JPH0445363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic racing tire that has a large ground contact area ratio and has improved braking and driving performance in the initial stage of use.

In recent years, there has been a growing demand for improved high-speed running performance of tires. For this reason, slick tires with no grooves on the ground contact surface and smooth tires, or semi-slick tires with slight grooves on the ground contact surface but without sipes, are suitable for racing, or have similar performance, so pneumatic tires for racing are suitable. It has come to be used as tires.

By the way, when vulcanizing is performed during tire manufacturing,
A lubricant is applied to the surface of the green tire to improve the slippage between the green tire (tire before vulcanization) and the mold. Therefore, under the influence of this lubricant, the physical properties of the rubber on the surface of the tread, that is, the contact surface of the tire, are lower than the physical properties of the rubber inside the tread. Specifically, the tread surface becomes harder than the tread interior. Further, even when no lubricant is used, the inner surface of the mold reaches a high temperature during vulcanization, which similarly causes the physical properties of the rubber on the tread surface to be lower than those inside the tread. This reduces the coefficient of friction μ on the tread surface, which improves braking and driving performance (traction performance) in the early stages of tire use.
will decrease. The influence of such a reduction in braking/driving performance becomes greater for tires with a larger tread contact area ratio, such as the above-mentioned slick tires and semi-slip tires.

Therefore, in the case of pneumatic tires for high-speed running, especially pneumatic tires for racing, the tread surface must be worn to some extent to remove portions with deteriorated physical properties from the tread surface before competing. Furthermore, even in general tires, especially those that require high-speed running performance with a large ground contact area ratio, it is necessary to break-in the tires until the tread surface wears out to a certain extent, rather than running at maximum speed from the beginning. In this way, in recent years, when pneumatic tires for high-speed running have a portion with deteriorated physical properties on the tread surface,
In other words, it was impossible to extract maximum high-speed driving performance from the beginning.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic racing tire that can maximize braking and driving performance from the initial stage of use.

Therefore, the racing pneumatic tire of the present invention is a semi-slick tire in which the tread contact surface includes ribs that are continuous in the circumferential direction and the tread contact area ratio is 65% or more. A plurality of sipes are provided at predetermined intervals in the circumferential direction of the tire so as to be continuous over at least the entire width of the ground contact area of the rib, and the sipes have a width of 1 mm or less and a depth of less than 1 mm. It is characterized by the following.

Here, the ground contact area ratio refers to the area ratio of the ground contact portion within the ground contact width on the tread ground plane, and is expressed by the following formula.

Ground contact area / Ground contact area + Groove area in plan view × 100 Also, rib means a continuous land area in the circumferential direction of the tire that does not have a minor groove, and the rib width extends to the maximum to the full width of the tread (ground contact width). The case is slick tires.

In this way, in the present invention, since the ribs are provided at least in the width direction of the tire with a width of 1 mm or less and a depth of less than 1 mm, the ribs can compensate for the decrease in the physical properties of the tread surface caused by the vulcanization process. Since this can be compensated for by the edge effect, it is possible to maximize the braking and driving performance in the early stages of tire use from the beginning.

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is an explanatory diagram partially showing the contact surface of an example of a pneumatic racing tire (semi-slip tire) according to the present invention, and FIG. 2 is a cross-sectional view taken along the line -2. In these figures, main grooves 2, 3, and 4 are located within the contact width W of the tread contact surface 1 in the tire circumferential direction.
A plurality of sub-grooves 5, 6, 7 are provided in the tire width direction in an annular manner around one circumference of the tire at EE', thereby forming a plurality of blocks 8 in the right half-width area.
However, there is also a rib 9 that continues in the circumferential direction in the left half width area.
is formed.

In such a structure, the present invention is directed to one in which the ground contact area ratio of the tread ground plane 1 is 65% or more. In other words, if it is less than 65%, the groove area ratio increases and the edge effect of the grooves is exerted, and the effect of decreasing the friction coefficient due to hardening of the tread surface during vulcanization is almost eliminated, so the tire This is because deterioration in braking drive performance does not occur during the initial stage of use.

In the tire of the present invention, the rib 9 in the left half width region is provided with a plurality of sipes a continuously in the tire width direction from one end of the rib width to the other end, and extends over the entire length in the tire circumferential direction EE'. They are arranged at predetermined intervals. This sipe a must be provided at least in the tire width direction in order to produce an edge effect, but as shown in FIG. 1, it may be additionally provided in the tire circumferential direction EE'. When sipe a is also provided in the tire circumferential direction EE', in order to avoid stress concentration at the intersection with sipe a in the tire width direction,
It is preferable to form a mortar-shaped recess 10.

Sipe a is not provided in block 8 in the right half-width area. This is because the sub-grooves 5 and 6 exhibit the edge effect even without providing the sipe a.

In the present invention, the sipe a must have a width l of 1 mm or less and a depth h of less than 1 mm as shown in FIG. This is because if the width l exceeds 1 mm or the depth h exceeds 1 mm, the rigidity of the tread contact surface 1 decreases, the edge effect of the sipe a decreases, and the control drive performance deteriorates. In particular, regarding the depth h, since the area where physical properties change due to vulcanization is within about 1 mm toward the inside of the tread, setting the depth h to 1 mm or more will not only unnecessarily provide sipes to the soft rubber area, but also cause the tread to contact the tread. This is because the ground 1 becomes too soft and becomes a cause of deterioration of steering stability. The spacing (pitch) of the sipes in the tire circumferential direction may be arbitrary and is not particularly limited. The mortar-shaped recess 10 in FIG. 1 has a diameter of about 6 mm in plan view and a depth of about 6 mm.

Examples are shown below.

Example: The following pneumatic tires were made with tire size 205/50 VR15, and μ-S was calculated for these tires.
I conducted a test. The results are shown in Figures 5a and 5b, respectively.

In the μ-S test, the test tire is moved at a predetermined speed (S).
After driving on a paved road surface and applying braking, the torque acting on the tire is measured, and μ (friction coefficient) is measured.
A test that requires The test conditions include rim
6JJ×15, air pressure 2.2Kg/cm ² , and load 300Kg.

(1) Tire 1 of the present invention.

A semi-slick tire having the tread pattern shown in FIG. Ground contact area ratio of approximately 70%. Rib 9
Multiple sipes are installed over the entire surface. Width of main groove 2 is 13mm. Width of main groove 3 is 10mm. Main groove 4 width 7
mm. The maximum width of the minor groove 5 is 10 mm, and the minimum width is 6 mm. Minor groove 6
Maximum width 6mm, minimum width 2mm. Maximum width 5 of minor groove 7
mm, minimum width 2mm. Installation width W150mm. Sipe a has a width l of 0.8mm, a depth of 0.5mm, and a tire circumferential spacing of 20
mm.

(2) Comparison tire 1.

Same as the tire of the present invention described above except that sipe a is not provided.

(3) Tire 2 of the present invention.

The tire according to the present invention is different from the above-mentioned tire 1 of the present invention, except that the ground contact area ratio is 65% and the width of the rib 9 is narrowed and the width of the main grooves 2, 3, and 4 is widened to adjust the ground contact area ratio. same.

(4) Comparison tire 2.

The above-described tire 1 of the present invention has a ground contact area ratio of approximately 60% and a tire in which the width of the rib 9 is narrowed and the width of the main grooves 2, 3, and 4 is widened in order to adjust the ground contact area ratio. Same as.

(5) Comparison tire 3.

A tire having a block-based tread pattern as shown in FIG. Ground contact area ratio of approximately 60%. Five main grooves 2, 3, 4, 3', and 4' are arranged in the tire circumferential direction EE' on the contact surface 1, and a secondary groove is arranged in the tire width direction with the tire equator line (not shown) as the boundary. Grooves 5, 6, 5', 6' are arranged. One sipe c is provided near both shoulder parts each around the tire, and these sipes c
A plurality of sipes c are provided in the tire width direction so as to intersect with each other. Width of main groove 2 is 12mm. Width of main groove 3 is 9mm. Width of main groove 4 is 6mm. Main groove 3' width 9
mm. Width of main groove 4' is 6mm. Maximum width of minor groove 5 is 10mm.
Minimum width 6mm. Maximum width of sub groove 6: 6 mm, minimum width: 2
mm. The maximum width of the minor groove 5' is 10 mm, and the minimum width is 6 mm. The maximum width of the minor groove 6' is 6 mm, and the minimum width is 2 mm. Ground contact width W150
mm. Sipe C has a width l of 0.8mm, a depth of 0.5mm, and a tire circumferential spacing of 20mm.

(6) Comparison tire 4.

Same as Comparative Tire 3 above except that Sipe C is not provided.

FIG. 5a shows the difference (Δμ) in the coefficient of friction of the μ-S test measurement data on a dry road surface for Tires 1 to 2 of the present invention and Comparative Tires 1 to 4. Figure 5b shows tires 1 and 2 of the present invention.
and the difference (Δμ) in the coefficient of friction of the μ-S test measurement data on a wet road surface for each of Comparative Tires 1 to 4. In these figures, ● indicates the difference between the present invention tire 1 and the comparison tire 1, △ indicates the difference between the present invention tire 2 and the comparison tire 2, and ○ indicates the difference between the comparison tire 3 and the comparison tire 4.
Each represents the difference between

As is clear from Figures 5a and 5b,
When the ground contact area ratio is as high as approximately 70%, providing sipes over the entire surface of the contact area will increase the difference in friction coefficient compared to when no sipes are provided, improving braking drive performance. can be seen (● mark).
In addition, when installing sipes, the ground contact area ratio is approximately
It can be seen that the difference in friction coefficient is larger at 65% than at 60%, so the braking drive performance improves (△
mark). Furthermore, in the case of a tire with a block-based tread pattern, it can be seen that the braking and driving performance is not much improved even when sipes are provided compared to when they are not provided (○ mark). Therefore, the present invention provides a tire in which circumferentially continuous ribs are arranged within the contact width of the contact surface, and the contact area ratio is set to 65% or more.

As explained above, according to the present invention, in a tire with a contact area ratio of 65% or more in which ribs are arranged within the contact width of the contact surface, sipes are provided on the entire surface of the ribs with a width of 1 mm or less and a depth of less than 1 mm. Since the sipes are provided at least in the width direction of the tire and are continuous from one end of the rib in the width direction to the other end, high-speed running performance such as braking drive performance can be maximized from the beginning without running-in or the like. It becomes possible to perform.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram partially showing the tread contact surface of an example of a pneumatic racing tire of the present invention, FIG. 2 is a cross-sectional view taken along the - line, and FIG. FIG. 4 is an explanatory diagram showing the case where sipes are provided on the tread ground plane having a block-based tread pattern.
FIGS. 5a and 5b are diagrams showing the relationship between the running speed (S) and the difference in friction coefficient (Δμ). 1... Ground plane, 2, 3, 4... Main groove, 5, 6,
7...minor groove, 8...block, 9...rib.

Claims (1)

[Claims] 1. In a semi-slick tire whose tread contact surface includes ribs that are continuous in the circumferential direction and whose tread contact area ratio is 65% or more, the ribs are provided with sipes extending at least in the width direction of the tire so that the ribs extend at least over the entire width of the contact area. A pneumatic tire for racing, wherein a plurality of sipes are provided continuously at predetermined intervals in the tire circumferential direction over the entire circumference, and the width of the sipes is 1 mm or less and the depth is less than 1 mm.