JPH06316205A - Pneumatic tire for passenger car - Google Patents

Abstract

PURPOSE:To provide a pneumatic tire for passenger car suitable for achievement of a lightweight construction by reducing the thickness of the side wall rubber. CONSTITUTION:The position P where a pneumatic tire concerned has the max. section width, is substantially identical to the position A of the wound-up end of a carcass 2. The wall thickness of the side wall rubber 6 in the position P is represented by (t) while the radial direction distance between the position P and the position B of the bead base reference point is represented by H1, and the condition 0.5<=t1<=0.8t should be met, where t1 is the mean wall thickness of the rubber 6 between a position C apart by 0.2XH1 inward in the radial direction from the position P and another position D at the rubber inner extremity in the radial direction. Also the radial direction distance between the position P and a position E at the rubber outer extremity in the radial direction is represented by Hu, and the condition 0.5t<=tu<=0.8t should be met, where tu is the mean wall thickness of the rubber 6 between a position F apart by 0.3XHu outward in the radial direction from the position P and a position G apart by 0.8XHu outward in the radial direction.

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 passenger cars, which is lightened by thinning sidewall rubber.

[0002]

2. Description of the Related Art In a radial tire, the outer periphery of a carcass is covered with a belt, the outer periphery of the belt is covered with a tread rubber, and both outer sides of the carcass are covered with sidewall rubbers. Further, both ends of the carcass are wound up from the inside of the tire toward the outside to cover the bead core.

Conventionally, the thickness of the sidewall rubber is uniform over almost the entire side portion, and in the tire for passenger cars, it has been set within the range of 3 to 5 mm. Further, the position of the winding end of the carcass was arranged either radially outward or radially inwardly from the position of the maximum sectional width of the tire. That is, to improve the rigidity of the sidewalls, the roll-up end is arranged radially outward of the position of the maximum cross-sectional width of the tire. To reduce the material cost, the roll-up end is set to the maximum cross-sectional width of the tire. It was arranged radially inward of the position.

[0004]

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.

As described above, the radial tire is a carcass,
It is mainly composed of a belt, a tread rubber, and a sidewall rubber. When the tread rubber is made thin, abrasion resistance is lowered, and when the carcass and the belt are made lighter, the strength is lowered and durability is lowered.

On the other hand, the side wall rubber has a main purpose of preventing deterioration of the carcass due to sunlight, oxygen, water, etc., and is less likely to be damaged by the recent improvement in road conditions.

However, if the side wall rubber is made thin, the carcass may be damaged at the position of the maximum sectional width of the tire due to curbs or the like. Since the winding tip of the carcass ply has a step, when the green tire is vulcanized and molded, the sidewall rubber flows in to fill this step, and the thickness of the sidewall rubber near the winding end becomes thin. Since the coefficient of thermal expansion of rubber is larger than that of fibers, the rubber is cooled and its volume is reduced, and the tip of the winding portion is relatively raised. Therefore, if the thickness of the side wall is thin, the rolled-up portion of the carcass ply is visible and loses its commercial value, and the tip of the rolled-up portion is stimulated, and the sidewall rubber is apt to crack. Further, if the sidewall rubber is made thin, the carcass at the position of the maximum cross-sectional width of the tire may be damaged by curbs or the like.

In view of the above technical problems, an object of the present invention is to provide a pneumatic tire for passenger cars suitable for thinning sidewall rubber.

[0009]

A feature of the present invention is that each end of a carcass ply hung between one and the other of a pair of bead cores extends from the inside to the outside around each bead core. The carcass is wound up and extends in the tire radial direction along the inner surface of the sidewall to terminate in the tire side part to form a carcass. The carcass crown part is covered with tread rubber, and the tire side part is covered with sidewall rubber. In a tire that is covered and has a hardness higher than that of the sidewall rubber, covers the outer surface of the lower end of the sidewall rubber and the part that contacts the rim of the tire. A bead base measured in a state where it is terminated near the position, the tire is mounted on the rim, and a regular internal pressure is filled. The radial distance from the reference point B to the maximum sectional width position P is H1, the distance from the maximum sectional width position P to the radial outer end position E of the sidewall rubber is Hu, and the sidewall rubber at the maximum sectional width position P is The wall thickness is t, the radial inner end position D of the sidewall rubber is from a point C on the sidewall that is 0.2 Hl radially inward from the maximum sectional width position P.
The average wall thickness of the sidewall rubber up to tl, and the radial outer end position G of the sidewall rubber from a point F on the sidewall that is 0.3 Hu radially outward from the maximum sectional width position P.
Let t be the average thickness of the side wall rubber up to
Is 0.5 to 0.8 times t, and tu is 0.5 to 0.8 times t.

The wall thickness t at the position P of the maximum sectional width
Is preferably 2.5 mm ≦ t ≦ 3.5 mm.
This is because when the t is less than 2.5 mm, the rolled-up end of the carcass appears to be raised, and the possibility of cracking in the sidewall rubber increases, and when it exceeds 3.5 mm, sufficient weight reduction cannot be achieved.

[0011]

According to the structure of the present invention, since the wall thickness t of the sidewall rubber at the position P of the maximum cross-sectional width of the tire becomes large, it is possible to prevent the carcass from being damaged by a curbstone or the like.

Since the wall thickness t of the sidewall rubber at the position P of the maximum sectional width of the tire becomes large and the position A of the carcass winding end is set in the vicinity of the position P where the wall thickness is large, the carcass winding The rubber thickness on the winding end does not become so thin that the end appears to float.

When the tire cross-section height decreases due to a load acting on the tire, the maximum cross-section width position is projected and deformed. Therefore, if there is a winding-up end at this position, cracks in the sidewall rubber tend to occur. It is preferable to remove the maximum sectional width position and set the winding end at a point 3 to 5 mm radially inward or outward from the maximum sectional width position.

The average wall thicknesses tl and tu are 0.5t ≦ tl ≦
0.8t and 0.5t ≦ tu ≦ 0.8t are set to tl
Alternatively, if tu is less than 0.5 t, the wall thickness between the carcass ply and the bottom of the display such as the manufacturing symbol engraved in the sidewall becomes small, and the stress concentrated at the bottom of the display is relaxed. This is because the required rubber is insufficient and the possibility of cracking increases, and when tl or tu exceeds 0.8 t, sufficient weight reduction cannot be achieved.

It should be noted that the positions C and 0.3 × radially inwardly separated from the position P of the maximum sectional width of the tire by 0.2 × Hl.
It is preferable that the thickness of the sidewall rubber between the position F and the position F which is radially outwardly separated by Hu be determined so that the outer surface of the sidewall is a smooth continuous surface. Also,
The wall thickness of the sidewall rubber between the position G separated by 0.8 × Hu from the position P of the maximum cross-sectional width of the tire and the position E of the radial outer end of the sidewall rubber is the outside of the sidewall rubber in the radial direction. It is preferable to set the thickness as small as possible at the end.

[0016]

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

FIG. 1 shows the left half of the tire cross section. In the tire 1, each end of the carcass ply 2 hung between one side and the other side of the pair of bead cores is wound up from the inside to the outside around each bead core 7 to form a winding portion 2B. The portion 2B extends outward in the tire radial direction along the inner surface of the sidewall rubber 6 and ends 3 mm above the maximum sectional width position P. The crown portion of the carcass 2 is covered with the tread rubber 5, the tire side portion is covered with the sidewall rubber 6, and the rim strip 10 made of rubber having a hardness higher than that of the sidewall rubber 6 is provided on the outer surface of the lower end portion of the sidewall rubber 6. The belt 3 is provided between the carcass 2 and the tread rubber 5, and the inner surface of the carcass 2 is covered with the inner liner 9. Carcass ply body 2A and hoist 2B
The bead filler 8 is filled in the space surrounded by the bead core 7. The radial outer end position of the sidewall rubber 6 and the widthwise end positions of the first layer belt 3 are substantially aligned with each other.

The radial distance from the bead base reference point B to the maximum cross sectional width position P measured with the tire mounted on the rim and filled with the normal internal pressure is Hl, and from the maximum cross sectional width position P to the sidewall rubber diameter. H to the outer end position E in the direction
Let u. The bead base reference point B is a position on the tire bead base that is in contact with the point where the rim diameter is measured.

The wall thickness t of the sidewall rubber at the maximum sectional width position P is in the range of 2.5 mm to 3.5 mm.

0.2 inward in the radial direction from the maximum sectional width position P
The average thickness tl of the sidewall rubber from the point C on the sidewall away from Hl to the radially inner end position D of the sidewall rubber is in the relationship of tl = 0.5t to 0.8t,
The average thickness tu of the sidewall rubber from a point F on the sidewall radially outwardly 0.3 Hu from the maximum sectional width position P to a radial outer end position G of the sidewall rubber is
There is a relationship of tu = 0.5t to 0.8t.

Table 1 below shows the data of the examples of the present invention and the data of the comparative examples.

[0022]

[Table 1]

The size of the radial tire for which the data in Table 1 above was obtained is 175 / 70R13, and as described above, the position P of the maximum cross-sectional width of the tire and the position A of the winding end of the carcass substantially match. The weight of the sidewall rubber is shown as an index with the sidewall rubber weight of the tire of Comparative Example G being 100, and the smaller the number, the lighter the weight. The average wall thickness tl is obtained by dividing the radial distance between the position P and the position B into 10 equal parts, and measuring the wall thickness of the sidewall rubber 6 at each equal point between the position C and the position D. , And obtained by arithmetically averaging the measured values. The average wall thickness tu is obtained by dividing the radial distance between the position P and the position E into 10 equal parts and measuring the wall thickness of the sidewall rubber 6 at each equal point between the position F and the position G. , And obtained by arithmetically averaging the measured values. Further, the presence or absence of cracks was confirmed after 10 tires were mounted on an actual vehicle and run for 10,000 km. In Comparative Examples F and H, two out of 10 characters were inscribed on the sidewall surface. A crack was confirmed at the bottom of the.

From Table 1 above, Examples A, B, and
According to C and D, it is recognized that the weight of the sidewall rubber is reduced, cracks are not generated, and the carcass winding end portion is not protruded as compared with Comparative Example G. On the other hand, in the comparative examples E and H in which the thickness t of the sidewall rubber at the maximum width position P of the tire was less than 2.5 mm, the carcass hoisting end was found to be raised. Also, the average thickness t
Crack generation was observed in Comparative Example F in which l and tu were less than 0.5 times the wall thickness t at the position P of the maximum width and Comparative Example H in which the wall thickness t was less than 2.5 mm.

[0025]

According to the pneumatic tire for passenger cars of the present invention, when the sidewall rubber is made thin to reduce the weight,
It is possible to prevent the carcass from being damaged by a curb, etc., and it is possible to prevent the side wall rubber from becoming thin enough to make the rolled-up end of the carcass appear to be raised, and to prevent cracking.

[Brief description of drawings]

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

[Explanation of symbols]

 2 carcass 6 sidewall rubber

Claims (1)

[Claims] 1. Each end of a carcass ply hung from one to the other of a pair of bead cores is wound up from the inside to the outside around each bead core,
This winding portion extends along the inner surface of the sidewall in the tire radial direction and terminates in the tire side portion to form a carcass, and the carcass crown portion is covered with tread rubber,
The tire side part is a rubber rim strip that is covered with sidewall rubber and has a hardness higher than that of the sidewall rubber.In a tire that covers the outer surface of the lower end of the sidewall rubber and the part that contacts the rim of the tire, A radial distance from the bead base reference point B measured in a state where the tire is mounted on a rim and filled with a normal internal pressure, which is terminated in the vicinity of the maximum cross sectional width position indicating the maximum width, in the radial direction, is Hl, The distance from the maximum sectional width position P to the radial outer end position E of the sidewall rubber is Hu, the thickness of the sidewall rubber at the maximum sectional width position P is t, and 0 from the maximum sectional width position P in the radial direction. The average wall thickness of the sidewall rubber from the point C on the sidewall at a distance of 2Hl to the radial inner end position D of the sidewall rubber is tl, and the maximum sectional width position P is The average wall thickness of the sidewall rubber from the point F on the sidewall 0.3 Hu apart outward in the direction to the radial outer end position G of the sidewall rubber is tu, and tl is 0.5 to 0.8 of t. Tw, tu is 0.5 to t
Pneumatic tire for passenger cars characterized by being 0.8 times.