JP2014088116A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve uneven abrasion capacity while suppressing detachment of an end of a belt.SOLUTION: The pneumatic tire comprises first and second lug grooves extending from a buttress longitudinal groove extending in the tire circumferential direction toward inside in the tire shaft direction. An inner end of the first lug groove terminates inner in the tire shaft direction from a tread grounding edge and within a shoulder rib. An inner end of the second lug groove terminates outside in the tire shaft direction from the tread grounding edge. The shoulder rib is provided with an array of longitudinal sipings in which longitudinal siping pieces extending in the circumferential direction between the first lug grooves are arrayed at intervals in a straight line and a longitudinal siping passes between the array of longitudinal sipings and an outermost longitudinal main groove and extends in the tire circumferential direction.

Description

  The present invention relates to a pneumatic tire that suppresses belt end peeling by suppressing a temperature rise of a shoulder rib and improves uneven wear performance.

  Conventionally, as a tire having both the advantages of the rib pattern (for example, running stability, drainage, difficulty of skidding, etc.) and the advantage of the lug pattern (for example, driving performance, braking performance, etc.), for example, FIG. A tire with a rib lug pattern as shown in FIG. 1 is used (for example, see Patent Document 1).

  In the tire, a lug groove c whose inner end terminates in the shoulder rib bs is formed in a shoulder rib bs which is the outermost rib among the ribs b divided by the longitudinal main groove a extending in the tire circumferential direction. ing. The lug groove c extends beyond the tread grounding edge TE, and the outer end of the lug groove usually terminates at a buttress vertical groove f extending in the tire circumferential direction. A zigzag vertical sipe g extending in the tire circumferential direction is formed between the outermost vertical main groove as and the inner end of the lug groove c, and a horizontal sipe h on the tread ground edge Te. Are formed in parallel, and the uneven wear performance is improved.

  However, it cannot be said that uneven wear performance is sufficient, and further studies are desired.

Japanese Patent Laid-Open No. 08-91023

  Accordingly, an object of the present invention is to provide a pneumatic tire capable of further improving the uneven wear performance and at the same time suppressing the temperature rise of the shoulder rib and suppressing the belt end peeling.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application is characterized in that the tread portion is composed of three longitudinal main grooves extending in the tire circumferential direction than the crown rib between the longitudinal main grooves and the outermost longitudinal main groove. Is a pneumatic tire divided into a shoulder rib outside the tire axial direction,
The buttress region that continues from the tread contact edge to the tire axial direction outer side includes a buttress vertical groove extending in the tire circumferential direction and a buttress lug groove extending from the buttress vertical groove inward in the tire axial direction,
In addition, the buttress lug groove includes a first lug groove whose inner end in the tire axial direction terminates in the tire axial direction and within the shoulder rib with respect to the tread grounding edge, and the tire axially inner end is outside the tread grounding edge in the tire axial direction. And the second lug grooves arranged alternately with the first lug grooves,
The shoulder rib is
The vertical sipe piece extends in the tire circumferential direction without intersecting the first lug groove between the adjacent first lug grooves, and at the position on the inner side in the tire axial direction from the tread contact edge. A longitudinal siping row in which sipe pieces are arranged in a straight line at intervals in the tire circumferential direction,
And vertical siping extending in the tire circumferential direction through the space between the vertical siping row and the outermost vertical main groove.

  According to a second aspect of the present invention, each of the longitudinal sipe pieces is divided into sipe piece portions on one side and the other side in the tire circumferential direction by a break portion.

  According to a third aspect of the present invention, the vertical sipe includes a rectangular sipe portion that is an inner longitudinal sipe portion that connects the inner longitudinal sipe portion and the outer longitudinal sipe portion. It has a wave shape and is characterized in that a cutout portion is provided in the outer vertical sipe portion.

  According to a fourth aspect of the present invention, the pitch number of the rectangular wave of the longitudinal siping is equal to the pitch number of the first lug groove.

  According to a fifth aspect of the present invention, the longitudinal siping row passes through an inner end in the tire axial direction of the first lug groove.

  The tread grounding edge means the outermost position in the tire axial direction of the tread grounding surface that is grounded when a normal load is applied to a tire that is assembled with a regular rim and filled with a regular internal pressure. The distance in the tire axial direction between the tread ground edges is referred to as a tread ground width.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, Means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The “regular load” is a load determined by the standard for each tire. The maximum load capacity in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it is "LOAD CAPACITY".

  As described above, the present invention includes first and second lug grooves extending inward in the tire axial direction from the buttress longitudinal groove in the buttress region. Of these, the first lug groove extends over the tread surface of the shoulder rib beyond the tread grounding edge. Therefore, like the conventional lug groove, it contributes to driving performance and braking performance.

The second lug groove terminates in the buttress area and does not affect driving performance and braking performance, but is deformed in a direction in which the groove width widens when grounded. Therefore, the contact pressure on the contact end side of the shoulder rib is reduced and heat generation is suppressed. Moreover, since the surface area is increased by the second lug groove, the heat dissipation effect is also enhanced. These synergistic effects reduce the thermal deterioration of the rubber on the outer side of the belt layer, and as a result, belt end peeling can be suppressed.

  A vertical siping row is disposed on the shoulder rib on the inner side in the tire axial direction of the tread grounding edge. This longitudinal siping row is formed by arranging longitudinal sipe pieces extending in the tire circumferential direction between the first lug grooves in a straight line at intervals in the tire circumferential direction, so that the rigidity of the shoulder rib is moderately relaxed. Is done. Therefore, uneven wear such as shoulder drop wear caused by slippage between the shoulder rib and the road surface generated during rolling can be suppressed.

  In addition, when the horizontal sipe extending in the tire axial direction is arranged in parallel in the tire circumferential direction instead of the vertical sipe row, the rigidity of the shoulder rib is excessively reduced, and H & T wear or the like is formed around the first lug groove. It tends to cause uneven wear. Even when the second lug groove extends to the tread surface in the same manner as the first lug groove, the rigidity is excessively lowered and uneven wear such as H & T wear tends to occur.

It is an expanded view of one Example of the tread pattern of the pneumatic tire of this invention. It is an expanded view which expands and shows a part. It is sectional drawing of a tread part. It is an expanded view which shows an example of the tread pattern of the conventional tire.

  Hereinafter, embodiments of the present invention will be described in detail.

  As shown in FIG. 1, the pneumatic tire 1 of the present embodiment has a symmetrical tread pattern in which a tread portion 2 is divided into four ribs 4 by three longitudinal main grooves 3 extending in the tire circumferential direction. Have.

  Specifically, the tread portion 2 includes a central vertical main groove 3c extending on the tire equator Co, and outer vertical main grooves 3s on both sides thereof. Accordingly, the tread portion 2 is positioned on the outer side in the tire axial direction with respect to the crown rib 4c between the central vertical main groove 3c and the outer vertical main groove 3s and the outer vertical main groove 3s which is the outermost side. It is divided into shoulder ribs 4s.

  The size of the vertical main groove 3 is not particularly restricted, and those in the conventional range are preferably used. For example, in the case of a tire for a passenger car, as shown in FIG. 3, the groove width W3 of the longitudinal main groove 3 is in the range of 3.0 to 8.0% of the tread ground contact width TW from the viewpoint of tread rigidity and drainage. The groove depth H3 is preferably in the range of 6.0 to 9.0 mm. As the longitudinal main groove 3, a straight groove can be suitably employed from the viewpoint of excellent drainage and straight running stability, but for example, a zigzag groove can also be used.

  Also, a buttress vertical groove 6 extending in the tire circumferential direction and a buttress lug groove 7 extending inward in the tire axial direction from the buttress vertical groove 6 are arranged in the buttress region 5 connected to the tire axial direction outer side from the tread grounding edge TE. The

  The buttress longitudinal groove 6 is formed as a shallow narrow groove having a groove width of about 2 to 4 mm and a groove depth of about 1 to 2 mm.

  As shown in FIG. 2, the buttress lug groove 7 extends inward in the tire axial direction from the buttress longitudinal groove 6 at an angle θ of 50 ° or more, preferably 80 ° or more with respect to the tire circumferential direction. In this example, the buttress lug groove 7 is a straight groove, but it may be an arcuate curved groove. In such a case, the angle of the tangent is within the above range.

  The buttress lug groove 7 includes first lug grooves 7A and second lug grooves 7B that are alternately arranged in the tire circumferential direction. Of these, the first lug groove 7A has an inner end in the tire axial direction that terminates in the tire axial direction inside the shoulder tread edge TE and within the shoulder rib 4s. The distance D7 from the tread grounding edge TE at the inner end of the first lug groove 7A is preferably in the range of 2 to 8% of the tread grounding width TW. Further, the inner end of the second lug groove 7B in the tire axial direction terminates on the outer side in the tire axial direction of the tread grounding edge TE.

  The first and second lug grooves 7A and 7B are narrow grooves having the same groove width as the buttress longitudinal groove 6 (for example, about 2 to 4 mm), and the groove depth (shown in FIG. 3) is. , Gradually increasing from the outer end toward the inner end. The depth at the inner end of the first lug groove 7A is set to be approximately equal to the groove depth H10 of the vertical sipe piece 10 to be described later. The second lug groove 7B can include a sipe-shaped portion having a groove width of 2 mm or less. The length L7B of the second lug groove 7B from the buttress vertical groove 6 is preferably 40 to 60% of the length L7A of the first lug groove 7A.

  Next, in the shoulder rib 4s, the longitudinal siping row 8 extending in the tire circumferential direction from the tread contact edge TE in the tire axial direction, and between the longitudinal siping row 8 and the outer longitudinal main groove 3s. A vertical siping 9 extending in the tire circumferential direction is arranged.

  The vertical siping row 8 is formed in a broken line shape in which a plurality of vertical sipe pieces 10 are arranged in a straight line at intervals in the tire circumferential direction. The distance D8 from the tread grounding edge TE of the vertical siping row 8 is preferably in the range of 2 to 8% of the tread grounding width TW. The vertical siping row 8 of this example passes through the position of the inner end in the tire axial direction of the first lug groove 7A.

  Each of the vertical sipe pieces 10 extends between the first lug grooves 7A and 7A adjacent to each other in the tire circumferential direction without intersecting with the first lug grooves 7A. The sipe width of the vertical sipe piece 10 is in the range of 0 to 2.0 mm, and the sipe depth H10 (shown in FIG. 3) is preferably in the range of 66 to 86% of the groove depth of the vertical main groove 3. .

  In this example, the case where each vertical sipe piece 10 is divided into the sipe piece portions 10A and 10B on one side and the other side in the tire circumferential direction by the discontinuous portion 11 is shown. The gap Ga between the discontinuous portions 11 is 0.5 to 2 mm in this example, and is preferably smaller than the gap Gb between the vertical sipe piece 10 and the first lug groove 7A. The ratio La / Lb between the lengths La and Lb of the sipe pieces 10A and 10B is preferably 0.5 to 1.5, and more preferably the lengths La and Lb are equal to each other.

  Next, the longitudinal sipe 9 includes a longitudinal sipe portion 9a on the inner side in the tire axial direction, a longitudinal sipe portion 9b on the outer side in the tire axial direction, and a joint sipe portion 9c that connects the inner longitudinal sipe portion 9a and the outer longitudinal sipe portion 9b. A rectangular wave consisting of In this example, the joint sipe portion 9c is inclined at an angle β of, for example, 20 to 45 ° with respect to the tire axial direction, thereby suppressing a decrease in rigidity at the bent portion. The vertical siping 9 may be linearly extending in the tire circumferential direction without being bent. In the case of a rectangular wave, the pitch number of the rectangular wave of the longitudinal siping 9 is equal to the pitch number of the first lug groove 7A.

  The sipe width of the vertical siping 9 is also in the range of 0 to 2.0 mm, and the sipe depth H9 (shown in FIG. 3) is also preferably in the range of 66 to 86% of the groove depth H3 of the vertical main groove 3. . Further, the ratio Lc between the distance Lc from the center of the vertical siping 9 (the center of its amplitude in the case of a rectangular wave shape) to the vertical siping row 8 and the distance Ld from the center of the vertical siping 9 to the outer vertical main groove 3s. / Ld is preferably 0.9 to 1.1. That is, the vertical siping 9 is disposed at a substantially central position of the region YA between the vertical siping row 8 and the outer vertical main groove 3s. The distance L9 from the center of the vertical siping 9 to the tire equator Co is in a range of 30 ± 40% of the tread ground contact width TW.

  The vertical siping 9 includes a discontinuous portion 12 in the outer vertical sipes 9b. The gap Gc between the discontinuous portions 12 is larger than the gap Ga, and is 1.0 to 3.0 mm in this example.

  In such a pneumatic tire 1, out of the first and second lug grooves 7A and 7B formed in the buttress region 5, the first lug groove 7A extends on the tread surface of the shoulder rib 4s. Accordingly, the first lug groove 7A contributes to drivability and braking performance like the conventional lug groove. Further, since the second lug groove 7B terminates in the buttress area 5, it does not affect the driving performance and the braking performance, but is deformed in the direction in which the groove width increases at the time of grounding. Therefore, the ground pressure on the ground end side of the shoulder rib 4s is reduced and heat generation is suppressed. Furthermore, since the surface area is increased by the second lug groove 7B, the heat dissipation effect is also increased, and the synergistic effect suppresses the thermal deterioration of the rubber on the outer side of the belt layer. As a result, belt end peeling can be suppressed.

  When the second lug groove 7B is extended to the tread surface in the same manner as the first lug groove 7A, the rigidity of the shoulder rib 4s is excessively lowered, and the H & T is formed around the first and second lug grooves 7A and 7B. Induces wear.

  A vertical siping row 8 is disposed on the tread on the shoulder rib 4s. Since the vertical sipe row 8 is formed by arranging the small sipe pieces 10 in a straight line, the rigidity of the shoulder rib 4s on the ground contact end TE side is moderately moderated. For this reason, the ground pressure is reduced and the heat generation is further suppressed while suppressing the shoulder wear caused by the slip between the shoulder rib 4s and the road surface. In particular, when the longitudinal sipe piece 10 is divided into sipe piece portions 10A and 10B by the cut-off portion 11, the rigidity of the shoulder rib 4s can be more uniformly relaxed, which is preferable for shoulder drop wear and H & T wear.

  When there is no vertical siping row 8, the shoulder rib 4s has a high rigidity, which deteriorates the shoulder fall wear. In addition, when the horizontal sipes extending in the tire axial direction are arranged in parallel in the tire circumferential direction instead of the vertical siping row 8, the rigidity of the shoulder rib 4s is excessively lowered. As a result, H & T wear is exacerbated.

  Next, the vertical siping 9 improves the rigidity balance of the entire shoulder rib 4s, for example, by reducing the rigidity of the region YA. If the vertical siping 9 is not provided, the rigidity difference between the area YA inside the vertical siping row 8 and the area YB outside thereof becomes large, so that the shoulder drop wear is worsened. In particular, when the vertical siping 9 has a rectangular wave shape, the effect of improving the rigidity balance of the entire shoulder rib 4 s is high, such as relieving the rigidity of the region YA over a wide range. However, when the vertical sipe 9 has a rectangular wave shape, the outer vertical sipe portion 9b approaches the vertical sipe row 8, so that the rigidity is reduced at this approaching portion, which adversely affects H & T wear. Therefore, in this example, the rigidity of the approaching portion can be maintained by providing the discontinuous portion 12 in the outer vertical sipe portion 9b, and adverse effects on H & T wear are suppressed.

  In order to maintain a rigidity balance with the shoulder rib 4s, the crown rib 4c can be appropriately provided with a discontinuous groove 20 and a siping 21 that are interrupted in the crown rib 4c according to the custom.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

A pneumatic tire (size: 195 / 65R15) having the tread pattern of FIG. Each sample tire was tested for belt end peeling performance and uneven wear performance. Except for the description in Table 1, the specifications are substantially the same. The common specifications are as follows.
Tread grounding width TW: 154mm
Center vertical main groove ・ Groove width W3 = 7.5mm
・ Groove depth H3 = 8.6mm
Side vertical main groove ・ Groove width W3 = 9.5mm
・ Groove depth H3 = 10.0mm
Buttress vertical groove ・ Groove width = 0.7mm
・ Groove depth = 7.0mm
First lug groove 7A
・ Groove width = 3.0mm
・ Maximum groove depth = 8.6mm
・ Distance from the tread ground edge D7 = 10.0mm
Spacing Ga = 2.0mm
Spacing Gb = 3.5mm
Spacing Gc = 3.8 mm
Siping width of each siping = 0.6mm
The test method is as follows.

(1) Belt end peeling performance:
Using a drum testing machine, a sample tire was run for 20000 km under the conditions of a rim (6.00 JJ), an internal pressure (250 kPa), a load (8.15 kN), and a speed of 100 km / h. And the tire after driving | running | working was disassembled and the presence or absence of generation | occurrence | production of belt end peeling was determined visually.

(2) Uneven wear performance:
A sample tire was mounted on all wheels of a vehicle: Prius (model: NHW20) manufactured by Toyota under the conditions of a rim (6.00 JJ) and an internal pressure (250 kPa), and traveled 200,000 km in an urban area. Then, the shoulder drop wear and H & T wear of the tire after running are visually determined, and evaluation is performed with an index in which Comparative Example 1 is set to 100. The larger the value, the less uneven wear and the better.

As shown in Table 1, it can be confirmed that the tire can improve the uneven wear performance (shoulder fall wear, H & T wear) while suppressing belt end peeling.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Vertical main groove 4c Crown rib 4s Shoulder rib 5 Buttress area 6 Buttress vertical groove 7 Buttress lug groove 7A First lug groove 7B Second lug groove 8 Vertical siping row 9 Vertical siping 9a Inner vertical sipe Part 9b vertical sipe part 9c joint sipe part 10 vertical sipe piece 10A, 10B sipe piece part 11 break part 12 break part TE tread grounding edge

Claims (5)

A pneumatic tire in which the tread portion is divided into a crown rib between the vertical main grooves and a shoulder rib on the outer side in the tire axial direction than the outermost vertical main groove by three vertical main grooves extending in the tire circumferential direction. Because
The buttress region that continues from the tread contact edge to the tire axial direction outer side includes a buttress vertical groove extending in the tire circumferential direction and a buttress lug groove extending from the buttress vertical groove inward in the tire axial direction,
In addition, the buttress lug groove includes a first lug groove whose inner end in the tire axial direction terminates in the tire axial direction and within the shoulder rib with respect to the tread grounding edge, and the tire axially inner end is outside the tread grounding edge in the tire axial direction. And the second lug grooves arranged alternately with the first lug grooves,
The shoulder rib is
The vertical sipe piece extends in the tire circumferential direction without intersecting the first lug groove between the adjacent first lug grooves, and at the position on the inner side in the tire axial direction from the tread contact edge. A longitudinal siping row in which sipe pieces are arranged in a straight line at intervals in the tire circumferential direction,
A pneumatic tire characterized by comprising a vertical siping extending between the vertical siping row and the outermost vertical main groove in the tire circumferential direction.   2. The pneumatic tire according to claim 1, wherein each of the longitudinal sipe pieces is divided into sipe piece portions on one side and the other side in the tire circumferential direction by a break portion.   The longitudinal sipe has a rectangular wave shape composed of a longitudinal sipe portion on the inner side in the tire axial direction, a longitudinal sipe portion on the outer side in the tire axial direction, and a joint sipe portion connecting the inner longitudinal sipe portion and the outer longitudinal sipe portion, and The pneumatic tire according to claim 1 or 2, wherein a discontinuous portion is provided in an outer vertical sipe portion.   The pneumatic tire according to claim 3, wherein the pitch number of the rectangular waves of the longitudinal siping is equal to the pitch number of the first lug grooves. The pneumatic tire according to any one of claims 1 to 4, wherein the vertical siping row passes through an inner end in the tire axial direction of the first lug groove.

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