JP4529680B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that suppresses air column resonance generated in a main groove extending in a circumferential direction and does not deteriorate braking performance on a wet road surface.

  In automobiles, ensuring braking performance on wet road surfaces is a very important factor. This braking performance is governed by a water film interposed between the pneumatic tire and the wet road surface. For this reason, a main groove extending in the tire circumferential direction is formed on the tread surface of the pneumatic tire in order to improve drainage on a wet road surface. However, since such a circumferential groove forms an air column tube with the road surface at the time of ground contact, a vibration wave of compressed air passing through the air column tube resonates to generate a so-called air column resonance sound, which is This is one of the causes of noise.

  There are many proposals for suppressing resonance of vibration waves of compressed air by partially raising the bottom surface of the main groove as a countermeasure for reducing such air column resonance noise (for example, Patent Document 1, 2). However, making the inside of the main groove shallow even partly has a problem that the drainage performance is lowered by that amount, so that the braking performance on the wet road surface as a main required characteristic is lowered.

In particular, there are undulations and steps on the actual road surface, and the depth of the road surface when wet varies depending on the location. There was a problem.
Japanese Patent Laid-Open No. 11-208219 JP 2002-211210 A

  An object of the present invention is to provide a pneumatic tire which eliminates such conventional problems and suppresses air column resonance generated in a main groove extending in the circumferential direction, while preventing a reduction in braking performance on a wet road surface. It is to provide.

  In order to achieve the above object, the pneumatic tire of the present invention has a main groove extending in the tire circumferential direction formed on the tread surface within the ground contact surface when 50% of the maximum load capacity specified by JATMA is applied at an air pressure of 180 kPa. The groove depth is made shallower than the remaining portion in at least one place in the tire circumferential direction, and the groove cross-sectional area of the main groove is made substantially the same over the entire ground contact surface.

  In the pneumatic tire of the present invention, when the air pressure is 180 kPa and 50% of the maximum load capacity specified by JATMA is applied, the groove depth of the main groove in the ground contact surface is shallower than the remaining portion in at least one place in the tire circumferential direction. As a result, the vibration waves of the compressed air passing through the air column tube formed between the main groove and the road surface are disturbed to suppress the generation of air column resonance, and at the same time, the cross-sectional area of these main grooves is reduced. Since it is made substantially the same in the entire area of the ground contact surface, it is possible to ensure good drainage on a wet road surface and to prevent a decrease in braking performance.

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

  1 is a cross-sectional view of a pneumatic tire according to an embodiment of the present invention, FIG. 2 is a partial plan view showing a tread surface of the pneumatic tire of FIG. 1, and FIG. 3 is a cross-sectional view taken along line AA of FIG. .

  FIG. 1 shows a case where the pneumatic tire 1 of the present invention is a radial tire for passenger cars. The pneumatic tire 1 is embedded in the bead portions 4 and 4 from the tread portion 2 through the side wall portions 3 and 3. A carcass layer 6 that is folded and locked around the bead cores 5 and 5, and belt layers 7 a and 7 b that are disposed radially outside the carcass layer 6 and inside the tread portion 2. It has.

  The tread surface of the pneumatic tire 1 is formed with four main grooves 8 extending in the tire circumferential direction, and a plurality of lug grooves 9 that intersect and extend in the tire width direction. The main groove 8 has a different groove depth with respect to the tire circumferential direction, and is formed so as to include at least one portion having a shallow groove bottom in the ground contact surface of the tread portion 2.

  That is, according to the present invention, the groove depth of the main groove 8 in the contact surface of the tread portion 2 in a state where the pneumatic tire 1 is filled with an air pressure of 180 kPa and a load corresponding to 50% of the maximum load capacity specified by JATMA is applied. Is formed so as to include a portion that is shallower than the remaining portion at at least one location in the tire circumferential direction.

  Further, the cross-sectional area of the main groove 8 is formed so as to be substantially the same over the entire area of the ground contact surface of the tread portion 2. That is, the groove width in the portion P having a large groove depth is small, the groove width in the portion Q having a small groove depth is large, and the cross-sectional area of the main groove 8 is the same on the circumference.

  Thereby, the vibration wave of the compressed air passing through the air column tube formed between the main groove 8 and the road surface is disturbed to suppress the generation of air column resonance, and at the same time, the cross-sectional area of these main grooves 8 Is made substantially the same over the entire area of the ground contact surface, so that it is possible to ensure good drainage on a wet road surface and to prevent a reduction in braking performance.

  In the present invention, the cross-sectional area in the width direction of the main groove 8 is most preferably formed on the circumference, but from the viewpoint of ensuring good drainage on the wet road surface and not reducing the braking performance. The ratio α1 / α2 between the cross-sectional area α1 in the width direction at the position where the groove depth of the main groove 8 is maximum and the cross-sectional area α2 in the width direction at the position where the groove depth of the main groove 8 is minimum is 0.9 to α2. It may be adjusted to be 1.1.

  Furthermore, the groove depth on the circumference of the main groove 8 may be formed in a wave shape that periodically changes in the circumferential direction as illustrated in FIG. 3. Thereby, the compressed air passing through the air column tube formed between the main groove 8 and the road surface can be smoothly disturbed and interfered, and the generation of air column resonance can be more efficiently suppressed.

  In the case described above, it is further preferable that the wave shape formed by the groove bottom surface is formed into a sine wave shape in which the wavelength and the amplitude are substantially constant. Further, depending on the tread pattern, the wavy periodic change may be mixed with at least two types of wavelengths and / or amplitudes in relation to the rigidity of the land portions arranged on both sides of the main groove 8. it can.

  In the present invention, the difference D1- between the maximum groove depth D1 and the minimum groove depth D2 on the circumference of the main groove 8 from the viewpoint of more efficiently disturbing the compressed air passing through the air column tube in the tread contact surface. D2 may be set to 1.0 mm or more and D1 / 2 or less. When D1-D2 deviates from the above range, the disturbance of the compressed air passing through the air column tube becomes irregular, and the suppression effect of the air column resonance noise is reduced.

  As described above, in the pneumatic tire of the present invention, the groove depth of the main groove in the ground contact surface of the main groove formed in the tire circumferential direction formed on the tread surface is set at least at one place in the tire circumferential direction from the remaining place. By making shallow, the generation of air column resonance noise is suppressed, and at the same time, the cross-sectional area of these main grooves is formed almost the same in the entire contact surface to ensure drainage on wet road surfaces. Without being limited, it can be widely applied to all pneumatic tires.

  The tire size is 215 / 60R16, the tread pattern is shown in FIG. 2, and the conventional tire (conventional example) in which the groove depth of the main groove is the same and the groove width is constant is shown in Table 1. The tires according to the present invention (Examples 1 and 2) were made different from each other. The wavy shape formed by the bottom surface of the main groove in each tire was a sine wave having a wavelength of 30 mm and an amplitude of 1.6 mm, and the angle of the main groove wall was 10 ° with respect to the normal line of the tread surface.

These three types of tires are fitted to a rim (16 x 7 JJ), filled with air (220 kPa) and mounted on a domestic car (2000 cc), and a test course consisting of a wet road surface with an average water depth of 5.0 mm is average speed The vehicle was allowed to travel straight for 5 km at 100 km / h and was subjected to sensory evaluation of drainage by a test driver. The results are shown in Table 1 by index display with the conventional example as 100. The larger the value, the better.

表１の結果から、本発明タイヤは、従来タイヤに比較して排水性が向上していることがわかる。

From the results in Table 1, it can be seen that the drainage of the tire of the present invention is improved as compared with the conventional tire.

It is sectional drawing which shows an example of the pneumatic tire by embodiment of this invention. It is a top view which shows the tread surface of the pneumatic tire of FIG. It is AA arrow sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass layer 7a, 7b Belt layer 8 Main groove 9 Lug groove

Claims (6)

  In the ground contact surface when 50% of the maximum load capacity specified by JATMA is applied at an air pressure of 180 kPa, the remaining groove depth of the main groove extending in the tire circumferential direction formed on the tread surface is at least one in the tire circumferential direction. A pneumatic tire that is shallower and has the same cross-sectional area of the main groove over the entire surface of the contact surface.   The ratio α1 / α2 between the cross-sectional area α1 in the width direction at the position where the groove depth of the main groove is maximum and the cross-sectional area α2 in the width direction at the position where the groove depth of the main groove is minimum is 0.9 to α2. The pneumatic tire according to claim 1, which is 1.1.   The pneumatic tire according to claim 1 or 2, wherein a groove depth of the main groove is formed in a wave shape that periodically changes in a circumferential direction.   The pneumatic tire according to claim 3, wherein each of the wavy wavelength and amplitude is substantially constant.   The pneumatic tire according to claim 3, wherein at least two types of wavelengths and / or amplitudes are mixed in the wavy periodic change. The pneumatic tire according to any one of claims 1 to 5, wherein a difference D1-D2 between a maximum groove depth D1 and a minimum groove depth D2 of the main groove is 1.0 mm or more and D1 / 2 or less.

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