JP5185989B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that has improved noise performance and steering stability while minimizing a decrease in drainage or maintaining drainage.

  For example, as shown in FIG. 8, an inner circumferential main groove b extending on the tire equatorial plane Co or on both sides of the tire equatorial plane Co, and an outer circumferential main groove c arranged on both outer sides thereof, as shown in FIG. , C is widely used as a pneumatic tire in which a middle rib d is formed between the inner circumferential main groove b and the outer circumferential main groove c. The middle rib d is usually formed with a circumferential narrow groove e extending linearly in the circumferential direction in order to maintain the circumferential rigidity and ensure straight running stability while improving drainage (for example, a patent) Reference 1).

  However, when such a linear circumferential narrow groove e is formed, there is a problem in that air column resonance occurs in the circumferential narrow groove e and noise performance is degraded. Further, although the circumferential rigidity of the middle rib d is maintained, the lateral rigidity is reduced, and the steering stability tends to be lowered.

JP 2001-206020 A

  Therefore, the present invention forms a circumferential narrow groove provided in the middle rib by a plurality of narrow groove pieces, and wide overlaps by juxtaposing the ends of the narrow groove pieces adjacent in the circumferential direction inside and outside the tire axial direction. Air with improved noise performance and steering stability while keeping the drainage performance to a minimum or maintaining the drainage performance based on connecting the narrow groove pieces in the circumferential direction via the section The purpose is to provide tires.

In order to solve the above-mentioned problems, the invention of claim 1 of the present application is characterized in that a tread portion has a circumferential main groove extending on the tire equatorial plane or on both sides of the tire equatorial plane, and both outer sides of the circumferential main groove in this A pneumatic tire in which a middle rib is formed between the inner circumferential main groove and the outer circumferential main groove by providing an outer circumferential main groove disposed on the outer circumferential main groove,
In the middle rib, by providing a circumferential narrow groove extending in the tire circumferential direction, the middle rib is divided into inner and outer rib portions in the tire axial direction,
The circumferential narrow groove has a linear shape or an arc shape extending in the circumferential direction at an angle θ of 0 to 25 ° with respect to the tire circumferential direction, and a plurality of narrow grooves having a groove width smaller than the inner and outer circumferential main grooves. Consisting of groove pieces,
And each fine Mizohen, the end portions of the narrow groove pieces adjacent in the circumferential direction, are connected in the circumferential direction via a wide overlap of width than the thin groove piece by being juxtaposed in the tire axial direction and out ,
The middle rib includes a middle inclined groove that is interrupted in the outer rib portion beyond the circumferential main groove from the inner circumferential main groove, and a tire shaft of the middle inclined groove having a groove width smaller than the middle inclined groove. It is characterized by comprising a middle inclined narrow groove extending from the outer end in the direction to the outer circumferential main groove .

  Further, in the invention of claim 2, the narrow groove piece has an arc shape in which the angle θ gradually increases toward one side in the circumferential direction, and the end of the narrow groove piece on one side in the circumferential direction is the overlapping portion. The thin groove pieces adjacent in the circumferential direction are juxtaposed on the outer side in the tire axial direction with respect to the end portion on the other circumferential side.

  In the invention of claim 3, the overlapping portion is characterized in that the overlapping width in the tire axial direction is 1.1 to 2.5 times the groove width of the narrow groove piece.

  According to a fourth aspect of the present invention, the overlap width in the tire axial direction of the overlap portion increases toward one side in the circumferential direction.

  Further, in the invention of claim 5, the middle rib performs middle siping extending from the outer end in the tire axial direction to the outer circumferential main groove among the ends of the narrow groove pieces juxtaposed inside and outside in the tire axial direction. It is characterized by comprising.

According to a sixth aspect of the present invention, the outer rib portion includes a middle slot that inclines in the same direction as the middle siping from the outer circumferential main groove and is interrupted in the outer rib portion. It is characterized by.

According to a seventh aspect of the present invention, the rib portion includes a minimum width portion where the rib width in the tire axial direction is minimum and a maximum width portion where the rib width is maximum, and a ratio between the minimum width Wi1 and the maximum width Wi2. Wi1 / Wi2 is set to 0.65 to 0.90 .

In the invention according to claim 8, the end of the narrow groove piece on the outer side in the tire axial direction among the ends of the narrow groove pieces juxtaposed inside and outside in the tire axial direction is the inner side in the tire axial direction at a position beyond the overlapping portion. It is characterized by comprising a branch portion extending away from the narrow groove piece .

The invention of claim 8, the rib portion before Kigai is characterized by having an acute angle portion sandwiched between said branch portion and said axially inward of the thin groove piece.

  In the present invention, as described above, the circumferential narrow groove provided in the middle rib is formed by connecting a plurality of narrow groove pieces in the circumferential direction. At this time, the end portions of the narrow groove pieces adjacent in the circumferential direction are juxtaposed inside and outside in the tire axial direction, so that each narrow groove piece is connected in the circumferential direction via an overlapping portion wider than the narrow groove piece. Is done. Thus, since the said circumferential direction narrow groove continues in the circumferential direction, drainage property can be maintained highly.

  Further, since the ends of the narrow groove pieces adjacent in the circumferential direction are connected in parallel in the tire axial direction, the groove center of the circumferential narrow groove is bent in a substantially Z shape at the overlapping portion. Therefore, the air passing through the circumferential narrow groove is stagnated at the bent portion. Therefore, the occurrence of air column resonance can be prevented and noise performance can be improved.

  Further, since the circumferential narrow groove is bent in a substantially Z shape, a minimum width portion where the rib width in the tire axial direction is minimum and a maximum width portion where the maximum width is maximum are formed in the inner rib portion. Therefore, the lateral rigidity of the inner rib portion can be increased as compared with the case where the rib width is constant, and the steering stability can be improved.

It is an expanded view of the tread pattern which shows one Example of the pneumatic tire of this invention. It is a top view which expands and shows a middle rib with the circumferential direction fine groove. It is a top view which exaggerates the circumferential direction fine groove. It is a top view which expands and shows an overlapping part further. It is sectional drawing which shows the inner and outer circumferential main groove, a thin groove piece, a middle sloping groove, and a middle sloping narrow groove. It is a top view which shows the other example of the circumferential direction fine groove. It is a top view which shows the other example of the circumferential direction fine groove. It is a top view which shows the conventional circumferential direction fine groove.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 of the present embodiment includes a pair of circumferential main grooves 3 </ b> A extending on both sides of the tire equatorial plane Co in the tread portion 2 and a pair of outer circumferential main grooves 3 </ b> A. An outer circumferential main groove 3B, whereby the tread portion 2 includes a center rib 4C between the inner circumferential main grooves 3A and 3A, an inner circumferential main groove 3A, and an outer circumferential main groove 3B. The middle ribs 4M, 4M between the outer circumferential main grooves 3B and the shoulder ribs 4S on the outer side in the tire axial direction are divided into five ribs.

  The inner circumferential main groove 3A may be one circumferential main groove extending on the tire equatorial plane Co. In such a case, the tread portion 2 is connected to the inner circumferential main groove 3A. The ribs are divided into four ribs, middle ribs 4M and 4M between the outer circumferential main grooves 3B and shoulder ribs 4S outside the outer circumferential main grooves 3B.

  The inner and outer circumferential main grooves 3A and 3B are wide grooves having a groove width W3 of 5 mm or more, preferably 6 mm or more, as shown in FIG. It is formed as a straight groove extending linearly in the circumferential direction. The groove depth H3 is about the same as that of a conventional tire, and in the case of a passenger car tire, 6 to 10 mm is preferably employed. In this specification, the groove width is defined as a groove width perpendicular to the groove length direction on the tread surface.

  Next, the middle rib 4M is provided with a circumferential narrow groove 5 extending continuously in the tire circumferential direction for the purpose of improving drainage, thereby dividing the middle rib 4M into rib portions 4Mi, 4Mo inside and outside in the tire axial direction. doing.

  In the present invention, the circumferential narrow groove 5 sequentially connects a plurality of linear or arcuate narrow groove pieces 6 extending in the circumferential direction at an angle θ of 0 to 25 ° with respect to the tire circumferential direction. It is formed by doing. The narrow groove piece 6 includes a composite shape having a linear portion and an arc-shaped portion. The formation position of the circumferential narrow groove 5 is preferably formed in a region range 0.2 to 0.6 times the rib width WR of the middle rib 4M in the tire axial direction from the side edge on the tire equatorial plane side. The rib width WR is preferably in the range of 0.1 to 0.35 times the tread ground contact width TW.

  As shown in an enlarged view in FIG. 2, the narrow groove piece 6 has an arc shape having an arc center on the outer side in the tire axial direction than the narrow groove piece 6 in this example, and the angle θ is on one side in the circumferential direction. Increasing gradually. That is, as exaggeratedly shown in FIG. 3, the inner edge 6e in the tire axial direction of the narrow groove piece 6 is on one side in the circumferential direction with respect to the circumferential reference line X passing through the other circumferential end point P of the inner edge 6e. The distance ΔL increases as the distance increases, and the rate of increase of the distance ΔL increases as the distance increases toward one side in the circumferential direction. In addition, when making circular arc shape, various curves, such as an ellipse and a parabola, can be employ | adopted suitably, for example, the curvature radius R increases sequentially toward the circumferential direction one side other than a single circular arc with constant curvature radius R. In this example, the case where the thin groove piece 6 is formed by a single arc having a curvature radius R of 100 to 1500 mm is shown. However, the narrow groove piece 6 is not restricted to an arc shape, and may be a linear shape inclined at an angle θ larger than 0 ° as shown in FIG. Also in this case, the inner edge 6e increases the separation amount ΔL as it goes to the one side in the circumferential direction with respect to the reference line X.

  Further, as shown in an enlarged view in FIG. 4, each narrow groove piece 6 has end portions 6 </ b> E and 6 </ b> E of the narrow groove pieces 6 adjacent in the circumferential direction juxtaposed inside and outside in the tire axial direction. The pieces 6 are connected in the circumferential direction via an overlapping portion 10 having a width W10 wider than the groove width W6. The groove width W6 of the narrow groove piece 6 is smaller than the groove width W3 of the inner and outer circumferential main grooves 3A and 3B, particularly from the viewpoint of drainage and tread rigidity, 1.0 mm or more and less than 5.0 mm. More preferably, the range of 1.5 to 4.0 mm is desirable. The groove depth H6 of the narrow groove piece 6 is not more than the groove depth H3 of the inner and outer circumferential main grooves 3A and 3B, preferably in the range of 0.3 to 0.9 times H3. In the overlapping portion 10, the end 6E1 on one side in the circumferential direction of the narrow groove piece 6 is juxtaposed on the outer side in the tire axial direction with respect to the end 6E2 on the other circumferential side of the narrow groove piece 6 adjacent in the circumferential direction. doing.

  Since the circumferential narrow groove 5 formed in this way continuously extends in the circumferential direction, the drainage can be maintained. In addition, since the ends 6E and 6E of the narrow groove pieces 6 adjacent in the circumferential direction are connected in parallel in the tire axial direction, the circumferential narrow groove 5 is substantially Z-shaped in the overlapping portion 10 which is a connecting portion. Bend to. Therefore, the air passing through the circumferential narrow groove 5 is stagnated at the bent portion (overlapping portion 10), and the occurrence of air column resonance is prevented. Further, the increase in the width W10 in the overlapping portion 10 can also contribute to disturbing the air flow and suppressing air column resonance. As a result, noise caused by the circumferential narrow groove 5 can be suppressed.

  Further, the circumferential narrow groove 5 bends in a substantially Z shape, that is, the distance ΔL of the inner edge 6e with respect to the circumferential reference line X increases or decreases in the circumferential direction. A minimum width portion 7 where the rib width in the tire axial direction is minimum and a maximum width portion 8 where the rib width is maximum are formed. Therefore, the lateral rigidity of the inner rib portion 4Mi can be increased as compared with the case where the rib width is constant, and the steering stability can be improved. Further, since the lateral rigidity of the inner rib portion 4Mi is increased, it is possible to exert an effect of preventing the inner rib portion 4Mi from being deformed and being crushed in the circumferential narrow groove 5 at the time of ground contact, thereby reducing drainage. The ratio Wi1 / Wi2 between the minimum width Wi1 in the minimum width portion 7 and the maximum width Wi2 in the maximum width portion 8 is preferably in the range of 0.65 to 0.9. Is not demonstrated. On the other hand, if the ratio Wi1 / Wi2 is less than 0.65, the drainage of the circumferential narrow groove 5 may be adversely affected.

  In each of the circumferential narrow grooves 5, at least one overlapping portion 10 is disposed in the ground contact surface where the tire contacts the road surface. That is, the distance Q between the overlapping portions 10 and 10 in the tire circumferential direction is smaller than 1.0 times the circumferential length of the ground contact surface. The lower limit of the pitch distance Q is preferably 0.25 times or more the circumferential length of the ground contact surface from the viewpoint of securing rigidity.

  As shown in FIG. 4, the width W10 of the overlapping portion 10 in the tire axial direction (overlapping width W10) is equal to 1 of the groove width W6 of the narrow groove piece 6 in order to disturb airflow and suppress air column resonance. The upper limit is preferably no less than 2.5 times the groove width W6 from the viewpoint of ensuring rigidity. In this example, the overlap width W10 increases toward one side in the circumferential direction, that is, toward the side where the angle θ increases. Thus, when the overlap width W10 is not constant, the maximum width W10max is set to a range of 1.8 to 2.5 times the groove width W6.

  In this example, the end 6E1 of the narrow groove piece 6 on the outer side in the tire axial direction out of the ends 6E1 and 6E2 of the narrow groove pieces 6 juxtaposed inside and outside in the tire axial direction is a position beyond the overlapping portion 10. A branching portion 9 extending away from the narrow groove piece 6 on the inner side in the tire axial direction is provided. Thereby, an acute angle portion 11 sandwiched between the branch portion 9 and the narrow groove piece 6 on the inner side in the tire axial direction is formed in the outer rib portion 4Mo. The formation of the branch portion 9 or the formation of the acute angle portion 11 is effective for stagnating and disturbing the air passing through the circumferential narrow groove 5 and can further improve the noise performance. The circumferential protruding distance L of the branching portion 9 from the overlapping portion 10 is preferably 0.5 times or more of the groove width W6 of the narrow groove piece 6 in order to improve the noise performance. From the viewpoint of ensuring, 5.0 times or less of the groove width W6 is preferable.

  Since the acute angle portion 11 may become a starting point of uneven wear, it is preferable to chamfer the tip of the acute angle portion 11 with a chamfered surface 11S.

Further, in this example, in order to improve the wet performance, as shown in FIG. 2, the middle rib 4M is cut off in the outer rib portion 4Mo from the inner circumferential main groove 3A beyond the circumferential narrow groove 5 in the outer rib portion 4Mo. A middle inclined groove 12 and a middle inclined narrow groove 13 extending from the outer end in the tire axial direction of the middle inclined groove 12 to the outer circumferential main groove 3B are provided. The middle inclined groove 12 and the middle inclined narrow groove 13 are not particularly restricted, but the groove depths H12 and H13 are preferably smaller than the groove depth H6 of the narrow groove piece 6 as shown in FIG. Is preferably 0.5 to 0.9 times the groove depth H6 in order to improve wet performance while ensuring rigidity. The middle inclined groove 12 and the middle inclined narrow groove 13 are connected in series, and are inclined linearly or arcuately at an angle α of 20 to 60 ° with respect to the tire circumferential direction. Further, in this example, the groove width W12 of the middle inclined groove 12 is larger than the groove width W6 of the narrow groove piece 6 and smaller than the groove width W3 of the inner circumferential main groove 3A. The groove width W13 of the middle inclined narrow groove 13 is smaller than the groove width W6 of the narrow groove piece 6, and in this example, the groove width W13 is formed as a siping in which the groove width becomes substantially zero (0) at the time of grounding.

  The middle rib 4M has an end 6E1 of the narrow groove piece 6 on the outer side in the tire axial direction among the ends 6E1 and 6E2 of the narrow groove pieces 6 juxtaposed inside and outside in the tire axial direction. A middle siping 17 extending from the end portion to the outer circumferential main groove 3B is formed. The middle siping 17 is formed substantially parallel to the middle inclined narrow groove 13, and the groove depth is formed substantially equal to the middle inclined narrow groove 13.

  Further, a middle slot 18 is formed in the outer rib portion 4Mo of the middle rib 4M so as to incline in the same direction as the middle siping 17 from the outer circumferential main groove 3B and to be interrupted in the outer rib portion 4Mo. Is done. In this example, the middle slot 18 is formed at an intermediate position between the middle siping 17 and the middle inclined narrow groove 13.

  The narrow groove piece 6 may be a linear groove parallel to the tire circumferential direction (θ = 0 °) as shown in FIG. In such a case, the entire narrow groove pieces 6 adjacent in the circumferential direction are alternately arranged inside and outside in the tire axial direction, and end portions thereof are juxtaposed inside and outside in the tire axial direction. Thereby, each narrow groove piece 6 can be connected to the circumferential direction via the overlapping part 10. Also in this case, the noise performance can be improved because the air passing through the circumferential narrow groove 5 can be stagnated and disturbed at the bent portion (overlapping portion 10) as in the circumferential narrow groove 5 described above. Further, the formation of the minimum width portion 7 and the maximum width portion 8 increases the lateral rigidity, which can contribute to the improvement of steering stability.

  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 tire for a passenger car (tire size 195 / 65R15) having the tread pattern of FIG. 1 was prototyped based on the specifications in Table 1, and the noise performance, wet performance, and steering stability of the sample tire were tested. Each tire has substantially the same specifications except for the circumferential narrow groove. The common specifications are as follows.
Inner and outer zigzag main grooves ・ Groove width --7.5 mm
・ Groove depth ---- 8.2mm
Circumferential narrow groove (or narrow groove piece)
・ Groove width ---- 2.0mm
・ Groove depth --- 5.7mm
Middle inclined groove ・ Groove width −−− 3.0mm
・ Groove depth ---- 3.8mm
Middle inclined narrow groove ・ Groove width −−− 0.8mm
・ Groove depth ---- 3.8mm
Middle slot ・ Groove width ---- (maximum width 3.5, minimum width 2.0mm)
・ Groove depth --- (Maximum depth 6.7mm, Minimum depth 3.8mm)
Middle siping ・ Groove width −−− 0.8mm
・ Groove depth ---- 3.8mm
Middle rib rib width WR --- 0.16 × TW
Tread grounding width TW --- 152mm
Middle rib distance from tire equator side edge --- 0.3 to 0.5 x WR
The distance Q between the overlapping portions 10 and 10 in the tire circumferential direction is 0.5 times the circumferential length of the contact surface.

(1) Noise performance Each sample tire is mounted on all wheels of a vehicle (2000cc domestic FR car) under the conditions of rim (6 x 15 JJ) and internal pressure (200 kPa). The in-vehicle noise when traveling on the (asphalt rough road) at a speed of 60 km / h was displayed as an index with Comparative Example 1 as 100 by sensory evaluation of the driver. The larger the value, the better.

(2) Wet performance Using the test vehicle described above, the vehicle was allowed to enter the course of a 100 m radius asphalt road surface with a water pool of 10 mm in depth and 20 m in length while increasing the speed stepwise. The lateral G) was measured, and the average lateral G of the front wheels at a speed of 50 to 80 km / h was calculated. The results were expressed as an index with Comparative Example 1 as 100. The larger the value, the better.

(3) Steering stability Using the above test vehicle, run on a dry asphalt road test course, and compare straightness, turning stability, vehicle behavior during braking, etc. by comparing the driver's sensory evaluation. Example 1 is represented by an index of 100. The larger the value, the better.

As shown in the table, it can be confirmed that the tires of the examples can improve the noise performance and the steering stability while minimizing the deterioration of the drainage property or maintaining the drainage property.

2 Circumferential main groove 3B in the tread portion 3A Outer circumferential main groove 4M Middle rib 4Mi, 4Mo Inner and outer rib portion 5 Circumferential narrow groove 6 Fine groove piece 6E End portion 7 Minimum width portion 8 Maximum width portion 9 Branch portion 10 Overlapping part 11 Sharp corner part 12 Middle inclined groove 13 Middle inclined narrow groove 17 Middle siping 18 Middle slot Co Tire equatorial plane

Claims (8)

By providing an inner circumferential main groove extending on the tire equatorial plane or both sides of the tire equatorial plane, and an outer circumferential main groove arranged on both outer sides of the inner circumferential main groove in the tread portion, A pneumatic tire in which a middle rib is formed between the inner circumferential main groove and the outer circumferential main groove,
In the middle rib, by providing a circumferential narrow groove extending in the tire circumferential direction, the middle rib is divided into inner and outer rib portions in the tire axial direction,
The circumferential narrow groove has a linear shape or an arc shape extending in the circumferential direction at an angle θ of 0 to 25 ° with respect to the tire circumferential direction, and a plurality of narrow grooves having a groove width smaller than the inner and outer circumferential main grooves. Consisting of groove pieces,
And each fine Mizohen, the end portions of the narrow groove pieces adjacent in the circumferential direction, are connected in the circumferential direction via a wide overlap of width than the thin groove piece by being juxtaposed in the tire axial direction and out ,
The middle rib includes a middle inclined groove that is interrupted in the outer rib portion beyond the circumferential main groove from the inner circumferential main groove, and a tire shaft of the middle inclined groove having a groove width smaller than the middle inclined groove. A pneumatic tire characterized by comprising a middle inclined narrow groove extending from the outer end in the direction to the outer circumferential main groove .   The narrow groove piece has an arc shape in which the angle θ gradually increases toward one side in the circumferential direction, and an end portion on one circumferential side of the narrow groove piece in the overlapping portion is a narrow groove adjacent in the circumferential direction. 2. The pneumatic tire according to claim 1, wherein the pneumatic tire is juxtaposed on the outer side in the tire axial direction with respect to the end portion on the other circumferential side of the piece.   The pneumatic tire according to claim 1 or 2, wherein the overlapping portion has an overlapping width in a tire axial direction of 1.1 to 2.5 times a groove width of the narrow groove piece.   The pneumatic tire according to claim 2 or 3, wherein an overlap width in the tire axial direction of the overlap portion increases toward one side in the circumferential direction.   The middle rib includes middle siping extending from an end portion on the outer side in the tire axial direction to an outer circumferential main groove among end portions of the narrow groove pieces juxtaposed inside and outside in the tire axial direction. Item 5. The pneumatic tire according to any one of Items 1 to 4. Rib portion outside the can according to claim 5 Symbol, characterized in that it comprises the outer circumferential main from said groove middle sipes and middle slot interruption in the rib portion of and the outer extending inclined in the same direction Pneumatic tire listed. The inner rib portion has a minimum width portion where the rib width in the tire axial direction is minimum and a maximum width portion where the rib width is maximum, and the ratio Wi1 / Wi2 between the minimum width Wi1 and the maximum width Wi2 is 0.65. The pneumatic tire according to claim 1, wherein the pneumatic tire is 0.90 . Of the ends of the narrow groove pieces juxtaposed inside and outside in the tire axial direction, the end of the narrow groove piece on the outer side in the tire axial direction is separated from the narrow groove piece on the inner side in the tire axial direction at a position beyond the overlapping portion. together comprises a branch portion extending rib portion of the outside, any claim 1-7, characterized in that it has a sharp portion that is sandwiched between said branch portion and said axially inward of the thin groove piece The pneumatic tire according to Crab.

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