JPS6213202B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a bias tire that is excellent in various performances such as high-speed durability, pliesteer, and ride comfort. Conventionally, 6-ply rating tires for passenger cars and tires for light trucks have generally been so-called 4-ply tires.
It has a ply carcass structure. In this laminated structure, the carcass cords are +θ, -θ, +θ, -θ in the circumferential direction of the tire, as shown in Figure 1a and b.
Therefore, the adjacent layers intersect with each other and are laminated, which is called an asymmetric four-layer laminated structure from a mechanical point of view. It is widely known that by adopting this structure, each ply becomes a cross ply, which is advantageous in terms of so-called strength and rigidity.
However, since this structure is mechanically asymmetrical, it suffers from the coupling effect peculiar to rubber-based composite materials (when in-plane stress is applied to a laminate, bending, deflection, and torsional deformation generally occur). It will happen. It is a well-known fact that this effect is caused by tire plysteer (a phenomenon in which the direction of travel of the vehicle and the orientation of the vehicle body deviate from each other when driving straight). In addition, in FIGS. 1a and b, 1 indicates the tread part, 2-a indicates the first layer of the carcass, and 2-
b represents the second layer of the carcass, 2-c represents the third layer of the carcass, 2-d represents the fourth layer of the carcass, 3 represents the breaker, 4 represents the side portion, and 5 represents the bead. Note that the arrow T represents the tire circumferential direction. On the other hand, as shown in Fig. 2 a and b, it has a mechanically symmetrical four-layer laminated structure, that is, the middle layer is parallel to the tire circumferential direction, with the carcass cords at +θ, -θ, -θ, and +θ. By stacking them so that
It is theoretically possible to eliminate the coupling effect in the asymmetric laminated structure. In addition, the present inventors have found that in actual tires with this structure, the amount of plysteer is smaller than that with an asymmetric laminated structure. However, in this symmetrical laminated structure, as shown in Figure 2a and b, there are parallel plies between two and three plies.
Since the cord directions are in the same direction, the strength of the laminated material is reduced, and ply peeling is likely to occur between the plies, resulting in a disadvantage that the durability performance of the tire is reduced. Furthermore, a tire has been proposed that has at least two carcass layers, one of which is composed of high modulus cord, and the other layer is composed of low modulus cord (Special Publication No. 47-
In the case of this tire, the cords constituting the carcass are different in one layer and the other layer, so the heat shrinkage rate etc. are different, so the vulcanization process during tire manufacturing etc. The process becomes complicated, and furthermore, the characteristics of the tire cannot be said to be excellent. The present invention has been made in view of the above circumstances, and provides a bias tire that is free from the above-mentioned problems and has excellent performance such as high-speed durability, pliesteer, and ride comfort. The purpose is to provide. In order to achieve the above object, the present inventors have found that in order to accommodate the above-mentioned contradictory phenomena and provide a bias tire with low plysteer and excellent durability, (1) a symmetrical laminated structure is adopted. ,(2)
Considering that it is a necessary condition to ensure that the cord direction is not the same between each laminated layer, we conducted research to make the above two points possible. As a result, the carcass was structurally changed from a 4-layer laminated structure to a 3-layer laminated structure, with a single intermediate layer, which has approximately half the tensile rigidity per unit width in the cord direction of the intermediate carcass layer. By arranging the carcass layers having tensile rigidity on both sides and arranging them so that they intersect with each other, it is possible to create a mechanically symmetrical laminated structure, and furthermore, it is possible to create a mechanically symmetrical laminated structure. By making the two layers of carcass cords of the same quality, it is possible to better improve the characteristics of the tire, which led to the present invention. The present invention made as described above provides a bias tire having a carcass layer, in which three carcass layers are arranged such that the carcass cord of the intermediate layer and the carcass cord of another layer laminated to that layer intersect with each other. The cords are arranged at a constant cord angle with respect to the circumferential direction of the tire, and among these three carcass layers, each side layer has a tensile rigidity of the intermediate layer per unit width in the carcass cord direction. 45～
It has a tensile stiffness of 55%, and is further characterized in that the carcass cord of the middle layer and the carcass cords of the other two layers are mutually homogeneous. DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below based on an embodiment of the present invention shown in the accompanying drawings. Figures 3a and 3b show an example of a bias tire of the present invention, which has a three-layer carcass 2-a, 2-
b, 2-c are carcass cords 6 and 6', 6' and 6''
are laminated in a manner that they intersect with each other. in this case,
The cord angles -θ and +θ, which are the inclination angles of the carcass cords 6, 6', and 6'' with respect to the circumferential direction of the tire, may be angles in a general bias tire and are not particularly limited.
Among the carcass layers 2-a, 2-b, and 2-c, the layers 2-a and 2-c on both sides have the tensile rigidity of the intermediate layer 2-b per unit width in the carcass cord direction.
Each has a tensile stiffness of 45-55%, preferably 50%. If the tensile rigidity of both side layers is outside the range of 45 to 55%, the carcass layer is likely to twist due to the unevenness of the tensile rigidity of the entire both side layers and the tensile rigidity of the middle layer, causing plysteer. At the same time, the durability of the tire also deteriorates. In general, various types of tensile rigidity can be considered, but here, the tensile rigidity in the tire cord direction is taken as a representative value. That is, JIS L-1017
Tensile rigidity is determined by multiplying the "initial tensile resistance" in the "Chemical Fiber Tire Cord Test Method" by the cross-sectional area of the tire cord. In addition, as a method to make the tensile rigidity of the middle layer twice that of the both-side layers, (1) the carcass cord diameter of the middle layer is made thicker than the cord diameter of the both-side layer carcass, and (2) the unit width of the middle layer is (3) making the number of cords per unit substantially twice the number of cords per unit width of both layers;
It is conceivable to make the code modulus of the middle layer substantially twice the code modulus of both side layers. However, making the number of cords per unit width in (2) above approximately twice the number of cords per unit width of both layers means that the cord spacing becomes very small, that is, the cords come into contact with each other. This may cause problems in terms of tire durability. Furthermore, making the cord modulus of the middle layer in (3) above approximately twice the cord modulus of both layers causes problems in tire durability due to differences in heat shrinkage between different materials during tire vulcanization. .
For this reason, in the present invention, we conducted research to achieve the above (1), that is, to make the cords of the intermediate layer thicker than the cords of both side layers, and focused on the tensile rigidity. Furthermore, in the present invention, in the three-layer carcass, by making the middle layer carcass cord and the other two layer carcass cords the same,
The aim was to improve tire productivity and characteristics. Hereinafter, the effects of the present invention will be specifically explained with reference to Examples. EXAMPLE The test tire was a small truck tire with a 5.50-13 and 6-ply rating. In other words, each carcass ply of the conventional tire A shown in Fig. 1 is made of 840d/2 66 nylon cord (cord diameter 0.5mm) with the number of ends (the number of cords inserted per 50mm width in the direction perpendicular to the cord direction). 46
I used a rubberized cloth with a blind weave at the end. In this case, the tensile rigidity of the carcass layer per 50 mm width (crown center portion) in the cord direction was 2732 kg. The improved tire B shown in FIG. 2 uses the same materials as the conventional tire A shown in FIG. 1, but only the lamination method is changed. In the tire C of the present invention shown in FIG. 3, the above materials and the same number of ends are used for the first and third layers, and the second layer, which is the intermediate layer, is made of 1890d/2 66 nylon cord (cord A rubberized blind weave fabric with a diameter of 0.83 mm and 48 ends (crown center) was used.
In this case, the tensile rigidity of the carcass layer per 50 mm width in the cord direction was 5816 kg. Further, the breaker layer is inserted in each tire. These three different types of tires were evaluated for high-speed durability performance, durability performance, ride comfort performance, and plysteer as described below. The results are shown in Table 1 below. (1) High-speed durability performance: To evaluate the high-speed durability performance of tires,
A test was conducted in accordance with the "high-speed durability performance" test stipulated in JIS D4230 "Automotive Tires". The test speed specified in JIS D4230 is
For small truck tires, the speed is up to 130 km/h, but here the speed was increased stepwise by 10 km/h every 30 minutes until the tire was destroyed. As a result, the conventional tire A, which has an asymmetric 4-layer laminated structure, breaks at a speed of 180 km/h, while the improved tire B, which has a symmetrical 4-layer laminated structure, breaks at a speed of 190 km/h.
The tire C of the present invention, which has a laminated structure, can be used for 200km/
The tire C was broken at a speed of 100 m, demonstrating that the tire C of the present invention has excellent high-speed durability performance. This is due to a decrease in the mass of the tire lead due to a decrease in the number of laminated tires.
This shows that it greatly contributes to improving high-speed durability performance. (2) Durability: In order to evaluate the durability performance of tires, JIS
A test was conducted in accordance with the "durability" test specified in D4230 "Automotive Tires". JIS
The test load specified in D4230 is up to 115% for small truck tires, but here the test load is increased by 19% every 8 hours, and the total test load is increased until the tire breaks. Durability performance was evaluated based on mileage. In this test, conventional tire A, which has an asymmetrical four-layer laminated structure, broke after a total traveling distance of 5,792 km, whereas improved tire B, which has a symmetrical four-layer laminated structure, failed.
was destroyed after a total mileage of 5366 km, and the conventional tire A
Durability is slightly lower than that of . This is because two or three of the carcass layers are parallel plies, which reduces the strength of the laminated material.
A peeling phenomenon occurred between these layers, leading to failure. On the other hand, Tire C of the present invention, which has a symmetrical three-layer laminated structure, exhibited a total mileage of 5744 km, which is equivalent to the durability performance of the conventional Tire A, even though it is essentially three-ply. The effectiveness of the present invention can also be seen from this aspect. (3) Ride comfort performance: Next, in order to evaluate the ride comfort performance of the tire, a semicircular cleat with a diameter of 10 mm was placed on a drum with a diameter of 2500 mm perpendicular to the drum rotation surface.
The longitudinal impact force generated when the tire rides over this protrusion (it is generally said that the longitudinal impact force is largely responsible for the ride comfort of a tire) was measured. Tests were conducted under the conditions of a load of 520Kg and an air pressure of 3.25Kg/ ^cm2 .
Comparing the impact force when running at a normal running speed of 60 km/h, the conventional tire A has 231 kg, the improved tire B has 237 kg, and the inventive tire C has 215 kg, which is about 7% compared to conventional tire A. The tire C of the present invention had a small impact force, indicating that the tire C of the present invention had excellent ride comfort performance. The reason for this decrease in impact force is that while the conventional tire A and the improved tire B have a four-layer laminated structure, the present tire C has a three-layer laminated structure. This is because the weight of the tire C of the present invention is lighter than the weight of the tire C. (4) Plysteer: Next, let's consider tire plysteer. Tire plysteer caused by the coupling effect peculiar to rubber-based anisotropic composite materials was reduced to 854 mm in diameter at an air pressure of 2.0 Kg/cm and a load of 400 Kg.
The measurements were taken on a drum. As a result, while the plysteer of the conventional tire A was 6.7Kg, the plysteer of the tire C of the present invention was 2.1Kg, which was about 1/3, making it possible to reduce the plysteer. This is because the tire of the present invention has a symmetrical structure, which reduces the coupling effect. Furthermore, it is estimated that it can be virtually eliminated if no breaker layer is inserted. In addition, the tire C of the present invention can substantially reduce the number of layers by one layer compared to the conventional tire A, and while the weight of the conventional tire A is 6.9 kg, the weight of the tire C of the present invention is In addition to being able to reduce the weight by approximately 3% to 6.7 kg, the tire C of the present invention also enables the reduction of the tire manufacturing process, which brings about a great effect on tire manufacturing.

[Table] As described above, it is clear that the tire of the present invention maintains or improves the performance of conventional tires, and also makes it possible to reduce tire weight and improve productivity in the tire industry. Although this example uses a nylon cord, it is clear from the above that the same effect can be achieved by using other cords such as polyester, vinylon, and rayon. Dew.

[Brief explanation of the drawing]

FIG. 1a is a partial perspective view of a conventional bias tire having a carcass lamination structure of an asymmetric four-layer lamination structure, FIG. 1b is an explanatory diagram of the carcass lamination structure of the bias tire shown in FIG. 1a, Figure 2a
is a partial perspective view of a conventional bias tire having a carcass lamination structure with a symmetrical four-layer lamination structure, FIG. 2b is an explanatory diagram of the carcass lamination structure of the bias tire shown in FIG. 2a, and FIG. 3a FIG. 3b is a partial perspective view of an example of the bias tire of the present invention having a carcass laminated structure with a symmetrical three-layer laminated structure;
It is an explanatory view of the carcass lamination structure of the bias tire shown in Drawing 3a. 1...Tread section, 2-a...Carcass 1st
Layer, 2-b... Carcass second layer, 2-c... Carcass third layer, 2-d... Carcass fourth layer, 3...
Breaker, 4... side part, 5... bead,
6, 6', 6''... Carcass cord, T... Tire circumferential direction.

Claims (1)

[Claims] 1. In a bias tire having a carcass layer, the three carcass layers are each coated with a constant cord in the circumferential direction of the tire so that the carcass cord of the intermediate layer and the carcass cord of the other layer laminated on that layer intersect with each other. The carcass layers are arranged at an angle, and among these three carcass layers, the layers on both sides are
It has a tensile rigidity of 45 to 55% of the tensile rigidity of the intermediate layer per unit width in the carcass cord direction, and is further characterized in that the carcass cord of the intermediate layer and the carcass cords of the other two layers are of the same quality. bias tires.