JP2010208379A - Tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire with improved driving performance and braking performance while maintaining anti-wear performance. <P>SOLUTION: In this tire, a tread (1) is blocked into a plurality of blocks (2), and the blocks (2) are provided with a plurality of sipes (3) extending in a direction crossing with an equator (0) of the tire. Also, in this tire, maximum depth DE<SB>max</SB>of an outermost sipe (3e) in a tread circumferential direction of the block (2) is shallower than the maximum depth of a sipe (3c) at a center in the tread circumferential direction of the block (2). There is a tread width direction distribution of depth such that each of the sipes (3) gets deeper gradually or step-by-step as it goes toward the center part in the tread width direction of the block (2) from a tread width direction end (8) of the same sipe (3), and that depth D<SB>end</SB>at the tread width direction end (8) is not less than a half of the maximum depth D<SB>max</SB>of the sipe (3). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tire, particularly a tire excellent in driving performance and braking performance.

  As a heavy-duty tire mounted on a drive shaft of a tire, especially a bus or truck, the tread tread surface has a plurality of circumferential grooves extending in the tread circumferential direction and a plurality of width directions extending in a direction crossing the tire equator. A groove having a tread pattern partitioned into a plurality of blocks is used.

  In a tire employing such a tread pattern, in order to improve driving performance and braking performance, particularly driving performance, a block is provided with a sipe extending in a direction crossing the tire equator (for example, , See Patent Document 1). By disposing such a sipe, the edge component increases and the frictional force with the road surface increases, so that the driving performance and braking performance are improved. In addition, since the effective edge component with respect to the circumferential direction becomes larger as the width direction length of the sipe increases, the driving performance and the braking performance are improved in proportion to the length direction length of the sipe.

  However, if sipes are installed on the block, the driving performance and braking performance will be improved, but the rigidity of the block will decrease, so the amount of deformation of the block will increase during tire rolling, and so-called heel and toe wear will occur. Is a problem. This heel-and-toe wear is caused by uneven wear that occurs as a result of the amount of wear at the kicking end (the last part to be grounded) larger than the amount of wear at the stepping end (the part to be grounded first) in the block in the ground plane. Say that.

  As a countermeasure against this uneven wear, Patent Document 1 proposes to improve the anti-wear performance and to make the sipe a zigzag shape in which a plurality of long sides and a plurality of short sides are alternately arranged. ing.

Japanese Patent Application No. 2000-94909

  However, in the tire described in Patent Document 1, sipe disappears early with block wear, and therefore, a new problem arises in that driving performance and braking performance are deteriorated after the middle stage of wear when sipe disappears.

  Accordingly, an object of the present invention is to provide a tire that solves the above-mentioned problems and improves uneven wear resistance performance, while suppressing a decrease in driving performance and braking performance after the middle stage of wear.

The inventors diligently studied the means for maintaining the driving performance and the braking performance for a long period of time without reducing the block rigidity, and found that the maximum depth of the sipe at the center in the tread circumferential direction of each block was determined. It has been found that it is very effective to arrange deeper than the depth of the sipe on the outermost side in the tread circumferential direction and to give each sipe a depth distribution that deepens the depth of the central part in the width direction. The invention has been completed.
The gist of the present invention for achieving the above object is as follows.

(1) The tread surface is partitioned into a plurality of blocks by a plurality of circumferential grooves extending in the circumferential direction of the tread and a plurality of widthwise grooves extending in a direction crossing the equator of the tire. In tires with multiple sipes extending across the equator,
The maximum depth of the sipe at the tread circumferential center of the block is deeper than the sipe depth at the outermost tread circumferential direction of the block, and each sipe extends from both ends of the sipe to the middle. A tire characterized by having a depth distribution such that the depth becomes deeper as it goes and the depth at both ends of the same sipe is half or more of the maximum depth.
The term “circumferential groove” as used herein is not limited to a linear groove extending along the equator of the tire, but extends in a zigzag or wave shape along the equator of the tire. A groove that goes around the tire. Furthermore, “extending in a direction crossing the equator of the tire” is not limited to extending at a right angle to the equator of the tire, it can be inclined at a certain angle, and has a zigzag shape or a wave shape. It means that it can be taken. “Sipe” refers to a so-called notch given to the block.
In addition, “the sipe in the center in the tread circumferential direction” means a sipe that is closest to the geometric center of gravity of each block on the tread contact surface of the tire when it is new. Furthermore, in each sipe, the center part means the intersection of the perpendicular bisector of both ends of the same sipe and the sipe, or the vicinity thereof.

(2) Of the two sipes adjacent in the block, the maximum depth of one sipe located on the center side in the tread circumferential direction is equal to or greater than the maximum depth of the other sipe. Tires.

(3) The difference between the maximum depth of the sipe at the outermost circumferential direction of the tread of the block and the maximum depth of the sipe at the central portion of the circumferential direction of the tread of the block is 0.1 times or more of the block height, The tire according to (1) or (2).
Here, the “block height” is the length in the tire radial direction from the bottom surface of the circumferential groove to the surface of the block.

(4) The difference between the maximum depth of the sipe at the outermost circumferential direction of the tread of the block and the maximum depth of the sipe at the central portion of the block in the tread circumferential direction is 0.2 times or more of the block height, The tire according to (1) or (2).

(5) The tire according to any one of (1) to (4), wherein a maximum depth of a sipe on the outermost side in the tread circumferential direction of the block is 0.3 to 1.0 times the block height.

(6) The tire according to any one of (1) to (5), wherein a maximum depth of a sipe at a central portion in the tread circumferential direction of the block is 0.6 to 1.1 times the block height.

(7) The tire according to any one of (1) to (5), wherein a maximum depth of a sipe at a central portion in the tread circumferential direction of the block is 0.65 to 0.8 times the block height.

(8) The tire according to any one of (1) to (7), wherein the sipe has a zigzag shape that changes in a tread circumferential direction.
Here, the “zigzag shape changing in the tread circumferential direction” means a line bent in the tread circumferential direction, and includes a waveform, a lightning bolt shape, a Z shape, etc., or a combination or repetition thereof.

(9) The tire according to any one of (1) to (8), wherein one end or both ends of the sipe are in the block.

  According to the present invention, the uneven wear resistance can be improved, and the decrease in driving performance and braking performance after the middle stage of wear, which is remarkable in the conventional products, can be reliably suppressed.

(A) is a development view showing a tread pattern of a tire according to the present invention having four sipes in each block, and (b) is a cross-sectional view taken along line II of the tire block shown in FIG. FIG. 2C is a cross-sectional view taken along the line I′-I ′ of the tire block shown in FIG. (A) is a development view showing a tread pattern of a tire according to the present invention having six sipes in each block, and (b) is a sectional view taken along line II-II of the tire block shown in FIG. 2 (a). (C) is the II'-II 'sectional view taken on the line of the tire block shown in FIG. 2 (a). (A)-(c) is a figure which shows the depth distribution of the sipe introduced into a block. (A) is a figure which shows the shape of the zigzag-shaped open sipe introduced into a block, (b) is a figure which shows the shape of the wavy open sipe introduced into a block, (c) is a zigzag-shaped one side introduced into a block It is a figure which shows the shape of an opening sipe, (d) is a figure which shows the shape of the zigzag-shaped open sipe introduce | transduced into a block. (A) is an expanded view which shows the tread pattern of the tire of Example 1 by this invention, (b) is an enlarged view of the block of the tire shown to Fig.5 (a), (c) is Fig.5 (a). 4 is a cross-sectional view of the tire block shown in FIG. (A) is an expanded view which shows the tread pattern of the tire of Example 2 by this invention, (b) is an enlarged view of the block of the tire shown to Fig.6 (a), (c) is FIG.6 (a). It is a VV sectional view taken on the line of the tire block shown in FIG.

Embodiments according to the present invention will be described in detail with reference to the drawings.
Here, FIG. 1 (a) is a developed view showing a tread pattern of a tire according to the present invention having four sipes in each block, and FIG. 1 (b) is shown in FIG. 1 (a). It is sectional drawing which cut | disconnected the block of the tire in the cross section along an II line, FIG.1 (c) cut | disconnected the block of the tire shown in FIG.1 (a) in the cross section along an I'-I 'line. It is sectional drawing.
FIG. 2 (a) is a development view showing a tread pattern of a tire according to the present invention having six sipes in each block, and FIG. 2 (b) is a block of the tire shown in FIG. 2 (a). 2 is a cross-sectional view taken along the line II-II, and FIG. 2C is a cross-sectional view of the tire block shown in FIG. 2A taken along the line II′-II ′. It is.
3A to 3C are diagrams showing the depth distribution of sipes introduced into the block.
4A to 4D are diagrams showing other sipe shapes to be introduced into the block.
FIG. 5A is a development view showing a tread pattern of a test tire provided with a zigzag closed sipes, and FIG. 5B is an enlarged view of a block provided with the tread shown in FIG. 5A. Fig. 5 (c) is a cross-sectional view of the tire block shown in Fig. 5 (a) cut along a cross section taken along line IV-IV.
FIG. 6A is a development view showing a tread pattern of the test tire, FIG. 6B is an enlarged view of a block provided with the tread shown in FIG. 6A, and FIG. c) It is sectional drawing which cut | disconnected the block of the tire shown to Fig.6 (a) by the cross section along a VV line.

  In the tire shown in FIG. 1, the tread surface 1 is partitioned into a plurality of blocks 2 by a plurality of circumferential grooves 4 extending in the circumferential direction and a plurality of widthwise grooves 5 extending in a direction crossing the equator 0 of the tire. Do it. Each block 2 includes a plurality of sipes 3 extending in a direction crossing the equator 0 of the tire, and four sipes 3 in the illustrated example.

Here, as shown in FIG. 1 (b), each sipe 3 in the block 2 includes the maximum depth DE _max of the sipe 3 e located on the outermost side in the tread circumferential direction of the block 2, and the central portion in the tread weekly direction of the block 2. It is important that the maximum depth DC _max of the sipe 3c in the above satisfies the relationship of DC _max > DE _max . By setting the depth of the sipe 3 as described above, it is possible to increase the rigidity of the tread circumferential direction end portion 6 of the block in which the occurrence of wear is remarkable. In addition, since the central sipe 3c formed deeper than the other sipe 3 exists even after the middle stage of wear, a sufficient edge effect is exhibited by this sipe 3, so that the driving performance and the braking performance are reduced. It can be avoided.

At the same time, as shown in FIG. 1C, each sipe 3 becomes deeper from both ends of the same sipe toward the center thereof, and the maximum depth D _max and the depth D _end at the end 8 in the tread width direction. However, it is important to satisfy the relationship of D _end ≧ 0.5D _max . For example, when each block 2 has four sipes 3 as in the illustrated example, the relationship of DE _end ≧ 0.5 DE _max and DC _end ≧ 0.5 DC _max is satisfied. By doing so, the sipe 3 exhibits a sufficient edge effect even after the middle stage of wear without impairing the rigidity of the end portion 7 in the tread width direction of the block. Subsequent drive performance and braking performance can be improved. In addition, D _end ≧ 0.5D _max was set because the width direction component of the sipe 3 was kept constant until the middle stage of wear. It is possible to prevent the tire driving performance and braking performance from being deteriorated. In other words, the depth distribution in the width direction of the sipe 3 needs to satisfy the relationship of D _end ≧ 0.5D _max in order to prevent a decrease in tire driving performance and braking performance until the middle of wear.

Further, since the present invention does not limit the number of sipes 3, for example, as shown in FIG. 2, it is possible to arrange 6 (or more) sipes 3 in each block 2. Also in this case, as shown in FIG. 2B, the maximum depth of the sipe at the center in the tread circumferential direction of the block is equal to or greater than the depth of the sipe at the outermost circumferential direction of the block. Further, as shown above, as shown in FIG. 2 (c), the depth of each sipe 3 gradually or stepwise increases from both ends toward the center thereof, and D _end ≧ 0.5D It is important to satisfy the relationship of _max . For example, in the illustrated example, the maximum depth DD _max of the intermediate sipe 3d between the sipe 3c and the sipe 3e satisfies the relationship of DD _end ≧ 0.5DD _max .

  Furthermore, since the present invention does not limit the mode of the depth distribution of the sipe 3, for example, as shown in FIG. 3 (a), from the tread width direction end 8 of the sipe 3 to the center in the width direction of the block, A depth distribution that gradually increases linearly with a certain gradient, or a depth that gradually increases to an arc shape having a certain curvature, toward the center in the width direction of the block, as shown in FIG. Or a stepwise depth distribution as shown in FIG. 3 (c).

In these cases, the same effect as described above, that is, the effect of improving the block rigidity and the effect of suppressing the decrease in the driving performance and the braking performance can be obtained.
In the embodiment according to the present invention, since the distance from the geometric center of gravity of the block 2 ground plane is equal, when there are two sipes 3c, the maximum depth of the deeper sipes is DC _max . Further, in the embodiment according to the present invention, as shown in FIG. 3C, when the depth of the tread width direction end 8 of the sipe 3 is different at both ends of the same sipe, the shallower depth is set to the sipe end depth. _Let D _end .

  The sipe 3 in the present invention only needs to extend in a direction crossing the equator 0 of the tire, and can have a zigzag shape that changes in the tread circumferential direction as shown in FIGS. . By making the sipe 3 into such a shape, both cross-sections facing each other across the sipe 3 in the block 2 mesh with each other, and it is possible to obtain an effect of suppressing a decrease in block rigidity.

  Furthermore, the sipe 3 in the present invention is an open sipe that communicates with the two circumferential grooves 4 at both ends 7 in the width direction of the block 2 as shown in FIGS. 3 (b), 4 (a) and 4 (b). Thus, drainage and block rigidity can be improved by improving drainage in particular, or by using a one-side opening sipe that opens in one circumferential groove 4 of the block 2 as shown in FIGS. 3 (c) and 4 (c). The block rigidity can be particularly improved by improving both of these, or by using a closed sipe that terminates in the block 2 as shown in FIGS. 3 (a) and 4 (d).

The block 2 is not limited to the quadrangle shown in FIGS. 1 to 4, but may be any other polygon, circle, or any other shape. For example, the tread pattern shown in FIGS. 5A to 5C and FIGS. 6A to 6C includes a circumferential groove 4 extending in a zigzag manner along the equator 0 of the tire, and a width direction. Each of the blocks 2 is formed with a closed sipe 3 that extends in a zigzag manner and is divided into polygonal blocks 2 by a widthwise groove 5 that is shallower than the circumferential groove. Also in such a block 2, as shown in FIGS. 5 (c) and 6 (c), the maximum sipe depth in the tread circumferential center of each block is on the outermost tread circumferential direction of the block. As shown in FIG. 3, the depth of each sipe 3 becomes gradually or stepwise deeper toward the center of the block 2 in the tread width direction, and D _end ≧ It is important to set appropriately so as to satisfy the relationship of 0.5D _max .

In the present invention, as shown in FIGS. 2 (b) and 5 (c), of the two adjacent sipes 3 in the block 2 in the above-described embodiment, the block 2 is located on the center side. It is more preferable that the depth of one sipe 3 is equal to or greater than the depth of the other sipe 3. For example, when the block 2 includes six sipes 3 as illustrated, the depth DD _max of the intermediate sipe 3d between the sipe 3c and the sipe 3e has a relationship of DE _max ≦ DD _max ≦ DC _max . It is preferable to satisfy. Thereby, in the block 2, the block rigidity gradually or stepwise increases from the tread circumferential center to the tread circumferential end 6, so that the closer to the tread circumferential end 6 of the block 2, the more pronounced it becomes. It is possible to reduce the wear that tends to become more effective, and to further suppress the occurrence of heel and toe wear.

In the present invention, it is more preferable that DE _max , DC _max , and the height BH of the block 2 satisfy the relationship of DC _max −DE _max ≧ 0.1 BH, and more preferably, DC _max −DE _max ≧ 0.2 BH. Because, when DC _max −DE _max <0.1 BH, the difference in the maximum depth between the sipes is very small, and thus the above-described effect of the present invention may not be sufficiently obtained. This is because if DC _max −DE _max ≧ 0.2 BH, the effects of the present invention can be obtained more reliably.

Furthermore, in the present invention, DE _max , DC _max and BH are more preferably and more preferably satisfy the relations of 0.6BH ≦ DC _max ≦ 1.1BH and 0.3BH ≦ DE _max ≦ 1.0BH. Satisfies the relationship of 0.65 BH ≦ DC _max ≦ 0.8 BH. Because
[1] When DC _max <0.6 BH, the frictional force due to the edge effect of the sipe 3c cannot be obtained after the middle stage of wear, and the tire according to the present invention may not be able to exhibit sufficient driving performance and braking performance. Because.
[2] When 1.1BH <DC _max , since the sipe 3c is too deep, the rubber gauge to the tire belt becomes thin and the block rigidity cannot be maintained, and the wear resistance may be reduced. Because there is.
[3] When DE _max <0.3BH, the sipe 3e is too shallow, so that there is a possibility that the frictional force due to the edge effect cannot be sufficiently obtained in the early stage of wear.
[4] When 1.0BH <DE _max , since the sipe 3e is too deep, the block rigidity cannot be sufficiently maintained at the tread circumferential end 6 of the block, and heel and toe wear is suppressed. This is because the effect may not be sufficiently obtained.
On the other hand, when DE _max , DC _max and BH satisfy the relationship of 0.65 BH ≦ DC _max ≦ 0.8 BH, the block rigidity can be sufficiently maintained, and by obtaining the frictional force due to the edge effect of sipe 3, This is because the effects of the present invention can be acquired more reliably.

  Furthermore, in the present invention, it is more preferable that the sipe 3 has a zigzag shape that changes in the tread circumferential direction. By making the sipe 3 in this way, the edge component is increased and the driving performance and the braking performance are improved, and the both cross-sections facing each other across the sipe 3 mesh with each other, thereby obtaining an effect of suppressing the block rigidity reduction. This improves uneven wear resistance.

  In addition, in the present invention, the sipe 3 is a so-called closed sipe that terminates in the block 2 shown in FIGS. 3 (a), 4 (d), and 5 (b). It is more preferable that the sipe is a so-called one-sided opening sipe that opens in one circumferential groove 4 of the block 2 shown in FIGS. 3 (c) and 5 (c). By doing so, a decrease in block rigidity can be suppressed, and uneven wear resistance can be improved.

  The above description shows only a part of the embodiment of the present invention, and these configurations can be combined alternately or various modifications can be made without departing from the gist of the present invention. .

In accordance with what is shown in FIG. 5, the tread tread 1 is divided into polygonal blocks 2 by zigzag circumferential grooves 4 and zigzag width grooves 5 shallower than the circumferential grooves 4, and four in each block 2. A test tire having a zigzag-shaped closed sipe 3 was manufactured in a size of 295 / 75R22.5. At that time, as shown in FIG. 3A, the depth distribution of the sipe 3 formed in each block 2 is a distribution that becomes linearly deep from both ends to the center with a constant gradient, and the maximum depth of the sipe 3c at this time. The thickness DC _max and the sipe end depth DC _end , the maximum depth DE _max of the sipe 3e, and the sipe end depth DE _end were as shown in Table 1, and the height BH of each block 2 was 21.6 mm. Further, as compared with the case where the sipe 3 having another shape is disposed, the depth of the sipe other than the tire (Example 1-C) in which the sipe 3 is a zigzag closed sipe as shown in FIG. A total of three patterns of a tire with a straight open sipe (Example 1-A) and a tire with a zigzag open sipe (Example 1-B), which are identical, were manufactured.

The test tire thus obtained is attached to a standard rim defined in JATMA standard as a tire wheel, the tire wheel is mounted on a vehicle, and the air pressure corresponding to the maximum load capacity in the applicable size / ply rating defined in the standard, and With the tire load load corresponding to the maximum load capacity in the application size / ply rating defined in the above standards applied, the wear resistance performance as well as the driving performance and braking performance at 60% and 75% wear when new, This will be described below with reference to the chart.
Table 2 shows the performance evaluation results (Example 1-C) of each test tire provided with a zigzag closed sipe. Table 3 shows the linear open sipe and zigzag open for the conventional tire 3. The performance evaluation results when the sipe and the zigzag closed sipe are respectively arranged are compared. Table 4 shows the linear open sipe, the zigzag open sipe, and the zigzag closed sipe for the tire 2 of the invention. The results of performance evaluation in the case where they are arranged are compared.

  For uneven wear resistance, each test tire (Example 1-C) provided with a zigzag closed sipe was attached to the rim, and the general road was run at 100,000 km with normal load and normal internal pressure. The level difference was measured. Moreover, the wear energy in the said field test was computed by performing FEM analysis about a test tire (Example 1-C). For the test tires (Examples 1-A and B) provided with the linear open sipe and the zigzag closed sipe, the wear energy was calculated by FEM analysis, and the test tires (Example 1-C) were The wear calculated by the FEM analysis of the test tires (Examples 1-A and B) in consideration of the correlation between the heel and toe wear level difference measured in the test and the numerical value of the friction energy calculated from the FEM analysis. From the energy, a numerical value of the predicted wear level was calculated. Here, the uneven wear resistance performance is represented by an index value obtained by comparing the values of other tires with the uneven wear resistance performance of the conventional tire 3 being 100, and is shown in Tables 2 to 4. In addition, it is excellent in the uneven wear-proof performance, so that a numerical value is large.

  The drive performance at 60% and 75% wear when new was calculated from the edge component in the width direction and the block stiffness at each wear stage. The edge component is the total sum of projection lengths in the traction direction in the width direction of lugs, block grooves, and sipes in one tire pitch. The block stiffness is calculated by FEM.

  The braking performance at 60% and 75% wear was calculated from the edge component in the width direction and the block stiffness at each wear stage. The edge component is the total sum of projection lengths in the braking direction in the width direction of lugs, block grooves, and sipes in one tire pitch. The block stiffness is calculated by FEM.

  Here, the driving performance and braking performance at each wear stage were calculated as index values comparing the numerical values of the other tires with the driving performance and braking performance of the conventional tire 3 as new. In addition, since there is a correlation between the driving performance and the braking performance among the tire performances, in the following table, the average values of both performances of the index values are calculated, and the driving / braking is performed using the average values. Shown as an index of performance. The larger the value, the better the driving performance and braking performance.

  According to Tables 2 to 4, the inventive tires 1C and 2C are superior to the conventional tire 1C in driving / braking performance at 60% and 75% wear, and the conventional tire 2 in uneven wear resistance. It can be seen that both of these are superior. Further, when comparing the conventional tire 3 and the inventive tires 1 and 2 with different depths between the sipes without giving the depth distribution in the tread width direction in the sipe, the inventive tires 1 and 2 are more It can be said that each performance is improved in a balanced manner.

  From this, it can be said that the present invention achieves both the wear resistance performance and the driving performance and braking performance after the middle stage of wear at a high level that is impossible with the conventional products.

As shown in Table 1, Comparative Example tire 1 is a tire that does not satisfy the relationship of DE _end ≧ 0.5DE _max and DC _end ≧ 0.5DC _max. Here, referring to Table 2, when the inventive tires 1C and 2C are compared with the comparative tire 1, the inventive tires 1C and 2C are comparative examples with respect to driving performance and braking performance at 60% and 75% wear. It turns out that it is superior to tire 1C.

  Next, referring to Table 3, when comparing the result of the conventional tire 3A with the linear open sipe and the result of the conventional tire 3B with the zigzag open sipe, the uneven wear resistance performance is as follows. The conventional tire 3B provided with zigzag open sipes is superior, because the sipes are provided in a zigzag manner, and both of the sipe between the sipes are deformed along with the deformation of the block at the time of tire load rolling. This is because the cross section is engaged, the block rigidity as a whole is improved, and deformation is suppressed.

  Therefore, referring to Table 4, when comparing the result of the inventive tire 2A provided with the linear open sipe and the result of the inventive tire 2B provided with the zigzag open sipe, the result described above with respect to Table 3 was obtained. Similarly, the invention example tire 2B provided with the zigzag open sipe is superior in terms of uneven wear resistance. Accordingly, it can be seen that when the zigzag sipe is arranged on the tire block according to the present invention, the uneven wear resistance is improved as in the case of the tire according to the prior art.

  From this, it can be said that it is more preferable to arrange the zigzag sipe in the present invention.

  Further, referring to Table 3, when comparing the result of the conventional tire 3B with the zigzag open sipe and the result of the conventional tire 3C with the zigzag closed sipe, the conventional tire 3C is more Excellent in uneven wear resistance. This is because the block rigidity is improved and the deformation of the block is suppressed by making the sipe a closed sipe as described above. Further, with respect to driving / braking performance, open sipe with many edge components is excellent. However, this is particularly effective in the case of tires that place importance on the performance, for example, mainly on snow, but is unnecessary in tires that are mainly used on the road surface. Only the deterioration in uneven wear resistance remains.

  Therefore, referring to Table 4, when comparing the result of the inventive tire 2B with the zigzag open sipe and the result of the inventive tire 2C with the zigzag closed sipe, the zigzag Inventive tire 2C provided with a closed closed sipe is more excellent in uneven wear resistance, and is a well-balanced tire in each performance. Therefore, it can be seen that when the zigzag closed sipe is arranged on the tire block according to the present invention, the uneven wear resistance is further improved as in the case of the tire according to the prior art.

  From this, it can be said that it is more preferable to arrange a zigzag closed sipe in the present invention.

  Next, a test tire having the same tread pattern as that of the test tire of Example 1 and having the same size and the depth of the sipe 3 was changed was experimentally manufactured. At this time, each block 2 is provided with the zigzag closed sipe that is optimal in the first embodiment, and the depth distribution of the sipe 3 formed in each block 2 is as shown in FIG. The distribution is such that it has a constant gradient and linearly increases from both ends to the center, and the depth of each sipe 3 is as shown in Table 5.

  The test tires thus obtained were evaluated by the same evaluation method for driving / braking performance at 40% wear in addition to the same performance under the same conditions as in Example 1. The evaluation results are shown in Table 6.

Inventive tire 2-1 is a tire according to the present invention, wherein the depth of each sipe 3 is such that DC _max −DE _max ≧ 0.2 BH, 0.3 BH ≦ DE _max ≦ 1.0 BH and 0.65 BH ≦ DC _max ≦ 0.8 BH. It is a tire that satisfies all of the above.

Here, invented Example tire 2-1, in the tire according to the present invention, the depth of each sipe 3 is compared with the DC _max -DE _max ≧ 0.2BH Not satisfied relationship Example tire 2-2 and 2-3 The inventive tire 2-1 is superior to the inventive tires 2-2 and 2-3 in terms of uneven wear resistance.

Further, in the example tire 2-3 in which the depth of each sipe 3 is in the range of 0.1 BH ≦ DC _max −DE _max <0.2 BH, the depth of each sipe 3 is in the range of DC _max −DE _max <0.1 BH. Compared to a certain example tire 2-2, the example tire 2-1 is more excellent in uneven wear resistance, and very excellent in driving / braking performance at 75% wear.

From the above results, in the present invention, it is preferable that the outermost sipe 3d and the central sipe 3c satisfy the relationship of DC _max −DE _max ≧ 0.1BH, and further DC _max −DE _max ≧ 0.2BH. It can be said that it is more preferable to satisfy this relationship.

Next, inventive tires 2-1 and 2-inventive tires 2-4 and 2- in which the depth DE _max of the outermost sipe 3d does not satisfy the relationship of 0.3BH ≦ DE _max ≦ 1.0BH in the tire according to the present invention. Compared to 5, the inventive tire 2-4 with DE _max of 1.0BH ≦ DE _max is excellent in driving / braking performance, but is inferior in uneven wear resistance, so it can be said that it is somewhat lacking in leveling. Inventive tire 2-5 in which DE _{max is set} to DE _max ≦ 0.3BH is excellent in uneven wear resistance, but is inferior in driving / braking performance from the initial wear to the middle wear (40%), so this is also an inventive example. It can be said that the tire 2-1 is more suitable in balance.

From this, in the present invention, it can be said that the depth DE _max of the outermost sipe 3d preferably satisfies the relationship of 0.3BH ≦ DE _max ≦ 1.0BH.

Next, inventive tire 2-1, in the tire according to the present invention, the depth DC _max of the central sipe 3c does not satisfy the relationship of 0.65BH ≦ DC _max ≦ 0.8BH. In comparison with 9, the inventive tires 2-7 and 2-9 having a DC _max of DC _max ≦ 0.65 BH are slightly inferior to the inventive tire 2-1, in terms of driving / braking performance, and the DC _max is 0.8. Inventive tires 2-6 and 2-9 with BH ≦ DC _max are slightly inferior to inventive tires 2-1 in terms of uneven wear resistance.

Further, inventive tires 2-8 and 2-9 in which the maximum depth DC _max of the central sipe 3c is in the range of 0.80BH <DC _max ≦ 1.1BH or 0.6BH ≦ DC _max <0.65BH are used. In comparison with the inventive tires 2-6 and 2-7, the maximum depth DC _{max of} 3c does not satisfy 0.6BH ≦ DC _max ≦ 1.1BH, the inventive tires 2-8 and 2-9 are more resistant to unevenness. It is excellent in either wear performance or driving / braking performance, and it can be said that it has the stable performance next to the tire 2-1 of the invention.

Therefore, in the present invention, it is preferable that the central part sipe 3c depth DC _max satisfies the relationship of 0.6BH ≦ DC _max ≦ 1.1BH, and further, the relationship of 0.65BH ≦ DC _max ≦ 0.85BH. It can be seen that it is more preferable if the condition is satisfied.

  Next, in the tire having the same tread pattern as the test tire of Example 1 and the same size, as shown in FIG. 6, six sipes 3 are arranged in each block 2, and the depth of the sipes 3 is set. A prototype of a modified test tire was made. At this time, each block 2 is provided with the zigzag closed sipe that is optimal in the first embodiment, and the depth distribution of the sipe 3 formed in each block 2 is as shown in FIG. The distribution is such that it has a constant gradient and linearly increases from both ends to the center, and the depth of each sipe 3 is as shown in Table 7.

  The test tires thus obtained were evaluated for the same performance under the same conditions as in Example 2 by the same evaluation method. This evaluation result 8 is shown in the table.

  Inventive Example Tire 3-1 is a tire according to the present invention, in which the maximum depth of one sipe located closer to the center side in the tread circumferential direction is the maximum depth of the other sipe among two adjacent sipes in each block. Inventive tires 3-2 and 3-3 are examples of tires that do not satisfy the above conditions in the tire according to the present invention.

  Here, when the inventive tire 3-1 is compared with the inventive tires 3-2 and 3-3, it can be said that the driving / braking performance is basically the same. The best. This is because the occurrence of uneven wear, which is a problem, is prominent mainly in the vicinity of the end 6 in the tread circumferential direction of the block 2, and the block rigidity is obtained by disposing the sipe 3 as in the tire 3-1 of the invention. This is because it can be gradually or gradually increased from the circumferential center portion of the tread to the tread circumferential end portion 6 and uneven wear represented by so-called heel and toe wear can be effectively suppressed.

  From the above results, in the present invention, in the block 2, the maximum depth of the sipe 3 gradually or stepwise increases from the tread circumferential end 6 toward the tread circumferential center. It can be said that it is preferable.

  Further, in accordance with what is shown in FIG. 1, the tread tread surface 1 has a linear circumferential groove 4 extending in the tread circumferential direction parallel to the tire equator 0 and a linear width direction extending in a direction perpendicular to the tire equator 0. A tire was made as a trial, which was divided into a plurality of blocks 2 by grooves 5 and each block 2 was provided with four linear open sipes 3 extending in a direction perpendicular to the equator 0 of the tire. At that time, as shown in FIG. 2 (c), the depth distribution of the sipe 3 formed in each block 2 is a distribution that linearly deepens from both ends to the center with a constant gradient, and the tire size and the block height BH are The depth of the sipe 3 formed in each block 2 was set as shown in Table 9 while being the same as in Example 1.

  The test tires thus obtained were evaluated for the same performance under the same conditions as in Example 1 by the same evaluation method. Table 10 shows the evaluation results.

According to Table 10, the inventive tires 4-1 and 4-2 are very excellent in wear resistance performance and driving / braking performance in each wear stage as compared with the conventional tires 4-1 and 4-2. also, compared with Comparative example tire 4-1 not satisfying the 0.5 D _max ≦ Dend, in particular, it is excellent for wear after the middle period of the driving / braking performance. The present invention improves the driving performance and braking performance that must be sacrificed in order to improve the uneven wear resistance performance of the conventional product, and it can be said that each performance is compatible at a high level.

  From the above results, the present invention crosses the tread pattern as shown in FIG. 1, that is, the tread surface 1 perpendicularly with the linear circumferential groove 4 extending in the tread circumferential direction parallel to the tire equator 0 and the tire equator 0. It can be said that this is also effective in a tire that employs a tread pattern partitioned into a plurality of blocks 2 by the linear widthwise grooves 5 extending in the direction.

  As is apparent from the above, the present invention can solve the external noise caused by heel and toe wear and the decrease in driving performance and braking performance after the middle stage of wear, which are the main problems of conventional tires. In other words, the drive performance and braking performance at the initial stage of wear are maintained, while the uneven wear resistance performance of the block is maintained, while the drive performance and braking performance that are higher than those of conventional products are exhibited after the middle stage of wear. It has become possible to provide tires that are excellent in performance, economy, and environmental performance.

0 tire equator 1 tread tread 2 block 3 sipe 3e tread circumferential outermost sipe 3c tread circumferential center sipe 3d intermediate sipe 4 circumferential groove 5 width groove 6 block tread circumferential end 7 block tread width direction End 8 Sipe tread width direction end

Claims (9)

The tread tread is divided into a plurality of blocks by a plurality of circumferential grooves extending in the circumferential direction of the tread and a plurality of widthwise grooves extending in a direction crossing the tire equator, and the block crosses the tire equator. In tires with multiple sipes extending in the direction,
The maximum depth of the sipe at the tread circumferential center of the block is deeper than the sipe depth at the outermost tread circumferential direction of the block, and each sipe extends from both ends of the sipe to the middle. A tire characterized by having a depth distribution such that the depth becomes deeper as it goes and the depth at both ends of the same sipe is half or more of the maximum depth.   2. The tire according to claim 1, wherein a maximum depth of one of the two sipes adjacent to each other in the block is closer to a center side in the tread circumferential direction than a maximum depth of the other sipes.   The difference between the maximum depth of the sipe at the outermost circumferential direction of the tread of the block and the maximum depth of the sipe at the central portion in the circumferential direction of the tread of the block is 0.1 times or more of the block height. 2. The tire according to 2.   The difference between the maximum depth of the sipe at the outermost circumferential direction of the tread of the block and the maximum depth of the sipe at the central portion of the circumferential direction of the tread of the block is 0.2 times or more of the block height. 2. The tire according to 2.   The tire according to any one of the preceding claims, wherein a maximum depth of a sipe located on the outermost side in the tread circumferential direction of the block is 0.3 to 1.0 times the block height.   The tire according to any one of the preceding claims, wherein a maximum depth of a sipe at a central portion of the block in the tread circumferential direction is 0.6 to 1.1 times the block height.   The tire according to any one of claims 1 to 5, wherein the maximum depth of the sipe at the center portion in the tread circumferential direction of the block is 0.65 to 0.8 times the block height.   The tire according to claim 1, wherein the sipe has a zigzag shape that changes in a tread circumferential direction.   The tire according to any of the preceding claims, wherein one or both ends of the sipe are in the block.

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