JP2008221977A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of high frequency noise by reducing air-column tube resonance sound generated from short circumferential grooves of a pneumatic tire wherein both ends of the short grooves end in land part rows. <P>SOLUTION: The plurality of short circumferential grooves 15 of which both ends end in a block 22B of a shoulder land part row 22 are formed in the shoulder land part row 22 sandwiched between an outside main groove 11 and a tread end TE of the pneumatic tire 1 and fine grooves 16 are provided in each short circumferential groove 15. The fine groove 16 is formed in a substantial tire width direction wherein an end opens to the short circumferential groove 15 and another end ends in the block 22B of the shoulder land part row 22. One ends of the fine grooves 16 are respectively opened at both ends of the short circumferential grooves 15 which generate the air-column tube resonance sound at high frequency and thus the grooves communicate with one another. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire provided with a circumferential short groove whose both ends terminate in a land portion row in a land portion row defined by a main groove extending in the tire circumferential direction of a tread portion. The present invention relates to a pneumatic tire in which air column resonance noise generated in a groove is reduced to reduce high-frequency noise during high-speed traveling or the like.

  In general, in a pneumatic tire, a tread pattern including various grooves, sipes, and the like is formed on an outer peripheral surface (tread surface) in contact with a road surface of a tread portion according to a required tire performance. As a typical example of this tread pattern, conventionally, a plurality of land portion rows are formed by a plurality of main grooves extending in the tire circumferential direction, and a plurality of lug grooves extending in the tire width direction are provided in a part of the land portion rows. A block pattern divided into blocks is known.

Although FIG. 3 is not described in patent documents, it is a top view which expands and shows an example of the tread pattern of such a conventional pneumatic tire, and shows the part of the tire circumferential direction typically. .
As shown in the figure, the pneumatic tire 90 includes four main grooves 10 and 11 extending in the tire circumferential direction (vertical direction in the figure), and five (five rows) land portion rows 20 partitioned by them. 21 and 22, and a plurality of lug grooves 12 and 13 extending in the tire width direction (left and right direction in the drawing) and extending in the tire width direction (left and right in the figure).

  The main grooves 10 and 11 are alternately arranged with parallel portions extending substantially parallel to the tire circumferential direction and inclined portions extending inclined with respect to the tire circumferential direction, and the positions of the parallel portions are along the tire circumferential direction. Thus, it is formed in a bent shape (hereinafter, such a shape is referred to as a crank shape) alternately arranged on both sides in the tire width direction.

  In this pneumatic tire 90, the central main groove 10 is arranged on both sides of the tire equatorial plane CL, and the outer main grooves 11 are arranged on both outer sides in the tire width direction. The center land portion row 20, the intermediate land portion row 21 on both outer sides in the tire width direction, and the shoulder land portion row 22 on the outermost side in the tire width direction (shoulder portion side) are formed. Further, a plurality of lug grooves 12 extending substantially incline in the tire width direction are formed in the intermediate land portion row 21 and partitioned into a plurality of blocks 21B arranged in the tire circumferential direction. Similarly, the shoulder land portion row A plurality of lug grooves 13 extending substantially curved in the tire width direction are formed in 22 and partitioned into a plurality of blocks 22B arranged in the tire circumferential direction.

  Further, in each of these blocks 21B and 22B, a plurality of sipes 19 extending in an inclined or curved manner in the substantially tire width direction or the circumferential direction are formed, and the tire circumferential direction is provided in each block 22B of the shoulder land portion row 22. One circumferential short groove 15 extending obliquely is arranged. The circumferential short groove 15 is a groove having a short length in the longitudinal direction (tire circumferential direction) that ends in the shoulder land portion row 22 (block 22B). It is provided in order to increase the edge component in the tire width direction while suppressing a decrease in rigidity of the shoulder land portion row 22 by not opening the shoulder land portion 22 or the like.

  Such a tread pattern of the pneumatic tire 90 has a high drainage performance and excellent steering stability performance, and is widely used in various pneumatic tires such as tires for passenger cars and heavy load tires such as trucks and buses. Yes. However, in the pneumatic tire 90 having such a tread pattern, a relatively loud sound is generated from the groove portions such as the main grooves 10 and 11 and the circumferential short groove 15 at the time of ground contact, and noise during running becomes a problem. Sometimes.

  This noise is mainly due to a resonance phenomenon in a tubular cavity (air column tube) in the groove formed between the groove 10, 11, 15 of the tread portion and the road surface when the groove is grounded. Since it is generated, it is called air column resonance sound, and it is generated when the air in the air column tube vibrates and resonates by external force due to rolling and grounding. Therefore, the resonance frequency of this air column resonance sound is almost determined by the length of the air column tube (the contact length of each groove) and the speed of sound, and the resonance sound of a specific frequency band increases depending on the shape of each groove. As such, it is recognized as noise inside or outside the vehicle. For example, the circumferential short groove 15 whose both ends terminate in the shoulder land portion row 22 has a shorter length of the air column tube than the main grooves 10 and 11, and therefore, when traveling at high speed (for example, 100 km / h or more), etc. In addition, there is a tendency for higher frequency noise to be generated. This is because, when the pneumatic tire 90 rolls at a high speed, the groove width of the circumferential short groove 15 suddenly changes due to an external force due to rolling and grounding, and its volume changes. Is generated when the air in the closed air column tube vibrates and resonates, and the sound pressure level increases particularly in the frequency band near about 4500 Hz. Therefore, in the conventional pneumatic tire 90, in addition to the relatively low frequency noise generated from the main grooves 10, 11 and the like, the generation of high frequency noise from the circumferential short groove 15 becomes a problem during traveling.

  In order to deal with such a problem, conventionally, the interval (pitch) of the repeated pattern along the tire circumferential direction of the tread pattern is irregularized (irregularized) by sequentially changing the pattern in a predetermined pattern, etc. A so-called pitch variation method is widely used in which noise during running is reduced to white noise (see Patent Document 1).

  In this pitch variation method, a predetermined pattern (tread constituent element) repeatedly arranged in the tread pattern along the tire circumferential direction is composed of a plurality of similar shapes having different lengths in the tire circumferential direction, etc. The tread pattern is formed by randomly arranging the patterns in the tire circumferential direction. In this method, such a random arrangement disperses the frequency of the resonance sound generated from the main grooves 10 and 11 and makes it difficult to sense, and the sound pressure level of each frequency is smoothed to reduce noise generated during traveling. Is reduced.

  However, this method is intended to reduce noise generated mainly from the entire tread pattern such as the main grooves 10 and 11 as a whole, and a specific high frequency generated from a relatively short air column tube. There is a problem that it is difficult to obtain a sufficient reduction effect for specific noise such as band resonance. Therefore, this method cannot effectively reduce the air column resonance noise generated from the circumferential short grooves 15 whose both ends terminate in the shoulder land portion row 22, such as when the pneumatic tire 90 is traveling at high speed. It is difficult to reduce high frequency noise.

JP 7-179103 A

  The present invention has been made in view of the above-described conventional problems, and the object thereof is to provide a pneumatic tire including a land portion row partitioned by a main groove extending in the tire circumferential direction, in which both ends are within the land portion row. It is to reduce the air columnar resonance generated from the circumferential short groove that terminates, and to suppress the generation of high-frequency noise.

The invention according to claim 1 intersects the tread portion with a plurality of main grooves extending in the tire circumferential direction, a plurality of land portion rows defined by the main grooves, and the main grooves arranged in the land portion rows. A plurality of lug grooves extending in the direction of the tire, and extending in the tire circumferential direction within the at least one land portion row in which the lug grooves are disposed (here, in the tire circumferential direction). In addition to the parallel case, it means that the tire extends in an inclined or curved manner at a predetermined angle with respect to the same direction. It has a circumferential short groove, and at least one narrow groove having one end opened in the circumferential short groove and the other end terminating in the land portion row is communicated with the circumferential short groove. To do.
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the narrow groove is communicated with both ends of the circumferential short groove.
According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the narrow groove is formed in the tire width direction from one end opening to the circumferential short groove toward the other end (here. In addition to being parallel to the tire width direction, it means that it is formed to include elements in the tire width direction such as extending at a predetermined angle with respect to the same direction. Features.
According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the depth of the narrow groove in the tire radial direction is shallower than the depth of the circumferential short groove in the tire radial direction. It is characterized by that.
A fifth aspect of the present invention is the pneumatic tire according to any one of the first to fourth aspects, wherein the groove width of the narrow groove is in a range of 1 to 2 mm.
A sixth aspect of the present invention is the pneumatic tire according to any one of the first to fifth aspects, wherein the circumferential short grooves and the narrow grooves are arranged in the land portion row on the outermost side in the tire width direction. It is characterized by that.

  According to the present invention, air columnar resonance sound generated from a circumferential short groove whose both ends are terminated in a land portion row of a pneumatic tire provided with a land portion row partitioned by a main groove extending in the tire circumferential direction. This can reduce the generation of high-frequency noise.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The pneumatic tire of the present embodiment is a pneumatic tire such as a passenger tire or a heavy duty tire, for example, a bead core disposed in a pair of tire bead portions, and at least one carcass layer extending in a toroidal shape therebetween. It has a known pneumatic tire structure including a belt layer disposed on the outer peripheral side of the carcass layer of the tread portion and a tread rubber formed with a predetermined tread pattern.

FIG. 1 is a plan view showing a developed tread pattern of the pneumatic tire 1 of the present embodiment, and schematically shows a part of the tire circumferential direction.
As shown in the figure, the pneumatic tire 1 includes a plurality of (here, four) main grooves 10 and 11 extending in the tire circumferential direction (vertical direction in the figure) in the tread portion 2 and a tire circumferential direction partitioned by them. A plurality of (in this case, five) land portion rows 20, 21, and 22 extending in the direction intersecting the main grooves 10, 11 disposed in the land portion row (here, the land portion rows 21, 22), For example, it includes a plurality of lug grooves 12 and 13 extending in a substantially tire width direction (left and right direction in the drawing) in an inclined or curved manner.

  The main grooves 10 and 11 are provided between the two center side main grooves 10 disposed with the tire equatorial plane CL interposed therebetween, and the center side main groove 10 and the outer end (tread end) TE of the tread portion 2 in the tire width direction. And two outer main grooves 11 arranged respectively. These main grooves 10 and 11 are respectively arranged at predetermined substantially symmetrical positions in the tire width direction across the tire equatorial plane CL, and the central main groove 10 is arranged at a position relatively close to the tire equatorial plane CL. Thus, the distance (distance) in the tire width direction is shortened. On the other hand, the outer main groove 11 is disposed in the vicinity of a substantially intermediate position between the center side main groove 10 and the tread end TE, and the distance in the tire width direction between the center side main groove 10 and the tread end TE is the center side. It is longer than the distance between the main grooves 10.

  Each of the main grooves 10 and 11 is formed to extend in the tire circumferential direction while being bent into, for example, a linear shape, a zigzag shape, a wave shape, or a crank shape according to the required tire performance. In the pneumatic tire 1, all the main grooves 10 and 11 are formed in the above-described crank-like bent shape. Further, the main grooves 10 and 11 are formed so that the outer main grooves 11 are slightly wider, but the depth in the tire radial direction, the shift width and the pitch in the tire width direction of the crank shape, and the like are formed to the same extent. They are both bent with a length shorter than the tire contact length, and are arranged so that their phases (bending positions) are shifted in a predetermined pattern in the tire circumferential direction.

  The land portion rows 20, 21, and 22 are formed by the center land portion row 20 located on the tire equatorial plane CL disposed between the two center side main grooves 10, the center side main groove 10, and the outer main groove 11. Two middle land portion rows 21 arranged between the two, and two shoulder land portion rows 22 located on the outermost side in the tire width direction (shoulder portion side) arranged on the outer side in the tire width direction of the outer main groove 11 Become.

  Each of the land portion rows 20, 21, and 22 has an edge portion and a groove wall in the tire width direction bent in the tire width direction in a crank shape corresponding to the shape of each main groove 10 and 11 that divides them. However, it is formed to extend in the tire circumferential direction. That is, the center land portion row 20 and the intermediate land portion row 21 are on both sides in the tire width direction (on the central main groove 10 and the outer main groove 11 side), and the shoulder land portion row 22 is on the inner side (outer main portion in the tire width direction). Only the groove 11 side) is formed in a crank shape. Further, the width in the tire width direction of each of the land portion rows 20, 21, and 22 corresponds to the arrangement of the main grooves 10, 11 and the like that divide them, and the center land portion row 20 is the narrowest, and the intermediate land portion row 21 and the shoulder land portion row 22 are widened in this order.

  In this intermediate land portion row 21, a plurality of lug grooves 12 that are slightly curved and extend substantially incline in the tire width direction are formed to have a groove width narrower than the groove width of the main grooves 10, 11, so that the tire circumference Repeatedly arranged in the direction. Each lug groove 12 is formed between the middle land portion rows 21 on both sides of the tire equatorial plane CL so as to be inclined in substantially the same direction with respect to the tire width direction, and both ends thereof define the middle land portion row 21. It opens to the center side main groove 10 and the outer side main groove 11 to be sandwiched, and crosses the intermediate land portion row 21 in the tire width direction. In addition, the lug groove 12 is opened at each inclined portion extending inclined with respect to the tire circumferential direction of each main groove 10, 11, and the inclined edges in the both tire width directions of the corresponding intermediate land portion row 21. The intermediate land portion row 21 is divided in the tire circumferential direction by connecting the portions and the groove walls. As a result, the intermediate land portion row 21 is partitioned into a plurality of block-like portions (hereinafter referred to as blocks) 21B arranged in the tire circumferential direction.

  Similarly, a plurality of lug grooves 13 that are curved and extend substantially in the tire width direction are formed in the shoulder land portion row 22 so as to be narrower than the groove widths of the main grooves 10 and 11, and are repeated in the tire circumferential direction. Has been placed. Each lug groove 13 is formed so as to bend in the opposite direction between the shoulder land portion rows 22 on both tread ends TE side, and both ends are formed on the outer main groove 11 and the tread end TE sandwiching the shoulder land portion row 22. Opening and crossing the shoulder land portion row 22 in the tire width direction. Further, the lug groove 13 is opened at each parallel portion having one end extending substantially parallel to the tire circumferential direction of the outer main groove 11 and at a substantially intermediate position in the tire circumferential direction, and the shoulder land portion row 22 is connected to the tire circumferential row. It is divided into a plurality of blocks 22B arranged in the tire circumferential direction.

  In the pneumatic tire 1 of the present embodiment, the center land portion row 20 is not arranged with a groove such as a lug groove that traverses in the tire width direction with respect to the land portion rows 21 and 22 partitioned in the block shape, The center land portion row 20 is a continuous land portion row extending continuously in the tire circumferential direction. In addition to the lug grooves 12 and 13, the intermediate land portion row 21 (block 21 </ b> B) and the shoulder land portion row 22 (block 22 </ b> B) have a plurality of extending in a substantially tire width direction or a circumferential direction inclined or curved. The sipes 19 are respectively arranged at predetermined positions.

  Further, in the pneumatic tire 1, a plurality of tires extending in the tire circumferential direction in at least one land portion row 21, 22 in which the lug grooves 12, 13 are disposed, and both ends of the plurality of tires terminating in the land portion rows 21, 22. The circumferential short grooves 15 have at least one narrow groove 16 communicating with each circumferential short groove 15. In the present embodiment, a plurality of circumferential short grooves 15 extend substantially parallel to the tire circumferential direction or inclined or curved (inclined in this case) in the shoulder land portion row 22 on both tread ends TE side. These are formed in the tire circumferential direction and are repeatedly arranged in the tire circumferential direction. Further, one end of each of the two narrow grooves 16 is opened in each circumferential short groove 15 so that the inside of each of the grooves 15 and 16 is communicated with each other.

  The circumferential short grooves 15 are formed so that the groove width is narrower than the groove widths of the main grooves 10, 11 and the lug grooves 12, 13, one in each block 22 </ b> B of the shoulder land portion row 22. It is arranged at a position in the tire width direction. Each circumferential short groove 15 extends while inclining in the tire circumferential direction, and is substantially in the same direction with respect to the tire circumferential direction in each shoulder land portion row 22 and between the shoulder land portion rows 22 on both tread ends TE side. It is formed so as to be inclined. The circumferential short groove 15 has both ends opened to the shoulder land portion without opening to any of the outer main groove 11 defining each block 22B, the pair of lug grooves 13 adjacent to the tire circumferential direction, and the tread end TE. This is a groove that ends in the row 22 (block 22B) and has a short length in the longitudinal direction (tire circumferential direction), and prevents a decrease in rigidity of the shoulder land portion row 22 by not opening it to the surrounding grooves 11, 13 and the like. However, it is provided to increase the edge component in the tire width direction.

  The narrow groove 16 is formed so that the groove width is narrower (narrower) than the groove widths of the other main grooves 10 and 11, the lug grooves 12 and 13, and the circumferential short groove 15. Opening and the other end terminating in the shoulder land portion row 22 (block 22B) similarly to the circumferential short groove 15, for example, a groove extending substantially parallel to the tire width direction or the circumferential direction, or inclined or curved. is there.

  In this pneumatic tire 1, one end of one narrow groove 16 is opened at each end of each circumferential short groove 15 in the tire circumferential direction, and the narrow groove 16 is communicated with each of both ends of the circumferential short groove 15. Yes. Further, the narrow groove 16 extends from one end opening to the circumferential short groove 15 to the other end (terminal) substantially in parallel to the tire width direction or inclined or curved (here, slightly inclined), etc. Formed in the tire width direction, toward one end of the circumferential short groove 15 toward the inner side in the tire width direction (outer main groove 11 side), and toward the other end side toward the outer side in the tire width direction (tread end TE side) It is formed in a predetermined length. In addition, the narrow groove 16 is formed in a range in which the depth in the tire radial direction is shallower than the depth in the tire radial direction of the circumferential short groove 15 that communicates, and the groove width is within a range of 1 to 2 mm. The length between the parts is shorter than the length of the circumferential short groove 15.

  In the pneumatic tire 1 of the present embodiment, each tread component described above is sequentially changed in a predetermined pattern along the tire circumferential direction by the above-described pitch variation method. It is irregular along the direction. That is, the tire circumferential direction length of each crank-shaped portion of each main groove 10, 11 is changed in a predetermined pattern, and the arrangement interval and shape in the tire circumferential direction of each lug groove 12, 13 and the circumferential direction are adjusted accordingly. The length and the shape (size) of the tire circumferential direction of each block 21B, 22B, and the tire circumferential direction length and tire width direction of the groove wall of each main groove 10, 11 are changed by changing the length of the direction short groove 15 and the like. Each tread component, such as the position, is sequentially changed along the tire circumferential direction. Thus, the predetermined pattern repeatedly arranged along the tire circumferential direction is composed of a plurality of similar shapes having different intervals (lengths) and shapes in the tire circumferential direction, and the plurality of patterns are A tread pattern is formed by, for example, random arrangement along the direction.

  As a result, in this pneumatic tire 1, the resonance frequency generated from the main grooves 10, 11, etc. is dispersed and white noise is generated, so that the increase in the sound of a specific frequency can be suppressed and difficult to detect. At the same time, the sound pressure level of each frequency can be smoothed, and noise generated from the entire tread pattern during traveling can be reduced overall.

  Further, in this pneumatic tire 1, since the narrow groove 16 is communicated with each of the circumferential short grooves 15 that generate high-frequency air column resonance sound, the volume of the air column tube can be increased, and high speed When traveling (for example, 100 km / h or more), a rapid volume change that occurs in a closed air column tube and high-frequency vibrations that accompany it can be made relatively small. As described above, the high-frequency vibration acting on the air in the air column tube (circumferential short groove 15) is alleviated, and at the same time, the shape of the air column tube formed in the circumferential short groove 15 portion by the narrow groove 16 is reduced. Since the resonance hardly occurs due to irregularity or the like, the vibration and resonance of the air can be reduced. As a result, the sound pressure level of the air columnar resonance generated from the circumferential short groove 15, particularly the high frequency resonance around the frequency band near about 4500 Hz, can be reduced.

  Therefore, according to the pneumatic tire 1 of the present embodiment, high-frequency air columnar resonance noise generated from the circumferential short groove 15 that ends in the shoulder land portion row 22 at both ends can be effectively reduced, and high-speed running is achieved. The generation of high-frequency noise at times is suppressed, and more comfortable high-speed traveling and the like can be realized.

  In the pneumatic tire 1, since the narrow grooves 16 are communicated with both ends of the circumferential short grooves 15, the effect of reducing vibration and resonance of the air in the air column tube is reduced. Thus, air columnar resonance can be more effectively reduced from both sides in the longitudinal direction. Furthermore, since the narrow grooves 16 are formed in the tire width direction, that is, in a direction substantially perpendicular to the extending direction of the circumferential short grooves 15 that communicate with each other, the extending direction of the grooves extending in the block 22B is dispersed, etc. The rigidity reduction of the block 22B is suppressed, and the necessary block rigidity can be ensured.

  Here, since the shoulder land portion row 22 on the outermost side in the tire width direction tends to be subjected to a large load or external force during rolling, the circumferential short groove is formed in the shoulder land portion row 22 as in the present embodiment. If 15 is formed, large high-frequency vibrations and air column resonance noise may be generated therefrom. Therefore, it is desirable to connect at least one narrow groove 16 to the circumferential short groove 15.

  Further, it is desirable that the depth of the narrow groove 16 in the tire radial direction is shallower than the depth of the circumferential short groove 15 in communication with the tire radial direction, and in this way, while reducing high-frequency noise, A reduction in rigidity of the shoulder land portion row 22 (block 22B) can be suppressed as much as possible. Furthermore, when the groove width of the narrow groove 16 is narrower than 1 mm, the effect of reducing the air columnar resonance noise may be reduced and high-frequency noise may be easily generated, and conversely, it is wider than 2 mm. In such a case, the rigidity of the block 22B may be reduced. Therefore, the groove width of the narrow groove 16 is preferably formed within a range of 1 to 2 mm. By doing so, it is possible to reduce the rigidity of the block 22B as much as possible while reducing high-frequency noise. In addition, when the length of the narrow groove 16 is increased, the rigidity of the block 22B may be lowered. Therefore, the narrow groove 16 is formed to be shorter than the circumferential short groove 15, and so on. What is necessary is just to form in sufficient length which can suppress a sound.

  In the present embodiment, the pneumatic tire 1 in which the circumferential short grooves 15 are formed in the shoulder land portion row 22 has been described as an example, but the circumferential short portion 15 is short in other land portion rows such as the intermediate land portion row 21. When the grooves 15 are formed, the same effects as described above can be obtained by providing the narrow grooves 16 in the grooves 15. Further, one or three or more narrow grooves 16 may be connected to one circumferential short groove 15 according to the length of the circumferential short groove 15, etc., except for both ends of the circumferential short groove 15. In addition, for example, it may be opened at another position such as a substantially intermediate position in the longitudinal direction. Furthermore, in the present embodiment, the circumferential short groove 15 for increasing the edge component of the shoulder land portion row 22 has been described as an example, but for example, for adjusting the rigidity of the land portion row or the block, Similarly to the circumferential short grooves 15 such as those for suppressing the narrow grooves 16, the narrow grooves 16 may be provided in other short circumferential grooves whose ends are terminated in the land portion row.

(Tire test)
In order to confirm the effect of the present invention, the pneumatic tire 1 (hereinafter referred to as an “implemented product”) having the tread pattern (see FIG. 1) described above and a narrow groove 16 in the circumferential short groove 15 are provided. A pneumatic tire 90 (hereinafter referred to as a conventional product) of a conventional example (comparative example) (see FIG. 3) that was not manufactured was prototyped and a noise comparison test was performed under the following conditions.

  Both the implementation product and the conventional product are radial ply tires for passenger cars having a tire size of 235 / 60R16 99T defined by JATMA YEAR BOOK (2006, Japan Automobile Tire Association Standard). These were all formed substantially the same except for the narrow grooves 16, and the circumferential short grooves 15 were each formed with a groove width of 3 mm, a length of 10 mm, and a depth of 5 mm. Further, the narrow groove 16 of the product was formed with a groove width of 1.5 mm, a length of 3 mm, and a depth of 2 mm.

  In the noise test, the sound pressure distribution in all frequency regions generated from the implementation product and the comparison product was measured under the following conditions, and the results were compared and evaluated. In the test, a rim of 16 × 6.5 J was used, and the tire pressure was adjusted to 210 kPa by assembling the rim of the actual product and the comparative product. Each of these tires was mounted on a vehicle, and the road surface noise (noise) was measured by running the test course at a speed of 60 mph (mile per hour) under a load condition where one person got on.

  FIG. 2 is a diagram (graph) showing the results of the noise test, in which the horizontal axis represents frequency (unit, Hz) and the vertical axis represents sound pressure level (unit, dB (A)). In the figure, the measurement result of the implemented product is indicated by a solid line X, and the measurement result of the conventional product is indicated by a dotted line Y.

  As a result of the measurement, as shown in the figure, in the conventional product (dotted line Y), the sound pressure level suddenly rises in the high frequency region centered around 4500 Hz (K region in the figure), and a large peak-like noise is generated. It was. On the other hand, in the implementation product (solid line X), the distribution of the sound pressure level as a whole changed in the same manner as the conventional product, but the sound pressure level in the vicinity of about 4500 Hz decreased and the peak disappeared. It was found that the noise in the high frequency region was greatly reduced.

  In addition, as a result of sensory evaluation by mounting these implementation products and comparative products on a real vehicle and running at a high speed of 100 km / h, a high-frequency continuous sound “sher, shear, shear” felt with conventional products However, it was not felt with the product, and it was confirmed that high frequency noise could be suppressed.

  From the above results, according to the present invention, an air column tube generated from a circumferential short groove whose both ends are terminated in a land portion row of a pneumatic tire provided with a land portion row defined by main grooves extending in the tire circumferential direction. It was proved that resonance noise can be reduced and generation of high frequency noise can be suppressed.

It is a top view which expands and shows the tread pattern of the pneumatic tire of this embodiment. It is a diagram which shows the result of a noise test. It is a top view which expands and shows an example of the tread pattern of the conventional pneumatic tire.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Tread part, 10 ... Central side main groove, 11 ... Outer side main groove, 12 ... Lug groove, 13 ... Lug groove, 15 ... Circumferential short groove, 16 ... narrow groove, 19 ... sipe, 20 ... center land portion row, 21 ... intermediate land portion row, 21B ... block, 22 ... shoulder land portion row 22B: Block, CL: Tire equatorial plane, TE: Tread end.

Claims (6)

In the tread portion, a plurality of main grooves extending in the tire circumferential direction, a plurality of land portion rows partitioned by the main grooves, and a plurality of lugs extending in a direction intersecting with the main grooves arranged in the land portion rows A pneumatic tire having a groove,
In the at least one land portion row in which the lug grooves are arranged, there are a plurality of circumferential short grooves that extend in the tire circumferential direction and that both ends terminate in the land portion row,
A pneumatic tire characterized in that the circumferential short groove is connected to at least one narrow groove having one end opened to the circumferential short groove and the other end terminating in the land portion row. In the pneumatic tire according to claim 1,
A pneumatic tire characterized in that the narrow groove communicates with both ends of the circumferential short groove. In the pneumatic tire according to claim 1 or 2,
The pneumatic tire according to claim 1, wherein the narrow groove is formed in a tire width direction from one end opened to the circumferential short groove toward the other end. In the pneumatic tire according to any one of claims 1 to 3,
The pneumatic tire is characterized in that a depth of the narrow groove in the tire radial direction is shallower than a depth of the circumferential short groove in the tire radial direction. In the pneumatic tire according to any one of claims 1 to 4,
The pneumatic tire according to claim 1, wherein a groove width of the narrow groove is in a range of 1 to 2 mm. In the pneumatic tire according to any one of claims 1 to 5,
The pneumatic tire according to claim 1, wherein the circumferential short grooves and the narrow grooves are arranged in the land part row on the outermost side in the tire width direction.

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