pneumatic tires

Abstract

We offer pneumatic tires that reduce external noise. [Solution] The pneumatic tire according to the present invention has multiple main grooves, has a specified mounting direction to the vehicle body, and when mounted on a regular rim and filled with air to achieve the regular internal pressure, when a load of 85% of the regular load (maximum load capacity) at the regular internal pressure is applied, in the contact area that contacts a flat road surface, the circumferential length L1 at a position 1 / 10 of the tire contact width inward from the outer contact edge of the vehicle and the circumferential length L2 at the tire equator satisfy the relationship L1 / L2 ≤ 0.7, and the cross-sectional area of ​​the outermost main groove, which is located furthest out of the multiple main grooves, is smaller than the cross-sectional area of ​​any of the other main grooves.

Description

Technical Field

[0001] The present invention relates to pneumatic tires, and more particularly to pneumatic tires with reduced external vehicle noise.

Background Art

[0002] In recent years, there has been an increasing demand for reducing the external vehicle noise generated when an automobile runs. The external vehicle noise includes, in addition to the engine noise, the noise from the tires, and the development of low external noise tires capable of reducing the noise from the tires has been vigorously promoted. In the development of low external noise tires, it is important to reduce the air injection resonance noise generated in the main grooves.

[0003] Patent Document 1 discloses a technique for reducing the air injection resonance noise generated in the main grooves by providing longitudinal narrow grooves extending in the circumferential direction on the land portions and periodically changing the depth of the longitudinal narrow grooves in the circumferential direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the longitudinal narrow grooves provided on the land portions can become another noise source. The technique described in Patent Document 1 is not sufficient for reducing the external vehicle noise, and there is still room for improvement.

[0006] An object of the present disclosure is to provide a pneumatic tire with reduced external vehicle noise.

Means for Solving the Problems

[0007] The pneumatic tire according to the present invention has multiple main grooves, has a specified mounting direction to the vehicle body, and when mounted on a regular rim and filled with air to the regular internal pressure, and when a load of 85% of the regular load (maximum load capacity) at the regular internal pressure is applied, the circumferential length L1 at a position 1 / 10 of the tire contact width inward from the outer contact edge of the vehicle and the circumferential length L2 at the tire equator satisfy the relationship L1 / L2 ≤ 0.7, and the cross-sectional area of ​​the outermost main groove, which is located furthest out of the multiple main grooves, is smaller than the cross-sectional area of ​​any of the other main grooves. [Effects of the Invention]

[0008] According to the pneumatic tire of the present invention, external noise can be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This is a plan view showing a portion of the tread pattern of a pneumatic tire, which is an example of an embodiment. [Figure 2] This figure shows the contact area of ​​a pneumatic tire, which is an example of an embodiment. [Figure 3] This figure shows the area of ​​the main groove in the ground contact area. [Figure 4] This figure shows the length of the main groove in the contact area. [Modes for carrying out the invention]

[0010] Hereinafter, an example of an embodiment of the pneumatic tire 10 according to the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the embodiments described below. Furthermore, forms obtained by selectively combining each component of the embodiments described below are included in the present invention.

[0011] The pneumatic tire 10 of this embodiment has a general configuration as a pneumatic tire 10, except for the tread, which is the part that contacts the road surface. Specifically, bead portions including a bead core and a bead filler are provided on both sides in the tire axial direction, and a carcass ply is provided extending from one bead portion to the other in the tire axial direction. A belt is provided on the outer diameter side of the carcass ply, and a tread is provided on the outer diameter side of the belt. In addition, an inner liner is provided inside the carcass ply, and sidewall rubber is provided on both sides of the carcass ply in the tire axial direction. The pneumatic tire 10 may also be provided with a plurality of other rubber members besides those described above.

[0012] In this specification, the shape of the pneumatic tire 10 refers to the shape when it is mounted on a regular rim and filled with air to the regular internal pressure. The contact area 30, described later, is the area that makes contact with a flat road surface when a load of 85% of the regular load (maximum load capacity) at the regular internal pressure is applied. The contact ends E1 and E2 are defined as the axial ends of the contact area 30.

[0013] Here, "standard rim" refers to the rim defined by the tire standard, which is "standard rim" for JATMA and "Measuring Rim" for TRA and ETRTO. "Standard internal pressure" is "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. The standard internal pressure is usually 180kPa for passenger car tires, but it is 220kPa for tires marked as Extra Load or Reinforced. "Standard load" is "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

[0014] The external noise generated by the pneumatic tire 10 can be measured, for example, according to JIS D8301:2020. The external noise is measured by a microphone placed on the road surface on the side of the vehicle when the vehicle, with its engine off, passes through the driving line. The pneumatic tire 10 described below has the effect of reducing external noise, and this effect is particularly noticeable with respect to external noise around 1 kHz.

[0015] Figure 1 is a plan view showing a portion of the tread pattern of a pneumatic tire 10, which is an example of an embodiment. The tread pattern of the pneumatic tire 10 is composed of the pattern shown in Figure 1 being repeated in the circumferential direction of the tire. The circumferential length of one pitch of the tread pattern (pitch length) may be the same for all pitches, but from the viewpoint of reducing external and internal vehicle noise, it is preferable that the pitch length varies in the circumferential direction of the tire.

[0016] The pneumatic tire 10 is a tire with a specified mounting direction to the vehicle body. That is, the tread pattern of the pneumatic tire 10 is not point-symmetrical, and when rotated 180° around a point on the tire equator CL, it takes on a different shape than before the rotation. The tire equator CL is an imaginary line along the tire circumferential direction that passes through the center of the tread in the tire axial direction.

[0017] The pneumatic tire 10 has multiple main grooves. Each main groove extends parallel to the other along the circumferential direction of the tire. The width of each main groove is constant in the circumferential direction of the tire. The depth of each main groove may be the same. In the example shown in Figure 1, the pneumatic tire 10 has four main grooves 11, 12, 13, and 14. The tread also has two shoulder ribs 15 and 19, two mediate ribs 16 and 18, and one center rib 17, all demarcated by the main grooves 11, 12, 13, and 14. The number of main grooves is not particularly limited and can be, for example, two to five. The number of ribs varies depending on the number of main grooves.

[0018] Among the plurality of main grooves, the width of the main groove located farthest outside the vehicle (hereinafter referred to as the outer main groove) is smaller than the width of any of the main grooves other than the outer main groove. Thereby, the relationship between the length and cross-sectional area in the grounding area 30 can be adjusted as described later. The width of the outer main groove is, for example, 0.7 times or more and 0.8 times or less the width of the main groove with the largest width. In adjacent main grooves, the width of the main groove located outside the vehicle may be less than or equal to the width of the main groove located inside the vehicle. In the example shown in FIG. 1, the main grooves 12, 13, 14 have substantially the same width, and the width of the outer main groove 11 is 0.7 times or more and 0.8 times or less the width of the main grooves 12, 13, 14. Note that the widths of the main grooves 11, 12, 13, 14 are not particularly limited to the example shown in FIG. 1.

[0019] In the tread, a plurality of transverse grooves extending in a direction intersecting the main grooves and connected to the main grooves are formed. The transverse grooves are grooves narrower than the main grooves, and the groove width may vary. The maximum width of the transverse grooves is, for example, 0.1 times or more and 0.5 times or less the width of the main grooves to which the transverse grooves are connected. The transverse grooves may be shallower than the main grooves. The transverse grooves may extend straight in the tire axis direction, but from the viewpoint of wear resistance and the like, it is preferable that they are inclined at a predetermined angle with respect to the tire axis direction.

[0020] The tread has a transverse groove 20 communicating from the outer main groove 11 to the outside of the tire. Thereby, the drainage performance of the pneumatic tire 10 is improved. In the example shown in FIG. 1, the shoulder rib 15 on the outside of the vehicle has a transverse groove 20 communicating from the outer main groove 11 to the outside of the tire in the tire axis direction. That is, the transverse groove 20 has an inner end connected to the outer main groove 11 and an outer end extending outside the tire beyond the grounding end E1 and reaching the outer end of the shoulder rib 15. The transverse groove 20 is inclined at a predetermined angle with respect to the tire axis direction in the vicinity of the portion connected to the outer main groove 11, but becomes substantially parallel to the tire axis direction as it approaches the outside of the vehicle.

[0021] The lateral groove 21 has its outer end on the vehicle outer side connected to the outer main groove 11 and its inner end on the vehicle inner side closed within the mediate rib 16. The lateral groove 22 has its inner end on the vehicle inner side connected to the main groove 13 and its outer end on the vehicle outer side closed within the center rib 17. Also, the outer end of the lateral groove 22 is located on the vehicle inner side of the tire equator CL. The lateral groove 23 has its inner end on the vehicle inner side connected to the main groove 14 and its outer end on the vehicle outer side closed within the mediate rib 18. The lateral grooves 21, 22, and 23 are all inclined at substantially the same angle with respect to the tire axial direction. In the example shown in FIG. 1, the lateral grooves 21, 22, and 23 are all inclined at the same predetermined angle as the lateral groove 20 with respect to the tire axial direction. The lengths of the lateral grooves 21, 22, and 23 are substantially the same as each other.

[0022] The lateral groove 24 has its outer end closed within the shoulder rib 19 and its inner end extending beyond the grounding end E2 to the vehicle outer side of the tire and reaching the inner end of the shoulder rib 15 on the vehicle inner side. The lateral groove 24 is inclined at the same predetermined angle as the lateral groove 20 with respect to the tire axial direction near the closed outer tip portion, but becomes substantially parallel to the tire axial direction as it approaches the vehicle inner side.

[0023] As described above, by providing a lateral groove communicating with the outermost rib while providing lateral grooves that are closed within the ribs for ribs other than the outermost rib to ensure the rigidity of the tire, it is possible to achieve both drainage performance and braking characteristics. Note that the shapes of the lateral grooves 20, 21, 22, 23, and 24 are not particularly limited to the example shown in FIG. 1.

[0024] Next, while referring to FIGS. 2 to 4, the grounding region 30 of the pneumatic tire 10 will be described. Here, the grounding region 30 is the region where the pneumatic tire 10 contacts a flat road surface when a load of 85% of the normal load (maximum load capacity) at the normal internal pressure is applied. FIG. 2 is a view showing the grounding region 30 of a pneumatic tire which is an example of the embodiment. FIG. 3 is a view showing the areas of the main grooves 11, 12, 13, and 14 in the grounding region 30. FIG. 4 is a view showing the lengths of the main grooves 11 and 12 in the grounding region 30.

[0025] As shown in Figure 2, the contact area 30 has a first area 31, a second area 32, a third area 33, a fourth area 34, and a fifth area 35. The first area 31, the second area 32, the third area 33, the fourth area 34, and the fifth area 35 are areas formed by the contact of the shoulder rib 15, mediate rib 16, center rib 17, mediate rib 18, and shoulder rib 19 with the road surface, respectively. The first area 31, the second area 32, the third area 33, the fourth area 34, and the fifth area 35 all have an elongated shape, with the length in the circumferential direction of the tire being longer than the length in the axial direction of the tire. In particular, the second area 32, the third area 33, and the fourth area 34 are longer in the circumferential direction of the tire and shorter in the axial direction of the tire than the first area 31 and the fifth area 35. Traces of lateral grooves can be seen in the contact area 30. The first region 31 is divided into five sections by a horizontal groove, and the second region 32, third region 33, fourth region 34, and fifth region 35 each consist of a single continuous region.

[0026] In the contact area 30, the circumferential length L1 at a position 1 / 10 of the tire contact width W on the inside of the vehicle from the outer contact end E1, and the circumferential length L2 at the tire equator CL satisfy the relationship L1 / L2 ≤ 0.7. For example, a shoulder rib 15 exists at a position 1 / 10 of the tire contact width W on the inside of the vehicle from the outer contact end E1. L2 is the maximum length of the contact area 30 in the circumferential direction of the tire.

[0027] The ratio L1 / L2 serves as an indicator of the outer shape of the ground contact area 30. The maximum value L1 / L2 can take is 1, and when L1 / L2 = 1, the ground contact area 30 is rectangular. As L1 / L2 decreases from 1, the ground contact area 30 approaches an elliptical shape.

[0028] The shape of the contact area 30 can be changed, for example, by the curvature of the tread. Increasing the curvature of the tread makes the shape of the contact area 30 closer to a rectangle, while decreasing the curvature of the tread makes the shape of the contact area 30 closer to an ellipse. By decreasing the curvature of the tread, it is possible to satisfy the relationship L1 / L2 ≤ 0.7.

[0029] As shown in Figure 3, in the grounding region 30, the cross-sectional area S11 of the outer main groove 11 is smaller than the cross-sectional areas S12, S13, S14 of any of the other main grooves 12, 13, 14 other than the outer main groove 10A. Here, the cross-sectional areas S11, S12, S13, S14 are obtained by calculating the area of ​​the parts corresponding to each of the main grooves 11, 12, 13, 14 within the virtual line 40 drawn from the outer edge of the grounding region 30. The virtual line 40 has a shape close to an ellipse, as described above.

[0030] The cross-sectional areas S11, S12, S13, and S14 can be calculated, for example, using image processing software. Alternatively, an image of the ground contact area 30 can be imported into image processing software, and a virtual line 40 can be drawn by specifying the outer edge of the ground contact area 30. The area of ​​each part corresponding to the main grooves 11, 12, 13, and 14 can then be calculated while ensuring that the lateral grooves are not included.

[0031] As described above, in the contact area 30, by making the cross-sectional area of ​​S11 smaller than the cross-sectional area of ​​any of the other main grooves 12, 13, and 14 while satisfying the relationship L1 / L2 ≤ 0.7, external noise can be reduced.

[0032] The cross-sectional area S11 of the outer main groove is preferably 70% to 80% of the cross-sectional areas S12, S13, and S14 of any of the other main grooves 12, 13, and 14. By setting S11 to 80% or less of each of S12, S13, and S14, the effect of reducing external noise becomes more pronounced. Furthermore, by setting S11 to 70% or more of each of S12, S13, and S14, drainage performance can be improved.

[0033] In the contact area 30, the length L11 of the outer main groove 11 is preferably 90% to 95% of the length of the main groove closest to the tire equator CL among the multiple main grooves. By setting the length L11 of the outer main groove 11 to 95% or less of the length of the main groove closest to the tire equator CL among the multiple main grooves, the effect of reducing external noise becomes more pronounced. Furthermore, by setting the length L11 of the outer main groove 11 to 90% or more of the length of the main groove closest to the tire equator CL among the multiple main grooves, drainage performance can be improved.

[0034] In the example shown in Figure 4, both main grooves 12 and 13 are the same distance from the tire equator CL, and main grooves 12 and 13 are the main grooves closest to the tire equator CL among the multiple main grooves. As shown in Figure 4, the length L11 of main groove 11 is measured on a straight line passing through the center point in the width direction of main groove 11, and is the distance between the two intersection points where this line intersects with the imaginary line 40. The length L12 of main groove 12 is measured in the same way as L11. In Figure 4, the length L13 of main groove 13 is not shown, but L13 is also measured in the same way as L11 and L12.

[0035] As described above, by using the pneumatic tire according to the present invention and shaping the contact area to a predetermined form, external vehicle noise can be reduced. [Explanation of Symbols]

[0036] 10 Pneumatic tire, 11 (outer) main groove, 12,13,14 Main groove, 15,16,17,18,19 Rib, 20,21,22,23,24 Lateral groove, 30 Contact area, 31 First area, 32 Second area, 33 Third area, 34 Fourth area, 35 Fifth area, 40 Imaginary line, CL Equator, E1,E2 Contact end

Claims

1. A pneumatic tire having multiple main grooves and a specified mounting direction to the vehicle body, When mounted on a standard rim and inflated to the standard internal pressure, and when a load of 85% of the standard load (maximum load capacity) at the standard internal pressure is applied, in the contact area that makes contact with a flat road surface, The circumferential length L1 at a point on the inside of the vehicle, 1 / 10 of the tire contact width from the outer contact edge, and the circumferential length L2 at the tire equator satisfy the relationship L1 / L2 ≤ 0.

7. A pneumatic tire in which the cross-sectional area of ​​the outermost main groove, located on the outermost side of the vehicle, is smaller than the cross-sectional area of ​​any of the other main grooves.

2. The pneumatic tire according to claim 1, wherein the cross-sectional area of ​​the outer main groove is 70% or more and 80% or less of the cross-sectional area of ​​any of the other main grooves.

3. The pneumatic tire according to claim 1, wherein in the contact area, the length of the outer main groove is 90% or more and 95% or less of the length of the main groove closest to the tire equator among the plurality of main grooves.

4. The pneumatic tire according to claim 1, having a lateral groove that communicates from the outer main groove to the outer side of the tire.

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