JP4708100B2 - Vulcanizing bladder - Google Patents

Description

  The present invention relates to a bladder used for vulcanizing a tire, and more particularly to a bladder that does not cause poor appearance on the inner surface of a tire when vulcanizing a tire with a small aspect ratio.

  Conventionally, as an expandable / contractable core for vulcanizing a tire, a rubber bladder having a cylindrical shape and having openings at both ends in the axial direction has been used. Such a bladder is configured to attach metal fittings that close the openings at both ends thereof to make the inside a sealed space, and to bulge by introducing a pressure fluid therein to press the inner surface of the raw tire.

1 to 3, the green tire, after placing in the open vulcanization mold, bladder schematic meridian section showing the change in shape of the bladder until the start of closure to vulcanizing the mold FIG. First, as shown in FIG. 1, the raw tire GT is placed on the lower side plate 81 with the raw tire GT positioned on the radially outer side of the bladder 91 whose inside is in a vacuum state.

  Next, as shown in FIG. 2, the center post 82 is operated to lower the upper ring 92 that closes the upper opening of the bladder 91, and at the same time, a pressurized fluid such as air is introduced into the bladder 91. Then, the bladder 91 is bulged so as to follow the inner surface shape of the raw tire GT. This process is called a pre-shaping process.

  Then, as shown in FIG. 3, while lowering the upper side plate 83, the sector mold 84 is displaced radially inward to form a cavity corresponding to the shape of the product tire, and then a high-pressure fluid is applied to the inside of the bladder. Introduce and press the tire against the outer mold from the inside to start vulcanization. This process until vulcanization is started is called a vulcanization start process.

  In the steps from the pre-shaping step to the start of vulcanization, if air is caught between the raw tire GT and the bladder 91, the raw tire GT is vulcanized while the air remains there. The outer surface shape of the bladder 91 is not transferred as it is as the tire inner surface shape, and there is a possibility that an appearance defect such as a bear may occur in a portion where air is accumulated.

As a countermeasure to deal with this, when the bladder 91 is fitted to the inner surface of the raw tire GT in the pre-shaping step, the bladder 91 sequentially contacts from the center in the width direction of the raw tire GT toward the end in the width direction. In this way, a device that defines the shape of the bladder 91 has been proposed (see, for example, Patent Document 1).
JP 2003-11125 A

  However, even in accordance with this proposal, particularly in the case of a flat tire bladder with a flatness ratio of 30 to 50%, or when the lubricant is not applied to the inner surface of the raw tire GT or the outer surface of the bladder 91, the vulcanized It was found that poor appearance due to the formation of an air layer between the bladder 91 and the inner surface of the tire was observed.

  As a result of inspecting the cause, the inventor, after the pre-shaping process, in the vulcanization start process, the raw tire is deformed from the original shape to a shape close to the product tire, and the tire foot width (distance between beads) However, when it changes from the raw tire wg to the product tire wp, the bladder that has been pressure-bonded to the sidewall part is separated from the sidewall part as shown in FIG. It was determined that air would enter 96.

The present invention has been made in view of such problems, has a cylindrical shape, has openings at both ends in the axial direction, and bulges out by pressing the inside to press the inner surface of the raw tire. in vulcanization bladder, in particular, in low aspect ratio tires, provide a vulcanization bladder which can eliminate the air layer enters between the tire to prevent bad appearance of the tire inside surface that occurs due to this The purpose is to do.

<1> is a vulcanizing bladder that is molded using a mold, has a cylindrical shape, has openings at both ends in the axial direction, and bulges by pressurizing the inside to press the inner surface of the raw tire ,
An outer contour line in a meridian cross section including a central axis in a molding state arranged in the mold includes an edge adjacent to the opening, a shoulder extending from the edge in an outer diameter direction, and a shaft. A crown portion extending in the direction and constituting the outer periphery of the cylinder, and a curved portion smoothly connected to each of the crown portion and the shoulder portion, and the curved portion protrudes outward in the axial direction from the shoulder portion. In the state of pressing the inner surface of the corresponding size of the raw tire, it is configured to contact the maximum width portion of the tire ,
The vulcanization bladder is configured such that the distance from the central axis of the crown portion is the smallest at the center in the axial direction and is increased toward the outer side in the axial direction .

  <2> in <1>, in the molded state, the shoulder portion is configured by a straight line extending in a direction perpendicular to the central axis, and the curved portion is smoothly connected to the shoulder portion and is connected to the inside. Consists of a first curved part that is convex and a second curved part that is smoothly connected to the crown part and convex outward, and the first curved part and the second curved part are configured to be smoothly and directly connected. It is a vulcanizing bladder.

  According to <1>, the outer contour line in the meridian cross section including the central axis in the molding state disposed in the mold extends in the outer diameter direction from the edge adjacent to the opening and the edge. A shoulder portion, a crown portion extending in the axial direction and constituting the outer periphery of the cylinder, and a curved portion smoothly connected to each of the crown portion and the shoulder portion. In addition to projecting outward in the axial direction and pressing the inner surface of the corresponding size of the raw tire, it is configured to contact the maximum width portion of the tire. When used for vulcanization, the shape of the bladder in the vulcanization start process can be made to substantially match the shape of the inner surface of the product tire, preventing excessive tension on the bladder and preventing the bladder from separating from the tire inner surface. Therefore, the air layer is tire It is possible to prevent the appearance defect of the tire inner surface from being formed between the tire and the bladder.

Moreover, it does not generate excessive tension, for bladder repeating repeated swelling and shrinkage deformation, which means that it is possible to suppress the occurrence of a failure due to fatigue of the repetition, thus, the bladder life in addition to the effects described above It can also contribute to improvement.
In addition, here, the distance from the central axis of the crown portion is made the smallest at the center in the width direction and increased toward the outer side in the axial direction, so that the tension of the bladder in the vulcanization start process is further reduced. And the life can be further improved.

  According to <2>, in the molded state of the bladder, the shoulder portion is configured by a straight line extending in a direction orthogonal to the central axis, and the curved portion is smoothly connected to the shoulder portion and protrudes inwardly. It consists of a curved portion and a second curved portion that is smoothly connected to the crown and convex outward, and the first curved portion and the second curved portion are configured to be smoothly and directly connected, so that the vulcanization start step The curved portion of the odor bladder outer contour line can be more faithfully fitted to the inner surface of the tire, which can more effectively achieve the prevention of the appearance failure of the tire inner surface and the improvement of the life of the bladder.

Incidentally, the bladder as described above, the highest frequency of occurrence of tire inside surface appearance defects, if the flattening ratio is used in vulcanization molding of 30-50% of the tire, more effectively the occurrence of tire inside surface appearance defects Can be prevented.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 4 is a cross-sectional view showing the shape of a vulcanizing bladder according to the basic embodiment of the present invention in a state where it is placed in a mold for molding the vulcanizing bladder. The vulcanizing bladder 10 uses a mold. It is molded, has a cylindrical shape, and has openings 11 and 12 at both ends in the axial direction.

The outer contour line in the meridian cross section including the central axis C in the molding state arranged in the mold is connected to the edge 1 adjacent to the openings 11 and 12 and the edge 1 at the point P _1. A point P ₄ and a point P are respectively formed on the shoulder 2 extending from P _{1 in the} outer diameter direction, the crown 5 constituting the outer periphery of the cylinder facing the central axis C, and the crown 5 and the shoulder 2 respectively. _The curved portion 6 is smoothly connected to the curved portion 6, and the curved portion 6 has a shape that protrudes by D outside the shoulder portion 2 in the axial direction.

Here, in the molded state, the shoulder portion 2 is constituted by a straight line extending in a direction orthogonal to the central axis C, and the curved portion 6 is smoothly formed at the point P ₂ on the shoulder portion 2 in the illustrated sectional view. The first curved portion 3 having a radius of curvature R ₃ that is connected and convex inward, and the second curved portion 4 having a radius of curvature R ₄ that is smoothly connected to the crown portion 5 at point P ₄ and convex outward. Thus, it is preferable that the first curved portion 3 and the second curved portion 4 are configured to be smoothly and directly connected at the point P ₃ .

  In FIG. 4, reference numeral 90 denotes a conventional bladder outer contour line for a tire corresponding to the vulcanizing bladder 10 according to the present invention in a molded state arranged in a mold. In the bladder outer contour line 90, the curved portion connecting the shoulder portion 2 and the crown portion 5 did not protrude outward in the axial direction from the shoulder portion 2.

FIG. 5 is a cross-sectional view showing a vulcanizing bladder 20 in which the crown portion 5 of the vulcanizing bladder 10 is replaced with a crown portion 5A as an embodiment of the present invention, which is different from that shown in FIG. vulcanization bladder 20, the distance from the center axis C of the crown portion 5A is the smallest and Pb / 2 in the axial direction center, increases toward axially outward, the maximum, Pa / 2 at point P ₄ This is a feature, and this is preferable in that it is possible to prevent the local concentration of elongation.

However, since the vulcanization bladder 20 axial center is in the concave, hit the shaping bladder 20, the mold, the outer mold for specifying the outer contour of the bladder, the structure is divided in the axial direction In such a case , if these are opened in the axial direction, they will interfere with the core, so that the mold cannot be opened or closed. Therefore, in this case, to divide the outer mold in the circumferential direction, it is necessary to have a structure to open the mold by moving them radially outwardly, if the case has lightning use such mold A new mold is required.

6, in the molding condition, the bladder 10 having a shape shown in FIG. 4 is a sectional view showing the vulcanizing start state, after the flop les shaping process such as illustrated in FIG. 2, the upper side plate 83 While lowering, the sector mold 84 is displaced radially inward to deform the raw tire GT from its original shape to a shape close to the product tire, and the foot width is changed from wg to wp. The one curved portion 6 can be brought into contact with the maximum width portion Q that gives the maximum width W of the tire without a gap. This is because the curved portion 6 protrudes by D toward the outer side in the axial direction than the shoulder portion 2, thereby preventing a bad appearance of the tire inner surface and improving the life of the bladder.

In particular, the bladders oblateness corresponds to 30-50% of the tire, conventionally, in vulcanization initiation step, possibly appearance defect occurs by a gap between the bladder and tire maximum width portion Q was high, according to the blanking ladder 10, it is possible to solve this problem by the above-described configuration.

The bladders 10 having the outer contour shape shown in FIG. 4 corresponding to three types of tire sizes 205 / 40R17, 235 / 40R18, and 265 / 35R18 are respectively molded into reference examples 1 to 3, respectively. Using a bladder, 1000 tires of each size were vulcanized, and the air biting rate at the tire maximum width position Q was investigated. Also, the conventional shape bladders indicated by reference numeral 90 in FIG. 4 corresponding to these tire sizes are designated as Conventional Examples 1 to 3, respectively, and for these, 500 tires of each size are vulcanized, and the same Further, the occurrence rate of air biting at the tire maximum width position Q was investigated. The results are shown in Table 1.

  In addition, the presence or absence of the occurrence of air biting was determined by visual inspection and visual inspection of the inspector. Table 1 also shows the amount of protrusion D (see FIG. 4) of the curved portion 5 from the shoulder 2 to the outside in the axial direction.

Moreover, about the reference example 1 and the prior art example 1, what showed the stretch in each part of the bladder in a vulcanization | cure start process, ie, the value which added 1 to elongation, was shown in FIG.7 and FIG.8. . 7 corresponds to Conventional Example 1, and FIG. 8 corresponds to Reference Example 1. In these drawings, a stretch of 100% means that the elongation from the molded state of the bladder is zero, and a stretch of less than 100% means that deformation on the compression side has occurred. In addition, the stretch is measured by placing transferable marks on the surface of the bladder at equal intervals, and after vulcanization, the distance between the marks transferred from the bladder and formed on the inner surface of the tire is measured. Compared with the distance on the bladder surface, the stretch was determined from the result.

As is apparent from Table 1 and FIGS. 7 and 8, the bladder of the reference example can fit the bladder to the tire inner surface in the vulcanization start process, and can suppress local elongation of the bladder. it can.

  The vulcanization bladder according to the present invention can be applied to vulcanization of various types of tires.

It is a schematic meridian cross-sectional view of a bladder for vulcanization showing changes in the bladder after placing the green tire in an opened mold and then closing the mold and starting vulcanization. FIG. 2 is a schematic meridian cross-sectional view of a vulcanizing bladder showing a state following FIG. 1. FIG. 3 is a schematic meridian cross-sectional view of a vulcanizing bladder showing a state following FIG. 2. It is meridian sectional drawing which shows the bladder for vulcanization | cure of the basic form of this invention. 1 is a meridian cross-sectional view showing a vulcanizing bladder according to one embodiment of the present invention . It is a schematic meridian sectional view of a bladder for vulcanization showing a state in a vulcanization start process. It is a graph which shows the change for every site | part of the stretch of the bladder of the prior art example 1. FIG. It is a graph which shows the change for every site | part of the stretch of the bladder of the reference example 1. FIG.

DESCRIPTION OF SYMBOLS 1 Edge part 2 Shoulder part 3 1st curve part 4 2nd curve part 5, 5A Crown part 6 Curved part 10 , 20 Vulcanization bladder 11, 12 Opening part 81 Lower side plate 82 Center post 83 Upper side plate 84 Sector mold 91 Upper bladder ring GT Raw tire

Claims (2)

In a vulcanizing bladder that is molded using a mold, has a cylindrical shape, has openings at both ends in the axial direction, and bulges by pressurizing the inside to press the inner surface of the raw tire,
An outer contour line in a meridian cross section including a central axis in a molding state arranged in the mold includes an edge adjacent to the opening, a shoulder extending from the edge in an outer diameter direction, and a shaft. A crown portion extending in the direction and constituting the outer periphery of the cylinder, and a curved portion smoothly connected to each of the crown portion and the shoulder portion, and the curved portion protrudes outward in the axial direction from the shoulder portion. In the state of pressing the inner surface of the corresponding size of the raw tire, it is configured to contact the maximum width portion of the tire ,
A vulcanizing bladder in which the distance from the central axis of the crown portion is the smallest at the center in the axial direction and is increased toward the outer side in the axial direction .   In the molded state, the shoulder portion is configured by a straight line extending in a direction orthogonal to a central axis, and the curved portion is smoothly connected to the shoulder portion and protrudes inward, and The vulcanizing bladder according to claim 1, comprising a second curved portion that is smoothly connected to the crown portion and protrudes outward, and is configured such that the first curved portion and the second curved portion are directly connected smoothly. .

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