JP2000094904A - Bias tire for heavy load and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent separation between carcass plies in accompany with the flow of a rubber layer. SOLUTION: Since a rubber layer 25 increasing hardness by applying a preliminary bridging by irradiation of an electron beam is arranged between carcass plies 12, the flow of the rubber layer 25 in the periphery of almost prevented in the case of vulcanization in the rubber layer 25 even by applying a high temperature and high pressure, as a result, a gage between the carcass plies 12 is maintained in a proper value, and generation of separation between these carcass plies is effectively prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty bias tire having a rubber layer disposed between carcass plies and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional heavy load bias tire is, for example, formed by laminating a plurality of carcass plies each having an organic fiber cord covered with coating rubber, and a carcass layer extending in a substantially toroidal shape, and a radius of the carcass layer. Treads located at least two
There is a known carcass ply provided with a rubber layer disposed between two carcass plies so as to secure a gauge between the carcass plies and extending over a point corresponding to a tread end.

[0003]

However, in such a conventional heavy duty bias tire, the rubber layer is composed of only rubber, whereas the carcass ply sandwiching the rubber layer from both sides is not provided. Because it is configured by coating the organic fiber cord with the coating rubber, the rubber layer becomes softer than the coating rubber of the carcass ply when unvulcanized, and as a result, high temperature and high pressure are applied to the unvulcanized tire. When vulcanization is performed, the rubber layer flows around during vulcanization and becomes thinner as a whole, thereby causing a problem that the gauge between carcass plies is insufficient and separation between plies may occur. .

[0004] It is an object of the present invention to provide a heavy duty bias tire capable of effectively preventing separation between plies due to the flow of a rubber layer, and a method of manufacturing the same.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to form a carcass ply having a plurality of carcass plies each having an organic fiber cord covered with a coating rubber, and to extend the carcass layer in a substantially toroidal shape. A heavy-duty bias tire comprising a tread disposed on the outer side in the direction and a rubber layer disposed between at least two carcass plies and extending across a point T1 corresponding to the tread end T, wherein the carcass ply is This can be achieved by performing pre-crosslinking by electron beam irradiation before disposing and assembling between them. And such a heavy load bias tire can be manufactured by the manufacturing method as described in claim 6.

The above-mentioned rubber layer is preliminarily cross-linked by irradiation with an electron beam during unvulcanization to increase the hardness, and is then arranged between the carcass plies to be assembled and molded. That is, the rubber layer is arranged between the carcass plies. Since the pre-crosslinking was previously performed by electron beam irradiation, even if vulcanization was performed by applying high temperature and high pressure, the rubber layer hardly flowed to the surroundings. The gauge is maintained at an appropriate value to effectively prevent ply separation.

[0007] Further, according to the second aspect of the present invention, it is possible to reliably suppress the flow of a portion that receives a large compressive force during vulcanization. Further, according to the structure of the third aspect, the thickness of the rubber layer can be maintained at an appropriate value while co-vulcanizing the interface between the carcass ply and the coating rubber. Further, according to the structure described in claim 4, the gauge between plies can be set to an appropriate value while preventing cracks at the rubber layer end. Furthermore, according to the structure described in claim 5, the rigidity step at both ends of the rubber layer can be reduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1 and 2, reference numeral 11 denotes a heavy load bias tire to be mounted on a large construction vehicle or the like.
The tire 11 has a plurality of carcass plies, here 12 carcass plies.
It has a carcass layer 13 extending in a substantially toroidal shape formed by superimposing 12 carcass plies, and these carcass plies 12 are bundled into plural pieces (here, six, four, two pieces) to form a plurality (three pieces). Ply bundle 14 of the innermost, middle,
The outermost ply bundles 14a, 14b, 14c are formed. Each carcass ply 12 is formed by coating a large number of organic fiber cords 15 made of nylon or the like inclined with respect to the tire equatorial plane S with a coating rubber 16. Since the inclination direction with respect to S is opposite in the adjacent carcass ply 12, the organic fiber cords in these carcass plies 12
15 cross each other in each ply. Reference numeral 19 denotes a plurality of pairs, here two pairs of bead cores, and these bead cores 19a,
b, both ends in the width direction of the innermost ply bundle 14a and the middle ply bundle 14b of the ply bundle 14 are folded back from the axially inner side to the axially outer side, and are moored. Both ends in the width direction of the outer ply bundle 14c extend along the axially outer surface of the folded portion of the intermediate ply bundle 14b, and are then bent substantially perpendicularly inward in the axial direction. Further, a breaker layer 21 and a tread 22 are sequentially arranged radially outside the carcass layer 13, and sides 23 are arranged on both axial sides of the carcass layer 13, respectively.

[0009] Of the carcass plies 12, at least between two carcass plies, in this case, between the ninth carcass ply 12i and the tenth carcass ply 12j from the innermost, and the tenth carcass ply 12j ( Intermediate ply bundle 14b
Between the 11th carcass ply 12k (the innermost carcass ply of the outermost ply bundle 14c) and the 11th carcass ply 12k and the 12th (the In order to secure the gauge between the carcass plies 12 between the outer) carcass plies 12m,
Rubber layers 25a, b, and c made of only rubber are arranged, and each of these rubber layers 25a, b, and c extends in the meridian direction across a point T1 corresponding to the tread end T. Here, the point T1 corresponding to the tread end T is the tread end T
When the perpendicular is drawn down to the outermost carcass ply 12m, the point of intersection between the perpendicular and the outermost carcass ply 12m. Also, certain points on the tire outer surface described later, that is, the first and second outer points U and V, the first inner point N, and points U1, V1, N1, and B1 corresponding to the tire maximum width position B, When perpendiculars are dropped from the points (positions) U, V, N, and B to the outermost carcass ply 12m, the intersection points between these perpendiculars and the outermost carcass ply 12m. Here, the rubber layer 25
The outer end 26 of the tire has a point U1 corresponding to a first outer point U on the tire outer surface separated from the tread end T by 1/8 of the tread width W on the tire equatorial plane S side (inward in the axial direction), and the tread width. W's
It is located between the point V1 corresponding to the second outer point V on the tire outer surface separated by 1/4 on the tire equatorial plane S side (axially inward), and the inner end thereof is away from the tread end T. A point N1 corresponding to the first inner point N on the tire outer surface separated from the bead core 19 side (radially inward) by 1/4 of the tire height H, and a tire maximum width position B on the tire outer surface. Point B1
Is preferably located between The reason is that if the outer end 26 of the rubber layer 25 is located closer to the tread end T (axially outer side) than the point U1 corresponding to the first outer point U, a gap between the carcass plies 12 may be insufficient. On the other hand, if it is located on the tire equatorial plane S side (inside in the axial direction) from the point V1 corresponding to the second outside point V, the rubber layer is located at a place where the gauge between the carcass plies 12 does not become thin. This is because 25 is arranged, which causes an increase in tire weight. The inner end 27 of the rubber layer 25 is located at the first inner point N.
If it is located on the tread end T side (radially outward) from the point N1 corresponding to the above, there may be a place where the gauge between the carcass plies 12 is insufficient, and on the other hand, it corresponds to the tire tire maximum width position B If it is located on the bead core 19 side (inward in the radial direction) from the point B1, the crack may occur around the inner end 27.

[0010] Here, the rubber layer 25 disposed at such a position is softer than the coating rubber 16 of the carcass ply 12 when not vulcanized, and therefore flows around when subjected to high temperature and high pressure due to vulcanization. It becomes thin. For this reason, in this embodiment, at least the rubber layer 25 at the most easily flowable portion, specifically, the rubber layer 25b arranged between the carcass plies 12 constituting the middle and outermost ply bundles 14b and 14c, Before the entire rubber layer 25 including the rubber layer 25b is disposed between the above-mentioned carcass plies 12 (when the rubber layer 25b is an unvulcanized rubber), it is subjected to pre-crosslinking by irradiation with an electron beam. An effective cross-linking reaction of carbon between the rubber molecules is caused in the rubber layer 25 to increase the hardness of at least the surface portion. As a result, even if high temperature and high pressure of vulcanization act on the rubber layer 25, the rubber layer 25 hardly flows around, and as a result, the gauge between the carcass plies 12 is maintained at an appropriate value. As a result, the occurrence of separation between plies is effectively prevented. Here, it is preferable that the rubber layer 25 subjected to preliminary crosslinking by electron beam irradiation as described above has a Mooney value in the range of 60 to 90 measured at 130 ° C. using a Mooney viscometer.
The reason is that the Mooney value is 60 even after the preliminary crosslinking is performed.
If it is less than 1, the resistance to flow is too small, and the rubber layer 25 flows during molding vulcanization, and it becomes difficult to maintain the thickness at an appropriate value.On the other hand, by performing preliminary crosslinking, If the Mooney value exceeds 90, co-vulcanization at the interface between the rubber layer 25 and the coating rubber 16 of the carcass ply 12 may be hindered.

The thickness of the pre-crosslinked rubber layer 25 is preferably in the range of 0.3 mm to 1.2 mm. The reason is that if the thickness of the rubber layer 25 is less than 0.3 mm, it is difficult to secure a proper gauge between the plies, while if it exceeds 1.2 mm, the end of the rubber layer 25 This is because cracks may occur. When the thickness of the rubber layer 25 is within the above range, the acceleration voltage of the electron beam irradiation is set in the range of 300 to 700 kV, and the radiation dose to the rubber layer 25 is set in the range of 3 to 7 MRAD. Pre-crosslinking can be properly performed.

Next, when manufacturing such a tire 11, first, a plurality of carcass plies 12 are supplied to a cylindrical tire forming drum 31 as shown in FIG. After the application, the bead core 19 is set around the carcass ply 12 and the carcass ply 12 axially outside the bead core 19 is folded inward in the axial direction to form the innermost ply bundle 14a. Thereafter, an intermediate ply bundle 14b is formed around the innermost ply bundle 14a in the same manner as described above. At this time, a rubber layer 25 is arranged between predetermined carcass plies 12. Thereafter, the rubber layer 25 and the carcass ply 12 are alternately supplied to the forming drum 31 and are successively attached around the intermediate ply bundle 14b, so that the rubber layer 25 is disposed between the carcass plies 12. The outer ply bundle 14c is formed. At this time, the above-mentioned rubber layer 25 is disposed at a position straddling a position T1 corresponding to the tread end T when the tire becomes a product tire. The carcass layer 13 is formed by stacking a plurality of carcass plies 12 in this manner,
The rubber layer 25 disposed between the carcass plies 12 of the carcass layer 13 has been subjected to preliminary crosslinking by electron beam irradiation before being disposed between the carcass plies 12. Next, after arranging the breaker layer 21 and the side 23 outside the carcass layer 13,
While bringing the bead cores 19 closer to each other, the carcass layer 13
Air is supplied into the inside to deform the carcass layer 13 substantially toroidally. Thereafter, a thin rubber sheet is spirally wound around the breaker layer 21 many times, and the tread 22 is arranged radially outside the breaker layer 21 to obtain an unvulcanized tire.
Next, after carrying the unvulcanized tire into a vulcanizing device, the high temperature,
This vulcanization is performed under high pressure to produce a product tire. At this time,
Since the rubber layer 25 is preliminarily cross-linked by electron beam irradiation, even if vulcanization is performed as described above, the rubber layer 25 hardly flows to the surroundings. The gauge is maintained at an appropriate value to effectively prevent inter-ply separation. When the precured rubber layer 25 is subjected to the main vulcanization, the modulus increases due to the vulcanization reaction. The 300% modulus of the rubber layer 25 after the main vulcanization is the same as that of the rubber layer 25. After the main vulcanization of the coating rubber 16 constituting the carcass ply 12 for the reason of reducing the rigidity step at both ends
It is preferable to be within the range of 0.7 to 1.3 times the 300% modulus.

[0013]

Next, test examples will be described. In this test, the ninth, tenth, tenth and eleventh from the innermost side of the carcass layer composed of 12 carcass plies overlapped
Conventional tires and test tires each having a rubber layer disposed between the first, eleventh, and twelfth carcass plies were prepared. Here, the rubber layer of the conventional tire remains unvulcanized rubber that has not been subjected to electron beam irradiation, extends from one tire maximum width position to the other tire maximum width position, and has a thickness before placement. 1.0 mm, 1.0 mm and 0.5 mm. On the other hand, the rubber layer of the test tire had been subjected to preliminary crosslinking by electron beam irradiation before being arranged, and the outer end was up to the point V1 corresponding to the second outer point V, and the inner end was the tire maximum width position B.
The thickness before each placement is 0.8 mm, the Mooney value measured at 130 ° C is 62, and the 300% modulus value after this vulcanization is the carcass ply coating. It was identical to that of rubber. In addition, the size of these tires is ORS 16.00-2
It was 5 24PR. Next, the vulcanized tires were dissected, and the thickness of the rubber layer disposed between the tenth and eleventh carcass plies from the innermost side was measured. The result was that the thickness of the conventional tire was reduced to 0.1 mm, but that of the test tire was 0.7 mm.
There was almost no change in wall thickness to mm. Next, after filling each of these tires with an internal pressure of 675 kPa, the tires were run on a test drum at a speed of 10 km / h until a failure occurred while applying a load of 14500 kg, and the failure occurrence distance of the conventional tire was set to an index of 100. . As a result, no failure occurred in the test tires up to index 180. Here, the failure of the conventional tire is
The separation occurred between the 10th and 11th carcass plies from the innermost side, and the failure of the test tire was the occurrence of a broken cord in the bead portion.

In the above-described embodiment, the breaker layer 21 is disposed between the carcass layer 13 and the tread 22. However, in the present invention, the breaker layer may be omitted, or the breaker layer may be used instead of the breaker layer. You may make it arrange | position a belt layer.

[0015]

As described above, according to the present invention, separation between plies due to the flow of the rubber layer can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a meridian sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II of FIG.

FIG. 3 is a partially cutaway front view illustrating a manufacturing process.

[Explanation of symbols]

 11 ... heavy load bias tire 12 ... carcass ply 13 ... carcass layer 15 ... organic fiber cord 16 ... coating rubber 22 ... tread 25 ... rubber layer 26 ... outer end 27 ... inner end T ... tread end W ... tread width H ... tire height B: Tire maximum width position

Claims (6)

[Claims] 1. A carcass ply comprising a plurality of carcass plies each having an organic fiber cord covered with a coating rubber, and each of the carcass layers extending in a substantially toroidal shape, and a tread disposed radially outside the carcass layer. In a heavy duty bias tire having a rubber layer disposed between two carcass plies and extending across a point T1 corresponding to a tread end T, the rubber layer is disposed between the carcass plies and an electron beam is formed before assembly and molding. A bias tire for heavy load, which has been subjected to preliminary crosslinking by irradiation. 2. An outer end of the rubber layer is the tread end T.
Is located between a point U1 corresponding to a first outer point U separated by 1/8 of the tread width W and a point V1 corresponding to a second outer point V separated by 1/4 of the tread width W, The inner end is located between a point N1 corresponding to a first inner point N separated from the tread end T by 1/4 of the tire height H and a point B1 corresponding to a tire maximum width position B. 2. The bias tire for heavy loads according to 1. 3. The heavy load bias tire according to claim 1, wherein the rubber layer preliminarily crosslinked by the electron beam irradiation has a Mooney value measured at 130 ° C. within a range of 60 to 90. 4. The rubber layer preliminarily crosslinked by electron beam irradiation has a thickness in the range of 0.3 mm to 1.2 mm.
The bias tire for heavy load as described. 5. The ratio of the 300% modulus of the rubber layer preliminarily crosslinked by electron beam irradiation after vulcanization with the coating rubber of the carcass ply is in the range of 0.7 to 1.3 times. Heavy load bias tire. 6. A method in which a rubber layer preliminarily cross-linked by electron beam irradiation is disposed between at least two carcass plies so as to straddle a point T1 corresponding to a tread end T when a product tire is formed. Superposing the carcass plies to form a carcass layer, arranging a tread radially outside the carcass layer, and deforming the carcass layer into a substantially toroidal shape, vulcanizing these carcass layers and the tread Manufacturing a heavy duty bias tire.