TIRE MOLDING ELEMENT, TIRE VULCANIZATION MOLD, AND TIRE

Abstract

Disclosed herein is a tire molding element. The tire molding element includes at least a molding surface for molding a plurality of ground contact elements of the tire tread, comprising: a ground contact surface which contacts a road surface, and a transverse side surface and a circumferential side surface connected to said ground contact surface; and a plurality of thin plates, comprising: a main body, provided in such a way as to cut a covering layer arranged in advance on an unvulcanized green tire.

Claims

1. A tire molding element for vulcanization molding a tire tread comprising: a molding surface for molding a plurality of ground contact elements of the tire tread, comprising: a ground contact surface which contacts a road surface, and a transverse side surface and a circumferential side surface connected to said ground contact surface; and a plurality of thin plates, comprising: a main body, provided in such a way as to cut a covering layer arranged in advance on an unvulcanized green tire, at least one thin plate comprises a protrusion which protrudes from the main body in the thickness direction of the thin plate and guides the cut covering layer in the depth direction of the green tire in such a way as to cover at least a portion of the transverse side surface of the ground contact element, and at least two adjacent thin plates comprise an enlarged-width portion provided at an end portion on the opposite side to the molding surface, and a cutting means protruding from the enlarged-width portion toward the opposite side to the molding surface.

2. The tire molding element according to claim 1, wherein a thickness-direction distance H between enlarged-width portions of adjacent thin plates is between 40% and 90% of a distance L between main body center lines of adjacent thin plates.

3. The tire molding element according to claim 1, wherein an angle A between an imaginary line parallel to the molding surface passing through an end portion on the cutting means side of the enlarged-width portion of the thin plate, and an imaginary line joining the maximum width portion of the enlarged-width portion and the end portion on the cutting means side, is between 10and 80.

4. The tire molding element according to 3, wherein the cross-sectional shape from the end portion on the cutting means side of the enlarged-width portion of the thin plate to the maximum width portion is arcuate.

5. The tire molding element according to claim 3, wherein the cross-sectional shape from the end portion on the cutting means side of the enlarged-width portion of the thin plate to the maximum width portion is linear.

6. The tire molding element according to claim 1, wherein the cross-sectional shape of the enlarged-width portion of the thin plate has line symmetry, taking the main body center line as a reference.

7. The tire molding element according to claim 1, wherein the cross-sectional shape of the protrusion of the thin plate is triangular.

8. A tire vulcanization mold comprising the tire molding element according to claim 1.

9. A method for manufacturing a tire, comprising vulcanizing the tire via the tire vulcanization mold according to claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 schematically illustrates a portion of the surface of a tire tread molded by means of a molding element according to a first mode of embodiment of the present disclosure.

[0032] FIG. 2 is an oblique view schematically illustrating a portion of a ground contact element of the tire tread in FIG. 1.

[0033] FIG. 3 is a view in cross section schematically illustrating a green tire on which a covering layer is arranged, and a tire molding element according to a first mode of embodiment of the present disclosure, corresponding to a portion along the line III-III in FIG. 2 and provided in such a way as to mold the tire tread in FIG. 2.

[0034] FIG. 4 is an oblique view schematically illustrating a thin plate of the tire molding element in FIG. 3.

[0035] FIG. 5 is a view in cross section schematically illustrating a step of the molding employing the tire molding element in FIG. 3.

[0036] FIG. 6 is a view in cross section schematically illustrating a step of the molding employing the tire molding clement in FIG. 3.

[0037] FIG. 7 is a view in cross section schematically illustrating a step of the molding employing the tire molding element in FIG. 3.

[0038] FIG. 8 is a view in cross section schematically illustrating a step of the molding employing the tire molding element in FIG. 3.

[0039] FIG. 9 is a view in cross section schematically illustrating a molding element according to a second mode of embodiment of the present disclosure.

DETAILED DESCRIPTION

[0040] A tire molding element, a tire vulcanization mold comprising said molding element, and a tire vulcanization molded by means of said mold in accordance with a preferred mode of embodiment of the present disclosure will be described below with reference to the appended drawings.

[0041] A tire molding element, a tire vulcanization mold comprising said molding element, and a tire vulcanization molded by means of said mold according to a first mode of embodiment of the present disclosure will be described first of all with the aid of FIG. 1 to FIG. 8.

[0042] FIG. 1 schematically illustrates a portion of the surface of a tire tread molded by means of the molding element according to a first mode of embodiment of the present disclosure; FIG. 2 is an oblique view schematically illustrating a portion of a ground contact element of the tire tread in FIG. 1; FIG. 3 is a view in cross section schematically illustrating a green tire on which a covering layer is arranged, and a tire molding element according to a first mode of embodiment of the present disclosure, corresponding to a portion along the line III-III in FIG. 2 and provided in such a way as to mold the tire tread in FIG. 2; FIG. 4 is an oblique view schematically illustrating a thin plate of the tire molding element in FIG. 3; and FIG. 5 to FIG. 8 are views in cross section schematically illustrating a step of the molding employing the tire molding element. Here, in FIG. 1 to FIG. 8, the direction of the arrows indicated by Circumferential Orientation denotes the tire circumferential direction (direction of rotation), the direction of the arrows indicated by Axial Orientation denotes the tire axial direction, and the direction of the arrows indicated by Radial Orientation denotes the tire radial direction.

[0043] As illustrated in FIGS. 1 and 2, a plurality of ground contact elements 4 are formed on a tire tread 2, said plurality of ground contact elements 4 being defined by a plurality of circumferential grooves 41 extending in the tire circumferential direction and a plurality of transverse grooves 42 extending in the tire axial direction (tire transverse direction).

[0044] The ground contact elements 4 comprise: a ground contact surface 43 which contacts a road surface when the tire is rolling, and a plurality of transverse side surfaces 44 extending in a transverse direction and a plurality of circumferential grooves 45 extending in a circumferential direction, connected to the ground contact surface 43, further comprises two incisions 46 opening in the ground contact surface 43 and the circumferential grooves 41 and extending inwardly in the tire radial direction and in the tire axial direction (tire transverse direction). Here, side surfaces of the incisions 46 extending in the tire radial direction also constitute the transverse side surfaces 44 of the ground contact element 4. Enlarged-width portions 47 of the ground contact element 4 are provided on the inside in the radial direction of the transverse side surface 44 of the incisions 46. A notch 48 is provided in the region of an intermediate portion in the radial direction of one transverse side surface 44 of the incisions 46, and one transverse side surface 44 of the incisions 46 in a range from the notch 48 to the ground contact surface 43, also including a portion of the ground contact surface 44, is covered by a covering layer 10 comprising a different material than that of the ground contact element 4, intended to improve specific tire performance. Moreover, as illustrated in FIG. 2, the covering layer 10 is provided only on the transverse side surface 44 in a single direction (specifically the front side) with respect to the tire rotation direction.

[0045] The tire molding element for molding the tread 2 will be described next with the aid of FIG. 3 and FIG. 4.

[0046] As illustrated in FIG. 3, a molding surface 3 intended for molding the tread 2 is provided on a surface of the tire molding element 1 opposite a green tire 9 vulcanization molded as a tire by means of the molding element 1. Thin plates 5 extending in the radial direction toward the green tire 9 for forming the incisions 46 in the ground contact elements 4 are provided on the molding surface 3. The thin plates 5 comprise a main body 51 and a protrusion 6 having a substantially triangular cross section is provided in the region of an intermediate portion in the radial direction of the thin plates 5, said protrusion 6 forming the notch 48 in the ground contact element 4, protruding in the thickness direction (tire circumferential direction) of the thin plates 5, and being intended to guide a cut covering layer 10 in the depth direction of the green tire 9 so that the covering layer 10 covers a part or all of the transverse side surface 44 of the ground contact element 4; an enlarged-width portion 8 having a circular cross section and forming an enlarged-width portion 47 of the ground contact element 4 is further provided at an end portion of the thin plates 5 on the opposite side to the molding surface 3, and a cutting means 7 protruding from the enlarged-width portion 8 toward the opposite side to the molding surface 3 and provided in such a way as to cut the covering layer 10 arranged in advance on the unvulcanized green tire 9 is further provided. The thin plates 5 and the main body 51 thereof have a flat plate shape extending linearly in the width direction (tire axial direction) of the thin plates 5, as illustrated in FIG. 4.

[0047] The enlarged-width portion 8 of the thin plate 5 has a cross-sectional shape with line symmetry, taking a center line 52 of the main body 51 as a reference, and the cross-sectional shape from an end portion 81 on the cutting means 7 side of the enlarged-with portion 8 to a maximum width portion is arcuate. Furthermore, an angle A between an imaginary line parallel to the molding surface 3 passing through an end portion 81 on the cutting means 7 side of the enlarged-width portion 8 of the thin plates 5, and an imaginary line joining the maximum width portion of the enlarged-width portion 8 and the end portion 81 on the cutting means 7 side, is set at between 10 and 80. In addition, a thickness-direction distance H between enlarged-width portions 8 of adjacent thin plates 5 is set at between 40% and 90% of a distance L between center lines 52 of the main bodies 51 of adjacent thin plates 5. Here, the abovementioned angle A is preferably between 30 and 70, more preferably between 45 and 60, and the thickness-direction distance H between enlarged-width portions 8 of adjacent thin plates 5 is preferably between 50% and 90% of the distance L between the center lines 52 of the main bodies 51 of adjacent thin plates 5. The absolute value of the angle A is more preferably equal between enlarged-width portions 8 of two adjacent thin plates 5, or the difference between angles is no greater than 10. According to this mode of embodiment, the angle A is 45, and the thickness-direction distance H between enlarged-width portions 8 of adjacent thin plates 5 is 66% of the distance L between the center lines 52 of the main bodies 51 of adjacent thin plates 5,

[0048] Examples of materials which may be used as the covering layer 10 include a composition (including a rubber composition) based on a natural resin having a higher elastic modulus than the elastic modulus of the rubber composition which is the constituent material of the ground contact element 4, a material in which fibers are mixed or impregnated with a composition based on a natural resin, a thermoplastic resin, and a laminate or mixture thereof; it is also possible to use a combination of a nonwoven fabric or woven fabric etc. impregnated with a composition based on a natural resin, with the aim of providing further reinforcement or improving adhesion with the ground contact element 4. A fibrous material such as a nonwoven fabric or woven fabric impregnated with a composition based on a natural resin may be used alone as the covering layer 10. According to this mode of embodiment, the rubber composition has a dynamic shear complex modulus (dynamic shear modulus: G*) when subjected to a maximum shear stress of 0.7 MPa at a frequency of 10 Hz and a temperature of 10 C. in excess of 200 MPa, and preferably in excess of 200 MPa, with the aim of improving the performance on snow. The storage elastic modulus represented by G and the loss elastic modulus represented by G, which are dynamic properties known to a person skilled in the art, are measured by means of a viscosity analyzer (viscoanalyzer: Metravib VB4000) using a test piece molded from the raw composition or a test piece which is combined with the composition after vulcanization. The test piece which is used is described in Figure X2.1 (a circular method) of the standard ASTM D 5992-96 (version published September 2006, initially approved in 1996. The diameter d of the test piece is 10 mm (consequently the test piece has a circular cross section of 78.5 mm.sup.2), the thickness L of each part of the rubber compound is 2 mm, and the ratio d/L, is 5 (described in paragraph X2.4 of the ASTM standard, unlike the ratio d/L, of 2 recommended in the standard ISO 2856). The test involves recording the response of a test piece comprising a vulcanized rubber composition subjected to a simple alternating sinusoidal shear load at a frequency of 10 Hz. The maximum shear stress reached during the test is 0.7 MPa, The measurement is taken by varying the temperature from Train, which is a temperature lower than the glass transition temperature (Tg) of the rubber material, to a maximum temperature Tmax in the vicinity of 100 C., at a rate of 1.5 C. per minute, The test piece is stabilized for approximately 20 minutes at Train prior to the start of the test in order to obtain a satisfactory uniformity of temperature within the test piece. The results obtained are the storage elastic modulus (G) and the loss elastic modulus (G) at the prescribed temperature. The complex elastic modulus G* is defined in terms of the absolute values of the storage elastic modulus and the loss elastic modulus using the following formula:

G*={square root over (G.sup.2+G.sup.2)}[Numerical Formula 1]

[0049] Molding of the tire tread using the tire molding element according to this mode of embodiment will be described next with the aid of FIG. 5 to FIG. 8.

[0050] As a first step illustrated in FIG. 5, the cutting means 7 of the thin plates 5 provided on the tire molding element 1 according to this mode of embodiment, which protrudes from the enlarged-width portion 8 provided at the end portion on the opposite side to the molding surface 3 toward the opposite side to the molding surface 3 and is provided in such a way as to cut the covering layer 10 arranged in advance on the unvulcanized green tire 9, is placed in contact with the covering layer 10, and the covering layer 10 is cut to a predetermined length by the cutting means 7 of two adjacent thin plates 5.

[0051] Next, as a second step illustrated in FIG. 5, the molding element 1 is pushed forward and inwardly in the radial direction toward the green tire 9, and the covering layer 10 cut to a predetermined length in the first step remains together with a portion of the green tire 9 in a space between the enlarged-width portions 8 of two thin plates 5 on the opposite side to the molding surface 3 in the region of maximum width of the enlarged-width portions 8.

[0052] Next, as a third step illustrated in FIG. 6, the molding element 1 is pushed further forward and inwardly in the radial direction toward the green tire 9, and the covering layer 10 cut to a predetermined length in the first step and remaining together with a portion of the green tire 9 in the space between the enlarged-width portions 8 of two depressed plates 5 on the opposite side to the molding surface 3 in the region of maximum width of the enlarged-width portions 8, is pushed forward as far as the protrusion 6 protruding in the thickness direction of the thin plates 5.

[0053] In addition, as a fourth step illustrated in FIG. 7, the tire molding element 1 is pushed further forward inwardly in the radial direction toward the green tire 9, and the covering layer 10 cut to a predetermined length in the first step, remaining together with a portion of the green tire 9 in the space between the enlarged width portions 8 of two thin plates 5 on the opposite side to the molding surface 3 in the region of maximum width of the enlarged-width portions 8, and then pushed forward as far as the protrusion 6 protruding in the thickness direction of the thin plates 5, is guided in the depth direction of the green tire 9 by means of the protrusion 6 while sliding on the surface of the green tire 9 in such a way as to cover a part or all of the transverse side surface 44 of the ground contact element 4, and vulcanization molding is performed in this state.

[0054] The effect of the tire molding element according to this mode of embodiment will be described next.

[0055] With the tire molding element 1 according to this mode of embodiment, the thin plates 5 comprising the main body 51 are provided with the protrusion 6 that protrudes from the main body 51 of said thin plates 5 in the thickness direction of the thin plates 5, said thin plates 5 being provided in such a way as to cut the covering layer 10 without the use of the blade described in abovementioned Patent Documents 1 and 2, so the cut covering layer 10 arranged in advance on the unvulcanized green tire 9 is guided in the green tire 9 depth direction by means of the protrusion 6 on the thin plates 5, and therefore it is possible to increase the degree of freedom in the arrangement of the covering layer 10 that covers the ground contact element 4 on the tire,

[0056] In addition, at least two adjacent thin plates 5 comprise the enlarged-width portion 8 provided at the end portion on the opposite side to the molding surface 3, and the cutting means 7 protruding from the enlarged-width portion 8 toward the opposite side to the molding surface 3, and therefore the covering layer 10 which has been cut by the cutting means 7 remains in the space on the opposite side to the molding surface 3 in the region of maximum width of the enlarged-width portion 8 between two enlarged-width portions 8, after which the covering layer 10 is pushed out in the direction of the molding surface 3 by means of the green tire 9, then caught by means of the protrusion 6 protruding in the thickness direction of the thin plates 5, and guided in the depth direction of the green tire in such a way as to cover a part or all of the transverse side surface 44 of the ground contact element 4, and therefore even if the covering layer 10 has not been simultaneously cut by the cutting means 7, it is still possible to reduce the risk of the covering layer 10 being dragged by the thin plate 5 on the wrong side, and the covering layer 10 can be stably arranged at a predetermined position with greater reliability.

[0057] Furthermore, the cross-sectional shape of the protrusion 6 of the thin plates 5 is substantially triangular, so the thin plates 5 provided with the protrusion 6 are easily separated from the tire after vulcanization molding, and as a result it is possible to mold a tire in which a part or all of the transverse side surface 44 of the ground contact element 4 is covered by the covering layer 10, with greater stability.

[0058] In addition, the cross-sectional shape of the enlarged-width portions 8 of adjacent thin plates 5 has line symmetry, taking the center line of the main body 51 of the thin plates 5 as a reference, so the enlarged-width portion 8 of the thin plates 5 which is exposed to the greatest amount of stress during vulcanization molding and which is in contact with the green tire 9 for the longest time has a stable shape in relation to the thin plate 5, and therefore it is possible to mold a tire in which a part or all of the transverse side surface 44 of the ground contact element 4 is covered by the covering layer 10, with greater stability.

[0059] The thickness-direction distance H between enlarged-width portions 8 of adjacent thin plates 5 is set at no less than 40% of the distance L between the center lines 52 of the main bodies 51 of adjacent thin plates, and therefore it is possible to prevent the covering layer 10 cut to a predetermined length by the cutting means 7 from deforming under excessive stress while it remains in the space between two enlarged-width portions on the opposite side to the molding surface 3 in the region of maximum width of the enlarged-width portions 8, and the covering layer 10 can be stably arranged at a predetermined position with greater reliability, Furthermore, the distance H is set at no greater than 90% of the distance L, and therefore it is possible to reduce the risk of the covering layer 10 being dragged by the thin plate 5 on the wrong side.

[0060] In addition, the angle A between an imaginary line parallel to the molding surface 3 passing through an end portion 81 on the cutting means 7 side of the enlarged-width portion 8 of the thin plates 5, and an imaginary line joining the maximum width portion of the enlarged-width portion 8 and the end portion 81 on the cutting means 7 side, is set at between 10 and 80, and therefore it is possible to stably arrange the covering layer 10 at a predetermined position with greater reliability. That is to say, if the angle A is smaller than 10, the cut covering layer 10 remaining in the space on the opposite side to the molding surface 3 in the region of maximum width between enlarged-width portions 8 of two thin plates 5 is not readily pushed out in the molding surface 3 direction, the cut covering layer 10 deforms as a result of a large amount of stress being applied thereto, and there is a risk of it not being possible to stably arrange the covering layer 10 at a predetermined position; on the other hand, if this angle A is greater than 80, the cut covering layer 10 does not readily remain in the space on the opposite side to the molding surface 3 in the region of maximum width between enlarged-width portions of two plates 5, and there is a risk of it not being possible to stably arrange the covering layer 10 at a predetermined position, so the abovementioned range is preferred.

[0061] A variant example of this mode of embodiment will be described next.

[0062] The cutting means 7 provided on the enlarged-width portions 8 may have a saw blade shape in the width direction (=tire axial direction) of the thin plates 5.

[0063] Furthermore, the shape of the thin plates 5 may be modified in such a way that the incision 44 from when said incision 44 is formed by the thin plates 5 in the ground contact surface 41 of the ground contact element 4 has an arcuate shape, a serrated shape, or a combination of a serrated shape and straight lines, when seen in a plan view of the ground contact surface of the ground surface element 4.

[0064] Furthermore, the protrusion 6 that protrudes in the thickness direction of the thin plates 5 may be formed in such a way as to be discontinuous from the main body 51 of the thin plates 5 in the width direction ( tire axial direction) of the thin. plates 5.

[0065] A tire molding element according to a second mode of embodiment of the present disclosure will be described next with the aid of FIG. 9. FIG. 9 is a view in cross section schematically illustrating a tire molding element according to a second mode of embodiment of the present disclosure. In the same way as in FIG. 3, the direction of the arrows indicated by Circumferential Orientation in FIG. 9 denotes the tire circumferential direction (direction of rotation), and the direction of the arrow indicated by Radial Orientation denotes the tire radial direction. It should be noted that the description of the second mode of embodiment relates to structural elements which are different than those of the abovementioned first mode of embodiment, and structural elements which are the same will not be described again.

[0066] As illustrated in fig, 9, the tire molding element 1 according to the second mode of embodiment is provided with the molding surface 3 intended for molding the tread 2, on the surface of the tire molding element 1 opposite the green tire 9 (not depicted) which is vulcanization molded as a tire, in the same way as the molding element 1 according to the abovementioned first mode of embodiment. The thin plates 5 which extend in the radial direction toward the green tire 9, form the incisions 46 in the ground contact element 4 and comprise the main body 51 are provided on the molding surface 3, and the protrusion 6 having a substantially square cross section is provided in the region of an intermediate portion in the radial direction of the main body 51, said protrusion 6 forming the notch 48 in the ground contact element 4, protruding in the thickness direction (tire circumferential direction) of the thin plates 5, and being intended to guide the cut covering layer 10 in the depth direction of the green tire 9 so that the covering layer 10 covers a part or all of the transverse side surface 44 of the ground contact element 4; the enlarged-width portion 8 having a substantially diamond-shaped cross section and forming the enlarged-width portion 47 of the ground contact element 4 is further provided at an end portion of the thin plates 5 on the opposite side to the molding surface 3, and the cutting means 7 protruding from the enlarged-width portion 8 toward the opposite side to the molding surface 3 and for cutting the covering layer 10 arranged on the unvulcanized green tire 9 is further provided.

[0067] The cross-sectional shape of the enlarged-width portion 8 of the thin plates 5 has line symmetry, taking the center line 52 of the main body 51 of the thin plates 5 as a reference, the cross-sectional shape from the end portion 81 on the cutting means 7 side of the enlarged-width portion 8 to the maximum width portion of the enlarged-width portion 8 is linear, and the angle A between an imaginary line parallel to the molding surface 3 passing through the end portion 81 on the cutting means 7 side, and an imaginary line joining the maximum width portion of the enlarged-width portion 8 and the end portion 81 of the cutting means 7 is set in such a way as to be between 10 and 80, while the thickness-direction H between enlarged-width portions 8 of adjacent thin plates 5 is set in such a way as to be between 40% and 90% of the distance L between the center lines 52 of the main bodies 51 of adjacent thin plates 5. The angle A is preferably between 30 and 60, and the thickness-direction distance H between enlarged-width portions 8 of adjacent thin plates 5 is preferably between 50% and 90% of the distance L between the center lines 52 of the main bodies 51 of adjacent thin plates 5. According to this mode of embodiment, the angle A is 35, and the thickness-direction distance H between enlarged-width portions 8 of adjacent thin plates 5 is 58% of the distance L between the center lines 52 of the main bodies 51 of adjacent thin plates 5.

[0068] The effect of the tire molding element according to the abovementioned second mode of embodiment will be described next.

[0069] In the tire molding element 1 according to the second mode of embodiment, the cross-sectional shape from the end portion 81 on the cutting means 7 side of the enlarged-width portion 8 of the thin plates 5 is linear, and as a result the space on the opposite side to the molding surface 3 in the region of maximum width of the enlarged-width portions 8 between the enlarged-width portions 8 of two thin plates 5 decreases linearly toward the molding surface 3, and therefore it is possible to stably arrange the covering layer 10 at a predetermined position with greater reliability.

[0070] Particularly preferred modes of embodiment of the present disclosure were described above, but the present disclosure is not limited to the modes of embodiment illustrated and a number of modifications and variations are possible within the scope of the patent claims.