JPS6350165B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for heating a resin body, such as a large rubber tire, which has a plurality of steel wires embedded therein to increase its strength, and a method for carrying out this method. The present invention relates to a microwave heating device used. As is well known, large rubber tires are manufactured by embedding a plurality of steel wires with a diameter of several millimeters in parallel in a circumferential shape inside the tire and vulcanizing the wires. Prior to this vulcanization, preheating is performed, and when microwave power is used as the heat source, there is an advantage that heating can be done relatively uniformly to a desired temperature due to the internal heating phenomenon of microwaves. By the way, when microwaves are irradiated from the outer circumference of this type of rubber tire, as shown by curves A and B in FIG. Uniform heating may not be obtained. This is because the density of the resin is relatively higher on the inside than on the outside, or the inside is often filled with a material such as nylon that has a relatively large high-frequency loss coefficient. This is due to the heat dissipation phenomenon at the surface. Furthermore, if a steel wire is embedded inside the tire, a portion of the microwave is reflected by this wire and travels from the position of wire 11 back to the inner surface, as shown by curve B in the figure. As a result, the temperature distribution suddenly becomes low, making it difficult to achieve a uniform temperature distribution. The present invention provides a method for heating a resin body such as this type of rubber tire in which steel wires are embedded by microwave irradiation, with a desired uniform temperature distribution across the thickness of the resin body. The present invention provides an apparatus that can easily carry out this method. Examples thereof will be described below with reference to the drawings. Note that the same parts are represented by the same symbols. Furthermore, although the embodiments shown below show a case where a rubber tire is used as the resin body, the present invention is not limited to rubber tires, but can be widely applied to resin structures having a plurality of parallel steel wires inside. The apparatus shown in FIGS. 2 and 3 has the following structure. A microwave oven 12 made of a conductive plate has a door (not shown) on one side, and a hanger 15 that hangs a rubber tire 13 as an object to be heated from the ceiling and is rotatable in the direction of an arrow 14. As shown in a partially enlarged view of FIG. 3, the rubber tire 13 has, for example, rubber near the outer surface, and a plurality of steel strips along the circumference of the tire approximately at the center in the thickness direction. Wires 11 are arranged in parallel, and the inside thereof is made of rubber with a nylon cord. This tire is inflated into a predetermined shape by a rubber bag 16 which is inflated with high pressure steam fed through a hanger 15. Now, this tire 1
Horn-shaped rectangular waveguide microwave radiators 17 (part 1 in the figure) are installed near the outer periphery of 3 and placed at four locations on the circumference.
(one shown) is provided. This radiator 17 is connected to a rectangular waveguide 18 and electrically connected to a microwave oscillator 19 placed outside the oven 12. These rectangular waveguide 18 and radiator 17 are rotatable at appropriate positions relative to the tire by at least 90 degrees as shown by arrow 14. This rotational operation may be performed by mechanical remote control using the circular waveguide rotary coupler 20. The microwave oscillator 19 is, for example,
Something like a magnetron with an oscillation frequency in the 2450MHz band can be used. To heat using this device, first place a rubber tire in an oven, hang it in a predetermined position with a hanger, and rotate it as shown by arrow 14. The oven is closed to prevent microwaves from leaking outside, the microwave oscillator is activated, and the radiator irradiates the tires with microwaves. At this time, the waveguide and radiator are set in the relationship shown in FIG. That is, the rectangular waveguide 18 and the radiator 17 are positioned such that their long side center line C is inclined by an angle θ with respect to the longitudinal direction of the steel wire 11 inside the rubber tire. TE01 mode microwave power is supplied to the rectangular waveguide 18 and the radiator 17, and as shown in FIG.
It has only a directional component perpendicular to . Therefore, the microwave power is propagated within the tire placed close to the radiator with its plane of polarization unchanged. Normally, when the distance t between the steel wires 11 is sufficiently smaller than 1/2 of the wavelength of the microwave, the electric field component parallel to the longitudinal direction of the wire is reflected at the position of the wire. On the other hand, the electric field component perpendicular to the wire passes through the position of the wire. As can be understood from this phenomenon, in the present invention, the microwave power radiated from the radiator located obliquely with respect to the longitudinal direction of the wire is such that the electric field E is parallel to the wire as shown in Figure 6. It can be seen as a combination of component E ₁ and perpendicular component E ₂ , and the parallel component E ₁ is reflected at this wire position and absorbed by the tire again near the outer surface of the tire, contributing to the heating of this area. , and the component E ₂ perpendicular to the wire passes through the wire position and penetrates deeply into the inside of the tire, contributing to heating of the inner part. As a result, when the method of the present invention is used to heat the tire by irradiating microwaves from the outside as shown by the solid line curve D in Figure 1B, the temperature is almost uniform throughout the thickness direction of the tire, although the maximum is at the center. temperature distribution. The degree of this distribution varies depending on the wire spacing t and the microwave wavelength, but once these are determined, it can be easily controlled by adjusting the inclination angle θ. Furthermore, if the rubber tires and the radiator are separated significantly,
It is undesirable that most of the microwave power is not directly absorbed by the tire, but is diffusely reflected by the inner wall of the oven, increasing the amount of components whose polarization planes are not constant. To eliminate such inconveniences, the distance from the opening end of the rectangular waveguide to the outer surface of the rubber tire should be within about 10 wavelengths, and preferably a horn-shaped radiator as in the above embodiment may be used to prevent disturbances in the polarization plane and radio waves. The structure is configured to suppress the undesirable spread of. However, the horn shape is not essential, and the open end of the rectangular waveguide may be used as it is as a radiator. As described above, according to the present invention, it is possible to easily achieve desired uniform heating over the thickness direction of a resin body in which a conductive steel wire is embedded.

[Brief explanation of the drawing]

Figure 1A is a sectional view of a rubber tire, Figure 1B is a temperature distribution diagram, Figure 2 is a schematic diagram showing an embodiment of the present invention, Figure 3 is an enlarged view of its main parts, and Figure 4 is a steel wire and FIG. 5 is a diagram showing the positional relationship with the radiator, FIG. 5 is a diagram showing the electric field component within the rectangular waveguide, and FIG. 6 is a diagram showing the relationship between the steel wire and the electric field component. 11...Steel wire, 12...Oven, 13
...Rubber tire, 15...Hanger (heated object installation means), 17, 18...Rectangular waveguide (radiator), 19...
Microwave oscillator, E... electric field direction.

Claims (1)

[Claims] 1. A method of heating a resin body in which a plurality of steel wires arranged in parallel are buried by irradiating microwave power, the method comprising: embedding the steel wires in the resin body; A microwave heating method characterized in that irradiation is performed such that the direction of the electric field of the microwave is oblique with respect to the direction. 2. A microwave oven, a means for installing an object to be heated at a predetermined position within the oven, and a rectangular waveguide type radiation radiator installed close to the means for installing an object to be heated and irradiating the object to be heated with microwave power. What is claimed is: 1. A microwave heating device comprising: a radiator, the opening surface of the radiator being rotatable around its longitudinal direction;