JP7832485B2 - tire - Google Patents

Description

This invention relates to a tire having holes in the tread for inserting stud pins, and more particularly to a tire that improves pin detachment resistance without worsening road surface damage.

Stud tires have numerous holes in the tread where stud pins are inserted, and are used with stud pins inserted in each hole (see, for example, Patent Documents 1-4).

Studless tires, configured in this way, belong to the category with the best performance on ice, and this high level of ice performance is, of course, due to the stud pins. On the other hand, in order to improve road surface damage, which is regulated by law, stud pins are becoming smaller year by year, and there are concerns that their resistance to pin detachment will worsen compared to before. Pin detachment resistance is related to the product lifespan and can be said to be one of the most important issues for studless tires these days.

Patent No. 5406921 Patent No. 6099668 Patent No. 6565574 Patent No. 4488099

The objective of this invention is to provide a tire that improves pin detachment resistance without worsening road surface damage.

To achieve the above objective, the present invention provides a tire having holes in the tread portion into which stud pins are inserted, wherein a flat portion exists around the hole that is connected in an annular shape and coincides with the profile line of the tread portion, and when an annular region is defined around the flat portion at a distance of 4 mm to 8 mm from the center of the hole, the annular region contains a mixture of convex portions that are raised higher than the flat portion and concave portions that are recessed lower than the flat portion.
The recess is arranged on concentric circles centered on the hole, and the recess has an intermittent shape in a part of the circumferential direction of the concentric circles .

In this invention, a tire equipped with holes in the tread portion into which stud pins are inserted has a flat portion that is connected in an annular shape around the hole and coincides with the profile line of the tread portion, so that the stud pins can be held stably. Furthermore, when an annular region is defined around the flat portion at a distance of 4 mm to 8 mm from the center of the hole, the annular region contains a mixture of convex portions that are higher than the flat portion and concave portions that are lower than the flat portion. Therefore, when a stud pin collapses, the force acting in the direction of collapse is dispersed based on the presence of the concave portions, preventing the stud pin from falling out. In this case, if the rigidity is drastically reduced due to the presence of the concave portions, the stud pin may collapse easily and the resistance to pin detachment may worsen. However, the presence of convex portions along with concave portions in the annular region can compensate for the lack of rigidity. Therefore, the presence of both convex and concave portions in the annular region effectively improves the resistance to pin detachment. In addition, the structure that disperses the force when a stud pin collapses, as described above, also has the effect of improving road surface damage by reducing the force with which the stud pin attacks the road surface when driving on a dry road surface. Therefore, according to the present invention, it is possible to improve pin detachment resistance without worsening road surface damage.

In this invention, it is preferable that the recesses are arranged on concentric circles centered on the hole, and that the recesses have an intermittent shape in a portion of the circumferential direction of the concentric circles. If the recesses are continuous in the circumferential direction of the concentric circles centered on the hole, insufficient rigidity can easily cause the stud pin to collapse, which is disadvantageous from the viewpoint of pin detachment resistance. However, by having an intermittent shape in a portion of the circumferential direction of the concentric circles, rigidity around the stud pin can be ensured, preventing the stud pin from falling out.

The recess is preferably positioned so as not to overlap with the circumferential line that passes through the center of the hole and is parallel to the tire's circumferential direction. This suppresses excessive tilting of the stud pin during rapid acceleration and deceleration, effectively preventing the stud pin from falling out.

The recess is preferably positioned so as not to overlap with the widthwise line perpendicular to the tire's circumferential direction, passing through the center of the hole. This suppresses excessive tilting of the stud pin during sharp turns, effectively preventing the stud pin from falling out.

When defining an annular region with an inner annular region where the distance from the center of the hole is 4 mm to 6 mm and an outer annular region where the distance from the center of the hole is 6 mm to 8 mm, it is preferable that the area of the recess included in the inner annular region is larger than the area of the recess included in the outer annular region. This effectively distributes the force generated when a strong force is applied to the stud pin, thereby improving the pin-pull-out resistance.

The recesses are preferably arranged on multiple concentric circles centered on the hole. This effectively distributes the force acting on the stud pin when it tilts, preventing it from falling out. In this case, the recesses on the multiple concentric circles should overlap each other in the radial direction of the concentric circles. This effectively distributes the force acting on the stud pin when it tilts, preventing it from falling out, while also significantly improving road surface damage resistance. Alternatively, the recesses on the multiple concentric circles should not overlap each other in the radial direction of the concentric circles. This effectively distributes the force acting on the stud pin when it tilts, while also ensuring rigidity to prevent excessive tilting of the stud pin, thus significantly improving resistance to pin detachment.

When the body portion of a stud pin inserted into a hole has a longitudinal direction in a plan view of the tread portion, and when an inner annular region is defined within the annular region at a distance of 4 mm to 6 mm from the center of the hole and an outer annular region at a distance of 6 mm to 8 mm from the center of the hole, it is preferable that the recess is positioned within the inner annular region at a location that does not coincide with a virtual line passing through the center of the hole and parallel to the longitudinal direction of the body portion. If the distance between the stud pin body portion and the recess is too short, insufficient rigidity may worsen the pin's resistance to coming loose. However, by positioning the recess within the inner annular region at a location that does not coincide with a virtual line passing through the center of the hole and parallel to the longitudinal direction of the body portion, pin resistance can be effectively improved.

Preferably, the depth Hy of the recess satisfies the relationship 0.05Hs ≤ Hy ≤ 0.25Hs with respect to the height Hs of the stud pin, and the height Hx of the protrusion satisfies the relationship 0.10Hy ≤ Hx ≤ 0.80Hs with respect to the depth Hy of the recess. This effectively improves the resistance to pin detachment.

The tire of the present invention is preferably a pneumatic tire, but may also be a non-pneumatic tire. In the case of a pneumatic tire, its interior can be filled with air, an inert gas such as nitrogen, or other gases.

This is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. Figure 1 is a cross-sectional view showing the stud pin installation area in the tread portion of a pneumatic tire. Figure 1 is a plan view showing the stud pin installation area on the tread of a pneumatic tire. This is a perspective view showing an example of a stud pin. Figure 4 is a plan view showing the stud pin. Figure 4 is a side view showing the stud pin. Figure 4 is a cross-sectional view showing the stud pins inserted into the holes in the tread. (a) to (c) are plan views showing modified examples of the stud pin installation area [however, Figure 8(a) is a reference example] . (a) to (d) are plan views showing other variations of the stud pin installation area. This is a plan view showing yet another variation of the stud pin installation area. Figures (a) to (e) are plan views showing yet another modified example of the stud pin installation area [however, Figures 11(a) and (b) are for reference only] . This is a plan view showing yet another variation of the stud pin installation area.

The configuration of the present invention will be described in detail below with reference to the attached drawings. Figure 1 shows a pneumatic tire according to an embodiment of the present invention, Figures 2 and 3 show the stud pin installation area in the tread portion, Figures 4 to 6 show examples of stud pins, and Figure 7 shows the state in which the stud pins are inserted into the holes in the tread portion.

As shown in Figure 1, the pneumatic tire of this embodiment comprises a tread portion 1 extending in the circumferential direction of the tire and forming an annular shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged radially inward of these sidewall portions 2.

A carcass layer 4 is mounted between a pair of bead sections 3, 3. This carcass layer 4 includes multiple reinforcing cords extending in the tire's radial direction, and is folded back from the inside to the outside of the tire around the bead core 5 located in each bead section 3. A bead filler 6, made of a rubber composition with a triangular cross-section, is positioned on the outer circumference of the bead core 5.

On the other hand, multiple belt layers 7 are embedded on the outer circumference of the carcass layer 4 in the tread portion 1. These belt layers 7 include multiple reinforcing cords inclined with respect to the tire's circumferential direction, and the reinforcing cords are arranged to intersect each other between layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire's circumferential direction is set to, for example, a range of 10° to 40°. Steel cords are preferably used as the reinforcing cords in the belt layers 7. On the outer circumference of the belt layers 7, at least one belt cover layer 8 is arranged, with the reinforcing cords arranged at an angle of, for example, 5° or less with respect to the tire's circumferential direction, for the purpose of improving high-speed durability. Organic fiber cords such as nylon or aramid are preferably used as the reinforcing cords in the belt cover layer 8.

The tire internal structure described above is a typical example for pneumatic tires, but is not limited to this. Furthermore, the tread pattern formed on the tread portion 1 is also not particularly limited.

In the above-described pneumatic tire, the tread portion 1 has circumferential grooves 11 extending in the tire's circumferential direction, and these circumferential grooves 11 divide the tread into multiple land portions 12. These land portions 12 are further divided into numerous blocks by, for example, transverse grooves (not shown) extending in the tire's width direction. Multiple holes 13 are formed in the land portions 12 of the tread portion 1 into which stud pins 20 are inserted. As shown in Figures 4 to 6, the stud pin 20 consists of a columnar body portion 21, a tip portion 22 disposed on the tip side of the body portion 21, and a flange portion 23 disposed on the base end side of the body portion 21. The tip portion 22 is made of a material with higher hardness than the body portion 21. The flange portion 23 has a larger outer diameter than the body portion 21. The stud pin 20 is disposed in the tread portion 1 such that the body portion 21 and flange portion 23 are inserted into the holes 13, while the tip portion 21 protrudes from the profile line L of the tread portion 1 (see Figure 7). Since the inner diameter of hole 13 is slightly smaller than the outer diameter of the body portion 21 of the stud pin 20, the stud pin 20 inserted into hole 13 is firmly held in place by the tread portion 1.

In a tire equipped with holes 13 into which stud pins 20 are inserted, as shown in Figures 2 and 3, a flat portion 14 exists around the holes 13, having a height that coincides with the profile line L of the tread portion 1 and forming a ring-like structure. The profile line L of the tread portion 1 is the arc that forms the outline of the tread portion 1 in the meridional cross-section of the tire. In Figures 2 and 3, there is a portion around the holes 13 that is slightly shallower than the profile line L for design reasons, but this portion is not necessarily required.

In Figure 3, a virtual circle C1 is depicted with a distance X1 of 4 mm from the center O of the hole 13, a virtual circle C2 is depicted with a distance X2 of 6 mm from the center O of the hole 13, and a virtual circle C3 is depicted with a distance X3 of 8 mm from the center O of the hole 13. Here, an annular region A is defined around the flat portion 14, with a distance from the center O of the hole 13 ranging from 4 mm to 8 mm. The annular region A is the region sandwiched between the virtual circles C1 and C3. The annular region A is composed of an inner annular region Ai, with a distance from the center O of the hole 13 ranging from 4 mm to 6 mm, and an outer annular region Ao, with a distance from the center O of the hole 13 ranging from 6 mm to 8 mm. At this time, within the annular region A, there are multiple convex portions 15 that rise outward in the tire radial direction from the flat portion 14 and multiple concave portions 16 that are recessed inward in the tire radial direction from the flat portion 14, and these convex portions 15 and concave portions 16 are mixed within the annular region A. In Figure 3 and subsequent drawings, the recess 16 is indicated with diagonal lines for ease of understanding.

As described above, in a tire equipped with a hole 13 in the tread portion 1 into which a stud pin 20 is inserted, a flat portion 14 exists around the hole 13 that is connected in an annular shape and coincides with the profile line L of the tread portion 1. Therefore, as shown in Figure 7, the stud pin 20 can be stably held when it is inserted into the hole 13 of the tread portion 1. Moreover, when an annular region A is defined around the flat portion 14 at a distance of 4 mm to 8 mm from the center O of the hole 13, a convex portion 15 that is raised higher than the flat portion 14 and a concave portion 16 that is recessed lower than the flat portion 14 are mixed within this annular region A. Therefore, when the stud pin 20 collapses, the force acting in the direction of collapse is distributed based on the presence of the concave portion 16, preventing the stud pin 20 from falling out. In this case, if the rigidity is drastically reduced due to the presence of the concave portion 16, the stud pin 20 may become more prone to collapse, potentially worsening the pin-loosening resistance. However, the presence of the convex portion 15 along with the concave portion 16 within the annular region A compensates for this lack of rigidity. Therefore, the presence of both the convex portion 15 and the concave portion 16 within the annular region A effectively improves pin detachment resistance. Furthermore, as described above, the structure that distributes the force when the stud pin 20 collapses weakens the force with which the stud pin 20 attacks the road surface during dry road driving, thus improving road surface damage. This allows for improved pin detachment resistance without worsening road surface damage.

To optimize the cushioning effect of the recess 16, the maximum width of the recess 16, measured radially from the center O of the hole 13, should be 0.5 mm or more and less than 2 mm. Furthermore, to optimize pin pull-out resistance, the area ratio of the recess 16 to the annular region A should be 10% to 50%, the area ratio of the convex portion 15 to the annular region A should be 10% to 90%, and the area ratio of the convex portion 15 and the recess 16 to the annular region A should be less than 90%.

In the above-described pneumatic tire, as shown in Figure 3, the recesses 16 are arranged on a concentric circle P1 centered on the hole 13, and the recesses 16 have an intermittent shape in a part of the circumferential direction of the concentric circle P1. In Figure 3, multiple protrusions 15 and multiple recesses 16 are arranged alternately at intervals on the concentric circle P1. Furthermore, multiple protrusions 15 are arranged at intervals on a concentric circle P2 set outside the concentric circle P1 centered on the hole 13. If the recesses 16 were continuous in the circumferential direction of the concentric circle P1 centered on the hole 13, the stud pins 20 would be prone to collapsing due to insufficient rigidity, which would be disadvantageous in terms of pin detachment resistance. However, by having the recesses 16 have an intermittent shape in a part of the circumferential direction of the concentric circle P1, rigidity around the stud pins 20 can be ensured, preventing the stud pins 20 from falling out.

Figures 8(a) to 8(c) show modified examples of the stud pin installation portion. In Figure 8(a), the protrusion 15 is positioned on a concentric circle P2 and has a continuous shape in the circumferential direction of the concentric circle P2, while the recess 16 is positioned on a concentric circle P1 and has a continuous shape in the circumferential direction of the concentric circle P1. In Figure 8(b), the protrusion 15 is positioned on a concentric circle P2 and has a continuous shape in the circumferential direction of the concentric circle P2, while the recess 16 is positioned on a concentric circle P1 and has an intermittent shape in a part of the circumferential direction of the concentric circle P1. In Figure 8(c), the protrusion 15 is positioned on a concentric circle P2 and has a continuous shape in the circumferential direction of the concentric circle P2, while the recess 16 is positioned on a concentric circle P1 and has a circular shape in plan view. Thus, the shape and arrangement of the protrusion 15 and recess 16 can be changed according to the required performance and design.

Figures 9(a) to 9(d) show other modified examples of the stud pin installation portion. In the embodiment of Figure 1 described above, the convex portion 15 and the concave portion 16 are arranged symmetrically on concentric circles P1 and P2. In contrast, in Figures 9(a) to 9(c), the convex portion 15 and the concave portion 16 are arranged asymmetrically on concentric circle P1. Also, in Figure 9(d), a portion of the convex portion 15 is straight.

Figure 10 shows yet another modification of the stud pin installation portion. In Figure 10, the recess 16 is positioned so as not to overlap with the circumferential line Lc, which passes through the center O of the hole 13 and is parallel to the tire's circumferential direction. In this case, excessive tilting of the stud pin 20 is suppressed during rapid acceleration and deceleration, effectively preventing the stud pin 20 from falling out.

Furthermore, in Figure 10, the recess 16 is positioned so as not to overlap with the widthwise line Lw, which passes through the center O of the hole 13 and is perpendicular to the tire circumferential direction. In this case, excessive tilting of the stud pin 20 is suppressed during sharp turns, and the detachment of the stud pin 20 can be effectively prevented.

In Figure 3, an inner annular region Ai is defined within the annular region A, where the distance from the center O of the hole 13 is 4 mm to 6 mm, and an outer annular region Ao is defined where the distance from the center O of the hole 13 is 6 mm to 8 mm. The inner annular region Ai is the region enclosed by virtual circles C1 and C2, and the outer annular region Ao is the region enclosed by virtual circles C2 and C3. In this case, it is preferable that the area of the recess 16 included in the inner annular region Ai is set to be larger than the area of the recess 16 included in the outer annular region Ao. By arranging a relatively large number of recesses 16 in the inner annular region Ai in this way, the force generated when a strong force acts on the stud pin 20 is effectively distributed, thereby improving the pin-pull-out resistance.

Figures 11(a) to (e) show further variations of the stud pin installation portion. In Figures 11(a) to (e), the recesses 16 are positioned on two of the multiple concentric circles P1 to P3 centered on the hole 13. That is, in Figure 11(a), the recesses 16 that are continuous along the concentric circles P1 and P2 are positioned on the concentric circles P1 and P2, and the convex portion 15 that is continuous along the concentric circle P3 is positioned on the concentric circle P3, with the portions between the recesses 16, 16 positioned on the concentric circles P1 and P2 being at the height of the profile line L. In Figure 11(b), the recesses 16 that are continuous along the concentric circles P1 and P3 are positioned on the concentric circles P1 and P3, and the convex portion 15 that is continuous along the concentric circle P2 is positioned on the concentric circle P2. In Figures 11(c) and (d), recesses 16 having an intermittent shape in a part of the circumferential direction of concentric circles P1 and P2 are arranged on concentric circles P1 and P2, and protrusions 15 continuous along concentric circle P3 are arranged on concentric circle P3. In Figure 11(e), protrusions 15 and recesses 16 having an intermittent shape in a part of the circumferential direction of concentric circles P1 and P2 are arranged alternately on concentric circles P1 and P2, and protrusions 15 continuous along concentric circle P3 are arranged on concentric circle P3. By arranging the recesses 16 on multiple concentric circles P1 to P3 centered on the hole 13 in this way, the force acting in the direction of the stud pin 20 falling when it falls can be effectively distributed, preventing the stud pin 20 from falling out.

In particular, as shown in Figures 11(a) and (b), when the recesses 16 on multiple concentric circles P1 to P3 are arranged so as to overlap each other in the radial direction of the concentric circles P1 to P3, the force acting on the stud pin 20 when it falls over is effectively distributed, preventing the stud pin 20 from falling out, while also significantly improving road surface damage resistance. Furthermore, as shown in Figures 11(c) to (e), when the recesses 16 on multiple concentric circles P1 to P3 are arranged so as not to overlap each other in the radial direction of the concentric circles P1 to P3, the force acting on the stud pin 20 when it falls over is effectively distributed, and rigidity can be ensured to prevent excessive falling of the stud pin 20, thus significantly improving pin detachment resistance.

Figure 12 shows yet another modification of the stud pin installation portion. As shown in Figure 5, the body portion 21 of the stud pin 20 has a dimension D1 in a first direction and a dimension D2 in a second direction perpendicular to the first direction in a plan view of the tread portion 1 (i.e., a plan view of the stud pin 20), with dimension D1 being larger than dimension D2, and the first direction being the longitudinal direction T. When the body portion 21 of the stud pin 20 has a longitudinal direction T in a plan view of the tread portion 1 in this way, as shown in Figure 12, when an inner annular region Ai is defined within the annular region A where the distance from the center O of the hole 13 is 4 mm to 6 mm, and an outer annular region Ao is defined where the distance from the center O of the hole 13 is 6 mm to 8 mm, it is preferable that the recess 16 be positioned within the inner annular region Ai so as not to overlap with a virtual line Tx that passes through the center O of the hole 13 and is parallel to the longitudinal direction T of the body portion 21. In other words, if the distance between the body portion 21 of the stud pin 20 and the recess 16 is too short, insufficient rigidity may worsen the pin's resistance to coming loose. However, by positioning the recess 16 within the inner annular region Ai at a location that does not overlap with a virtual line Tx that passes through the center O of the hole 13 and is parallel to the longitudinal direction T of the body portion 21, the pin's resistance to coming loose can be effectively improved.

In the above-described pneumatic tire, the depth Hy of the recess 16 (see Figure 2) should satisfy the relationship 0.05Hs ≤ Hy ≤ 0.25Hs with respect to the height Hs of the stud pin 20 (see Figure 6), and the height Hx of the protrusion 15 (see Figure 2) should satisfy the relationship 0.10Hy ≤ Hx ≤ 0.80Hy with respect to the depth Hy of the recess 16. This effectively improves pin detachment resistance. If the depth Hy of the recess 16 and the height Hx of the protrusion 15 fall outside these ranges, the improvement in pin detachment resistance decreases. For example, if the height Hs of the stud pin 20 is 9 mm to 10 mm, the depth Hy of the recess 16 can be set to a range of 0.5 mm to 2.0 mm, and the height Hx of the protrusion 15 can be set to a range of 0.2 mm to 1.0 mm.

In a pneumatic tire with a tire size of 205/55R16 and a hole in the tread portion into which stud pins are inserted, pneumatic tires of the Conventional Example, Comparative Examples 1-4 and Examples 1-9 were manufactured, with the following characteristics set as shown in Tables 1 and 2: presence or absence of a flat portion formed around the hole, presence or absence of a recess in the annular region, presence or absence of a convex portion in the annular region, presence or absence of intermittent recesses, presence or absence of a recess overlapping with a circumferential line passing through the center of the hole, presence or absence of a recess overlapping with a widthwise line passing through the center of the hole, area of recesses included in the inner annular region, area of recesses included in the outer annular region, area ratio of recesses to the annular region, area ratio of convex portion to the annular region, number of overlapping recesses in the radial direction of concentric circles, and presence or absence of a recess overlapping with an imaginary line passing through the center of the hole and parallel to the longitudinal direction of the stud pin body in the inner annular region. The stud pins are inserted into the holes so that the longitudinal direction of the body is oriented in the tire width direction. In this specification, Example 1 is a reference example.

These test tires were evaluated for pin detachment resistance and road surface damage resistance using the test methods described below, and the results are shown in Tables 1 and 2.

Pin pull resistance:
Each test tire was mounted on a 16 x 6.5J rim wheel and fitted to a 1.4L front-wheel-drive vehicle. The tire was then inflated to the vehicle's specified air pressure, and after 20,000 km of driving in a predetermined urban driving mode on an outdoor test course consisting of asphalt, the number of pins that came loose was measured. The evaluation results were shown as an index using the reciprocal of the measured value, with the conventional example set to 100. A higher index value indicates better pin-loosening resistance.

Road surface damage:
Each test tire was mounted on a 16 x 6.5J rim wheel and fitted to a 1.4L front-wheel-drive vehicle. The tire pressure was set to 250 kPa, and the vehicle was driven 200 times at a speed of 100 km/h on a granite plate placed on the road surface. After the test, the amount of road surface wear was measured based on the weight difference of the plate before and after the test. The evaluation results were shown as an index using the reciprocal of the measured value, with the conventional example set to 100. A larger index value indicates less road surface wear and superior road surface damage resistance.

As can be seen from Tables 1 and 2, the tires of Examples 1 to 9 showed improved road surface damage resistance and pin detachment resistance compared to the conventional example. On the other hand, the tires of Comparative Examples 1 and 2, while having recesses in the annular region, lacked protrusions in the annular region, resulting in insufficient rigidity and poor pin detachment resistance. The tire of Comparative Example 3, while having protrusions in the annular region, lacked recesses in the annular region, thus failing to achieve improved pin detachment resistance. The tire of Comparative Example 4 lacked flat surfaces around the holes, resulting in poor pin detachment resistance.

This disclosure encompasses the following inventions:
Invention [1] A tire having holes in the tread portion into which stud pins are inserted, wherein a flat portion exists around the holes in an annular shape that coincides with the profile line of the tread portion, and when an annular region is defined around the flat portion at a distance of 4 mm to 8 mm from the center of the holes, the annular region is characterized in that a convex portion that is raised higher than the flat portion and a concave portion that is recessed lower than the flat portion are mixed together.
Invention [2] The tire according to Invention [1], characterized in that the recesses are arranged on concentric circles centered on the hole, and the recesses have an intermittent shape in a part of the circumferential direction of the concentric circles.
Invention [3] The tire according to Invention [2], characterized in that the recess is positioned so as not to overlap with a circumferential line that passes through the center of the hole and is parallel to the circumferential direction of the tire.
Invention [4] The tire according to Invention [2], characterized in that the recess is positioned so as not to overlap with a widthwise line that passes through the center of the hole and is perpendicular to the circumferential direction of the tire.
Invention [5] The tire according to any one of Inventions [1] to [4], characterized in that when an inner annular region is defined within the annular region such that the distance from the center of the hole is 4 mm to 6 mm and an outer annular region such that the distance from the center of the hole is 6 mm to 8 mm, the area of the recess included in the inner annular region is larger than the area of the recess included in the outer annular region.
Invention [6] The tire according to any one of Inventions [1] to [5], characterized in that the recesses are arranged on a plurality of concentric circles centered on the hole.
Invention [7] The tire according to Invention [6], characterized in that the recesses on the plurality of concentric circles are arranged to overlap each other in the radial direction of the concentric circles.
Invention [8] The tire according to Invention [6], characterized in that the recesses on the plurality of concentric circles are arranged so as not to overlap each other in the radial direction of the concentric circles.
Invention [9] The tire according to any one of Inventions [1] to [8], characterized in that when the body portion of the stud pin inserted into the hole has a longitudinal direction in a plan view of the tread portion, and when an inner annular region is defined within the annular region at a distance of 4 mm to 6 mm from the center of the hole and an outer annular region at a distance of 6 mm to 8 mm from the center of the hole, the recess is positioned within the inner annular region at a location that does not overlap with a virtual line passing through the center of the hole and parallel to the longitudinal direction of the body portion.
Invention [10] A tire according to any one of Inventions [1] to [9], characterized in that the depth Hy of the recess satisfies the relationship 0.05Hs ≤ Hy ≤ 0.25Hs with respect to the height Hs of the stud pin, and the height Hx of the protrusion satisfies the relationship 0.10Hy ≤ Hx ≤ 0.80Hy with respect to the depth Hy of the recess.

1. Tread section 2. Sidewall section 3. Bead section 4. Carcass layer 5. Bead core 6. Bead filler 7. Belt layer 8. Belt cover layer 11. Circumferential groove 12. Land section 13. Hole 14. Flat section 15. Convex section 16. Recessed section 20. Stud pin 21. Body section 22. Tip section 23. Flange section

Claims (9)

In a tire having holes in the tread portion into which stud pins are inserted, a flat portion exists around the hole that is connected in an annular shape and coincides with the profile line of the tread portion, and when an annular region is defined around the flat portion at a distance of 4 mm to 8 mm from the center of the hole, a convex portion that is raised higher than the flat portion and a concave portion that is recessed lower than the flat portion are mixed within the annular region.
A tire characterized in that the recesses are arranged on concentric circles centered on the holes, and the recesses have an intermittent shape in a part of the circumferential direction of the concentric circles . The tire according to claim 1 , characterized in that the recess is positioned so as not to coincide with a circumferential line that passes through the center of the hole and is parallel to the circumferential direction of the tire. The tire according to claim 1 , characterized in that the recess is positioned so as not to overlap with a widthwise line that passes through the center of the hole and is perpendicular to the tire circumferential direction. The tire according to any one of claims 1 to 3, characterized in that, when an inner annular region is defined within the annular region such that the distance from the center of the hole is 4 mm to 6 mm, and an outer annular region such that the distance from the center of the hole is 6 mm to 8 mm, the area of the recess included in the inner annular region is larger than the area of the recess included in the outer annular region. The tire according to any one of claims 1 to 3 , characterized in that the recesses are arranged on a plurality of concentric circles centered on the hole. The tire according to claim 5 , characterized in that the recesses on the plurality of concentric circles are arranged to overlap each other in the radial direction of the concentric circles. The tire according to claim 5 , characterized in that the recesses on the plurality of concentric circles are arranged so as not to overlap each other in the radial direction of the concentric circles. The tire according to any one of claims 1 to 3, characterized in that the body portion of the stud pin inserted into the hole has a longitudinal direction in a plan view of the tread portion, and when the annular region is defined as an inner annular region at a distance of 4 mm to 6 mm from the center of the hole and an outer annular region at a distance of 6 mm to 8 mm from the center of the hole, the recess is positioned within the inner annular region at a location that does not overlap with a virtual line passing through the center of the hole and parallel to the longitudinal direction of the body portion. The tire according to any one of claims 1 to 3, characterized in that the depth Hy of the recess satisfies the relationship 0.05Hs ≤ Hy ≤ 0.25Hs with respect to the height Hs of the stud pin, and the height Hx of the protrusion satisfies the relationship 0.10Hy ≤ Hx ≤ 0.80Hy with respect to the depth Hy of the recess.