JP5852724B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly, to a pneumatic tire with improved wet brake performance and reduced rolling resistance as compared with the conventional one.

  Conventionally, in a pneumatic tire, various tread patterns that can improve wet performance that is drivability and braking performance on a wet road surface have been proposed for the purpose of improving safety. For example, in Patent Document 1, the first circumferential groove is formed on the tread, and the first narrow groove is formed in which the groove walls come into contact with each other when the tread is grounded and compressed and deformed, thereby dividing the center rib. A center block is defined by forming a second circumferential groove and a center lug groove extending from the first narrow groove to the second circumferential groove on the outer side in the tire width direction of the groove, and the center block surface is separated from one wall surface to the other. A first sipe that extends in the tire circumferential direction toward the wall surface and terminates in the block, and extends from the other wall surface to the one wall surface in the tire circumferential direction, opens in the curved wall surface, and does not intersect the first sipe in plan view. Tires with two sipes have been proposed.

  In addition, demands for reducing fuel consumption of automobiles are also increasing in connection with the movement of global carbon dioxide emission regulations accompanying the recent increase in interest in environmental problems. In order to meet such demands, reduction of rolling resistance is required. In order to meet such demands, studies have also been made on improvement of tread rubber constituting the tread. For example, Patent Document 2 discloses a rubber composition that realizes improvement of tire wet performance and reduction of rolling resistance by controlling tan δ at around 0 ° C., 30 ° C., and 60 ° C. of a tread rubber within a predetermined range. Things have been proposed.

JP 2010-23549 A JP 2006-274049 A

  However, in today's market, further improvements in braking performance (safety performance) on wet road surfaces and further reduction in rolling resistance (improvement in fuel consumption performance) are required. The tread pattern proposed in Patent Document 1 In addition, the rubber composition proposed in Patent Document 2 is not necessarily satisfactory, and the present situation is that further improvement is required.

  Accordingly, an object of the present invention is to provide a pneumatic tire with improved wet brake performance and reduced rolling resistance as compared with the prior art.

  As a result of intensive studies to solve the above problems, the present inventors have achieved a reduction in rolling resistance and an improvement in wet brake performance by using a predetermined tread rubber, and an appropriate tread pattern. As a result, the drainage performance, the ground contact area, and the ground contact state are ensured, and as a result, it has been found that the wet brake performance can be improved and the rolling resistance can be reduced at a higher level than before, and the present invention has been completed. It was.

That is, the pneumatic tire of the present invention is a pneumatic tire having a plurality of circumferential main grooves provided within the tread contact surface width, and a land portion defined by the circumferential grooves.
The tread rubber constituting the tread has a tan δ of 1.00 or more under the conditions of 0 ° C., frequency 52 Hz, initial strain 2.0%, and dynamic strain rate 1.0%, 60 ° C., frequency 52 Hz, initial strain 2. 0%. Tan δ under the condition of a dynamic strain rate of 1.0% is 0.12 or less, and
The negative rate within the contact width of the tread is 20 to 40%,
When two land portions on both outer sides in the tread width direction are shoulder land portions and a land portion sandwiched between the shoulder land portions is a center land portion, a curved sipe that connects both sides is provided on the center land portion. Further, 5 to 50 parts by mass of silica is blended with 100 parts by mass of the rubber component of the tread rubber.

  Here, the contact surface width means that the tire is mounted on a standard rim stipulated in JATMA YEAR BOOK (2008 edition, Japan Automobile Tire Association Standard) and the maximum load capacity in the applicable size and ply rating in JATMA YEAR BOOK. This indicates the outermost contact portion in the tire width direction when 100% of the air pressure (maximum air pressure) corresponding to (internal pressure-load capacity correspondence table) is filled, and 80% of the maximum load capacity is loaded. When the TRA standard or ETRTO standard is applied at the place of use or manufacturing, the respective standards are followed. The negative rate is the ratio of the total groove area to the total area within the ground plane width.

  In the pneumatic tire of the present invention, the contact width of the tread has three circumferential grooves, and four rows of land portions partitioned by the three circumferential grooves, It is preferable that the ratio of the two shoulder land portions to 20 to 35% of each and the ratio of the two center land portions to the entire land portion to be 15 to 30%, respectively. Further, in the pneumatic tire of the present invention, a sipe that connects both sides to at least one of the center land portions, and a straight line that connects both ends of the sipe is inclined by 16 to 24 ° with respect to the tread width direction. It is preferable. Further, in the pneumatic tire of the present invention, the tread rubber constituting the tread has a tan δ of 1.00 or more under the conditions of 0 ° C., a frequency of 52 Hz, an initial strain of 2.0%, and a dynamic strain rate of 1.0% (however, , Except 1.00).

  According to the present invention, it is possible to provide a pneumatic tire with improved wet brake performance and reduced rolling resistance as compared with the prior art.

1 is a partial development view of a tread pattern of a pneumatic tire according to a preferred embodiment of the present invention. 1 is a cross-sectional view in the width direction of a pneumatic tire according to a preferred embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial development view of a tread pattern of a pneumatic tire according to a preferred embodiment of the present invention. The pneumatic tire according to the present invention includes a plurality of tires (within a contact surface width w of the tread ( In the illustrated example, there are three circumferential grooves 1 and land portions (four rows in the illustrated example) partitioned by the circumferential grooves 1. In the illustrated example, when the two rows of land portions on both outer sides in the tread width direction are the shoulder land portions 2a and 2d, and the two rows of land portions sandwiched between the shoulder land portions 2a and 2d are the center land portions 2b and 2c, Each shoulder land portion 2a, 2d is provided with a width direction groove 3a, 3b extending in the tread width direction.

  In the illustrated example, the width direction groove 3a provided in the shoulder land portion 2a is a curved shape having a gentle curve, and the width direction groove 3b provided in the shoulder land portion 2d is inclined with respect to the tread width direction. However, in the tire of the present invention, the shape of the width direction groove is not limited to this. In the illustrated example, the center land portion 2b is provided with a curved sipe 4a connecting both sides, and the center land portion 2c is provided with a straight sipe 4b connecting both sides.

  In the pneumatic tire of the present invention, the tan δ of the tread rubber constituting the tread is 0.90 or more under the conditions of 0 ° C., frequency 52 Hz, initial strain 2.0%, and dynamic strain rate 1.0%. By using a tread rubber having a tan δ of 0.9 or more at 0 ° C., excellent wet brake performance can be obtained. Preferably it is 1.0 or more. In the pneumatic tire of the present invention, tan δ under the conditions of 60 ° C., frequency 15 Hz, and strain 5% is 0.12 or less. By using a tread rubber having a tan δ at 60 ° C. of 0.12 or less, excellent rolling resistance can be obtained. Preferably it is 0.10 or less. The tan δ of the tread rubber can be appropriately adjusted according to a conventional method. For example, it can be appropriately adjusted by increasing or decreasing the amount of resin, carbon black, silica or the like in the rubber composition. The composition of the tread rubber will be described later.

  Further, in the pneumatic tire of the present invention, the ratio of the total groove area (in the illustrated example, the sum of the areas of the circumferential groove 1 and the width grooves 3a and 3b) to the total area within the contact surface width w of the tread. The negative rate is 20 to 40%, preferably 25 to 30%. By setting the negative rate within the range of 20 to 40%, drainage performance can be ensured while maintaining braking performance and rolling resistance on wet road surfaces. That is, if the negative rate is less than 20%, sufficient drainage performance on a wet road surface cannot be obtained, and wet brake performance is degraded. On the other hand, if the negative rate is less than 20%, the proportion of the land portion 2 in the ground contact surface width w increases, and thus the rolling resistance increases. Furthermore, if the ratio of the land portion 2 within the ground contact surface width w increases, the tire weight increases, which also causes a deterioration in rolling resistance. On the other hand, if the negative rate exceeds 40%, the ratio of the land portion 2 in the ground contact surface width w is too small, so that the wet brake performance is degraded.

  In the pneumatic tire of the present invention, as shown in the figure, three circumferential grooves 1 and four land portions 2 are arranged, and two land portions 2 on both outer sides in the tread width direction are shoulder land portions 2a, 2d, When the two land portions 2 sandwiched between the shoulder land portions 2a and 2d are the center land portions 2b and 2c, the ratio of the two shoulder land portions 2a and 2d to the entire land portion is 20 to 35%, respectively. The ratio of the two central land portions 2b and 2c to the entire land portion is preferably 15 to 30%.

  By making the ratio of the two rows of shoulder land portions 2a, 2d and the two rows of center land portions 2b, 2c within the above range, the rigidity of each land portion 2a, 2b, 2c, 2d is made uniform, and the ground pressure is reduced. It can be made uniform, and since the local resistance at the time of freeroll that rolls without applying a brake can be reduced, the rolling resistance can be further reduced. Furthermore, since the braking force can be equalized in each land portion, the wet brake performance can be further improved. In order to obtain this effect better, the ratio of the two shoulder land portions 2a and 2d to the entire land portion is 26 to 27%, respectively, and the ratio of the two central land portions 2b and 2c to the entire land portion is Is preferably 23 to 24%.

  Further, in the pneumatic tire of the present invention, a sipe that connects both sides to at least one of the center land portions 2b and 2c, and an angle formed by a straight line connecting both ends of the sipe and the tread width direction is θ. Then, it is preferable to have a sipe (in the illustrated example, sipe 4b) in which θ is in the range of 16 to 24 °. By adopting such a configuration, the water film within the contact surface width w can be scraped out when kicking out, so that the wet brake performance when traveling on a wet road surface can be improved satisfactorily. In the tire of the present invention, sipes may be provided also on the shoulder land portions 2a and 2d. In this case, openings may be provided on both sides of the shoulder land portions 2a and 2b. You may have an opening.

Next, the tread rubber of the pneumatic tire of the present invention will be described.
As described above, the tread rubber of the pneumatic tire of the present invention has a tan δ of 0.90 under the conditions of 0 ° C., frequency 52 Hz, initial strain 2.0%, and dynamic strain rate 1.0% of the tread rubber constituting the tread. The tan δ under the conditions of 60 ° C., frequency 52 Hz, initial strain 2.0%, and dynamic strain rate 1.0% is 0.12 or less. By satisfying such physical properties, it is possible to improve wet brake performance and reduce rolling resistance. As described above, the tan δ of the tread rubber can be appropriately adjusted by adjusting the amounts of the resin, carbon black, silica, and the like in the rubber composition. For example, when it is desired to increase the value of tan δ, the amounts of carbon black and silica in the rubber composition may be increased, and when it is desired to decrease the value of tan δ, the amounts of carbon black and silica may be decreased.

  In the pneumatic tire of the present invention, as the rubber component of the tread rubber, specifically, for example, styrene / butadiene copolymer rubber (SBR), natural rubber (NR), styrene / isoprene copolymer rubber ( Synthetic rubbers such as SIR), polyisoprene rubber (IR), polybutadiene rubber (BR), butyl rubber (IIR), and ethylene / propylene copolymer can be used.

  Further, in the pneumatic tire of the present invention, carbon black is not particularly limited, but FEF, SRF, HAF, ISAF, SAF grades and the like can be used. (IA) of 60 mg / g or more and dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or more are suitable. Various physical properties of the rubber composition can be improved by adding carbon black to the tread rubber, but HAF, ISAF, and SAF grades are more preferable from the viewpoint of wear resistance. In the tire of the present invention, the amount of carbon black is preferably 0 to 50 parts by mass with respect to 100 parts by mass of the rubber component. The silica is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Wet silica is preferable because it is excellent in both wet performance and rolling resistance. In addition, when using a silica, it is preferable to add a silane coupling agent at the time of a mixing | blending from a viewpoint of improving the reinforcement property further. Such silane coupling agents include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilyl). Ethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltri Methoxysilane, 2-mercaptomethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarba Yl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate Monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxy Methylsilylpropylbenzothiazole tetrasulfide, and the like. Among these, bis (3 Triethoxysilylpropyl) tetrasulfide and 3-trimethoxysilylpropyl benzothiazole tetrasulfide are preferable. These silane coupling agents may be used alone or in combination of two or more. Moreover, in the tire of this invention, it is preferable that the compounding quantity of a silica is 0-50 mass parts with respect to 100 mass parts of rubber components.

  In the pneumatic tire of the present invention, a general rubber crosslinking system can be used for the tread rubber, and it is preferable to use a combination of a crosslinking agent and a vulcanization accelerator. In addition to the above, for example, additives usually used in the rubber industry such as softeners, anti-aging agents, zinc oxide, stearic acid, antioxidants, ozone deterioration inhibitors, and the like, within a range that does not impair the purpose of the present invention. It can select and mix | blend suitably. For example, the range of 0.1-10 mass parts is preferable as a sulfur content with respect to 100 mass parts of rubber components, and, as for a crosslinking agent, the range of 1-5 mass parts is more preferable. Moreover, the range of 0.1-5 mass parts is preferable with respect to 100 mass parts of rubber components, and, as for a vulcanization accelerator, the range of 0.2-3 mass parts is more preferable. When adding a softener, it can be 0-30 mass parts with respect to 100 mass parts of rubber components.

  The pneumatic tire of the present invention has a plurality of circumferential main grooves 1 provided in the tread contact width w, and land portions 2 defined by the circumferential grooves 1, and the tread contact width of the tread. The negative rate in w is 20 to 40%, and the tread rubber constituting the tread has a tan δ of 0.90 at 0 ° C., a frequency of 52 Hz, an initial strain of 2.0%, and a dynamic strain rate of 1.0%. That is all, it is only important that tan δ is 0.12 or less under the conditions of 60 ° C., frequency 52 Hz, initial strain 2.0%, and dynamic strain rate 1.0%. The structure and material of other members Is not particularly limited.

  FIG. 2 is a cross-sectional view in the width direction of a pneumatic tire according to a preferred embodiment of the present invention. The illustrated tire has a pair of left and right bead portions 21 and a pair of sidewall portions 22 in which the bead cores 11 are embedded, and a tread portion 23 connected to both sidewall portions 22, and spans between the pair of left and right bead cores 11. A carcass ply 12 is provided that extends in a toroidal shape and reinforces each part. Further, on the outer side in the tire radial direction of the crown portion of the carcass ply 12, two belt layers 13a and 13b made of rubberized layers of reinforcing cords arranged to be inclined with respect to the tire circumferential direction, and the tire circumferential direction A cap layer 14 and a layer layer 15 which are belt reinforcing layers made of rubberized layers of organic fiber cords arranged substantially in parallel are arranged.

  In the example shown in FIG. 2, the number of carcass plies 12 is one, but in the present invention, the number of carcass plies 12 is not limited to this, and may be two or more. Further, the structure is not particularly limited. The locking structure of the carcass ply 12 in the bead part 21 is not limited to the structure in which the carcass ply 12 is wound around the bead core 11 as shown in the drawing, and the structure in which the end of the carcass ply 12 is sandwiched between the two layers of the bead cores 11 is also possible. Good (not shown).

  Further, the belt layers 13a and 13b are made of, for example, a rubberized layer of a cord, preferably a steel-cored rubberized layer that extends with an inclination of ± 15 to 40 ° with respect to the tire circumferential direction. In the example shown in the figure, the two belt layers 13a and 13b are laminated so that the cords constituting each belt layer intersect with each other across the tire equator plane. Is not limited to the illustrated example as long as at least one belt layer is disposed.

  Further, in the illustrated example, the belt reinforcing layer according to the present invention includes a cap layer 14 disposed over the entire width of the belt layers 13a and 13b and a layer layer disposed in a region covering both ends of the belt layers 13a and 13b. However, the present invention is not limited to this, and only the cap layer 14 or the layer layer 15 or a combination of two or more cap layers 14 and / or two or more layer layers 15 may be used. Such a belt reinforcing layer can be formed, for example, by spirally winding a strip of a certain width formed by aligning a plurality of organic fiber cords and covering them with rubber in the tire circumferential direction.

  Further, although not shown in the drawings, in the present invention, an inner liner is usually disposed in the innermost layer of the tire, and a tread pattern that satisfies the above range of the negative rate is appropriately formed on the tread surface. Furthermore, in the pneumatic tire of the present invention, as the gas filled in the tire, normal or changed oxygen partial pressure, or inert gas such as nitrogen can be used.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Examples 1-7, Reference Examples and Comparative Examples 1-5>
A pneumatic tire of the type shown in FIG. 2 was produced with a tire size of 195 / 65R15. The tread pattern of the tire is the type shown in FIG. In the tread rubber, the amounts of carbon black, silica, and silane coupling agent added are within the ranges shown in Table 1 so that the values of tan δ at 0 ° C. and 60 ° C. are the values shown in Tables 2 and 3 according to the formulation shown in Table 1. And adjusted appropriately. Further, the width of the circumferential groove 1 of each test tire was adjusted so that the negative rate of each test tire had the values shown in Tables 2 and 3. The ratio of both shoulder land portions 2a and 2d to the entire land portion was 26.0%, and the ratio of the two central land portions 2b and 2c was 24.0%.

  Each test tire obtained was assembled to a rim of 6.0 J × 15, the internal pressure was 180 kPa, and the load condition was 0.8 times the maximum load capacity of the tire. evaluated. In addition, the angle with respect to the tire width direction of the sipe 4b provided in the center land portion 2c was 20 °.

<Measurement of tan δ>
Using a viscoelasticity measuring device manufactured by Rheometrics, tan δ at 0 ° C. and 60 ° C. was measured under the conditions of a frequency of 52 Hz, an initial strain of 2.0%, and a dynamic strain rate of 1.0%.

<Rolling resistance>
When the tire mounted on the rim is placed on a drum having an outer diameter of 1.7 m, the drum is rotated, the rotation speed is increased to 120 km / hour, and then the drum is coasted, and the rotation speed is 80 km / hour. The moment of inertia was calculated and evaluated based on the following formula. The results are shown as an index with the comparative example as 100. The larger the index value, the smaller the rolling resistance and the better.
Index value = [(moment of inertia of test tire) / (moment of inertia of tire of Example 1)] × 100
The obtained results are shown in Tables 2 and 3.

<Wet brake performance>
Each test tire was mounted on an actual vehicle, and the vehicle was run, and the braking performance on a wet road surface was evaluated by a feeling test with a driver's feeling. The obtained results are shown in Tables 2 and 3 as indexes with Example 1 as 100. The larger this value, the better the wet brake performance.

  From the above Tables 2 and 3, it can be seen that the pneumatic tire of the present invention has improved wet brake performance and reduced rolling resistance.

1 Circumferential groove 2a, 2b, 2c, 2d Land portion 3a, 3b Width direction groove 4a, 4b Sipe 10 Pneumatic tire 11 Bead core 12 Carcass ply 13a, 13b Belt layer 14 Cap layer 15 Layer layer 21 Bead portion 22 Side wall portion 23 Tread

Claims (4)

In a pneumatic tire having a plurality of circumferential main grooves provided in the width of the contact surface of the tread, and a land portion defined by the circumferential grooves,
The tread rubber constituting the tread has a tan δ of 1.00 or more under the conditions of 0 ° C., frequency 52 Hz, initial strain 2.0%, and dynamic strain rate 1.0%, 60 ° C., frequency 52 Hz, initial strain 2. Tan δ under the conditions of 0% and dynamic strain rate of 1.0% is 0.12 or less, and
The negative rate within the contact width of the tread is 20 to 40%,
When two land portions on both outer sides in the tread width direction are shoulder land portions, and a land portion sandwiched between the shoulder land portions is a center land portion, a curved sipe that connects both sides is provided in the center land portion. And 5 to 50 parts by mass of silica is blended with 100 parts by mass of the rubber component of the tread rubber .   The ground contact width of the tread has three circumferential grooves and four rows of land portions defined by the three circumferential grooves, and two rows of the shoulder land portions with respect to the entire land portion. 2. The pneumatic tire according to claim 1, wherein the ratio is 20 to 35%, and the ratio of the two central land portions to the entire land portion is 15 to 30%.   3. The pneumatic system according to claim 1, wherein a sipe connecting both side portions to at least one of the center land portions, and a straight line connecting both ends of the sipe is inclined at 16 to 24 ° with respect to the tread width direction. tire.   The tread rubber constituting the tread has a tan δ of 1.00 or more (excluding 1.00) under the conditions of 0 ° C., frequency 52 Hz, initial strain 2.0%, and dynamic strain rate 1.0%. The pneumatic tire according to any one of 1 to 3.

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