JPS6060004A - Pneumatic radial tire for muddy area or snow area - Google Patents

Abstract

PURPOSE:To enhance the rolling resistance and control ability of a radial tire by providing block patterns having a large negative ratio, and by appropriately changing the profile of the carcass radiation surface of the radial tire having a relatively large pattern groove depth. CONSTITUTION:Denoting, as B, the crossing point at which a line, in parallel with the tire rotating axis, passing through a departing point A with respect to the outer surface of the flange 9 bead part of a rim 8 intersects the carcass line, and, as C, the terminal point of a line perpendicularly extending from the crossing point B to the carcas line, a ratio R/R' between the radius R' of an imaginary reference circle having a line BC as its chord and the radius R of curvature of a shoulder section contour curve passing through the terminal point C of the carcass line is set at a value of 0.65 to 0.85. Further, the maximum distance (f) of the remaining part of the carcass line having an inflection point between the point at which the carcass line is contiguous with the above-mentioned curve and the crossing point B from the reference circle arc, is set at a value of 5 to 10mm.. Further, the tread section is formed with a block type relatively deep pattern grooves having a negative ratio of 33 to 10%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention aims to propose improvements to pneumatic radial tires for passenger cars that are particularly suitable for use on muddy terrain and/or snow.

(Prior art) In order to improve the traction performance of muddy and/or snow tires, a block pattern is used to improve the traction performance. Increasing the ratio of the partial to total enclosing and increasing the groove depth are generally adopted.

However, when these measures are used to reinforce conventional radial tires, ■ the rigidity of the tread decreases, resulting in lower cornering power (CP) and self-lining torque (SAT).
decreases, and handling stability deteriorates.

■ It is necessary to use thick tread rubber to increase the groove depth, which increases the phase ratio of the tread rubber and increases shear deformation, resulting in increased rolling resistance due to the distortion of the tread rubber. causes deterioration.

There were usually some drawbacks. Therefore, currently, in order to secure traction performance, it is necessary to sacrifice steering stability and rolling resistance.

(Objective of the Invention) As described above, by using a block pattern to increase the perturbation ratio and deepening the groove depth of the pattern, traction as a pneumatic radial tire for muddy terrain and/or snow can be achieved. By reinforcing the tire, which can advantageously overcome the conventional problems that were unavoidable when ensuring performance, in particular by appropriately changing the radial surface profile of the carcass, rolling resistance and maneuverability can be achieved without compromising traction performance. It is an object of the present invention to propose a pneumatic radial tire of this type with improved stability1 performance. be done.

It has a pair of annular sidewall parts each having a bead part and a tread part that spans these sidewall parts on the outside in the radial direction, and each of these parts is made of at least one ply of an organic fiber cord layer and has the above-mentioned σ). A carcass in which both ends of the ply are wound outward around a bead core embedded in each bead portion, and this side wraps around the blade and is arranged to intersect with each other at a relatively small angle with respect to the center circumference of the tire. The tire is reinforced with at least two layers of high elasticity cord rubber [FFL], filled with rubber filler between the carcass and its ply rewind, and hardened at the bead, and assembled with the regular rim. Filled with the inner surface of the flange of the rim... Under the flying attitude, the intersection point B of the carcass line and a straight line flat on the axis of rotation of the tire passing through the point of departure from the outer surface of the bead of the flange of the rim. A reference circular arc that passes through the end point C of a line segment that originates from the intersection point B, intersects perpendicularly with the above-mentioned straight line, and ends at the carcass line, with a distance equal to the maximum separation distance of the carcass line from the line segment, and that the line segment is assumed to be a chord. The ratio R/R' of the radius of curvature R of the shoulder contour curve passing through the end point C of the carcass line to the radius R' of the carcass line is in the range of 0.65 to 0.85, and the carcass line is smoothly connected to the curve. The carcass radial surface profile has a maximum distance f of the residual area of the carcass line with a single inflection point in the range of 5 to 105 m with respect to the reference arc, and the tread portion has a negative A muddy and/or muddy land characterized by having a block type pattern with a ratio of 83 to 401%, and this pattern having a relatively deep groove depth.
Or pneumatic radial tires for snow.

In this invention, the negative ratio of the tread part is 33 to 40%, and the groove depth l is relatively deep, with a stiffness of 180 to 140% compared to that of a normal tire. is less than 3a%, groove depth is 1
If it is less than 30%, the traction performance on muddy ground or snow will be insufficient, but if the child protection ratio is 40% and the groove depth is 14%.
If it exceeds 0%, the rigidity of the tread portion becomes too weak, resulting in poor handling stability when driving on general roads. In this case, the radial profile of the carcass is appropriately changed, as shown by the solid line in FIG. 1, to intentionally deviate from the natural equilibrium shape.

i.e. of the carcass corresponding to the lower area of the sidewall)
'The curvature of the Pi part contour curve is the radius R of the reference arc in Fig. 1.
The ratio R/R' is in the range of 0.65 to 0.85, and in addition to this, the curvature of the lower area of the sidewall is reduced, or
It is particularly important that the maximum distance f between the carcass line FB and the circular arc 0 in FIG. 1 be between 5 and 10 so as to form an inverted R shape.

What should be noted here is that the arc B E shown in Figure 1 G
G G'i is just a reference arc, so-called natural.

・Although it is originally separate from the carcass radial surface profile based on the equilibrium shape, the upper region of the sidewall is relatively thin and has low rigidity due to the Z section itself, so natural equilibrium The carcass radiation surface profile (based on the shape) will closely approximate the portion n of this circular arc.

That is, the above ratio R/R' is between 0.65 and 0.65.
It must be noted that a value of 85 can only occur as a result of deliberately deviating from the natural equilibrium shape.

On the other hand, the lower area of the sidewall does not roll up radially outward around the carcass core, and the bead part is hardened by filling a rubber filler between the rolled up parts. It is a part with size 1 stiffness, and is based on a natural equilibrium shape. \ f shown in this invention is 5 to l
0IIIl! 1 αLt is a value that cannot be obtained unless the natural equilibrium shape is deliberately removed and the curvature of the carcass in the lower region of the sidewall is made smaller, or an inverted R shape is given.This value is different from the conventional natural equilibrium shape. completely distinguishable.

The reason why the rolling resistance of a tire having a carcass radial surface profile that intentionally deviates from the above-mentioned natural equilibrium shape is improved is as stated in the specification of the previously filed Japanese Patent Application No. 158018/1982. In order to manufacture such a tire, it is necessary to take measures such as those shown in the previously filed Japanese Patent Application No. 57-40231.

Here, when R/R' is larger than 0.85, the natural equilibrium shape is intentionally removed to reduce the shear deformation of the upper side part, and the rolling The effect of improving resistance cannot be sufficiently obtained, and if R/R' is less than 0.65, one bending deformation will be concentrated on the relatively thick padtress, making it difficult to reduce shear deformation. The effect of improving rolling resistance obtained by using this method is canceled out.

Furthermore, if the value of f is less than 511IjI, energy...
・The effect of reducing energy consumption cannot be fully demonstrated,
Furthermore, if f exceeds 10, the tension of the carcass in the area below the sidewall becomes too high when the internal pressure is increased, which not only has a negative effect on durability, but also causes damage to the outer surface of the tire as the carcass gets inside the tire. This results in disadvantages such as poor compatibility with the rim due to the relatively inner position.

The peculiar shape of the above-mentioned solid carcass line is that the carcass tension in the upper region of the sidewall is relatively low, and in M, the carcass tension in the lower region of the sidewall is relatively high.

It is this characteristic of tension behavior that provides improved handling stability in addition to improved rolling resistance even under a tread pattern adapted for use on muddy and/or snowy terrain.

That is, when a slip angle is added to the tire and a lateral force is applied to the tire, the tire of the present invention has a high carcass tension near the bead and a high apparent rigidity, resulting in high cornering power. At this time, the carcass tension in one area on the sidewall is relatively low, which increases the pneumatic trail, that is, the distance between the center of contact with the ground and the cornering force absorption point located behind it. This is because the high cornering force synergistically increases the compensating torque.

Hereinafter, specific effects will be shown with examples.

The contents of the tires of Examples and Comparative Examples are shown in Table 1, and FIGS. 2 and 3 show cross-sections of each tire of Examples of the present invention, and FIG. 4 shows tires of Comparative Examples.

In the figure, 1 is a beat part, 2 is an annular sidewall part, 8 is a tread part, 4 is a carcass, 5 is a belt, 6 is a rubber filler, 7 is a rim, and 8 is a flange thereof.

Tire contents in Table 1 and Ratio All of these test tires had a carcass of 15oO”A.
The belt consists of two sheets of steel cord (twisted structure I x 5 x 0.25++ m) crossed with each other at a cord angle of 20' with respect to the tire equator. Additionally, tread rubber Get 50 Hz 1%
Tensile strain of , loss tangent (tan δ) -0 measured at 60°C with a spectrometer manufactured by Script Manufacturing Co., Ltd.
, 28, Shore A hardness (Hd) -5.9°, and the undertread rubber in the case of the two-layer structure according to Example 2 has Shore A hardness (Hd) of J'fP (tan δ) - o, oe on the loss. Hardness IHd) -56°. A traction performance test was conducted as follows, and the results shown in Table 2 were obtained.

Test method.

The time required to travel 100 m after starting on a snow surface with an average slope of 8° was measured, and the time of Comparative Example 1 was 1.
00 for comparison. The larger the index, the shorter the time required for running and the better the traction performance.

Table 2 Traction performance test results The example of the present invention has overwhelmingly superior traction performance compared to Comparative Example 1, and also has a larger traction ratio and deeper groove depth than Comparative Example 2. The traction performance is slightly better.

Next, a rolling resistance test was conducted as follows and the results are compared in Table 8.

The tire was pressed against a drum at rolling resistance test conditions + 1707 m, rotated to a predetermined speed, then coasted and calculated from the degree of deceleration during continuous rotation.The rolling resistance of Comparative Example 1 was set as 100, and the performance of other tires was evaluated. Comparison was made using an index. A high index indicates low rolling resistance.

Note: All tire pressures are 1 and 7)! 9/C-・Example of the present invention] showed substantially the same rolling resistance as Comparative Example 1, which had a shallow groove depth, despite having a deep groove depth and a large negative ratio. There is. Also, compared to Comparative Example 2 in which the radiation surface profile of the carcass was not changed appropriately, the carcass line was considered to be 10 to 1
It can be seen that the rolling resistance is improved by 5%.

It can be seen that Example 2 shows improved rolling resistance than Comparative Example 1, which has a shallower groove depth, and is particularly preferable in terms of implementing the present invention.

The following tests were conducted regarding steering stability, and the results are shown in Table 4.

Test method: Press the tire against a 1707+m drum, add a slip angle, measure the cornering power, and simultaneously measure the restoring torque, find its maximum value, Comparative Example 1
An index comparison was made with the score as 100. The larger the index,
It has large cornering power and restoring torque, indicating good handling stability.

Table 4 Steering stability test results Note All tire internal pressures were 1.7 kg/Cm.Although the tire according to the present invention has a deep groove depth and a large negative ratio, the groove depth is shallow and the negative ratio is low. It shows a 1,1 steering stability performance that is almost equal to or better than that of the smaller Comparative Example 1.

Comparing Example 1 and Comparative Example 2, it can be seen that the steering stability is much improved by appropriately changing the radiation surface profile of the carcass.

(Effects of the Invention) As described above, according to the present invention, a radial tire for muddy terrain and/or snow, which has a block pattern with a large negative ratio and whose groove depth is relatively large. By appropriately changing the carcass radiation surface pro 7a il, that tiger.

The performance can be advantageously improved, and the above solid results show that it is also suitable as an all-weather type tire.

[Brief explanation of the drawing]

The first factor is an explanatory diagram of the relationship between the radial surface profile (solid line) and the reference arc (broken line) of the tire according to the present invention.
The figure is a cross-sectional view of the tire of Example 2, and FIG. 4 is a cross-sectional view of the tire of Comparative Example 1 when the internal pressure is filled. 1... Bead part 2... Annular side part 3... Tread part' +-carcass 5... Belt 6... Rubber filler 7... Rim 8... Flange. Figure 2 Figure 3

Claims (1)

[Scope of Claims] L has a pair of annular sidewall parts each having a bead part and a tread part spanning these sidewall parts on the outside in the radial direction, and each of these parts is connected to at least one of the organic fiber cord layers. A carcass consisting of one ply with both edges of the bra wound outward around a bead core buried in each of the above-mentioned bead parts, and a carcass wrapped around the carcass at a relatively small angle with respect to the center circumference of the tire. The tire is reinforced with at least two layers of rubber-coated belts made of high-modulus cords arranged crosswise with each other, and filled with rubber filler between the carcass and its ply rewind to harden the bead part. In combination with the rim and in the mounting position filled with the normal internal pressure, the intersection point B of the carcass line and a straight line parallel to the axis of rotation of the tire passing through the point of departure from the outer surface of the bead of the flange of the rim, starting from this intersection B, and the above-mentioned The radius R' of a reference arc that passes through the end point C of a line segment that is orthogonal to the straight line and reaches the carcass line, with a distance equal to the maximum separation distance of the carcass line from the line segment, and that is imaginary with the line segment as a chord.
, the ratio R/R' of the radius of curvature R of the shoulder contour curve passing through the end point C of the carcass line is 0.65 to 0.
．． 85, and the maximum distance f of the residual area of the carcass line, which has a single inflection point while smoothly connecting with the curve and reaching the intersection B, with respect to the reference arc is in the range of 5 to 10 lines. The tread has a certain carcass radial surface profile, and the tread portion has a block-type pattern with an I-G tape ratio of 38 to 40%, and this pattern has a relatively deep groove depth. Pneumatic radial tire for ground and/or snow.