JPH02303903A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve driving stability and durability by specifying the structure of a carcass layer and arrangement of each cord of a carcass layer and a belt layer, respectively, and applying an untwisted polyamide fiber cord consisting of a simple filament to the carcass cord. CONSTITUTION:A carcass layer is made of inner and outer two layers 4d and 4u, and the inner layer 4d is turned up around a bead wire 31, and also the outer layer 4u is divided left and right in two. And the end a on the tread part 1 side of the outer layer being divided in two is superposed on belt layers 5 (d and u) and the end b on the beard part 3 side is arranged, being separated at the specified height from a bead wire 31. The inner and outer two layers 4d and 4u are arranged so that the average value of each angle alpha1 and alpha2 to the tire circumferential direction E-E' of inner and outer each carcass cord may be 95 deg.-120 deg. and the difference may be 10 deg.-60 deg.. Furthermore, each carcass cord is severally made of an untwisted polyamide fiber consisting of a simple monofilament.

Description

[Detailed Description of the Invention] [Industrial Applications] The present invention improves straight-line running performance by reducing plysteer that is noticeable in radial tires, and improves the handling stability, high-speed durability, and high-speed durability inherent in radial tires. The present invention relates to a pneumatic tire that is further lightweight and has improved side cut resistance without impairing load durability.

[Conventional technology]

Conventional radial tires for passenger cars generally have a structure in which at least two belt layers are interposed on the outside of a carcass layer of a tread portion, substantially parallel to the circumferential direction of the tire.

The belt cords reinforcing these belts are inclined at an angle of 15° to 30° with respect to the tire circumferential direction and intersect with each other. In addition, in a carcass layer consisting of one or two layers, at least the end of IN is folded back and rolled up from the inside of the tire to the outside around the bead wire, and furthermore, the carcass cord of the carcass layer is approximately 90 degrees with respect to the tire circumferential direction. are arranged at an angle.

Compared to bias tires, radial tires with this structure have superior braking performance, wear resistance, and fuel efficiency due to the reinforcing effect of the belt layer, but on the other hand, they have poor straight-line running stability due to the belt layer. There is a problem of inferiority. In other words, when a radial tire rotates, a lateral force is generated in either the left or right direction with respect to the direction of travel, even if the slip angle is zero, and this lateral force causes the vehicle to move in a direction different from the direction intended by the driver. There are cases where this progresses.

The lateral force when the slip angle is zero is -a,
It consists of force components generated by two different mechanisms that are classified as part of the tire uniformity characteristic, one of which is called conicity (CT).
The other one is called Plysteer (PS). On the other hand, the uniformity test method for automobile tires (JASO
According to C607), when the average value of lateral force when the tire rotates once is LP, LFDw measured on the front side of the tire, LFDs measured on the back side by replacing the same tire, and the above-mentioned conicity CT, From its definition, plysteer PS is defined as the following formula (1) and 2 (
2).

LFDw = PS + CT ・・・・・・・・・
...... (mmLFDs = PS - CT
・・・・・・・・・・・・・・・・・・ (2) 2 (mm
From (2), PS and CT are calculated using the following equation (3):
and formula (4).

CT='A (LFDw−LFDs) −・−−
-----0-(31PS='A (LFDw-LF
Ds) −= (4) Above (mm, (21, (3
The relationships in 1 and (4) can be expressed as shown in FIG. 5.

By the way, among the above-mentioned conicity and plystea,
Conicity is considered to be the geometric asymmetrical shape of a tire with respect to its circumferential center, that is, the force generated when a truncated conical tire shifts. This is mainly due to the position of the belt layer inserted into the tire tread, which can be reduced by manufacturing improvements. On the other hand, plysteer is an inherent force caused by the structure of the belt layer, and it has been virtually difficult to reduce it significantly unless the structure of the belt layer itself is changed.

If we consider the belt layer now, it can be represented as a two-layer laminate 50 of belt layers 50u and 50d, as shown in FIG. 6(8). When a tensile force is applied to the two-layer laminate 50 in the tire circumferential direction E-E', the two-layer laminate 50 will not only move in the two-dimensional plane on which the tension acts, but also in the three-dimensional plane.
It is well known that deformation occurs dimensionally out of the plane, resulting in torsional deformation as shown in FIG. 6(B).

The above-mentioned plysteer occurs due to such torsional deformation of the belt layer.

In the past, various attempts have been made to reduce this price steer by adding and reinforcing a new belt layer to the belt layer, but adding this new belt layer inevitably increases the tire weight. This increases the fuel efficiency and other characteristics of the radial tire, which is not desirable from the standpoint of weight reduction.

What is even more difficult to bear is that radial tires, due to their structure, have poor side cut resistance due to contact with curbstones, etc. That is, although the radial carcass exhibits good strength in the radial direction, the restraining force in other directions, particularly in the circumferential direction at the side portions, depends only on the rubber.

Therefore, in order to improve side cut resistance, there are tires in which the carcass layer has a slight crossing angle. In this case, in order to maintain the characteristics of a radial tire, it is desirable to use a cord with a high modulus, such as a polyester fiber cord or a rayon cord, as the carcass cord, but in either case, the durability of the intersection between the cords decreases. , difficult to put into practical use.

This is because polyester fiber cords do not have sufficient adhesion to rubber and chemical stability, and deteriorate due to vulcanization and running, resulting in reduced strength and adhesion, whereas rayon cords have insufficient chemical stability. This is because it has poor fatigue resistance and high hygroscopicity, resulting in a decrease in strength and modulus due to moisture absorption. Furthermore, although nylon cord is actually used, in this case the modulus of the nylon cord is low, and the characteristics of a radial tire, such as maintenance of steering stability and side cut resistance, are not satisfactory.

[Problems to be Solved by the Invention] An object of the present invention is to devise the layer structure of the carcass layer using a special carcass cord without adding or reinforcing another belt layer, and in addition, to improve the layer structure of the carcass layer. By combining the carcass cord arrangement in the carcass layer with the belt cord arrangement in the belt layer, plysteer is reduced and straight running stability is improved. To provide a pneumatic tire that is extremely lightweight and has excellent side cut resistance without impairing load durability.

[Means to solve the problem]

The present invention provides a pneumatic tire in which two belt layers are laminated and arranged on the outside of the carcass layer of the tread portion, the angle of the belt cord with respect to the tire circumferential direction is 15 to 30 degrees, and the cords intersect with each other between plies. Requirements (a), (b)
) and (C).

+8+ The carcass layer is composed of two layers, an inner and outer layer, and both ends of the inner carcass layer are folded back and rolled up from the inside of the tire to the outside around a pair of left and right bead wires, and the outer carcass layer is formed into two layers on the left and right in the width direction at the tread portion. The ends on the tread side are overlapped with the belt layer with a width of 10 m or more, and the ends on the bead side are separated from the bead toe by 0 of the tire cross-sectional height.
．． (b) from the side where the belt cord reinforcing the belt layer adjacent to the outer carcass layer has an acute angle with respect to the tire circumferential direction; ! 2 (α1 +
α2) is between 95″ and 1206, and the difference (α2 minus) is 1
These two inner and outer carcass layers are arranged so that the angle is 0° to 606 mm, and further, (C) the carcass cord of these two inner and outer carcass layers is composed of untwisted polyamide fiber made of a single monofilament. , the monofilament has a flat cross-sectional shape with a ratio ε of major axis a to minor axis 1.5 or more, and the monofilaments are arranged in parallel with the major axis direction parallel to the belt layer.

Hereinafter, this means will be explained in detail with reference to the drawings.

(a) FIG. 1(A) is a partially cutaway half-sectional perspective view showing an example of the pneumatic tire of the present invention, and FIG. 1(B) is a meridional direction half-sectional explanatory view of the same tire. FIG. 2 is a developed plan view of the carcass layer and belt layer of this tire.

Moreover, FIG. 3 is a developed plan view of a carcass layer and a belt layer of another tire of the present invention.

In these figures, 1 is a tread part, 2 is a pair of left and right sidewall parts provided so as to extend on both sides of the tread part, and 3 is a pair of left and right sidewall parts that are continuous with the pair of left and right sidewall parts 2. This is the bead part. A carcass layer 4 is arranged along the inner peripheral surface of the tire, spanning from one bead part 3 to the other bead part 3, and a belt layer 5 made of steel cord is laminated on this carcass layer 4. ing.

The belt layer 5 is an outer (hereinafter referred to as upper) belt layer 5u.
It has a two-layer structure with an inner (hereinafter referred to as lower) belt layer 5d, and the belt cord reinforcing each belt I'l is at an angle of 15° to the tire circumferential direction E-E'.
30'', and the belt cord of the upper belt [5u] and the belt cord of the lower belt layer 5d are arranged in a mutually intersecting relationship.

The carcass layer 4 is composed of upper and lower layers, and both ends of the lower carcass Ji4d are wound around the bead wire 31 of the bead portion 3 and are arranged so as to wrap around the bead filler 32. On the other hand, the upper carcass mm4u is divided into two halves so as to form a pair on the left and right sides, and is spaced apart from each other, and this carcass layer 4u does not exist in the central portion of the tread portion 1. The upper carcass layer 4u, which is divided into left and right parts, overlaps with the belt layer 5 by a width indicated by the upper end a on the tread part side, and the lower end part on the bead part side extends from the bead toe part b. It is located at the height shown and is arranged so as not to reach (do not touch) the bead wire 31.

As mentioned above, by dividing and arranging the upper carcass M4u in two, the weight of the tire is significantly reduced, and the upper carcass L14u is not divided into two, but has a full structure like the lower carcass layer 4d. Compared to radial tires, the carcass weight can be reduced by about 10 to 30%.

However, in order to reduce the weight of this tire and at the same time maintain the high-speed durability and load durability inherent to radial tires, the overlapping width a between the upper end of the tread portion of the upper carcass 1J4u and the belt FJ5d must be adjusted. The lower end of the upper carcass 1i4u on the bead side is located at a height b from the bead toe, and this b is less than 0.3 of the tire cross-sectional height H. It is necessary. The overlapping width a of this upper end on the tread side is 10
If it is smaller than 1, the high-speed durability as a radial tire cannot be maintained (also, the height b from the bead toe, which indicates the position of the lower end on the toe side, is 0 of the tire cross-sectional height H).
．． If it is larger than 3, the load durability as a radial tire cannot be maintained.

The upper end of the tread part side of the upper carcass N4u and the belt layer 5
The overlap width a with d is preferably within 0.4 of the width l of the belt layer 5d in the cross-sectional direction. By setting the overlapping width a to 0.41 or less, it is possible to reduce rolling resistance due to weight reduction, and to further significantly improve riding comfort due to softening of the tread portion.

(bl The angle that the carcass cord, which reinforces the carcass layer 4 consisting of the upper and lower 2N, makes with respect to the tire circumferential direction is important in order to reduce the above-mentioned plysteer. In other words, the angle between the upper and lower parts of the carcass layer 4 The angles of the carcass cords reinforcing the carcass layers 4u and 4d with respect to the tire circumferential direction are respectively set so that the belt cords forming the lower bell l [5a located on the side in contact with the carcass/layer 4 are at acute angles with respect to the tire circumferential direction. The average value β of the angle α1 of the lower carcass cord and the angle α2 of the upper carcass cord [z (α1 + α2)] is between 95° and 120', and the difference between these two angles is (α2−
αI) is within the range of 10'' to 60''.

Here, the angle α is measured at the center in the width direction of the tread, and the angle α2 is measured at the end of the upper carcass layer on the tread side.

As described above, the angles α1 and α2 are measured from the side where the belt cord of the lower belt layer 5d, which is in contact with the carcass layer 4, is at an acute angle with respect to the tire circumferential direction E-E'. If the belt cord of the lower bell (1W5d) is arranged downward to the left as in the example of G
The angle must be measured clockwise with respect to the circumferential direction E-E' of the tire.

As is clear from the relationship between the angles α5 and α2 described above, the angle α2 of the carcass cords of the upper carcass FJ4u is always larger than the angle α1 of the carcass cords of the lower carcass layer 4d, and they intersect with each other. are placed in a relationship where When the average value β of the angles α1 and α2 mentioned above is smaller than 95°, plysteer is not sufficiently improved, and when it is larger than 120＠, although plysteer is further improved, the load durability decreases. This is not desirable because it causes Also, even if the angles α1 and α2
Even when the average value β is within the range of 95° to 120°, if the difference (α2−α1) is smaller than 10°, plysteer is not improved and steering stability deteriorates. Furthermore, if the difference (α2−αl) is larger than 60°, plysteer is improved, but load durability is lowered and ride comfort is deteriorated, which is not preferable.

In order to facilitate tire molding and vulcanization, the average value β is preferably within mm0', and in order to further improve high-speed durability and load durability, the above difference (α2-
αI) is preferably 20″ to 40″.

Note that based on the above figure, in the embodiment, the end of the upper carcass layer 4u constituting the carcass layer on the bead side is held between the lower carcass layer 4d and the bead filler 32; may be held between the winding upper end of the lower carcass N4d and the bead filler 32. Also,
In the above-mentioned embodiment, the belt layer 5 is a lamination of two belt layers made of steel cord, one of which is a belt layer of steel cord, and the other layer is made of an aromatic compound called "Kevlar" (trade name). Commonly used materials can be used, such as a belt layer made of polyamide fiber cord, or a belt layer made of both textile cords. Naturally, the end portion of the belt layer may be bent inward. In addition, if necessary,
It is also possible to apply belt layers of other textile cords in addition to the layers.

As mentioned above, the pneumatic tire according to the present invention has an upper carcass]! ! When measured from the side where the belt cord of the belt Fg5d adjacent to 4Ll has an acute angle with respect to the tire circumferential direction, the angle α2 of the carcass cord of the upper carcass mmi4u and the angle α of the carcass cord of the lower carcass Ji4d, The average value β is [〃(α1+α2
)] is 95″ to 120°, and the difference (α2 − α1)
By arranging the tires so that the angle is 10'' to 60°, significant plysteer can be reduced in the radial tire and the weight can be reduced without adding a belt layer.

On top of that, the carcass layer is composed of two layers, upper and lower, and the lower carcass layer is continuous in the cross-sectional direction (tire width direction), and its both ends are wound around a pair of left and right bead wires.
The upper carcass layer is divided into two parts separated from each other on the left and right in the tread part, and the overlapping width a between the end on the tread part side and the belt layer is at least 10 mm, and the end on the bead part side By placing the part at a height b from the bead toe, making the value of b 0.3 or less of the tire cross-sectional height H, and placing it without contacting the bead wire, it is possible to significantly reduce weight. , it is possible to improve the handling stability, high-speed durability, and load durability inherent to radial tires compared to conventional radial tires.

Furthermore, since the upper carcass layer is largely removed at the center of the tread, the tread becomes significantly more flexible than conventional radial tires, further improving ride comfort.

(C) The carcass cord of the carcass layer has a high modulus close to that of a polyester fiber cord, yet has excellent chemical stability and excellent adhesive properties equivalent to a nylon cord. Since it is constructed from untwisted polyamide fiber cord made of monofilament, it maintains a higher level of handling stability as a radial tire, while significantly improving high speed and durability, and side cut resistance. can be made significantly better.

Here, the untwisted polyamide fiber cord will be explained in detail below.

Generally, a conventional tire cord is made up of a plurality of thin filaments bound together, and is twisted to a certain degree to give the cord convergence and fatigue resistance. In contrast, in the present invention, a single monofilament untwisted polyamide fiber is used for the carcass cord. This is because the fibers that make up the cord are made of a single monofilament with a relatively large denier, and are not twisted to obtain a high modulus. Examples of the polyamide fibers include nylon 66 (polyhexamethylene adipamide), nylon 6 (polycaprolactam), and nylon 46 (polytetramethylene adipamide), which have fiber-forming properties.

Further, in the present invention, the cross-sectional shape of the untwisted monofilament is flat.

The reason for making it flat is to improve durability (fatigue resistance) as described below. That is, Fig. 7 (A), (B)
As shown in FIG.
The bending strain generated in the cord when the same bending deformation is applied to each cord is expressed by the following formula.

ε=ε. +ZK However, ε. : Strain at the neutral axis t of bending Z: Distance from the neutral axis t of bending: Change in curvature Therefore, Z becomes thicker (the bending strain that occurs becomes larger. Maximum value of Z of circular code m, Since □ is larger than the maximum value ZIIIM of 2 of the flat cord n, in the case of an untwisted cord consisting of a single filament, the decrease in fatigue resistance due to no twisting can be reduced by changing the cross-sectional shape to the cord n. By making the cord flat, it is possible to reduce and prevent bending strain that occurs within the cord.

Furthermore, in the present invention, the ratio of the major axis to the minor axis of the cord is ε
is set to be 1.5 or more (ε = h/ ≧1.5). This makes the short axis direction of the cord (direction perpendicular to the long axis)
Since the bending rigidity of the cord becomes smaller, the cord becomes easier to bend.

As a result, when the carcass cords are arranged in parallel with the long diameter direction parallel to the belt layer, the contact length becomes longer than when a circular cord is used, and the cornering power increases, thereby improving the steering stability. The reason why the bending rigidity of the cord is lower than that of the cord m having a circular cross section is as follows.

As shown in FIGS. 8(A) and 8(B), consider the case where a cord m having a circular cross-section and a cord n having a flat cross-section having the same cross-sectional area and the same Young's modulus but different cross-sectional shapes are bent. However, in the case of code n, it shall be bent in the minor axis direction.

The bending rigidity of a cord is proportional to the moment of inertia of area calculated from its cross-sectional shape when its Young's modulus is the same. Since code m and code n have the same cross-sectional area, the following formula holds true.

πr2 = πhk If the ratio of the major axis to the minor axis (h/k) of code n is ε, then πr2 = πε is 2, ', r = J, and the moment of inertia of code m is: ■= πr,'/4 The moment of inertia of code n is: Bi=(π/4) hk3 = (π/4) ε to 4,', I'/I=ak'/r' = ε k47εmk4 ;1/ ε=k/h Therefore, the second moment of area I' of the cord n becomes smaller as the major axis becomes larger.

The bending rigidity of the cord n decreases in proportion to this. However, when using it for carcass cords and trying to reduce its rigidity from the perspective of improving steering stability, ε-h/
When k<1.5, the effect is not sufficient.

Therefore, in the present invention, ε-h/ is set to ≧1.5.

Further, when arranging the cords n, as is clear from the above, the cords must be arranged in parallel with their long diameter sides parallel to the belt layer.

As a result, the same effect as substantially increasing the number of ends of the cord can be obtained, so that the circumferential rigidity of the tire side portion can be increased.

Furthermore, since the distance between the neutral axis of bending and the cord surface can be made smaller, the bending stiffness in the cross-sectional direction can be increased without reducing the tensile stiffness compared to when using a cord with a nearly circular cross-sectional shape. It is possible to make it smaller. Therefore, it is possible to increase the ground contact length of the tire to increase cornering power, and in combination with increasing the circumferential rigidity of the tire side portion, it is possible to further improve steering stability.

In addition to the above, in the present invention, the physical properties of the cord after adhesive heat treatment are as follows: elongation rate at a load of 2.25 g/d is 6.
It is preferable that the thermal shrinkage rate at 150°C is 0% or less and 4.5% or less.

Here, the term "adhesive heat treatment" refers to heat treatment after the cord is subjected to RFL treatment by a conventional method in order to improve adhesiveness with rubber. Moreover, the heat shrinkage rate is the shrinkage rate after processing at 150° C. for 30 minutes.

If the elongation rate of the cord at a load of 2.25 g/d exceeds 6.0%, the initial modulus will be low, and when used as a carcass cord, no improvement in high speed performance will be obtained. Also, 15
If the heat shrinkage rate at 0°C is more than 4.5%, the cord will shrink significantly during tire vulcanization, and the unevenness between the splice and other parts of the carcass layer will become noticeable, resulting in poor uniformity. In particular, unevenness occurs on the side portions.

In the present invention, the number of cords implanted in the carcass layer varies depending on the type of tire, but the carcass cord interval (inter-thread distance) on the tire equatorial plane is 0.1 to 2.0.
+n may be sufficient, preferably 0.2 to 1. On is better.

Further details will be explained below using specific experimental examples.

Experimental Example 1 The structure of the carcass layer and the belt layer shown in FIGS. 1 (A), (B) and 2 was used, and the difference in carcass cord angles (α2-α1) for reinforcing the upper and lower carcass layers was set at 30". We made prototype radial tires in which the angle average value β was kept constant and the angle average value β was variously changed.

In addition, the carcass cord that forms the carcass layer is as follows:
The following untwisted polyamide fiber and polyester fiber cord consisting of a single monofilament were used.

Cords with flattening ratios of ε-1, 2, and 3 were made using 4,000 denier untwisted monofilament of fiber nylon 66 with coarse length 1''9 (
The case where ε=1 is the comparative tire 1, and the case where ε=2.3 is the tire of the present invention).

This cord was treated with resorcinol-formalin-rubber latex (RF L) adhesive and 2.0 /
Heat treated under a tension of 1.0 g/d (Ileatset/Normal), the elongation rate under a load of 2.25 g/d is 5.5%, and the dry heat shrinkage rate at 150°C is 3.7%. An adhesive-treated cord was created.

This treated cord was embedded in unvulcanized rubber at a number of implants of 37.5 cords/5 cm.

Two polyester fiber cords of polyester IΔ゛, cord 15000 are aligned and twisted, the number of first twists is 40 times/10cm, and the number of first twists is 40 times/1.
A twisted cord with a twist coefficient K of 2191 was created.

After pretreating this cord using a polyester adhesive "Vulkabond E" manufactured by Vulnax, the RFL
Treated with adhesive, heat treated at 235°C under tension of 0.5 g/d, elongation rate under load of 2.25 g/d is 4.8%,
An adhesive-treated cord having a dry heat shrinkage rate of 4.5% at 150°C was produced. 50 of these processing codes/5 cn+
It was embedded in unvulcanized rubber with the number of implants.

In each of these tires, the belt cords reinforcing the belt layer intersect with each other at 20'' in the tire circumferential direction for both the upper and lower layers, a = 35 mm, b = 25 mm, l = 1
40 dragon, H = 142mm steel cord.

Tire size is 195/70 R14, rim is 14x5
%-JJO was used.

For each of the above tires, plysteer was measured based on the automobile tire uniformity test method JASOC607, and the results shown in FIG. 9 were obtained.

In Figure 9, those plotted with ☆ are α, ±αz
This is a conventional radial tire with a diameter of 90. As is clear from this figure, tires with a large average value β of angles α3 and α2 of 95” or more have less plysteer than conventional radial tires. It can be seen that straight running performance is improved even without adding a belt layer.

Tires with an angle average value β smaller than 90° have larger plysteer than conventional radial tires.

Experimental Example 2 The carcass layer shown in FIGS. 1 (A), (B) and 2 has the structure of JEJ, and the average value β of the sum of the angles of the carcass cords reinforcing the upper and lower carcass layers is set to 100. °
We made prototype radial tires in which the difference (α2-α1) was set constant and the difference (α2−α1) was varied.

Two types of carcass layers were used: a layer using a non-twisted polyamide fiber cord (ε=2) made of monofilament in Experimental Example 1 and a layer using a polyester fiber cord.

The reinforcing cords of the belt layer of each tire intersect with each other at 20' in the tire circumferential direction for both the upper and lower layers, and a = 35 mm.
, b = 25mm, jl! =14(ha,
A steel cord with H=1421 m was used.

Tire size is 195/70HR14, rim is 14x5
%-JJO was used.

For each of the above tires, plysteer was measured based on the automobile tire uniformity test method JASOC607, and the results shown in FIG. 10 were obtained.

In Figure 10, those plotted with ☆ are α1 =
A conventional radial tire with αz=90' is shown.

As is clear from this figure, tires with an angle difference (α2 - α1) of 10" or more have less plysteer than conventional radial tires, and can improve straight running even without adding a belt layer. There is.

Furthermore, it can be seen that tires with a negative angle difference (α2-α1) have larger pliesteer than conventional radial tires.

Experimental Example 3 It has the structure of the carcass layer and belt layer shown in Fig. 1 (^), (B) and Fig. 2, and the average value β of the sum of the carcass cord angles reinforcing the upper and lower carcass layers is 100°, Difference (α
2-αl) was kept constant at 30°, and prototype radial tires were produced in which the overlap width a between the upper carcass layer and the belt layer was varied.

Two types of carcass layers were used: a layer using untwisted polyamide fiber cord (ε=2) made of a single monofilament as in Experimental Example 1, and a layer using polyester fiber cord.

For each tire, the belt cords that reinforce the belt layer intersect with each other at 20 degrees to the tire circumferential direction for the upper and lower layers, and b =
A steel cord of 25 m, l = 1401 m, and H = 142 was used.

Tire size is 195/70 R14, rim is 14x5
'A JJ's was used.

For these radial tires, the air pressure is 2.1kIr/
A high-speed indoor durability test was conducted under cI+1 to measure high-speed durability, and the results shown in the mm diagram were obtained.

The drum diameter used for this high-speed indoor durability test was 1707 m.
, the load is 550 kg, and the running conditions are FMVSS10.
9. However, the running speed is 81 km/
hr and 8km/h every 30 minutes until the tire breaks.
Increased speed by r.

As is clear from Fig. mm, it can be seen that tires with an overlapping width a of 1 (hn or more) have significantly improved high-speed durability.

Experimental Example 4 The structure of the carcass layer and belt layer shown in FIGS. 1(A), (B) and 2 was used, and the average value β of the sum of the carcass cord angles reinforcing the upper and lower carcass layers was 102°, Difference (α
2-α1) was kept constant at 28″, and radial tires were prototyped in which the height b of the bead side end of the upper carcass layer was varied.

Two types of carcass layers were used: a layer using untwisted polyamide fiber cord (ε-2) made of a single monofilament as in Experimental Example 1, and a layer using polyester fiber cord.

The upper and lower belt layers of each tire intersect with each other at an angle of 20'' in the tire circumferential direction, and have an ax of 35 m.

A steel cord with ff = 140+m and H = 142mm was used.

Tire size is 195/70 R14, rim is 14x5
'A JJ's was used.

Air pressure 2.1kg/- for these radial tires
The load durability was measured by a high-speed drum load durability test under the above conditions, and the relationship between the bead side end height of the upper carcass layer and the tire cross-sectional height ratio b/H as shown in FIG. 12 was obtained.

The conditions for this indoor drum load durability test were: drum diameter: 1707 mm, speed: 80 km/hr, initial load: 525 kg, and the load was increased by 100 kg every 5 hours.

From FIG. 12, it can be seen that when the b/H ratio is 0.3 or less, extremely good load durability is exhibited.

Experimental example 5 Radial tire A configured under the conditions shown in Table 1.

B, C, D, E, and F were prototyped respectively. In both cases, the belt layers had a relationship in which the upper and lower belt cords intersected each other at 20' with respect to the tire circumferential direction.

Tire size is 195/70 R14, rim is 14x5
%-JJO was used. Among these tires, A is a conventional radial tire that uses polyester fiber cord as the carcass cord, and B and C are tires that use untwisted polyamide fiber cord (ε = 2) made of a single monofilament as the carcass cord. Invention radial tire D has the same structure as B, and the aspect ratio of the carcass cord is ε=
A radial tire of the present invention using a code of 3, E is B
, using the same carcass cord as C, the angle difference (α2−α1
) is negative, the comparative tire IF uses an untwisted polyamide fiber cord made of a single monofilament as the carcass cord, but the aspect ratio ε of the cord is 1.0.
This is Comparative Tire 2.

(Margins below actual text) The following tests were conducted on each of the above tires.

10 Reaction force when riding over a bump due to indoor drum driving as a substitute for ride comfort, ■ Cornering power (cornering force when a slip angle of 2″ is applied to the tire) as a substitute for steering stability, ■, Low Transfer resistance due to indoor drum running as a substitute value for fuel efficiency, ■ JASO automobile tire uniformity test method
Plysteer based on C607.

The tire pressure in the above tests r, n, and m was 1.9 kg.
/c++! , or the tire pressure in the test ■ is JA
In accordance with SOC607.

Test 1. II and I are expressed as a ratio with conventional tire A as 100, and test ■
When expressed in kg, it was as shown in Table 2.

(Blank below actual text) Table 1-"- Note) For ride comfort and uniformity, smaller values are better; for other values, larger numbers are better.

From Table 2, radial tire B according to the invention.

Both C and D have significantly improved plysteer compared to conventional radial tires, as shown in test (2), and are also lighter and have further improved fuel efficiency, as shown in test (2).

Moreover, despite these conditions, Test I.

As shown in (2), it can be seen that the ride comfort and steering stability are improved compared to conventional radial tires.

〔Effect of the invention〕

According to the present invention, without adding another belt layer, it is possible to specify a carcass layer with a specific layer configuration, a cord arrangement in this carcass layer and a cord arrangement in a belt layer, and to apply a single filament to the carcass layer. By applying a non-twisted polyamide fiber cord, the radial tire maintains a high level of handling stability, and has outstanding high-speed durability, load resistance, straight-line running stability, and side cut resistance. It can be a lightweight pneumatic tire.

[Brief explanation of the drawing]

FIG. 1(A) is a partially cutaway half-section perspective explanatory view of a radial tire according to an embodiment of the present invention, and FIG.
A) A meridian direction half-section explanatory diagram of the radial tire, 2nd
The figure is a developed view showing the laminated state of the carcass layer and belt layer constituting the tire of FIG. 1, and FIG. FIG. 4 is a developed view showing the laminated state of the carcass layer and belt layer of a comparative tire not according to the present invention, FIG. 5 is a relationship diagram between running distance and lateral force of a radial tire, and FIG. (A) and (B) are model diagrams showing the state of deformation of the belt layer, Fig. 7 (A) and (B)
and FIG. 8(A). (B) is a cross-sectional explanatory diagram showing the shape of a non-twisted polyamide fiber cord made of a single monofilament used in the present invention and a contrasting polyamide fiber cord, FIG. 9 is a relationship diagram between plysteer PS and angle average value β, Figure 10 is a relationship diagram between plysteer PS and angle difference (α2-α1), mm diagram is a relationship diagram between high-speed durability and overlapping width a, and Figure 12 is a relationship diagram between load durability and ratio b/H. It is a relationship diagram. DESCRIPTION OF SYMBOLS 1... Tread part, 3... Bead part, 4u... Upper carcass layer, 4d... Lower carcass layer, 5u...
Upper belt layer, 5d...lower belt layer.

Claims (1)

[Scope of Claims] A pneumatic tire in which two belt layers are laminated and arranged on the outside of the carcass layer of the tread portion, the angle of the belt cord with respect to the tire circumferential direction is 15 to 30 degrees, and the cords intersect with each other between plies. , the following requirements (a), (b) and (
A pneumatic tire that satisfies c). (a) The carcass layer is composed of two layers, an inner layer and an outer layer, and both ends of the inner carcass layer are folded back and rolled up from the inside of the tire to the outside around a pair of left and right bead wires, and the outer carcass layer is rolled up from the inside of the tire to the left and right in the width direction at the tread portion. It is divided into two parts and separated from each other, and the end on the tread side is overlapped with the belt layer with a width of 10 mm or more, and the end on the bead side is separated from the bead toe by 0.5 mm of the tire cross-sectional height.
(b) from the side where the belt cord reinforcing the belt layer adjacent to the outer carcass layer has an acute angle with respect to the tire circumferential direction; When measuring the angles of the carcass cords with respect to the tire circumferential direction that reinforce the carcass layer, 1/2 (α_1+
α_2) is between 95° and 120°, and the difference (α_2−α_
(1) These two inner and outer carcass layers are arranged so that the angle is 10° to 60°, and (c) The carcass cord of these two inner and outer carcass layers is made of untwisted polyamide made of a single monofilament. It is composed of fibers, and its cross-sectional shape is the ratio of the major axis h to the minor axis k
1.5 or more, and the monofilaments are arranged in parallel with the major axis direction being parallel to the belt layer.