JPS60203505A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To enhance draining-, stable steering-, and ground gripping-performance at the time of cornering by forming a side wall, which is situated on the outside in the direction of the tire axis, of a groove provided in a tread by means of two inclined surfaces whose angles against each tread-normal line differ with each other within a prescribed range. CONSTITUTION:Side walls 5a and 5b of a longitudinal groove G2 provided in a tire tread surface are inclined by angles alpha and beta against lines L and L normal to the tire tread surface. And the side wall 5a situated on the outside in the direction of the tire axis is formed by both a wall 5aa neighboring to the tread surface and a wall 5ab neighboring to the tread bottom. In addition, angles beta1 and beta2 against each tread-normal line L and L are determined in such a manner that they range from 5 deg. to 30 deg. and moreover they satisfy the relation beta1<beta2. On the other hand, distance D1 between the tread surface and a border line P between an inclined surface 5aa and an inclined surface 5ab is set at 30-80% of depth D of the groove G2, while both the beta1 and beta2 are made larger than alpha. With this constitution, draining-, stable steering-, and ground gripping-performance can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention minimizes deformation of the longitudinal groove during running by forming the axially outer sidewall of the longitudinal groove on the tire tread surface with a first slope and a second slope with different inclination angles. This invention relates to a pneumatic tire that improves drainage performance, handling stability, and grip during cornering by suppressing the amount of water.

In general, the tread surface of a tire is provided with a plurality of vertical grooves that are continuous in the tire circumferential direction in order to improve drainage performance and grip performance on a wet road surface. From the viewpoint of improving drainage performance, it can be said that it is effective to increase the groove volume by increasing the width, depth, or number of vertical grooves. However, when the width of the longitudinal groove is increased, the value of the so-called sea/land ratio of the tread increases, the rigidity of the tread decreases, and the handling stability and wear resistance decrease, and the former characteristics are inferior to the latter. It has a contradictory relationship with the characteristics. Therefore, conventionally, the shape of the grooves on the tread surface has been designed with consideration to the balance of these characteristics, and the groove width, groove depth, and number of grooves are naturally limited to a certain range. The cross-sectional shape of the vertical groove is formed so that the side walls of the groove are symmetrical to each other from the viewpoint of preventing uneven wear and aesthetic appearance. With such conventional groove design technology,
It is difficult to simultaneously improve drainage performance, handling stability, and wear resistance.

Therefore, in order to solve the above problems, the present inventor modeled the deformation behavior of the tread surface during tire running, studied in detail the relationship between the cross-sectional shape of the groove and its deformation state, and based on this knowledge, the cross-sectional shape of the groove By optimizing this, we were able to improve handling stability and wear resistance without sacrificing drainage performance.

The present invention has a plurality of vertical grooves continuous in the tire circumferential direction on the tread surface, and at least one of the vertical grooves has a cross-sectional shape such that the outer side wall in the tire axial direction is a first groove adjacent to the tread surface. a second adjacent to the slope and the bottom of the tread;
The angles (β, ) (β2) of these slopes with respect to the normal to the tire tread surface are different from each other, and the angles (β1) (β2) of the first slope and the second slope with respect to the normal to the tire surface are different from each other. ) is a pneumatic tire characterized by having a tread portion having an angle in the range of 5° to 30°.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is the right half of a schematic cross-sectional view of a pneumatic tire with a radial structure according to the present invention, and FIG. 2 is an enlarged view of the longitudinal grooves in FIG. 1. 1st
In the figure, xx is a line parallel to the tire axis, and YY is the tire equatorial plane.

The pneumatic tire (1) of the present invention has a pair of bead cores (2
), a carcass (3) that is folded back from the inside to the outside around the carcass, and a belt layer (4) disposed on the outside of the crown portion of the carcass. Then, there are two vertical grooves (Gl,
G2) is located. The side walls (5a, 5b) of one longitudinal groove (G2) are aligned with the normal (L) of the tire tread surface.
(α) and (β1) (β2
) is inclined to form a. The outer side wall 5a in the tire axial direction is a first slope (
5aa) and a second slope (5ab) adjacent to the tread bottom.
The angles (β, ) (β2) of these slopes with respect to the normal line of the tire tread surface are different from each other. The angle (β1) of the first slope is preferably smaller than the angle (β2) of the second slope.

Also, the distance from the tread surface to the boundary (P) between the first slope (5aa) and the second slope is 30% of the groove depth D) of the vertical groove G2.
~80%.

Here, each slope (5aa) of the outer side wall in the tire axial direction
It is preferable that the angles (β1) and (β2) of (5ab) are asymmetrical grooves that are inclined more than the angle (α) of the axially inner side wall (5b) of the tire. Here the side wall (5a15b)
Both can be formed with a substantially constant inclination in the tire circumferential direction, or can be formed with an inclination angle that changes in the tire circumferential direction. By forming the cross-sectional shape of the vertical groove as described above, the 'i@1 slope is reinforced by the second slope, which improves the rigidity of the tread part when the tire is running, which reduces the amount of deformation of the vertical groove and provides stability. The vertical groove volume is maintained, drainage performance is maintained, and operational safety is further improved. This was confirmed by modeling the deformation behavior of the tread surface during tire running and from the relationship between the cross-sectional shape of the groove and its changing state.

That is, in FIG. 3, when the tire T corners in the left direction (PL direction) while traveling in the p direction, the tread portion of the right half (shaded area) of the tire undergoes deformation in the f direction. To explain this with reference to FIG. 4, which shows a right half sectional view of the tread section, the tread surface contour (OL) in an unloaded state deforms during cornering, and the vertical groove G
The groove width of a5Gb will be significantly narrowed, and the grounding characteristics will deteriorate accordingly. For example, during cornering, the groove width of the vertical groove Ga is deformed so as to decrease from Wl to W2, so the volume of the vertical groove decreases and drainage performance deteriorates. Therefore, it is preferable to reduce the amount of change in the width of the longitudinal groove as much as possible, but when we examined the relationship between the amount of change in groove width and the side wall angle of the longitudinal groove, we found that the amount of change in groove width is the same as the amount of change in the width of the longitudinal groove on the outer side wall in the axial direction of the tire. It was found that the angle (β) decreases as the angle (β) increases, and that the axially inner sidewall Gal of the tire has a smaller contribution rate to the sidewall angle of the amount of deformation than the axially outer sidewall Ga2 of the tire.

For example, when a force in the f direction is applied to the tread shown in FIGS. 5 and 6, the amount of deformation of the respective side walls of the longitudinal grooves GΔ and G'B differs as shown in Table 1 due to the difference in the inclination angle. It's coming. In Fig. 5, α is 5 degrees, β is 5 degrees, and in Fig. 6, G1 is 5 degrees, β1β2 is 5 degrees, and the distance from the tread surface to the boundary between the first slope and the second slope is 60 degrees of the groove depth. %. From the front, place the axially outer side wall of the tire first.
The vertical groove GC1G in Fig. 6 is configured in two stages: a slope and a second slope.
It is recognized that in case of D, the decrease in groove width can be significantly reduced.

Table 1 Note that if the inclination angle of the vertical groove is increased, the ground contact area of the tread portion will be reduced, and the drainage effect and wear resistance of the vertical groove will be reduced, so there is naturally a limit to the inclination angle. In the present invention, the angle (al>(a'2) of the inner sidewall (5b) (6b) in the tire axial direction with respect to the normal line of the tire tread surface is O
o - 10°, on the other hand, the outer side wall in the tire axial direction (5
The angle (β, ) (β2) of each slope with respect to the normal line of the tire tread surface where a>(6a) is preferably set in the range of 5° to 30°.

In this way, in the present invention, the side wall of the longitudinal groove on the outside in the tire axial direction is composed of two slopes with different inclination angles, and the inclination angle of the side wall is made smaller on the inside in the axial direction of the tire and larger on the outside in the tire axial direction. By setting the inclination angle within a specific range, it is possible to minimize the deformation of the sidewall and maintain the volume of the vertical groove almost constant, which improves drainage performance, braking performance, and wear resistance during cornering. improve.

Although the present invention is suitably employed in radial tires whose tire tread portions include a belt layer reinforced with high-elastic fiber cords such as steel cords, it can also be similarly employed in belted bias tires and cross-ply tires. can.

In addition to the so-called rib pattern having vertical grooves continuous in the circumferential direction of the tire, the present invention also applies to block patterns, rib patterns, etc.
Rag patterns and rib-block patterns can also be applied in the same way.

[Brief explanation of the drawing]

Fig. 1 is the right half of the cross-sectional view of the tire of the present invention, Fig. 2 is an enlarged view of the vertical groove portion, and Fig. 3 is the tread of the tire when running.
4, 5, and 6 are partial cross-sectional views of the tread portion. ■... Tire, 2... Bead core, 3... Carcass, 4... Belt layer, 5a, 5b, 6a, 6b
-・-・・・・Side wall, G1, G2, GΔ, GB,
GCGD... vertical, patent applicant Sumitomo Com Industries Co., Ltd. Agent Patent attorney Nakamura Post'A 1 F!

Claims (2)

[Claims] (1) The tread surface has a plurality of longitudinal grooves continuous in the tire circumferential direction, and at least one of the longitudinal grooves has a cross-sectional shape that is the first groove adjacent to the tire axially outer sidewall metred surface. a second slope adjacent to the bottom of the sloped tread, the angles (β1) (β2) of these slopes with respect to the normal to the tire tread surface are different from each other; A pneumatic tire comprising a tread portion whose angle (βl) (β2) with respect to the normal to the surface is in the range of 5° to 30°. (2) The pneumatic tire according to claim 1, wherein the angle (l) of the axial side wall of the longitudinal groove with respect to the normal line of the tire tread surface is in the range of 0 to 10 degrees.