JP2014079958A - Bladder for vulcanizing tire, and method for producing pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bladder for vulcanizing a tire, which can allow durability of the vulcanized tire to be improved by reducing the strain to be generated at the end of a belt layer in the width direction of the tire when the tire is vulcanized and which can allow a high-quality pneumatic tire to be produced and to provide a method for producing the pneumatic tire by using the bladder for vulcanizing the tire.SOLUTION: The film thickness of a cylindrical bladder body part 2 is set constant and a rubber rib extending to the peripheral direction is formed in the vertically central part of the bladder on the inside surface thereof. The rubber rib comprises a plurality of circular ribs 4A, which are placed at regular intervals in the vertical direction, or spiral ribs 4B, which are connected spirally to one another at regular intervals in the vertical direction. When a green tire G is set horizontally in a mold 10 and the bladder 1 is expanded, the expansion quantity of the vertically central part of the bladder is controlled to correct such a phenomenon that the vertically central part of the bladder is expanded more largely than other portions.

Description

  The present invention relates to a tire vulcanization bladder and a method for manufacturing a pneumatic tire. More specifically, the present invention improves the durability by reducing distortion generated at the end of the belt layer in the tire width direction during tire vulcanization, and high quality. TECHNICAL FIELD The present invention relates to a tire vulcanizing bladder that can produce a pneumatic tire and a method for producing a pneumatic tire using the tire vulcanizing bladder.

  When manufacturing a pneumatic tire, a green tire is set in a mold, and a vulcanizing bladder is inflated inside the green tire for vulcanization. Green tires are generally set horizontally in a mold. A cylindrical vulcanizing bladder generally has a constant film thickness (circumferential rigidity is constant in the vertical direction), and its upper and lower ends are fixed by a clamp member so as to expand. Will expand the most. As a result, during tire vulcanization, a relatively large strain is generated at both ends in the tire width direction of the belt layer embedded in the green tire. If this distortion is excessive, it will adversely affect the durability of the manufactured pneumatic tire.

  Although the object is different from that of the present invention, for example, it has been proposed to arrange a reinforcing layer only on a specific portion of the inner surface of the vulcanizing bladder to increase the rigidity of this portion (see Patent Document 1). However, if such a reinforcing layer is provided, the portion provided with the reinforcing layer is difficult to expand, and there is a concern that the internal pressure does not sufficiently act on the inner surface of the green tire and the pressing force is reduced. Further, if a reinforcing layer is simply added, there is a problem that the tire quality is deteriorated due to a large difference in thermal conductivity between the portion and other portions.

JP 2008-126495 A

  An object of the present invention is to provide a tire vulcanizing bladder capable of improving the durability by reducing distortion generated at the end of the belt layer in the tire width direction during tire vulcanization, and capable of producing a high-quality pneumatic tire. An object of the present invention is to provide a method for manufacturing a pneumatic tire using the tire vulcanizing bladder.

  In order to achieve the above object, a tire vulcanizing bladder according to the present invention is a cylindrical bladder main body part in a tire vulcanizing bladder used when vulcanizing a green tire set horizontally in a mold. Is set to a constant thickness, a rubber rib extending in the circumferential direction is formed at the center of the bladder in the bladder vertical direction on the inner surface of the bladder, and the ribs are spaced apart in the vertical direction to form a plurality of annular ribs, or The ribs are connected in a spiral shape with an interval in the vertical direction to form a spiral rib.

  The method for producing a pneumatic tire of the present invention is characterized in that a green tire is vulcanized using the tire vulcanization bladder.

  According to the present invention, a rubber rib extending in the circumferential direction is formed in the bladder vertical center portion of the inner surface of the bladder, and the ribs are spaced apart in the vertical direction to form a plurality of annular ribs or the ribs in the vertical direction. Since the spiral ribs are formed by being connected to each other in a spiral manner, the circumferential rigidity of the center portion in the vertical direction of the bladder is greater than that of the other portions. Therefore, when the bladder is inflated, the amount of expansion at the center in the vertical direction of the bladder is regulated, and the phenomenon of large expansion with respect to other portions is corrected. Thereby, the distortion which arises in the tire width direction both ends of the belt layer embed | buried under a green tire can be reduced, and it becomes possible to improve the durability of the pneumatic tire to manufacture in connection with this.

  Since the thickness of the bladder main body is set to a constant thickness and a plurality of ribs are formed at intervals in the vertical direction, the increase in the vertical rigidity of the bladder and thermal conductivity caused by the ribs are formed. Can be minimized. Therefore, a high quality pneumatic tire can be manufactured.

  Here, for example, by changing at least one of the cross-sectional area or the vertical interval of the rubber rib, the circumferential rigidity of the bladder at the center in the vertical direction of the bladder is maximized toward the vertical center. Use the specifications set in. With this specification, when the bladder is inflated, it becomes easier to inflate the center portion in the vertical direction of the bladder more flatly, which is advantageous in reducing the strain generated at both ends of the belt layer in the tire width direction. More preferably, the circumferential rigidity of the bladder is symmetric with respect to the center in the vertical direction of the bladder.

  It can also be set as the specification by which the groove | channel extended in the circumferential direction is formed between the said ribs adjacent on the upper and lower sides. With this specification, the vertical rigidity of the bladder can be reduced and adjusted to a desired vertical rigidity.

  The cross-sectional shape of the rib may be an undercut shape in which the head portion is larger than the root portion. This specification makes it easy to suppress the increase in vertical rigidity while improving the circumferential rigidity of the bladder.

  In order to obtain a good effect, for example, the ratio Wr / Gb of the width Wr of the base portion of the rib to the film thickness Gb of the bladder main body portion is set to 0.2 or more and 0.5 or less. Further, the ribs may be arranged at a predetermined constant pitch P in the circumferential direction of the bladder, and a ratio Wr / P of the width Wr of the root portion of the rib to the pitch P may be 0.1 or more and 0.5 or less. . It can also be set as the specification whose cross-sectional shape of the said groove | channel is circular arc shape. Further, the cross-sectional shape of the groove may be a semicircular shape, and the ratio Rd / Gb of the groove radius Rd to the film thickness Gb of the bladder main body may be 0.1 or more and 0.5 or less.

It is explanatory drawing which illustrates embodiment of the bladder for tire vulcanization | cure of this invention in a longitudinal cross-section. It is an enlarged view of the rib periphery of FIG. It is explanatory drawing which illustrates the state which the bladder for tire vulcanization | cure of FIG. 1 is expanding in a half vertical cross section. FIG. 4 is an explanatory view illustrating a state in which the tire vulcanizing bladder of FIG. 3 is in contact with the entire inner surface of the green tire in a half vertical section. It is sectional drawing which illustrates the rib arrange | positioned by changing the space | interval of an up-down direction. It is sectional drawing which shows the modification of a rib and a groove | channel. It is explanatory drawing which illustrates another embodiment of the bladder for tire vulcanization | cure of this invention in a longitudinal cross-section.

  Hereinafter, a tire vulcanizing bladder and a pneumatic tire manufacturing method according to the present invention will be described based on the embodiments shown in the drawings.

  A tire vulcanizing bladder 1 (hereinafter referred to as a bladder 1) of the present invention illustrated in FIGS. 1 and 2 is made of rubber made of butyl rubber or the like and is formed in a cylindrical shape. The film thickness Gb of the bladder main body 2 is a predetermined constant thickness, and both upper end portions (opening edge portions) in the cylinder axis direction are formed to be thicker than the film thickness Gb of the bladder main body 2. 3a and the lower clamp part 3b. The film thickness Gb varies depending on the size of the tire to be vulcanized, but is, for example, about 4 mm to 20 mm.

  A rubber rib extending in the circumferential direction is formed at the center in the vertical direction of the inner surface of the bladder, and this rib constitutes a plurality of annular ribs 4A (ribs that go around the inner surface of the bladder) at intervals in the vertical direction. Then, by changing at least one of the cross-sectional area of these annular ribs 4A or the vertical interval, the circumferential rigidity of the bladder 1 at the center in the vertical direction of the bladder is maximized toward the vertical center CL of the bladder 1. Is set to

  That is, in the annular rib 4A of FIG. 2, the rib height increases in the order of H3, H2, and H1 toward the vertical center CL. Since the width Wr of the root portion 4b of each rib 4 is the same, the cross-sectional area of the rib 4 is set so as to become maximum toward the center CL in the vertical direction of the bladder 1.

  In the range where the annular rib 4A is formed, the circumferential rigidity of the bladder 1 gradually increases up to about 40% to 60% toward the vertical center CL of the bladder 1. Details of the annular rib 4A will be described later.

  The bladder 1 is attached to the central mechanism 7 of the vulcanizer. Specifically, the upper clamp portion 3a and the lower clamp portion 3b of the bladder 1 are held by disk-like upper holding portions 8a and lower holding portions 8b attached to the center post of the center mechanism 7, respectively. The center post of the center mechanism 7 is provided with an injection nozzle 9a for injecting a heat medium H such as steam (and a pressure medium) into the bladder 1.

  The annular rib 4A is formed integrally with the bladder main body 2 by rubber constituting the bladder main body 2, and is formed only in the center in the bladder vertical direction (the portion corresponding to the tire tread). The center in the vertical direction of the bladder is 5% to the vertical length of the bladder 1 (the length from the upper clamp portion 3a to the lower clamp portion 3b) in the vertical direction with respect to the vertical center CL of the bladder 1. The range is about 20%. Alternatively, it is in the range of about 8% to 30% of the length BL of the belt layer B embedded in the green tire G to be vulcanized in the vertical direction with respect to the vertical center CL of the bladder 1.

  The annular rib 4A extends substantially parallel to the direction perpendicular to the cylinder axis of the bladder 1 (that is, the horizontal direction). In this embodiment, the cross-sectional shape of the annular rib 4A is a mountain shape with the head 4a tapered, but various shapes can be employed. The annular ribs 4A are formed at intervals in the circumferential direction of the bladder 1 and are, for example, in a fixed arrangement (pitch P). As the pitch P, for example, about 20 mm to 100 mm, or three to 20 annular ribs 4A are formed at equal intervals in the vertical direction at the center in the vertical direction of the bladder.

  The height Hr of the annular rib 4A is, for example, about 5 mm to 20 mm, or about 50% to 200% of the film thickness Gb. When the rib height Hr is less than 50% of the film thickness Gb, the circumferential rigidity of the bladder 1 is likely to be excessively improved. If the rib height Hr is more than 200% of the film thickness Gb, the circumferential rigidity of the bladder 1 is likely to be excessively improved, resulting in manufacturing difficulties (including high costs), and other parts. The difference in thermal conductivity is likely to be excessive.

  The width Wr of the base portion 4b of the annular rib 4A is, for example, about 4 mm to 20 mm, or about 10% to 70% of the pitch P. When the width Wr of the root portion 4b of the annular rib 4A is less than 10% of the pitch P, the improvement in the circumferential rigidity of the bladder 1 tends to be excessive. If the width Wr of the root portion 4b of the annular rib 4A is more than 70% of the pitch P, the circumferential rigidity of the bladder 1 is likely to be excessively improved, and the difference in thermal conductivity from other portions is excessive. Easy to be.

  In this embodiment, an annular groove 5 extending in the circumferential direction is formed between the annular ribs 4a adjacent to each other in the vertical direction. This groove 5 can be arbitrarily provided. The groove 5 preferably extends in parallel with the annular rib 4A at an intermediate position between the annular ribs 4A adjacent in the vertical direction. As the cross-sectional shape of the groove 5, various shapes such as a quadrangle and a polygon can be adopted. However, it is preferable to use an arc shape like this embodiment from the viewpoint of durability and the like.

  As illustrated in FIG. 3, the bladder 1 is used when vulcanizing a green tire G set in a horizontally placed state in a mold 10 installed in a vulcanizing device 6. In this embodiment, the mold 10 includes an upper mold 10a, a lower mold 10b, an annular upper plate 10c, and an annular lower plate 10d. The green tire G is disposed inside the opened mold 10, and the bladder 1 is disposed inside the green tire G. A belt layer B having a predetermined width is embedded in the green tire G.

  Next, after the mold is closed, the heat medium H (and the pressure medium) is injected and filled into the bladder 1 from the injection nozzle 9a. Specifically, the bladder 1 is annularly expanded along the inner surface of the green tire G using various gases such as steam, air, and nitrogen gas, and heated while pressing the inner surface of the green tire G.

  After the bladder 1 is inflated as illustrated in FIG. 3, the bladder 1 is further inflated to press the entire inner surface of the green tire G and vulcanize the green tire G as illustrated in FIG. 4. The bladder 1 of the present invention uses the annular rib 4A extending in the circumferential direction, so that the circumferential rigidity of the center portion in the vertical direction of the bladder is greater than that of other portions. Therefore, when the bladder 1 is inflated, the amount of expansion at the center portion in the vertical direction of the bladder is regulated, and the phenomenon of large expansion with respect to other portions is corrected.

  That is, in the center portion of the bladder in the vertical direction, the pressing force against the inner surface of the green tire G by the inflated bladder 1 is substantially uniform. The size of the white arrow described in FIG. 4 schematically indicates the magnitude of the pressing force with which the inflated bladder 1 presses the inner surface of the green tire G. In FIG. 4, the annular rib 4 </ b> A is omitted to ensure easy viewing of the drawing.

  Because the pressure distribution presses the inner surface of the green tire G, the belt layer B embedded in the green tire G also has a relatively small amount of bulging toward the outer peripheral side of the central portion in the tire width direction, and the belt The whole layer B expands to the outer peripheral side in a state close to flat. Therefore, it is possible to reduce the distortion generated at both ends of the belt layer B in the tire width direction, and this is advantageous in improving the durability of the pneumatic tire to be manufactured.

  Since the annular ribs 4A extending in the circumferential direction are formed at intervals in the vertical direction, the increase in the vertical rigidity of the bladder 1 due to the presence of the annular ribs 4A is slight. Further, since the film thickness Gb of the bladder main body 2 is constant, the change in thermal conductivity is also minimized. Therefore, according to the pneumatic tire manufacturing method of the present invention in which the bladder 1 is used to vulcanize the green tire G, a high-quality pneumatic tire can be manufactured.

  When the bladder 1 is inflated, it is more effective to apply the present invention when manufacturing a large tire in which the amount of expansion in the center portion in the vertical direction of the bladder is likely to increase. For example, in terms of tire size, it is suitable for manufacturing a large tire having a rim diameter of 20 inches or more.

  When the bladder 1 is inflated, the amount of expansion is the largest in the vicinity of the center CL in the vertical direction, so that the circumferential rigidity of the bladder 1 is set to be maximized toward the center CL in the vertical direction. Good. This specification makes it easier to inflate the center portion of the bladder in the flat direction more flatly, and is advantageous for reducing the strain generated at both ends of the belt layer B in the tire width direction. More preferably, the circumferential rigidity of the bladder 1 is symmetric with respect to the vertical center CL.

  By forming the groove 5 extending in the circumferential direction between the annular ribs 4A adjacent in the vertical direction, the vertical rigidity of the bladder 1 can be reduced. Therefore, the desired vertical rigidity can be adjusted by appropriately setting the specifications of the annular rib 4A.

  The width Wg of the groove 5 is preferably 20% to 70% of the pitch P, for example, and the depth Dg of the groove 5 is preferably about 10% to 30% of the film thickness Gb, for example. If the width Wg of the groove 5 is less than 20% of the pitch P, the effect of reducing the vertical rigidity of the bladder 1 tends to be too small. If the width Wg of the groove 5 is more than 70% of the pitch P, the effect of reducing the vertical rigidity of the bladder 1 is likely to be excessive, and the difference in thermal conductivity from other portions is likely to be excessive. When the depth Dg of the groove 5 is less than 10% of the film thickness Gb, the effect of reducing the rigidity in the vertical direction of the bladder 1 tends to be excessive. When the depth Dg of the groove 5 is more than 30% of the film thickness Gb, the effect of reducing the vertical rigidity of the bladder 1 is likely to be excessive, and the difference in thermal conductivity from other portions is likely to be excessive. .

  As illustrated in FIG. 5, the circumferential area rigidity of the bladder 1 at the center in the vertical direction of the bladder is changed by keeping the cross-sectional areas of the respective annular ribs 4A the same and changing the vertical interval of the annular ribs 4A. It can also be set to be maximized toward the vertical center CL. The annular ribs 4A in FIG. 5 are all the same (the same shape, the rib height H and the width Wr of the root portion 4b are the same), and the vertical spacing (pitch) between the annular ribs 4A that are vertically adjacent to each other toward the vertical center CL. However, it becomes small in order of pitch P3, P2, and P1.

  Alternatively, by changing both the cross-sectional area of the annular rib 4A and the interval in the vertical direction of the annular rib 4A, the circumferential rigidity of the bladder 1 can be set to be maximized toward the vertical center CL. In other words, in the present invention, at least one of the cross-sectional area or the vertical interval of the annular rib 4A is changed so that the circumferential rigidity of the bladder 1 is maximized toward the vertical center CL.

  As illustrated in FIG. 6, the cross-sectional shape of the annular rib 4 </ b> A may be an undercut shape in which the head portion 4 a is larger than the root portion 4 b. In this embodiment, the head 4a is circular. By making the undercut shape in this way, it is easy to suppress the increase in the vertical rigidity while improving the circumferential rigidity of the bladder 1.

  In order to obtain a good effect by the bladder 1 of the present invention, for example, the ratio Wr / Gb of the width Wr of the root portion 4b of the annular rib 4A to the film thickness Gb of the bladder main body 2 is set to 0.2 or more and 0.5 or less. It is good, and more preferably 0.3 or less. If Wr / Gb is less than 0.2, the circumferential rigidity of the bladder 1 is likely to be excessively improved. When Wr / Gb is more than 0.5, the improvement in the circumferential rigidity of the bladder 1 tends to be excessive, and the difference in thermal conductivity from other parts tends to be excessive.

  When the annular rib 4A is arranged at a predetermined pitch P in the vertical direction of the bladder 1, the ratio Wr / P of the width Wr of the root portion 4b of the rib 4 to the pitch P may be set to 0.1 or more and 0.5 or less. Preferably it is 0.3 or less. If Wr / P is less than 0.1, the circumferential rigidity of the bladder 1 is likely to be excessively improved. When Wr / P is more than 0.5, the improvement in the circumferential rigidity of the bladder 1 is likely to be excessive, and the difference in thermal conductivity from other portions is likely to be excessive.

  When the cross-sectional shape of the groove 5 is semicircular as illustrated in FIG. 6, the ratio Rd / Gb of the groove radius Rd to the film thickness Gb of the bladder main body 2 may be 0.1 or more and 0.5 or less. Preferably it is 0.3 or less. When Rd / Gb is less than 0.1, the effect of reducing the vertical rigidity of the bladder 1 tends to be excessive. If Rd / Gb is more than 0.5, the effect of reducing the rigidity in the vertical direction of the bladder 1 tends to be excessive, and the difference in thermal conductivity from other parts tends to be excessive.

  As in the embodiment illustrated in FIG. 7, a rubber rib extending in the circumferential direction is formed at the center in the vertical direction of the bladder on the inner surface of the bladder, and the rib is spirally connected with a space in the vertical direction. The specification which comprised the rib 4B can also be made. According to the embodiment, substantially the same effect as the previous embodiment can be obtained.

  Further, when such a spiral rib 4B is provided, when the heat medium H (and the pressure medium) is injected and filled into the bladder 1 from the injection nozzle 9a in the vulcanization process, the heat medium H is spiral. It can be expected that the fluid medium flows along the ribs 4B and the heat medium H is easily stirred inside the bladder 1.

  The same specification and the same arrangement described in the previous embodiment can also be applied to this embodiment.

  When the tires (2700R49) of the same specification are vulcanized with hot water, the specifications of the ribs and grooves of the bladder are changed as shown in Table 1 (a total of 8 types of Examples 1 to 6 and Comparative Examples 1 and 2). The durability and vulcanization time of the vulcanized tire was measured. The center portion in the vertical direction of the bladder is provided with a plurality of annular ribs with normal film thickness in Examples 1 to 6, with no ribs with normal film thickness in Comparative Example 1, and compared with other parts in Comparative Example 2. And 5mm thick and no ribs. The ribs of Examples 1 to 5 have an undercut shape in which the head is formed in a circular shape as illustrated in FIG. 6, and the ribs of Example 6 are mountain shapes in which the head is tapered as illustrated in FIG. 2. It is a straight shape formed. The materials of the bladders of Examples 1 to 6 and Comparative Examples 1 and 2 and the wall thickness (15 mm) of the main body are the same. The groove shape of Examples 1, 2, 4 to 6 is an arc shape, and is provided at an intermediate position between adjacent ribs. The measurement results were as shown in Table 1.

[Tire durability]
The distance that was able to run without any problem in the drum running test was evaluated by an index with Comparative Example 1 being 100 as a reference. It shows that it is excellent in durability, so that a numerical value is large.

[Vulcanization time]
Comparative Example 1 was evaluated as an index with reference 100. The larger the value, the longer the vulcanization time.

  From the results of Table 1, it can be seen that Examples 1 to 6 are superior in tire durability as compared with Comparative Examples 1 and 2. Further, in Examples 1 to 6, the vulcanization time is shorter than that in Comparative Example 2, and the vulcanization time does not change significantly as compared with Comparative Example 1. Therefore, in Examples 1-6, it turns out that it is effective in suppressing the influence with respect to the thermal conductivity of a bladder, adjusting the rigidity of a bladder by providing a rib and a groove | channel.

DESCRIPTION OF SYMBOLS 1 Bladder 2 Bladder main-body part 3a Upper side clamp part 3b Lower side clamp part 4A Annular rib 4B Spiral rib 4a Root part 4b Head part 5 Groove 6 Vulcanization device 7 Center mechanism 8a Upper holding part 8b Lower holding part 9a Injection nozzle 10 10a, 10b, 10c, 10d Mold G Green tire B Belt layer H Heat medium

Claims (10)

  In the tire vulcanization bladder used when vulcanizing a green tire set horizontally in the mold, the thickness of the cylindrical bladder body is set to a certain thickness, and A rubber rib extending in the circumferential direction is formed at the center in the direction, and the ribs are spaced apart in the vertical direction to form a plurality of annular ribs, or the ribs are spirally connected in the vertical direction to be spiraled. A tire vulcanizing bladder characterized by comprising a rib-like rib.   By changing at least one of the cross-sectional area of the rubber ribs or the interval in the vertical direction, the circumferential rigidity of the bladder at the center in the vertical direction of the bladder is set to be maximized toward the center in the vertical direction. The tire vulcanizing bladder according to claim 1.   The bladder for tire vulcanization according to claim 2, wherein the circumferential rigidity of the bladder is symmetric with respect to the center in the vertical direction of the bladder.   The tire vulcanization bladder according to any one of claims 1 to 3, wherein a groove extending in the circumferential direction is formed between the ribs adjacent to each other in the vertical direction.   The tire vulcanizing bladder according to any one of claims 1 to 4, wherein a cross-sectional shape of the rib is an undercut shape in which a head portion is larger than a root portion.   The tire vulcanization bladder according to any one of claims 1 to 5, wherein a ratio Wr / Gb of a width Wr of a base portion of the rib to a film thickness Gb of the bladder main body portion is 0.2 or more and 0.5 or less.   The ribs are arranged at a predetermined constant pitch P in the vertical direction of the bladder, and a ratio Wr / P of a width Wr of the root portion of the rib to the pitch P is 0.1 or more and 0.5 or less. The tire vulcanization bladder according to any one of the above.   The tire vulcanizing bladder according to claim 4, wherein a cross-sectional shape of the groove is an arc shape.   9. The tire vulcanizing bladder according to claim 8, wherein a cross-sectional shape of the groove is a semicircular shape, and a ratio Rd / Gb of a groove radius Rd to a film thickness Gb of the bladder main body is 0.1 or more and 0.5 or less. .   The manufacturing method of the pneumatic tire which vulcanizes a green tire using the bladder for tire vulcanization in any one of Claims 1-9.

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