JP2007196740A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire with the low rolling resistance, which is capable of reducing the flat spot and reliably reducing the road noise. <P>SOLUTION: The pneumatic tire has a center part belt reinforcing layer 3 for covering only a center portion of a main belt and a shoulder part belt reinforcing layer 4 for covering only an end of the main belt on an outer side in the tire radial direction of the main belt 1. The center part belt reinforcing layer 3 and a shoulder part belt reinforcing layer 4a adjacent thereto overlap at least partly each other. An outer end P<SB>4</SB>in the tire width direction of the shoulder part belt reinforcing layer 4 is located outside in the tire width direction from an outer end P<SB>1</SB>in the tire width direction of the main belt 1. A single-twisted nylon 6, 6 cord is used for the center part belt reinforcing layer 3, and a double-twisted PEN cord is used for the shoulder part belt reinforcing layer 4, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having low road noise and rolling resistance and reduced flat spots.

  Along with the recent upgrades and quality of vehicles, especially in passenger cars, the reduction of vehicle vibration and the improvement of ride comfort are advancing rapidly, and tires are also required to have low noise and high ride comfort. It has been. In other words, it is desired to improve the riding comfort and reduce the noise generated inside the vehicle. As one of such noises, the running tire spreads the unevenness of the road surface and the vibration is transmitted to remove the air inside the vehicle. There has been a strong demand to reduce so-called road noise generated due to vibration. On the other hand, as vehicle fuel efficiency and pollution are advancing, there is a strong demand for low rolling resistance for tires.

  Various methods have been devised for reducing the road noise. One of them is a rubberized cord made of polyethylene-2,6-naphthalate, which is a high-rigidity fiber, and a cross belt layer (main belt). A method of suppressing the vibration of the belt portion by forming a belt reinforcing layer by spirally winding the upper portion of the belt) is known.

  However, if the cord that reinforces the center of the belt is made of fibers with excessively high rigidity, energy loss due to deformation that occurs in response to tire rolling increases, and when there is no belt reinforcement layer and when the low rigidity cord is used as a belt reinforcement layer It is known that the rolling resistance is increased as compared with the case used in the above. In addition, tires with a belt reinforcement layer, when the vehicle is parked and cooled naturally after high temperature running, the tires are shaped and the amount of flat spots increases, resulting in poor ride comfort. There is also a problem to do.

  In contrast, by disposing a highly rigid belt reinforcement layer only at the belt end and not providing a belt reinforcement layer at the center of the belt, it is possible to prevent the deterioration of rolling resistance as described above. Further, since the radius of curvature of the tire crown portion becomes excessively small, it leads to a decrease in uneven wear resistance and steering stability, and an important road noise reduction effect cannot be obtained sufficiently.

  As a method for simultaneously solving such problems, that is, a method capable of simultaneously reducing road noise and rolling resistance, a highly rigid belt reinforcement layer such as polyethylene-2,6-naphthalate is disposed at the belt end. A method has been developed in which a low-rigidity belt reinforcing layer such as nylon 6,6 is installed in the center of the belt (see Patent Documents 1 to 3).

JP 11-208212 A JP-A-2003-320813 JP 2004-224074 A

  However, when tires having a belt reinforcing layer having the above structure are produced in various sizes, in many cases, the belt is completely reinforced between the reinforcing layer at the belt end and the reinforcing layer at the belt center. There were some cases where there was no “gap” of 5 to 10 mm. In particular, in the process of expanding the raw tire during vulcanization and pressing it against the vulcanization mold, the stress generated in the belt reinforcing layer resisting expansion greatly differs between the belt end and the belt center. That is, since a highly rigid fiber is arranged in the reinforcing layer at the belt end, a large stress is generated during expansion, and as a result, the rubber around the fiber tends to flow during vulcanization, while the reinforcement at the center of the belt Since the low-rigidity fibers are arranged in the layer, the stress generated during expansion is relatively small, and the rubber does not flow and the arrangement is almost the same as that of the raw tire. As a result, such a “gap” is generated. It has been found that the tires produced in this manner have abnormally concentrated stress in the “gap” of the belt reinforcing layer during rolling, and as a result, the effect of reducing road noise cannot be obtained sufficiently.

  Accordingly, an object of the present invention is to solve the above-described problems of the prior art and provide a pneumatic tire in which road resistance is reliably reduced in addition to low rolling resistance and reduced flat spots. .

  As a result of intensive studies to achieve the above object, the present inventor used a single-strand polyhexamethylene adipamide (nylon 6, 6) cord as a reinforcing element of a belt reinforcing layer that reinforces the central portion of the belt. By using double-twisted polyethylene-2,6-naphthalate (PEN) cord as the reinforcement element of the belt reinforcement layer that reinforces the end, the tire road noise is optimized by optimizing the rigidity of the belt reinforcement layer in the tire circumferential direction. In addition, the belt reinforcement layer that reinforces the center of the belt and the belt reinforcement layer that reinforces the belt end overlap each other, thereby expanding the vulcanization process. Since there is no part that changes suddenly in the width direction distribution of the stress that sometimes occurs, and there is an overlapping part, as described above in the vulcanization process Nylon 6,6 cords with a single twist structure used as a reinforcing element for the belt reinforcement layer that reinforces the center of the belt can be reliably reduced as a result of the "gap" being reliably prevented. Rigidity is lower than the twisted nylon 6,6 cord, and the volume occupied by the crown structure of the tire is small. Therefore, the present inventors have found that the flat spot of the tire can be reduced and have completed the present invention.

That is, the pneumatic tire according to the present invention includes a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, and a carcass extending in a toroidal shape between the pair of bead portions. A main belt composed of at least two belt layers arranged on the outer side in the tire radial direction of the crown portion of the carcass, and arranged on the outer side in the tire radial direction of the main belt and arranged substantially parallel to the tire circumferential direction Comprising at least two belt reinforcing layers made of a rubberized layer of the reinforcing element,
The belt reinforcing layer comprises a pair of one or more center belt reinforcing layers covering only the central portion of the main belt and a pair of one or more shoulder belt reinforcing layers covering only the end portions of the main belt, The center portion belt reinforcing layer and the shoulder portion belt reinforcing layer adjacent to the center portion belt reinforcing layer are at least partially overlapped, and the outer end in the tire width direction of the shoulder portion belt reinforcing layer is the tire width of the main belt. It is located on the outer side in the tire width direction than the outer end in the direction,
The reinforcing element constituting the center belt reinforcing layer is a single twisted polyhexamethylene adipamide (nylon 6,6) cord, and the reinforcing element constituting the shoulder belt reinforcing layer is a double twisted polyethylene-2 , 6-Naphthalate (PEN) code.

  In a preferable example of the pneumatic tire of the present invention, the outer end in the tire width direction of the center portion belt reinforcing layer is the outer end in the tire width direction of the narrowest belt layer among the belt layers constituting the main belt. It is located on the inner side in the tire width direction than the portion. In this case, the road noise of the tire can be sufficiently reduced.

  In another preferred embodiment of the pneumatic tire of the present invention, the width of the overlapping portion between the center belt reinforcing layer and the shoulder belt reinforcing layer adjacent to the center belt reinforcing layer is 1 to 20 mm. In this case, it is possible to sufficiently prevent a gap from being generated between the center portion belt reinforcing layer and the shoulder portion belt reinforcing layer regardless of the section width of the tire.

  In another preferred embodiment of the pneumatic tire of the present invention, the total width of the belt reinforcing layer composed of the center belt reinforcing layer and the shoulder belt reinforcing layer is 2 to 10 mm than the total width of the main belt. wide. In this case, the road noise of the tire can be sufficiently reduced.

  In another preferred embodiment of the pneumatic tire of the present invention, the width of the shoulder portion belt reinforcing layer is 5 to 20% of the total width of the main belt. In this case, the road noise of the tire can be sufficiently reduced, and the rolling resistance is not deteriorated.

  In another preferred embodiment of the pneumatic tire of the present invention, the reinforcing element constituting the shoulder belt reinforcing layer twists two filament bundles of polyethylene-2,6-naphthalate (PEN) having a total fineness of 500 to 2000 dtex. It is a combined code. In this case, the road noise of the tire can be sufficiently reduced, and the occurrence of a separation failure between the tread and the shoulder belt reinforcing layer can be prevented.

In the pneumatic tire of the present invention, the polyethylene-2,6-naphthalate (PEN) cord constituting the shoulder belt reinforcing layer has the following formula (I):
R = N × (0.125 × D / ρ) ^1/2 × 10 ^-3 (I)
[Where N is the number of twists of the cord (times / 10 cm), D is the total number of decitex of the cord (dtex), and ρ is the specific gravity of the cord (g / cm ³ )] R is preferably 0.20 to 0.72. In this case, road noise of the tire can be sufficiently reduced while preventing the occurrence of a separation failure between the tread and the shoulder belt reinforcement layer.

  In another preferred embodiment of the pneumatic tire of the present invention, the reinforcing element constituting the center belt reinforcing layer is a filament bundle of polyhexamethylene adipamide (nylon 6, 6) having a total fineness of 500 to 2000 dtex. This is a cord that has been twisted. In this case, the rolling resistance and road noise of the tire can be sufficiently reduced, and the uneven wear resistance and steering stability of the tire can be prevented from being lowered.

In the pneumatic tire of the present invention, the polyhexamethylene adipamide (nylon 6, 6) cord constituting the center portion belt reinforcing layer has the following formula (I):
R = N × (0.125 × D / ρ) ^1/2 × 10 ^-3 (I)
[Where N is the number of twists of the cord (times / 10 cm), D is the total number of decitex of the cord (dtex), and ρ is the specific gravity of the cord (g / cm ³ )] R is preferably 0.12 to 0.31. In this case, the occurrence of a separation failure between the tread and the center belt reinforcing layer can be prevented, the cord is not crimped, and the workability during tire production is good.

  In another preferred embodiment of the pneumatic tire of the present invention, the number of cords forming the center belt reinforcing layer and the shoulder belt reinforcing layer is 30/50 mm to 70/50 mm. In this case, the main belt can be sufficiently reinforced, and the occurrence of a separation failure between the tread and the center belt reinforcing layer and / or the shoulder belt reinforcing layer can be prevented.

  In the pneumatic tire of the present invention, each of the center belt reinforcing layer and the shoulder belt reinforcing layer is a ribbon-like sheet obtained by rubberizing one or more reinforcing elements having a width smaller than the arrangement width. Is preferably formed by spiral winding a plurality of times in the width direction of the tire until a predetermined width dimension is reached. In this case, a joint part does not arise in the tire circumferential direction, and the main belt can be reinforced uniformly.

  According to the present invention, a single-strand nylon 6,6 cord is used for the center belt reinforcing layer, a double-twisted PEN cord is used for the shoulder belt reinforcing layer, and the center belt reinforcing layer and the shoulder belt reinforcing layer are used. By providing a portion that overlaps with each other, it is possible to reliably prevent a gap from being generated between the center belt reinforcing layer and the shoulder belt reinforcing layer when the tire is expanded in the vulcanization process. Rolling resistance can be reliably reduced. Also, by using a single twisted nylon 6,6 cord for the center belt reinforcement layer, the rigidity of the center belt reinforcement layer is reduced, the volume occupied by the crown structure is reduced, and the tire is molded. Even if it occurs, the flat shape of the tire can be reduced because the original shape is quickly recovered by subsequent running.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional view of an example of a tread portion of a pneumatic tire according to the present invention. The pneumatic tire of the present invention has a pair of bead portions and a pair of sidewall portions, a tread portion connected to both sidewall portions, and a carcass extending in a toroidal shape between the pair of bead portions, A main belt 1 composed of at least two belt layers arranged on the outer side in the tire radial direction of the crown portion of the carcass, and arranged on the outer side in the tire radial direction of the main belt 1 and arranged substantially parallel to the tire circumferential direction And at least two belt reinforcing layers 2 made of a rubberized layer of the reinforcing element.

  In the pneumatic tire according to the present invention, the belt reinforcing layer 2 includes one or more center belt reinforcing layers 3 that cover only the central portion of the main belt 1 and one or more shoulder portions that respectively cover only the end of the main belt 1. It consists of a pair of belt reinforcement layers 4. Here, in the pneumatic tire of the present invention, it is preferable that the center belt reinforcing layer 3 is located on the inner side in the tire radial direction than the shoulder belt reinforcing layer 4 as in the illustrated example. In the illustrated tire, the center belt reinforcing layer 3 is composed of one layer, but the center belt reinforcing layer 3 of the tire of the present invention may be two or more layers. Furthermore, in the illustrated tire, the shoulder portion belt reinforcing layer 4 is composed of two layers, a layer 4a adjacent to the center portion belt reinforcing layer 3 and a layer 4b located on the outer side in the tire radial direction of the layer 4a. The tire belt reinforcing layer 4 of the tire of the present invention may be a single layer or three or more layers.

In the pneumatic tire of the present invention, the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4a adjacent to the center belt reinforcing layer 3 must be at least partially overlapped. Furthermore, the tire width direction outer end portion P ₄ in the shoulder regions belt reinforcing layer 4 is positioned outside the tire width direction than the tire width direction outer end portion P ₁ of the main belt 1. Here, when the shoulder portion belt reinforcing layer 4 is composed of two or more layers, the outer end portion P _{4 in} the tire width direction of the shoulder portion belt reinforcing layer 4 is the most among the end portions of each layer of the shoulder portion belt reinforcing layer 4. An end located on the outer side in the tire width direction refers to an outer end P _{1 of} the main belt 1 in the tire width direction. The tire of the belt layer 1a having the widest belt layer constituting the main belt 1 It corresponds to the width direction outer side end. In addition, although each layer 4a, 4b of the shoulder part belt reinforcement layer 4 of the tire of the illustrated example has the tire width direction outer side end part P ₄ aligned, in the pneumatic tire of the present invention, each layer of the shoulder part belt reinforcement layer The outer ends in the tire width direction may be uneven.

  The belt layers 1a and 1b constituting the main belt 1 are usually composed of a rubberized layer of a cord extending preferably inclining with respect to the tire equatorial plane, preferably a rubberized layer of a steel cord. Then, the two belt layers 1a and 1b are laminated so that the cords constituting the belt layers intersect with each other across the tire equatorial plane to constitute the main belt 1. The main belt 1 of the illustrated tire has two layers, a belt layer 1a having the widest width and a belt layer 1b that is positioned on the outer side in the tire radial direction of the belt layer 1a and narrower than the belt layer 1a. However, in the pneumatic tire of the present invention, the structure of the main belt 1 is not limited to this, and the number of belt layers constituting the main belt 1 may be three or more.

  On the other hand, the belt reinforcement layer 2 is composed of a rubberized layer of reinforcement elements arranged substantially parallel to the tire circumferential direction, and the reinforcement element constituting the center belt reinforcement layer 3 is a single-stranded polyhexamethylene adipa. On the other hand, the reinforcing element constituting the shoulder belt reinforcing layer 4 is a twisted polyethylene-2,6-naphthalate (PEN) cord. By using a double twisted PEN cord for the shoulder belt reinforcing layer 4, the road noise of the tire can be reduced, and for the center belt reinforcing layer 3, a single twisted nylon 6,6 cord is used. Thus, increase in rolling resistance of the tire can be suppressed.

  In the pneumatic tire of the present invention, since the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 are at least partially overlapped, the distribution of stress generated during expansion of the vulcanization process changes abruptly in the width direction. There is no part, and the stress generated during expansion changes continuously in the tire width direction. Therefore, at the time of expansion of the vulcanization process, the degree of rubber flow continuously changes in the belt reinforcing layer 2 to prevent a gap from being generated between the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4. Can do. Further, since the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 are at least partially overlapped, the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 are slightly deviated from each other when the vulcanization process is expanded. However, the presence of the overlap portion can surely prevent the occurrence of a gap in which the main belt 1 is not reinforced at all, so that the tire having the target structure can be easily manufactured.

  As described above, the rolling resistance of the tire can be reduced by using one-twisted nylon 6,6 cord as the reinforcing element constituting the center belt reinforcing layer 3, but the effect of reducing this rolling resistance can be reduced. In addition, it has surprisingly been found that the flat spot of the tire can be reduced. In general, when a tire having a belt reinforcing layer is naturally cooled by parking after being brought to a high temperature state by high speed running, the tire is shaped and riding comfort is greatly impaired. However, the cord of the single twist structure has lower rigidity than the cord of the double twist structure, and the volume occupied in the crown portion structure can be reduced. Recover to shape. Therefore, it is possible to reduce the flat spot of the tire by using one-twisted nylon 6,6 cord as the reinforcing element constituting the center belt reinforcing layer 3.

In the pneumatic tire of the present invention, as shown in FIG. 1, the outer end portion P _{3 in} the tire width direction of the center portion belt reinforcing layer 3 is the widest of the belt layers 1 a and 1 b constituting the main belt 1. it is preferably located on the inner side in the tire width direction than the tire width direction outer end portion P _1b of the narrow belt layer 1b. In this case, since the end portion of the main belt 1 is reinforced by the PEN cord, tire road noise can be sufficiently reduced.

  In the pneumatic tire of the present invention, the width W of the overlapping portion between the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4a adjacent to the center belt reinforcing layer 3 depends on the tire size and the expansion rate during vulcanization. Although it is necessary to set appropriately, it is not particularly limited, but a range of 1 to 20 mm is preferable, and a range of 1 to 12 mm is more preferable. If the tire has a small section width and a belt end expansion rate of 1% or less, the width W of the overlapping portion of the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4a adjacent to the layer 3 may be 1 mm. If the width W of the overlapping portion between the center portion belt reinforcing layer 3 and the shoulder portion belt reinforcing layer 4a adjacent to the layer 3 is 20 mm even in a large tire for SUV or the like, the center portion Generation of a gap between the belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 can be sufficiently prevented.

In the pneumatic tire of the present invention, the total width W ₂ of the belt reinforcing layer 2 composed of the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 is _{2 to 10} mm wider than the total width W ₁ of the main belt 1. It is preferable. The total width W ₂ of the belt reinforcing layer 2 made larger than 2mm than the total width W ₁ of the main belt 1, by securely cover the end portion of the main belt 1 in the belt reinforcing layer 2 sufficiently reduce road noise can do. On the other hand, be increased beyond the 10mm than the total width W ₂ of the belt reinforcing layer 2 total width W ₁ of the main belt 1, it is impossible to further reduce the road noise.

In the pneumatic tire of the present invention, the width W ₄ of the shoulder belt reinforcing layer 4 is preferably 5 to 20% of the total width W ₁ of the main belt 1. If the width W _{4 of the} shoulder portion belt reinforcing layer 4 is less than 5% of the total width W ₁ of the main belt 1, the road noise of the tire may not be sufficiently reduced. On the other hand, if the width W _{4 of} the shoulder portion belt reinforcing layer 4 exceeds 20% of the total width W ₁ of the main belt 1, the rolling resistance of the tire may deteriorate. Here, when the shoulder portion belt reinforcing layer 4 is composed of two or more layers, the width W ₄ of the shoulder portion belt reinforcing layer 4 refers to the width of each layer of the shoulder portion belt reinforcing layer 4. The width W _4a of the layer 4a adjacent to the center belt reinforcing layer 3 and the width W _{4b of the} layer 4b located on the outer side in the tire radial direction of the layer 4a are indicated.

  In the pneumatic tire of the present invention, the reinforcing element constituting the shoulder belt reinforcing layer 4 is a cord formed by twisting two filament bundles of polyethylene-2,6-naphthalate (PEN) having a total fineness of 500 to 2000 dtex. Is preferred. If a cord in which a filament bundle of PEN having a fineness of less than 500 dtex is twisted is used, the rigidity of the shoulder belt reinforcing layer 4 may be insufficient, and the road noise of the tire may not be sufficiently reduced. On the other hand, if a cord made of twisted PEN filament bundles with a fineness exceeding 2000dtex is used, the amount of rubber existing between the cords will be reduced, and the resistance to peeling between the shoulder belt reinforcing layer 4 and the tread rubber will be deteriorated. When doing so, there is a risk that a separation failure may occur between the tread and the shoulder belt reinforcing layer 4.

  In the pneumatic tire of the present invention, the polyethylene-2,6-naphthalate (PEN) cord constituting the shoulder belt reinforcing layer 4 has a twist coefficient R defined by the above formula (I) of 0.20 to 0.72. preferable. When the twist coefficient R of the PEN cord to be used is less than 0.20, the adhesion between the cord and the rubber is poor, and a separation failure is likely to occur between the tread and the shoulder belt reinforcing layer 4. On the other hand, if the twist coefficient R of the PEN cord used exceeds 0.72, the stiffness of the cord may be low, and the road noise of the tire may not be sufficiently reduced.

  In the pneumatic tire of the present invention, the reinforcing element constituting the center belt reinforcing layer 3 is twisted on one filament bundle of polyhexamethylene adipamide (nylon 6, 6) having a total fineness of 500 to 2000 dtex. A code is preferred. If a cord of nylon 6,6 filament bundle with a fineness of less than 500dtex is twisted, the rigidity of the center belt reinforcement layer 3 will be insufficient, and the radius of curvature of the tire crown will be too small. In addition, the uneven wear resistance and steering stability of the tire are lowered, and further, the essential road noise reduction effect may not be sufficiently obtained. On the other hand, if a cord made by twisting one nylon 6,6 filament bundle with a fineness exceeding 2000 dtex is used, the rigidity of the center belt reinforcement layer 3 will be too great and the rolling resistance of the tire cannot be reduced sufficiently. There is.

  In the pneumatic tire of the present invention, the polyhexamethylene adipamide (nylon 6, 6) cord constituting the center belt reinforcing layer 3 has a twist coefficient R defined by the above formula (I) of 0.12 to 0.31. It is preferable. If the twist coefficient R of the nylon 6,6 cord used is less than 0.12, the adhesion between the cord and the rubber is poor, and a separation failure is likely to occur between the tread and the center belt reinforcing layer 3. On the other hand, if the twist coefficient R of the nylon 6,6 cord used exceeds 0.31, the cord may be crimped, and the workability during tire production may be greatly deteriorated.

  In the pneumatic tire of the present invention, the number of cords constituting the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 is preferably in the range of 30/50 mm to 70/50 mm. If the number of cords forming the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 is less than 30/50 mm, the main belt 1 may not be sufficiently reinforced. On the other hand, when the number of cords constituting the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 exceeds 70/50 mm, the amount of rubber existing between the cords decreases, and the center belt reinforcing layer 3 and the tread The peel resistance between the rubber and the peel resistance between the shoulder belt reinforcing layer 4 and the tread rubber deteriorates, and when running, the tread and the center belt reinforcing layer 3 and / or the shoulder belt reinforcing layer 4 Separation failure may occur.

  The nylon 6,6 cord has a single twist structure, and can be produced by, for example, twisting one filament bundle made of nylon 6,6. On the other hand, the PEN cord has a double twist structure, for example, by applying a lower twist to a filament bundle made of PEN, and then combining a plurality, preferably two, and applying an upper twist in the opposite direction. can do.

  By cording the nylon 6,6 cord and the PEN cord obtained as described above, a cord / rubber composite used for the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 can be obtained. Here, there is no restriction | limiting in particular as a coating rubber of nylon 6, 6 cord and PEN cord, The coating rubber used for the conventional belt reinforcement layer can be used. Prior to rubberizing the nylon 6,6 cord and PEN cord, the nylon 6,6 cord and PEN cord may be subjected to an adhesive treatment to improve the adhesion to the coating rubber.

  In the pneumatic tire of the present invention, a cord / rubber composite formed by rubberizing nylon 6,6 cord is applied to the center belt reinforcing layer 3, and a PEN cord is rubberized to the shoulder belt reinforcing layer 4. The cord / rubber composite can be applied, and the center part belt reinforcing layer 3 and the shoulder part belt reinforcing layer 4 can be partially overlapped to produce a conventional method. In the pneumatic tire of the present invention, as the gas filled in the tire, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

  In the production of the pneumatic tire of the present invention, a ribbon-like sheet obtained by rubberizing one or more nylon 6,6 cords having a width that is narrower than the width of the center belt reinforcing layer 3 is applied to a predetermined width. It is preferable to form the center portion belt reinforcing layer 3 by spirally winding a plurality of times in the width direction of the tire until it becomes. In the production of the pneumatic tire of the present invention, a ribbon-like sheet obtained by rubberizing one or more PEN cords having a width smaller than the width of the shoulder belt reinforcement layer 4 is made to have a predetermined width. It is preferable to form the shoulder portion belt reinforcing layer 4 by spiral winding a plurality of times in the width direction of the tire until it becomes. By continuously spirally winding the ribbon-shaped sheet to form the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4, it is possible to reinforce the main belt 1 uniformly without generating a joint portion in the tire circumferential direction. it can.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

A radial tire for a passenger car having a size of 185/70 R14 having the structure shown in FIG. 1 was produced according to a conventional method. The width of the belt layer 1a on the inner side in the tire radial direction of the main belt 1 is 150 mm, the width of the belt layer 1b on the outer side in the tire radial direction of the main belt 1 is 140 mm, and the width of the center belt reinforcing layer 3 is 104 mm. The width of the layer 4a on the inner side in the tire radial direction of the shoulder portion belt reinforcing layer 4 is 37 mm, and the width of the layer 4b on the outer side in the tire radial direction of the shoulder portion belt reinforcing layer 4 is 25 mm. The ratio of the shoulder portions belt reinforcing layer 4 having a width W ₄ for the difference (mm), the total width W ₁ of the main belt 1 between the total width W ₂ of the belt reinforcing layer 2 and the total width W ₁ of the main belt 1 (% ), The width W (mm) of the overlap portion between the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4a adjacent to the layer 3, and the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 The material, fineness, twisting coefficient, and number of cords applied were as shown in Tables 1-3.

  Next, the vulcanized tire is dissected to expose the center belt reinforcement layer 3 and the shoulder belt reinforcement layer 4, and a gap is generated between the center belt reinforcement layer 3 and the shoulder belt reinforcement layer 4. I confirmed whether or not. Moreover, road noise, rolling resistance, high-speed durability, and a flat spot were evaluated by the following method with respect to the tire produced similarly. The results are shown in Tables 1-3.

(1) Road noise The prototype tire is assembled to the rim, filled with 200kPa internal pressure, mounted on all four wheels of a sedan type passenger car with a displacement of 2000cc, and two people get on the road noise evaluation road test course for 60km While driving at a speed of / h, measure the total sound pressure (decibel) at frequencies of 100 to 500 Hz and 300 to 500 Hz via a sound collecting microphone attached to the center of the backrest of the driver's seat, and calculate road noise from the measured values. Evaluation was made, and the road noise of the tire of Comparative Example 1 was set as 100 and indicated as an index. The larger the index value, the smaller the road noise and the better.

(2) Rolling resistance Using a rotating drum with a steel smooth surface with an outer diameter of 1707.6mm, a width that is greater than the maximum width of the test tire and a constant rotational speed, 0 to 180km under the action of a load of 400kgf The rolling resistance was measured by the coasting method when rotating at a speed of / h, the rolling resistance was evaluated from the measured value, and the rolling resistance of the tire of Comparative Example 1 was indicated as an index. It shows that rolling resistance is so small that index value is large.

(3) High speed durability The prototype tire is assembled to the rim, filled with 200kPa internal pressure, run at a speed of 150km / h for 30 minutes, and if there is no failure, the speed is increased by 6km / h. Measured, and indexed with the failure occurrence rate of Comparative Example 1 as 100. The larger the index value, the higher the endurance limit speed and the higher the high speed durability.

(4) Flat spot Measure the deformation of the tire as a change in roundness after mounting the test tire on a real vehicle and letting it run for a certain period of time and applying a load to the tire that has become sufficiently hot and allowing it to cool completely. It was evaluated by doing. That is, the roundness before and after the load was measured, the difference was obtained as a flat spot amount, and the flat spot amount of Comparative Example 1 was set as 100 and displayed as an index. It shows that the amount of flat spots was reduced as the index value increased.

  From the comparison between Comparative Example 1 and Example 1, using a double twisted PEN cord for the shoulder belt reinforcing layer and a single twisted nylon 6,6 cord for the center belt reinforcing layer, the shoulder belt reinforcing It can be seen that the road noise and rolling resistance of the tire can be reduced by providing an overlap portion between the layer and the center belt reinforcing layer. Further, from the result of Comparative Example 2, if the overlap portion is not provided in the shoulder portion belt reinforcing layer and the center portion belt reinforcing layer, the shoulder portion belt reinforcing layer and the center portion belt reinforcing layer are formed by expanding the tire during vulcanization. It can be seen that there is a gap between the tires and the road noise of the tire cannot be reduced.

  From the results of Example 1, Example 2, Example 7 and Example 8, the road noise of the tire cannot be reduced if the number of nylon 6,6 cords driven in the center belt reinforcing layer is less than 30/50 mm. In addition, high-speed durability is reduced. On the other hand, if it exceeds 70 / 50mm, the rolling resistance of the tire increases, so the number of nylon 6,6 cords to be driven is 30 / 50mm to 70 / 50mm. It can be seen that the range is preferred.

  Further, from the results of Example 1, Example 9 and Example 10, when the number of driving PEN cords in the shoulder belt reinforcement layer is less than 30/50 mm, in addition to reducing the road noise of the tire, high-speed durability On the other hand, if it exceeds 70/50 mm, the high-speed durability of the tire decreases, and it can be seen that the number of PEN cords to be driven is preferably in the range of 30/50 mm to 70/50 mm.

  Furthermore, from the results of Example 1, Example 3, Example 12 and Example 13, when the twist coefficient R of the PEN cord used for the shoulder belt reinforcing layer is less than 0.20, the high-speed durability of the tire decreases, If it exceeds 0.72, in addition to not being able to sufficiently reduce the road noise of the tire, the high-speed durability is lowered. Therefore, it is understood that the twist coefficient R of the PEN cord is preferably in the range of 0.20 to 0.72.

  Furthermore, from the results of Example 1, Example 4 and Example 11, if the twist coefficient R of the nylon 6,6 cord used for the center belt reinforcing layer is less than 0.12, the high-speed durability of the tire decreases. Since the rolling resistance also increases, it can be seen that the twist coefficient R of the nylon 6,6 cord is preferably 0.12 or more.

  Furthermore, from the results of Example 1, Example 5, Example 15 and Example 16, if the total fineness of the PEN cord used for the shoulder belt reinforcing layer is less than 500 dtex, the road noise of the tire cannot be sufficiently reduced. In addition, the high-speed durability of the tire is lowered. On the other hand, when the tire exceeds 2000 dtex, the high-speed durability of the tire is lowered. Therefore, it is understood that the total fineness of the PEN cord is preferably in the range of 500 to 2000 dtex.

  In addition, from the results of Example 1, Example 6 and Example 14, when the total fineness of the nylon 6,6 cord used for the center portion belt reinforcing layer is less than 500 dtex, the high-speed durability of the tire is lowered, Since rolling resistance increases, it turns out that the total fineness of nylon 6,6 cord has preferable 500 dtex or more.

It is a fragmentary sectional view of an example of the tread part of the pneumatic tire of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main belt 1a The widest belt layer in the belt layer which comprises a main belt 1b The narrowest belt layer in the belt layer which comprises a main belt 2 Belt reinforcement layer 3 Center part belt reinforcement layer 4 Shoulder part Belt reinforcing layer 4a Layer adjacent to the center belt reinforcing layer 4b Layer positioned on the outer side in the tire radial direction of the layer adjacent to the center belt reinforcing layer P ₁ Outer end in the tire width direction of the main belt P _1b The narrowest belt Tire width direction outer edge of the layer P ₄ shoulder width outer edge of the shoulder belt reinforcement layer W width of the overlapping portion of the center belt reinforcement layer and the shoulder belt reinforcement layer adjacent thereto W ₁ total width of the main belt width W _4b center of W ₂ belt reinforcing layer total width W ₄ shoulder portion belt reinforcing layer width W _4a Center section shoulder portion belt reinforcing layer adjacent to the belt reinforcing layer of the Width of the layer located on the radially outer side of the shoulder portion the belt reinforcing layer adjacent to the section belt reinforcing layer

Claims (11)

A carcass having a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and extending in a toroid shape between the pair of bead portions, and a tire radius of a crown portion of the carcass A main belt composed of at least two belt layers arranged on the outer side in the direction, and at least a rubberized layer of reinforcing elements arranged on the outer side in the tire radial direction of the main belt and arranged substantially parallel to the tire circumferential direction. In a pneumatic tire provided with two belt reinforcement layers,
The belt reinforcing layer comprises a pair of one or more center belt reinforcing layers covering only the central portion of the main belt and a pair of one or more shoulder belt reinforcing layers covering only the end portions of the main belt, The center portion belt reinforcing layer and the shoulder portion belt reinforcing layer adjacent to the center portion belt reinforcing layer are at least partially overlapped, and the outer end in the tire width direction of the shoulder portion belt reinforcing layer is the tire width of the main belt. It is located on the outer side in the tire width direction than the outer end in the direction,
The reinforcing element constituting the center belt reinforcing layer is a single twisted polyhexamethylene adipamide (nylon 6,6) cord, and the reinforcing element constituting the shoulder belt reinforcing layer is a double twisted polyethylene-2 , 6-Naphthalate (PEN) cord, a pneumatic tire.   The outer end portion in the tire width direction of the center belt reinforcing layer is located on the inner side in the tire width direction than the outer end portion in the tire width direction of the narrowest belt layer among the belt layers constituting the main belt. The pneumatic tire according to claim 1.   2. The pneumatic tire according to claim 1, wherein a width of an overlapping portion between the center belt reinforcing layer and a shoulder belt reinforcing layer adjacent to the center belt reinforcing layer is 1 to 20 mm.   2. The pneumatic according to claim 1, wherein the total width of the belt reinforcing layer including the center belt reinforcing layer and the shoulder belt reinforcing layer is 2 to 10 mm wider than the total width of the main belt. tire.   2. The pneumatic tire according to claim 1, wherein a width of the shoulder portion belt reinforcing layer is 5 to 20% of a total width of the main belt.   The reinforcing element constituting the shoulder belt reinforcing layer is a cord in which two filament bundles of polyethylene-2,6-naphthalate (PEN) having a total fineness of 500 to 2000 dtex are twisted together. The described pneumatic tire. The polyethylene-2,6-naphthalate (PEN) cord constituting the shoulder belt reinforcing layer has the following formula (I):
R = N × (0.125 × D / ρ) ^1/2 × 10 ^-3 (I)
[Where N is the number of twists of the cord (times / 10 cm), D is the total number of decitex of the cord (dtex), and ρ is the specific gravity of the cord (g / cm ³ )] The pneumatic tire according to claim 1, wherein R is 0.20 to 0.72.   The reinforcing element constituting the center belt reinforcing layer is a cord obtained by twisting one filament bundle of polyhexamethylene adipamide (nylon 6, 6) having a total fineness of 500 to 2000 dtex. The pneumatic tire according to claim 1. The polyhexamethylene adipamide (nylon 6, 6) cord constituting the center belt reinforcing layer is represented by the following formula (I):
R = N × (0.125 × D / ρ) ^1/2 × 10 ^-3 (I)
[Where N is the number of twists of the cord (times / 10 cm), D is the total number of decitex of the cord (dtex), and ρ is the specific gravity of the cord (g / cm ³ )] The radial tire according to claim 1, wherein R is 0.12 to 0.31.   2. The pneumatic tire according to claim 1, wherein the number of cords forming the center belt reinforcing layer and the shoulder belt reinforcing layer is 30/50 mm to 70/50 mm.   Each of the center belt reinforcing layer and the shoulder belt reinforcing layer has a predetermined width dimension obtained from a ribbon-like sheet obtained by rubberizing one or more reinforcing elements having a narrower width dimension than the arrangement width. The pneumatic tire according to claim 1, wherein the pneumatic tire is formed by spirally winding a plurality of times in the tire width direction.

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