JP3205880B2 - 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 pneumatic tire mainly for a passenger car, and more particularly to a tire having a tread pattern including a slit (lateral groove) in the tire width direction and a small groove such as a sipe or a notch.

[0002]

2. Description of the Related Art Vehicles, such as passenger cars, differ depending on the type of vehicle, but drift to the tire due to the curvature and cord angle of the belt layer of the tire, the carcass structure, or the shape of the tire peripheral surface. The force acts, causing a phenomenon of skew, a so-called one-sided flow phenomenon, which may impair the straightness of the vehicle.

[0003] It is known that such a one-way flow phenomenon of a vehicle has a very high correlation with a residual cornering force (hereinafter abbreviated as RCF) of a tire of a front wheel.
FIG. 12 mainly shows the relationship between the RCF of a general tire and the amount of one-sided flow (the amount of lateral displacement during hand-off traveling). This is represented by the following equation: Y = a × RCF + b.

In the above, a and b are constants that differ depending on the vehicle, and b is a value close to 0. Therefore, it is a condition of a tire having a good straight running property that the one-sided flow amount (Y) is close to 0, and therefore, it is desirable that the RCF is a value close to 0. However, the road surface has a slope (cant) due to the drainage of rainwater. Therefore, in order to drive a car straight against this road cant, RCF is negative (-) for the right-hand traffic area. It is desirable to be positive (+) for the left-hand traffic area.

[0005] The RCF can be adjusted by the cord angle and direction of the belt layer. Conventionally, in general, the straightness is ensured by changing the cord direction of the belt layer depending on, for example, the destination.

However, depending on the shape of the tread pattern, a pattern component of the RCF may be generated depending on the directionality of the pattern, and a large amount of one-sided flow may appear only by adjusting the belt structure. That is, even in a tire whose belt structure is directed to the right-hand traffic area, RCF may be positive (+) depending on the shape of the tread pattern.

In view of this, the inventor of the present application considers the directionality of the tread pattern, that is, the slit (in the tire width direction) in order to ensure the straightness of the vehicle in consideration of the RCF pattern component due to the directionality of the tread pattern. A pneumatic tire that performs various studies on the relationship between the inclination direction and angle of the so-called lateral groove) and the RCF and specifies the range of the inclination angle of the slit in the tread pattern, particularly in the tire width direction, to ensure the straightness of the vehicle. (Japanese Patent Application No. 3-227328).

[0008] Although the tire according to the above proposed pattern is effective under certain conditions, if the conditions of use change, the problem of one-way flow may remain. This will be described.

Generally, RCF is expressed by the following equation. RCF = a × Fc + PRCF PRCF: ply steer component of RCF Fc: conicity a: coefficient that varies depending on the tire, in the range of 1.5 to 3

In the above description, Fc is caused by variation in the manufacturing process, and it is difficult to control the coefficient a by design. Therefore, PRCF should be managed when designing a tire. However, in the tread pattern proposed above, when the tire structure (belt structure, etc.) is changed, when the mold shape is changed, when it is worn, For example, when the use conditions are changed, the one-sided flow amount may greatly change.

It is considered that this is caused by a change in the contact shape of the tire.

For example, the inclination of the left and right slits of the tread portion
In the tread pattern shown in FIG. 11 in the same direction, the slits (1) of the block row of the inner area (19a) divided by the main groove (15a) are separated on the left and right sides.
Assuming that the angle of 6a) is -40 ° and the angle of the slit (16b) of the block row of the outer area (19b) is -30 °, the PRCF component is on the (+) side in the block row of the inner area (19a), It acts on the (-) side in the block row of the outer region (19b).

Here, in FIG. 10, a substantially rectangular ground shape shown in FIG. 10A and a substantially round ground shape shown in FIG.
Think about the types. In the case of the substantially rectangular grounding shape (A), the ground pressure in the outer region is high, and the effect of the PRCF component acting on the (−) side of the block array in the outer region increases.
On the other hand, in the substantially round contact shape B, the contact pressure is low in the outer region,
It becomes higher in the inner region, and the influence of the PRCF component acting on the (+) side of the block sequence in the inner region becomes larger. therefore,
If the grounding shape changes from a substantially rectangular shape to a substantially round shape in the above pattern, the PRCF component changes to the (+) side.

FIG. 9A shows a belt structure.
As shown in the figure, a case where a reinforcing layer (4a) called a cap ply that covers substantially the entire surface is provided outside the belt layer (2);
The grounding shape is different from the case where a reinforcing layer (4b) called an edge ply that covers both ends of the belt layer (2) is provided as shown in FIG. A in
And in the case of the same (B) structure, it becomes a substantially round shape as B in the figure.

Further, the contact shape of the tire changes even when the load increases or decreases. For example, when the load increases, the contact shape changes from a broken line to a solid line in FIG. 11, especially at the outer region (19b). Because the area is greatly increased,
The influence of the PRCF component of the block sequence in the outer region increases.

As described above, the grounding shape of the tire changes depending on not only the tire structure (belt structure, etc.) but also the molding shape, wear and buff correction, or usage conditions such as load, air pressure and speed. Due to the change in the shape, the PRCF components of the block rows in both the inner and outer regions also change.

Therefore, if the PRCF components of the block rows in both the inner and outer regions are originally reduced, the PRCF components are less likely to change even if the grounding shape changes due to the load or other use conditions or the structure, etc. This is particularly desirable with few restrictions on structural changes.

In view of the above, the present invention provides a tire in which the PRCF component of the block row of the tread pattern is reduced, and the change in the PRCF component caused by the change in the grounding shape due to the structure, use conditions, and the like is reduced. .

[0019]

SUMMARY OF THE INVENTION According to the present invention, a tread pattern has a plurality of main grooves continuous in the tire circumferential direction, a number of slits extending from the main grooves in the tire width direction, and small grooves such as sipes or notches. And the tread section
In a pneumatic tire in which the direction of inclination of the lit is in the same direction, in order to solve the above-described problem, the main groove or the line existing on a line that bisects the center between the center and both ends of the tread in the tread portion. The inner and outer regions are divided by the closest main groove as a boundary, and the inclination angles of the slits in both the inner and outer regions with respect to the tire width direction are set in the following ranges (a) or (b). Is characterized in that the small grooves, such as sipes or notches, which have the same absolute value as the slit angle in the block row in which they are present, are formed at a reverse inclination angle.

(A) Slit angle of the inner region 32 °
４０40 ° Slit angle in the outer region 0 ° -40 ° (b) Slit angle in the inner region −32 ° -40 ° Slit angle in the outer region 0 ° -40 ° (However, + indicates a right-upward angle,- Is the angle to the left

That is, when the slit angle in both the inner and outer regions is greater than 40 °, a large pattern component is generated in the RCF, which undesirably affects the amount of one-sided flow. On the other hand, if the inner slit angle is smaller than 32 °, the pattern component of the RCF is small, but the occurrence of pattern noise becomes remarkable, which is not preferable. It is particularly preferable to set the slit angle in the outer region smaller than the slit angle in the inner region from the viewpoint of preventing uneven wear.

In the above, it is preferable that the difference between the inclination angle of the small groove such as a sipe or a notch and the absolute value of the slit angle in each block row in both the inner and outer regions is substantially equal to or less than 5 °. That is, if the angle difference is larger than 5 °, the change in the PRCF component due to the change in the grounding shape also increases, and a sufficient effect on the change in the grounding shape cannot be obtained.

Further, it is desirable that the total length of the small grooves in the inner row of blocks is substantially the same as the total length of the small grooves in the outer row of blocks. In other words, if there is a large difference in the total length, the influence of the PRCF component by the small grooves of the block row having the longer total length becomes large, which is not preferable.

The slit angle and the angle of the small groove in the block rows in both the inner and outer regions are the average inclination angles of the respective slits and the average of the small grooves.

[0025]

According to the pneumatic tire of the present invention having the above configuration, the inclination directions of the left and right slits of the tread portion are the same.
Oite the tread pattern of the shed which forms an inclination angle of the slit, ie, to have the same inclination direction by the slit angle of the inner and outer band to a specific angular range, the pattern component of the RCF affecting straightness And the amount of one-sided flow caused by the directionality of the pattern does not increase. In addition, pattern noise can be suppressed low, and occurrence of uneven wear can be suppressed.

In particular, in the case of the present invention, small grooves such as sipes or notches, which are respectively provided in the block rows in both the inner and outer regions,
Since the absolute value is substantially the same as the slit angle in the block row in which each exists, and is formed at an inclination angle of reverse inclination, the directionality due to the inclination of the slit is appropriately suppressed by small grooves such as sipes and notches, and therefore, Even if the use conditions such as load, air pressure, speed, etc. or the tire structure change, the grounding shape changes, and as a result, the grounding pressure and grounding area of the inner and outer block rows change, the inner and outer block row change in PRCF component is small, RCF in Pas
The influence on the turn component is also reduced.

[0027]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional structure of the tire (T). In the figure, (1) is a carcass ply, (2) is a two-layer belt layer disposed between the carcass ply (1) and an outer tread portion (3), and is a steel cord or various industrial layers. Both belts made of fiber cord (2a)
(2b) is laminated at a required inclination angle and direction with respect to the tire circumferential direction. This belt may have three or more layers, and if necessary, a cap ply covering the entire outer surface of the belt layer (2) as shown in FIGS. 9A and 9B, or an edge ply covering both side edges. In some cases, reinforcing layers (4a) and (4b) made of nylon fiber cords or the like are provided.

As shown in FIG. 2, the tread pattern on the surface of the tread portion (3) includes a plurality of (four in the figure) main grooves (5) continuous in the tire circumferential direction, and the main grooves (5). ), Slits (6a) and (6b) extending in the tire width direction (lateral direction), and a block (7) defined by the main groove (5) and the slits (6a) and (6b).
The pattern is formed by small grooves (8a) and (8b) such as sipes or notches in the block (7). In particular, as shown in the figure, in the tread portion (3)
Left and right slits (6) at the center (C) in the width direction
a) The inclination direction of (6b) is the same direction. Figure
The turns are symmetric .

FIG. 2 shows a case where sipes as small grooves (8a) and (8b) are inserted one by one into each block (7), and FIG. 3 shows a case where two sipes as described above are inserted into each block (7). FIG. 4 shows a case where two notches as small grooves (8a) and (8b) are provided in each block (7).

In the present invention, the slit (6
a) and (6b)) are grooves having a width larger than 1.5 mm and open at both ends, and small grooves (8a) and (8b)
Is a groove having a very narrow width (1.5 mm or less), and a notch is a groove having a groove width of 1.5 mm or more and at least one end of which is closed.

The center in the tread portion (3)
The center (C) on the left and right of the border
Boundary and main grooves residing on the tire circumferential direction of the line (L) of each bisecting between the ground plane ends (E) (5a), or the main groove closest to the該線(L) and (5a) Then, the tread pattern is divided into an inner area (9a) and an outer area (9b).

The slit (6a) existing in the row of the block (7) in the inner area (9a) and the slit (6b) in the outer area (9b)
The inclination angle (.theta.1) (.theta.2) with respect to the tire width direction with respect to the slit (6b) in the row of the block (7) is set to the angle range of (a) or (b) in Table 1 below.

Small grooves (8a) (8b) such as sipes existing in each block (7) row of both the inner and outer regions (9a) (9b)
As shown in (a) and (b) of Table 1 below, the absolute values of the slit angles (θ1) and (θ2) in the row of the block (7) in which And the minus sign are opposite to each other, that is, the inclination angles (β1) and (β2) of the reverse inclination are formed. This small groove (8
a) The difference between the absolute values of the angles (β1) (β2) of (8b) and the slit angles (θ1) (θ2) is at most 5 °.

[0035]

[Table 1] Here, (+) indicates a right-upward angle, and (-) indicates a left-upward angle. FIGS. 2 to 4 all correspond to the structure (b) in Table 1.

In the above, the slit angle (θ1) (θ
2) In the case of forming a straight line having a fixed angle as shown in FIGS. 2 to 4, the angle is formed with respect to a straight line in the tire width direction of the slit center line.

The slits (6a) and (6b) are often partially bent as shown in FIG. In this case, the slit angle is an angle formed by a straight line connecting the intersection of the circumferential straight line and the slit center line at the block (7) side end with respect to the tire width direction straight line.
a) and respective slits (6a) in the outer zone (9b)
The average angle for (6b) is used. However, the outside area (9
The intersection of the outermost end of the slit (6b) in (b) is the intersection between the slit center line and the end (E) on the side of the largest contact surface, and the angle formed by the straight line connecting this intersection and the intersection with the tire width direction. And

Further, for the purpose of reducing the pattern noise, it is general that three to five types of slits having different slit angles are arranged at different pitches in the circumferential direction. In this case, the average of the plurality of slit angles is used.

Furthermore, the small groove (8) of each block (7)
a) (8b), similarly to the above-mentioned slit angle, when a straight line having a certain angle is formed, the angle is formed with respect to a straight line in the tire width direction of the small groove center line. The straight line connecting the intersection of the small groove center line and the tire circumferential direction straight line at the block side end is defined as the angle formed with respect to the tire width direction straight line, and several different types are defined as the average angles of both the inside and outside regions.

The total length of the small grooves (8a) in the block row in the inner area (9a) is substantially the same as the total length of the small grooves (8b) in the block row in the outer area (9b).

As described above, as shown in the figure, the tread
The left and right slits (6a) and (6b) have the same inclination direction
In the tread pattern, the inner and outer regions (9
a) When small grooves (8a) (8b) such as sipes or notches are formed in each block (7) of (9b), the directionality due to the inclination of the slits (6a) (6b) is changed to the small grooves (8a). (8b) moderately suppresses. Therefore, even if the grounding shape changes due to changes in the use conditions such as load, air pressure and speed, or changes in the tire structure, etc., even if the grounding area of the block row in the inner and outer regions (9a) and (9b) changes, the inner and outer regions (9a ) (9b) P in each
The change in the RCF component, particularly the change in the PRCF component in the outer region (9b), is small, and the effect thereof is also small.

Example 1 In order to confirm the above effects,
The tire structure shown in FIG. 9B with two layers of steel belts is used, and a tire for a right-hand traffic area with a tread pattern shown in FIG. 2 (tire size: 185/60 R1)
Regarding 4), the relationship between the load change and the PRCF component was examined. FIG. 6 shows the result. In addition, speed (7km / h)
And the tire internal pressure (2.0 kgf / cm ² ) was kept constant.

The relationship between the change in tire internal pressure and the PRCF component was examined for the same tires as described above. FIG. 7 shows the result. At this time, the load (300 kgf) and the speed (7 km / h) were constant.

Further, the relationship between the change in speed and the PRCF component of the same tire was examined. The result is shown in FIG.
Shown in At this time, the load (300 kgf) and the tire internal pressure (2.0 kgf / cm ² ) were constant.

In any of the above cases, for comparison, a change in the PRCF component was similarly examined for a tire (comparative product) having no small grooves such as sipes, and the results were shown in FIGS. 8 together with the broken line.

As is clear from the above, in the product of the present invention, the change in the PRCF component due to a change in the use conditions such as load, tire internal pressure (air pressure), speed, etc. is smaller than that of the comparative product and hardly changes. PRCF due to shape change
The change in the components was small, making it less susceptible to the effects.

That is, in general, as the load becomes smaller and the air pressure becomes larger, the contact area decreases. In particular, the contact area decreases in the outer region than in the inner region. Therefore, in the comparative product, as the load becomes smaller and the air pressure becomes larger, the contribution of the PRCF component (−) side by the outer block row becomes smaller, and the contribution of the PRCF component (+) side by the inner block row becomes larger. Become. On the other hand, in the case of the product of the present invention, since a small groove such as a sipe is formed by the inclination angle of the reverse inclination with substantially the same absolute value as the slit angle, the PRCF component of each block due to the slit angle is suppressed, The contribution of the PRCF components of the blocks in both the inner and outer regions is reduced.

(Example 2) Two types of tires (tire size: 185/60 R14) having the same pattern structure as described above and having a belt structure shown in FIGS. 9A and 9B.
, The PRCF component was measured. The results are shown in Table 2 below. In addition, the PRCF component was similarly measured for a tire having a pattern structure having no small grooves such as sipes (Comparative Example).

[0049]

[Table 2]

According to the above results, the PRCF component of the comparative example is largely changed, but according to the pattern structure of the example, the change of the PRCF component is small even if the belt structure is different.

[0051]

As described above, according to the pneumatic tire of the present invention, the inclination directions of the left and right slits of the tread portion are the same.
Despite the single-sided tread pattern
However, the pattern component of the RCF that affects the straightness is small, and the amount of one-sided flow caused by the directionality of the pattern does not increase. In particular, in the case of the present invention, a small groove such as a specific sipe corresponding to the slit angle is formed in each block row of the inner and outer regions, so that the PRCF of each block is formed.
Even if the component is originally small and the contact shape changes due to the load and other operating conditions, the change in the contact shape affects the PRCF.
The change in the component is small, and the influence on the pattern component of the RCF is small. Therefore, even if the grounding shape changes, P
The RCF component, and consequently, the pattern component of the RCF becomes a pattern that is difficult to change, and the restrictions on the use conditions and the structure change are reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a part of a tire showing one embodiment of the present invention.

FIG. 2 is a partial plan view schematically showing a belt structure and a tread pattern shape according to the first embodiment;

FIG. 3 is a partial plan view illustrating another tread pattern.

FIG. 4 is a partial plan view illustrating still another tread pattern.

FIG. 5 is an explanatory diagram of a slit angle and a small groove of the above.

FIG. 6 is a graph showing a relationship between a ply steer component (PRCF) of RCF and a load.

FIG. 7 is a graph showing a relationship between a ply steer component (PRCF) of RCF and a tire internal pressure.

FIG. 8 is a graph showing the relationship between the plysteer component (PRCF) of RCF and speed.

FIG. 9 is a schematic cross-sectional view showing a belt structure (A) in which a kip ply is arranged outside the belt layer and a belt structure (B) in which an edge ply is arranged.

FIG. 10 is a schematic plan view showing a tire grounding shape by the belt structure of the preceding figure.

FIG. 11 is a schematic plan view showing a pattern shape in which small grooves such as sipes are not provided.

FIG. 12 is a graph showing a correlation between a residual cornering force (RCF) and a one-sided flow amount.

[Explanation of symbols]

 (1) Carcass ply (2) Belt layer (3) Tread portion (5) Main groove (6a) Inner slit (6b) Outer slit (7) Block (8a) Inner small groove such as sipe (8b) Small groove such as outer sieve (9a) Inner area (9b) Outer area

Claims (2)

(57) [Claims] 1. A tread pattern having a main groove continuous in the tire circumferential direction of the plurality of the plurality of slits extending from the main groove in the tire width direction, and a small groove such sipe or notch, tread lateral The direction of inclination of the slit is the same
In the pneumatic tire, which is divided into an inner region and an outer region with a main groove existing on a line bisecting the line between the center and both ends of the tread in the tread portion or a main groove closest to the line as a boundary, The inclination angle of the slits in both the inner and outer regions with respect to the tire width direction is set in the range of the following (a) or (b), and small grooves such as sipes or notches in the blocks in both the inner and outer regions are formed in the block row in which each exists. Absolute value difference with slit angle
A pneumatic tire, wherein the tire is formed to have a reverse inclination angle of 5 ° or less . (A) Slit angle of the inner zone 32 ° to 40 ° Slit angle of the outer zone 0 ° to 40 ° (b) Slit angle of the inner zone −32 ° to −40 ° Slit angle of the outer zone 0 ° to −40 ° ( However, + is a right-upward angle,-is a left-upward angle. 2. The pneumatic tire according to claim 1, wherein the total length of the small grooves in the inner block row is substantially the same as the total length of the small grooves in the outer block row.