JP2015231812A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent riding comfortableness while maintaining high levels of steering stability and abrasion resistance.SOLUTION: A middle rib 5m includes: middle sipes 9 which extend from a rib side edge Ma of one side toward a rib side edge Mb of the other side, and end parts 9b of which discontinue in the middle rib 5m; and middle lug grooves 10 which extend from the rib side edge Mb of the other side toward the rib side edge Ma of the one side, and end parts 10a of which discontinue in the middle rib 5m. Each middle sipe 9 and each middle lug groove 10 are disposed in the same inclination direction and also alternately disposed in a tire circumferential direction, and have an overlapping part 11 where they overlap with each other in the tire circumferential direction. The middle sipe 9 includes a chamfer part 12 at a corner part P where a sipe wall surface 9w and a tread surface 2S intersect with each other.

Description

  The present invention relates to a pneumatic tire that can exhibit excellent ride comfort while maintaining steering stability and wear resistance at a high level.

  For example, a tread pattern tire shown in FIG. 5 is known (see FIG. 1 of Patent Document 1).

  In this tread pattern, the shoulder land portion a, the middle land portion b, and the center land portion c are formed as rib bodies extending continuously in the tire circumferential direction, respectively, thereby increasing the pattern rigidity, steering stability and wear resistance. The improvement of the property is aimed at. In the middle land portion b, a middle sipe d penetrating the middle land portion b in the tire axial direction, a middle sub-groove e having an outer end communicating with the shoulder main groove g1 and an inner end being interrupted in the middle land portion b, Are alternately arranged in the tire circumferential direction.

  However, in the tread pattern, since the middle sipe d extends through the middle land portion b in the tire axial direction, the rigidity is reduced as compared with a complete rib body. Therefore, there remains room for improvement in handling stability and wear resistance.

  In view of such a situation, the present inventor has proposed that one end of the middle sipe d is interrupted in the middle land portion b. However, in such a case, there arises a new problem to be solved that the ride comfort decreases as the rigidity increases.

JP2013-193464A

  Therefore, the invention is based on the fact that one end of the middle sipe is interrupted in the middle land portion, and a chamfered portion is formed in the middle sipe, and while maintaining a high level of driving stability and wear resistance, excellent riding comfort is achieved. It is an object to provide a pneumatic tire that can be demonstrated.

In the tread portion, a middle rib disposed between a shoulder main groove extending in the tire circumferential direction on the most ground contact end side and a center main groove extending in the tire circumferential direction on the inner side in the tire axial direction of the shoulder main groove. A pneumatic tire,
The middle rib is
A plurality of middle sipes that incline from the rib side edge on one side in the tire axial direction toward the rib side edge on the other side and the other end is interrupted in the middle rib;
A plurality of middle lug grooves extending from the other rib side edge to the one rib side edge and having one end cut off in the middle rib;
The middle sipe and the middle lug groove have the same inclination direction and are alternately arranged in the tire circumferential direction, and the middle sipe and the middle lug groove have a weight portion that overlaps in the tire circumferential direction,
The middle sipe includes a chamfered portion at a corner portion where one sipe wall surface of the middle sipe and a tread surface intersect.

  In the pneumatic tire according to the present invention, it is preferable that the middle sipe and the middle lug groove are parallel and an angle θ with respect to the tire circumferential direction is in a range of 35 to 65 degrees.

  In the pneumatic tire according to the present invention, a weight of the chamfered portion in the tire axial direction is 50% or more of a middle sipe tire axial length, and the chamfered portion and the middle lug groove overlap in the tire circumferential direction. It is preferable to have a part.

  In the pneumatic tire according to the present invention, it is preferable that the middle rib includes a slot between the middle sipes and on a rib side edge on one side in the tire axial direction.

  In the pneumatic tire according to the present invention, it is preferable that the rib side edge on one side in the tire axial direction faces the center main groove, and the rib side edge on the other side in the tire axial direction faces the shoulder main groove.

In the pneumatic tire according to the present invention, a center rib is provided between the center main grooves, and a center sipe that passes through the center rib in the tire axial direction is disposed on the center rib.
The distance in the tire circumferential direction between both ends of the center sipe and one end of the middle sipe is preferably 1.5 mm or less.

  In the pneumatic tire according to the present invention, the chamfer width of the chamfered portion is preferably in the range of 1.0 to 2.0 mm, and the chamfer depth is preferably in the range of 1.0 to 2.0 mm.

  In the pneumatic tire according to the present invention, the length of the middle lug groove in the tire axial direction is in a range of 33% to 50% of the width of the middle rib in the tire axial direction, and the length of the middle sipe in the tire axial direction is a middle rib tire. A range of 50% to 80% of the axial width is preferable.

  The above-mentioned contact end means the outermost end in the tire axial direction of the tread contact surface that comes into contact when a normal load is applied to a tire that is assembled with a normal rim and filled with a normal internal pressure. 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".

  The middle sipe and the center sipe mean a notched or ultrafine groove having a groove width of 1.0 mm or less, and the groove wall surfaces come into contact with each other at the time of grounding to close the groove.

  In the present invention, as described above, middle sipes and middle lug grooves having the same inclination direction are alternately arranged on the middle rib in the tire circumferential direction. The middle sipe is interrupted at one end in the middle rib, and the middle lug groove is interrupted at the other end in the middle rib. Therefore, the rigidity of the middle rib is increased, and the steering stability and the wear resistance are improved.

  Further, in the middle sipe, a chamfered portion is formed at a corner portion where one sipe wall surface and the tread surface intersect, and thereby, rigidity relaxation in the tire circumferential direction and the tire axial direction is performed in a balanced manner. As a result, riding comfort can be improved while maintaining the steering stability and wear resistance.

It is an expanded view of the tread pattern which shows one Embodiment of the pneumatic tire of this invention. It is the elements on larger scale of the principal part. (A), (B) is sectional drawing of a center main groove and a shoulder main groove. (A), (B), (C) is sectional drawing of a middle sipe, a middle lug groove, and a center sipe. 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.
FIG. 1 shows a case where the pneumatic tire 1 of the present embodiment is formed as a passenger car tire.

  As shown in FIG. 1, the tread portion 2 of the pneumatic tire 1 includes a pair of shoulder main grooves 3 extending in the tire circumferential direction on the most ground contact end Te side, and a tire on the inner side in the tire axial direction of the shoulder main grooves 3. And at least one center main groove 4 extending in the circumferential direction. As a result, a pair of middle ribs 5m disposed between the shoulder main groove 4 and the center main groove 4 and a pair of shoulder ribs 5s disposed between the shoulder main groove 4 and the ground contact Te on the tread portion 2. And are formed. In this example, two center main grooves 4 are provided, and a center rib 5c extending on the tire equator Co is further formed between the center main grooves 4 and 4 thereby.

  The shoulder rib 5s, the middle rib 5m, and the center rib 5c are formed as rib bodies extending continuously in the tire circumferential direction without being divided into a plurality of blocks by lug grooves. A rib pattern tire made of such a rib body has high pattern rigidity, and therefore can improve steering stability and wear resistance.

  The shoulder main groove 3 and the center main groove 4 of this example are formed as straight grooves extending linearly in the tire circumferential direction. Such a straight groove is useful for improving the wet performance since the drainage resistance is small.

  As shown in FIGS. 3A and 3B, the groove widths W3 and W4 in the shoulder main groove 3 and the center main groove 4 are groove widths measured in the direction perpendicular to the groove center line. The same shall apply.) And the groove depths H3 and H4 can be variously determined in accordance with common practice. However, from the balance between the wet performance and the handling stability, the groove widths W3 and W4 of the shoulder main groove 3 and the center main groove 4 are 3.0 to 6.0% of the ground contact width TW (shown in FIG. 1), respectively. The groove depths H3 and H4 are preferably in the range of 6 to 12 mm, for example. Since the drainage is more demanded on the tire equator Co side, it is preferable to make the groove width W4 of the center main groove 4 larger than the groove width W3 of the shoulder main groove 3 in order to improve the wet performance.

  Next, middle sipes 9 and middle lug grooves 10 are alternately arranged in the tire circumferential direction on the middle rib 5m.

  As shown in FIG. 2, the middle rib 5m does not have lug grooves and sipes penetrating the middle rib 5m in the tire axial direction, and the middle sipe 9 is formed on the other side from the rib side edge Ma on one side in the tire axial direction. The end 9b on the other side inclines toward the rib side edge Mb and is interrupted in the middle rib 5m. On the other hand, the middle lug groove 10 is inclined from the rib side edge Mb on the other side toward the rib side edge Ma on the one side, and the end portion 10a on the one side is interrupted in the middle rib 5m.

  In this example, the case where one rib side edge Ma faces the center main groove 4 and the other rib side edge Mb faces the shoulder main groove 3 is shown. That is, the middle sipe 9 of this example has one end portion 9a communicating with the center main groove 4 and the other end portion 9b terminating in the middle rib 5m. Further, in the middle lug groove 10 of this example, the end 10b on the other side communicates with the shoulder main groove 3, and the end 10a on one side terminates in the middle rib 5m.

  The middle sipe 9 and the middle lug groove 10 have the same inclination direction, and the middle sipe 9 and the middle lug groove 10 include a weight portion 11 that overlaps in the tire circumferential direction. The angle θ9 of the middle sipe 9 with respect to the tire circumferential direction is preferably in the range of 35 to 65 degrees, and the angle θ10 of the middle lug groove 10 with respect to the tire circumferential direction is preferably in the range of 35 to 65 degrees. In this example, the middle sipe 9 and the middle lug groove 10 are each curved in a substantially circular arc shape, and the angles θ9 and θ10 are gradually decreased toward the outside in the tire axial direction within the range. However, the middle sipes 9 and the middle lug grooves 10 can also be formed in a straight line with the angles θ9 and θ10 being constant. Particularly preferably, the middle sipe 9 and the middle lug groove 10 are formed substantially in parallel. “Substantially parallel” means a difference between an angle θ9 of the virtual extension line of the middle sipe 9 with respect to the tire circumferential direction and an angle θ10 of the virtual extension line of the middle lug groove 10 with respect to the tire circumferential direction on an arbitrary tire circumferential line | θ9− This means that θ10 | is 5 degrees or less.

  As described above, since the middle sipes 9 and the end portions 9b and 10a of the middle lug groove 10 are interrupted in the middle rib 5m, the middle rib 5m can have a high rigidity and can exhibit excellent steering stability and wear resistance. It becomes possible. In particular, the middle sipe 9 and the middle lug groove 10 are substantially parallel and the angles θ9 and θ10 are in the above range, whereby the rigidity distribution is made uniform in the tire circumferential direction and the tire axial direction. Therefore, the above-described excellent steering stability and wear resistance can be more effectively exhibited. If the angles θ9 and θ10 are less than 35 degrees or more than 65 degrees, the rigidity balance in the tire circumferential direction and the tire axial direction is lowered, and the effect of improving steering stability and wear resistance is not sufficiently exhibited. From such a viewpoint, the lower limit of the angles θ9 and θ10 is more preferably 40 degrees or more, and the upper limit is more preferably 60 degrees or less.

  Further, the tire axial direction width W11 of the weight part 11 is preferably in the range of 15 to 25% of the tire axial direction width Wm of the middle rib 5m. The length L10 of the middle lug groove 10 in the tire axial direction is preferably 33% to 50% of the width Wm, and the length L9 of the middle sipe 9 in the tire axial direction is preferably 50% to 80% of the width Wm. If the length L10 of the middle lug groove 10 is less than 33% of the width Wm, the wet performance tends to be reduced. Conversely, if it exceeds 50%, it is disadvantageous for securing the rigidity of the middle rib 5m. If the length L9 of the middle sipe 9 is out of the range, it is difficult to secure the width W11 of the weight portion 11.

  The width Wm of the middle rib 5m is preferably 0.12 to 0.18 times the ground contact width TW from the viewpoint of handling stability and wet performance.

  As shown in FIGS. 4A and 4B, the depths H9 and H10 of the middle sipe 9 and the middle lug groove 10 are smaller than the groove depths H3 and H4 of the shoulder main groove 3 and the center main groove 4. Is preferred. In this example, the depth H9 and the depth H10 are substantially equal, and the case where it is set as the range of 4.0-7.0 mm, respectively is shown. Note that “substantially equal” means that the ratio H9 / H10 is 0.9 to 1.1.

  As shown in FIGS. 2 and 4A, the middle sipe 9 is formed with a chamfered portion 12 at a corner portion P where one sipe wall surface 9w of the middle sipe 9 and the tread surface 2S intersect. The tire axial direction length L12 of the chamfered portion 12 is preferably 50% or more, more preferably 65% or more of the tire axial direction length L9 of the middle sipe 9. Further, the chamfered portion 12 preferably has a weight portion 13 that overlaps the middle lug groove 10 in the tire circumferential direction.

  Such a chamfered portion 12 can relieve the tire circumferential rigidity and the tire axial rigidity of the middle rib 5m in a well-balanced manner, and can improve riding comfort while maintaining the above-described excellent steering stability and wear resistance. it can. In addition, when the length L12 of the chamfered portion 12 is less than 50% of the length L9, it is difficult to sufficiently exhibit the riding comfort improvement effect.

  The chamfer width W12 of the chamfered portion 12 is preferably in the range of 1.0 to 2.0 mm, and the chamfer depth H12 is preferably in the range of 1.0 to 2.0 mm. When the chamfering width W12 and the chamfering depth H12 are each less than 1.0 mm, the rigidity relaxation effect is reduced, and it is difficult to sufficiently exhibit the riding comfort improvement effect. When the chamfering width W12 and the chamfering depth H12 exceed 2.0 mm, the rigidity is lowered and the steering stability and the wear resistance tend to be adversely affected. From such a viewpoint, the lower limit of the chamfering width W12 and the chamfering depth H12 is more preferably 1.2 mm or more, and the upper limit is more preferably 1.8 mm or less.

  In this example, the chamfered portion 12 is formed of an inclined surface portion 12A extending downward from the tread surface 2S and a concave arcuate arc surface portion 12B connecting the inclined surface portion 12A and the sipe wall surface 9w. However, the chamfered portion 12 can be formed only by the inclined surface portion 12A.

  In the middle rib 5m of this example, slots 15 can be formed between the middle sipes 9, 9 and at the rib side edge Ma on one side in the tire axial direction in order to make the rigidity distribution more uniform. The length 15 in the tire axial direction of the slot 15 is preferably sufficiently smaller than the length L10 of the middle lug groove 10, and is preferably regulated to 0.2 times or less the width Wm of the middle rib 5m.

  The middle rib 5m has no sipes penetrating the middle rib 5m in the tire axial direction.

  Next, the center rib 5c of the present example is provided with a center sipe 20 that penetrates the center rib 5c in the tire axial direction. The distance LA in the tire circumferential direction between both ends of the center sipe 20 and one end portion 9a of the middle sipe 9 is preferably 1.5 mm or less. As a result, the middle sipe 9 and the center sipe 20 are arranged so as to be continuous with each other via the center main groove 4. As a result, drainage is improved, and wet performance is improved.

  The center sipe 20 of this example includes an end portion 20E extending substantially parallel to the tire axial direction line from each center main groove 4 toward the inner side in the tire axial direction, and a central portion 20C connecting the end portions 20E and 20E. It is approximately Z-shaped. The central portion 20C is different from the middle sipe 9 in the inclination direction. As a result, the middle sipes 9, 9 and the center sipes 20 on both sides are made almost one while shifting the phases of the middle sipes 9 disposed on one side in the tire axial direction and the middle sipes 9 disposed on the other side in the circumferential direction. Can be connected.

  As shown in FIGS. 2 and 4C, the end portion 20E of the center sipe 20 is provided with a chamfered portion 21 at a corner portion Q where one sipe wall surface 20w and the tread surface 2S intersect. Similar to the chamfered portion 12, the chamfered portion 21 is useful for improving riding comfort. In this example, the chamfered portion 21 is formed of an inclined surface portion 21A extending downwardly from the tread surface 2S, and a concave arcuate arc surface portion 21B connecting the inclined surface portion 21A and the sipe wall surface 20w. However, the chamfered portion 21 can be formed only by the inclined surface portion 21A. The chamfering width W21 and the chamfering depth H21 of the chamfered portion 21 are larger than the chamfered width W12 and the chamfered depth H12 of the chamfered portion 12. The depth H20 of the center sipe 20 and the depth H9 of the middle sipe 9 are preferably substantially equal to each other.

  Next, the shoulder rib 5s of this example includes a shoulder lug groove 25, a shoulder sipe 26, and a shoulder auxiliary sipe 27.

  The shoulder lug groove 25 extends inward in the tire axial direction from the ground contact end Te, and the inner end is interrupted in the shoulder rib 5s. The length L25 of the shoulder lug groove 25 in the tire axial direction is preferably 0.60 times or more, more preferably 0.65 times or more the width Ws of the shoulder rib 5s. Moreover, the upper limit becomes like this. Preferably it is 0.80 times or less, More preferably, it is 0.75 times or less. Such a shoulder lug groove 25 ensures the rigidity and drainage of the shoulder rib 5s.

  The shoulder auxiliary sipe 27 extends from the inner end of the shoulder lug groove 25 to the shoulder main groove 3. The shoulder assist sipe 27 further improves drainage in cooperation with the shoulder lug groove 25, relaxes rigidity in the tire circumferential direction, and suppresses uneven wear such as shoulder drop wear. In this example, the shoulder lug groove 25, the shoulder auxiliary sipe 27, and the middle lug groove 10 are arranged so as to be substantially continuous. This enhances drainage.

  The shoulder sipes 26 extend substantially parallel to the shoulder lug grooves 25 and are alternately arranged in the tire circumferential direction with the shoulder lug grooves 25. Both ends of the shoulder sipe 26 are interrupted in the shoulder rib 5s. Such a shoulder sipe 26 makes the rigidity distribution of the shoulder rib 5s uniform, further suppresses uneven wear, and improves wet performance.

  Although the pneumatic tire of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be implemented with various modifications.

A pneumatic tire (195 / 65R15) having the basic tread pattern shown in FIG. 1 was prototyped based on the specifications shown in Table 1. These tires were mounted on the following test vehicles and tested for wear resistance, handling stability, and riding comfort.
The common specifications, test conditions, and test methods for each tire are as follows.
<Tire>
Center main groove: groove width W4 (7.9 mm), groove depth H4 (8.1 mm)
・ Shoulder main groove: groove width W3 (5.9 mm), groove depth H3 (7.9 mm)
-Middle lug groove: groove width (3.7 mm), groove depth (5.6 mm)
・ Middle sipe: width (0.6mm), depth (5.6mm)
・ Center sipe: Width (0.6mm), Depth (5.6mm)
・ Shoulder lug groove: groove width (4.0 mm), depth (5.6 mm)
・ Shoulder sipe: width (0.6mm), depth (5.2mm)
・ Shoulder auxiliary sipe: width (0.6mm), depth (5.6mm)
-Circumferential distance LA between the ends of the center sipe and middle sipe: 1.5 mm
<Test conditions>
・ Installed rim: 15 × 6J
・ Tire internal pressure: 200kPa
・ Test vehicle: Front-wheel drive vehicle, displacement 1600cc
-Tire mounting position: all wheels

(1) Abrasion resistance:
The amount of wear was measured when the test vehicle traveled 30000 km on a general road. The evaluation was performed by the reciprocal of the amount of wear, and displayed as an index with the value of Comparative Example 1 being 100. The higher the value, the better the wear resistance.

(2) Steering stability:
With the above test vehicle, the driving characteristics relating to steering response, rigidity, grip, etc. when driving on a dry asphalt test course were displayed as an index with Comparative Example 1 as 100 by sensory evaluation of the driver. The larger the value, the better the steering stability.

(3) Riding comfort:
Riding comfort when running on a test course in the above steering stability test was displayed as an index with Comparative Example 1 as 100 by sensory evaluation of the driver. The larger the value, the better the ride comfort.

  As a result of the test, it was confirmed that the tires of the examples can exhibit excellent ride comfort while maintaining high handling stability and wear resistance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2S Tread surface 3 Shoulder main groove 4 Center main groove 5c Center rib 5m Middle rib 9 Middle sipe 9w Sipe wall surface 10 Middle lug groove 11, 13 Weight part 12 Chamfer part 15 Slot 20 Center sipe Ma, Mb Rib side edge P Corner part Te Grounding end

Claims (8)

Pneumatic with a middle rib arranged in the tread between the shoulder main groove extending in the tire circumferential direction at the most ground contact end side and the center main groove extending in the tire circumferential direction on the inner side in the tire axial direction of the shoulder main groove Tire,
The middle rib is
A plurality of middle sipes that incline from the rib side edge on one side in the tire axial direction toward the rib side edge on the other side and the other end is interrupted in the middle rib;
A plurality of middle lug grooves extending from the other rib side edge to the one rib side edge and having one end cut off in the middle rib;
The middle sipe and the middle lug groove have the same inclination direction and are alternately arranged in the tire circumferential direction, and the middle sipe and the middle lug groove have a weight portion that overlaps in the tire circumferential direction,
The pneumatic tire according to claim 1, wherein the middle sipe includes a chamfered portion at a corner portion where one sipe wall surface and the tread surface of the middle sipe intersect.   The pneumatic tire according to claim 1, wherein the middle sipe and the middle lug groove are parallel to each other, and an angle θ with respect to the tire circumferential direction is in a range of 35 to 65 degrees.   The length of the chamfered portion in the tire axial direction is 50% or more of the length of the middle sipe in the tire axial direction, and the chamfered portion and the middle lug groove have a weight portion that overlaps in the tire circumferential direction. The pneumatic tire according to 1 or 2.   The pneumatic tire according to any one of claims 1 to 3, wherein the middle rib includes a slot between the middle sipes and at a rib side edge on one side in a tire axial direction.   The rib side edge on one side in the tire axial direction faces a center main groove, and the rib side edge on the other side in the tire axial direction faces a shoulder main groove. Pneumatic tires. A center sipe that includes a center rib between the center main grooves and that passes through the center rib in the tire axial direction is disposed on the center rib.
The pneumatic tire according to claim 5, wherein a distance in a tire circumferential direction between both end portions of the center sipe and one end portion of the middle sipe is 1.5 mm or less.   The air according to any one of claims 1 to 6, wherein the chamfered portion has a chamfered width of 1.0 to 2.0 mm and a chamfered depth of 1.0 to 2.0 mm. Enter tire. The length of the middle lug groove in the tire axial direction is in the range of 33% to 50% of the tire rib axial width of the middle rib, and the length of the middle sipe in the tire axial direction is 50% to 80% of the middle rib tire axial width. The pneumatic tire according to claim 1, wherein the pneumatic tire is in a range.

Images