JPH10297216A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the CF characteristic while keeping the superior low noise and the wet performance, by forming at least rows of blocks partitioned by longitudinal grooves and lateral grooves, at both sides of an equatorial plane more than one row, under the conditions that each block has specific block length under specific arrangement pitches, and the specific numbers of long blocks and short blocks are alternately arranged. SOLUTION: At least one row of a number of blocks is respectively partitioned at both sides gripping an equatorial plane (central periphera line E), by the lateral grooves 3, 4 and the longitudinal grooves 5, 6. The rows of blocks 7, 8 are positioned near the central peripheral line E, and the rows of blocks 9, 10 are positioned near the edges TE. Each block comprises two kinds of arrangement pitches, that is, the pitches PL of larger arrangement pitch and the pitches PS of smaller arrangement pitch. The arrangement of the block is formed by alternately arranging up to two long blocks 9 and up to two short blocks 8, and the rows of the blocks 9, 10 at the both sides, are similarly formed. The wet performance and the low noise, can be kept, and the CF characteristic (grip performance) can be remarkably improved by the alternate arrangements of the large and small blocks on the basis of the large and small pitches.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly, to a high performance tire for a passenger car having a block pattern, and more particularly, to a high wet performance and a low performance by optimizing a block arrangement of a tread pattern. The present invention relates to a pneumatic radial tire having improved cornering force performance, especially grip performance on a road surface, while maintaining noise performance.

[0002]

2. Description of the Related Art To improve noise, pneumatic radial tires, especially passenger tires, employ a so-called pitch variation method in which a plurality of or a large number of pitches are randomly arranged in a tread pattern to achieve white noise. Is customary.

In a tread pattern with a pitch variation, in particular, in a block pattern, the rigidity of a block included in a small pitch portion is small, whereas the rigidity of a block included in a large pitch portion is large. The random arrangement of the blocks causes a large unevenness in the rigidity of the tread surface.

[0004] When a cornering force (hereinafter abbreviated as CF) is generated by applying a slip angle to a tire that rolls under load, CF characteristics are deteriorated due to uneven rigidity of a tread surface. In other words, the amount of CF generated in a portion where small rigid blocks are connected is greatly reduced, so that the CF characteristics of the tire as a whole are degraded.

Therefore, from the viewpoint of maintaining or improving the CF characteristics, it is natural that the maximum value of the ratio of a plurality of pitches or a large number of pitches used for pitch variation should be as small as possible. The value is 1.6
At present, the value of the pitch ratio of each adjacent block is set to about 1.3, and at present, attention is paid so as not to cause an extreme difference in rigidity between adjacent blocks.

[0006]

SUMMARY OF THE INVENTION Pneumatic radial tires, which are also advanced CFs for high performance passenger car tires
It is required to have both characteristics and to be able to exhibit a highly excellent wettability, so it is advantageous to adopt a block pattern as this conformable tread pattern, but it also has the disadvantages described above. Therefore, it is conceivable to increase the block size and improve the block rigidity to improve the CF characteristics.

To increase the size of the block, the pitch defined by the center line of the tread (the line on the equatorial plane of the tire) must be made longer, and the ratio of the ratio of the area occupied by the groove surface to the total surface area of the tread will be expressed as a percentage. It is practical to reduce the negative ratio that it represents.

However, increasing the former pitch is nothing less than reducing the number of pitches, which results in an increase in the level of noise (decibel value), which is a current requirement for further noise reduction. This is a means of reversing, and the latter decrease in the negative ratio impairs the drainage property and, as a result, decreases the wet performance.

Therefore, the inventions described in claims 1 to 6 of the present invention have a CF characteristic (grip performance) which is notably superior to conventional ones, while maintaining a high level of low noise and excellent wet performance. It is an object of the present invention to provide a pneumatic radial tire mainly used for passenger cars, which can exhibit the following.

[0010]

Means for Solving the Problems In order to achieve the above object, the invention described in claim 1 of the present invention comprises a tread portion, a pair of sidewall portions and a pair of bead portions connected to both sides thereof, A carcass that becomes a radially arranged cord ply that reinforces these parts between bead cores buried in a bead gutter, and a belt that becomes two or more cord cross layers that strengthen the tread portion at the outer periphery of the carcass, The tread rubber on the tread side of the tread portion is provided with two or more circumferential vertical grooves and a large number of horizontal grooves which open to these or cross and extend toward the end of the tread, and a large number of these vertical grooves and horizontal grooves define In a pneumatic radial tire having a tread pattern having a row of blocks, the pneumatic radial tire has at least one row of the plurality of blocks on both sides of the tire equatorial plane, Each block of these block column 2
It is defined under different arrangement pitches, and at least the block length along the tread circumference in the tread center region exceeds the block length under the larger arrangement pitch, the block length under the larger arrangement pitch, Each block row is 2
It is characterized by an alternating arrangement of up to two longer blocks and up to two shorter blocks.

Here, the arrangement pitch of the tire is based on the convention defined on the central circumference where the equatorial plane of the tire and the tread intersect, as mentioned above, and the arrangement pitch includes one lateral groove along the circumference of one tread. Contains width component. Further, the lateral groove does not always extend in the tread width direction (direction orthogonal to the tire equatorial plane), but rather extends in a direction inclined with respect to the tread width direction in order to maintain good wet performance. Therefore, when an inclined horizontal groove is provided, a block defined (partitioned) by a circumferential direction (a direction along the tread surface circumference) and a vertical groove and a horizontal groove is located outside a region surrounded by a pitch division line under a certain arrangement pitch. Protrude.

The tread center region refers to a region where half of the tread width measured along the curved surface of the tread is equally divided on both sides of the tread center peripheral line. The length of the block along the circumference of the tread in both side regions of the central region is, in particular, a block length under a larger arrangement pitch and a block length under a smaller arrangement pitch depending on the arrangement of the lateral grooves near the tread edge. There are cases where a difference occurs and cases where it hardly occurs. When the lateral groove opens to the buttress portion radially inward of the tread end from the tread end, the buttress portion participates in the block definition. The vertical groove includes not only a straight groove extending along the circumference of the tread surface, but also a gently bent groove or a curved groove that does not adversely affect wet performance.

A preferred embodiment of the invention described in claim 1 is:
As in the second aspect of the present invention, the value of the ratio of the large pitch to the small pitch is in the range of 1.8 to 2.2.

Further, there are several adaptations of the main aspect of the present invention, that is, the alternate arrangement of longer blocks and shorter blocks. One of the adaptations is as described in the third aspect of the present invention. , A longer block and a shorter block are arranged alternately. One of them is that each block row is composed of a longer block and a shorter block. Are alternately arranged to each two, and the third is that the value of the ratio of the total number of longer blocks to the total number of shorter blocks in each block sequence is 0.8 to 1.
It is an example in the range of 2.

Among the three conforming examples, the case where the value of the ratio is 1.0 corresponds to the first and the second conforming examples, and the ratio values excluding the first and the second have a certain width. This is to provide a degree of freedom by setting a pitch value, and sometimes to realize a block arrangement aiming at further lowering noise and further improving CF characteristics.

Further, for improving or maintaining wet performance,
As in the invention described in claim 6, it is suitable that the negative ratio is substantially the same between the tread regions in the long and short pitch sections. Here, the pitch division refers to a part defined by two line segments that pass through a certain two set pitch positions and are orthogonal to the tread surface center circumferential line.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 are tread developments of a pneumatic radial tire (hereinafter referred to as a tire). However, in practice, the length of the tread edge is shorter than the length of the tread center circumference. It is a figure shown according to length.

1 and 2, a tread 2 of a tread 1 is shown.
The tread rubber (not shown) on the side has two or more (four in the illustrated example) longitudinal grooves 3, 3 (hereinafter abbreviated as longitudinal grooves 3) and longitudinal grooves 4, 4 (extending along the circumference of the tread surface 1). These vertical grooves 3 and 4 form straight main grooves on both sides of a tread center peripheral line E where the equatorial plane of the tire and the tread 2 intersect.

The lateral grooves 5, 5 (hereinafter abbreviated as the lateral groove 5) and the lateral grooves 6, 6 (hereinafter abbreviated as the lateral groove 6) open in the vertical groove 3, and are inclined in the same direction from the opening position toward the tread edge TE on both sides. And intersects the longitudinal groove 4 while extending, and each tread edge T
At E, it opens toward the outside of the tire.

The vertical grooves 3, 4 and the horizontal grooves 5, 6 define at least one row on both sides of the tire equatorial plane (the tread center circumferential line E), and in the illustrated example, two rows of many blocks are defined. In the example shown in FIG. 1 near the center line E, the rows of blocks 7 and 8 are shown in FIG.
In the example shown in FIG. 2, rows of blocks 12, 13, 14, and 15 are respectively defined, and the rows of blocks 9, 10 in the example of FIG. 1 and the blocks 16, 1 in the example shown in FIG.
Rows 7, 18, and 19 are defined, respectively. Reference numeral 11
Is a rib extending to the center of the tread 2. Although illustration is omitted as a modified example, the rib 11 may be used as a block.

The above-mentioned block is an array pitch type described below.
Define based on That is, on the center line E of the tread,
Constant larger pitch P_LAnd a predetermined smaller pitch
P_SIn order to define the arrangement of
Pitch distribution point p based on point_n-3, P_n-2, P_n-1,
p_n, P_{n + 1}, P_{n + 2}, P_{n + 3}In the example shown in FIG.
Point p_n-2~ Point p_n-1Length between points and point p_n~ Point p_{n + 1}Among
Length is pitch P_LSo that the point p_n-1~ Point p_nAmong
Length and point p_{n + 1}~ Point p_{n + Two}The pitch between them is the pitch P_STona
In the example shown in FIG._n-1
~ Point p_nLength between points and point p_n~ Point p_{n + 1}The length between
Chi-P_LAnd the point p_n-3~ Point p_n-2Length between
The point p_n-2~ Point p _n-1Length between points and point p_{n + 1}~ Point p
_{n + 2}Length between points, point p_{n + 2}~ Point p_{n + 3}The pitch between them is the pitch P
_SEach is set so that. Here P_L> P_S
And no other pitch exists.

As apparent from the above description, the pitch arrangement shown in FIG. 1 is one in which one larger pitch P _L and one smaller pitch P _S are alternately arranged, and the pitch arrangement shown in FIG. The form is two larger pitches P _L and 2
The smaller pitches P _S are alternately arranged.

The pitch distribution points p _n-3 , p _n-2 ,
Assuming a line segment L passing through p _n−1 , p _n , p _{n + 1} , p _{n + 2} , p _{n + 3} and orthogonal to the center line E, the example shown in FIGS. Each block 7, 8, 12, 13, 14, near E
The inside edge of one of the tread surfaces 15 and the inside edge of the tread of an adjacent block on the other inside edge side are located on two line segments L. Alternatively, the central position along the circumference of the tread surface 2 of the lateral grooves 5, 6 opening to the vertical groove 3 may be located on the line segment L.

Accordingly, the length of each block along the circumference of the tread surface 2 is such that, at least in the vicinity of the tread edge TE, at least a half of the developed width TW of the tread surface 2 is equally divided on both sides of the central circumferential line E. In CW, the length of the blocks 7, 12, 13 below the larger arrangement pitch P _L exceeds the length of the blocks 8, 14, 15 below the smaller arrangement pitch P _S.

Therefore, in the row of blocks 7 and 8 shown in FIG. 1, one longer block 7 and one shorter block 8 are alternately arranged, and the rows of blocks 9 and 10 on both sides can be seen from the whole. Similarly, an alternate arrangement of one longer block 9 and one shorter block 10 results. In the column of blocks 12, 13, 14, and 15 shown in FIG.
The alternating arrangement of the two longer blocks 12, 13 and the two shorter blocks 14, 15 results in a row of blocks 16 to 19 on both sides as well as two longer blocks 16, 17 as a whole. And two shorter blocks 18,
19 alternately.

A tread pattern having a block row in which blocks having long lengths along the circumference of a tread under a large arrangement pitch are arranged in a ground contact surface under a rolling load of a tire has a large block rigidity. When the slip angle is applied, a large force acts on the belt, and the belt is excessively deformed by the large force. When the large force continuously and repeatedly acts on the belt, the belt is excessively deformed, so that the belt exhibits a saturated state while maintaining the excessively deformed state.

On the other hand, a tread pattern having a block row in which blocks having a short length along the circumference of the tread are arranged at a small arrangement pitch has an excessively large deformation due to a low block rigidity when a tire is provided with a slip angle. However, the deformation of the block becomes excessive, and the excessive deformation exhibits a saturated state.

Both the maintenance of the saturated state of the belt under excessive deformation and the maintenance of the saturated state of the block under excessive deformation act in the direction of lowering the CF characteristics. For example, when the negative ratio is fixed at 40 (%) and the pitch number is 30 (longer block) at the same pitch (length), and when the pitch number is 60 (shorter block) at the same pitch (length). , The block stiffness and CF characteristics (maximum cornering force value CF _max , cornering power CP) are set to a pitch number of 3
When the tires with 0 are compared with an index of 100, the tire with a pitch number of 60 has a block rigidity of about 50 and a CF characteristic of about 96.

On the other hand, as in the case of the tire, the negative ratio is set to 40, and the pitch number is set to 40. The CF characteristics of a tire in which the tires are alternately arranged are the CF characteristics of a tire having a constant pitch number of 30.
It has been confirmed that the exponent with the characteristic being 100 is 104.

As is apparent from this, the block 7 (9) or the block 1 having a longer length along the tread circumference is used.
2, 13 (16, 17) and the shorter block 8 (1
0) or the blocks 14, 15 (18, 19) are alternately arranged, so that when the tire is slip angled, the longer blocks 7 (9) or blocks 12, 13 (16, 17) on the ground contact surface. In conjunction with the shorter block 8 (10) or the blocks 14, 15 (18, 19), a moderate relaxation phenomenon occurs in the shorter block portion with respect to the belt deformation, and as a result, in the longer block portion. Therefore, moderately large deformation is generated without causing excessive deformation saturation, and the effect of further increasing the CF proportional to the reaction force of the belt deformation is exerted.

The alternating arrangement of the large and small blocks based on the large and small pitches for exhibiting the above-mentioned effects can be set with a large degree of freedom so that the desired wet performance and superior low noise characteristics are not adversely affected. Since it is possible, the wet performance and low noise characteristics are not impaired.

In order to exert the above effects more advantageously,
A smaller arrangement pitch P _{S of a} larger arrangement pitch P _L
The value of the ratio value of (P _L / P _S) adapted to set in the range of 1.8 to 2.2, the ratio (P _L / P _S) for one.
If it is less than 8, the effect of alleviating the excessive deformation saturation of the belt cannot be obtained, and if it exceeds 2.2, the difference in block rigidity becomes too large, and disadvantageously promoting uneven wear occurs.

As described above, the longer block 7
(9) and the shorter blocks 8 (10) or the longer blocks 12, 13 (16, 17) and the shorter blocks 14, 15 (18, 19) are arranged in the same number on the circumference of the tread. In particular, alternately arranging the latter two long and short blocks as a group brings about an effect of making the average block rigidity in the tire tread surface uniform at the time of rolling of the tire. There is a great advantage that a stable CF is generated by suppressing it advantageously.

However, in each case, the same number arrangement is not always required. For example, in order to obtain better CF characteristics or to maintain low noise, a longer block 7 (9) or blocks 12, 13 is used. (16, 1
The block arrangement can be adjusted so that the value of the ratio of the total number of blocks 7) to the total number of the shorter blocks 8 (10) or blocks 14, 15 (18, 19) is in the range of 0.8 to 1.2. . That is, two longer blocks can be combined as a group or two shorter blocks can be combined as a group in an alternate arrangement for one long and short block.
The reason that the value of the ratio is in the range of 0.8 to 1.2 is that when the lower limit is less than 0.8, the deformation action of the longer block on the belt becomes insufficient, and when the upper limit exceeds 1.2, the shorter block becomes shorter. Is insufficient to alleviate the belt deformation saturation, and no satisfactory CF characteristics can be obtained.

Further referring to FIGS. 1 and 2, pitch distribution points _pn-3 , pn _{- 2} , _pn-1 , _pn , on the tread center peripheral line E are shown.
Pitch lines L passing through p _{n + 1} , p _{n + 2} , p _{n + 3} and perpendicular to the central circumferential line E and terminating at both side tread edges TE are sandwiched between adjacent pitch line L. It is desirable that the negative ratio be substantially the same in each region of the tread surface 2 in order to maintain a high wet performance. Because the wet performance depends on the quality of drainage, and the drainage is greatly affected by the negative ratio, so the negative ratio is made almost the same on the circumference of the tread 2 to achieve uniform drainage over the entire circumference of the tread 2. Because you can.

Although not shown, the above-described tire includes a tread portion 1, a pair of sidewall portions and a pair of bead portions connected to both sides thereof, and these portions extend between bead cores embedded in the bead portions. The tread portion 1 is reinforced by a carcass that becomes a radially arranged cord ply, and the tread portion 1 is reinforced by a belt disposed on the outer periphery of the carcass. It is customary that the belt has two or more cord cross layers.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A radial ply tire for a passenger car, having a size of 255/40 ZR17, is provided with a tread pattern according to FIG. 1, and is a tire in which long and short blocks are alternately arranged one by one. 2 is a tire having a tread pattern according to No. 2 and alternately arranged long and short blocks. In each of Examples 1 and 2, the number of pitches was 40, the number of arrangement pitches P _{L and the} number of arrangement pitches P _S were 20, which are the same, and (P _L / P _S ) = 2. The negative ratio is 40% between the line segments L to L.

[0038] In contrast to prepare a tire of Comparative Example 1, Comparative Example 1 is the number of pitch and 60 in accordance with the arrangement pitch P _S of Examples 1 and 2, Comparative Example 2 of Examples 1 and 2 Except that the pitch number was set to 30 in accordance with the arrangement pitch P _L , all were the same as in Examples 1 and 2. The width of each vertical groove 3 is 8.3 m.
m. The reason why the pitch numbers of Comparative Examples 1 and 2 are determined as described above is that the tire using the same tread pattern has a better CF characteristic as the pitch number is smaller. 2 pitch numbers of 6
This is for verifying what CF characteristics the tires of the first and second embodiments of the present invention having the pitch number of 40 show as 0 and 30.

Using Examples 1 and 2 and Comparative Examples 1 and 2 as test tires, the following four tests were carried out. In addition, each test tire is JATMA YEAR BOOK (199
(7 years), applied to the standard rim 9JJ-17 among the applied rims, and filled with an internal pressure of 2.5 kgf / cm ² (cold). (1) Evaluation test of actual vehicle on dry road surface; Porsche Carrera was used as a test vehicle, and 20 dummy tires were used at the front.
5 / 50ZR17 (rim 7JJ-17, the internal pressure is 2.5 kgf / cm ² by cold) fitted with the respective test tires were mounted on two wheels rear skilled driver traveling on a test course at various run method, The feeling evaluation for the grip performance (CF performance) of the driver is rated out of 10 points.
The higher the score, the better. Table 1 shows the test results. (2) Actual vehicle evaluation test on wet road surface; Porsche Carrera was used as a test vehicle, and dummy tires were used as front tires.
05/50 ZR17 (7 JJ-17 rim, cold 2.5 kgf / cm ² internal pressure), two test tires on the two rear wheels, and a skilled driver runs a course of about 2 mm in water depth of about 700 mm. The average maximum speed at this time was represented by an index with Comparative Example 1 being 100, and the higher the index, the better. Table 1 shows the test results. (3) Indoor CF evaluation test; CF (kgf / degree) and C were measured by measuring CF with a drum tester under a load of 560 kgf.
_Fmax (kgf) was determined. In each case, the larger the value, the better.
The test results are summarized in Table 1, and in particular, CF _max (kgf) is shown as a bar graph in FIG. 3 with the values in Table 1 further indicating the relationship with the pitch arrangement. A on the horizontal axis in FIG. 3 represents Comparative Example 1, B represents Comparative Example 2, C represents Example 1, and D represents Example 2. (4) Indoor bench noise evaluation test: The sample was pressed against a rotating drum having a diameter of 2 m with a load of 400 kgf, and the average sound pressure level (dBA) in the drum surface speed range of 40 to 100 km / h was measured. Average sound pressure level (dB
A) is represented by an index of 100, and the higher the index, the better. Table 1 shows the test results.

[0040]

[Table 1]

As is clear from the numerical values shown in Table 1 and FIG. 3, Examples 1 and 2 have improved grip performance on dry road surfaces as compared with Comparative Examples 1 and 2.
This can be supported by the significant improvement of P (kgf / degree) and CF _max (kgf) in Comparative Examples 1 and 2. In Examples 1 and 2, the average value of the maximum speed on a wet road surface was improved as compared with Comparative Examples 1 and 2, and the noise level (dBA) was improved.
It can also be seen that Comparative Examples 1 and 2 are significantly superior to Comparative Examples 1 and 2.

[0042]

According to the first to sixth aspects of the present invention, while maintaining a high level of low noise and an excellent wet performance, the CF characteristic which determines the quality of the grip performance and the level of the grip performance. Can be provided as a pneumatic radial tire mainly used for passenger cars, which is significantly improved as compared with conventional tires.

[Brief description of the drawings]

FIG. 1 is a developed view of a tread showing an example of an embodiment of the present invention.

FIG. 2 is a developed view of a tread showing another embodiment of the present invention.

FIG. 3 is a bar graph showing a relationship between a pitch arrangement and CF _max .

[Explanation of symbols]

1 tread portion 2 tread 3,4 shorter than longer block 8,10,14,15,18,19 than the longitudinal grooves 5 and 6 transverse grooves 7,9,12,13,16,17 block 11 central rib P _L larger pitch than P _S smaller pitch L pitch section line E tread center circumferential line TW tread developed width CW tread central region TE tread edge

Claims (6)

[Claims] 1. A carcass comprising a tread portion, a pair of side wall portions and a pair of bead portions connected to both sides thereof, and a carcass serving as a radially arranged code ply for reinforcing these portions between bead cores buried in beads. A belt serving as two or more cord crossing layers for reinforcing the tread portion at the outer periphery of the carcass, and two or more circumferential vertical grooves and two or more circumferential longitudinal grooves are formed in the tread rubber on the tread side of the tread portion, or In a pneumatic radial tire having a tread pattern having a number of blocks which are provided with a plurality of transverse grooves which intersect and extend toward a tread end, and the longitudinal grooves and the transverse grooves define, the two sides sandwiching the tire equatorial plane Has at least one row of said plurality of blocks, each block of said block row being defined under two different arrangement pitches. At least the block length along the circumference of the tread in the tread center region is greater than the block length under the larger array pitch, with the block length under the larger array pitch being smaller than the block length under the smaller array pitch. A pneumatic radial tire characterized by being alternately arranged with shorter blocks within. 2. The value of the ratio of the large pitch to the small pitch is:
The tire according to claim 1, which is in a range from 1.8 to 2.2. 3. The tire according to claim 1, wherein each block row has an alternate arrangement of one longer block and one shorter block. 4. The tire according to claim 1, wherein each block row has an alternate arrangement of two each of a longer block and a shorter block. 5. The tire according to claim 1, wherein a value of a ratio of a total number of longer blocks to a total number of shorter blocks in each block row is in a range of 0.8 to 1.2. 6. The tire according to claim 1, wherein the negative ratio is substantially the same between the tread regions of the long and short pitch sections.