Process for vulcanizing a green tire

Abstract

Method for vulcanizing a green tire (12) in a heating press with a multi-part vulcanization mold, which has sidewall shells (2, 4), bead rings (5, 15) and a segment ring (6) composed of a number of radially movable segment shoes (7) with held profile segments (8), and wherein an external heater is provided, which has heating chambers (11) for heating the segment ring (6) and heating chambers (10a, 10b) for heating the lower sidewall shell (2) together with the lower bead ring (5) and the upper sidewall shell (4) together with the upper bead ring (15), wherein the profile segments (8) shape and heat the tread region of the green tire (12), wherein the sidewall shells (2, 4) and bead rings (5, 15) shape and heat the sidewalls of the green tire, and wherein the external heater (10a, 10b, 11) is supplied with a heating medium,wherein the lower sidewall shell (2) and the lower bead ring (5) are operated at a temperature T1 and wherein the upper sidewall shell (4) and the upper bead ring (15) are operated at a temperature T2, where T1 ≠ T2, characterized in that the lower sidewall shell (2) and the lower bead ring (5) are operated at a temperature T1, that the upper sidewall shell (4) and the upper bead ring (15) are operated at a temperature T2, where T1 < T2, so that the sidewalls of the tire are differently vulcanized and thus differently crosslinked.

Description

[0001] The invention relates to a method for vulcanizing a green tire in a heating press with a multi-part vulcanization mold, which has sidewall shells, bead rings and a segment ring composed of a number of radially movable segment shoes with held profile segments, and wherein an external heater is provided, which has heating chambers for heating the segment ring and heating chambers for heating the lower sidewall shell including the lower bead ring and the upper sidewall shell including the upper bead ring, wherein the profile segments shape and heat the tread area of ​​the green tire, wherein the sidewall shells and bead rings shape and heat the sidewalls and bead areas of the green tire and wherein the external heater is supplied with a heating medium,wherein the lower sidewall shell and the lower bead ring are operated at a temperature T1 and wherein the upper sidewall shell and the upper bead ring are operated at a temperature T2, where T1 ≠ T2.,

[0002] Such a process is known, for example, from DE 600 14 423 T2. In this process, heating is achieved via an external heater and an internal heater. The external heater comprises annular heating tables for heating the lower and upper sidewall shells, respectively, including the bead rings. The heating tables are cavities and therefore heating chambers. The external heater is supplied with a heating medium. The lower sidewall shell and the lower bead ring are operated at a temperature that is higher than the temperature at which the upper sidewall shell and the upper bead ring are operated. This temperature control ensures homogeneity of heat transfer, whereby the tire is evenly vulcanized, which subsequently leads to uniform properties of both sidewalls of the tire.

[0003] DE 11 2010 004 993 B4 discloses another method for vulcanizing a green tire. Since the temperature in the area of ​​the upper sidewall shell and the upper bead ring tends to decrease, the upper sidewall shell and the upper bead ring are operated at a temperature higher than the temperature at which the lower sidewall shell and the lower bead ring are operated. This is intended to ensure uniform heating of the vulcanization mold, the vulcanized tire exhibits uniform physical properties, and the vulcanization time is shortened.

[0004] In a vulcanization mold, the green tires are heated externally via the tread segments, sidewall shells, and bead rings. These parts are heated via heating chambers inside heating plates that are supplied with at least one heating medium. The interior of the green tire is usually heated and shaped into its final shape using a heating bladder, into which at least one gaseous or liquid heating medium is introduced under a specific pressure.

[0005] It is known that the temperature at which the heating chambers are operated has an impact on the material and tire properties of the vulcanized tire. If, for example, the material damping increases, the rolling resistance of the tire is affected. It is common practice during tire vulcanization to operate the external heater at a relatively low temperature (temperature of the heating medium), in the range of 165°C to 175°C, with the temperature of the external heater being kept largely constant throughout the entire vulcanization period. The internal heating via the heating bladder takes place at a temperature of 190°C to 205°C, which is reduced during the vulcanization period. In order to bring the green tire to the desired vulcanization temperature at the beginning of the vulcanization cycle, it is common practice to initially operate the internal heater at a relatively high temperature.To prevent undesirable cross-linking of certain tire components during vulcanization, the temperature is regulated to the desired target level at a defined rate starting at a certain point in the vulcanization cycle. In conventional vulcanization processes, the external heating is therefore cooler than the internal heating, meaning there is a thermal gradient from the inside to the outside. Until now, efforts have always been made to operate the lower sidewall shell and the lower bead ring, as well as the upper sidewall shell and the upper bead ring, at the same temperature.

[0006] The invention is based on the object of optimizing the operation of the external heating with the aim of improving the handling behavior of the vulcanized tire.

[0007] The term “handling behavior” here means driving behavior.

[0008] The object is achieved according to the invention in that the lower sidewall shell and the lower bead ring are operated at a temperature T1, and the upper sidewall shell and the upper bead ring are operated at a temperature T2, where T1 < T2, so that the sidewalls of the tire are differently vulcanized and thus differently cross-linked.

[0009] Surprisingly, it has been shown that a tire whose sidewalls are vulcanized by upper and lower sidewall shells and bead rings operating at different temperatures exhibits improved handling characteristics than a tire whose sidewalls are vulcanized by upper and lower sidewall shells and bead rings operating at the same temperature. This phenomenon may be explained by the fact that the tire sidewalls are exposed to different loads during driving, with the differently vulcanized and thus differently cross-linked sidewalls having a positive effect on handling.

[0010] "Tire sidewall" refers to the sidewall including the bead area of ​​a tire. "Sidewall" of a vulcanizing mold refers to the sidewall shell including the bead ring...

[0011] It is advantageous to operate the heating chamber for heating the segment ring at a temperature T3, where T3 = T1 ≠ T2 or where T3 = T2 ≠ T1 or where T3 ≠ T2 = T1 or where T3 ≠ T2 ≠ T1. This allows for individually adapted heating to the tread and / or sidewalls to achieve optimal tire tread and / or tire sidewall crosslinking.

[0012] It is useful to allow the temperatures T1, T2 and T3 to differ from each other by up to + / - 25°C.

[0013] Further features, advantages, and details of the invention will now be described in more detail with reference to the schematic drawings, which illustrate exemplary embodiments. The drawings show: Fig. 1 a sectional view of a part of a tire vulcanization mold in the closed state with a tire, Fig. 2 a sectional view through a tire vulcanization mold with specific temperature control, Fig. 3 a sectional view through a tire vulcanization mold with a different temperature control, Fig. 4 a sectional view through a tire vulcanization mold with yet another temperature control.

[0014] The Fig. Figure 1 schematically shows the essential components of a conventional vulcanization mold or heating mold for a pneumatic vehicle tire for passenger cars. The vulcanization mold is located within a heating press, the components of which are not shown. Such a heating press typically comprises an upper press section and a lower press section and has the corresponding mechanisms for positioning the tire to be vulcanized, for operating the components of the vulcanization mold, for introducing the heating media, and for removing the fully vulcanized tire.

[0015] The Fig. The vulcanization mold shown in Figure 1 is a multi-part container mold with a lower heating plate 1, a lower side wall shell 2, an upper heating plate 3, an upper side wall shell 4, a lower bead ring 5 and an upper bead ring 15. The components of the vulcanization mold that are moved in the vertical direction (arrow P1) for opening and closing include the upper heating plate 3 with the upper side wall shell 4 arranged on it. The vulcanization mold further comprises a segment ring 6, which is usually composed of seven to nine annular segment shoes 7, which hold the shaping profile segments 8. The segment shoes 7 are moved radially in the direction of the arrow P2 when the vulcanization mold is opened. Fig. 1, are moved apart, thus releasing the fully vulcanized tire. On the inside of the segment shoe 7 shown, a profile segment 8 can be seen, which forms the profiled tread of the tire. A closing ring 9 is arranged on the upper heating plate 3. This closing ring has a beveled inner surface which interacts with beveled outer surfaces of the segment shoes 7 of the segment ring 6 in such a way that when the vulcanization mold is closed, the segment shoes 7 are moved together in the radial direction to form the closed segment ring 6. The lower heating plate 1, the upper heating plate 3 and the closing ring 9 contain heating chambers 10a, 10b, 11, into which at least one heating medium, in particular saturated steam (steam), is introduced to vulcanize the tire.In this way, the green tire 12 is heated from the outside via the segment shoes 7, the sidewall shells 2, 4 and the bead rings 5, 15, so that this heating is usually referred to as external heating.

[0016] The heating chamber 10a contained in the lower heating plate 1 essentially heats the lower tire sidewall and the lower tire bead area, i.e., the so-called lower tire sidewall, while the heating chamber 10b contained in the upper heating plate 3 essentially heats the upper tire sidewall and the upper tire bead area, i.e., the so-called upper tire sidewall of the green tire 12. The heating chamber 11 located in the locking ring 9 primarily heats the segment shoes 7 in the segment ring 6, which transfer their heat to the profile segments 8, which are responsible for shaping the tread of the tire 12. Fig. 1 also shows a conventional heating bladder 14, which is arranged in a known manner and is filled with at least one heating medium under pressure to center the green tire 12 in the mold from the inside, whereby the heating bladder 14 is formed into a torus shape appropriate for the tire. Since the green tire 12 is heated from the inside via the heating bladder 14, this type of heating is referred to as internal heating.

[0017] FU refers to the so-called bottom of the mold, in which the tire sidewall facing outward when mounted on the vehicle is vulcanized. FO refers to the so-called top of the mold, in which the tire sidewall facing inward when mounted on the vehicle is vulcanized.

[0018] According to the invention, the external heating is designed as a so-called “zone heating”, in which the lower side wall shell 2 and lower bead ring 5 (= lower side flank) are operated by the lower heating chamber 10a at a temperature T1 and in which the upper side wall shell 4 and the upper bead ring 15 (= upper side flank) are operated by the upper heating chamber 10b at a temperature T2, where T1 ≠ T2.

[0019] The Fig. Figure 2 shows a sectional view through a tire vulcanization mold with a specific temperature control, in which the lower sidewall shell 2 and the lower bead ring 5 are heated through the lower heating chamber 10a at a temperature T1, and in which the upper sidewall shell and the upper bead ring are heated through the upper heating chamber 10b at a temperature T2, where T1 < T2. The temperature T3 of the tread segments is heated through the heating chamber 11 such that T3 = T2.

[0020] The Fig. Figure 3 shows a sectional view through a tire vulcanization mold with a specific, different temperature control, which does not fall under the wording of claim 1, and in which the lower sidewall shell and the lower bead ring are heated through the lower heating chamber 10a at a temperature T1, and in which the upper sidewall shell and the upper bead ring are heated through the upper heating chamber 10b at a temperature T2, where T1 > T2. The temperature T3 of the tread segments is heated through the heating chamber 11 such that T3 = T1.

[0021] The Fig.Figure 4 shows a sectional view through a tire vulcanization mold with a specific, yet different temperature control, which also does not fall under the wording of claim 1, and in which the lower sidewall shell and the lower bead ring are heated through the lower heating chamber 10a at a temperature T1, and in which the upper sidewall shell and the upper bead ring are heated through the upper heating chamber 10b at a temperature T2, where T1 > T2. The temperature T3 of the profile segments in the heating chamber 11 is controlled such that T1 ≠ T2 ≠ T3. List of reference symbols 1 lower heating plate 2 lower side wall shell 3 upper heating plate 4 upper side wall shell 5 lower bead ring 6 segment ring 7 segment shoe 8 profile insert 9 locking ring 10a lower heating chamber 10b upper heating chamber 11 Heating chamber 12 raw tires 14 Heating bladder 15 upper bead ring T1 Temperature lower sidewall flank T2 Temperature upper sidewall flank T3 temperature profile segment FU mold bottom FO mold top

Claims

[1] Method for vulcanising a green tyre (12) in a heating press with a multi-part vulcanisation mould, which has sidewall shells (2, 4), bead rings (5, 15) and a segment ring (6) composed of a number of segment shoes (7) movable in the radial direction with held profile segments (8), and wherein an external heating system is provided, which has heating chambers (11) for heating the segment ring (6) and heating chambers (10a, 10b) for heating the lower sidewall shell (2) together with the lower bead ring (5) and the upper sidewall shell (4) together with the upper bead ring (15), wherein the profile segments (8) shape and heat the tread region of the green tyre (12), wherein the sidewall shells (2, 4) and bead rings (5, 15) shape and heat the sidewalls of the green tyre, and wherein the external heating system (10a, 10b, 11) is supplied with a heating medium,wherein the lower sidewall shell (2) and the lower bead ring (5) are operated at a temperature T1 and wherein the upper sidewall shell (4) and the upper bead ring (15) are operated at a temperature T2, where T1 ≠ T2, , characterized by that the lower sidewall shell (2) and the lower bead ring (5) are operated at a temperature T1, that the upper sidewall shell (4) and the upper bead ring (15) are operated at a temperature T2, where T1 < T2, so that the sidewalls of the tyre are vulcanised differently and thus cross-linked differently. [2] Method according to claim 1, characterized by that the heating chamber (11) for heating the segment ring (6) is operated at a temperature T3, where T3 = T1 or where T3 = T2 or where T3 ≠ T1 and ≠ T2. [3] Method according to claim 1 or 2, characterized by that the temperatures T1, T2 and T3 can differ from each other by up to + / - 25°C.

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