JPS6060003A - Pneumatic radial tire improved in rolling resistance and durability - Google Patents

Abstract

PURPOSE:To enhance the rolling resistance of a tire without deteriorating the separation-resistivity of the end section of a belt, by covering the end part of a reinforcing belt layer with a cover obtained by covering heat-shrinkable cords with a rubber, and as well by appropriately changing the radiation surface profile of a carcass. 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 carcass 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 end section of a belt which is embeded in the tread section is covered with a cover obtained by covering heat-shrinkable cords with a rubber.

Description

[Detailed Description of the Invention] (Technical Field) This invention relates to pneumatic radial tires, particularly in relation to improving tire durability when the radial surface profile of the carcass is intentionally deviated from its natural equilibrium shape to improve rolling resistance. The technical content described in the specification is located in the field of technology to which radial tires primarily used for passenger cars belong.

Here is the natural per radial profile of the carcass.

Equilibrium shape means that the carcass line, which lies along the center line of the thickness of the carcass ply in the cross section that includes the radial plane, i.e., the meridian of the tire, has a bending force due to only the tension of the carcass ply against the internal pressure of the tire. This means a carcass line shape that can resist shearing forces without accompanying them.

(Problem) Regarding how the rolling resistance can be advantageously improved by appropriately changing the radiation surface profile of the carcass and deliberately removing it from the above-mentioned natural equilibrium shape, we have previously filed Japanese Patent Application No. No. 40231, and patent application No. 57-1580
No. 18 and both specifications are as described in l): details.

The carcass radiation surface profile, which intentionally deviates from this natural equilibrium shape, has a large curvature of the shoulder contour curve of the carcass corresponding to the upper sidewall area when the normal internal pressure is applied, and the carcass in the lower sidewall area has an inverted R shape. The main point is that the tire has a carcass radiation surface profile that conforms to a normal natural equilibrium shape. Become.

This also means that the tension of the belt is greater than that of a normal tire when the internal pressure is normal, and as a result of this, the interlaminar shear strain of the belt increases and the edges of the belt become loose under severe conditions. As a result of mechanical examination of the tire, it has become clear that there is no risk of separation occurring.

(Objective of the Invention) In order to solve the above-mentioned problems, the belt end of the tire is coated with rubber of a heat-shrinkable cord in a tire whose natural equilibrium shape is deliberately removed by appropriately changing the radiation surface profile of the carcass. By covering with at least one layer,
It is an object of the invention to advantageously improve the rolling resistance without deteriorating the separation resistance of the belt ends.

(Structure of the Invention) The present invention 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 connected to an organic fiber cord layer. A carcass consisting of at least 1 bly and having both ends of the plies wound outwards around a bead core buried in each of the above-mentioned bead portions, and a carcass wrapped around the carcass and relatively relative to the center circumference of the tire. Reinforce with at least two layers of rubber-covered belts made of high-elasticity cords arranged crosswise with each other at a small angle, and fill the space between the force-resistance and its braai winding with rubber filler to harden the bead part. The intersection point of the carcass line with a straight line parallel to the axis of rotation of the tire passing through the separation point of the flange of the rim from the outer surface of the beat part under the device configuration e in which the tire is combined with the regular rim and filled with the regular internal pressure. B. Pass through the end points C of the line segments starting from this intersection B, intersecting the apex of the above straight line, and ending at the carcass line, leaving a distance equal to the maximum separation distance of the carcass line with respect to the line segment, and then forming the line segment. 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 a reference arc hypothetically assumed to be a chord is in the range of 0.65 to 0.85, and The carcass has a radial surface profile in which the maximum distance f of the residual area of the carcass spline with a single inflection point between the curve and the intersection AB is in the range of 5 to 101+Il+1. , a rubber coating of a heat-shrinkable cord having a heat shrinkage rate of more than 5%, and having a cord angle smaller than the angle with respect to the center circumferential line of the reinforcing high elastic modulus cord of the belt;
This pneumatic radial tire has improved rolling resistance and durability by combining a pair of belt end covers made of at least one layer.

To create a shape that intentionally deviates from the natural equilibrium shape by appropriately changing the radial surface profile of the carcass, first, the radius R of the reference arc shown in Figure 1 is ' R/ R/ is 0.
In addition, the maximum distance between the carcass line FB and the circular arc BE in Fig. 1 should be set within the range of 65 to 0.85, and in addition, the curvature of the lower region of the sidewall should be reduced, or the maximum distance between the carcass line FB and the circular arc BE in Fig. 1 should be reduced to give an inverted R shape. This can be obtained by setting f between 5 and 10.

What should be noted here is that the arcs B and EC shown in Figure 1 are simply reference arcs, and are originally separate from the carcass radiation surface profile based on the so-called natural equilibrium shape, but Since the area is relatively thick or thin and has low rigidity itself, the carcass radial surface profile based on the natural equilibrium shape will be very close to a portion of this arc EC.

That is, it must be noted that the values of 0.65 to 0.85 for the above ratio' can only occur as a result of deliberately removing the natural shape; The lower area of the wall is a part that has relatively high rigidity because it is rolled up radially outward around the carcass bead core, and the bead part is hardened by filling the rolled up part with rubber filler. However, the value of 5 to lQsm for the maximum distance f of the carcass, which is based on the natural equilibrium shape, is generally located inside the circular arc This value cannot be obtained unless the shape is changed and the curvature of the carcass in the lower region of the sidewall is reduced or an inverted R shape is provided, and thus it can be completely distinguished from the conventional natural equilibrium shape.

The reason why the rolling resistance of a tire having a carcass radial surface profile that intentionally deviates from the natural equilibrium shape as described above is improved is as already described in the specification of Japanese Patent Application No. 158018/1982. In order to manufacture tires, it is necessary to take measures such as those shown in Japanese Patent Application No. III Sho'57-41281 filed earlier.

Here, when R/R' is larger than 0.85, the natural equilibrium shape is intentionally removed as described in the specification of Dogu Patent Application No. 158013/1985 to reduce the shear deformation of the upper part of the side. , the effect of improving rolling resistance cannot be sufficiently obtained, and if R/R1 is less than 0.66, the deformation of the bend will concentrate on the relatively thick buttress part, reducing shear deformation. The rolling resistance improvement effect obtained by doing so is canceled out. Furthermore, the value of f is 511f
If the value is less than f+, the clay figurine patent application was filed in 1980-1580.
The principle shown in Specification No. 18 cannot fully demonstrate the effect of reducing energy consumption, and if f exceeds 10 degrees, the tension in the carcass in the lower area of the sidewall becomes too high when the internal pressure is filled, resulting in poor durability. Not only does this have a negative impact on the tire's performance, but as the carcass moves inside the tire, the outer surface of the tire also becomes relatively soft, causing problems such as poor bonding with the rim. Put it away.

For a tire having the characteristics of the carcass radial surface profile described above, the heat-shrinkable cord used for the belt end cover is made by leaving the cord under a weight of 202 for 30 minutes at a constant temperature of 177°C in 1-Rt. The initial shrinkage rate determined by measuring the change in cord length must be greater than 5%.

The reason why the belt end is covered with at least one layer of heat-shrinkable cord that is covered with rubber is that when the tire is vulcanized, the cord layer shrinks and creates a so-called hoop effect on the belt end. This is to make it happen.

The effect of this weight, for example, suppresses the protruding deformation of the shoulder portion due to centrifugal force during high-speed running, and can suppress an increase in interlaminar shear strain at the heald end.

Further, even when a slip angle is added, it helps to suppress deformation in which the two belt layers tend to shift from each other.

This improves the separation resistance of the belt end of the tire having the carcass radial surface profile of the present invention, in which the belt tension is higher than in a normal tire when the internal pressure is filled, and therefore the shear strain between the belt layers is relatively large. That's why.

When a cord having a heat shrinkage rate of less than 5% is used, the effect of the above-mentioned load is not sufficient, and the separation resistance at the belt end is hardly improved.

Now, FIGS. 2 and 3 show left half cross sections of the tire according to the present invention and the conventional tire, in which 1 is a bead part, 2 is an annular side part, 8 is a tread part, 4 is a bead core, and 5
is the carcass, 6 is the belt, 7 is the rubber filler, and 8
is the rim, 9 is its flange, 10 is the separation point, and the second
In the figure, 11 is a belt end cover. The specific configuration contents of the tires of Example' and Comparative Example are shown in Table 1, but Comparative Example 2 particularly has R/R/ and f
deviates from the conditions of the present invention, and Examples 2 to 5 differ from Example 1 in that the belt end cover 11 shown in FIGS. 4 to 7 is
An example of a modified application of .

Table 1 Tire contents of Examples and Comparative Examples Tire size: 185/70HR18 Rim 255-1
8 Regular content = 1°7 kg/c, 12 The carcass of the tires listed above are all made of 1500 d/2 polyester cord 9o0 to the tire equator.

The belt 6 has a twist structure of I X 5 X O, 25 mm, as shown by the solid line in the figure.
2 and 4 to 7, the dashed lines indicate 1° and 1°. Heat-shrinkable cord (840 (1/2 66mm).

One or two cord layers made of Iron (heat shrinkage rate: 9.5%) arranged substantially parallel to the tire equator are shown.

The rubber used for the tread part 3 of the stiff tire is all the same and has the physical properties of loss tangent (tan δ) = 0,110 and Shore A hardness (Ha) = 57, and the rubber filler 7 is also the same. Shore A hardness (H(1)=96°).

Note that tan δ is a value that was measured using a spectrometer manufactured by Script Seisakusho at a stagnation temperature of 1 degree and 60° C. with a tensile strain of 1% applied at a frequency of 50 Hz.

The belt edge durability during high-destruction running was evaluated by the following test.

Test conditions ■Rim + 5J-13 ■Internal pressure: 2.1 to 9/cnI2 ■Load: 450 to 9 ■Drum: diameter 1.7WL surface smooth For each test tire, first B Okm7Hte2 RII
J After running for 3 hours, after adjusting the internal pressure to 11, ran for 30 minutes at 1,121'/H, and completed the run without any abnormalities. Continuously stepped up.

The test results were as shown in Table 2.

Comparing Comparative Example 1 and Comparative Example 2, it is found that the belt edge durability in Comparative Example 1 using only the Force 1-Cass radiation surface profile of this invention is rather steeper than that in Comparative Example 2, and the separation resistance of the belt edge is It turns out that it is one rank inferior. However, all examples of this invention are 241"
In addition to being able to complete the run up to Jl/), the separation resistance at the belt end was clearly improved.

Next, the belt end durability when a slip angle was added was evaluated using the following method.

Test conditions ■Rim: 5J-13 ■Internal pressure: 1.7"9/cm2 ■Load 9 to 7450 ■Drum: diameter 1,7yz smooth surface For each sample tire, ±11 at a speed of 80"/H
The tire was run for 3 hours without alternating slip angles of °, then the tire was removed from the test machine and
The belt was cut at 0 points, the length of the crack that occurred at the end of the belt was measured, and the average value was calculated and compared.

As shown in Table 3, the cracks in Comparative Example 2 were compared with other cracks, with the length set at 100. The higher the index, the shorter the cracks and the better the belt end durability.

. From this result, it is clear that the embodiment of the present invention more than compensates for the deterioration in belt end durability when a slip angle is added, which is caused by changing the carcass line radiation surface profile.

The comparative measurement results of rolling resistance are as follows.

First, the test method was to press a tire against a drum with a diameter of 17o7I+1111, rotate it to a predetermined speed, then coast and calculate the degree of deceleration during continuous rotation.The rolling resistance of Comparative Example 2 was set at 100, and other tires were compared. The results are shown in Table 4. Here, the larger the index, the lower and better the rolling resistance.

Comparative Example 1, which has a carcass radiation surface profile l similar to that of the present invention, exhibits a large rolling resistance improvement effect compared to Comparative Example 2.
It has substantially the same effect of improving rolling resistance as compared to the above, and is the most preferable embodiment when considering the improvement in the durability of the belt end. Even in Examples 3 to 5, in addition to the durability of the belt end, It is noteworthy that it has the effect of improving rolling resistance.

(Effects of the Invention) As described above, according to the present invention, by appropriately changing the carcass radiation surface profile and covering the belt end with at least one layer that becomes the rubber coating of the heat-shrinkable cord, It can sufficiently compensate for the previous weak point, which was the deterioration in durability of the belt ends, and can exhibit the advantage of reducing rolling resistance.

[Brief explanation of the drawing]

FIG. 1 is an illustrative 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, and FIG. 2 is a sectional view of the tire according to the embodiment of the present invention (when filled with internal pressure). Figure 8 is a cross-sectional view of the tire of Comparative Example 1 (at the time of internal pressure filling),
7 to 7 are arrangement diagrams of different embodiments of the belt cover. l... Bead part 2... Annular side part 3... Tread part 4... Bead core 5... Carcass 6.
...Belt 7...Rubber filler 8...Rim 9...Flange 10...Separation point 11...Belt cover Patent applicant Proridgestone Tire Co., Ltd. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. A tire comprising a pair of annular sidewall portions each having a bead portion and a tread portion spanning these sidewall portions on the outside in the radial direction, and each of these portions is covered with an organic fiber cord layer. A carcass consisting of at least one ply of The tire is reinforced with at least two layers of rubber-covered belts made of high-modulus cords arranged crosswise with each other at a small angle, and a rubber filler is filled between the carcass and its ply turn to harden the bead part, Combined with the regular rim and filled with regular internal pressure, 7 layers installed?
), the intersection point between the carcass line and a straight line parallel to the axis of rotation of the tire passing through the separation point from the outer surface of the bead of the flange of the rim ・B1 A line starting from this intersection B and perpendicular to the above straight line and ending at the carcass line passing through the end point C of each minute,
The maximum l of the carcass line for the line segment! The ratio R/R1 of the radius of curvature R of the shoulder contour curve passing through the end point QQ of the carcass line to the radius RI of a reference arc with the line segment as a chord, spaced equidistant from the distance llt, or 0.65. ~0.85, and the maximum distance f of the residual area of the cartokas line that smoothly connects to the curve and has a single inflection point to the intersection point B from the reference arc is 5.
~lQm+a flJ 9J], the rubber coating is a heat-shrinkable cord with a heat shrinkage rate greater than 5%, and A pneumatic radial tire with improved rolling resistance and durability, comprising a pair of belt end covers made of at least one layer having a cord angle smaller than the cord angle. □