JP3017677B2 - Winter passenger car tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire for a winter passenger car which can sufficiently exhibit the performance on ice of a tread pattern from an early stage of use and can be suitably used as, for example, a studless tire, a snow tire, and an all-weather tire.

[0002]

2. Description of the Related Art In general, as winter tires, studless tires having enhanced running performance (performance on ice), especially on icy roads, snow tires having increased traction / braking force on snowy roads, and dry road surfaces (normal road surfaces) However, there are known all-weather tires and the like designed to exhibit performance. In these winter tires, a block pattern having a high snow biting property is employed to provide a grip force on a snowy road, and each block a In addition, as shown in FIG. 6, a plurality of sipings b are formed, a road surface is dug by a siping edge to increase a frictional force, and the like, and the performance on ice is improved.

Conventionally, a pattern has been designed based on the shape and size of the block a, the length of the siping b, and the like so that the characteristics according to the type of the tire can be optimally exhibited.

[0004]

However, in the case of a new tire, since the rubber molecules contain short molecular branches at the time of vulcanization molding and bond irregularly in a network, the tire rubber itself is relatively hard plastic. In addition, the tread surface is mirror-finished and the release agent from the vulcanizing mold permeates. As a result, in the early stage of use of the tire, the frictional force tends to be insufficient particularly on a frozen road surface. For example, there is a problem that the performance on ice at the time of design is not sufficiently exhibited until running-in of about 100 km.

Therefore, the invention of the present application is based on the fact that, in addition to the conventional siping, the auxiliary sipes having a minute depth are densely formed at small pitch intervals in the block, and the degree of freedom of pattern design according to the type of tire is increased. It is an object of the present invention to provide a tire for a winter passenger car that can sufficiently exhibit the performance on ice from the initial stage of use without any damage.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the invention of the present application is directed to forming a plurality of circumferential grooves extending in a circumferential direction on a tread surface and a space between the vertical grooves or between a vertical groove and a tread edge. A tire for a winter passenger car having a block pattern having a plurality of blocks in which a tread portion is arranged in a circumferential direction by providing a connecting lateral groove, wherein the block has a depth D of 60% or more of the block height H. A main siping having a depth d shallower than the main siping and an auxiliary siping spaced in the tire circumferential direction across the block, and the depth d of the auxiliary siping.
Is 0.02 times or more and 0.03 times or less of the block length L of the block in the tire circumferential direction, and the ratio L / P of the block length L to the tire circumferential pitch P between auxiliary sipes is It is characterized by being 10 or more and 15 or less.

Further, according to the present invention, the main siping is:
It said auxiliary sipes substantially parallel to form a zigzag part, is crossed with the auxiliary sipes in the zigzag portions.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a winter passenger car tire 1 includes a carcass 6 that is turned around a bead core 5 of a bead portion 4 from a tread portion 2 to a sidewall portion 3.
And a belt layer 7 disposed radially outside of the carcass 6 and inside the tread portion 2. In this example, the belt layer 7 is formed as a studless tire having a tire size of 195 / 65R15, for example.

The carcass 6 has carcass cords arranged at an angle of 70 to 90 degrees with respect to the tire equator C.
Formed from one or more carcass plies in this example,
As the carcass cord, an organic fiber cord such as nylon, rayon, polyester or the like is used in addition to the steel cord.

[0010] The belt layer 7 includes a plurality of belt cords arranged at an angle of 0 to 30 degrees with respect to the tire equator C.
In this example, two belt plies are used inside and outside, and the belt cords are arranged in different directions so as to cross each other between the plies. In addition, as a carcass cord, a metal fiber cord such as steel, nylon,
Organic fiber cords such as polyester and rayon can be used.

On the tread surface S, as shown in FIG.
A plurality of, in this example, four longitudinal grooves G extending in the tire circumferential direction.
1, G1, G2, G2 (collectively referred to as vertical grooves G), a horizontal groove Y1 connecting the vertical grooves, and a horizontal groove Y2 connecting the outer vertical groove G2 and the tread edge 2e. By disposing Y, a block pattern including a plurality of blocks B arranged in the circumferential direction is formed on the tread surface S.

Therefore, the lateral groove Y extends in a direction intersecting the circumferential direction of the tire, and its end is formed at the tread edge 2.
e or the vertical groove G and the block B
The vertical wall block Bg consisting wall or buttress surface 9 of the longitudinal groove G, and Bg, lateral wall block By comprised from the wall surface of the lateral grooves Y, is defined by the By. Block B is
In the present example, the horizontal block wall By is formed in a rectangular shape having a high snow biting property, such as a parallelogram, arranged at an angle θ of 0 to 30 degrees with respect to the tire axial direction. At least the lateral block wall By is inclined at an angle of about 5 to 15 degrees in the tire circumferential direction with respect to the normal to the tread surface S in order to maintain the tire performance and exhibit high snow performance.

As shown in FIG. 1, each of the vertical grooves G and the horizontal grooves Y has a groove depth Dg and Dy of 8 mm or more and 0.16 times or less of the tread width TW, for example, about 10 mm. Therefore, the groove depth Dy of the horizontal groove Y is preferably set to be equal to or slightly smaller than the groove depth Dg of the vertical groove G. In this example, the groove depths Dg and Dy are equal to each other, so that they match the block height H. However, when the groove depths Dg and Dy are different from each other, the block height is set to be smaller than the block height H. Defined as H.

In the present application, as shown in FIG. 3, a main siping 10 having the same depth D as the conventional one and an auxiliary siping 1 having a small depth d are provided in the block B.
1 are formed together. Each siping 10, 1
1 is a cut where the groove width is substantially 0, and 1.
Including narrow grooves of 0 mm or less.

The main siping 10 has a direction crossing the vertical groove G, for example, an angle of 30 degrees or less with respect to the tire axial direction,
It preferably extends at an angle of 5 degrees or less, and in this example, is formed as an open type having both ends opened by a vertical block wall Bg. Also main siping 10
Has a zigzag portion 20 that is bent in a wavy shape
This increases the substantial length of the main siping 10, enhances the performance on ice by digging up the road surface by the edge and increasing the frictional force, and restrains each other when the lateral force acts, thereby restraining the tire shaft of the block B. The rigidity in the direction can be increased, and the skid resistance and turning performance on a dry road surface can be improved.

In order for the main siping 10 to excavate the road surface and exert the frictional force, the depth D must be 60% or more of the block height H, and the upper limit is the block height. 100% or less of H, preferably 9%
0% or less. This depth D is 100 of the block height H.
%, Stress concentration occurs at the bottom of the siping, and durability is impaired due to crack damage and the like. The number of the main sipings 10 is generally about 1 to 5 per block, but is appropriately set according to the type of winter tires such as snow tires and all-weather tires. The shape itself may be linear, wavy, or partially wavy, and various shapes such as a semi-open type and a closed type having one end and both ends terminated in a block may be adopted as required.

The auxiliary siping 11 is an open type siping that is spaced apart from the block B in the tire circumferential direction.
An angle of less than or equal to degrees, preferably an angle of less than or equal to 5 degrees, in this example,
The main siping 10 is formed substantially linearly at an angle of substantially 0 degrees, which is substantially parallel to the main siping 10. The main siping 10 intersects only at the zigzag portion 20.

Here, the auxiliary siping 11 suppresses a temporary decrease in performance on ice in the initial stage of use of a new tire. Therefore, the depth d is set to the block length L of the block B in the tire circumferential direction. Is set to a minute depth of 0.02 times or more and 0.03 times or less.

The block length L is defined as the circumferential length on the tread surface S between the horizontal block walls By. Accordingly, for example, as shown in FIG. 4A, even when the horizontal block walls By, By are formed by refraction lines, curves, or the like, when the block walls By, By are parallel to each other, the circumferential length is equal. It is fixed, and this fixed circumferential length is defined as a block length L. FIG. 4
As shown in (B) and (C), when the block walls By and By are in a non-parallel state, the circumferential length varies depending on the position, and therefore, the circumferential length between the horizontal block walls By and By. Is defined as the block length L. Note that, in a normal passenger car tire, the block length L is generally about 50 mm or less, and therefore, the depth d of the auxiliary siping 11 is about 1.5 mm or less at most, in other words, the block height H is 0.1 mm or less. It is 19 times or less.

The auxiliary siping 11 has a dense pitch arrangement in which the ratio L / P of the block length L to the pitch P in the tire circumferential direction between the adjacent auxiliary sipings 11 and 11 is 10 or more and 15 or less. In addition to the regular pitch arrangement as in this example, the pitches may be arranged at an incorrect pitch in the range of 10 to 15.

By forming the auxiliary siping 11 at a minute depth and densely, the tread surface is apparently roughened and softened without affecting the block rigidity, so that only the surface properties of the tread are improved. To improve. Thereby, the contact state with the road surface in the early stage of use of the new tire, that is, the frictional force with the frozen road can be improved. Incidentally, when the depth d of the auxiliary siping 11 is less than 0.02 times or more than 0.03 times the block length L, and when the ratio L / P is less than 10 or more than 15, any However, the contact state with the road surface is not sufficiently improved, and the effect of improving the frictional force with the frozen road is insufficient.

[0022] Also, the auxiliary sipes 11 are for the purpose of improving the surface properties of the tread as described above, the shape of the main sipes 10 without relating to the size and formation position or the like, Ru can form an auxiliary sipes 11. Therefore , as shown in FIG. 5, for example, one of the auxiliary sipes 11 may be formed so as to overlap the main siping 10. At this time, if the main siping 10 is formed by a straight line without the zigzag portion 20, the main siping 10 and the auxiliary siping 11 completely match, so that the existence of the auxiliary siping 11 is blindfolded. And the presence of the auxiliary siping 11 is recognized. In addition, it is preferable that the auxiliary siping 11 has a partially incorrect pitch in order to avoid overlapping with the main siping 10.

In the present application, the formation of the main siping 10 and the auxiliary siping 11 may be performed on only some of the blocks in the block pattern. And most preferably for all blocks.

Block B other than auxiliary siping 11
The shape and size of the main siping 10, the shape and size of the main siping 10, the number of formation, and the like can be appropriately set according to the type and characteristics of the winter tire, without impairing the degree of freedom of design for these settings. An auxiliary siping 11 is provided.

[0025]

[Specific example] The tire size is 195 / 65R15,
In addition, a tire having the configuration shown in FIG. 1 and the block pattern shown in FIG. 2 is prototyped based on the specifications in Table 1, and the performance on ice of the test tire is tested, and only the auxiliary siping is eliminated in the same block pattern. It was compared with a tire (conventional example).

On-ice performance The test tire was mounted on all wheels of a front-wheel-drive vehicle under standard rim (15 × 6JJ) and standard internal pressure (2.0 kgf / cm ² ), and was driven on an ice road surface, with an approach speed of 30 km / h. , The braking distance when all the wheels were locked was measured. The braking distance after 100 km break-in running of the conventional tire was evaluated by an index, and the higher the index value, the shorter the braking distance and the better the performance on ice.

[0027]

[Table 1]

As shown in Table 1, the tires of the examples were
It can be confirmed that almost the same level of on-ice performance as after the running-in of the conventional tire can be exhibited from the initial use.

[0029]

Since the present invention is configured as described above,
The performance on ice at the time of design from the beginning of use can be sufficiently exhibited without impairing the degree of freedom of pattern design according to the type of tire.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a developed view showing the tread pattern.

FIG. 3 is a perspective view illustrating one of the blocks as a representative.

FIGS. 4A, 4B, and 4C are diagrams illustrating a block length L together with a block contour shape.

FIG. 5 is a partial perspective view showing another example of the auxiliary siping.

FIG. 6 is a cross-sectional view illustrating a frictional force caused by digging a road surface by siping.

[Explanation of symbols]

 2 Tread portion 2e Tread edge 10 Main siping 11 Auxiliary siping B block G Vertical groove S Tread surface Y Horizontal groove

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11 / 11,11 / 12

Claims (1)

(57) [Claims] 1. A plurality of blocks in which tread portions are arranged in a circumferential direction by providing a plurality of circumferential grooves extending in a circumferential direction and a horizontal groove connecting between the vertical grooves or between the vertical grooves and a tread edge on a tread surface. And a block pattern having a main siping having a depth D of 60% or more of the block height H, a depth d shallower than the main siping, and An auxiliary siping that is spaced in the tire circumferential direction across the block, and the depth d of the auxiliary siping is equal to or greater than 0.02 times a block length L of the block in the tire circumferential direction and is equal to or less than 0.02 times. 03 times or less, and the block length L with respect to the pitch P in the tire circumferential direction between auxiliary sipes
The ratio L / P with the 10 or more and 15 or less, prior to
The lord siping is a jig that bends zigzag in the middle
Having a zag portion and extending substantially parallel to the auxiliary siping,
And intersect with the auxiliary siping at this zigzag part
A tire for a winter passenger car , characterized in that: