KR20120001592A - Method for manufacturing tyre - Google Patents

Abstract

PURPOSE: A method of manufacturing a tire is provided to prevent a tire from having scratches using a two-piece mold when the tire is taken from a mold. CONSTITUTION: A method of manufacturing a tire is as follows. A low cover is obtained by pre-molding. A mold is opened by the combination of an upper mold and a lower mold(54). The cavity surface of the mold makes contact with the low cover to form the outer surface of a tire(20). The low cover is put in the mold. A pressure medium is filled in a bladder(52), which is located in the low cover. The mold is closed and the low cover is pressurized and heated in the mold. The pressure medium is taken from the bladder. The mold is opened, and another pressure medium is filled in the bladder.

Description

Tire manufacturing method {METHOD FOR MANUFACTURING TIRE}

The present invention relates to a tire manufacturing method. Specifically, the present invention relates to a tire manufacturing method using a two-piece mold.

6 is a schematic view showing a part of the vulcanizing device 2 for a tire. The code | symbol T shows the tire manufactured by this vulcanization apparatus 2. As shown in FIG. In this FIG. 6, the situation where this tire T is taken out from the vulcanization apparatus 2 is shown.

The vulcanizing device 2 includes a mold 4, a bladder 6, an upper clamp 8, and a lower clamp 10. This mold 4 has a lower mold 12. Although not shown, this mold 4 also has an upper mold. This mold 4 is a two-piece mold. In this mold 4, by combining this upper mold and lower mold 12, the cavity surface 14 which forms the outer surface of the tire T is comprised.

The bladder 6 is made of crosslinked rubber. The bladder 6 has shown the substantially cylindrical shape. Although not shown, the upper end edge of the bladder 6 is held by the upper clamp 8. The lower edge portion of the bladder 6 is held by the lower clamp 10. The bladder 6 is filled with gas. This filling causes the bladder 6 to expand. The bladder 6 contracts when gas is discharged from the inside thereof. The bladder 6 shown in FIG. 6 is in a retracted state.

In this vulcanization apparatus 2, the tire T is manufactured as follows. In the opened mold 4, a low cover (also referred to as an uncrosslinked tire) obtained by preforming is put. The bladder 6 expands by filling gas. The mold 4 is closed and heated with the low cover pressed in the cavity surrounded by the mold 4 and bladder 6. The rubber composition of the low cover flows in the cavity by pressing and heating. The rubber causes a crosslinking reaction by heating, thereby obtaining a tire T. As shown in FIG. 6, the bladder 6 contracts by the discharge of the gas, the mold 4 is opened, and the tire T is taken out.

From the viewpoint of running performance, grooves may be inscribed in the tread surface 16 of the tire T. When manufacturing such a tire T, the mold 4 in which the convex part corresponding to this groove | channel was formed in the cavity surface 14 is used. In this mold 4, since the convex part is bitten by the tread of the tire T, when the tire T is taken out from the mold 4, a defect such as crushing on the surface of the tire T occurs. There is.

As described above, in the two-piece mold 4, there is a problem that a defect is likely to occur when the tire T is taken out from the mold 4. In order to solve this problem, various examination is made about the taking-out method of the tire T manufactured by the two-piece mold 4. As shown in FIG. This examination example is disclosed in Japanese Patent Laid-Open No. 8-25364 and Japanese Patent Laid-Open No. 2007-185855.

Japanese Patent Laid-Open No. 8-25364 Japanese Patent Publication No. 2007-185855

From the standpoint of straightness stability and drainage of the tire T, a groove extending in the circumferential direction may be formed in the center region of the tread surface 16.

The two-piece mold 4 has a parting line which is a boundary between the upper mold and the lower mold 12. When the convex portion corresponding to the groove crosses this parting line, the dividing surface 18 of each of the upper mold and the lower mold 12 includes an end face of the convex portion. The edge of this end face is sharp. In this mold 4, when the tire T is taken out, the sharp edges may cause scratches on the surface of the tire T. FIG.

The smaller the inclination angle with respect to the equator plane of the convex portion, the sharper the edge of the end face of this convex portion. When the tire T is taken out, the sharp edge easily scratches the tire T surface. In the two-piece mold 4, it is difficult to manufacture a tire T having a groove extending in the circumferential direction in the center region of the tread surface 16 without scratching the surface thereof.

It is an object of the present invention to provide a tire manufacturing method using a two-piece mold, in which a tire excellent in straightness stability and drainage can be obtained without scratching its surface.

The manufacturing method of the tire which concerns on this invention,

(1) the process of obtaining a low cover by preforming,

(2) A mold having an upper mold and a lower mold, wherein a combination of the upper mold and the lower mold forms a cavity surface which contacts the row cover to form an outer surface of the tire is opened, and the row cover is provided with the lower mold. The process that is put into the mold,

(3) a step in which the pressurized medium is filled into the bladder located inside the row cover,

(4) the mold is closed and the row cover is pressurized and heated in the mold;

(5) a step of discharging the pressurized medium from the bladder, and

(6) A tire manufacturing method comprising the step of opening the mold and filling the bladder with another pressurized medium.

Preferably, in this tire manufacturing method, the temperature of the other pressurized medium is lower than the temperature of the pressurized medium. The pressure of the other pressurized medium is lower than the pressure of the pressurized medium.

Preferably, the tire produced by this manufacturing method has a tread whose outer surface forms a tread surface. The tread surface is engraved with a groove extending inclined with respect to the equator surface. The inclination angle of this groove is 5 degrees or more and 45 degrees or less.

Preferably, in the tire manufacturing method, the groove is located in the center region of the tread surface.

Preferably, in the tire manufacturing method, the lower mold has a split surface that is in contact with the upper mold. This dividing plane is located above the equator.

According to the present invention, a tire excellent in straightness stability and drainage property can be stably manufactured without scratching the surface when taken out from the mold.

1 is a cross-sectional view showing a part of a pneumatic tire manufactured by a manufacturing method according to an embodiment of the present invention.
FIG. 2 is a developed view of the tread surface of the tire of FIG. 1.
FIG. 3 is a schematic diagram showing a part of the vulcanization apparatus for manufacturing the tire of FIG. 1.
4 is a flowchart illustrating a method of manufacturing the tire of FIG. 1.
5 is a schematic diagram showing a situation in which the tire is taken out from the vulcanizing apparatus.
6 is a schematic view showing a part of a vulcanizing device for a tire.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on preferable embodiment, referring drawings suitably.

1 is a cross-sectional view of the pneumatic tire 20 manufactured by the manufacturing method according to one embodiment of the present invention. In this FIG. 1, the up-down direction is a radial direction, the left-right direction is an axial direction, and the perpendicular direction to the ground is a circumferential direction. This tire 20 has a substantially left-right symmetrical shape centering on the dashed-dotted line CL in FIG. This dashed-dotted line CL shows the equator plane of the tire 20. The tire 20 has a tread 22, a side wall 24, a bead 26, a carcass 28, a belt 30 and an inner liner 32. This tire 20 is of tubeless type. This tire 20 is mounted on a two-wheeled vehicle.

The tread 22 is made of a crosslinked rubber having excellent wear resistance. The tread 22 has a radially outwardly convex shape. The tread 22 has a tread surface 34. This tread surface 34 is grounded with the road surface. It is the end of the tread 22 indicated by the sign TE.

The side wall 24 extends radially inward from the end TE of the tread 22. This side wall 24 is made of crosslinked rubber.

The beads 26 are located approximately radially inward from the sidewalls 24. Bead 26 has a core 36 and an apex 38 extending radially outward from the core 36. Core 36 is ring-shaped. The core 36 is made of a non-stretchable wire wound. Apex 38 is tapered radially outward. Apex 38 is made of a crosslinked rubber of high hardness.

The carcass 28 consists of the carcass ply 40. Carcass splice 40 spans between both beads 26 and follows the inside of tread 22 and sidewall 24. The carcass splice 40 is folded back from the inner side in the axial direction to the outer side of the core 36.

Although not shown, the carcass splice 40 is made up of multiple cords and topping rubbers in parallel. The absolute value of the angle formed by each cord with respect to the equator is usually 70 ° to 90 °. In other words, this carcass 28 has a radial structure. Cords usually consist of organic fibers. As preferable organic fiber, polyester fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber are illustrated.

The belt 30 is located radially outward of the carcass 28. The belt 30 is stacked with the carcass 28. The belt 30 reinforces the carcass 28. The belt 30 consists of an inner layer 42 and an outer layer 44. Although not shown, each of the inner layer 42 and the outer layer 44 consists of a plurality of cords and topping rubbers in parallel. Each cord is inclined with respect to the equator plane. The absolute value of the inclination angle is 10 degrees or more and 35 degrees or less. The inclination direction of the cord of the inner layer 42 is opposite to the inclination direction of the cord of the outer layer 44. The preferred material for the cord is steel. You may use organic fiber for a cord. As preferable organic fiber, polyester fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber are illustrated.

FIG. 2 is a developed view of a portion of the tread surface 34 of the tire 20 of FIG. 1. In this FIG. 2, the up-down direction is a circumferential direction, and the left-right direction is an axial direction. The dashed-dotted line CL is an equator plane of this tire 20. Both arrows WT represent the distance between the ends TE of both treads 22. This distance WT is the circumferential length of this tread surface 34. Reference numeral RC denotes the center region of the tread surface 34. This center area RC is located on the equator. In this tire 20, the center of the axial direction of the area RC coincides with the equator plane. Both arrows WC represent the width of the area RC. The width WC of this region RC is set to 40% of the distance WT. Reference sign RS denotes a side region of the tread surface 34.

As shown, a plurality of grooves 46 are inscribed on the tread surface 34. These grooves 46 form a tread pattern. Each groove 46 extends inclined with respect to the equator plane. In this tire 20, the inclination angle of the groove 46 located in the center region RC is smaller than the inclination angle of the groove 46 located in the side region RS. In other words, the tire 20 has a groove 46 extending in the circumferential direction in the center region RC of the tread surface 34. This tire 20 is excellent in straight stability because the tread 22 has appropriate rigidity. Since the groove 46 promotes drainage, the tire 20 is also excellent in drainage.

In FIG. 2, the angle α represents the angle formed by the edge of one groove 46a across the equator with respect to the equator plane. In this specification, angle (alpha) is measured about each groove | channel 46 located in center area | region RC, and the minimum value is displayed as an inclination angle. From the viewpoint of straightness stability and drainage, the inclination angle α of the groove 46 located in the center region RC is preferably 5 ° or more, and preferably 45 ° or less.

This tire 20 is obtained by pressurizing and heating a low cover (also referred to as an uncrosslinked tire) using the vulcanizing device 48 shown in FIG. In Fig. 3, the symbol R denotes a row cover. In FIG. 3, the dashed-dotted line CL is an equator plane of the tire 20 manufactured by this vulcanization apparatus 48. As shown in FIG.

The vulcanizing device 48 includes a mold 50 and a bladder 52. This mold 50 has a lower mold 54. Although not shown, the mold 50 also includes an upper mold. This mold 50 is a two piece mold. In the mold 50, the upper mold and the lower mold 54 are combined to form a cavity surface 56 that forms the outer surface of the tire 20. In this mold 50, the shift | offset | difference at the time of combining the upper metal mold | die and the lower metal mold | die 54 is small, and the roundness of the cavity surface 56 is high.

As described above, the tire 20 has a groove 46 extending in the circumferential direction in the center region RC of the tread surface 34. Although not shown, a convex portion corresponding to the groove 46 is formed in the cavity surface 56 of the mold 50.

In the mold 50, the lower mold 54 is provided with a dividing surface 58 that can contact the upper mold. When the upper mold and the lower mold 54 are combined, the upper mold is disposed on this divided surface 58. This divided surface 58 constitutes a parting line which is a boundary between the upper mold and the lower mold 54. As shown, the dividing surface 58 of the lower mold 54 is located above the equator surface. In other words, the parting line of this mold 50 is located above the equator plane.

The bladder 52 is made of crosslinked rubber. Bladder 52 has a substantially cylindrical shape. A pressurized medium is filled in the bladder 52. This filling causes the bladder 52 to expand. The bladder 52 contracts when the pressurized medium is discharged from the inside thereof.

This tire 20 is manufactured using the vulcanizing device 48 as follows. 4 is a flowchart of the manufacturing method of the tire 20.

In this manufacturing method, the low cover R is obtained by preforming (STEP 1). The low cover R is introduced into the mold 50 in a state in which the mold 50 is open and the bladder 52 is retracted (STEP 2). Inside the bladder 52, as a 1st pressurizing medium, the steam whose temperature was adjusted from 180 degreeC to 200 degreeC is filled (STEP3). By this filling, the internal pressure of the bladder 52 is adjusted to 1.5 MPa. In this manufacturing method, the nitrogen gas whose temperature was adjusted to 180 degreeC may be used for this 1st pressurized medium. From the viewpoint of easy heating of the low cover R described later, steam is preferable as the first pressurized medium.

By filling of the first pressurized medium, the bladder 52 expands. The bladder 52 is in contact with the inner circumferential surface 60 of the low cover R. By the bladder 52, the shape of the low cover R is provided. The row cover R in this state is shown in FIG. This process (STEP3) is also called a molding process.

The mold 50 is closed, loaded and fastened (STEP4). The mold 50 is heated using steam which is a heating medium whose temperature is adjusted from 180 ° C to 200 ° C. The low cover R is heated by this heated mold 50 (STEP5). In this heating step (STEP5), the row cover R is heated while the mold 50 is fastened.

Inside the bladder 52, a second pressurized medium is further supplied (STEP6). By supplying this second pressurized medium, the internal pressure of the bladder 52 is increased. The internal pressure of the bladder 52 is adjusted from 2.1 MPa to 2.4 MPa. The low cover R is pressed against the cavity surface 56 of the mold 50 by the bladder 52 and pressed. At the same time the row cover R is heated. In this pressurization process (STEP6), a rubber composition flows by pressurization and a heating. The rubber generates a crosslinking reaction by heating, and the tire 20 is formed. It is preferable that this 2nd pressurized medium has a temperature lower than the temperature of a 1st pressurized medium from a viewpoint that the temperature rise by adiabatic compression is prevented and an appropriately vulcanized tire is obtained. In this manufacturing method, a particularly preferable second pressurized medium is nitrogen gas at room temperature. Nitrogen gas can contribute to the long life of the bladder 52.

As mentioned above, the cavity surface 56 of this mold 50 is provided with the convex part extended in the circumferential direction in the part corresponded to the center area | region RC of the tread surface 34 of the tire 20. As shown in FIG. . Although not shown, the convex portion is bitten by the tread 22 of the tire 20. By this bite, a groove 46 is formed in the tread 22.

After the pressing step, the first pressing medium and the second pressing medium are discharged from the inside of the bladder 52, and the load applied to the mold 50 is removed. The upper mold of this mold 50 is separated, and compressed air is filled inside the bladder 52 as a third pressurized medium. In this way, the mold 50 is opened and the tire 20 is extracted (STEP7).

5 shows a situation in which the upper mold is removed from the mold 50 and the tire 20 is taken out. As described above, the upper mold is separated and a third pressurized medium is filled in the bladder 52. By this filling, the bladder 52 expands. The expanded bladder 52 widens the bead 26 portion of the tire 20 axially outward. The tire 20 is deformed so that the equator portion of the tread 22 recesses radially inward. Although not shown, by this deformation, the convex portion of the mold 50 is pulled out of the groove 46 of the tread 22. In this manufacturing method, the tire 20 is taken out from the mold 50 with the convex part pulled out from the groove 46. In addition, in FIG. 5, what the code | symbol C shows is the clamp which moved upwards as the bladder 52 expands. This clamp C can hold the upper edge of the bladder 52.

Since the tire 20 is taken out of the mold 50 without contacting the convex portion, the surface of the tire 20 is effectively prevented from being scratched by the convex portion. This manufacturing method stably fixes the tire 20 having the grooves 46 extending substantially in the circumferential direction in the center region RC of the tread surface 34, which has been difficult to manufacture with the two-piece mold 50 so far. It can manufacture. This manufacturing method can contribute to manufacture of the tire 20 which is excellent in straight stability and drainage property. Moreover, since this manufacturing method is inexpensive compared with the division mold 50 which the mold 50 consists of many members, production cost can be reduced.

As described above, the parting line of the mold 50 is located above the equator plane. However, since the equator portion of the tread 22 is recessed, the tire 20 is easily taken out from the mold 50. In this manufacturing method, even if the parting line of the mold 50 is located above the equator plane, the tire 20 can be easily taken out without causing scratches on the tire 20 by the convex portion. According to this manufacturing method, the tire 20 excellent in appearance, straight stability, and drainage property can be manufactured stably. The tire 20 manufactured by this manufacturing method is high quality.

In this manufacturing method, the internal pressure of the bladder 52 by the filling of the third pressurized medium is lower than the internal pressure of the bladder 52 by the filling of the second pressurized medium. The internal pressure of the bladder 52 by the filling of the third pressurized medium is lower than the internal pressure of the bladder 52 by the filling of the first pressurized medium. For this reason, deformation of the tire 20 by the bladder 52 filled with the 3rd press medium is controlled suitably. In this manufacturing method, since the rapid deformation and the unusual deformation of the tire 20 due to the filling of the third pressurizing medium are suppressed, damage of the tire 20 when the tire 20 is detached from the mold 50 is prevented. Effectively prevented. From this viewpoint, 0.02 MPa or more is preferable and, as for the internal pressure of the bladder 52 by the filling of this 3rd pressurized medium, 0.10 MPa or less is preferable. Especially preferably, this internal pressure is 0.04 MPa.

In this manufacturing method, the temperature of the third pressurized medium is lower than the temperature of the first pressurized medium. The low temperature third pressurized medium can prevent overvulcanization of the tire 20. This manufacturing method can obtain the tire 20 vulcanized suitably. This manufacturing method can manufacture a high quality tire 20. In this respect, as the third pressurized medium, compressed air at normal temperature is preferable. Moreover, you may use nitrogen gas of normal temperature as this 3rd pressurized medium.

Example

Hereinafter, although the effect of this invention becomes clear according to an Example, based on description of this Example, this invention should not be interpreted limitedly.

Example 1

The row cover obtained by the preforming was put into a mold having the configuration shown in FIG. 3. At the time of a shaping | molding process, the inside of bladder was filled with the steam whose temperature was adjusted to 200 degreeC. By this filling, the bladder internal pressure was adjusted to 1.5 MPa. After the mold was closed, the bladder was further filled with nitrogen gas at room temperature. By this filling, the bladder internal pressure was adjusted to 2.1 MPa. The low cover was pressed and heated in this mold. After the pressurization process, steam and nitrogen gas were discharged from the inside of the bladder. After discharge, the upper mold of this mold was separated, and compressed air at normal temperature was filled in the bladder to expand the bladder. The bladder internal pressure was adjusted to 0.04 MPa. From this mold, the tire with the structure shown in FIG. 1 was taken out.

The size of this tire is 120 / 70ZR17. The groove extending in the circumferential direction is engraved in the center region RC of the tread surface of the tire. The inclination angle α of this groove is 5 degrees. The carcass of this tire consists of one carcass splice. This carcass splice comprises a cord made of nylon fibers. The angle of this cord with respect to the equator is 90 degrees. Each of the inner and outer layers of the belt includes a cord consisting of aramid fibers. The angle of this cord with respect to the equator is 19 degrees.

[Examples 2 and 3 and Reference Example 1]

The tire was manufactured like Example 1 except having changed the tread pattern of a tire and making the inclination-angle (alpha) of the groove | channel carved in the center area | region RC as shown in Table 1 below.

Comparative Example 1

The row cover obtained by the preforming was put into a mold having the configuration shown in FIG. 3. During the molding process, the bladder was filled with steam whose temperature was adjusted to 200 ° C. By this filling, the bladder internal pressure was adjusted to 1.5 MPa. After the mold was closed, the bladder was further filled with nitrogen gas at room temperature. By this filling, the bladder internal pressure was adjusted to 2.1 MPa. The low cover was pressed and heated in this mold. After the pressurization process, steam and nitrogen gas were discharged from the inside of the bladder. The mold was opened and the tire was taken out. The groove extending in the circumferential direction is engraved in the center region RC of the tread surface of the tire. The inclination angle α of this groove is 45 degrees. This comparative example 1 is a conventional tire manufacturing method.

Comparative Example 2

A tire was manufactured in the same manner as in Comparative Example 1 except that the tread pattern of the tire was changed and the inclination angle α of the groove inscribed in the center area RC was as shown in Table 1 below.

[Observation of appearance]

The appearance of the manufactured tire (100 pieces) was visually observed. The results are shown in Table 1 below. In Table 1, when a scratch is not recognized on the tire surface, it displays as "G", and when a scratch is confirmed, it displays as "NG".

[Straight Stability]

The tire was assembled to a regular rim, and the tire was filled with air to obtain an internal pressure of 290 kPa. This tire was attached to the drum type | mold running test machine, and the load of 1.3 kN was loaded on the tire. This tire was run on the drum at a speed of 30 km / h. The reaction force when the protrusion of 10 mm x 10 mm was overturned was measured. This result is shown in following Table 1 as the index value which makes the comparative example 1 100. The larger the value, the better.

[Drainage]

The tire was assembled to a regular rim, and the tire was filled with air to obtain an internal pressure of 290 kPa. This tire was attached to the drum type | mold running test machine, and the load of 1.3 kN was loaded on the tire. The tire was run on a drum having a slip angle of 1 ° and a water film of 1.0 mm formed thereon, and the limit speed was measured. This result is shown in following Table 1 as the index value which makes the comparative example 1 100. The larger the value, the better.

As shown in Table 1, in the manufacturing method of an Example, evaluation is high compared with the manufacturing method of a comparative example. From this evaluation result, the superiority of this invention is clear.

The method described above can also be applied to the production of various tires.

2, 48: Vulcanizer 4, 50: Mold
6, 52: bladder 12, 54: lower mold
14, 56: cavity surface 16, 34: tread surface
18, 58: split surface 20: tire
22: Tread 46: Home
60: inner circumference

Claims (5)

The process of obtaining a low cover by preforming,
The upper mold and the lower mold are provided, and the combination of the upper mold and the lower mold opens a mold having a cavity surface in contact with the low cover to form an outer surface of the tire, and the low cover is fed into the mold. Process and
A step of filling the bladder positioned inside the low cover with a pressurized medium;
The mold is closed and the row cover is pressurized and heated in the mold;
Discharging the pressurized medium from the bladder;
The mold is opened, and the bladder is filled with another pressurized medium
Tire manufacturing method comprising a. The method of claim 1, wherein the temperature of the other pressurized medium is lower than the temperature of the pressurized medium,
And the pressure of the other pressurized medium is lower than the pressure of the pressurized medium. The tire according to claim 1 or 2, wherein the tire has a tread whose outer surface forms a tread surface,
On this tread surface, a groove inclined with respect to the equator surface is inscribed,
The inclination angle of this groove | channel is a tire manufacturing method of 5 degrees or more and 45 degrees or less. 4. The method of claim 3, wherein the groove is located in the center area of the tread surface. The lower mold of claim 1 or 2, wherein the lower mold includes a split surface in contact with the upper mold.
The split surface is located above the equator.

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