JP5506426B2 - Pneumatic tire - Google Patents

Description

    The present invention relates to a pneumatic tire in which a plurality of main grooves are formed on a tread surface.

    In recent years, as the proportion of tire noise in automobile noise has increased with the quietness of vehicles, reduction of tire noise has become a major issue. In particular, noise in the frequency band of 1000 to 2000 Hz that is generated from the tire due to air column resonance when the tire is running, so-called air column resonance, has a high peak and wide band, and is sensitive to human hearing. Because of this noise, immediate countermeasures are desired.

  Here, the air columnar resonance sound means that when a tire having a main groove extending continuously in the circumferential direction is grounded, a tube having the same length as the ground contact length is formed between the groove wall of the main groove and the ground contact surface. However, in such a pipe, noise generated by repeated compression and release of air as the tire travels, and its peak frequency depends on the length of the pipe (contact length). . Conventionally, as a technique for reducing noise based on such air column resonance, for example, a technique described in Patent Document 1 below is known.

JP 2008-155798 A

  This is provided with a number of Helmholtz resonators on the tread tread, each of which is composed of an air chamber that opens to the surface of the land portion at a position away from the main groove, and a narrow neck that communicates the air chamber and the main groove. By absorbing the energy in the vicinity of the resonance frequency of the air column resonance sound, the noise is effectively reduced.

    However, in such a conventional pneumatic tire, since a large number of resonators are disposed on the land surface, the tread pattern becomes a complicated shape, resulting in an increase in manufacturing cost. was there. In addition, when a large number of resonators are disposed on the land as described above, the degree of freedom is limited when designing a tread pattern, and tire performance other than noise reduction, such as wear durability performance, wet performance, etc. There is also a problem that it is difficult to improve the value to a sufficient value.

  An object of the present invention is to provide a pneumatic tire that is inexpensive to manufacture and that can easily improve tire performance other than noise reduction.

    In order to achieve such an object, the inventors have conducted various tests and studies on the air column resonance of the tire. As a result, when the groove width of the main groove is widened, the groove bottom of the main groove is likely to vibrate. It was found that the vibration energy of the columnar resonance sound was absorbed, and thereby the air columnar resonance sound could be reduced. However, if the width of the main groove is simply widened, the volume of the tread rubber is reduced and the wear durability of the tire is lowered, which is not practical. For this reason, the inventor conducted further tests and examinations, and found that if it is a groove, the air columnar resonance noise can be reduced regardless of the groove depth, that is, even if the groove depth is shallower than the main groove. .

The present invention has been made on the basis of the above-described knowledge. In a pneumatic tire in which a plurality of main grooves extending continuously in the circumferential direction is formed on the tread surface, at least the width direction of at least one main groove is provided. One side communicates with the main groove and continuously extends in the circumferential direction to form a shallow groove having a groove depth shallower than the main groove. The shallow groove has a groove depth equal to the groove depth of the main groove. In the pneumatic tire, the width of the shallow groove is set in the range of 0.5 to 1.5 times the width of the main groove while being in the range of 0.1 to 0.5 times .

  In the present invention, at least one side of the main groove is formed in at least one side in the width direction and communicates with the main groove and continuously extends in the circumferential direction, so that a shallow groove having a groove depth shallower than the main groove is formed. In addition to the groove bottom of the main groove, the groove bottom of the shallow groove also vibrates (the area of the vibrating groove bottom increases), and more vibration energy of the air column resonance sound is absorbed. Sound is effectively reduced. At this time, since the groove depth of the shallow groove is shallower than that of the main groove, the volume reduction of the tread rubber is small, and as a result, a decrease in wear durability can be effectively suppressed. In addition, since it is only necessary to form the shallow grooves as described above on the tread surface, the manufacturing cost is low, and the tread pattern design is more flexible and tire performance other than noise reduction can be easily improved. it can.

Further, while sufficiently suppressing the wear resistance, it can be low reducing air columnar resonance noise Rutotomoni, while adjacent contact main grooves each other to prevent a situation that communicates with shallow grooves, air columnar resonance noise Can be sufficiently reduced. In addition, if configured as described in claim 2 , the air columnar resonance can be further effectively reduced. Further, if configured as described in claim 3 , the manufacturing cost of the vulcanization mold can be reduced and the cost can be reduced, and if configured as described in claim 4 , the wear durability can be reduced. Reduction can be more effectively suppressed.

It is a top view of the pneumatic tire which shows Embodiment 1 of this invention. It is the meridian sectional view. It is meridian sectional drawing of the main groove vicinity. It is meridian sectional drawing similar to FIG. 3 which shows other embodiment of this invention. It is a graph which shows the spectrum of noise.

Embodiment 1 of the present invention will be described below with reference to the drawings.
In FIGS. 1, 2, and 3, reference numeral 11 denotes a pneumatic tire. The tread tread 12 of the pneumatic tire 11 continuously extends in the circumferential direction, that is, a plurality of tires that are not interrupted in the middle, four here. The main grooves 13 are formed, and these main grooves 13 are spaced apart in the width direction of the pneumatic tire 11. Here, the main groove 13 may extend linearly as in this embodiment, but it may be bent in a zigzag shape, and the groove depth e is usually constant, but in the circumferential direction. It may change periodically or irregularly.

  Then, after mounting the pneumatic tire 11 on the applicable rim and running on the road surface with the internal pressure filled, the contact length between the groove wall of the main groove 13 and the road surface (from the stepping end in the footprint) The length of the tube is the same as the length of the kicking end), but the compression and release of air is repeated in this tube as the tire travels, generating noise (air column tube resonance) To do.

  Shallow grooves 14 and 15 are formed in the tread tread 12 on the inner side in the width direction (the tire equator S side) and the outer side in the width direction (the tread end T side) of each main groove 13, respectively. While extending continuously in the circumferential direction along the main groove 13, the groove depth d is shallower than the groove depth e of the main groove 13. And the side end of the shallow groove 14 close to the main groove 13, the outer end in the width direction here communicates with the inner end of the main groove 13 in the width direction, while the side end of the shallow groove 15 close to the main groove 13; Here, the inner end in the width direction communicates with the outer end in the width direction of the main groove 13.

  In this way, on the side in the width direction of the main groove 13, while communicating with the main groove 13, and continuously extending in the circumferential direction, forming shallow grooves 14, 15 having a groove depth shallower than the main groove 13, In addition to the groove bottom 13a of the main groove 13, the groove bottoms 14a and 15a of the shallow grooves 14 and 15 also vibrate (increase in the area of the vibrating groove bottom), and the vibration energy of the above-described air column resonance sound is increased. Absorbed, thereby effectively reducing air column resonance. At this time, since the groove depth of the shallow grooves 14 and 15 is shallower than that of the main groove 13, the volume reduction of the tread rubber is small, and as a result, a decrease in wear durability can be effectively suppressed. Moreover, since it is only necessary to form the shallow grooves 14 and 15 on the tread tread 12 as described above, the manufacturing cost is low, and the tread pattern design is more flexible and the tire performance other than noise reduction is easily performed. Can be improved.

  In this embodiment, the shallow grooves 14 and 15 are formed on both sides of each main groove 13 in the width direction. However, in the present invention, either one of the main grooves 13 in the width direction (inward in the width direction) is formed. Alternatively, the shallow groove may be formed on the outer side in the width direction, and may be formed on at least one side of the width direction of at least one main groove 13. Here, if the shallow grooves 14 and 15 are formed on both sides in the width direction of the main groove 13 as in this embodiment, vibration occurs as compared with the case where the shallow grooves are formed only on one side in the width direction of the main groove 13. Since the area of the groove bottom is increased, air columnar resonance can be further effectively reduced. And when forming a shallow groove in the width direction side of some main grooves 13, since the main groove 13 close | similar to the tire equator S has contributed largely to generation | occurrence | production of air columnar resonance noise, tire equator Preferably, it is formed on the side in the width direction of the main groove 13 arranged close to S.

  In this embodiment, the groove bottoms 14a and 15a of the shallow grooves 14 and 15 are formed of flat surfaces parallel to the tread surface 12, and the groove depth d of the shallow grooves 14 and 15 is set at any position. Same value. When the shallow grooves 14 and 15 are configured as described above, the manufacturing cost of the vulcanization mold is reduced, and the cost can be reduced. Here, the groove bottoms 14a and 15a of the shallow grooves 14 and 15 described above are inclined surfaces inclined with respect to the tread tread 12 so that the groove depth d becomes deeper as the main groove 13 is approached, as shown in FIG. When the shallow grooves 14 and 15 are configured in this way, the volume reduction amount of the tread rubber is smaller than that of FIG. 3 and the deterioration of wear durability is more effectively suppressed. can do.

  In the present invention, the groove bottoms 14a and 15a of the shallow grooves 14 and 15 are formed of inclined surfaces that are inclined with respect to the tread tread 12 so that the groove depth d increases as the distance from the main groove 13 increases. Alternatively, it may be composed of a plurality of flat surfaces formed so that the groove depth d increases stepwise as the main groove 13 is approached. Furthermore, the groove bottoms 14a and 15a of the shallow grooves 14 and 15 may be waved in the circumferential direction, and the groove depth d may be changed in the circumferential direction.

The groove depth d of the shallow grooves 14 and 15 shall be the groove depth range from 0.1 to 0.5 times the e of the main groove 13. The reason is that if the groove depth d is less than 0.1 times the groove depth e, the groove bottoms 14a and 15a are grounded when the pneumatic tire 11 is running and cannot absorb vibration energy of air column resonance noise. On the other hand, when the groove depth d exceeds 0.5 times the groove depth e, the volume of the tread rubber may be considerably reduced and the tire wear durability may be reduced. This is because air columnar resonance noise can be sufficiently reduced while sufficiently suppressing the wear durability of the pneumatic tire 11. Here, when the groove bottoms 14a and 15a of the shallow grooves 14 and 15 are formed of inclined surfaces as shown in FIG. 4, the above-mentioned groove depth d is a break in the meridian section of the shallow grooves 14 and 15. The average depth divided by the maximum width.

The groove width v of the shallow grooves 14, 15 described above shall be the range from 0.5 to 1.5 times the groove width w of the main groove 13. The reason is that if the groove width v is less than 0.5 times the groove width w, the area of the groove bottoms 14a and 15a may be narrow and the air column resonance noise may not be sufficiently reduced. If the width v exceeds 1.5 times the groove width w, the adjacent main grooves 13 may be communicated with each other by the shallow grooves 14 and 15, but if they are within the above-described range, the adjacent main grooves 13 are shallow. This is because air columnar resonance noise can be sufficiently reduced while preventing a situation where the grooves 14 and 15 communicate with each other. Here, when the groove bottoms 14a and 15a of the shallow grooves 14 and 15 are formed of inclined surfaces as shown in FIG. Is the average width divided by the maximum depth.

    Next, test examples will be described. In this test, the comparative tire 1 in which one main groove having a groove width w of 10 mm and a groove depth e of 8 mm is formed on the tread surface on the tire equator S, and the groove width on the tread surface on the tire equator S are formed. A comparative tire 2 having one main groove having w of 30 mm and a groove depth e of 8 mm, and a tread surface on the tire equator S having a groove width w of 10 mm and a groove depth e of 8 mm. In addition to forming the main groove, an implementation tire was prepared in which shallow grooves as shown in FIG. 3 having a groove depth d of 2 mm and a groove width v of 10 mm were formed on both sides in the width direction of the main groove. The reason why only one main groove extending linearly is formed on the tire equator S is that the effect can be easily confirmed.

  Here, the size of each tire was 195 / 65R15. Next, each of such tires is mounted on an applicable rim, and after being filled with an internal pressure (gauge pressure) of 220 kPa, it is pressed against the rotating drum of the indoor drum tester while applying a load of 4 kPa, and 20, 40 , 60 and 80 km / h, and the noise at the side of the tire was measured under the conditions defined in JASO C606. The overall sound pressure level dB (A) at each speed described above is shown in Table 1 below, and the implemented tire exhibits a noise reduction effect equivalent to that of the comparative tire 2. In Table 1, the numerical value in parentheses is the value of the sound pressure level reduced as compared with the comparative tire 1.

  FIG. 5 shows the spectrum of noise generated by each tire at the speed of 80 km / h in the test described above. Comparative tire 1 is a triangle (Δ) and comparative tire 2 is a white circle (◯). The tire is represented by a cross (x). As apparent from FIG. 5, compared with the comparative tire 1, the implemented tire effectively reduced noise at 1000 to 2000 Hz, that is, air column resonance noise.

  The present invention can be applied to the industrial field of pneumatic tires in which a plurality of main grooves are formed on the tread surface.

11 ... Pneumatic tire 12 ... Tread tread
13 ... Main groove 14, 15 ... Shallow groove
14a, 15a ... groove bottom d ... groove depth e ... groove depth v ... groove width w ... groove width

Claims (4)

In a pneumatic tire in which a plurality of main grooves extending continuously in the circumferential direction are formed on the tread surface, at least one main groove communicates with the main groove at least on one side in the width direction and is continuous in the circumferential direction. A shallow groove having a shallower groove depth than the main groove, and the groove depth of the shallow groove is within a range of 0.1 to 0.5 times the groove depth of the main groove. A pneumatic tire characterized in that the width is in the range of 0.5 to 1.5 times the groove width of the main groove . The pneumatic tire of claim 1 Symbol placement were formed the shallow groove in the width direction both sides of the main groove. The pneumatic tire according to claim 1 or 2, wherein a groove bottom of the shallow groove is constituted by a flat surface parallel to a tread surface. 3. The pneumatic tire according to claim 1, wherein a groove bottom of the shallow groove is formed of an inclined surface inclined with respect to the tread surface so that the groove depth becomes deeper as the main groove is approached.

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