JPH0465207A - Manufacture of pneumatic tire - Google Patents

Abstract

PURPOSE:To improve a high speed durability, facilitate the workability of a green tread member and reduce manufacturing cost by a method wherein a peripheral groove having a V-shaped cross section is provided at the 1/4 shoulder part of a tread member and a formed recess part and the peripheral groove of the tread member are matched, followed by vulcanization. CONSTITUTION:A tread member 50 is provided with a peripheral groove 51 defined by gently inclined surfaces and having a V-shaped cross section in only 1/4 shoulder part thereof. A molding recess part 62 for forming rims or blocks R2 end R6 at the 1/4 shoulder part and the peripheral groove 51 of the tread member 50 ere matched in a metal die 60, followed by vulcanization. When an inner pressure is zero, by this method, a belt member 75, a carcass ply 72 and a car ply 74 are merged into a raised part 75 continuously extending in the peripheral direction at an intermediate part between the blocks R2 and R6 in the 1/4 shoulder part, i.e., the part facing the peripheral groove 51. When this tire T is inflated, the belt member 73, the carcass ply 72 and the car ply 74 are set in a straight line. Therefore, since the surface of the blocks R2 and R6 is depressed into a recess part 75A, blow-out or the like produced in a high speed operation can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for simply and efficiently manufacturing a pneumatic radial tire with high speed durability.

(Prior Art) Generally, the outer contour shape and belt structure of the tread portion of pneumatic radial tires used for passenger cars, trucks, buses, etc. are almost common to ultra-high speed tires and general tires. It is formed by a plurality of circumferential grooves and lateral grooves.

The outer profile in the cross-sectional direction of the tread, which is made up of hooks and/or ridges, usually lies on one circular arc, and is also made of reinforcing material mainly consisting of high-elastic cords such as metal cords. The cross-sectional shape of the belt layer, such as the inextensible belt used, is also arranged substantially parallel to the outer contour of the tread.

Incidentally, such pneumatic radial tires are generally manufactured by the steps shown in FIGS. 4(1) to 4(3).

That is, as shown in FIG. 4(1), the carcass ply 2 is first wound around the cylindrical former 1.

Here, the carcass ply 2 has cords made of fibers such as polyester, polyamide, rayon, and aromatic polyamide substantially aligned with the direction of the rotation axis of the former 1;
It consists of one or two plies, and at most three plies, of a rubberized layer.

Next, bead rings 3 are set at concentric positions on both sides of the former 1, and bead filler rubber 4 is placed on the bead rings 3, and then both ends of the carcass ply 2 are turned outward in the axial direction. Fold it back and attach a pair of side rubbers 5 to both sides of the carcass ply 20 with a gap in the center as shown in the figure.

Next, as shown in FIG. 4(2), the carcass portion is inflated into a toroidal shape using a Prader 6, and a belt member 7 and a tread member 8 are placed in the empty space between both side rubbers 5 on the carcass ply 2. The green tire 10 as shown in FIG. 4(3) is obtained by sequentially pasting the tires and applying a stating roller 9.

The attachment of the belt member 7 and tread member 8 in FIG. 4 (3) involves a plurality of rubberized layers in which cords with high elastic modulus, such as metal cords, are arranged at a shallow angle with respect to the circumferential direction. The belt member 7 and the tread member 8 are formed integrally in a separate process, and then the belt member 7 and the tread member 8 are formed into a carcass ply at once. Either of the two methods of attaching it to the crown part is adopted.

As the tread member 8, a band-shaped member having a trapezoidal shape with a substantially flat radially outer side, as shown in FIG. 4(2), has been used.

This tread member 8 includes a tread rubber 8^ having excellent wear resistance and the side rubber 5 disposed on both sides of the tread rubber 8^.
Although it is integrally formed from the miniskirt 8B, it is also possible to form the tread member 8 with the tread rubber 8 alone. In this case, the tip of the side rubber 5 can be attached to the tread member 8. It is desirable to attach them so that both sides are covered.

The green tire 10 thus formed is put into a mold (not shown) having protruding ribs for forming circumferential grooves, and is vulcanized and hardened under high temperature and high pressure by a conventional method, as shown in FIG. A pneumatic radial tire having the shape shown in is obtained.

That is, the pneumatic radial tire T shown in FIG. 5 has a tread layer 8 having a ridge area 8C made of blocks and/or ribs parallel to the belt member 7 on the carcass ply 2 via the belt member 7. are formed across the circumferential groove 8D.

However, when the pneumatic radial tire obtained by the above-mentioned conventional method is filled with air at a predetermined internal pressure, the tread outer contour becomes the state shown by the chain line in Fig. 5, which is particularly noticeable during low-speed or normal driving. There is no problem, but 2
When driving at high speeds of 00 to 300 km/h,
The outer tread contour generally bulges out radially outwards, in particular in the rib area 8 consisting of blocks and/or ribs.
Due to the large volume of the central part of C,
This results in a protrusion like the chain line in Figure 5.

In this way, when the central part of the ridge area 8C swells in the tread outer contour, the ground pressure at that bulge becomes locally excessive, and each time this overload occurs, the ridge area 8C is pulled and compressed. is repeated, the tread rubber layer 8
As the internal temperature of A increases, the tread rubber decomposes and its rubber strength rapidly decreases, making it impossible to withstand the centrifugal force associated with high-speed rotation, and the protrusions consisting of blocks and/or ribs. There has been a problem in that a phenomenon called blow chunk out, which is caused by the area 8C peeling off, is likely to occur.

Therefore, a method for manufacturing a pneumatic tire disclosed in Japanese Patent Application Laid-Open No. 1-130921 has been proposed.

That is, in this conventional technology, on a cylindrical former,
After a pair of bead rings, a carcass ply and side rubber extending between both bead rings are pasted together and expanded into a toroidal shape, a belt member and a tread member are successively pasted onto the crown portion of the carcass ply, or separately. In the process, a green tire is molded by setting a cylindrical body in which the belt member and tread member are bonded together in the crown part of the carcass ply, and then the green tire is vulcanized and hardened in a mold. ,
In a method for manufacturing a pneumatic tire having a circumferential groove in the circumferential direction of the tread, as shown in FIG. , a raised portion 21 extending in the circumferential direction
is provided in advance, and after aligning the protruding bone 31 and the protrusion 21 of the trend member 20 in the mold 30, vulcanization hardening is performed.

The pneumatic radial tire obtained by this technique has the shape and structure shown by the solid line in FIG. 7 after completion of molding.

That is, the belt layer 40 has a wavy shape with valleys corresponding to the circumferential grooves 23 of the tread portion and peaks corresponding to the centers of the protrusion areas 22 made of blocks and/or ribs.

This is because when the protruding portion 21 of the tread member 20 is pressed by the protruding rib 31 of the mold 30, the portion of the belt layer 40 corresponding to the circumferential groove 23 is selectively depressed.

When this tire T is filled with air at a predetermined internal pressure or is run at high speed, the outer contour structure of the tread and the belt structure change as shown by the chain lines in FIG.

That is, the belt layer 40 is subjected to tension due to the internal pressure, and becomes a straight line substantially parallel to the outer trend contour, while the outer surface of each protrusion section 22 has both ends swollen outward in the radial direction relative to the center.

Therefore, in the pneumatic radial tire having the above structure, the ground contact pressure at the center of the ridge area 22 is suppressed during high-speed running, so that the high-speed stability is dramatically improved compared to the conventional tire.

(Problems to be Solved by the Invention) Although the manufacturing method according to the above-mentioned publication (FIGS. 6 and 7) is recognized to have some usefulness, it has the following problems.

Since the raised portions 21 are alternately formed in the tread width direction of the tread member, the workability of the green trend member is deteriorated.

In flat tires for high-speed running, lifting at ultra-high speeds increases the ground contact pressure at the 2nd shoulder area, which increases the heat generation of the block/or rib in this area, resulting in high heat generation.
Rubber damage (blowout) is likely to occur due to accumulation, and it is difficult to suppress blowout at the shoulder portion by adjusting the gauge based on the extruded shape of the green tread member.

In view of these circumstances, the present invention provides a technology for manufacturing a pneumatic tire that has excellent processability of green tread members, has the highest ground contact pressure, suppresses heat generation in the shoulder area, and has excellent high-speed durability. That is the purpose.

(Means for Solving the Problems) The present invention includes a pair of bead rings 70, a carcass ply 72 extending between both bead rings 70, and a side rubber 72.
1 on a cylindrical former 1 and expanded into a toroidal shape, a belt member 73 and a tread member 5 are formed.
0 on the crown portion of the carcass ply 72, or a cylindrical body obtained by pasting the belt member 73 and the trend member 50 together in a separate process.
Green tire GT by setting it on the crown part of 2.
After that, a protruding bone 61 for forming the circumferential grooves 61 to G6 of the tire T and a molding recess 62 for forming the ribs or blocks R1 to R7 between the circumferential grooves 61 to G6 are provided between the protruding bones 61. The green tire G in the mold 60
In a method of manufacturing a pneumatic tire having circumferential grooves 61 to G6 in the circumferential direction of the tread by vulcanizing and hardening T, the following technical measures are taken to achieve the above-mentioned object.

That is, in the present invention, the tread member 50 has two
A circumferential groove 51 having a V-shaped cross section with a gently sloped surface is provided in advance only in the shoulder portion, and a molding recess 62 and the tread are formed in the mold 60 to form the rim or block R2°R6 of the two shoulder portions. This is characterized in that vulcanization hardening is performed after aligning the circumferential groove 51 of the member 50.

(Function) In the method of the present invention, two
A circumferential groove 51 having a V-shaped cross section with a gently sloped surface is provided in advance only in the shoulder portion, and a molding recess 62 for forming the rim or block R2°R6 of the shoulder portion in the mold 60 and the tread are formed. Since vulcanization hardening is performed after aligning the member 500 with the circumferential groove 51, the resulting pneumatic tire has ribs or blocks R2, R that form the circumferential groove 51 with a V-shaped cross section in the tread member 50 when the internal pressure is zero.
Belt member 73 and carcass ply 72 at the center of 6
becomes a convex portion 75 as shown in FIG.

Then, when the internal pressure is filled, the heald member 73 and the carcass ply 72 tend to become straight, so the surfaces of the ribs or blocks R2 and R6 form the recesses 75A as shown in FIG.
As a result, heat generation can be reduced, blowout can be suppressed, and high-speed durability can be improved.

(Example) Examples of the present invention will be described in detail below.

In the present invention, the extruded green tread member 5
04, a circumferential groove 51 having a V-shaped cross section with a gently sloped surface is provided in advance in a portion corresponding to the second shoulder portion, and until a green tire GT is formed using this tread member 50, as shown in FIG. 1) (2) It is the same as the conventional example explained with reference to (3), etc., and therefore, Fig. 4 0) (
2) In (3), the reference numerals of corresponding tire constituent members are also shown. Note that in the present invention, the belt member 7. A cap ply 74 is added to ,, β, and Ki.

In FIG. 3, the mold 60 has circumferential grooves G1 to G6 of the tire T.
It has protruding bones 61 for molding, and molding recesses 62 for molding blocks or ribs R1 to R7 between the protruding bones 61, where WT is the mold tread width and the evaluation is -T/ 2, and is symmetrical with respect to the tread center line 〇-〇.

Here, the bottom of the circumferential groove 51 is aligned to match the center of the blocks R2 and R6, that is, the center of the molded recess 62, and the circumferential groove 51 is arranged as follows in FIG.

-=0.65~0.85 (preferably 0.7~0.
8) a = 0-0.4 (preferably 0.1-0.2) b = 0.5-0.75 (preferably 0.55-0.7
) l4C −=0.65 to 0.8 However, Wc −Wb (preferably 0.7 to 0.75) ≧5.0 m That is, the present invention provides a pair of bead rings 70 and both bead rings 70. After the carcass ply 72 and side rubber 71 extending between the carcass ply 72 and the side rubber 71 are pasted together on the cylindrical former 1 and expanded into a toroidal shape, the heald member 73 and the tread member 50 are sequentially pasted onto the crown portion of the carcass ply 72, or In a separate process, a cylindrical body in which the belt member 73 and the tread member 50 are bonded together is set in the crown portion of the carcass ply 72 to form a green tire GT, and then the circumferential groove G1 of the tire T is formed.
~A molding recess 6 for molding ribs or blocks R1 to R7 between the protruding bone 61 for molding G6 and the circumferential grooves 61 to 66
In a method for manufacturing a pneumatic tire having circumferential grooves 61 to G6 in the circumferential direction of the tread, the green tire GT is vulcanized and hardened in a mold 60 having a tread member 2 between the protruding bones 61. A circumferential groove 51 having a V-shaped cross section with a gently sloped surface is provided in advance only at the second shoulder portion in the mold 60, and a molding recess 62 for forming the rim or blocks R2, R6 of the A shoulder portion in the mold 60. After aligning the circumferential groove 51 of the tread member 50, vulcanization hardening is performed.As a result, when the internal pressure is zero, as shown in FIG. Block R2, R6
The heald member 73, carcass ply 72, and cap ply 74 form a convex portion 75 continuous in the circumferential direction at the center of the tire T. When the tire T is filled with internal pressure as shown in FIG. Since the ply 72 and the cap ply 74 tend to be straight, the surfaces of the blocks R2 and R6 become recessed portions 75A.
The most heat is generated during high-speed driving, and blowouts and the like caused by this are suppressed.

Incidentally, in Figures 1 and 2, the heat generation in the high-speed drum test with 4° camber is R6>R5>R7>
R4<R1<R3<R2 f, K ri, '/, :>
The ribs or blocks R2 and R6 in the YoJL/Da portion generate the most heat.

Next, the tire with the so-called trapezoidal tread member shown in FIG.
The test results for the tire according to the present invention with C were as follows.

Test conditions Tire size: 205/55R1588V Rim: 5'/2JX15 Internal pressure: 3.05 kg/C1ft load
: 403kgf (ETRTO51dX0.7
4) Camber angle: 4+ Drum diameter: 1.7m Travel step: Speed 240km/h → 250km/h
- → time 60 minutes → 10 minutes - → → 10 km/h increase test result every 10 minutes thereafter (effect of the invention) The present invention is as described above, and the heat generation in the shoulder part where the heat generation amount is the largest during high speed driving It can reduce blowout and significantly improve high-speed durability.
Since the green tread member is easy to work with, manufacturing costs can also be reduced.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the tire obtained by the present invention when the internal pressure is zero, Fig. 2 is a sectional view when the internal pressure is filled, Fig. 3 is a sectional view showing the tire set in the mold, and Fig. 4. (1)(2
)(3) is a process diagram of the conventional example, FIG. 5 is an explanatory diagram of a tire obtained by the conventional example, FIG. 6 is a sectional view of the improved conventional example when the mold is set, and FIG. 7 is the same ( It is an explanatory view of a tire. 70- bead ring, 71- side rubber, 72-
carcass ply, 73-belt member, 50---) red member, 51--circumferential groove, 60--mold, 61-protruding bone, 62--molding recess.

Claims (1)

[Claims] (1) A pair of bead rings (70), a carcass ply (72) extending between both bead rings (70), and a side rubber (71) are pasted together on a cylindrical former (1) and then expanded into a toroidal shape. , belt member (73)
and the tread member (50) to the carcass ply (7).
2) by sequentially pasting it on the crown part of the carcass ply (72) or by setting a cylindrical body in which the belt member (73) and the tread member (50) are pasted together in a separate process on the crown part of the carcass ply (72). A green tire (GT) is molded, and then the circumferential grooves (G1) to (G6) of the tire (T) are formed.
) and the protruding bone (61) that molds the circumferential groove (G1) to (
G6) The green tire (GT) is vulcanized and hardened in a mold (60) having molding recesses (62) between the protruding bones (61) in which ribs or blocks (R1) to (R7) are molded. By this, a circumferential groove (G1) is formed in the circumferential direction of the tread.
~ (G6) In the method of manufacturing a pneumatic tire comprising (G6), a circumferential groove (51
) are provided in advance, and a molding recess (62) for forming the rim or block (R2) (R6) of the 1/4 shoulder portion in the mold (60) and the tread member (50).
A method for manufacturing a pneumatic tire, characterized in that vulcanization hardening is performed after aligning the circumferential groove (51) of the pneumatic tire.