NZ215319A - Radial passenger tyre:belt width,carcass turnup,apex modulus and extent combination - Google Patents

Description

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Priority Date(s): 9 <?-. 7 <? / Complete Specification Filed: pi-,.,.. 8 Co C j/2 9- <JX % Go US/oC , I "V S.ofeb i987| Publication Date: I P.O. Journal, No: . j PATENTS FORM NO. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION A RADIAL PASSENGER TIRE 2153 o WE, SUMITOMO RUBBER INDUSTRIES, LTD., of 1-1 Tsutsuicho 1-chome, Chuo-ku, Kobe-shi, Hyogo-ken, Japan, a Japanese company, hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: Vy QAV ^ b y P£t 2 1 53 A RADIAL PASSENGER TIRE BACKGROUND OF THE INVENTION This invention relates to a radial passenger tire, which reduces a road noise without sacrificing the steering stability.

In recent years, there is requested a reduction of the fuel consumption on automobiles. Therefore, a weight reduction of the car body is promoted. However, it is generally known that such a weight reduction has a bad influence upon the road noise. In this specification, the above-mentioned road noise is defined as a phenomenon which is unrestful to the driver and is caused by the following steps : rough of roads vibrates the tire tread face, this vibration of the tire tread face propagates through the bead portion to the car body, and the vibration propagated to the car body vibrates the inside air of the car body.

In the past, there have been proposed such a method as reducing the road noise : 1. To shorten the bead apex, 2. To soften the bead apex, 3. To lower the turnup portion of the carcass, 4. To employ a carcass of one ply structure.

However, these methods diminish the tire stiffness to the side force, and the cornering power, as a result, they have a bad influence upon the steering stability. Therefore, these methods have their limits. 1 A c2\5313 SUMMARY OF THE INVENTION It is an object of this invention to provide a radial passenger tire, which reduce the road noise without sacrificing the steering stability which becomes worse by the deterioration of the tire stiffness to the side force.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view of a radial passenger tire according to this invention.

DETAILED DESCRIPTION OF THE INVENTION According to this invention,.there is provided a radial passenger tire comprising: a carcass turned up around a pair of oppositely-opposed bead cores from the axial inner to the axial outer side; a bead apex disposed between a main portion of said carcass and a turnup portion of said carcass, and extending toward the sidewall of the tire; a belt layer disposed outside the crown portion of said carcass; the width of said belt layer being within a range of 75 to 90% of the maximum tire section width; the complex elastic modulus of said bead apex being within a range of 150 to 300 kgf/cm* ; the length of said bead apex being within a range of 20 to 34% of the tire section height; and the height of the end of the turnup portion being within a range of 15 to 40% of the tire section height.

Description will be now directed to an embodiment of this invention with reference to the drawing: In the figure, a radial passenger tire (1) includes: a carcass (3) turned up around a pair of oppositely-opposed bead cores (2) and (2) from the axial inner to the axial outer side, a bead apex (5) disposed between a main portion (3a) and a turnup 2 portion (3b) of the carcass (3) and extending toward the sidewall (4) of the tire, and a belt layer (6) disposed outside the crown portion of the carcass (3).

The width (BW) of the above-mentioned belt layer (6) is defined as the width of its widest ply, and the width (BW) is within a range of 75 to 90% of the maximum tire section width (MW). If the width of the belt layer (6) is less than 75% of the maximum tire section width (MW), the reduction of the road noise will be insufficient. On the other hand, if the width exceeds 90% of the width (MW), each of the terminal ends of the belt layer (6) will get near the buttress surface. As a result, the terminal ends are susceptible.to injure, and this injury extend to the buttress surface. Therefore, the tire becomes a dangerous condi tion.

The length (L), as shown in Fig. 1, of the above-mentioned bead apex (5) is within a range of 20 to 34% of the tire section height (H). In the past, the long bead apex was employed to improve a steering stability. However, such a long bead apex has a bad influence upon the road noise. Therefore the length (L) is concluded to be within the above-mentioned range from the compatibility of the stability and the noise level. Further, the optimum range for the above-mentioned length (L) varies with hardness of the bead apex (5).

The complex elastic modulus (E*) of the above-mentioned bead apex (5) is within a range of 150 to 300 kgf/cm2, and this value was measured with a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho on the following condition: temperature of 70 C, initial compressibility of 10 %, amplitude of±l %.

The height (h) of the upper end of the turnup portion (3b) is fixed within a range of 15 to 40% of the tire section height (H) from the point of view of compatibility of the steering stability and the road noise. If the height (h) is less than 15% of the height (H)> the steering stability will become worse. On the other hand, if the height (h) exceeds 40% of the heigth (H), the road noise level will increase.

As described above, the radial passenger tire according to the invention is such a one which attempt to keep the steering stability and the road noise in harmony by an exquisite combination of the width of the belt layer; the height of the turnup portion; and the length and the hardness of the bead apex.

The radial passenger tires of 185/70 SR14 have been produced as an experiment in accordance with details shown in Table 1. These tires have been set on LAUREL (trade name); a turbo-charged car manufactured by NISSAN, and the road noise level was measured at the side of the driver's left ear. On the other hand, the cornering power was measured on the condition of 300 kgf load, a running speed of 100 km/h, and an internal pressure of 1.8 kgf/cm2. The results are shown in Table 1. 4 2 15319 TABLE 1 Tire 1 for comparison Tire 2 for comparison Tire 1 of the invention Width of belt layer (BK) mm 130 / 118 130 / 118 152 / 140 BW / MW 0.70 0.70 0.82 Length of bead apex (L) mm 50 L / H 0.37 0.22 0.22 Complex elastic modulus of bead apex (E*) 2 kgf/cm 620 250 250 Carcass structure 2-0 1-0 1-0 Height of turnup portion (h) mm 75 / 65 70 70 h / H 0.41 0.38 0.38 Road noise level dB (A) 64.5 63.5 63.0 Cornering power kgf/deg. 63.2 56.5 63.3 As apparent from Table 1, in the tire according to the . present invention both the road noise and the cornering power, that is to say, the steering stability were improved.

As described above, the present invention can reduce the road noise without sacrificing the steering stability because of exquisit combination of the width of the belt layer; the height of the turnup portion; and the length and hardness of the bead apex.

Claims (3)

2153i9 WHAT37WE CLAIM IS:-

1. A radial passenger tire, comprising: a carcass turned up around a pair of oppositely-opposed bead cores from the axial inner to the axial outer side; a bead apex disposed between a main portion of said carcass and each turnup portion of said carcass, and extending toward the sidewall of the tire; a belt layer disposed outside the crown portion of said carcass; the width of said belt layer being within a range of 75 to 90% of the maximum tire section width; the complex elastic modulus of said bead apex being within a range of 150 to 300 kgf/cma ; the length of said bead apex being within a range of 20 to 34% of the tire section height; and the height of the end of each turnup portion being within a range of 15 to 40% of the tire section height.

2. A tire substantially as herein described with reference to tire 1 or tire 2 of the invention as defined in Table 1.

3. A tire substantially as herein described with reference to the accompanying drawing. SUMITOMO RUBBER INDUSTRIES, LTD By Their Attorneys BALDWIN, SON & CAREY