pneumatic tires

Abstract

To provide a pneumatic tire configured so as to suppress deterioration in uniformity caused by attachment of stud pins.SOLUTION: A tread 3 includes a plurality of main grooves 11 extending continuously along a tire circumferential direction. The tread 3 is divided into shoulder areas SA closer to outsides in a tire axial direction than shoulder main grooves 11s positioned at outermost sides in the tire axial direction of the plurality of main grooves 11 and a center area CA closer to inside in the tire axial direction than the shoulder main grooves 11s. When an area corresponding to 28% of a grounding width TW with a tire equator TC as a center is defined as an equatorial area RA and areas between the equatorial area RA and the shoulder main grooves 11s are defined as equator neighboring areas NA, attachment holes 10 formed in the equator neighboring areas NA on one side in the tire axial direction and the attachment holes 10 formed in the equator neighboring areas NA on the other side in the tire axial direction are arranged zigzag along the tire circumferential direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a pneumatic tire having mounting holes for attaching stud pins formed in a tread.

Background Art

[0002] A pneumatic tire with stud pins attached to its tread, also known as a stud tire or a spike tire, is mainly used for driving on icy and snowy roads. Generally, since stud pins are made of metal materials, attaching a large number of stud pins may deteriorate the uniformity of the tire. Therefore, although it is desirable to adopt a structure considering this point, no specific configuration suitable for this has been proposed.

[0003] In Patent Document 1, a region partitioned between a pair of tire meridians arranged such that the interval on the tire equator line is 0.8% of the tire circumference is defined as a strip region, and when a plurality of strip regions are arranged over the entire tire circumference by shifting them one by one along the tire circumferential direction, the plurality of strip regions include a concentrated region where four or more stud pins are present and a scattered region where three or fewer stud pins are present, and a stud tire has been proposed in which such concentrated regions intermittently exist along the tire circumferential direction. However, intermittently having such concentrated regions is considered to cause deterioration of the uniformity of the tire.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide a pneumatic tire capable of suppressing deterioration of uniformity associated with the attachment of stud pins. [Means for solving the problem]

[0006] The pneumatic tire of this disclosure has a tread formed with mounting holes for attaching stud pins, the tread includes a plurality of main grooves that extend continuously along the circumferential direction of the tire, the tread is divided into a shoulder region on the outer side in the axial direction of the tire and a center region on the inner side in the axial direction of the tire, with respect to the groove width center of the shoulder main groove located on the outermost side in the axial direction of the tire, the equatorial region being defined as the region directly below the equator of the center region, and the region between the equatorial region and the shoulder main groove being defined as the equatorial adjacent region, the mounting holes formed in the equatorial adjacent region on one side in the axial direction of the tire and the mounting holes formed in the equatorial adjacent region on the other side in the axial direction of the tire are arranged in a staggered pattern along the circumferential direction of the tire. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic cross-sectional view of the tire meridian showing the pneumatic tire of this embodiment. [Figure 2] Plan view of the tread of the pneumatic tire of this embodiment [Figure 3] Enlarged view of the main part in Figure 2 [Figure 4] Enlarged view of the main part in Figure 2 [Figure 5] Diagram showing a modified example regarding the arrangement of mounting holes. [Figure 6] Diagram illustrating the relative positions of mounting holes. [Modes for carrying out the invention]

[0008] One embodiment of this disclosure will be described with reference to the drawings.

[0009] As shown in Figure 1, the pneumatic tire T of this embodiment (hereinafter sometimes simply referred to as "tire T") comprises a pair of bead portions 1, sidewalls 2 extending radially outward from each of the bead portions 1, and treads 3 connected to the radially outer ends of each of the sidewalls 2. The tire T further comprises a carcass 4 provided between the pair of bead portions 1, a belt 5 laminated on the radially outer side of the carcass 4, and an inner liner 6 disposed on the inner surface of the tire.

[0010] Here, the tire radial direction is the direction along the diameter of tire T, and corresponds to the vertical direction in Figure 1. In Figure 1, the upper side is the outer side in the tire radial direction, and the lower side is the inner side in the tire radial direction. The tire axial direction is the direction parallel to the rotation axis of tire T, and corresponds to the left-right direction in Figure 1. The side approaching the tire equator TC is the inner side in the tire axial direction, and the side moving away from the tire equator TC is the outer side in the tire axial direction. The tire equator TC is located at the center of tire T in the tire axial direction and is an imaginary line perpendicular to the tire rotation axis in a plan view. The tire circumferential direction is the direction around the rotation axis of tire T.

[0011] An annular bead core 1a is embedded in the bead portion 1. The bead core 1a is formed by covering a converging body such as steel wire with rubber. A bead filler 1b is positioned on the radially outer side of the bead core 1a. The bead filler 1b is formed of triangular-shaped rubber extending radially outward from the bead core 1a. Rim strip rubber 7, which forms the outer surface of the bead portion 1, is provided on the axially outer side of the bead core 1a and bead filler 1b.

[0012] The carcass 4 extends in a toroidal shape across a pair of bead portions 1. The carcass 4 is wound from the inside to the outside in the tire axial direction, sandwiching the bead core 1a and the bead filler 1b. The carcass 4 is formed from carcass plies formed by covering carcass cords with rubber. The carcass cords are aligned in a direction intersecting the tire circumferential direction (for example, in a direction at an angle of 75 to 90 degrees with respect to the tire circumferential direction). Sidewall rubber 8, which forms the outer surface of the sidewall 2, is provided on the tire axial outer side of the carcass 4.

[0013] The belt 5 is formed by multiple belt plies 5a and 5b that are laminated together. Each belt ply 5a and 5b is formed by covering belt cords with rubber, which are aligned in a direction inclined with respect to the circumferential direction of the tire. The belt plies 5a and 5b are laminated so that the belt cords intersect each other in opposite directions. On the radially outer side of the belt 5, there is tread rubber 9 which forms the outer surface of the tread 3. The inner liner 6 is made of a rubber with excellent air-shielding properties, such as butyl rubber. The inner liner 6 maintains the internal pressure of the tire T.

[0014] The tread 3 has mounting holes 10 for attaching stud pins. The tire T is configured as a stud tire (also called a spiked tire) by attaching stud pins (not shown) to each of the mounting holes 10. Generally, stud pins are made of cylindrical metal members. The shape, material, and size of the stud pins to be attached to the tire T are not particularly limited. In this embodiment, the mounting holes 10 have a flask-shaped cross-section, but are not limited to this.

[0015] The outer circumferential surface of the tread 3 has a tread pattern as shown in Figure 2. In this embodiment, a tread pattern is employed that is symmetrical with respect to the tire equator TC and has a phase shift in the circumferential direction of the tire. Tire T is a directional tire in which the direction of tire rotation is specified. Arrow RD indicates the direction of tire rotation when moving forward. The forward direction of rotation RD1 is also called the push-off side, and the rearward direction of rotation RD2 is also called the push-off side. Tire T is not limited to such a directional pattern and may have a non-directional pattern. For example, a tread pattern formed symmetrically with a center point on the tire equator TC may also be used.

[0016] The tread 3 includes a plurality of main grooves 11 that extend continuously along the circumferential direction of the tire. The groove width W11 of the main grooves 11 on the outer surface of the tread 3 is, for example, 10 mm or more. Of the plurality of main grooves 11, the one located on the outermost side in the axial direction of the tire is called the shoulder main groove 11s. In this embodiment, the tread 3 includes two main grooves 11, which correspond to the shoulder main grooves 11s. However, the tread 3 may include three or more main grooves. The tread 3 is divided into a shoulder region SA on the outer side in the axial direction of the tire and a center region CA on the inner side in the axial direction of the tire, based on the groove width center of the shoulder main groove 11s.

[0017] A pair of shoulder main grooves 11s are positioned to straddle the tire equator TC. The distance D11 from the center of the groove width of the shoulder main groove 11s to the tire equator TC is, for example, 52-62% of the contact patch width HW. The contact patch width HW is the axial distance of the tire from the tire equator TC to the contact edge TE. The contact edge TE is the outermost position in the axial direction of the contact surface when a tire T mounted on a regular rim, filled with the regular internal pressure, is placed perpendicular to a flat road surface and a regular load is applied. The contact width TW is the axial distance of the tire between the pair of contact edges TE, and half of this contact width TW is the contact patch width HW.

[0018] The regular rim is the "Standard Rim" in the JATMA standard, the "Design Rim" in the TRA standard, or the "Measuring Rim" in the ETRTO standard. The regular internal pressure is the "Maximum Air Pressure" in the JATMA standard, the "Maximum Value" described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard. The regular load is the load determined for each tire in the standard system including the standard on which the tire is based. For JATMA, it is the maximum load capacity; for TRA, it is the maximum value described in the above table; for ETRTO, it is "LOAD CAPACITY". However, when the tire is for a passenger car, the load shall be 88% of the above load.

[0019] Figure 3 is an enlarged view of the main part of Figure 2, and depicts the land portion provided in the center region CA. In this tire T, in the center region CA, the region of 28% of the grounding width TW centered on the tire equator TC is defined as the region RA directly below the equator, and when the region between the region RA directly below the equator and the shoulder main groove 11s is defined as the region NA adjacent to the equator, the mounting holes 10 formed in the region NA adjacent to the equator on one side in the tire axial direction and the mounting holes 10 formed in the region NA adjacent to the equator on the other side in the tire axial direction are arranged in a staggered manner along the tire circumferential direction.

[0020] According to such a configuration, uneven distribution of the mounting holes 10 in the center region CA of the tread 3 can be prevented, and deterioration of uniformity associated with the attachment of the stud pins can be suppressed. In particular, since deterioration of uniformity as the tire shape in the tire circumferential direction can be suppressed, deterioration of fuel consumption performance (rolling resistance) and noise performance can be well suppressed. In addition, since the stud pins are evenly arranged on the tread 3, the scraping effect of the stud pins on the ice and snow road is enhanced.

[0021] In the region RA directly under the equator, a rib 15 extending continuously in the tire circumferential direction is provided. Thereby, a ground contact surface of the region RA directly under the equator where a high load acts during driving and braking on an ice and snow road can be secured, and the grip force can be improved well. Instead of the rib 15, a block row in which a plurality of blocks are arranged may be provided in the region RA directly under the equator.

[0022] In the present embodiment, the mounting hole 10 is not formed in the region RA directly under the equator. Therefore, the mounting hole 10 formed in the center region CA is arranged in the region NA adjacent to the equator avoiding the region RA directly under the equator. By not arranging the stud pin in the region RA directly under the equator, it is convenient for securing the ground contact surface of the region RA directly under the equator where a high load acts during driving and braking on an ice and snow road. Further, from the viewpoint of securing the ground contact surface of the region RA directly under the equator, it is preferable that no main groove is provided in the region RA directly under the equator.

[0023] The central point CP (midpoint) of the interval between the mounting holes 10 formed in the region NA adjacent to the equator on one side in the tire axial direction and the central point CP of the interval between the mounting holes 10 formed in the region NA adjacent to the equator on the other side in the tire axial direction are arranged offset from each other in the tire circumferential direction such that a line connecting them sequentially along the tire circumferential direction draws a waveform (zigzag shape).

[0024] Also, as shown in FIG. 2, the mounting holes 10 formed in the region NA adjacent to the equator and the mounting holes 10 formed in the shoulder region SA adjacent to the region NA adjacent to the equator with the shoulder main groove 11s interposed therebetween are arranged in a staggered manner along the tire circumferential direction. Thereby, deterioration of uniformity associated with the attachment of the stud pin can be effectively suppressed. In the present embodiment, such a staggered arrangement of the mounting holes 10 is applied to each of the pair of tread halves, and the above-described improvement effect is excellent.

[0025] As shown in Figures 2 and 4, the tread 3 includes lateral grooves 12 that extend across the shoulder main groove 11s and divide the tread 3 into multiple strip-shaped areas BA within their extended range. The groove width W12 of the lateral grooves 12 at the connection point with the main groove 11 is, for example, 5 mm or more. Multiple lateral grooves 12 are formed at intervals in the circumferential direction of the tire. The lateral grooves 12 extend outward in the tire axial direction from one end located in the center region CA, crossing the shoulder main groove 11s and reaching the contact end TE. The lateral grooves 12 extend at an inclination with respect to the tire axial direction. The lateral grooves 12 as a whole are gently curved in a direction that is convex toward the push-off side (rearward in the rotation direction RD2).

[0026] Figure 4 is a magnified view of the main part of Figure 2, schematically showing the strip-shaped area BA demarcated by the transverse groove 12. Although each of these strip-shaped areas BA is contained within a pair of tread halves separated by the tire equator TC, Figure 4 shows the strip-shaped area BA contained within one of them (the tread half located on the right side of Figure 2). As previously described, the transverse groove 12 demarcates the tread 3 into multiple strip-shaped areas BA within its extent. The strip-shaped areas BA extend in a strip shape from the center area CA to the shoulder area SA. The strip-shaped areas BA are curved along the transverse groove 12. Each of the strip-shaped areas BA contains one shoulder block 13 and one block-shaped land portion 14, which will be described later.

[0027] The strip-shaped area BA comprises strip-shaped areas BAs that include mounting holes 10 formed in the shoulder area SA, and strip-shaped areas BAc that include mounting holes 10 formed in the center area CA. The strip-shaped areas BAs do not include mounting holes 10 formed in the center area CA, and the strip-shaped area BAc does not include mounting holes 10 formed in the shoulder area SA. In this tire T, in at least one of the pair of tread halves separated by the tire equator TC, strip-shaped areas BAs that include mounting holes 10 formed in the shoulder area SA and strip-shaped areas BAc that include mounting holes 10 formed in the center area CA are alternately arranged along the circumferential direction of the tire.

[0028] Figure 4 shows an example where strip-shaped areas BAs and BAc are arranged alternately, one at a time, but it is not limited to this. For example, as shown in Figure 5, multiple strip-shaped areas BAs may be arranged between strip-shaped areas BAC in the tire circumferential direction. Conversely, multiple strip-shaped areas BAC may be arranged between strip-shaped areas BAs in the tire circumferential direction. In that case, it is preferable that the number of consecutively arranged strip-shaped areas BAs or strip-shaped areas BAC is 3 or less. That is, it is preferable that strip-shaped areas BAs and BAc are arranged alternately in groups of 1 to 3.

[0029] The strip-shaped area BA may include a strip-shaped area in which mounting holes 10 are formed in both the shoulder area SA and the center area CA, or a strip-shaped area in which mounting holes 10 are not formed in both the shoulder area SA and the center area CA. However, in the tread half, the number of such strip-shaped areas is preferably less than 30% of the total number of strip-shaped areas BA around the entire circumference of the tire, and more preferably less than 20%. That is, in the tread half, it is preferable that 70% or more of the total number of strip-shaped areas BA around the entire circumference of the tire are occupied by strip-shaped areas BAs and strip-shaped areas BAc.

[0030] The number of mounting holes 10 formed in the shoulder region SA is preferably greater than the number of mounting holes 10 formed in the center region CA. This enhances the scratching effect in the shoulder region SA, which is under high load during cornering, thereby improving handling stability. This relationship only needs to be satisfied when at least one (preferably both) half of the tread is viewed along the entire circumference of the tire. In the tread half, the difference between the number of mounting holes 10 formed in the shoulder region SA and the number of mounting holes 10 formed in the center region CA is preferably 3 or more, and more preferably 5 or more.

[0031] As shown in Figure 6, in this embodiment, a mounting hole 10 formed in the shoulder region SA (more precisely, the center of the mounting hole 10) is positioned in a section S in the tire circumferential direction, sandwiched between the central point CP of the spacing of mounting holes 10 formed in the center region CA and the mounting hole 10 adjacent to the kicking side (rearward RD2 in the rotational direction) of the central point CP. With this configuration, the scratching effect when driving on icy or snowy roads can be enhanced, and the grip force can be improved.

[0032] In the shoulder region SA, multiple shoulder blocks 13, separated by lateral grooves 12, are arranged in the circumferential direction of the tire. This creates an edge effect from the block edges of the shoulder blocks 13, improving driving performance on icy and snowy roads. In the shoulder region SA, shoulder blocks 13 with mounting holes 10 and shoulder blocks 13 without mounting holes 10 are alternately arranged in the circumferential direction of the tire. These are arranged one by one alternately, but they may be arranged in groups of 1 to 3 alternately. From the viewpoint of suppressing deterioration of uniformity, it is preferable that the number of mounting holes 10 formed in a single shoulder block 13 is one or less.

[0033] In the center region CA, multiple block-shaped land sections 14, separated by lateral grooves 12, are arranged in the circumferential direction of the tire. This creates an edge effect from the block edges of the block-shaped land sections 14, improving driving performance on icy and snowy roads. In the center region CA, block-shaped land sections 14 with mounting holes 10 and block-shaped land sections 14 without mounting holes 10 are alternately arranged in the circumferential direction of the tire. These are arranged one at a time in alternation, but they may also be arranged one to three at a time in alternation. From the viewpoint of suppressing deterioration of uniformity, it is preferable that the number of mounting holes 10 formed in one block-shaped land section 14 is one or less.

[0034] Multiple sipes 16 are formed on the shoulder block 13, block-shaped land portion 14, and rib 15, respectively. The sipes 16 are formed by cuts with a width of 1.0 mm or less. The sipes 16 may be two-dimensional sipes whose shape does not change along the depth direction, or three-dimensional sipes which include a portion whose shape changes along the depth direction. Each shoulder block 13 has sipes 16 that extend along the tire axis direction. Multiple sipes 16 are formed, extending substantially parallel to the lateral groove 12 that divides the shoulder block 13, and spaced apart in the thickness direction. The shoulder block 13 may also have sipes that extend parallel to the tire circumferential direction or sipes that extend at an angle.

[0035] When the shoulder blocks 13 are arranged at a variable pitch in the circumferential direction of the tire, that is, when the pitch length (circumferential length of the tire) of the pitch element which is the basis for repeating the pattern design is varied in various ways, it is preferable that the number of sipes 16 on the shoulder block 13 with the minimum circumferential length is smaller than the number of sipes 16 on the shoulder block 13 with the maximum circumferential length. With this configuration, the difference in contact area per unit area of ​​the shoulder block 13 due to the difference in pitch is reduced, which is advantageous in suppressing uneven wear on a block-by-block basis.

[0036] The center region CA is provided with a land area comprising a centrally located rib 15 and an arrangement of block-shaped land areas 14 located on both sides thereof. In the center region CA, lateral grooves 12 extending in a substantially straight line and lateral grooves 12 bent in an L-shape are alternately arranged in the circumferential direction of the tire, and these divide the block-shaped land areas 14. In the equatorial region NA, block-shaped land areas 14 containing sipes 16 inclined in the same direction as the lateral grooves 12 that divide the block-shaped land areas 14, and block-shaped land areas 14 containing sipes 16 inclined in the opposite direction are alternately arranged in the circumferential direction of the tire. The rib 15 has sipes 16 that extend substantially parallel to the tire axis direction.

[0037] The pneumatic tire T of this embodiment is equivalent to a normal stud tire (however, before stud pins are attached to the mounting holes 10) except for the arrangement of the mounting holes 10 as described above, and any conventionally known materials, shapes, structures, etc., can be used. The pneumatic tire T may also be one in which stud pins are attached to the mounting holes 10 of the tread 3.

[0038] [1] As described above, the pneumatic tire T of this embodiment is equipped with a tread 3 having mounting holes 10 for attaching stud pins. The tread 3 includes a plurality of main grooves 11 that extend continuously along the circumferential direction of the tire. The tread 3 is divided into a shoulder region SA on the outer side in the axial direction of the tire and a center region CA on the inner side in the axial direction of the tire, based on the groove width center of the shoulder main groove 11s, which is located on the outermost side in the axial direction of the tire. Within the center region CA, the area corresponding to 28% of the contact width TW centered on the tire equator TC is defined as the equatorial region RA, and the area between the equatorial region RA and the shoulder main groove 11s is defined as the equatorial adjacent region NA. The mounting holes 10 formed in the equatorial adjacent region NA on one side in the axial direction of the tire and the mounting holes 10 formed in the equatorial adjacent region NA on the other side in the axial direction of the tire are arranged in a staggered pattern along the circumferential direction of the tire. This makes it possible to suppress the deterioration of uniformity that occurs when stud pins are attached.

[0039] [2] In the pneumatic tire T described in [1] above, it is preferable that the equatorial region RA is provided with a rib 15 that extends continuously in the circumferential direction of the tire, or a row of blocks arranged in a plurality of blocks. This ensures a contact surface in the equatorial region RA, where a high load acts during braking on icy or snowy roads, and improves grip performance.

[0040] [3] In the pneumatic tire T described in [2] above, it is preferable that no mounting holes 10 are formed in the region RA directly below the equator. This is advantageous in ensuring a contact surface in the region RA directly below the equator, where a high load is applied during braking on icy or snowy roads.

[0041] [4] In any one of the above [1] to [3] pneumatic tire T, it is preferable that the mounting holes 10 formed in the equatorial adjacent region NA and the mounting holes 10 formed in the adjacent shoulder region SA across the shoulder main groove 11s from the equatorial adjacent region NA are arranged in a staggered pattern along the circumferential direction of the tire. This effectively suppresses the deterioration of uniformity associated with the installation of stud pins.

[0042] While embodiments of this disclosure have been described with reference to the drawings, it should be understood that the specific configurations are not limited to these embodiments. The scope of this disclosure is defined not only by the above-described embodiments but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0043] The pneumatic tire of this disclosure is not limited in any way to the embodiments described above, nor is it limited to the effects and advantages described above. The pneumatic tire of this disclosure can be modified in various ways without departing from its essence. [Explanation of Symbols]

[0044] 1. Bead section 2 sidewalls 3 tread 10 mounting holes 11 Main groove 11s Shoulder main groove 12 Yokomizo 13 Shoulder Block 14 Block-shaped land area 15 Ribs 16 sipes

Claims

1. It features a tread with mounting holes formed for attaching stud pins, The tread includes a plurality of main grooves that extend continuously along the circumferential direction of the tire, and a transverse groove that extends across the shoulder main groove located on the outermost side in the axial direction of the tire, and divides the tread into a plurality of strip-shaped areas within its extended range. The tread is divided into a shoulder region on the outer side of the tire axial direction and a center region on the inner side of the tire axial direction, with reference to the groove width center of the shoulder main groove located on the outermost side of the multiple main grooves in the tire axial direction. In each of the pair of tread halves separated by the tire equator, the strip-shaped area including the mounting hole formed in the shoulder region and the strip-shaped area including the mounting hole formed in the center region are alternately arranged along the circumferential direction of the tire. Of the aforementioned center region, the region representing 28% of the contact width centered on the tire equator is defined as the region directly below the equator, and the region between the region directly below the equator and the shoulder main groove is defined as the region adjacent to the equator. The mounting holes formed in the equatorial region on one side of the tire axial direction and the mounting holes formed in the equatorial region on the other side of the tire axial direction are arranged in a staggered pattern along the circumferential direction of the tire. In the center region, a pneumatic tire is characterized in which block-shaped land portions with mounting holes and block-shaped land portions without mounting holes are alternately arranged one at a time in the circumferential direction of the tire.

2. The pneumatic tire according to claim 1, wherein the region directly below the equator is provided with ribs extending continuously in the circumferential direction of the tire, or rows of blocks arranged in a plurality of blocks.

3. The pneumatic tire according to claim 2, wherein the mounting holes are not formed in the region directly below the equator.

4. The pneumatic tire according to any one of claims 1 to 3, wherein the mounting holes formed in the equatorial region and the mounting holes formed in the shoulder region adjacent to the equatorial region, with the shoulder main groove in between, are arranged in a staggered pattern along the circumferential direction of the tire.

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