JPS6185205A - Tire for heavy duty vehicle - Google Patents

Abstract

PURPOSE:To maintain accurately the thickness of a non-skid base of a repaired tire by embedding steel wires which are for detecting the amount of tread rubber cut at the stated location of both the center line and its both sides of the outermost ply. CONSTITUTION:Steel wires 8 which are for detecting the amount of tread rubber cut are embedded in parallel with a belt ply 5 along the circumference of a tire in such a manner that they are located at the center line and its both sides of the outermost belt ply 5 so as to be the depth of d (0.5-5.0mm) apart outward from steel cords 7 of the outermost belt ply 5. This configuration enables the tread rubber 3 to be shaved with rasps deeply to the outer surface of the steel wires 8 at the time of repair permitting the thickness of a non-skid base of a repaired tire to be accurately maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Field of Application The present invention is useful when the tread is worn out! - Concerning tires for heavy-duty vehicles that can be retreaded into high-quality retreaded tires by repainting red.

0) Prior Art Tires for large, heavy-duty vehicles are expensive, and when the tread becomes worn out, the tread is replaced and used again as a retreaded tire. To replace the tread of a worn tire, it is necessary to scrape away the tread rubber remaining on the old tire so that a certain thickness of rubber remains on the belt.

The lifespan of a retreaded tire depends on the accuracy of this cutting.

The operating limit conditions for tires used on heavy-duty vehicles are determined by the tire's heat generation temperature. Higher internal temperatures of the tire accelerate the aging and fatigue of the cord and rubber, causing tire components to separate and rapidly deteriorating the tire. The amount of heat generated by a tire changes depending on the tire's running speed and load.

When the running speed of a tire increases, heat generation due to hysteresis loss due to repeated deformation increases, and the internal temperature of the tire increases. Furthermore, when the load applied to the tire increases, the hysteresis loss also increases and heat generation increases. Therefore, the usage limit condition of a tire is related to the load applied to the tire and the running speed, so the usage limit condition is expressed as the product of the load (tons) applied to the tire and the running speed (kg/h),
This is usually called TKPH.

Since heat generation in a tire is mainly due to hysteresis loss in the tread rubber, the thickness of the tread rubber of a retreaded tire needs to be regenerated to the original design value. If the thickness from the belt to the bottom of the tread groove, the so-called non-skid base thickness, is 1 mm thicker than the design value, the internal temperature of the tire will be 2 to 5 degrees.
C increases, TKPH becomes 15 to 25% smaller than the design value, and each member of the tire tends to separate. Also, if the non-skid base is too thin, the bottom of the tread groove will crack during use, shortening the life of the tire.

Therefore, when retreading a tire, it is most important to precisely cut the tread rubber remaining on the old tire until it reaches a certain thickness17, and to ensure that the thickness of the non-skid base after re-lining the L/Red matches the designed value. It is.

Typical tire retreading is performed through the following steps.

That is, a rotary blade called a rasp, which is made up of a number of laminated steel disks with many notches on the entire circumference, is attached to the motor of a puffing machine, and the tread rubber of the used old tire is scraped off. As mentioned above, at this time, it is necessary to cut the rubber covering the belt so that only a precisely predetermined thickness remains. Since the thickness of the old rubber remaining on the belt cannot be directly measured, the outer diameter of the belt is estimated, and from this the outer diameter of the tire where the old rubber remains at a predetermined thickness is determined. A method is used in which the tread rubber is cut until the outer diameter reaches this value.

However, the tire expands irreversibly during use, and the belt diameter also increases. Moreover, the amount of inflation changes depending on the conditions of use of the tire, and the amount of expansion is small when used on a light-loaded bus or the like, and becomes large when used on an overloaded dump truck or the like. The amount of expansion of the belt diameter is usually 0 to 7 mm. Therefore, when the tread rubber of an old tire is cut until the outer diameter of the tire reaches a constant size, the thickness of the old rubber remaining on the belt varies in the range of 0 to 3.5H. This was a major cause of the decrease in TKPT of retreaded tires.

As a way to improve this, for example,
As described in Publication No. 1, there is a method in which a tire is manufactured in which a fiber rope is placed on the outside of the belt in advance, and when the tire is retreaded, the tread rubber is cut with a puff until the rope is exposed, or a method in which the belt is A method has been proposed in which tires are manufactured with colored rubber embedded to a certain depth along the outside, and then cut until it is exposed during retreading.

(C) Problems to be Solved by the Invention When the above-mentioned conventional tires embedded with ropes or colored rubber are cut using a puff machine equipped with a rasp, these ropes or colored rubber are removed during cutting in order to rotate the tire at high speed. Even if the rubber is exposed, it is difficult to detect, and if the rope or colored rubber is made large enough to be easily detected, it will cause separation, which has not been put to practical use.

Therefore, in order to increase the T' K P I-1 of a retreaded tire, it is necessary to accurately cut the tread rubber until a certain thickness of rubber remains on the belt of the old tire. There is no easy way to measure the thickness or detect that the tire has been cut to a certain thickness, and it has been difficult to maintain the TK P J-1 of a retreaded tire above a certain level.

The present invention is capable of easily detecting when the tread rubber has been cut to a predetermined position on the outside of the tire during retreading, and allows the non-skid base of the retreaded tire to be accurately made to the predetermined thickness under heavy load. The purpose is to provide tires for vehicles.

(d) Means for Solving the Problems The present invention provides a method for retreading old tires by applying a steel layer in advance along the outer position of a rubber layer of a predetermined thickness to be left on the outer side of the belt after cutting the tread rubber of the tire. It consists of a tire with a wire embedded in it. When retreading this tire, when the tread rubber is cut with a rasp, sparks are generated when the rasp or the above-mentioned steel wire is cut, so if you use this as a signal to stop cutting, the old rubber will remain at the correct thickness. be able to.

Next, the contents of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional view of the right half of the tire for heavy-duty vehicles of the present invention, and FIG. 2 is a sectional view of the same tire after retreading. In the drawing, (1) is a carcass in which cords are arranged in the radial direction, and is provided along the inner surface of the tire, and its both ends are folded back to wrap around a pair of bead wires (2) and fixed thereto. There is.

The outside of the carcass (1) is covered with a central tread rubber (3) and continuous sidewall rubber (4) on both sides. Three-layer belt ply with steel cords arranged at an angle of 15 to 45 degrees to the
).

A belt (6) made of (6) is provided. On the center line and at both ends of the outermost belt ply (5), from the steel cord (7) of the outermost belt ply (5) - Ube #t
The steel wires (8) are placed at distant positions parallel to the ply (5) along the circumferential direction of the tire.
It is buried in The distance between the steel cord F (7) of the outermost belt ply (5) and the steel wire (8) is from the outer surface of the steel cord (7) to the steel wire (8).
is arranged such that the distance d to the outer surface of is 0.5 to 5 NM. During tire retreading, the tread rubber (3) is scraped down to the outer surface of the steel wire (8) with the rasp, so if the above distance d is smaller than Q, 5 III, the rasp will be scraped onto the belt during the puffing process during tire retreading. When the remaining rubber is torn off, the belt cord (7) is exposed, making retreading difficult.If it is larger than 5H, the non-skid base of the retreaded tire becomes thicker and TKPJ-T becomes smaller.

The thickness t of the non-skid base between the bottom of the L-red groove (9) provided in the tread comb (3) and the steel cord (7) of the outermost belt ply (5) is preferably 3 to 7 mm, and 3 If it is less than 7wm, cracks will easily form at the bottom of the tread groove (9), and if it exceeds 7wm, it will generate a lot of heat while driving.
PH decreases.

The steel wire (8) is preferably a steel wire with a breaking elongation of 4% or more; for example, a brass-plated steel wire with a diameter of 0.22 MM is coated with rubber and made into a coil with an outer diameter of 1.2H and a pitch of 8 MN. Preferably used is a curled wire or a steel cord made of brass-plated steel wire with a wire diameter of 0.22 mm twisted in a 3×7 twist structure with the first twist and the second twist in the same direction.

During the tire manufacturing process, when the center of a cylindrical belt is expanded to form a drum shape, the circumference of the belt is extended at the center, so the steel wire must also be elongated. Wire required.

(e) Function: To retread a worn tread using the heavy-duty vehicle tire of the present invention, after washing the old tire with water, the tire is rotated at a speed of 10 to 100 rpm with a cylindrical blade. The rubber is pressed against the tread to remove excess rubber, and then the tread rubber is cut using a puff machine equipped with a rasp. The tread comb is cut along an arc of the same curvature as the tread or a predetermined curvature until the surfaces of the steel wires (8), (8) arranged on the belt centerline and at both ends are exposed. If the steel wire is exposed, it will come into contact with the rasp and produce a spark, which can be immediately detected. If the tread rubber is scraped off until the surface of the steel wire (8) is just exposed, the thickness of the old rubber left on the outside of the belt will be uniform and equal to the predetermined thickness d.

Next, after applying adhesive to the cut tire, a cushion of unvulcanized rubber is pasted, and a vulcanized tread rubber with tread grooves formed thereon is pasted.
Vulcanize in high-temperature pressurized air at °C to bond and integrate the base tire and tread rubber.

Instead of using the above-mentioned vulcanized tread rubber, unvulcanized tread rubber may be attached and integrated by vulcanization in a mold having a tread groove shape.

(Example 0) A tire of the present invention having a structure shown in FIG.
, 7 tttts was used, and in order to improve adhesion with the rubber, it was plated with brass and coated with a com composition containing an organic acid cobalt salt to a thickness of Q, 3 ays. Place one steel wire on the center line of the belt and two at each end of the belt so that the outer surface of the steel wire is at the same position.

A conventional tire having the same structure as the tire of the present invention was manufactured as a comparative tire except that the steel wire was not provided. A combination of the tire of the present invention and a comparative tire was mounted on a heavy-duty vehicle and run, and when the tread groove depth, which was initially 13 mm, reached 5 mm, running was stopped and the tire was retreaded.

Tires that had been used were washed with water, inspected for damage, and defective tires were removed. First, three tires of the present invention were retreaded by the following method, and the results of testing the retreaded tires are shown in Table 1 for Example 1.
Shown as ~3.

The tire is mounted on a rotating shaft, and while rotating at a rotation speed of 1 orpm, the tread rubber is scraped off with a cylindrical blade until the grooves on the tire disappear.Then, a puff machine equipped with a rasp is used to scrape off the tread rubber along an arc with a radius of curvature of 50 fl. Puff cutting was stopped at the point where the surface of the steel wire was exposed.

A rubber paste prepared by dissolving a natural rubber composition in gasoline was applied to the puffed surface, and an unvulcanized rubber composition consisting of 100 parts by weight of natural comb, 2 parts by weight of cobalt stearate, and ordinary compounding agents was prepared with a thickness of 8 mW. A green tire was formed by pasting a sheet of and then pasting vulcanized red rubber on top of it. A green tire is attached to the rim, a tube is placed in the inner cavity, the outer surface is covered with a rubber bag, the can is placed in a vulcanizing can, and the can is vulcanized for 4 hours at an air pressure of eicqica and an air temperature of 120°C.

Three comparative tires that were the same as the conventional tires were retreaded in the same way, and the results are shown in Table 1 for Comparative Examples 1 to 3.
It was shown as At this time, since there is no steel wire at the end point of cutting the tread rubber with the puff, the tire outer diameter is 101 mm.
The point where the value was 8111 was taken as the point.

The thus retreaded tires of the present invention and comparative tires were subjected to a drum test in accordance with the durability test method of the US Motor Vehicle Safety Standard 1i'MVSS119.

FMVSS] After completing the conditions set by 19, an additional 12
The speed was increased by 8 b/h every hour, and the vehicle continued to run until a tire failure occurred. The results are shown in Table 1 as an index, with the conventional tire Comparative Example 3 set as 100. After completing the drum test, we dismantled the tire and measured the belt outer diameter and non-skid base thickness.
Shown in the table.

The exothermic temperature was measured during the second step of the drum test (load 2.3 tons, speed 56 b/h) by drilling a hole that reached the end of the belt and inserting a thermistor thermometer.

The inflation of the tire varies depending on the usage conditions of the tire, and in Example 3 and Comparative Example 3, the inflation was small and the belt outer diameter was small. In Comparative Example 3, where a tire with low inflation was retreaded by the conventional method, the thickness of the remaining old rubber was large, so the non-skid base of the retreaded tire was thick, the heat generation was low, and the drum test results were inferior.

03 Re-QO Xun Comparative Example 1 had a large expansion, the belt diameter was large, and the puff cutting was performed to have a constant outer diameter, so the thickness tl of the remaining old comb was too thin, and some of the rubber was removed from the heald. There is a risk of tearing, and the drum test results are poor despite the low heat generation temperature.

On the other hand, in the tires of the present invention, even if the belt diameter changes, the thickness of the retreaded tire's non-skid base is thin and can always be kept constant, so the drum test results are superior to those of conventional retreaded tires. .

(g) Effects of the Invention According to the tire for heavy-duty vehicles of the present invention, when retreading the tire, if the tread rubber is scraped until the steel wire is exposed and sparks are emitted, the belt can be removed regardless of the degree of expansion of the tire. Since the thickness of the old rubber left on the outside can always be kept exactly constant, the thickness of the non-skid base of the retreaded tire can be set to the optimal design value, resulting in a large 'I'KPH and improved durability. Excellent retreaded tires can be easily obtained. The spark generated from the steel wire is sufficient to be easily detected, and there is no risk that the steel wire will become a foreign object and cause separation.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the tire for heavy-duty vehicles of the present invention, and FIG. 2 is a cross-sectional view of the same tire after retreading. Explanation of symbols (1)...Carcass, (2)...Bead wire, (
3)...Tread rubber, (4)...Side wall rubber, (5), (g), (g)...Belt ply, (6
)...Belt, (7)...Steel cord, (8)
・・・Steel wire, (9)...L・Red groove.

Claims (2)

[Claims] (1) A carcass in which cords are arranged substantially in the radial direction, tread rubber covering the center of the outside of the carcass, sidewall rubber covering the outside of the carcass continuously on both sides of the tread rubber, and both ends of the carcass. A belt made by superimposing at least three belt plies, each consisting of a bead wire fixed to the tire and a belt ply arranged between the carcass and the tread rubber at an angle of 15 to 45 degrees with respect to the inner circumferential direction of the tire. In a radial tire, the tire is attached along the circumferential direction of the tire so that the outer surface is located at a distance of 0.5 to 5 mm from the steel cord surface on the center line and at both ends of the outermost ply of the belt. A radial tire for heavy-duty vehicles featuring a steel wire for detecting the amount of tread rubber cut during retreading. (2) The radial tire for a heavy-duty vehicle according to claim 1, wherein the steel wire is a steel wire having an elongation at break of 4% or more.