JP2011079469A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having a superior wear resistance performance and reduced rolling resistance, and ensuring the durability of the exterior of the side parts. <P>SOLUTION: In this pneumatic tire, the ratio BD/BW of the difference in diameter BD between the lateral center and the lateral ends of the outermost layer of an inclined belt layer to the width BW of the outermost layer of the inclined belt layer in the cross section of the tire in the lateral direction when the tire is attached to an applicable rim is 0.01-0.04. Carcass ply reinforcing layers are disposed on the lateral outsides of a carcass at the maximum width positions of the tire, respectively. The ratio CPFw/CSH of the width CRFw of the carcass ply reinforcing layer to the distance CSH in the tire radial direction between the radial outermost side of the carcass and a bead toa is 0.2-0.6. A reinforcing element buried in the carcass ply reinforcing layer is inclined at an angle of 30-90° relative to the equatorial plane of the tire. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having excellent uneven wear resistance and low rolling resistance.

In recent years, development of products with a smaller environmental load has been actively conducted. This is due to environmental problems such as global warming, and tires are no exception. With respect to this tire, in order to cope with the environmental problem, it is important to secure performance that contributes to reducing fuel consumption of the automobile. One means for achieving this is to reduce the rolling resistance of the tire, and various technical developments have been made in the past.
The following introduces some conventional improvements.

  First, it is known that a large amount of tire rolling resistance occurs in the rubber of the tread portion. As a direct improvement method, it is effective to change the rubber used for the tread portion to one having a small loss tangent. However, it is also known that this method sacrifices other performance of the tire, such as wear resistance. On the other hand, a method of reducing the tread thickness can be easily considered in order to reduce the rubber that is a source of increasing rolling resistance. However, in this case, the problem is that the wear life of the tire cannot be ensured.

  Furthermore, Patent Document 1 proposes reducing the rolling resistance by devising the cross-sectional shape of the tire. This proposal will surely reduce rolling resistance, but the durability of the appearance of the side is not sufficient, and more detailed tire design is required when considering other performance, especially excellent wear resistance. It has been demanded.

JP 2006-327502 A

  Therefore, an object of the present invention is to propose the details of the tire shape for providing a tire having excellent wear resistance performance and low rolling resistance, and also to ensure the durability of the appearance of the side portion of the new shape. is there.

Inventors are able to improve the expected performance by regulating the shape of the tire in detail, especially in the case of shape design, not only the shape of the outer surface of the tire but also the reinforcement that becomes the skeleton of the tire Since the shape of the structure has a great influence on the tire performance, we have learned that it is effective to regulate it individually. In other words, suppressing the shear deformation in the tire width direction cross section, particularly in the tread on the outer side in the width direction, reduces the rolling resistance as a result of energy loss due to this deformation, and the shear force and slip resulting from this deformation. It has been found that the wear often described can be improved at the same time.
Furthermore, the durability of the appearance of the side portion of the tire, which is often seen in tires with flat beltlines, can be improved without impairing the above-mentioned wear resistance performance and rolling resistance reduction performance by providing a carcass ply reinforcement layer. As a result, the present invention has been completed.

The gist of the present invention is as follows.
In addition, regarding the tire dimension mentioned later, please refer FIG. 1 which shows the width direction cross section of a common tire.
(1) A diameter of a crown portion of the carcass having a carcass made of a carcass ply formed between a bead portion embedding a pair of bead cores in a toroidal shape and folded back from the inner side to the outer side in the tire width direction around the bead core. A pneumatic tire in which a belt having at least one inclined belt layer and a tread are sequentially arranged on the outer side in the direction,
The ratio of the diameter difference BD between the widthwise central portion and the widthwise end of the outermost layer to the width BW of the outermost layer of the inclined belt layer in the tire widthwise cross-section when the tire is mounted on the applicable rim. In the pneumatic tire whose BD / BW is 0.01 or more and 0.04 or less,
A carcass ply reinforcement layer is disposed on the outer side in the width direction of the carcass at the maximum width position of the tire,
The ratio CRFw / CSH of the width CRFw of the carcass ply reinforcement layer to the distance CSH in the tire radial direction between the outermost radial direction of the carcass and the bead toe is 0.2 or more and 0.6 or less,
A pneumatic tire, wherein a reinforcing element embedded in the carcass ply reinforcing layer is inclined at an angle of 30 ° or more and 90 ° or less with respect to the tire equatorial plane.

  Here, the state in which the tire is mounted on the applicable rim is a state in which the tire is incorporated in a standard rim or other applicable rim stipulated in the Japan Automobile Tire Association Standard (JATMA), without applying internal pressure, or about 30 kPa. This means a state with an extremely low internal pressure of up to.

(2) A line segment drawn parallel to the rotation axis of the tire at the maximum width position of the carcass with respect to a distance CSH in the radial direction of the tire between the radially outermost side of the carcass and the bead toe, and the rotation axis of the tire on the bead toe The pneumatic tire according to (1) above, wherein a ratio CSWh / CSH of the shortest distance CSWh to the line drawn in parallel is 0.6 or more and 0.9 or less.

(3) The ratio of the shortest distance SWh between the line segment drawn parallel to the tire rotation axis at the maximum width position of the tire and the line segment drawn parallel to the tire rotation axis at the bead toe relative to the tire cross-section height SH SWh / SH is 0.5 or more and 0.8 or less, The pneumatic tire as described in said (1) or (2) characterized by the above-mentioned.

It is a figure which shows the width direction cross section of a common tire. It is a figure which shows the cross section of the width direction of the tire of this invention. It is a figure which shows the behavior before and behind the load load of the conventional tire. It is a figure which shows the behavior before and behind the load load of the tire of this invention. It is a figure for demonstrating the tensile distortion at the time of changing the neutral axis | shaft of bending. It is a figure which shows the width direction cross section of the conventional tire. It is a figure which shows the cross section of the conventional tire 2 in the width direction.

Hereinafter, the present invention will be specifically described with reference to the drawings.
FIG. 2 shows a cross section in the width direction of the pneumatic tire of the present invention (hereinafter referred to as a tire). The tire 6 of the present invention has a toroidal shape between the bead portions in which the pair of bead cores 1 are embedded, and at least one layer that is folded around the bead core 1 from the inner side to the outer side in the tire width direction. At least one layer in which a carcass 2 made of ply is used as a skeleton, and a large number of cords extending in a direction inclined with respect to the equator plane CL of the tire are coated with rubber on the radially outer side of the crown portion of the carcass 2, illustrated example Then, two inclined belt layers 3a and 3b are arranged, and one circumferential belt layer 4 in which a large number of cords extending along the equatorial plane CL of the tire are covered with rubber on the radially outer side thereof is arranged. A tread 5 is disposed outside the belt in the radial direction.
The inclined belt layer may be a single layer, but in that case, it is preferable that the belt is constituted by a combination with at least one circumferential belt layer.

Such a tire 6 is mounted on the application rim 7 and used. Here, in the cross section in the tire width direction in a state where the tire 6 is mounted on the application rim 7, the width direction central portion (equatorial plane CL) of the outermost layer 3b with respect to the width BW of the outermost layer 3b of the inclined belt layer. And the ratio BD / BW of the diameter difference BD between the width direction end portions is 0.01 or more and 0.04 or less.
The inclined belt layer referred to here has a width of 0.6 times or more the maximum width CSW of the carcass 2.

This definition means that the inclined belt layer 3 has a small diameter difference in the width direction. That is, it shows that the belt is almost flat.
As described above, the rolling resistance is dominated by the energy loss generated in the rubber of the tire tread part, and suppressing shear deformation in the cross section in the width direction, which is one of the deformations, reduces rolling resistance. It is valid. This shear deformation is shown in FIG. 3 in a solid line in a radial tire (ratio BD / BW: 0.052) having a normal sectional shape of size 195/65 R15 before filling with an internal pressure of 210 kPa. As indicated by a dotted line later, a state in which a load of 4.41 kN is applied is caused by deformation in which the belt bent at the ground contact portion is stretched flat by deformation before and after the load application (see arrows). Further, as shown in FIG. 3, in a normal radial tire, since the radius of the shoulder relative to the tire center is small and has a diameter difference, the belt near the shoulder is extended in the tire circumferential direction. Then, since the inclined belt layer arranged with the cords crossing is deformed into a pantograph shape and stretches in the circumferential direction, it shrinks in the width direction, which promotes the shear deformation, and as a result, the tread rubber This will increase the hysteresis loss.

  In order to suppress this deformation most simply from the shape of the tire, it is necessary to make the belt as flat as possible. That is, for a tire of the same size as the tire of FIG. 3 with a flat belt (ratio BD / BW: 0.026), the deformation before and after loading under the same conditions as in FIG. 3 is shown in FIG. As shown, when the ratio BD / BW is set to 0.04 or less, deformation (see arrows) before and after the load can be suppressed to an extremely small level. Therefore, by setting the ratio BD / BW to 0.04 or less, the hysteresis loss of the tread rubber is reduced, and a tire having a low rolling resistance can be obtained.

  In addition, from the viewpoint of the tread shape, when the above-described improvement for suppressing shear deformation is performed, the shearing force and the slip distribution in the ground plane change in a direction to be reduced, so that the wear resistance performance can be improved at the same time. Also came to elucidate.

  In actual tire design, it is necessary to consider the deformation component accompanying the deformation of the side part, the ground contact shape to prevent uneven wear, and the contact pressure distribution. It is important to set the range. As a result of diligent research on this appropriate range, it was found that the above-mentioned ratio BD / BW was 0.01 or more.

Further, in FIG. 2, the carcass ply reinforcement layer 8 is arranged on the outer side in the width direction of the carcass 2 so as to cover the maximum width position W _MAX of the tire at the maximum width position W _MAX of the tire. Further, the ratio CRFw / CSH of the width CRFw of the carcass ply reinforcing layer 8 to the distance CSH in the tire radial direction between the radially outermost side of the carcass 3 and the bead toe 10 is 0.2 or more and 0.6 or less, and It is important that the reinforcing element embedded in the carcass ply 8 reinforcing layer is inclined at an angle of 30 ° to 90 ° with respect to the tire equatorial plane CL. Hereinafter, the reason will be described.

As described above, in a tire with a belt that is nearly flat, when the tire bends under load, there is little deflection of the crown portion including the belt, and bending due to deflection tends to concentrate on the side portion. Thereby, the problem on the tire appearance that a crack arises in a side surface layer part has arisen.
In order to suppress cracking of the side surface layer portion, that is, to suppress distortion of the side surface layer portion, it is conceivable to increase the bending rigidity of the side portion so as to suppress the deflection of the side portion. However, as described above, the bending due to the bending is concentrated on the side portion in order to reduce the deformation in the tread portion and reduce the energy loss of the tread portion. It is necessary to reduce the surface strain. The present inventors have found that while the deflection of the side portion is large, a way of reducing the side surface strain was various attempts, at the maximum width position W _MAX of the tire, so as to cover the maximum width position W _MAX of the tire, the carcass It was confirmed that by disposing the carcass ply reinforcing layer 8 on the outer side in the width direction of 2, the distortion of the side surface layer portion can be suppressed. At the maximum width position W _MAX of the tire where the bending of the side part is concentrated, the neutral axis of the bending at this part is moved to the surface layer side by overlapping the carcass ply reinforcing layer 8 on the main part of the carcass ply and making it double. I am letting. As a result, the distortion of the surface layer can be suppressed.

That is, with reference to FIG. 5, a compressive stress acts on the inner side of the bending neutral axis, and a tensile stress acts on the outer side. Rubber has high rigidity against compressive stress but low rigidity against tensile stress. Therefore, as shown in FIG. 5 (a), if the distance d from the neutral axis of the bending to the side surface is large, the tensile strain acting on the outside of the neutral axis of the bending becomes large, so that this portion is likely to crack. . Therefore, as shown in FIG. 5B, if the distance d from the neutral axis of the bending to the side surface is decreased, the tensile strain acting on the outer side of the neutral axis of the bending is reduced, so that it is difficult for cracks to occur in this portion. .
In the present invention, at the maximum width position W _MAX of the tire, so as to cover the maximum width position W _MAX of the tire, the width direction outer side of the carcass 2, by placing the carcass ply reinforcing layer 8, concentrated bending of the side portions At the maximum width position W _MAX of the tire, the same effect as the double carcass ply is obtained, and the neutral axis of the bending can be moved to the surface layer side to suppress the distortion of the surface layer of the side portion.
In addition, since only the carcass ply reinforcement layer 8 is disposed, the deflection of the entire tire is not greatly affected.

In addition, the ratio CRFw / CSH of the width CRFw of the carcass ply reinforcement layer 8 to the distance CSH in the tire radial direction between the radially outermost side of the carcass 3 and the bead toe 10 may be 0.2 or more and 0.6 or less. It is essential.
When the ratio CRFw / CSH is less than 0.2, the width CRFw of the carcass ply reinforcing layer 8 is narrow and does not make sense as a reinforcing layer. On the other hand, when the ratio CRFw / CSH is more than 0.6, the width CRFw of the carcass ply reinforcement layer 8 is wide, and in many cases, the carcass ply reinforcement layer 8 is connected to any one of the inclined belt layers 3a and 3b and the circumferential belt layer 4. Overlapping positional relationship affects tire deflection and causes a deterioration in ride comfort due to increased vertical springs.
Furthermore, the carcass ply reinforcement layer 8 is preferably disposed at a position where the center position of the carcass ply reinforcement layer 8 in the tire radial direction substantially coincides with the maximum width position W _MAX of the tire.

Furthermore, it is important that the reinforcing element embedded in the carcass ply reinforcing layer 8 is inclined at an angle of 30 ° or more and 90 ° or less with respect to the tire equatorial plane CL.
This is because when the inclination angle of the reinforcing element is less than 30 °, it affects the deflection of the tire and causes a deterioration in riding comfort due to an increase in the vertical spring.
The reinforcing element is preferably made of a material having an elastic modulus comparable to that of the element embedded in the carcass 2. This is because the use of a member having a high elastic modulus, such as a steel cord, affects the deflection of the tire and may cause a deterioration in riding comfort due to an increase in the vertical spring.

Next, as shown in FIG. 2, the maximum width position W _CMAX of the main body of the carcass 2 is parallel to the tire rotation axis with respect to the distance CSH in the tire radial direction between the radially outermost side of the carcass 2 and the bead toe 10. It is preferable that the ratio CSWh / CSH of the shortest distance CSWh between the line segment drawn on the bead 10 and the line segment drawn on the bead toe 10 in parallel with the rotation axis of the tire is 0.6 or more and 0.9 or less. More desirably, it is 0.7 or more and 0.8 or less.

  According to this rule, the carcass line of the tire side portion has a region that is locally bent particularly at a position close to the road surface, and the bending rigidity is reduced at this portion. Then, since the periphery of the bent portion, which is on the outer side in the width direction than the belt width, is greatly deformed when loaded, deformation at the tread portion is reduced. That is, the shear deformation in the cross section can be reduced in the tread. As a result of various trials of dimensions for effectively reducing deformation during loading, it was found that the ratio CSWh / CSH was 0.6 or more and 0.9 or less.

  Further, as shown in FIG. 2, the line segment drawn parallel to the tire rotation axis at the maximum width position of the tire and the line segment drawn parallel to the tire rotation axis at the bead toe with respect to the tire cross-section height SH. The ratio SWh / SH of the shortest distance SWh is preferably 0.5 or more and 0.8 or less. More preferably, it is 0.6 or more and 0.75 or less.

  Now, it is important to originally define the shape of the side portion with a carcass line that is a skeleton. However, in the phenomenon that energy loss occurs inside the rubber and contributes to rolling resistance, the side portion is no exception. In other words, it can be said that taking the shape of the side portion following the carcass line and different from that of the conventional tire leads to efficient improvement. This means, for example, that the side rubber is thinned. If it is obvious that the side rubber can be eliminated, this dimension indicates the same position as the maximum width of the carcass line. Actually, since it is necessary to give the side rubber a predetermined thickness from the role of protecting the carcass when contacting the curbstone, the maximum width position of the side part at this time is compared with the tire cross section height, It was found to be in the ratio range. Moreover, in the tire design, the design of the vulcanization mold is also an important point, so it is necessary as a tire design method to define it as the outer surface dimension.

Conventional tires of the size 195 / 65R15, invention tires and comparative tires were prototyped according to the specifications shown in Table 1, and for each prototype tire, the side wall cracking durability performance, rolling resistance, longitudinal spring performance and A wear resistance performance test was performed and will be described below.
Conventional tire 1 has the tire shape and structure shown in FIG.
Conventional tire 2 has the tire shape and structure shown in FIG.
The invention example tire and the comparative example tire both have the tire shape and structure shown in FIG. 2, and the width CRFw of the carcass ply reinforcing layer 8 and the inclination angle of the reinforcing element are changed.

  The endurance test for the occurrence of cracks in the side part was carried out by mounting each test tire on a standard rim, adjusting the internal pressure to 210 kPa, and then loading conditions 2.5 times the normal load (conditions that promote the occurrence of side cracks) Below, the running distance until a crack generate | occur | produces in the side part was measured using the drum tester (speed: 80.0 km / h) which has an iron plate surface of a diameter of 1.7 m. The measurement results are indexed with the traveling distance of the conventional tire 2 as 100, and the larger the value, the less likely the cracking occurs.

In the rolling resistance test, each test tire was mounted on a standard rim, the internal pressure was adjusted to 210 kPa, and then the axle rolling was performed using a drum testing machine (speed: 80 km / h) having a steel plate surface with a diameter of 1.7 m. This was done by determining the resistance. The rolling resistance was measured according to ISO18164, using a smooth drum and force type. The measurement results shown in Table 1 are indexed with the rolling resistance of the conventional tire 1 as 100, and the smaller the value, the lower the rolling resistance.
The longitudinal spring performance is obtained by measuring the amount of deflection during the rolling resistance test and indexing the spring calculated by “load / deflection amount” with the conventional tire 2 as 100, and the greater the value, the more the deflection. It is difficult. That is, it means that the smaller the value is, the more flexible and the ride comfort is. The amount of deflection is determined by the tire shaft height when no load is applied-the shaft height when a load is applied.

In the abrasion resistance test, each test tire was mounted on a standard rim, the internal pressure was adjusted to 210 kPa, and then an indoor drum test having a safety walk on the surface with a diameter of 1.7 m under the same load conditions as the rolling resistance test. Machine (speed: 80 km / h). Input is 10 minutes for free rolling and 0.1G for 10 minutes in the braking direction. Under these conditions, the wear weight (amount of worn rubber) after traveling 1200 km was measured. The measurement results shown in Table 1 are indexed assuming that the wear weight of the conventional tire 1 is 100. The smaller the wear weight, the better, and a difference of less than 5% is considered equivalent, and there is a difference of 10% or more. It can be said that there is a remarkable difference.
In this test method, since the worn weight is compared, the meaning of the wear resistance test is strong. However, tires with poor uneven wear performance are worn out early, and can be detected in this test. That is, this view can be viewed from both sides of uneven wear resistance and wear resistance.

From Table 1, it can be seen that the invention example tire is improved as compared with the conventional example tire 1 in terms of rolling resistance performance and wear resistance performance.
Regarding side crack durability, the performance is poor in Comparative Example 1 where the ratio CRFw / CSH is 0.1, and good results are obtained when the ratio CRFw / CSH is 0.2 or more.
Regarding the longitudinal spring performance, good results (increase in increase of 5%) are obtained when the reinforcing element angle is 30 ° to 90 ° and the ratio CRFw / CSH is 0.6 or less.
From the above results, it can be seen that the invention example tire has improved durability against side cracks while maintaining the rolling resistance performance and the wear resistance performance as compared with the comparative example tire.

1 Bead core 2 Carcass 3a Inclined belt layer 3b Inclined belt layer (outermost layer)
4 circumferential belt layer 5 tread 6 tire 7 rim 8 carcass auxiliary layer 10 bead toe

Claims (3)

A carcass made of a carcass ply formed by wrapping a pair of bead cores in a toroidal shape between the bead parts and turning back from the inside in the tire width direction around the bead cores, and radially outside the crown part of the carcass. A pneumatic tire in which a belt having at least one inclined belt layer and a tread are arranged in order,
The ratio of the diameter difference BD between the widthwise central portion and the widthwise end of the outermost layer to the width BW of the outermost layer of the inclined belt layer in the tire widthwise cross-section when the tire is mounted on the applicable rim. In the pneumatic tire whose BD / BW is 0.01 or more and 0.04 or less,
A carcass ply reinforcement layer is disposed on the outer side in the width direction of the carcass at the maximum width position of the tire,
The ratio CRFw / CSH of the width CRFw of the carcass ply reinforcement layer to the distance CSH in the tire radial direction between the outermost radial direction of the carcass and the bead toe is 0.2 or more and 0.6 or less,
A pneumatic tire, wherein a reinforcing element embedded in the carcass ply reinforcing layer is inclined at an angle of 30 ° or more and 90 ° or less with respect to the tire equatorial plane.   With respect to the distance CSH in the tire radial direction between the outermost radial direction of the carcass and the bead toe, a line segment drawn parallel to the tire rotation axis at the maximum width position of the carcass and a bead toe parallel to the tire rotation axis. 2. The pneumatic tire according to claim 1, wherein a ratio CSWh / CSH of the shortest distance CSWh to the line segment is 0.6 or more and 0.9 or less.   Ratio SWh / SH of the shortest distance SWh between the line segment drawn parallel to the tire rotation axis at the maximum width position of the tire and the line segment drawn parallel to the tire rotation axis at the bead toe with respect to the tire cross-section height SH The pneumatic tire according to claim 1 or 2, wherein is 0.5 or more and 0.8 or less.

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