JP6125142B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which noise caused by a groove formed in a tread of a tire is reduced, and more particularly to a pneumatic tire for a passenger car and a small truck.

  With the recent quietness of vehicles, the proportion of tire noise in automobile noise has become relatively large, so reducing tire noise has become a major issue. Above all, tire noise around 1000 Hz, which is easily heard by humans, is a major factor of noise outside the vehicle, and an immediate countermeasure is desired from the viewpoint of environmental problems.

By the way, tire noise belonging to a frequency band of about 800 to 1400 Hz is generated by so-called air column resonance, in which the air column defined by the circumferential groove formed in the tread and the road surface resonates within the tire contact surface. It is generally known.
That is, when a tire having a circumferential groove is in contact with the ground, a pipe having the same length as the ground contact length is formed between the groove wall of the circumferential groove and the ground contact surface. As a result of repeated air compression and release, noise called air column resonance is generated. The frequency f ₀ of the air column resonance sound has a sound velocity v, a tube length, that is, a circumferential groove length L, and
f ₀ = v / 2L
It is a constant frequency represented by

  In order to suppress such air column resonance, in Patent Document 1, the tread is provided with two or more circumferential grooves continuous linearly or zigzag in the circumferential direction, and at least one circumferential groove is provided. In this arrangement, a plurality of sub-grooves having one end opened in the circumferential groove and the other end ending in the land portion are formed, and each sub-groove is always completely included in the ground plane. A tread pattern as an aspect has been proposed.

In this way, by providing the sub-groove branched from the circumferential groove, the frequency of the air column resonance can be dispersed. When the frequency is dispersed, it feels that the sound on the ear has softened and quieted, and this effect is called white noise.
The frequency dispersion effect varies depending on the shape of the sub-groove. Specifically, if the length of the sub-groove is l and the speed of sound is v, the frequency f of the newly generated sound that is dispersed is
f = (2n−1) × v / 4l
n: vibration order (n = 1, 3, 5...)
It is known that

  Further, as another conventional technique for suppressing air column resonance, Patent Document 2 discloses that at least two circumferential grooves are provided in a tire tread, and these circumferential grooves are centered at least at the center of the tread. There has been proposed a pneumatic tire in which a rib is defined and a V-shaped auxiliary groove having one end opened to the circumferential groove is provided in the central rib.

International Publication No. 2004/1037737 Pamphlet JP 2009-137712 A

The pneumatic tire described in Patent Document 2 described above is a so-called rotation direction designation tire in which the mounting direction to the vehicle is designated, although the steering stability and quietness are achieved at a high level. In a tire with a specified rotation direction, rotation of the mounting position and recombination of the mounting direction are difficult, and the problem is that the versatility is low and the tire life is short compared to a tire in which the rotation direction is not specified.
Therefore, an object of the present invention is to provide a pneumatic tire that achieves steering stability and quietness at a high level and that does not specify a rotational direction.

The gist of the present invention is as follows.
(1) A pair of central circumferential grooves extending in the tire circumferential direction and a pair of lateral circumferential grooves having a groove width smaller than the groove width of the central circumferential groove are formed on the tread of the tire, In the pneumatic tire in which the intermediate rib is defined by the circumferential groove and the lateral circumferential groove,
A first inclined groove portion that opens in the lateral circumferential groove and extends in an inclined manner in the tire circumferential direction; and one end connected to an end portion of the first inclined groove portion; extends bent at an acute angle to the portion, the other end and a second inclined groove portions terminating in said intermediate rib, the minor groove of V-shaped bent at an acute angle is formed,
The secondary grooves are arranged point-symmetrically with respect to a point on the tire equator plane, and the secondary grooves on both sides arranged symmetrically are arranged with a predetermined phase difference in the tire circumferential direction,
The groove width of the second inclined groove portion gradually increases from an end portion on the opposite side to the portion connected to the first inclined groove portion toward an acute angle bent portion between the first inclined groove portion and the second inclined groove portion. And at least one side wall of the both side walls defining the second inclined groove portion has a chamfered portion inclined with respect to the tread surface.
The intermediate rib is formed with a sipe that is connected to the at least one side wall, and the intermediate rib is formed between a portion that is connected to the sipe and a portion on the terminal side of the at least one side wall of the second inclined groove portion. A pneumatic tire characterized by acute angles.

( 3 ) The second inclined groove portion of the sub-groove has a chamfered portion that is inclined with respect to the tread surface on at least one of the side walls defining the second inclined groove portion. The pneumatic tire according to (1) or (2) above.

It is an expanded view of the tread pattern of the pneumatic tire which concerns on reference embodiment of this invention. (A) is an expanded view of the tread pattern of the pneumatic tire which concerns on one Embodiment of this invention, (b) is an enlarged view of a subgroove, (c) is the AA line in FIG. 2 (a). (D) is sectional drawing which follows the BB line in Fig.2 (a). It is an expanded view of the tread pattern of the conventional pneumatic tire.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
Note that the internal reinforcement structure of the tire is the same as that of a general radial tire, and a description thereof will be omitted.

FIG. 1 is a development view of a tread pattern of a pneumatic tire according to a reference embodiment of the present invention.
A pair of central circumferential grooves 1 extending in the tire circumferential direction across the tire equatorial plane CL and a pair of lateral circumferential grooves 2 on the outer side in the tire width direction of the central circumferential groove 1 are formed on the tread of the tire. Yes. A central rib 3 continuous in the tire circumferential direction is defined by the pair of central circumferential grooves 1, and an intermediate rib 4 continuous in the tire circumferential direction is defined by the central circumferential groove 1 and the lateral circumferential grooves 2. Side ribs 5 that are continuous in the tire circumferential direction are defined by the circumferential groove 2 and the tread end TE.
A sub groove 6 is formed in the intermediate rib 4. The sub-groove 6 opens to the lateral circumferential groove 2 and extends from the first inclined groove portion 6a to the first inclined groove portion 6a from the end portion of the first inclined groove portion 6a. And a second inclined groove portion 6b that bends and extends at an acute angle. The first inclined groove portion 6a is inclined at an angle of 30 ° to 80 ° with respect to the tire circumferential direction, and the second inclined groove portion 6b is inclined at an angle of 0 ° to 45 ° with respect to the tire circumferential direction. doing.
The sub-grooves 6 are arranged point-symmetrically with respect to a point on the tire equatorial plane CL, and are arranged with a predetermined phase difference d in the tire circumferential direction. The optimum value of the phase difference d is appropriately designed in consideration of other grooves, but in the tread pattern of FIGS. 1 and 2, the phase difference d of the first inclined groove portion 6a is 10% of the pitch of the sub-groove 6. It is preferable that it is a grade.

Hereinafter, effects of the pneumatic tire according to the reference embodiment of the present invention will be described.
By opening the auxiliary groove 6 in the lateral circumferential groove 2, the frequency of air column resonance generated in the lateral circumferential groove 2 can be dispersed as described above. Note that in order for the sub-groove 6 to function as a resonator, the entire sub-groove 6 needs to be grounded. However, since the sub-groove 6 is V-shaped and bent at an acute angle, the whole is grounded. Cheap.
Further, by arranging the left and right sub-grooves 6 (hereinafter also referred to as a pair of left and right sub-grooves 6) with a predetermined phase difference d in the tire circumferential direction with the tire equatorial plane CL interposed therebetween, Each of the first inclined groove portions 6a may not be grounded at the same time. Then, the pattern noise (pitch noise) resulting from the first inclined groove portion 6a whose inclination angle is close to the tire width direction can be suppressed.
In addition to quietness, the circumferential rigidity of the intermediate rib 4 can be made uniform by arranging the pair of left and right sub-grooves 6 with a predetermined phase difference d in the tire circumferential direction. If the pair of left and right sub-grooves 6 are aligned in the tire circumferential direction so that the first inclined groove portions 6a of the pair of left and right sub-grooves 6 are simultaneously grounded, that is, when the phase difference d = 0 is set, The circumferential rigidity of the intermediate rib 4 is greatly reduced, while the circumferential rigidity of the intermediate rib 4 at the portion where the first inclined groove portion 6a is not disposed is increased. Then, the circumferential rigidity of the intermediate rib 4 becomes non-uniform, leading to a decrease in steering stability. In addition, by not forming a groove | channel in the center rib 3, the circumferential direction rigidity of the center rib 3 can be ensured, and steering stability can be ensured. Further, if the secondary groove 6 is formed in the side rib 5, the steering stability is lowered and uneven wear may occur. Therefore, the secondary groove 6 needs to be formed in the intermediate rib 4.
In consideration of drainage, it is preferable to provide a large number of grooves having a certain length in the tread. Accordingly, by arranging the sub-groove 6 to be bent at an acute angle, a large number of grooves can be arranged while securing the rigidity of the intermediate rib 4 without dividing the intermediate rib 4. Furthermore, drainage can be further improved by connecting the sub-groove 6 to the lateral circumferential groove 2.
As described above, by dispersing the frequency of the air column resonance sound and reducing the pitch noise, quietness can be achieved, and good steering stability and drainage can be ensured.

In the reference embodiment , the second inclined groove portion 6b is connected to the end of the first inclined groove portion 6a, but is connected to the intermediate portion of the first inclined groove portion 6a, and the sub-groove 6 as a whole is V-shaped. Instead of a shape, it can be a T-shape.
The second inclined groove portion 6b has one end connected to the first inclined groove portion 6a and the other end terminated in the intermediate rib 4. However, a further groove portion is connected to the other end, and the sub groove 6 As a whole, it may be N-shaped instead of V-shaped.
Moreover, although the subgroove 6 showed the example opened to the side circumferential direction groove | channel 2, the subgroove 6 may open to the center circumferential direction groove | channel 1. FIG. Further, considering the dispersion effect of the air column resonance sound, it is preferable to provide the auxiliary grooves 6 for all the circumferential grooves as much as possible.
The central circumferential groove 1 and the lateral circumferential groove 2 extend linearly in the tire circumferential direction, but may extend in a zigzag shape in the tire circumferential direction.

Since the pneumatic tire according to the reference embodiment has a tread pattern in which the rotation direction is not specified, rotation of the mounting position (front wheel and rear wheel) and recombination of the mounting direction (vehicle inner side and vehicle outer side) are possible, and versatility is achieved. In addition, it is preferable because a long life can be achieved.

FIG. 2A is a development view of a tread pattern of a pneumatic tire according to an embodiment of the present invention, FIG. 2B is an enlarged view of a secondary groove, and FIG. 2C is FIG. FIG. 2D is a cross-sectional view taken along the line BB in FIG. 2A. In the tread pattern of the pneumatic tire according to the embodiment , the same components as those of the tread pattern of the pneumatic tire according to the embodiment are denoted by the same reference numerals, and the description thereof is omitted.
Although the groove width of the first inclined groove portion 6a is substantially constant, the groove width of the second inclined groove portion 6b gradually increases from the portion 6be terminating in the intermediate rib 4 toward the acute angle bent portion 6K. . The second inclined groove portion 6b has a tapered chamfered portion 6m inclined with respect to the tread surface on the side wall on the side circumferential groove 2 side among both side walls defining the second inclined groove portion 6b. Yes. As shown in FIG. 2C, the chamfered portion 6m has a width W6m and a depth D6m.
Lug grooves 7 extending in the tire width direction are formed in the side ribs 5. One end of the lug groove 7 opens to the tread end TE, and the other end 7 e ends in the side rib 5. The lug groove 7 has a tapered chamfered portion 7m that is inclined with respect to the tread surface on one side surface from the end portion 7e. As shown in FIG. 2 (d), the chamfered portion 7m has a width W7m and a depth D7m.

The groove width Wb of the second inclined groove portion 6b indicates the width of the opening including the chamfered portion 6m when the second inclined groove portion 6b has the chamfered portion 6m.
The groove width Wb of the second inclined groove portion 6b in the acute angle bent portion 6K is a line segment passing through the center of the groove width of the second inclined groove portion 6b including the chamfered portion 6m in the second inclined groove portion 6b ( 2B), of the intersections Ki and Ko between the groove wall of the second inclined groove portion 6b and the groove wall of the first inclined groove portion 6a of the acute angle bent portion 6K, The distance from the intersection Ki to the point where the perpendicular to the line segment intersects the groove wall of the second inclined groove portion 6b is indicated.

In the pneumatic tire according to the embodiment , a plurality of sipes are formed over the entire tread surface. Specifically, the central rib 3 is formed with a first sipe s1 that extends in an inclined manner in the tire circumferential direction. The intermediate rib 4 is connected to the central circumferential groove 1 and the second inclined groove portion 6b, and a second sipe s2 parallel to the first inclined groove portion 6a is formed, and the second inclined groove portion 6b and the side periphery are formed. A third sipe s3 that connects the directional groove 2 and is parallel to the first inclined groove portion 6a is formed. The side rib 5 is connected to the side circumferential groove 2 and the lug groove 7, and a fourth sipe s 4 is formed parallel to the lug groove 7. The side rib 5 opens at the tread end TE and terminates in the side rib 5. A fifth sipe s5 parallel to the lug groove 7 is formed. These sipes are closed when grounded.

Hereinafter, effects of the pneumatic tire according to the embodiment of the present invention will be described.
As described above, by providing the V-shaped sub-groove 6 bent at an acute angle, it becomes possible to reduce the air column resonance generated by the lateral circumferential groove 2, but the sub-groove 6, in particular, There is a problem that stone biting occurs in the acute angle bent portion 6K and the second inclined groove portion 6b. The reason why stone biting occurs in the acute angle bent portion 6K is that the land portion near the intersection Ki has low rigidity, and the reason why stone biting occurs in the second inclined groove portion 6b is that the second inclined groove portion 6b. This is due to the low rigidity of the land on both sides. The first inclined groove portion 6a is inclined in the tire width direction as compared with the second inclined groove portion 6b, and the groove inclined in the tire width direction is depressed and kicked out during rolling of the tire. As the groove opens and closes with the deformation, the stone in the groove is discharged, so that the problem of stone biting hardly occurs.
By widening the groove width Wb of the second inclined groove portion 6b in the acute angle bent portion 6K, the opening and closing of the second inclined groove portion 6b is promoted during tire rolling, and stone biting generated in the acute angle bent portion 6K is eliminated. Can do. Further, by providing the chamfered portion 6m in the second inclined groove portion 6b, it is possible to remove locally low rigidity and further improve the stone biting resistance.
Further, by providing the chamfered portion 6m in the second inclined groove portion 6b, the cross-sectional area of the sub-groove 6 is increased, so that the volume of the sub-groove 6 is increased and the frequency dispersion effect is increased. This will lead to a reduction in drainage and improve drainage. In addition, since the ground contact area of the tread is reduced by providing the chamfered portion 6m in the second inclined groove portion 6b, the steering stability is in a direction to be lowered, but the portion with low rigidity is removed and the area to be removed is reduced. It is considered that the effect on steering stability is small due to the small size.

In one embodiment , the chamfered portion 6m is formed on the side wall on the side circumferential groove 2 side, that is, the side wall on the side opposite to the tire equatorial plane CL, but the chamfered portion 6m is formed on the central circumferential groove 1 side. It may be formed on the side wall, that is, the side wall on the tire equatorial plane CL side, or may be formed on both side walls that define the second inclined groove portion 6b.
Moreover, although the groove bottom of the 2nd inclination groove part 6b was shown flat, the groove bottom may have a curvature radius.
In addition, as described above, the first inclined groove portion 6a is less liable to cause stone biting than the second inclined groove portion 6b. However, in order to further improve the stone biting resistance, the first inclined groove portion 6a is directed toward the acute angle bent portion 6K. Thus, the groove width of the first inclined groove portion 6a may be increased. Further, it is preferable to narrow the groove width of the first inclined groove portion 6a on the side circumferential groove 2 side because the rigidity of the land portions on both sides of the opening can be secured.

Examples of the present invention will be described below, but the present invention is not limited thereto.
Invention tires and conventional tires were prototyped and evaluated for steering stability, quietness, and stone biting resistance.
Invention Example Tire 1 (tire size: 195 / 65R15, tread width: 150 mm) has the tread pattern shown in FIG. 2 and the specifications shown in Table 1. In Table 1, the width W6m and the depth D6m of the chamfered portion 6m are measured values at a position of 10 mm along the groove wall from the intersection Ki, and the width W7m and the depth D7m of the chamfered portion 7m are grooves from the terminal end 7e. It is a measured value at a position of 5 mm along the wall. The groove width of the second inclined groove portion 6b refers to the groove width of the second inclined groove portion 6b from the intersection Ki to the end portion 6be up to 30 mm. The groove wall angle is an angle of the groove wall with respect to the normal of the tread surface. The phase difference d of the first inclined groove portion 6a is 6 mm.
The reference example tire 2 is the same as the example tire 1 except that the groove width of the auxiliary groove 6 is constant.
Invention Example Tire 3 is the same as Invention Example Tire 1 except that there is no chamfered portion 6m.
The conventional tire 2 is the same as the inventive tire 1 except that the phase difference d = 0.

Conventional tire 1 (tire size: 195 / 65R15, tread width: 150 mm) has the tread pattern shown in FIG. 3 and the specifications shown in Table 2.
As shown in FIG. 3, the conventional tire 1 has a pair of central circumferential grooves 11 extending in the tire circumferential direction with the tire equatorial plane CL sandwiched between the tire treads, and the tire width of the central circumferential groove 11. A pair of intermediate circumferential grooves 12 on the outer side in the direction are formed, and a pair of lateral circumferential grooves 13 on the outer side in the tire width direction of the intermediate circumferential grooves 12 are formed. A central rib 14 that is continuous in the tire circumferential direction is defined by a pair of central circumferential grooves 11, and a lateral rib 15 that is continuous in the tire circumferential direction is defined by intermediate circumferential grooves 12 and lateral circumferential grooves 13. .
A land portion between the central circumferential groove 11 and the intermediate circumferential groove 12 has a first inclined groove 16a that opens to the intermediate circumferential groove 12 and extends while being inclined with respect to the tire circumferential direction, and a central circumferential groove. 11 and the intermediate circumferential groove 12 are connected, and a second inclined groove 16b extending obliquely with respect to the tire circumferential direction is formed, and a block-like land portion is defined by these grooves.
The land portion between the lateral circumferential groove 13 and the tread end TE is formed with a lug groove 17 that connects the lateral circumferential groove 13 and the tread end TE and extends in the tire width direction. The block-like land is divided.
The land between the central circumferential groove 11 and the intermediate circumferential groove 12 is connected to the central circumferential groove 1 and the second inclined groove 16b, and a first sipe s1 parallel to the first inclined groove 16a. Is formed, connecting the second inclined groove portion 16b and the intermediate circumferential groove 12, and a second sipe s2 parallel to the first inclined groove portion 16a is formed. The side rib 15 is formed with a third sipe s3 that connects the intermediate circumferential groove 12 and the lateral circumferential groove 13 and is parallel to the lug groove 17. In the land portion between the lateral circumferential groove 13 and the tread end TE, a fourth sipe s4 that opens to the tread end TE, terminates in the land portion, and is parallel to the lug groove 17 is formed. The phase difference d of the second inclined groove 16b is 14 mm.

Each test tire was mounted on an applicable rim, filled with internal pressure (220 kPa), and then mounted on four wheels of a normal passenger car to give a load (equivalent to two passengers).
“Applicable rim” is an industrial standard that is valid for the region where tires are produced and used, and is defined by JATMA YEAR BOOK in Japan, ETRTO STANDARD MANUAL in Europe, TRA YEAR BOOK in the US, etc. .

(Maneuvering stability)
Wet handling stability was evaluated based on the feeling of a test driver when driving on a wet circuit course in various driving modes.
Dry handling stability was evaluated based on the feeling of a test driver when driving on a dry circuit course in various driving modes.
The results are shown as indexes with the evaluation of the conventional tire 1 as 100. The larger the index, the better the performance.

(Silence)
The quietness was evaluated based on the feeling of the test driver when driving in a smooth road in various driving modes.
The results are shown as indexes with the evaluation of the conventional tire 1 as 100. The larger the index, the better the performance.

(Stone chewing resistance)
The road surface covered with pebbles was measured, and the number of pebbles remaining in the tire grooves after running was measured.
The results are shown as indexes with the measured value of the conventional tire 1 as 100. The smaller the index, the better the performance.

From Table 3, it has been confirmed that the inventive tire 1 has the same or improved steering stability performance, quietness and stone biting resistance as compared with the conventional tires 1 and 2.
Since the reference example tire 2 has an increased groove volume, the hydroplaning resistance is improved, but the block rigidity is lowered, so that the wet steering stability is equivalent to that of the invention example tire 1. Since the block rigidity is lowered, the dry steering stability is deteriorated as compared with one tire of the invention. Since the groove volume is increased and the effect of the resonator is increased, the quietness is improved as compared with one tire of the invention. Since stones are likely to be clogged in the back of the first inclined groove portion, the stone biting resistance is deteriorated as compared with the invention example tire 1.
The inventive tire 3 has no chamfered portion and the groove volume is reduced, so that the wet steering stability is deteriorated as compared with the inventive tire 1. Since the block rigidity is increased, the dry handling stability is improved as compared with one tire of the invention. When the chamfered portion is eliminated and the groove volume is reduced, the effect of the resonator is reduced. Since the chamfered portion is eliminated and the stone discharging performance is reduced, the stone biting resistance is deteriorated as compared with the one of the inventive tires.
Since the conventional tire 2 has only a phase difference, the wet steering stability, the dry steering stability, and the stone biting resistance are the same as those of the invention example tire 1. Since it deviates from the optimum phase and the pattern noise is worsened, the quietness is worsened as compared with one tire of the invention example.

DESCRIPTION OF SYMBOLS 1 Central circumferential groove 2 Side circumferential groove 3 Central rib 4 Intermediate rib 5 Side rib 6 Sub groove 6a 1st inclination groove part 6b 2nd inclination groove part 6m Chamfering part 6K Acute angle bending part 7 Lug groove 7m Chamfering part 11 Central circumferential groove 12 Intermediate circumferential groove 13 Lateral circumferential groove 14 Central rib 15 Lateral rib 16a First inclined groove 16b Second inclined groove 17 Lug groove s1 sipe s2 sipe s3 sipe s4 sipe s5 sipe CL tire equatorial plane TE Tread edge

Claims (1)

A pair of central circumferential grooves extending in the tire circumferential direction and a pair of lateral circumferential grooves having a groove width smaller than the groove width of the central circumferential groove are formed in the tread of the tire, and the central circumferential groove In the pneumatic tire in which the intermediate rib is defined by the lateral circumferential groove,
A first inclined groove portion that opens in the lateral circumferential groove and extends in an inclined manner in the tire circumferential direction; and one end connected to an end portion of the first inclined groove portion; extends bent at an acute angle to the portion, the other end and a second inclined groove portions terminating in said intermediate rib, the minor groove of V-shaped bent at an acute angle is formed,
The secondary grooves are arranged point-symmetrically with respect to a point on the tire equator plane, and the secondary grooves on both sides arranged symmetrically are arranged with a predetermined phase difference in the tire circumferential direction,
The groove width of the second inclined groove portion gradually increases from an end portion on the opposite side to the portion connected to the first inclined groove portion toward an acute angle bent portion between the first inclined groove portion and the second inclined groove portion. And at least one side wall of the both side walls defining the second inclined groove portion has a chamfered portion inclined with respect to the tread surface.
The intermediate rib is formed with a sipe that is connected to the at least one side wall, and the intermediate rib is formed between a portion that is connected to the sipe and a portion on the terminal side of the at least one side wall of the second inclined groove portion. A pneumatic tire characterized by acute angles.

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