Pneumatic tires

Abstract

A tire (1) as an example of an embodiment includes a tread portion (10) having: a plurality of land portions; and sipes (61) formed on at least a portion of the land portions. Inclined surfaces (71, 72) having a straight cross-section continuous from the contact surface (S) are formed between an opening end of at least one side of the sipes (61) in the width direction and a contact surface (S). An intermediate surface (73) having an inclination angle of 0 degrees relative to the contact surface (S) or an inclination angle smaller than the inclination angle of the inclined surfaces (71, 72) relative to the contact surface (S) is formed between the inclined surfaces (71, 72) and the sipes (61).

Description

[0001] The present disclosure is based on Japanese Patent Application No. 2022-10901 filed on January 27, 2022, and the contents thereof are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to a pneumatic tire, and more particularly, to a pneumatic tire including a tread portion including: a plurality of land portions; and sipes formed in at least a portion of the land portions. Background Art

[0003] Conventionally, pneumatic tires are known that include a tread portion comprising a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of land portions formed by dividing the plurality of circumferential grooves in the tire width direction, wherein sipes are formed in the plurality of land portions (see, for example, International Publication No. 2016 / 125814). The pneumatic tire described in International Publication No. 2016 / 125814 has a chamfer formed between the open end of one or both sides of the sipe in the width direction and the contact surface. Summary of the Invention

[0004] Regarding the pneumatic tire of International Publication No. 2016 / 125814, in the mold that forms the shape of the tread portion, including chamfers and sipes, the protrusions that form the sipes and the main body that forms the portion including the chamfers are sometimes formed from different components. In this case, after the tread portion is formed, if the mold is subjected to a spray cleaning method such as dry ice blasting accompanied by a jet of high-pressure gas, the chamfered portion of the main body may deform by flipping up from the protrusions. This may reduce the durability of the mold depending on the mold cleaning method. Furthermore, there is room for improvement in terms of improving drainage performance of the tire.

[0005] An object of the present disclosure is to provide a pneumatic tire that can improve the durability of the mold even when a mold forming the tire shape is subjected to spray cleaning with high-pressure gas, and can also improve drainage during tire use.

[0006] A pneumatic tire according to the present disclosure includes a tread portion, the tread portion comprising: a plurality of land portions; and sipes formed in at least a portion of the land portions, wherein an inclined surface, whose cross-section is linear and continuous from the ground contact surface, is formed between an open end on at least one side in the width direction of the sipe and a ground contact surface, and an intermediate surface is formed between the inclined surface and the sipe, the intermediate surface having an inclination angle relative to the ground contact surface of 0 degrees or an inclination angle relative to the ground contact surface that is smaller than the inclination angle of the inclined surface relative to the ground contact surface.

[0007] According to the above-mentioned pneumatic tire, in the mold that forms the tire shape, when the protrusions forming the sipes and the main body forming the portion including the inclined surface are formed by different components, a top surface that contacts the protrusion at an angle close to right angles relative to the protrusion is provided in the main body, corresponding to the portion in contact with the protrusion and the intermediate surface. As a result, even when the mold is subjected to jet cleaning accompanied by a jet of high-pressure gas, the top surface contacts the side of the protrusion on the mold's internal space side at a smaller angle than in a case where the intermediate surface is absent. This prevents the main body from deforming by tilting away from the protrusion. Consequently, the durability of the mold can be improved. Furthermore, the formation of the intermediate surface increases the area within the tire's grooves that can hold water, thereby improving the tire's drainage during use.

[0008] According to the pneumatic tire of the present disclosure, even when a mold forming the tire shape is subjected to spray cleaning with high-pressure gas, the durability of the mold can be improved, and drainage performance during tire use can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a perspective view of a pneumatic tire as an example of an embodiment.

[0010] Figure 2 yes Figure 1 Top view of part A.

[0011] Figure 3 Viewed from the circumferential main groove side of the first groove Figure 2 An enlarged stereogram of part B.

[0012] Figure 4 Yes Figure 2 Diagram of the C-C line cross section.

[0013] Figure 5 Observed from the circumferential main groove side of the second groove Figure 2 An enlarged stereogram of the D portion.

[0014] Figure 6 Yes Figure 5 Diagram of the E-E line section.

[0015] Figure 7 yes Figure 1 Enlarged stereogram of part F

[0016] Figure 8 is formed Figure 1 The tread portion of the tire is formed in the tire vulcanization mold Figure 3 A schematic cross-sectional view of the first groove portion.

[0017] Figure 9It is a schematic cross-sectional view of a portion where a groove is formed in a mold for forming the tread portion of a tire according to a comparative example.

[0018] Figure 10 Other examples of implementations are Figure 4 The corresponding figure. DETAILED DESCRIPTION

[0019] Hereinafter, an embodiment of a pneumatic tire according to the present disclosure will be described in detail with reference to the accompanying drawings. The embodiment described below is merely an example, and the present disclosure is not limited to the following embodiment.

[0020] Figure 1 1 is a perspective view of a pneumatic tire 1 as an example of an embodiment. Figure 1 As shown, the pneumatic tire 1 includes a tread portion 10 that contacts the road surface. Hereinafter, the "pneumatic tire 1" is referred to as "tire 1." The tread portion 10 has a tread pattern including a plurality of land portions and is formed in an annular shape along the tire circumferential direction.

[0021] The tread portion 10 includes land portions 40, 41, 42, 43, and 44 defined by, for example, four circumferential main grooves 20, 21, 22, and 23. The land portions are protruding from a reference plane of the tread portion 10 toward the outside in the tire radial direction. The "reference plane" refers to an imaginary plane along the bottom surface of the deepest circumferential main groove and is the outer peripheral surface of the tread portion 10 when no land portions are present. As the land portions, the tread portion 10 includes, by means of the four circumferential main grooves 20, 21, 22, and 23, a central land portion 40 encompassing the tire widthwise center CL; intermediate land portions 41 and 42 disposed on either side of the central land portion 40 in the tire widthwise direction, separated by the first circumferential main grooves 20 and 21; and shoulder land portions 43 and 44 disposed on the tire widthwise outer sides of each of the two intermediate land portions 41 and 42, separated by the second circumferential main grooves 22 and 23.

[0022] The center land portion 40, the two middle land portions 41, 42, and the two shoulder land portions 43, 44 are each rib-shaped and continuous over the entire circumference of the tire.

[0023] The tire 1 includes a sidewall portion 12, which is positioned further outward in the tire width direction than the tread portion 10 and bulges most outward in the tire width direction; and a bead portion (not shown) secured to the wheel rim. The sidewall portion 12 and the bead portion form an annular shape along the tire circumference. The sidewall portion 12 extends radially inward from both ends of the tread portion 10 in the tire width direction.

[0024] The tire 1 is a pneumatic tire filled with air at a predetermined pressure. The tread portion 10 and the sidewall portion 12 are made of, for example, different types of rubber.

[0025] The shoulder land portions 43 and 44, located at both ends of the tread portion 10 in the width direction, include contact edges T at the outer ends in the tire width direction, serving as the contact patch. The tire width direction ends of each shoulder land portion 43 and 44 are exposed further outward in the tire width direction than contact edges T, and the outer peripheral surface curves gently inward in the tire radial direction, convexly outward. The portion of each shoulder land portion 43 and 44 that is exposed further outward in the tire width direction than contact edges T is called a buttress.

[0026] The "ground contact edge T" refers to the tire widthwise ends of the area in contact with a flat road surface when an unused tire 1 is mounted on a regular rim, filled with air to a regular internal pressure, and subjected to a load 70% of the regular load at the regular internal pressure.

[0027] Here, the "regular rim" is the rim defined by the tire specifications. For JATMA standards, this is the "standard rim," for TRA standards, it's the "design rim," and for ETRTO standards, it's the "measuring rim." For JATMA standards, the "regular internal pressure" is the "maximum air pressure," for TRA standards, it's the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO standards, it's the "INFLATION PRESSURE." For JATMA standards, the "maximum load capacity" is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO standards, it's the "LOAD CAPACITY."

[0028] Although the tire 1 is not shown, it includes a carcass, a belt, and an inner liner. The carcass is a rubber-covered cord layer that forms the skeleton of the tire 1, capable of withstanding loads, impacts, and air pressure. The belt is a reinforcing belt disposed between the rubber forming the tread portion 10 and the carcass. The belt strongly secures the carcass, thereby increasing the rigidity of the tire 1. The inner liner is a rubber layer provided on the inner circumference of the carcass and is used to maintain the air pressure of the tire 1. Furthermore, the bead portion includes a bead core and a bead outer rubber.

[0029] Multiple lug grooves 60 are formed at various locations in the tire circumferential direction of each shoulder land portion 43, 44, extending generally in the tire width direction. The inner end of each lug groove 60 in the tire width direction terminates within the shoulder land portion 43, 44, without opening into the wall surface of the shoulder land portion 43, 44. The formation of these lug grooves 60 improves drainage toward the outer side in the tire width direction.

[0030] The contact surfaces of the center land portion 40 and the intermediate land portions 41 and 42 are formed with a plurality of sipes 61, 62, 63, 64, 65, and 66 extending in a direction inclined relative to the tire width direction or formed in a V-shape. Each sipe 61, 62, 63, 64, 65, and 66 enhances the edge grip on snow and ice, thereby achieving excellent braking and drivability and steering stability on icy and snowy roads.

[0031] exist Figure 2 In the illustrated embodiment, sipes 61 to 63, 65, and 66 inclined relative to the tire width direction are formed in the center land portion 40 and the middle land portions 41 and 42, and a V-shaped sipe 64 is formed in the middle land portion 41 on one side in the tire width direction.

[0032] Furthermore, a circumferential auxiliary groove 46 having a width smaller than that of each of the circumferential main grooves 20 , 21 , 22 , 23 and extending in the tire circumferential direction is formed in the center land portion 40 .

[0033] Below, as an example of a sipe pattern inclined relative to the tire width direction, the first and second sipe patterns 61 and 62 of the central land portion 40 are described as the center, and as an example of a sipe pattern formed in a V shape, the fourth sipe pattern 64 formed in the middle land portion 41 on one side in the tire width direction is described. Figure 2 yes Figure 1 Top view of part A. Figure 3 The first groove 70 is viewed from the side end of the circumferential main groove 20. Figure 2 An enlarged stereogram of part B. Figure 4 Yes Figure 2 Diagram of the C-C line cross section.

[0034] A plurality of first sipes 61 are formed on one first circumferential main groove 20 side of the center land portion 40. A plurality of second sipes 62 are formed on the other first circumferential main groove 21 side of the center land portion 40. The plurality of first sipes 61 are formed at multiple locations in the tire circumferential direction, spaced apart from one another. The plurality of second sipes 62 are formed at multiple locations in the tire circumferential direction, spaced apart from one another. The tire widthwise inner ends of the first and second sipes 61, each serving as one longitudinal end, terminate at a position in the center land portion 40 that does not reach the circumferential secondary groove 46. When viewed from the tire radially outer side, the first sipes 61 are longer than the second sipes 62.

[0035] The first groove 70, which extends in a direction oblique to the tire width direction, includes the first sipe 61. The opening of the first groove 70, when viewed from the tire radially outer side, is tapered and approximately triangular in shape. The first groove 70 comprises the first sipe 61; two first inclined surfaces 71 and 72 formed on either side of the first sipe 61 in the width direction; and an intermediate surface 73 formed between the first inclined surfaces 71 and 72 and the first sipe 61. Similar to the first sipe 61, the first groove 70 terminates at its inner end in the tire width direction, which is one of its longitudinal ends, at a position in the center land portion 40 that does not reach the circumferential auxiliary groove 46.

[0036] The first sipe 61 is a groove extending in a straight line inclined relative to the tire width direction and having a rectangular cross-sectional shape in a plane perpendicular to the longitudinal direction of the first sipe 61. One of the two first inclined surfaces 71 and 72 is a straight cross-sectional surface that continues from the contact patch S between the open end on one side of the width direction of the first sipe 61 and the contact patch S.

[0037] The other of the two first inclined surfaces 71 and 72 is a surface whose cross section is straight and continuous from the contact patch S, between the open end on the other side of the first sipe 61 in the width direction and the contact patch S. Each of the two first inclined surfaces 71 and 72 comprises multiple surfaces that are twisted so that the angle of inclination relative to the contact patch gradually changes along the longitudinal direction of the first groove 70, connected by ridgelines M1, M2, and M3 located in the middle of the longitudinal direction of the first groove 70. Alternatively, each of the first inclined surfaces 71 and 72 may be formed with multiple planar regions connected by a ridgeline located in the middle of the longitudinal direction of the first groove 70. Alternatively, each of the first inclined surfaces 71 and 72 may be formed of only a single planar surface.

[0038] like Figure 4 As shown, the inclination angle θ1 of one first inclined surface 71 relative to the ground contact surface S is larger than the inclination angle θ2 of the other first inclined surface 72 relative to the ground contact surface S.

[0039] The intermediate surface 73 is a flat surface formed between each of the two first inclined surfaces 71 and 72 and the first sipe 61, and is substantially parallel to the contact patch S. Thus, the intermediate surface 73 has an inclination angle of 0 degrees relative to the contact patch S. The intermediate surface 73 is formed so as to surround the open end of the first sipe 61 when viewed from the outside in the tire radial direction. Thus, the intermediate surface 73 includes a rectangular region 74 formed between one first inclined surface 71 and the open end of the first sipe 61, and a rectangular region 75 formed between the other first inclined surface 72 and the open end of the first sipe 61. A wall surface 76, rising in the tire radial direction toward the contact patch S, is connected to the distal edge of the intermediate surface 73, which is sandwiched between the distal edges of the two first inclined surfaces 71 and 72.

[0040] Thus, one end of the first groove 70 in the longitudinal direction is tapered when viewed from the contact surface S side. In addition, when viewing the first groove 70 from the contact surface S side, the width of each of the first inclined surfaces 71, 72 decreases toward one end of the first groove 70 in the longitudinal direction. In addition, when viewing the first groove 70 from the contact surface S side, the first sipe 61 is offset to one side in the width direction of the first groove 70 ( Figure 4 on the left side of the ).

[0041] The two first inclined surfaces 71 and 72 are formed on both sides of the first sipe 61 in the width direction, and the intermediate surface 73 is formed on both sides of the first groove 70 in the width direction relative to the first sipe 61. As described later, even when the mold forming the shape of the tire 1 is subjected to jet cleaning accompanied by a jet of high-pressure gas, the durability of the mold can be improved, and the drainage performance of the tire 1 can be enhanced.

[0042] In addition, the intermediate surface 7 is formed in the first groove 70 and on both sides of the first sipe pattern 61 in the width direction. However, the intermediate surface only needs to be formed on one side of the width direction to which the first sipe pattern 61 is biased in the first groove 70, and the intermediate surface on the other side in the width direction can be omitted.

[0043] Figure 5 The second groove 80 is viewed from the circumferential main groove side 21 end. Figure 2 An enlarged stereogram of the D portion. Figure 6 Yes Figure 5 Diagram of the E-E line section.

[0044] The second groove 80, which extends in a direction inclined relative to the tire width direction, includes the second sipe 62. The second groove 80 extends approximately parallel to the first groove 70. The opening end of the second groove 80, when viewed from the outside in the tire radial direction, is tapered and approximately triangular. The second groove 80 includes: the second sipe 62; a second inclined surface 81 formed on one side in the width direction of the second sipe 62; and an intermediate surface 82 formed between the second inclined surface 81 and the second sipe 62. As with the second sipe 62, the second groove 80 terminates at its inner end in the tire width direction, which is one end in the longitudinal direction, at a position in the central land portion 40 that does not reach the circumferential auxiliary groove.

[0045] like Figure 2 As shown, the second sipe 62 extends along a straight line inclined relative to the tire width direction. The second inclined surface 81 is a surface whose cross section is straight and continuous from the contact patch S between the open end on one side of the second sipe 62 in the width direction and the contact patch S. The second inclined surface 81 is a surface that is twisted so that its angle of inclination relative to the contact patch S gradually changes along the longitudinal direction of the second groove 80. Similar to the first inclined surfaces 71 and 72, the second inclined surface 81 can be formed with a structure consisting of multiple flat surfaces connected by ridgelines at multiple locations along the longitudinal direction of the second groove 80. Alternatively, the second inclined surface 81 can be formed with only a single flat surface.

[0046] The intermediate surface 82 is a flat surface formed between the second inclined surface 81 and the second sipe 62, with an inclination angle of 0 degrees relative to the contact patch S and generally parallel to the contact patch S. The intermediate surface 82 is a rectangular region connecting the open end of one width direction side of the second sipe 62 and the second inclined surface 81 when viewed from the tire radial outside. A wall surface 84, rising toward the contact patch S in the tire radial direction, is connected to the distal edge of the second sipe 62 via a planar region 83 generally parallel to the contact patch S.

[0047] As a result, one end of the second groove 80 in the longitudinal direction has a tapered shape when viewed from the contact patch S. Furthermore, when viewing the second groove 80 from the contact patch S, the width of the second inclined surface 81 decreases toward one end of the second groove 80 in the longitudinal direction. As with the first groove 70, this improves the durability of the mold and the drainage performance of the tire 1 even when the mold forming the shape of the tire 1 is subjected to jet cleaning with high-pressure gas.

[0048] The third groove 90 formed on one side of the middle land portion 41 in the tire width direction is Figure 5 、 Figure 6 The second groove 80 shown is the same and includes: a third sipe 63; an inclined surface formed only on one side in the width direction of the third sipe 63; and an intermediate surface between the third sipe 63 and the inclined surface.

[0049] The fifth groove 92 formed on one side of the tire width direction of the other middle land portion 42 is similar to the fifth groove 92 formed on the other side of the tire width direction of the middle land portion 42. Figure 3 、 Figure 4 The first groove 70 shown is the same and includes: a fifth sipe 65; two inclined surfaces formed on both sides of the fifth sipe 65 in the width direction; and an intermediate surface between the fifth sipe and each inclined surface.

[0050] The sixth groove 93 formed on the other side of the other middle land portion 42 in the tire width direction is similar to the sixth groove 93 formed on the other side of the middle land portion 42 in the tire width direction. Figure 5 、 Figure 6 The second groove 80 shown is the same and includes: a sixth sipe 66; an inclined surface formed only on one side in the width direction of the sixth sipe 66; and an intermediate surface between the sixth sipe 66 and the inclined surface.

[0051] Figure 7 yes Figure 1 An enlarged stereoscopic view of the F portion. A 4th groove 91 is formed on the other side of an intermediate land portion 41 in the tire width direction. Regarding the 4th groove 91, the opening end when viewed from the radially outer side of the tire is approximately V-shaped, and the front end is tapered. The 4th sipe 64 is formed along the long side direction of the 4th groove 91. Therefore, regarding the 4th sipe 64, the shape when viewed from the radially outer side of the tire is approximately V-shaped. In addition, the 4th groove 91 includes: the 4th sipe 64; two 4th inclined surfaces 91a, 91b, which are formed on both sides of the 4th sipe 64 in the width direction; and an intermediate surface 91c, which is formed between each 4th inclined surface 91a, 91b and the 4th sipe 64. The structure of the 4th groove 91 is similar to that of the 4th groove 91 simply by making the whole approximately V-shaped. Figure 3 、 Figure 4 The same applies to the first groove 70 shown.

[0052] The manufacturing method of the tire 1 including the tread portion 10 described above involves forming intermediate products of the tread portion 10, carcass portion, and bead portion from tire raw materials. These are then assembled to form an unvulcanized tire, or green tire. The green tire is then heated and pressurized in a tire vulcanization mold to vulcanize the tire 1 into a predetermined shape. At this point, protrusions corresponding to the shape of the grooves are pre-formed in the tire vulcanization mold, where the grooves having sipes are to be formed.

[0053] Figure 8 The tire vulcanization mold 100 for forming the tread portion 10 of the tire 1 is formed. Figure 3 A schematic cross-sectional view of the first groove 70 of the embodiment. Figure 3 As shown, when the first groove 70 having the intermediate surface 73 is formed on both sides of the width direction of the first sipe 61, the Figure 81 shows a portion of a tire vulcanization mold 100. In this mold 100, a plate portion 110 forming a protrusion 108 is embedded and fixed to the top of a mountain-shaped portion 102 formed on the main body 101 of the mold 100, and a protrusion 108 is embedded and fixed to the top of the mountain-shaped portion 102 and between the inclined surfaces 103 and 104 and the plate portion 110 and the intermediate surface 73 ( Figure 3 ) is provided with a top surface 105 that is substantially perpendicular to the side surface of the plate portion 110. For example, the plate portion 110 made of stainless steel alloy is partially embedded and fixed to the main body portion 101 of the aluminum alloy mold in a manner protruding from the inner surface of the main body portion 101.

[0054] In the tire vulcanization mold 100, a mountain-shaped portion and a plate portion including a top surface are also formed in the portion corresponding to the second to sixth grooves 80, 90, 91, 92, and 93. Figure 8 Regarding the tire vulcanization mold 100, the shapes corresponding to the second groove 80, the third groove 90 and the sixth groove 93 are the same as those shown. Figure 8 In the illustrated shape, one of the two inclined surfaces 103 and 104 of the mountain-shaped portion 102 is omitted, and the shape of the top surface between the one inclined surface and the plate portion 110 is the same.

[0055] The tire 1 is manufactured using such a tire vulcanizing mold 100 , and grooves corresponding to the plate portion 110 and the mountain-shaped portion 102 are formed in the tread portion 10 of the tire 1 , the grooves having intermediate surfaces between the sipes and the inclined surfaces.

[0056] According to the tire 1 described above, in the tire vulcanization mold 100 that forms the shape of the tire 1, when the protrusions 108 that form the sipes and the main body 101 that forms the portion including the inclined surface of the groove are formed by separate members, a top surface 105 that contacts the protrusions 108 at an angle approximately perpendicular to the protrusions 108 is provided on the main body 101, corresponding to the portion in contact with the protrusions 108 and the intermediate surface. Thus, when the tire vulcanization mold 100 is subjected to spray cleaning accompanied by the injection of high-pressure gas, even when the high-pressure air as the gas is injected toward the vicinity of the protrusions 108 of the main body 101, deformation of the main body 101 in such a manner as to flip up from the protrusions 108 can be suppressed.

[0057] For example, the tire vulcanization mold 100 is sometimes cleaned by dry ice blasting, which is a type of spray cleaning. In dry ice blasting, high-pressure air is used to spray relatively low-hardness dry ice particles onto the inner surface of the tire vulcanization mold 100 to clean the tire vulcanization mold 100. In this case, the high-pressure air and the dry ice particles are sprayed along the inner surface of the tire vulcanization mold 100. Figure 8The injection molding machine is ejected in the direction of arrow α between the main body 101 and the plate 110 of the mold 100. At this time, the top surface 105 of the mountain-shaped portion 102 contacts the side surface of the plate 110 forming the protrusion 108 at a smaller angle than when there is no top surface 105, for example, at a substantially right angle. As a result, the force is easily directed in the outward direction ( Figure 8 The lower side of the protrusion 108 acts on the top surface 105, and high-pressure air is less likely to enter the gap between the top surface 105 and the plate portion 110. This prevents the main body 101 from deforming so as to flip up from the protrusion 108. As a result, the durability of the tire vulcanization mold 100 can be improved. Furthermore, the formation of the intermediate surface increases the water storage area within the grooves of the tire 1, thereby improving drainage during tire use.

[0058] Figure 9 This is a schematic cross-sectional view of the portion forming the groove portion in the tire vulcanization mold 100a that forms the tread portion of the tire of the comparative example. In the tire of the comparative example, an intermediate surface between the opening end of the sipe pattern and the inclined surface continuous from the ground contact surface is not formed in the groove portion having the sipe pattern. Therefore, in the tire vulcanization mold 100a, a top surface that intersects approximately at right angles with the side surface of the plate portion 110 is not formed between the mountain-shaped portion 102 of the main body 101a and the plate portion 110 fixed to the top thereof. Therefore, the inclined surfaces 103 and 104 of the mountain-shaped portion 102 and the side surface of the protrusion 108 formed by the plate portion 110 are in contact at an angle much larger than 90 degrees on the internal space side of the mold 100a. As a result, along the Figure 9 When high-pressure air and dry ice particles are ejected in the direction of arrow β, the high-pressure air is likely to enter the gap between the inclined surfaces 103 and 104 of the peak-shaped portion 102 and the plate portion 110. Consequently, due to an increase in the number of cleanings of the mold 100a and the increase in the number of injections of high-pressure air, the main body 101a of the mold 100a may deform, flipping up from the protrusion 108. Consequently, the durability of the tire vulcanization mold 100a may be reduced. According to the embodiment, this disadvantage can be eliminated.

[0059] Furthermore, in the embodiment, for example, one longitudinal end of the first groove 70, including the first sipe 61, terminates within the corresponding land portion 40, and the longitudinal end of the first groove 70 is tapered when viewed from the contact patch S. Furthermore, when viewing the first groove 70 from the contact patch S, the widths of the inclined surfaces 71 and 72 decrease toward the longitudinal end of the first groove 70. In this configuration, in the mold forming the first groove 70, the angle of inclination of the inclined surfaces 103 and 104 of the mountain-shaped portion 102 relative to the tire radial direction decreases at the portion corresponding to the longitudinal end of the first groove 70. In this case, without an intermediate surface between the inclined surfaces 103 and 104 and the first sipe 61, the mountain-shaped portion 102 of the corresponding mold 100 is more likely to deform by rising from the protrusion 108. Consequently, in the embodiment, the formation of the intermediate surface 73 significantly enhances the durability of the mold 100.

[0060] In the embodiment, regarding the first groove 70, when viewed from the ground contact surface S side, the first sipe 61 is offset to one side in the width direction of the first groove 70 ( Figure 4 (left side), the intermediate surface 73 is formed on at least one side of the first groove 70 in the width direction relative to the first sipe 61. In this case, regarding the inclination angles θ1 and θ2 of the inclined surfaces 71 and 72 of the first groove 70 relative to the ground contact surface S, the angle θ1 of the inclined surface 71 on one side of the first groove 70 in the width direction is greater than the angle θ2 of the inclined surface 72 on the other side in the width direction. In this case, if there is no intermediate surface between the inclined surface 71 on one side of the first groove 70 in the width direction and the first sipe 61, the main body 101 of the corresponding mold 100 is easily deformed so as to flip up from the protrusion 108. Therefore, in this embodiment, the formation of the intermediate surface significantly improves the durability of the mold 100.

[0061] When the angle of the inclined surface of each groove 70, 80, 90, 91, 92, and 93 relative to the contact surface is less than 20 to 90 degrees, the main body of the mold is easily deformed by jet cleaning so that it flips up from the protrusion. Therefore, when the angle of the inclined surface relative to the contact surface is less than 20 to 90 degrees, the effect of forming an intermediate surface between the inclined surface and the sipe, which can further improve the durability of the mold, becomes more significant.

[0062] In the above embodiment, the intermediate surface of the groove is described as a surface provided between the groove's inclined surface and the sipe, and having an inclination angle of 0 degrees relative to the ground contact surface S. However, the intermediate surface is not limited to this, and may be a surface having an inclination angle relative to the ground contact surface S that is greater than 0 degrees and smaller than the inclination angle of the inclined surface relative to the ground contact surface.

[0063] Figure 10 Other examples of embodiments are shown. Figure 4 The corresponding figure. Figure 10 As shown, intermediate surfaces 73a, 73b are provided between the two first inclined surfaces 71, 72 of the first groove 70a and the first sipe 61. The inclination angles θ3, θ4 of the intermediate surfaces 73a, 73b relative to the ground contact surface S are greater than 0 degrees and smaller than the inclination angles θ1, θ2 of the first inclined surfaces 71, 72 connected to the intermediate surfaces 73a, 73b relative to the ground contact surface S (θ3 < θ1, θ4 < θ2).

[0064] In the above embodiment, the case where the intermediate surface is formed in the groove including the sipes formed in the center land portion 40 and the intermediate land portions 41 and 42 is described. However, the groove including the intermediate surface may be formed in only a portion of the plurality of land portions.

[0065] In the above embodiment, the multiple land portions are described as being rib-shaped and continuous throughout the entire circumference of the tire. Alternatively, each land portion may be configured as a plurality of blocks divided in the tire circumferential direction by a plurality of lug grooves extending from a first side to a second side in the tire width direction.

Claims

1. A pneumatic tire, characterized in that: The pneumatic tire includes a tread portion including: a plurality of land portions; and sipes formed in at least a portion of the land portions. An inclined surface having a linear cross-section continuous from the ground contact surface is formed between at least one open end of the sipe in the width direction and the ground contact surface, the cross-section being a cross-section on a plane perpendicular to the longitudinal direction of the sipe. An intermediate surface is formed between the inclined surface and the sipe, wherein the intermediate surface has an inclination angle of 0 degrees relative to the ground contact surface or an inclination angle smaller than the inclination angle of the inclined surface relative to the ground contact surface. One end of the groove in the longitudinal direction including the sipe, the inclined surface and the intermediate surface terminates in the land portion. One end of the groove in the longitudinal direction is tapered when viewed from the ground contact surface. When the groove is viewed from the ground contact surface side, the width of the inclined surface decreases toward one end in the longitudinal direction of the groove.

2. The pneumatic tire according to claim 1, wherein: When the groove including the sipe, the inclined surface, and the intermediate surface is viewed from the ground contact surface side, the sipe is biased toward one side in the width direction of the groove. The inclined surfaces are two inclined surfaces formed on both sides of the sipe in the width direction. The intermediate surface is formed at least on one side in the width direction of the groove relative to the sipe.

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