JP5475476B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which noise generated by air column resonance in a pipe formed by a circumferential groove extending in the circumferential direction and a road surface in a tread contact surface is reduced by a resonator.

  In recent years, with the quietness of vehicles, there has been a demand for reduction of automobile noise caused by load rolling of pneumatic tires, and in particular, it extends continuously in the circumferential direction of the tread tread within the tire contact surface. The air column resonance generated by the resonance of the air in the pipe formed by the existing circumferential groove and the road surface in the contact area of the tread tread is often observed at about 800 to 1200 Hz in a general passenger car. Since the peak sound pressure level is high and the frequency band is wide, the reduction is demanded.

  For this reason, in order to reduce the noise outside the vehicle due to the air column resonance sound, the number and the volume of the circumferential main grooves are widely reduced. For example, Patent Document 1 discloses only one end. A technology has been proposed in which a long horizontal groove having an opening in the circumferential groove (circumferential main groove) and the other end terminated in the land portion is provided, and air column resonance noise is reduced by using anti-resonance in the horizontal groove. In Patent Document 2, a so-called Helmholtz resonator composed of a sipe (constriction passage) opening in a circumferential groove and a resonance chamber (air chamber portion) connected to the constriction passage is used. Techniques for absorbing noise energy near the resonance frequency have been proposed.

  However, in such a tire, for example, a lateral groove, a resonance chamber, and the like are intermittently arranged in the tread circumferential direction in a land portion partitioned between circumferential grooves, and the land portion has a tread circumference. Rigidity changes depending on the direction position, and due to this change in rigidity, there is a risk of generating in-vehicle sound that can be heard in the passenger compartment during traveling.

International Publication No. 04/103737 Pamphlet Japanese Patent Laid-Open No. 5-338411

  Accordingly, an object of the present invention is to provide a pneumatic tire capable of suppressing outside noise caused by air column resonance and effectively reducing in-vehicle noise.

The pneumatic tire according to the present invention includes at least one circumferential main groove extending continuously in the tread circumferential direction on the tread ground surface, and intermittently in the tread circumferential direction in a land portion adjacent to the circumferential main groove. A circumferential sub-groove extending and opening to the circumferential main groove via a single inclined groove is provided, wherein the circumferential sub-groove and the inclined groove include the circumferential main groove and the road surface. A resonator that reduces noise generated by air column resonance in the tube formed by the above, provided at the groove bottom of the central portion in the extending direction of the circumferential sub-groove is provided with a raised portion that connects both groove walls , The raised portion has a tread circumferential length of 1 to 25 mm and a height of 1 to 7.2 mm, and the ratio of the surface area of the top of the raised portion to the area of the transverse sub-groove is 0. and it is characterized in that formed by a 3 to 0.9.

Here, the circumferential main groove and the circumferential sub-groove can be extended not only in a linear shape but also in a groove shape such as a zigzag shape, a wavy line shape, a curved shape, or a crank shape.
The “protruding portion” can be inclined in the tread width direction as well as extending in the tread width direction, and the shape thereof can be a rectangular shape, an arc shape, or the like in the circumferential cross section.

Also preferably arranged 20 to 40 of the circumferential sub groove across the tread circumferential direction.

  In the pneumatic tire of the present invention, in particular, by providing a raised portion that connects both groove walls at the groove bottom of the circumferential sub-groove, the rigidity of the land portion near the raised portion is increased. It is possible to reduce the change in rigidity in the tire to suppress the noise generated during rolling of the tire and to improve the tire uniformity (R.F.V.).

(A) is the expanded partial expanded view of the tread pattern which shows one Embodiment of the pneumatic tire of this invention, (b) is an expanded sectional view of the BB cutting part of (a). It is a partial development view of a tread pattern showing one embodiment of a pneumatic tire of the present invention.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
Since the reinforcing structure inside the tire is the same as that of a general radial tire or bias tire, illustration is omitted.

In FIG. 1 showing an embodiment of a pneumatic tire, reference numeral 1 in the drawing denotes a part of a tread ground surface, and the tread ground surface 1 has one or more circumferential mains extending continuously in the tread circumferential direction. The groove 2 is disposed.
Then, a plurality of circumferential sub-grooves 4 extending intermittently in the tread circumferential direction are arranged in the land portion 3 adjacent to the circumferential main groove 2 in parallel with the circumferential main groove 2, and each circumferential sub-groove is arranged. One end of the groove 4 is opened by an inclined groove 5 extending obliquely from the circumferential main groove 2 with respect to the tread circumferential direction.
Therefore, here, the other end of the circumferential sub-groove 4 ends in the land portion 3.

  Here, the circumferential main groove 2 has, for example, a groove width of 8 to 18 mm and a groove depth of 6.9 to 8.2 mm, and each circumferential sub groove 4 has a groove length of 20 to 20 mm, for example. The inclined groove 5 has a groove length of 20 to 50 mm, a groove width of 1 to 10 mm, and a groove depth of 2 to 7 mm, and 65 mm, a groove width of 2 to 10 mm, and a groove depth of 2 to 8.2 mm. The range can be inclined at 20 to 90 ° with respect to the circumferential direction of the tread.

  The air column resonance sound is generated by the air column partitioned by the circumferential main groove 2 and the road surface in the ground contact surface based on the vibration of each part of the tire during rolling. It is generated on the basis of resonant oscillation with a wavelength twice the length.

Such air column resonance is caused by a circumferential sub-groove 4 in which a plurality of circumferential main grooves 2 extending continuously in the tread circumferential direction extend across the circumferential main groove 2 in the tread pattern of the tire, and When communicating with the inclined groove 5, only air column resonance with one specific frequency is generated.
Here, the width, depth, and number of the circumferential main grooves 2 greatly affect the sound pressure level of the resonance rather than the resonance frequency.

  And when the influence of the circumferential sub-groove 4 and the inclined groove 5 on the resonance phenomenon of the circumferential main groove 2 was examined, when the circumferential sub-groove 4 and the inclined groove 5 were terminated in the middle of the land portion, Due to the length of the circumferential sub-groove 4 and the inclined groove 5 in the ground plane, sound is absorbed at a desired frequency. When this sound absorption frequency is brought close to approximately 800 to 1400 Hz, which is the air column resonance frequency of the circumferential main groove 2, the resonance noise can be reduced.

  In order for the circumferential sub-groove 4 and the inclined groove 5 to sufficiently exhibit such a sound absorbing function, the groove walls of the circumferential sub-groove 4 and the inclined groove 5 do not contact each other in the ground plane and It is necessary that at least one of the circumferential sub-groove 4 and the inclined groove 5 opening in the predetermined circumferential main groove 2 is always completely included in the ground plane.

  Further, here, the other circumferential main groove 2 is opened with the circumferential sub-groove 4 and the inclined groove 5 having one end opened in the specific circumferential main groove 2 and the other end terminated in the land portion. By forming the circumferential sub-groove 4 and the inclined groove 5 so as not to intersect with each other, and controlling the resonance frequency of the specific circumferential main groove 2, a plurality of tires can be used for rolling the tire. The resonance frequency of the circumferential main groove 2 can be effectively dispersed. As a result, the noise peak level is reduced as compared with the case where the air column resonance sound is generated by only one specific frequency, and White noise can be greatly promoted.

And in this pneumatic tire, the protruding part 6 connected to both groove walls is provided in the groove bottom of the circumferential sub-groove 4, and in the drawing, at the center in the extending direction of the circumferential sub-groove 4.
The raised portion 6 can increase the rigidity in the vicinity of the circumferential sub-groove 4 without abruptly deteriorating drainage even when the tread ground surface 1 is worn.

  In such a pneumatic tire, preferably, the ridge 6 is provided at the center in the extending direction of the circumferential sub-groove 4 so that the rigidity of the circumferential sub-groove 4 and the land portion 3 extending in the tread circumferential direction is increased. The level difference can be improved to improve uniformity and reduce noise.

  Here, the protruding portion 6 has a circumferential length of 1 to 25 mm and a height of 1 to 7.2 mm, and the ratio between the surface area of the top of the protruding portion 6 and the area of the transverse sub-groove 4 in the cross section. Can be set to 0.3 to 0.9. In this range, noise generation can be reduced without sacrificing various performances of the tire.

By the way, it is preferable to arrange 20 to 40 circumferential sub-grooves 4 in the tread circumferential direction.
In this range, in particular, it is possible to reduce the vicinity of 200 to 250 Hz (80 to 160 kph), which is an in-vehicle sound due to resonance with vehicle characteristics, and to improve steering stability during cornering.

  In such a tire, the circumferential sub-groove 4 and the inclined groove 5 can be formed only on one side of the circumferential main groove 2 with respect to the specific circumferential main groove 2 of interest. It can also be performed on both sides, and in any of these, the function as expected can be sufficiently exhibited in the circumferential sub-groove 4 and the inclined groove 5 that open in the circumferential main groove 2.

  Here, when the circumferential sub-groove 4 and the inclined groove 5 are provided on both sides of the circumferential main groove 2, assuming that the circumferential sub-groove 4 and the inclined groove 5 are all the same size, the circumferential sub-groove 4 in the tread surface. And by increasing the number of the inclined grooves 5, a larger sound absorbing effect can be obtained than in the case of only one side. In addition, since the decrease in compression / shear rigidity of the tread block due to the increase in the circumferential sub-groove 4 and the inclined groove 5 can be suppressed as compared with the case where the same number of grooves are provided only on one side, the steering stability and the like are deteriorated. Can be prevented.

  Further, in this tire, two or more specific circumferential main grooves with the inclined grooves and the circumferential sub-grooves opened can be provided on the tread ground surface 1, and this also allows other circumferential main grooves to be provided. By dispersing the resonance frequency between the two, it is possible to bring about the same effect as described above.

  According to the tire configured in this way, as described above, the steering stability on the dry road surface and the limit grip characteristics are made compatible under the formation of the plurality of circumferential main grooves and the like. In addition, while maintaining excellent wet performance, the air column resonance frequency of each circumferential main groove can be made different from each other, for example, the resonance frequency of the circumferential main groove can be changed to another circumferential main groove. The peak level of the air column resonance noise can be effectively reduced, and at the same time, white noise can be greatly promoted.

  In addition, although the kind of resonator is not limited, For example, it can also be set as the stepped type resonator which consists of a Helmholtz type resonator and a connection pipe line.

  Example tires 1 and 2 and comparative tires 1 and 2 having a size of 255 / 40ZR19 and having various specifications changed as shown in Table 1 as shown in FIGS. Is mounted on a 9.5 J rim, filled with air pressure of 270 kPa and subjected to a load equivalent to 5 kN, running on a flat road at 80 to 140 km / h, and from 80 km / h to 10 km. The vehicle was run at a constant speed per hour and evaluated by the feeling of the evaluation driver. The results are shown in Table 2.

  According to Table 2, both the example tires 1 and 2 were able to reduce vehicle interior noise compared to the comparative example tires 1 and 2.

DESCRIPTION OF SYMBOLS 1 Tread ground surface 2 Circumferential main groove 3 Land part 4 Circumferential sub groove 5 Inclined groove 6 Raised part

Claims (2)

At least one circumferential main groove extending continuously in the tread circumferential direction on the tread ground surface,
In a pneumatic tire formed by disposing a circumferential sub-groove extending intermittently in a tread circumferential direction in a land portion adjacent to the circumferential main groove and opening to the circumferential main groove via a single inclined groove. ,
The circumferential sub-groove and the inclined groove are resonators that reduce noise generated by air column resonance in a pipe formed by the circumferential main groove and the road surface,
Providing a ridge that connects both groove walls at the groove bottom in the center in the extending direction of the circumferential sub-groove ,
The raised portion has a tread circumferential length of 1 to 25 mm and a height of 1 to 7.2 mm, and the ratio of the surface area of the top of the raised portion to the area of the transverse sub-groove is 0. a pneumatic tire which is characterized by comprising a .3～0.9. The pneumatic tire according to claim 1, wherein 20 to 40 circumferential sub-grooves are disposed in the tread circumferential direction.

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