JPH0257406A - Pneumatic bias tire - Google Patents

Abstract

PURPOSE:To improve rigidity and the like of a carcass ply cord by forming the carcass ply code out of a twisted cord consisted of a monofilament cord and a multifilament cord having specific air permeability. CONSTITUTION:The tire has a pair of bead parts, right and left, and a carcass ply in bias cord arrangement from one side of the bead part to the other side of the bead part through a crown part. Besides, it has a tread layer covering the outside of the carcass ply, and a breaker positioned in the crown part inside the tread and outside the carcass ply. In the above-stated constitution, the carcass ply cord has respectively monofilament cord over 2/3 portion and multifilament cord remaining under 1/3 portion, and is formed as a twisted cord. And air permeability of the multifilament cord is instituted over 4kgcm<2>/hr.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to preventing air from entering a pneumatic bias tire.

(Prior art) Conventionally, carcass ply cords for pneumatic bias tires are made by plying several hundred fine denier filaments of about 2 to 10 denier/filament, first twisting them, and then heating them.
Additionally, ply-twisted and heated tire cord is used. Such a so-called twisted yarn cord requires a large amount of energy, human labor, and equipment in the heating process. From this point of view, countermeasures such as reducing the number of twists have been considered, but reducing the number of twists has disadvantages such as a decrease in fatigue resistance and a decrease in adhesive strength. Reducing the number was difficult.

On the other hand, US Patent No. 39
No. 63678, No. 3984600, No. 46346
No. 25° and other publications disclose cords with monofilament or elliptical cross sections, but they have problems with fatigue resistance, adhesion, cost, etc., and have been judged to be unsuitable for practical use as tire cords. Ta.

However, since monofilament cords do not require a twisting process as described above, the inventors of the present invention have conducted intensive studies on the applicability of monofilament cords to tires and have found the following problems.

(Problems to be Solved by the Invention) The inventors of the present invention have made various types of tires using monofilament cords, but have found that monofilament cords have serious drawbacks. This drawback is that there are many places where air can enter the bias tire. Generally, with bias tires, multiple carcass plies of rubberized fabric are pasted together on a tire molding machine, so air tends to get in during the pasting process, and even more so since bias tires have to be pasted together at an angle. There is a problem in that air can easily enter. In this way, since bias tires are inherently prone to air infiltration, the following two measures are usually taken.

(1) After tire molding and before vulcanization, perform drilling around the entire tire circumference5 to allow air to escape during vulcanization.(2) Improve the air permeability of the ply cord itself to prevent the cord from vulcanizing during vulcanization. Normally, there are no tires that contain air due to the above two methods, but when using a monofilament coat for the carcass, drilling will damage the monofilament cord, and the cord itself will not allow air to pass through at all. Due to these problems, normal measures against air intrusion cannot be applied to monofilament cords at all.

For reference, Table 1 below shows the air-filled defect rate when monofilament cord is applied to the carcass ply of a bias tire.

Table 1 From Table 1, it can be seen that the higher the number of plies, the higher the defective rate due to air inclusion. Generally, when carcass ply is pasted on a drum molding machine, a sufficient amount of stitching is applied to allow air to escape, and most of the time there is no air in it.
Since the tire is exposed to high temperatures of 150° C. or higher during vulcanization, even air as small as bubbles left inside the tire will create large cavities within the tire after vulcanization, particularly in the shoulder and bead portions.

(Means for Solving the Problems) In response to the above problems, the inventors of the present invention made extensive studies and found that a pair of left and right bead portions and one bead portion cross the crown portion to reach the other bead portion. A carcass ply consisting of a bias cord array that intersects at an angle of 30 to 45 degrees with respect to the tire circumferential direction fixed to a bead part, a tread layer covering the outside of this carcass ply, and a crown part inside the tread outside of the carcass ply. In a bias tire equipped with a breaker made of organic fiber or steel cord, two of the carcass ply cords are
They discovered that air inflow could be significantly improved in a bias tire characterized by having monofilament cords of 73 or more, leading to the completion of the present invention.

However, the air permeability of the remaining multifilament twisted cord carcass ply cord is 4kg-cnf/
This is the minimum necessary condition to prevent air from permeating through the twisted cord made of multifilaments, and if the air permeability of the twisted cord made of multifilaments is 4 kg-cnf/hour or less, It becomes impossible to prevent air from entering.

The air permeability is preferably 8 kg-CI (per hour) as it allows air to pass through more easily. Also, it is preferable that 2/3 or more of the carcass ply cords are monofilament cords, and the monofilament cords are the entire carcass ply cords. If it is less than 273, the effect of improving tire rigidity and plunger energy, which are characteristics of monofilament cord, will be reduced, which is not preferable.

In addition, bias tires in which all carcass plies are made of monofilament cords are prone to air intrusion, but most of the air intrusion occurs in the outermost layer of the carcass ply, so air permeability is 4 kg/ct/hour or more. Preferably, some multifilament twisted cord is applied to the outermost ply. Furthermore, by applying a twisted cord consisting of a multifilament cord with good air permeability to the outermost layer, it becomes possible to perform drilling before vulcanization, which was impossible with a monofilament cord. In the case of a twisted multifilament cord, this type of spigot will not seriously damage the multifilament cord even if the tip of the spigot touches the cord, but with monofilament cords, the tip of the spigot will also damage the cord, causing damage to the cord. is 70 strong
% or less, and the fatigue resistance is also significantly inferior. Therefore, it is absolutely necessary to avoid damaging the monofilament cord by drilling. Therefore, a twisted multifilament cord is used for the outermost layer of the carcass ply,
By drilling an air release hole in the tire before vulcanization until the tip of the drill bit reaches the outermost carcass ply, the air release effect can be dramatically improved. .

Further, in the present invention, only the outermost layer of the plurality of carcass ply layers of the bias tire is a twisted cord made of multifilament, and the air permeability of the multifilament cord is 4 kg-c/hour or more, It is expressed by the following formula, N ar N The twist coefficient NT of the cord is 0.37.
≦N7≦0.57, and it is preferable that the carcass ply cords other than the outermost layer of the carcass are composed of monofilament cords.

Generally, tire cords are required to have fatigue resistance, so the twist coefficient must be 0.37 or more and 0.57 or less. If the twist coefficient is greater than 0.57, the strength and fatigue resistance will decrease. Therefore, the twist ratio N7 is preferably within the range of 0.43≦NT≦0.53.

Such monofilament cords are preferably polyamide fibers from the viewpoint of fatigue resistance, but monofilament cords of polyester, polyvinyl alcohol, etc. may also be used for bias tires where a particularly high tire spring constant is required.

However, even though the monofilament cord is referred to as a monofilament cord, it is preferable that the cross-sectional shape of the monofilament is an ellipse. This is because if the cross-sectional shape of the monofila is a perfect circle, the compressive strain and tensile strain within one filament will be large, and the fatigue resistance will be significantly reduced. Therefore, it is preferable that the cross-sectional shape is an ellipse, and the ratio b of the major axis to the minor axis of the filament cross section is
/ c is 15<b/c<5 (where b is the major axis of the cross section, C
is the minor axis of the cross section). In addition, b/c is 1.
If it is less than 5, the fatigue resistance will be poor, and if b/c≧5, the cord will be too flat and the total strength defined by the so-called cord strength x number of strokes will not be achieved, which is not preferable.

The minor axis of the monofilament cord having such an elliptical cross section is preferably 0.15n++n or more, and in terms of denier, it is preferably 1000 deniers or more. There is no particular problem if the denier of this monofilament cord is less than 1000 denier, but if the denier is too small, the number of carcass plies must be increased to obtain the total tire carcass ply strength defined by the strength x number of strokes. This resulted in an increase in tire weight and a reduction in the molding process.
Undesirable.

For this reason, it is preferably at least 1000 denier or more, more preferably about 2000 d to 5000 d.

(Function) As described above, in a bias tire formed by a composite cord of a monofilament cord according to the present invention and a carcass ply cord made of multifilament yarns spliced and twisted, air intrusion is not only significantly reduced, but also Tire performance will also be significantly improved. That is, by improving the rigidity of the carcass ply cord, rolling resistance, handling stability, drum life, etc. can be dramatically improved.

(Examples) Next, the present invention will be specifically explained using Examples and Comparative Examples.

Tires are LT37.00-158 PR, 6°6-nylon, twisted structure 1260d/ as control.
2. We prototyped a normal multifilament yarn twisted cord consisting of filaments (6 denier) with a twist count of 39 x 39T/10cm, and made 30 tires each by changing the material of the ply cord or processing conditions, etc. Inflated tires and tested tire performance. Note that pre-vulcanization drilling was performed on the bead and part of the shoulder of all tires, but the penetration depth of the drilling was shallower than usual to avoid damaging the carcass plies. Further, in Comparative Examples 1 and 2, normal nylon or polyester twisted cords were used, and the number of cords inserted in a part of the crown center was 21.2 cords/inch. Comparative Examples 3 to 6, Examples 1 to 3 are 1
A monofilament cord was used for the first to third plies, and a multifilament twisted cord whose air permeability was changed by changing various treatment conditions was used for the fourth ply.

In Example 4 and Comparative Examples 7 and 8, a carcass ply cord in which a monofilament and a multifilament twisted cord were mixed was used as the carcass ply cord. In addition, in Comparative Examples 1 to 6 and Examples 1 to 3, a rubberized cloth was used as a carcass ply by applying a dip liquid to a normal sudare weave, subjecting it to tension heat treatment, and then covering it with a rubber sheet. In Example 4 and Comparative Examples 7 and 8, single cord wires were coated with a dip liquid and twisted and heat-treated multifilament twisted cords and monofilament cords were wound one by one on a drum, and then wrapped with rubberized cloth. A carcass ply layer was used.

The air permeability of a multifilament twisted cord is determined by the heat treatment conditions (usually referred to as 3T conditions) during the heat treatment process (dry zone, heat set zone, normalize zone) of the cord (usually referred to as 3T conditions, and is determined by a combination of degree, time, and tension). )
This could be determined by selecting various values. Table 2 below shows the processing conditions for the multifilament twisted cords used in the comparative examples and examples.

Table 2 Prior to such treatment conditions, a dip liquid having the liquid composition shown in Table 3 below was applied.

Table 3 Table 4 Also, the processing conditions for monofilament cord are dry zone 130°C x 120 seconds XI, 3 kg/piece, hot zone 215°C x 36 seconds x 1.3 kg/piece, norm zone 210°C x 36 seconds The weight was 1.3 kg/piece, and the dip liquid had the same composition as the multifilament twisted cord. The monofilament cords used in the present invention are all 4,000 denier nylon 6.6 monofilament cords with an elliptical cross section, and the major axis is 1. Im
m, and the short axis is 0.4 mm.

For reference, the physical properties of such cords are shown in Table 4 below.

The following tests were conducted on the above prototype tire.

(1) Occurrence of air intrusion After vulcanization, the entire circumference of the tire is inspected by porography to determine whether or not there is air inside the tire. The tires were identified as air-filled tires, and the number of air-filled tires among the 30 tires was investigated under each condition. Note that tires containing no air at all were subjected to drum tests or performance tests.

(2) A coated fabric (approximately 1 inch thick) coated with multifilament twisted cord air-permeable rubber is prepared as shown in Fig. 1, then set in the apparatus shown in Fig. 2, and the initial pressure is 5. The pressure drop rate (kg/cm2/hr) was read from 4 kg/cm2. The pressure was measured every 5 minutes, or every 2 minutes for samples with a large pressure drop, for 10 to 30 minutes.

The measurements were performed at room temperature of 25±2° C., and the measured values were averaged and calculated as the amount of pressure decrease per hour, which was referred to as air permeability.

Sample vulcanization conditions: 153°C x 20 minutes, vulcanization pressure 20k
A sample was prepared at g/cm2, the number of cords implanted in the sample was 50 (15c+n), and the fabricator layer was one layer.

(3) Low fuel consumption performance measurement test The test tire was placed on a drum with an outer diameter of 1708 mm.
7.0O-158PR tire with 1180kg load, 5.
Installed under various conditions of 75kg/cm2 internal pressure, 80k
After preliminary running at a speed of 30 minutes per hour, the internal pressure was readjusted with no load, the above load was applied again, the drum rotation speed was increased to a speed of 150km/hour, and the drum was coasted to a speed of 150km/hour. The rolling resistance of the tire was calculated from the moment of inertia from 20 k[Il/hour to 20 k[Il/hour] according to the following formula.

Resistance formula for a single drum Medium ID: Moment of inertia of the drum ■t: Moment of inertia of the tire RD: Drum radius Rt: Tire radius Using the rolling resistance value of 50 kg/hour obtained from the above formula as a representative value, the fuel efficiency performance index is calculated. was calculated according to the following formula.

Fuel efficiency performance index = 100+lOOx Note that the larger the fuel economy performance index is, the smaller and better the rolling resistance value becomes.

(4) Driving stability and vibration ride comfort Each prototype tire was installed on a light truck, and a professional driver conducted a feeling test for handling stability and vibration ride comfort. The evaluation was based on a relative evaluation using a 10-point scale, with the control tire set as 5, compared to the control, and was divided into 0: No change, 2; Slightly good (bad), 4: Good (bad). Note that the tire numbered 10 indicates that the steering stability is better than that of the control tire.

(5) Drum life A (high speed performance) outer diameter 1708
The test tire LTS7.00-1 was placed on a drum of mm.
58PR tires 1040kg, internal pressure 5.75kg/
cm2 under various conditions, and the speed was gradually increased in stages under the conditions shown in Table 5 below. However, the test tires were left indoors at 38±3° C. for more than 24 hours, and the air pressure was readjusted again just before the drum device.

Table 5 (6) Drum life B (load-bearing performance) The same drum as drum A has an internal pressure of 4.2 kg/Crl and a speed of 81 km/hour, and the load is gradually increased at regular intervals as shown in Table 6. and measured the steps leading up to tire failure.

Table 6 (7) Plunger energy measurement plunger test method Tire rim size 5.5J-15, air pressure 5.75K
Assemble the rim at gf/cm2, fix it on the test machine under no load, and push a plunger pin with a hemispherical tip (φ19++ on) vertically into the tire crown center position at 50±2.5n+m/min. , the amount of plunger movement Y from the time the plunger touches the tire until it breaks (
cm) and the plunger pushing force F at the time of tire destruction
Plunger energy (PE) was calculated from (kg) according to the following formula; % formula %) and indexed with the control tire as 100.

The test results are shown in Table 6 below.

Comparative example 1 Tires on the general market were used as controls.

The 1st to 3rd plies were made of rubberized fabric with a stitch count of 56.6 lines/5 am, and the 4th ply was made of a rubberized fabric with a stitch rate of 51 lines/5 cm as the carcass ply.

None of the 30 tires were filled with air, and various tire performance drum tests were conducted.

Comparative Example 2 A rubberized cloth made of monofilament cords was used as a carcass ply, with the number of threads being 27 threads/5 cm for the first to third plies and 24.4 threads/5 cm for the fourth ply. The actual strength was reduced to about 80% compared to the control tire, but the plunger energy was maintained at the same level as the control tire. However, because it was a monofilament cord, air permeability was poor, and air was trapped in 19 out of 30 cords. In addition, handling stability, rolling resistance, drum life, etc. have been significantly improved compared to the control.

Example 1 A monofilament cord was used for the first to third plies, and a multifilament twisted cord of 1260d/2.39X39T/10cm was used for the fourth ply. In addition, 1 to 3 ply is 33.8 pieces 15cm, and 4 ply is 51 pieces/5 c.
The number of strokes was n+, and the carcass strength was the same as the control, but the plunger energy was improved by 20% compared to the control, despite the carcass strength being the same.

In addition, rolling resistance, handling stability, and drum life are all improved compared to the control, and air intake is also better.

Example 2.3 Monofilament cord was used for the 1st to 3rd ply, and 1260d/2.39 X39 T/1 (
A 1 cm multifilament twisted cord was used.

1 to 3 ply is 27 pieces 15cm, 4 ply is 51 pieces 15cm
cm, the carcass strength was reduced by about 15% compared to Example 1, but the plunger energy was improved by 3% compared to the core control, and both tire performance and drum durability were improved. It went up a lot.

Furthermore, due to the reduction in the number of carcass strikes, the rolling resistance and drum life were significantly improved compared to Example 1.

Furthermore, a twisted cord made of multifilament cord was used for the outermost layer of the 4-ply, but since this deep cord has good air permeability, no air was trapped.

Comparative Examples 3 and 4 Tire performance and drum life were the same as Examples 2 and 3, but air intrusion occurred because the air permeability of the 4-ply multifilament cord deteriorated.

Example 4 1 to 4 plastics 3 were placed in the same rubberized cloth so that the number of 1260 d/2 multifilaments was 33.3 15 cm, and the number of monofilament cords was 7.0/5 am. A carcass ply consisting of a mixture of monofilament and multifilament twisted cords was used. The air permeability of the multifilament twisted cord is 5J/cm2/
hr, so I couldn't keep up with the air-generating tires.

Comparative Example 5 Monofilament and multifilament were applied to the same com-lined cloth from 1st to 4th ply so that the number of 1260d/2 multifilaments was 26.2 15c+n, and the number of monofilament cords was 11 of 5clII. A carcass ply mixed with twisted cord was used. Since the amount of multifilament was increased compared to Example 4, the drum life was decreased. Also, the plunger energy decreased slightly despite the fact that the total braking force was the same. This is thought to be due to the fact that the monofilament cord and the multifilament twisted cord have different moduli, resulting in increased shear strain.

A tire was prototyped in the same manner as Comparative Example 5, with the number of 1260d/2 multifilament twisted cords being 17.4/5 cm and the number of monofilaments being 16.4/5 cm for the 1st to 4th plies. . The drum life and plunger energy were further reduced than in Comparative Example 5.

In addition, the air permeability of the multifilament twisted cord was also poor, which caused air to enter.

(Effects of the Invention) As explained above, in the pneumatic bias tire of the present invention, air inflow is significantly reduced, and at the same time,
Improved rigidity of carcass ply cord improves rolling resistance.
The effect is that tire performance such as steering stability and drum life is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a sample used in the air permeability test of a multifilament twisted cord, and FIG. 2 is an explanatory diagram showing the method of the air permeability test. Patent applicant Bridgestone Corporation

Claims (1)

[Scope of Claims] 1. A pair of left and right bead portions, which extend from one bead portion across the crown portion to the other bead portion, and are fixed to each bead portion at an angle of 30 to 45° with respect to the tire circumferential direction. A pneumatic bias comprising a carcass ply consisting of an array of bias cords intersecting at an angle, a tread layer covering the outside of the carcass ply, and a breaker consisting of organic fiber or steed cord at the crown part outside the carcass ply and inside the tread. In a tire, 2/3 or more of the carcass ply cord is composed of monofilament cord, and the remaining 1/3 or less of the carcass ply cord is a twisted cord composed of multifilament, and the air permeability of the multifilament cord is 4K.
A pneumatic bias tire characterized in that it has a resistance of more than g・cm^2/hour. 2. The outermost layer of the plurality of carcass ply layers of the bias tire is a twisted cord made of multifilament, and the air permeability of the multifilament cord is 4 kg.
- The pneumatic bias tire according to claim 1, characterized in that the tire speed is at least cm^2/hour. 3. Only the outermost layer of the plurality of carcass ply layers of the bias tire is a twisted cord made of multifilament, and the error transparency of the multifilament cord is 4.
kg・cm^2/hour or more, and the following formula: N_T=N×(√0.139×D/ρ)×10^-^3
(In the formula, N is the number of twists of the cord (twists/10cm), D is 1/2 of the total denier of the cord, and ρ is the cord specific gravity.) The twist coefficient N_T of the cord is 0.37≦
The pneumatic bias tire according to claim 1 or 2, wherein N_T≦0.57 and the carcass ply cords other than the outermost layer of the carcass are composed of monofilament cords. 4. The cross section of the monofilament cord is elliptical, and the ratio b/c of the major axis (b) to the minor axis (c) of the cross section is 1.
The pneumatic bias tire according to any one of claims 1 to 3, characterized in that 5<b/c<5.