JP2017213829A - Method for manufacturing green tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve uniformity by reducing un-uniformity of strain in stitch down without causing a decline in productivity.SOLUTION: A tread ring formation step S1 includes: a first step S11 of forming a belt layer 7 on a straight cylindrical drum 13; and a second step S12 of forming a tread rubber 2G by winding a tread rubber strip 15 spirally. In the second step S12, tensile force TAo of the tread rubber strip 15 in an outside region Yo is set larger than tensile force TAi in an inside region Yi.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a green tire manufacturing method for improving tire uniformity by reducing non-uniform distortion when stitching down a tread ring.

  In the production process of the raw tire in the radial tire, as shown in FIG. 10, the inner peripheral surface of the tread ring a formed in advance and the outer peripheral surface of the raw tire base c expanded in a toroidal shape by the shaping former b, The raw tire t is formed by joining together.

  At this time, the inner peripheral surface of the tread ring a has a right cylindrical shape, whereas the outer peripheral surface of the green tire base c is curved in a convex arc shape. Therefore, in order to affix both side portions a1 of the tread ring a to the green tire base c, so-called stitch down is required to press the both side portions a1 radially inward using a stitch roller (not shown) or the like (for example, Patent Document 1).

  However, in this stitch-down, compressive strain is unevenly generated in the tread rubber due to the reduced diameter deformation of the both side portions a1.

  On the other hand, in recent years, a so-called strip winding method has been proposed in which a tread rubber or the like is formed by spirally winding a tape-like unvulcanized rubber strip (see, for example, Patent Document 2). However, in particular, when the stitch down is performed on a tread ring having a tread rubber formed by the strip winding method, the arrangement of the rubber strips and separation between the rubber strips may occur due to compression. As a result, there is a problem that the unevenness of the distortion increases and the uniformity of the tire is further deteriorated.

  Although it is possible to reduce distortion non-uniformity to some extent by performing stitchdown slowly over time, in this case, productivity is lowered.

JP 2012-131167 A JP 2006-043908 A

  Accordingly, the present invention provides a raw tire manufacturing method capable of improving tire uniformity by reducing non-uniform distortion when stitching down a tread rubber formed by a strip wind method without causing a decrease in productivity. The challenge is to do.

The present invention provides a tread ring forming step for forming a tread ring,
And a manufacturing method of a green tire including a joining step of integrally joining the inner circumferential surface of the tread ring and the outer circumferential surface of the green tire base expanded in a toroidal shape by a shaping former,
The tread ring forming step includes
A first step of winding a belt ply to form a belt layer on a right cylindrical drum; and a second step of forming a tread rubber by winding a tread rubber strip spirally with tension. ,
In the second step, the tension TAo of the tread rubber strip wound in the region Yo on the outer side in the tire axial direction with respect to the outer end position P in the tire axial direction of the belt layer It is characterized by being larger than the tension TAi of the tread rubber strip wound around Yi.

  In the raw tire manufacturing method according to the present invention, the tension TAo is preferably 103% or more of the tension TAi.

  In the raw tire manufacturing method according to the present invention, the winding start position Pa of the tread rubber strip may be located in the inner area Yi or may be located in the outer area Yo. When the winding start position Pa is located in the outer region Yo, it is preferable that the tread rubber strip is wound with the tension TAo after one turn from the winding start.

  In the raw tire manufacturing method according to the present invention, when the winding start position Pa is located in the inner region Yo, it is preferable that the tension TAo sequentially increases toward the outer side in the tire axial direction.

  In the raw tire manufacturing method according to the present invention, when the winding start position Pa is located in the outer region Yo, the tension TAo is sequentially increased toward the outer side in the tire axial direction except for the first round from the winding start. It is preferable to become strong.

  In the raw tire manufacturing method according to the present invention, when the winding start position Pa is located in the outer region Yo, the tension TA1 in the first round from the start of winding may be greater than the tension TAi. preferable.

  In the raw tire manufacturing method according to the present invention, in the tread ring forming step, after the second step, the wing rubber strip is spirally connected to the outer end portion in the tire axial direction of the tread rubber with a tension TU. It is preferable that a third step of forming a wing rubber by wrapping around the tension TU and the tension TU is greater than the tension TAi.

  In the raw tire manufacturing method according to the present invention, the tread ring forming step forms a tread base rubber by winding a base rubber strip in a spiral shape with tension between the first step and the second step. Preferably, the base rubber strip tension TBo in the outer region Yo is set to be larger than the base rubber strip tension TBi in the inner region Yi.

  As described above, according to the present invention, the tension TAo of the tread rubber strip wound in the region Yo outside the tire axial direction of the belt layer in the tire axial direction outer end position P is set to the tension TAo of the tread rubber strip wound in the inner region Yi. It is larger than TAi.

  In such a tread ring, the tread rubber strip in the outer region Yo tends to shrink in the length direction by a large tension TAo. For this reason, when the drum is removed from the drum, the outer region Yo is deformed in a reduced diameter, and the amount of stitch down can be reduced. As a result, the distortion itself at the time of stitching down is reduced, and the unevenness of distortion can be reduced, so that the uniformity of the tire can be improved.

  Further, the gap between the tread rubber strips, in particular, the gap between the tread rubber strip and the outer end of the belt layer is reduced by the contraction of the tread rubber strip, which is effective in suppressing air accumulation.

It is sectional drawing which shows one Embodiment of the pneumatic tire formed using the manufacturing method of the raw tire of this invention. It is sectional drawing which shows joining process S2. It is sectional drawing which shows a tread ring formation process. It is a side view which shows notionally the sticking apparatus which performs a 2nd step. (A), (b) is a graph which shows the relationship between a tire axial direction position and tension | tensile_strength TAi, TAo. It is sectional drawing which shows the other example of a 2nd step. It is a conceptual diagram explaining the tension | tensile_strength of the 1st round of the winding start in a tread rubber strip. It is sectional drawing which shows a 3rd step. It is sectional drawing which shows a 4th step. It is sectional drawing explaining the conventional problem by stitchdown. It is a conceptual diagram explaining the tension | tensile_strength in the part which a tread rubber strip passes along an outer end position.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a cross-sectional view of a pneumatic tire 1 formed based on the raw tire manufacturing method of the present embodiment. In FIG. 1, the pneumatic tire 1 of this example is arranged in a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of the bead portion 4, and on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. Belt layer 7 to be applied.

  The carcass 6 is formed of at least one carcass ply 6A, in this example, one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator C. The carcass ply 6A includes a series of folded portions 6b that are folded around the bead core 5 from the inner side to the outer side in the tire axial direction at both ends of the body portion 6a straddling the bead cores 5 and 5. Further, a bead apex rubber 8 extending in a tapered manner from the bead core 5 toward the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b.

  The belt layer 7 is formed of at least two belt plies 7A and 7B in this example, in which a belt cord is arranged with respect to the tire equator C at an angle of 15 to 45 °, for example.

  A band layer (not shown) may be formed on the outer side in the radial direction of the belt layer 7. In this case, the outer end of the band layer in the tire axial direction ends at substantially the same position as the outer end of the belt layer 7 in the tire axial direction. The band layer is formed of at least one band ply in which a band cord is spirally wound in the tire circumferential direction.

  A tread rubber 2G forming a tread ground surface 2s is disposed outside the belt layer 7 in the radial direction.

  Next, as shown in FIGS. 2 and 3, the production method of the green tire 1N for the pneumatic tire 1 is formed by the tread ring forming step S1 (shown in FIG. 3) and the tread ring forming step S1. 2 includes a joining step S2 (shown in FIG. 2) in which the inner peripheral surface 10s of the tread ring 10 and the outer peripheral surface 12s of the raw tire base 12 expanded in a toroidal shape by the shaping former 11 are integrally joined.

  Since the raw tire base 12 is formed by the same formation process as that of the prior art, the description thereof is omitted. Also, the joining step S is the same as the conventional step including stitch down, and the description thereof is omitted. Therefore, in this specification, tread ring formation process S1 different from the conventional manufacturing method is demonstrated below.

  As shown in FIG. 3, the tread ring forming step S1 includes a first step S11 and a second step S12.

  In the first step S <b> 11, the belt ply 7 </ b> A and 7 </ b> B are sequentially wound on the right cylindrical drum 13 to form the belt layer 7.

  In the second step S12, after the first step S11, the tread rubber strip 15 is wound spirally with tension on the drum 13 and the belt layer 7, thereby forming the tread rubber 2G. .

  In the second step S12, the tension TAo of the tread rubber strip 15 wound in the region Yo on the outer side in the tire axial direction from the outer end position P in the tire axial direction of the belt layer 7 is set to the inner side in the tire axial direction from the outer end position P. The tension TAi of the tread rubber strip 15 wound in the region Yi is set to be larger.

  The “outer end position P” is defined as the position of the radial line passing through the outer end of the widest belt ply. Further, as exaggeratedly shown in FIG. 11, in the portion 15m where the tread rubber strip 15 passes through the outer end position P, the tension TAm may be equal to the tension TAi or the tension TAo. And a value between the tension TAo and the tension TAo.

  In the tread ring 10 thus formed, the tread rubber strip 15 in the outer region Yo tends to shrink in the length direction by a large tension TAo. Therefore, when the tread ring 10 is removed from the drum 13, as shown in FIG. 2, the diameter reduction deformation occurs in the area Yo outside the tread rubber 2 </ b> G, and the amount of stitch down can be reduced. As a result, distortion at the time of stitching down is reduced, and nonuniformity can be reduced and tire uniformity can be improved.

  The tension TAo is preferably 103% or more of the tension TAi. When the tension TAo is less than 103%, the above effect is not sufficiently exhibited. Further, the upper limit of the tension TAo is preferably 110% or less of the tension TAi. When the tension TAo exceeds 110%, the accuracy of attaching the tread rubber strip 15 tends to decrease.

  As shown in FIG. 3, in the second step S12, it is preferable that the winding start position Pa of the tread rubber strip 15 is located in the inner region Yi. In this case, the winding start end E of the tread rubber strip 15 is firmly adhered to the belt layer 7 and the tread rubber strip 15 starts to be wound with a low tension TAi. Therefore, the tread rubber strip 15 can be wound with high accuracy and ease with a predetermined tension TAi from the start of winding.

  At this time, as shown in FIG. 5A, the tensions TAi and TAo can be set to constant values. The change from TAi to TAo is performed in a portion 15m (shown in FIG. 11) passing through the outer end position P. Further, as shown in FIG. 5B, the tension TAo can be increased gradually toward the outer side in the tire axial direction. In this case, the reduced diameter of the tread rubber 2G increases toward the end of the tread, and distortion nonuniformity is further reduced. Note that “sequentially increasing” includes a case of gradually increasing in addition to the gradual increase. In the case where the tension TAo is increased sequentially, it is preferable that the maximum value of the tension TAo be in the range of 103% to 110% of the tension TAi.

  As shown in FIG. 6, in the second step S12, the winding start position Pa of the tread rubber strip 15 can be positioned in the outer area Yo. In this example, a case where the start position Pa is located at the outer end in the tire axial direction of the tread rubber 2G is shown. In this case, since the winding start end E of the tread rubber strip 15 is adhered to the drum 13, it becomes easy to slip. Therefore, as shown in FIG. 7, it is preferable to wind with the tension TAo after one turn from the start of winding. The tension TA1 in the first round may be smaller than the tension TAi, but is preferably larger than the tension TAi. In this case, it is preferable to increase the tension TAo sequentially toward the outer side in the tire axial direction except for the first round from the start of winding in order to reduce non-uniform distortion.

  Said 2nd step S12 can be performed by the sticking apparatus 20 shown, for example in FIG. The affixing device 20 of this example includes upper and lower conveyors 21U and 21L that convey the tread rubber strip 15 to the drum 13. The conveyor belts Ua and La of the upper and lower conveyors 21U and 21L are transported to the drum 13 with the tread rubber strip 15 interposed therebetween. And the tension | tensile_strength TA of the tread rubber strip 15 is controllable by controlling the conveyance speed of the sticking apparatus 20 with respect to the circumferential speed of the drum 13. FIG. The conveyance speed can be controlled by the drive motor M. Reference numeral 22 in the drawing is a pressure roller that presses the tread rubber strip 15 against the drum 13, and can move forward and backward toward the drum 13 by the cylinder 23.

  FIG. 8 shows another example of the tread ring forming step S1. The tread ring forming step S <b> 1 of this example includes a third step S <b> 13 for forming the wing rubber 24. As is well known, the wing rubber 24 is connected to the outer side in the tire axial direction of the tread rubber 2G, and improves the adhesion to the side wall rubber.

  In the third step S13, after the second step S12, the wing rubber 24 is formed by wrapping the wing rubber strip 25 in a spiral shape with a tension TU continuously to the tire axial direction outer end portion of the tread rubber 2G. . The tension TU of the wing rubber strip 25 is also set larger than the tension TAi in order to reduce the stitch down amount. In particular, the tension TU is preferably in the range of 103 to 110% of the tension TAi, and more preferably not less than the tension TAo. In the third step S13, as in the second step S12, it is preferable that the tension TU is sequentially increased toward the outer side in the tire axial direction.

  FIG. 9 shows still another example of the tread ring forming step S1. The tread ring forming step S <b> 1 of this example includes a fourth step S <b> 14 for forming the tread base rubber 26. As is well known, the tread base rubber 26 is arranged on the inner side in the radial direction of the tread rubber 2G, and is formed for the purpose of improving the tread rigidity and rolling resistance while maintaining the grip and wear performance of the tread rubber 2G. The

  The fourth step S14 is performed between the first step S11 and the second step S12. In the fourth step S14, the tread base rubber 26 is formed by winding the base rubber strip 27 spirally with tension. In the fourth step S14, as in the second step S12, the tension TBo of the base rubber strip 27 wound in the outer area Yo is set larger than the tension TBi of the base rubber strip 27 wound in the inner area Yi. . Thereby, even when the tread base rubber 26 is present, the stitch down amount can be reduced. The tension TBo and the tension TBi are preferably set according to the tension TAo and the tension TAi.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A pneumatic tire (195 / 65R15) having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and productivity, uniformity, air accumulation, and rolling resistance were tested for each sample tire. The specifications are substantially the same except in the table.

(1) Productivity:
When 1000 raw tires were produced, the total process time in the joining process including stitchdown was evaluated using an index with Comparative Example 1 as 100. The smaller the value, the shorter the process time and the better the productivity.

(2) Uniformity:
Based on the uniformity test conditions of JASO C607, radial force variation (RFV) was measured for 20 tires, and the average value (N) was evaluated by an index with Comparative Example 1 as 100. Smaller numbers are better.

(3) Air pool:
The number of scratches caused by air accumulation in the tread portion was evaluated by an index with Comparative Example 1 being 100. Smaller numbers are better with fewer scratches.

(4) Rolling resistance:
Using a rolling resistance tester, rolling resistance was measured under the conditions of a specified rim (15 × 6JJ), internal pressure (230 kPa), load (3.43 kN), and speed (80 km / h). The results are indicated by an index with Comparative Example 1 as 100. Smaller numbers are better.

  As shown in the table, the embodiment can improve the tire uniformity by reducing non-uniform distortion when stitching down the tread rubber formed by the strip wind method without causing a decrease in productivity. I can confirm.

2G tread rubber 7 belt layer 7A, 7B belt ply 10 tread ring 11 shaping former 12 raw tire base 13 drum 15 tread rubber strip 24 wing rubber 25 wing rubber strip 26 tread base rubber 27 base rubber strip S1 tread ring forming step S11 first Step S12 Second step S13 Third step S14 Fourth step S2 Joining step

Claims (9)

A tread ring forming process for forming a tread ring;
And a manufacturing method of a green tire including a joining step of integrally joining the inner circumferential surface of the tread ring and the outer circumferential surface of the green tire base expanded in a toroidal shape by a shaping former,
The tread ring forming step includes
A first step of winding a belt ply to form a belt layer on a right cylindrical drum; and a second step of forming a tread rubber by winding a tread rubber strip spirally with tension. ,
In the second step, the tension TAo of the tread rubber strip wound in the region Yo on the outer side in the tire axial direction with respect to the outer end position P in the tire axial direction of the belt layer A method for producing a raw tire, characterized in that the tension is greater than the tension TAi of a tread rubber strip wound around Yi.   2. The raw tire manufacturing method according to claim 1, wherein the tension TAo is 103% or more of the tension TAi.   The raw tire manufacturing method according to claim 1 or 2, wherein the winding start position Pa of the tread rubber strip is located in the inner region Yi.   2. The winding start position Pa of the tread rubber strip is located in the outer region Yo, and the tread rubber strip is wound with the tension TAo after one turn from the start of winding. Or the manufacturing method of the raw tire of 2.   The method for manufacturing a raw tire according to any one of claims 1 to 3, wherein the tension TAo is increased sequentially toward the outer side in the tire axial direction.   The method for manufacturing a raw tire according to claim 4, wherein the tension TAo is gradually increased toward the outer side in the tire axial direction except for the first round from the start of winding.   The raw tire manufacturing method according to claim 4 or 6, wherein a tension TA1 in the first round from the start of winding is greater than the tension TAi.   In the tread ring forming step, after the second step, a wing rubber is formed by wrapping a wing rubber strip spirally with a tension TU continuously to the tire axial direction outer end portion of the tread rubber. The raw tire manufacturing method according to claim 1, wherein the tension TU is greater than the tension TAi.   The tread ring forming step includes a fourth step of forming a tread base rubber by spirally winding a base rubber strip with tension between the first step and the second step. A raw tire manufacturing method characterized in that the tension TBo of the base rubber strip in the region Yo is larger than the tension TBi of the base rubber strip in the inner region Yi.

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