JP4800610B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to an all-season or mud & snow pneumatic radial tire, and more particularly to a pneumatic radial tire capable of improving on-snow performance without deteriorating pattern noise and wear performance.

  For RV and 4WD vehicles, mud and snow tires that are mainly assumed to run on muddy roads and snowy roads, and all-season tires that have both high-speed driving performance and on-snow performance and are usable throughout the year (for example, , See Patent Document 1).

Mud & snow tires and all-season tires are required to have two performances that can start and brake reliably on a snowy road surface and can be surely operated by steering.
JP-A-5-139121

  In order to satisfy the above-mentioned performance, it has been conventionally practiced to provide grooves and sipes on the tread to enhance the edge effect of the land part. However, if grooves are provided unnecessarily or the groove width is widened, air column resonance Pattern noise due to noise and impact noise of land, etc. increase, wear performance deteriorates, and tire appearance deteriorates due to wear.

  In view of the above facts, an object of the present invention is to improve on-snow performance without deteriorating pattern noise and wear performance of all-season or mud & snow pneumatic radial tires.

The invention of claim 1 comprises a tread having a plurality of circumferential main grooves formed in the tire circumferential direction, and a plurality of transverse main grooves formed in a direction intersecting the circumferential main grooves and arranged in the tire circumferential direction. , A pneumatic radial tire having a land portion row in the tire circumferential direction composed of a land portion partitioned by the lateral main groove and the circumferential main groove, wherein the circumferential main groove has an amplitude in a tire width direction. A sub main groove is formed along the tire circumferential direction in a part of the land portion rows, and the groove width of the sub main groove changes periodically in the tire circumferential direction. In the tire width direction outer side of the land portion row at both ends of the tread, the vertical sipe and the horizontal sipe communicate with each other in an L shape, the vertical sipe opens in the horizontal main groove, and the tire width of the land portion row On the inner side in the direction, the longitudinal sipe and the lateral sipe are independent from each other, and Is open to the horizontal main groove, and in the land portion row located on the tire equatorial plane, the vertical sipe and the horizontal sipe communicate with each other in an L shape, and the horizontal sipe opens to the circumferential main groove. And a portion where both the longitudinal sipe and the lateral sipe terminate in the land portion row, and the land portion row at both ends of the tread and the land portion row located on the tire equatorial plane In the land portion row on both sides of the tire equator except the vertical sipe and the horizontal sipe communicate with each other in an L shape, and the horizontal sipe opens in the circumferential main groove or the sub main groove. Yes.

  In the pneumatic radial tire according to claim 1, the circumferential main groove is formed in a wave shape having an amplitude in the tire width direction, and the sub main groove is formed in a part of the land portion row. Not only can the main grooves in the circumferential direction be straight, but can increase the force in the tire traveling direction and braking direction, and the vehicle can be started, braked, and steered (turned) on the snowy road surface. it can.

  Moreover, since the groove is not provided unnecessarily or the groove width is not increased, the performance on snow can be improved without deteriorating the pattern noise and the wear performance.

  According to a second aspect of the present invention, in the pneumatic radial tire according to the first aspect, the maximum groove width of the auxiliary main groove is 10 to 50% of an average groove width of the circumferential main groove, and the auxiliary main groove The groove depth is 30 to 70% of the groove depth of the circumferential main groove.

  Here, the lower limit is set for the maximum groove width and the groove depth of the sub main groove because, if the lower limit is not reached, the sub main groove is clogged with snow and the function as a groove becomes ineffective. If the upper limit is exceeded, pattern noise may be deteriorated, and the surface of the land portion on the both sides of the sub-main groove will be greatly displaced, resulting in poor wear performance and uneven wear. Because.

  In the pneumatic radial tire according to claim 2, since the maximum groove width and groove depth of the sub main groove are appropriately set, snow does not clog in the sub main groove, and the sub main groove Uneven wear is unlikely to occur in the land between the grooves.

  According to a third aspect of the present invention, in the pneumatic radial tire according to the first or second aspect, the number of rows of the land portion rows is four or five rows, and sipes are respectively formed in the land portions. It is characterized by being.

  Here, the reason why the lower limit of the number of rows in the land portion row is set to 4 rows is that if the number is less than this, the number of circumferential main grooves is too small and the performance on snow is not improved, and the upper limit is 5 rows. The reason for this is that if it exceeds this, the rigidity of the land portion becomes too low, and the wear performance deteriorates.

  In the pneumatic radial tire according to the third aspect, since the number of rows in the land portion row is four or five, both on-snow performance and wear performance can be achieved.

  Moreover, since the sipe is provided in the land part, the edge effect of a land part increases and the performance on snow improves. Note that sipes may be provided not only in the tire width direction but also in the tire circumferential direction. This is because the lateral force during the steering operation is more effectively generated and the turning performance of the vehicle is enhanced. The shape of the sipe may be linear or zigzag.

  According to a fourth aspect of the present invention, in the pneumatic radial tire according to the third aspect, at least four of the auxiliary main grooves are formed.

  The fact that at least four sub main grooves are formed means that at least one sub main groove is formed in every land section row when the number of land section rows is four. When the number of sub-rows is 5, except when at least one sub-main groove is formed in each land portion row, for example, excluding the land portion row (center rib) located on the tire equatorial plane, This means that at least one sub main groove may be formed in each of the other four rows.

  In the pneumatic radial tire according to claim 4, since an appropriate number of auxiliary main grooves are provided, pattern noise is not deteriorated, and vehicle start and braking on a snowy road surface and steering operation (turning) are ensured. Can be done.

  As described above, according to the pneumatic radial tire of the present invention, it is possible to improve performance on snow without deteriorating pattern noise and wear performance for all-season or mud & snow pneumatic radial tires. It has the excellent effect of being able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The pneumatic radial tire 10 according to the present embodiment is a land divided into a tread 12 by a circumferential main groove 14, a transverse main groove 16, and the transverse main groove 16 and the circumferential main groove 14 in FIG. And a land portion row 18, 20, and 22 in the tire circumferential direction.

  A plurality of (for example, four) circumferential main grooves 14 are formed in the tire circumferential direction, and are formed in a wave shape having an amplitude in the tire width direction.

  For example, the circumferential main grooves 14 are arranged in a zigzag manner with grooves parallel to the tire circumferential direction, and the grooves are sequentially connected by an inclined groove to form a single groove, which is configured in a periodic wave shape. Has been. The circumferential main groove 14 may not have a groove portion parallel to the tire circumferential direction, for example, may have a zigzag wave shape, or may have a rectangular wave shape without an inclined groove portion.

  The horizontal main grooves 16 are grooves formed in a direction intersecting with the circumferential main grooves 14 and in the tire circumferential direction. The horizontal main grooves 16 are formed in the land portion row 18 and the land portion row 20. The horizontal main grooves 16 </ b> B and 16 </ b> C are formed on the land portion row 22, and the horizontal main grooves 16 </ b> D are formed on the land portion row 22.

  Some land rows (for example, the land rows 20 on both sides of the tire equatorial plane CL excluding the land rows 18 on both ends of the tread and the land rows 22 located on the tire equatorial plane CL) are arranged in the tire circumferential direction. A sub-main groove 24 is formed along. The auxiliary main groove 24 has a groove width that periodically changes in the tire circumferential direction, and wide portions 24A and narrow portions 24B are alternately formed.

  The maximum groove width of the sub main groove 24 is 10 to 50% of the average groove width of the circumferential main groove 14, and the groove depth of the sub main groove 24 is 30 to 70 of the groove depth of the circumferential main groove 14. %.

  Here, the lower limit is set for the maximum groove width and the groove depth of the sub-main groove 24 because, if the lower limit is not reached, snow clogging occurs and the function as a groove becomes ineffective. The reason for this is that if the upper limit is exceeded, pattern noise may be deteriorated, and the land portion 17 is greatly deformed at the time of ground contact, wear performance is deteriorated, and uneven wear occurs.

  In FIG. 1, when the horizontal main groove 16 is viewed from the left ground contact end 12 </ b> A of the tread 12, first, in the land portion row 18, the land portion with the horizontal main groove 16 </ b> A inclined upward to the tire width direction. It penetrates between the rows 18, crosses the center of the wide portion 24 </ b> A of the sub main groove 24, and opens to the circumferential main groove 14 </ b> A adjacent to the land portion row 18.

  Here, the horizontal main groove 16 </ b> B enters the space between the land portion rows 20 with the inclination direction descending to the right, and reduces the inclination angle when entering the space between the land portion rows 20. Opened at the lower end of 24A and once terminated.

  Next, the horizontal main groove 16C penetrates between the land portion rows 20 downward from the upper end of the wide portion 24A, and opens to the circumferential main groove 14B near the tire equatorial plane CL adjacent to the land portion row 20. The lateral main groove 16D enters the land portion row 22 at an increased inclination angle when opening in the circumferential main groove 14B, and goes up to the right when entering the land portion row 22 and penetrates the land portion row 22. Terminate without.

  When the tread 12 is viewed in plan, as shown in FIG. 1, the wide main portion 24A of the sub main groove 24 in the land portion row 20 and the horizontal main groove 16 communicating with the upper and lower ends thereof are regarded as one crank-shaped groove. You can also.

  Since the portion where the horizontal main groove 16 is largely inclined overlaps the circumferential main groove 14, the large inclined portion may not be considered as a part of the horizontal main groove 16.

  Sipes 26 are respectively formed in the land portion rows 18, 20, and 22. Specifically, in FIG. 1, a longitudinal sipe 26A in the tire circumferential direction and a lateral sipe 26B that is inclined with respect to the tire width direction are provided. Each of the vertical sipe 26A and the horizontal sipe 26B is formed independently of each other or in a substantially L-shape.

  On the outer side in the tire width direction of the land portion row 18, the vertical sipe 26A and the horizontal sipe 26B communicate with each other in a substantially L shape, and the vertical sipe 26A opens into the horizontal main groove 16A. On the inner side in the tire width direction of the land portion row 18, the vertical sipe 26 </ b> A and the horizontal sipe 26 </ b> B are independent from each other and open to the circumferential main groove 14 or the horizontal main groove 16 </ b> A, respectively.

  In the land portion row 20, the vertical sipe 26 </ b> A and the horizontal sipe 26 </ b> B communicate with each other in a substantially L shape, and the horizontal sipe 26 </ b> B opens into the circumferential main groove 14 or the sub main groove 24.

  Also in the land portion row 22, the vertical sipe 26 </ b> A and the horizontal sipe 26 </ b> B communicate with each other in a substantially L shape, and neither the portion in which the horizontal sipe 26 </ b> B opens in the circumferential main groove 14 nor the land portion row 22 There is a part that ends with.

  The arrangement of the sipe 26 is not limited to the above, and the shape of the sipe is not limited to a linear shape, and may be, for example, a zigzag sipe.

  The number of rows of the land portion rows 18, 20, and 22 is 5 rows in FIG. 1, but the land portion row 22 may be eliminated to be 4 rows.

  That is, the number of rows in the land portion row is 4 or 5. The reason why the lower limit is set to 4 rows is that the number of the circumferential main grooves 14 is too small below this, and the performance on snow is not improved, and the upper limit is set to 5 rows when exceeding this, This is because the rigidity of the land portion rows 18, 20, and 22 becomes too low and the wear performance deteriorates.

  In FIG. 1, a total of two sub main grooves 24 are formed, one on each of the land portion rows 20 on both sides of the tire equatorial plane CL. The main land grooves 18 and 22 may also be provided with the sub main grooves 24 so that the number of the sub main grooves 24 is four or five.

  In the land portion row 20, sipes 28 and short grooves 30 are alternately formed in the tire circumferential direction, and the short grooves 30 intersect the horizontal main grooves 16A. The width of the short groove 30 is equal to, for example, the wide portion 24A of the sub main groove 24.

  In FIG. 1, the tread pattern is formed point-symmetrically with respect to the tire equatorial plane CL.

With the above configuration, the pneumatic radial tire 10 does not deteriorate pattern noise or wear performance, and can reliably start and brake the vehicle on a snowy road surface and perform steering operation (turning).
(Test example)
With respect to the conventional pneumatic radial tire 100 having the tread pattern shown in FIG. 2 and the pneumatic tire 10 according to the embodiment of the present invention having the tread pattern shown in FIG. Table 1 shows the results of tests on the turning performance on snow.

  In FIG. 2, 102 is a circumferential main groove, 104 is a horizontal main groove, 106 is a sipe, and 108 is a land portion row. The circumferential main groove 102 is a groove formed in a wave shape having an amplitude in the tire width direction due to the shape of the land portion 108, but no sub main groove is formed in the land portion 108.

  The measurement performance of the noise is that a tire that is mounted on a regular rim and filled with air at a regular internal pressure is pressed against a drum in an anechoic chamber with a regular load and traveled at a speed of 60 km / h. The measurement was performed with a microphone installed at a position 1 m away from the side.

  Here, the regular rim refers to a standard rim in an applicable size defined in the 2004 version YEAR BOOK issued by TRA. Similarly, the normal load and the normal internal pressure refer to the maximum load and the air pressure with respect to the maximum load in the application size / ply rating defined in the YEAR BOOK.

  The amount of wear was evaluated by the difference in height between the tread at the center of the land and the tread at a position 5 mm from the circumferential main groove and the sub main groove in the land after running at 5000 km slalom at 60 km / h.

  The braking performance on snow was evaluated by the reciprocal of the braking distance from 30 km / h to stopping.

  The turning performance on snow was evaluated based on the maximum speed at which the vehicle can run during a circular turn with a radius of 20 m.

  The evaluation values are all indicated by an index with the conventional example being 100, and the larger the numerical value, the better the result.

  As a result, the pneumatic radial tire of the example has a braking performance on snow without deteriorating noise and wear amount as compared with a tire having a circumferential main groove and a sub main groove having a linear shape and a constant groove width. It was also found that the turning performance on snow can be greatly improved.

It is a figure which expands and shows a tread pattern of a pneumatic radial tire concerning this embodiment. It is a figure which expands and shows a tread pattern of a pneumatic radial tire concerning a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic radial tire 12 Tread 14 Circumferential main groove 14A Circumferential main groove 14B Circumferential main groove 16 Horizontal main groove 16A Horizontal main groove 16B Horizontal main groove 16C Horizontal main groove 16D Horizontal main groove 17 Land portion 18 Land portion row 20 Land part row 22 Land part row 24 Sub-main groove 26 Sipe
26A vertical sipe
26B horizontal sipe
CL tire equator

Claims (4)

In the tread, a plurality of circumferential main grooves formed in the tire circumferential direction, a plurality of transverse main grooves formed in a direction intersecting the circumferential main grooves and in the tire circumferential direction, the transverse main grooves and the above-mentioned A pneumatic radial tire having a land portion row in the tire circumferential direction composed of land portions partitioned by a circumferential main groove,
The circumferential main groove is formed in a wave shape having an amplitude in the tire width direction,
In some of the land portion rows, a sub main groove is formed along the tire circumferential direction,
The secondary main groove has a groove width that periodically changes in the tire circumferential direction .
On the outer side in the tire width direction of the land portion row at both ends of the tread, a vertical sipe and a horizontal sipe communicate with each other in an L shape, and the vertical sipe opens in the horizontal main groove. The vertical sipe and the horizontal sipe are independent from each other, and open to the circumferential main groove or the horizontal main groove, respectively.
In the land portion row located on the tire equator plane, the vertical sipe and the horizontal sipe communicate with each other in an L shape, the horizontal sipe is open to the circumferential main groove, and the vertical sipe and the horizontal sipe Both have a portion that terminates in the land part row,
In the land portion rows on both sides of the tire equator plane except for the land portion rows on both ends of the tread and the land portion row located on the tire equator plane, a vertical sipe and a horizontal sipe communicate with each other in an L-shape. Opening in the circumferential main groove or the sub main groove ;
Pneumatic radial tire characterized by. The maximum groove width of the sub main groove is 10 to 50% of the average groove width of the circumferential main groove,
The groove depth of the sub main groove is 30 to 70% of the groove depth of the circumferential main groove;
The pneumatic radial tire according to claim 1. The number of rows of the land portion rows is 4 rows or 5 rows,
In the land part, sipes are respectively formed,
The pneumatic radial tire according to claim 1 or 2, characterized in that.   The pneumatic radial tire according to claim 3, wherein at least four sub main grooves are formed.

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