JPH106712A - Pneumatic tire and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the grounding pressure distribution of a shoulder part and to suppress early wear and uneven wear by burying a rubber sheet having a particular characteristic in a tread part immediately below a peripheral direction main groove in a pneumatic tire having a shoulder land part formed by the peripheral direction main groove. SOLUTION: A load up to 70% is applied to a pneumatic tire having shoulder land parts 2 in both side parts of a tread part 1. On a tire width direction line passing through a grounding center in a grounding surface at this time, a grounding pressure P1 from a groove side wall outside the tire width direction to a shoulder land part position outside the 3mm tire axial direction and a grounding pressure P2 from a grounding end position to the shoulder land position inside the 3mm tire width direction are measured. An unvulcanized rubber sheet having M100 (tensile stress when rubber is expanded by 100%) higher than surrounding tread rubber when P1<P2 and M100 lower than the surrounding tread rubber when P1>P2 is placed or made integral in a position immediately below the peripheral direction main groove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to an improvement in uneven wear of a shoulder portion of a radial tire for a passenger car.

[0002] Here, to describe the terminology used herein, "the M _100], a physical property value according to the test method of the rubber shown in JIS-K6301, rubber 10
This is the tensile stress when elongating by 0%. It is one of the general properties representing the physical properties of rubber, and is sometimes referred to as 100% modulus. The “skid base gauge” is a gauge obtained by removing a groove depth from a tread gauge.

[0003]

2. Description of the Related Art In a pneumatic tire having a shoulder land portion formed by a circumferential main groove extending in a circumferential direction on both sides of a tread portion, early wear or uneven wear of this portion becomes a problem. Various measures have been taken such as changing the tread rubber, optimizing the tire shape, and changing the tread pattern. However, at present, no drastic solution has been found. A number of improvements have been made to the contact surface shape and contact pressure distribution of tires, but they can be applied only in a very limited range and are not at a stage that can be said to be a versatile method.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a tire having improved early wear or uneven wear by paying attention to the contact pressure distribution in a contact surface, particularly the contact pressure distribution in a shoulder portion, and optimizing the distribution. It was made for the purpose of providing.

[0005]

In order to achieve the above object, a pneumatic tire according to the present invention includes a shoulder land portion formed on both sides of a tread portion by a circumferential main groove extending in a circumferential direction. The pneumatic tire is assembled on a standard applicable rim, filled with the maximum internal pressure specified in the JATMA standard, and when a load of 70% of the maximum load capacity is applied, the circumferential direction is determined on a tire width direction line passing through a ground contact center in a ground contact surface. 3 m from the groove sidewall on the outer side in the tire width direction of the groove sidewall forming the main direction groove
When the contact pressure at the shoulder land portion at the outer side in the m tire axial direction is P1, and the contact pressure at the shoulder land portion at a position 3 mm inward in the tire width direction from the contact end position is P2,
(1) P1 <When P2, embedded M ₁₀₀ is a high rubber sheet than the tread rubber of the peripheral tread portion directly under the circumferential direction main groove, (2) P1> When P2, circumferential direction main grooves immediately below M ₁₀₀ adopts the configuration in which buried lower rubber sheet than the tread rubber surrounding the tread portion.

The thickness of the rubber sheet is preferably 30 to 90% of the skid base gauge.

Further, it is preferable that the width of the rubber sheet is 60 to 400% of the width of the circumferential main groove on the tire surface.

In order to achieve the above object, a method of manufacturing a pneumatic tire according to the present invention is directed to a pneumatic tire having a shoulder land portion formed on both sides of a tread portion by a circumferential main groove extending in a circumferential direction. In the production method, (1) a step of molding and vulcanizing a reference tire, and (2)
The tire is assembled on a standard applicable rim, filled with the maximum internal pressure specified in the JATMA standard, and when a load of 70% of the maximum load capacity is applied, on the tire width direction line passing through the contact center in the contact surface, the circumferential main direction is set. The contact pressure P1 at the shoulder land portion 3 mm outward in the tire axial direction from the outer groove sidewall in the tire width direction, and the shoulder 3 mm inward in the tire width direction from the contact end position. A step of measuring the contact pressure P2 at the land portion position, (3) when P1 <P2, a portion of the unvulcanized tread rubber which corresponds to immediately below the circumferential main groove when the tire product is unvulcanized tread rubber, More M
Place or unify a high unvulcanized rubber sheet of ₁₀₀
1> When P2, the position portion of which corresponds to the circumferential direction main grooves immediately below when the tire products unvulcanized tread rubber, placed or integrated low unvulcanized rubber sheet having a M ₁₀₀ than the tread rubber around the (4) a step of attaching the unvulcanized tread rubber produced in the above step to a green case to produce a green tire, and (5) a step of vulcanizing the green tire to produce a product. The manufacturing method is adopted.

[0009] A method for producing a tire in which the thickness of the rubber sheet is 30 to 90% of the skid base gauge is preferred.

[0010] Further, a manufacturing method is preferred in which the width of the rubber sheet is 60 to 400% of the width of the circumferential main groove on the tire surface.

It is preferable that the contact pressure of the tire be uniform within the contact surface under the conditions of use in terms of both wear and handling stability. It can be expected to make the ground pressure uniform in the ground plane to some extent at the design stage, but it depends on various conditions such as groove arrangement, belt rigidity and width, so we have to rely on trial and error means. The situation. In the present invention, attention is paid particularly to a pneumatic tire having a shoulder land portion formed by a circumferential main groove extending in the circumferential direction on both side portions of the tread portion, and is most problematic in such a tire. It is the result of a study to improve the early wear or uneven wear of the shoulder land portion. That is, it is based on the following knowledge obtained as a result of conducting detailed observation and examination of the above-mentioned tire. (1) The tire is mounted on the standard applicable rim, filled with the maximum internal pressure specified in the JATMA standard, and the ground contact surface when a load of 70% of the maximum load capacity (70% is selected as a load closer to actual use conditions) is applied. On the tire width direction line passing through the center of contact with the ground, the contact pressure P1 at the position of the shoulder land portion 3 mm outward in the tire axial direction from the groove side wall on the outer side in the tire width direction of the groove side wall forming the circumferential main groove. And when the contact pressure P2 at the position of the shoulder land portion 3 mm inward in the tire width direction from the position of the contact end is P2 and P1 and P2 contact pressures are substantially the same, premature wear or uneven wear of this portion will occur. Occurrence is small. In addition, when the location where P1 and P2 are measured cannot be measured due to a groove, a sipe, or the like, the tire may be rotated and displaced, or the vicinity thereof may be measured. (2) With respect to the tire satisfying P1 <P2, the wear near the shoulder land portion 7 shown in FIG.
As for the tires, the shoulder land portion 6 shown in FIG.
Abrasion in the vicinity tends to be faster. In other words, the side where the contact pressure is higher wears faster. (3) And, regarding the tire satisfying P1 <P2,
In the portion directly below the circumferential groove 3, the tread rubber around
_If the rubber having a high rubber of ₁₀₀ is buried to increase the bending rigidity in the tire width direction, it is possible to make the contact pressure uniform, and in a tire satisfying P1> P2, if so lower the tire width direction bending rigidity by embedding the lower rubber having M ₁₀₀ than the tread rubber around it, it is possible to equalize the ground pressure.

The grounding pressure measurement conditions are set on the standard applicable rim, filled with the maximum internal pressure specified in the JATMA standard, and a load of 70% of the maximum load capacity (70% is selected as a load closer to actual use conditions). Although it is assumed that the tire is loaded, if a tire is developed only for a specific vehicle type, a more favorable result can be obtained by measuring the contact pressure according to the load, internal pressure, etc. of the vehicle type. In addition, there is some trial and error in the implementation of the present invention, and it is necessary to slightly modify the optimization method for the width, thickness and physical properties of the rubber sheet to be embedded depending on the intended tire each time. It is easy for those skilled in the art.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pneumatic tire according to an embodiment of the present invention will be described. The reference tire is a pneumatic tire for a passenger car, and the size is 185 in Example 1.
Example 2 is 225 / 50R16 at / 70R14.
As shown in FIG. 1, these tires have a shoulder portion formed by a circumferential main groove extending in the circumferential direction on both sides of the tread portion.

[Embodiment 1] In Embodiment 1, a case of a tire satisfying P1 <P2 will be described. Tire size is 1
85 / 70R14, and the rim size is 14 × 5J. First, in order to confirm the effects of the present invention, P1 and P2 were measured by applying a reference tire with an internal pressure of 2.4 kgf / cm ² and a load of 390 kgf, and it was found that P2 / P1 was 3.5. Based on this result, a tire was prototyped with the specifications shown in Table 1 and the contact pressure was measured. And the wear of the shoulder part was measured on the following conditions using the flat belt wear tester.・ Road surface: Safety walk ・ Room temperature: 30 ° C. ・ Slip angle: 0.5 ° ・ Load: 390 kgf ・ Load braking force: 39 kgf ・ Speed: 50 km / h ・ Distance: 300 km The abrasion at the position 7 is shown as an index with the abrasion amount of the reference tire being 100. The smaller the value, the better the wear and the better.

[0015]

[Table 1]

[0016] According to the above evaluation results, tires buried high M ₁₀₀ rubber sheet directly below the circumferential main groove 3 is found to be improved premature wear with a uniform ground contact pressure of the shoulder land portion did.

[Embodiment 2] In Embodiment 2, a case of a tire satisfying P1> P2 will be described. Tire size is 2
25 / 50R16 and the rim size is 16 × 7JJ. First, in order to confirm the effect of the present invention, P1 and P2 were measured by applying a reference tire with an internal pressure of 2.4 kgf / cm ² and a load of 440 kgf.
Met. Based on this result, a tire was prototyped with the specifications shown in Table 1 and the contact pressure was measured. And the wear of the shoulder part was measured on the following conditions using the flat belt wear tester. -Road surface: safety walk,-Room temperature: 30 ° C,-Slip angle: 0.5 degree,-Load: 440 kgf-Load braking force: 45 kgf,-Speed: 50 km / h-Driving distance: 300 km, Comparative evaluation is shown in Fig. 2. The abrasion at the position No. 6 is shown as an index with the abrasion loss of the reference tire being 100. The smaller the value, the better the wear and the better.

[0018]

[Table 2]

[0019] According to the above evaluation results, tires buried low M ₁₀₀ rubber sheet directly below the circumferential main groove 3 is found to be improved premature wear with a uniform ground contact pressure of the shoulder land portion did.

[0020]

As described above, it is possible to provide a tire with improved early wear or uneven wear by paying attention to the contact pressure distribution in the shoulder land portion and optimizing it.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view in the width direction of a pneumatic tire according to the present invention.

FIG. 2 is a diagram showing a contact surface shape showing a position where a contact pressure is measured.

[Explanation of symbols]

E Equatorial line (Pattern center) C Grounding center A P1 measurement point B P2 measurement point 1 Tread part 2 Shoulder land part 3 Circumferential main groove 4 Rubber sheet 5 Skid base gauge 6 Shoulder part groove side wall 3 mm outside from the tire axial direction 7 Position 3 mm inward in the tire width direction from the position of the ground contact edge

Claims (6)

[Claims] 1. A pneumatic tire having a shoulder land portion formed by a circumferential main groove extending in a circumferential direction on both sides of a tread portion, assembled on a standard applicable rim, and filled with a maximum internal pressure specified in JATMA standards. On a tire width direction line passing through the center of contact in the ground contact surface when a load of 70% of the maximum load capacity is applied, a tire 3 mm from the groove side wall on the outer side in the tire width direction of the groove side wall forming the circumferential main groove. When the contact pressure at the shoulder land portion on the outside in the axial direction is P1 and the contact pressure at the shoulder land portion on the inner side in the tire width direction by 3 mm from the position of the contact end is P2, (1) P1 < when P2, M ₁₀₀ is embedded a higher rubber sheet than the tread rubber of the peripheral tread portion directly under the circumferential direction main groove, (2)
When P1> P2, the pneumatic tire characterized in that M ₁₀₀ from the tread rubber of the peripheral tread portion directly under the circumferential direction main grooves embedded low rubber sheet. 2. The rubber sheet according to claim 1, wherein the thickness of the rubber sheet is 30 to 90% of the skid base gauge.
The pneumatic tire as described. 3. The pneumatic tire according to claim 1, wherein the width of the rubber sheet is 60 to 400% of the width of the circumferential main groove on the tire surface. 4. A method for manufacturing a pneumatic tire having a shoulder land portion formed on both sides of a tread portion by a circumferential main groove extending in a circumferential direction. (1) Molding and vulcanizing a reference tire (2) assembling the tire on a standard applicable rim, filling the tire with the maximum internal pressure specified in the JATMA standard, and passing a load of 70% of the maximum load capacity through the ground contact center in the ground contact surface On the width direction line, the contact pressure P1 at the position of the shoulder land portion 3 mm outward from the inner groove side wall of the groove side wall forming the circumferential main groove in the tire axial direction, and the position of the contact end Contact pressure P2 at the shoulder land portion inward in the 3 mm tire width direction
Measuring a, (3) P1 <When P2, the position portion of which corresponds to the circumferential direction main grooves immediately below when the tire products unvulcanized tread rubber, high unvulcanized of M ₁₀₀ than the tread rubber around the Place or integrate the rubber sheet, P1> P2
Time, the located portion of which corresponds to the circumferential direction main grooves immediately below when the tire products unvulcanized tread rubber, the step of placing or integrated low unvulcanized rubber sheet having a M ₁₀₀ than the tread rubber around them, (4) a step of attaching the unvulcanized tread rubber produced in the above step to a green case to produce a green tire, and (5) a step of vulcanizing the green tire to produce a product. Method for manufacturing tires containing steel. 5. The rubber sheet according to claim 4, wherein the thickness of the rubber sheet is 30 to 90% of the skid base gauge.
A method for manufacturing the pneumatic tire according to the above. 6. The method according to claim 4, wherein the width of the rubber sheet is 60 to 400% of the width of the circumferential main groove on the tire surface.