JP2015229326A - Method for molding green tire, and band drum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a green tire-molding technique capable of surely preventing occurrence of dents in a ply joint part and capable of inhibiting productivity slowdown due to joint defect by properly preventing the degradation of joint accuracy.SOLUTION: There is provided a green tire molding method comprising winding a sheet-like ply material on the outer peripheral face of a cylindrical band drum formed from plural segments retractable in a radial direction, and forming the ply having a ply joint part by overlapping the leader and dead end parts of the ply material and pressure-bonding them. The method includes using a band drum having a band drum segment corresponding to the width of the ply joint part to be formed, and after forming the ply joint part on the band drum segment, forcibly expanding the interval of the cords in the ply joint part by expanding the band drum segment in the radial direction.

Description

  The present invention relates to a raw tire molding method and a band drum used in the raw tire molding method.

  In the manufacturing process of a pneumatic tire, generally, a sheet-like ply material is wound around a cylindrical band drum, and a ply joint part is formed by overlapping a start end part and a terminal end part to form a cylindrical ply. After that, the diameter of the band drum is reduced and the molded ply is removed and sent to the next process.

  At this time, since the ply joint (the density of the cord) is dense in the ply joint portion where the ply material is superimposed, if a large ply joint portion is formed, the product tire assembled with the rim is inflated (tire) At the time of inflation, the modulus of the ply joint portion becomes larger than that of other portions, and the binding force becomes very strong. As a result, the ply joint portion becomes difficult to extend, and a dent is generated on the surface of the product tire, which may cause a deterioration of the dent level.

  Therefore, as a method for solving such problems, conventionally, by reducing the modulus of the ply joint part by reducing the ply joint part or providing a convex part on the outer peripheral surface of the band drum, Various methods for suppressing the deterioration of the dent level have been proposed.

  For example, in Patent Document 1, as shown in FIG. 4, a convex portion 21 is formed on the outer peripheral surface of the band drum 20, and a ply joint portion is formed on the convex strip portion 21. The modulus is lowered to suppress the generation of dents. In FIG. 4, a perspective view (a) and a side view (b) of the band drum 20 are shown.

JP 2013-184295 A

  However, in the case of the conventional method described above, since it is necessary to form the ply joint part on a non-flat ridge, it is necessary to strictly manage the joint accuracy. There is a reality that the rate is remarkably deteriorated up to about 5 times the normal value, and this has led to a decrease in productivity due to defective joints.

  Therefore, the present invention provides a raw tire molding technique that can sufficiently suppress the occurrence of dents at the ply joint portion, and appropriately prevent deterioration of joint accuracy to suppress a decrease in productivity due to joint failure. Is an issue.

The invention described in claim 1
A ply joint is formed by winding a sheet-like ply material around the outer peripheral surface of a cylindrical band drum formed of a plurality of radially expandable / contractable segments, and overlapping and crimping the start and end portions of the ply material. A green tire molding method for molding a ply having a portion,
As the band drum, using a band drum having a band drum segment corresponding to the width of the ply joint part to be formed,
After forming the ply joint portion on the band drum segment, the ply joint portion is forcibly opened by expanding the band drum segment in a radial direction.

The invention described in claim 2
As the band drum, a band drum whose cross-sectional shape is 10 mm or less in width is used.
2. The raw tire molding method according to claim 1, wherein after forming the ply joint portion on the band drum segment, the band drum segment is expanded in a radial direction by 1 mm to 10 mm.

The invention according to claim 3
3. The ply joint portion is pressed from one end to the other end of the band drum using a roller provided above the band drum after the band drum segment is expanded. The raw tire molding method described in 1. above.

The invention according to claim 4
A band drum used in the green tire molding method according to any one of claims 1 to 3,
It has a band drum segment corresponding to the width of the ply joint part,
The band drum is characterized in that the band drum segment is configured to expand in a radial direction.

The invention described in claim 5
5. The band drum according to claim 4, wherein a cross-sectional shape of the band drum segment is 10 mm or less in width, and an expansion allowance is 1 mm to 10 mm.

  According to the present invention, it is possible to provide a raw tire molding technique that can sufficiently suppress the occurrence of dents in a ply joint part and appropriately prevent deterioration of joint accuracy and suppress a decrease in productivity due to joint failure. Can do.

It is the schematic diagram explaining the state of (a) band drum before the band drum segment expansion in the raw tire shaping | molding method which concerns on embodiment of this invention, (b) The schematic diagram explaining the state of a ply joint part. It is the schematic diagram explaining the state of (a) band drum after the band drum segment expansion in the raw tire shaping | molding method which concerns on embodiment of this invention, (b) The schematic diagram explaining the state of a ply joint part. In the raw tire shaping | molding method which concerns on other embodiment of this invention, it is a schematic diagram explaining the state which is pressing the ply joint part after expansion with the roller. It is (a) perspective view and (b) side view which show typically the shape of the band drum used for the raw tire shaping | molding method by a prior art.

  Hereinafter, the present invention will be described based on embodiments.

  FIG. 1 is a schematic diagram for explaining the state of the band drum before expansion of the band drum segment in the raw tire molding method according to the present embodiment, and (b) a schematic diagram for explaining the state of the ply joint part. As shown in FIG. 1, the green tire molding method according to the present embodiment winds a sheet-like ply material 4 around the outer peripheral surface of a cylindrical band drum formed of a plurality of segments that can be expanded and contracted in the radial direction. A ply joint part 3 is formed by overlapping and crimping the start and end parts of the ply material 4 to form a cylindrical ply.

  However, the green tire molding method according to the present embodiment uses a band drum having a band drum segment 11 corresponding to the width of the ply joint portion 3 at a position where the ply joint portion 3 is formed. After the ply joint part 3 is formed on 11, the ply joint part 3 is forcibly opened by expanding the band drum segment 11 in the radial direction, which is different from the conventional method.

  That is, as shown in FIG. 1A, the band drum according to the present embodiment is formed of the band drum segment 11 and the other segment 1, and each segment is an air cylinder or servo. The ring can be expanded and contracted in the radial direction by using a drive mechanism such as a motor.

  In the green tire molding method according to the present embodiment, first, as shown in FIGS. 1A and 1B, the ply material 4 is wound around the outer peripheral surface of the band drum, and the ply material 4 is formed on the band drum segment 11. After the start end and the end are overlapped, the ply joint 3 is formed by pressing the start end and the end using a joint roller or the like. At this time, since the band drum segment 11 is disposed so as to have the same diameter as the other segments 1 by reducing the diameter, the joint portion 3 can be formed with a flat surface on the outer periphery, and high joint accuracy is achieved. Can be secured.

  Next, as shown in FIGS. 2 (a) and 2 (b), only the band drum segment 11 is expanded in the radial direction among the plurality of segments, and the interval between the cords 5 of the ply material 4 in the joint portion 3 is forced. Open your eyes. The distance between the cords 5 in the joint portion 3 of the ply after molding is close as described above. When the product tire is filled with air by forcibly opening the cords 5 as described above, each cord 5 , And the modulus can be lowered, so that the generation of dents can be suppressed.

  As described above, according to the present embodiment, when the ply joint portion is formed, the band drum is in a flat state, and after the ply joint portion is formed, the band drum segment is expanded so that the cord spacing in the ply joint portion is increased. By forcibly opening the opening, it is possible to appropriately prevent deterioration of joint accuracy and suppress productivity reduction due to joint failure, and to sufficiently suppress generation of dent in the ply joint portion.

  The band drum segment has a cross-sectional width of 10 mm or less from the viewpoint of preventing the ply cord interval from opening more than necessary and appropriately suppressing the occurrence of dent in the ply joint portion. It is preferable. On the other hand, if the width of the cross-sectional shape is too narrow, the stress may concentrate on the joint portion, and the joint may be detached. Therefore, the lower limit value of the width of the cross-sectional shape is preferably 3 mm.

  Similarly, from the viewpoint of preventing the ply cord interval from opening more than necessary, it is preferable that the expansion allowance, which is the distance that the band drum segment can be expanded, is 1 mm to 10 mm.

  Then, as shown in FIG. 3, after the roller 6 is arranged above the position where the ply joint portion 3 is formed (the position of the band drum segment of the band drum) and the band drum segment is expanded, More preferably, the ply joint 3 is pressed.

  When the product tire is inflated, a specific elongation is given to the ply joint part in the tensile direction. However, the ply joint part causes a tensile stress that resists the original shape and causes a dent.

  On the other hand, when the ply joint portion 3 is pressed using the roller 6 after the band drum segment 11 is expanded as described above, another cord 5 enters the gap between the opened cords 5 and the above-described inflation. Since the tensile stress at the time can be reduced, the generation of dents can be more sufficiently suppressed.

1. Example Table 1 shows the width (a) [mm] and expansion allowance (b) [mm] of the cross-sectional shape of the band drum segment 11 and the presence or absence of the roller 6 using the raw tire molding method according to the present embodiment described above. A green tire was molded under the same conditions except that it was changed as shown in Fig. 1, and then vulcanized under the same conditions to produce 100 test tires each having a tire size of 195 / 65R15 EC202 (Examples 1 to 4). ).

  Similarly, the test tire of Conventional Example 1 was manufactured using the conventional band drum, and the test tire of Conventional Example 2 was manufactured using the band drum having the ridges shown in Patent Document 1 ( 100 each).

2. Measurement Conditions and Evaluation in Examples and Conventional Examples Each test tire was inflated so that the tire internal pressure was 200 KPa, and the ply joint unevenness difference (c) [mm] in this state was measured.

  It can be said that the smaller the value of the unevenness (c) of the ply joint, the better the appearance quality without unevenness, and in general, tires having an unevenness difference (c) of 0.6 mm or more have an appearance. It is bad, and it is judged that it cannot be put on the market and is scrapped.

  Also, the ply joint amount (overlapping amount of the start and end portions) in each test tire is measured, and the ply joint amount that does not fall within the standard 3 mm to 8 mm is counted as a joint out, and the out rate Was measured. The results are shown in Table 1.

  According to Table 1, the value of the difference (c) in the unevenness of the ply joint of Conventional Example 1 was 0.6, which is a lower limit value that is judged as an appearance defect. On the other hand, the width (a) of the band drum segment and the unevenness difference (c) of the ply joint in the case of Examples 1 to 4 manufactured using the band drum in which the expansion allowance is set to an appropriate value. It was 0.5 or less, and it was confirmed that the appearance quality was good.

  Further, the joint-out rate was a good level of 3% except for Conventional Example 2 in which the ply material was jointed on the ridges. From this, it was confirmed that high joint accuracy can be ensured by reducing the diameter of the band drum segment and forming the joint portion on a flat surface.

  In addition, from the results of Examples 1 to 4, it was confirmed that the dent level can be improved by expanding the band drum segment after the formation of the ply joint, but when Example 1 and Example 2 are compared, Example 1 However, it was confirmed that the dent level could be further improved by pressing the ply joint portion 3 using the roller 6 after the band drum segment was expanded.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

1 Segment 3 Ply Joint 4 Ply Material 5 Cord 6 Roller 11 Band Drum Segment 20 Band Drum 21 Projection

Claims (5)

A ply joint is formed by winding a sheet-like ply material around the outer peripheral surface of a cylindrical band drum formed of a plurality of radially expandable / contractable segments, and overlapping and crimping the start and end portions of the ply material. A green tire molding method for molding a ply having a portion,
As the band drum, using a band drum having a band drum segment corresponding to the width of the ply joint part to be formed,
A raw tire molding method, wherein after forming the ply joint portion on the band drum segment, the ply joint portion is forcibly opened by expanding the band drum segment in a radial direction. As the band drum, a band drum whose cross-sectional shape is 10 mm or less in width is used.
The raw tire molding method according to claim 1, wherein after forming the ply joint portion on the band drum segment, the band drum segment is expanded in a radial direction by 1 mm to 10 mm.   3. The ply joint portion is pressed from one end to the other end of the band drum using a roller provided above the band drum after the band drum segment is expanded. The green tire molding method according to 1. A band drum used in the green tire molding method according to any one of claims 1 to 3,
It has a band drum segment corresponding to the width of the ply joint part,
A band drum, wherein the band drum segment is configured to expand in a radial direction.   5. The band drum according to claim 4, wherein a cross-sectional shape of the band drum segment is 10 mm or less in width and an expansion allowance is 1 mm to 10 mm.

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