JPH08164716A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE: To improve traveling stability by forming block rows by combining trapezoidal blocks sideways with each other in a tire having a large number of block rows divided by plural circumferential directional main grooves and inclined lug grooves crossing these between the circumferential directional main grooves and the tread ends on a tread. CONSTITUTION: In a tire 1, a belt layer 4 has a tread 5 on the circumference of a crown part 3 of a radial carcass 2, and rows 9 of blocks 8 divided by plural straight line-shaped circumferential directional main grooves 6 and inclined lug grooves 7 crossing these, are provided between circumferential directional main grooves 61 and the tread ends E on the tread 5. In this case, main grooves 61 and 62 are symmetrically arranged on an equatorial surface O, and are divided into respective block rows 9C and 9M of the center, left, right and intermediate parts and a shoulder, and shoulder block rows 9S are formed by arranging trapezoidal blocks 81 sideways. In the tread 5, its thickness is gradually increased over a block 8 forming position from the center, and its ratio is set in 1.1 to 1.3 of a thickness in the center.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a pneumatic radial tire having excellent running stability.

[0002]

2. Description of the Related Art Pneumatic radial tires have recently been improved in high-speed running performance, and in radial tires for passenger cars, the tire cross section tends to be flattened accordingly. When the tire cross section becomes flat, the tire width becomes wider, and the width of the tread becomes wider accordingly.However, in the case of such a relatively wide tread, the drainage property of the ground contact surface in rainy weather is deteriorated, and therefore a plurality of treads are provided. A parallelogram block by arranging main grooves extending straight in the circumferential direction of the book (3 to 6) and a large number of inclined lug grooves between the main grooves and between the main groove and the tread end. , Or a block pattern similar to this, is preferably used.

FIG. 5 is a plan view of a tread having parallelogram blocks as an example. In FIG. 5, a tread 5 is two pairs of straight circumferential main grooves 6 centering on the equatorial plane O of the tire and a large number of lug grooves intersecting these main grooves at an angle.
It is formed by a parallelogram block 8 divided by 7. And often center-block rows
The lug groove 7 included in 9 _C is slightly inclined with respect to the equatorial plane O to facilitate drainage in the circumferential direction, while the shoulder groove
The lug groove 7 included in the block row 9 _S has a relatively small inclination angle because it is necessary to divide a block having high lateral rigidity during cornering, and the lug groove 7 included in the intermediate block row 9 _M is , It is inclined at an angle between the left and right lug grooves.

[0004]

However, a tire provided with a tread having such a block arrangement is
There is a problem that the pattern steer is generated during traveling, and the straight running stability of the vehicle is impaired. FIG. 6 shows the shoulder of FIG.
FIG. 6 is a view showing a case in which a carcass and a belt layer are viewed from inside a cavity of a tire when a block in a block row advances in a direction of an arrow R and enters a ground contact surface. In Fig. 6, when displacement x _C acts parallel to the equatorial plane O with respect to block 8 and acts on the upper part of the tread (base part of the block), the main axis of the block is tilted to the upper left, and the force F deviates to the upper left. Occurs in the opposite direction, and the side force F _S , which is the reaction force exerted on the tire by the road surface, is generated in the direction of the arrow, so that a flow in the same direction is generated in the tire. When the displacement x _C is opposite to the direction of the arrow, the side force F _S occurs leftward.

On the other hand, by arranging the shoulders and the blocks in the intermediate block rows 9 _S and 9 _M shown in FIG. 5 in plane symmetry with respect to the equatorial plane O, the side force generated in the blocks is left and right blocks. It is possible to offset them, but the tread does not always touch the ground evenly, so that an unbalance of the entire side force constantly occurs between the left and right regions. In view of the above problems, it is an object of the present invention to provide a pneumatic radial tire having excellent running stability.

[0006]

SUMMARY OF THE INVENTION The present invention sequentially comprises an inextensible belt layer and a tread of approximately equal width on the crown circumference of a toroidal radial arcus, the tread having a plurality of linear circumferential major grooves. In a tire having at least a row of blocks divided by inclined lug grooves intersecting with the row between at least a circumferential main groove and a tread end, the block row is formed by laterally combining trapezoidal blocks. It is a pneumatic radial tire.

It is preferable that the thickness of the tread gradually increases from the center of the tread to the block forming position, and the ratio is within the range of 1.1 to 1.3 at the maximum of the tread thickness at the center of the tread.

[0008]

In the radial tire according to the present invention, the tread is divided into a plurality of linear circumferential main grooves and inclined lug grooves intersecting with the linear circumferential main grooves, and a large number of blocks are arranged between at least the circumferential main groove and the tread end. The block row is structurally characterized in that it is formed by horizontally combining trapezoidal blocks. When the block rows are arranged laterally with trapezoidal blocks, the blocks are deformed only in the direction of the acting force against the force in the front-rear direction when traveling parallel to the circumferential main groove, and the side force is generated. do not do.

It goes without saying that the trapezoidal block row can be applied to all the tread block rows. However, due to the radius difference of the rounded belt layers arranged at the base position of the tread (the radius at both ends is short compared to the center position), the shoulder block row in which the braking force is significantly generated during running is At least by applying it, the wheel flow based on the side force, that is, the pattern steer can be advantageously suppressed.

Regarding the difference in radius of the belt layer, the thickness of the tread gradually increases from the center of the tread to the block forming position, and the ratio thereof is 1.1 to 1.3 at the maximum of the tread thickness at the center of the tread. Is more effective. The reason is that it is necessary to suppress the influence of the anisotropy of the belt layer which is a laminate of the tilt-arranged layers of the steel cords arranged in the base portion of the tread. If the above value is 1.1 or less, it is greatly affected by the belt layer, that is, the plysteer. On the other hand, if it exceeds 1.3, the rigidity of the shoulder block is excessively reduced, which adversely affects the steering stability. Become.

When the square and rectangular blocks are arranged with their main axes parallel to the equatorial plane or the circumferential main groove, or with isosceles triangles arranged horizontally, the same effect can be obtained as far as the pattern steer is concerned. However, in the former case, the lug groove interposed between the blocks faces in a direction orthogonal to the equatorial plane, which causes a problem in drainage on a wet road. If the triangular block is arranged at the shoulder position where rigidity is required, the steering stability is particularly impaired, and neither can be practically adopted.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to the drawings. FIG. 1 is a sectional view of a tire showing an embodiment of the present invention, FIG. 2 is a tread plan view of the tire, and FIG. 3 is an enlarged plan view of a trapezoidal block. In the present invention, the tire 1 is provided with a belt layer 4 and a tread 5 of substantially equal width on the circumference of the crown portion 3 of the toroidal radial arcus 2 in sequence, and a plurality of linear circumferential main grooves 6 and this tread are provided in this tread. It has a row 9 of a number of blocks 8 divided by intersecting inclined lug grooves 7 at least between the circumferential main groove 6 ₁ and the tread end E. The block row 9 _S adjacent to the tread edge is formed by horizontally combining the trapezoidal blocks 8 ₁ .
In Figure 1, the left side of the equatorial plane O is omitted, but it is symmetrical.

The carcass 2 has a known structure comprising at least one, usually two plies in which fiber cords represented by polyester and rayon are arranged in a direction substantially perpendicular to the equatorial plane O. In addition, the belt layer 4 also has a non-stretchable cord such as a steel cord at a shallow angle (15
Up to 35 °), multiple plies, usually two, arranged in a slanting arrangement are stacked so that the cords cross each other, and multiple heat-shrinkable cords such as nylon are lined up around the entire periphery of the ply to make rubber. A known structure including a cap layer formed by circumferential spiral winding of a drawn strip.

[0014] In the embodiment shown in FIG. 2, two pairs of stress - Place bets circumferential main groove 6 _and 62 symmetrically with respect to the equatorial plane O,
Center-block row 9 _C with equal width and left and right middle block row 9 _M ,
It also divides the slightly wider shoulder-block row 9 _S. The shoulder-block row 9 _S is formed by arranging trapezoidal blocks 8 ₁ in a staggered manner and arranged in the circumferential direction.

Trapezoidal block 8 ₁ applied to this embodiment
Is the main groove 6 ₁ stress in the circumferential direction - are combined from the need to place the bets, two principal axes x, parallel to the equatorial plane O of the horizontal axis x of y, i.e. sideways. Therefore, the block ₈₁ against a force acting parallel to the x-axis at the time of traveling is deformed coaxially, thus Saidofuo - scan does not occur. Note trapezoidal shaped blocks ₈₁ of the bottom and side angle α of 7
It is 0 °. Thus lug grooves ₇₁ (FIG. 2) with respect to the equatorial plane are inclined at the same angle. This angle α is preferably in the range of 65 to 80 °. In Fig. 1, the thickness of the tread 5 is the equatorial plane O.
Gradually increases in the direction of the tread edge E from the position of, and the maximum thickness g _S at the shoulder block row 9 _S position from the surface of the belt layer 4 is 1.1 to the thickness g _{C at} the equatorial plane O or the tread center.
1.3 times is preferable.

The center - block row 9 _C does not relatively require a lateral stiffness, since it is a position that requires the circumferential direction of the drainage Instead, isosceles block inclined at 40 ° relative to the equatorial plane O 8 ₃ are arranged side by side. Also in the case of this block arrangement, the side force due to the force acting in parallel with the equatorial plane O does not occur.

[0017] Then an intermediate block row 9 _M is a center that position in both drainage and steering stability -, shoulder - require an intermediate nature between both block rows, whereas during running, vibration in the block - Kingufo - This is a part where the occurrence of spurs is relatively small. Therefore, at this position, 45 with respect to the equatorial plane O
Parallelogram block 8 ₂ with walls inclined at an angle of ° 8 ₂
Are arranged side by side to form a column.

FIG. 4 is a plan view of a tread showing another embodiment of the present invention. The feature of this embodiment resides in that the same-shaped blocks are arranged in the center-block row 9 _C for the same reason as the parallelogram block is arranged in the intermediate block row 9 _M in the previous embodiment. The angle of the inclined wall surface of the block 8 ₃ or the lug groove 7 ₃ with respect to the equatorial plane O is 40 ° as in the case of the triangular block row. The center
It is needless to say that the trapezoidal blocks 8 ₁ can be laterally combined and arranged for the middle block rows 9 _C and 9 _{M as} in the shoulder-block rows 9 _S.

[0019]

[Effect] To confirm the effect of the tire according to the present invention, FIG.
A radial structure tire for passenger cars having a cross-sectional shape of 195 / 65R14 size shown in FIG. 2 was used, and the tires of Example 1 shown in FIG. 2, Example 2 shown in FIG. 4 and the comparative example shown in FIG. Two types of g _S / g _C of 1.08 and 1.20 were prepared, and the pattern steering force (cornering force at zero slip angle) between these tires was measured and evaluated. In this case, all the tires have a uniform radius of curvature (crown r) of 640 mm on the tread surface.

At the test, tires were assembled on a 14 × 6 rim,
An internal pressure of 2.0 Kgf / Cm ² and a load of 400 KGf were applied.
The test results are shown in Table 1.

[0021]

[Table 1] From Table 1, it can be seen that when the g _S / g _C value is 1.08, the effect of the plysteer is dominant and the effect of the present invention is small, but when it is 1.20, a remarkable effect appears.

As described above, by forming the block row between the linear circumferential main groove and the tread end in the tread by the horizontal combination of the trapezoidal blocks, the pattern steer is reduced and the running stability is thereby improved. It can be improved advantageously.

[Brief description of drawings]

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

FIG. 2 is a plan view of the tread of the same embodiment.

FIG. 3 is an enlarged plan view of a trapezoidal block.

FIG. 4 is a tread plan view of another embodiment.

FIG. 5 is a tread plan view of a tire of a comparative example.

FIG. 6 is an enlarged plan view of a parallelogram block.

[Explanation of symbols]

 1 Tire 2 Carcass 3 Crown 4 Belt layer 5 Tread 6 Circumferential main groove 7 Inclined lug groove 8 Block 9 Block row

Claims (2)

[Claims] 1. A non-stretchable belt layer of substantially equal width and a tread are sequentially provided on the circumference of a crown portion of a toroidal radial arc, and the tread is provided with a plurality of linear circumferential main grooves and inclined lug grooves intersecting with the linear circumferential main grooves. A pneumatic radial tire having a row of a large number of divided blocks between at least a circumferential main groove and a tread end, wherein the block row is formed by laterally combining trapezoidal blocks. 2. The thickness of the tread gradually increases from the center of the tread to the block forming position, and the ratio is 1.1 to 1.3 of the maximum tread thickness at the center of the tread.
The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is in the range of 1.