JP5206142B2 - Tire and wheel assembly - Google Patents

Description

  The present invention relates to a tire / wheel assembly including a wheel whose center of gravity is shifted from the center position of the rim to one side in the axle direction, and a pneumatic tire fitted to the rim, and more particularly, steering stability. The present invention relates to a tire and wheel assembly that can reduce road noise while maintaining good tire performance.

  Road noise is noise generated by vibrations picked up from a road surface by a tire being transmitted to a vehicle compartment through an axle and resonating in the vehicle compartment. Conventionally, in order to reduce road noise generated in a low frequency region around 125 Hz, a device has been devised to lower the primary natural frequency of a pneumatic tire. In other words, the radial primary natural frequency f of the pneumatic tire has a relationship of f = 1 / 2π × √ (K / M) with respect to the rigidity (K) of the sidewall portion and the mass (M) of the tread portion. Therefore, by reducing the rigidity of the sidewall portion or increasing the mass of the tread portion, the primary natural frequency f is reduced to avoid resonance between the pneumatic tire and the vehicle (for example, And Patent Documents 1 and 2).

However, when the rigidity of the sidewall portion is lowered or the mass of the tread portion is increased, there is a drawback that the steering stability is deteriorated. In addition, when the mass of the tread portion is increased, the rolling resistance tends to increase. For this reason, it is difficult to effectively reduce road noise without sacrificing other tire performances with these methods.
JP-A-6-32119 JP-A-10-76816

  An object of the present invention is to provide a tire / wheel assembly which can reduce road noise while maintaining good tire performance such as steering stability.

To achieve the above object, a tire / wheel assembly according to the present invention comprises a wheel having a center of gravity shifted from the center position of the rim to one side in the axle direction, and a pneumatic tire fitted to the rim. In the wheel assembly, when the pneumatic tire is divided with the center position of the rim as a boundary, the mass of the portion of the tread portion on the opposite side of the wheel center of gravity of the tread portion of the pneumatic tire is set to the portion of the wheel center of gravity side. A tire / wheel assembly in which the rigidity of the sidewall portion on the opposite side of the wheel center of gravity of the pneumatic tire is lower than the rigidity of the sidewall portion on the wheel center of gravity side, which is greater than the mass ;
The cross-sectional thickness T1 of the portion on the opposite side of the wheel center of gravity position of the tread portion of the pneumatic tire is made larger than the cross-sectional thickness T2 of the portion on the wheel center of gravity side, and the wheel center of gravity position of the pneumatic tire is While making the cross-sectional thickness S1 of the opposite side wall part smaller than the cross-sectional thickness S2 of the side wall part of the wheel center of gravity side,
The tan δ value at 60 ° C. of the rubber composition used for the portion on the opposite side of the wheel center of gravity position of the tread portion of the pneumatic tire is the tan δ at 60 ° C. of the rubber composition used for the wheel centroid side portion. It is characterized by being smaller than the value A2 .

  The inventor found that the primary natural vibration mode of a pneumatic tire related to a frequency band near 125 Hz is a symmetrical vibration mode in the meridian section in the tire alone, but the influence of the position of the center of gravity of the wheel when the rim is assembled. It was found that the vibration mode becomes asymmetrical. That is, when a pneumatic tire is mounted on a wheel whose center of gravity is shifted from the center position of the rim to one side in the axle direction, the deformation of the pneumatic tire in the primary natural vibration mode is opposite to the wheel center of gravity position. It becomes relatively large at the site.

  Therefore, in the present invention, in view of the left-right asymmetric vibration mode at the time of assembling the rim, the portion selected on the opposite side of the wheel center of gravity position where the contribution to the primary natural vibration mode of the pneumatic tire is relatively large is selected. Therefore, a structure for lowering the primary natural frequency is applied.

  According to the present invention, the mass of the portion on the opposite side of the wheel center of gravity of the tread portion of the pneumatic tire is relatively increased, and the rigidity of the sidewall portion on the opposite side of the wheel center of gravity of the pneumatic tire is relatively increased. Therefore, road noise can be effectively reduced while minimizing adverse effects on tire performance such as steering stability.

In the present invention, as means for increasing the mass of the portion on the opposite side of the wheel center of gravity of the tread portion of the pneumatic tire to the mass of the portion on the side of the wheel center of gravity, it is opposite to the wheel center of gravity of the tread portion of the pneumatic tire. The cross-sectional thickness T1 of the portion on the side is made larger than the cross-sectional thickness T2 of the portion on the wheel gravity center side . On the other hand, as a means for lowering the rigidity of the sidewall portion on the opposite side of the wheel center of gravity of the pneumatic tire than the rigidity of the sidewall portion on the wheel center of gravity side, the sidewall on the opposite side of the wheel center of gravity position of the pneumatic tire is used. The cross-sectional thickness S1 of the portion is made smaller than the cross-sectional thickness S2 of the sidewall portion on the wheel gravity center side .

  In particular, the relationship between the cross-sectional thickness T1 of the portion on the opposite side of the wheel center of gravity of the tread portion of the pneumatic tire and the cross-sectional thickness T2 of the portion on the wheel center of gravity side is 1 mm ≦ T1-T2 ≦ 4 mm. It is preferable that the relationship between the sectional thickness S1 of the sidewall portion on the opposite side of the wheel center of gravity position and the sectional thickness S2 of the sidewall portion on the wheel center of gravity side is 0.4 ≦ S1 / S2 ≦ 0.9. . Thereby, tire performance such as steering stability and reduction of road noise can be achieved at a high level.

Further, the tan δ value at 60 ° C. of the rubber composition used for the portion on the opposite side of the wheel gravity center position of the tread portion of the pneumatic tire is the tan δ at 60 ° C. of the rubber composition used for the wheel gravity center portion. It is made smaller than the value A2 . By using a low tan δ rubber composition in the thick part of the tread gauge in this way, the heat generation state of the tread part on both sides of the tire center (center position of the rim) can be made equal, so at high speed running It is possible to promote the improvement of steering stability and the reduction of rolling resistance.

  Particularly, the value A1 of tan δ at 60 ° C. of the rubber composition used for the portion on the opposite side of the wheel center of gravity of the tread portion of the pneumatic tire and the tan δ at 60 ° C. of the rubber composition used for the portion on the wheel center of gravity side. It is preferable that the ratio A2 / A1 with the value A2 is in a relationship of T1 / T2 <A2 / A1 with respect to the ratio T1 / T2 of the cross-sectional thickness of the tread portion. That is, by changing the value of tan δ at a ratio larger than the ratio of the cross-sectional thickness at the tread portion, it is possible to further promote the improvement of steering stability and the reduction of rolling resistance during high speed running.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 each show a tire / wheel assembly according to an embodiment of the present invention. FIG. 3 shows the main part of FIG.

  1 and 2, W is a wheel, and T is a pneumatic tire. The wheel W includes a rim 1 for fitting the pneumatic tire T and a disk portion 2 that connects the rim 1 and the axle. The center-of-gravity position G of the wheel W as a single unit is shifted from the center position C of the rim 1 to one side in the axle direction. In FIG. 1, the center of gravity position G of the wheel W is offset to the outside with respect to the vehicle, but in FIG. 2, the center of gravity position G of the wheel W is offset to the inside of the vehicle.

  The pneumatic tire T includes a tread portion 11, a pair of left and right sidewall portions 12, and a pair of left and right bead portions 13. Here, when the pneumatic tire T is divided with the center position C of the rim 1 as a boundary, the mass of the portion 11A on the opposite side to the wheel center of gravity position of the tread portion 11 of the pneumatic tire T is the portion 11B on the wheel center of gravity side. The rigidity of the sidewall portion 12A on the side opposite to the wheel center of gravity position of the pneumatic tire T is lower than the rigidity of the sidewall portion 12B on the wheel center of gravity side.

  Note that the rigidity relationship between the sidewall portions 12A and 12B can be easily determined based on the difference in the configuration. However, when the rigidity is obtained as a numerical value, the following measurement is performed. good. That is, a load detector for preparing split rims to be fitted respectively to the right and left bead portions, each split rim being configured to be displaceable in the tire radial direction, and measuring the reaction force in the tire radial direction received by the split rim. Is installed. Then, the divided rims are attached to the left and right bead portions, respectively, while the tread portion is fixed from the outside. For fixing the tread portion, for example, 12 clamps having a tire width direction dimension of 500 mm and a tire circumferential direction dimension of 130 mm may be prepared, and the tread portion may be gripped from the outside by these clamps. Next, the reaction force when the same displacement is applied to the left and right divided rims in the tire radial direction is measured. Here, when the displacement (mm) of each side wall portion is taken on the horizontal axis and the reaction force (N) of each side wall portion is taken on the vertical axis, an approximate straight line is obtained. It is the rigidity (N / mm) of the wall portion.

  Examples of means for making the mass of the portion 11A opposite to the wheel center of gravity position of the tread portion 11 of the pneumatic tire T larger than the mass of the wheel center of gravity portion 11B include a cap tread, an under tread, a wing tip, etc. It is possible to adjust the volume of the rubber, adjust the dimensions of the belt layer and the belt cover layer, and embed a weight adjusting member in the tread portion. In particular, as shown in FIG. 3, the cross-sectional thickness T1 of the portion 11A opposite to the wheel center of gravity position of the tread portion 11 of the pneumatic tire T is made larger than the cross-sectional thickness T2 of the wheel center-of-gravity portion 11B. Is desirable.

  On the other hand, as means for lowering the rigidity of the sidewall portion 12A on the opposite side of the wheel center of gravity of the pneumatic tire T from the rigidity of the sidewall portion 12B on the wheel center of gravity side, for example, bead filler, rim cushion, black side It is conceivable to adjust the volume of a rubber such as a wall, adjust the hardness of the rubber, adjust the winding height of the carcass layer, or adjust the size of the side reinforcing layer. In particular, as shown in FIG. 3, the sectional thickness S1 of the sidewall portion 12A opposite to the wheel center of gravity position of the pneumatic tire T is made smaller than the sectional thickness S2 of the sidewall portion 12B on the wheel center of gravity side. Is desirable.

  In the tire / wheel assembly described above, since the pneumatic tire T is attached to the wheel W whose center of gravity G is shifted from the center position C of the rim 1 to one side in the axle direction, Deformation in the natural vibration mode becomes relatively large in a portion opposite to the wheel center of gravity position. For example, FIG. 5 shows a deformed state of a tire when a left-right symmetric primary natural vibration mode is generated, and FIG. 6 shows a deformed state of the tire when a left-right asymmetric primary natural vibration mode is generated. However, in the pneumatic tire T with respect to the wheel W in which the gravity center position G is shifted from the center position C of the rim 1 to one side in the axle direction, there is a tendency that a left-right asymmetric primary natural vibration mode as shown in FIG. And in the site | part on the opposite side to the wheel gravity center position of the pneumatic tire T, a deformation | transformation in a primary natural vibration mode becomes comparatively large like the X part of FIG.

  On the other hand, the mass of the portion 11A on the opposite side to the wheel center of gravity position of the tread portion 11 of the pneumatic tire T is relatively increased, and the sidewall portion 12B on the opposite side of the wheel center of gravity position of the pneumatic tire T is obtained. Therefore, road noise can be effectively reduced while minimizing adverse effects on tire performance such as steering stability.

  Further, the cross-sectional thickness S1 of the sidewall portion 12A opposite to the wheel gravity center position of the pneumatic tire T is relatively reduced, while the wheel gravity center position of the tread portion 11 of the pneumatic tire T is opposite to the wheel gravity position. When the cross-sectional thickness T1 of the portion 11A is relatively increased, that is, when the tread gauge is increased while reducing the rigidity of the sidewall portion 12A, the ground contact shape is left and right of the tire center (center position of the rim). The effect of equalization is obtained.

  The relationship between the cross-sectional thickness T1 of the portion 11A opposite to the wheel center of gravity position of the tread portion 11 of the pneumatic tire T and the cross-sectional thickness T2 of the wheel center-of-gravity portion 11B is 1 mm ≦ T1−T2 ≦ 4 mm. Is preferred. Thereby, tire performance such as steering stability and reduction of road noise can be achieved at a high level. If the difference between the two is less than 1 mm, the effect based on the mass difference of the tread portion 11 is reduced. Conversely, if the difference is more than 4 mm, it is necessary to ensure the minimum groove depth on the thin side of the tread portion, and the thickness is reduced. Since it cannot be made too small, the thick side of the tread portion needs to be thickened, resulting in an increase in the mass of the entire tire. Thereby, there exists a possibility of causing the increase in rolling resistance and the fall of steering stability.

  The relationship between the sectional thickness S1 of the sidewall portion 11A opposite to the wheel center of gravity of the pneumatic tire T and the sectional thickness S2 of the sidewall portion 11B on the wheel gravity center side is 0.4 ≦ S1 / S2 ≦ 0. 9 is preferable. Thereby, tire performance such as steering stability and reduction of road noise can be achieved at a high level. If the ratio between the two is less than 0.4, it is difficult to ensure the rigidity of the tire. Conversely, if it exceeds 0.9, the effect based on the difference in rigidity of the sidewall portion 12 is reduced.

  Here, a method for measuring the cross-sectional thickness of the tread portion and the sidewall portion will be described with reference to FIG.

  The cross-sectional thickness of the tread portion is the cross-sectional thickness (a1, b1) at the belt edge portion and the cross-sectional thicknesses (a2-a4, b2-b4) at positions 1 mm away from the edges of the main groove on both sides. Measured and defined as the average value obtained from these measured values. The main groove is a groove extending in the tire circumferential direction and having a groove depth of 4 mm to 15 mm and a groove width of 3 mm to 20 mm. The cross-sectional thickness of the tread portion is measured in a direction perpendicular to the carcass ply.

  In FIG. 4, the cross-sectional thickness T1 of the portion 11A on the opposite side of the wheel center of gravity of the tread portion 11 is T1 = (a1 + a2 + a3 + a4 + a5) / 5. On the other hand, the cross-sectional thickness T2 of the portion 11B on the wheel gravity center side of the tread portion 11 is T2 = (b1 + b2 + b3 + b4 + b5) / 5.

  The cross-sectional thickness of the sidewall portion is 10% of the cross-sectional thickness (c2, d2) at the position where the tire maximum width (SW) is reached and the tire cross-sectional height (SH) from the tire maximum width position outward in the tire radial direction. The cross-sectional thickness (c1, d1) at the position of the tire and the cross-sectional thickness (c3, d3) at the position of 20% of the tire cross-sectional height (SH) from the tire maximum width position to the inside in the tire radial direction are measured. , Defined as the average value obtained from these measured values. The cross-sectional thickness of the sidewall portion is measured in a direction perpendicular to the main body portion of the carcass ply.

  In FIG. 4, the cross-sectional thickness S1 of the sidewall portion 12A opposite to the wheel center of gravity position of the pneumatic tire T is S1 = (c1 + c2 + c3) / 3. On the other hand, the cross-sectional thickness S2 of the sidewall portion 12B on the wheel gravity center side of the pneumatic tire T is S2 = (d1 + d2 + d3) / 3.

  In the pneumatic tire T, the value A1 of tan δ at 60 ° C. of the rubber composition used for the portion 11A on the side opposite to the wheel center of gravity of the tread portion 11 is 60 ° C. of the rubber composition used for the portion 11B on the wheel center of gravity side. It is preferable to make it smaller than the tan δ value A2. In this way, by using the rubber composition of low tan δ in the portion 11A where the tread gauge is thick, the heat generation state of the tread portion 11 on both sides of the tire center (center position of the rim) can be made equal. It is possible to promote improvement in steering stability during traveling and reduction in rolling resistance. The interface between the two rubber compositions is preferably disposed at the tire center (center position of the rim), but may be disposed within a range of ± 10% of the ground contact width from the center position C of the rim 1.

  The tan δ value A1 at 60 ° C. of the rubber composition used for the portion 11A opposite to the wheel gravity center position of the tread portion 11 and the tan δ value A2 at 60 ° C. of the rubber composition used for the wheel gravity center portion 11B The ratio A2 / A1 is preferably in a relationship of T1 / T2 <A2 / A1 with respect to the ratio T1 / T2 of the cross-sectional thickness of the tread portion 11. That is, by changing the value of tan δ at a ratio larger than the ratio of the cross-sectional thicknesses in the tread portion 11, it is possible to further promote the improvement of steering stability and the reduction of rolling resistance during high speed running. Further, the portion 11A with a thick tread gauge contributes to the reduction in rolling resistance, and conversely the portion 11B with a thin tread gauge contributes to an improvement in steering stability, so that both improvement in steering stability and reduction in rolling resistance are achieved. be able to. The tan δ values A1 and A2 at 60 ° C. are preferably set to 0.1 to 0.5.

  Tan δ is measured in accordance with JIS K6394. More specifically, it is tan δ measured using a viscoelastic spectrometer (manufactured by Ueshima Seisakusho) under measurement conditions of a frequency of 20 Hz and an elongation deformation strain of 10 ± 2%.

A tire / wheel assembly comprising a wheel (rim size: 17 × 7JJ) whose center of gravity is shifted from the center position of the rim to one side in the axle direction and a pneumatic tire (tire size: 215 / 55R17) fitted to the rim. The conventional example, comparative examples 1 to 3 and the test in which the cross-sectional thickness of the tread part, the cross-sectional thickness of the side wall part, and the tan δ value at 60 ° C. of the rubber composition used for the tread part were set as shown in Table 1. The tire / wheel assemblies of Examples 1 to 3 were produced. As the wheel, an aluminum wheel having a center of gravity shifted from the center position of the rim by 40 mm toward the vehicle outer side was used.

  For these tire / wheel assemblies, road noise, steering stability, and rolling resistance were evaluated by the following test methods, and the results are also shown in Table 1.

Road noise:
Each tire and wheel assembly is mounted on a 2500cc domestic FR vehicle with an air pressure of 230kPa, a microphone is installed at the position on the driver's seat window side, and road noise of 0 to 500Hz when driving on a rough road surface at 60km / h. It was measured. Then, road noise in the 125 Hz band was analyzed.

Steering stability:
Each tire and wheel assembly was mounted on a 2500 cc domestic FR vehicle with an air pressure of 230 kPa, and a sensory evaluation was conducted by a test driver on the handling stability. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability.

Rolling resistance:
For each tire / wheel assembly, the rolling resistance was measured under the condition of an air pressure of 230 kPa. The evaluation results are shown as an index with the conventional example being 100. It means that rolling resistance is so small that this index value is small.

  As shown in Table 1, in Comparative Example 1, since the cross-sectional thickness of the tread portion was increased as compared with the conventional example, a road noise reduction effect was observed, but the steering stability was lowered and the rolling resistance was increased. It was. In Comparative Example 2, since the cross-sectional thickness of the side wall portion was made smaller than that in the conventional example, an effect of reducing road noise was observed, but an increase in steering stability was incurred. In Comparative Example 3, since the cross-sectional thickness of the tread portion was increased and the cross-sectional thickness of the sidewall portion was reduced compared to the conventional example, an effect of reducing road noise was observed, but the steering stability was lowered and the rolling resistance was reduced. An increase was incurred.

On the other hand, in Test Examples 1 to 3, the cross-sectional thickness T1 of the portion on the opposite side of the wheel center of gravity position of the tread portion is made larger than the cross-sectional thickness T2 of the portion on the wheel center of gravity side. Since the cross-sectional thickness S1 of the opposite side wall portion is made smaller than the cross-sectional thickness S2 of the side wall portion of the wheel center of gravity, road noise is effectively reduced while maintaining good steering stability and rolling resistance. I was able to.

1 is a meridian cross-sectional view showing a tire / wheel assembly according to an embodiment of the present invention. It is meridian sectional drawing which shows the tire wheel assembly which consists of other embodiment of this invention. It is sectional drawing which shows the principal part of FIG. It is tire sectional drawing for demonstrating the measuring method of the cross-sectional thickness of a tread part and a side wall part. FIG. 3 is a partially cutaway cross-sectional view schematically showing a deformed state of a tire when a bilaterally symmetric primary natural vibration mode is generated. FIG. 4 is a partially cutaway cross-sectional view schematically showing a deformed state of a tire when a left-right asymmetric primary natural vibration mode is generated.

Explanation of symbols

1 rim 2 disc part 11 tread part 12 sidewall part 13 bead part C rim center position G wheel center of gravity position T pneumatic tire W wheel

Claims (3)

In a tire / wheel assembly comprising a wheel whose center of gravity is shifted from the center position of the rim to one side in the axle direction and a pneumatic tire fitted to the rim, the pneumatic tire is separated from the center position of the rim. The mass of the portion on the opposite side of the wheel center of gravity of the tread portion of the pneumatic tire is larger than the mass of the portion on the wheel center of gravity side, and the wheel center of gravity position of the pneumatic tire is A tire / wheel assembly in which the rigidity of the opposite side wall is lower than the rigidity of the side wall of the wheel,
The cross-sectional thickness T1 of the portion on the opposite side of the wheel center of gravity position of the tread portion of the pneumatic tire is made larger than the cross-sectional thickness T2 of the portion on the wheel center of gravity side, and the wheel center of gravity position of the pneumatic tire is While making the cross-sectional thickness S1 of the opposite side wall part smaller than the cross-sectional thickness S2 of the side wall part of the wheel center of gravity side,
The tan δ value at 60 ° C. of the rubber composition used for the portion on the opposite side of the wheel center of gravity position of the tread portion of the pneumatic tire is the tan δ at 60 ° C. of the rubber composition used for the wheel centroid side portion. Tire and wheel assembly smaller than value A2 .   The relationship between the cross-sectional thickness T1 of the portion of the tread portion of the pneumatic tire opposite to the wheel gravity center position and the cross-sectional thickness T2 of the wheel gravity center side portion is 1 mm ≦ T1-T2 ≦ 4 mm, and the pneumatic The relation between the cross-sectional thickness S1 of the side wall portion opposite to the wheel center of gravity position of the tire and the cross-sectional thickness S2 of the side wall portion on the wheel center of gravity side is set to 0.4 ≦ S1 / S2 ≦ 0.9. Item 14. The tire / wheel assembly according to Item 1. The value A1 of tan δ at 60 ° C. of the rubber composition used for the portion on the opposite side of the wheel center of gravity position of the tread portion of the pneumatic tire and the tan δ of the rubber composition used for the portion on the wheel center of gravity side at 60 ° C. The tire / wheel assembly according to claim 1 or 2 , wherein the ratio A2 / A1 with respect to the value A2 is in a relationship of T1 / T2 <A2 / A1 with respect to the ratio T1 / T2 of the cross-sectional thickness of the tread portion. .

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