JPH0516617A - Pneumatic tire for passenger car - Google Patents

Abstract

PURPOSE:To prevent the reduction of uniformity by eliminating a flapping phenomenon of the belt layer in a tire in which the groove width of a main groove is set larger than the groove depth, and 6% or more of the tread development width. CONSTITUTION:At least one main groove 2 whose groove width is larger than the groove depth, and the groove size is 6 to 9% of the tread development width, extending in the tire circular direction, numerous subgrooves 3 extending in the tire width direction, and plural associate main grooves 4 extending obliquely at the angle 3 to 30 deg. to the tire circular direction and larger than the earthing length of the tire, are provided on a tread surface 1, and on the groove bottoms of the main groove 2 and the associate main grooves 4, at least one projection line 5 extending along the main groove 2 of the associate main groove 4 is formed respectively to form this pneumatic tire for passenger car.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for a passenger vehicle, which does not deteriorate the uniformity of the tire.

[0002]

2. Description of the Related Art When a green tire is inserted into a mold and vulcanized and molded, the unvulcanized rubber in the tread portion is pushed by the groove-forming bone of the mold to flow and form a tread pattern. In such molding, since the amount of rubber removed by the main groove forming bone is larger than that by the sub groove forming bone, depending on the configuration conditions of the main groove, disturbance such as waviness may occur in the belt layer near the groove bottom. Sometimes.

The applicant of the present invention has previously filed Japanese Patent Application No. 2-222520.
As a tire with improved drainage, a semi-main groove in which the groove width of the main groove extending in the tire circumferential direction is made larger than the groove depth, and adjacent to this main groove, the groove width is also made larger than the groove depth. We proposed a pneumatic tire for passenger vehicles, in which the tire extends diagonally at a small angle in the tire circumferential direction and is provided so as to intersect the sub groove.

However, as described above, the groove width of the main groove or the quasi-main groove is larger than the groove depth and is 6% of the tread spread width.
With a size that exceeds the above, in the case of pneumatic tires for passenger cars, the thickness of the tread portion is thinner than that of pneumatic tires for heavy loads, so unvulcanized rubber to be excluded by the main groove molding bone during vulcanization molding A phenomenon occurs in which the lower belt layer is pressed without flowing to both outer sides of the main groove-formed bone in the central region in the width direction of the main groove-formed bone, causing wavy deformation in the belt layer. And, the tire with the undulating phenomenon in the belt layer deteriorates the uniformity,
The radial force variation (RFV) and radial runout (RRO) are increased.

[0005]

An object of the present invention is to make the groove width of the main groove larger than the groove depth and 6% of the tread spread width.
It is an object of the present invention to provide a pneumatic tire for a passenger vehicle in which the undulation phenomenon of the belt layer in the tire set as described above is eliminated to prevent a decrease in uniformity.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to at least one main tire extending in the tire circumferential direction having a groove width larger than the groove depth on the tread surface and having a size of 6 to 9% of the tread spread width. A groove, a large number of sub-grooves extending in the tire width direction, and a plurality of quasi-main grooves extending obliquely at an angle of 3 to 30 ° with respect to the tire circumferential direction and longer than the ground contact length of the tire were provided. The pneumatic tire is characterized in that at least one ridge extending along the main groove and the quasi-main groove is formed on the groove bottoms of the main groove and the quasi-main groove, respectively.

As described above, since the structure of the main groove having a large groove width and the ridge on the groove bottom of the quasi-main groove are provided, the outside of the groove forming bone is formed in the widthwise central region of the groove forming bone during vulcanization molding. The unvulcanized rubber that has not completely flowed into the region flows into the recesses corresponding to the ridges, and the pressing force on the belt layer side is relaxed. For this reason, wavy deformation does not occur in the belt layer, and no deterioration in tire uniformity is observed.

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view showing an example of a tread pattern of a tire of the present invention, and FIG. 2 shows a meridional section of a main groove. Reference numeral 1 denotes a tread surface having a tread development width W, and one straight main groove 2 having a very wide groove width is formed in the widthwise center thereof. A large number of sub-grooves 3 are provided on both the left and right sides of the main groove 2 in the tire width direction to the shoulder end portion, respectively,
It intersects these sub-grooves 3 and is 3 to 3 in the tire circumferential direction.
A plurality of quasi-main grooves 4 extending obliquely in the range of 30 ° are provided.

The straight main groove 2 has a groove width A which is larger than the groove depth and is 6 to 9% of the tread spread width W.
It is within the range. In this way, by setting the groove width of the main groove 2 to be as wide as 6% or more of the spread width W of the tread, high drainage performance can be exhibited. However, if the width is wider than 9%, the rigidity in the width direction is lowered and the wear resistance is lowered.
Must be within. Such a wide groove width is the semi-main groove 4
Is also formed in a partial region thereof.

On the groove bottom of the above-mentioned main groove 2, two ridges 5 are provided in the central region in parallel along the main groove direction. Similarly, in the wide groove area of the quasi-main groove 4, one ridge 5 is provided at the groove bottom. It suffices that at least one ridge 5 is provided, the upper surface thereof forms an arc having a radius of curvature of 0.5 mm or more, and the ridge 5 has a radius of 0.5 to 0.5 mm.
A height of 1.6 mm is desirable. When two or more ridges 5 are provided, it is desirable that the distance be 1 mm or more.

The ridge portion in which the main groove having the wide groove width is provided on the groove bottom of the quasi-main groove as described above becomes a recess in the molding die and is formed in the central portion of the end face of the groove molding bone. Therefore, when the green tire is vulcanized and molded, the unvulcanized rubber that has not completely flowed out of the region in the central region of the wide groove-formed bone can be absorbed in the recesses, thereby pushing the lower belt layer. The pressure can be relieved.
As a result, the belt layer will not be wavy and deformed,
It is possible to improve the uniformity of the tire.

[0012]

Example: Tire size is 245/40 ZR17,
An inventive tire having the tread pattern shown in FIG. 1 and having the following dimensions and a comparative tire having the same structure as the inventive tire except that no ridge was provided were manufactured. Tread deployment width 222 mm Groove width of quasi-main groove (maximum width) 13 mm Groove width of main groove 18 mm Groove depth of quasi-main groove 7.2
mm Groove depth of main groove 8.2 mm Height of ridge in quasi-main groove 1.5 mm Height of ridge in quasi-main groove 1.5 mm Angle of quasi-main groove with respect to tire circumferential direction 10 ° RFV and RRO were measured under the following measurement conditions at an air pressure of 2 kgf / cm ² , respectively, and the results shown in Table 1 were obtained.

RFV: According to the measuring method defined in JASO C607-87. RRO: The absolute value of the runout (roundness) of the tire in the radial direction was determined according to the above RFV measurement method. The measured values of RFV and RRO are both represented by an index whose reciprocal is 100 when the value of the comparative tire is 100, and the higher the index value, the better the uniformity.

[0014] As can be seen from Table 1, the tire of the present invention has RFV and RRO.
Both are better than the comparative tires, and it can be seen that the uniformity is improved.

Further, when the crown portion of the above-mentioned tire of the present invention and the comparative tire were cut, and the distribution of the rubber thickness of the crown portion was measured, it was confirmed that the tire of the present invention had little variation in the rubber thickness. ..

[0016]

As described above, according to the present invention, when the groove width of the main groove and the quasi-main groove is set to be larger than the groove depth and 6 to 9% of the tread development width is set, the groove bottom has a groove direction. Since at least one ridge extending along the ridge is provided, the unvulcanized rubber can be absorbed in the recess of the groove-forming bone corresponding to the ridge during vulcanization molding. Therefore, the unvulcanized rubber with incomplete flow can reduce the pressing force applied to the lower belt layer and prevent wavy deformation from occurring in the belt layer, thereby improving the tire uniformity. Does not lower.

[Brief description of drawings]

FIG. 1 is a plan development view showing an example of a tread pattern of a tire of the present invention.

2 is a cross-sectional view of the main groove of FIG. 1 taken along a meridional section.

[Explanation of symbols]

 1 tread surface 2 main groove 3 sub groove 4 semi-main groove 5 ridge

Claims (1)

Claim: What is claimed is: 1. On a tread surface, at least one main groove extending in the tire circumferential direction having a groove width larger than the groove depth and having a size of 6 to 9% of a tread development width. Including a plurality of sub-grooves extending in the tire width direction and a plurality of quasi-main grooves extending obliquely at an angle of 3 to 30 ° with respect to the tire circumferential direction and longer than the contact length of the tire A pneumatic tire for a passenger vehicle, which is a tire having at least one ridge extending along the main groove and the quasi-main groove on the groove bottoms of the main groove and the quasi-main groove, respectively.