JP2008030660A - Pneumatic tire and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of effectively preventing the breakdown of a side wall portion during low air traveling. <P>SOLUTION: In the pneumatic tire, a splice portion 12d of a carcass member 12 is formed to make the tire circumferential direction length of a part 12b corresponding to the side wall portion 2 shorter than the tire circumferential direction length S2 of a part 12c corresponding to a tread portion 1, so that splice amount on the side wall portion 2 side can be made less than that on the tread portion 1 side. Therefore, stiffness changes in the tire circumferential direction is suppressed, and bending amount can be made uniform. Therefore, concentration of stress to the splice portion 12d of the side wall portion can be reduced during run-flat traveling. Consequently, the occurrence of the breakdown of the side wall portion 2 from a reinforcing cord 12a of the splice portion 12a can be effectively prevented, and long distance traveling performance during run-flat traveling can be improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire used as, for example, a run flat tire for a passenger car and a method for manufacturing the same.

In general, this type of pneumatic tire is provided with a crescent-shaped reinforcing layer on the left and right sidewalls to suppress the longitudinal deflection of the tire due to the rigidity of the reinforcing layer when the air pressure drops, such as punctures, in a low air pressure state. One that enables run-flat running is known (for example, see Patent Document 1).
JP-A-2005-47441

  By the way, during run flat running of the pneumatic tire, the load on the sidewall portion increases, so that there is a problem that the sidewall portion is liable to be broken and durability during run flat running is lowered. In this case, as a cause of breakage, stress concentrates on the splice portion of the material, particularly the splice portion of the carcass member in the side wall portion, and the breakage often proceeds based on the reinforcing cord of the splice portion.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a pneumatic tire capable of effectively preventing the destruction of the sidewall portion during low-air running and a method for manufacturing the same. There is to do.

  In order to achieve the above object, the present invention provides a pneumatic tire in which a carcass layer is formed by splicing both ends in the tire circumferential direction of a carcass member in which a plurality of reinforcing cords are arranged in the tire circumferential direction. The splice portion of the member is formed such that the tire circumferential length of the portion corresponding to the sidewall portion is shorter than the tire circumferential length of the portion corresponding to the tread portion.

  Accordingly, the splice portion of the carcass member is formed so that the tire circumferential length of the portion corresponding to the sidewall portion is shorter than the tire circumferential length of the portion corresponding to the tread portion. The splice amount on the part side is smaller than that on the tread part side.

  In order to achieve the above object, the present invention provides a pneumatic tire in which a carcass layer is formed by splicing both ends in the tire circumferential direction of a carcass member in which a plurality of reinforcing cords are arranged in the tire circumferential direction. In the manufacturing method, the splice portion of the carcass member is formed so that the tire circumferential length of the portion corresponding to the sidewall portion is shorter than the tire circumferential length of the portion corresponding to the tread portion.

  As a result, the splice portion of the carcass member is formed so that the tire circumferential length of the portion corresponding to the sidewall portion is shorter than the tire circumferential length of the portion corresponding to the tread portion. The splice amount on the side is smaller than that on the tread portion side.

  According to the present invention, the amount of splice on the side wall portion side can be made smaller than that on the tread portion side, so that the change in rigidity in the tire circumferential direction can be suppressed and the amount of deflection can be made uniform. In addition, stress concentration on the splice portion of the sidewall portion can be reduced during run flat running. Therefore, it is possible to effectively prevent the side wall portion from being broken from the reinforcing cord of the splice portion, and to improve the long-distance running performance in the run flat running.

  1 to 5 show an embodiment of the present invention. FIG. 1 is a partial front sectional view of a pneumatic tire, FIG. 2 is a partial side view of a carcass member in an intermediate process, and FIG. 3 is a carcass member in an intermediate process. FIG. 4 is a plan view showing a splice portion of a carcass member, and FIG. 5 is a view showing test results.

  The pneumatic tire includes a tread portion 1 formed on the outer peripheral surface side, sidewall portions 2 formed on both sides in the width direction, bead portions 3 formed on the tire radial direction inner side of the sidewall portions 2, It is comprised from the reinforcement layer 4 formed in the tire width direction inner side of the wall part 2, and is used as a run flat tire.

  The pneumatic tire is formed into a cylindrical shape after an inner liner 10 formed in a sheet shape, a pair of left and right reinforcing members 11, a carcass member 12, and a plurality of belts 13 are overlapped on a forming drum and formed into a cylindrical shape. 12 is formed in a toroidal shape so as to straddle between a pair of left and right bead members 14, and a tread member 15 and a sidewall member 16 are attached to the outer peripheral surface thereof.

  The inner liner 10 is made of a sheet-like rubber having airtightness, and is disposed on the inner peripheral surface side of the carcass member 12.

  The reinforcing member 11 is made of hard rubber having a crescent-shaped cross section, and is disposed between the carcass member 12 and the inner liner 10 on the side wall 2 side.

  The carcass member 12 is made of sheet-like rubber in which a plurality of reinforcing cords 12a are arranged in the tire circumferential direction, and is formed in a cylindrical shape by splicing one end and the other end in the longitudinal direction (tire circumferential direction). At the same time, the both ends of the width direction are folded back toward the sidewall portion 2 from the inner side to the outer side in the tire width direction so as to wind the bead member.

  Each belt 13 is formed by covering a reinforcing wire made of a steel cord, high-strength fiber or the like with a sheet-like rubber material, and is arranged on the outer peripheral surface side of the carcass member 12 so as to overlap each other.

  The bead member 14 includes a bead core 14a formed by bundling wires such as metal wires, and a bead filler 14b formed of rubber having a substantially triangular cross section. The bead filler 14b is fixed to the outer periphery of the bead core 14a.

  The tread member 15 is made of rubber formed by extrusion molding, and is disposed so as to cover the center side in the width direction of the carcass member 12 and the outer peripheral surface side of each belt 13. A groove 15a forming a predetermined tread pattern is formed on the outer peripheral surface of the tread member 15 at the time of vulcanization molding.

  The side wall member 16 is made of rubber formed by extrusion molding, and is disposed so as to cover both ends of the carcass member 12 in the width direction.

  Next, a method for manufacturing the pneumatic tire will be described. In addition, the process demonstrated below shows the shaping | molding process of the carcass member 12, Since it is equivalent to the former, about another manufacturing process, it abbreviate | omits.

  First, as shown in FIGS. 4 (a) and 4 (b), the portion 12 b corresponding to the sidewall portion 2 at each end in the width direction of the longitudinal end portion of the carcass member 12 is more than the portion 12 c corresponding to the tread portion 1. Cut to a predetermined length L in the tire circumferential direction. Thereafter, one end and the other end of the carcass member 12 are spliced to form a cylindrical shape. At that time, in the splice portion 12d of the carcass member 12, the tire circumferential length S1 of the portion 12b corresponding to the sidewall portion 2 is equal to the tire circumferential length S2 of the portion 12c corresponding to the tread portion 1 as shown in FIG. Therefore, the splice amount on the side wall portion 2 side of the tire formed in a toroidal shape as shown in FIG. 2 is smaller than that on the tread portion 1 side. In this case, the tire circumferential direction length S1 of the portion 12b corresponding to the sidewall portion 2 is formed to be 0 mm or more and 4 mm or less, and the tire circumferential direction length S2 of the portion 12c corresponding to the tread portion is 1 mm or more and 7 mm or less. It is formed to become. In addition, the dashed-dotted line in FIG. 3 shows the folding | turning part (turnup part) of the carcass member 12. In FIG.

  Here, as shown in FIG. 5, when the run flat travel distance and the RFV evaluation test were performed for each of the three types of Examples 1 to 3, the following results were obtained. In this test, tires having a tire size of 225 / 45R17 were used and a passenger car with a displacement of 2500 cc (load equivalent to four passengers) was used. In this case, run-flat running was performed by removing the valve core, and the distance until the driver stopped the vehicle due to vibration or off-flavor was evaluated using an index based on Comparative Example 1. In the uniformity test, the average of 10 measured values was calculated for the difference between the maximum value and the minimum value of RFV, and the higher the numerical value with reference to Comparative Example 1, the better the reference ratio. evaluated.

  As a result of the test, it was carried out for Comparative Example 1 (the tire circumferential direction length of the splice portion 12d corresponding to the tread portion 1: 4 mm, the tire circumferential direction length of the splice portion 12d corresponding to the sidewall portion 2: 4 mm). Example 1 (the tire circumferential direction length of the splice portion 12d corresponding to the tread portion 1: 4 mm, the tire circumferential direction length of the splice portion 12d corresponding to the sidewall portion 2: 1 mm), Example 2 (corresponding to the tread portion 1) The circumferential length of the splice portion 12d is 4 mm, the circumferential length of the splice portion 12d corresponding to the sidewall portion 2 is 2 mm, and Example 3 (the circumferential direction of the splice portion 12d corresponding to the tread portion 1). The length of the splice portion 12d corresponding to the side wall portion 2 is 4 mm, and the length in the circumferential direction of the tire is 2 mm. Evaluation of RFV was good results as the respective all 105 or higher. Further, in comparative example 2 (compared to comparative example 1 in the tire circumferential direction length of the splice portion 12d corresponding to the tread portion 1: 7 mm, and in the tire circumferential direction length of the splice portion 12d corresponding to the sidewall portion 2: 7 mm), The results of the flat mileage and RFV were less than 100 respectively. Therefore, the tire circumferential direction length S1 of the portion 12b corresponding to the sidewall portion 2 is preferably 0 mm or more and 4 mm or less, and the tire circumferential direction length S2 of the portion 12c corresponding to the tread portion 1 is preferably 1 mm or more and 7 mm or less.

  As described above, according to this embodiment, the splice portion 12d of the carcass member 12 has the tire circumferential direction length S1 of the portion 12b corresponding to the sidewall portion 2 and the tire circumferential direction length S1 of the portion 12c corresponding to the tread portion 1. Since it is formed to be shorter than the length S2, the amount of splice on the side wall portion 2 side can be made smaller than that on the tread portion 1 side. As a result, the change in rigidity in the tire circumferential direction is suppressed and the amount of deflection can be made uniform, so that the concentration of stress on the splice portion 12d of the sidewall portion 2 can be reduced during run-flat running. Accordingly, it is possible to effectively prevent the sidewall portion 2 from being broken with the reinforcing cord 12a of the splice portion 12d as a base point, and to improve the long-distance running performance in the run-flat running. In this case, since the side wall portion 2 has a lower carcass lift rate than the tread portion 1, it is sufficiently possible to reduce the splice amount of the carcass member 12 of the side wall portion 2 in recent low-flat tires.

  Further, the splice portion 12d of the carcass member 12 is formed so that the tire circumferential direction length S1 of the portion 12b corresponding to the sidewall portion 2 is 0 mm or more and 4 mm or less, and the tire circumference of the portion 12c corresponding to the tread portion 1 is formed. Since the direction length S2 is formed so as to be 1 mm or more and 7 mm or less, the run-flat travel distance and RFV can be effectively improved.

  When cutting both ends in the width direction at one end in the longitudinal direction of the carcass member 12, as shown in the modification of FIG. 6, a portion 12b corresponding to the sidewall portion 2 and a portion 12c corresponding to the tread portion 1 The space may be cut obliquely with respect to the tire circumferential direction.

  Moreover, in the said embodiment, although the width direction both ends side in the longitudinal direction one end part of the carcass member 12 is cut | disconnected, as shown to Fig.7 (a), the tire width direction in the tire circumferential direction one end part By extending the center side in the tire circumferential direction from both ends in the width direction, the tire circumferential direction length of the splice portion 12d of the carcass member 12 corresponding to the sidewall portion 2 is increased as shown in FIG. 7 (b). The predetermined length L may be shorter than the length in the tire circumferential direction of the portion 12c corresponding to the tread portion 1.

  Furthermore, in the above-described embodiment, the case where the carcass member 12 is a single layer is shown. However, when the carcass member 12 is formed in at least two layers, the positions of the splice portions 12d of the carcass members 12 are shifted from each other in the tire circumferential direction. By providing in this way, stress concentration on the splice portion 12d of the sidewall portion 2 can be effectively prevented.

  Furthermore, in the said embodiment, although the case where this invention was applied to a run flat tire was shown, it is applicable also to the tire which does not have the reinforcement layer 4. FIG.

Partial front sectional view of a pneumatic tire showing an embodiment of the present invention Partial side view of carcass member in intermediate process Plan view of carcass member in intermediate process Plan view showing splice part of carcass member Diagram showing test results A plan view of a carcass member in an intermediate process showing a modified example The top view of the carcass member in the intermediate process which shows other embodiment of a manufacturing method

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Tread part, 2 ... Side wall part, 12 ... Carcass member, 12a ... Reinforcement cord, 12d ... Splice part

Claims (6)

In a pneumatic tire formed by splicing both ends in the tire circumferential direction of a carcass member in which a plurality of reinforcing cords are arranged in the tire circumferential direction to form a carcass layer,
A pneumatic tire characterized in that the splice portion of the carcass member is formed such that a tire circumferential length of a portion corresponding to the sidewall portion is shorter than a tire circumferential length of a portion corresponding to the tread portion. The overlapping part of the splice part is formed so that the tire circumferential length of the part corresponding to the sidewall part is 0 mm or more and 4 mm or less, and the tire circumferential direction length of the part corresponding to the tread part is 1 mm or more and 7 mm or less. The pneumatic tire according to claim 1, wherein the pneumatic tire is formed as follows. 3. The pneumatic tire according to claim 1, wherein the carcass layer is formed in at least two layers, and splice portions of the carcass layers are provided so as to be displaced from each other in the tire circumferential direction. In the method for manufacturing a pneumatic tire, wherein a carcass layer is formed by splicing both ends in the tire circumferential direction of a carcass member in which a plurality of reinforcing cords are arranged in the tire circumferential direction.
The spliced portion of the carcass member is formed so that the tire circumferential length of the portion corresponding to the sidewall portion is shorter than the tire circumferential length of the portion corresponding to the tread portion. Method. By cutting the both ends of the carcass member in the tire width direction at one end in the tire width direction by a predetermined length in the tire circumferential direction, the tire circumferential length of the portion corresponding to the sidewall portion of the splice portion of the carcass member is a tread. It forms so that it may become shorter than the tire circumferential direction length of the part corresponding to a part. The manufacturing method of the pneumatic tire of Claim 4 characterized by the above-mentioned. By extending the center side in the tire width direction at one end in the tire circumferential direction of the carcass member by a predetermined length in the tire circumferential direction from both ends in the width direction, the splice portion of the carcass member corresponds to the sidewall portion. The method for manufacturing a pneumatic tire according to claim 4, wherein the length in the direction is shorter than the length in the tire circumferential direction of the portion corresponding to the tread portion.

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