JP2912437B2 - Pneumatic radial tire - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire in which an inner tread and an outer tread are made of different rubber materials.

(Prior art)

Conventionally, in a pneumatic radial tire suitable for traveling at high speed on a road surface having a straight road or a curved road, particularly, a pneumatic radial tire for motor sports, as shown in FIG. A pneumatic radial tire 52 made of a rubber material different from that of the outer tread 50B is used.

As shown in FIG. 5, the pneumatic radial tire 52 for motor sports is mounted on the vehicle at a large camber angle θ in the minus direction as shown in FIG. 5 in order to sufficiently exhibit the motion characteristics during cornering. For this reason, during straight running, as shown in FIG.
Inside tread 50A that forms the inside of the tread 50 in the vehicle width direction
And the heat generation amount increases. On the other hand, at the time of cornering, as shown in FIG.
The outer tread 50B constituting the outside of the vehicle 50 in the vehicle width direction is grounded over a wide area, and the ground area of the entire tread 50 is increased.

Therefore, conventionally, as a pneumatic radial tire for motor sports, a rubber material having heat resistance and abrasion resistance is used for the inner tread 50A to improve the tire life, and a rubber material having a high grip is used for the outer tread 50B. A pneumatic radial tire 52 is known which is used to improve the motion characteristics at the time of cornering (Japanese Patent Laid-Open No. Hei 2
-185802).

[Problems to be solved by the invention]

However, in the pneumatic radial tire 52, as shown in FIG. 4, the joint surface 54 between the inner tread 50A and the outer tread 50B is substantially the center of the entire tread width L. For this reason, heat resistance and abrasion resistance during straight running are ensured, but grip characteristics during cornering are limited. Further, since the bonding area of the bonding surface 54 is small and the rigidity difference of the tread rubber at the bonding surface 54 is large, there is a problem that the bonding surface 54 is easily peeled off by the side force.

In consideration of the above facts, the present invention improves the gripping property at the time of cornering without lowering the heat resistance and the abrasion resistance, and also improves the separation resistance of the joint surface between the inner tread and the outer tread. The aim is to obtain a pneumatic radial tire that can be driven.

[Means for solving the problem]

The present invention relates to a carcass having a folded portion extending between a pair of bead cores and folded around the bead core, a belt layer extending in a tire circumferential direction outside a crown portion of the carcass, and a belt width end. A reinforcing layer covering the part,
A side wall covering the outside of the side portion of the carcass, an inner tread forming an inner side in the vehicle width direction of the tire outer peripheral portion in a vehicle mounted state, and an outer tread arranged in parallel with the outer side of the inner tread in the vehicle width direction. A pneumatic radial tire using a heat-resistant and abrasion-resistant rubber material for the inner tread and a high-grip rubber material for the outer tread. The width of the inner tread is set to 25% to 30% of the total tread width, and the joint surface between the inner tread and the outer tread is arranged from the inside in the vehicle width direction to the outside in the vehicle width direction from the inside in the tire radial direction to the outside. It is characterized by being substantially linearly inclined and having a cross-sectional line length of the bonding surface being 1.5 times or more and 7.0 times or less of the tread thickness at the bonding surface.

[Action]

In the tread of the pneumatic radial tire of the present invention, a heat-resistant and abrasion-resistant rubber material is used for an inner tread in the vehicle width direction when the vehicle is mounted, and a high grip property is applied to the outer tread in the vehicle width direction. Using a rubber material, the width of the inner tread is set to 25% to 30% of the entire tread width.

This is because, in pneumatic radial tires for motorsports, since the kyamba angle is set to a large negative value, the part where the calorific value increases during straight running is the tire with a reinforcing layer provided to reinforce the belt end. This is based on the fact that the present inventors have found that the end is closer to the center in the width direction.

That is, the inner tread made of a heat-resistant and abrasion-resistant rubber material is placed outward of the reinforcing layer in the tire radial direction such that the end near the center in the tire width direction of the reinforcing layer on the inner side in the vehicle width direction is located at the center. It is sufficient that the width of the inner tread is 25% to 30% of the total width of the tread, which is sufficient. Abrasion can be maintained.

In addition, the remaining portion of the tread, that is, the outer tread is made of a highly gripping rubber material, and the width of the outer tread can be widened, so that the high gripping rubber material can be grounded during cornering. The area becomes large, and the gripping property at the time of cornering can be improved. Therefore, without deteriorating heat resistance and wear resistance,
The gripping property at the time of cornering can be improved.

Further, in the tread of the pneumatic radial tire of the present invention, the joint surface between the inner tread and the outer tread is inclined substantially linearly from the vehicle width direction outside to the vehicle width direction inside from the tire radial direction inside to the outside, In addition, the cross-sectional line length of the joint surface is set to be 1.5 times or more and 7.0 times or less the tread thickness of the joint surface. For this reason, the bonding area increases, the bonding force increases, and the rigidity step in the tire width direction of the tread at the bonding portion is reduced, and the shearing force at the bonding surface when receiving side force is reduced, making it difficult to peel. .

If the cross-sectional line length of the bonding surface is less than 1.5 times the tread thickness at the bonding surface, the bonding surface of the bonding surface is small, and the rigidity difference of the tread rubber at the bonding surface is large. If it exceeds 7.0 times, the tip of each rubber material at the joint becomes too thin and easily peels off. For this reason, the cross-sectional line length of the joint surface is set to be 1.5 times or more and 7.0 times or less the tread thickness of the joint surface.

In addition, by inclining the joint surface between the inner tread and the outer tread from the inside in the tire radial direction to the outside in a substantially linear manner from the outside in the vehicle width direction to the inside in the vehicle width direction, particularly in cornering where a large side force acts. The force received from the tread surface of the outer tread acts in the direction in which the joint surface is pressed, so that the inner tread is not pushed up and peeling is less likely to occur.

〔Example〕

Next, a first embodiment of the present invention will be described with reference to FIGS.

Pneumatic radial tire of the present embodiment shown in FIG.
10 is 10A on the left side in FIG.
The right side 10B of FIG. 1 is located on the outside in the vehicle width direction, and has a large camber angle in the minus direction (the mounting state in which the lower side is opened with respect to the upper side of the vehicle body).

As shown in FIG. 1, the carcass 12 of the pneumatic radial tire 10 extends substantially radially between the pair of bead cores 14. The carcass 12 includes an inner first carcass ply 12A and an outer second carcass ply 12B. The first carcass ply 12A is folded around the bead core 14 from the inside of the tire to the outside, and the second carcass ply 12B is folded around the bead core 14 from the outside of the tire to the inside, and has a so-called up-down structure.

At least two or more non-extensible belts 18, 20 extending in the tire circumferential direction are arranged outside the crown portion of the carcass 12. A substantially cylindrical tread 22 is arranged outside the belts 18 and 20 in the tire radial direction, and covers the belts 18 and 20. A side wall 24 that covers the side portion of the carcass 12 is provided outside the side portion of the carcass 12 in the tire width direction.

At the positions covering the ends 18A, 18B and 20A, 20B of the belts 18, 20, layer layers 25, 26 as reinforcing layers for reinforcing the ends 18A, 18B, 20A, 20B of the belts 18, 20 respectively. Are located.

The tread 22 includes an inner tread 28 that forms the inside of the tire outer peripheral portion in the vehicle width direction when mounted on the vehicle, and an outer tread 30 that is arranged in parallel with the inner tread 28 outside in the vehicle width direction. The width W1 of the inner tread 28 is 25% to 30% of the total tread width W of the tread 22, and the end 25A of the layer layer 25 on the inner side in the vehicle width direction near the center in the tire width direction is the tire width of the inner tread 28. It is located in the approximate center of the direction.

The inner tread 28 is made of a relatively hard rubber material having excellent heat resistance and abrasion resistance, and the outer tread 30 is made of a relatively soft rubber material having high grip. For example, the hardness of the inner tread 28 is higher than the hardness of the outer tread 30 within 6 mm,
The value obtained by dividing nδ by tanδ of the outer tread 30 is in the range of 0.78 to 0.99.

As shown in FIG. 2, the thickness H of the tread 22 is 3 mm to 5 mm.
mm is preferable, and the cross-sectional line length CL of the joint surface 32 between the inner tread 28 and the outer tread 30 is the thickness TG of the tread 22 at the joint.
Is not less than 1.5 and not more than 7.0 (1.5TG ≦ CL ≦ 7.0TG). The joining surface 32 is inclined substantially linearly from the outside in the vehicle width direction (right side in FIG. 2) to the inside in the vehicle width direction (left side in FIG. 2) from the inside to the outside in the tire radial direction.

 Next, the operation of the present embodiment will be described.

In the pneumatic radial tire 10 of the present embodiment, the inner tread 28 which is on the inner side in the vehicle width direction when the vehicle is mounted.
A rubber material having heat resistance and abrasion resistance is used for the outside, and a high grip rubber material is used for the outer tread 30 on the outer side in the vehicle width direction. The width W1 of the inner tread 28 is 25% to 30% of the total tread width W.
%.

Therefore, by disposing the inner tread 28 outside the end 25A of the layer layer 25 at a width of 25% to 30% of the total tread width W, the heat resistance of the inner tread portion where the calorific value and the ground pressure increase during straight running is increased. And abrasion resistance can be maintained.

Also, the rest of the tread, namely the outer tread 30
Is made of high-grip rubber material, and the width of the outer tread 30 can be increased, so that the contact area of the high-grip rubber material becomes large at the time of cornering, and the grip at the time of cornering is reduced. improves. That is, the gripping property at the time of cornering can be improved without lowering the heat resistance and the wear resistance.

Further, in the tread 22 of the pneumatic radial tire 10 of the present invention, the joint surface 32 between the inner tread 28 and the outer tread 30 extends from the inside in the tire radial direction to the outside, and substantially from the outside in the vehicle width direction to the inside in the vehicle width direction. The cross section line length CL of the joint surface 32 is inclined linearly, and the tread thickness TG at the joint surface is
1.5 times or more and 7.0 times or less. For this reason, the bonding area increases, the bonding force increases, the rigidity step of the tread 22 in the tire width direction at the bonding portion is reduced, and the shearing force at the bonding surface 32 when receiving a side force decreases,
It becomes difficult to peel off.

Also, a joint surface 32 between the inner tread 28 and the outer tread 30
By inclining substantially linearly from the vehicle width direction outside to the vehicle width direction inside from the tire radial direction inside to the outside,
In particular, when cornering where a large side force acts, the force received from the tread surface of the outer tread 30 is
Will act in the direction of crimping
Is not pushed up and peeling is less likely to occur.

It should be noted that the pneumatic radial tire of the present invention is not limited to the pneumatic radial tire 10 having the structure shown in FIG. 1, for example, as shown in FIG. 3 instead of the layer layer 25 described in FIG. Of the at least two layers of belts 34, 36, both ends 36A, 36B in the tire width direction of one of the belts 36 may be folded outward in the tire radial direction to form reinforcing layers. In this case, the inner belt in the vehicle width direction may be used. The position of the tip 36C of the end 36A in the tire width direction 36 is 13 of the total tread width W.
% To 17%, that is, the inner tread where the position of the tip 36C of the belt 36 is defined by a width of 25% to 30% of the total tread width W.
It is located approximately at the center of the width W1 of 28.

(Experimental example 1) Joining surface of pneumatic radial tire 10 shown in FIG.
The pneumatic radial tire (tire size 195/70 R1) of the present invention in which the lengths of the sectional line lengths CL of 32 were as shown in Table 1 respectively.
4) Prototype, drum test (test condition: 100km / h × 500kGw)
× SA1 ゜ × 2 hours) to check the separation length of the joint surface, and also to mount it on an actual vehicle to perform a running test to check the appearance quality. The results are shown in Table 1.

From Table 1, it became clear that the cross-sectional line length CL of the joint surface of the present invention needs to be 1.5 times or more and 7.0 or less of the tread thickness TG at the joint surface.

(Experimental Example 2) The pneumatic radial tire (tire size 195/70 R14) of the present invention shown in FIG. 3 and the conventional pneumatic radial tire (tire size 195/70 R1) shown in FIG.
4) was mounted on each vehicle (Chamber angle: minus 3 °), and a running test was performed. The results are shown in Table 2.

The wear amount and lap time in Table 2 are represented by indices when each data of the inventive tire is set to 100.

From Table 2, it is clear that the pneumatic radial tire of the present invention maintains damage and abrasion caused by heat generation and improves lap time as compared with the conventional pneumatic radial tire.

〔The invention's effect〕

Since the present invention is configured as described above, the gripping property at the time of cornering is improved without lowering the heat resistance and the abrasion resistance, and the separation resistance of the joint surface between the inner tread and the outer tread is also improved. It has an excellent effect that it can be performed.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a pneumatic radial tire according to an embodiment of the present invention, in which hatching is omitted, FIG. 2 is a schematic cross-sectional view showing a tread of FIG. 1, and FIG. FIG. 4 is a partial cross-sectional view of the conventional pneumatic radial tire with hatching omitted, FIG. 4 is a partial cross-sectional view of the conventional pneumatic radial tire without hatching, and FIG. FIGS. 6 (A) and 6 (B) are schematic views as viewed from the front of the vehicle when mounted on the vehicle at an angle, and show straightforward and cornering when mounted on the vehicle at a large camber angle in the minus direction, respectively. It is the schematic which shows a grounding shape. 10, 38 ... pneumatic radial tire, 12 ... carcass, 14 ... bead core, 18, 20 ... belt, 22 ... tred, 24 ... side wall, 25 ... layer layer, 28 ... inner tread, 30 ... outer tread, 32 ... joint surface, 34, 36 ... belt.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-25003 (JP, A) JP-A-61-275008 (JP, A) JP-A-61-27707 (JP, A) JP-A-1 67404 (JP, A) JP-A-62-59104 (JP, A) JP-A-2-53605 (JP, A) JP-A-2-162104 (JP, A) Japanese Utility Model Laid-Open No. 63-194004 (JP, U) Patent 2728286 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 11/00

Claims (1)

(57) [Claims] 1. A carcass having a folded portion extending between a pair of bead cores and folded around the bead core, a belt layer extending in a tire circumferential direction outside a crown portion of the carcass, and a belt width direction. A reinforcing layer covering the end,
A side wall covering the outside of the side portion of the carcass, an inner tread forming an inner side in the vehicle width direction of the tire outer peripheral portion in a vehicle mounted state, and an outer tread arranged in parallel with the outer side of the inner tread in the vehicle width direction. A pneumatic radial tire using a heat-resistant and abrasion-resistant rubber material for the inner tread and a high-grip rubber material for the outer tread. The width of the inner tread is 25% to 30% of the total tread width, and the joining surface between the inner tread and the outer tread is from the inside in the tire radial direction to the outside from the vehicle width direction outside to the vehicle width direction inside. A pneumatic radial tire characterized by being substantially linearly inclined and having a cross-sectional line length of a joining surface being 1.5 times or more and 7.0 times or less of a tread thickness at the joining surface.