JP2005188975A - Breaker impact testing method of air tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To early and reliably test an anti-breaking property of a breaker cord. <P>SOLUTION: A breaker impact testing method of a tire uses a drum body 10 having a drum base 11 and a plurality of protrusions 12 with a knob shape rising from an outer circumference of the drum base 11. The tire 1 rotates and contacts the outer circumference of the drum base 11. A protrusion line X1 passing through the center of the protrusion 12, is inclined to an inclination direction line X0 of the breaker cord at an angle α of 10° or less. A running distance until the breaker cord is broken, is evaluated by an impact received when the tire runs on the protrusions 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a breaker impact test method for a pneumatic tire capable of early and appropriate evaluation of breakage resistance of a breaker cord.

  In a pneumatic tire, a breaker cord may be broken and damaged due to an impact when riding over a protrusion such as a stone on the road or a curb on the road side during traveling. For this reason, when producing tires, it is necessary to check the breakage resistance of the breaker cord.

  Conventionally, as a method for testing the breakage resistance performance of this breaker cord, as schematically shown in FIG. 5, a prism-shaped projection b extending in the tire axial direction (in the width direction) is provided on the outer peripheral surface of the drum base a. The pneumatic tire was rotated using the drum c with protrusions, and the travel distance until the breaker cord was broken by the impact when riding on the protrusions b was evaluated.

  However, this test method has a problem that the distance traveled until the breaker cord breaks becomes long and the test takes a long time, and the reproducibility of the test results is poor and the reliability is poor. As another test method, for example, as described in Patent Document 1, a wedge-shaped weight is dropped on the tread, and evaluation is performed using the drop energy when the breaker cord breaks. Lack of practicality.

JP 2003-106968 A

  Therefore, the present invention can reduce the test time and reproducibility of the test results on the basis of arranging a plurality of knob-shaped protrusions along the inclination direction line of the breaker cord instead of the prismatic protrusions. An object of the present invention is to provide a breaker impact test method for a pneumatic tire that can improve the reliability of the tire.

In order to achieve the above-mentioned object, the invention of claim 1 of the present application is directed to an air having a breaker composed of one or more breaker plies in which breaker cords are aligned and arranged radially outward of the carcass and inward of the tread portion. Breaker impact test method for entering tire,
Using a drum body having a rotating drum base and a plurality of knob-shaped projections that protrude from the outer peripheral surface and impact the tread portion, the pneumatic tire rotates while contacting the outer peripheral surface of the drum base As well as
The breaker cord breaks due to an impact received when riding on the protrusion, with the protrusion line connecting the center of the protrusion being set to an angle α of 10 ° or less with respect to the inclination direction line of the breaker cord of the measurement breaker ply to be measured. It is characterized by evaluating the travel distance.

  In the invention of claim 2, the measurement breaker ply is the second breaker ply from the carcass side.

  According to a third aspect of the present invention, the plurality of protrusions are formed as impact slats attached to the outer peripheral surface of the drum base.

  According to a fourth aspect of the present invention, the impact slats are provided on the outer peripheral surface of the drum base at two to four locations at intervals in the circumferential direction.

  According to a fifth aspect of the present invention, the impact slat includes two protrusions, and the two protrusions are arranged at a distance that can be positioned within one ground plane shape.

  Since the present invention is configured as described above, the test time can be shortened, the reproducibility of the test results can be improved, and the breakage resistance of the breaker cord can be evaluated early and with high reliability. It becomes.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing an example of a pneumatic tire to be tested by the breaker impact test method of the present invention. FIGS. 2A and 2B are a side view and a plan view showing a drum body used in the breaker impact test method. is there.

  In FIG. 1, a pneumatic tire 1 is disposed on a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, inside the tread portion 2, and radially outside the carcass 6. And a breaker 7. In addition, in this example, the case of the radial tire for passenger cars is illustrated.

  In the carcass 6, the carcass cord is arranged at an angle of 30 ° to 90 ° with respect to the tire circumferential direction (for example, 70 ° to 90 ° for a radial structure and 30 ° to 70 ° for a bias structure). 1 or more, in this example, one carcass ply 6A. The carcass ply 6A is provided with a series of folded portions 6b that are folded and locked around the bead core 5 at both ends of the ply body portion 6a straddling the bead cores 5 and 5, and the ply body portion 6a is folded back. An apex rubber 8 for bead reinforcement rising from the bead core 5 is disposed between the portions 6b. The breaker 7 includes one or more breaker cords such as steel cords arranged at an angle of, for example, 15 ° to 70 ° with respect to the tire circumferential direction, and in this example, two breaker plies 7A and 7B. Are stacked with different inclination directions so that the plies cross each other.

  Then, the breakage resistance performance of the breaker cord of the tire 1 is evaluated by a breaker impact test method using the drum body 10 with protrusions shown in FIG.

  In this breaker impact test method, the tire 1 is rotated on a drum body 10 having a protrusion, and the travel distance until breakage damage occurs in the breaker cord due to the impact received when the tire 1 rides on the protrusion 12 is obtained. It is something to evaluate. In the present invention, the protrusion 12 has a knob shape and is arranged along the breaker cord.

  Specifically, the drum body 10 includes a rotating drum base 11 and a plurality of knob-shaped protrusions 12 that protrude from the outer peripheral surface and apply an impact to the tread portion 2. In this example, the case where the plurality of protrusions 12 are formed as impact slats 13 attached to the outer peripheral surface of the drum base 11 is illustrated. The impact slats 13 are formed on the outer periphery of the drum base 11. It is preferable to provide 2-4 places on the surface at intervals in the circumferential direction.

  The drum base 11 is not particularly defined, but has a smooth surface and a width equal to or greater than the total tire width, for example, similar to a steel drum used for “Testing durability performance of automobile tires” in Section 6.3 of JIS D4230. In addition, a metal drum having a diameter of about 1.5 to 2.5 mm and a diameter larger than that of the tire 1 can be suitably used. The drum base 11 is pivotally supported by a support shaft between the columns 14 and 14, and is driven to rotate at a peripheral speed of, for example, 20 to 100 km / h.

  The pneumatic tire 1 is pivotally supported by a tire pressing machine 15 provided on the drum base 11. The tire pressing machine 15 includes pressing means 16 such as a cylinder, for example, and is pressed at the substantially same speed as the drum base 11 while the pneumatic tire 1 is pressed against the outer peripheral surface of the drum base 11 by being pressed by the pressing means 16. Rotate with

  Next, as shown in FIGS. 3A and 3B, the impact slat 13 is a rectangular plate-like thin slat plate 17 which is detachably attached to the outer peripheral surface of the drum base 11 using, for example, screw fittings. And a plurality of protrusions 12 in this example, which protrude from the outer surface of the slat plate 17.

  The slat plate 17 has an arc plate shape that curves along the outer peripheral surface of the drum base 11, and both circumferential ends E of the slat plate 17 are inclined portions 17e inclined at an angle θ of 60 to 30 ° with respect to the radial direction. Yes. This facilitates the riding of the tire. In addition, when the thickness T of the slat plate 17 is too thick, it is not possible to ride smoothly, and conversely, if it is too thin, the necessary durability cannot be ensured. Therefore, the upper limit of the thickness T is preferably 20 mm or less, more preferably 15 mm or less, and the lower limit thereof is preferably 5 mm or more, more preferably 10 mm or more. The width W of the slat plate 17 is larger than the tread width TW of the tire 1.

  The protrusion 12 is a substantially hemispherical knob-like protrusion, and its height H is preferably set in the range of 10 to 15 mm assuming a general protrusion on the road. In this example, a case of a hemisphere having a radius r of 12.5 mm is illustrated. Further, as shown in FIG. 3A, the measurement breaker ply for measuring the projection line X1 that connects the center of the projection 12 so that the projection 12 formed on one slat plate 17 is arranged along the breaker cord. It is set at an angle α of 10 ° or less with respect to the inclination direction line X0 of the 20 breaker cords.

  Here, the measurement breaker ply 20 is a breaker ply to be subjected to an impact test, and the breakage resistance of the breaker cord is tested. The measurement breaker ply 20 can be freely selected from the plurality of plies when the breaker 7 is composed of a plurality of plies, but because the cord breakage is more likely to occur than other plies, The second breaker ply 7B from the carcass side is preferably used as the measurement breaker ply 20.

  Thus, by arranging the projections 12 along the breaker cord, the same breaker cord can be distorted simultaneously as shown exaggeratedly in FIG. As a result, breakage damage can occur early and the test time can be shortened. In addition, since the breaker cord is greatly damaged by the distortion, it is possible to improve the reliability of the test result by reducing the variation in the break time and increasing the reproducibility of the test result. If the angle α exceeds 10 °, the effect cannot be exhibited.

  In order to maximize the effect, it is preferable that the two projecting portions 12 be arranged at a distance that can be located in one ground plane shape F. The contact surface shape F is a contact surface shape that the tread portion 2 contacts when the internal pressure and load applied during the breaker impact test are applied to the tire 1. In the case of a passenger car tire, the protrusion 12 , 12 can be positioned within the ground contact surface shape F by setting the distance L to 12 mm or less, preferably 100 mm or less. If the distance L is too small, the distortion to the breaker cord tends to be small and the effect of the present invention tends to be reduced. Therefore, the distance L is preferably 30 mm or more.

  The internal pressure, load load, rotation speed, and the like at the time of performing the breaker impact test are not particularly defined in the present application, but in particular, the conditions specified in “Automotive tire durability test” in Section 6.3 of JIS D4230. It is preferable from the viewpoint of standardization.

As the internal pressure and load load, it is also preferable to adopt so-called “normal internal pressure” and “normal load” determined by the standard for each tire in a standard system including the standard on which the tire is based. Specifically, the “regular internal pressure” is the maximum air pressure for JATMA, the maximum value listed in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA, and “INFLATION PRESSURE” for ETRTO. This means 200 kPa in the case of passenger car tires. The “regular load” means maximum load capacity for JATMA, maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA, and “LOAD CAPACITY” for ETRTO.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention can be implemented to the tire of various categories, without being limited to the tire for passenger cars.

  A breaker impact test was performed on radial tires for passenger cars having a tire size of 265 / 70R16 using the drum body of the specifications shown in Table 1, and the running time until the breaker cord broke was measured and compared with each other.

  As test conditions, a steel drum having a diameter of 1707.6 mm was used in accordance with JIS D4230 “6.3 Durability test of automobile tires”, rim (16 × 8.0JJ), internal pressure (200 kPa). , Load (9.8 kN), speed 80 km / h.

It is sectional drawing which shows an example of the pneumatic tire tested by the breaker impact test method of this invention. (A), (B) is the side view and top view which show the drum body used for the breaker impact test method. (A), (B) is the top view and circumferential direction sectional drawing which show an impact slat. It is a diagram explaining the effect. It is a perspective view explaining a prior art.

Explanation of symbols

2 Tread portion 6 Carcass 7A, 7B Breaker ply 7 Breaker 10 Drum body 11 Drum base 12 Protrusion 13 Impact slat 20 Measurement breaker ply X1 Protrusion line X0 Inclination direction line

Claims (5)

A breaker impact test method for a pneumatic tire comprising a breaker composed of one or more breaker plies in which a breaker cord is aligned and arranged radially outside the carcass and inside a tread portion,
Using a drum body having a rotating drum base and a plurality of knob-shaped projections that protrude from the outer peripheral surface and impact the tread portion, the pneumatic tire rotates while contacting the outer peripheral surface of the drum base As well as
The breaker cord breaks due to an impact received when riding on the protrusion, with the protrusion line connecting the center of the protrusion being set to an angle α of 10 ° or less with respect to the inclination direction line of the breaker cord of the measurement breaker ply to be measured. A breaker impact test method for a pneumatic tire, characterized by evaluating a travel distance up to.   The breaker impact test method for a pneumatic tire according to claim 1, wherein the measurement breaker ply is the second breaker ply from the carcass side.   The pneumatic tire breaker impact test method according to claim 1, wherein the plurality of protrusions are formed as impact slats attached to the outer peripheral surface of the drum base.   The pneumatic tire breaker impact test method according to claim 3, wherein the impact slats are provided on the outer peripheral surface of the drum base body at 2 to 4 locations at intervals in the circumferential direction.   The pneumatic shock according to claim 3 or 4, wherein the impact slat includes two protrusions, and the two protrusions are arranged at a distance that can be located within one ground plane shape. Tire breaker impact test method.

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