JPH04218407A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To prevent excessive wear and generate a high cornering force by providing a small hole having a specific dia. in the end part adjoining to a circumferential groove in each of the blocks arranged in a plurality of rows, and equipping each small hole with a depth which decreases as going apart from the circumferential groove. CONSTITUTION:In the form of rows, small holes 9a, 9b having a dia. between 0.5 and 2.0mm are provided at the end part adjoining to circumferential grooves 3, 4 in any block belonging to block rows 7, 8 - for example a block 7a - and the depth of these small holes 9a, 9b is decreased as going apart from the respective grooves 3, 4. This depth of small holes is also decreased as going apart from a groove 5 stretching across the width. Thereby the rigidity at the end part of each block in the tread width direction is reduced through the action of small holes, and a rigidity difference is generated between the center of block and its end part, and the block end part at the tread end is compressively deformed largely in the tread width direction when the block receives the reaction force from the road surface at the time of cornering, which will produce a fast contact with the road surface with a large grounding pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a high-performance pneumatic radial tire for passenger cars, and in particular exhibits excellent maneuverability when the vehicle is running at high speed.

(Conventional technology) The block of a normal pneumatic radial tire for a passenger car is
Mainly, it is a land area defined by grooves formed in the tread surface to ensure wet drainage performance of the tire, and the rigidity of such blocks has a large effect on the tire's maneuverability and other aspects. Conventionally, it has been common to adjust the rigidity of a block in whole or in part by forming a plurality of sipes on the surface of the block.

By the way, in recent years, high-performance tires have been required to have extremely high tread rigidity in response to the increasing power of vehicles. The type of pattern that generates μ has become mainstream, and therefore,
Many of them do not have their rigidity adjusted by sipes,
The blocks have a surface profile that remains defined by grooves and a substantially uniform stiffness throughout the block.

(Problems to be Solved by the Invention) Tire blocks are deformed by large road reaction forces directed from the outside to the inside of the turn, particularly when the vehicle is turning at high speed. In this case, when the rigidity is almost uniform throughout the block, such as the block of the high-performance tire mentioned above, the block edge in the tread width direction and its vicinity are largely deformed, but the central part of the block is relatively deformed. Due to the small amount of ground, the center part has a different grounding condition from the block edge and its neighboring parts, making the grounding pressure of the entire block uneven, and as a result, the occurrence of abnormal wear on the block becomes effective. In addition to being unable to prevent this, there is a problem in that it is not possible to guarantee the generation of large cornering force.

In other words, in a block having almost uniform rigidity as a whole, if the rigidity is relatively high, as shown in Fig. 6(a)
As shown by the arrow, in response to the road reaction force that acts from the outside to the inside of the turn, the block edge at the end of the tread and its surrounding areas are deformed relatively significantly, but are able to sufficiently resist the road reaction force. However, the center part of the block also effectively supports part of the road reaction force under small deformation, but the block edge near the center of the tread and its neighboring parts are completely lifted from the road surface. The ground pressure of the block at this time is as shown in Fig. 6 (b).
As shown in FIG. 2, it gradually decreases from the block edge on the tread end side toward the block edge near the center of the tread, and reaches zero at the part where the block rises from the road surface.

On the other hand, if the rigidity of the block is relatively low,
), the block edge on the tread end side and its vicinity are unable to resist the large road reaction force and are rolled into the center of the block. The block edge and its neighboring parts both rise from the road surface, and the block ground pressure at this time is
As shown in Figure (b), it is largest in the part that resists large road reaction forces and is located somewhat closer to the center of the tread than the block edge on the tread end side, and in the part of the block that rises from the road surface. It becomes zero.

This invention has been made by focusing on these points, and when the block has respective end portions partitioned by respective circumferential grooves having a general cross-sectional shape in the tread width direction, When a road reaction force is applied to the block from the outside to the inside of the turn, the end of the block located on the tread end will normally be rolled up, and the end of the block on the opposite side will be rolled up. This will cause the block to lift up from the road surface, and to prevent such curling and lifting, each end of the block should be made to have a lower rigidity than the center of the block.
Based on the knowledge that deformation of these end portions can be effectively prevented by making it sufficiently easy to deform, the ground pressure of the block is made sufficiently uniform throughout the block, thereby preventing abnormal wear of the block and increasing the To provide a pneumatic radial tire that can generate cornering force.

(Means for Solving the Problems) This invention provides at least two circumferential grooves provided in a tread surface portion and extending in the tire circumferential direction, and at least two circumferential grooves provided at intervals in the tire circumferential direction and extending in the tread width direction. A pneumatic radial tire comprising a plurality of extending widthwise grooves and at least separate blocks partitioned between the circumferential grooves and the tread edge, the blocks comprising one or more block rows,
At least 0.5 to 2.
A plurality of small holes having a diameter in the range of 0 mm are provided, and the depth of the small holes becomes shallower as the distance from the circumferential groove increases.

More preferably, the depth of the plurality of small holes provided in the block becomes shallower as the distance from the width direction groove increases.

This will be explained more specifically using a tire having a tread pattern illustrated in FIG. 1.

Note that this figure shows a front view of the tire as it is mounted on a vehicle.

Here, a single circumferential narrow groove 2 is provided in the center portion of the tread surface portion 1 and extends linearly in the circumferential direction of the tire, and a circumferential groove 2 is provided at a predetermined distance from the circumferential narrow groove 2 toward the tread end. Also, two circumferential thick grooves 3 are provided which are line symmetrical to the circumferential thin grooves 2, and are also spaced a predetermined distance from each of these circumferential thick grooves 3 toward the tread end side. Two straight circumferential intermediate grooves 4 are provided which are line symmetrical to the circumferential narrow grooves 2, and a substantially "H"-shaped groove is provided between each circumferential thick groove 3 and the tread end. A plurality of width direction grooves 5 are formed at predetermined intervals in the tire circumferential direction, and further extend from each of the circumferential thick grooves 3 in the direction of the circumferential narrow grooves 2, so that the width direction grooves 5 are formed at predetermined intervals in the tire circumferential direction. By forming the slanted groove 6 that faces diagonally downward when viewed and ends without reaching the circumferential narrow groove 2, there is a gap between the circumferential thick groove 3 and the circumferential intermediate groove 4, and between the intermediate groove 4 and the tread. In the place where the block rows 7 and 8 are formed between the ends, at least one example of the block row, in the figure, each block 7a of the block row 7, at least at the end portion adjacent to the circumferential grooves 3 and 4, A plurality of small holes 9a, 9b having a diameter in the range of 0.5 to 2.0 mm are provided, for example, in a row, and the depths of these small holes 9a, 9b are shown in a cross-sectional perspective view in FIG. The grooves become shallower as they move away from the respective circumferential grooves 3 and 4.

By the way, in this example, two rows of small holes 9a and 9b are formed in a staggered manner only at each side end portion of the block 7a, but the small holes may be formed over the entire block 7a. Also, instead of or in addition to block 7a, block 8a of block column 8,
It is also possible to form small holes in the end portion adjacent to the circumferential intermediate groove 4 or in the entire block surface.

More preferably, as shown in FIG. 3, for example,
In addition to making the depth of the small hole shallower as it goes away from the circumferential grooves 3 and 4, it also becomes shallower as it goes away from the widthwise groove 5.

The depth of the small holes formed as described above is preferably 20% or more and 80% or less of the groove depth of the circumferential grooves 3 and 4, and the arrangement density of these small holes is In relation to the diameter d of the small holes and the center distance a between the small holes, it is preferable that a≧2d.

(Function) In such a pneumatic radial tire, in the tread width direction, the rigidity of at least the block end portion is equal to the small hole 9.
In addition to being advantageously reduced by the action of holes 9a and 9b, resulting in the desired stiffness difference between the central part of the block and the end parts of the block, the difference in depth of the respective small holes 9a and 9b provides The rigidity of the block end portion adjacent to the circumferential grooves 3 and 4 is particularly low.

Therefore, when the block 7a receives a large road reaction force directed inward from the outside of the turn as shown in FIG. 4, the block end portion A on the tread end side As a result, the block end portion A is compressed and deformed greatly in the tread width direction under the crushing of the small holes 9a and 9b. This will ensure firm contact with the road surface. Furthermore, the block end portion B on the opposite side of the block 7a is largely tensilely deformed in the tread width direction under the required low rigidity due to the action of the road reaction force thereon, and the end portion B The block end portion B is almost completely prevented from lifting off the road surface, so the end portion B of the block is always maintained in contact with the ground, and the end portion B also contributes to the generation of some cornering force. I can do it.

By the way, both the block end portions A and B are
By maintaining the proper grounding condition as described above, the central part of the block is also always maintained in the grounding condition as shown in FIG. 4(b), and at this time, the entire block The ground pressure becomes substantially uniform throughout the block as shown in FIG. 4(c), and the non-uniformity shown in FIGS. 6(b) and 7(b) is eliminated.

Thus, according to this tire, when the vehicle is turning, the block is brought into contact with the ground over its entirety, and the ground contact pressure of the block is made almost uniform over the entirety, thereby effectively preventing the occurrence of abnormal wear on the block. At the same time, it is possible to ensure the generation of high grip force and cornering force.

Here, the diameter of each small hole is 0.5 mm.
If it is less than that, sufficient compressibility cannot be achieved,
If the value exceeds 2.0 mm, the deformability becomes too high, and the resistance against deformation such as elongation of the small hole is small, resulting in deformation beyond the intention of this invention.
Since it becomes difficult to maintain ground contact pressure, the diameter of the small holes in this tire is set to a value within the range of 0.5 to 2.0 mm.

Furthermore, if the depth of such small holes is set to a value exceeding 80% of the groove depth of the circumferential grooves 3 and 4, the block rigidity tends to become too low in relation to the arrangement density of the small holes. On the other hand, if it is less than 20%, the stiffness cannot be sufficiently reduced against compression and tension in the tread width direction. The value should be in the range of 20-80%.

Furthermore, regarding the arrangement density of the small holes, it is important that the rubber between the small holes has enough rigidity to work as a rubber that generates μ. When the center distance is a, it is preferable that a≧2d.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a tread pattern showing an embodiment of the invention.

Note that the inner reinforcing structure of the tire is generally similar to that of a radial tire, so illustration thereof is omitted here.

In this example, when the size is 225/50VR16 and the tread surface width is 186 mm, the groove width of one circumferential narrow groove 2 formed in the center part of the tread surface portion 1 and extending linearly in the tire circumferential direction. 4.5 mm, the groove width of the circumferential thick grooves 3 extending on each side of the narrow groove 2 is 9.5 mm, and the circumferential middle groove extending at a position closer to the tread end than each of these thick grooves 3. The groove width of the groove 4 is 7.0 mm, and the groove width of the width direction groove 5 extending from the circumferential thick groove 3 to the tread end in a substantially "H" shape when viewed from the front of the installed tire is 7.0 mm. Then, the width of block column 7 is 2
Small holes 9a, 9 with a hole diameter of 1.0 mm are formed in the respective end portions of each 6 mm block 7a adjacent to the circumferential grooves 3, 4.
Form b into two rows.

Here, the small hole 9a has its center at a position of 3.0 mm from the end of the block, and the center of the small hole 9b has its center at a position of 6.0 mm from the end of the block, and each of these small holes 9a, 9b is as follows.
They are formed at a circumferential arrangement pitch of 5.0 mm, and are located in a staggered manner in the tire circumferential direction.

Further, here, the small hole 9a has a depth of 50% of the groove depth of the circumferential grooves 3 and 4, which is 8.0 mm, and the small hole 9b has a depth of 25%.

When a vehicle using the tire configured as described above turns, the ground pressure of the block 7a is measured when a road reaction force directed from the outside to the inside of the turn acts on the block 7a, and the tread width is The ground pressure distribution in this direction was as shown in Fig. 4(c).

According to this, it is clear that in the invented tire, the entire block can be brought into contact with the ground sufficiently effectively and the ground contact pressure can be made almost uniform throughout the entire block. It is possible to sufficiently prevent abnormal wear of the block caused by such factors, and it is possible to generate high cornering force.

Therefore, using a commonly used bench testing machine (flat belt machine), the cornering force at each slip angle was measured under the conditions of an internal pressure of 2.5 kg/cm2, a load of 400 kg, and a speed of 50 km/H. As a result, the result is as shown by the broken line in Fig. 5, and the invention tire has the following results:
It has become clear that compared to the tire without small holes, which is shown by the solid line in the figure, it is possible to effectively improve the rate of decrease in cornering force, especially when the slip angle is 5 degrees or more.

Therefore, according to the invented tire, even if the slip angle increases, the road surface grip force does not suddenly decrease, making it possible to perform smooth cornering. Since this tire is almost the same as that of the tire, there is no risk that the turning response will deteriorate until the slip angle reaches 5 degrees.

(Effects of the Invention) As is clear from the above description, according to the present invention, a plurality of small holes are formed at least in the end portion of the block adjacent to the circumferential groove, and the rigidity of the small hole forming portion is improved. By reducing it as required, the block can be sufficiently grounded over its entire length, thus effectively preventing abnormal wear on the block and generating high road grip and cornering force. can.

[Brief explanation of the drawing]

FIG. 1 is a tread pattern showing an embodiment of the present invention, FIG. 2 is a cross-sectional perspective view of FIG. 1, FIG. 3 is a cross-sectional perspective view illustrating the depth of small holes, and FIG. FIG. 5 is a diagram showing the relationship between slip angle and cornering force; FIGS. 6 and 7 are diagrams showing the deformation state and ground pressure distribution of the conventional tire, respectively. It is. 1... Tread surface portion 2... Circumferential narrow groove 3... Circumferential thick groove 4... Circumferential intermediate groove 5... Width direction groove 7, 8... Block row

Claims (2)

[Claims] 1. At least two circumferential grooves provided in a tread surface portion and extending in the tire circumferential direction; and a plurality of width direction grooves provided at intervals in the tire circumferential direction and extending in the tread width direction. , a pneumatic radial tire comprising at least a row of blocks defined between a circumferential groove and a tread edge, wherein at least an end portion of a block in one or more rows of blocks is adjacent to the circumferential groove. , a plurality of small holes having a diameter in the range of 0.5 to 2.0 mm are provided, and the depth of the small holes is
A pneumatic radial tire that becomes shallower as it gets farther away from the circumferential groove. 2. The tire according to claim 1, wherein the depth of the plurality of small holes provided in the block decreases as the distance from the widthwise groove increases.