pneumatic tires

Abstract

In a pneumatic tire, the grooves reinforce the opposing tread, suppress excessive force on the tread, prevent a decrease in the tire's performance, and prevent foreign objects from getting stuck. [Solution] The pneumatic tire includes a tread. The tread includes a plurality of landforms demarcated by a plurality of grooves, the plurality of landforms having a first landform and a second landform facing each other via some grooves 22. A bridge 38 is positioned within some of the grooves 22. The bridge 38 includes a first bridge element 39 protruding from the side of the first landform and a second bridge element 40 protruding from the side of the second landform, with at least a portion of the first bridge element 39 and the second bridge element 40 overlapping in the groove depth direction.

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] In Patent Document 1, a pair of center lands are arranged on both sides of the center circumferential groove of the tread. Each center land is divided into a plurality of center blocks arranged in the tire circumferential direction by a plurality of center shallow grooves, and a center groove bottom sipe is provided at the groove bottom of the center shallow groove.

[0003] In Patent Document 2, on both of the opposing side surfaces of the lands facing each other across the groove of the tread, protrusions protruding in the groove width direction from a position deeper than the tread surface of the land are formed. A protrusion protruding from the side surface of the other land is arranged between the two protrusions protruding from the side surface of one of the opposing lands in the groove longitudinal direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] One possible approach is to reinforce the tread by placing a bridge in the groove between two opposing treads, connecting the treads with the bridge. In this case, the tire's circular tread deforms according to the road surface, forming a planar contact shape with the road surface. The tire surface deforms mainly using grooves such as the main grooves as folds. However, when a bridge is placed in the groove to reinforce the tread, the tire tread becomes less flexible when it contacts the road surface, which tends to reduce the effective contact area. Furthermore, the tire tread becomes less able to fit into the unevenness of the road surface caused by stones, etc., further reducing the effective contact area. This can lead to a decrease in the tire's performance. Also, because the treads are pulled by the bridge, they may deform under excessive force. Additionally, the flexibility of the treads during turns may decrease, potentially reducing turning performance. Furthermore, if sipes are formed on the top surface of the bridge, foreign objects such as stones and snow may become trapped in the sipes.

[0006] In the configurations described in Patent Documents 1 and 2, there is room for improvement in terms of suppressing a decrease in rotational performance and preventing foreign objects from getting stuck.

[0007] The object of the present invention is to reinforce the opposing land surface through grooves in a pneumatic tire, to suppress excessive force on the land surface, to suppress a decrease in the tire's performance, and to suppress the trapping of foreign objects such as stones and snow. [Means for solving the problem]

[0008] The pneumatic tire according to the present invention is a pneumatic tire having a tread, wherein the tread includes a plurality of landforms demarcated by a plurality of grooves, the plurality of landforms having a first landform and a second landform facing each other via some of the grooves, a bridge disposed within the portion of the grooves, the bridge including a first bridge element protruding from the side surface of the first landform and a second bridge element protruding from the side surface of the second landform, and at least a portion of the first bridge element and the second bridge element overlapping in the groove depth direction. [Effects of the Invention]

[0009] The pneumatic tire according to the present invention can reinforce the opposing ground through grooves, suppress excessive force on the ground, ensure the ease of bending of the tire tread when in contact with the ground and the flexibility of the blocks when turning, thereby suppressing a decrease in the tire's performance, and suppressing the entanglement of foreign objects such as stones and snow. [Brief explanation of the drawing]

[0010] [Figure 1] This is a plan view of a pneumatic tire, one example of an embodiment. [Figure 2] This is an enlarged view of section A in Figure 1. [Figure 3] Figure 2 is a cross-sectional view of BB. [Figure 4] This is an enlarged perspective view corresponding to part A in Figure 1, exaggerating the deformation state when the block on which the first bridge element protrudes and the block on which the second bridge element protrudes deform outwards in the tire tread. [Figure 5] This is an enlarged perspective view corresponding to part A in Figure 1, which exaggerates the deformation state of the tire tread when a turning force is applied to it. [Figure 6] This figure corresponds to Figure 5, showing an alternative embodiment of a pneumatic tire. [Figure 7] This figure corresponds to Figure 5, showing an alternative embodiment of a pneumatic tire. [Figure 8] This is a cross-sectional view showing the longitudinal middle portion of a groove when the bridge is cut along the longitudinal direction of the groove in a pneumatic tire of another embodiment. [Figure 9] This is an enlarged perspective view of a portion of the block from which the first bridge element protrudes in a pneumatic tire of another embodiment. [Figure 10] This is an enlarged perspective view of a portion of the block from which the second bridge element protrudes in a pneumatic tire of another embodiment. [Figure 11] This figure corresponds to Figure 8, showing a pneumatic tire in another embodiment. [Figure 12] In the pneumatic tire of another example of the embodiment, it is a figure corresponding to FIG. 8. [Figure 13] In the pneumatic tire of another example of the embodiment, it is a figure corresponding to FIG. 3. [Figure 14] In the pneumatic tire of another example of the embodiment, it is a figure corresponding to FIG. 5. [Figure 15] In the pneumatic tire of another example of the embodiment, it is an enlarged perspective view of a part of a block where the first bridge element protrudes. [Figure 16] In the pneumatic tire of another example of the embodiment, it is an enlarged perspective view of a part of a block where the second bridge element protrudes.

Mode for Carrying Out the Invention

[0011] Hereinafter, an example of an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. The embodiments described below are merely examples, and the present invention is not limited to the following embodiments. In addition, a form formed by selectively combining the respective components of the embodiments described below is included in the present invention.

[0012] FIG. 1 is a plan view of a pneumatic tire 1 which is an example of an embodiment. As shown in FIG. 1, the pneumatic tire 1 includes a tread 10 which is a portion that contacts the road surface. The tread 10 extends from the equator CL side toward the grounding ends E1 and E2 sides, and has a plurality of main grooves 20 and 21 whose inclination angles with respect to the tire axial direction (the left - right direction in FIG. 1) are larger on the equator CL side than on the grounding ends E1 and E2 sides, a plurality of sub - grooves 22 that connect adjacent main grooves 20 and 21 in the tire rotation direction or in a direction inclined with respect to the tire rotation direction, and a plurality of lands 28 partitioned by the plurality of main grooves 20 and 21 and the plurality of sub - grooves 22. Hereinafter, the pneumatic tire 1 will be referred to as the tire 1.

[0013] The plurality of lands 28 have blocks 30, 31 formed along the main grooves 20, 21. The main groove 20 and the block 30 extend from the equator CL side to the ground end E1 side, and the main groove 21 and the block 31 extend from the equator CL side to the ground end E2 side.

[0014] The equator CL means a line along the tire circumferential direction passing through the center in the tire axial direction of the tread 10 (a position equidistant from the ground ends E1, E2). In this specification, the ground ends E1, E2 are defined as both ends in the tire axial direction of the area that contacts the flat road surface when a predetermined load is applied in a state where the unused pneumatic tire 1 is mounted on a regular rim and filled with air to reach the regular internal pressure. In the case of a passenger car tire, the predetermined load is a load corresponding to 88% of the regular load.

[0015] Here, the "regular rim" is a rim defined by the tire standard. In the case of JATMA, it is the "standard rim", and in the case of TRA and ETRTO, it is the "Measuring Rim". The "regular internal pressure" is the "maximum air pressure" in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO. The regular internal pressure is usually 180 kPa for a passenger car tire, but 220 kPa for a tire marked as Extra Load or Reinforced. The "regular load" is the "maximum load capacity" in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO. In the case of a racing kart tire, the regular load is 392 N.

[0016] Tire 1 is a directional tire with a specified main rotation direction. Figure 1 illustrates arrow α indicating the main rotation direction of the tire. In this specification, the "main rotation direction" of a tire means the direction of rotation when the vehicle on which the tire is mounted is moving forward. Also, in this specification, for convenience of explanation, the term "left and right" is used, but this left and right refers to the left and right when the tire is mounted on the vehicle and facing the direction of travel of the vehicle. It is preferable that the pneumatic tire 1 has an indication for the mounting direction relative to the vehicle. For example, at least one of letters and an arrow indicating the main rotation direction is provided on the side of the pneumatic tire 1.

[0017] The tread 10 has a tread pattern in which blocks 30 and 31 are arranged in a staggered pattern along the circumferential direction of the tire. Most of the blocks 30 and 31 are arranged on the left and right sides of the tread 10, with the equator CL in between.

[0018] The blocks 30 are formed along the main grooves 20 and are arranged alternately with the main grooves 20 in the circumferential direction of the tire. The blocks 30 include a center block 32 located on the equator CL side, a shoulder block 34 located on the contact end E1 side, and a mediate block 33 sandwiched between the center block 32 and the shoulder block 34. Sub-grooves 22 are formed between the center block 32 and the mediate block 33, and between the mediate block 33 and the shoulder block 34, respectively, connecting two main grooves 20 in the main rotation direction of the tire. The sub-grooves 22 divide the block 30 into three blocks. As will be described in more detail later, bridges 38 are provided in the sub-grooves 22 to connect adjacent blocks 30.

[0019] The blocks 31 are formed along the main grooves 21 and are arranged alternately with the main grooves 21 in the circumferential direction of the tire. The blocks 31 include a center block 35 located on the equator CL side, a shoulder block 37 located on the contact end E2 side, and a mediate block 36 sandwiched between the center block 35 and the shoulder block 37. Sub-grooves 23 are formed between the center block 35 and the mediate block 36, and between the mediate block 36 and the shoulder block 37, respectively, connecting two main grooves 21 in the main rotation direction of the tire. The sub-grooves 23 divide the block 31 into three blocks. As will be described in more detail later, bridges 38 are provided in the sub-grooves 23 to connect adjacent blocks 30.

[0020] The tire 1 comprises a pair of sidewalls that bulge outward in the tire axial direction and a pair of beads. The beads are the portion that is fixed to the rim of the wheel and have a bead core and a bead filler. The sidewalls and beads are formed in an annular shape along the tire circumferential direction and form the side surface of the pneumatic tire 1. The sidewalls extend radially from both ends of the tread 10 in the tire axial direction.

[0021] The tread pattern of tire 1 will be described in detail below. The main grooves 20 are formed at arbitrary intervals in the circumferential direction of the tire. Similarly, the main grooves 21 are formed at arbitrary intervals in the circumferential direction of the tire. The tread 10 has a tread pattern in which most of the main grooves 20 and blocks 30 are located on the side of the equator CL towards the contact edge E1 (the left side of the tread 10), and most of the main grooves 21 and blocks 31 are located on the side of the equator CL towards the contact edge E2 (the right side of the tread 10). Blocks are portions that protrude outward in the radial direction of the tire.

[0022] In the tread 10, center blocks 32 and 35 are arranged alternately along the tire's circumferential direction, centered in the axial center of the tire. Furthermore, center blocks 32 and 35 are arranged in a staggered pattern along the equator CL.

[0023] The tread pattern of this embodiment is, in a plan view, a pattern in which blocks 30 and 31 are arranged symmetrically on the left and right sides, offset by a predetermined pitch in the tire circumferential direction with respect to the equator CL. The shape of block 30 is the same as the shape of block 31 when it is inverted with respect to the equator CL (the same applies to the main grooves 20 and 21). If block 31, which has been inverted at the equator CL, is slid in the tire circumferential direction, it will coincide with block 30. The tread pattern of this embodiment has good left-right balance and is effective in improving handling stability.

[0024] The main groove 20 and block 30 have a plan view shape that is curved so as to be convex toward the rear in the direction of tire rotation. Similarly, the main groove 21 and block 31 also have a plan view shape that is curved so as to be convex toward the rear in the direction of tire rotation. The main grooves 20, 21 and blocks 30, 31 are inclined with respect to the tire axis so that they are gradually positioned toward the rear in the main rotation direction α of the pneumatic tire 1, starting from the center side in the tire axis direction toward both sides in the axial direction.

[0025] As described above, the main grooves 20 and 21 have a greater angle of inclination with respect to the tire axis on the equator CL side than on the contact end E1 and E2 side. The angle of inclination of the main grooves 20 and 21 is determined by its relationship to a straight line connecting the centers of the main grooves 20 and 21. In other words, the main grooves 20 and 21 gradually become more aligned with the tire axis from the equator CL side toward the contact end E1 and E2, and the inclination with respect to the tire axis becomes gentler. The angle of inclination of the main grooves 20 and 21 with respect to the tire axis is, for example, 30° to 60° or 40° to 50° on the equator CL side.

[0026] The main groove 20 connects to the main groove 21 near the equator CL. The main groove 20 extends from the intersection with the main groove 21 toward the contact end E1 and extends beyond the contact end E1 to the left annular side rib (not shown). The main groove 21 extends from the intersection with the main groove 20 near the equator CL toward the contact end E2 and extends beyond the contact end E2 to the right annular side rib (not shown). Each side rib is formed at its respective end in the tire axial direction between the contact ends E1, E2 of the tread 10 and the part of the sidewall 11 that protrudes most outward in the tire axial direction. The side ribs protrude outward in the tire axial direction and are formed in an annular shape along the tire circumferential direction. The side ribs may be omitted.

[0027] The width of the main grooves 20 and 21 may be constant along their entire length, but in this embodiment, it gradually increases from the equator CL side toward the ground contact ends E1 and E2. The width of the main grooves 20 and 21 may be maximum, for example, at or near the ground contact ends E1 and E2, or at or near the intersection with the secondary grooves 22 and 23. In this case, drainage performance is improved, and the snow column shear force that grips and compacts the snow is also improved, resulting in good snow performance. The main grooves 20 and 21 are formed to the same depth, for example.

[0028] The sub-grooves 22 and 23 are grooves that are narrower in width (maximum width) than the main grooves 20 and 21. The sub-groove 22 extends in the circumferential direction of the tire, dividing the block 30 and connecting adjacent main grooves 20. The sub-groove 22 is inclined with respect to the circumferential direction of the tire so as it moves gradually away from the contact edge E1 from the front to the rear in the main rotation direction α of the tire. Similarly, the sub-groove 23 divides the block 31 and connects adjacent main grooves 21, and is inclined with respect to the circumferential direction of the tire so as it moves gradually away from the contact edge E2 from the front to the rear in the main rotation direction α of the tire. The sub-grooves 22 and 23 may be shallower or deeper than the main grooves 20 and 21, but it is preferable that they are formed to the same depth as the main grooves 20 and 21.

[0029] Slits may be formed in each of blocks 32, 33, 34, 35, 36, and 37 along the main grooves 20 and 21. The slits may terminate within each block 32, 33, 34, 35, 36, and 37 without dividing the block. This increases the edge area and improves the snow performance of tire 1. The slits may also penetrate each of blocks 30 and 31. In this case, it is possible to improve the snow performance and drainage performance of tire 1.

[0030] Furthermore, bridges 38 are formed in each of the sub-grooves 22 and 23, specifically between the center block 32 and the mediate block 33, between the center block 35 and the mediate block 36, between the mediate block 33 and the shoulder block 34, and between the mediate block 36 and the shoulder block 37. The bridges 38 may be formed over substantially the entire longitudinal portion of the sub-grooves 22 and 23, or they may be formed only on a portion of the longitudinal portion of the sub-grooves 22 and 23, such as on the front or rear side of the main tire rotation direction α.

[0031] Furthermore, a bridge 38 is formed between the two center blocks 32 and 35 as part of each main groove 20 and 21. Although not shown in the illustration, a bridge 38 may also be formed between the two center blocks 32 and between the two center blocks 35, which are located on each side in the axial direction of the tire.

[0032] The bridge 38 will be explained in detail below using Figures 2 to 5. In the following, the bridge 38 provided in the sub-groove 22 of a part of block 30, between the mediate block 33 which is the first landmass and the shoulder block 34 which is the second landmass, will be mainly described. The same applies to the bridges 38 provided in the other sub-grooves 22 of block 30, the sub-grooves 23 of block 31, and each of the main grooves 20 and 21. In this case, one of the blocks facing each other via the groove having the bridge 38 corresponds to the first landmass, and the other corresponds to the second landmass.

[0033] Figure 2 is an enlarged view of section A in Figure 1. Figure 3 is a cross-sectional view of section BB in Figure 2. Figure 4 is an enlarged perspective view corresponding to section A in Figure 1, exaggerating the deformation state when the mediate block 33, on which the first bridge element 39 protrudes, and the shoulder block 34, on which the second bridge element 40 protrudes, deform outwards in the tread 10 of the tire 1.

[0034] As shown in Figures 2 and 3, the mediate block 33 and the shoulder block 34 face each other via a sub-groove 22, and a bridge 38 is positioned in the sub-groove 22. The bridge 38 includes a first bridge element 39 protruding from the side of the mediate block 33 on the sub-groove 22 side, and a second bridge element 40 protruding from the side of the shoulder block 34 on the sub-groove 22 side. Each bridge element 39, 40 is plate-shaped with a substantially uniform thickness in the tire radial direction. In Figure 2, for clarity, the second bridge element 40 and the shoulder block 34 from which the second bridge element 40 protrudes are shown in a sandy area. In the cross-sectional view of Figure 3, for clarity, the second bridge element 40 and the shoulder block 34 are shown in a portion where sandy area has been added to the hatching.

[0035] The portions of the first bridge element 39 and the second bridge element 40, excluding the areas near their roots, overlap in the groove depth direction. The second bridge element 40 overlaps the first bridge element 39 on the radial side of the tire. The bridge 38 is formed by the bridge elements 39 and 40, whose portions overlap in this way. As a result, as described later, the opposing blocks 33 and 34 can be reinforced via the sub-groove 22, the blocks 33 and 34 can be prevented from being subjected to excessive force, and the ease of bending when the tire tread makes contact with the ground and the flexibility of the blocks 33 and 34 during turning can be ensured, thereby suppressing a decrease in the performance of the tire 1. Furthermore, it can prevent foreign objects such as stones and snow from getting stuck in the tire 1.

[0036] The first bridge element 39 is formed to protrude radially outward from the bottom surface of the sub-groove 22, but the first bridge element 39 may be formed separately from the bottom surface of the sub-groove 22.

[0037] The first bridge element 39 may have a protruding length d1 that is 70% or more of the width da of the sub-groove 22. The second bridge element 40 may have a protruding length d2 that is 70% or more of the width da of the sub-groove 22. This increases the connection strength between blocks 33 and 34 and provides further reinforcement to each block 33 and 34.

[0038] Furthermore, the bridge 38 is formed by combining one first bridge element 39 and one second bridge element 40 so that a total of five or fewer bridge elements 39 and 40 interlock in the groove depth direction. This prevents the thickness of each bridge element 39 and 40 from becoming too thin, thus preventing an excessive reduction in the rigidity of each bridge element 39 and 40. This makes it easier to ensure the strength of the bridge 38.

[0039] Furthermore, the first bridge element 39 may overlap the second bridge element 40 on the outer side in the tire radial direction. Also, the first bridge element 39 and the second bridge element 40 may both overlap completely in the groove depth direction. In this case, no space is formed between the tip of the first bridge element 39 and the side surface of the block 34 at the groove bottom side of the root end of the second bridge element 40.

[0040] In this example, the tire 1 having the bridge 38 allows for reinforcement of opposing blocks, such as blocks 33 and 34, via grooves such as the sub-groove 22 having the bridge 38. Furthermore, since the bridge 38 is formed by two bridge elements, such as bridge elements 39 and 40, which are capable of relative displacement, it is possible to suppress the opposing blocks from receiving excessive force via the groove having the bridge 38. In addition, it is possible to ensure the ease of bending of the tire tread when it makes contact with the ground and the flexibility of the opposing blocks via the groove having the bridge 38 during turning. This suppresses a decrease in the performance of the tire 1. Moreover, unlike cases where a bridge with a groove formed on its top surface is provided, it is possible to prevent foreign objects such as stones and snow from getting stuck in the groove on its top surface, thus suppressing the entanglement of foreign objects in the tire 1.

[0041] Figure 4 shows that the configuration in this example ensures the flexibility of the tire tread when it makes contact with the road surface. When the tire tread makes contact with the road surface, depending on the unevenness of the road surface, the mediate block 33 and the shoulder block 34 may attempt to deform outward, moving away from each other toward the radially outward direction of the tire, in the direction of arrow β in Figure 5. In this case, in this example, the two bridge elements 39 and 40 that form the bridge 38 can deform outward in a drawbridge-like manner, thus ensuring the flexibility of the top surfaces of each block 33 and 34, which are the tire tread, when they make contact with the road surface, that is, the flexibility of the top surfaces from a state where they are located on the same plane. This makes it easier for the tire tread to fit the unevenness of the road surface.

[0042] Furthermore, in tire 1, the circular structure of the tire tread deforms in accordance with the road surface, forming a planar contact shape with respect to the road surface. At this time, the tire surface deforms mainly using grooves such as the main grooves 20 and 21 as folds. In this example, although bridges 38 are placed in the grooves to reinforce the blocks, the ease of bending of the tire tread when it contacts the road surface can be ensured, and the reduction in the effective contact area can be suppressed. This suppresses the deterioration of the performance of tire 1.

[0043] Figure 5 shows that the configuration of this example ensures the flexibility of blocks 33 and 34 during turns. As shown in Figure 5, when a vehicle turns, a force is applied to the tire tread in the direction of the turn, which may cause deformation in the directions of arrows γ1 and γ2 in Figure 5. At this time, since displacement in the sliding direction along the surface direction of the opposing faces of each bridge element 39 and 40 is permitted, it is possible to allow the opposing blocks 33 and 34 to deform so that they open up to each other in a V-shape in a plan view via grooves such as the sub-groove 22, as exaggeratedly shown in Figure 5. This ensures the flexibility of blocks 33 and 34 during turns.

[0044] As described above, with the configuration of this example, opposing blocks can be reinforced via grooves having bridges 38, which prevents the blocks from collapsing towards the grooves and ensures the flexibility of the blocks during turning, thereby improving the turning performance of the tire. In addition, the outward swinging motion of the drawbridge between opposing blocks via the grooves is made easier, which ensures that the tire tread can turn easily when it comes into contact with the road surface.

[0045] Figure 6 is a diagram corresponding to Figure 5, showing a tire of another embodiment. In this example, of the blocks 33, 34, etc., facing each other via a groove having a bridge 38a, two first bridge elements 39a protrude from the groove-side side of one block, such as block 33, separated in the groove depth direction. A second bridge element 40a protruding from the groove-side side of the other block, such as block 34, is sandwiched between the two first bridge elements 39a in the groove depth direction, with the bridge elements 39a and 40a overlapping in the groove depth direction. The bridge 38a is composed of two first bridge elements 39a and one second bridge element 40a.

[0046] As a result, the bridge 38a is formed by combining two first bridge elements 39a and one second bridge element 40a so that a total of five or fewer bridge elements 39a, 40a interlock in the groove depth direction. This prevents the thickness of each bridge element 39a, 40a from becoming too thin, thus preventing excessive reduction in the rigidity of each bridge element 39a, 40a, and further suppressing the tilting of opposing blocks such as blocks 33, 34 toward the groove side via the bridge 38a. This makes it easier to further reinforce each block. On the other hand, from the viewpoint of facilitating the outward opening movement of two opposing blocks via the groove having the bridge 38a, the configurations shown in Figures 1 to 5 are more preferable than the configuration in this example.

[0047] Furthermore, in this example as well, as shown in Figure 6, flexibility during rotation of opposing blocks such as blocks 33 and 34 can be ensured via the bridge 38a. In this example, the other configurations and functions are the same as those in Figures 1 to 5. Similar to the configurations described in the explanation of Figures 1 to 5, the first bridge element 39a and the second bridge element 40a may each overlap completely in the groove depth direction.

[0048] Figure 7 is a diagram corresponding to Figure 5, showing a tire of another embodiment. In this example, among blocks such as blocks 33 and 34 that face each other via a groove such as a sub-groove 22 having a bridge 38b, a corrugated first bridge element 39b protrudes from the groove-side surface of one block such as block 33. A corrugated second bridge element 40b protrudes from the groove-side surface of the other block such as block 34. As a result, each bridge element 39b, 40b has a shape that has amplitude in the groove depth direction of the sub-groove 22. The bridge 38b is composed of two bridge elements 39b, 40b.

[0049] Similar to Figure 3, in the state before tire deformation due to contact with the ground, etc., the portions of the first bridge element 39b and the second bridge element 40b, excluding the areas near their respective roots, overlap in the groove depth direction. The first bridge element 39b overlaps the outer side of the second bridge element 40b in the tire radial direction. The waveforms of each bridge element 39b and 40b are approximately the same.

[0050] Furthermore, the second bridge element 40b may overlap the first bridge element 39b on the radially outer side of the tire. The first bridge element 39b and the second bridge element 40b may each overlap completely in the groove depth direction.

[0051] According to the configuration of this example, opposing blocks such as blocks 33 and 34 can be reinforced via grooves such as the sub-grooves 22, and the flexibility of blocks such as blocks 33 and 34 during turning can be ensured, thereby suppressing a decrease in the dynamic performance of the tire 1.

[0052] Furthermore, since each bridge element 39b and 40b has a shape that has amplitude in the groove depth direction, each bridge element 39b and 40b engages with the sub-groove 22 and other grooves in the longitudinal direction, thereby suppressing lateral displacement in the longitudinal direction of the groove. This also suppresses lateral displacement of blocks such as blocks 33 and 34, which have each bridge element 39b and 40b, in the longitudinal direction of the groove. In this example, the other configurations and functions are the same as those in Figures 1 to 5. As with the configurations described in the explanation of Figures 1 to 5, the first bridge element 39b and the second bridge element 40b may each completely overlap in the groove depth direction.

[0053] Figure 8 is a cross-sectional view showing the longitudinal middle portion of the sub-groove 22 when the bridge 38c is cut along the longitudinal direction of the groove in a tire of another embodiment. Figure 9 is an enlarged perspective view of a part of block 33 in which the first bridge elements 39c1 and 39c2 protrude in a tire of another embodiment. Figure 10 is an enlarged perspective view of a part of block 34 in which the second bridge element 40c protrudes in a tire of another embodiment.

[0054] In this example, the bridge 38c provided in the sub-groove 22 and the like is composed of two first bridge elements 39c1 and 39c2 and one second bridge element 40c. As shown in Figure 9, the two first bridge elements 39c1 and 39c2 protrude from the groove-side portion of the groove-side surface of the block, such as the mediate block 33, away from the longitudinal direction of the sub-groove 22 and the like. Each first bridge element 39c1 and 39c2 has projections 42 and 43 that protrude toward each other on opposite sides in the longitudinal direction of the groove. Each projection 42 and 43 is stepped, and its length of projection in the longitudinal direction of the groove increases in a stepped manner toward the groove bottom.

[0055] On the other hand, as shown in Figure 10, the second bridge element 40c protrudes from the groove-side portion of the groove-side surface of a block such as the shoulder block 34, including the groove bottom side, so as to be sandwiched between the two first bridge elements 39c1 and 39c2. As a result, as shown in Figure 8, the second bridge element 40c is positioned between the two first bridge elements 39c1 and 39c2 in the longitudinal direction of the groove within a groove such as the sub-groove 22. Furthermore, protrusions 44 and 45 protrude from both sides of the second bridge element 40c in the longitudinal direction of the groove. Each protrusion 44 and 45 is stepped, and the length of the protrusion in the longitudinal direction of the groove increases in a stepped manner toward the opposite side from the groove bottom. The protrusions 44 and 45 of the second bridge element 40c overlap in the groove depth direction on the radially outer side of the protrusions 42 and 43 of each first bridge element 39c1 and 39c2.

[0056] In this example, the first bridge elements 39c1, 39c2 and the second bridge element 40c can be brought into contact on a plane perpendicular to the longitudinal direction of the groove, such as on the side surfaces of the protrusions 42, 43, 44, 45 facing the longitudinal direction of the groove, thereby allowing them to face each other in the longitudinal direction of the groove. This further suppresses lateral displacement of blocks such as blocks 33, 34, each having bridge elements 39c1, 39c2, 40c in the longitudinal direction of the groove compared to the configuration in Figure 8. On the other hand, in terms of facilitating outward opening of two opposing blocks via a groove having a bridge 38c, the configurations in Figures 1 to 5 are more preferable than the configuration in this example. In this example, the other configurations and operations are the same as those in Figures 1 to 5.

[0057] Figure 11 is a diagram corresponding to Figure 8 in a tire of another embodiment. In this example, the length of the bridge 38d in the groove depth direction is smaller than that of the bridge 38c in the configuration of Figure 8. In this example, the bridge 38d is composed of two first bridge elements 39d1, 39d2 and one second bridge element 40d. Each first bridge element 39d1, 39d2 protrudes from the groove bottom side of the groove-side surface of a block such as a mediate block 33. Each first bridge element 39d1, 39d2 has protrusions 42a, 43a that protrude from the groove bottom side of the mutually opposing sides in the longitudinal direction of the groove.

[0058] The second bridge element 40d protrudes from the groove bottom side of the groove-side surface of a block such as a shoulder block 34, sandwiched in the longitudinal direction of the groove by two first bridge elements 39d1 and 39d2. Each first bridge element 39d1 and 39d2 has projections 44a and 45a that protrude from the opposite side of the groove bottom on both sides in the longitudinal direction of the groove. On the radially outer side of the projections 42a and 43a of each first bridge element 39d1 and 39d2, the projections 42a, 43a, 44a, and 45a of the second bridge element 40d overlap in the groove depth direction. In this example as well, similar to the configuration in Figures 8 to 10, the projections 42a, 43a, 44a, and 45a can be brought into contact with each other in the longitudinal direction of the groove on the sides facing the longitudinal direction of the groove, using a plane perpendicular to the longitudinal direction of the groove. This prevents blocks such as blocks 33 and 34, each having bridge elements 39d1, 39d2, and 40d, from shifting laterally in the longitudinal direction of the groove. In this example, the other configurations and functions are the same as those in Figures 1 to 5.

[0059] Figure 12 is a diagram of a tire in another embodiment, corresponding to Figure 8. In this example, the projections 42b and 43b of each first bridge element 39e1 and 39e2 and the projections 44a and 45a of the second bridge element 40e are arranged in the opposite direction in the tire depth direction to the projections 42a and 43a of each first bridge element 39d1 and 39d2 and the projections 44a and 45a of the second bridge element 40d in the configuration shown in Figure 11. In this example, the other configurations and operations are the same as in the configuration of Figure 11.

[0060] Figure 13 is a diagram corresponding to Figure 3, showing a tire of another embodiment. In this example, the bridge 38f is composed of a first bridge element 39f and a second bridge element 40f. The first bridge element 39f protrudes from the groove bottom side of the groove-side surface of a block such as a mediate block 33. A concave curved surface 46 with a circular arc cross-section is formed on the upper surface of the tip side of the first bridge element 39f. The lower end of the first bridge element 39f protrudes the most in the groove width direction.

[0061] The second bridge element 40f protrudes from the groove bottom side of the groove-side surface of a block such as the shoulder block 34. The second bridge element 40f has a curved surface 47 with a circular arc cross-section on its lower tip side. The curved surface 47 of the second bridge element 40f overlaps the concave curved surface 46 of the first bridge element 39f on the outer side in the tire radial direction in the groove depth direction.

[0062] In this example, as with the configurations in Figures 1 to 5, the reinforcement of the blocks prevents them from collapsing towards the groove and ensures flexibility during turning, thereby improving the turning performance of the tires. Furthermore, the outward-opening, upward-sweeping motion of the opposing blocks across the groove facilitates the turning of the tire tread when it makes contact with the road surface, thus ensuring ease of turning. In this example, the other configurations and functions are the same as those in Figures 1 to 5.

[0063] Figure 14 is a diagram corresponding to Figure 5, showing a tire of another embodiment. In this example, two first bridge elements 39g protrude from the groove-side surface 48 of a block such as a mediate block 33, separated in the groove depth direction. The two first bridge elements 39g are separated from the groove bottom of a groove such as a sub-groove 22a. In addition, one second bridge element 40g protrudes from the groove-side surface 49 of a block such as a shoulder block 34, sandwiched in the groove depth direction by the two first bridge elements 39g. The bridge 38g is composed of two first bridge elements 39g and one second bridge element 40g.

[0064] The sides 48 and 49 of the grooves of the sub-grooves 22a of the two blocks, such as blocks 33 and 34, which face each other via the bridge 38g, are formed in a wave-like shape in the groove depth direction and have amplitude in the groove width direction. In this example configuration as well, when turning, the two blocks, such as blocks 33 and 34, tend to deform so that they open up to each other in a V-shape in a plan view, as shown in the directions of arrows η1 and η2 in Figure 14. This ensures the flexibility of the blocks when turning, thereby improving the turning performance of the tire. In this example, the other configurations and functions are the same as in the configuration of Figure 6. In the configuration of Figure 14, the lower first bridge element 39g may be placed at the bottom of the groove, similar to the configuration of Figure 6. In this case, the two first bridge elements 39g and the one second bridge element 40g may each overlap almost entirely in the groove depth direction.

[0065] Figure 15 is an enlarged perspective view of a portion of block 33 in another embodiment of the tire, on which the first bridge element 39h protrudes. Figure 16 is an enlarged perspective view of a portion of block 34 in another embodiment of the tire, on which the second bridge element 40h protrudes.

[0066] In this example, the bridge is composed of a first bridge element 39h shown in Figure 15 and a second bridge element 40h shown in Figure 16. As shown in Figure 15, the first bridge element 39h protrudes from the groove-side surface of a block such as the mediate block 33 in a corrugated shape that deforms in a wave-like manner in the longitudinal direction of the groove. The first bridge element 39h is inclined toward the groove bottom side in one direction along the longitudinal direction of the groove, while changing in a wave-like manner.

[0067] As shown in Figure 16, the second bridge element 40h protrudes from the groove-side surface of a block such as the shoulder block 34 in a corrugated shape that deforms in a wave-like manner along the longitudinal direction of the groove. Similar to the first bridge element 39h, the second bridge element 40h also slopes toward the groove bottom side, changing in a wave-like shape toward one side in the longitudinal direction of the groove.

[0068] The first bridge element 39h overlaps the second bridge element 40h on the radially outer side of the tire. The second bridge element 40h may also overlap the first bridge element 39h on the radially outer side of the tire. Furthermore, the groove-side surfaces of blocks such as the mediate block 33 and the groove-side surfaces of blocks such as the shoulder block 34 are formed in a wavy shape in the groove depth direction and have amplitude in the groove width direction, similar to the configuration in Figure 14.

[0069] In this example, the first bridge element is less prone to lateral displacement in the direction that is higher on the outer side of the tire radially relative to the second bridge element. In this example, the other configurations and functions are the same as those in Figures 1 to 5, or Figure 7.

[0070] Furthermore, in each of the above examples, a bridge 38 is formed in each sub-groove 22, 23 and between the two center blocks as part of each main groove 20, 21. In this configuration, it is not necessary to form a bridge at the bottom of the groove on both sides of the tire axial direction away from the equator CL in each main groove 20, 21, thus reinforcing many blocks while suppressing a decrease in drainage performance. The bridge can be configured to be located in at least one of the grooves between the two center blocks, between the center block and the mediate block, and between the mediate block and the shoulder block.

[0071] The tire of the present invention can be applied to summer tires with a small number of sipes, all-season tires, or winter tires with a large number of sipes. [Explanation of Symbols]

[0072] 1 pneumatic tire (tire), 10 tread, 11 sidewall, 20,21 main groove, 22,23,22a secondary groove, 28 ground, 30,31 blocks, 32,35 center block, 33,36 mediate block, 34,37 shoulder block, 38,38a~38g bridge, 39,39a,39b,39c1,39c2,39cd,39d2 first bridge element, 40,40a,40b,40c,40d second bridge element, 42,43,44,45 protrusion, 46 concave curved surface, 47 convex curved surface, 48,49 side, CL equator, E1,E2 contact end.

Claims

1. A pneumatic tire having a tread, The tread includes a plurality of land areas separated by a plurality of grooves, The plurality of landmasses have a first landmass and a second landmass facing each other via some of the grooves, A bridge is placed within one of the grooves, The bridge includes a first bridge element protruding from the side surface of the first land and a second bridge element protruding from the side surface of the second land, wherein at least a portion of the first bridge element and the second bridge element overlap in the groove depth direction. Pneumatic tires.

2. The main rotation direction is specified. The plurality of grooves extend from the equator towards the contact end, and have a plurality of main grooves whose inclination with respect to the tire axis is greater on the equator side than on the contact end side, and a plurality of sub-grooves that connect adjacent main grooves in the direction of tire rotation or in an inclined direction with respect to the direction of tire rotation. The plurality of land areas include a center block, a mediate block, and a shoulder block, which are sequentially divided on both sides in the tire axial direction from the equator side toward the ground contact end side by the plurality of main grooves and the plurality of sub-grooves. The bridge is positioned between the first land and the second land, within at least one of the grooves between the two center blocks, between the center block and the mediate block, and between the mediate block and the shoulder block. The pneumatic tire according to claim 1.

3. Each of the first bridge element and the second bridge element has a protruding length of 70% or more of the width of the part of the groove. The pneumatic tire according to claim 1.

4. The bridge is formed by combining at least one first bridge element and at least one second bridge element such that a total of five or fewer bridge elements interlock in the groove depth direction. The pneumatic tire according to claim 1.

5. The first bridge element and the second bridge element each have a shape with amplitude in the groove depth direction. The pneumatic tire according to claim 1.

6. From the side surface of the first land, the two first bridge elements protrude apart in the longitudinal direction of the groove, Within the groove, the second bridge element is positioned between the two first bridge elements in the longitudinal direction of the groove. Each of the first bridge element and the second bridge element has a projection that protrudes in the longitudinal direction of the groove, The projections of each of the first bridge elements and the projections of the second bridge element overlap in the groove depth direction. The pneumatic tire according to claim 1.

7. The projections of the first bridge element and the second bridge element are stepped. The pneumatic tire according to claim 6.

Images