JP2016068907A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve mud performance and durability performance.SOLUTION: A pneumatic tire 1 has a plurality of shoulder blocks 6 arranged in a tire circumferential direction. The shoulder blocks 6 have side faces 11 extending inward in a tire radial direction from grounding ends 6t outside in a tire shaft direction of step faces 6a thereof. On a tire meridian cross section including a tire rotary shaft in a normal state, the side faces 11 include first circular arc parts 12 which have a center further outside in a tire shaft direction than the grounding ends 6t and have an outline in a recessed circular arc shape whose curvature radius is 50% to 100% of a tread grounding width TW. A distance Ha in a tire radial direction between an outermost end 2e in the tire radial direction of a step face 2a of a tread part 2 and an inner end 12i in the tire radial direction of the first circular arc part 12 is 5% to 10% of the maximum width of the tire.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pneumatic tire with improved mud performance and durability performance.

  For example, in a pneumatic tire mounted on a four-wheel drive vehicle or the like, since there is an opportunity to travel on a road surface such as a muddy ground, it is required to exhibit sufficient traction performance even on such a road surface. (Such performance is sometimes referred to below as “mad performance”). In order to improve the mud performance, the tread ground contact width of the tread portion is increased to increase the groove volume of the lateral groove formed between the blocks of the tread portion, thereby increasing the shearing force against mud.

  However, such a tire has a problem that since the block has a large rubber volume, the block generates a large amount of heat during running, and the durability of the block is low.

Japanese Patent Application Laid-Open No. 6-171311

  The present invention has been devised in view of the above problems, and provides a pneumatic tire capable of improving the mud performance and the durability performance based on improving the shape of the side surface of the shoulder block. The main purpose.

  The present invention is a pneumatic tire in which a plurality of shoulder blocks are arranged in the tire circumferential direction on at least one tread end side of the tread portion, and the shoulder block is a grounding end on the outer side in the tire axial direction of the tread surface. In a tire meridian cross section including a normal state tire rotation axis that has a side surface extending inward in the tire radial direction and is assembled with a normal rim and filled with a normal internal pressure, the side surface extends from the ground contact end. Includes a first arc portion having a concave arc-shaped contour having a center on the outer side in the tire axial direction and a radius of curvature of 50% to 100% of the tread ground contact width. The distance in the tire radial direction between the outer end and the inner end in the tire radial direction of the first arc portion is 5% to 10% of the maximum tire width.

  In the pneumatic tire according to the present invention, it is preferable that a part of the first arc portion extends inward in the tire axial direction from the ground contact end.

  In the pneumatic tire according to the present invention, the tread portion includes a shoulder lateral groove between the shoulder blocks arranged in the tire circumferential direction, and the shoulder lateral groove includes an inner portion in the tire axial direction and the tread end side. It is preferable that the groove width of the outer portion is 2.0 to 4.0 times the groove width of the inner portion.

  In the pneumatic tire according to the present invention, the inner portion has an angle of 45 to 65 degrees with respect to the tire axial direction, and the outer portion has an angle of 25 degrees or less with respect to the tire axial direction. desirable.

  In the pneumatic tire according to the present invention, the side surface of the shoulder block is provided with a side groove extending inward in the tire radial direction from the ground end, and in the tire meridian cross section, the groove bottom of the side groove is the ground contact. It is desirable to include a second arc portion having a concave arc-shaped contour centered on the outer side in the tire axial direction from the end.

  In the pneumatic tire according to the present invention, it is preferable that a radius of curvature of the second arc portion is smaller than a radius of curvature of the first arc portion.

  In the pneumatic tire of the present invention, the side surface of the shoulder block has a concave arc-shaped contour having a center on the outer side in the tire axial direction from the ground contact end and a radius of curvature of 50% to 100% of the tread ground contact width. 1 arc portion is included. Such a first arc portion effectively reduces the rigidity of the shoulder block in the radial direction of the tire, and promotes deformation of the shoulder block when traveling on a muddy ground. For this reason, the mud clogged between the shoulder blocks is effectively discharged and the mud can be newly grasped greatly, so that the shearing force against the mud can be increased, and excellent mud performance is exhibited. Moreover, the first arc portion effectively reduces the rubber volume of the shoulder block. For this reason, the heat generation of the shoulder block during traveling is suppressed, and the durability performance is improved.

  The distance in the tire radial direction between the outermost end in the tire radial direction of the tread surface and the inner end in the tire radial direction of the first arc portion is set to 5% to 10% of the tire maximum width. As a result, the effect of reducing the rigidity of the shoulder block and the effect of reducing the rubber volume are exerted in a balanced manner, so that the shearing force against mud due to the deformation of the shoulder block is further increased and the heat generation of the shoulder block is more effectively suppressed. Is done.

  Therefore, the pneumatic tire of the present invention can exhibit excellent mud performance and durability performance.

It is an expanded view of the tread part of the pneumatic tire of one embodiment of the present invention. It is an enlarged view of FIG. It is the sectional view on the AA line of FIG. It is tire meridian sectional drawing of the tread end vicinity of other embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a pneumatic tire (hereinafter simply referred to as “tire”) 1 showing an embodiment of the present invention. As shown in FIG. 1, the tire 1 of the present embodiment is suitably used as an all-season tire for a four-wheel drive vehicle, for example.

  In the tread portion 2 of the present embodiment, a pair of circumferential grooves 3, 3 extending continuously on both sides of the tire equator C in the tire circumferential direction, a plurality of center lateral grooves 4 connecting between the circumferential grooves 3, 3, and A plurality of shoulder lateral grooves 5 that connect the circumferential groove 3 and the tread end Te are provided.

  The “tread end” Te is obtained when a normal load is applied to a normal tire 1 that is assembled with a normal rim and filled with a normal internal pressure, and a normal load is applied to the flat tire with a camber angle of 0 degrees. It is determined as the ground contact position on the outermost side in the tire axial direction. In the normal state, the distance in the tire axial direction between the tread ends Te and Te is determined as the tread contact width TW. Unless otherwise noted, the dimensions and the like of each part of the tire are values measured in a normal state.

  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, “Standard Rim” for JATMA, “Design Rim” for TRA, ETRTO Then "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JAMATA” is the “maximum air pressure”, TRA is the table “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO. When the tire is for a passenger car, the normal internal pressure is 180 kPa.

  “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” is “maximum load capacity”, TRA is “TIRE LOAD” The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO. When the tire is for a passenger car, the normal load is a load corresponding to 88% of the load.

  The circumferential groove 3 extends in a zigzag shape. Since such a circumferential groove 3 has a tire axial component, it exerts a large shearing force against mud that has been consolidated in the groove. Therefore, the mud performance is improved.

  FIG. 2 is an enlarged view of the tread portion 2 of FIG. As shown in FIG. 2, the angle α <b> 1 of the circumferential groove 3 with respect to the tire circumferential direction increases the shearing force against mud and from the viewpoint of ensuring a large rigidity in the tire circumferential direction of the land portion in the vicinity of the circumferential groove 3, Preferably, it is 30 to 40 degrees.

  In order to effectively exhibit the above-described action, the groove width W1 perpendicular to the longitudinal direction of the circumferential groove 3 is preferably 3% to 8% of the tread ground contact width TW. Further, the groove depth (not shown) of the circumferential groove 3 is preferably 4% to 9% of the tread ground contact width TW.

  The center lateral groove 4 extends linearly, for example. Thereby, the rigidity of the land part near the center horizontal groove 4 and the sludge performance in the center horizontal groove 4 are improved.

  The center lateral groove 4 has a first center lateral groove 4A inclined to one side with respect to the tire axial direction (upward to the left in the figure), and a second center lateral groove inclined in the opposite direction to the first center lateral groove 4A. 4B and these are provided alternately in the tire circumferential direction. As a result, the lateral force acting on the first center lateral groove 4A and the second center lateral groove 4B is offset, so that the straight running stability performance in the muddy area is improved.

  The angle α2 of the center lateral groove 4 with respect to the tire circumferential direction is preferably 50 to 60 degrees. When the angle α2 of the center lateral groove 4 is less than 50 degrees, the shearing force against mud may be reduced. When the angle α2 of the center lateral groove 4 exceeds 60 degrees, there is a possibility that the discharge property of mud to the circumferential groove 3 is deteriorated.

  The groove width W2 perpendicular to the longitudinal direction of the center lateral groove 4 is preferably 35% to 55% of the groove width W1 of the circumferential groove 3. The groove depth (not shown) of the center lateral groove 4 is preferably 70% to 90% of the groove depth of the circumferential groove 3. Thereby, the shearing force with respect to mud and the rigidity of the land part near the center lateral groove 4 can be enhanced effectively.

  The shoulder lateral groove 5 includes an inner portion 8 in the tire axial direction and an outer portion 9 closer to the tread end Te than the inner portion 8.

  The inner portion 8 has a constant groove width in the present embodiment. The outer portion 9 of the present embodiment has a larger groove width than the inner portion 8.

  The groove width W3 perpendicular to the longitudinal direction of the inner portion 8 is, for example, a groove of the circumferential groove 3 in order to maintain the durability performance without improving the mud performance and excessively reducing the rigidity of the land portion near the inner portion 8. 35% to 75% of the width W1 is desirable. Similarly, the groove depth (not shown) of the inner portion 8 is preferably 55% to 75% of the groove depth of the circumferential groove 3.

  The groove width W4 of the outer portion 9 is preferably 2.0 to 4.0 times the groove width W3 of the inner portion 8. If the groove width W4 of the outer portion 9 is less than 2.0 times the groove width W3 of the inner portion 8, the shearing force against mud cannot be increased on the tread end Te side where a large lateral force acts. May decrease. When the groove width W4 of the outer portion 9 exceeds 4.0 times the groove width W3 of the inner portion 8, the rigidity of the land portion in the vicinity of the outer portion 9 is excessively lowered, and the durability performance may be lowered. The groove width W4 of the outer portion 9 is the maximum width in the tire circumferential direction.

  The inner portion 8 is inclined with respect to the tire axial direction. Such an inner portion 8 can smoothly discharge mud in the inner portion 8 to the outer portion 9 or the circumferential groove 3 while ensuring rigidity in the vicinity of the inner portion 8.

  The angle α3 of the inner portion 8 with respect to the tire axial direction is preferably 45 to 65 degrees. Thereby, the shear force with respect to mud and the mud drainage performance of the inner part 8 by tire rolling are improved with good balance.

  The outer portion 9 is also inclined with respect to the tire axial direction. It is desirable that the angle α4 of the outer portion 9 with respect to the tire axial direction is smaller than the angle α3 of the inner portion 8. As a result, the rigidity in the tire axial direction of the land portion on the tread end Te side on which a large lateral force acts can be maintained, so that the turning performance during mud traveling is greatly improved. In order to effectively exhibit such an action, the angle α4 of the outer portion 9 with respect to the tire axial direction is preferably 25 degrees or less. The angle α4 of the outer portion 9 is an angle of the center line 9c that smoothly joins the intermediate position of the outer portion 9 in the tire circumferential direction.

  The outer portion 9 has a gradually decreasing portion 10 in which the angle α4 gradually decreases toward the tread end Te. Thereby, the above-mentioned operation is more effectively exhibited.

  As shown in FIG. 1, the tread portion 2 is divided into a pair of shoulder block rows 6R and a center block row 7R by a circumferential groove 3, a center lateral groove 4, and a shoulder lateral groove 5. The shoulder block row 6R has a plurality of shoulder blocks 6 arranged in the tire circumferential direction on both tread ends Te, Te side. The center block row 7R includes a plurality of center blocks 7 arranged in the tire circumferential direction between the pair of circumferential grooves 3 and 3.

  The shoulder block 6 is formed between the circumferential groove 3, the tread end Te, and the shoulder lateral grooves 5 and 5 adjacent to each other in the tire circumferential direction.

  3 is a cross-sectional view taken along line AA in FIG. As shown in FIG. 3, the shoulder block 6 has a tread surface 6a and a side surface 11 extending inward in the tire radial direction from the ground contact end 6t on the outer side in the tire axial direction of the tread surface 6a. In the present embodiment, the grounding end 6t of the shoulder block 6 and the tread end Te coincide.

  The side surface 11 includes a first arc portion 12 having a concave arc-shaped contour centered on the outer side in the tire axial direction from the ground contact end 6t. Such a first arc portion 12 effectively reduces the rigidity of the shoulder block 6 in the tire radial direction, and promotes deformation (vertical deflection) of the shoulder block 6 in the tire radial direction when traveling on muddy ground. For this reason, the mud clogged in the shoulder lateral groove 5 is effectively discharged by the deformation of the shoulder block 6, and the mud can be newly grasped greatly, so that the shearing force against the mud is improved, so that excellent mud performance is exhibited. Is done. Moreover, since the 1st circular arc part 12 reduces the rubber volume of the shoulder block 6, the heat_generation | fever of the shoulder block 6 at the time of driving | running | working is suppressed. Thereby, the durability performance of the shoulder block 6 improves.

  In the present embodiment, the first arc portion 12 extends continuously from the ground contact end 6t inward in the tire radial direction. The curvature radius R1 of the first arc portion 12 is 50% to 100% of the tread ground contact width TW. When the curvature radius R1 is less than 50% of the tread contact width TW, the rigidity in the tire radial direction in the vicinity of the contact end 6t of the shoulder block 6 becomes excessively small, and the durability performance deteriorates. When the curvature radius R1 exceeds 100% of the tread contact width TW, the rubber volume of the shoulder block 6 cannot be effectively reduced, and the heat generation of the shoulder block 6 during traveling cannot be suppressed. For this reason, the curvature radius R1 is preferably 60% to 90% of the tread ground contact width TW.

  The first arc portion length Ha, which is the distance in the tire radial direction between the inner end 12i in the tire radial direction of the first arc portion 12 and the outermost end 2e in the tire radial direction of the tread surface 2a of the tread portion 2, is the tire maximum width. 5% to 10% (not shown). When the first arc portion length Ha is less than 5% of the maximum tire width, the rigidity reduction effect of the shoulder block 6 and the rubber volume reduction effect are not sufficiently exhibited. When the first arc portion length Ha exceeds 10% of the maximum tire width, the rigidity of the shoulder block 6 is reduced, and the shearing force against mud is reduced. For this reason, the first arc portion length Ha is preferably 6% to 9% of the maximum tire width. The “tire maximum width” refers to the tire axial direction between the tire maximum width positions (not shown) that protrudes most outward in the tire axial direction, excluding protrusions such as letters and rim protectors provided on the sidewall SW. Distance.

  On the side surface 11 of the shoulder block 6, a side surface groove 13 extending from the ground contact end 6t inward in the tire radial direction is provided. Such a side groove 13 effectively reduces the rigidity and rubber volume of the shoulder block 6 and improves the mud performance and the durability performance.

  The ground contact edge 6t of the shoulder block 6 of the present embodiment is indicated by a clear edge (corner) that connects the tread surface 6a and the side surface 11. However, the grounding end 6t is not limited to such a mode, and may be a mode provided on a small arc 6b (indicated by a two-dot chain line) that connects the tread surface 6a and the side surface 11. In this case, since the rigidity in the vicinity of the ground contact 6t is increased as compared with the case formed by the edges, the durability performance is further improved.

  In the present embodiment, the side groove 13 extends linearly along the tire radial direction. Thereby, since the rigidity of the shoulder block 6 in the tire circumferential direction is lowered, the shoulder lateral groove 5 can be easily opened and closed, and the shearing force against mud and the mud drainage performance are increased.

  The groove bottom 13s of the side surface groove 13 includes a second arc portion 14 having a concave arc-shaped contour centered on the outer side in the tire axial direction from the ground contact end 6t. Such a 2nd circular arc part 14 makes the rubber volume of the shoulder block 6 at the time of muddy ground travel effectively small, and further promotes the deformation. For this reason, the mud clogged in the shoulder lateral groove 5 is effectively discharged, and the heat generation of the shoulder block 6 during traveling is further suppressed.

  The curvature radius R2 of the second arc portion 14 is preferably smaller than the curvature radius R1 of the first arc portion 12. Thereby, the groove | channel volume of the side surface groove | channel 13 can be enlarged more effectively, and the rubber volume of the shoulder block 6 can be made small by extension. In order to effectively exhibit such an action, the radius of curvature R2 of the second arc portion 14 is preferably 60% or less of the tread ground contact width TW.

  The inner end 13 i in the tire radial direction of the side groove 13 is located on the outer side in the tire radial direction with respect to the inner end 12 i of the first arc portion 12. Thereby, the excessive rigidity fall of the inner end 12i vicinity of the 1st circular arc part 12 is suppressed. From such a viewpoint, the distance Hb in the tire radial direction of the second arc portion 14 is preferably 30% to 50% of the first arc portion length Ha.

  As shown in FIG. 1, a shoulder lug groove 17 and a shoulder sipe 18 are provided on the tread surface 6 a of the shoulder block 6. The shoulder lug groove 17 has an inner end 17i that terminates in the shoulder block 6 and an outer end 17e that communicates with the grounding end 6t. The shoulder sipe 18 is disposed on the inner side in the tire axial direction than the inner end 17 i of the shoulder lug groove 17. Thereby, the rigidity of the shoulder block 6 is further effectively reduced.

  An outer end 17 e of the shoulder lug groove 17 communicates with the side surface groove 13. Thereby, the deformation (vertical deflection) of the shoulder portion and the movement of the shoulder block 6 in the tire circumferential direction are further facilitated, and the shoulder lateral groove 5 can be opened / closed greatly, so that the mud performance is further improved.

  As shown in FIG. 2, the shoulder sipe 18 includes a first sipe 18A, a second sipe 18B, and a third sipe 18C. The first sipe 18A, the second sipe 18B, and the third sipe 18C extend linearly. The first sipe 18 </ b> A communicates with the inner end 17 i of the shoulder lug groove 17 and terminates in the shoulder block 6. The second sipe 18B connects the first sipe 18A and the circumferential groove 3. The third sipe 18C connects the first sipe 18A and the inner portion 8. Such a sipe 18 further reduces the rigidity of the shoulder block 6 more effectively, and further promotes deformation and movement of the shoulder block 6 during mud traveling.

  The center block 7 is divided by a pair of circumferential grooves 3, 3, a first center lateral groove 4A, and a second center lateral groove 4B.

  In the present embodiment, the center block 7 has a tread surface 7a formed in a substantially pentagonal shape. Such a center block 7 exerts edges in multiple directions to exert a shearing force on the muddy ground.

  FIG. 4 is a cross-sectional view of a shoulder block 6 according to another embodiment of the present invention. As shown in FIG. 4, the side surface 11 of the shoulder block 6 of this embodiment is such that the first arc portion 12 has an inner arc portion 21 extending inward in the tire axial direction from the ground contact end 6 t and a tire than the ground contact end 6 t. And an outer arc portion 22 extending outward in the axial direction. Such an inner circular arc portion 21 further accelerates the deformation of the shoulder block 6, so that the mud clogged in the shoulder lateral groove 5 can be discharged more effectively.

  When the length H1 in the tire radial direction of the inner circular arc portion 21 is large, the rigidity of the shoulder block 6 is excessively lowered, and the durability performance may be deteriorated. For this reason, the length H1 of the inner circular arc portion 21 in the tire radial direction is preferably 55% to 75% of the length H2 of the outer circular arc portion 22 in the tire radial direction.

  The land ratio of the tread portion 2 is preferably 55% to 70%. When the land ratio is less than 55%, the rigidity of the blocks 6 and 7 becomes excessively small, and the durability performance may be deteriorated. If the land ratio exceeds 70%, the traction in the muddy area may decrease. The land ratio is the ratio of the total area of the treads 6a and 7a of the blocks 6 and 7 to the area of the virtual tread of the tread 2 when it is assumed that all the grooves and sipes of the tread 2 are filled.

  In the tire 1 of the present embodiment, it is desirable that the tread contact width TW is 70% to 90% of the maximum tire width. Such a tire 1 can increase the contact area with the muddy road surface, and can obtain excellent mud performance.

  As mentioned above, although embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention is not limited to illustrated embodiment, and can be deform | transformed and implemented in a various aspect.

  A pneumatic tire of size 225 / 95R16C having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1, and the mud performance, durability performance, and deflection rate of each sample tire were tested. The main common specifications and test methods for each sample tire are as follows.

<Mad performance>
Each sample tire was mounted on all wheels of a 3600cc four-wheel drive vehicle under the following conditions. Then, the test driver drove the test course on the muddy road surface, and the driving characteristics regarding the steering stability performance and the straight running stability performance at this time were evaluated by the test driver's sensuality. The results are displayed with a score of Comparative Example 1 being 100. The larger the value, the better.
Rim: 6.0J
Internal pressure: 475kPa

<Durability>
Using a drum type tire testing machine, each sample tire was run on a drum under the following conditions, and the durability performance was measured. The result is displayed as the distance traveled when an abnormal noise is generated from the inside of the sample tire. The upper limit of the travel distance is 30000 km.
Rim: 6.0J
Internal pressure: 475kPa
Load: 17kN
Speed: 100km / h

<Deflection rate>
The deflection rate when a load under the following conditions was applied to the sample tire was measured.
The deflection rate is obtained by the vertical deflection / the length of the first arc portion (real number). The results are displayed as an index with the deflection rate of Comparative Example 1 as 100. A numerical value of 104 to 110 is particularly good.
Internal pressure: 475kPa
Load: 10kN
The test results are shown in Table 1.
* 1 The first arc part length is the first arc part length Ha / the maximum tire width (%).

  As a result of the test, it can be confirmed that in the tire of the example, the durability performance and the mud performance are improved in a well-balanced manner as compared with the tire of the comparative example. In addition, tests were performed on tire sizes different from the above, but the same tendency was shown.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2a Tread part tread part 2e Outermost end of tread part 6 Shoulder block 6a Shoulder block tread part 6t Shoulder block grounding end 11 Side face 12 First arc part 12i Inner end TW tread of first arc part Ground width

Claims (6)

A pneumatic tire in which a plurality of shoulder blocks are arranged in the tire circumferential direction on at least one tread end side of the tread portion,
The shoulder block has a side surface extending inward in the tire radial direction from a ground contact end in the tire axial direction of the tread surface,
In a tire meridian cross section including a normal state tire rotating shaft that is assembled with a normal rim and filled with a normal internal pressure, the side surface has a center on the outer side in the tire axial direction than the ground contact end and has a curvature. A first arc portion having a concave arc-shaped contour having a radius of 50% to 100% of a tread ground contact width;
The distance in the tire radial direction between the outermost end in the tire radial direction of the tread surface and the inner end in the tire radial direction of the first arc portion is 5% to 10% of the maximum tire width. Pneumatic tire characterized by.   The pneumatic tire according to claim 1, wherein a part of the first arc portion extends inward in the tire axial direction from the ground contact end. The tread portion has a shoulder lateral groove between the shoulder blocks arranged in the tire circumferential direction,
The shoulder lateral groove includes an inner portion in the tire axial direction and an outer portion on the tread end side,
The pneumatic tire according to claim 1 or 2, wherein a groove width of the outer portion is 2.0 to 4.0 times a groove width of the inner portion.   The pneumatic tire according to claim 3, wherein the inner portion has an angle of 45 to 65 degrees with respect to the tire axial direction, and the outer portion has an angle of 25 degrees or less with respect to the tire axial direction. On the side surface of the shoulder block, a side groove extending inward in the tire radial direction from the ground contact end is provided,
In the tire meridian cross section, the groove bottom of the side surface groove includes a second arc portion having a concave arc-shaped contour centered on the outer side in the tire axial direction from the ground contact end. Pneumatic tires.   The pneumatic tire according to claim 5, wherein a radius of curvature of the second arc portion is smaller than a radius of curvature of the first arc portion.

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