NZ215320A - Radial passenger tyre:narrow tread relative to section width - Google Patents

Description

215320 n , . /. 3- Pf Priority Date(s). .../••••• 2%. a ieie opetiin<oii«i* ■ — o2 Class: Complete Specification Filed: Publication Date: I p.o. Journal, No: 2 O.FEB.1987 yp.fj.

PATENTS FORM NO. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION .jWi A RADIAL PASSENGER TIRE K, WE SUMT3XM0 RUBBER INKJSTRIES, LTD, of 1-1, Tsutsuicho 1-chome, Chuo-ku, Kobe-shi, Hyogo-ken, Japan, a Japanese Company, hereby declare the invention, for which fi/we pray that a patent may be granted to roe/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- \a>i JilM S1 P^4- 2 % 53 2D 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. 1a c W 2 1 5320 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 o 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; a tread portion disposed outside said belt layer; the width of said tread portion being within a range of 45 to 58% of the maximum tire section width; and the width of said belt layer being within a range of 75 to 90% of the maximum tire section width.

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 portion (3b) of the carcass (3) and extending toward the sidewall (4) of the tire, and a belt layer (6) disposed outside the crown 2 2 15320 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 width (TW) of the tread portion is defined as a distance between the intersections of the tread surface and buttress surfaces positioned on both sides of the tread portion, and the width (TW) is within a range of 45 to 58% of the maximum tire section width (MW). In the conventional tire, the width of the tread portion has been set within a range of 60 to 75% of the maximum tire section width (MW). On the contrary, this invention is such a one which attempt to low noise level by setting the width (TW) relatively narrower. If the width (TW) exceeds 58%. the effect will be insufficient. On the other hand, if the width (TW) is less than 45%, the steering stability will become extremely worse.

In this embodiment, it is preferred to' set the length (L) of the above-mentioned bead apex (5) 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 2/53 from the compatibility of the stability and the noise level.

The complex elastic modulus (E*) of the above-mentioned bead apex (5) is within a range of 150 to 300 kgf/cm , 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.

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 condition of a running speed of 50 km/h, and an internal pressure of 1.8 kgf/cna. 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 TABLE 1 Tire 1 for comparison Tire 2 for comparison Tire 1 of the invention Tire 2 of the invention Width of tread portion (TW) mm 115 115 98 98 TW / MW 0.62 0.62 0.53 0.53 Width of belt layer (BW) mm 130/118 130/118 130/118 152/140 BW / MW 0.70 0.70 0.75 0.82 Length of bead apex (L) mm .50 50 50 L / H 0.37 0.22 0.37 0.37 Complex elastic modulus of 2 bead apex (E*) kgf/cm 620 250 620 620 Carcass structure 2-0 1-0 2-0 2-0 Hight of turnup portion (h) mm 75/65 70 75/65 75/65 Road noise level dB (A) 64.5 63.0 63.8 63.3 Cornering power kgf/deg . 63.2 56.5 59.7 63.0 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 the width of the belt layer and the width of the tread portion are optimalized in relation to the maximum tire section width.

Claims (3)

WHAT#WE CLAIM IS> 215320

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; 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; a tread portion disposed outside said belt layer; the width of said tread portion being within a range of 45 « to 58% of the maximum tire section width; and the width of said belt layer being within a range of 75 to 90% of the maximum tire section width.

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. a bead apex disposed between a main portion of said carcass and BALDWIN, SON & CAREY ATTORNEYS FOR THE APPLICANTS >■ 6