JPS5818246B2 - bias structure pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bias structure pneumatic tire used for large vehicles, construction vehicles, industrial vehicles, aircraft, etc., and more particularly, by using thick yarn as the tire cord, weight reduction and durability are achieved. This invention relates to a tire with an improved bias structure φ.

So-called bias structure tires, which have a carcass structure in which a large number of plies with organic fiber cords embedded in rubber are laminated on the bias, have a higher strength than radial structure tires, which have steel cords, etc. laminated radially. It has the disadvantage that a large number of ply cords are required to apply this to the tire.

For example, in the case of tires for large trucks and buses, it is usually sufficient to use one layer of steel cord ply for radial construction tires, whereas it is sufficient to use up to eight or more ply layers for bias construction tires. There is.

Furthermore, the current situation is that some of the super large dump trucks used in mines etc. have more than 40 plies.

In this way, a large number of plies increases the weight of the tire, hindering productivity, and not only increases costs, but also causes large energy loss during driving, and reduces heat dissipation due to thickening of the gauge skin. When driving at high speeds or under heavy loads, the temperature inside the tire rises significantly, resulting in a serious performance problem.

Therefore, it is desired to reduce the number of plies in bias structure tires, and many attempts have been made.

In the past, ply coated rubber with a 100% modulus of 20k19/d and tire cord strength of 55k
A tire using 100 g/tire was proposed and put on the market, but there were performance problems and production was soon discontinued.

On the other hand, today, for example, the most widely used bias structure tires for large trucks and buses have a cord strength of 22 ky.
The modulus of the ply coating rubber at 100% elongation is 15 to 25 kg/i, and the number of plies is 8.

The thread of this ply cord was thickened, that is, 34 kg/strand, and the same ply coating rubber was used, and the number of plies was increased to 6.
Although flat tire tires also exist, their use was limited to users with so-called mild usage conditions, where the tire load is small and on good roads.

This is because under such mild conditions of use, the mileage until complete wear is extremely long, so the wear resistance decreases, but this is not a disadvantage.

This is to avoid becoming

However, if the usage conditions are heavy loads, the cord will become fatigued and the rubber between the plies will tend to separate at the tread surface, and if driving on rough roads, cut-through failures will easily occur. was limited.

Although reducing the number of plies is an ideal method for improving productivity, reducing weight, and improving performance of bias structure tires, as mentioned above, it is difficult to reduce the number of plies in tires with a strong cord of around 34 kg/piece. JIF was only used up to that point, and in terms of performance, it was only possible to make products for extremely limited users.

Regarding this, firstly, it has been said that increasing the strength of the cord by making it thicker reduces the fatigue resistance of the cord, and it is generally thought that it is effective to simulate tires relatively well. According to the results tested using a tube-type fatigue tester, it appears that cord fatigue becomes more pronounced as the yarn becomes thicker.

That is, a hollow rubber cylinder with an outer diameter of 40 mm and an inner diameter of 20 mm, in which test cords were arranged at equal intervals parallel to the axial direction near the thick outer layer, was closed at both ends, and air was sealed inside to maintain the internal pressure. In addition, this rubber cylinder was bent so that the axes of both ends formed an angle of 90°, and the cord was rotated at a speed of 1100 rpm to perform a fatigue test on the cord. With a cord of 63 kg/piece compared to 22ky/piece, the lifespan is approximately 1. /10, and the fatigue resistance of the cord is extremely reduced due to the thick thread count.

For this reason, the increase in strength due to thicker ply cords was only increased from the conventional 22.7 cords to 34 kg/cord at most.

However, the present inventors had doubts about the above results and found that they were unfounded for the following reasons.

In other words, cord fatigue progresses rapidly under conditions of repeated stretching and compression, but in the above tests, the thicker the denier, the smaller the curvature and the greater the input force, which accelerated the progression of fatigue. When the elongation and compression conditions are the same, a decrease in fatigue properties can be seen due to thicker yarns, but tire test results have shown that there is no problem in practical use.

Furthermore, if the cord strength is less than 40 to 9/piece, it is not possible to reduce the number of plies sufficiently to reduce heat generation during high-speed running, and if the cord strength is 100 kg/piece or more, the cord will inevitably become too thick. The heat shrinkage force of the cord that occurs during tire vulcanization increases, and the cord is heated until defects such as cracks are likely to occur in the curing of the tire edge at the end of the ply where the bead is wound from the inside of the tire bead. It was confirmed that the preferred range of strength is 45 to 95 yen.

Secondly, regarding the modulus of the ply coating rubber, according to the conventional bias structure concept, the cord undergoes free pantograph deformation, and in order to allow free pantograph deformation, the lower the modulus of the ply coating rubber, the lower the modulus of the ply coating rubber. It was considered appropriate.

On the other hand, pantograph deformation means that the input to the ply coating rubber is a fixed type input, and a rubber with a high modulus has lower bending fatigue resistance in response to a fixed type input.

Therefore, the idea is to use a material with the lowest possible modulus within the range that satisfies the bending fatigue properties.

The present inventors carefully observed the deformation behavior of the ply coating rubber inside the tire using X-rays, micro-strain sensors, etc. As a result, the deformation of the ply coating rubber on the tread portion was found to be in a fixed form or a target on a completely flat road surface. It was found that when the road surface exhibits uneven behavior, constant energy deformation or constant stress deformation becomes predominant.

It was also found that the side and bead parts exhibit constant stress or constant energy deformation behavior as the load is increased.

Simply using equal modulus ply coating rubber and increasing the thickness to reduce the number of pieces will result in a thinner carcass gauge, lower bending rigidity, increased cord elongation and compression, and increased input to the ply rubber itself. produce a result.

The above 34kg/cord is strong and has 22 plies and rubber.
kg/ctr1. This was found to be the reason why tires with a modulus of

This restricts the movement of the ply-coated cord and reduces the elongation and compression of the cord in tires with thicker yarns to increase the strength of the cord and reduce the number of plies, thereby preventing cord fatigue and improving wear resistance on the tire tread. It was confirmed that this could be improved by reducing the wiping action, and that the occurrence of ply rubber separation could be suppressed by reducing the input to the ply coating rubber.

Furthermore, in bias structure tires where the carcass ply strength is 450 to 12,000 kg/CrrL, which is required to reduce the weight of the tire, the strength of the cord obtained by bundling and twisting a large number of nylon or polyester filaments is 40 to 95 kg/piece. The 1oo% modulus of ply coated rubber is 35 kg/f.
Below fl, carcass rigidity is insufficient, cord fatigue resistance, abrasion resistance, ply rubber separation properties, etc. are reduced, and
kg/cIi! If it exceeds L, the carcass rigidity will become too high, stress will tend to concentrate at the bottom of the pattern, and the cord will become more constrained, so the fatigue resistance of the cord will tend to decrease, so the preferred range is 40-80
kg/ffl.

Therefore, the carcass ply strength of the present invention is 450 to 1200.
A pneumatic tire with a bias structure that has a speed of 0ky/cm is
The strength of the tire cord obtained by bundling and twisting many nylon or polyester filaments is 40~
It is characterized by using a ply of rubberized cord in the carcass, in which a cord weighing 95 kg/piece is embedded in a ply coding rubber having a modulus of 40 to 80 ky/ffl at 100 extension.

The ply coating rubber used in the present invention has a modulus of 40 to 80 kg/cm at <100% elongation as described above.
All natural rubbers and other diene rubbers commonly used as ply coating rubbers can be used.

Among these, it mainly consists of a polymer obtained by block polymerization or graft polymerization of cis-1,4-polybutadiene and syndiotactic (5Vn)-1,2-polybutadiene, which is described in Japanese Patent Application No. 53-96198, and has a microstructure. 5yn-1,2-structure accounts for 6 to 20% by weight, and Syn L2-polybutadiene forms short fibers with an average diameter of 0.05 to 1 μm and an average length of 0.8 to 10 μm, of which at least 40% by weight It is best to use a polymer containing crystalline polybutadiene polymer (hereinafter referred to as VCR) in a polymer ratio of 10 to 70.

The reason why this butadiene polymer is limited to a polymer ratio of 10 to 70% in the present invention is that if the polybutadiene polymer is less than 10%, there is no effect when using it, whereas if it exceeds 70%, the coating will be applied to VCR with low green strength. This is because the arrangement of the cords becomes irregular, which is not desirable.

As mentioned above, the bias structure pneumatic tire of the present invention includes:
By using a ply of rubberized cord in the carcass, in which a specific cord with a tire cord strength of 40 to 95 kg/piece is embedded in a specific ply coating rubber, it is possible to improve durability and at the same time reduce the weight of the tire (e.g. This makes it possible to reduce the weight of tires for trucks and buses by 10 to 20%, making them extremely useful.

The invention will be illustrated with reference to the following examples.

Example 1 Large truck tires io:oo-2014PR lug pattern tires A to F were made using case rubbers having the compounding ratios (parts by weight) shown in Table 1 below, and tire performance tests were conducted.

The results obtained are shown in Table 2.

The structure of each tire is also listed in Table 2. In the table *1: N-oxydiethylene-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name Tsuxela MSA, F *2: Poly(js2*4)limethyl-1,2-dihydroquinoline ), manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name TSCRACK 224° From the table above, it can be seen that all 7 cords with 63 strength cords have significantly improved drum heat generation.

When a tire with a case rubber modulus of 35 kg/ffl was run under good road load conditions until it was completely worn out, the degree of rim slippage was moderate, and an autopsy of the tire revealed that separation had occurred at the bead. Even when running under road load conditions, the rate of cut-burst tires increases, which is inappropriate.

In a tire with a case rubber modulus of 80 kg/cri't, rough chipping occurs in some parts when driving under heavy loads on good roads, and the upper limit of the modulus is 80 to 9/cyf.

VCR is cis-1,4-structure 85.0 weight tra
ns-1s4 structure 2.4 weight ratio 5yn-1.2-structure 12.6 weight ratio short fiber average diameter 0.25 μm short fiber average length 3.1 μm average length/average diameter 12.4, polymer ratio 40 Tire F with a weight factor of m0 had no problems in a heavy load test on a good road, and the number of punctures and cut bursts were greatly improved when running on a heavy load on a rough road, which is a great effect.

Example 2 A tire GL similar to that of Example 1 was made using case rubber having the compounding ratio (parts by weight) shown in Table 3 below, and a tire performance test was conducted.

The obtained results are also listed in Table 3.

■ In the above table ■ Durable drum is 60km/h at JIS 140% load
r, 8.0 kg, 7'cyrt, and was driven until tire failure occurred, and the distance is expressed as a ratio of the control.

The higher the number, the better. 2. VCR is the same as in Example 1.

Example 3 A construction tire with an OR2400-4942PR lug pattern was made using case rubber having the compounding ratio (parts by weight) shown in Table 4 below, and a tire performance test was conducted.The obtained results are shown in Table 4 along with the tire structure. show.

If the tire heat generation humidity decreases by about 10℃, the heat separation resistance will decrease, the wear resistance will improve, the burst failures will decrease, the cut failures will decrease, etc., and the overall life will be reduced by 10℃.
Since it is clear from past experience that weight reduction improves the weight by 20%, it can be seen that significant effects can be achieved by reducing the weight.

Example 4 LT550 was manufactured using case rubber with the following blending ratio (parts by weight).
-13 6PR rib pattern tires were made with the tire structure shown in Table 5 below, and the results of a maneuverability test are also listed in Table 5.

The maneuvering test is a slalom test, and the evaluation is based on the time required and the feeling when driving safely.

From the above results, it can be seen that there was no significant difference in the maneuvering test and there were no problems at all.

Claims (1)

[Claims] 1 Carcass ply strength is 450 to 12000 kg/c
In a pneumatic tire with a bias structure, the strength of the tire cord obtained by bundling and twisting a large number of nylon or polyester filaments is 40 to 95.
A bias structure pneumatic tire characterized in that a ply of rubberized cord is used for the carcass, in which a cord having a k19/cord is embedded in a ply coating rubber having a modulus of 40 to 80 ky/ffl at 100% elongation. 2 ply coating rubber with cis-1,4-polybutadiene and syndiotactic (syn)-1,2-
It mainly consists of polymers obtained by block polymerization or graft polymerization with polybutadiene, and contains 5y in the microstructure.
n-1,2-structure accounts for 6 to 20 weight units, and 5yn
-1,2-polybutadiene has an average diameter of 0.05 to 1 μm1
The bias structure according to claim 1, which uses a polybutadiene polymer which is in the form of short fibers with an average length of 0.8 to 10 μm and contains at least 40% by weight of a polybutadiene polymer in the form of crystals in a polymer ratio of 10 to 70%. pneumatic tires.