JP2763066B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire capable of improving one-way flow of a vehicle and improving straight running performance.

[0002]

2. Description of the Related Art With the recent improvement in the performance of vehicles and the improvement of road networks, tires are required to have various characteristics such as durability, steering stability and riding comfort, for example, when a steering wheel is released. It is desired to further improve the driving comfort, such as reducing the so-called one-sided flow of the vehicle and increasing the straight-running stability while traveling sideways while being displaced to one side with respect to the straight line while traveling the distance of the straight line. ing.

Conventionally, this one-sided flow of the vehicle is caused by a so-called conicity which is formed in a cone shape due to a difference in the circumferential length of the belt layer, particularly in the right and left directions of the tread portion in the tire axial direction. Various measures have been taken to increase the uniformity of the data.

[0004]

However, it has been found that the improvement of the conicity does not sufficiently prevent one-way flow of the vehicle.

On the other hand, due to recent advances in tire measurement technology, as shown schematically in FIG. 9, when a small slip angle α is given to the tire traveling direction X, the tire lateral direction Y
The self-aligning torque SAT that rotates in the direction of the slip angle α around the vertical axis Z passing through the center of the tire can be measured with high accuracy.

[0006] Such a measurement result is shown, assuming that the camber angle β is 0, for example, as shown in FIG. 10, using a straight line K using the horizontal axis as the self-aligning torque SAT and the vertical axis using the lateral force F. It is. On the straight line K, the slip angle α
Are 0 degrees, −0.2 degrees, and +0.4 degrees are indicated by black circles.

Thus, in a radial tire,
Generally, even in the straight running state, the lateral force F and the self-aligning torque SAT are generated. The lateral force F when the slip angle α and the camber angle β are both 0 is
It is called LFD (Lateral Force Deviation).

[0008] Such a self-aligning torque SA
T, the lateral force F at the intersection k1 where the straight line K intersects the vertical axis, that is, the self-aligning torque S
The lateral force F when no AT occurs is referred to as a residual CF. It has been found that this residual CF affects the one-way flow of the vehicle. That is, when the residual CF is in the plus direction, it means that the vehicle is flowing in the right direction, so that the direction and size of the residual CF can be used to evaluate the vehicle's one-sidedness. It is necessary to reduce this residual CF.

In a tire having a so-called conicity in which a difference in radius occurs on the left and right sides of the tire equator, the residual CF and the self-aligning torque SAT are set such that the large diameter side travels in the traveling direction when the tire is assembled. Is changed to the right or to the left, and when a so-called front and back facing is performed, as shown in FIG. 11, the straight line K is, as shown in a front straight line K1 and a back facing straight line K2, It becomes two parallel straight lines. As shown in FIG. 11, the average value of the lateral force when the slip angle α is 0 and the camber angle β is 0 is called ply steer, and the deviation from each average value is defined as the connectivity at the lateral force F. ing.

Further, in the relationship between the one-way flow of the vehicle, the residual CF, and the residual self-aligning torque SAT, the total self-aligning torque SAT becomes zero when the vehicle is driven away from the steering wheel. When
Residual CF will be generated in the tire. Usually, a force based on the connectivity acts on this, and a resultant force of the residual CF and a lateral force based on the connectivity are generated in the vehicle with respect to the tires.

FIG. 12 shows an example of the residual CF and the vehicle flow.
Shown in One-sided flow of this vehicle is 100m at 50km / h
Is the amount of lateral displacement that occurs when the steering wheel is moved away from the steering wheel, and is measured using a tire of size 215SR15 in FIG. Thus, it was found that the residual CF and the vehicle flow had a correlation, and it was found that the residual CF should be reduced to prevent the vehicle flow.

The present inventor has conducted various studies on reducing the residual CF on the premise that the conicity is not more than a predetermined value. As a result, the residual CF varies depending on the tread pattern of the tire and the structure of the belt layer. I found to do.

Here, the effect of the tread pattern on the residual CF means that, as shown in FIGS. 14 and 15, especially when the outer surface divided by the oblique horizontal groove has a substantially parallelogram block, FIG. As shown in FIG. 5, based on the traction FT and the braking force FB generated in the block due to the difference in radius between the tire equator and the tread edge, and the point of application in the block, the rotational moment M acting on the tread surface of the block results from It is thought that.

[0014] In the block shown in FIG.
It has been found that F moves to the positive side, and in the block shown in FIG. 15, the residual CF moves to the negative side. As described above, in the crown portion, the application point of the traction FT is a block Bcr in an upward-sloping pattern located to the left in the figure, and in the shoulder portion, the application point of the braking force FB is a pattern in a downward-sloping right position to the right in the diagram. Block Bsr generates a clockwise rotation moment M, and the blocks Bcr and Bsr having the opposite inclination generate a counterclockwise rotation moment M in each of the crown region and the shoulder region.

Further, the magnitude of the rotational moments M, M is influenced by the block rigidity and the inclination angle of the lateral groove.

On the other hand, in recent years, as shown in FIG. 7, a unidirectional pattern having a circumferential vertical groove G and a horizontal groove y inclined in the same direction from one tread edge to the other tread edge, as shown in FIG. A tire having a symmetrical pattern that is inclined in a C-shape symmetrically with respect to the tire equator C is aesthetically preferred.

However, for example, in the tire having the pattern shown in FIG. 7, the right and left blocks Bcl and Bcr in the crown region sandwiching the tire equator transmit the clockwise rotation moment M, and the blocks Bsl and Bsr in the shoulder region provide the right rotation torque M.
A counterclockwise rotational moment M is generated.

In the tire having the pattern shown in FIG. 8, the clockwise and counterclockwise rotation moments M and M are applied to the left and right blocks Bcl and Bcr of the crown area, and the left and right blocks Bsl and Bsr are applied to the left and right blocks Bsl and Bsr of the shoulder area. A clockwise and clockwise rotational moment M is generated. In this way, the one-way, symmetrical pattern can be said to be a pattern in which the rotational moments M, M counterclockwise in the left and right directions are balanced in the left and right directions, and thus the flow of the vehicle is theoretically tentatively balanced.

However, in reality, the sum of the rotational moments over the entire contact surface cannot be zero due to the alignment of the vehicle, the breaker structure, and the like, and the residual rotational moment greatly affects the flow of the vehicle. That has been confirmed.

Based on these facts, the present inventor has conducted various studies on a tire having a block pattern of a one-way pattern or a symmetrical pattern that is theoretically well-balanced and is advantageous for vehicle flow. The present inventors have found that the total of the rotational moments on the entire ground contact surface can be made close to zero by reducing the rotational moment generated in each block itself by providing the present invention, and completed the present invention.

An object of the present invention is to provide a pneumatic tire capable of improving the flow of a vehicle by reducing the rotational moment generated in the block.

[0022]

According to the present invention, a tread portion is provided with a plurality of vertical grooves extending in a tire circumferential direction and a lateral groove having a slope inclined obliquely in the same direction with respect to the tire equator. A tire having a block pattern including a plurality of block rows including a parallelogram block row in which substantially parallelogram-shaped blocks provided on both sides in the circumferential direction with bevels inclined obliquely to the tire equator, The tread portion is divided into a shoulder region from the tread edge to a length of 1/3 of the distance between the tread edges in the tire axial direction, and a crown region between the shoulder regions. Blocks of the parallelogram block row of the shoulder portion including the center of gravity of the outer surface of the block in the region are virtually divided in the tire axial direction by a circumferential line passing through the center of gravity. 3 with respect to the tire axis One of the division area
A plurality of sipes extending at an angle of 0 ° or less are circumferentially spaced from each other, and the siping of the section area including the beveled edge portion that first arrives at the time of rotation is performed in a direction in which the groove bottom is on the rear arrival side. In a region, the pneumatic tire is characterized by being inclined in the direction of the first arrival.

[0023]

According to the present invention, a plurality of sipings are provided in a block of a parallelogram block row of a shoulder portion including the center of gravity of the outer surface of the block in the shoulder region of the tread portion. The siping extends in the tire axial direction and is separated in the circumferential direction into two sections that are virtually divided in the tire axial direction by a circumferential line passing through the center of gravity.

Also, in this siping, when the tire rotates, the groove bottom is directed to the rear side in the section area including the beveled edge portion where the block comes first, and the groove bottom is directed to the first arrival side in the other section area. It is formed to be inclined in the wrong direction.

Therefore, when the block comes into contact with the ground, the brake acts on the section including the leading edge portion of the block due to the vertical force received, but the rotational moment generated by the braking force due to the siping can be absorbed by the deformation of the block. , The rotational moment generated in each block can be reduced.

[0026]

An embodiment of the present invention will be described below with reference to the drawings. In the figure, a pneumatic tire 1 of the present invention has bead portions 3 on both sides through which a bead core 2 passes, and a sidewall portion 4 extending radially outward from the bead portion 3 in the tire.
4 and a tread portion 5 joining the upper end thereof, and a carcass 6 that turns around the bead core 2 of the bead portion 3 from the tread portion 5 through the sidewall portion 4 and a carcass 6 at the tread portion 5. And a belt layer 7 disposed radially outward of the tire.

The carcass 6 is a semi-radial or radial array in which carcass cords are arranged at an angle of 45 to 90 degrees with respect to the tire equator CO. In addition to steel cords, carcass cords include nylon, polyester and rayon. Etc. is adopted.

The belt layer 7 is formed from the carcass 6 radially outward, that is, toward the outer surface of the tread portion 5 in the first order.
Ply B1 and the second belt ply B2 in this order. The first belt ply B <b> 1 is arranged, for example, such that its cord is inclined leftwardly up to the tire equator CO in a range of 15 to 70 degrees,
The second belt ply B2 is arranged to be inclined in the range of 15 to 70 degrees to the upper right, contrary to the first belt ply B1. Therefore, the first and second belt plies B1 and B2 are connected to each other by their cords crossing each other.
The tag effect is produced by B2, so that the rigidity of the tread portion 5 in the circumferential and axial directions can be increased.

The first and second belt plies B1, B2
Each of the belt cords is made of not only steel cords but also fiber cords such as nylon, polyester and rayon having a relatively high elastic modulus, as well as Teflon and aromatic polyamide fibers.

As shown in FIG. 2, the tread portion 2 has six longitudinal grooves G1, G1, G2, G2, G3, G3 extending in the tire circumferential direction symmetrically on both sides of the tire equator CO.
Is provided.

As a result, the tread portion 2 is divided into a rib R1 passing through the tire equator CO and ribs R2, R3, R4 going from the rib R1 to the tread edges e1, e2 sequentially.

The tread portion 2 extends from the tread edges e1 and e2 virtually in the tire axial direction.
1, a shoulder area S up to 1/3 of the distance between e2 and
The ribs R1 and R2 are located in the crown region C, and the ribs R3 and R4 belong to the shoulder region S.

In the present embodiment, the ribs R1 to R4 are connected from the outer edge e1 of one tread to the outer edge e2 of the other tread.
The horizontal grooves g1 extending in the same direction (in this example, the downward direction in FIG. 2) are circumferentially spaced at a constant pitch P1 between the horizontal grooves.

Thus, the tread surface is provided with a central rib R1, longitudinal grooves G1 to G3 extending in the circumferential direction of the tire, and a lateral groove g1 obliquely inclined in substantially the same direction with respect to the tire equator CO. A parallelogram block row 11 is formed by arranging, in the circumferential direction, substantially parallelogram blocks 10 provided with bevels 9 obliquely inclined with respect to the tire equator CO on both sides in the circumferential direction.

A plurality of sipes 12A are provided in the parallelogram block row 11S of the shoulder portion including the center of gravity of the outer surface of the block in the shoulder region S.

The siping 12A is provided in the block 1
0 by the circumferential line L passing through the center of gravity P
Are divided into two sections 13A virtually in the tire axis direction,
13B, it extends at an angle of 30 ° or less with respect to the tire axis and is spaced apart therefrom.

As shown in FIGS. 4 (C) and 4 (D), the siping 12A has a groove bottom 14 at the rear end of the block in a section 13A including a beveled portion 9A which comes first when the tire rotates. In the direction of the side 15 and in the other sectioned area 13B, it is inclined and provided in the direction of the first arrival side 16.

Further, in this embodiment, the crown region C is provided with a siping 12B also in the parallelogram block row 11C of the crown portion including the position of the center of gravity of the outer surface of the block 10.

This siping 12B is shown in FIG.
As shown in (B), in the division area 13A including the beveled edge portion 9A that comes first when the tire rotates, the groove bottom 1A is formed.
4 is inclined in the direction of the first arrival side 16 of the block, and in the other section 13B, in the direction of the rear arrival side 15.

By inclining the groove bottoms 14 of the sipes 12A and 12B in accordance with the shape of the block, the vertical force and the braking force acting on the block 10 at the time of touching the ground are reduced.
As a result of the driving force being absorbed by the deformation of the block, the rotational moment can be reduced.

In the above-mentioned siping, the angle θ between the intersection of the siping and the outer surface of the block with respect to a reference line drawn on the tire axis at an angle of 5 ° or more and 15 ° or less in the tire circumferential section. It is desirable to tilt the groove bottom.

That is, if it is smaller than 5 °, it is not enough to reduce the rotational moment generated in the block, while 15
When it is larger than °, a large moment acts when the tire is removed from the entire mold at the time of molding, and a crack may occur between sipes, which is not preferable.

In this embodiment, the sipings 12A, 1A
2B illustrates an example that does not reach the vertical grooves G1 to G3, but is not limited thereto, and the siping 12A,
12B can be formed so as to reach the vertical grooves G1 to G3. According to such a configuration, the deformation of the block 10 can be largely tolerated, so that the braking force and the driving force can be further absorbed and the block 10 is generated. It is possible to reduce the rotational moment.

The depth of the sipes 12A and 12B is 6 to 5 mm in the crown region and 4 in the shoulder region.
~ 5 mm is desirable. If the value is larger than this value, the rigidity of the block is impaired, while if it is too small, the moment cannot be absorbed.

As shown in FIG. 5, in a tire having a symmetrical pattern provided with symmetrical lateral grooves g2 toward the tread edges e1 and e2 around the tire equator CO, a central rib 17 including the tire equator is provided. Does not form a parallelogram, and as a result, a rotational moment is hardly generated. Therefore, the siping of the present invention can be adopted except for the center rib 17.

[0046]

[Specific Example] For a tire having a tread pattern shown in FIG. 1 with a tire size of 225 / 50R16, a trial tire provided with a siping according to the present invention was prototyped (Examples 1 to 5).
4) Comparative Example 1 without siping
Was also tested.

As for the tire having the tread pattern shown in FIG. 5, test tires (Examples 5 to 6) provided with the siping of the present invention were also produced, and a test was also performed on Comparative Example 2 without the siping. .

In the test, four test tires were mounted on a vehicle, and the vehicle was released for one hour on the test course at a speed of 50 km / h.
The reciprocal of the distance that the vehicle traveled by 00 m and laterally flowed was represented by an index with the comparative example being 100 each. Therefore, the larger the numerical value is, the smaller and the better the lateral flow amount is. Tables 1 and 2 show the test results.

[0049]

[Table 1]

[0050]

[Table 2]

As a result of the test, it can be confirmed that the cross-flow rate of the example is smaller than that of the comparative example.
It can be confirmed that the tread pattern has a greater effect of reducing the lateral flow.

[0052]

As described above, according to the present invention, the amount of lateral flow of the vehicle can be reduced and the straight traveling performance can be improved.

[Brief description of the drawings]

FIG. 1 is a meridional section of a tire showing one embodiment of the present invention.

FIG. 2 is a development view showing the tread pattern in a developed manner.

FIG. 3 is an enlarged diagram showing a main part of a tread pattern showing an operation of the present invention.

FIGS. 4A to 4D show AA, BB, and C in FIG.
It is sectional drawing of -C and DD.

FIG. 5 is a developed view showing another tread pattern in a developed manner.

FIG. 6 is an enlarged diagram showing a main part of a tread pattern showing an operation of the present invention.

FIG. 7 is a plan view illustrating a conventional tread pattern.

FIG. 8 is a plan view illustrating a conventional tread pattern.

FIG. 9 is a perspective view illustrating a residual CF.

FIG. 10 is a diagram thereof.

FIG. 11 is a diagram thereof.

FIG. 12 is a diagram illustrating measurement results of residual CF and one-sided flowability.

FIG. 13 is a diagram illustrating a radius difference between a crown portion and a shoulder portion of a tire.

FIG. 14 is a diagram illustrating a tread pattern.

FIG. 15 is a diagram illustrating a tread pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead core 3 Bead part 4 Side wall part 5 Tread part 6 Carcass 7 Belt layer 9 Bevel 10 Parallelogram-shaped block 11 Parallelogram block row 12 Siping 13A, 13B Division area 14 Groove bottom 15 Rear side 16 First arrival side

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-21905 (JP, A) JP-A-57-147902 (JP, A) JP-A-60-234005 (JP, A) 178810 (JP, A) JP-A-5-139121 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 11/04 B60C 11/12 B60C 11/12

Claims (3)

(57) [Claims] 1. A tire which is inclined obliquely with respect to the tire equator by providing a plurality of longitudinal grooves extending in the circumferential direction of the tire and a lateral groove which is inclined obliquely in the same direction with respect to the tire equator. A tire having a block pattern including a plurality of block rows including a parallelogram block row in which substantially parallelogram-shaped blocks provided with beveled edges on both sides in the circumferential direction, wherein the tread portion extends from the tread edge. A shoulder region and a crown region between the shoulder regions up to a length of 1/3 of the distance between the tread edges in the tire axial direction, and the center of gravity of the outer surface of the block in the shoulder region of the block row. The block of the parallelogram block row of the shoulder portion, which includes the shoulder portion, includes two sections, which are virtually divided in the tire axis direction by the circumferential line passing through the center of gravity, with respect to the tire axis. And a plurality of sipings extending at an angle of 30 ° or less are circumferentially spaced, and the siping of the section area including the beveled edge portion that first arrives at the time of rotation is in the direction in which the groove bottom is on the rear arrival side, The pneumatic tire is characterized in that it is inclined in a direction to be a first-come-first-served side in the divided area. 2. A block of a parallelogram block row of a crown portion in which a center of gravity of an outer surface of the block is included in the crown area of the block row, a virtual line extending in the tire axial direction by a circumferential line passing through the center of gravity. A plurality of sipes extending in the tire axis direction are circumferentially spaced in the two divided areas, and the siping of the divided area including the beveled edge portion that comes first in rotation is directed in such a direction that the groove bottom is the first arrival side. 2. The pneumatic tire according to claim 1, wherein the other sectioned area is inclined in a direction of a rear-wearing side. 3. The tire according to claim 1, wherein said siping is at least 5 ° and 15 ° from a reference line drawn on the tire axis from a point where the siping intersects with the outer surface of the block.
3. The pneumatic tire according to claim 1, wherein the groove bottom is inclined at an angle of not more than .degree.