JP2563673B2 - Cooling structure for electrical equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a cooling structure for an electric device using a cooling tube in which eddy current is not generated.

(Prior Art) Due to the demand for larger capacity, smaller size and lighter weight of electrical equipment,
Various cooling methods have been developed. Although a gas cooling method using a gas such as air is widely used, it is not possible to meet the above-mentioned demand because of a problem such as poor cooling efficiency and noise.

A liquid cooling method using a liquid such as water has been widely used because it has a significantly improved cooling efficiency as compared with a gas and does not have a problem such as noise. For example, a turbine generator employs a method of flowing water through a hollow conductor. In addition, it is also conceivable that a stainless tube or the like is piped and then the entire coil is fixed with a resin and then cooled by a liquid cooling method.

However, when a magnetic field is applied to a metal material, an eddy current is generated, and therefore a metal tube cannot be used when high magnetic field accuracy is required, such as in an MRI apparatus using the nuclear magnetic resonance phenomenon.

(Problems to be Solved by the Invention) As described above, since an eddy current is generated when a magnetic field is applied to a metal material, high magnetic field accuracy is required as in an MRI apparatus using a nuclear magnetic resonance phenomenon. In that case, a metal tube cannot be used.

The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a cooling structure for an electric device in which an eddy current is not generated by applying a magnetic field.

[Structure of Invention]

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a plastic cooling tube for circulating a cooling medium is provided inside,
The cooling tube and the coil are fixed by resin impregnation, and the adhesive strength between the cooling tube and the impregnated resin is set to be equal to or lower than the tensile strength of the cooling tube.

(Operation) Since no eddy current is generated in the plastic tube, it does not adversely affect the magnetic field accuracy. Also, by making the adhesive strength between the tube and the impregnated resin less than the tensile strength of the cooling tube, even if the resin cracks, peeling occurs between the tube and the impregnated resin before the cooling tube breaks. Therefore, it is not affected by the stress generated in the resin. Therefore, a plastic tube having inferior mechanical properties to a metal tube can be used. Furthermore, when an impregnating resin having shrinkage property is used during curing, even if there is no adhesive force between the impregnating resin and the tube, peeling between the resin and the tube can be prevented by the shrinkage of the impregnating resin, which adversely affects the cooling performance. Can be reduced,
Even if there is no adhesive force between the impregnated resin and the tube, there is no practical problem.

(Embodiment) FIG. 1 and FIG. 2 are drawings showing the concept of an embodiment of the present invention.

As shown in FIG. 1, a coil (not shown) is attached to the inner cylinder 1 (length 2 m, outer diameter 0.6 m), and a prepreg glass sheet (not shown) is wound to smooth the coil surface. , Complete the inner coil 2. After this, the Fluoro resin tube 3 (Product name: PFA Tube Junko, external diameter 8m
m, inner diameter 7 mm) is spirally wound to form a cooling tube. A glass sheet (not shown) is wound around the surface of the tube 3 for the purpose of preventing damage.

Then, a coil (not shown) is attached to the FRP middle cylinder (length 2 m, outer diameter 0.7 m) to manufacture the outer coil 4.

As shown in FIG. 2, after the inner coil 2 and the outer coil 4 are assembled, the outer cylinder 5 (length 2.2 m, outer diameter 0.8 m) is attached to hold the impregnated resin, and the epoxy resin is vacuum-applied. After pressure impregnation, the gradient magnetic field coil for MRI was completed.

 Next, the operation of the above configuration will be described.

By using a non-metallic plastic tube, it was confirmed that eddy currents do not occur, the magnetic field accuracy is improved, and a clearer image is obtained compared to the conventional gradient magnetic field coil for MRI. For example, it was found that the distortion of an image was 1.5% in the conventional coil, but was 0.5% or less.

Also, since the PFA medium tube has non-adhesiveness, the adhesive strength with the impregnated resin is much smaller than the tensile strength of the cooling tube. The tensile strength of the epoxy resin used in this example is 60 MPa, and the tensile strength of PFA is 30 MPa. Therefore, if the resin cracks and the adhesive strength between the resin and PFA tube is greater than the tensile strength of PFA, if the resin cracks, the PFA tube will break and cause a serious accident such as water leakage. .

In order to verify that the tube does not break even if the resin cracks, we manufactured the same tubular model (outer diameter 0.7 m, thickness 20 mm) using the tubes shown in Table 1. A thermal cycle (0 ° C-120 ° C) was performed. As a result, as shown in Photo 1 and Photo 2, in Sample 1, peeling occurs between the tube and the impregnated resin before the cooling tube breaks, so that the tube is not affected by the stress generated in the resin. No breakage occurs. Sample 2 is a sodium etching treatment (Junkosha product name: Tetra H treatment)
As a result, the tube was broken.

When the cross section of Sample 1 was observed with an electron microscope, the peeling distance between the tube and the impregnated resin was as small as 1 to 10 μm. This is because the epoxy resin used this time shrinks during curing, so the tube and epoxy resin are in close contact,
Even if peeling occurs, it is considered that the distance becomes smaller. Therefore, the temperature rise due to the release layer is slight, and there is no problem in practical use.

As explained above, by using a non-metallic plastic tube, eddy current does not occur, and even if the resin cracks, the tube does not break, for water-cooled MRI A gradient coil could be manufactured.

Although the gradient magnetic field coil for MRI has been described as an example of the present invention, it goes without saying that it can be used for cooling all electric devices.

Note that, even when the cooling medium is hardened with a resin as a cooling medium without being directly incorporated in an electric device, if the adhesive strength with the resin is much smaller than the tensile strength of the cooling tube, the scope of the present invention include.

〔The invention's effect〕

According to the present invention, it is possible to provide a cooling structure for an electric device when high magnetic field accuracy is required, and it is possible to downsize the device and increase the current.

[Brief description of drawings]

1 and 2 are drawings showing the concept of one embodiment of the present invention. 1 ... Inner cylinder, 2 ... Inner coil, 3 ... Cooling tube, 4 ... Outer coil, 5 ... Outer cylinder.

Claims (2)

(57) [Claims] 1. In an electric device impregnated with a resin to fix a coil, a plastic cooling tube for circulating a cooling medium is provided inside, and the cooling tube and the coil are fixed by impregnation of the resin. A characteristic cooling structure for electrical equipment. 2. The cooling structure for an electric device according to claim 1, wherein the adhesive strength between the cooling tube and the impregnated resin is not more than the tensile strength of the cooling tube.