Green tire warming device for retreading, green tire warming method for retreading, and retread tire manufacturing method

Abstract

This green tire warming device for retreading for warming a green tire for retreading before vulcanization comprises: a warming chamber body 2 configured to partition a warming chamber 21; a microwave oscillation unit 3 provided on an inner wall surface of the warming chamber body and configured to irradiate the inside of the warming chamber with microwaves; a pair of shielding plates 4 configured to shield the microwaves; and a rotating tool 5 configured to rotate the green tire for retreading placed in the heating chamber in the tire circumferential direction relative to the warming chamber body. While the green tire for retreading, in which a pair of side portions of the green tire for retreading are covered from both outer sides in the tire width direction by the pair of shielding plates, is rotated in the tire circumferential direction relative to the warming chamber body by the rotating tool, a green tread rubber of the green tire for retreading that is not covered by the pair of shielding plates is warmed by microwaves radiated from the microwave oscillation unit.

Description

Retread green tire heating device, retread green tire heating method, and retread tire manufacturing method

[0001] The present invention relates to a raw tire warming device for retreading, a raw tire warming method for retreading, and a method for manufacturing a retread tire. This application claims priority to Japanese Patent Application No. 2024-150071, filed in Japan on August 30, 2024, the entire contents of which are incorporated herein by reference.

[0002] Conventionally, there has been a method (generally referred to as a "re-molding method") of obtaining a retread tire by vulcanizing a raw tire for retreading, which is made by assembling raw tread rubber onto a used base tire, using a vulcanization mold (for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 2007-076269

[0004] In obtaining a retread tire as described above, the raw tire to be retreaded may be heated before vulcanization. In this heating, it is considered desirable to focus on heating the raw tread rubber, while avoiding heating the base tire that has already been vulcanized as much as possible.

[0005] An object of the present invention is to provide a green tire heating device for retreading, a green tire heating method for retreading, and a retread tire manufacturing method that can intensively heat the green tread rubber.

[0006] [1] A retread green tire heating device for heating a retread green tire before vulcanization, comprising: a heating chamber body configured to partition a heating chamber; a microwave oscillator provided on an inner wall surface of the heating chamber body and configured to irradiate microwaves into the heating chamber; a pair of shielding plates configured to shield microwaves; and a rotating tool configured to rotate the retread green tire placed in the heating chamber in a tire circumferential direction relative to the heating chamber body, wherein the retread green tire, a pair of side portions of which are covered from both outer sides in the tire width direction by the pair of shielding plates, is rotated in the tire circumferential direction relative to the heating chamber body by the rotating tool, and the green tread rubber of the retread green tire that is not covered by the pair of shielding plates is heated by microwaves irradiated from the microwave oscillator.

[0007] [5] A method for warming a raw tire for retread before vulcanization using the raw tire for retread heating device described in [1], wherein the raw tire for retread, in which a pair of side portions of the raw tire for retread are covered from both outer sides in the tire width direction by the pair of shielding plates, is rotated by the rotating tool relative to the heating chamber body in the tire circumferential direction, and the raw tread rubber of the raw tire for retread that is not covered by the pair of shielding plates is heated by microwaves irradiated from the microwave oscillator.

[0008] [6] A method for producing a retread tire, comprising: an assembling step of assembling raw tread rubber onto a base tire to obtain a raw tire for retreading; a heating step of heating the raw tire for retreading using the method for heating a raw tire for retreading described in [5]; and a vulcanizing step of vulcanizing the raw tire for retreading heated in the heating step using a vulcanizing mold.

[0009] According to the present invention, it is possible to provide a green tire heating device for retreading, a green tire heating method for retreading, and a retread tire manufacturing method that can intensively heat the green tread rubber.

[0010] 1 is a perspective view showing a schematic view of a green tire for retreading according to an embodiment of the present invention, together with a green tire for retreading, and FIG. 2 is a tire width direction cross-sectional view showing the green tire for retreading warming apparatus and the green tire for retreading of FIG.

[0011] The retread green tire warming device, retread green tire warming method, and retread tire manufacturing method according to the present invention can be used to manufacture any type of retread tire (e.g., retread tires for trucks and buses, retread tires for passenger cars, etc.), and can be suitably used when manufacturing retread tires by a re-mold method.

[0012] Hereinafter, embodiments of a raw tire warming device for retreading, a raw tire warming method for retreading, and a retread tire manufacturing method according to the present invention will be described by way of example with reference to the drawings. Common members and parts in the various drawings are designated by the same reference numerals.

[0013] First, an outline of a retread tire manufacturing method according to one embodiment of the present invention will be described. This retread tire manufacturing method manufactures retread tires by a re-molding process, and can be used to manufacture any type of retread tire (for example, retread tires for trucks and buses, retread tires for passenger cars, retread tires for aircraft, etc.). The retread tire manufacturing method of this embodiment includes an assembly step, a heating step (FIGS. 1 and 2), and a vulcanization step.

[0014] In an assembling step (not shown), a green tread rubber T61 is assembled (attached) to the base tire T1 to obtain a green tire for retread T (see FIG. 2 ). The green tire for retread T obtained in this manner includes the base tire T1 and the green tread rubber T61. The base tire T1 is obtained by removing the tread rubber from a used tire by buffing or the like. The base tire T1 includes, for example, a pair of bead cores T4, a carcass T2 extending in a toroidal shape between the pair of bead cores T4, and a belt T3 disposed on the outer side of the crown region of the carcass T2 in the tire radial direction TRD. The base tire T1 (specifically, the rubber constituting the base tire T1) is entirely vulcanized. In the green tire for retread T, the green tread rubber T61 is made of a strip-shaped green rubber (unvulcanized rubber) and is disposed on the outer circumferential surface of the base tire T1. Thus, the green tread rubber T61 is disposed on the outer side of the belt T3 in the tire radial direction TRD. The green tread rubber T61 is a portion that will constitute the (vulcanized) tread rubber of a retread tire obtained after the vulcanization step. The green tire T for retreading is composed of a tread portion T6, a pair of sidewall portions T51 extending from both ends of the tread portion T6 in the tire width direction TWD toward the inner side in the tire radial direction TRD, and a pair of bead portions T52 continuing from the pair of sidewall portions T51 toward the inner side in the tire radial direction TRD. The tread portion T6 includes the green tread rubber T61, the belt T3 located on the inner side in the tire radial direction TRD of the green tread rubber T61, and a crown region of the carcass T2 located on the inner side in the tire radial direction TRD of the belt T3. The pair of bead portions T52 located on both sides in the tire width direction TWD include a pair of bead cores T4. The raw tire for retread T has a pair of side portions T5 on both sides in the tire width direction TWD. On each side in the tire width direction TWD, the side portion T5 is configured by a sidewall portion T51 and a bead portion T52.

[0015] After the assembling step, in a heating step (FIGS. 1 and 2), the green tire for retread T obtained in the assembling step is heated using a method for heating a green tire for retread according to any embodiment described in this specification. In the heating step, as will be described later, heating of the base tire T1 is suppressed while heating of the green tread rubber T61 is focused.

[0016] After the heating step, in a vulcanization step (not shown), the retread green tire T heated in the heating step is vulcanized using a vulcanization mold. In the vulcanization step, a tread pattern is formed on the tire outer peripheral surface (and therefore the tread surface) of the green tread rubber T61 of the retread green tire T by the vulcanization mold, and the green tread rubber T61 is vulcanized to become vulcanized tread rubber. After the vulcanization step, a retread tire (not shown) is obtained.

[0017] In this way, by intensively heating the raw tread rubber T61 made of raw rubber in a pre-heating step before the vulcanization step, the quality of the retread tire that is finally obtained can be improved and the vulcanization time required for the vulcanization step can be shortened.

[0018] A method for warming a green tire for retread according to an embodiment of the present invention, which is carried out in the warming step, will be described in more detail below with reference to Figures 1 and 2. This method for warming a green tire for retread is used to warm a green tire for retread T before vulcanization (before the vulcanization step) using a green tire for retread warming device 1 according to any embodiment described in this specification. The green tire for retread T is obtained in advance in an assembly step.

[0019] Here, a retread green tire warming apparatus 1 according to one embodiment of the present invention will be described with reference to Figures 1 and 2. The retread green tire warming apparatus 1 includes a heating chamber body 2, one or more microwave oscillators 3, a pair of shielding plates 4, and a rotating tool 5.

[0020] The heating chamber body 2 is configured to define an internal space (hereinafter referred to as the "heating chamber 21"). A retread green tire T, which is to be heated during the heating step, is placed inside the heating chamber 21 defined by the heating chamber body 2. In this embodiment, the heating chamber body 2 is substantially box-shaped (substantially rectangular), and is configured so that one side (the front side in FIG. 1) can be opened and closed. For ease of explanation, in this specification, as shown with arrows in FIGS. 1 and 2 , the openable and closable side of the heating chamber body 2 (the front side in FIG. 1) is referred to as the "front," and the opposite side is referred to as the "rear." The left and right sides of the heating chamber body 2 when viewed from the front to the rear are referred to as the "left" and "right," respectively, and the upper and lower sides in the vertical direction are referred to as the "upper" and "lower," respectively. In this embodiment, the heating chamber body 2 has a substantially box-shaped (substantially rectangular) main body 23 with an open front, and a door 24 configured to close the front open surface of the main body 23. The main body 23 and the door 24 may be connected to each other via a hinge or the like. When the door 24 closes the open surface of the main body 23, the closed heating chamber 21 is defined by the inner wall surface 22 of the heating chamber body 2. In this embodiment, the inner wall surface 22 of the heating chamber body 2 includes a lower wall surface 22a facing upward, an upper wall surface 22b facing downward and opposing the lower wall surface 22a, a left wall surface 22c facing right, a right wall surface 22d facing left and opposing the left wall surface 22c, a rear wall surface 22e facing forward, and a front wall surface 22f. The lower wall surface 22a, the upper wall surface 22b, the left wall surface 22c, the right wall surface 22d, and the rear wall surface 22e are provided on the main body 23, and the front wall surface 22f is provided on the door 24. When the closed heating chamber 21 is partitioned (and thus when the door 24 closes the open surface of the main body 23), the front wall surface 22f faces rearward and faces the rear wall surface 22e. However, the shape and configuration of the heating chamber body 2 are not limited to this embodiment and may be arbitrary. It is preferable that the inner wall surface 22 of the heating chamber body 2 is configured to reflect microwaves. This allows the microwaves irradiated from the microwave oscillator 3 to be more uniformly diffused within the heating chamber 21, thereby suppressing uneven heating of the green tread rubber T61 of the green tire T for retreading.From this viewpoint, the inner wall surface 22 of the heating chamber body 2 can be made of, for example, a non-magnetic metal.

[0021] One or more (six in this embodiment) microwave oscillators 3 are each provided on the inner wall surface 22 of the heating chamber body 2 and configured to irradiate microwaves into the heating chamber 21. The microwaves irradiated from the microwave oscillators 3 are non-directional and diffuse within the heating chamber 21. Microwaves are electromagnetic waves with a wavelength of 1 mm to 1 m and a frequency of approximately 300 MHz to 300 GHz. A frequency of 2000 to 3000 MHz is particularly suitable for the microwaves irradiated from the microwave oscillators 3, and may be, for example, 2450 MHz (ISM band). The microwave oscillators 3 may be configured, for example, as openings on the inner wall surface 22 of the heating chamber body 2 in a waveguide (not shown) connecting a microwave generator (not shown) to the heating chamber body 2. The microwave generator (not shown) is configured to generate microwaves and may be, for example, a magnetron. The microwave generator is disposed, for example, outside the heating chamber 21. A waveguide (not shown) is configured to transmit microwaves generated by the microwave generator into the heating chamber 21. In this embodiment, four microwave oscillators 3 are provided on the rear wall surface 22e of the heating chamber body 2, and two microwave oscillators 3 are provided (one on each of the left wall surface 22c and right wall surface 22d) of the heating chamber body 2. By arranging the microwave oscillators 3 in this manner, the microwaves irradiated from the microwave oscillators 3 can be more uniformly diffused within the heating chamber 21, thereby suppressing uneven heating of the green tread rubber T61 of the green tire T for retreading. However, the number and positions of the microwave oscillators 3 may be arbitrary. The microwave oscillators 3 (and thus the microwave generator) may be configured to be activated and stopped by an operator operating an input unit (such as a switch) (not shown). And / or, the microwave oscillator 3 (and thus the microwave generator) may be stopped automatically by a timer function or the like.

[0022] Each of the pair of shielding plates 4 is configured to have a plate-like shape and to block microwaves (i.e., to block microwaves). Each shielding plate 4 is made of, for example, stainless steel. Each shielding plate 4 may be configured to be flat (even flat-plate-like) as shown in the examples of FIGS. 1 and 2. Each shielding plate 4 may have one or more (multiple in the illustrated examples) through holes 42 as shown in the examples of FIGS. 1 and 2. Each through hole 42 penetrates the shielding plate 4 in the thickness direction of the shielding plate 4. Each through hole 42 is configured to block microwaves. From this perspective, the diameter of each through hole is approximately Φ10 mm for 2.45 GHz. Here, the diameter of the through hole 42 refers to the diameter of a circumscribed circle of the shape of the through hole 42 when the shape (planar shape) of the through hole 42 is non-circular. The shape (planar shape) of each through hole 42 may be any shape, such as a circle or a polygon. Alternatively, each shielding plate 4 may not have the through-hole 42 .

[0023] The rotating tool 5 is configured to rotate the retread green tire T placed in the heating chamber 21 relative to the tire circumferential direction TCD with respect to the heating chamber body 2. Here, when rotating the retread green tire T relative to the heating chamber body 2 in the tire circumferential direction TCD, for example, the retread green tire T may be rotated in the tire circumferential direction TCD without moving the heating chamber body 2, or the heating chamber body 2 may be rotated in the tire circumferential direction TCD of the retread green tire T without moving the retread green tire T. Note that in this specification, when describing the retread green tire heating method or the retread green tire heating device 1, the tire width direction TWD, tire radial direction TRD, and tire circumferential direction TCD of the retread green tire T placed in the heating chamber 21 will be simply referred to as the "tire width direction TWD," the "tire radial direction TRD," and the "tire circumferential direction TCD," respectively. 1 and 2, for ease of understanding, the tire width direction TWD, tire radial direction TRD, and tire circumferential direction TCD of the green tire for retread T placed in the heating chamber 21 are indicated by arrows, respectively. In this embodiment, the rotating tool 5 includes a rotary table 51 placed in the heating chamber 21. In the heating step, the green tire for retread T is placed on the rotary table 51. The rotary table 51 is configured to be rotatable around a predetermined rotation axis 52 relative to the heating chamber body 2. The rotation axis 52 coincides with the central axis of the rotary table 51, and therefore the rotary table 51 is configured to be rotatable around the rotation axis 52 relative to the heating chamber body 2. Note that the rotary table 51 may be rotated in the tire circumferential direction TCD without moving the heating chamber body 2, or the heating chamber body 2 may be rotated in the tire circumferential direction TCD without moving the rotary table 51. In addition to the rotary table 51, the rotating tool 5 may further include a shaft 53 fixed to the rotary table 51 and a motor (not shown) configured to rotate the shaft 53 around a rotation axis 52. In this case, the shaft 53 may extend downward from the rotary table 51, penetrate the inner wall surface 22 of the heating chamber 21, and extend to the outside of the heating chamber 21. The central axis of the shaft 53 coincides with the rotation axis 52. The motor may be disposed outside the heating chamber 21, for example.The rotating tool 5 may be configured to be activated and stopped by an operator operating an input unit (such as a switch) (not shown), and / or the rotating tool 5 may be stopped automatically by a timer function, etc. However, the rotating tool 5 may have a configuration different from that of this embodiment.

[0024] When heating a green tire T for retreading in the green tire heating method for retreading (heating step) using the green tire heating apparatus 1 for retreading described above, first, a pair of side portions T5 of the green tire T for retreading is covered from both outer sides in the tire width direction TWD by a pair of shielding plates 4 in advance (FIGS. 1 and 2), and the green tire T for retreading in this state is set on the rotating tool 5. Specifically, in this embodiment, the pair of shielding plates 4 are brought into contact with the pair of side portions T5 of the green tire T for retreading from both outer sides in the tire width direction TWD, and the green tire T for retreading in this state is placed on the rotating table 51 of the rotating tool 5 together with the pair of shielding plates 4. At this time, as shown in FIGS. 1 and 2 , it is preferable to orient the retread green tire T so that the tire axis TO of the retread green tire T is perpendicular to the rotary table 51 (and thus parallel to the rotation axis 52 of the rotating tool 5), as this improves stability. At this time, it is preferable that the shielding plates 4 are oriented so that the central axis of each shielding plate 4 is parallel to the tire axis TO of the retread green tire T, and it is more preferable that the central axis of each shielding plate 4 is aligned with the tire axis TO of the retread green tire T (and thus so that each shielding plate 4 and the retread green tire T are concentric). This allows for more uniform heating in the tire width direction TWD and the tire circumferential direction TCD. At this time, it is preferable that the shielding plates 4 are oriented so that they are parallel to each other and parallel to the tire radial direction TRD. 1 and 2 , the rotation axis 52, the tire axis TO, and the central axes of the shielding plates 4 may be arranged to coincide with each other. In this state, the shielding plates 4 are arranged not to cover the green tread rubber T61 of the green tire for retread T from the outside in the tire radial direction TRD (i.e., not positioned on the outside in the tire radial direction TRD of the green tread rubber T61). As a result, at least the outer surface in the tire radial direction TRD of the green tread rubber T61 of the green tire for retread T (the outer peripheral surface of the tire) is not covered by the shielding plates 4 and is exposed in the heating chamber 21.Thereafter, the worker operates an input unit (not shown) or the like to operate the rotating tool 5 and also operate the microwave oscillator 3 (and thus the microwave generator). As a result, the green tire for retread T, in which a pair of side portions T5 of the green tire for retread T are covered from both outer sides in the tire width direction TWD by the pair of shielding plates 4, is rotated by the rotating tool 5 relative to the heating chamber body 2 in the tire circumferential direction TCD, and the green tread rubber T61 of the green tire for retread T that is not covered by the pair of shielding plates 4 is heated by microwaves irradiated from the microwave oscillator 3. More specifically, in this embodiment, during this time, the turntable 51 of the rotating tool 5 rotates (spins) around the rotation axis 52, and accordingly, the pair of shielding plates 4 and the green tire for retread T placed thereon rotate around the rotation axis 52 integrally with the turntable 51. Thereafter, for example, the operator operates an input unit (not shown), or automatically stops the rotating tool 5 and stops the microwave oscillator 3 (and thus the microwave generator). This ends the heating of the raw tire for retread T, completing the raw tire for retread heating method (heating step). Note that, in order to prevent the temperature from rising too high and the rubber from vulcanizing, when applying microwaves to heat the raw tire for retread T (e.g., the raw tread rubber T61), the surface temperature may be measured periodically or continuously using a thermovision or the like, and when the surface temperature reaches a predetermined set temperature (e.g., a temperature at which vulcanization does not start: approximately 80°C), the microwave oscillator 3 (and thus the microwave generator) may be stopped, thereby ending the microwave irradiation.

[0025] In the retread green tire warming device 1 and retread green tire warming method (warming step) according to the present embodiment described above, as described above, in a state in which a pair of side portions T5 of the retread green tire T are covered from both outer sides in the tire width direction TWD by a pair of shielding plates 4, the green tread rubber T61 of the retread green tire T that is not covered by the pair of shielding plates 4 is heated by microwaves irradiated from the microwave oscillator 3. In this way, the pair of shielding plates 4 can prevent the microwaves from the microwave oscillator 3 from hitting the pair of side portions T5 of the retread green tire T, and thus can prevent the pair of side portions T5 from being heated by the microwaves, while the green tread rubber T61 that is not covered by the pair of shielding plates 4 can be heated intensively by the microwaves (i.e., it is possible to heat substantially only the green tread rubber T61). In this way, by intensively heating the raw tread rubber T61 made of raw rubber in the pre-heating step prior to the vulcanization step, the quality of the retread tire obtained as a final product can be improved and the vulcanization time required for the vulcanization step can be shortened. Furthermore, heating of the already-vulcanized base tire T1 of the retread raw tire T can be suppressed, thereby avoiding deterioration in durability due to heating of the base tire T1. Furthermore, since the retread raw tire T is heated while being rotated relative to the heating chamber body 2 in the tire circumferential direction TCD by the rotating tool 5, the raw tread rubber T61 of the retread raw tire T can be heated more uniformly in the tire circumferential direction TCD, thereby suppressing uneven heating of the raw tread rubber T61 in the tire circumferential direction TCD. This also improves the quality of the retread tire obtained as a final product.

[0026] It is preferable that each shielding plate 4 has a circular planar shape, as in the example of FIGS. 1 and 2 . As a result, when each shielding plate 4 is arranged concentrically with the raw retread tire T as shown in FIGS. 1 and 2 , the position of the outer edge 41 of each shielding plate 4 in the tire radial direction TRD relative to the raw retread tire T becomes uniform over the entire circumference of the tire. Therefore, each shielding plate 4 can uniformly cover each side portion T5 of the raw retread tire T over the entire circumference of the tire, so that in the heating step, the raw tread rubber T61 of the raw retread tire T can be heated more uniformly in the tire circumferential direction TCD. However, the planar shape of each shielding plate 4 may be other than circular (e.g., polygonal). It is preferable that each shielding plate 4 has the same shape and dimensions. This allows for more uniform heating in the tire width direction TWD.

[0027] From the viewpoint of intensively heating the green tread rubber T61 with microwaves while suppressing the pair of side portions T5 from being heated by microwaves, it is preferable to cover the pair of side portions T5 from both sides in the tire width direction TWD with the pair of shielding plates 4 to prevent the microwaves from hitting them, and to allow the green tread rubber T61 to be hit by the microwaves by not covering it from both sides in the tire width direction TWD with the pair of shielding plates 4. From this viewpoint, it is preferable that the radius R1 ( FIG. 2 ) of each shielding plate 4 is approximately equal to the inner diameter R2 ( FIG. 2 ) of the green tread rubber T61 on the tire side surface T7 of the green tire for retread T. Here, the inner diameter R2 of the green tread rubber T61 on the tire side surface T7 of the green tire for retread T is the tire radial direction TRD distance from the inner end in the tire radial direction TRD of the green tread rubber T61 to the tire axis line TO when viewing the tire side surface T7 (the outer surface on the outside in the tire width direction TWD) of the green tire for retread T. Specifically, for example, the absolute value of the difference between R1 and R2 is preferably 5 mm or less, and more preferably 2 mm or less. Also, it is preferable that R1≦R2, and for example, it is preferable that R1<R2. Note that when the shape (planar shape) of the shielding plate 4 is non-circular, the radius R1 of the shielding plate 4 refers to the radius of a circumscribing circle of the shape of the shielding plate 4.

[0028] The thickness of each shielding plate 4 is preferably 2 mm or more, and in consideration of weight, aluminum is a suitable material.

[0029] The retread green tire warming device, retread green tire warming method, and retread tire manufacturing method according to the present invention can be used to manufacture any type of retread tire (for example, retread tires for trucks and buses, retread tires for passenger cars, retread tires for aircraft, etc.), and can be suitably used when manufacturing retread tires by a re-mold method.

[0030] 1: Green tire heating device for retreading, 2: Heating chamber body, 21: Heating chamber, 22: Inner wall surface, 22a: Lower wall surface, 22b: Upper wall surface, 22c: Left wall surface, 22d: Right wall surface, 22e: Rear wall surface, 22f: Front wall surface, 23: Main body, 24: Door portion, 3: Microwave oscillator portion, 4: Shielding plate, 41: Outer edge, 42: Through hole, 5: Rotating tool, 51: Rotating table, 52: Rotation axis, 53: Shaft, T: Green tire for retreading, T1: Base tire, T2: Carcass, T3: Belt, T4: Bead core, T5: Side portion, T51: Sidewall portion, T52: Bead portion, T6: Tread portion, T61: Green tread rubber, T7: tire side, T8: boundary, TO: tire axis, TWD: tire width direction, TRD: tire radial direction, TCD: tire circumferential direction

Claims

1. A retread green tire heating device for heating a retread green tire before vulcanization, comprising: a heating chamber body configured to partition a heating chamber; a microwave oscillator provided on an inner wall surface of the heating chamber body and configured to irradiate microwaves into the heating chamber; a pair of shielding plates configured to shield microwaves; and a rotating tool configured to rotate the retread green tire placed in the heating chamber in a tire circumferential direction relative to the heating chamber body, wherein the retread green tire, a pair of side portions of which are covered from both outer sides in the tire width direction by the pair of shielding plates, is rotated in the tire circumferential direction relative to the heating chamber body by the rotating tool, and the green tread rubber of the retread green tire that is not covered by the pair of shielding plates is heated by microwaves irradiated from the microwave oscillator.

2. The green tire warming device for retreading according to claim 1, wherein each of said shielding plates is circular.

3. A green tire heating device for retreading according to claim 1, wherein the radius R1 of each of the shielding plates is approximately equal to the inner diameter R2 of the green tread rubber on the tire side surface of the green tire for retreading.

4. A raw tire heating device for retreading as described in claim 1, wherein the rotating tool includes a rotary table arranged within the heating chamber, and the rotary table is configured to be rotatable relative to the heating chamber body around a predetermined rotation axis.

5. A method for heating a raw tire for retreading using the apparatus for heating a raw tire for retreading according to any one of claims 1 to 4 to heat the raw tire for retreading before vulcanization, the method comprising: rotating the raw tire for retreading, a pair of side portions of which are covered from both outer sides in the tire width direction by the pair of shielding plates, relative to the heating chamber body in the tire circumferential direction by the rotating tool; and heating the raw tread rubber of the raw tire for retreading that is not covered by the pair of shielding plates by microwaves irradiated from the microwave oscillator.

6. A method for manufacturing a retread tire, comprising: an assembling step of assembling raw tread rubber onto a base tire to obtain a raw tire for retreading; a heating step of heating the raw tire for retreading using the method for heating a raw tire for retreading described in claim 5; and a vulcanizing step of vulcanizing the raw tire for retreading heated in the heating step using a vulcanizing mold.

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