Tire molding element, tire vulcanization mold, and tire

Abstract

A tire molding element for vulcanization molding a tire tread is disclosed herein. The tire includes at least one thin plate including 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 the at least one thin plate comprises at least two cutting means separated in the thickness direction of the at least one thin plate, at an end portion on the opposite side to the molding surface.

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 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 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 at least one 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, the at least one thin plate comprises at least two cutting means separated in the thickness direction of the at least one thin plate, at an end portion on the opposite side to the molding surface; the at least one thin plate comprising an enlarged-width portion at the end portion on the opposite side of the molding surface, and the cutting means protruding from the enlarged-width portion; and the enlarged-width portion of the at least one thin plate protrudes in the opposite direction to the direction of protrusion of the protrusion from the main body of the at least one thin plate.

2. The tire molding element according to claim 1, wherein the cross-sectional shape of the protrusion of the at least one thin plate is substantially triangular.

3. A tire vulcanization mold, comprising at least one tire molding element according to claim 1.

4. A method for manufacturing a tire, comprising vulcanizing said tire via the tire vulcanization mold according to claim 3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

(3) 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.

(4) FIG. 4 is an oblique view schematically illustrating a thin plate of the tire molding element in FIG. 3.

(5) FIG. 5 is a view in cross section of a tire molding element and a green tire, schematically illustrating a step of the molding employing the tire molding element in FIG. 3.

(6) FIG. 6 is a view in cross section of a tire molding element and a green tire, schematically illustrating a step of the molding employing the tire molding element in FIG. 3.

(7) FIG. 7 is a view in cross section of a tire molding element and a green tire, schematically illustrating a step of the molding employing the tire molding element in FIG. 3.

(8) FIG. 8 is a view in cross section of a tire molding element and a green tire, schematically illustrating a step of the molding employing the tire molding element in FIG. 3.

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

(10) FIG. 10 is a view in cross section schematically illustrating a molding element according to a third mode of embodiment of the present disclosure.

DETAILED DESCRIPTION

(11) 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.

(12) 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.

(13) FIG. 1 schematically illustrates a portion of the surface of a tire tread molded by means of the tire 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 of a tire molding element and a green tire, schematically illustrating a step of the molding employing the tire molding element in FIG. 3. 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 (tire transverse direction), and the direction of the arrows indicated by Radial Orientation denotes the tire radial direction.

(14) 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).

(15) 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 side surfaces 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. A notch 47 is provided in the region of an intermediate portion in the radial direction of one transverse side surface of the incisions 46, and one transverse side surface of the incisions 46 in a range from the notch 47 to the ground contact surface 43, also including a portion of the ground contact surface 43, 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.

(16) The molding element for molding the tread 2 in FIG. 2 will be described next with the aid of FIG. 3 and FIG. 4.

(17) As illustrated in FIG. 3, a molding surface 3 intended for molding the tread 2 is provided on a surface of the 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 main body 51 of the thin plates 5, said protrusion 6 forming the notch 47 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; two cutting means 7 separated in the thickness direction of the thin plates 5 and provided in such a way as to cut the covering layer 10 arranged in advance on the unvulcanized green tire 9 are further provided at an end portion of the thin plates 5 on the opposite side to the molding surface 3. 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. It should be noted that the cutting means 7 are not limited to two cutting means, and three or more may be provided.

(18) 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 300 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 Tmin, 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 Tmin 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]

(19) 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. As a first step illustrated in FIG. 5, the two cutting means 7 of the thin plates 5 provided on the molding element 1 according to this mode of embodiment, which are provided in such a way as to protrude in the radial direction from the end portion on the opposite side to the molding surface 3 toward the green tire 9 and in such a way as to cut the covering layer 10 arranged in advance on the unvulcanized green tire 9, are placed in contact with the covering layer 10, and the covering layer 10 is cut to a predetermined length by the two adjacent cutting means 7 of the thin plates 5.

(20) Next, as a second step illustrated in FIG. 6, 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 is pushed forward together with the green tire 9 to the protrusion 6 protruding in the thickness direction of the thin plates 5 from the main body 51 of the thin plates 5. The covering layer 10 in the portion not pushed forward to the protrusion 6 remains between the two cutting means 7 provided on the thin plates 5.

(21) Next, as a third step illustrated in FIG. 7, 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 is pushed forward as far as the protrusion 6 protruding in the thickness direction of the thin plates 5.

(22) In addition, as a fourth step illustrated in FIG. 8, the 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 and 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.

(23) The effect of the tire molding element according to the abovementioned first mode of embodiment will be described next.

(24) 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 etc., 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.

(25) In addition, when the covering layer 10 arranged on the green tire 9 is cut by the at least two cutting means 7 separated in the thickness direction of the thin plates 5 and provided at an end portion of the thin plates 5 on the opposite side to the molding surface 3, it is possible to make slipping unlikely to occur between the covering layer 10 and the cutting means 7, so it is possible to cut the covering layer 10 more reliably to a predetermined length, and it is furthermore possible to reduce the risk of the covering layer 10 being dragged by the thin plate 5 on the wrong side, and therefore the covering layer 10 can be stably arranged at a predetermined position with greater reliability.

(26) Furthermore, the cross-sectional shape of the protrusion 6 is substantially triangular, so the thin plates 5 provided with the protrusion 6 are easily detached 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 ground contact element 4 is covered by the covering layer 10, with greater stability.

(27) It should be noted that Patent Document 3 describes the series of processes up to molding in such a way that the cut covering layer 10 is guided in the thickness direction of the green tire 9 and covers a part or all of the side surface 42 of the ground contact element 4 by virtue of the protrusion 6 protruding in the thickness direction of the thin plates 5 from the main body 51 of the thin plates 5.

(28) A variant example of a mode of embodiment of the present disclosure will be described next.

(29) The cutting means 7 provided on the thin plates 5 of the tire molding element 1 may have a saw blade shape in the width direction (=tire axial direction) of the thin plates 5, in which case the gap between the saw blades is preferably equal between the at least two cutting means 7 separated in the thickness direction of the thin plates 5, but said gap may equally be different.

(30) Furthermore, the shape of the thin plates 5 may be modified in such a way that the incision 46 formed by the thin plates 5 in 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 43 of the ground contact element 4.

(31) 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.

(32) 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 FIG. 9, in the same way as in FIG. 3, the direction of the arrows indicated by Circumferential Orientation denotes the tire circumferential direction (direction of rotation), and the direction of the arrows 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.

(33) 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 a surface of the molding element 1 opposite the green tire 9 (see 3) vulcanization molded as a tire, in the same way as the tire 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 (see FIG. 2) in the ground contact element 4 (see FIG. 2) 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 of the thin plates 5, said protrusion 6 forming the notch 47 (see FIG. 2) 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 (see FIG. 3) 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 42 of the ground contact element 4; the enlarged-width portion 8 having a substantially flask-shaped cross section is provided at an end portion of the thin plates 5 on the opposite side to the molding surface 3, and the two cutting means 7 separated in the thickness direction of the thin plates 5 and provided in such a way as to cut the covering layer 10 arranged in advance on the unvulcanized green tire 9 are further provided in such a way as to protrude from the enlarged-width portion. Moreover, in the second mode of embodiment also, the cutting means 7 are not limited to two cutting means, and three or more may be provided.

(34) The two cutting means 7 separated in the thickness direction of the thin plates 5 and provided in such a way as to protrude from the enlarged-width portion 8 of the thin plates 5 are arranged in such a way that the maximum separation distance on each thin plate 5 of the two cutting means 7 in the thickness direction of the thin plates 5 is equal to or less than the width of the enlarged-width portion 8, and the maximum width of the enlarged-width portion 8 measured in the thickness directions of the thin plates 5 is provided in such a way as to be between 1.5 and 5 times the thickness of the thin plates 5.

(35) The effect of the tire molding element according to the abovementioned second mode of embodiment will be described next.

(36) In the tire molding element 1 according to the second mode of embodiment, the enlarged-width portion 8 is provided on the end portion of the thin plates 5 on the opposite side to the molding surface 3 and the two cutting means 7 protrude from the enlarged-width portion 8, so it is possible to maintain a distance between the at least two cutting means 7 separated in the thickness direction of the thin plates 5, and it is possible to make slipping less likely to occur between the covering layer 10 and the cutting means 7; as a result, it is possible to stably arrange the covering layer 10 at a predetermined position on the ground contact element 4 of the tire, with greater reliability. Furthermore, it is a simple matter to make a large number of cutting means 7 protrude, namely three or more cutting means.

(37) The maximum separation distance on each tin plate 5 of the two cutting means 7 in the thickness direction of the thin plates 5 is equal to or less than the width of the enlarged-width portion 8, so it is possible to further reduce the risk of slipping being produced with the covering layer 10 by the cutting means 7, and it is possible to more reliably cut the covering layer 10 to a predetermined length so the covering layer 10 can be stably arranged at a predetermined position with greater reliability.

(38) In addition, the maximum width of the enlarged-width portion 8 measured in the thickness direction of the thin plates 5 is set at between 1.5 and 5 times the thickness of the thin plates 5, and therefore a tire in which a part or all of the ground contact element 4 is covered by the covering layer 10 can be molded more stably. That is to say, if the maximum width of the enlarged-width portion 8 is more than five times the thickness of the thin plates 5, then it becomes difficult to separate the thin plates 5 provided with the enlarged-width portion 8 from the tire after vulcanization molding, and there is a risk of damaging the molding element 1; furthermore, if the maximum width of the enlarged-width portion 8 is less than 1.5 times the thickness of the thin plates 5, then the advantage of providing the enlarged-width portion 8 in the incision 44 when the tire is molded is reduced, and there is a risk of it not being possible to adequately demonstrate tire performance, so the maximum width of the enlarged-width portion of the thin plates is preferably in the abovementioned range.

(39) In the ground contact element 4 of the tread 2 vulcanization molded using the tire molding element 1 according to the second mode of embodiment, a portion corresponding to a portion of the enlarged-width portion 8 interposed between the two cutting elements 7 provided in such a way as to protrude from the enlarged-width portion 8 provided at the end portion of the thin plates 5 on the opposite side to the molding surface 3, i.e. a radially inside portion of the incision 44 provided on the ground contact element 4 is also covered by the covering layer 10, and the covering layer 10 in this portion also serves as a layer for protecting a portion of the incision 44 on the inside in the tire radial direction.

(40) A tire molding element according to a third mode of embodiment of the present disclosure will be described next with the aid of FIG. 10. FIG. 10 is a view in cross section schematically illustrating a tire molding element according to a third mode of embodiment of the present disclosure. In FIG. 10, in the same way as in FIG. 3, the direction of the arrows indicated by Circumferential Orientation denotes the tire circumferential direction (direction of rotation), and the direction of the arrows indicated by Radial Orientation denotes the tire radial direction. It should be noted that the description of the third mode of embodiment also relates to structural elements which are different than those of the abovementioned first and second modes of embodiment, and structural elements which are the same will not be described again.

(41) As illustrated in FIG. 10, the tire molding element 1 according to the third mode of embodiment is provided with the molding surface 3 intended for molding the tread 2, on a surface of the molding element 1 opposite the green tire 9 vulcanization molded as a tire by means of the molding element 1, in the same way as the tire molding element 1 according to the abovementioned first and second modes of embodiment. The thin plates 5 which extend in the radial direction toward the green tire 9, form the incisions 44 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 of the thin plates 5, said protrusion 6 forming the notch 45 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 42 of the ground contact element 4; the enlarged-width portion 8 having a substantially triangular shape and protruding in the opposite direction to the direction of protrusion of the protrusion 6 from the main body 51 of the thin plates 5 is provided at the end portion of the thin plates 5 on the opposite side to the molding surface 3, and the two cutting means 7 separated in the thickness direction of the thin plates 5 and provided in such a way as to cut the covering layer 10 arranged in advance on the unvulcanized green tire 9 are provided in such a way as to protrude from the enlarged-width portion 8. Moreover, in the third mode of embodiment also, the cutting means 7 are not limited to two cutting means, and three or more may be provided.

(42) The effect of the tire molding element according to the third mode of embodiment will be described next.

(43) The tire molding element 1 according to the third mode of embodiment includes the enlarged-width portion 8 which protrudes in the opposite direction to the direction of protrusion of the protrusion 6 from the main body 51 of the thin plates 5, and therefore the covering layer 10 cut by means of the cutting elements 7 is reliably guided in the depth direction of the green tire 9 without being obstructed by the enlarged-width portion 8 and is also guided to the protrusion 6. As a result, the covering layer 10 can be stably arranged at a predetermined position with greater reliability.

(44) 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.