AU606425B2

AU606425B2 - Radial tire for passenger cars

Info

Publication number: AU606425B2
Application number: AU17769/88A
Authority: AU
Inventors: Hiroaki Sakuno
Original assignee: Sumitomo Rubber Industries Ltd
Current assignee: Sumitomo Rubber Industries Ltd
Priority date: 1984-09-14
Filing date: 1988-06-16
Publication date: 1991-02-07
Anticipated expiration: 2005-09-13
Also published as: NZ213462A; AU578308B2; AU4744185A; JPS6171202A; AU1776988A

Description

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(ORIGINAL)

FOR OFFICE USE: 0 "00 0 0 0 00 00 o0 0 0 00 0 C.00 0 0000.0 0 0 o 0.0 00 o 0,4 00 S0 0 00 0 8000 0 4001 Complete Specification Lodged: Accepted: Published: Priority: Class Int Class 1Ihis (11. 11-: menl4d.

Related Art: Name and Address of Applicant: Sumitomo Rubber Industries, Ltd.

No 1-1, Tsutsuicho 1-chome Chuo-Ku, Kobe-Shi Hyogo

JAPAN

Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Males, 2000, Australia Address for Service: Complete Specification for the invention entitled: RADIAL TIRE FOR PASSENGER CARS The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3 ABSTRACT OF THE DISCLOSURE A radial tire for passenger cars which comprises tread rubber having a complex elastic modulus of 50 to 150 kg/cm 2 a carcass of polyester cord arranged substantially in the radial direction, with the edges thereof folded oack around a pair of bead cores, a belt layer arranged outside said carcass in the crown part at a comparatively shallow angle with respect to the circumferential direction of the tire, side rubber having a complex elastic modulus of 30 to 50 kg/cm 2 0 9 S and a bead apex having a complex elastic modulus of 200 kg/cm 2 and /iQ above, said bead apex extending in the space between said carcass and "o the folded part thereof from the upper side of the bead core to a position beyond the region where the tire width is maximum or to a position lower than the upper end of the rim flange.

oo0 The tire of this invention is improved in maneuverabilty and 0 09 "o 0 generates a low level of noise.

9 0 4 i Q I s i. i .I, BACKGROUND OF THE INVENTION 1. Field of the Invention: The present invention relates to a radial tire for passenger cars which has improved maneuverability and generates a low level of noise.

2. Description of the Prior Art: As the pavement of expressways is improved, the tire is required to have a high-speed performance. To meet this requirement, the radial Oo tire has come into general use. The radial tire is superior in "o maneuvarability under the conditions of high-speed running because of IQCoo its radial structure. According to the radial structure, the carcass cord is arranged in the radial direction of the tire and a belt layer is o° placed in the tire crown. The belt layer is arranged at a comparatively °o shallow angle with respect to the circumferential direction of the tire.

o 4 The radial tire, however, has the disadvantage of generating noise while o0o0 running at medium and low speeds. This is an important problem to be tI solved.

It is generally believed that the tire noise depends largely on the tread pattern. It is also known that the tire noise is associated with the natural frequency of the tire which is determined by the tire O 'structure. The present inventors studied the relationship between tire noise and tire structure and completed this invention.

1., SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a new radial tire for passenger cars which exhibits improved maneuverability while running at high speeds and yet generates a low level of noise while running at medium and low speeds.

The gist of this invention resides in a radial tire for passenger cars which comprises tread rubber having a complex elastic modulus of 50 to 150 kglcm 2 a carcass of polyester cord arranged substantially in the radial direction, with the edges thereof folded back around a [Z pair of bead cores, a belt layer arranged outside said carcass in the o 0 crown part at a comparatively shallow angle with respect to the osooa circumferential direction of the tire, side rubber having a complex elastic modulus of 30 to 50 kg/cm 2 and a bead apex having a complex elastic modulus of 200 kg/cm 2 and above, said bead apex 4044 extending in the space between said carcass and the folded part thereof from the upper side of the bead core to a position beyond the region where the tire width is maximum or to a position lower than the upper end of the rim flange.

BRIEF DESCRIPTION OF THE DRAWING S Fig. 1 is a sectional view showing the right half of the radial tire of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of this invention will be described with reference to the accompanying drawing. Fig. 1 is a sectional view showing the right half of the radial tire of this invention. The radial tire has a I 2 _1 r i i .rr I. L .I ^I I I o 00 0o 0 0 00 o 0

IQ

0 0 o a 0 00 o 0 0 0 0 010 carcass which is folded back from inside to outside around the bead core a belt layer which is arranged outside the crown at a comparatively shallow angle with respect to the circumferential direction of the tire, a bead apex which extends upward in the side wall direction from the upper side of the bead core in the space between said carcass and the folded part (2a) thereof, tread rubber in which said belt layer is embedded, and side rubber which extends from the end of the tread rubber to the bead.

The radial tire of this invention made of specific rubber material and cord material has improved mtrneuvarability with a low level of noise generation on account of the bead apex which extends extremely high or low. In other words, the upper end of the bead apex reaches a height (hb) which is above the height (hw) where the tire width is maximum, or the upper end of the bead apex is below the height (hf) which the upper end of the rim flange In the conventional radial tire, the height of the bead apex is above the upper end of the rim'flange and below the position where the tire width is maximum. The bead apex in this invention increases or decreases the flexibility of the-side part more than the conventional one, whereby shifting the natural frequency of the tire from the frequency band of noise and reducing the noise level.

The bead apex used in this invention should have a complex elastic modulus of 200 kg/cm 2 and above, and preferably 500 to 1500 kg/cm 2 The reduction of noise level is achieved only when the tire structure and materials specified below are used. Otherwise, the object 3 i IL 77 i complex elastic modulus of 50 to 150 kg/cma, and preferably 60 to 100 kg/cm 2 and has a loss factor (tan 6) of 0.200 to 0.350. The tread rubber having a complex elastic modulus lower than 50 kg/cm 2 adversely affects the maneuverability, and the one having a value in excess of 150 kg/cm 2 leads to a high level of noise.

The side rubber should have a complex elastic modulus of to 50 kg/cm 2 It should alleviate the shocks transmitted from the of tread rubber and should withstand the flexural deformation it f undergoes repeatedly while running. To meet this requirement, the o l °o above-mentioned value of complex elastic modulus is necessary.

According to this invention, the carcass cord is made of polyester.

The material of the carcass cord is associated with the natural o 0 frequency of the tire, and it effectively alleviates shocks to the tire.

00" These all play an important part in the improvement of maneuverability o and smooth riding and the reduction of noise level. The polyester cord oo in this invention is also effective in the reduction of noise level and the improvement of maneuverability. This effect is enhanced by the dynamic properties of the tread rubber, side rubber, and bead apex 9 rubber.

The belt layer in this invention is constructed of steel cord, rayon cord, or aramide cord having a comparatively high modulus which is arranged at an angle of 50 to 350 with respect to the circumferential direction of the tire.

0^0 rubber i C i 1 In order to confirm the effect of this invention, the following experiments were carried out. Two kinds of steel tires as specified in Table 1 were prepared and they were examined for noise level and maneuverability. (The tire size was 185/70SR14 in Examples B, C, E, and F and Comparative Example H, and 185/70SR13 in Examples A and D and Comparative Example The complex elanstic modulus was measured using a viscoelastic spectrometer (made by Iwamoto Seisakusho Co., Ltd.) at 70 0 C with a frequency of 10 Hz and an amplitude of The noise was °measured at the position of the driver's left ear. For the noise test, 00 0 a car provided with the sample tires was driven at 50 km/h on a road o o0 0 which is liable to noise. The maneuverability was evaluated by driver's 0oo o feeling in actual driving. The highest ranking is point It is noted from Table 1 that Example A having a low bead apex and Son Example D having a high bead apex are superior in noise reduction to Comparative Example G having a bead apex of medium height. In addition, Examples A and D are improved in maneuverability. Examples B and C in which the height of the bead apex is below the upper end of the rim flange and Examples E and F in which the height of the bead apex is 0 o9 above the position where the tire width is maximum are superior in noise reduction and maneuverability to Comparative Example H in which the bead apex has a conventional height.

As mentioned above, the tire of this invention is made up of tread IJ rubber and side rubber each having a specific complex elastic modulus and polyester carcass cord. In addition, according to this invention, the height of the bead apex is higher or lower than the conventional i. one. Because of these features, the tire of this invention is improved in maneuverability and noise reduction.

0000 0 00 00 0 o 90 09 i 0090 00 00 0 000 00 0 0 0 090 000000 0 0 0 ~0 00 0 0 00 0 90 09 0 0 0~ 00 0 0000 0 0 0 00~ at- 6 o 04 00 03 o 0 S0 4 G0 0 0 Q 0 00&.0 00 0 0. 0 0 G 0 0 60 0 o 0 o 0 0 0 90 C o 0 3 A 0 o0 Q (>00 00 0 0 0 0 0- 0 00 0 oc *o o a 0 0 00 Table 1 Compar. Compar.

Example A Example B Example C Example D Example E Example F Example G Example H Complex elastic modulus 100 100 100 100 100 100 70 of tread rubber Complex elastic modulus 40 40 43 40 43 40 30 of side rubber Carcass: Material Polyester Polyester Polyester Polyester Polyester Polyester Polyester Polyester Denier 1500 d/2 1000 d/2 1000 d/2 1500 d/2 1000 d/2 1000 d/2 1500 d/2 1000 d/2 /0 Plies 1 2 2 1 2 2 1 2 Bead apex: Height (mm) 10 10 10 70 70 70 45 53 Complex modulus 250 250 250 350 350 350 600 250 Noise level (dB) recorded on an actual car Frequency 100 Hz 56.5 61.0 60.3 55.8 64.1 63.5 60.0 64.5 125 Hz 62.7 58.3 59.8 63.5 59.2 60.1 64.8 63.3 160 Hz 63.0 61.2 62.0 63.6 63.5 62.7 65.8 65.7 315 Hz 57.7 58.1 59.8 57.3 60.4 60.9 62.3 62.3 Maneuverability: ao Response 3.1 3.1 3.1 3.1 3.1 3.1 3.0 Contact 3.0 3.0 3.1 3.1 3.1 3.1 3.0 Convergence 3.0 3.0 3.1 3.1 3.1 3.2 3.0 Steerability 3.0 3.1 3.0 3.0 3.0 3.0 3.0 Structure of folding-up is shown in the parenthesis.

4.

0 4

Claims

1. A radial tire for passenger cars which comprises tread rubber having a complex elastic modulus of 50 to 150 kg/cm 2 a carcass of polyester cord arranged substantially in the radial direction, with edges thereof folded back around a pair of bead cores, a belt layer arranged outside said carcass in the crown part at a comparatively shallow angle with respect to the circumferential direction of the tire, side rubber 2 having a complex elastic modulus of 30 to 0 kg/cm 2 and a bead apex having a complex elastic modulus of 200 kglcm 2 and above, said bead apex extending in the space between said carcass and the folded part thereof from the upper side of the bead core to a position beyond the ct.. region where the time width is maximum.

2. A radial tire for passenger cars as defined in claim 1 and to: substantially as described herein with reference to any one of Examples D, E and F. 4 ,i DATED this SECOND day of NOVEMBER 1990 Sumitomo Rubber Industries Ltd O Patent Attorneys for the Applicant SPRUSON FERGUSON 0 t 4 -8- RLF/1205h