JPH05270207A - Radial tire for passenger car - Google Patents

Abstract

PURPOSE:To reduce the load noise and enhance the comfort with sitting in a car cabin without causing increase of the tire weight by forming a reinforcing member from a pair of rubber tapes, which are embodied so that they enclose the periphery of carcass and their insides in the direction across the width are pinched by belt and carcass, and giving specific values respectively to the tape width, hardness, and thickness. CONSTITUTION:A reinforcing member is formed from a pair of rubber tapes 10, which are arranged so that they enclose the periphery of carcass 2 and the insides in the direction across the width are pinched by a belt 3 and the carcass 2, wherein the width Y of each tape 10 is put in the range 30mm<=Y<=50 mm and the width P of the tape portion pinched by belt 3 and carcass 2 in the range 15-25mm. Further the hardness H of the tape 10 is made between 95-98 deg. while the thickness X between 0.8-1.0mm, According to this arrangement, the load noise can be reduced without impairing the comfort in the car cabin with no risk of causing increase of the tire weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire which can contribute to reduction of road noise in passenger cars.

[0002]

2. Description of the Related Art In recent years, as the performance and quality of passenger cars have increased, it has been desired to reduce noise generated inside the cars. As one of such noises, there is road noise due to vibration of tires during traveling being transmitted to vibrate air in the vehicle compartment. The magnitude of this road noise differs depending on the frequency, and is emphasized by having a peak value of noise in a specific frequency range according to the natural frequency of the tire, the acoustic characteristics of the vehicle interior, and the like, and it is felt as noise.

Road noise emphasized by having a peak at a relatively high frequency (about 250 HZ or more) is present between the maximum cross-section width portion of the tire and the widthwise ends of the ground contact portion and is caused by the vibration applied to the ground contact portion. It has been found by the applicant of the present application that this can be reduced by disposing a reinforcing member that covers the carcass in a portion that swings inward in the cross-sectional direction and becomes a protruding end (see Japanese Patent Application No. 2-50676).

That is, when the response characteristics when vibration is input to the tread portion of the radial tire is analyzed, it is about 200.
Vibration modes can be classified into a relatively low frequency range below HZ and a relatively high frequency range above about 250 HZ,
Road noise corresponds to this vibration characteristic, and its peak value is in a relatively low frequency range of about 100 to 200 HZ and about 2
It exists in the high frequency range of 50 HZ and above. Observing the vibration mode when the tread is vibrated in the high frequency range, as shown by the solid line and the broken line in FIG. 3, the maximum cross-sectional width (W) portion of the tire and the width direction both ends of the ground contact portion (T) are observed. Part (A) that swings inward and becomes the protruding end
Is observed to occur. This is because the tread portion is reinforced by the belt and the lower portion of the sidewall portion is reinforced by bead filler, carcass folding, etc., so that the rigidity is relatively large, while the maximum cross-sectional width (W) portion and the ground contact portion (T) are This is because the rigidity between the both ends in the width direction is relatively small.

Therefore, by arranging a reinforcing member for covering the carcass in the portion (A) which is swung inward by the vibration applied to the tread portion and becomes the projecting end, the rigidity of the portion (A) is increased, It suppresses vibrations in the high frequency range and shifts the natural frequency to a higher one so that the relationship with the acoustic characteristics in the passenger compartment in the high frequency range can be made different, and road noise in the relatively high frequency range can be made small. ..

[0006]

As a structure for concretely implementing the road noise reduction structure, conventionally, a new reinforcing member is added or the width of the belt is extended to vibrate the grounding portion. Thus, the part that swings inward in the radial direction and becomes the protruding end is covered.

However, in recent years, there has been a demand for improving the fuel efficiency of automobiles due to the emission control of carbon dioxide, and the weight reduction of automobiles including tires has been studied. Therefore, if a new reinforcing member is added or the width of the belt is widened to reduce road noise, there is a problem that the weight of the tire increases.

Further, when a new reinforcing member is added or the belt width is widened, there is a problem that the rigidity becomes excessive and the riding comfort deteriorates.

An object of the present invention is to provide a radial tire for a passenger vehicle which can solve the above-mentioned problems of the prior art.

[0010]

The feature of the present invention is that the ratio B / T between the belt width B and the tire ground contact width T is 1.
The ratio B / W between the belt width B and the tire maximum cross-section width W is 0.84 or less, and it is between the maximum cross-section width portion of the tire and the widthwise ends of the grounding portion and is grounded. In a radial tire for a passenger vehicle in which a reinforcing member that covers the carcass is disposed at a portion that is swung inward in the cross-sectional direction by vibration to the portion, the reinforcing member covers the outer periphery of the carcass and the widthwise inner side. Is composed of a pair of rubber tapes sandwiched between the belt and the carcass, and the width of each tape is Y, and 30mm ≦ Y ≦ 50mm, and the width of the rubber tape portion sandwiched between the belt and the carcass is 15mm or more and 25mm. The hardness of each tape is H
Is 95 ° ≦ H ≦ 98 °, and the thickness of each tape is X
Is 0.8 mm ≦ X ≦ 1.0 mm.

[0011]

In the conventional radial tire, the separation of the belt from the tire rubber and the carcass is prevented by the rubber tape covering the outer periphery of the carcass and sandwiching the widthwise inner side between the belt and the carcass. The present invention utilizes the rubber tape for reducing road noise. That is, the inventors of the present invention, by defining the hardness, the thickness and the width of the rubber tape in the radial tire for passenger cars, have little influence on the tire weight and reduce the road noise without reducing the riding comfort. It was found that

According to the present invention, the ratio B / T between the belt width B and the tire ground contact width T is 1 or more and 1.15 or less, and the ratio B / W between the belt width B and the tire maximum sectional width W is 0.84. Applies to the following radial tires. This is because radial tires out of the range are not generally used for passenger cars and have little significance in reducing road noise. Since the tire ground contact width differs depending on the mounting rim, the load applied and the air pressure, the tire ground contact width T in the present invention is JA
It is a value when a standard rim regulated according to the tire size is mounted in the standard defined by TMA, a design riding load is applied, and an air pressure determined according to the design riding load is filled.

When the width of each tape is Y, 30 mm ≦
Y ≦ 50 mm, and the width of the tape portion sandwiched between the belt and the carcass is 15 mm or more and 25 mm or less. This is because the width of the rubber tape is less than 30 mm, and the width of the rubber tape part sandwiched between the belt and the carcass is 25 mm.
This is because the road noise cannot be sufficiently reduced when the value exceeds. Further, if the tape width Y exceeds 50 mm, the rigidity of the tire increases and the riding comfort deteriorates. Further, if the width of the rubber tape portion sandwiched between the belt and the carcass is less than 15 mm, a large repeated shear strain occurs during running, and fatigue damage occurs between the belt and the carcass.

The conventional hardness H of the rubber tape is 60 °
However, if it is less than 95 °, the road noise cannot be sufficiently reduced, and if it exceeds 98 °, the rigidity of the tire increases and the riding comfort deteriorates. ing. The rubber hardness in the present invention is measured according to JIS K 6301, A-type spring hardness test.

The conventional thickness X of the rubber tape is 0.7.
However, if it is less than 0.8 mm, the road noise cannot be sufficiently reduced, and if it exceeds 1.0 mm, the rigidity of the tire increases and the riding comfort deteriorates.
It is set to 0.8 mm or more and 1.0 mm or less.

According to the constitution of the present invention, the rubber tape becomes larger than the conventional one, but since the weight of the rubber tape in the total weight of the tire is small, it hardly affects the weight of the tire.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross section of the radial tire 1 for a passenger car, which is orthogonal to the equatorial plane and includes a rotation axis. The radial tire 1 includes a carcass 2, two layers of belts 3 and 4 that cover the outer circumference of the carcass 2, a tread rubber 5 that covers the outer circumferences of the belts 3 and 4, and a sidewall that covers both outer sides of the carcass 2. The rubber 6 is provided with a bead core 7 and a bead filler 8 which are covered by the winding portions on both ends of the carcass 2. A pair of rubber tapes 10 that covers the outer periphery of the carcass 2 and is sandwiched between the belt 3 and the carcass 2 on the inner side in the width direction is provided.

The ratio B / T of the width B of the belt 3 on the radially inner side to the tire ground contact width T is set to 1 or more and 1.15 or less,
The ratio B / W between the belt width B and the tire maximum sectional width W is 0.8.
4 or less. If the width of each tape 10 is Y, then 3
The width P of the tape portion sandwiched between the belt 3 and the carcass 2 is 15 mm or more and 25 mm or less. Hardness H of each tape 10 is 95 ° or more and 98
° or less. The thickness X of each tape 10 is 0.8 mm or more and 1.0 mm or less.

Table 1 below shows a vehicle equipped with the radial tires of the conventional example, the example of the present invention and the comparative example.
Road noise peak sound pressure at 250Hz and 315H
Road sound peak sound pressure at Z, total road noise sound pressure, and riding comfort data are shown. Table 1 also shows hardness H, tape thickness X, and tape width Y of each tape.
Further, FIG. 2 shows the relationship between the frequency of road noise and the sound pressure in the conventional example and the example B.

[0021]

[Table 1]

The radial tire size obtained from the data in Table 1 above was 185 / 65R14-85S, the tire internal pressure was 2.0 kgf / cm ² , the steel belt had two layers, and the width was 138 mm on the inner diameter side and 138 mm on the outer diameter side. 126mm, rim size is 14 × 5 1 / 2JJ, running speed is 60km / h, passenger car equipped with radial tires (trade name Levin GT-Z
(E-AE92)), the displacement was 1600 cc, the tire load was the passenger car and two occupants and the weight of the measuring instrument, the test course was the road noise evaluation path, and the sound pickup microphone was installed in the front seat. The width of the rubber tape portion sandwiched between the belt and the carcass was set to 1/2 of the total width.

In FIG. 2, the horizontal axis shows the frequency of road noise, the vertical axis shows the sound pressure of road noise, the solid line shows the measurement result of the conventional example, and the broken line shows the measurement result of the embodiment.

From Table 1 and FIG. 2 described above, it can be confirmed that the radial tires of Examples A to F reduce the road noise without lowering the riding comfort as compared with the radial tires of the conventional example. Further, in Comparative Example G having a tape hardness of less than 95 °, Comparative Example H having a tape width of less than 30 mm, and Comparative Example I having a tape thickness of less than 0.8 mm, the reduction of road noise is insufficient. This is because it is not possible to sufficiently suppress the vibration of the portion that becomes the protruding end by vibrating inward in the cross-sectional direction due to the vibration applied to the ground contact portion. Further, in Comparative Example J having a tape hardness of more than 98 °, Comparative Example K having a tape width of more than 50 mm, and Comparative Example L having a tape thickness of more than 1.0 mm, the riding comfort was lower than that of the conventional example. .. This is because the tire rigidity becomes excessive.

[0025]

According to the radial tire for a passenger car of the present invention, road noise can be reduced without increasing the weight of the tire and without reducing the riding comfort.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a configuration of a radial tire according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between road noise frequency and sound pressure according to an embodiment of the present invention.

FIG. 3 is a diagram showing a principle of generation of road noise.

[Explanation of symbols]

 2 Carcass 3 Belt 10 Rubber tape

Claims (1)

[Claims] 1. A ratio B / of a belt width B and a tire ground contact width T.
T is 1 or more and 1.15 or less, the ratio B / W of the belt width B and the tire maximum cross-sectional width W is 0.84 or less, and the maximum cross-sectional width portion of the tire and the widthwise ends of the ground contact portion are In the passenger car radial tire in which a reinforcing member that covers the carcass is arranged in a portion that is oscillated inward in the cross-sectional direction by vibration to the ground contact portion and is a protruding end, the reinforcing member is,
It is composed of a pair of rubber tapes that cover the outer periphery of the carcass and are sandwiched between the belt and the carcass on the inner side in the width direction, where the width of each tape is Y, and 30 mm ≤ Y ≤ 50 mm, and the rubber sandwiched between the belt and the carcass. The width of the tape-making portion should be 15 mm or more and 25 mm or less, the hardness of each tape is 95 ° ≦ H ≦ 98 °, and the thickness of each tape is 0.8 mm ≦ X ≦ 1.0 mm. Radial tires for passenger cars characterized by.