JP2010023586A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire, which can improve the tire performance over ice and snow, without deteriorating the wear resistance, moreover even when the number of sipes is increased, and will not cause problems in manufacturing. <P>SOLUTION: By having first sipes 30 which extend along a tire axial direction with amplitudes and at least one part of which extends in a depth direction with amplitudes, and second sipes 32, which extends along the tire axial direction with amplitudes but linearly extend in the depth direction without amplitudes, arranged alternately to a center block 20 in a tire circumferential direction, a small block 20A falls over at a proper degree, so as to secure a tire performance against ice and snow. Also, rigidity distribution in a circumferential direction in the block is made uniform, so as to restrain eccentric friction due to unevenness of the rigidity distribution. Furthermore, since a blade of a mold forming the sipes extending in the depth direction with amplitudes is not formed into a crank shape, hook removal property is secured. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire including a sipe in a land portion provided in a tread.

Conventionally, in the technical field of studless tires, in order to improve the performance on ice, it is generally known that a notch called a sipe is formed in a land portion provided in a tread and an edge portion is increased by this sipe. ing.
However, if multiple sipes are formed on the land, the rigidity of the land will decrease, so the load capacity is particularly large, and in light-duty truck vehicles that are severely worn, the wear resistance will be reduced, uneven wear will occur, block chunks, etc. Is likely to occur.

Accordingly, in the present situation, tires used for small trucks having a first priority for durability and large vehicles have extremely few sipes compared to tires used for one-box commercial vehicles and the like.
Therefore, various sipe shapes have been proposed in order to prevent the rigidity of the land portion from being lowered by providing the sipe in the land portion (see, for example, Patent Documents 1 and 2).

For example, the sipe described in Patent Documents 1 and 2 has a so-called crank shape that is formed in a zigzag shape in the tire axial direction and includes a bent portion in the intermediate portion in the depth direction. And in the tire of patent documents 1 and 2, prevention of falling of a land part is aimed at by the crank shape formed in the sipe.
JP 2006-188184 A JP 2001-188185 A

By the way, because the tires for light trucks have deep grooves and hard rubber, if the crank shape is formed in the sipe, it will be easy to remove the vulcanized tire from the vulcanization mold in the vulcanization molding process. We can't recommend it because of concerns.
As a sipe that does not cause a problem in the ability to pull out and can suppress the falling of the land portion, there is a zigzag or uneven sipe having an amplitude and extending in the depth direction.

  However, when zigzag or uneven sipe having such amplitude and extending in the depth direction is used for all the sipe in the block, the block rigidity is ensured, thereby improving the wear resistance and resistance. Although uneven wear can be ensured, there is a problem that the function of scratching snow is deteriorated and the performance on snow is deteriorated because the collapse of the block at the time of traveling becomes too small.

  In view of the above facts, the present invention is to provide a pneumatic tire that can improve the performance on ice and snow without impairing the wear performance even if the sipe is increased, and that does not cause a problem even during production.

  The inventor has conducted various experimental studies, and as a result, the sipe extending in the depth direction without having an amplitude that can exert the edge effect of the sipe on the snow by falling down the small block, and the purpose of suppressing the collapse of the small block Optimal combination with a sipe that has an amplitude with a depth and extends in the depth direction can improve the performance on ice and snow without damaging the wear performance even if the sipe is increased, and it does not cause problems even during production It was found that tires can be obtained.

  The pneumatic tire according to claim 1 is a product made in view of the above-described fact, and includes a tread in which a plurality of land portions partitioned by a plurality of grooves are formed. A first sipe having an amplitude section extending in the depth direction and the tire axial direction and having at least an amplitude and extending in the depth direction; and extending in the depth direction and the tire axial direction and having no amplitude in the depth direction. Extending second sipes are alternately formed in the tire circumferential direction.

Next, the operation of the pneumatic tire according to claim 1 will be described.
According to the pneumatic tire according to claim 1, the first sipe including an amplitude portion extending in the depth direction and at least an amplitude extending in the depth direction and the tire axial direction, and the depth direction and the tire shaft. Since the second sipes extending in the direction and extending in the depth direction without amplitude are alternately formed in the tire circumferential direction, the rigidity distribution (circumferential direction) in the block becomes a uniform direction, and the rigidity is increased. It is possible to suppress uneven wear due to non-uniform distribution.

  When the tire rotates as the vehicle travels and a force is applied in a tangential direction from the road surface to the grounded land portion, the small land portion partitioned by alternately arranging the first sipes and the second sipes It falls down moderately, and a good edge effect by sipe can be exhibited not only on ice but also on snow.

In other words, the sipe configuration according to claim 1 can sufficiently ensure the function of scraping snow compared to a configuration in which all the sipe in the land portion are sipe having an amplitude and extending in the depth direction. And good snow performance can be secured.
Further, as described above, by alternately arranging the first sipe and the second sipe on the land portion, the land portion rigidity that causes excessive collapse is not obtained, so that wear resistance is ensured, and Also, chunk resistance can be secured.

  Further, in a vulcanization mold for vulcanizing a tire, a blade (a thin metal plate) for forming a sipe having an amplitude and extending in the depth direction forms a sipe having a crank shape. Compared to the blades, the catch is less when the vulcanized tire is taken out. Therefore, the pneumatic tire having the structure described in claim 1 has good hooking property even when the rubber is hard and the sipe has a deep sipe depth.

  According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the first sipes are formed on both ends of the land portion in the tire circumferential direction.

Next, the operation of the pneumatic tire according to claim 2 will be described.
In the block-shaped land portion, the vicinity of the land portion end on the tire circumferential direction side is the most severe part against wear.
In the pneumatic tire according to claim 2, the first sipes having an amplitude portion having at least an amplitude and extending in the depth direction are disposed on both ends of the land portion in the tire circumferential direction. Thus, the collapse of the small land portion on the land portion end side can be suppressed, and wear near the land portion end on the tire circumferential direction side can be effectively suppressed.

  As described above, since the pneumatic tire of the present invention has the above-described configuration, it has an excellent effect that it can improve the performance on ice and snow and does not cause a problem even during production.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the members, configurations, arrangements, and the like described below do not limit the present invention, and it is needless to say that various modifications can be made in accordance with the spirit of the present invention.

(Tire composition)
First, the configuration of the pneumatic tire according to the present embodiment will be described. FIG. 2 is a developed view of the tread of the pneumatic tire according to the present embodiment. In FIG. 2, the symbol R represents the tire circumferential direction, and the symbol W represents the tire axial direction.
As shown in FIG. 2, the tread 12 of the pneumatic tire 10 is provided with first circumferential main grooves 14 extending substantially along the circumferential direction on both sides of the tire equatorial plane CL. A second circumferential main groove 16 extending substantially along the circumferential direction is disposed outside the main groove 14 in the tire axial direction.

  Between the pair of first circumferential main grooves 14, the first circumferential main groove 14 and the other first circumferential main groove 14 communicate with each other along the approximate tire width direction. A plurality of first lug grooves 18 extending in the tire circumferential direction are provided at intervals in the tire circumferential direction. The first lug groove 18 of the present embodiment is formed with a groove depth shallower than that of the first circumferential main groove 14, but has the same groove depth as the first circumferential main groove 14. May be. Thus, a plurality of substantially rectangular center blocks 20 defined by the first circumferential main groove 14 and the first lug groove 18 are formed on the tire equatorial plane CL in the tire circumferential direction.

  A plurality of second lug grooves 22 extending substantially along the tire width direction are provided between the first circumferential main groove 14 and the second circumferential main groove 16 at intervals in the tire circumferential direction. ing. The second lug groove 22 of the present embodiment is formed to have a groove depth shallower than that of the first circumferential main groove 14 and the second circumferential main groove 16, but the same groove depth as these. It may be. Thereby, between the 1st circumferential main groove 14 and the 2nd circumferential main groove 16, the 1st circumferential main groove 14, the 2nd circumferential main groove 16, and the 2nd lug groove A plurality of substantially rectangular second blocks 24 partitioned by 22 are formed in the tire circumferential direction.

On the outer side in the tire axial direction of the second circumferential main groove 16, a third lug groove 26 extending along the tire width direction from the second circumferential main groove 16 toward the ground contact end extends in the tire circumferential direction. It is provided at intervals. Thereby, a substantially rectangular shoulder block 28 defined by the second circumferential main groove 16 and the third lug groove 26 is provided in the tire circumferential direction on the outer side in the tire axial direction of the second circumferential main groove 16. A plurality are formed.
Although the first circumferential main groove 14 and the second circumferential main groove 16 are formed in a zigzag shape along the tire circumferential direction, they may be formed in a straight line shape.

(Center block)
As shown in FIGS. 2 to 4, the center block 20 extends with an amplitude along the tire axial direction (the direction of the amplitude is the tire circumferential direction: arrow R direction), and the depth direction (inner side in the tire radial direction). In the direction: arrow D direction in FIGS. 3 and 4, at least a portion of the first sipe 30 extending with an amplitude (the direction of the amplitude is the tire circumferential direction: arrow R direction) and the tire axial direction (arrow W) The second sipe 32 extends in a straight line without amplitude in the depth direction, and has an amplitude along the direction (amplitude direction is the tire circumferential direction: arrow R direction). Alternatingly arranged in the direction.

  As shown in FIG. 1, the first sipe 30 includes an amplitude portion 30 </ b> A extending on the bottom side with an amplitude in the depth direction, and a linear portion 30 </ b> B extending linearly in the depth direction on the tread side. Yes. The first sipe 30 only needs to have an amplitude portion 30A extending at an amplitude in the depth direction at least in a part of the depth direction, and the amplitude portion 30A is not necessarily formed on the groove bottom side. Alternatively, the entire portion may be the amplitude portion 30A without providing the straight portion 30B. Moreover, although the 1st sipe 30 of this embodiment has the amplitude A1 in the tire axial direction, it may extend linearly.

  Moreover, it is preferable to arrange | position the 1st sipe 30 to the tire circumferential direction both ends of a block, and in this embodiment, as shown in FIG. And the second sipe 32 includes a first sipe 30 at the center in the tire circumferential direction and a first sipe 30 at both ends in the tire circumferential direction. Arranged between.

  The first sipe 30 has a form in which both ends are connected to the block side wall surface (circumferential main groove), a form in which both ends are not connected to the block side wall, and only one of the ends is connected to the block side wall. Can take the form. Further, the first sipe 30 may be divided at the middle portion in the tire axial direction.

  As shown in FIG. 4, the second sipe 32 of the present embodiment has an amplitude A2 and extends in the tire axial direction, and extends linearly without an amplitude in the depth direction. In the present invention, the second sipe 32 only needs to extend linearly without amplitude in the depth direction, and may extend without amplitude in the tire axial direction. As for the second sipe 32, similarly to the first sipe 30, either one of both ends connected to the block side wall surface (circumferential main groove), or both ends not connected to the block side wall surface, either one of them. It is possible to take a form in which only the end part of the tire is connected to the side wall surface of the block, and there is a form in which the part is divided at an intermediate part in the tire axial direction.

(Second block)
As shown in FIG. 2, also in the second block 24, like the center block 20, the first sipe 30 and the second sipe 32 are alternately arranged in the tire circumferential direction, and the second sipe 32 is disposed at both ends in the tire circumferential direction. One sipe 30 is arranged.

(Shoulder block)
Also in the shoulder block 28, the first sipe 30 and the second sipe 32 are alternately arranged in the tire circumferential direction as in the case of the center block 20 and the second block 24, and the first sipe 30 and the first sipe 32 are arranged on both ends of the tire circumferential direction. Although the sipe 30 is disposed, in the shoulder block 28, a third sipe 34 extending in a zigzag shape along the tire circumferential direction is formed in the middle portion in the tire axial direction. The second sipe 32 is divided at the central portion in the axial direction of the shoulder block 28 so as not to be connected to the third sipe 34.
In FIG. 2, reference numeral 12 </ b> E denotes a ground contact end (an end on the shoulder side of the shoulder block 28).

(Function)
Next, the effect | action of the pneumatic tire 10 of this embodiment is demonstrated.
Here, FIG. 5 is a diagram illustrating a state in which the center block 20 of the pneumatic tire 10 according to the present embodiment contacts the road surface and a force F acts in a tangential direction from the road surface 36 during braking.
As shown in FIG. 5, when a force is applied to the center block 20 from the road surface 36 in the direction indicated by the arrow F in the figure, the small block 20 </ b> A partitioned by the first sipe 30 and the second sipe 32 falls down. However, the inclined portions of the amplitude portion 30A of the first sipe 30 that are opposed to each other strongly come into contact with each other to support the small block 20A.
On the other hand, since the second sipe 32 extends linearly in the depth direction, the fall-suppressing effect is inferior to the first sipe 30.
That is, it can be said that the portion where the first sipe 30 is formed has high block rigidity, and the portion where the second sipe 32 is formed has relatively low block rigidity.

  In the center block 20 of the present embodiment, the first sipes 30 and the second sipes 32 are alternately arranged in the tire circumferential direction, and two or more of the same sipes are not continuously provided. The stiffness distribution becomes a uniform direction, and uneven wear due to the non-uniform stiffness distribution can be suppressed.

  In addition, by arranging the first sipe 30 and the second sipe 32 alternately in the tire circumferential direction, when the force F acts in the tangential direction from the road surface 36, the small block 20A falls down moderately. In addition to being able to exhibit a good edge effect due to sipes not only when traveling on snow.

  If all the sipes of the center block 20 are the first sipes 30 having an amplitude and extending in the depth direction, the fall-suppressing effect becomes excessive, and the fall of the small block 20A is insufficient and scratches snow. Although the function is insufficient, in the sipe configuration of the present embodiment, the small block 20A falls down moderately, so that the function of scratching snow can be sufficiently secured, and good on-snow performance can be secured.

  Further, by alternately arranging the first sipe 30 and the second sipe 32 on the center block 20 as described above, the block rigidity does not fall excessively, so wear resistance is ensured, Chunk resistance can be secured.

  Moreover, in a vulcanization mold for performing vulcanization molding of a tire, a metal thin plate-like blade for forming a first sipe 30 extending with a zigzag amplitude in the depth direction is provided. The blade for forming the first sipe 30 has the same shape as the first sipe 30, but compared to the blade for forming the sipe having the conventional crank shape, There is less catch when removing vulcanized tires. Therefore, the pneumatic tire 10 of the present embodiment is good even in the case of a small truck tire using a relatively hard rubber for the tread, or when the sipe depth of the first sipe 30 is deep. Capability is obtained.

  Although the present embodiment has been described with respect to braking, it is needless to say that during the traction, the direction in which the small block 20A is tilted is reversed, and the same effect as that during braking is obtained.

  In addition, since the second block 24 and the shoulder block 28 have the same sipe configuration as that of the center block 20, it is needless to say that the same operational effects as those of the center block 20 can be obtained.

  As described above in detail, according to the pneumatic tire 10 of the present embodiment, the first sipe 30 and the second sipe 32 are alternately arranged in the tire circumferential direction on the center block 20, the second block 24, and the shoulder block 28. Therefore, even if the sipe is increased, the performance on ice and snow can be improved without impairing the wear performance, and there is no problem in manufacturing.

In addition, the 1st sipe 30 and the 2nd sipe 30 are not restricted to what extends in parallel with a tire axial direction, You may be inclined and extended with respect to a tire axial direction (arrow W direction).
Further, the amplitude A3 of the amplitude portion 30A of the first sipe 30 is preferably in the range of 1.0 to 2.0 mm and the wavelength λ is 1.4 to 3 if the pneumatic tire 10 is a small truck tire. Within the range of 6 mm is preferred. In the case where the pneumatic tire 10 is a tire other than a small truck tire, the amplitude of the amplitude section 30A and the wavelength λ are appropriately changed according to the tire size. If the amplitude and wavelength are out of the preferred ranges, the block collapse-inhibiting effect may be insufficient, or good pothole removal may not be obtained.
The sipe depth is desirably 50 to 90% of the groove depth of the circumferential main groove. If it is less than 50%, the edge effect cannot be exhibited sufficiently, and if it exceeds 90%, the wear resistance is deteriorated.

In the above embodiment, the cross-sectional shape of the amplitude portion 30A of the first sipe 30 is a triangular wave shape. However, if a good hook-out property is obtained and the collapse of a small block can be suppressed, other waveform shapes such as a sine curve can be used. There may be.
In the above-described embodiment, a total of five sipes, that is, three first sipes 30 and two second sipes 30 are formed in each block. However, the number of sipes formed in the block is limited to this. First, depending on the size of the block, 5 or more sipes may be formed.

(Test example)
Next, performance evaluation of the pneumatic tire 10 according to the present embodiment will be described. In order to confirm the effect of the present invention, one type of pneumatic tire according to a conventional example, two types of pneumatic tires according to comparative examples, and a pneumatic tire according to an embodiment to which the present invention was applied were prepared, and a sipe edge Comparative tests were conducted on ice performance, snow performance, and wear resistance.

The tire used was a small truck tire having a tire size of 195 / 85R16 114L, and a domestic 2t truck was used for the vehicle. Vehicle conditions such as air pressure and alignment were specified by the vehicle.
Sipe edge: The sum of the sipe edge lengths (per tread) included per unit length in the tire circumferential direction of the tread was indexed. The evaluation is represented by an index with the sum of the edge lengths of the conventional example being 100, and the larger the numerical value, the more sipe edges.

Performance on ice: An empty vehicle was driven at a speed of 40 km / h, and the stopping distance with a full lock brake was measured. In the evaluation, the reciprocal of the stop distance in the conventional example is indexed as 100, and the larger the value, the better the performance on ice.
Performance on snow: An empty vehicle was run at a speed of 40 km / h, and the stopping distance with a full lock brake was measured. In the evaluation, the reciprocal of the stop distance in the conventional example is indexed as 100, and the larger the value, the better the performance on snow.

  Abrasion resistance: A vehicle is run on a dry road surface in a loaded state, and the remaining groove depth after running 30000 km is measured. The life estimated by the remaining groove depth is defined as wear resistance on the dry road surface. The evaluation of the wear resistance performance on the dry road surface is represented by an index with the life estimated by the remaining groove depth of the conventional example as 100. That is, the larger the index value, the better the wear resistance performance on the dry road surface.

Next, the type of sipe used in the test and the configuration of the tire will be described.
First sipe (falling suppression sipe): As shown in FIG. 1, in the depth direction, a straight line extends in the depth direction from the tread surface to a depth of 1.5 mm, and thereafter the amplitude A3 = 3. It extends in a zigzag shape with 2 mm. Further, the tread surface extends in a zigzag shape with an amplitude A1 = 3.2 mm along the tire axial direction. The sipe thickness t1 is 0.5 mm, and the sipe depth is 9.0 mm (the circumferential main groove depth is 12.8 mm, which is 70% of the circumferential main groove depth).
Second sipe: As shown in FIG. 4, on the tread surface, the tire extends in a zigzag shape with an amplitude A2 = 3.2 mm along the tire axial direction, and has a linear shape without amplitude in the depth direction. It extends. The sipe thickness t2 is 0.5 mm, and the sipe depth is 9.0 mm.

Conventional tire: Four second sipes were formed per block.
Tire of Comparative Example 1: Five same second sipes as in the conventional example were formed per block.
Tire of Comparative Example 2 Five first sipes were formed per block.
Example tire: a tire to which the present invention is applied, in which three first sipes and two second sipes are used per block, and the first sipes are arranged at both ends in the tire circumferential direction of the block. The sipes were alternately arranged in the tire circumferential direction (see FIG. 3).
Table 1 below shows the results of a comparative test conducted in the above manner.

As a result of the test, in Comparative Example 1, the number of second sipes inferior in the collapse-suppressing effect was simply increased as compared with the conventional example, so that the block rigidity was lowered and the wear resistance was deteriorated.
Although the comparative example 2 made all the sipes the 1st sipes excellent in the fall-down suppression effect (fall-down suppression sipes) and increased the number of sipes as compared with the conventional example, the performance on ice and the wear resistance were improved as compared with the conventional example. The fall of the small blocks on the snow was suppressed too much, and the performance on the snow deteriorated.
In the example, since the first sipe and the second sipe are alternately arranged, the small blocks are moderately fallen, and the performance is higher than the conventional example in all items of wear resistance, performance on ice, and performance on snow. Improved.

It is a figure which shows in detail the part in which the 1st sipe of the center block was formed. It is a top view of the tread of the pneumatic tire concerning one embodiment of the present invention. FIG. 3 is a cross-sectional view of the center block shown in FIG. 2 taken along line 3-3. It is a figure which shows in detail the part in which the 2nd sipe of the center block was formed. It is a figure explaining a mode that force acts on a center block from a road surface in a tangential direction.

Explanation of symbols

10 Pneumatic tire 12 Tread 14 First circumferential main groove (groove)
16 Second circumferential main groove (groove)
18 First lug groove (groove)
20 Center block (Land)
22 Second lug groove (groove)
24 Second block (Land)
26 Third lug groove (groove)
28 Shoulder block (Land)
30 First sipes 30A Amplitude part 30B Linear part 32 Second sipes

Claims (2)

Provided with a tread formed with a plurality of land portions divided by a plurality of grooves,
The land portion includes a first sipe having an amplitude portion extending in a depth direction and a tire axial direction and having an amplitude extending at least in the depth direction, and a depth extending in the depth direction and the tire axial direction. A pneumatic tire in which second sipes extending without amplitude in the direction are alternately formed in the tire circumferential direction.   The pneumatic tire according to claim 1, wherein the first sipes are formed on both ends of the land portion in the tire circumferential direction.

Images