JPS6349505A - Radial tire for passenger car - Google Patents

Abstract

PURPOSE:To obtain the quietness of a vehicle and improve drive feeling by setting the groove area of each region of a tire which is divided by a plurality of main grooves and subgrooves to a specific value and reducing the pattern noise in a specific frequency region. CONSTITUTION:Two main grooves G extending in the tire peripheral direction and two subgrooves (g) which has the narrower width than that of the main groove G and extend in the peripheral direction between the main grooves G are arranged. The inner region M formed between the main groove G and the subgroove (g) and the side region S starting from the main groove G to the tread edge are divided into a plurality of blocks B1 and B2 by the lateral grooves GM and GS aslantly extending for the tire equator. In this case, the ratio of all the groove area for the apparent grounded area is set to 18-25%, and the ratio of the total area of the main groove and the subgroove for the apparent grounded area is set to 10-15%. Further, the groove width of the lateral groove GM, GS of the inner region M is set to 1-2mm, and the ratio of all the lateral groove area in the inner region M for the apparent grounded area is set to 2-4%. Therefore, the noise level of the tread pattern in the region of 800-1,000Hz can be improved markedly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radial tire for passenger cars that has a block pattern tread portion and has improved pattern noise.

[Conventional technology]

Recently, with the development of the expressway RAI network and the increase in the number of roads being installed, vehicles have become faster and more capable, and high-end cars in particular are required to have a comfortable ride and comfort.

Therefore, tires mounted on this type of vehicle are also required to have excellent noise characteristics and ride comfort.

Here, in-vehicle noise caused by tires includes pattern noise, road noise, squealing noise, etc. The pattern noise is known to be caused by the pattern on the tread surface, that is, the tread pattern. There are three different patterns on the car (Figure 8 (a) - (
C))) was installed on an asphalt paved road in a slightly rough condition (a general road that has been paved for several months or more) at a speed of Ro.
In Figure 7, which shows the results of 1/3 octave band analysis of the interior sound measured when driving at kIm/h, the tread patterns in Figure 8 (C1) are plain tires. (1st NAL), the sound pressure level is 4 to 5 dB in the 800 summer fzs l k lz band.
(A) It is high pitched and can be heard as a harsh sound and causes discomfort to the driver and passengers.

[Purpose of the invention]

An object of the present invention is to provide a passenger military radial tire that reduces pattern noise in the 800-1 kHz range and reduces discomfort caused by noise inside a vehicle.

[Means for solving problems]

This invention provides two main grooves extending in the circumferential direction of the tire, and two sub-grooves extending in the circumferential direction of the tire with a narrower groove width than the main grooves in a region sandwiched between the main grooves. The inner region sandwiched between the main groove and the tread edge, and the side region from the main groove to the tread end are all divided into blocks by the lateral groove, and (1) the total groove area (with respect to the apparent ground contact surface iff (A)) Ag) ratio is 18 to 25%, and the ratio of the total area of the main groove and minor groove to the apparent ground contact area is in the range of 10 to 15% (11) The horizontal groove in the inner area is 1 to 2 mm in apparent width. A radial tire for a passenger car, characterized in that the ratio of the total width area of the inner region to the ground contact area is 2 to 4%.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, the tire has two main grooves g, g, which extend in the circumferential direction and are 111 narrower than the main groove aG in a region sandwiched between two main grooves g and g.
are arranged, and the ratio of the total groove area Ag to the apparent ground contact area A is set to 18 to 259 g.

The apparent ground contact area A of the tire in the pattern shown in Figure 1 is the total area of the area surrounded by the outer circumferential contour of the ground contact shape when in contact with the ground under the standard conditions specified by the JATMA standard for radial tires for passenger cars (Figure 2). means.

Further, the total groove surface aAg means the sum of all groove areas included in the ground contact shape. In addition, in FIG. 2, the main groove G, 01
Let the length of the groove g within the ground contact area A be 1, and the groove width be W and w, then the total surface of the main groove G and the minor groove g, 1lJIAG, is 2 (
LW-1-j! w) becomes.

The inner area M sandwiched between the main groove G and the sub groove g and the side area S from the main groove G to the tread edge are formed by a block B1
-, B2...-.

Note that the blocks B1 and B2 are provided with slit-shaped sipings S1 and S2, but the sipings S1 and S2 are not included in the groove area A1K.

Therefore, if the sum of the groove areas of the lateral grooves GM in the inner region M is AGM, and the sum of the groove areas of the lateral grooves GS in the side region S is AGS, then the sum of the groove areas is Ag+AGM+AGS.

Therefore, the ratio of the total groove area Ag to the apparent ground contact area A is set to 18 to 25 minus 6 as described above, and the total surface bond AG of the main groove G and sub grooves G to the apparent ground contact area A. Set in the range of 10-15%. Regarding pattern noise, noise in the frequency band 800 to 100 Q fiz is 1ffl for various patterns with different number of grooves and groove width.
When conducting irI, it was found that this back pressure is mainly caused by air column resonance in the circumferential grooves, and that the back pressure level is proportional to the sum of the cross-sectional areas of the circumferential grooves when the full depth is constant. . Therefore, FIG. 3 shows the relationship between the sound pressure level of one octave 1 kHz band at 801 ua/h and the total area.

This noise due to air column resonance is excited by the addition of images of the road surface and tread pattern, and its size has been found to be related to the radius and depth of the lateral grooves of the tread pattern. . Furthermore, among the lateral grooves, the lateral groove located in the center of the tread has a greater influence than the lateral groove located on the tread shield side. Figure 4 shows the respective a widths WM and WS of the lateral groove GM in the internal force area M and the lateral groove GS in the side area S.
This shows the relationship between the sound pressure level and the horizontal groove GM of the inner region M.
In this case, it can be seen that when the groove width WM exceeds 2B, the sound pressure level increases dramatically. This is the groove width WM of the horizontal groove GM.
As the excitation force of the pattern increases and the back pressure level increases as the
3 is released from the grounding end to the outside, so it is easy to be discharged from the inside of the grounding surface to the outside through the horizontal groove GS, and as a result,
Air column resonance is unlikely to occur. On the other hand, since the air in the minor groove g is difficult to be released outside the ground plane through the lateral groove, the excitation force excites the air in the circumferential grooves in both the inner and side areas, creating air column resonance. This increases the sound pressure level.

Therefore, the groove width WM of the lateral groove GM in the inner region M was reduced to reduce the noise level, while the lateral groove GS in the Ill region S was made a relatively large groove @WS to maintain wet grip performance and steering stability. As a matter of fact, the groove width WM of the horizontal iGM should be 2 fl or less.However, if it is smaller than 1 cut, the tread rubber will be deformed in the contact area and the groove wall will adhere to vFi and the groove will no longer function as a groove. , a groove width of one cut or more is required.

Furthermore, the ratio of the entire surface fiAGM of the lateral grooves GM in the inner region M to the area A is set to 2 to 4% to prevent deterioration of wet braking performance etc. due to a decrease in the grooves.

Also, for the same reason, the groove width W of the main groove G is preferably set to 1.8 times the groove [w] of the sub-groove g.

It should be noted here that in the present invention, the pinch ratio is changed using the conventionally used pinch Balini silane method, so the width of the lateral groove changes accordingly, but the lateral groove width here is the average value of these. shall be.

〔Example〕

A prototype tire was manufactured using a radial tire for a passenger car with a tire size of 205/65R15 having the tread pattern shown in FIG. 1 and the specifications shown in Table 1. This was installed in a 31 sedan car and the sound inside the car was measured at a speed of 80 km/h. As a comparative example, a tread pattern shown in FIG. 5 was similarly measured.

As shown in FIG. 3, the noise level could be significantly improved in the range <800 to 1000 Hz.

In addition, we were able to minimize the deterioration of performance due to groove width in other performance areas such as wet grip and handling stability.

Table 1 [Effects of the Invention] As described above, the tire of the present invention has a tire with a diameter of 800 to 1 km by optimally selecting the groove area of each region of the tire divided into two main grooves and a sub groove. ) Reduces harsh pattern noise in the Iz region, making the vehicle quieter and improving ride comfort.

[Brief explanation of the drawing]

Fig. 1 is a developed view of a tre/nod pattern showing an embodiment of the present invention, Fig. 2 is a plan view showing its ground contact part, Fig. 3 is a diagram showing the relationship between groove area and sound pressure level, and Fig. 3 is a diagram showing the relationship between groove area and sound pressure level. Figure 4 is a diagram showing the influence of the groove area in the inner region and side region, Figure 5 is a developed diagram showing the tread pattern of the comparative example, Figure 6 is a diagram illustrating the sound pressure level, and Figure 7 is a diagram showing the influence of the groove area in the inner region and the side region. The figure is a diagram illustrating the sound pressure level of a conventional tire, and FIGS. 8(a) to 8(C) are developed views illustrating the tread pattern of the conventional tire. G...-major groove, g...-minor groove, GM, GS--lateral groove, M--medial region, S--lateral region. Patent applicant Sumitomo Rubber Industries Co., Ltd. Agent
Patent Attorney Tadashi Naemura Figure 4 1181m (a) Figure 8 (1)) Figure 8 (
C) Figure 6 Hz (!/'3 octakadendo) Figure 7

Claims (2)

[Claims] (1) Two main grooves extending in the circumferential direction of the tire, and two sub-grooves extending in the circumferential direction of the tire having a groove width narrower than the main groove are arranged in a region sandwiched between the main grooves, and the main groove and the The inner area sandwiched between the minor grooves and the side area from the main groove to the tread edge are both divided into blocks by lateral grooves, and (i) the ratio of the total groove area to the apparent ground contact area is 18
-25%, and the ratio of the total area of the main groove and the minor groove to the apparent ground contact area is in the range of 10 to 15%, (ii) The groove width of the lateral groove in the inner area is 1 to 2 mm, and the apparent The ratio of the total lateral groove area in the inner area to the ground contact area is 2 to 4%.
A radial tire for passenger cars characterized by: (2) The radial tire for a passenger car according to claim 1, wherein the groove width of the main groove is at least 1.8 times the groove width of the auxiliary groove.