that of the outer belt layer 15, the rigidity of the tread portion 25 is sufficiently increased and the size is reduced. The increase in rolling resistance due to the weight of the pneumatic radial tire 1 for trucks can be suppressed, and the heat inside the tire can be efficiently radiated during high speed running. For the same reason, the belt reinforcing layers 19 and 21 are not damaged by the buffing at the time of correction.

  As described above, according to the embodiment of the present invention, while increasing the rigidity of the tread portion 25 sufficiently, the increase in rolling resistance due to the weight of the small truck pneumatic radial tire 1 is suppressed, and the inside of the tire is increased during high-speed running. Since heat can be efficiently radiated, the pneumatic radial tire 1 for small trucks can maintain high-speed durability and low fuel consumption while further improving wear resistance.

  In addition, since the first belt reinforcing layer 19 and the second belt reinforcing layer 21 are not damaged by the buffing at the time of correction, the pneumatic radial tire 1 for a small truck with a worn tread portion 25 is reliably reused as the correction tire. And the tire life can be further extended.

  The present invention is not limited to the above description of the embodiments of the present invention, and can be implemented in various other modes. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

  Pneumatic radial tire for small trucks according to the embodiment (when the distance between the virtual curve and the belt reinforcing layer is 3.5 mm and the tread gauge is 16 mm) as an invention, the pneumatic radial for small trucks according to Comparative Example 1 A pneumatic radial tire for a small truck according to Comparative Example 2 (when the distance between the virtual curve and the belt layer is 4.0 mm and the tread gauge is 15 mm) is a comparative product 1 (control product) (virtual curve and belt) A pneumatic radial tire for small trucks according to Comparative Example 3 (in which the distance between the virtual curve and the belt reinforcing layer is 7.0 mm) when the distance from the reinforcing layer is 2.5 mm and the tread gauge is 15 mm) as a comparative product 2 In the case where the tread gauge is 19.5 mm), a comparative product 3 was manufactured as a prototype under a tire size of 205 / 85R16. Then, the following wear test, high-speed drum durability test, and correctability determination test are performed on the invention product, comparative product 1 to comparative product 3, respectively.

  Here, the pneumatic radial tire for a small truck according to the example has the same configuration as the pneumatic radial tire 1 for a small truck according to an embodiment of the present invention. The pneumatic radial tire for a small truck according to Comparative Example 1 is different from the pneumatic radial tire for a small truck 1 according to the embodiment of the present invention in that the belt reinforcing layers 19 and 21 are omitted, and the belt layer is It has 3 layers. Further, the pneumatic radial tire for small trucks according to Comparative Example 2 and Comparative Example 3 is different from the radial radial tire for small truck 1 according to the embodiment of the present invention except that the distance between the virtual curve and the belt layer is different. It has the same configuration.

(i) Abrasion test Inventive product, comparative product 1 to comparative product 3 are assembled on a 5.5 J rim and filled with 600 KPa of air and mounted on a vehicle (3-ton truck). Then, after traveling a travel distance of 50000 km at a speed of about 60 km / h, the average value of the wear amount of the tread portion is calculated by measuring the depth of the remaining groove, and the wear test results are summarized as shown in Table 1 below. become. In addition, the average value of the wear amount of the tread portion in the comparative product 1 (control product) is 100, and the wear resistance of the invention product, the comparative product 1 to the comparative product 3 is displayed as an index, and the wear resistance index is A larger value indicates better wear resistance.

(ii) High-speed drum endurance test The invention, comparative product 1 to comparative product 3 were assembled on a 5.5J rim and filled with 600 KPa air, and a high-speed drum test was conducted in accordance with JIS. The drum speed is obtained and the high-speed drum test results are summarized as shown in Table 1 below. The speed at the time of failure of the comparative product 1 (control product) is 100, and the high-speed durability of the invention product, comparative product 1 to comparative product 3 is displayed as an index. It shows that the property is good.

(iii) Correctability judgment test If the worn tread part of the invention, comparative product 1 to comparative product 3 is buffed and the belt reinforcing layer or the belt layer is damaged, it is determined that the correction cannot be made and the belt is reinforced. When the layer and the belt layer are not damaged, it is determined that the correction can be performed, and the correction determination test results are summarized as shown in Table 1 below.

  In other words, as shown in Table 1, the invention product has higher wear resistance than the comparative product 1 (control product) and the comparative product 2 and also has higher durability than the comparative product 1 and the comparative product 3. The improvement was confirmed. Moreover, it was determined that the inventive product can be corrected in the same manner as the comparative product 1 and the comparative product 3.

It is a figure which shows the principal part of the pneumatic radial tire for small trucks concerning embodiment of this invention. 1 is a cross-sectional view of a pneumatic radial tire for a small truck according to an embodiment of the present invention. FIG. 5 is a partial perspective view showing one carcass layer and two belt layers.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic radial tire for light trucks 3 Bead part 5 Bead core 9 Carcass layer 11 Steel cord 13 Belt layer 15 Belt layer 17 Steel cord 19 1st belt reinforcement layer 21 2nd belt reinforcement layer 23 Nylon cord 25 Tread part 27 Main groove 29 rib

Claims (2)

A pair of bead portions each having a bead core; at least one carcass layer provided between the pair of bead cores so as to extend in a toroidal shape and having a plurality of steel cords covered with rubber; and At least two belt layers provided on the outer side in the tire radial direction of the crown region and rubber-coated with a plurality of steel cords, and a ribbon provided on the outer side in the tire radial direction of the belt layers and covered with an organic fiber cord Reinforcement layer formed by spirally winding a strip-shaped strip material in the tire circumferential direction, and a tread provided on the outer surface in the tire radial direction of the belt reinforcement layer and having a plurality of main grooves extending in the tire circumferential direction on the surface In a pneumatic radial tire for a small truck provided with a portion,
The belt reinforcement layer includes a first belt reinforcement layer disposed on the outer side in the tire radial direction of the belt layer, and an outer side in the tire radial direction of the first belt reinforcement layer, the tread width direction of the first belt reinforcement layer A pair of second belt reinforcing layers disposed at both ends of the
The first belt reinforcing layer is provided across the pair of second belt reinforcing layers,
An area in the tire width direction in which the distance between the imaginary curve passing through the bottom of the main groove near the edge of the tread portion and parallel to the surface of the tread portion and the belt reinforcing layer is the same as that of the outer belt layer A pneumatic radial tire for small trucks, characterized by being 3 to 6 mm inside. The pneumatic radial tire for a small truck according to claim 1 , wherein a rib extending in a tire circumferential direction is defined by an edge of the tread portion and the main groove close to the edge of the tread portion.

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