JP5039376B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire for a passenger car, and air column resonance that is unavoidably generated by a circumferential groove extending linearly or zigzag continuously in the circumferential direction of the tread surface. In addition to reducing the sound, it aims to improve steering stability especially during cornering.

  The air column resonance is noise generated by resonance of air in the pipe surrounded by the circumferential groove extending continuously in the circumferential direction of the tread surface and the road surface in the tread surface area. This frequency 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, it occupies a large part of the noise generated by the tire.

  In addition, since human hearing is particularly sensitive in the above frequency band as shown by the A characteristic, reduction of air column resonance is effective in improving quietness in the feeling surface. .

To reduce air column resonance, it is effective to reduce the volume of the circumferential groove. Usually, this method is generally adopted, but in recent years, only one end is opened in the circumferential groove and the other end is opened. It has been proposed to provide a long horizontal groove that terminates in the land and reduce air column resonance using anti-resonance in the circumferential groove (see, for example, Patent Document 1). Apart from this, a technique of absorbing energy in the vicinity of the resonance frequency of the air column resonance by a Helmholtz resonator has also been proposed (see, for example, Patent Documents 2 to 4).
WO04 / 103737 pamphlet JP-A-5-338411 JP 2000-118207 A Japanese Patent Laid-Open No. 2001-191734

  However, in the conventional technique for reducing the groove volume of the circumferential groove, the drainage performance is inevitably lowered, and it is essential to dispose a long lateral groove.

  In addition, in the method of reducing the air column resonance sound by using an anti-resonance in the circumferential groove by providing a long horizontal groove that opens only at one end into the circumferential groove and the other end ends in the land, the design of the tread pattern There was a problem that there was a difficulty in ensuring the degree of freedom of the land and the appropriate rigidity of the land.

  On the other hand, the technology for absorbing energy in the vicinity of the resonance frequency of the air column resonance sound by the Helmholtz resonator has no drawbacks as in the prior art and is an effective means, but the overall performance of the tire (for example, In consideration of the pitch noise depending on the resonance air chamber, uneven wear around the large cavity called the air chamber, steering stability during cornering, etc., and the possibility of mass production of tires, etc., the Helmholtz resonator, It is difficult to say that a specific and effective arrangement method of the tread is disclosed, and it has not yet been put into practical use.

  The present invention has been made to solve such problems of the prior art, and its purpose is to sufficiently ensure the total performance and mass productivity of the tire without causing a decrease in drainage performance. In addition, it achieves a high degree of freedom in design and the expected land rigidity, while effectively reducing the air column resonance noise generated by the circumferential groove, as well as steering stability, especially during cornering. The improvement of the handling stability is also planned.

The present invention passes through a region from the tread step end to the kick end of the tread on the ground contact surface of the tire, and at least one circumferential groove extending along the direction of rotation of the tire, and is defined by the circumferential groove. In a pneumatic tire provided with a plurality of rows of ribs,
The rib comprises a recess that forms a closed space by contact with a road surface within the ground contact surface of the tire, and a narrowed passage that is connected to the recess and opens in the groove wall of the same circumferential groove, and the noise that the tire contacts the ground A resonance part that resonates at a frequency substantially equivalent to noise and reduces the sound is provided.
When the rib is divided into the center in the width direction of the tire and the shoulder side of the tire with respect to the center in the width direction, the volume of the region located on the center in the width direction of the tire This is a pneumatic tire characterized by having a larger arrangement than the volume of the region located on the shoulder side.

In the pneumatic tire configured as described above, it is desirable that the region on the center side in the width direction of the tire has a two-dimensional planar shape and has an opening area of 60% or more of the opening area of the recess of the resonance portion .

Further, the present invention provides at least one circumferential groove that extends through the tire rotating direction and passes through a region from the tread stepping end to the kicking end on the tire contact surface, and the circumferential groove. In a pneumatic tire having a plurality of rows of ribs partitioned by
The rib comprises a recess that forms a closed space by contact with a road surface within the ground contact surface of the tire, and a narrowed passage that is connected to the recess and opens in the groove wall of the same circumferential groove, and the noise that the tire contacts the ground A resonance part that resonates at a frequency substantially equivalent to noise and reduces the sound is provided.
The recess of the resonance part is located on the tire width side center side when the rib is divided into the tire width direction center side and the tire shoulder side with respect to the width direction center of the rib. Tire.

ここに、ｒ :狭窄通路の半径、
l₀ :狭窄通路の長さ、
S :狭窄通路の断面積、
V :凹部の容積、
C :音速 For the above resonance part, a Helmholtz type resonator having a resonance frequency f ₀ of 700 to 1400 Hz obtained by the following formula is advantageously adapted.
Record

Where r: radius of the constriction passage,
l ₀ : length of the stenosis passage,
S: cross-sectional area of constricted passage,
V: Volume of the recess,
C: speed of sound

Further, the resonance part is composed of a connecting pipe that regards the recess and the narrowing passage as the first pipe and the second pipe, respectively, and connects them to each other. It can be thought of as a type of resonator.
Record
tan (kl ₁ ) tan (kl ₂ ) − (S ₂ / S ₁ ) = 0, k = 2πf / c
c: speed of sound
l ₁ : Length of the first pipe
l ₂ : Length of the second tube furnace
S _1: cross-sectional area of the first conduit
S ₂ : Cross section of the second pipe

  A resonance part is provided on the land part of the tire, and the resonance frequency of this resonance part is matched to the frequency band of the circumferential groove, so that the primary resonance energy of the circumferential groove is absorbed by the vibration of the air in the narrowed passage of the resonance part. The air column resonance in the circumferential groove can be effectively reduced without reducing the groove volume of the circumferential groove.

  Further, in the case where the rib is divided into the center in the width direction of the tire and the shoulder side of the tire with respect to the center in the width direction, the volume of the region located on the center side in the width direction of the tire of the concave portion of the resonance portion is By providing a recess in the resonance part so that it is larger than the volume of the region located on the shoulder side of the tire, a shear force opposite to the lateral force of the tire (especially, a large lateral force is generated due to the increased load) The cornering-out block that receives the force during vertical compression is suppressed, and the cornering power is increased (the steering stability during cornering is improved).

Hereinafter, the present invention will be described more specifically with reference to the drawings.
FIG. 1 schematically shows a main part of an embodiment of a pneumatic tire according to the present invention. Such a tire forms a contact surface as shown in FIG. 2, where the contact surface is filled with a specified air pressure into a tire mounted on an applicable rim and placed vertically on a flat plate. The surface area of the tread rubber that comes into contact with the flat plate when a load corresponding to 80% of the specified mass (maximum load load) is applied.

  1 in the figure passes through the region from the tread stepping end to the kicking end and extends along the direction of rotation of the tire, for example, a circumferential groove that extends continuously in a straight line and forms an annular shape as a whole. It is.

Reference numeral 2 denotes a rib defined by the circumferential groove 1, and reference numeral 3 denotes a resonance part for reducing air column resonance generated during rolling contact with the tire. The resonance part 3 is a recess 3a that functions as an air chamber that forms a closed space by contact with the road surface within the ground contact surface of the tire, and opens individually to the groove wall of the circumferential groove 1 connected to the recess 3a. Consists of a narrowed passage 3b, as shown in FIG. 2, when the tire width direction center side A and the tire shoulder side B are divided from the width direction center C of the rib 2 as a boundary, the tire width direction center The volume V _{1 of} the region located on the side A is arranged to be larger than the volume V _{2 of} the region located on the shoulder side B of the tire.

  In the tire configured as described above, by adjusting the resonance frequency of the resonance portion 3 to the frequency band of the circumferential groove 1, the primary resonance energy of the circumferential groove 2 is reduced by the air in the narrowed passage 3b of the resonance portion 3. The air column resonance in the circumferential groove 1 is absorbed by the vibration and is effectively reduced without reducing the groove volume of the circumferential groove 1. In addition, since the shearing force is suppressed, the cornering power is reduced. Steering stability during cornering is improved.

  Here, with respect to the recess 3a of the resonance part 3, the steering stability during cornering is improved by making the volume of the region located on the center side in the width direction of the tire larger than the volume of the region located on the shoulder side of the tire. The reason is as follows.

  That is, during cornering, the tire generates a lateral force as shown in FIG. 3, while the tire rubber is deformed to swell into a barrel shape as shown in FIG. 4 due to the load on the frictional road surface. A force (shearing force) as shown in the figure is generated.

  Of these two forces, the lateral force mainly received from the outside (out) of the tire is canceled out at the center side in the width direction of the tire, and the vehicle load during cornering is also outside ( out), but the force generated with this load bias will be offset at the center of the rib in the width direction of the tire, and to improve steering stability during cornering It is particularly effective to eliminate such an offset relationship.

  The force (shearing force) shown in FIG. 4 is related to the compression rigidity of the tread rubber, and a gap such as the recess 3a of the resonance part 3 is used to direct the rubber flow to the gap as shown in FIG. This makes it possible to eliminate the above canceling relationship, and the concave portion of the resonance portion has a larger volume in the region located on the center side in the width direction of the tire than the volume in the region located on the shoulder side of the tire. In such a case, the generation efficiency of the lateral force can be increased, thereby improving the steering stability during cornering.

In order to increase the lateral force generation efficiency, an effect appears when the area on the center side in the width direction of the tire is set to an opening area of 60% or more of the opening area of the recess of the resonance part. This becomes conspicuous when the entire recess is disposed on the center side in the width direction of the tire.

FIG. 6 schematically shows a Helmholtz resonator. In the state where the land portion opening of the recess 3a and the narrowed passage 3b in the resonance portion 3 of the present invention are both closed by the road surface, they constitute a resonator as shown in the figure, and the resonance frequency f of the resonance portion 3 ₀ is obtained by the above-described equation.

  When the cross-sectional shape of the constricted passage 3b of the resonance part 3 is not a circular shape but a slit type as shown in FIG. 1, the radius r in the above formula is based on the cross-sectional area of the constricted passage 3b. And calculating backwards.

As described above, the resonance frequency f ₀ of the resonance part 3 is changed by appropriately selecting the cross-sectional area S of the constriction passage 3b, the volume V of the recess 3a, etc., and the coefficient 1.3 in the equation has a different value depending on the literature. However, in general, it can be obtained from an empirical formula and is used as one coefficient in the present invention.

  The recess 3a of the resonance part 3 can be applied with the same cross-sectional area as the opening area over the entire depth direction, but with the cross-sectional area gradually increasing or decreasing in the depth direction. May be. The bottom wall of the recess 3a can be a flat surface, or can be provided with a convex or concave curved surface toward the opening. When unevenness (unevenness) is provided on the bottom wall, the height of the convex portion is 1.6 mm or more, more preferably 3.0 mm or more.

  Further, the opening shape of the concave portion 3a to the rib surface may be a polygonal shape, a circular shape, an elliptical shape or other curved contour shapes.

  The constriction passage 3b can have an arbitrary planar shape having at least one straight part, curved part or bent part, and a plurality of constrictions 3a can be provided. The cross-sectional area of the passage 3b is the sum (the sum of the cross-sectional areas), and the recess 3a is set using an average value for the length.

狭窄通路１：l₀₁，r₁，S₁
狭窄通路２：l₀₂，r₂，S₂ For example, when two narrowing passages 3b are provided, the following formula can be applied.

Stenosis passage 1: l ₀₁ , r ₁ , S ₁
Constriction passage 2: l ₀₂ , r ₂ , S ₂

When there are more than three stenosis passages 3b, (l ₀ + 1.3r) within √ is added according to the number, and the coefficient in the numerator is changed to an expression displaying the number.

  The concave portion 3a of the resonance portion 3 can be formed by a cast portion (bone) of a vulcanization mold, and the narrow passage 3b can be formed by a sipe blade of the vulcanization mold.

  Further, only one resonance part 3 can be provided for one circumferential groove 1 forming an annular shape, but more preferably, the tire mounted on the applicable rim is filled with the prescribed air pressure and the tire is prescribed. In the state where a load corresponding to 80% of the load is applied, there is always one or more in the ground contact surface of the tire (meaning that all of them including the constricted passage 3b as well as the constricted passage 3b are completely present) And a plurality of resonance portions 3 (resonance portions having different resonance frequencies) having different sizes may be arranged.

  Here, the “applicable rim” is a rim defined in the following standard according to the size of the tire, and the “specified air pressure” is defined in accordance with the maximum load capacity in the following standard. The maximum load capacity is the maximum mass that is allowed to be loaded on a tire according to the following standards. The “specified mass” refers to the above maximum load capacity. The air here can be replaced with an inert gas such as nitrogen gas or the like.

  In addition, the standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, in the United States, “THE TIRE AND RIM ASSOCIATION INC. YEAR BOOK”, in Europe, It is “STANDARDS MANUAL” of THE European Tire and Rim Technical Organization, and “JATMA YEAR BOOK” of Japan Automobile Tire Association in Japan.

  The average depth h of the recess 3a from the surface of the rib 2 (see FIG. 1) should be 20% or more, particularly 40 to 80% of the maximum depth H of the circumferential groove 1 defining the rib 2. .

  Further, the depth d (see FIG. 1) of the constricted passage 3b from the surface of the rib 2 should be 70% or less, particularly 50% or less of the average depth h of the recess 3a, and its width t ( The diameter (when the constriction passage is circular) is preferably 3 to 50% (more preferably 3 to 20% or less) of the width T of the recess 3.

In general passenger cars, the frequency of air column resonance is often observed in the range of 800 to 1200 Hz, so the resonance frequency f ₀ is preferably set in the range of 700 to 1400 Hz or in the range of 700 to 1800 Hz. .

The opening shape of the recess 3a is shown as an example of a rectangular shape, but can be changed to various shapes according to the characteristics of the tire, and the opening area is 25 to 300 mm ² , more preferably 72 to it can be in the range of 180 mm ^2. The reason is, while effectively exhibiting its essential functions in the recess 3a, the recess opening edge, is because it is possible to effectively suppress an increase in the road crash noise, in the opening area is less than 25 mm ^2, the recess to ensure the required volume, even if the depth of the recess 3a, whereas it is difficult to sufficiently exhibit the function as the resonance portion, exceeds 300 mm ^2, the length of the opening edge is long For this reason, it becomes impossible to deny the manifestation of road surface collision noise.

  When the Helmholtz type resonator as described above cannot be applied (resonance part shape is “bite” and there is a problem in the design), or when there is a region where the resonance frequency cannot be predicted in the above formula, etc. 7 and 8, as shown in FIG. 7 and FIG. 8, the recessed portion 3a and the narrowed passage 3b are regarded as the first conduit 3a ′ and the second conduit 3b ′, respectively, and are connected to each other. Resonance frequency f is obtained according to the following formula using a type of resonator.

Per stepped type resonator, 'Z ₁₂ the acoustic impedance of the side, second conduit 3b in the boundary' first conduit 3a at the boundary if the acoustic impedance of the side and Z _21,
From continuous conditions,
Z ₂₁ = (S ₂ / S ₁ ) · Z ₁₂

For the second pipe line 3b ′, if the boundary conditions are x = 0, V ₂ = V ₀ e ^jwt , x = l ₂ and P ₂ / V ₂ = Z ₂ , the sound pressure distribution in the second pipe line 3b ′ P ₂ is
P ₂ = Z _s · {Z ₂₁ cos (k (l ₂ −x)) + jZ _c sin (k (l ₂ −x)) / Z _c cos (kl ₂ ) + jZ ₂₁ sin (kl ₂ )} · V ₀ e ^jwt
V ₂ : Particle velocity distribution in the second pipe 3b ′
V ₀ : Particle velocity at the input point
j: Imaginary unit
Z _c : ρc (ρ: density of air, c: speed of sound)

Further, 'the, boundary conditions and with _{V 1 = 0, x = l} 2 with x = l ₁ and _{P 2 / V 2 = Z 21} , first conduit 3a' first conduit 3a sound pressure distribution P ₁ is
P ₁ = Z _s · [Z ₂₁ cos (k (l ₂ −x)) / cos (kl ₁ ) · {Z _c cos (kl ₂ ) + jZ ₂₁ sin (kl ₂ )}] · V ₀ e ^jwt

Here, since resonance condition x = 0 and P ₂ = 0,
tan (kl ₁ ) tan (kl ₂ ) − (S ₂ / S ₁ ) = 0, k = 2πf / c, and k, l ₁ , l ₂ , S ₂ , S ₁ , c is determined to obtain the resonance frequency f.

  In the illustrated example, the stepped pipe type resonator is a combination of pipes that are rectangular parallelepiped. However, in order to obtain the resonance frequency using the above conditional expression, the cross-sectional area S and the length l of each pipe are determined. The shape of the pipe line is not limited to a rectangular parallelepiped, and various shapes can be applied.

  In addition, it is indispensable that one end of the second pipe line 3b ′ is opened by the groove wall of the circumferential groove 1. However, the first pipe line 3a ′ and the second pipe line 3b ′ are arranged on the ground surface of the tread tread surface. Since the closed space is formed by contact with the road surface, the upper end of the closed space can be opened on the surface of the rib 2, and this point is not limited.

Example 1
The dimension along the circumferential direction of the recess L: 18mm, width T: 6mm, depth h: 7mm, constriction passage length L ': 6mm, depth d: 2mm, width t: 1mm, working frequency: 1061Hz) 60 Helmholtz-type resonators around the tire (the pitch length is about 34 mm (60 cm per tire), the length varies depending on the tire center and shoulder). Tires of size 195 / 65R15 (rib width 20mm, thickness 8mm, groove width 8mm, depth 8mm) with a ground contact surface as shown in Fig. 2 provided with a case of 60mm on the circumference. (With four circumferential grooves), fitted to a 6JJ rim as a conforming tire 1, and with an air pressure of 210 kPa, an indoor drum tester and a speed of 80 km / h under the action of a load of 4 kN Measure the lateral sound of the tire at this time according to the conditions specified in JASO C606, and 1/3 octave The overall value of the band center frequency 800 Hz-1000 Hz-1250 Hz band was evaluated together with the comparative tire (compared to a tire having only four linear circumferential grooves).

  In this case, the effect was judged to be a sound pressure drop of 2 dB or more, which can be expected to be improved by the driver's feeling evaluation in the actual vehicle test.

で求められる値（音速cは343.7m/sで計算）とした。 Note that the tire 1 having a contact surface as shown in FIG. 9 is used as the comparative tire 1, and the tire having the contact surface as shown in FIG. 10 is used as a comparison tire 2, and the resonance frequency f ₀ of the resonance portion is As previously mentioned,

(Sound velocity c is calculated at 343.7 m / s).

  As a result, regarding the noise level, the noise generated in the frequency band of 1000 Hz is reduced by about 2.5 dB compared to the tire with only four linear circumferential grooves in both the comparative tires 1 and 2 and the compatible tire 1. It was confirmed that

  In addition, for the above-mentioned conforming tire 1 and comparative tires 1 and 2, the driver's steering stability performance was evaluated in the actual vehicle test on the test course (the lane change was performed at a speed of 100 KPH, and the vehicle response at this time was evaluated as a feeling score. ).

  This evaluation is expressed in the form of a comparative score for a comparative tire (compared to a tire with only four straight circumferential grooves), and it is effective when the difference is +3 or more as a difference that a general driver can recognize the difference. It was judged that there was.

  As a result, the comparative tire 1 has a comparative score of -1 and the comparative tire 2 has a negative score of 2, while the conforming tire 1 has a positive score of +5. It was done.

Example 2
In the case of a tire having a Helmholtz type resonator having the same size as in Example 1, when the arrangement position of the resonator (concave portion) is changed along the width direction of the rib (center side relative to the center in the width direction of the rib) The noise reduction effect and the steering stability improvement effect in the opening area (%) of the recessed portion that enters are changed (the test is the same as in Example 1). The results are shown in Table 1.

  As can be seen from Table 1, more than 60% of the opening area of the recess in the resonance part exists on the center side of the tire (center side in the width direction of the tire) with respect to the center in the width direction of the ribs. It has been found that the noise level can be reduced while improving.

  It is possible to provide a pneumatic tire that can effectively reduce air column resonance while improving steering stability.

It is the figure which showed typically the principal part of the pneumatic tire according to this invention. FIG. 2 is a view showing a ground contact surface of the tire shown in FIG. It is the figure which showed the cross section of the tire at the time of cornering. It is the figure which showed typically the cross section of the tread rubber before the load of the load and after the load. It is a figure for demonstrating rubber | gum flow. It is the figure which showed the Helmholtz resonator typically. It is explanatory drawing of a stepped type resonator. It is the figure which showed the outer surface of the tire to which the stepped type resonator was applied about the principal part. 2 is a view showing a contact surface of a comparative tire 1. FIG. 2 is a view showing a contact surface of a comparative tire 2. FIG.

Explanation of symbols

1 circumferential groove
2 Ribs (Land)
3 Resonance part
3a recess
3b narrowed passage

Claims (4)

At least one circumferential groove extending along the direction of rotation of the tire and passing through an area from the tread stepping edge to the kicking edge on the ground contact surface of the tire, and a plurality of rows partitioned by the circumferential groove In pneumatic tires with ribs,
The rib comprises a recess that forms a closed space by contact with a road surface within the ground contact surface of the tire, and a narrowed passage that is connected to the recess and opens in the groove wall of the same circumferential groove, and the noise that the tire contacts the ground A resonance part that resonates at a frequency substantially equivalent to noise and reduces the sound is provided.
When the rib is divided into the center in the width direction of the tire and the shoulder side of the tire with respect to the center in the width direction, the volume of the region located on the center in the width direction of the tire A pneumatic tire characterized in that the arrangement is larger than the volume of the region located on the shoulder side of the tire. 2. The pneumatic tire according to claim 1, wherein the region on the center side in the width direction of the tire has an opening area of 60% or more of the opening area of the recess of the resonance portion . At least one circumferential groove extending along the direction of rotation of the tire and passing through an area from the tread stepping edge to the kicking edge on the ground contact surface of the tire, and a plurality of rows partitioned by the circumferential groove In pneumatic tires with ribs,
The rib comprises a recess that forms a closed space by contact with a road surface within the ground contact surface of the tire, and a narrowed passage that is connected to the recess and opens in the groove wall of the same circumferential groove, and the noise that the tire contacts the ground A resonance part that resonates at a frequency substantially equivalent to noise and reduces the sound is provided.
The recess of the resonance part is located on the tire width side center side when the rib is divided into the tire width direction center side and the tire shoulder side with respect to the width direction center of the rib. tire. 4. The pneumatic tire according to claim 1, wherein the resonance part is a Helmholtz type resonator capable of obtaining a resonance frequency f ₀ according to the following formula.
Record

Where r is the radius of the constriction passage,
l ₀ : length of the stenosis passage,
S: Cross-sectional area of the narrowed passage
V: Volume of the recess,
C: speed of sound

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