JPH01285404A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve a fastening effect of a shoulder portion and to uniformalize ground pressure by specifying the distances between points of the respective tread surfaces on the equator at the time of charging the standard internal pressure and charging 10% of the standard internal pressure, the distance between points at designated positions on both tread surfaces and the ratio thereof. CONSTITUTION:The tread surface at the time of charging the standard internal pressure is let be Tn, the tread surface at the time of 10% of the standard internal pressure is let be Ts, and the distance LA between the points where the respective tread surfaces intersect the equator, that is, the standard first point An and the 10% first point As is let be 1.0mm or less. The radial distance LC between a point Cn positioned 0.9 times as long as the tread width TWn from the point An on the tread surface Tn and a point Cs where the radial line passing the point Cn and the tread surfaces Ts intersect each other is set with in the range of 1.0mm to 4.0mm both inclusive. Further, LC/LA is let be 4.0 or more. By this arrangement, the hoop effect in a shoulder portion can be improved and the ground pressure on the ground surface can be uniformalized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic tire that can improve tire performance such as wear resistance, uneven wear resistance, and fuel efficiency in a well-balanced manner.

[Prior art]

In recent years, tires with a radial structure in which carcass cords are arranged substantially perpendicular to the tire's equator plane have been widely used as they have excellent wear resistance, handling stability, and the like. In addition, in such radial tires, by providing a relatively rigid so-called belt layer surrounding the outer surface of the carcass and having organic or inorganic cords arranged at a relatively small angle with respect to the equatorial plane of the tire, It gives a hoop effect to the tires.

On the other hand, conventionally, the shape of such radial tires is set so that the tire molded in a vulcanization mold has a so-called natural equilibrium shape in which the carcass does not deform even when a standard internal pressure is applied. has been done.

Here, the natural equilibrium shape refers to the carcass profile determined by the natural equilibrium shape theory, and this natural equilibrium shape theory is defined by the Honkoaverse.

)1offerberth ) is )(autsch
, Gun+mi (8-1955, 124-130
), and this theory considers the belt layer located in the tread part of the tire to be a rigid ring that does not deform when filled with internal pressure, and the relationship between this belt layer and the other bead core that does not deform. It is intended that the carcass disposed between the two and extending from the sidewall part to the bead part be pre-formed using a vulcanization mold into a shape that will not be deformed even by filling with the internal pressure.

The carcass profile based on this natural equilibrium shape theory is intended, as mentioned above, to prevent deformation of the carcass due to internal pressure filling, that is, to apply tension uniformly to the carcass cord.

This Honkoaverse theory is about bias tires, but Mr. Akasaka writes, "About the cross-sectional shape of radial tires," Journal of the Japan Society for Composite Materials, Vol. 3.
．． 4 (1977), 149-154, it has been extended to be applicable to radial tires as well.

Regarding the application of this natural equilibrium shape theory, it is preferable to supplement at least the following two points.

First, even when the belt layer is made of metal cords, etc., it is not actually a completely rigid body, and some deformation occurs due to internal pressure.In particular, the smaller the aspect ratio of a flat tire, the more the carcass is pushed up due to internal pressure filling. The belt layer tends to be deformed due to

Secondly, near the bead, the folded part of the carcass,
The bead apex and other reinforcing layers provide high rigidity, so in the range from the bead core to the inflection point of the carcass profile, usually called the rim point, that is, the equivalent bead position, the natural equilibrium shape theory does not fail.
Therefore, the curve based on this theory should be considered with the above-mentioned equivalent and one-do position as the starting point.

However, in a radial tire with a carcass profile based on the natural equilibrium shape theory, especially in a tire with a relatively high aspect ratio and a carcass shape that is close to circular,
As shown in FIG. 8, even when the standard internal pressure is filled, the outward deformation in the radial direction between the carcass 6 and the belt layer 7, especially in the vicinity of the end of the belt layer 7, is small in the shoulder part of the carcass 6. Due to certain reasons (natural equilibrium shape theory assumes that there is no elongation of the carcass due to internal pressure filling, in reality the carcass elongates slightly, and the carcass profile according to this natural equilibrium shape theory swells to a substantially similar shape), The bonding force between the carcass 6 and the belt layer 7 due to pressing is not very large, and the binding force between the carcass 6 and the belt layer 7 is poor.

Therefore, in the belt layer 7, especially near the ends, the carcass 6
It is difficult for the tension that acts on the belt layer 7 to act on the belt layer 7, and the belt layer 7 cannot exhibit the necessary hoop effect. As a result, the surface shape of a portion of the shoulder of the tread tends to become uneven, and combined with the reduction in the restraining force of the belt layer 7, uneven wear occurs when the tire runs, which deteriorates the wear resistance. In particular, in highly flat tires with a high aspect ratio, spot wear is more likely to occur, in which areas of the tread with low ground pressure and large slippage with the road surface are partially worn. Furthermore, as the amount of bending in the radial direction that acts on the belt layer 7 during rolling increases, the stress that acts on the belt N7 increases, which increases rolling resistance and impairs fuel efficiency.

Therefore, the present applicant disclosed in Japanese Patent Application No. 61-252465 that when the tread surface is filled with standard internal pressure, the radius of curvature of the tread surface becomes large, and a part of the shoulder protrudes outward in the radial direction. Based on 27, which increases the
By applying the tension of the carcass 6 smoothly to the belt layer 7 and increasing the hoop effect by the bell 117, we are developing a radial tire for passenger cars that can improve wear resistance, uneven wear resistance, and fuel efficiency. I was worried. The manufacturing method for manufacturing such a radial tire for passenger cars is disclosed in the specification and drawings of Japanese Patent Application No. 13408/1983.

The present invention mainly focuses on wear resistance, fuel efficiency, etc.
The present invention was completed as a result of further research focusing on the amount of protrusion at each position on the tread surface when filling with standard internal pressure.Therefore, the present invention has been completed by focusing on the amount of protrusion at each position on the tread surface when filling with standard internal pressure. The object of the present invention is to provide a pneumatic tire that can greatly improve the performance of the tire described above compared to conventional tires.

Note that this tire has a large amount of bulge in a portion of the shoulder, thereby increasing the hoop effect in that portion and increasing the restraining force by the belt layer, thereby achieving the above-mentioned improvement effect.

As a result, as shown in FIG. 4, the contact patch shape of a conventional tire is approximately circular, and a large portion K of contact pressure exists in the crown portion centered on the tire equator, whereas the present invention In this tire, as shown in Fig. 5, the area of the contact patch is large and the shape is approximately square, and K is present at the side edge, that is, the shoulder part, where the contact pressure is large.
This makes it possible to achieve the effects described above.

However, in order to further improve tire performance, in addition to improving the ground contact pressure at the shoulder part, it is also necessary to maintain an appropriate level of ground pressure at the crown part, thereby approximately equalizing the ground contact pressure as a whole. was found to be more preferable.

Therefore, the present inventors further developed the tread surface shape and the tread thickness at each position from the viewpoint of making the ground pressure uniform. As a result, by making the tread surface a so-called double-radius arc with different radii of curvature at the crown and shoulder areas,
As shown in Fig. 6, a tire having a relatively large ground contact surface having an approximately angular shape and a large part K of ground contact pressure in the crown portion is formed with scales and a tread surface having the shape of the contact patch shown in Fig. 6. The inventors have discovered that by combining the above-mentioned method shown in FIG. 5, the ground pressure distribution can be made relatively uniform, as shown in FIG. 7, and the tire performance can be further improved.

Accordingly, an object of the present invention is to provide a further improved pneumatic tire that can enhance the hoop effect in a portion of the shoulder and equalize the ground contact pressure on the ground contact surface.

[Means to solve the problem]

The first invention is the tread surface T when filled with standard internal pressure.
a standard first point An, which is a point on the tire equator at n;
Tread surface Ts when filled with 10% internal pressure of standard internal pressure
The first point-to-point length LA, which is the distance in the radial direction from the 10% first point As, which is a point on the tire equator, is 1. On
Tread width T when filled with standard internal pressure, smaller than +n
a standard third point Cn, which is a point on the tread surface Tn separating 0.9 times Wn from the standard first point An;
The third point length LC, which is the radial distance between the radial line passing through this point Cn and the 10% third point Cs, which is the point where the radial line intersects with the tread surface Ts, is 1.0 mm or more and 4.0 days. This is a pneumatic tire in which the ratio LC/LA of the third point-to-point length LC and the first point-to-point length LA is 4.0 or more.

A second invention is the pneumatic tire according to claim 1, in which the standard first point An and 0.5 times the tread width TWn when filled with a standard internal pressure are centered around the standard first point An. The standard inner radius R is the radius of curvature of an arc passing through the standard second point Bn, which is a point on the tread surface Tn that is separated by
Cn, the standard first point An, and the standard third points Cn on both sides.
The ratio of the standard outer radius RSn, which is the radius of curvature of the circular arc passing through RCn/RSn, is the common logarithm value fog10(RC
n/RSn) is 0.1 or more and 0.7 or less, and the standard inner radius RCn is the tread width TWn when filled with standard internal pressure, the tire height Hn when filled with standard internal pressure, and the tire maximum width S. Ratio to W n Hn/S W
2 of the value TWn/S divided by the tire aspect ratio S, which is n.
7 times or more and 5.0 times or less, and the first point A
The absolute value Ia-bI of the difference between the tread thickness a at point n and the tread thickness b at the standard second point Bn is 0.3 mm.
The thickness b - c obtained by subtracting the tread thickness C at the standard third point Cn from the tread thickness b is 0.5 m.
m or less and 3.0 mm or less, and when filled with the standard internal pressure, the standard fourth point En on the sidewall 30 degrees apart in the radial direction from the lower end of the bead and 10% of the standard internal pressure.
The length LE between the fourth points, which is the axial distance from the 10% fourth point ES at the same position when filled, is 1. It is a pneumatic tire with a diameter of 0mm or less.

[Effect]

As a result of having such a structure, the amount of change in the external bulge of a part of the shoulder becomes larger than that of the crown part, and therefore, as the internal pressure fills, the carcass pushes up the belt layer, especially near the part of the shoulder, and the carcass and the belt layer This makes it possible to increase the bonding strength of the belt layer and apply the tensile force acting on the carcass, particularly to the ends of the belt layer. Therefore, the hoop effect of the belt layer is enhanced. As shown in FIG. 5, the shape of the contact patch is such that K exists in a part of the shoulder of the tire where the contact pressure is large, and the area of the contact patch can be increased. the result,
In addition to improving wear resistance and reducing uneven wear such as spot wear resistance, it also improves fuel efficiency by reducing rolling resistance, increases wet braking performance, and increases cornering force, cornering stability, straight-line stability, etc. It can improve handling stability.

Further, in the second invention, the standard inner radius RCn is set to 2.7 times or more and 5°0 times or less of the value TW n /S obtained by dividing the tread width TWn by the aspect ratio S when filled with the standard internal pressure. do. This is the radius of curvature of the circular arc of the crown portion with respect to the unit tread width in the shape of the tread surface Tn when the standard internal pressure is filled, that is, the standard inside radius RC.
n will be optimized. Moreover, this is the same as properly determining the radius difference between the standard first point An on the tire equator and the standard third point Cn on the shoulder side, and this value is determined by taking into account the aspect ratio S. By doing so, the functions and effects of the first invention are enhanced.

Further, in the second invention, the common logarithm value of the ratio of the standard inner radius RCn to the standard outer radius RSn is set to be 0.1 or more and 0.7 or less.

As a result, as explained in FIG. 6, when the standard internal pressure is filled, the requirement is added that the ground contact surface is relatively large and the crown part has a double radius shape with a portion K where the ground pressure is large. becomes. With this addition, as shown in FIG. 8, it is possible to provide a substantially uniform ground pressure distribution over the entire ground plane.

Furthermore, the difference between the tread thicknesses a and b at the first standard point An and the second standard point Bn is set to 0.3 mm or less, and the tread thickness C at the third standard point Cn is subtracted from the tread thickness b. Thickness b - c is 0.5 mm or more and 3.
0 mm or less. By slightly reducing the tread thickness at a portion of the shoulder in this manner, it is possible to increase the force for pushing up the portion of the shoulder described above, optimize the tread surface shape, maintain a preferable double radius shape, and enhance the above-mentioned effect.

Further, the axial distance LE between the standard fourth point En and the 10% fourth point ES is set to 1.0 mm or less. This prevents an increase in the rigidity of the bead portion due to internal pressure filling and prevents a decrease in riding comfort. As mentioned above, the deformation of a part of the shoulder increases the hoop effect, which tends to reduce ride comfort. Conventionally, the deformation at this position was relatively large, but if the LE is 1.0 or less By doing so, it is possible to effectively prevent a decrease in riding comfort.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1 illustrating a case where a pneumatic tire 1 is mounted on a standard rim 10 and filled with air at a standard internal pressure, for example, 2.1 kg/afl, the tire 1 has bead portions on both sides through which bead cores 2 pass. 3.3, a sidewall portion 4.4 extending radially outward from the bead portion 3, and a tread portion 5 connecting both ends thereof, and the sidewall portion 4 and the tread portion 5 include the bead core 2. The main body of the carcass 6, which is folded back from the inside to the outside, is straddled. Further, a belt N7 is arranged on the outside of the carcass 6 on the tread part 5, and a bead apex 9 is arranged between the main body part of the carcass 6 and its folded part.
On the other hand, this tire 1 has a so-called standard rim 1.
The bead portion 3 is fitted to the rim 10 by fitting the bead portion 3 into the flange 11.11 of the rim 10.

The carcass 6 is a so-called radial cord arrangement body in which cords are arranged at an angle of about 80° to 90° with respect to the tire equator CL, and organic fibers such as nylon, polyester, rayon, and aromatic polyamide fibers are used as the cords. be done. Note that inorganic fibers such as metal may also be used, and the carcass 6 may be made of one to three ply layers.

The belt layer 7 is, for example, a two-layer structure consisting of a first ply 7A disposed on the carcass 6 side and a second ply 7B above it, and both the first and second plies 7A and 7B are made of metal cords. Moreover, each tire is arranged at a relatively shallow angle with respect to the tire equator CL and inclined in the opposite direction. Further, the first ply 7A is wider than the second ply 7B, and both ends of the first ply 7A extend below the edge where the sidewall portion 4 and the tread portion 5 intersect.

In addition, in the tire 1 of this example, when the standard internal pressure is filled, the distance is from the lower end of the bead portion 3 to the highest point on the tread surface Tn, which is the standard first point, which is usually a point on the tire equator CL on the tread surface Tn. The tire is formed in a slightly flat shape with a ratio of the tire height Hn to the tire maximum width Wn smaller than 1, for example about 0.9.

Furthermore, Tire 1 was filled with standard internal pressure as shown in Figure 2, where the solid line indicates the case where the standard internal pressure was added and the broken line indicates the state where 10% of the standard internal pressure (hereinafter referred to as 10% internal pressure) was added. As described above, the point on the tire equator on the tread surface Tn is the standard first point An, and the tread surface is separated by a length 0.5 times the tread width TWn on both sides centering on the standard first point An. The point on Tn is the standard second
Point Bn, similarly 0.9 times the tread width is the standard first point An
A point on the tread surface An separated from the center is defined as a standard third point Cn. Also, the point on the tire equator on the tread surface Ts when filled with 10% internal pressure is the 10% first point As.
In addition, the point where the radius line passing through the standard second point Bn intersects with the tread surface Ts when filled with 10% internal pressure is the 10% second point Bs, and the radius line passing through the standard third point Cn is the tread surface Ts. The point where it intersects is defined as the 10% third point Cs.

Tire 1-'' has the standard first point An and the 10% first point A.
The length LA between the first points, which is the radial distance between s, is 1
．． It is assumed to be smaller than 0 mm. Furthermore, the third point-to-point length LC, which is the radial distance between the standard third point Cn and the 10χ third point Cs, is set to 1. ON or more and less than 4.0 Peng, and the ratio L of the third point-to-point length LC and the first point-to-point length LA
C/LA is 4.0 or higher.

In this way, in the crown portion which is the range between the standard second point Bn sandwiching the standard first point An, the amount of deformation of the tread surfaces Ts and Tn between the 10% internal pressure and the standard internal pressure is made small, while The amount of outward bulge in the radial direction in a portion of the shoulder near the standard third point Cn, that is, the length LC between the third points, is increased. As a result, as the internal pressure is filled, the carcass 6 pushes up the belt layer 7, especially near the ends, thereby increasing the bonding force between the carcass 6 and the belt layer 7, and reducing the tensile force acting on the carcass 6, especially at the ends of the belt layer 7. This makes it possible to increase the hoop effect of the belt layer 7.

As a result, as shown in FIG. 5, the ground plane has a relatively large substantially rectangular shape, and a portion K having a large ground pressure can be located in a part of the shoulder. As a result, wear resistance can be reduced, and uneven wear such as drop-off wear, spot wear, and two-tooth wear can be reduced. It also reduces rolling resistance and improves fuel efficiency.
Improves wet braking performance. It also improves handling stability, such as improved steering response, cornering force, cornering stability, and straight-line stability.

In the present invention, with respect to the length LA between the first points, the standard first point An is reduced by 10% to the first point A by filling with the standard internal pressure.
It also includes a case where the deformation occurs inward in the radial direction of s, as if the diameter is reduced.

Also, the ratio LC/L of the third point-to-point length LC and the first point-to-point length LA
When A is smaller than 4.0, the above-mentioned functions and effects cannot be fully exhibited.

Furthermore, the radius of curvature of the circular arc passing through the standard first point An and the standard second points Bn on both sides is defined as the standard inner radius RCn, and the circular arc passing through the standard first point An and the standard third points Cn on both sides. The radius of curvature of is defined as the standard outer radius R3, and the standard inner radius R
The ratio of Cn to the standard outer radius R3 is the common logarithm (!fog+) of the ratio RCn/RS n.

(RCn/RS'n) is set to 0.1 or more and 0.7 or less. Note that this means that the ratio RCn/RSn is approximately 1
It is in the range of 36° to 5.01°.

In this way, by making the standard outer radius RSn smaller than the standard inner radius RCn within the range of the ratio, the curvature of the circular arc that passes through a portion of the shoulder increases. Therefore, the crown portion of the tread surface Tn is formed by an arc with a large radius of curvature, and a portion of the shoulder is formed by an arc with a small radius of curvature, resulting in a so-called double-radius shape. This is the 6th
As shown in the figure, these are the conditions for the ground plane to have a hexagonal shape and for the crown portion to have a large portion K of ground pressure.By adding these requirements in addition to the above conditions, As shown in Figure 7, on the ground plane,
This makes it possible to obtain a tread surface shape with a nearly uniform ground pressure distribution. Furthermore, this further improves the above-mentioned wear resistance, handling stability, and fuel efficiency.

In addition, the common logarithm value fog+o (RCn/RSn) is set to 0.
．． The reason why it is set to be 1 or more is because if it is smaller than this, the above characteristics as a double radius cannot be exhibited. Also 0.
When it exceeds 7, the standard outer radius RSn becomes excessively small compared to the standard inner radius RCn, and the radius of curvature of the circular arc of a part of the shoulder decreases. The effect of invention No. 1 is inhibited. It is also preferable to change this value depending on the aspect ratio S, and when the aspect ratio S is up to 0.8, the value is changed to 0.
゜10~0.40, 0.25~ for aspect ratio S up to 0.6
0°55, and when the aspect ratio S is 0.6 or less, it is preferably about 0.35 to 0.65. As described above, as the aspect ratio S decreases and the tire becomes flatter, the radius RCn/RSn is increased because the tire maximum width SWn becomes relatively larger than the tire height Hn due to the flattening. This is because by increasing the amount of deflection at the time of contact with the ground on the tread surface Tn, the amount of deflection at the time of contact with the ground increases, making it easier to contact the ground with a portion of the shoulder.

The standard inner radius RCn is equal to 2.0% of the value T W n /S obtained by dividing the tread width TWn by the ear aspect ratio S.
It is set to be 7 times or more and 5.0 times or less.

By setting the standard inner radius RCn within the above range, this value is useful for optimizing the shape of the tread surface Tn, increasing the amount of bulge in a portion of the shoulder, and enhancing the hoop effect of the portion of the shoulder. This is to determine the standard inner radius RCn for the tread width TWn, and this also means the radius for the tread width per unit length. Therefore, this value is the radius between the standard third point Cn and the standard first point An. The radius difference will be determined qualitatively. In addition, by adjusting this value using the aspect ratio S, the amount of bulge in the shoulder portion due to filling with the standard internal pressure is increased, contributing to an increase in the hoop effect in a part of the shoulder, and the tread surface T
Optimize the shape of n. Note that when this value is smaller than 2.7, the standard outer radius RS for the tread width
As n becomes small, the amount of bulge in a portion of the shoulder tends to be excessive, and it becomes difficult to ground the portion of the shoulder. Also 5.0
If it is larger than 1, the tread surface becomes excessively flat, and the ground contact pressure at a portion of the shoulder becomes excessively large.

Regarding the tread thickness distribution, the absolute value 1a-bI of the difference between the tread thickness a at the standard first point An and the tread thickness b at the standard second point Bn is 0.3 mm or less and the tread thickness b The thickness b-C obtained by subtracting the tread thickness C at the standard third point Cn from the tread thickness b-C is set to be 0.5 mm or more and 3.0 M or less, preferably about 1°3 to 3.0 mm.

In this way, the absolute value of the difference between the tread thicknesses a and b is 0.
．． It should be approximately uniform and approximately 3 mm or less. Also, the thickness b − c obtained by subtracting the tread thickness C from the tread thickness b
0.5 mm or more and 3.0 mm or less, and in this way, by reducing the tread thickness C at the standard third point Cn portion, the amount of swelling of a part of the shoulder due to internal pressure filling is increased, and the preferred double The tread surface shape can be a radius. Note that the tread thickness here is a value measured from the tread surface Tn to the upper surface 7a of the belt N7 in a direction perpendicular to the tread surface Tn. Further, when the thickness b-'c is smaller than 0.5 am,
If the tread thickness becomes excessively uniform at each position, resulting in inferior effects described above, and exceeding 3.0ff111, the strength in a part of the shoulder will decrease, impeding durability, etc., and the amount of bulge in this part will decrease. is too large, making it difficult to scale the preferred double radius shape.

Such a tire 1 can be manufactured using a vulcanization mold having an inner piece shape that intentionally deviates from the natural equilibrium shape theory.

Note that, depending on the natural equilibrium shape theory, the carcass profile can be determined by the following equation.

Here, as shown in FIG. 9, D: An intersection point where a perpendicular line X extending radially from the end d of the belt layer 7 and perpendicular to the axle axis Z, that is, the Z axis in this example, intersects with the carcass 6B.

C: Maximum position of the carcass.

r: Height in the tire radial direction from the Z-axis (r-axis in this example)
.

rThe height in the radial direction from the CrZ axis to the point C on the carcass 6.

rDr Height in the radial direction from the Z-axis to the above-mentioned intersection of the carcass 6.

ΦD: An angle between the normal Y of the carcass 6 and the Z axis at the intersection.

Note that the Z axis may be replaced by a line passing horizontally through the bead bottom 3A, and in equation (1), it is determined that the carcass 6 forms an arc at least near the end of the belt layer 7. In addition, formula (1) is obtained with the intersection 0 of the r-axis passing through the intersection and the Z-axis as the origin,
In this way, by giving the height r, the horizontal deviation position from the r axis, that is, the Z value, can be calculated, and the curve according to the natural equilibrium shape theory can be obtained.

In the natural equilibrium shape theory, as is clear from equation (1), when the positions of the heights rC and rD and the angle ΦD are given, the curve is determined. In addition, point C 2
When the values are given in advance, by giving one of the angle ΦD and the height rC, the other can be found.

On the other hand, the tire 1 of the present invention has a molded tire 1 formed using a vulcanization mold.
The height in the radial direction from the bead bottom 3A is made smaller than the height in the natural equilibrium shape theory, and the carcass profile is formed into a downwardly bulging shape.

Also, this height is 3% relative to the molded tire height Hn.
5 to 55%, and the ratio of the maximum of force/-scasses 6 is 1 to 55% compared to the maximum of the natural equilibrium shape theory.
The basic idea is to make it large within the range of 1.1, and in this way,
The tire 1 of the present invention can be produced by removing the natural equilibrium shape.

Furthermore, in the tire of this example, when the standard internal pressure is filled, a point on the sidewall that is 30 mm apart in the radial direction from the lower end of the bead, which is the standard for the rim diameter, is
Standard 4th point En and 10% when filling with 10% internal pressure
The fourth point ES is defined, and the axial distance LE between these two points is 1.
0 mm or less.

As a result, it is possible to maintain and improve ride comfort, which tends to decrease due to an increase in tire rigidity due to a large change in the outward bulge of a portion of the shoulder.

[Specific Example 1] A tire with a tire size of 5.60R13 having the structure shown in Figure 1.2 was prototyped according to the specifications shown in Table 1, and a rim 4-JX
Installed on 13. Note that a 2N ply of steel cord is used as the belt layer 7, and the carcass is formed of one ply of polyester cord. In addition, the dimensions of each part, such as the standard 1st point An, the standard 3rd point Cn, and the 10% 1st point AS to 10% 3rd point Cs, were measured using a laser displacement measuring device at the time of standard internal pressure filling and 10% internal pressure filling, respectively. It was calculated from the drawing by drawing the cross-sectional contour of the tire. Note that the tread thicknesses a, b, and c were measured by cutting the tire after measuring the dimensions.

Figure 3 shows the results of installing this tire on the rear wheel of a 1800cc FF car, adding 4M of toe-in, and driving once every 50,000. It can be seen that in Example 1, the traveling distance per unit thickness is relatively large, and the spot wear rate is low.

Rolling resistance was also measured using a rotating drum.

The drum was rotated at a rotation speed corresponding to a speed of 80 km/hour, and the resistance value (kg) at that time was expressed as an index with Comparative Example 1 set as 100. The smaller the number, the smaller the rolling resistance. As shown in Table 1, it can be seen that the Example Product 1 has low rolling resistance and improved fuel efficiency.

It is also installed on the four wheels of a 1500cc FF car, and the speed is 60 km.
The wet braking performance was measured by the distance traveled until the vehicle stopped when the vehicle was driven on a wet asphalt road and the tires were locked. The distance to a stop is shown as an index with Comparative Example 1 set as 100. As shown in Table 1, Example Product 1 is superior.

(Specific Example 2) Similarly, a tire with a tire size of 205/60R1487H was prototyped according to the specifications shown in Table 2, and 51/2JJx14
The rolling resistance and wet braking performance were measured in the same manner as above, and the results are also shown in Table 2. In addition, a 2000 cc F was used to measure wet brake performance.
I am using an R car.

Furthermore, it was installed in a 2,000 cc front-wheel drive vehicle, driven on a test course, and the steering response, cornering limit height, stability near the cornering limit, and high-speed straight-line stability performance were measured through a driver's feeling test. It is shown by an index with Comparative Example 1 set to 3. It can be seen that the larger the numerical value, the better the result, and that the Example Product 2 was excellent in all cases.

(Effects of the Invention) As a result of having such a configuration, the amount of change in the external bulge of the part of the shoulder is larger than that of the crown part, and therefore, as the internal pressure is filled, the carcass pushes up the belt layer, especially in the vicinity of the part of the shoulder. It is possible to increase the bonding force between the carcass and the belt layer, and to apply the tensile force acting on the carcass, especially to the ends of the belt layer.Therefore, the hoop effect of the belt layer is enhanced.The shape of the ground contact surface is shown in Figure 5. As shown, K exists in a part of the shoulder of the tire where the ground pressure is large, and the area of the contact patch can be increased.As a result,
In addition to improving wear resistance and reducing uneven wear such as spot wear resistance, it also improves fuel efficiency by reducing rolling resistance, increases wet braking performance, and increases cornering force, cornering stability, straight-line stability, etc. It can improve steering stability.

Further, in the second invention, the standard outer radius RSn is set to 2.7 times or more and 5°0 times or less of the value TW n /S, which is the tread width TWn when filled with the standard internal pressure, expressed by the aspect ratio S. do. This is the radius of curvature of the circular arc of a part of the shoulder with respect to the unit tread width in the shape of the tread surface Tn when the standard internal pressure is filled, that is, the standard outer radius R.
This will optimize Sn. This also means that the standard first point An on the tire equator and the standard third point Cn on the shoulder side
This is the same as properly determining the radius difference between the two, and by determining this value in consideration of the aspect ratio S,
Enhance the functions and effects of the invention.

Further, in the second invention, the common logarithm value of the ratio of the standard inner radius RCn to the standard outer radius RSn is set to be 0.1 or more and 0.7 or less.

As a result, as explained in FIG. 6, when the standard internal pressure is filled, the requirement is added that the ground contact surface is relatively large and the crown part has a double radius shape with a large part K of ground pressure. Become. With this addition, as shown in FIG. 8, it is possible to provide a substantially uniform ground pressure distribution over the entire ground plane.

Furthermore, the difference between the tread thicknesses a and b at the first standard point An and the second standard point Bn is set to 0.3 mm or less, and the tread thickness C at the third standard point Cn is subtracted from the tread thickness b. Thickness b - c is 0.5 mm or more and 3
．． 0 mm or less. By slightly reducing the tread thickness at a portion of the shoulder in this manner, it is possible to increase the force for pushing up the portion of the shoulder described above, optimize the tread surface shape, maintain a preferable double radius shape, and enhance the above-mentioned effect.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a diagram illustrating tire profiles at standard internal pressure and 10% internal pressure, and Fig. 3 shows the relationship between wear resistance and spot wear rate. Figures 4 to 7 are diagrams schematically showing the shape of the ground contact surface and ground pressure distribution. Figure 8 is a diagram showing a tire with a conventional structure using only the carcass and belt layer. Figure 9 is a diagram showing the tire with a conventional structure. It is a line diagram explaining an equilibrium shape. 2.-Bead core, 3.--Bead portion, 4.-Side wall portion, 5.--Tread portion, 6.-Carcass, 7.--Belt layer, 10.--Rim. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura 2nd wI Figure 153E Figure 8

Claims (1)

[Claims] 1. A standard first point An, which is a point on the tire equator on the tread surface Tn when filled with standard internal pressure, and a point on the tire equator on the tread surface Ts when filled with 10% internal pressure of the standard internal pressure. The first point length LA, which is the radial distance between the 10% first point As, which is the point, is smaller than 1.0 mm, and the tread width TWn when filled with the standard internal pressure is 0.9
and a standard third point Cn, which is a point on the tread surface Tn that separates the standard point An from the standard first point An, and a point where a radial line passing through this point Cn intersects the tread surface Ts.
%The third point-to-point length LC, which is the radial distance between the third point Cs, is 1.0 mm or more and less than 4.0 mm, and the third point-to-point length LC and the first point A pneumatic tire with a ratio LC/LA of 4.0 or more. 2. The pneumatic tire according to claim 1, wherein the tread surface is separated from the standard first point An by 0.5 times the tread width TWn when filled with standard internal pressure, with the standard first point An as the center. A standard inner radius RCn, which is the radius of curvature of an arc passing through a second standard point Bn, which is a point on Tn, and a standard radius of curvature, which is the radius of curvature of an arc passing through the first standard point An, and the third standard point Cn on both sides. Ratio RCn/R to outer radius RSn
The common logarithm value log_1_0 (RCn/RSn) of Sn is 0.1 or more and 0.7 or less, and the standard inner radius RCn is the tread width TWn when filled with standard internal pressure, and the tire height when filled with standard internal pressure. Tire aspect ratio S which is the ratio Hn/SWn of width Hn and tire maximum width SWn
2.7 times or more and 5.0 times or less of the value TWn/S divided by , and the tread thickness a at the standard first point An
The absolute value I a−b I of the difference between the tread thickness b at the standard second point Bn and the tread thickness b at the second standard point Bn is 0. 3mm or less and the standard third point C from the tread thickness b
The thickness b-c obtained by subtracting the tread thickness c at n is 0.5
mm or more and 3.0 mm or less, and when filled with standard internal pressure, the standard fourth point En on the sidewall 30 mm apart in the radial direction from the lower end of the bead and 10 of the standard internal pressure.
A pneumatic tire in which the length LE between the fourth points, which is the axial distance from the 10% fourth point ES at the same position when filled with 10%, is 1.0 mm or less.