JPH03169709A - Radial tire for passenger car - Google Patents

Abstract

PURPOSE:To improve riding sensation without deteriorating high speed stability and drive stability by setting a ratio between the height at the maximum width of a carcass and the height of a section and a ratio between the curvature of radius of an arc of a circle curved along the carcass and the maximum width of the carcass to respective specified values. CONSTITUTION:In the profile of a carcass 6 in a state that a tire 1 is filled with a normal internal pressure, a ratio h/H between height (h) at a carcass maximum width, being a radial direction from a bead base B of the tire 1 to a carcass maximum width position (a), and a carcass section height H being a radial distance from the bead base B to a carcass highmost position (b) is set to a value within a range of 0.460-0.495. A ratio R/W between a curvature of radius R of an arc of a circle extending through the carcass maximum width position (a) and a carcass position (c) of the inner edge in a radial direction of a buttress and curved along the carcass 6 therebetween and a carcass maximum width W being the distance in an axial direction of the tire in the carcass maximum width position (a) is set to a value within a range of 0.45-0.60.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radial tire for passenger cars that has improved riding comfort without impairing steering stability. [Prior Art] In recent years, as the power performance of passenger cars has improved, so-called high-performance tires that have a high rigidity that can withstand this increase are being used as radial tires for passenger cars. Such radial tires for passenger cars have excellent performance in terms of high-speed performance and handling stability, but due to the improvement in tire rigidity, they have poor envelope performance when going over bumps, impairing ride comfort. Therefore, in order to improve this riding comfort performance, attempts are being made to increase the thickness of the tread rubber or to make the tread rubber using multiple types of rubber having different viscoelastic coefficients. [Problem to be solved by the invention] However, although increasing the tread rubber thickness is useful for improving ride comfort, it has the problem of increasing internal heat generation, decreasing tire durability, and impairing rolling resistance. ．． Also, when multiple types of rubber are used, manufacturing is complicated and costs increase. The purpose of the present invention is to provide a radial tire for a passenger car, which is based on a carcass profile having a downward bulge compared to conventional tires, and which can improve riding comfort without impairing high-speed stability and handling stability. There is.

[Means to solve the problem]

The present invention provides the carcass maximum width height, which is the radial distance from the bead base B of the tire to the maximum width position a of the carcass, in a carcass profile in a normal internal pressure state where the tire is assembled on a normal rim and filled with normal internal pressure. h and the carcass cross-sectional height H, which is the radial distance from the bead base B to the highest position of the carcass.
/H to 0. 4 6 0 or more and 0. 4 9 5 or less, and the radius of curvature R of an arc passing through the maximum width position a of the carcass and the carcass position C on the radially inner edge of the buttress part and along the carcass between them, and the maximum width position a of the carcass. This is a radial tire for a passenger car, in which the ratio R/W to the carcass maximum width W, which is the distance in the tire axial direction between , and a, is 0.45 or more and 0.60 or less. [Operation] The ratio h/H of the carcass maximum width height h, which is the height of the carcass maximum width position, to the carcass cross-sectional height H is set to 0. 4 6
0 or more and 0. 495 or less. As a result, the height h of the maximum width ifa of the carcass becomes a downward bulge curved below the height center line X passing through half the height of the carcass cross-sectional height H. Therefore, the center of deformation due to the load is located below the center line X. Also, the height between the center of deformation and the ground contact surface is larger than that of conventional tires. Therefore, the amount of deformation in the radial direction of the contact patch relative to the amount of deformation in the deformed portion is greater than that of conventional tires. In this way, ride comfort is improved by reducing only the longitudinal stiffness compared to conventional tires. Furthermore, the fact that the center of deformation is located below the center line X makes the radius of curvature of the lower part smaller and increases the bending deformation, further reducing the longitudinal rigidity. In addition, the above ratio hs/ in the conventional tire
H is set to approximately 0.5 or more and 0.6 or less.

Further, in the tire of the present invention, the ratio h/W of the radius of curvature R along the carcass passing between the carcass maximum width position a and the carcass position C at the lower end of the buttress of the tire and the maximum width W is set to 0. 45 or more and 0.60 or less, which is higher than that of conventional tires. In this way, increasing the radius of curvature R in this range enables smooth deformation of the upper part of the sidewall,
In addition to improving the ride comfort of the tire, by preventing excessive local deformation, it reduces stress generation and increases tire durability. [Example] An example of the present invention will be described below based on the drawings. In the figure, a radial tire 1 for a passenger car includes bead portions 3, 3 on both sides through which a bead core 2 passes, a sidewall portion 4 extending outward in the radial direction of the tire from the bead portion 3, and a tread portion 5 joining the upper end of the sidewall portion 4. and a carcass 6 which passes from the tread portion 5 through the sidewall portion 4 and folds back around the bead core 2, and a belt layer 7 disposed inside the tread portion 5 and outside the carcass in the radial direction. I get it. Furthermore, in this example, when the tire l is mounted on the regular rim 15 and is filled with the regular internal pressure, the tire l has the tire maximum width WD between the maximum outer surface of the sidewall portion 4 and the maximum width of the tread surface from the bead base B. The ratio of the height HD of the tire up to the point, that is, the aspect ratio HD/WD is greater than 0.45 and 0.45.
It is popular as a flat tire smaller than 8. In this embodiment, the carcass 6 has two layers of carcass braai 9.
, 9, the carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire equator C. In addition to organic fiber cords such as nylon, polyester, and rayon, steel cords can also be used as car force cords. The belt layer 7 consists of belt plies 10 and l1 arranged in two layers, the inner and outer layers, and the belt ply 1 on the outer side.
The width of 1 is narrower than the width of the inner belt ply lO. The belt plies 10 and 11 each have a belt cord that is relatively small and arranged at an angle and intersecting the tire equator, and this belt cord is made of a highly elastic material such as steel or aromatic polyamide. There is. Further, the carcass profile F1 connecting the thickness midpoint of the carcass 6 of the tire 1 of the present invention in the normal internal pressure state is:
As shown by the solid line in FIG. 2 and the carcass profile F2 of the conventional tire shown by the dashed line, in the tire 1, the carcass maximum width is the radial distance from the bead base B of the tire to the maximum width position a of the carcass 6. The ratio h/H of the width height h and the carcass cross-sectional height H, which is the distance in the radial direction from the bead base B to the highest position of the carcass.
0. 4 6 0 or more and 0. 495 or less. In this way, the tire of the present invention has a carcass maximum width height h smaller than 0.5, that is, a low point on the radial inner side of the center line The maximum width position a of the carcass is located at , thereby making the carcass profile F1 a downward bulge. Note that the ratio h
In conventional tires with s/H of 0.50 or more, the tire bulges upward. In the passenger car radial tire 1 of the present invention, by bulging downward in this manner, the center of deformation due to the tire load is located below the center line X, as described above. Also, the height between the center of deformation and the ground contact surface is larger than that of conventional tires. Therefore, the amount of deformation in the radial direction of the contact patch relative to the amount of deformation in the deformed portion is greater than that of conventional tires. In this way, ride comfort is improved by reducing only the longitudinal stiffness compared to conventional tires. Furthermore, the fact that the center of deformation is located below the center 1ix reduces the radius of curvature of the lower portion and increases bending deformation, further reducing the longitudinal rigidity.

Furthermore, in the tire of the present invention, the maximum width position 3a of the carcass and the carcass position C at the radially inner edge of the buttress portion
The ratio R/W of the radius of curvature R of the circular arc passing through and along the carcass and the maximum width W of the carcass, which is the distance in the tire axial direction between the maximum width positions of the carcass, is 0.45.
above and below 0.60. As a result, as described above, the upper part of the sidewall is smoothly deformed and the riding comfort is improved. The carcass position on the radially inner edge of the buttress portion is the length between the point e where the radial line from the axially outer edge d of the tread intersects with the carcass and the carcass maximum width position a. The position that separates 1/4 of the point from the point e.

In comparison, the ratio R/W of the conventional tire is 0.35.
or more and 0.45 or less.

For this reason, in the tire of the present invention, the ratio R/W
is set to be 0.45 or more and 0.60 or less. In addition, from the above point of view, by setting the value to preferably 0.50 or more, and more preferably larger than 0.52, deformation at the curved portion is further facilitated, and the durability of the tire is increased.
It also improves riding comfort. The tire of the present invention can be used not only as a flat tire but also as a standard tire. [Specific Example] An example tire with a tire size of 185/70R14 was manufactured according to the specifications shown in Table 1. Along with a conventional tire as a comparative example, we measured steering stability, straight-line running stability, ride comfort, cornering force, self-lining torque, and envelope characteristics. Steering stability, straight-line driving stability, and ride comfort are evaluated using a 5-point system based on the driver's feeling in the actual vehicle, with higher scores indicating better results. Cornering power CP and Selfa lining power are values measured on a cornering measurement drum tester at a slip angle of 1°. In addition, the reaction force was measured by rotating a drum tester at a rotation speed equivalent to 601 aa per hour and at a height of 1
By providing cIIl protrusions on the drum, the reaction force generated when passing over the protrusions is measured as envelope performance and expressed as an index. The smaller this reaction force is, the better the envelope characteristics and ride comfort performance will be. As the results are shown in Table 1, it can be seen that the example products improved the ride comfort without impairing the handling stability etc. [Effects of the Invention] As described above, the radial tire for passenger cars of the present invention can improve ride comfort performance without impairing other performances.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, and Fig. 2 is a line diagram illustrating its carcass profile. 2--bead core, 3--bead part, 4--
・Sidewall section, 5--tread section, 6-carcass, 7-belt layer.

Claims (1)

[Claims] 1. In the carcass profile in the normal internal pressure state where the tire is assembled on the normal rim and filled with the normal internal pressure, the maximum width position a of the carcass from the bead base B of the tire
carcass maximum width height h, which is the radial distance from
The ratio h/H to the carcass cross-sectional height H, which is the distance in the radial direction from the bead base B to the highest position of the carcass, is 0.460 or more and 0.495 or less, and the maximum width position a of the carcass is , the carcass position c on the radial inner edge of the buttress portion, the radius of curvature R of the circular arc along the carcass between them, and the maximum width position a of the carcass, the carcass maximum width W which is the distance in the tire axial direction between a. A radial tire for a passenger car having a ratio R/W of 0.45 or more and 0.60 or less.